JP7238238B2 - liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device used for personal computer monitors, televisions and the like.

In order to reduce the weight of the liquid crystal display device, there is a tendency to make the glass substrate thinner. It is considered to progress. Since the glass substrate in the liquid crystal display device has the effect of suppressing curl due to the thermal behavior of the polarizing plate, as the thickness of the glass substrate decreases, the effect of suppressing curling decreases significantly, and the polarizing plate/liquid crystal present in the liquid crystal display device. The problem of warpage of laminates consisting of cells and polarizers has become apparent.

Conventionally, there have been many proposals for suppressing the curling of a laminate consisting of a polarizing plate/liquid crystal cell/polarizing plate. By controlling the elastic modulus in the long side direction of each polarizing plate in the side polarizing plate, and by considering the difference in the environment where the upper and lower polarizing plates are placed and providing a difference in the elastic modulus of the upper and lower polarizing plates It proposes to improve the warpage of the liquid crystal display device. In Patent Document 2, attention is paid to the difference in shrinkage force between the absorption axis direction and the transmission axis direction of the polarizing plate. are improving.

JP-A-2006-267503 WO2014-204165

However, in Patent Document 1 and Patent Document 2, improvement studies have been made by controlling strain due to temperature change and strain due to absorption/desorption of moisture, while using a film with a low glass transition temperature such as a polyethylene terephthalate film. It did not take into consideration the influence of the residual strain (thermal shrinkage rate) originally possessed by the film, which should be considered in some cases.

That is, the problem to be solved by the present invention is to provide a liquid crystal display device capable of highly controlling the curling of a laminate composed of polarizing plate/liquid crystal cell/polarizing plate in the liquid crystal display device.

In a liquid crystal display device, a polarizing plate is usually laminated on one side of a liquid crystal cell so that the transmission axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device, and the absorption of the polarizer is laminated on the other side. The polarizing plates are laminated such that the axial direction is parallel to the long side of the liquid crystal display device. As a result of intensive studies using various types of commercially available liquid crystal display devices, it was found that the problem of the shape factor that curling is likely to occur due to the shrinkage of the polarizing plate whose long side is in the direction of the polarizer absorption axis where the contraction force is large (curl is In general, it tends to occur in the long side direction) and the asymmetrical configuration of the upper and lower polarizing plates in the liquid crystal panel. The present inventors have found that the essence of the problem is the convexity on the side of the polarizing plate.

Furthermore, as a result of intensive studies, it became clear that the contraction force in the long-side direction of the polarizing plate, in which the transmission axis of the polarizer is the long side, can be controlled by the residual strain of the protective film. It was found that the curl of the device could be controlled.

Here, a method for measuring the shrinkage force of the polarizing plate will be described. In general, the shrinkage force of a film is measured by using a TMA or the like, setting the initial length with a minimal load at the start of the test at a low temperature, and measuring the force in the shrinkage direction while the temperature is rising while maintaining the initial length. do. However, in the process of temperature rise, the contraction due to the recovery of the residual strain accompanying the conformational change of the polymer (hereinafter simply referred to as thermal contraction), and at the same time, the thermal expansion due to the increase in the free volume and occupied volume of the polymer due to the temperature rise ( hereinafter, simply referred to as thermal expansion) occurs, so in the temperature range near the glass transition temperature of the polyester film (for example, about Tg + 50 ° C.), the relationship is often thermal contraction < thermal expansion, so the film as a whole It expands and no contractile force is observed.

As a result of the investigation, it was found that even if the shrinkage force was not generated during the TMA heating process, the shrinkage force was generated during the TMA cooling process. This is because the strain due to thermal expansion is a reversible change, so it returns to its original state after heating and cooling. This is because In other words, the strain of thermal stress can be replaced with the thermal shrinkage rate of the film, and the shrinkage force after cooling is expressed by the following formula. Incidentally, the thermal shrinkage rate in the present invention includes the change in moisture content during the heat treatment.
Contraction force (N/m)
= film thickness (mm) x elastic modulus (N/mm ² ) x heat shrinkage (%) ÷ 100 x 1000

That is, the representative present invention is as follows.
Section 1.
In a liquid crystal display device having a liquid crystal cell, a polarizing plate A attached to one surface of the liquid crystal cell, and a polarizing plate B attached to the other surface of the liquid crystal cell,
The polarizing plate A has a structure in which the transmission axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device, and a polyester film is laminated on at least one side of the polarizer,
The polarizing plate B has a structure in which the absorption axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device, and a protective film is laminated on at least one side of the polarizer,
The shrinkage force F _f of the polyester film in the long side direction of the liquid crystal display device and the shrinkage force F _p of the polarizer included in the polarizing plate B in the long side direction of the liquid crystal display device are characterized by satisfying the following formula (1). liquid crystal display device.
Formula (1) 0.1≦F _f /F _p ≦2
(However, the shrinkage force F _f (N/m) is the thickness (mm) of the polyester film x the elastic modulus (N/mm ² ) x the heat shrinkage rate (%) ÷ 100 x 1000, and the shrinkage force F _p (N /m) is the thickness (mm) of the polarizer of the polarizing plate B × elastic modulus (N/mm ² ) × heat shrinkage (%) / 100 × 1000.)
Section 2.
Item 2. The liquid crystal display device according to item 1, wherein the elastic modulus in the longitudinal direction of the liquid crystal display device of the polyester film is 1000 to 9000 N/mm ² .
Item 3.
Item 3. The liquid crystal display device according to Item 1 or 2, wherein the polyester film liquid crystal display device has a heat shrinkage rate of 0.1 to 5% in the long side direction.
Section 4.
Item 4. The liquid crystal display device according to any one of Items 1 to 3, wherein the polyester film has a thickness of 40 to 200 μm.
Item 5.
Item 5. The liquid crystal display device according to any one of Items 1 to 4, wherein the inclination of the main axis of alignment of the polyester film with respect to the long side direction or the short side direction of the liquid crystal display device is 15 degrees or less.
Item 6.
Item 6. The liquid crystal display device according to any one of Items 1 to 5, wherein the inclination of the shrinkage principal axis of the polyester film with respect to the long side direction or the short side direction of the liquid crystal display device is 15 degrees or less.
Item 7.
In a liquid crystal panel having a liquid crystal cell, a polarizing plate A attached to one surface of the liquid crystal cell, and a polarizing plate B attached to the other surface of the liquid crystal cell,
The polarizing plate A has a structure in which the transmission axis direction of the polarizer is parallel to the long side direction of the polarizing plate A, and a polyester film is laminated on at least one side of the polarizer,
The polarizing plate B has a structure in which the absorption axis direction of the polarizer is parallel to the long side direction of the polarizing plate B, and a protective film is laminated on at least one side of the polarizer,
A liquid crystal panel in which the contractile force _Ff of the polyester film in the long side direction of the polarizing plate A and the contractile force _Fp of the polarizer of the polarizing plate B in the long side direction of the polarizing plate B satisfy the following formula (1).
Formula (1) 0.1≦F _f /F _p ≦2
(However, the shrinkage force F _f (N/m) is the thickness (mm) of the polyester film x the elastic modulus (N/mm ² ) x the heat shrinkage rate (%) ÷ 100 x 1000, and the shrinkage force F _p (N /m) is the thickness (mm) of the polarizer of the polarizing plate B × elastic modulus (N/mm ² ) × heat shrinkage (%) / 100 × 1000.)
Item 8.
Item 8. The liquid crystal panel according to Item 7, wherein the elastic modulus in the long side direction of the polarizing plate A of the polyester film is 1000 to 9000 N/mm ² .
Item 9.
Item 9. The liquid crystal panel according to Item 7 or 8, wherein the heat shrinkage in the long side direction of the polarizing plate A of the polyester film is 0.1 to 5%.
Item 10.
Item 10. The liquid crystal panel according to any one of Items 7 to 9, wherein the polyester film has a thickness of 40 to 200 μm.
Item 11.
Item 11. The liquid crystal panel according to any one of items 7 to 10, wherein the inclination of the alignment principal axis of the polyester film with respect to the long side direction or the short side direction of the liquid crystal panel is 15 degrees or less.
Item 12.
Item 6. The liquid crystal panel according to any one of Items 1 to 5, wherein the inclination of the shrinkage principal axis of the polyester film with respect to the long side direction or the short side direction of the liquid crystal panel is 15 degrees or less.

