JP7613464B2 - Method for producing laminated film, polarizing plate, display device, and polarizing plate roll - Google Patents

Description

The present invention relates to a laminated film, a polarizing plate, a display device, and a method for manufacturing a polarizing plate roll that include the laminated film. More specifically, the present invention relates to a laminated film that is thin but can be handled in the same way as conventional polarizing plate protective films, and further has excellent curl controllability during polarizing plate processing, thereby improving the productivity of polarizing plate processing.

Liquid crystal display devices are widely used as image display devices in televisions (TVs), personal computers (PCs), and other devices because they consume low power and can be made thin.

In recent years, as televisions (TVs) have become larger, thinner, and have improved display quality, there is a demand for thinner components to suppress optical unevenness that occurs due to stress caused by bending of the display panel and dimensional changes in the components.

Furthermore, for applications such as notebook and small to medium-sized personal computers, smartphones, and slate PCs, there is a particularly high demand for thinner components, and the functional films used (e.g., viewing angle compensation films, polarizing plate protective films, etc.) need to be made even thinner.

However, if the film is made too thin, it loses its stiffness and rigidity, which reduces the film transportability and the yield of the lamination process. For this reason, Patent Document 1 proposes a method in which a thin functional film is formed on a base film (also called a "carrier film") in a peelable manner, and the film is transported as a thick laminated film until lamination, and the unnecessary base film is removed after lamination with the polarizer.

However, when two films made of different materials, such as a base film and a thin functional film placed on top of it, are laminated in this way, if the materials have different inherent coefficients of humidity expansion, curling will occur due to humidity fluctuations. If the curling is very slight, it may actually make the lamination and peeling processes easier, but if severe curling occurs, lamination becomes more difficult, creating a problem that reduces the yield of the polarizing plate manufacturing process.

As mentioned above, Patent Document 1 describes a method for laminating a thin functional film onto a substrate film in a peelable manner in order to handle the functional film. However, because there is a difference in humidity dependency between the material for forming the functional film and the substrate film, there is a problem that curling occurs due to moisture absorption during processing of the polarizing plate or during storage, making it difficult to handle during transport and lamination. These problems become particularly noticeable when the laminated film becomes thin.

JP 2018-45220 A

The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a laminated film which, despite being thin, has excellent transportability, can be handled in the same way as conventional polarizing plate protective films, and further has excellent curl controllability during polarizing plate processing, improving the productivity of polarizing plate processing (bonding ability with polarizers), and a method for manufacturing a high-quality polarizing plate, display device, and polarizing plate roll that are equipped with the same and are free of optical unevenness.

In the course of investigating the causes of the above problems in order to solve the above problems, the inventors discovered that when a laminate film having a peelable functional layer laminated on a base film, in which the base film and the functional layer each have a thickness within a specific range, and the humidity expansion coefficient and thickness of the base film and the humidity expansion coefficient and thickness of the functional layer satisfy a specific relationship, a laminate film can be obtained that is thin but has excellent transportability, can be handled in the same way as conventional polarizing plate protective films, and further has excellent curl controllability during polarizing plate processing, and has improved productivity (bonding to polarizer) in polarizing plate processing.

In other words, the above problem of the present invention is solved by the following means.

1. A laminated film in which a peelable functional layer is laminated on a base film,
The base film contains polyethylene terephthalate,
the functional layer contains a fumaric acid diester resin or a (meth)acrylic resin containing rubber particles ,
The thickness of the functional layer is within the range of 1 to 19 μm;
The total thickness of the laminated film is 50 μm or less,
A laminated film characterized by satisfying the relationship of the following formula ₍₁ ) when the humidity expansion coefficient of the base film at 23°C is _CHE1 (ppm/% RH), the thickness is _d1 (μm), and the humidity expansion coefficient of the functional layer at 23°C is CHE2 (ppm/% RH) and the thickness is _d2 (μm).
Formula (1) 0.20<|(CHE ₁ −CHE ₂ )|×(d ₂ /d ₁ )<2.00

2. The laminate film described in paragraph 1, characterized in that the thickness of the functional layer is within the range of 2 to 10 μm.

3. The laminate film described in paragraph 1 or 2, characterized in that the total thickness of the laminate film is within the range of 30 to 45 μm.

4. The laminate film according to any one of items 1 to 3, characterized in that the functional layer has a retardation value Ro defined by the following formula (i) in the range of 0 to 20 nm, and a retardation value Rt defined by the following formula (ii) in the range of -25 to 25 nm.
Formula (i) Ro = ( _nx - _ny ) x d
Formula (ii) Rt={(n _x + n _y )/2-n _z }×d
(In the above formulas (i) and (ii), Ro represents the retardation value in the in-plane direction of the functional layer, Rt represents the retardation value in the thickness direction of the functional layer, _nx represents the refractive index in the in-plane direction of the slow axis of the functional layer, _ny represents the refractive index in the in-plane direction of the fast axis of the functional layer, _nz represents the refractive index in the thickness direction of the functional layer (the refractive index is measured at a wavelength of 590 nm under an environment of 23° C. and 55% RH), and d represents the thickness of the film (nm).)

5. The laminate film according to any one of items 1 to 4, characterized in that, when the content of the residual solvent in the base film is _S1 and the content of the residual solvent in the functional layer is _S2 , the following formula (2) is satisfied:
Formula (2) 10<S ₁ <S ₂ <1000 (ppm)

6. The laminate film described in paragraph 5, wherein the boiling point of the main residual solvent among the residual solvents is 100°C or less under atmospheric pressure.

7. The laminate film described in paragraph 5 or 6, wherein the residual solvent is a chlorine-based solvent.

8. The laminate film described in any one of paragraphs 5 to 7, wherein the residual solvent is dichloromethane.

9. The laminate film described in any one of paragraphs 5 to 8, characterized in that the residual solvent contains dichloromethane and alcohols.

10. The laminate film according to any one of items 1 to 9, wherein the base film is a biaxially stretched polyester film, and the humidity expansion coefficient CHE ₁ of the polyester film at 23° C. is within the range of 10 to 20 ppm/% RH.

11. The laminate film described in any one of paragraphs 1 to 10, characterized in that the functional layer contains a polymer material having a carbonyl group in a side chain.

12. A laminate film described in any one of paragraphs 1 to 10, characterized in that the functional layer contains a polymer material having a cyclic structure in its main chain.

13. A polarizing plate comprising a laminate film described in any one of items 1 to 12.

14. A display device comprising a laminate film described in any one of paragraphs 1 to 12 or a polarizing plate described in paragraph 13.

15. A method for producing a polarizing plate roll, comprising: rolling up the laminate film according to any one of items 1 to 12 while bonding the laminate film to at least one surface of a polarizer,
A method for producing a polarizing plate roll, comprising a step of winding up the laminate film while bonding the laminate film to the polarizer in the layered order from the inside of the roll: polarizer, adhesive layer, functional layer, and base film .

The above-mentioned means of the present invention make it possible to provide a laminated film which, despite being thin, has excellent transportability, can be handled in the same way as conventional polarizing plate protective films, and further has excellent curl controllability during polarizing plate processing, improving the productivity of polarizing plate processing (bonding to polarizers), as well as a high-quality polarizing plate, display device, and method for manufacturing a polarizing plate roll that are equipped with the same and are free of optical unevenness.

Although the mechanism by which the effects of the present invention are expressed or acted upon has not been clarified, it is speculated as follows.

When forming a laminated film (hereinafter also referred to as a "laminate") in which a functional layer is disposed on a base film, warping and curling of the films to be laminated are extremely important factors in increasing yield. The mechanism of warping is complex, and the mechanism by which it occurs has been unclear until now, so no method for controlling warping without sacrificing productivity had been investigated.

In particular, when dealing with laminated films that have very thin functional layers, very little is known about predicting or improving the magnitude of curl in the laminate of the base film (which functions as a protective film) and the functional layer, especially curl affected by humidity.

The inventors have investigated how this humidity-based warping mechanism can be predicted and further improved by referring to a formula for predicting curl of laminates due to heat.

Regarding curling of laminates due to heat, the following formula has been proposed, but as a result of further investigation, we have obtained an index that can accurately predict curling of laminates under certain conditions, such as curling due to humidity changes and even curling in warm water, using a relatively simple formula based on the assumptions shown below.

In other words, it was found that the curling of the laminate in warm water (or high humidity) is greatly influenced by two factors: (1) the difference in the coefficient of hydroscopic expansion (CHE) between the base film and the functional layer, and (2) the ratio of the thicknesses of the base film and the functional layer.

It is known that the curl prediction formula for a bimetal laminate due to heat is expressed by the following formula (a).

Formula (a) Curl curvature 1/R ∝ 6 (α ₂ -α ₁ ) (ΔT) (1+m ² )/h [3 (1+m) ² + (1+mn) {m ² + (mn) ^-1 }]
(In the formula, α represents the thermal expansion coefficient, _α1 represents the functional layer, and _α2 represents the base film. ΔT represents the temperature rise width. h represents the sum of the thickness ( _d1 ) of the base film and the thickness ( _d2 ) of the functional layer. m represents the thickness ratio ( _d1 / _d2 ) of the base film thickness ( _d1 ) and the functional layer thickness ( _d2 ). n represents the elastic modulus ratio ( _f1 / _f2 ) of the base film elastic modulus ( _f1 ) and the functional layer elastic modulus ( _f2 ).)

Where:
1) The difference in humidity expansion coefficient between the base film and the functional layer is directly converted into the difference in thermal expansion coefficient (α ₂ - _{α 1} ) = ΔCHE.

2) When comparing various films under constant conditions, such as immersion in water, the humidity difference (ΔT) can be treated as a constant.

3) The elastic modulus ratio n is assumed to be n ≒ 1, as it does not change significantly for organic polymer materials.

4) The thickness ratio m, which is the thickness of the base film ( _d1 )/the thickness of the functional layer ( _d2 ), is actually the thickness of the functional layer ( _d2 ) < the thickness of the base film ( _d1 ), so 1 << m, and (1/m) << 1.

5) The total thickness h is also within a certain numerical range as a thickness that can be realistically handled, and is treated as a constant.

Therefore, by adding the approximation conditions 1) to 5) above, equation (a) can finally be expressed as equation (f).

If “h” in formula (a) is considered to be a constant, formula (a) becomes:
Formula (b) Curve curvature 1/R∝ΔCHE×(1+m)/[3+3m+m ² +m ⁻¹ ]
Assuming that m ⁻¹ ≈0 in formula (a), formula (b) becomes:
Formula (c) Curve curvature 1/R≈ΔCHE×(1+m)/[3+3m+m ² ]
Formula (d) Curve curvature 1/R ≒ ΔCHE × (1 + m) / 3 (1 + m) ²
Since "m" in formula (a) is 1<<m, formula (d) is
Formula (e) Curve curvature 1/R ∝ ΔCHE × 1/(1 + m)
Furthermore, in formula (e), since m is 1<<m, if "1+m" is set to "m", then
Formula (f) Curve curvature 1/R ∝ ΔCHE/m
That is, the present invention was discovered by conducting a demonstration experiment based on the supposition that the curl curvature 1/R can be expressed by formula (1) according to the present invention, that is, "|(CHE ₁ -CHE ₂ )|×(d ₂ /d ₁ )."

Conceptually, this can also be understood from the qualitative phenomenon that hair expands easily with humidity, but the thicker the layer, the more severe the curl.

On the other hand, we also found that if the laminate does not curl at all, there is no trigger to peel the base film when it is peeled off, which reduces workability and decreases yield.

When bonding the polarizer and the functional layer, if the humidity expansion coefficient of the base film is too large compared to that of the functional layer, the base film is likely to curl outward, causing the center of the functional layer to rise above the surface of the polarizer, and preventing the functional layer and the polarizer from being adequately bonded together (see Figure 1). Furthermore, if the curl is large, it is thought that optical unevenness is more likely to occur due to internal stress in the functional layer.

In addition, when the laminate film is stored in a rolled state under high humidity conditions, if there is a large difference in the amount of humidity expansion between the layers, this can easily cause delamination or deformation such as wrinkles in the functional layer. If delamination occurs, the transport stability is likely to decrease during transport of the laminate film or during production of the polarizing plate, and if deformation such as wrinkles occurs in the functional layer, the flatness of the functional layer is impaired, resulting in a problem that the adhesion between the functional layer and the polarizer cannot be sufficiently improved.

Therefore, the present invention has been made in consideration of the above circumstances, and it is presumed that by suppressing delamination between layers and deformation of the functional layer during storage of the laminate film under high humidity conditions while adjusting the humidity expansion coefficients and thicknesses of the base film and functional layer, which are factors that cause curling, to satisfy the relationship in formula (1) above, it is possible to obtain a laminate film that not only has excellent curl controllability during polarizing plate processing, but also improves the productivity of polarizing plate processing (bonding ability to polarizer) and suppresses the occurrence of optical unevenness in the functional layer.

Specifically, by making the humidity expansion coefficient of the base film and the functional layer at 23°C appropriately larger than that of the functional layer and by appropriately designing the thickness ratio of each to satisfy the range of formula (1), it is possible to control the appropriate curl direction and magnitude of the laminated film, thereby improving the productivity of polarizing plate processing (bonding ability with the polarizer), and it is believed that this also has the effect of suppressing the occurrence of wrinkles and optical unevenness in the functional layer.

A schematic diagram explaining the mechanism by which curling occurs in a high-humidity environment when a polarizing plate is produced using a peelable film laminate. Schematic diagram showing a cross section of the laminated film of the present invention. FIG. 1 is a schematic diagram showing a method for producing a laminated film according to an embodiment of the present invention. Cross-sectional view of a polarizing plate with a substrate film is a cross-sectional view of a polarizing plate with the base film peeled off.

The laminated film of the present invention is a laminated film having a peelable functional layer laminated on a base film, the base film containing polyethylene terephthalate, the functional layer containing a fumaric acid diester resin or a (meth)acrylic resin containing rubber particles , the thickness of the functional layer being within a range of 1 to 19 μm, the total thickness of the laminated film being 50 μm or less, and satisfying the relationship of formula (1) above, when the humidity expansion coefficient of the base film at 23° C. is CHE ₁ (ppm/% RH), the thickness is d ₁ (μm), and the humidity expansion coefficient of the functional layer at 23° C. is CHE ₂ (ppm/% RH) and the thickness is d ₂ (μm). This feature is a technical feature common to or corresponding to the following embodiments.

