WO2023149253A1

WO2023149253A1 - Method for producing composite polarizing plate

Info

Publication number: WO2023149253A1
Application number: PCT/JP2023/001860
Authority: WO
Inventors: 範充江端; 慎也萩原; 裕史太田; 成志中里; 辰徳荒木
Original assignee: 住友化学株式会社
Priority date: 2022-02-04
Filing date: 2023-01-23
Publication date: 2023-08-10
Also published as: JP2023114075A; TW202346984A

Abstract

Provided is a method for producing a composite polarizing plate capable of suppressing air bubbles from becoming entrapped between a polarizing plate and/or a surface-treated film and an adhesive layer.　In the composite polarizing plate, the surface-treated film and the polarizing plate are laminated. The surface-treated film has a substrate film and a surface-treated layer formed on the surface of the substrate film. The polarizing plate includes at least a polarizing element. The method for producing a composite polarizing plate includes: step (a) for obtaining a laminate by bonding a surface-treated film and a polarizing plate through an adhesive layer having a stress of at most 0.8 N/mm² at 800% elongation and step (b) for performing adjustment such that in the laminate, the stress of the adhesive layer at 800% elongation at a temperature of 23 °C becomes at least 0.9 N/mm^2.

Description

Manufacturing method of composite polarizing plate

The present invention relates to a method for manufacturing a composite polarizing plate.

Liquid crystal display devices (LCDs) are widely used not only for liquid crystal televisions, but also for mobile terminals such as personal computers and mobile phones, and in-vehicle applications such as car navigation systems. Generally, a liquid crystal display device has a liquid crystal panel in which a linear polarizing plate including a polarizing element is attached to both sides of a liquid crystal cell, and displays an image or the like by controlling light from a backlight with the liquid crystal panel. . In recent years, like liquid crystal display devices, organic EL display devices have also been widely used for mobile terminals such as televisions and mobile phones, and in-vehicle applications such as car navigation systems. In an organic EL display device, a circular polarizing plate (a polarizing element and a λ/4 plate) is provided on the viewing side surface of the image display element in order to prevent external light from being reflected by the metal electrode (cathode) and viewed as a mirror surface. ) may be placed.

　In display devices such as liquid crystal display devices and organic EL display devices, surface treatment films are sometimes used in order to improve visibility and suppress scratches. Display devices using a laminate in which an antiglare hard-coated film is bonded to a polarizing element in order to suppress deterioration in visibility due to reflection of external light and improve visibility are known (for example, , Patent Document 1, etc.).

JP 2011-81219 A

When manufacturing a composite polarizing plate in which a polarizing plate including a polarizing element and a surface-treated film are laminated, the polarizing plate and the surface-treated film are sometimes bonded together using an adhesive layer. In order to secure the surface hardness of the composite polarizing plate, a hard (hardly plastically deformable) adhesive layer may be used as the adhesive layer. It has been found that when a polarizing plate and a surface treatment film are laminated using a hard adhesive layer, air bubbles are mixed between the polarizing plate and/or the surface treatment film and the adhesive layer.

An object of the present invention is to provide a method for producing a composite polarizing plate that can suppress air bubbles from entering between the polarizing plate and/or surface treatment film and the pressure-sensitive adhesive layer.

The present invention provides the following method for manufacturing a composite polarizing plate.
[1] A method for manufacturing a composite polarizing plate in which a surface-treated film and a polarizing plate are laminated,
The surface-treated film has a base film and a surface-treated layer formed on the surface of the base film,
The polarizing plate includes at least a polarizing element,
The manufacturing method is
Step (a) of obtaining a laminate by bonding the surface-treated film and the polarizing plate via an adhesive layer having a stress of 0.8 N/mm ² or less at 800% elongation;
A method for producing a composite polarizing plate, comprising the step (b) of adjusting the stress of the adhesive layer at 800% elongation at a temperature of 23° C. to 0.9 N/mm ² or more in the laminate.
[2] The step (a) is
A step (a1) of forming the pressure-sensitive adhesive layer on the surface-treated film;
The method for producing a composite polarizing plate according to [1], comprising the step (a2) of laminating the polarizing plate on the pressure-sensitive adhesive layer formed on the surface-treated film.
[3] The method for producing a composite polarizing plate according to [2], wherein the step (a2) is performed within 6 days after the step (a1).
[4] The method for producing a composite polarizing plate according to any one of [1] to [3], wherein the step (b) is a step of storing the laminate.
[5] The surface-treated film has the surface-treated layer on one side of the base film, and the laminate has the pressure-sensitive adhesive layer on the base film side of the surface-treated film, [1] A method for producing a composite polarizing plate according to any one of [4].
[6] The method for producing a composite polarizing plate according to any one of [1] to [5], wherein the polarizing plate has a protective film on one or both sides of the polarizing element.
[7] The method for producing a composite polarizing plate according to any one of [1] to [6], wherein the pressure-sensitive adhesive layer has a thickness of 10 μm or less.
[8] The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing a (meth)acrylic resin,
The method for producing a composite polarizing plate according to any one of [1] to [7], wherein the (meth)acrylic resin has a glass transition temperature of −30° C. or lower.
[9] The surface treatment layer according to any one of [1] to [8], wherein the surface treatment layer is one or more selected from the group consisting of an antireflection layer, an antiglare layer, a hard coat layer, and an antifouling layer. A method for manufacturing a composite polarizing plate.