It is possible to provide a liquid crystal display device in which curling of a laminate (liquid crystal panel) composed of polarizing plate/liquid crystal cell/polarizing plate, which occurs in a high temperature or high temperature and high humidity environment, is reduced.

The screen of a liquid crystal display device is usually rectangular and has long sides and short sides. In this specification, the “long side direction of the liquid crystal display device” is a direction parallel to the long side of the liquid crystal display device, and the “long side direction of the polarizing plate A”, the “long side direction of the polarizing plate B”, It is the same as the "long side direction of the polarizer of the polarizing plate B" and the "long side direction of the polyester film of the polarizing plate A". Therefore, in this specification, the "long side direction of the liquid crystal display device" includes "the long side direction of the polarizing plate A", "the long side direction of the polarizing plate B", and "the long side of the polarizer of the polarizing plate B. direction" and "long side direction of the polyester film of the polarizing plate A". The “short-side direction of the liquid crystal display device” is a direction parallel to the short-side direction of the liquid crystal display device and means a direction perpendicular to the long-side direction.

The liquid crystal display device of the present invention has at least a liquid crystal cell, a polarizing plate A attached to one surface of the liquid crystal cell, and a polarizing plate B attached to the other surface of the liquid crystal cell. A liquid crystal cell and a polarizing plate can usually be attached together via an adhesive layer. In addition to the liquid crystal cell, the polarizing plate A and the polarizing plate B, the liquid crystal display device can include constituent members normally used in the liquid crystal display device, such as a backlight. A liquid crystal cell has a structure in which liquid crystal is sandwiched between two glass substrates. In one embodiment, the thickness of the glass substrate constituting the liquid crystal cell is 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, or 0.25 mm or less. preferable.

In the polarizing plate A, the transmission axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device (that is, it is synonymous with the transmission axis direction of the polarizer being parallel to the long side direction of the polarizing plate A). It has a structure in which a polyester film (used as a polarizer protective film) is laminated on at least one side of the element. A protective film or an optical compensation film with low retardation such as a TAC film, a cyclic olefin film, or an acrylic film can be laminated on the surface of the polarizer opposite to the surface on which the polyester film is laminated. Here, the protective film with low retardation may be, for example, a protective film with a retardation of 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. Another preferred embodiment of the polarizing plate A has a structure in which a polyester film is laminated only on one side of the polarizer and no protective film or optical compensation film is laminated on the other side of the polarizer. The polyester film can be placed either on the liquid crystal cell side of the polarizer or on the distal side (outside) of the liquid crystal cell (or on both sides), but on the distal side (outside) of the polarizer. Arrangement is preferred.

It is most desirable for the transmission axis direction of the polarizer to be completely parallel to the long side direction of the liquid crystal display device, but the concept allows for a slight deviation. That is, the angle between the transmission axis direction of the polarizer and the long side direction of the liquid crystal display device is preferably 7 degrees or less, preferably 5 degrees or less, preferably 3 degrees or less, preferably 2 degrees or less, and 1 degree or less. is preferred, most preferably 0 degrees.

In the polarizing plate B, the absorption axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device (that is, it is synonymous with the absorption axis of the polarizer being parallel to the long side direction of the polarizing plate B), and the polarizer It is a structure in which a protective film is laminated on at least one side of the A protective film having a low retardation such as a TAC film, a cyclic olefin film, an acrylic film, or an optical compensation film can be laminated on the protective film. Here, the protective film with low retardation may be, for example, a protective film with a retardation of 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. A polyester film can also be laminated on the polarizer as a protective film. When a polyester film is used, it is preferably laminated on the far side of the polarizer from the liquid crystal cell.

The polarizing plate B may have a structure in which a polyester film is laminated on one side of a polarizer and the protective film or optical compensation film described above is laminated on the other side. Another preferred embodiment of the polarizing plate B has a structure in which a polyester film is laminated only on one side of the polarizer and no protective film or optical compensation film is laminated on the other side of the polarizer.

It is most desirable that the direction of the absorption axis of the polarizer is completely parallel to the long side direction of the liquid crystal display device, but a slight deviation is allowed. That is, the angle between the absorption axis direction of the polarizer and the long side direction of the liquid crystal display device is preferably 7 degrees or less, preferably 5 degrees or less, preferably 3 degrees or less, preferably 2 degrees or less, and 1 degree or less. is preferred, most preferably 0 degrees.