In an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the thickness of the functional layer is within the range of 2 to 10 μm, from the viewpoint of suppressing wrinkles and curl deformation of the thin functional layer and providing a thinner polarizing plate when the base film is peeled off and the functional layer is bonded to a polarizer. Furthermore, it is also preferable from the viewpoint of suppressing optical unevenness in a liquid crystal display device using the polarizing plate.

In addition, from the viewpoint of being thin yet having excellent rigidity and transportability, and being able to be handled in the same way as conventional polarizing plate protective films, the total thickness of the laminate film is preferably within the range of 30 to 45 μm.

From the viewpoint of providing a thin polarizing plate to be applied to an IPS mode display device, the retardation value Ro of the functional layer defined by the formula (i) is within the range of 0 to 20 nm, and the retardation value Rt defined by the formula (ii) is within the range of -25 to 25 nm, which are preferable retardation value ranges. Furthermore, a functional layer with such optical properties is preferable in terms of usage in which a very thin functional layer is provided without affecting the optical properties of various films.

When the content of the residual solvent in the base film is _S1 and the content of the residual solvent in the functional layer is _S2 , it is preferable to satisfy the formula (2) from the viewpoint of controlling the humidity expansion coefficients ( _CHE1 and _CHE2 ) of the base film and the functional layer. By the solvent also penetrating into the base film, a slight mixed layer is formed between the laminated films, and it is possible to ensure good process suitability without easy peeling during various processes. When a mixed solvent is used, the value of the sum of all solvent types is used as an index.

In addition, the boiling point of the main solvent among the residual solvents is 100° C. or less under atmospheric pressure, the residual solvent is a chlorine-based solvent, and the residual solvent is dichloromethane, and among them, the residual solvent contains dichloromethane and alcohols. It is preferable from the viewpoint of ease of handling when preparing the dope for the base film and the functional layer and forming a film. By using a low boiling point solvent and a chlorine-based solvent having high solubility, the drying time after film formation can be shortened. It is estimated that a coating film with a short drying time is less dense than a coating film with a long drying time, and as a result, the permeability of moisture changes, and CHE ₂ can be controlled slightly. The main solvent refers to a solvent that is mixed in a ratio of more than 50 mass% in the solvent type in the coating liquid.

The base film is a biaxially stretched polyester film, and it is preferable that the humidity expansion coefficient CHE ₁ of the polyester film at 23° C. is within the range of 10 to 20 ppm/% RH from the viewpoint of suppressing curling of the entire laminated film by an appropriate humidity expansion coefficient CHE _1. Furthermore, by using a biaxially stretched polyester film, the anisotropy of CHE ₁ is eliminated, and the occurrence of unevenness can be suppressed.

In addition, it is preferable for the functional layer to contain, as the resin, a linear polymer material having a carbonyl group in the side chain, or a polymer material having a cyclic structure in the main chain, from the viewpoint of controlling physical properties such as the humidity expansion coefficient and improving optical properties.

By incorporating the laminate film of the present invention, the polarizing plate of the present invention can be processed using the same polarizing plate processing process as conventional ones, without compromising productivity or requiring complicated processing processes.

The display device of the present invention is a preferred embodiment from the viewpoint of obtaining a high-quality display device free of light leakage or optical unevenness by being equipped with the laminate film of the present invention or the polarizing plate of the present invention.

The method for producing a polarizing plate roll of the present invention is a method for producing a polarizing plate roll in which the laminate film of the present invention is laminated to at least one surface of a polarizer while being wound up, and is characterized by including a step of laminating the laminate film to the polarizer while winding it up so that the layers are arranged in the order of polarizer, functional layer, and base film from the inside of the roll. This method for producing a polarizing plate roll allows the base film to also serve as a protective film, leading to a reduction in the number of parts and a simplification of the processing steps .

The present invention, its components, and the modes and aspects for implementing the present invention will be described in detail below. In this application, the symbol "~" is used to mean that the numerical values before and after it are included as the lower and upper limits.

<Overview of the laminated film of the present invention>
The laminate film of the present invention is a laminate film having a peelable functional layer laminated on a base film, wherein the base film contains polyethylene terephthalate, the functional layer contains a fumaric acid diester resin or a (meth)acrylic resin containing rubber particles , the thickness of the functional layer is within the range of 1 to 19 μm, the total thickness of the laminate film is 50 μm or less, and when the humidity expansion coefficient of the base film at 23° C. is CHE ₁ (ppm/% RH) and the thickness is d ₁ (μm), and the humidity expansion coefficient of the functional layer at 23° C. is CHE ₂ (ppm/% RH) and the thickness is d ₂ (μm), the relationship of the following formula (1) is satisfied.
Formula (1) 0.20<|(CHE ₁ −CHE ₂ )|×(d ₂ /d ₁ )<2.00

(Measurement of coefficient of hygroscopic expansion (CHE) at 23°C)
A film sample is fixed in a thermo-hygrostat so that it has a width of 1 cm and a length of 15 cm, and is dehumidified to a constant humidity (approximately 30% RH). After the film length becomes constant, it is humidified (approximately 80% RH) and begins to elongate due to moisture absorption. After about 24 hours, the moisture absorption reaches equilibrium and the film elongation also reaches equilibrium. The amount of elongation at this time is calculated using the following formula. During this time, the atmospheric temperature is kept constant at 23°C.

Humidity expansion coefficient at 23°C (ppm/% RH) = elongation (cm)/(sample length (cm) x humidity difference) x ¹⁰⁶

As a means for controlling the coefficient of humidity expansion (hereinafter also referred to simply as "CHE"), it is preferable to adjust, for example, the drying speed (film density) after film formation of the base film and the functional layer. High-speed drying tends to form a sparse film, and CHE becomes large.

As a means for controlling the CHE of the base film, stretching (magnification) and thermal relaxation may be used during or after film formation. High stretching (magnification) results in a dense film being formed and the CHE being small, while thermal relaxation tends to form a coarse film and the CHE being large. Therefore, these may be used as a means for adjusting the CHE to fall within the range of formula (1) above, taking into account the relationship with the CHE of the functional layer.

In addition, the film-forming materials used for the base film and the functional layer are also related to the control of CHE. When the film-forming material for the functional layer is a linear polymer material having a carbonyl group in the side chain, in addition to controlling CHE, it can also have the effect of suppressing optical unevenness of the polarizer by giving it moderate moisture permeability. In particular, acrylic resins with low photoelasticity tend to exhibit good characteristics. Furthermore, it is also a preferred embodiment to use polymer materials having a cyclic structure in the main chain (e.g., cycloolefin resins) as the film-forming material, since these polymer materials have little change in optical properties due to humidity and are less likely to cause unevenness due to humidity.

When the value of the formula (1) of the laminated film is larger than 2.00, the film curls significantly as described above, and the lamination during the manufacture of the polarizing plate is difficult in practice. On the other hand, when the value of the formula (1) is 0.20 or less, the base film and the functional layer are difficult to peel off, and peeling errors may occur. Therefore, it is necessary to adjust the CHE and thickness within the range of the formula (1).
Furthermore, depending on the degree of curl, air bubbles or creases may occur when the film is attached to a polarizer (polyvinyl alcohol film).

The mechanism by which air bubbles are trapped during lamination is unclear, but it is believed to be as follows.
If the curl is too large, the unevenness in the TD direction (width direction of the long film) becomes too large, trapping air during lamination and generating air bubbles. Conversely, if the curl is too small, the film becomes too susceptible to the curl in the MD direction (width direction of the long film), trapping air and generating air bubbles.

In the present invention, the lamination property can be improved by controlling the curl within a specific range. From the viewpoint of improving lamination property, the index of the present application corresponding to the curl (|(CHE ₁ -CHE ₂ )|×(d ₂ /d ₁ )) ranges from more than 0.20 to less than 2.00, more preferably from 0.30 to 1.00, and particularly preferably from 0.40 to 0.70.

In addition, when a functional film is laminated to a polarizer (polyvinyl alcohol film), interference fringes may occur.

The exact cause of the interference fringes is not clear, but it is believed that the functional layer shrinks when the substrate film is peeled off after the laminated film of the present invention is bonded. At this time, minute refractive index irregularities occur at the interface between the polarizer and the functional layer, which is thought to be the cause of the observed interference irregularities.

It is believed that by controlling the curl within the specific range of the present invention, it is possible to make the shrinkage unevenness of the polarizer uniform and improve interference unevenness.

It is presumed that if the curl is too small, the effect of shrinkage of the polarizer becomes large, resulting in large interference unevenness, whereas if the curl is too large, the effect of shrinkage of the functional layer becomes large.
In the present invention, from the viewpoint of interference unevenness, the index of the present application corresponding to curl (|(CHE ₁ -CHE ₂ )|×(d ₂ /d ₁ )) is preferably in the range of 0.30 to 1.00, particularly preferably in the range of 0.40 to 0.70.

Furthermore, when equipped in a display device, if the value of formula (1) is 2.00 or more, internal stress remains in the functional layer and optical unevenness is likely to occur. On the other hand, if the value of formula (1) is 0.20 or less, there is a problem with the moisture permeability of the functional layer, and drying unevenness is likely to occur, and wrinkles due to drying unevenness and optical unevenness may be observed.

In addition, if the coefficient of humidity expansion CHE of the entire laminate film is large, for example, while the laminate film is stored in a rolled state at high temperatures, the difference in the amount of humidity expansion between the base film and the functional layer is likely to be large because the amount of humidity expansion of each is large. This makes it easy for delamination to occur between the base layer and the base film, and for the functional layer to deform. When delamination occurs, the transport stability of the laminate film is likely to decrease, and when the functional layer deforms, the flatness of the functional layer is likely to be impaired, and therefore the adhesion to the polarizer is likely to decrease.

In the present invention, it is preferable to reduce the humidity expansion coefficient CHE of the entire laminate film, and since the amount of humidity expansion of the entire laminate film under high humidity conditions can be reduced, the difference in the amount of humidity expansion between the base film and the functional layer can also be reduced. This can suppress peeling and deformation of the functional layer during storage of the laminate film under high temperatures, and can improve adhesion to the polarizer without impairing the transport stability of the laminate film.

(Layer structure of laminated film)
FIG. 2 shows an example of the layer structure of the laminated film of the present invention.

The laminated film 1 of the present invention has a base film 2 and a functional layer 3 on the base film 2. The base film 2 and the functional layer 3 may be configured by laminating a plurality of layers. In addition, the functional layer 3 may have other functional layers, such as a primer layer (not shown) or a protective layer (not shown), on the front or back surface.

The base film 2 may have an adhesive layer or pressure-sensitive adhesive layer (not shown) on the side opposite the functional layer, and the adhesive layer or pressure-sensitive adhesive layer can provide an adhesive function when the base film 2 is attached to the display element.

In this regard, the term "peelable functional layer" in this invention refers to a state in which the functional layer is in close contact with the base film during normal production or general use and does not easily peel off, but when it is desired to use only the functional layer during polarizing plate processing, the functional layer can be peeled off from the base film by external stress.

For example, the stress when peeling the base film from the functional layer can be evaluated by cutting a laminated film to a width of 25 mm and a length of 80 mm, bonding and fixing the surface of the functional layer opposite the interface with the base film to a glass substrate via an acrylic adhesive sheet, and then using a tensile tester (RTF-1210 manufactured by A&D Co., Ltd.) to grip one end of the base film in the longitudinal direction of the test piece (one side with a width of 25 mm) and carrying out a 90° peel test (in accordance with JIS K 6854-1:1999 "Adhesives - Test method for peel adhesion strength - Part 1: 90° peel") at a crosshead speed (gripping movement speed) of 200 mm/min in an atmosphere of a temperature of 23°C and a humidity of 60% RH. This can be an example of a state in which the base film and the functional layer can be peeled off with a stress of 0.05 to 2.00 N/25 mm. If the stress is 0.05 N/25 mm or more, peeling is less likely to occur during the polarizing plate processing process, which is preferable, and if the stress is 2.00 N/25 mm or less, folding does not occur in the polarizing plate when the base film is peeled off, which is preferable.

The structure of the laminated film of the present invention is described in detail below.

[1] Substrate Film The substrate film supports the functional layer and is not particularly limited as long as the difference in humidity expansion coefficient at 23° C. between the substrate film and the functional layer (|(CHE ₁ −CHE ₂ )|) can be adjusted to a range that satisfies the above formula (1). The substrate film usually contains a resin film.

Examples of resins that can be used include cellulose ester resins, cycloolefin resins, polypropylene resins, acrylic resins, polyester resins, polyarylate resins, and styrene resins or composite resins thereof. Among these, it is preferable to use polyester resins, which have a suitably large humidity expansion coefficient and are easy to control within the range of formula (1).

Examples of resin films include polyester-based resins (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.). Among these, polyester-based resin films containing polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) are preferred because the humidity expansion coefficient CHE of the laminated film at 23°C is easily adjusted to fall within the range of formula (1) above.

The resin film may be heat-treated (thermally relaxed) or stretched, and is preferably used to control CHE as described above.

The heat treatment reduces residual stress in the resin film (e.g., residual stress due to stretching), and can increase the humidity expansion coefficient CHE ₁ of the resin film and, ultimately, the base film. The heat treatment temperature is not particularly limited, but can be performed at (Tg+60) to (Tg+180)° C., where Tg is the glass transition temperature of the resin constituting the resin film.

The stretching treatment increases the residual stress of the resin film, and therefore can lower the humidity expansion coefficient CHE ₁ of the resin film and, in turn, the base film. The stretching treatment is preferably performed, for example, in the biaxial direction of the resin film. The stretching treatment can be performed under any conditions, for example, at a stretching ratio of about 120 to 900%. Whether the resin film is stretched can be confirmed, for example, by whether there is an in-plane slow axis (an axis extending in the direction in which the refractive index is maximum). The stretching treatment may be performed before or after laminating the functional layer, but it is preferable that the resin film is stretched before laminating.

The polyester resin film (simply referred to as polyester film) may be a commercially available product, for example, polyethylene terephthalate film TN100 (manufactured by Toyobo Co., Ltd.) or MELINEX ST504 (manufactured by Teijin DuPont Films Co., Ltd.).