According to the manufacturing method of the composite polarizing plate of the present invention, it is possible to suppress air bubbles from entering between the polarizing plate and/or the surface treatment film and the pressure-sensitive adhesive layer.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the composite polarizing plate which concerns on one Embodiment of this invention. 4 is a graph showing the results of measurement of stress with respect to elongation of pressure-sensitive adhesive layers produced in Examples.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

(composite polarizing plate)
FIG. 1 is a cross-sectional view schematically showing a composite polarizing plate according to one embodiment of the invention. The composite polarizing plate 1 is formed by laminating a surface treatment film 20 and a polarizing plate 10 . Composite polarizing plate 1 has adhesive layer 31 between surface-treated film 20 and polarizing plate 10 . The adhesive layer 31 in the composite polarizing plate 1 has a stress of 800% elongation at a temperature of 23° C. (hereinafter sometimes referred to as “elongation stress (23° C.)”) of 0.9 N/mm ² or more.

The surface-treated film 20 has a base film 21 and a surface-treated layer 22 formed on the surface of the base film 21 . In the composite polarizing plate 1 , it is preferable that the surface treatment layer 22 is provided on one side of the base film 21 of the surface treatment film 20 and that the base film 21 side of the surface treatment film 20 faces the adhesive layer 31 . The surface treatment layer 22 can be one or more selected from the group consisting of an antireflection layer, an antiglare layer, a hard coat layer, and an antifouling layer.

The polarizing plate 10 includes at least a polarizing element 11 . The polarizing plate 10 preferably has a protective film 13 on one side or both sides of the polarizing element 11 . The polarizing element 11 and the protective film 13 may be laminated via a bonding layer 12 (adhesive layer or adhesive layer), and the bonding layer 12 is in direct contact with the polarizing element 11 and the protective film 13. is preferred.

In the composite polarizing plate 1 , the adhesive layer 31 is in direct contact with the surface treatment film 20 and the polarizing plate 10 . The elongation stress (23° C.) of the pressure-sensitive adhesive layer 31 in the composite polarizing plate 1 is 0.9 N/mm ² or more, may be 1.0 N/mm ² or more, or is 1.2 N/mm ² or more. may be 1.3 N/mm ² or more. When the elongation stress (23° C.) of the adhesive layer 31 is within the above range, the surface hardness of the surface of the composite polarizing plate 1 on the surface treatment film 20 side can be improved. It can prevent injuries. The elongation stress (23° C.) of the adhesive layer 31 can be determined by the method described in Examples below.

The composite polarizing plate 1 may further have another adhesive layer on the polarizing plate 10 side, and on the side opposite to the other polarizing plate 10, a peeling adhesive layer for covering and protecting the other adhesive layer It may have a film. Another pressure-sensitive adhesive layer is, for example, a bonding layer for bonding to an image display element of a display device.
The other pressure-sensitive adhesive layer may be provided in direct contact with the polarizing plate 10, or may be provided via another layer arranged on the opposite side of the polarizing plate 10 to the surface treatment film 20 side. .

The composite polarizing plate 1 may further have a peelable protective film laminated on the surface treatment film 20 on the opposite side of the surface treatment film 20 from the polarizing plate 10 side. The protection film is for protecting the surface of the surface treatment film 20 .

The pencil hardness of the surface of the composite polarizing plate 1 on the surface treatment film 20 side is preferably HB or higher, more preferably F or higher, even more preferably H or higher, and particularly preferably 2H or higher. When the pencil hardness is equal to or higher than the hardness described above, it is easy to suppress the occurrence of scratches or the like on the surface of the composite polarizing plate 1 on the surface treatment film 20 side. The pencil hardness can be measured according to JIS K 5600-5-4:1999, as described in Examples below.

The composite polarizing plate 1 can be used by being laminated on an image display element of a display device such as a liquid crystal display device or an organic EL display device.

(Manufacturing method of composite polarizing plate)
The method for manufacturing the composite polarizing plate 1 is a method for manufacturing the composite polarizing plate 1 having the structure described above,
The surface treatment film 20 and the polarizing plate 10 are bonded via an adhesive layer having a stress at elongation of 800% (hereinafter sometimes referred to as “elongation stress”) of 0.8 N/mm ² or less. a step (a) of obtaining a laminate by
A step of adjusting the laminate obtained in the step (a) so that the stress of the pressure-sensitive adhesive layer 31 at 800% elongation at a temperature of 23° C. (elongation stress (23° C.)) is 0.9 N/mm ² or more ( b) and

The elongation stress of the adhesive layer 31 in step (a) may be 0.8 N/mm ² or less, may be less than 0.8 N/mm ² , or may be 0.75 N/mm ² or less. may be 0.7 N/mm ² or less. The elongation stress in step (a) is usually 0.2 N/mm ² or more, may be 0.3 N/mm ² or more, or may be 0.4 N/mm ² or more. The elongation stress can be measured by the method described in Examples below.

The elongation stress (23° C.) of the adhesive layer 31 in step (b) may be 1.0 N/mm ² or more, 1.1 N/mm ² or more, or 1.2 N/mm ² or more, or 1.3 N/mm ² or more, and usually 2.0 N/mm ² or less. The elongation stress (23° C.) can be measured by the method described in Examples below.

As a method of setting the elongation stress of the adhesive layer 31 in the above range in the step (a) and setting the elongation stress (23° C.) of the adhesive layer 31 in the above range in the step (b), the adhesive layer 31 is formed. A method of adjusting the components in the pressure-sensitive adhesive composition used to perform the step (a), a method of adjusting the environmental conditions for performing the step (a), and the like. Methods for adjusting the components in the pressure-sensitive adhesive composition include adjusting the type and/or molecular weight of the base polymer contained in the pressure-sensitive adhesive composition; adjusting the amount; adjusting the type and/or amount of the cross-linking agent contained in the pressure-sensitive adhesive composition; using a base polymer having a reactive group and a polymerization initiator as components in the pressure-sensitive adhesive composition. Examples of the method for adjusting the environmental conditions for performing step (a) include a method for adjusting the temperature for performing step (a).

