JP7591014B2 - Method for manufacturing polarizing plate with anti-reflection layer - Google Patents

Description

The present invention relates to a method for producing a polarizing plate with an anti-reflection layer.

Anti-reflection films are placed on the viewing side of image display devices such as liquid crystal displays and organic EL displays to prevent degradation of image quality due to reflection of external light and to improve contrast. Anti-reflection films have an anti-reflection layer made of a laminate of multiple thin films with different refractive indices on a film substrate.

One form of anti-reflection film is a polarizing plate with an anti-reflection layer (polarizing film with an anti-reflection layer). A polarizing plate with an anti-reflection layer is formed by laminating an anti-reflection film on the surface of a polarizing plate, or by laminating an anti-reflection film as a protective film on the surface of a polarizer. A method of forming a polarizing plate with an anti-reflection layer by forming an anti-reflection layer on a polarizing plate is also known (for example, Patent Document 1).

JP 2014-34701 A

Anti-reflective layers reduce the reflectance of visible light by utilizing the multiple reflection interference of a thin film. Therefore, if the refractive index or thickness of the thin film fluctuates, the reflected light characteristics such as the reflectance and the hue of the reflected light change. Even if the thin film formation conditions are strictly controlled and kept constant when forming an anti-reflective layer, the film thickness and refractive index may fluctuate due to variations in the characteristics of the raw materials and changes in the film formation environment over time.

In film manufacturing, in-line measurements are performed during the manufacturing process, and the measurement results are fed back to the previous process to maintain consistent film quality. For example, in Patent Document 1, in-line inspection is performed in the manufacturing process of a polarizing plate with an anti-reflection layer, in which the reflected light characteristics are measured in-line, and the measurement results are fed back to the thin film deposition conditions.

However, the technology described in Patent Document 1 still has room for improvement in terms of maintaining uniformity in the reflected light characteristics of a polarizing plate with an anti-reflection layer.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a method for manufacturing a polarizing plate with an anti-reflection layer that can maintain uniform reflected light characteristics.

<Aspects of the present invention>
The present invention includes the following aspects.

[1] A method for producing a polarizing plate with an antireflection layer, the polarizing plate having a film substrate and an antireflection layer provided on one main surface side of the film substrate, comprising the steps of:
a step Sa of forming the antireflection layer consisting of two or more thin films on the one main surface side of the film substrate;
and a step Sb of depositing at least one layer constituting the anti-reflection layer, irradiating the layer with visible light, and detecting reflected light,
The steps Sa and Sb are continuously performed while transporting the film substrate in one direction,
the film substrate is a laminate having, in this order, a first protective film, a first adhesive layer, a polarizer, a second adhesive layer, and a second protective film;
the first protective film and the polarizer are bonded to each other via the first adhesive layer,
the second protective film and the polarizer are bonded to each other via the second adhesive layer,
the first protective film and the second protective film each have a width greater than that of the polarizer and protrude from both ends of the polarizer in a width direction,
A method for manufacturing a polarizing plate with an antireflection layer, wherein the distance between the first protective film and the second protective film in at least a portion of the protruding portions from both ends is narrower than the distance between the first protective film and the second protective film at a location where the polarizer is sandwiched between the widthwise ends of the polarizer.

[2] The method for producing a polarizing plate with an antireflection layer according to [1], in which, in step Sb, after all layers constituting the antireflection layer are formed, visible light is irradiated onto the antireflection layer and the reflected light is detected.

[3] The method for manufacturing a polarizing plate with an antireflection layer according to [1] or [2], wherein the deposition conditions of the antireflection layer in the step Sa are adjusted according to the detection result of the reflected light in the step Sb.

[4] The method for producing a polarizing plate with an anti-reflection layer according to any one of [1] to [3], wherein in step Sb, visible light is irradiated to multiple locations in the width direction of the layer, and the reflected light is detected.

[5] The method for producing a polarizing plate with an antireflection layer according to any one of [1] to [4], wherein in step Sa, the antireflection layer is formed by a sputtering method.

[6] The method for producing a polarizing plate with an anti-reflection layer described in any one of [1] to [5], wherein the film substrate further comprises a third adhesive layer that bonds the first protective film and the second protective film in at least a portion of the width direction of the portions protruding from both ends.

[7] The second protective film comprises a transparent film and a hard coat layer provided on one main surface side of the transparent film,
The method for producing a polarizing plate with an antireflection layer according to any one of [1] to [6], wherein in the step Sa, the antireflection layer is formed on a side of the hard coat layer opposite to the transparent film side.

[8] The film substrate further includes a pressure-sensitive adhesive layer provided on a side of the first protective film opposite to the polarizer side,
The method for producing a polarizing plate with an antireflection layer according to any one of [1] to [7], wherein in the step Sa, the antireflection layer is formed on a side of the second protective film opposite to the polarizer side.

[9] The method for producing a polarizing plate with an anti-reflection layer described in [8], wherein the film substrate further comprises a release liner temporarily attached to the side of the pressure-sensitive adhesive layer opposite the first protective film.

[10] The method further includes a step Sc of forming a primer layer on the one main surface side of the film substrate before the step Sa,
The method for producing a polarizing plate with an antireflection layer according to any one of [1] to [9], wherein in the step Sa, the antireflection layer is formed on a main surface of the primer layer opposite to the film substrate.

The present invention provides a method for manufacturing a polarizing plate with an anti-reflection layer that can maintain uniform light reflection characteristics.

FIG. 2 is a cross-sectional view showing an example of a film substrate. FIG. 4 is a cross-sectional view showing another example of a film substrate. FIG. 4 is a cross-sectional view showing another example of a film substrate. FIG. 2 is a schematic diagram illustrating an example of a film forming apparatus for an antireflection layer. 1A, 1B and 1C are cross-sectional views illustrating steps in one example of a method for producing a polarizing plate with an antireflection layer according to the present invention. 1 is a graph showing the hue of light reflected from an antireflection layer before and after adjustment of film formation conditions in Examples. 1 is a graph showing the hue of light reflected from an antireflection layer after adjusting the film formation conditions in an example. 1 is a graph showing the hue of light reflected from an antireflection layer before and after adjustment of film formation conditions in a comparative example. 11 is a graph showing the hue of light reflected from an antireflection layer after adjusting the film formation conditions of a comparative example.

Preferred embodiments of the present invention are described in detail below, but the present invention is not limited to these. In addition, all academic and patent literature described in this specification is incorporated herein by reference.

First, the terms used in this specification are explained. "Refractive index" refers to the refractive index for light with a wavelength of 550 nm in an atmosphere at a temperature of 23°C. The "principal surface" of a layered material (more specifically, a film substrate, a first protective film, a second protective film, a transparent film, a hard coat layer, a primer layer, an adhesive layer, a release liner, a polarizer, etc.) refers to a surface perpendicular to the thickness direction of the layered material.

"Bombardment" refers to a surface treatment in which the surface of a film substrate is plasma-treated while a specific gas (rare gas, oxygen gas, etc.) is introduced.

Unless otherwise specified, the number-average primary particle diameter of particles is the number-average circle-equivalent diameter (Heywood diameter: diameter of a circle having the same area as the projected area of a primary particle) of 100 primary particles measured using a scanning electron microscope and image processing software (e.g., "ImageJ" manufactured by the National Institutes of Health, USA).

The unit of flow rate "sccm (Standard Cubic Centimeter per Minute)" is the unit of flow rate "mL/min" under standard conditions (temperature: 0°C, pressure: 101.3 kPa).

Hereinafter, the compound name may be followed by "system" to collectively refer to the compound and its derivatives. Also, when the compound name is followed by "system" to refer to the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative.

Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more types.