The substrate film may further have a release layer provided on the surface of the resin film. The release layer can make it easier to peel the functional layer from the substrate film when producing a polarizing plate.

The release layer may contain a known release agent and is not particularly limited. Examples of release agents contained in the release layer include silicone-based release agents and non-silicone-based release agents.

Examples of silicone-based release agents include known silicone-based resins. Examples of non-silicone-based release agents include long-chain alkyl pendant polymers obtained by reacting long-chain alkyl isocyanates with polyvinyl alcohol or ethylene-vinyl alcohol copolymers, olefin-based resins (e.g., copolymerized polyethylene, cyclic polyolefins, polymethylpentene), polyarylate resins (e.g., polycondensates of aromatic dicarboxylic acid components and dihydric phenol components), fluororesins (e.g., polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of tetrafluoroethylene and ethylene)), and the like.

The thickness of the release layer is not particularly limited as long as it is sufficient to exhibit the desired releasability, but it is preferable that it be, for example, 0.1 to 1.0 μm.

In addition, if the humidity expansion coefficient of the base film itself at 23°C is within the range of 10 to 20 ppm/% RH, warping is less likely to occur, which is preferable.

This is presumably because, if the RH is 10 ppm/% or higher, the base film can follow the fluctuations in the polarizer caused by environmental changes, and as a result, it is presumed that the occurrence of poor appearance can be avoided. Also, if the RH is 20 ppm/% or lower, it is presumed that the base film itself can be prevented from expanding due to humidity, and as a result, it is presumed that the occurrence of warping can be suppressed.

(Thickness)
The total thickness of the laminated film of the present invention is 50 μm or less, preferably in the range of 30 to 45 μm. The thickness d ₁ of the base film is thin but needs a certain degree of strength (flexibility and rigidity) as a support, so it is preferably in the range of 15 to 45 μm, more preferably in the range of 20 to 40 μm.

[1.2] Additives <Plasticizers>
The base film according to the present invention may contain a plasticizer. The plasticizer is not particularly limited, but is preferably selected from polyhydric alcohol ester plasticizers, phthalate ester plasticizers, citric acid plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, polycarboxylic acid ester plasticizers, polyester plasticizers, and the like.

<Ultraviolet absorber>
The substrate film according to the present invention may also contain an ultraviolet absorbing agent. Examples of the ultraviolet absorbing agent that may be used include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based agents. Examples of the ultraviolet absorbing agent that may be used include triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone.

<Antioxidants>
The substrate film according to the present invention may contain an antioxidant, which is also called an anti-deterioration agent.

Antioxidants have the role of delaying or preventing decomposition of the base film due to, for example, halogens contained in residual solvents in the base film or phosphoric acid in phosphate-based plasticizers, so it is preferable to include them in the base film.

As such antioxidants, hindered phenol compounds are preferably used, for example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate].

<Particles>
The substrate film according to the present invention preferably contains fine particles.

Examples of the fine particles used in the present invention include inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Fine particles of organic compounds can also be preferably used. Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resins, silicone resins, polycarbonate resins, benzoguanamine resins, melamine resins, polyolefin powders, polyester resins, polyamide resins, polyimide resins, polyethylene fluoride resins, and pulverized fractions of organic polymer compounds such as starch, and polymer compounds synthesized by suspension polymerization.

Fine particles containing silicon are preferred because they reduce turbidity, and silicon dioxide is particularly preferred. For example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (all manufactured by Nippon Aerosil Co., Ltd.) are commercially available and can be used.

[1.3] Manufacturing method of the base film As a manufacturing method of the base film according to the present invention, a general manufacturing method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, etc. can be used, but from the viewpoint of suppressing coloring, suppressing foreign matter defects, suppressing optical defects such as die lines, etc., the film formation method is preferably a solution casting method or a melt casting method. In the solution casting method, the temperature in the processing step is low, and therefore it is possible to impart high functionality by using various additives. In addition, in the solution casting method, the content of residual solvent in the base film can also be controlled to adjust CHE ₁ .
The "solution casting method" will be described below.

<Solution Casting Method>
When forming a film by the solution casting method, the manufacturing method of the substrate film according to the present invention preferably includes the steps of dissolving and dispersing a thermoplastic resin and additives such as the above-mentioned fine particles in a solvent to prepare a dope (dissolving step; dope preparation step), casting the dope onto an endless metal support that moves indefinitely (casting step), drying the cast dope as a web (solvent evaporation step), peeling it off from the metal support (peeling step), drying, stretching, and width retention (stretching, width retention, drying step), and winding the finished film into a roll (winding step). The solvent used in the dope preparation step of the solution casting method can be appropriately selected from the solvents used in the formation of the functional layer described below.

The content of the residual solvent in the web at the time of peeling the web (hereinafter also referred to as "residual solvent amount") is appropriately adjusted depending on the strength of the drying conditions, the length of the metal support, etc. In order for the film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass. If peeling is performed at a time when the residual solvent amount is greater, if the web is too soft, the flatness is impaired during peeling and wrinkles and vertical streaks are likely to occur due to the peeling tension, so the amount of residual solvent at the time of peeling is determined by taking into account the economic speed and quality. More preferably, it is 10 to 40% by mass or 60 to 130% by mass, and particularly preferably, it is 10 to 30% by mass or 70 to 120% by mass.

In the present invention, the amount of residual solvent in the base film is defined by the following formula:

Residual solvent amount (mass%) = [(M-N)/N] x 100
Here, M is the mass of a sample taken at any time during or after the production of the web or film, and N is the mass of M after heating for 1 hour at 115° C. The residual solvent type is basically the solvent type used, but can be appropriately measured and identified by gas chromatography or the like.

In the drying, stretching, and width retention process, the film is generally dried using a roll drying method (a method in which the web is dried by passing it alternately between multiple rollers arranged above and below) or a tenter method in which the web is dried while being transported. For example, after peeling, the web is dried using a drying device in which the web is transported by passing it alternately between multiple rollers arranged inside the drying device, and/or a tenter stretching device in which both ends of the web are clipped with clips and transported.

There are no particular limitations on the means for drying the web, and it can generally be done using hot air, infrared rays, heated rollers, microwaves, etc., but from the standpoint of simplicity, it is preferable to use hot air.

It is preferable to stretch the web in at least one direction. The orientation of the molecules in the film can be controlled by stretching. In particular, by performing biaxial stretching as described below, the anisotropy of CHE ₁ can be eliminated and the occurrence of unevenness can be suppressed.

Specific stretching methods include sequential or simultaneous biaxial or uniaxial stretching in the longitudinal direction of the web (film-forming direction; casting direction; MD direction) and the direction perpendicular to the web surface, i.e., the width direction (TD direction). A biaxially stretched film is preferably one that has been biaxially stretched in the casting direction (MD direction) and the width direction (TD direction). The stretching operation may be divided into multiple stages. When performing biaxial stretching, simultaneous biaxial stretching may be performed, or may be performed in stages. Simultaneous biaxial stretching also includes the case where one direction is stretched and the other direction is shrunk by relaxing the tension.

The final stretching ratio in the two mutually perpendicular axial directions is preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, and more preferably in the range of 0.8 to 1.2 times in the casting direction and 1.2 to 2.0 times in the width direction.

The stretching temperature is usually preferably in the range of Tg to Tg + 60°C of the resin that constitutes the film. Usually, the stretching temperature is preferably 120°C to 200°C, and more preferably 120°C to 180°C.

The amount of residual solvent in the web during stretching is preferably 0 to 20% by mass, and more preferably 0 to 15% by mass.

There are no particular limitations on the method of stretching the web. For example, there is a method in which a plurality of rollers are provided with different peripheral speeds, and the difference in roller peripheral speed is used to stretch the web in the vertical direction; a method in which both ends of the web are fixed with clips or pins, and the distance between the clips or pins is increased in the direction of travel to stretch the web in the vertical direction; a method in which the web is similarly spread in the horizontal direction and stretched in the horizontal direction; or a method in which the web is spread in both the vertical and horizontal directions at the same time to stretch the web in both the vertical and horizontal directions. Of course, these methods may be used in combination. Of these, it is particularly preferable to stretch the web in the width direction (horizontal direction) using a tenter method in which both ends of the web are held by clips or the like. It is preferable to use a tenter to hold the width or stretch the web in the horizontal direction during the film-forming process, and this may be a pin tenter or a clip tenter.

The base film of the present invention can be heat-relaxed to obtain the same effect as by stretching. The heat-relaxing temperature is usually preferably in the range of Tg to Tg+60°C of the resin constituting the film. Usually, the heat-relaxing temperature is preferably 120°C to 200°C, and more preferably 120°C to 180°C.

The film is then wound into a roll by a winding process. Any commonly used method can be used to wind the film, such as the constant torque method, constant tension method, taper tension method, or program tension control method with constant internal stress.

The substrate film according to the present invention is preferably a long film, specifically, approximately 100 m to 10,000 m long, and is usually provided in roll form. The longer the film length, the greater the amount that can be produced in one production run, and this is preferable. From the standpoint of transportability and handling, a compact roll form is required, so the thinner the total film thickness of the laminate film, the better.

[2] Functional Layer The functional layer according to the present invention is peeled off from the base film and then attached to a polarizer, or is peeled off after being attached to a polarizer to form a polarizing plate, and can function as an optical film such as a polarizing plate protective film or a retardation film.

The thickness of the functional layer according to the present invention is within the range of 1 to 19 μm, and preferably within the range of 2 to 10 μm, from the viewpoints of providing a thin polarizing plate while suppressing wrinkles and curl deformation of the thin functional layer.

[2.1] Resin The resin used in the functional layer according to the present invention is not particularly limited, but it is preferable to contain a linear polymer material having a carbonyl group in the side chain, or a polymer material having a cyclic structure in the main chain in order to control the humidity expansion coefficient. Therefore, preferred resins may be cycloolefin resins, fumaric acid diester resins, (meth)acrylic resins, or styrene-(meth)acrylate copolymers.

<Cycloolefin Resin>
The cycloolefin resin used in the functional layer is preferably a polymer of a cycloolefin monomer, or a copolymer of a cycloolefin monomer and another copolymerizable monomer.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

In general formula (A-1), R ¹ to R ⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. However, R ¹ to R ⁴ do not all represent hydrogen atoms at the same time, R ¹ and R ² do not both represent hydrogen atoms, and R ³ and R ⁴ do not both represent hydrogen atoms.

In general formula (A-1), the hydrocarbon group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ is, for example, preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, or a silicon atom. Examples of such linking groups include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

Examples of the polar group represented by R ¹ to R ⁴ in general formula (A-1) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. Among them, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferred, and from the viewpoint of ensuring solubility during solution casting, an alkoxycarbonyl group and an aryloxycarbonyl group are preferred.

In general formula (A-1), p is preferably 1 or 2 from the viewpoint of increasing the heat resistance of the optical film. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature is likely to be improved. In addition, there is the advantage that it becomes somewhat responsive to humidity, making it easier to control the curl balance of the laminate.

In formula (A-2), ^R5 represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. ^R6 represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0 to 2.

R ⁵ in formula (A-2) preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

In formula (A-2), R ⁶ preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group or an aryloxycarbonyl group, and from the viewpoint of ensuring solubility during solution casting, an alkoxycarbonyl group or an aryloxycarbonyl group is more preferable.

In general formula (A-2), p preferably represents 1 or 2 from the viewpoint of improving the heat resistance of the optical film. When p represents 1 or 2, the resulting polymer becomes bulky, and the glass transition temperature is likely to be improved.

Cycloolefin monomers having a structure represented by general formula (A-2) are preferred from the viewpoint of improving solubility in organic solvents. In general, by breaking the symmetry of an organic compound, the crystallinity is reduced, and the solubility in organic solvents is improved. ^R5 and ^R6 in general formula (A-2) are substituted only on the ring-constituting carbon atoms on one side of the axis of symmetry of the molecule, so that the symmetry of the molecule is low. In other words, cycloolefin monomers having a structure represented by general formula (A-2) have high solubility, and are therefore suitable for producing optical films by a solution casting method.

The content of the cycloolefin monomer having the structure represented by general formula (A-2) in the polymer of cycloolefin monomers can be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin resin. When a certain amount or more of the cycloolefin monomer having the structure represented by general formula (A-2) is contained, the orientation of the resin is increased, and the phase difference (retardation) value is likely to increase.

Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown below in exemplary compounds 1 to 14, and specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are shown below in exemplary compounds 15 to 34.

Examples of copolymerizable monomers copolymerizable with cycloolefin monomers include copolymerizable monomers capable of ring-opening copolymerization with cycloolefin monomers, and copolymerizable monomers capable of addition copolymerization with cycloolefin monomers.

Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

Examples of copolymerizable monomers capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl cyclic hydrocarbon monomers, and (meth)acrylates. Examples of unsaturated double bond-containing compounds include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), examples of which include ethylene, propylene, and butene. Examples of vinyl cyclic hydrocarbon monomers include vinylcyclopentene monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

The content of cycloolefin monomer in a copolymer of cycloolefin monomer and copolymerizable monomer may be, for example, 20 to 80 mol %, preferably 30 to 70 mol %, based on the sum of all monomers constituting the copolymer.

As described above, cycloolefin resins are polymers obtained by polymerizing or copolymerizing cycloolefin monomers having a norbornene skeleton, preferably cycloolefin monomers having a structure represented by general formula (A-1) or (A-2), examples of which include the following:

1) Ring-opening polymer of cycloolefin monomer; 2) Ring-opening copolymer of cycloolefin monomer and a copolymerizable monomer capable of ring-opening copolymerization therewith; 3) Hydrogenated product of ring-opening (co)polymer of 1) or 2) above; 4) (co)polymer obtained by cyclizing ring-opening (co)polymer of 1) or 2) above by Friedel-Crafts reaction and then hydrogenating it; 5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound; 6) Addition copolymer of cycloolefin monomer and vinyl cyclic hydrocarbon monomer and hydrogenated product thereof; 7) Alternating copolymer of cycloolefin monomer and (meth)acrylate.