When the step (b) is a step of storing a laminate, which will be described later, the adhesive composition used to form the adhesive layer 31 preferably contains a base polymer and a cross-linking agent. In this case, the pressure-sensitive adhesive layer 31 used for lamination in step (a) is preferably in a state in which the reaction between the base polymer and the cross-linking agent has not sufficiently progressed, and the pressure-sensitive adhesive layer that has undergone step (b) 31 is preferably in a state in which the reaction between the base polymer and the cross-linking agent has sufficiently progressed.

The bonding of the surface-treated film 20 and the polarizing plate 10 performed in step (a) as described above is performed using the pressure-sensitive adhesive layer 31 having an elongation stress of 0.8 N/mm ² or less. The pressure-sensitive adhesive layer 31 having an elongation stress in this range is in a soft state, so that the pressure-sensitive adhesive layer 31 can be easily adhered to the surface treatment film 20 and/or the polarizing plate 10 . As a result, in the laminate obtained in step (a), it is possible to suppress the inclusion of air bubbles between the surface-treated film 20 and/or the polarizing plate 10 and the pressure-sensitive adhesive layer 31 . In the step (b), in the laminate in which inclusion of air bubbles is suppressed, the elongation stress (23° C.) of the adhesive layer 31 is adjusted to fall within the above range, so that the hardness of the adhesive layer 31 is improved. can be done. This makes it possible to obtain the composite polarizing plate 1 having high surface hardness and in which air bubbles are suppressed.

The elongation stress described above is an index of the plastic deformation region of the adhesive layer 31, and is a value that changes with the elapsed time from the formation of the adhesive layer 31. On the other hand, it was confirmed that the Young's modulus, which is an index of the elastic deformation region of the pressure-sensitive adhesive layer 31, does not greatly differ with the elapsed time from the formation of the pressure-sensitive adhesive layer 31, and is approximately the same regardless of the elapsed time. rice field. Therefore, in the method for manufacturing the composite polarizing plate 1 of the present embodiment, the plastically deformed region of the pressure-sensitive adhesive layer 31 is suppressed in order to suppress air bubbles from entering between the pressure-sensitive adhesive layer and the polarizing plate and/or surface treatment film. The composite polarizing plate 1 is manufactured based on the elongation stress, which is an index of .

The manufacturing method of the composite polarizing plate 1 may be carried out using a sheet body or a long body. From the viewpoint of continuous production of the composite polarizing plate 1, it is preferable to use a long body.
In this case, the layer or film obtained in each process or during the process may be wound into a roll to form a roll, and the layer or film may be unwound from the roll for the next step. As used herein, a long body refers to a layer or film having a length of, for example, 30 to 10,000 m.

Each step of the method for manufacturing the composite polarizing plate 1 will be specifically described below.
(Step (a))
Step (a) is a step of obtaining a laminate by bonding the surface-treated film 20 and the polarizing plate 10 together using an adhesive layer having an elongation stress of 0.8 N/mm ² or less. The environmental conditions for the step (a) are not particularly limited as long as the elongation stress of the pressure-sensitive adhesive layer 31 can be 0.8 N/mm ² or less. A preferable temperature for performing the step (a) is, for example, 10° C. or higher, may be 15° C. or higher, or may be 20° C. or higher, and is, for example, 35° C. or lower, and may be 30° C. or lower. There may be. A preferable relative humidity for performing the step (a) is usually 30% RH or more, 40% RH or 45% RH, and usually 70% RH or less. It may be 65% RH or 60% RH.

The step (a) includes, for example, a step (a1′) of forming an adhesive layer 31 on one of the surface-treated film 20 and the polarizing plate 10, and on the adhesive layer 31 formed in the step (a1′), and a step (a2') of laminating the other of the surface treatment film 20 and the polarizing plate 10. When step (a) includes step (a1′) and step (a2′), the elongation stress of the adhesive layer 31 in step (a1′) and step (a2′) are both explained in step (a) above. It is a range (0.8 N/mm ² or less).

The step (a1') may be performed by a step of peeling off the release film after bonding the pressure-sensitive adhesive layer 31 formed on the release film and the surface treatment film 20 or the polarizing plate 10 together.
When this step is included, the elongation stress of the adhesive layer 31 in step (a1′) is the same as the elongation stress of the adhesive layer 31 in step (a2′), or the elongation stress of the adhesive layer 31 in step (a2′) It is preferably smaller than the elongation stress. The elongation stress of the pressure-sensitive adhesive layer 31 in step (a2') is preferably within the range described above as the elongation stress in step (a).

After step (a1′), the period until step (a2′) is performed may be within 6 days, may be within 5 days, may be within 4 days, or may be within 3 days. It may be within 2 days, or within 1 day. By being within the above period, step (a2′) can be easily performed in a state where the elongation stress of the adhesive layer 31 is 0.8 N/mm ² or less.

When performing the step (a1′), when using the adhesive layer 31 formed on the release film, immediately after forming the adhesive layer 31 on the release film, the adhesive layer 31 and the surface treatment film 20 or It is preferable to bond the polarizing plate 10 together. As a result, the period from the formation of the adhesive layer 31 on the release film to the step (a2′) is substantially the same as the period from the step (a1′) to the step (a2′). can be When the step (a1′) is performed using the adhesive layer 31 formed on the release film, the step (a2′) is performed after the step (a1′) is performed after the adhesive layer 31 is formed on the release film. The period to may be within 6 days, may be within 5 days, may be within 4 days, may be within 3 days, may be within 2 days, It may be within one day. By being within the above period, step (a2′) can be easily performed in a state where the elongation stress of the adhesive layer 31 is 0.8 N/mm ² or less.