The polarizing plate A may be used either as a polarizing plate on the viewing side of the liquid crystal cell or as a polarizing plate on the backlight side, but generally it is preferably arranged as a polarizing plate on the backlight side. The polarizing plate B may be used as either a polarizing plate on the viewing side or a polarizing plate on the backlight side of the liquid crystal cell, but it is generally preferable to arrange it as a polarizing plate on the viewing side. That is, a liquid crystal display device having a backlight source, a polarizing plate A, a liquid crystal cell, and a polarizing plate B in this order is preferable. Note that the liquid crystal display device may include other members between them.

In the liquid crystal display device of the present invention, it is desirable that 0.1≦F _f /F _p ≦2. The lower limit of F _f /F _p is preferably 0.2 or 0.3. The upper limits of F _f /F _p are 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, It is preferably 0.9, 0.8 or 0.7. In one embodiment, 0.1≦F _f /F _p ≦1.0, 0.1≦F _f /F _p <1.0, 0.1≦F _f /F _p ≦0.9, 0.1 Preferably, _≤Ff / _Fp≤0.8 , _0.2≤Ff / _Fp≤0.8 , or _0.3≤Ff / _Fp≤0.7 .

Here, _Ff refers to the shrinkage force of the polyester film of the polarizing plate A in the long side direction of the liquid crystal display device, and is polyester film thickness (mm) × elastic modulus (N/mm ² ) × heat shrinkage (%) ÷ 100. It is defined by ×1000. _Fp refers to the shrinkage force of the polarizer of the polarizing plate B in the long side direction of the liquid crystal display device, and is the thickness of the polarizer of the polarizing plate B (mm) × elastic modulus (N/mm ² ) × thermal shrinkage rate (%). It is defined as ÷100×1000. In the formulas for the contractile forces F _f and F _p , the elastic modulus and the thermal contraction rate are both values in the long side direction of the liquid crystal display device. The shrinkage force of the polarizing plate B is mainly expressed by the polarizer, and the shrinkage force changes depending on the thickness of the polarizer and film forming conditions. Therefore, it is desirable to adjust the shrinkage force of the polyester film used for the polarizing plate A accordingly.

The polyester film used for the polarizing plate A preferably has an elastic modulus of 1000 to 9000 N/mm ² in the long side direction of the liquid crystal display device. The shrinkage force of the polyester film can be controlled by the elastic modulus, but in order to increase the elastic modulus in the long side direction of the liquid crystal display device, it is highly oriented in the long side direction of the liquid crystal display device and the crystallinity is increased. need to be higher. Therefore, when the elastic modulus in the long side direction exceeds 9000 N/mm ² , problems such as easy tearing become apparent, so the upper limit is preferably 9000 N/mm ² , more preferably 8000 N/mm ² More preferably, it is 7000 N/mm ² . On the other hand, when the orientation is low and the degree of crystallinity is low, when the film is wound on a roll, the film is deformed due to unevenness of the roll caused by thickness unevenness, resulting in poor flatness. Therefore, the lower limit of the elastic modulus is preferably 1000 N/mm ² , more preferably 1500 N/mm ² and even more preferably 1800 N/mm ² . The elastic modulus can be measured by the method adopted in the examples described later.

The polyester film used for the polarizing plate A preferably has a heat shrinkage rate of 0.1 to 5% in the long side direction of the liquid crystal display device when heat-treated at 100° C. for 30 minutes. The lower limit of the heat shrinkage rate is preferably 0.3% or more, preferably 0.4% or more, preferably 0.5% or more, and preferably 0.7% or more. The upper limit of the heat shrinkage rate is preferably 4% or less, preferably 3% or less, and preferably 2% or less. When the heat shrinkage rate is lower than 0.1%, that is, in the range of 0.01 to 0.099%, it is difficult to control the heat shrinkage rate without variation. Further, in order to increase the thermal shrinkage to more than 5%, it is necessary to further lower the degree of crystallinity and the glass transition temperature, as will be described later. The thermal shrinkage rate can be measured by the method adopted in Examples described later.

The polyester film used for the polarizing plate A preferably has a thickness of 40 to 200 μm. When the thickness of the polyester film is less than 40 μm, it is likely to crack and to have poor flatness due to insufficient rigidity. In addition, if it is thin, it is necessary to increase the elastic modulus or thermal contraction rate in the long side direction accordingly, but since each parameter has an upper limit as described above, the lower limit is substantially 40 μm. On the other hand, if the film thickness exceeds 200 μm, the elastic modulus or thermal shrinkage in the long side direction will vary greatly, making it difficult to control and increasing the cost. The thickness of the polyester film can be measured by the method employed in the examples described later.

The polyester film used for the polarizing plate A preferably has an inclination of 15 degrees or less between the principal axis of orientation of the polyester film and the long side direction or the short side direction of the liquid crystal display device. A stretched polyester film usually has anisotropy of elastic modulus in the plane of the film, and the anisotropy of elastic modulus and optical anisotropy of the stretched polyester film generally match. Therefore, with respect to the main axis of alignment determined from optical anisotropy, by setting a narrow angle of 15 degrees or less with respect to the long side direction or the short side direction of the liquid crystal display device, the direction having a high elastic modulus is aligned with the long side of the liquid crystal display device. Since it approaches the direction or the short side direction, it is effective in suppressing the curling of the laminate composed of polarizing plate/liquid crystal cell/polarizing plate, which is the object of the present invention. When the narrow angle between the main axis of alignment and the long side direction or short side direction of the liquid crystal display device exceeds 15 degrees, the tendency of oblique curling to occur becomes pronounced. The inclination is more preferably 10 degrees or less, 9 degrees or less, or 8 degrees or less. The orientation principal axis of the polyester film can be measured according to the measurement method employed in the examples described later.

The polyester film used for the polarizing plate A preferably has a narrow angle of 15 degrees or less with respect to the principal axis of contraction of the polyester film with the long side direction or the short side direction of the liquid crystal display device. A stretched polyester film usually has an anisotropic heat shrinkage rate in the film plane and an inclination in the principal axis of shrinkage. If the narrow angle between the principal axis of shrinkage and the direction of the long side or the direction of the short side is larger than 15 degrees, the tendency of curling in oblique directions becomes pronounced, which is undesirable. Therefore, the narrow angle between the main shrinkage axis of the polyester film used for the polarizing plate A and the long side direction or short side direction of the liquid crystal display device is preferably 15 degrees or less, and more preferably 10 degrees or less, 9 degrees or less, or 8 degrees or less. preferable. The contraction principal axis can be measured according to the measurement method employed in the examples described later.