The polymers 1) to 7) above can be obtained by known methods, for example, the methods described in JP-A-2008-107534 and JP-A-2005-227606. For example, the catalyst and solvent used in the ring-opening copolymerization 2) above can be those described in paragraphs 0019 to 0024 of JP-A-2008-107534. The catalyst used in the hydrogenation 3) and 6) above can be those described in paragraphs 0025 to 0028 of JP-A-2008-107534. The acidic compound used in the Friedel-Crafts reaction 4) above can be those described in paragraph 0029 of JP-A-2008-107534. The catalyst used in the addition polymerization 5) to 7) above can be those described in paragraphs 0058 to 0063 of JP-A-2005-227606. The alternating copolymerization reaction of 7) above can be carried out, for example, by the method described in paragraphs 0071 and 0072 of JP-A No. 2005-227606.

Among them, the polymers of 1) to 3) and 5) are preferred, and the polymers of 3) and 5) are more preferred. That is, the cycloolefin resin preferably contains at least one of the structural units represented by the following general formula (B-1) and the structural units represented by the following general formula (B-2), and more preferably contains only the structural unit represented by the general formula (B-2), or contains both the structural unit represented by the general formula (B-1) and the structural unit represented by the general formula (B-2). The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-1), and the structural unit represented by the general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-2).

In formula (B-1), X represents --CH.dbd.CH-- or _{--CH.sub.2CH.sub.2--} , and ^R.sub.1 to _R.sub.4 and p have the same meanings as ^{R.sub.1 to R.sub.4} and p in formula (A-1), respectively.

In formula (B-2), X represents --CH.dbd.CH-- or _{--CH.sub.2CH.sub.2--} ^, and ^R.sub.5 to _R.sub.6 and p have the same meanings as ^R.sub.5 to ^R.sub.6 and p in formula (A-2), respectively.

The cycloolefin resin according to the present invention may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (e.g., G7810, etc.), Arton F, Arton R (e.g., R4500, R4900, and R5000, etc.), and Arton RX (e.g., RX4500, etc.), all manufactured by JSR Corporation.

The intrinsic viscosity [η]inh of the cycloolefin resin, measured at 30° C., is preferably 0.2 to 5 cm ³ /g, more preferably 0.3 to 3 cm ³ /g, and even more preferably 0.4 to 1.5 cm ³ /g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably 8,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 12,000 to 50,000. The weight average molecular weight (Mw) of the cycloolefin resin is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured in polystyrene equivalent terms by gel permeation chromatography (GPC).

<Gel permeation chromatography>
Solvent: methylene chloride Column: Shodex K806, K805, K803G (three columns manufactured by Showa Denko K.K. were connected and used)
Column temperature: 25°C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Sciences)
Pump: L6000 (Hitachi, Ltd.)
Flow rate: 1.0mL/min
Calibration curve: A calibration curve was used using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) in the range of Mw = 500 to 2,800,000. It is preferable to use the 13 samples at approximately equal intervals.

When the intrinsic viscosity [η]inh, number average molecular weight and weight average molecular weight are within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties and moldability as a functional layer.

The glass transition temperature (Tg) of cycloolefin resins is usually 110°C or higher, preferably 110 to 350°C, more preferably 120 to 250°C, and even more preferably 120 to 220°C. If the Tg is 110°C or higher, deformation under high temperature conditions is easily suppressed. On the other hand, if the Tg is 350°C or lower, molding processing is facilitated and deterioration of the resin due to heat during molding processing is also easily suppressed.

The content of cycloolefin resin in the functional layer is preferably 70% by mass or more, and more preferably 80% by mass or more.

<Fumaric acid diester resin>
The fumaric acid diester resin used in the functional layer is a fumaric acid diester resin containing a diisopropyl fumarate residue unit and a fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms.

Here, the alkyl groups having 1 or 2 carbon atoms in the fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms are each independent, and examples thereof include a methyl group and an ethyl group. These may be substituted with a halogen group such as fluorine or chlorine; an ether group; an ester group, or an amino group. Examples of the fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms include a dimethyl fumarate residue unit and a diethyl fumarate residue unit. These may be contained alone or in combination.

Specific examples of fumaric acid diester resins include diisopropyl fumarate/dimethyl fumarate copolymer resins, diisopropyl fumarate/diethyl fumarate copolymer resins, etc.

The fumaric acid diester resin may contain other monomer residue units as long as the residue does not exceed the scope of the present invention. Examples of other monomer residue units include styrene residue units such as styrene residue units and α-methylstyrene residue units; (meth)acrylic acid residue units; (meth)acrylic acid ester residue units such as methyl (meth)acrylate residue units, ethyl (meth)acrylate residue units, and butyl (meth)acrylate residue units; vinyl ester residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylonitrile residue units; methacrylonitrile residue units; methyl vinyl ether residue unit, an ethyl vinyl ether residue unit, a butyl vinyl ether residue unit, and the like; N-substituted maleimide residue units, such as an N-methylmaleimide residue unit, an N-cyclohexylmaleimide residue unit, and an N-phenylmaleimide residue unit; olefin residue units, such as an ethylene residue unit, a propylene residue unit, and the like; or fumaric acid diester residues other than the fumaric acid diester residue units, such as a di-n-butyl fumarate residue unit, a bis(2-ethylhexyl) fumarate residue unit, and cinnamic acid and a cinnamic acid ester unit, can be mentioned as one or more selected from the group consisting of cinnamic acid and cinnamic acid ester units.

The blending ratio of the fumaric acid diester resin used in the present invention is preferably 50 to 99 mol % of diisopropyl fumarate residue units and 1 to 50 mol % of fumaric acid diester residue units having an alkyl group having 1 or 2 carbon atoms, and a fumaric acid diester resin consisting of 60 to 95 mol % of diisopropyl fumarate residue units and 5 to 40 mol % of fumaric acid diester residue units having an alkyl group having 1 or 2 carbon atoms is particularly preferred because it provides excellent retardation properties and strength when used as a retardation film.

It is preferable that the fumaric acid diester resin used in the present invention has a number average molecular weight, calculated in terms of standard polystyrene, within the range of 50,000 to 250,000, obtained from the elution curve measured by the gel permeation chromatography.

(Synthesis Example of Fumaric Acid Diester Resin)
Into a 1 L autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer, 2 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metolose 60SH-50), 600 g of distilled water, 330 g of diisopropyl fumarate, 70 g of diethyl fumarate, and 3 g of t-butyl peroxypivalate as a polymerization initiator were placed, and after nitrogen bubbling for 1 hour, radical suspension polymerization was carried out by maintaining the mixture at 50° C. for 24 hours while stirring at 400 rpm. The mixture was cooled to room temperature, and the suspension containing the generated polymer particles was filtered and washed with distilled water and methanol to obtain a fumaric acid diester resin (yield: 75%).

The number average molecular weight of the obtained fumaric acid diester resin was 120,000. In addition, 1H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue units/diethyl fumarate residue units = 84/16 (mol%).

(Meth)acrylic resin
The (meth)acrylic resin used in the functional layer preferably contains at least a structural unit (U1) derived from methyl methacrylate and a structural unit (U2) derived from phenylmaleimide. The (meth)acrylic resin containing the structural unit (U2) derived from phenylmaleimide can reduce the humidity expansion coefficient _CHE2 of the functional layer. In addition, the photoelastic coefficient is also reduced, and there is an advantage that unevenness is unlikely to occur even if the functional layer expands due to moisture absorption.

The (meth)acrylic resin may further contain other structural units in addition to those described above. Examples of such other structural units include (meth)acrylic acid alkyl esters such as adamantyl acrylate; (meth)acrylic acid cycloalkyl esters such as 2-ethylhexyl acrylate; and the like. Among these, it is preferable to further contain a structural unit (U3) derived from an acrylic acid alkyl ester, from the viewpoint of reducing the deterioration of brittleness due to the inclusion of the structural unit (U2) derived from phenylmaleimide.

That is, it is more preferable that the (meth)acrylic resin contains a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from an alkyl acrylate.

The content of the structural unit (U1) derived from methyl methacrylate is preferably 50 to 95% by mass, and more preferably 70 to 90% by mass, of all structural units constituting the (meth)acrylic resin.

The structural unit (U2) derived from phenylmaleimide has a relatively rigid structure, and therefore can reduce the humidity expansion coefficient CHE2 of the functional layer. In addition, the structural unit (U2) derived from phenylmaleimide has a relatively bulky structure, and therefore can have microvoids that can move rubber particles in the resin matrix, and therefore can make it easier for the rubber particles to be unevenly distributed in the surface layer of the functional layer.

The content of the structural unit (U2) derived from phenylmaleimide is preferably 1 to 25% by mass relative to all structural units constituting the (meth)acrylic resin. If the content of the structural unit (U2) derived from phenylmaleimide is 1% by mass or more, the humidity expansion coefficient CHE2 at 23°C of the functional layer is easily reduced, and if it is 25% by mass or less, the brittleness of the functional layer is not likely to be excessively impaired. From the above viewpoint, it is more preferable that the content of the structural unit (U2) derived from phenylmaleimide is 7 to 15% by mass.

The structural unit (U3) derived from an alkyl acrylate ester can impart appropriate flexibility to the resin, thereby improving the brittleness caused by, for example, the inclusion of a structural unit (U2) derived from phenylmaleimide.

The alkyl acrylate ester is preferably an alkyl acrylate ester having an alkyl moiety with 1 to 7 carbon atoms, preferably 1 to 5 carbon atoms. Examples of alkyl acrylate esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, and 2-ethylhexyl acrylate.

The content of the structural unit (U3) derived from an acrylic acid alkyl ester is preferably 1 to 25% by mass relative to the total structural units constituting the (meth)acrylic resin. When the content of the structural unit (U3) derived from an acrylic acid alkyl ester is 1% by mass or more, the (meth)acrylic resin can be given an appropriate flexibility, so that the functional layer does not become too brittle and is difficult to break. When the content of the structural unit (U3) derived from an acrylic acid alkyl ester is 25% by mass or less, the Tg of the functional layer does not become too low, and the humidity expansion coefficient (CHE ₂ ) at 23° C. does not become too large. From the above viewpoint, the content of the structural unit (U3) derived from an acrylic acid alkyl ester is more preferably 5 to 15% by mass.

The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from an alkyl acrylate is preferably 20 to 70% by mass. If the ratio is 20% by mass or more, the tensile modulus G2 of the functional layer is easily increased, and if it is 70% by mass or less, the functional layer does not become too brittle.

The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 100°C or higher, and more preferably 120 to 150°C. If the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the functional layer is easily improved. In order to adjust the Tg of the (meth)acrylic resin, it is preferable to adjust the content of, for example, the structural unit (U2) derived from phenylmaleimide or the structural unit (U3) derived from an alkyl acrylate.

The weight average molecular weight (Mw) of the (meth)acrylic resin is not particularly limited and can be adjusted according to the purpose. The weight average molecular weight of the (meth)acrylic resin is preferably 100,000 or more, more preferably 1,000,000 or more, from the viewpoint of, for example, promoting entanglement between resin molecules to increase the toughness of the functional layer and make it difficult to break, and from the viewpoint of making the CHE ratio moderately large and making it easy to adjust the curl amount to a degree preferable for adhesion. If the weight average molecular weight of the (meth)acrylic resin is 1,000,000 or more, the toughness of the resulting functional layer can be increased. Thereby, when conveyed to the laminated film, it is possible to suppress the functional layer from breaking due to the conveying tension, and the conveying stability can be improved. From the same viewpoint, the weight average molecular weight of the (meth)acrylic resin is more preferably 1,500,000 to 3,000,000. The method for measuring the weight average molecular weight is as described above.

<Styrene/(meth)acrylate copolymer>
Styrene-(meth)acrylate copolymers (hereinafter also referred to as styrene-acrylic resins) have excellent transparency when used in functional layers. In addition, the moisture absorption expansion coefficient can be adjusted by the copolymerization ratio of the styrene portion, so curling of the laminate can be controlled by changing these ratios.

Styrene-acrylic resin is formed by addition polymerization of at least a styrene monomer and _a (meth)acrylic acid ester monomer. The styrene monomer includes styrene represented by the structural formula _CH2 =CH- _C6H5 , as well as styrene derivatives having known side chains or functional groups in the styrene structure.

In addition to acrylic acid esters and methacrylic acid esters represented by CH(R ₁ )=CHCOOR ₂ (R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 1 to 24 carbon atoms), the (meth)acrylic acid ester monomers include acrylic acid ester derivatives and methacrylic acid ester derivatives having known side chains or functional groups in the structure of these esters.

Examples of styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene and p-n-dodecylstyrene.

Examples of (meth)acrylic acid ester monomers include acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate (2EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylate.

In this specification, "(meth)acrylic acid ester monomer" is a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer" and means one or both of them. For example, "methyl (meth)acrylate" means one or both of "methyl acrylate" and "methyl methacrylate".

The (meth)acrylic acid ester monomer may be one or more kinds. For example, it is possible to form a copolymer using a styrene monomer and two or more kinds of acrylic acid ester monomers, to form a copolymer using a styrene monomer and two or more kinds of methacrylic acid ester monomers, or to form a copolymer using a styrene monomer in combination with an acrylic acid ester monomer and a methacrylic acid ester monomer.

From the viewpoint of easily controlling plasticity, the weight average molecular weight (Mw) of the above styrene-acrylic resin is preferably in the range of 5,000 to 150,000, and more preferably in the range of 10,000 to 70,000.

The styrene-acrylic resin according to the present invention may be a commercially available product, and one example is MS resin "TX320XL" manufactured by Denka Company Ltd.

<Polyarylate Resin>
The polyarylate resin has excellent toughness when used in the functional layer, and contains at least a structural unit derived from an aromatic dialcohol and a structural unit derived from an aromatic dicarboxylic acid.

The polyarylate resin according to the present invention may be a commercially available product, and an example thereof is PAR resin "U-100" manufactured by Unitika Ltd., with a weight average molecular weight (Mw) of 100,000.

[2.2] Additives The functional layer may further contain other components other than those mentioned above as necessary. Examples of other components include rubber particles, the above-mentioned matting agent (fine particles), plasticizers, ultraviolet absorbers, etc. Among them, rubber particles and plasticizers can be used as a means for imparting hydrophobicity to the film and controlling the humidity expansion coefficient CHE of the functional layer, so that the curl characteristics of the laminate can be controlled by appropriately adjusting the material and the amount of additive. In addition, from the viewpoint of imparting toughness (flexibility) to the functional layer, it is preferable to further contain rubber particles.