The step (a1′) is the step (a1) of forming the adhesive layer 31 on the surface-treated film 20, and the step (a2′) is the step of forming the polarizing plate 10 on the adhesive layer 31 formed on the surface-treated film 20. The step (a2) of laminating is preferred.

The polarizing plate 10 used in step (a) may be laminated with the above-described other pressure-sensitive adhesive layer (bonding layer for bonding to the image display element) and a release film. A protective film may be laminated on the surface-treated film 20 used in step (a).

Surface activation treatment such as corona treatment, plasma treatment, and Itro treatment may be performed on the bonding surfaces of the surface-treated film 20 and the polarizing plate 10 and the pressure-sensitive adhesive layer 31 in order to improve their adhesion. .

(Step (b))
The step (b) is a step of adjusting the elongation stress (23° C.) of the pressure-sensitive adhesive layer 31 in the laminate obtained in the step (a) so as to be 0.9 N/mm ² or more. Through the step (b), the pressure-sensitive adhesive layer 31, which is soft in the laminate obtained in the step (a), is hardened, and the surface hardness of the composite polarizing plate 1 can be improved. The step (b) may be performed with the laminated body in the form of a sheet, or with the laminated body wound into a roll.

Step (b) is not particularly limited as long as the elongation stress (23° C.) of the adhesive layer 31 can be within the above range. The step (b) can be performed according to the components contained in the adhesive layer 31, for example, it may be a step of storing the laminate obtained in the step (a), and the adhesive layer 31 is polymerized. When an initiator is included, the step of heating or irradiating with active energy rays may be used.
The step (b) is preferably a step of storing the laminate. The step of storing the laminate is, for example, a step of curing the laminate obtained in step (a) to advance the reaction of the reactive components (for example, the base polymer and the cross-linking agent) contained in the adhesive layer 31. may be

When the step (b) is a step of storing the laminate, the environmental conditions for storage are not particularly limited as long as the elongation stress (23° C.) of the adhesive layer 31 can be 0.9 N/mm ² or more.
The preferred temperature for step (b) is usually 10° C. or higher, may be 15° C. or higher, or may be 20° C. or higher, and is usually 35° C. or lower, and may be 30° C. or lower. There may be. A preferable relative humidity for performing the step (b) is usually 30% RH or higher, 40% RH or higher, 45% RH or higher, and usually 70% RH. RH or less, 65% RH or less, or 60% RH or less.

When the step (b) is a step of storing the laminate, the storage period may be selected according to the type of the adhesive composition used to form the adhesive layer 31, the environmental conditions described above, and the like. However, for example, it may be 6 days or more, 7 days or more, 8 days or more, 9 days or more, or 10 days or more. By being within the above period, it is easy to adjust the elongation stress (23° C.) of the adhesive layer 31 to 0.9 N/mm ² or more by the step (b).

Details of the layers and films constituting the composite polarizing plate 1 will be described below.
(Adhesive layer)
The adhesive layer is a layer formed using an adhesive composition. A pressure-sensitive adhesive composition exhibits adhesiveness when it is attached to an adherend, and is called a pressure-sensitive adhesive.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 10 μm or less, may be 8 μm or less, may be 7 μm or less, or may be 6 μm or less, and is usually 1 μm or more. Yes, and may be 3 μm or more. By setting the thickness of the pressure-sensitive adhesive layer within the above range, the surface hardness of the composite polarizing plate can be improved.

The adhesive composition for forming the adhesive layer contains (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, polyvinyl ether resin as a main component (base polymer). be able to. A main component means a component containing 50% by weight or more of the total solid content of the pressure-sensitive adhesive composition. Among them, a pressure-sensitive adhesive composition using a (meth)acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, etc., is suitable. The adhesive composition may be active energy ray-curable or heat-curable. (Meth)acrylic refers to at least one of acrylic and methacrylic.

Examples of the (meth)acrylic resin as the base polymer used in the pressure-sensitive adhesive composition include butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, Polymers or copolymers containing one or more of (meth)acrylic acid esters such as 2-ethylhexyl (meth)acrylate as monomers are preferably used.

It is preferable to copolymerize a monomer having a reactive functional group with the base polymer.
Examples of monomers having a reactive functional group include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl Monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylate and glycidyl (meth)acrylate, can be mentioned.

The glass transition temperature of the (meth)acrylic resin contained in the pressure-sensitive adhesive composition is preferably −30° C. or lower, more preferably −35° C. or lower, and is usually −50° C. or higher, It may be -45°C or higher. When the glass transition temperature of the (meth)acrylic resin is within the above range, it becomes easier to obtain a pressure-sensitive adhesive layer having the extension stress and the extension stress (23° C.) within the above ranges. The glass transition temperature can be measured by the method described in Examples below.

The adhesive composition may contain only the above base polymer, but usually further contains a cross-linking agent. Examples of cross-linking agents include those that are divalent or higher metal ions that form carboxylic acid metal salts and the like with carboxyl groups; polyamine compounds that form amide bonds and the like with carboxyl groups. polyepoxy compounds and polyols that form an ester bond or the like with a carboxyl group; and isocyanate compounds that form an amide bond or the like with a carboxyl group. Among them, isocyanate compounds are preferred.