The drawings referred to in the following description show each component mainly in a schematic manner for ease of understanding, and the size, number, shape, etc. of each component shown may differ from the actual size due to the convenience of creating the drawings. Also, for the convenience of explanation, in drawings described later, the same components as those in previously explained drawings may be given the same reference numerals and their explanation may be omitted.

<Method of manufacturing a polarizing plate with an antireflection layer>
The manufacturing method of the polarizing plate with an antireflection layer according to the present embodiment is a manufacturing method of a polarizing plate with an antireflection layer having a film substrate and an antireflection layer provided on one main surface side of the film substrate, and includes steps Sa and Sb. In step Sa, an antireflection layer consisting of two or more thin layers is formed on one main surface side of the film substrate. In step Sb, after forming at least one layer constituting the antireflection layer, the layer is irradiated with visible light and the reflected light is detected (in-line reflected light measurement). Steps Sa and Sb are performed continuously while transporting the film substrate in one direction. The film substrate is a laminate having a first protective film, a first adhesive layer, a polarizer, a second adhesive layer, and a second protective film in this order. The first protective film and the polarizer are bonded via the first adhesive layer. The second protective film and the polarizer are bonded via the second adhesive layer. Both the first protective film and the second protective film are wider than the polarizer and protrude from both ends in the width direction of the polarizer. The distance between the first protective film and the second protective film in at least a portion of the portions protruding from both ends of the polarizer in the width direction is narrower than the distance between the first protective film and the second protective film at the portion where the ends of the polarizer in the width direction are sandwiched.

According to this embodiment, since it has the above configuration, it is possible to provide a manufacturing method for a polarizing plate with an antireflection layer that can maintain uniform reflected light characteristics. Hereinafter, step Sa may be referred to as the "antireflection layer forming step." Also, step Sb may be referred to as the "in-line reflected light measuring step."

Hereinafter, the details of the manufacturing method of the polarizing plate with an anti-reflection layer according to this embodiment will be described with reference to the drawings as appropriate. First, the film substrate will be described.

[Film substrate]
FIG. 1 is a cross-sectional view showing an example of a film substrate usable in this embodiment. The film substrate 10 shown in FIG. 1 is a laminate having a first protective film 11, a first adhesive layer 12, a polarizer 13, a second adhesive layer 14, and a second protective film 15 in this order. The second protective film 15 includes a transparent film 16 and a hard coat layer 17 provided on one main surface side of the transparent film 16 (main surface 16a opposite to the second adhesive layer 14 side of the transparent film 16 in FIG. 1). The first protective film 11 and the polarizer 13 are bonded via the first adhesive layer 12. The second protective film 15 and the polarizer 13 are bonded via the second adhesive layer 14. Both the first protective film 11 and the second protective film 15 are wider than the polarizer 13 and protrude from both ends of the polarizer 13 in the width direction. The distance _D1 between the first protective film 11 and the second protective film 15 in at least a portion of the portion P protruding from both ends of the width direction of the polarizer 13 is narrower than the distance _D2 between the first protective film 11 and the second protective film 15 at the portion where the ends of the width direction of the polarizer 13 are sandwiched.

In general, a film substrate for a polarizing plate with an anti-reflection layer is used in a state in which the protruding portion P is slit when the anti-reflection layer described later is formed. The inventors have found that when the protruding portion P is slit, the moisture in the polarizer 13 is easily evaporated from the end face of the polarizer 13 when the anti-reflection layer is formed, and as a result, the reflected light characteristics tend to vary in the longitudinal or width direction of the obtained polarizing plate with an anti-reflection layer. In detail, when a film substrate with the protruding portion P slit is used, the moisture in the polarizer 13 is easily evaporated from the end face of the polarizer 13, and the gas composition in the film formation chamber when the anti-reflection layer is formed (especially the gas composition near the end face of the polarizer 13) tends to fluctuate. As a result, the thickness of the anti-reflection layer tends to vary greatly in the longitudinal or width direction of the obtained polarizing plate with an anti-reflection layer. Therefore, if a film substrate in which the protruding portion P is slit is used, the thickness of the antireflection layer will vary greatly in the longitudinal or width direction, and the reflected light characteristics (e.g., hue, etc.) will tend to vary in the longitudinal or width direction of the polarizing plate with the antireflection layer.

In this embodiment, the distance D ₁ between the first protective film 11 and the second protective film 15 at at least a part of the protruding portion P is narrower than the distance D ₂ between the first protective film 11 and the second protective film 15 at the portion where the end of the polarizer 13 in the width direction is sandwiched, so that it is considered that gas is less likely to be released from the end face of the polarizer 13 due to pressure loss. Therefore, in this embodiment, it is presumed that the evaporation of moisture from the end face of the polarizer 13 is suppressed, and as a result, the fluctuation of the gas composition in the film formation chamber when forming the antireflection layer is suppressed. This makes it easy to adjust the film formation conditions of the antireflection layer using the detection results obtained in the in-line reflected light measurement process described later, so that the variation in the thickness of the antireflection layer in the longitudinal direction or the width direction of the obtained polarizing plate with the antireflection layer is reduced. Therefore, according to this embodiment, the variation in the thickness of the antireflection layer in the longitudinal direction or the width direction is reduced, so that the variation in the reflected light characteristics (e.g., hue, etc.) in the longitudinal direction or the width direction of the polarizing plate with the antireflection layer is reduced. Therefore, according to this embodiment, it is possible to provide a method for manufacturing a polarizing plate with an antireflection layer, which is capable of maintaining uniform light reflection characteristics.

As a method for making the distance D ₁ narrower than the distance D ₂ , a method utilizing the curing shrinkage of an adhesive for forming the first adhesive layer 12 and the second adhesive layer 14 can be mentioned. In detail, when the first protective film 11 and the polarizer 13 are bonded with an adhesive while the second protective film 15 and the polarizer 13 are bonded with an adhesive, the ends of the first protective film 11 and the second protective film 15 are attracted to each other due to the curing shrinkage of the adhesive. In addition, the ends of the first protective film 11 and the second protective film 15 are also attracted to each other due to the interfacial tension when the adhesive spreads in the vicinity of the end in the width direction of the polarizer 13. As a result, as shown in FIG. 1, a film substrate 10 in which the distance D ₁ is narrower than the distance D ₂ is obtained.

In order to further suppress evaporation of moisture from the end faces of the polarizer 13, as shown in FIG. 2, it is preferable to use a film substrate 20 that further includes a third adhesive layer 21 that bonds the first protective film 11 and the second protective film 15 in at least a portion of the width direction of the portion P that protrudes from both ends. The adhesive that is the material for the third adhesive layer 21 can be the same type as or a different type of adhesive from the adhesive that is the material for the first adhesive layer 12 and the second adhesive layer 14. The adhesive that is the material for the third adhesive layer 21 can be, for example, an adhesive listed as the material for the first adhesive layer 12 described below.

In order to further suppress the evaporation of moisture from the end face of the polarizer 13, it is preferable that the third adhesive layer 21 is formed integrally with the first adhesive layer 12 and the second adhesive layer 14 as shown in FIG. 2. In order to further suppress the evaporation of moisture from the end face of the polarizer 13, it is preferable that the end face in the width direction of the polarizer 13 is sealed with the third adhesive layer 21 as shown in FIG. 2. When the third adhesive layer 21 is formed integrally with the first adhesive layer 12 and the second adhesive layer 14, the amount of adhesive applied may be adjusted so that the adhesive overflows onto the protruding portion P when the first protective film 11 and the polarizer 13 are bonded with the adhesive, and when the second protective film 15 and the polarizer 13 are bonded with the adhesive.

Next, the elements of the film substrate 10 will be described.