<Rubber particles>
The rubber particles are particles containing a rubber-like polymer. The rubber-like polymer is a soft crosslinked polymer having a glass transition temperature of 20° C. or less. Examples of such crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic crosslinked polymers, and organosiloxane crosslinked polymers. Among them, (meth)acrylic crosslinked polymers are preferred, and acrylic crosslinked polymers (acrylic rubber-like polymers) are more preferred, from the viewpoint of having a small refractive index difference with the (meth)acrylic resin and being less likely to impair the transparency of the functional layer.

That is, it is preferable that the rubber particles are particles containing an acrylic rubber-like polymer (a).

Regarding the acrylic rubber polymer (a):
The acrylic rubber-like polymer (a) is a crosslinked polymer containing a structural unit derived from an acrylic acid ester as a main component. The term "containing as a main component" means that the content of the structural unit derived from an acrylic acid ester is within the range described below. The acrylic rubber-like polymer (a) is preferably a crosslinked polymer containing a structural unit derived from an acrylic acid ester, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer having two or more radical polymerizable groups (non-conjugated reactive double bonds) in one molecule.

The acrylic acid ester is preferably an alkyl acrylate ester having an alkyl group of 1 to 12 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, or n-octyl acrylate. The acrylic acid ester may be one type or two or more types.

The content of the structural units derived from the acrylic acid ester is preferably 40 to 80 mass %, more preferably 50 to 80 mass %, based on all structural units constituting the acrylic rubber-like polymer (a1). When the content of the acrylic acid ester is within the above range, sufficient toughness is easily imparted to the protective film.
The copolymerizable other monomer is a monomer copolymerizable with the acrylic acid ester other than a polyfunctional monomer. That is, the copolymerizable monomer does not have two or more radical polymerizable groups. Examples of the copolymerizable monomer include methacrylic acid esters such as methyl methacrylate; styrenes such as styrene and methylstyrene; (meth)acrylonitriles; (meth)acrylamides; and (meth)acrylic acid. Among them, the copolymerizable other monomer preferably includes styrenes. The copolymerizable other monomer may be one type or two or more types.

The content of structural units derived from other copolymerizable monomers is preferably 5 to 55 mass % of the total structural units constituting the acrylic rubber-like polymer (a), and more preferably 10 to 45 mass %.

Examples of polyfunctional monomers include allyl (meth)acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate.

The content of structural units derived from the polyfunctional monomer is preferably 0.05 to 10% by mass, and more preferably 0.1 to 5% by mass, based on the total structural units constituting the acrylic rubber-like polymer (a). If the content of the polyfunctional monomer is 0.05% by mass or more, the degree of crosslinking of the resulting acrylic rubber-like polymer (a) is easily increased, so that the hardness and rigidity of the resulting functional layer are not excessively impaired, and if the content is 10% by mass or less, the toughness of the functional layer is not easily impaired.

The monomer composition constituting the acrylic rubber-like polymer (a) can be measured, for example, by the peak area ratio detected by pyrolysis GC-MS.

The glass transition temperature (Tg) of the rubbery polymer is preferably 0°C or lower, and more preferably -10°C or lower. If the glass transition temperature (Tg) of the rubbery polymer is 0°C or lower, the film can be imparted with appropriate toughness. The glass transition temperature (Tg) of the rubbery polymer is measured in the same manner as described above.

The glass transition temperature (Tg) of a rubber-like polymer can be adjusted by the composition of the rubber-like polymer. For example, in order to lower the glass transition temperature (Tg) of an acrylic rubber-like polymer (a), it is preferable to increase the mass ratio of the acrylic acid ester having an alkyl group with 4 or more carbon atoms to other copolymerizable monomers in the acrylic rubber-like polymer (a) (for example, 3 or more, preferably 4 to 10).

The particles containing the acrylic rubber-like polymer (a) may be particles made of the acrylic rubber-like polymer (a), or particles having a hard layer made of a hard crosslinked polymer (c) having a glass transition temperature of 20°C or higher and a soft layer made of the acrylic rubber-like polymer (a) arranged around it (these are also called "elastomers"); or particles made of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylic acid esters in at least one stage in the presence of the acrylic rubber-like polymer (a). The particles made of the acrylic graft copolymer may be core-shell type particles having a core containing the acrylic rubber-like polymer (a) and a shell covering the core.

Regarding core-shell type rubber particles containing acrylic rubber-like polymer:
(Core part)
The core portion contains an acrylic rubber-like polymer (a) and may further contain a hard crosslinked polymer (c) as necessary. That is, the core portion may have a soft layer made of an acrylic rubber-like polymer and a hard layer made of a hard crosslinked polymer (c) disposed inside the soft layer.

The crosslinked polymer (c) may be a crosslinked polymer mainly composed of a methacrylic acid ester. In other words, the crosslinked polymer (c) is preferably a crosslinked polymer containing a structural unit derived from a methacrylic acid alkyl ester, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer.

The alkyl methacrylate ester may be the alkyl methacrylate ester described above; the other copolymerizable monomer may be the styrenes or acrylic esters described above; and the polyfunctional monomer may be the same as those described above as the polyfunctional monomers.

The content of structural units derived from methacrylic acid alkyl esters may be 40 to 100% by mass relative to all structural units constituting the crosslinked polymer (c). The content of structural units derived from other copolymerizable monomers may be 60 to 0% by mass relative to all structural units constituting the other crosslinked polymer (c). The content of structural units derived from polyfunctional monomers may be 0.01 to 10% by mass relative to all structural units constituting the other crosslinked polymer.

(Shell part)
The shell portion contains a methacrylic polymer (b) (another polymer) containing, as a main component, a structural unit derived from a methacrylic acid ester, which is graft-bonded to the acrylic rubber-like polymer (a). "Containing as a main component" means that the content of the structural unit derived from a methacrylic acid ester falls within the range described below.

The methacrylic acid ester constituting the methacrylic polymer (b) is preferably a methacrylic acid alkyl ester having an alkyl group of 1 to 12 carbon atoms, such as methyl methacrylate. The methacrylic acid ester may be one type or two or more types.

The content of the methacrylic acid ester is preferably 50% by mass or more relative to all structural units constituting the methacrylic polymer (b). When the content of the methacrylic acid ester is 50% by mass or more, compatibility with a methacrylic resin containing a structural unit derived from methyl methacrylate as a main component is easily obtained. From the above viewpoint, the content of the methacrylic acid ester is more preferably 70% by mass or more relative to all structural units constituting the methacrylic polymer (b).

The methacrylic polymer (b) may further contain structural units derived from other monomers copolymerizable with the methacrylic acid ester. Examples of other copolymerizable monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; and (meth)acrylic monomers having an alicyclic, heterocyclic, or aromatic ring (ring-containing (meth)acrylic monomers) such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

The content of structural units derived from copolymerizable monomers is preferably 50% by mass or less, and more preferably 30% by mass or less, of all structural units constituting the methacrylic polymer (b).

In this embodiment, since the functional layer is not stretched, the shape of the rubber particles can be close to a perfect sphere. In other words, when observing the cross section or surface of the functional layer, the aspect ratio of the rubber particles can be about 1 to 2.

The average particle size of the rubber particles is preferably 100 to 400 nm. If the average particle size of the rubber particles is 100 nm or more, it is easy to impart sufficient toughness and stress relaxation properties to the functional layer, and if it is 400 nm or less, the transparency of the functional layer is less likely to be impaired. From the same viewpoint, it is more preferable that the average particle size of the rubber particles is 150 to 300 nm.

The average particle size of rubber particles can be calculated using the following method.

The average particle size of rubber particles can be measured as the average of the circle-equivalent diameters of 100 particles obtained by SEM or TEM photography of the surface or slice of the laminated film. The circle-equivalent diameter can be determined by converting the projected area of the particle obtained by photography into the diameter of a circle with the same area. In this case, the rubber particles observed by SEM observation and/or TEM observation at a magnification of 5000 times are used to calculate the average particle size.

The content of rubber particles is not particularly limited, but it is preferable that it be 5 to 40 mass% of the functional layer, and more preferably 7 to 30 mass%.

[2.3] Physical Properties <Coefficient of Humidity Expansion (CHE ₂ ) at 23° C.>
The humidity expansion coefficient (CHE ₂ ) of the functional layer at 23° C. is preferably in the range of 1 to 30 ppm/% RH from the viewpoint of controlling the direction and degree of curling in relation to the preferred humidity expansion coefficient (CHE ₁ ) of the base film. If the humidity expansion coefficient CHE ₂ of the transparent functional layer is 1 ppm or more, the effect of facilitating the peeling process after lamination is exhibited, and if it is 30 ppm or less, the effect of suppressing the occurrence of errors and unevenness during lamination is exhibited. It is more preferably in the range of 3 to 20 ppm/% RH, and even more preferably in the range of 5 to 15 ppm/% RH.

<Phase differences Ro and Rt>
The functional layer according to the present invention can function as an optical film such as a retardation film by being attached to a polarizer after being peeled off from the substrate film.
From the viewpoint of using the functional layer as a retardation film for an IPS mode, for example, the in-plane retardation Ro measured at a measurement wavelength of 590 nm under an environment of 23° C. and 55% RH is preferably 0 to 10 nm, more preferably 0 to 5 nm, and the thickness-direction retardation Rt of the functional layer is preferably −40 to 40 nm, more preferably −25 to 25 nm.

Ro and Rt are defined by the following formulas, respectively.

Formula (a): Ro = ( _nx - _ny ) x d
Formula (b): Rt=((n _x + n _y )/2-n _z )×d
(Wherein,
_nx represents the refractive index in the in-plane slow axis direction of the functional layer (the direction in which the refractive index is maximum),
n _y represents the refractive index in a direction perpendicular to the in-plane slow axis of the functional layer,
n _z represents the refractive index of the functional layer in the thickness direction,
d represents the thickness of the functional layer (nm).
The in-plane slow axis of the functional layer can be confirmed by an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter, manufactured by Axometrics).

Ro and Rt can be measured by the following method.

1) The functional layer is conditioned for 24 hours in an environment of 23°C and 55% RH. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured with a commercially available micrometer.

2) After humidity conditioning, the retardation Ro and Rt of the film at a measurement wavelength of 590 nm are measured in an environment of 23°C and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter, manufactured by Axometrics).

The phase differences Ro and Rt of the functional layer can be adjusted, for example, by the type of resin, the stretching conditions, and the drying conditions. For example, Rt can be lowered by increasing the drying temperature.

[3] Manufacturing method of laminated film The shape of the laminated film of the present invention is not particularly limited, but may be, for example, a belt-like shape. That is, the laminated film of the present invention is preferably wound into a roll in a direction perpendicular to its width direction to form a roll body.

[3.1] Manufacturing method of laminated film [Manufacturing method]
The method for manufacturing a laminated film of the present invention includes the steps of 1) obtaining a functional layer solution, 2) applying the obtained functional layer solution to the surface of a base film, and 3) removing the solvent from the applied functional layer solution to form a functional layer.

1) Step of Obtaining a Solution for a Functional Layer A solution for a functional layer containing the above-mentioned resin and a solvent is prepared.

The solvent used in the functional layer solution is not particularly limited as long as it can disperse or dissolve the resin well. For example, organic solvents used in the present invention include alcohols (methanol, ethanol, diols, triols, tetrafluoropropanol, etc.), glycols, cellosolves, ketones (acetone, methyl ethyl ketone, etc.), carboxylic acids (formic acid, acetic acid, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), esters (ethyl acetate, propyl acetate, etc.), ethers (isopropyl ether, THF, etc.), amides (dimethyl sulfoxide, etc.), hydrocarbons (heptane, etc.), nitriles (acetonitrile, etc.), aromatics (cyclohexylbenzene, toluene, xylene, chlorobenzene, etc.), alkyl halides (dichloromethane (also called "methylene chloride"), etc.), amines (1,4-diazabicyclo[2.2.2]octane, diazabicycloundecene, etc.), lactones, etc.

Among them, the solvent for the functional layer has a boiling point of 100° C. or less under atmospheric pressure, is a chlorine-based solvent, and is specifically dichloromethane (also called "methylene chloride"), which is preferable from the viewpoint of ease of handling and control of the humidity expansion coefficient when preparing a dope for the functional layer and forming a film. This is preferable from the viewpoint of high solubility and fast drying speed, thereby adjusting the film quality of the coating film and thus controlling the humidity expansion coefficient when preparing a dope for the functional layer and forming a film. In addition, the humidity expansion coefficient can be controlled by adding a hydrophilic solvent. Examples of hydrophilic solvents include ketones and alcohols, and alcohols are preferable. More preferable are isopropanol, ethanol, methanol, etc., and most preferable is methanol.
The amount added is preferably in the range of 1 to 20% by mass, and more preferably in the range of 3 to 10% by mass.

From the viewpoint of making it easier to adjust the viscosity to the range described below, the resin concentration of the functional layer solution is preferably, for example, 1.0 to 20 mass%. Furthermore, from the viewpoint of reducing the amount of shrinkage of the coating film when it dries, it is preferable that the resin concentration of the functional layer solution is moderately high, more preferably more than 5 mass% to 20 mass% or less, and even more preferably more than 5 mass% to 15 mass% or less. Furthermore, by adjusting the solution concentration, the time until the film is formed can be shortened, and the drying time can also be a means of controlling the CHE of the functional layer. To increase the concentration, a mixed solvent may be used as appropriate.

The viscosity of the functional layer solution is not particularly limited as long as it is sufficient to form a functional layer of the desired thickness, but is preferably, for example, 5 to 5000 mPa·s. If the viscosity of the functional layer solution is 5 cP or more, it is easy to form a functional layer of appropriate thickness, and if it is 5000 mPa·s or less, it is possible to suppress the occurrence of uneven thickness due to an increase in the viscosity of the solution. From the same viewpoint, it is more preferable that the viscosity of the functional layer solution is 100 to 1000 mPa·s. The viscosity of the functional layer solution can be measured at 25°C using an E-type viscometer.

2) Step of applying a solution for forming a functional layer Next, the obtained solution for forming a functional layer is applied to the surface of the base film. Specifically, the obtained solution for forming a functional layer is applied to the surface of the base film.