The polyester film used for the polarizing plate A preferably has an in-plane retardation within a specific range from the viewpoint of suppressing iridescence observed on the screen of a liquid crystal display device. The lower limit of in-plane retardation is preferably 3000 nm or more, 5000 nm or more, 6000 nm or more, 7000 nm or more, or 8000 nm or more. The upper limit of the in-plane retardation is preferably 30000 nm or less, more preferably 18000 nm or less, still more preferably 15000 nm or less. When a polyester film is also used as a protective film for the polarizing plate B, it is preferable that the polyester film also has an in-plane retardation within the above range.

The retardation of the polyester film can be determined by measuring the refractive index and thickness in the biaxial directions, or can be determined using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). The refractive index can be determined by an Abbe refractometer (measurement wavelength: 589 nm).

The polyester film used for the polarizing plate A has a ratio (Re/Rth) of in-plane retardation (Re) to thickness direction retardation (Rth) of preferably 0.2 or more, preferably 0.3 or more, preferably is 0.4 or more, preferably 0.5 or more, more preferably 0.5 or more, and still more preferably 0.6 or more. As the ratio of the in-plane retardation to the thickness direction retardation (Re/Rth) increases, the birefringence action becomes more isotropic, and rainbow-like color spots tend to be less likely to occur depending on the viewing angle. Since the ratio of the retardation to the thickness direction retardation (Re/Rth) is 2.0 in a perfect uniaxial (uniaxially symmetric) film, the ratio of the retardation to the thickness direction retardation (Re/Rth) The upper limit is preferably 2.0. A preferable upper limit of Re/Rth is 1.2 or less. The thickness direction retardation means the average retardation obtained by multiplying the two birefringences ΔNxz and ΔNyz when the film is viewed from the thickness direction section by the film thickness d. When a polyester film is used as a protective film for the polarizing plate B, the ratio (Re/Rth) of the in-plane retardation (Re) and the thickness direction retardation (Rth) of the polyester film is within the above range. is preferred.

The polyester film used for the polarizing plate A preferably has a NZ coefficient of 2.5 or less, more preferably 2.0 or less, and still more preferably 1, from the viewpoint of suppressing rainbow-like color spots. 0.8 or less, and even more preferably 1.6 or less. Since the NZ coefficient is 1.0 in a perfectly uniaxial (uniaxially symmetrical) film, the lower limit of the NZ coefficient is 1.0. However, it should be noted that the mechanical strength in the direction perpendicular to the orientation direction tends to decrease significantly as the film approaches a perfect uniaxial (uniaxially symmetrical) film. When a polyester film is used as a protective film for the polarizing plate B, it is preferable that the NZ coefficient of the polyester film is within the above range.

The NZ coefficient is represented by |Ny−Nz|/|Ny−Nx|, where Ny is the refractive index in the slow axis direction of the polyester film, and Nx is the refractive index in the direction perpendicular to the slow axis (fast axis direction), and Nz represents the refractive index in the thickness direction. The orientation axis of the film is obtained using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), and the biaxial refractive indices (Ny, Nx, where Ny>Nx) and the refractive index (Nz) in the thickness direction are determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measuring wavelength 589 nm). The NZ coefficient can be obtained by substituting the value obtained in this way for |Ny-Nz|/|Ny-Nx|.

In addition, the value of Ny-Nx of the polyester film used for the polarizing plate A is preferably 0.05 or more, more preferably 0.07 or more, and further from the viewpoint of suppressing rainbow-like color spots. It is preferably 0.08 or more, still more preferably 0.09 or more, and most preferably 0.1 or more. The upper limit is not particularly defined, but in the case of polyethylene terephthalate film, the upper limit is preferably about 1.5. When a polyester film is also used as the protective film for the polarizing plate B, it is preferable that the value of Ny-Nx of the polyester film is within the above range.

The polyester film used for the polarizing plate A can be obtained from any polyester resin. The type of polyester resin is not particularly limited, and any polyester resin obtained by condensing a dicarboxylic acid and a diol can be used. When a polyester film is used as a protective film for the polarizing plate B, the same applies to the polyester film.

Examples of dicarboxylic acid components that can be used in the production of polyester resins include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1 ,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid , hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyl adipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecadicarboxylic acid and the like.

Examples of diol components that can be used in the production of polyester resins include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1 ,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, etc. mentioned.

Both the dicarboxylic acid component and the diol component that constitute the polyester resin are one or two
More than one species can be used. Suitable polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and more preferably polyethylene terephthalate and polyethylene naphthalate. Furthermore, other copolymer components may be included. These resins are excellent in transparency as well as in thermal and mechanical properties. In particular, polyethylene terephthalate is a suitable material because it can achieve a high elastic modulus and its thermal shrinkage can be relatively easily controlled.

When it is necessary to highly increase the heat shrinkage of the polyester film, it is desirable to moderately lower the degree of crystallinity by adding a copolymer component. In addition, since the rate of elastic strain and permanent strain is high for deformation below the glass transition temperature, it is generally difficult to increase the heat shrinkage rate to a high level. Therefore, it is also a preferred embodiment to introduce a component with a low glass transition temperature as needed. Specific examples include propylene glycol and 1,3-propanediol.

(Addition of functional layer)
The polarizing plate A used in the liquid crystal display device of the present invention is preferably integrated with the glass plate of the liquid crystal cell while the heat shrinkage of the polyester film remains. Glare layer, antireflection layer, low reflection layer, low antireflection layer, antireflection antiglare layer, antistatic layer, etc. When applying functional layers such as, setting the drying temperature low, UV irradiation, In this embodiment, it is desirable to use a method with a small thermal history, such as electron beam irradiation. In addition, imparting these functional layers during the film-forming process of the polyester film makes it possible to integrate the polarizing plate A with the glass plate of the liquid crystal cell without impairing the increased thermal shrinkage rate. This is the preferred embodiment.

(Method for producing oriented polyester film)
The polyester film used in the present invention can be produced according to a general polyester film production method. For example, a polyester resin is melted and a non-oriented polyester extruded into a sheet is stretched in the longitudinal direction using the speed difference between rolls at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction with a tenter, A method of applying a heat treatment can be mentioned. It may be a uniaxially stretched film or a biaxially stretched film. In addition, MD is an abbreviation for Machine Direction, and in this specification, it may be referred to as the film flow direction, the longitudinal direction, and the vertical direction. Also, TD is an abbreviation for Transverse Direction, and is sometimes referred to as the width direction and the lateral direction in this specification.

The polyester film used as a polarizer protective film for the polarizing plate A preferably has a shrinkage force F _f adjusted to satisfy 0.1 F _p ≦F _f ≦2 F _p .