An isocyanate compound is a compound having at least two isocyanato groups (--NCO) in the molecule. Examples of isocyanate compounds include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, chlorophenylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, tri phenylmethane triisocyanate and the like. Isocyanate compounds include polyhydric alcohol compound adducts (adducts) of the above-described compounds (e.g., adducts with glycerol, trimethylolpropane, etc.), isocyanurates, burette-type compounds, polyether polyols, polyester polyols, and acrylic polyols. , polybutadiene polyol, polyisoprene polyol, etc., a urethane prepolymer type isocyanate compound, and a blocked isocyanate compound obtained by blocking the isocyanato group of an organic polyvalent isocyanate compound.

The content of the isocyanate compound is 0.1 parts by mass or more, may be 1 part by mass or more, or may be 3 parts by mass or more with respect to 100 parts by mass of the base polymer (especially (meth)acrylic resin). Also, it may be 10 parts by mass or less, may be 8 parts by mass or less, or may be 6 parts by mass or less.

(Surface treatment film)
The surface-treated film has a substrate film and a surface-treated layer formed on the surface of the substrate film. The surface treatment layer 22 may be a part of the base film 21 and may be a surface layer portion of the base film 21, or may be a layer separate from the base film 21 laminated on the base film 21. good. When the surface treatment layer 22 is a layer separate from the base film 21, it is preferable that the base film 21 and the surface treatment layer 22 are in direct contact with each other.

For the base film, the resin film described as the material used for the protective film described later can be used.

As described above, the surface treatment layer can be one or more selected from the group consisting of an antireflection layer, an antiglare layer, a hard coat layer, and an antifouling layer. The surface treatment layer may be a laminate of an antiglare hard coat layer, an antireflection layer and an antifouling layer. The surface treatment layer may be a coating layer formed by applying a coating liquid to the surface of the substrate film, or may be a film layer formed by chemical vapor deposition or physical vapor deposition.

The antireflection layer has the function of suppressing the reflection of external light. When the surface-treated film of the composite polarizing plate has an antireflection layer, it is possible to suppress a decrease in contrast due to reflection of external light.

The antireflection layer is, for example, one in which the surface treatment layer is an uneven pattern structure portion on the surface of the base film, and the period of the unevenness is controlled to the wavelength of visible light or less (base film having a moth-eye structure on the surface); Examples include those in which the surface-treated layer is a fine concavo-convex pattern formed on the surface of the substrate film by applying a composition or the like; and those in which the surface-treated layer has a single layer or multiple layers with an adjusted refractive index.

The antireflection layer is preferably a thin film whose thickness and refractive index are strictly controlled, or a laminate of two or more thin films. A thin film refers to a film having a thickness of 1 μm or less. The antireflection layer can be configured to exhibit an antireflection function by canceling out the reversed phases of the incident light and the reflected light using the interference effect of light. The wavelength region of visible light that exhibits the antireflection function is, for example, 380 to 780 nm, and the wavelength region with particularly high luminosity is in the range of 450 to 650 nm. It is preferable to design the antireflection layer so that The thickness of the antireflection layer is preferably 100 nm to 350 nm, more preferably 150 nm to 300 nm.

In designing an antireflection layer based on the interference effect of light, as a means for improving the interference effect, for example, there is a method of increasing the refractive index difference between the antireflection layer and the antiglare layer described later. In general, in a multilayer antireflection layer having a structure in which 2 to 15 thin films (thin films whose thickness and refractive index are strictly controlled) are laminated, by forming multiple layers of components with different refractive indices with a predetermined thickness, , the degree of freedom in the optical design of the antireflection layer increases, the antireflection effect can be further improved, and the spectral reflection characteristics can be made uniform (flat) in the visible light region. Since thin films require high thickness accuracy, each layer is generally formed by dry methods such as vacuum deposition, sputtering, and CVD (chemical vapor deposition). By using an antireflection film in which each layer is formed by sputtering, a composite polarizing plate with high scratch resistance can be obtained.

As the antireflection layer, one in which a low refractive index layer and a high refractive index layer are alternately laminated is preferably used. The high refractive index layers or the low refractive index layers may not have the same refractive index, but if they are made of the same material and have the same refractive index, the material cost and film formation cost can be suppressed. preferred from

Materials constituting the low refractive index layer include silicon dioxide (SiO ₂ ), silicon oxynitride (SiON), gallium oxide (Ga ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), lanthanum fluoride (LaF ₃ ), magnesium fluoride (MgF ₂ ), sodium aluminum fluoride (Na ₃ AlF ₆ ), and the like. Among them, silicon dioxide (SiO ₂ ) is most preferable from the viewpoints of low refractive index, no absorption in the visible light region, high film strength, and the like.

Materials constituting the high refractive index layer include niobium pentoxide (Nb ₂ O ₅ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), silicon oxynitride (SiON ), silicon nitride (Si ₃ N ₄ ) and silicon niobium oxide (SiNbO). Among them, niobium pentoxide (Nb ₂ O ₅ ) or titanium dioxide (TiO ₂ ) is more preferable from the viewpoint of high refractive index and high film strength. Niobium (Nb ₂ O ₅ ) is most preferred.

For any compound, the refractive index can be changed to some extent by controlling the composition ratio of the constituent elements to deviate from the stoichiometric composition ratio, or by controlling the film density and forming the film. Materials constituting the low-reflectance layer and the high-reflectance layer are not limited to the above compounds as long as they satisfy the above-described refractive index conditions. Moreover, unavoidable impurities may be contained.