(First protective film 11)
The first protective film 11 is, for example, a transparent resin film having flexibility. Examples of materials constituting the first protective film 11 include polyester resin, polyolefin resin, polystyrene resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, cellulose resin, norbornene resin, polyarylate resin, and polyvinyl alcohol resin. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of cellulose resins include triacetyl cellulose (TAC). These materials may be used alone or in combination of two or more. From the viewpoint of transparency and strength, the material of the first protective film 11 is preferably one selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin, more preferably one selected from the group consisting of PET, COP, and TAC, and even more preferably TAC. In other words, as the first protective film 11, a type of film selected from the group consisting of polyester resin film, polyolefin resin film, and cellulose resin film is preferable, a type of film selected from the group consisting of PET film, COP film, and TAC film is more preferable, and a TAC film is even more preferable.

From the viewpoint of strength, the thickness of the first protective film 11 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. From the viewpoint of handleability, the thickness of the first protective film 11 is preferably 300 μm or less, and more preferably 200 μm or less.

One or both main surfaces of the first protective film 11 may be subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

The total light transmittance (JIS K 7375-2008) of the first protective film 11 is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more and 100% or less, from the viewpoint of improving the transparency of the polarizing plate with an anti-reflection layer.

(Polarizer 13)
Examples of the polarizer 13 include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine and dichroic dyes, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among them, polyvinyl alcohol (PVA)-based polarizers are preferred, since they have a high polarization degree, and are obtained by adsorbing dichroic substances such as iodine and dichroic dyes to polyvinyl alcohol films such as partially formalized polyvinyl alcohol and oriented in a predetermined direction. The thickness of the polarizer 13 is, for example, 5 μm or more and 100 μm or less.

(Transparent film 16)
The material of the transparent film 16 is preferably the same as the material of the first protective film 11 described above. The preferred thickness range of the transparent film 16 is also the same as the preferred thickness range of the first protective film 11 described above. The material of the transparent film 16 and the material of the first protective film 11 may be the same type or different types. The thickness of the transparent film 16 and the thickness of the first protective film 11 may be the same or different.

(First adhesive layer 12)
The adhesive that is the material of the first adhesive layer 12 can be appropriately selected and used from those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyvinyl alcohol, a polyvinyl ether, a vinyl acetate/vinyl chloride copolymer, a modified polyolefin, an epoxy polymer, a fluorine-based polymer, or a rubber polymer. A polyvinyl alcohol-based adhesive is preferably used for bonding a PVA-based polarizer. The thickness of the first adhesive layer 12 is, for example, 0.1 μm or more and 5.0 μm or less, and preferably 0.2 μm or more and 3.0 μm or less.

(Second adhesive layer 14)
The adhesive that is the material of the second adhesive layer 14 is preferably the same as the adhesive that is the material of the first adhesive layer 12 described above. The preferred thickness range of the second adhesive layer 14 is also the same as the preferred thickness range of the first adhesive layer 12 described above. The adhesive that is the material of the second adhesive layer 14 and the adhesive that is the material of the first adhesive layer 12 may be the same type or different types. The thickness of the second adhesive layer 14 and the thickness of the first adhesive layer 12 may be the same or different.

(Hard Coat Layer 17)
The hard coat layer 17 is a layer that enhances mechanical properties such as hardness and elastic modulus of the anti-reflection layer-attached polarizing plate. The hard coat layer 17 is, for example, made of a cured product of a curable resin composition (composition for forming a hard coat layer). Examples of the curable resin contained in the curable resin composition include polyester resin, acrylic resin, urethane resin, urethane acrylate resin, amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more kinds. From the viewpoint of increasing the hardness of the hard coat layer 17, the curable resin is preferably one or more selected from the group consisting of acrylic resin and urethane acrylate resin, and more preferably urethane acrylate resin.

In addition, examples of the curable resin composition include an ultraviolet-curable resin composition and a thermosetting resin composition. From the viewpoint of improving the productivity of the polarizing plate with an antireflection layer, the curable resin composition is preferably an ultraviolet-curable resin composition. The ultraviolet-curable resin composition includes one or more selected from the group consisting of an ultraviolet-curable monomer, an ultraviolet-curable oligomer, and an ultraviolet-curable polymer. A specific example of the ultraviolet-curable resin composition is a composition for forming a hard coat layer described in JP-A-2016-179686.

The curable resin composition may also contain particles having a number-average primary particle diameter of 0.5 μm or more (hereinafter, sometimes referred to as "microparticles"). That is, the hard coat layer 17 may contain microparticles. By blending microparticles in the curable resin composition, it is possible to adjust the hardness, surface roughness, refractive index, and anti-glare properties of the hard coat layer 17. Examples of microparticles include metal (or semi-metal) oxide particles, glass particles, and organic particles. Examples of materials for metal (or semi-metal) oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of materials for organic particles include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

In order to easily adjust the antiglare properties of the hard coat layer 17, the number average primary particle diameter of the microparticles is preferably 1.0 μm or more and 5.0 μm or less, and more preferably 2.0 μm or more and 4.0 μm or less.

In order to easily adjust the antiglare properties of the hard coat layer 17, the amount of microparticles in the hard coat layer 17 is preferably 5 parts by weight or more, and may be 10 parts by weight or more, 20 parts by weight or more, or 30 parts by weight or more, relative to 100 parts by weight of the curable resin. The upper limit of the amount of microparticles in the hard coat layer 17 is, for example, 90 parts by weight, preferably 80 parts by weight, and may be 70 parts by weight, relative to 100 parts by weight of the curable resin.

The curable resin composition may also contain particles having a number-average primary particle diameter of less than 0.5 μm (hereinafter, sometimes referred to as "nanoparticles"). When the hard coat layer 17 is made of a cured product of a curable resin composition containing nanoparticles, fine irregularities are formed on the surface of the hard coat layer 17, which tends to improve adhesion between the hard coat layer 17 and the layer formed thereon.

From the viewpoint of forming a fine uneven shape that contributes to improved adhesion, the number average primary particle diameter of the nanoparticles is preferably 20 nm or more and 80 nm or less, more preferably 25 nm or more and 70 nm or less, and even more preferably 30 nm or more and 60 nm or less.

As the material for the nanoparticles, inorganic oxides are preferred. Examples of inorganic oxides include oxides of metals (or semi-metals), such as silicon oxide (silica), titanium oxide, aluminum oxide, zirconium oxide, niobium oxide, zinc oxide, tin oxide, cerium oxide, and magnesium oxide. The inorganic oxide may be a composite oxide of multiple (semi-)metals. Among the inorganic oxides listed above, silicon oxide is preferred because of its high adhesion improving effect. In other words, silicon oxide particles (silica particles) are preferred as nanoparticles. Functional groups such as acrylic groups and epoxy groups may be introduced onto the surface of inorganic oxide particles as nanoparticles in order to increase adhesion and affinity with resins.

The amount of nanoparticles in the hard coat layer 17 is preferably 5 parts by weight or more, and may be 10 parts by weight or more, 20 parts by weight or more, or 30 parts by weight or more, based on 100 parts by weight of the curable resin. If the amount of nanoparticles is 5 parts by weight or more, the adhesion with the layer formed on the hard coat layer 17 can be further improved. The upper limit of the amount of nanoparticles in the hard coat layer 17 is, for example, 90 parts by weight, preferably 80 parts by weight, and may be 70 parts by weight, based on 100 parts by weight of the curable resin.

The curable resin composition (composition for forming a hard coat layer) contains, for example, the above-mentioned curable resin and a polymerization initiator (e.g., a photopolymerization initiator), and optionally contains a solvent capable of dissolving or dispersing these components. In addition to the above-mentioned components, the curable resin composition (composition for forming a hard coat layer) may contain additives such as microparticles, nanoparticles, leveling agents, viscosity adjusters (thixotropic agents, thickeners, etc.), antistatic agents, antiblocking agents, dispersants, dispersion stabilizers, antioxidants, UV absorbers, defoamers, surfactants, and lubricants.