(Method for adjusting elastic modulus of polyester film)
The elastic modulus of the polyester film used as a polarizer protective film for the polarizing plate A is MD when the polarizer transmission axis direction (that is, the long side direction of the liquid crystal display device) matches the MD at the time of film formation of the polyester film. When the elastic modulus of is the same as the TD at the time of film formation of the polyester film, the elastic modulus of the TD may be adjusted by a conventionally known method for stretched polyester films. Specifically, when the direction is the stretching direction, the stretching ratio may be set high, and when the direction is the direction perpendicular to the stretching direction, the stretching ratio may be set low.

(Method for adjusting heat shrinkage of polyester film)
The thermal shrinkage rate of the polyester film used as the polarizer protective film for the polarizing plate A is when the transmission axis direction of the polarizer (that is, the long side direction of the liquid crystal display device) matches the MD during film formation of the polyester film. If the heat shrinkage rate of MD matches the heat shrinkage rate of TD at the time of film formation of the polyester film, the heat shrinkage rate of TD may be adjusted by a conventionally known method for stretched polyester films.

When adjusting the MD heat shrinkage rate of the polyester film, for example, in the cooling process after stretching and heat setting, the distance between the clip holding the end of the film in the width direction and the adjacent clip is expanded to stretch the film in the MD. It can be adjusted by shrinking the MD by reducing the clip interval. In the cooling process after stretching and heat setting, when the film is cut or separated from the clip that grips the ends in the film width direction, the film is stretched or shrunk in MD by adjusting the force to pull the film. It is possible to adjust by Also, in the offline process after film formation, when the temperature is raised for the purpose of imparting a functional layer, etc., the thermal shrinkage rate changes during the heating and cooling process, so the force to pull the film is adjusted to stretch or shrink in MD. It is also possible to adjust by

When adjusting the heat shrinkage rate of the TD of the polyester film, for example, in the cooling process after stretching and heat setting, increase the distance between the clip holding the end of the film in the width direction and the clip located on the opposite side in the width direction. By doing so, it is possible to adjust the method of stretching in the TD, or by shrinking the film in the TD.
In either case of MD or TD, it is desirable to adjust the thermal shrinkage rate within the temperature range targeted by the present invention.

(Method for adjusting the inclination of the main shrinkage axis of the polyester film)
As disclosed in PCT/JP2014/073451 (WO2015/037527), the inclination of the shrinkage principal axis of the polyester film used as the polarizer protective film of the polarizing plate A depends on the cooling process after stretching and heat treatment of the polyester film by a tenter. Alternatively, it can be adjusted in an off-line process after film formation. Specifically, in the cooling process, shrinkage due to stretching and thermal stress due to cooling, which could not be completely removed by heat setting, are generated. Entrainment occurs, and a phenomenon occurs in which the contraction principal axis is tilted. In order to reduce the inclination of the main axis of shrinkage, it is necessary to adjust the shrinkage force in the direction of film flow (the sum of the shrinkage force associated with stretching and the shrinkage force associated with cooling) in the cooling process so as to be uniform. For uniformity, it is desirable to shrink the film in the machine direction in a temperature range where the shrinkage force is high in the film machine direction, or to stretch the film in the film machine direction in a temperature range where the shrinkage force is low in the film machine direction. A conventionally known method may be used for shrinking or stretching. Also, when cutting or separating the ends of the film, it should be noted that the film shrinks freely in the width direction below the cutting/separating temperature range, and the thermal shrinkage rate becomes smaller below this temperature range.

(Method for adjusting inclination of main axis of orientation of polyester film)
The adjustment of the inclination of the orientation principal axis of the polyester film used as the polarizer protective film for the polarizing plate A is disclosed in Japanese Patent Application No. 2014-11438 (Japanese Unexamined Patent Application Publication No. 2015-136922) or Japanese Patent Application No. 2012-552162 (WO2013/031511). As described above, conventionally known methods may be used for stretched polyester films. To adjust the inclination of the main axis of orientation, it is preferable to make uniform the shrinkage force in the film flow direction in the stretching/heat setting section. In the stretching and heat setting section by the tenter, there is a distribution of shrinkage force in the film flow direction due to residual stress from MD stretching and Poisson's stress from TD stretching, and pulling occurs to the upstream or downstream side. A tilt occurs (so-called bowing phenomenon). A conventionally known method may be used to make the shrinkage force uniform in the film flow direction. Specifically, after satisfying the stretching conditions necessary for satisfying the optical properties required for the stretched polyester polarizer protective film, the temperature rising conditions considering the balance of the stretching ratios in MD and TD and the tenter dimension, It can be achieved by shrinkage due to the reduction of the distance between adjacent clips during stretching and heat setting.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate modifications within the scope of the gist of the present invention. Both of them are included in the technical scope of the present invention.

(1) Shrinkage force The shrinkage force of the polarizer and the polyester film was calculated from the following formula. The film thickness, elastic modulus, and heat shrinkage are measured values described below.
Contraction force (N/m)
= film thickness (mm) x elastic modulus (N/mm ² ) x heat shrinkage (%) ÷ 100 x 1000

(2) Film thickness The thickness (mm) of the polarizer and the polyester film is measured using an electric micrometer (Millitron 1245D manufactured by Finereuf Co., Ltd.) after standing for 168 hours in an environment of 25 ° C. and 50 RH%, and the unit is Converted to mm.

(3) Elastic modulus The elastic modulus of the polarizer and polyester film was measured by a dynamic viscoelasticity measuring device (DMS6100) manufactured by Seiko Instruments Inc. according to JIS-K7244 (DMS) after standing for 168 hours in an environment of 25° C. and 50 RH%. was used for evaluation. Under the conditions of tension mode, drive frequency of 1 Hz, distance between chucks of 5 mm, and temperature increase rate of 2° C./min, the temperature dependence was measured from 25° C. to 120° C., and the average storage modulus from 30° C. to 100° C. was calculated. The modulus of elasticity. The elastic modulus in the direction parallel to the long side direction of the liquid crystal display device was measured.

(4) Thermal shrinkage rate and inclination of shrinkage principal axis For the thermal shrinkage rate and inclination of the shrinkage principal axis of the polarizer and polyester film, draw a circle with a diameter of 80mm after standing for 168 hours in an environment of 25°C and 50RH%. Using a dimension measuring instrument (IM6500 manufactured by KEYENCE), the length was measured every 1° and taken as the length before treatment. Next, heat treatment is performed for 30 minutes using a gear oven set at 100° C., then after cooling for 10 minutes in an environment set at room temperature 25° C., evaluation is performed every 1° in the same manner as before treatment. , the length after treatment.