When the surface-treated film has a structure in which an antireflection layer is laminated on a base film, the arithmetic mean roughness Ra of the surface of the base film on the side where the antireflection layer is formed is 1.5 nm or less. It is preferably 1.0 nm or less, and more preferably 1.0 nm or less. The arithmetic mean roughness Ra may be 0.00 nm or more, and may be 0.05 nm or more. The arithmetic mean roughness Ra is obtained from an observation image of 1 μm square using an atomic force microscope (AFM).

The antiglare layer can have functions such as improving visibility, suppressing reflection of external light, and reducing moire (interference fringes). The antiglare layer can have a fine uneven shape on the surface. The fine irregularities can be formed by adding a filler or by finely embossing the surface.

The antiglare layer may be, for example, an antiglare hard coat layer formed by dispersing fine particles in a coating liquid containing a curable resin for forming a hard coat layer, which will be described later. Fine particles dispersed in the coating liquid include various metal oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide; glass fine particles; polymethyl methacrylate, polystyrene, polyurethane, Crosslinked or uncrosslinked organic fine particles made of various transparent polymers such as acryl-styrene copolymers, benzoguanamine, melamine, and polycarbonate; and transparent particles such as silicone fine particles can be used without particular limitation. These microparticles|fine-particles can be used by selecting suitably 1 type(s) or 2 or more types. Among them, fine particles having a refractive index higher than that of the curable resin contained in the coating liquid are preferable, and organic fine particles having a refractive index of 1.5 or more such as styrene beads (refractive index 1.59) are preferable. The fine particles preferably have an average particle size of 1 to 10 μm, more preferably 2 to 5 μm. Although the proportion of the fine particles is not particularly limited, it is preferably 6 to 20 parts by weight with respect to 100 parts by weight of the matrix resin.

The coating liquid for forming the antiglare layer may contain a thixotropic agent (silica, mica, etc. having a particle size of 0.1 μm or less). This makes it possible to easily form a fine concave-convex structure with protruding particles.

The hard coat layer has the function of improving the surface hardness of the base film and can improve the scratch resistance of the surface. When the surface treatment film is a hard coat layer, the surface hardness of the surface treatment layer side of the surface treatment film is, for example, HB or more, may be F or more, may be H or more, or may be 2H or more. may be 3H or more. The pencil hardness can be measured according to JIS K 5600-5-4:1999, as described in Examples below.

The hard coat layer can be formed, for example, by applying a coating liquid of a composition containing a curable resin onto the base film. The coating liquid may contain additives such as a leveling agent, a thixotropic agent, and an antistatic agent in addition to the curable resin.

Examples of curable resins include thermosetting resins, ultraviolet curable resins, and electron beam curable resins. Types of curable resins include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, amide resins, silicone resins, silicate resins, epoxy resins, melamine resins, oxetane resins, and acrylic urethane. Various resins, such as system resin, are mentioned. One or more of these curable resins can be appropriately selected and used.

Among these, the curable resins are (meth)acrylic resins, (meth)acrylic urethane resins, and epoxy resins because they have high hardness, can be cured by ultraviolet irradiation, and are excellent in productivity. Among them, (meth)acrylic urethane resins are preferred. UV-curable resins include UV-curable monomers, oligomers, polymers, and the like. UV-curable resins preferably used include, for example, those having UV-polymerizable functional groups, among which those containing (meth)acrylic monomers or oligomers having two or more, particularly 3 to 6, functional groups as components. mentioned.

Although the thickness of the hard coat layer is not particularly limited, it is preferably 0.5 μm or more, more preferably 1 μm or more, in order to achieve high hardness. Considering ease of formation by coating, the thickness of the hard coat layer is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less.

When the surface-treated film has a structure in which a hard coat layer is laminated on a base film, the arithmetic mean roughness of the hard coat layer is the arithmetic mean roughness of the surface of the base film on which the hard coat layer is formed. The arithmetic mean roughness Ra is obtained from an observation image of 1 μm square using an atomic force microscope (AFM). By forming the hard coat layer by coating as described above, the arithmetic mean roughness of the surface of the substrate film can be reduced.

The antifouling layer can impart functions such as water repellency, oil repellency, sweat resistance, and antifouling properties to the surface-treated film. The antifouling layer can contain antifouling agents such as fluorine-containing organic compounds such as fluorocarbons, perfluorosilanes, and polymeric compounds thereof.

(Polarizing element)
The polarizing element is an absorbing polarizing film that has the property of absorbing linearly polarized light with a plane of vibration parallel to its absorption axis and transmitting linearly polarized light with a plane of vibration perpendicular to the absorption axis (parallel to the transmission axis). be.

The polarizing element has a polyvinyl alcohol-based resin layer (hereinafter sometimes referred to as a "PVA-based resin layer") with a dichroic dye adsorbed and oriented. A known polarizing element can be used. As a polarizing element, a stretched film obtained by dyeing a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as a "PVA-based resin film") with a dichroic dye and uniaxially stretching the film; A laminate film having a coating layer formed by applying a coating liquid containing a polyvinyl alcohol resin (hereinafter sometimes referred to as "PVA resin") is used, and the coating layer is dyed with a dichroic dye to obtain a laminate film. A stretched layer obtained by uniaxially stretching the. Stretching may be performed after dyeing with a dichroic dye, stretching may be performed while dyeing, or dyeing may be performed after stretching.

PVA-based resin is obtained by saponifying polyvinyl acetate-based resin. Polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable therewith. Other copolymerizable monomers include, for example, unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, unsaturated sulfonic acids and the like.

The degree of saponification of the PVA-based resin is preferably 85 mol% or more, more preferably 90 mol% or more, and still more preferably 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA-based resin is, for example, 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The PVA-based resin may be modified, for example, aldehyde-modified polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like.