The thickness of the hard coat layer 17 is preferably 1 μm or more, more preferably 2 μm or more, from the viewpoint of increasing the hardness of the hard coat layer 17. The thickness of the hard coat layer 17 is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less, from the viewpoint of ensuring the flexibility of the polarizing plate with an antireflection layer.

(Method of forming hard coat layer 17)
The hard coat layer 17 is formed, for example, by applying a curable resin composition (composition for forming a hard coat layer) to one main surface of the transparent film 16 (in FIG. 1, the main surface 16a of the transparent film 16 opposite the second adhesive layer 14), and removing the solvent and curing the resin as necessary. By providing the hard coat layer 17 on one main surface of the transparent film 16, a second protective film 15 including the transparent film 16 and the hard coat layer 17 can be obtained as shown in FIG. 1.

As the coating method of the composition for forming a hard coat layer, any suitable method such as a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method, a comma coating method, etc. may be adopted. The drying temperature of the coating film after coating may be set to an appropriate temperature according to the composition of the composition for forming a hard coat layer, for example, 50°C or more and 150°C or less. When the resin component in the composition for forming a hard coat layer is a thermosetting resin, the coating film is cured by heating. When the resin component in the composition for forming a hard coat layer is a photocurable resin, the coating film is cured by irradiating it with active energy rays such as ultraviolet rays. The integrated light amount of the irradiation light is preferably 100 mJ/ ^cm2 or more and 500 mJ/ ^cm2 or less.

In order to increase the adhesion between the hard coat layer 17 and the layer formed thereon, the main surface of the hard coat layer 17 opposite the transparent film 16 may be bombarded. The gas used for the bombardment is preferably at least one selected from the group consisting of rare gases (specifically, argon gas, etc.) and oxygen gas.

In order to further increase the adhesion between the hard coat layer 17 and the layer formed thereon, it is preferable to bombard the main surface of the hard coat layer 17 opposite the transparent film 16 under pressure conditions of 0.1 Pa or more and 1.0 Pa or less.

In order to further increase the adhesion between the hard coat layer 17 and the layer formed thereon, the effective power density in the bombardment process is preferably 0.01 W·min/cm ² ·m or more, more preferably 0.02 W·min/cm ² ·m or more, and even more preferably 0.03 W·min/cm ² ·m or more. In order to suppress deformation of the film substrate in the bombardment process, the effective power density in the bombardment process is preferably 0.60 W·min/cm ² ·m or less, more preferably 0.55 W·min/cm ² ·m or less, and even more preferably 0.50 W·min/cm ² ·m or less. The effective power density is the value obtained by dividing the power density (W/cm ² ) of the plasma output by the film transport speed (m/min) by the roll-to-roll method. Even if the plasma output is the same, if the transport speed is high, the effective processing power decreases.

Although examples of film substrates that can be used in this embodiment have been described above, the film substrates that can be used in the present invention are not limited to the above-mentioned examples. For example, the film substrates that can be used in the present invention do not need to have a hard coat layer. When the film substrate does not have a hard coat layer, for example, a transparent film can be used as the second protective film.

In addition, in the present invention, a film substrate 30 may be used that further includes an adhesive layer 31 provided on the side of the first protective film 11 opposite the polarizer 13 side, as shown in FIG. 3. In the film substrate 30 shown in FIG. 3, the adhesive layer 31 is provided on the main surface 11a of the first protective film 11 opposite the polarizer 13 side.

The adhesive constituting the adhesive layer 31 is not particularly limited, and can be appropriately selected and used from transparent adhesives whose base polymer is, for example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyvinyl ether, a vinyl acetate-vinyl chloride copolymer, a modified polyolefin, an epoxy resin, a fluororesin, natural rubber, synthetic rubber, or the like. The thickness of the adhesive layer 31 is not particularly limited, but is preferably 5 μm or more and 100 μm or less from the viewpoint of achieving both a thin layer property and adhesiveness.

As shown in FIG. 3, a release liner 32 may be temporarily attached to the main surface 31a of the adhesive layer 31 opposite to the first protective film 11 side. The release liner 32 protects the surface of the adhesive layer 31, for example, until the polarizing plate with the anti-reflection layer is bonded to an image display cell (not shown). As a constituent material of the release liner 32, a plastic film formed from acrylic, polyolefin, cyclic polyolefin, polyester, etc. is preferably used. The thickness of the release liner 32 is, for example, 5 μm or more and 200 μm or less. The surface of the release liner 32 is preferably subjected to a release treatment. Examples of materials of the release agent used in the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, fatty acid amide-based materials, etc.

[Anti-reflection layer forming process and in-line reflected light measuring process]
Next, the antireflection layer forming process and the in-line reflected light measuring process will be described with reference to Fig. 4 and Figs. 5A to C. Fig. 4 is a schematic diagram showing an example of a film forming apparatus for the antireflection layer. Figs. 5A to C are cross-sectional views showing an example of the antireflection layer forming process.

First, an example of a film forming apparatus for an anti-reflection layer will be described. The film forming apparatus shown in FIG. 4 is a film forming apparatus that can continuously perform the anti-reflection layer forming process and the in-line reflected light measuring process while transporting the film substrate in one direction, and can reflect the detection results in the in-line reflected light measuring process in the film forming conditions of the anti-reflection layer forming process. The film forming apparatus shown in FIG. 4 includes a first film forming roll 281 and a second film forming roll 282. Four film forming chambers (first film forming chamber 210, second film forming chamber 220, third film forming chamber 230, and fourth film forming chamber 240) separated by partitions are provided along the circumferential direction of each film forming roll 281 and 282. A cathode is provided in each film forming chamber, and the cathodes 214, 224, 234, and 244 are connected to power sources 216, 226, 236, and 246, respectively. Targets 213, 223, 233, and 243 are disposed on the cathodes 214, 224, 234, and 244, respectively, so as to face the film-forming rolls 281 and 282. Gas inlet pipes are connected to the film-forming chambers 210, 220, 230, and 240, and valves 219, 229, 239, and 249 are provided upstream of the gas inlet pipes.

A roll of the film substrate 10 (see FIG. 5A) is set on the unwinding roll 251 in the preparation chamber 250. The film substrate 10 unwound from the unwinding roll 251 is transported onto the first film-forming roll 281 and is led to the first film-forming chamber 210 and the second film-forming chamber 220 in that order. In the first film-forming chamber 210, a high refractive index layer 102 is formed on the side of the hard coat layer 17 opposite the transparent film 16 side (main surface 17a opposite the transparent film 16 side of the hard coat layer 17 in FIG. 5A), and in the second film-forming chamber 220, a low refractive index layer 103 is formed on the high refractive index layer 102 (see FIG. 5B). The film substrate 10 on which the high refractive index layer 102 and the low refractive index layer 103 have been formed is transported onto the second film-forming roll 282, and the high refractive index layer 104 and the low refractive index layer 105 are sequentially formed in the third film-forming chamber 230 and the fourth film-forming chamber 240 (see FIG. 5C). Details of the high refractive index layer and the low refractive index layer will be described later. By the above anti-reflection layer forming process, an anti-reflection layer 101 having the high refractive index layer 102, the low refractive index layer 103, the high refractive index layer 104, and the low refractive index layer 105 in this order is formed on the main surface of the hard coat layer 17 opposite the transparent film 16 side, and a polarizing plate 100 with an anti-reflection layer (see FIG. 5C) is obtained.

The polarizing plate 100 with the anti-reflection layer 101 formed thereon is guided to the winding chamber 260 and wound up on the winding roll 261 to obtain a roll of the polarizing plate 100 with the anti-reflection layer.