The thermal shrinkage rate in the present invention is defined by the value in the direction parallel to the long side direction of the liquid crystal display device among the thermal shrinkage rates calculated by the following formula.
Heat shrinkage = (length before treatment - length after treatment) / length before treatment x 100
The inclination of the principal axis of shrinkage is the angle at which the thermal shrinkage rate measured every 1° is maximum, and is defined as a narrow angle from the direction of the long side or the direction of the short side. That is, the inclination of the contraction principal axis is in the range of 0 to 45°.

(5) Inclination of main axis of orientation The inclination of the main axis of orientation of the polyester film is determined by measuring the main axis of orientation using a molecular orienter (manufactured by Oji Keisoku Co., Ltd., MOA-6004 molecular orienter), and measuring in the long side direction or the short side. Defined at a narrow angle from the direction. That is, the inclination of the main axis of orientation is in the range of 0 to 45°.

(6) Curl height In the preparation of the liquid crystal panel prepared in each example described later, "a 50-inch size IPS type liquid crystal cell using a glass substrate with a thickness of 0.4 mm" is defined as "the length in the short side direction A liquid crystal panel for evaluation was prepared in the same manner, except that the glass plate was 125 mm long, 220 mm long and 0.4 mm thick. Next, the liquid crystal panel for evaluation was heat-treated for 30 minutes using a gear oven set to 100° C., then cooled for 10 minutes in an environment set to room temperature of 25° C. and 50% RH. and placed on a horizontal surface, the height of the four corners was measured with a tape measure, and the maximum value was taken as the curl height. A maximum curl height of 5 mm or less was defined as a favorable range. Curl is a phenomenon that should be expressed by curvature, but for the sake of simplicity, it is evaluated by height. In addition, the curl phenomenon becomes bowl-shaped as the sample size increases with respect to the stiffness of the sample, and a phenomenon in which the curvature is not constant in the film may occur, but the results of this example show that the curvature is constant is confirmed.

(7) Refractive index of polyester film Using a molecular orientation meter (manufactured by Oji Keisoku Co., Ltd., MOA-6004 type molecular orientation meter), the slow axis direction of the film is determined, and the slow axis direction is the long side of the sample for measurement. A rectangle of 4 cm x 2 cm was cut out so as to be parallel to , and used as a measurement sample. For this sample, the refractive index in the orthogonal biaxial direction (refractive index in the slow axis direction: Ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): Nx), and the refractive index in the thickness direction ( Nz) was determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., measuring wavelength 589 nm). These values were used to determine the NZ coefficient.

(8) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|Nx−Ny|) on the film and the film thickness d (nm). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the slow axis direction of the film was determined, and the slow axis direction was 4 cm so that it was parallel to the long side of the sample for measurement. A 2 cm x 2 cm rectangle was cut out and used as a measurement sample. For this sample, the refractive index in the biaxial direction perpendicular to each other (refractive index in the slow axis direction: Ny, refractive index in the direction perpendicular to the slow axis direction: Nx) and the refractive index in the thickness direction (Nz) were measured by the Abbe refractor. The absolute value of the biaxial refractive index difference (|Nx−Ny|) was defined as the anisotropy of the refractive index (ΔNxy) by using an index meter (NAR-4T, manufactured by Atago Co., measuring wavelength: 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co.) and converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(9) Thickness direction retardation (Rth)
The retardation in the thickness direction is obtained by multiplying the two birefringences ΔNxz (=|Nx−Nz|) and ΔNyz (=|Ny−Nz|) when viewed from the cross section in the thickness direction of the film by the film thickness d. is a parameter that indicates the average retardation obtained by Obtain Nx, Ny, Nz and film thickness d (nm) in the same manner as in the measurement of retardation, calculate the average value of (ΔNxz × d) and (ΔNyz × d), and calculate the thickness direction retardation (Rth ).

(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged, and 0.017 parts by mass of antimony trioxide as a catalyst was added while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Then, the temperature was increased under pressure to carry out a pressure esterification reaction under conditions of a gauge pressure of 0.34 MPa and 240° C., after which the pressure in the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, dispersion treatment was performed with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was performed at 280°C under reduced pressure.

After the completion of the polycondensation reaction, it is filtered through a NASLON filter with a 95% cut diameter of 5 μm, extruded from a nozzle in the form of a strand, and cooled and solidified using cooling water that has been previously filtered (pore size: 1 μm or less). , cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g and contained substantially no inert particles or internal precipitated particles. (Hereinafter abbreviated as PET (A).)

(Production Example 2-Polyester B)
10 parts by weight of dried UV absorber (2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one), particle-free PET (A) (intrinsic viscosity is 0.62 dl/g), and a kneading extruder was used to obtain a polyethylene terephthalate resin (B) containing an ultraviolet absorber (hereinafter abbreviated as PET (B)).

(Production Example 3-Adhesion-improving coating liquid preparation)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method to obtain 46 mol % of terephthalic acid, 46 mol % of isophthalic acid and 8 mol % of sodium 5-sulfonatoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components). A water-dispersible sulfonic acid metal base-containing copolymer polyester resin was prepared having a composition of 50 mol % ethylene glycol and 50 mol % neopentyl glycol as the glycol component (relative to the total glycol component). Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant are mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal group-containing copolymerized polyester resin and continuing to stir until the lumps of the resin disappear, the resin aqueous dispersion was cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A homogeneous water-dispersible copolyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silysia 310) in 50 parts by mass of water, Silysia 310 was added to 99.46 parts by mass of the water-dispersible copolymer polyester resin liquid. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added while stirring to obtain an adhesion-improving coating liquid.

(Example 1)
After drying under reduced pressure (1 Torr) at 135° C. for 6 hours, 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber as raw materials for the base film intermediate layer. , supplied to extruder 2 (for intermediate layer II layer), and PET (A) was dried by a conventional method, supplied to extruder 1 (for outer layer I layer and outer layer III), and melted at 285 ° C. . These two types of polymers are each filtered with a stainless sintered filter material (nominal filtration accuracy: 10 μm, 95% cut of particles), laminated in a two-type, three-layer confluence block, extruded in a sheet form from a nozzle, An unstretched film was produced by winding the film around a casting drum having a surface temperature of 30° C. and solidifying it by cooling using an electrostatic casting method. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, the adhesion-improving coating solution was applied to both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g/m ² , and then dried at 80°C for 20 seconds. .