The method for applying the solution for the functional layer is not particularly limited and may be a known method such as back-roll coating, gravure coating, spin coating, wire bar coating, or roll coating. Among these, the back-coating method is preferred from the viewpoint of forming a coating film that is thin and has a uniform thickness.

3) Step of Forming a Functional Layer Next, the solvent is removed from the functional layer solution applied to the substrate film to form a functional layer.

Specifically, the functional layer solution applied to the base film is dried. Drying can be performed, for example, by blowing air or heating. In particular, from the viewpoint of making it easier to suppress curling of the laminated film, drying can also be performed by blowing air.

By adjusting the drying conditions (e.g., drying temperature, drying air volume, drying time, etc.), the density of the functional layer can be controlled, and thus the CHE can be adjusted. To adjust the CHE in the direction of increasing it, it is preferable to adjust the film quality in the direction of becoming sparse, specifically, it is preferable to increase the drying speed, which is preferably 0.001 to 0.05 kg/ ^hr.m2 , and more preferably 0.002 to 0.01 kg/ ^hr.m2 .

Drying rate is expressed as the mass of solvent that evaporates per unit time and unit area. The drying rate can usually be adjusted by the drying temperature. The drying temperature depends on the type of solvent used, but can be, for example, 50 to 200°C ((Tb-50) to (Tb+50)°C, where Tb is the boiling point of the solvent used). Temperature control may be performed in multiple stages. After a certain degree of drying has progressed, the drying rate and film quality can be controlled by drying at a higher temperature.

As described above, the laminate film according to the present embodiment may be in a strip shape. Therefore, it is preferable that the method for producing the laminate film according to the present embodiment further includes a step 4) of winding the strip-shaped laminate film into a roll to form a roll body.

4) Step of Winding the Laminated Film to Obtain a Roll The obtained strip-shaped laminated film is wound into a roll in a direction perpendicular to its width direction to obtain a roll.

The length of the strip-shaped laminated film is not particularly limited, but may be, for example, about 100 to 10,000 m. The width of the strip-shaped laminated film is preferably 1 m or more, and more preferably 1.3 to 4 m. From the viewpoint of improving the uniformity of the film, it is more preferably 1.6 to 2.5 m.

[Manufacturing equipment]
The method for producing the laminated film of the present invention can be carried out, for example, by using a production apparatus shown in FIG.

Figure 3 is a schematic diagram of a manufacturing apparatus B200 for carrying out the laminated film manufacturing method according to this embodiment. The manufacturing apparatus B200 has a supply section B210, a coating section B220, a drying section B230, a cooling section B240, and a winding section B250. Ba to Bd indicate transport rolls that transport the base film B110.

The supply section B210 has a payout device (not shown) that pays out a roll body B201 of a strip-shaped base film B110 wound around a core.

The coating section B220 is a coating device that includes a backup roll B221 that holds the base film B110, a coating head B222 that applies a functional layer solution to the base film B110 held by the backup roll B221, and a reduced pressure chamber B223 provided upstream of the coating head B222.

The flow rate of the functional layer solution discharged from the coating head B222 can be adjusted by a pump (not shown). The flow rate of the functional layer solution discharged from the coating head B222 is set to an amount that can stably form a coating layer of a predetermined thickness when continuously coated under the previously adjusted conditions of the coating head B222.

The reduced pressure chamber B223 is a mechanism for stabilizing the bead (puddle of coating liquid) formed between the functional layer solution from the coating head B222 and the base film B110 during coating, and the degree of reduced pressure is adjustable. The reduced pressure chamber B223 is connected to a reduced pressure blower (not shown) so that the interior can be reduced in pressure. The reduced pressure chamber B223 is in a state where there is no air leakage, and the gap with the backup roll is adjusted to be narrow so that a stable bead of coating liquid can be formed.

The drying section B230 is a drying device that dries the coating applied to the surface of the base film B110, and has a drying chamber B231, an inlet B232 for drying gas, and an outlet B233. The temperature and volume of the drying air are determined appropriately depending on the type of coating and the type of base film B110. By setting conditions such as the temperature and volume of the drying air and the drying time in the drying section B230, the amount of residual solvent in the coating after drying can be adjusted. The amount of residual solvent in the coating after drying can be measured by comparing the unit mass of the coating after drying with the mass of the coating after it has been thoroughly dried.

(Residual Solvent Amount)
Since the functional layer is obtained by applying a solution for the functional layer, the solvent derived from the solution may remain. The amount of residual solvent can also be a means for controlling the humidity expansion coefficient, and can be controlled by the concentration of the solvent/application solution used, the wind speed for drying the functional layer, the drying temperature/time, the conditions of the drying room (outside air or internal air circulation), the heating temperature of the back roll during application, etc.

As described above, when the drying speed is high, the film becomes sparse and moisture permeates quickly, so the coefficient of humidity expansion CHE ₂ becomes large.

From the viewpoint of curl balance of the laminate film, it is preferable that the residual solvent amount in the functional layer satisfies the following formula (2), where the residual solvent amount in the base film is S ₁ and the residual solvent amount in the functional layer is S ₂ .
Formula (2) 10<S ₁ <S ₂ <1000 (ppm)
Specifically, the residual solvent content of the functional layer is preferably less than 1000 ppm, more preferably less than 800 ppm, and more preferably from 500 to less than 700 ppm, taking into consideration the curl balance of the laminated film. In addition, by selecting a solvent and coating process that leaves the solvent in the base film, the adhesion between the laminates is improved. The residual solvent content of the base film is preferably in the range of 10 to 100 ppm.

The amount of residual solvent in the functional layer and base film can be measured by headspace gas chromatography. In headspace gas chromatography, a sample is sealed in a container and heated, and when the container is filled with volatile components, the gas in the container is quickly injected into a gas chromatograph, and mass analysis is performed to identify the compounds and quantify the volatile components. The headspace method makes it possible to observe all peaks of the volatile components using a gas chromatograph, and by using an analytical method that utilizes electromagnetic interactions, it is also possible to quantify volatile substances, monomers, etc. with high accuracy.

The cooling section B240 cools the temperature of the base film B110 having the coating film (functional layer B120) obtained by drying in the drying section B230, and adjusts it to an appropriate temperature. The cooling section B240 has a cooling chamber B241, a cooling air inlet B242, and a cooling air outlet B243. The temperature and volume of the cooling air can be determined appropriately depending on the type of coating film and the type of base film B110. Furthermore, if an appropriate cooling temperature can be achieved without providing the cooling section B240, the cooling section B240 may not be necessary.

The winding section B250 is a winding device (not shown) for winding up the base film B110 on which the transparent functional layer B120 is formed, to obtain a roll body B251.
(Thickness)
The thickness d ₂ of the functional layer is usually thinner than the thickness d ₁ of the base film. Specifically, from the viewpoint of thinning the polarizing plate, the thickness d ₂ of the functional layer is preferably in the range of 1 to 19 μm, and more preferably in the range of 2 to 10 μm.

[4] Polarizing Plate The polarizing plate has a polarizer and a laminate film or a functional layer disposed on at least one surface of the polarizer. The polarizer and the laminate film or the functional layer are preferably bonded to each other via an adhesive layer.

Figures 4A and 4B show an example of the layer structure of the polarizing plate of the present invention, but the present invention is not limited to this.

Figure 4A is a cross-sectional view of a polarizing plate with a substrate film.

The functional layer 3 side of the laminated film 1 (substrate film 2 and functional layer 3) of the present invention is bonded to a polarizer 5 via an adhesive layer 4 to process a polarizing plate 10a. If necessary, an opposing film 6 may be bonded via an adhesive layer 4 to the surface of the polarizer 5 opposite to the surface to which the laminated film 1 of the present invention is bonded.

When the polarizing plate 10a is provided in, for example, a display device (not shown), the laminate film 1 of the present invention may be attached to the display element side via an adhesive layer (not shown), and the opposing film 6 may be attached to the display element side via an adhesive layer (not shown). When the laminate film 1 of the present invention is attached, it is preferable that the embodiment shown in FIG. 4(b) below in which the base film 2 is peeled off from the laminate film 1 is used.

Figure 4B is a cross-sectional view of a polarizing plate with the substrate film peeled off.

The functional layer 3 side of the laminated film 1 (substrate film 2 and functional layer 3) of the present invention is attached to a polarizer 5 via an adhesive layer 4 to process a polarizing plate 10b. During or after processing of the polarizing plate, the substrate film 2 is peeled off from the functional layer 3 to process a thin polarizing plate 10b. If necessary, an opposing film 6 may be attached via an adhesive layer 4 to the surface of the polarizer 5 opposite to the surface to which the functional layer 3 of the present invention is attached.

When the polarizing plate 10b is provided in, for example, a display device (not shown), the functional layer 3 according to the present invention may be attached to the display element side via an adhesive layer (not shown), and the opposing film 6 may be attached to the display element side via an adhesive layer (not shown).

[4.1] Polarizer A polarizer is an element that transmits only light with a certain polarization plane. The polarizer can usually be a polyvinyl alcohol-based polarizing film. Examples of polyvinyl alcohol-based polarizing films include polyvinyl alcohol-based films dyed with iodine and dichroic dyes.

The polyvinyl alcohol polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it with iodine or a dichroic dye (preferably further treating it with a boron compound for durability); or a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it with iodine or a dichroic dye (preferably further treating it with a boron compound for durability). The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm from the viewpoint of making the polarizing plate thinner.

[4.2] Laminated film or functional layer, and opposing film On at least one surface of the polarizer, a base film or a functional layer constituting the laminated film of the present invention is disposed. Either of the base film or the functional layer constituting the laminated film can function as a polarizer protective film. In this embodiment, it is preferable that a functional layer is disposed on one surface of the polarizer, and another protective film is disposed on the other surface.

Examples of the facing film include cycloolefin resin, polypropylene resin, acrylic resin, polyester resin, polyarylate resin, cellulose ester resin, and styrene resin or composite resin thereof. Among them, a resin film containing cycloolefin resin, acrylic resin, and polyester resin is preferable.

[4.3] Adhesive layer The adhesive layer is disposed between the functional layer and the polarizer, and between the opposing film and the polarizer. The adhesive layer disposed between the functional layer and the polarizer and the adhesive layer disposed between the opposing film and the polarizer may be the same or different.

The adhesive layer may be a cured layer of an active energy ray-curable adhesive, or a layer obtained from a water-soluble polymer.

The active energy ray-curable adhesive may be a photoradical polymerizable composition or a photocationically polymerizable composition. Of these, a photocationically polymerizable composition is preferred.

The photocationically polymerizable composition contains an epoxy compound and a photocationic polymerization initiator.

In the case of a water-soluble polymer, the adhesive can be applied via an adhesive made of, for example, a vinyl alcohol-based polymer, or an adhesive made of at least a water-soluble crosslinking agent for a vinyl alcohol-based polymer, such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. Such an adhesive layer is formed as a coating and drying layer of an aqueous solution, and other additives and catalysts such as acids can be added as necessary when preparing the aqueous solution. In the case of a process using a water-soluble polymer, the penetration of the water contained therein can cause curling of the laminate, which can reduce the yield of the polarizing plate. One of the objects of the present invention is to prevent errors in such processes.

The thickness of the adhesive layer is not particularly limited, but is preferably 0.01 to 10 μm, and more preferably 0.01 to 5 μm.

[4.4] Adhesive Layer The adhesive layer is a layer for attaching the polarizing plate to a display element such as a liquid crystal cell, and may be formed on either side of the polarizing plate, but may be disposed on the side of the functional layer opposite the polarizer.

The adhesive layer is preferably a pressure-sensitive adhesive composition that contains a base polymer, a prepolymer and/or a crosslinkable monomer, a crosslinking agent, and a solvent, and is dried and partially crosslinked. In other words, the pressure-sensitive adhesive composition may be at least partially crosslinked.

Examples of pressure-sensitive adhesive compositions include acrylic pressure-sensitive adhesive compositions using a (meth)acrylic polymer as the base polymer, silicone pressure-sensitive adhesive compositions using a silicone polymer as the base polymer, and rubber pressure-sensitive adhesive compositions using rubber as the base polymer. Among these, acrylic pressure-sensitive adhesive compositions are preferred from the standpoints of transparency, weather resistance, heat resistance, and processability.

If necessary, the adhesive composition may further contain various additives such as tackifiers, plasticizers, glass fibers, glass beads, metal powders, other fillers, pigments, colorants, fillers, antioxidants, UV absorbers, and silane coupling agents.

The thickness of the adhesive layer is usually about 3 to 100 μm, preferably 5 to 50 μm.

The surface of the adhesive layer is protected by a release film that has been treated for release. Examples of release films include plastic films such as acrylic films, polycarbonate films, polyester films, and fluororesin films.

[4.4] Manufacturing method of polarizing plate The polarizing plate according to the present embodiment can be manufactured by laminating the above-mentioned laminate film to at least one surface of a polarizer and peeling off the base film. The laminate film may be laminated to only one surface of the polarizer or to both surfaces. From the viewpoint of transmittance, it is preferable to laminate the laminate film to one surface of the polarizer and laminate an opposing film, which is another protective film, to the other surface.

In addition, the substrate film side of the laminate film of the present invention may be attached to the polarizer, or the functional layer side may be attached. It is preferable to attach the functional layer side and use the substrate film as a protective film, or to peel it off and use only the thin functional layer.

Therefore, when manufacturing a polarizing plate roll by winding up a laminate film while laminating it to at least one surface of a polarizer, a preferred manufacturing method for a polarizing plate roll includes a step of laminating the laminate film to the polarizer while winding it up so that the layers are polarizer, functional layer, and base film from the inside of the roll. Another preferred embodiment is a method in which the base film in the laminate film is peeled off while winding it up before laminating the laminate film to the polarizer, drying, and winding it up.

Basically, the polarizing plate of the present invention can be manufactured through the steps of 1) laminating a functional layer of the above-mentioned laminate film to one side of a polarizer (the base film arranged on the side of the functional layer opposite the polarizer may be left attached or may be peeled off as necessary), and 2) laminating an opposing film, which is another protective film, to the other side of the polarizer.