Iodine or dichroic dyes are examples of dichroic dyes that are adsorbed and oriented on the PVA-based resin layer. Preferably, the dichroic dye is iodine. Dichroic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black, and the like.

The thickness of the polarizing element is preferably 3 μm or more and 35 μm or less, more preferably 4 μm or more and 30 μm or less, and still more preferably 5 μm or more and 25 μm or less. When the thickness of the polarizing element is 35 μm or less, for example, it is possible to suppress the influence of the polyene conversion of the PVA-based resin on the deterioration of the optical properties in a high-temperature environment. When the thickness of the polarizing element is 3 μm or more, it becomes easy to achieve the desired optical characteristics.

(Manufacturing method of polarizing element)
The manufacturing method of the polarizing element is not particularly limited, but a method in which a pre-rolled PVA-based resin film is sent out and subjected to stretching, dyeing, cross-linking, etc. (hereinafter referred to as "manufacturing method 1"); A method comprising a step of applying a coating liquid containing a PVA-based resin onto a substrate film to form a PVA-based resin layer as a coating layer, and stretching the obtained laminate (hereinafter referred to as "manufacturing method 2" ) are typical.

Production method 1 includes a step of uniaxially stretching a PVA-based resin film, a step of dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, and a PVA system to which the dichroic dye is adsorbed. It can be produced through a step of treating the resin film with an aqueous boric acid solution and a step of washing with water after the treatment with the aqueous boric acid solution.

The swelling process is a treatment process in which the PVA-based resin film is immersed in a swelling bath. The swelling step can remove stains, blocking agents, and the like on the surface of the PVA-based resin film, and swelling the PVA-based resin film can suppress uneven dyeing. A medium containing water as a main component, such as water, distilled water, or pure water, is usually used for the swelling bath. Surfactants, alcohols and the like may be appropriately added to the swelling bath according to conventional methods. Potassium iodide may be used in the swelling bath from the viewpoint of controlling the potassium content of the polarizing element. In this case, the concentration of potassium iodide in the swelling bath should be 1.5% by mass or less. It is preferably 1.0% by mass or less, more preferably 0.5% by mass or less.

The temperature of the swelling bath is preferably 10°C or higher and 60°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C or higher and 30°C or lower. The immersion time in the swelling bath cannot be unconditionally determined because the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, but it is preferably 5 seconds or more and 300 seconds or less, and 10 seconds or more and 200 seconds or less. and more preferably 20 seconds or more and 100 seconds or less. The swelling step may be performed only once, or may be performed multiple times as necessary.

The dyeing process is a treatment process in which the PVA-based resin film is immersed in a treatment bath (dyeing bath) containing a dichroic dye, and the dichroic dye such as iodine can be adsorbed and oriented on the PVA-based resin film. The dyeing bath is a dyeing solution containing a dichroic dye, preferably an iodine solution. The iodine solution is preferably an aqueous iodine solution, and preferably contains iodine and iodide as a dissolution aid. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. mentioned. Among these, potassium iodide is preferable from the viewpoint of controlling the content of potassium in the polarizing element.

The concentration of iodine in the iodine solution is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.5% by mass or less. The concentration of iodide in the iodine solution is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and 0.1% by mass or more and 3 % by mass or less is more preferable.

The temperature of the dyeing bath is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C or higher and 30°C or lower. The immersion time in the dyeing bath cannot be unconditionally determined because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath, but it is preferably 10 seconds or more and 300 seconds or less, and 20 seconds or more and 240 seconds or less. is more preferable. The dyeing step may be performed only once, or may be performed multiple times as necessary.

The cross-linking step is a treatment step in which the PVA-based resin film dyed in the dyeing step is immersed in a treatment bath (cross-linking bath) containing a boron compound. Alternatively, dye molecules can be adsorbed on the crosslinked structure. Boron compounds include, for example, boric acid, borates, and borax. The cross-linking bath is generally an aqueous solution, but may be a mixed solution of an organic solvent miscible with water and water. The cross-linking bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of the boron compound in the cross-linking bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and 2% by mass or more and 5% by mass or less. It is more preferable to have When potassium iodide is used in the cross-linking bath, the concentration of potassium iodide in the cross-linking bath is preferably 1% by mass or more and 15% by mass or less, and is preferably 1.5% by mass or more and 10% by mass or less. More preferably, it is 2% by mass or more and 5% by mass or less.

The temperature of the cross-linking bath is preferably 20°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. The immersion time in the cross-linking bath cannot be unconditionally determined because the degree of cross-linking of the PVA-based resin film is affected by the temperature of the cross-linking bath, but it is preferably 5 seconds or more and 300 seconds or less, and 10 seconds or more and 200 seconds or less. is more preferable. The cross-linking step may be performed only once, or may be performed multiple times as necessary.

The stretching step is a processing step of stretching the PVA-based resin film in at least one direction to a predetermined magnification. In general, a PVA-based resin film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and both wet stretching and dry stretching can be employed. The stretching step may be performed only once, or may be performed multiple times as necessary. The stretching step may be performed at any stage in the production of the polarizing element.

For the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or a mixed solution of an organic solvent miscible with water and water can usually be used. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element. When potassium iodide is used in the drawing bath, the concentration of potassium iodide in the drawing bath is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less. , 3% by mass or more and 6% by mass or less. The treatment bath (stretching bath) can contain a boron compound from the viewpoint of suppressing film breakage during stretching. When a boron compound is included, the concentration of the boron compound in the drawing bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and 2% by mass. It is more preferable to be 5% by mass or less.