In the winding chamber 260, a light irradiation section 291 and a light detection section 293 are arranged so as to face the antireflection layer 101 of the polarizing plate with an antireflection layer 100. The light irradiated from the light irradiation section 291 may be white light or monochromatic light as long as it contains visible light. The light irradiation may be continuous or intermittent. In the in-line reflected light measurement process, the reflected light of the light irradiated from the light irradiation section 291 to the antireflection layer 101 is detected by the light detection section 293. The reflected light detected by the light detection section 293 is converted into an electrical signal by a light receiving element (not shown), and calculation is performed by the calculation section 273 as necessary. In the calculation section 273, calculation of the spectrum of the detected reflected light, conversion to a specific color system (for example, XYZ color system, L ^* a ^* b ^* color system, etc.), calculation of the film thickness, etc. are performed. In order to cut off the reflected light from the film substrate 10 including the polarizer 13, it is preferable to place a polarizing plate (not shown) that polarizes the visible light irradiated from the light irradiating unit 291. By cutting off the reflected light from the film substrate 10 including the polarizer 13, it is possible to measure only the reflected light characteristics of the antireflection layer 101 to be formed.

Furthermore, the calculation unit 273 determines the difference between the reflection characteristics of the detected reflected light and the desired reflected light characteristics, and if the difference exceeds a threshold, sends a signal to the control unit 275 to change the thin film deposition conditions. The control unit 275 adjusts the deposition conditions of the anti-reflection layer 101 so that the characteristics of the reflected light (reflectance, hue, etc.) are within a predetermined range.

The deposition conditions to be adjusted include the amount of gas introduced into the deposition chamber, the film transport speed, the amount of power input, etc. For example, in the deposition apparatus shown in FIG. 4, the control unit 275 can adjust the rotation speed of the unwind roll 251, the take-up roll 261, the first deposition roll 281, and the second deposition roll 282, the amount of power input to the power sources 216, 226, 236, and 246, and the opening of the valves 219, 229, 239, and 249 of the gas introduction pipes, thereby adjusting the deposition conditions of the thin film in each deposition chamber. The change in the characteristics of the reflected light is mainly caused by the variation in the film thickness of the thin film. Therefore, it is preferable to adjust the deposition conditions of the thin film so that the film thickness of the thin film formed in each deposition chamber approaches the set value. The deposition conditions are adjusted, for example, by PID control.

To determine the difference from the desired reflected light characteristics, it is necessary to determine the reference reflected light characteristics in advance. The reference reflected light characteristics are determined appropriately based on the product specifications, etc. Examples include a method of using the center of the product's specification range as the reference, or a method of using the reflected light spectrum calculated by optical calculation from the set film thickness and refractive index of each layer (see the examples in JP 2016-122173 A) as the reference. In addition, the reflected light spectrum of the product measured offline may be used as the reference.

In this embodiment, evaporation of moisture from the end face of the polarizer 13 (see FIG. 5A) is suppressed, which is thought to suppress fluctuations in the gas composition in the deposition chamber when depositing the anti-reflection layer 101. This makes it easier to adjust the deposition conditions for the anti-reflection layer 101 (specifically, to adjust the amount of gas introduced, etc.) using the detection results obtained in the in-line reflected light measurement process. In particular, according to this embodiment, the reflected light characteristics can be kept within the allowable range even at the ends in the width direction of the polarizing plate with an anti-reflection layer, so the width of the polarizing plate with an anti-reflection layer that can be used as a product is increased.

In order to further suppress the variation in the reflected light characteristics in the width direction of the polarizing plate with an anti-reflection layer, it is preferable to provide a plurality of light irradiation units 291 and light detection units 293 in the width direction of the anti-reflection layer 101, and perform in-line reflected light measurement (irradiation of visible light and detection of reflected light) at a plurality of locations in the width direction of the anti-reflection layer 101. In this case, for example, if a plurality of gas introduction tubes are provided in the width direction of the film in each film formation chamber, it becomes possible to individually adjust the amount of gas introduced at a plurality of locations in the width direction of the film. By performing in-line reflected light measurement at a plurality of locations in the width direction of the anti-reflection layer 101, it is also possible to suppress the variation in the reflected light characteristics in both the longitudinal direction and the width direction of the polarizing plate with an anti-reflection layer. In addition, in order to suppress the variation in the reflected light characteristics in the width direction of the polarizing plate with an anti-reflection layer, a measurement head equipped with a light irradiation unit and a light detection unit may be provided so as to be movable in the width direction of the film.

When forming the anti-reflection layer 101 by a reactive sputtering method, it is preferable to control the amount of reactive gas such as oxygen gas introduced by plasma emission monitoring (PEM) control when adjusting the film formation conditions of the anti-reflection layer 101. In PEM control, the plasma emission intensity of the sputtering film formation is detected, and the amount of reactive gas introduced is adjusted so that the emission intensity becomes a predetermined control value (set point, hereinafter sometimes referred to as "SP"). By automatically adjusting the amount of gas introduced so that the plasma emission intensity is constant, it is possible to maintain the transition region and form a film at a high rate, and in addition, the film formation rate can be kept constant. However, when film formation is performed continuously for a long period of time, the film formation rate changes even if the plasma emission intensity is the same due to the influence of erosion of the target, etc. Therefore, in order to suppress fluctuations in the reflection light characteristics in the longitudinal direction of the polarizing plate with the anti-reflection layer when performing continuous film formation for a long period of time, it is preferable to appropriately adjust the SP of the PEM based on the measurement results of the optical characteristics in the in-line reflection light measurement process.

In the PEM control, in order to control the state of sputtering in each deposition chamber, the plasma emission intensity is constantly monitored by the PEM, and the amount of gas introduced into each deposition chamber is feedback-controlled based on the SP of the emission intensity set within a predetermined range. By providing multiple PEMs in the width direction of the film, it is possible to set the SP individually for each PEM. This allows the balance of the amount of gas introduced at the width direction position corresponding to the PEM to be adjusted, so that the anti-reflection layer 101 having a uniform thickness in the width direction can be deposited. For example, the reflected light is detected in the in-line reflected light measurement process, the film thickness is calculated from the detection result, and the SP is changed according to the calculation result so that the film thickness of the anti-reflection layer 101 is uniform in the length direction or width direction of the film, thereby making it possible to maintain the reflection light characteristics in the length direction or width direction of the film uniform. Hereinafter, a series of operations in which the reflected light is detected in the in-line reflected light measurement process, the film thickness is calculated from the detection result, and the SP is changed according to the calculation result so that the film thickness of the anti-reflection layer is uniform in the length direction or width direction of the film may be referred to as a "feedback operation". The feedback operation is repeated, for example, until the variation in the film thickness of the antireflection layer 101 in the longitudinal or transverse direction falls within an acceptable range. According to this embodiment, the variation in the gas composition in the deposition chamber when depositing the antireflection layer can be suppressed, so the number of feedback operations is reduced. This improves the productivity of polarizing plates with an antireflection layer.

[Anti-reflection layer 101]
Next, the anti-reflection layer 101 will be described in detail. The anti-reflection layer 101 is made of two or more thin layers. The anti-reflection layer 101 shown in FIG. 5C includes, from the hard coat layer 17 side, a high refractive index layer 102, The polarizing plate has four layers, namely, a low refractive index layer 103, a high refractive index layer 104, and a low refractive index layer 105, in this order. The antireflection layer-coated polarizing plate may have a two-layer structure, a three-layer structure, a five-layer structure, or a laminate structure of six or more layers. It is preferable that the outermost layer (the layer farthest from the polarizer) is a low refractive index layer.