1) Step of bonding a functional layer The functional layer of the laminated film is bonded to one surface of a polarizer via an adhesive. If necessary, a pretreatment such as a corona treatment may be performed on the surface of the functional layer to be bonded or on one surface of the polarizer.

For example, when a water-soluble polymer adhesive is used as the adhesive, 1) the surface of the functional layer of the laminate film is subjected to a surface treatment such as corona treatment as necessary. Next, the functional layer of the laminate film is laminated onto one side of the polarizer via the water-soluble polymer adhesive. 2) Next, an opposing film, which is another protective film, is attached to the other side of the polarizer. Specifically, the surface of the opposing film is subjected to a surface treatment such as corona treatment as necessary. Next, the opposing film is laminated onto the other side of the polarizer via the water-soluble polymer adhesive, and then a drying process is performed in stages, for example in a temperature range of 50 to 80°C.

Steps 1) and 2) may be carried out simultaneously or sequentially. From the viewpoint of improving production efficiency, it is preferable to carry out steps 1) and 2) simultaneously.

The polarizing plate according to the present embodiment may be strip-shaped. Therefore, in steps 1) and 2), it is preferable to process the polarizing plate by unwinding the functional layer of the strip-shaped laminate film, the strip-shaped polarizer, and the strip-shaped other protective film (opposing film) from their respective rolls and laminating them together in a roll-to-roll manner.

It is also preferable to further carry out a step of winding the strip-shaped polarizing plate into a roll to form a roll body. In this step, the length and width of the strip-shaped polarizing plate are the same as the length and width of the strip-shaped laminated film in step 4) of the laminated film manufacturing method.

In addition, in the manufacturing method of the polarizing plate roll of the present invention, in the step of winding up the laminate film 1 while bonding it to at least one surface of the polarizer 5, it is also preferable to form a polarizing plate roll by a step of winding up the laminate film 1 while bonding it to the polarizer 5 so that the layers are polarizer 5, adhesive layer 4, functional layer 3, and base film 2 from the inside of the roll. In this case, since the base film 2 of the present invention is arranged on the outside of the polarizing plate roll, it functions as a protective film, prevents the occurrence of scratches, etc. on the functional layer 2 during processing of the polarizing plate, suppresses curling, and makes handling easier.

At this time, if necessary, an opposing film 6 may be attached to the polarizer 5 via an adhesive layer 4 on the side opposite to the side to which the laminate film 1 is attached, and the film may be wound up to form a polarizing plate roll.

[5] Display Device The display device according to the present embodiment has a display element such as a liquid crystal cell or an organic electroluminescence (also referred to as "EL") element, and a polarizing plate manufactured by the above manufacturing method. In particular, the display device according to the present embodiment is preferably a liquid crystal display device having a liquid crystal cell and a polarizing plate manufactured by the above manufacturing method.

That is, the liquid crystal display device includes a liquid crystal cell, a first polarizing plate arranged on one surface of the liquid crystal cell, and a second polarizing plate arranged on the other surface of the liquid crystal cell. At least one of the first polarizing plate and the second polarizing plate is a polarizing plate according to the present embodiment. It is preferable that the absorption axis of the first polarizer in the first polarizing plate and the absorption axis of the second polarizing plate are perpendicular to each other (crossed Nicols).

The display mode of the liquid crystal cell can be, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Opticaly Compensated Bend), HAN (Hybrid aligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment), PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), etc. For example, in liquid crystal display devices for mobile devices, the IPS mode is preferred.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass".

Example 1
[1] Laminated film material
[1-1] Base film <Base film A>
Polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo Co., Ltd., with release layer containing non-silicone release agent, thickness 38 μm)

<Base film B>
A polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) stretched 13% in the TD direction (thickness 30 μm)
<Base film C>
A polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) stretched 30% in the TD direction (thickness 25 μm)

<Base film D>
Polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) heat-relaxed at 150°C for 30 seconds (thickness 38 μm)
<Base film E>
Triacetyl cellulose film (TAC) (Konica Minolta KC4UA, no release layer, thickness 38 μm)
<Base film F>
Cycloolefin film (COP) (ARTON G7810 manufactured by JSR Corporation, no release layer, thickness 38 μm)
<Base film G>
High density polyethylene (HDPE) (Hi-Zex 2200J (Prime Polymer Co., Ltd.), thickness 38 μm)

The humidity expansion coefficient CHE ₁ at 23° C. of the base films A to G was measured by the following method.

(Humidity expansion coefficient CHE ₁ at 23°C)
The humidity expansion coefficient CHE ₁ of the base film at 23° C. was measured with reference to JIS K7197.
The film sample was fixed in a thermo-hygrostat so that the width was 1 cm and the sample length was 15 cm, and it was dehumidified to a constant humidity (about 30% RH). After the film length became constant, it was humidified (about 80% RH) and began to elongate due to moisture absorption. After about 24 hours, the moisture absorption reached equilibrium and the film elongation also reached equilibrium. The amount of elongation at this time was calculated using the following formula. At this time, the atmospheric temperature was kept constant at 23°C.
Humidity expansion coefficient at 23°C (ppm/% RH) = elongation (cm)/(sample length (cm) x humidity difference) x ¹⁰⁶

[1-2] Functional layer solution (1) Preparation of materials <Resin>
1. COP (G7810): ARTON G7810 manufactured by JSR Corporation, Mw: 140,000, cycloolefin resin having a carboxylic acid group 2. Fumaric acid resin: fumaric acid diester resin manufactured by Tosoh Corporation, number average molecular weight: 120,000 3. Acrylic: MMA/PMI/MADA copolymer (60/20/20 mass ratio), Mw: 1.5 million, Tg: 137°C (abbreviations indicate the following: MMA: methyl methacrylate, PMI: phenylmaleimide, and MADA: adamantyl acrylate)
4. Polyarylate: U-100 manufactured by Unitika Ltd.
5. COP (ZNX330R): ZNX330R manufactured by Nippon Zeon Co., Ltd.
6. A-DCP: Tricyclodecane dimethanol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
7. PSt/polyarylate (mass ratio 5:5) mixture: Pst (polystyrene: manufactured by PS Japan Co., Ltd., Mw: 500,000: manufactured by PS Japan Co., Ltd.), polyarylate (compound P below)
8. PSt: Polystyrene (Mw: 500,000: manufactured by PS Japan Co., Ltd.)
9. TAC: Acetyl cellulose with an acetyl substitution degree of 2.9

The glass transition temperature (Tg) and weight average molecular weight (Mw) of resins 1 to 9 were measured using the following method.

(Glass Transition Temperature)
The glass transition temperature (Tg) of the resin was measured in accordance with JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

(Weight average molecular weight)
The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series manufactured by Tosoh Corporation). 20 mg ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered with a 0.45 mm filter. 100 ml of this solution was injected into the column (temperature 40 ° C.), and the measurement was performed at a detector RI temperature of 40 ° C., and the value converted into styrene was used.

<Rubber particle R1>
Rubber particles R1 prepared by the following method were used.

The following materials were charged into an 8 L polymerization apparatus equipped with a stirrer.

Deionized water 180 parts by weight Polyoxyethylene lauryl ether phosphate 0.002 parts by weight Boric acid 0.4725 parts by weight Sodium carbonate 0.04725 parts by weight Sodium hydroxide 0.0076 parts by weight

After the inside of the polymerization machine was fully replaced with nitrogen gas, the inside temperature was set to 80°C, and 0.021 parts by mass of potassium persulfate was added as a 2% aqueous solution. Next, a mixture of 21 parts by mass of monomer mixture (c') consisting of 84.6% by mass of methyl methacrylate, 5.9% by mass of butyl acrylate, 7.9% by mass of styrene, 0.5% by mass of allyl methacrylate, and 1.1% by mass of n-octyl mercaptan and 0.07 parts by mass of polyoxyethylene lauryl ether phosphoric acid was added continuously to the above solution over a period of 63 minutes. The polymerization reaction was continued for another 60 minutes to obtain the innermost hard polymer (c).

Then, 0.021 parts by mass of sodium hydroxide was added as a 2% by mass aqueous solution, and 0.062 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution. Next, a mixture of 39 parts by mass of a monomer mixture (a') consisting of 80.0% by mass of butyl acrylate, 18.5% by mass of styrene, and 1.5% by mass of allyl methacrylate and 0.25 parts by mass of polyoxyethylene lauryl ether phosphoric acid was added continuously over 117 minutes. After the addition was completed, 0.012 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and the polymerization reaction was continued for 120 minutes to obtain a soft layer (a layer consisting of acrylic rubber-like polymer (a)). The glass transition temperature (Tg) of the soft layer was -30°C. The glass transition temperature of the soft layer was calculated by averaging the glass transition temperatures of the homopolymers of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio.

After that, 0.04 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and 26.1 parts by mass of a monomer mixture (b') consisting of 97.5% by mass of methyl methacrylate and 2.5% by mass of butyl acrylate was continuously added over 78 minutes. The polymerization reaction was continued for another 30 minutes to obtain polymer (b).

The obtained polymer was poured into a 3% by mass aqueous solution of sodium sulfate for salting out and coagulation. It was then repeatedly dehydrated and washed, and then dried to obtain acrylic graft copolymer particles (rubber particles R1) with a three-layer structure. The average particle diameter of the obtained rubber particles R1 was 200 nm.

The average particle size of rubber particles was measured using the following method.

(Average particle size)
The dispersed particle size of the rubber particles in the obtained dispersion was measured using a zeta potential/particle size measuring system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.).

(2) Preparation of Functional Layer Solution <Preparation of Functional Layer Solution for Laminated Film 201>
The following components were mixed to obtain a functional layer solution 201.

Toluene (boiling point 110° C.): 900 parts by mass COP (G7810): 100 parts by mass

<Preparation of Functional Layer Solutions for Laminated Films 202 to 205>
Functional layer solutions for laminate films 202 to 205 were obtained in the same manner as the functional layer solution for laminate film 201, except that the solvents shown in Table I were changed to cyclopentanone (boiling point 131°C) and dichloromethane (methylene chloride, boiling point 41°C).

<Preparation of Functional Layer Solutions for Laminated Films 206 to 215>
The following components were mixed to obtain functional layer solutions 206 to 215.
Methylene chloride (boiling point 41° C.): 760 parts by weight Methanol (boiling point 65° C.): 40 parts by weight COP (G7810): 200 parts by weight

<Preparation of Functional Layer Solutions for Laminated Films 216 to 222>
The following components were mixed to obtain a functional layer solution 216.
Methyl ethyl ketone (MEK: boiling point 80° C.): 900 parts by mass Fumaric acid diester resin (referred to as fumaric acid resin): 100 parts by mass

For the functional layer solutions for laminate films 217 to 222, the functional layer solutions for laminate films 217 to 222 were prepared in the same manner as the functional layer solution for laminate film 216, except that the solvent was changed appropriately to a mixture of MEK (boiling point 80°C): toluene (boiling point 110°C) = 7:3 (mass ratio), methylene chloride (boiling point 41°C), and the resin concentration (10% by mass or 20% by mass) as shown in Table II.

<Preparation of Functional Layer Solution for Laminated Film 223>
The following components were mixed to obtain a functional layer solution 223.
Methyl ethyl ketone (MEK: boiling point 80° C.) 900 parts by weight Acrylic: 100 parts by weight

<Preparation of Functional Layer Solution for Laminated Film 224>
The following components were mixed to obtain a functional layer solution 224.
Methyl ethyl ketone (MEK: boiling point 80° C.) 900 parts by weight Acrylic: 80 parts by weight Rubber particles R1: 20 parts by weight

<Preparation of Functional Layer Solution for Laminated Film 225>
The following components were mixed to obtain a functional layer solution 225.
Methylene chloride (boiling point 41°C) 900 parts by weight Acrylic: 100 parts by weight

<Preparation of functional layer solutions for laminated films 226 and 227>
The following components were mixed to obtain a functional layer solution 226.
Methylene chloride (boiling point 41° C.) 800 parts by weight Acrylic: 80 parts by weight Rubber particles R1: 20 parts by weight The following components were mixed to obtain a functional layer solution 227.
Methylene chloride (boiling point 41° C.) 800 parts by weight Acrylic: 160 parts by weight Rubber particles R1: 20 parts by weight

<Preparation of Functional Layer Solutions for Laminated Films 228 and 229>
The following components were mixed to obtain a functional layer solution 228.
Toluene (boiling point 110°C): 900 parts by weight Polyarylate (U-100 manufactured by Unitika): 100 parts by weight A functional layer solution for laminate film 229 was prepared in the same manner as the functional layer solution for laminate film 228, except that methylene chloride (boiling point 41°C) was used as the solvent, as shown in Table III.

<Preparation of Functional Layer Solution for Laminated Film 230>
With reference to Example 1 of JP 2020-3823 A, the following components were mixed to obtain a functional layer solution 230.
Cyclohexane (boiling point 81° C.): 900 parts by mass COP (ZNX330R) 100 parts by mass

<Preparation of Functional Layer Solution for Laminated Film 231>
With reference to Example 3 of JP 2018-45220 A, the following components were mixed to obtain a functional layer solution for laminate film 231.
Ethyl acetate (EA: boiling point 77°C) 100 parts by weight A-DCP 100 parts by weight Irgacure 127 2 parts by weight Leveling agent (F-784-F) 0.08 parts by weight

<Preparation of Functional Layer Solution for Laminated Film 232>
With reference to Example 3 of JP 2018-45220 A, the following components were mixed to obtain a functional layer solution for laminate film 232.
Methylene chloride (boiling point 41° C.) 900 parts by weight PSt: 70 parts by weight Polyarylate resin (compound P) 30 parts by weight Leveling agent (F-784-F) 0.08 parts by weight

<Preparation of Functional Layer Solution for Laminated Film 233>
With reference to Example 3 of JP 2018-41028 A, the following components were mixed to obtain a functional layer solution for laminate film 233.
Ethyl acetate (EA: boiling point 77° C.): 700 parts by weight PSt: 98 parts by weight Plasticizer (polyester compound): 2 parts by weight Leveling agent (F-784-F): 0.08 parts by weight

<Preparation of Functional Layer Solution for Laminated Film 234>
The following components were mixed to obtain a functional layer solution 234.
Methylene chloride (boiling point 41° C.): 800 parts by weight Ethanol (boiling point 78° C.): 100 parts by weight TAC: 90 parts by weight Plasticizer (ethyl phthalyl ethyl glycolate): 10 parts by weight

[2] Preparation of Laminated Film <Preparation of Laminated Film 201>
A PET film (TN100, base film A manufactured by Toyobo Co., Ltd.) was prepared as a base film. A solution for a functional layer for the laminated film 201 was applied onto the release layer of the PET film by a backcoat method using a die, and then the laminated film was dried in the drying step described below to form a functional layer with a thickness of 5 μm, thereby obtaining the laminated film 201.
1st step: 1 min at 40°C 2nd step: 1 min at 70°C 3rd step: 1 min at 100°C 4th step: 2 min at 130°C

<Preparation of Laminated Films 202 to 234>
Laminated films 202 to 234 were obtained in the same manner as in the preparation of laminated film 201, except that the type and thickness of the base film and the type and thickness of the functional layer solution were changed, as shown in Tables I to III. As for the drying temperature, only the dryer temperature in the fourth step was changed, and the temperatures in the first, second, and third steps were fixed.