The unstretched film having the coating layer formed thereon was guided to a tenter stretching machine, and while holding the ends of the film with clips, was guided to a hot air zone at a temperature of 105° C. and stretched 4.0 times in TD. Next, heat treatment is performed at a temperature of 180 ° C. for 30 seconds, then the film cooled to 100 ° C. is stretched 1% in MD, and then the clips holding both ends of the film cooled to 60 ° C. are released. The jumbo roll made of a uniaxially oriented PET film with a film thickness of about 80 μm is collected, and the obtained jumbo roll is divided into three equal parts, and three slit rolls (L (left side), C ( center), R (right side)). A polarizer protective film 1 was obtained from the slit roll positioned at R (the central portion of the slit roll positioned at R was used as the polarizer protective film 1).

A polarizer protective film 1 is attached to one side of a polarizer (shrinkage force in the direction of the absorption axis of the polarizer is 5100 N/m) made of PVA, iodine and boric acid so that the transmission axis of the polarizer and the MD of the film are parallel. attached. A TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 μm) was attached to the opposite surface of the polarizer. Thus, a polarizing plate (polarizing plate A) whose long side direction coincides with the transmission axis direction of the polarizer and a polarizing plate (polarizing plate B) whose long side direction coincides with the absorption axis direction of the polarizer were prepared. . A 50-inch size IPS type liquid crystal cell using a glass substrate with a thickness of 0.4 mm has a polarizing plate B on the viewing side, a polarizing plate A on the light source side, and a polarizer protective film 1 on the far side from the liquid crystal cell. A liquid crystal panel was prepared by pasting them together via PSA so that they were (opposite side). A liquid crystal display device was produced by incorporating this liquid crystal panel into a housing.

(Example 2)
A polarizer protective film 2 was obtained in the same manner as the polarizer protective film 1 in the film formation of the polarizer protective film 1 of Example 1, except that the film cooled to 100° C. was stretched by 2.5% in the longitudinal direction. . A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 2 in Example 1.

(Example 3)
A polarizer protective film 3 was obtained in the same manner as the polarizer protective film 1 of Example 1, except that the film cooled to 100° C. was stretched by 4% in the longitudinal direction. In Example 1, except that the polarizer having a shrinkage force in the direction of the absorption axis of 5100 N/m was replaced with a polarizer having a shrinkage force of 11200 N/m, and the polarizer protective film 1 was replaced with the polarizer protective film 3. A liquid crystal display device was produced in the same manner as above.

(Example 4)
Except for using a blend of 90% by mass of PET (A) and 10% by mass of PBT as raw materials for layers I, II, and III, and stretching the film by 4% in the longitudinal direction after cooling to 100°C. prepared a polarizer protective film 4 in the same manner as the polarizer protective film 1. In Example 1, except that the polarizer having a shrinkage force in the direction of the absorption axis of 5100 N/m was replaced with a polarizer having a shrinkage force of 11200 N/m, and the polarizer protective film 1 was replaced with the polarizer protective film 4. A liquid crystal display device was produced in the same manner as above. PBT used was Mitsubishi Engineering Plastics NV5020 (0.52 dl/g).

(Example 5)
A polarizer protective film 5 was obtained in the same manner as the polarizer protective film 1 except that the film thickness after stretching was 50 μm by adjusting the rotation speed of the casting roll. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 5 in Example 1.

(Example 6)
A polarizer protective film 6 was obtained in the same manner as the polarizer protective film 5 except that the film cooled to 100° C. was stretched by 2.5% in the longitudinal direction. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 6 in Example 1.

(Example 7)
A polarizer protective film 7 was obtained in the same manner as the polarizer protective film 5 except that the film cooled to 100° C. was stretched by 4% in the longitudinal direction.
Example 1 except that the polarizer having a shrinkage force in the direction of the absorption axis of 5100 N/m was replaced with a polarizer having a shrinkage force of 11200 N/m in Example 1, and the polarizer protective film 1 was replaced with the polarizer protective film 7. A liquid crystal display device was produced in the same manner as above.

(Example 8)
A polarizer protective film 8 was obtained in the same manner as the polarizer protective film 1 except that the film thickness after stretching was 160 μm by adjusting the rotation speed of the casting roll. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 8 in Example 1.

(Example 9)
A polarizer protective film 9 was obtained in the same manner as the polarizer protective film 8 except that the film cooled to 100° C. was stretched in the width direction by 2.5%. Next, the contraction force in the direction of the absorption axis is changed from 5100 N/m to 11200 N/m. A liquid crystal display device was obtained in the same manner as in Example 1, except that the plate A and the polarizing plate B were prepared, and that the polarizer protective film 1 was replaced with the polarizer protective film 9.

(Example 10)
A polarizer protective film 10 was obtained in the same manner as the polarizer protective film 1 except that the film was stretched 4.0 times in the MD and 1.0 times in the TD. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 10 in Example 1.

(Example 11)
A polarizer protective film 11 was obtained in the same manner as the polarizer protective film 10 except that the film cooled to 100° C. was stretched in MD by 1.5%. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 1 was replaced with the polarizer protective film 11 in Example 1.

(Example 12)
A polarizer protective film 12 was obtained in the same manner as the polarizer protective film 10 except that the film cooled to 100° C. was stretched in MD by 2.5%.
Same as Example 1, except that the shrinkage force in the absorption axis direction was changed from 5100 N/m to 11200 N/m, and that the polarizer protective film 1 was changed to the polarizer protective film 12. Thus, a liquid crystal display device was obtained.

(Example 13)
Except that a blend of 90% by mass of PET (A) and 10% by mass of PBT was used as the raw material for the I layer, II layer, and III layer, and that the film cooled to 100 ° C. was stretched 3% in MD. A polarizer protective film 13 was obtained in the same manner as the polarizer protective film 10 .
Same as Example 1, except that the polarizer having a shrinkage force in the direction of the absorption axis of 5100 N/m was replaced with a polarizer having a shrinkage force of 11200 N/m, and that the polarizer protective film 1 was replaced with the polarizer protective film 13. Thus, a liquid crystal display device was obtained. PBT used was Mitsubishi Engineering Plastics NV5020 (0.52 dl/g).

(Example 14)
A polarizer was prepared in the same manner as the polarizer protective film 10 except that the film thickness after stretching was 50 μm by adjusting the rotation speed of the casting roll, and the film cooled to 100 ° C. was stretched 1.5% in MD. A protective film 14 was obtained. A liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizer protective film 1 was replaced with the polarizer protective film 14 .