In general, the optical thickness (product of refractive index and thickness) of the thin film of an anti-reflection layer is adjusted so that the inverted phases of incident light and reflected light cancel each other out. By making the anti-reflection layer a multilayer laminate of two or more thin films with different refractive indexes, it is possible to reduce the reflectance over a wide wavelength range of visible light.

Examples of the thin film material constituting the anti-reflection layer 101 include metal (or semi-metal) oxides, nitrides, fluorides, etc. The anti-reflection layer 101 is preferably an alternating laminate of high-refractive index layers and low-refractive index layers, and more preferably an alternating laminate of two or more high-refractive index layers and two or more low-refractive index layers.

The high refractive index layer has a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of the material of the high refractive index layer include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and antimony-doped tin oxide (ATO). Among them, one or more selected from the group consisting of titanium oxide and niobium oxide are preferred. The low refractive index layer has a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of the material of the low refractive index layer include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride. Among them, silicon oxide is preferred. In particular, it is preferred to alternately stack a niobium oxide (Nb ₂ O ₅ ) thin film as the high refractive index layer and a silicon oxide (SiO ₂ ) thin film as the low refractive index layer. In addition to the low refractive index layer and the high refractive index layer, a medium refractive index layer having a refractive index of more than 1.6 and less than 1.9 may be provided.

The thickness of the high refractive index layer and the low refractive index layer is preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. The thickness of each layer may be designed so that the reflectance of visible light is small according to the refractive index and the layered structure. For example, the layered structure of the high refractive index layer and the low refractive index layer may be a four-layer structure consisting of, from the film substrate 10 side, a high refractive index layer with an optical thickness of 20 nm or more and 55 nm or less, a low refractive index layer with an optical thickness of 35 nm or more and 60 nm or less, a high refractive index layer with an optical thickness of 65 nm or more and 250 nm or less, and a low refractive index layer with an optical thickness of 100 nm or more and 150 nm or less.

When the antireflection layer 101 is a four-layer alternating laminate in which niobium oxide (Nb ₂ O ₅ ) thin films as high refractive index layers and silicon oxide (SiO ₂ ) thin films as low refractive index layers are alternately laminated, the antireflection layer 101 may be configured to have, from the hard coat layer 17 side, a niobium oxide thin film having a thickness of 5 nm to 20 nm, a silicon oxide thin film having a thickness of 20 nm to 60 nm, a niobium oxide thin film having a thickness of 25 nm to 120 nm, and a silicon oxide thin film having a thickness of 50 nm to 100 nm, in that order.

To obtain a polarizing plate with an antireflection layer that has excellent high-temperature durability, the thickness of the antireflection layer 101 is preferably 100 nm or more and 300 nm or less, more preferably 120 nm or more and 280 nm or less, even more preferably 140 nm or more and 260 nm or less, and even more preferably 160 nm or more and 240 nm or less. In this specification, the "thickness of the antireflection layer" refers to the sum of the thicknesses of the layers that make up the antireflection layer (total thickness).

The method for forming the anti-reflective layer 101 is not particularly limited, and may be either a wet coating method or a dry coating method. Since a thin film with a uniform thickness can be formed, dry coating methods such as vacuum deposition, CVD, and sputtering are preferred, and sputtering is more preferred. From the viewpoint of increasing productivity, the method for forming the anti-reflective layer 101 is preferably a method for forming a film using a roll-to-roll sputtering film-forming apparatus as shown in FIG. 4 (roll-to-roll sputtering method). In the sputtering method, film formation is performed while introducing an inert gas such as argon, and a reactive gas such as oxygen as necessary, into the film-forming chamber. When forming an oxide film by the sputtering method, either a method using an oxide target or a reactive sputtering method using a metal (or semimetal) target can be performed.

When an insulating oxide such as silicon oxide is formed using an oxide target, RF discharge is required, so the film formation rate tends to be low and productivity tends to be low. Therefore, the sputtering of oxide is preferably performed by reactive sputtering using a metal target. In the reactive sputtering method, film formation is performed while introducing an inert gas such as argon and a reactive gas such as oxygen into the film formation chamber. In the reactive sputtering method, it is preferable to adjust the amount of oxygen so that the transition region is intermediate between the metal region and the oxide region. When film formation is performed in a metal region where the amount of oxygen is insufficient, the amount of oxygen in the resulting oxide film becomes significantly smaller than the stoichiometric composition, and the oxide film tends to have a metallic luster and decrease in transparency. In addition, in an oxide region where the amount of oxygen is large, the film formation rate tends to decrease extremely. By adjusting the amount of oxygen so that the sputtering film formation is in the transition region, an oxide film can be formed at a high rate. When the anti-reflective layer 101 is formed by the reactive sputtering method, the amount of reactive gas introduced can be controlled by the above-mentioned PEM control, so that the film formation conditions of the anti-reflective layer 101 can be adjusted more easily. The sputtering power source used in the reactive sputtering method is preferably a DC power source or an MFAC power source (an AC power source with a frequency band of several kHz to several MHz).

The power density when performing the sputtering method is, for example, 0.1 W/cm ² or more and 20 W/cm ² or less, and preferably 1 W/cm ² or more and 15 W/cm ² or less. The surface temperature of the film-forming roll when performing the sputtering method is, for example, -25°C or more and 25°C or less, and preferably -20°C or more and 0°C or less. The pressure in the film-forming chamber when performing the sputtering method is, for example, 0.01 Pa or more and 10 Pa or less, and preferably 0.1 Pa or more and 1.0 Pa or less.

The polarizing plate with an anti-reflection layer obtained by the manufacturing method according to this embodiment is used in displays such as liquid crystal displays and organic EL displays. In particular, when used as the outermost surface layer of a display, the anti-reflection properties improve the visibility of the display.

[Preferable embodiment of the method for producing a polarizing plate with an antireflection layer]
In this embodiment, in order to maintain the reflected light characteristics more uniform, it is preferable to satisfy the following condition 1, it is more preferable to satisfy the following condition 2, and it is even more preferable to satisfy the following condition 3.
Condition 1: The film substrate further comprises the third adhesive layer.
Condition 2: The above condition 1 is satisfied, and the third adhesive layer is formed integrally with the first adhesive layer and the second adhesive layer.
Condition 3: The above condition 2 is satisfied, and the end face in the width direction of the polarizer is sealed with the above third adhesive layer.

[Other embodiments]
Although the manufacturing method of the polarizing plate with the anti-reflection layer according to the present embodiment has been described above, the present invention is not limited to the above-mentioned embodiment. For example, the in-line reflected light measurement process may be performed at any stage after at least one thin film is formed. For example, after forming the high refractive index layer 102 and the low refractive index layer 103 on the first film-forming roll 281, the light irradiation unit 297 (see FIG. 4) irradiates the low refractive index layer 103 with visible light, and the reflected light is detected by the light detection unit 299, thereby performing in-line detection of the reflected light. In addition, in-line detection of the reflected light may be performed at two or more locations. For example, after forming the high refractive index layer 102 and the low refractive index layer 103, the light irradiation unit 297 and the light detection unit 299 perform in-line detection of the reflected light, and further, after forming the high refractive index layer 104 and the low refractive index layer 105, the light irradiation unit 291 and the light detection unit 293 perform in-line detection of the reflected light. In this way, by performing in-line measurements at two or more locations, it becomes easier to determine which deposition chamber should have its deposition conditions adjusted, enabling more precise control.

As mentioned above, the method for forming the anti-reflection layer is not limited to sputtering, and various dry coating methods or wet coating methods may be used. Even when the thin film is formed by a method other than sputtering, a polarizing plate with an anti-reflection layer having excellent uniformity of reflected light characteristics can be obtained by adjusting the thin film formation conditions based on the results of in-line detection of reflected light.