Evaluation
(1) Qualitative and quantitative analysis of residual solvent The qualitative and quantitative analysis of residual solvent in the obtained laminated film was carried out by peeling the laminated film into the base film and the functional layer, and then carrying out headspace gas chromatography on each of them. In headspace gas chromatography, the sample was sealed in a container and heated, and the gas in the container was quickly injected into a gas chromatograph in a state where the container was filled with volatile components, and mass analysis was carried out to identify the compounds and to quantify the volatile components. The quantitative analysis of the volatile components was carried out by preparing a calibration curve in advance using samples with known concentrations, and comparing the peak area of the volatile components obtained by the measurement with the calibration curve.

(Measurement conditions)
Head space device: HP7694 Head Space Sampler (manufactured by Hewlett-Packard)
Temperature conditions: transfer line 200°C, loop temperature 200°C
Sample amount: 0.8 g/20 ml vial GC: HP5890 (Hewlett-Packard)
MS: HP5971 (manufactured by Hewlett-Packard)
Column: HP-624 (30 m x inner diameter 0.25 mm)
Oven temperature: initial temperature 40°C (holding time 3 minutes), heating rate 10°C/min, final temperature 200°C (holding time 5 minutes)
Measurement mode: SIM (select ion monitor) mode

(2) Measurement of the humidity expansion coefficient ( _CHE2 ) of the functional layer at 23°C In the obtained laminated film, the humidity expansion coefficient ( _CHE2 ) of the functional layer at 23°C was measured in the same manner as the humidity expansion coefficient ( _CHE1 ) of the above-mentioned base film on a sample from which the base film had been peeled off.

(3) Transportability (transport stability)
The transport stability of the laminated film was evaluated by checking for the presence or absence of breakage or cracking when the film was transported on a line with rolls while applying a transport tension of 350 N/m. The transport stability was evaluated based on the following criteria.
◯: The functional layer was not broken and could be transported. △: The functional layer had minor scratches and cracks, but could be transported. ×: The functional layer cracked and broke. If it was △ or better, it was judged to be good.

(4) Curl in Water The laminated film is cut into a strip of 35 mm (horizontal direction at the time of manufacture) x 2 mm (vertical direction at the time of manufacture) and immersed in warm water at 38°C for 30 minutes, and the degree of curl in the width direction in water is measured.
The measurement is made assuming that the side on which the functional layer is applied is concave.

[Curl degree]
The obtained laminated film was cut into a circular shape with a diameter of 5 cm to prepare a sample. The obtained sample was left in a constant temperature and humidity chamber at 23° C. and 55% RH for 24 hours. Thereafter, the sample was taken out of the constant temperature and humidity chamber and placed on a flat plate, and 1/r was calculated from the radius of curvature r (m) having a curve that matches the sample using a curvature scale. The curl amount was then evaluated based on the following criteria.
⊚: 1/r is less than 4 ◯: 1/r is 4 or more and less than 8 Δ: 1/r is 8 or more and less than 12 ×: 1/r is 12 or more If it was Δ or more, it was judged to be good.

(5) Adhesion to polarizer (evaluation of adhesion)
A 60 μm-thick long polyvinyl alcohol film containing polyvinyl alcohol (hereinafter referred to as "PVA") was continuously transported via guide rolls and immersed in a dye bath (30° C.) containing iodine and potassium iodide for dyeing and stretching by 2.5 times, and then stretched to a total of 5 times and crosslinked in an acid bath (60° C.) containing boric acid and potassium iodide, and the resulting 12 μm-thick iodine-PVA polarizer was dried in a dryer at 50° C. for 30 minutes to obtain a polarizer with a moisture content of 4.9%. The polarizer was cut to 10 cm×10 cm.
Next, the following components were mixed to prepare water-based adhesive 1.
Pure water: 100 parts by mass Polyvinyl alcohol-based resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFYMER Z200"): 3 parts by mass Water-based adhesive 1 was applied to a PVA polarizer with a wire bar (#0), and the film of the present application processed to 10 cm x 10 cm was laminated sheet-by-sheet using a high-precision desktop laminator HAL-215 (manufactured by Sankyo Co., Ltd.) so that the functional layer surface was adhered to the PVA surface. The substrate film was then peeled off to produce a laminate of PVA and functional layer.
The suitability of this laminate for the lamination process was evaluated as follows.
(Evaluation rank)
: Even after laminating 50 sheets, no air bubbles were found, no bent edges, no film misalignment, etc. were observed. 〇: Even after laminating 20 sheets, no air bubbles were found, no bent edges, no film misalignment, etc. were observed. △: Even after laminating 10 sheets, no air bubbles were found, no bent edges, no film misalignment, etc. were observed. ×: After laminating 10 sheets, air bubbles were found, no bent edges, no film misalignment, etc. were observed in one or more sheets. (6) Interference fringes <Preparation of polarizing plate>
Using the laminate films 201 to 234 prepared above, polarizing plates were prepared according to the following procedure.

(Preparation of Polarizer)
A long polyvinyl alcohol film having a thickness of 60 μm was continuously transported via guide rollers and immersed in a dye bath (30° C.) containing iodine and potassium iodide to be dyed and stretched 2.5 times, and then stretched 5 times in total and crosslinked in an acid bath (60° C.) containing boric acid and potassium iodide. The obtained iodine-PVA-based polarizer having a thickness of 12 μm was dried in a dryer at 50° C. for 30 minutes to obtain a polarizer with a moisture content of 4.9%.

(Preparation of Polarizing Plate)
The polarizers thus prepared were sandwiched from both sides between laminated films 201 to 234 and the optical films described below as opposing films, and bonded via the water-soluble adhesive liquid 1 described below to prepare polarizing plates 201 to 234.

At that time, the longitudinal direction of the polarizer and the longitudinal axis of the laminated film were aligned with each other.
<Facing film>
The opposing film used was a film containing the following resin.
COP (cycloolefin): ARTON G7810 manufactured by JSR Corporation
(Preparation of Water-Soluble Adhesive Liquid 1)
The following components were mixed and then degassed to prepare water-soluble adhesive solution 1.

Pure water 100 parts by weight "Epocross WS-300" manufactured by Nippon Shokubai Co., Ltd. 7.5 parts by weight "CROSSLINKER CL-427" manufactured by Menadiona
0.1 mass part The polarizing plate was prepared by subjecting the adhesive side surface of the laminate film to a corona discharge treatment at a corona output strength of 2.0 kW and a line speed of 18 m/min, and then coating the corona discharge-treated surface with the water-soluble adhesive liquid 1 prepared above using a bar coater so that the thickness after drying would be approximately 3 μm. The film was then dried at 50° C., 60° C., and 70° C. in that order for 60 seconds each to obtain a polarizing plate.
The prepared polarizing plate was placed on a black cloth such as a light-tight curtain with the side on which the functional layer was formed facing up, and illuminated with a three-wavelength fluorescent lamp (National fluorescent lamp: FL20SS-ENW/18, manufactured by Matsushita Electric Industrial Co., Ltd.). The surface of the polarizing plate was visually observed and evaluated according to the following criteria.
⊚: Ten samples were observed, but no interference unevenness was observed.
The manufacturing conditions of the obtained laminated films 201 to 234 are shown in Tables I, II and III, and the evaluation results are shown in Table IV. The content of rubber particles is shown as mass% in the coating film (functional layer) after drying.

As shown in Table IV, laminate films 201-208, 211-213, 216-218, 222, 224, and 226-229 of the present invention are superior overall to the laminate films of the comparative examples in terms of transportability, underwater curl, adhesion, and interference fringe evaluation. In particular, when the value shown by formula (1) is within the range of 0.30 to 1.00, adhesion is good, and when it is within the range of 0.40 to 0.80, the interference fringe characteristics tend to be even better.

Example 2
The retardation of the functional layers of the laminated films 204, 213, 214, 216, 218, 226 and 229 produced in Example 1 was measured by the following method, and the results are shown in Table V.

The retardations Ro and Rt were measured by the following method.
1) The substrate film is peeled off from the laminated film, and the functional layer is conditioned for 24 hours in an environment of 23° C. and 55% RH. The average refractive index of this layer is measured with an Abbe refractometer, and the thickness d is measured with a commercially available micrometer.
2) The retardation Ro and Rt of the film after humidity conditioning at a measurement wavelength of 590 nm are measured in an environment of 23° C. and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter, manufactured by Axometrics).

Ro and Rt are defined by the following formulas, respectively.
Formula (a): Ro=(nx-ny)×d
Formula (b): Rt=((nx+ny)/2-nz)×d
(In the formula, nx represents the refractive index of the functional layer in the in-plane slow axis direction, ny represents the refractive index of the functional layer in the direction perpendicular to the in-plane slow axis, nz represents the refractive index of the functional layer in the thickness direction, and d represents the thickness (nm) of the functional layer.)

From the results in Table V, it can be seen that the retardation values of the functional layer according to the present invention are Ro in the range of 0 to 20 nm and Rt in the range of -25 to 25 nm, both of which are suitable as phase difference films for IPS mode liquid crystal display devices.

According to the present invention, a laminate film is obtained which, while being thin, has excellent transportability and can be handled in the same way as conventional polarizing plate protective films, and furthermore has excellent curl control during polarizing plate processing, making it possible to provide high-quality polarizing plates and display devices which have excellent productivity (bonding to polarizers) during polarizing plate processing and are free of optical unevenness.

REFERENCE SIGNS LIST 1 Laminated film 2 Base film 3 Functional layer 4 Adhesive layer 5 Polarizer 6 Opposing film 10, 10' Polarizing plate B110 Base film B120 Functional layer B200 Manufacturing apparatus B210 Supply section B220 Coating section B230 Drying section B240 Cooling section B250 Winding section

Claims (15)

A laminated film in which a peelable functional layer is laminated on a base film,
The base film contains polyethylene terephthalate,
the functional layer contains a fumaric acid diester resin or a (meth)acrylic resin containing rubber particles ,
The thickness of the functional layer is in the range of 1 to 19 μm;
The total thickness of the laminated film is 50 μm or less,
A laminated film characterized by satisfying the relationship of the following formula ₍₁ ) when the humidity expansion coefficient of the base film at 23°C is _CHE1 (ppm/% RH), the thickness is _d1 (μm), and the humidity expansion coefficient of the functional layer at 23°C is CHE2 (ppm/% RH) and the thickness is _d2 (μm).
Formula (1) 0.20<|(CHE ₁ −CHE ₂ )|×(d ₂ /d ₁ )<2.00 The laminated film according to claim 1, characterized in that the thickness of the functional layer is within the range of 2 to 10 μm. The laminate film according to claim 1 or 2, characterized in that the total thickness of the laminate film is within the range of 30 to 45 μm. The retardation value Ro of the functional layer defined by the following formula (i) is in the range of 0 to 20 nm, and the retardation value Rt of the functional layer defined by the following formula (ii) is in the range of -25 to 25 nm. A laminate film according to any one of claims 1 to 3.
Formula (i) Ro = ( _nx - _ny ) x d
Formula (ii) Rt={(n _x + n _y )/2-n _z }×d
(In the above formulas (i) and (ii), Ro represents the retardation value in the in-plane direction of the functional layer, Rt represents the retardation value in the thickness direction of the functional layer, _nx represents the refractive index in the in-plane direction of the slow axis of the functional layer, _ny represents the refractive index in the in-plane direction of the fast axis of the functional layer, _nz represents the refractive index in the thickness direction of the functional layer (the refractive index is measured at a wavelength of 590 nm under an environment of 23° C. and 55% RH), and d represents the thickness of the film (nm).) The laminate film according to any one of claims 1 to 4, characterized in that, when the content of the residual solvent in the base film is _S1 and the content of the residual solvent in the functional layer is _S2 , the following formula (2) is satisfied.
Formula (2) 10<S ₁ <S ₂ <1000 (ppm) The laminated film according to claim 5, characterized in that the boiling point of the main residual solvent among the residual solvents is 100°C or less under atmospheric pressure. The laminate film according to claim 5 or 6, characterized in that the residual solvent is a chlorine-based solvent. The laminated film according to any one of claims 5 to 7, characterized in that the residual solvent is dichloromethane. The laminate film according to any one of claims 5 to 8, characterized in that the residual solvent contains dichloromethane and alcohols. The laminate film according to any one of claims 1 to 9, characterized in that the base film is a biaxially stretched polyester film, and the humidity expansion coefficient CHE ₁ of the polyester film at 23°C is within the range of 10 to 20 ppm/% RH. The laminated film according to any one of claims 1 to 10, characterized in that the functional layer contains a polymer material having a carbonyl group in the side chain. The laminated film according to any one of claims 1 to 10, characterized in that the functional layer contains a polymer material having a cyclic structure in the main chain. A polarizing plate comprising the laminate film according to any one of claims 1 to 12. A display device comprising the laminate film according to any one of claims 1 to 12 or the polarizing plate according to claim 13. A method for producing a polarizing plate roll, comprising: laminating the laminate film according to any one of claims 1 to 12 to at least one surface of a polarizer while winding the laminate film,
A method for producing a polarizing plate roll, comprising a step of winding up the laminate film while bonding the laminate film to the polarizer in the layered order from the inside of the roll: polarizer, adhesive layer, functional layer, and base film.

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