(Example 15)
A polarizer protective film 15 was obtained in the same manner as the polarizer protective film 14 except that the film cooled to 100° C. was stretched in MD by 2%. A liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizer protective film 1 was replaced with the polarizer protective film 15 .

(Example 16)
A polarizer protective film 16 was obtained in the same manner as the polarizer protective film 14 except that the film cooled to 100° C. was stretched in TD by 5%. Next, polarizing plate A and polarizing plate B were prepared by laminating the polarizer so that the transmission axis of the polarizer and the TD direction of the polarizer protective film were parallel, and polarizer protective film 1 was replaced with polarizer protective film 16. A liquid crystal display device was obtained in the same manner as in Example 1, except that

(Example 17)
A polarizer protective film 20 was obtained in the same manner as the polarizer protective film 10 except that the film cooled to 100° C. was stretched in MD by 2%. A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizer protective film 1 was replaced with the polarizer protective film 20 .

(Example 18)
A polarizer protective film 21 was obtained in the same manner as the polarizer protective film 10 except that the film cooled to 100° C. was stretched in MD by 2.5%. A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizer protective film 1 was replaced with the polarizer protective film 21 .

(Comparative example 1)
A polarizer protective film 17 was obtained in the same manner as the polarizer protective film 1 except that the clips holding both ends of the film were released at 95° C. in the cooling step after stretching and heat setting. Except that the polarizer protective film 1 was replaced with the polarizer protective film 17, and the polarizer A and the polarizer B were prepared by laminating the polarizer so that the transmission axis of the polarizer and the TD of the polarizer protective film were parallel. A liquid crystal display device was obtained in the same manner as in Example 1.

(Comparative example 2)
A polarizer protective film 18 was obtained in the same manner as the polarizer protective film 14 except that the film cooled to 100° C. was stretched in the width direction by 0.8%. A polarizer with a shrinkage force of 11200 N/m in the absorption axis direction was changed from a polarizer with a 5100 N/m contraction force, a polarizer protective film 1 was replaced with a polarizer protective film 18, and the transmission axis and polarization of the polarizer A liquid crystal display device was obtained in the same manner as in Example 1, except that the polarizing plate A and the polarizing plate B were prepared by laminating the protective films so that their TDs were parallel.

(Comparative Example 3)
A polarizer protective film 19 was obtained in the same manner as the polarizer protective film 8 except that the film cooled to 100° C. was stretched in the width direction by 0.3%. A polarizer with a shrinkage force of 11200 N/m in the absorption axis direction was changed from a polarizer with a 5100 N/m contraction force, a polarizer protective film 1 was replaced with a polarizer protective film 19, and the transmission axis and polarization of the polarizer A liquid crystal display device was obtained in the same manner as in Example 1, except that the polarizing plate A and the polarizing plate B were prepared by laminating the protective films so that their TDs were parallel.

The liquid crystal panels of the liquid crystal display devices of Examples 1 to 18 and the liquid crystal panels of the liquid crystal display devices of Comparative Examples 1 to 3 were heat-treated for 30 minutes using a gear oven set at 100 ° C., and then at room temperature 25. After cooling for 10 minutes in an environment set at ° C. and 50 RH%, the liquid crystal panel was observed. No curling was observed in Examples 1 to 16, but curling was observed in Comparative Examples 1 to 3. .

Table 1 shows the measurement results of each example.

According to the present invention, it is possible to provide a liquid crystal display device in which the curling of the laminate consisting of polarizing plate/liquid crystal cell/polarizing plate is highly controlled.

Claims (6)

A method for manufacturing a liquid crystal panel,
A step of stretching the polyester film in the TD direction in the cooling process after stretching and heat setting to obtain a polyester film having a shrinkage force in the TD direction of 1100 N/m or more;
obtaining a polarizer composed of PVA , iodine and boric acid;
A process of obtaining a viewer-side polarizing plate and a light source-side polarizing plate by pasting together so that the TD direction of the polyester film and the transmission axis direction of the polarizer are parallel,
The viewing side polarizing plate is arranged such that the absorption axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device, and the polyester film is arranged on the surface of the polarizer on the distal side with respect to the liquid crystal cell. A step of bonding to the viewing side of the liquid crystal cell in such a manner as to
The light source side polarizing plate is arranged such that the transmission axis direction of the polarizer is parallel to the long side direction of the liquid crystal display device, and the polyester film is arranged on the surface of the polarizer on the distal side with respect to the liquid crystal cell. A step of bonding to the light source side of the liquid crystal cell,
including
In both the viewer-side polarizing plate and the light source-side polarizing plate, the contraction force in the TD direction of the polyester film and the contraction force in the absorption axis direction of the polarizer satisfy the relationship of the following formula,
0.1 ≤ shrinkage force in the TD direction of the polyester film/shrinkage force in the absorption axis direction of the polarizer ≤ 2
(However, the shrinkage force ( N/m) in the TD direction of the polyester film is the thickness (mm) of the polyester film x the elastic modulus (N/mm ² ) in the TD direction x the heat shrinkage rate (%) / 100 x 1000. The shrinkage force of the polarizer in the direction of the absorption axis is the thickness of the polarizer (mm) × the elastic modulus of the polarizer in the direction of the absorption axis (N/mm 2 ) × the thermal contraction rate of the polarizer in the direction of the absorption axis (% ⁾ . ÷ 100 × 1000)
Both the viewer-side polarizing plate and the light source-side polarizing plate have a polarizer and the polyester film as a polarizer protective film on one side of the polarizer, and a protective film or optical film on the other side of the polarizer. A TAC film, a cyclic olefin film or an acrylic film is laminated as a compensation film, or a protective film or an optical compensation film is not laminated.
A method for manufacturing a liquid crystal panel. The method according to claim 1, wherein the polyester film has a shrinkage force in the TD direction of 1280 N/m or more. 3. The method according to claim 1, wherein the polyester film has a shrinkage force in the TD direction of 10000 N/m or less. 4. The method according to any one of claims 1 to 3 , wherein the inclination of the principal axis of orientation with respect to the TD direction of the polyester film is 15 degrees or less. 5. The method according to any one of claims 1 to 4 , wherein the inclination of the principal axis of shrinkage with respect to the TD direction of the polyester film is 15 degrees or less. A method for manufacturing a liquid crystal display device using the liquid crystal panel obtained by the method according to any one of claims 1 to 5 .