The manufacturing method of the present invention may further include a step Sc of forming a primer layer on one of the main surfaces of the film substrate before the anti-reflection layer forming step. When the manufacturing method of the present invention further includes step Sc, in the anti-reflection layer forming step, an anti-reflection layer is formed on the main surface of the primer layer opposite the film substrate side.

By providing a primer layer, the adhesion between the film substrate and the anti-reflection layer is increased. Examples of materials for the primer layer include metals (or semi-metals) such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, indium, tungsten, aluminum, zirconium, and palladium; alloys of these metals (or semi-metals); and oxides, fluorides, sulfides, and nitrides of these metals (or semi-metals). The oxide constituting the primer layer may be a composite oxide such as indium tin oxide (ITO). Among these, inorganic oxides are preferred as materials for the primer layer, with silicon oxide, indium oxide, or ITO being more preferred, and SiOx (x<2) being even more preferred.

To ensure the light transmittance of the primer layer while increasing the adhesion between the film substrate and the anti-reflection layer, the thickness of the primer layer is preferably 0.5 nm or more and 20 nm or less, more preferably 0.5 nm or more and 10 nm or less, and even more preferably 1.0 nm or more and 10 nm or less.

The method for forming the primer layer is not particularly limited, and may be either a wet coating method or a dry coating method. Since a thin film with a uniform thickness can be formed, dry coating methods such as vacuum deposition, CVD, and sputtering are preferred, and sputtering is more preferred. From the viewpoint of increasing productivity, the method for forming the primer layer is preferably a method for forming a film using a roll-to-roll sputtering film-forming device (roll-to-roll sputtering method) as a method for forming the primer layer. In the roll-to-roll sputtering method, for example, the primer layer and the anti-reflective layer can be continuously formed while transporting a long film substrate in the longitudinal direction (MD direction). When forming the primer layer by the sputtering method, for example, the film formation conditions can be appropriately set among the conditions described in the above-mentioned [anti-reflective layer 101].

The method for producing a polarizing plate with an antireflection layer according to the present invention may also include a step of forming an antifouling layer after the in-line reflected light measurement step. The material for the antifouling layer is preferably a fluorine-containing compound.

The method for producing a polarizing plate with an anti-reflection layer according to the present invention may also include a step of slitting the portions of the polarizer that protrude from both ends in the width direction after the in-line reflected light measurement step.

The method for manufacturing a polarizing plate with an antireflection layer according to the present invention may also include a preliminary film formation process for the purpose of setting initial film formation conditions at the start of film formation. In this case, the above-mentioned antireflection layer formation process and in-line reflected light measurement process are performed in the main film formation process after the preliminary film formation process. Details of the preliminary film formation process are described in, for example, JP 2017-218674 A.

The following describes examples of the present invention, but the present invention is not limited to the following examples.

<Example>
[Preliminary film formation]
First, the preliminary film formation will be described. In the preliminary film formation, a black PET film (1300 mm wide) having a thickness of 100 μm, a visible light transmittance of 0.01%, and a refractive index of 1.65 was set on the unwinding roll of a roll-to-roll sputtering device, and the film formation conditions of each layer were adjusted when a primer layer and an anti-reflection layer were sequentially formed on the black PET film by a reactive sputtering method. As the primer layer, a SiOx layer (x<2) having a target thickness of 3.5 nm was formed. As the anti-reflection layer, the first layer: a Nb ₂ O ₅ layer having a target thickness of 12 nm (refractive index: 2.33), the second layer: a SiO ₂ layer having a target thickness of 28 nm (refractive index: 1.46), the third layer: a Nb ₂ O ₅ layer having a target thickness of 100 nm, and the fourth layer: a SiO ₂ layer having a target thickness of 85 nm were formed in this order. When each layer (oxide film) was formed, argon gas and oxygen gas were introduced into the film formation chamber.

In addition, in the formation of each layer of the primer layer and the anti-reflection layer, the power source was an MFAC power source (frequency: 40 kHz). In the formation of the primer layer, a Si target was used as a target material, the power density was 3 W/ ^cm2 , and the pressure in the film formation chamber was 0.4 Pa. In the formation of the first and third layers of the anti-reflection layer, a Nb target was used, the power density was 13 W/ ^cm2 , and the pressure in the film formation chamber was 0.5 Pa. In the formation of the second and fourth layers of the anti-reflection layer, a Si target was used, the power density was 8 W/ ^cm2 , and the pressure in the film formation chamber was 0.5 Pa.

When forming each layer (oxide film), the pressure was kept constant by adjusting the amount of argon gas introduced and exhausted, while the amount of oxygen gas introduced was adjusted by plasma emission monitoring (PEM) control so that the film formation mode was maintained in the transition region. When adjusting the film formation conditions for each layer, adjustments were made using the method described in paragraphs [0124] to [0126] of JP 2017-218674 A, and the film thickness calculation and the change in the plasma emission intensity setting value (SP) were repeated until the film thickness distribution in the width direction of each layer was within the allowable range.

Next, we will explain how to prepare the film substrate used in the examples.

[Preparation of film substrate]
(Hard Coat Layer Forming Process)
100 parts by weight of ultraviolet-curable urethane acrylate monomer (refractive index: 1.51), 14 parts by weight of polystyrene beads (refractive index: 1.59, number-average primary particle size: 3.0 μm), 5 parts by weight of alkylphenone photopolymerization initiator, 135 parts by weight of toluene, and 10 parts by weight of ethyl acetate were mixed to prepare a composition for forming a hard coat layer with a solid content concentration of 45% by weight. Next, the composition for forming a hard coat layer was applied to one main surface of a TAC film (thickness: 80 μm, refractive index: 1.49) as a transparent film to form a coating film. Next, the coating film was dried by heating at a temperature of 80° C. for 2 minutes, and then cured by ultraviolet irradiation. As a result, an antiglare hard coat layer (a hard coat layer having a concave-convex structure on the surface) having a thickness of 5 μm was formed on one main surface of the TAC film, and a transparent film with a hard coat layer (second protective film) was obtained.

(Process for Producing Polarizing Plate)
A polarizing plate was produced by laminating the TAC film of the second protective film to one main surface of a separately prepared polarizer, and laminating a TAC film (thickness: 80 μm, refractive index: 1.49) as a separately prepared first protective film to the other main surface of the polarizer. A PVA-based polarizer was used as the polarizer, which was a polyvinyl alcohol film with an average polymerization degree of 2700 and a thickness of 75 μm that was stretched 6 times while being dyed with iodine. In addition, an adhesive consisting of an aqueous solution containing a polyvinyl alcohol resin (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) containing an acetoacetyl group and methylolmelamine in a weight ratio of 3:1 was used for laminating (adhering) the PVA-based polarizer and the TAC film, and the films were laminated with a roll laminator, and then heated and dried in an oven.

(Process for Producing Polarizing Plate with Pressure-Sensitive Adhesive Layer)
A release liner (a PET film treated with a silicone-based release agent) having a thickness of 38 μm was prepared separately, and an acrylic adhesive was applied to one main surface of the release liner, followed by drying at a temperature of 120° C. for 2 minutes to form an adhesive layer on one main surface of the release liner. The obtained adhesive layer was then bonded to the TAC film of the polarizing plate (specifically, the TAC film not in contact with the hard coat layer) to obtain a polarizing plate (film substrate) with an adhesive layer. The widths of each layer in the obtained film substrate were: release liner: 1317 mm, adhesive layer: 1250 mm, first protective film: 1330 mm, polarizer: 1280 mm, and second protective film: 1330 mm.

In the obtained film substrate, the first protective film and the polarizer were bonded via a first adhesive layer made of the cured product of the adhesive, and the second protective film and the polarizer were bonded via a second adhesive layer made of the cured product of the adhesive. In addition, both the first protective film and the second protective film protruded from both ends of the polarizer in the width direction.

In addition, in the obtained film substrate, the distance between the first protective film and the second protective film at the portions overhanging from both ends was narrower than the distance between the first protective film and the second protective film at the portions where the ends in the width direction of the polarizer are sandwiched. Furthermore, the obtained film substrate had a third adhesive layer (an adhesive layer made of a cured product of the above adhesive) that adhered the first protective film and the second protective film to each other in a portion of the width direction of the portions overhanging from both ends. This third adhesive layer was formed integrally with the first adhesive layer and the second adhesive layer. In addition, the end faces in the width direction of the polarizer were sealed by the third adhesive layer.

(Bombardment process)
The main surface of the hard coat layer ^of the film substrate (specifically, the main surface of the hard coat layer opposite to the TAC film side) was bombarded while the film substrate was being transported by a roll-to-roll plasma treatment device under conditions of a pressure of 0.6 Pa and an effective power density of 0.34 W·min/cm2·m2. During the bombardment treatment, argon gas (flow rate: 1049 sccm) and oxygen gas (flow rate: 1 sccm) were introduced into the device.

[Main film formation]
Next, the present film formation will be described. In the present film formation, the film substrate after the bombardment treatment is set on the unwinding roll of a roll-to-roll sputtering device, and the film formation conditions adjusted in the above [preliminary film formation] are used as the initial film formation conditions on one main surface of the hard coat layer (the main surface opposite to the TAC film side of the hard coat layer), and a SiOx layer, a Nb ₂ O ₅ layer, a SiO ₂ layer, a Nb ₂ O ₅ layer and a SiO ₂ layer are formed in this order (anti-reflection layer formation process), and an in-line reflection measurement of the obtained anti-reflection layer is performed (in-line reflection measurement process). The anti-reflection layer formation process and the in-line reflection measurement process are performed continuously while conveying the film substrate in one direction. The in-line reflection measurement is performed at 23 points in the width direction of the anti-reflection layer (width: 1274 mm), and the film thickness at the 23 points in the width direction is calculated based on the obtained reflection spectrum, and the set value (SP) of the plasma emission intensity is changed so that the film thickness is uniform in the width direction. In this film formation, a polarizing plate was placed to polarize visible light irradiated from a light irradiating section in order to cut reflected light from a film substrate containing a polarizer in the in-line reflected light measurement.

Comparative Example
Except for using a film substrate in which both end portions of the first protective film and the second protective film (more specifically, the portions protruding from both ends in the width direction of the polarizer) were slit, this film formation was carried out in the same manner as in the above example, and the film formation conditions for the antireflection layer were similarly adjusted.

<Results>
FIG. 6 is a graph (a ^* b* chromaticity diagram of L ^* a ^* b ^* color system) showing the hue of the reflected light from the anti-reflection layer before the adjustment of the film formation conditions of the above example (immediately after the start of the film formation of this film ⁾ . FIG. 7 is a graph showing the hue of the reflected light from the anti-reflection layer after the adjustment of the film formation conditions of the above example (after 15 feedback operations). FIG. 8 is a graph showing the hue of the reflected light from the anti-reflection layer before the adjustment of the film formation conditions of the above comparative example (immediately after the start of the film formation of this film). FIG. 9 is a graph showing the hue of the reflected light from the anti-reflection layer after the adjustment of the film formation conditions of the above comparative example (after 52 feedback operations). In each of FIGS. 6 to 9, the values of a* and b* are plotted for a total of five locations, including both ends (2 locations), the center (1 location), and locations between each of both ends and the center (2 locations), among the locations where the reflected light was measured ( ²³ locations in the width direction of the anti- ^reflection layer). Moreover, the regions indicated by dashed lines in FIGS. 6 to 9 are all regions that indicate the permissible range of hues.

As shown in Figure 7, in the above example, the hue was within the acceptable range after 15 feedback operations. On the other hand, as shown in Figure 9, in the above comparative example, the hue at both ends (two locations) did not fall within the acceptable range even after 52 feedback operations. Also, as shown in Figures 6 and 8, the above example had smaller variation in hue in the width direction before the film formation conditions were adjusted (immediately after the start of film formation) than the above comparative example.

These results demonstrate that the present invention can provide a method for manufacturing a polarizing plate with an anti-reflection layer that can maintain uniform light reflection characteristics.

Reference Signs List 10, 20, 30 Film substrate 11 First protective film 12 First adhesive layer 13 Polarizer 14 Second adhesive layer 15 Second protective film 16 Transparent film 17 Hard coat layer 21 Third adhesive layer 31 Pressure-sensitive adhesive layer 32 Release liner 100 Polarizing plate with anti-reflection layer 101 Anti-reflection layer

Claims (10)

A method for producing a polarizing plate with an antireflection layer, the polarizing plate having a film substrate and an antireflection layer provided on one main surface of the film substrate, comprising the steps of:
a step Sa of forming the antireflection layer consisting of two or more thin films on the one main surface side of the film substrate;
and a step Sb of depositing at least one layer constituting the anti-reflection layer, irradiating the layer with visible light, and detecting reflected light,
The steps Sa and Sb are continuously performed while transporting the film substrate in one direction,
the film substrate is a laminate having, in this order, a first protective film, a first adhesive layer, a polarizer, a second adhesive layer, and a second protective film;
the first protective film and the polarizer are bonded to each other via the first adhesive layer,
the second protective film and the polarizer are bonded to each other via the second adhesive layer,
the first protective film and the second protective film each have a width greater than that of the polarizer and protrude from both ends of the polarizer in a width direction,
A method for manufacturing a polarizing plate with an antireflection layer, wherein the distance between the first protective film and the second protective film in at least a portion of the protruding portions from both ends is narrower than the distance between the first protective film and the second protective film at a location where the polarizer is sandwiched between the widthwise ends of the polarizer. The method for producing a polarizing plate with an antireflection layer according to claim 1, wherein in step Sb, after all layers constituting the antireflection layer are formed, the antireflection layer is irradiated with visible light and the reflected light is detected. The method for manufacturing a polarizing plate with an antireflection layer according to claim 1, wherein the deposition conditions of the antireflection layer in the step Sa are adjusted according to the detection result of the reflected light in the step Sb. The method for producing a polarizing plate with an anti-reflection layer according to claim 1, wherein in step Sb, visible light is irradiated to multiple locations in the width direction of the layer, and the reflected light is detected. The method for producing a polarizing plate with an anti-reflection layer according to claim 1, wherein in step Sa, the anti-reflection layer is formed by a sputtering method. The method for manufacturing a polarizing plate with an anti-reflection layer according to claim 1, wherein the film substrate further comprises a third adhesive layer that bonds the first protective film and the second protective film in at least a portion of the width direction of the portions protruding from both ends. The second protective film includes a transparent film and a hard coat layer provided on one main surface side of the transparent film,
The method for producing a polarizing plate with an antireflection layer according to claim 1 , wherein in the step Sa, the antireflection layer is formed on a side of the hard coat layer opposite to a side of the transparent film. The film substrate further includes a pressure-sensitive adhesive layer provided on a side of the first protective film opposite to the polarizer side,
The method for producing a polarizing plate with an antireflection layer according to claim 1 , wherein in the step Sa, the antireflection layer is formed on a side of the second protective film opposite to a side of the polarizer. The method for producing a polarizing plate with an anti-reflection layer according to claim 8, wherein the film substrate further comprises a release liner temporarily attached to the side of the pressure-sensitive adhesive layer opposite the first protective film side. The method further includes a step Sc of forming a primer layer on the one main surface side of the film substrate before the step Sa,
The method for producing a polarizing plate with an antireflection layer according to claim 1 , wherein in the step Sa, the antireflection layer is formed on a main surface of the primer layer opposite to the film substrate side.

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