The temperature of the drawing bath is preferably 25° C. or higher and 80° C. or lower, more preferably 40° C. or higher and 80° C. or lower, further preferably 50° C. or higher and 75° C. or lower, and 65° C. or higher and 75° C. or lower. is particularly preferred. The immersion time in the stretching bath cannot be unconditionally determined because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath. is more preferable.
The stretching treatment in the wet stretching method may be performed together with one or more of the swelling process, dyeing process, cross-linking process and washing process.

Examples of the dry drawing method include a roll-to-roll drawing method, a heating roll drawing method, a compression drawing method, and the like. The dry stretching method may be applied together with the drying process.

The total draw ratio (cumulative draw ratio) applied to the PVA-based resin film can be appropriately set according to the purpose, but it is preferably 2 to 7 times, and 3 to 6.8 times. is more preferable, and more preferably 3.5 times or more and 6.5 times or less.

The washing process is a treatment process in which the PVA-based resin film is immersed in a washing bath, and foreign matter remaining on the surface of the PVA-based resin film can be removed. As the cleaning bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. Also, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is 1% by mass or more and 10% by mass. is preferably 1.5% by mass or more and 4% by mass or less, more preferably 1.8% by mass or more and 3.8% by mass or less.

The temperature of the washing bath is preferably 5°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower. The immersion time in the cleaning bath cannot be unconditionally determined because the degree of cleaning of the PVA-based resin film is affected by the temperature of the cleaning bath. and more preferably 3 seconds or more and 20 seconds or less. The washing step may be performed only once, or may be performed multiple times as necessary.

The drying process is a process of drying the PVA-based resin film washed in the washing process to obtain a polarizing element. Drying is performed by any appropriate method, such as natural drying, air drying, and heat drying.

Production method 2 includes a step of applying a coating liquid containing a PVA-based resin onto a base film, a step of uniaxially stretching the obtained laminated film, and a PVA-based resin layer of the uniaxially stretched laminated film with a dichroic dye. It can be produced through a step of dyeing to adsorb a polarizing element, a step of treating a film on which a dichroic dye is adsorbed with an aqueous boric acid solution, and a step of washing with water after treatment with an aqueous boric acid solution. The base film used to form the polarizing element may be used as a protective film for the polarizing element. If necessary, the base film may be peeled off from the polarizing element.

(Polarizer)
A polarizing plate includes at least a polarizing element. The polarizing plate may have a protective film on one side or both sides of the polarizing element. When the polarizing plate has protective films on both sides, the types and/or thicknesses of the protective films may be the same or different.

The polarizing element and the protective film are preferably laminated via a bonding layer (adhesive layer or adhesive layer). The lamination layer for laminating the polarizing element and the protective film is preferably an adhesive layer, and is preferably a cured layer of a water-based adhesive or an active energy ray adhesive, which will be described later.

The polarizing plate may be either a linear polarizing plate or a circular polarizing plate. If the polarizer is a circular polarizer, the polarizer has a λ/4 waveplate or the like. One or two or more retardation layers may be included in the polarizing plate, and the retardation layers can be laminated via bonding layers.

(Protective film)
The protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding property, stability of retardation value, and the like. A resin film is preferably used as the protective film.

Examples of resin materials constituting the protective film include methyl (meth)acrylate resins, polyolefin resins, cyclic olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, acrylonitrile-butadiene-styrene resins. Resins, acrylonitrile/styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, polyethylene terephthalate resins , polysulfone-based resins, polyethersulfone-based resins, polyarylate-based resins, polyamideimide-based resins, polyimide-based resins, and combinations of two or more of these. These resins can be used after being subjected to any appropriate polymer modification, and the polymer modification includes, for example, copolymerization, cross-linking, molecular terminal modification, stereoregularity control, and reaction between different polymers. Modifications, such as mixing, including cases.

The cellulosic resin can be an organic acid ester or mixed organic acid ester of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups and/or butyryl groups. Examples thereof include cellulose acetate, propionate, butyrate, and mixed esters thereof. Among them, triacetyl cellulose, diacetyl cellulose, cellulose acylate, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

Cyclic olefin-based resin is a general term for resins polymerized with cyclic olefins as polymerization units, and is described, for example, in JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137. resins. The cyclic olefin-based resin is preferably a norbornene-based resin. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene, and their copolymers (typically random copolymers), and graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Specific examples of cyclic olefins include norbornene-based monomers.

In addition to the resins described above, appropriate additives may be added to the resin material that constitutes the protective film as long as the transparency is not impaired. Additives such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retardation reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids , matting agents, antibacterial agents, antifungal agents, and the like. A plurality of types of these additives may be used in combination.

The thickness of the protective film is usually 1 μm or more and 100 μm or less, but from the viewpoint of strength, handleability, etc., it is preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and 15 μm or more and 50 μm or less. is more preferred.

The protective film may have other optical functions at the same time, and may be formed into a laminated structure in which multiple layers are laminated. The film thickness of the protective film is preferably thin from the viewpoint of optical properties, but if it is too thin, the strength will decrease and the processability will be poor. A suitable film thickness is 5 to 100 μm, preferably 10 to 80 μm, more preferably 15 to 70 μm.

The protective film may have a single layer structure or a multilayer structure. The protective film may have an antistatic layer on one side or both sides.

The protective film may have a retardation function for the purpose of viewing angle compensation, etc. In that case, the film itself may have a retardation function, or may have a separate retardation layer, It may be a combination of both. The protective film having a retardation function may be laminated via a lamination layer (adhesive layer or adhesive layer) via another protective film laminated to the polarizing element.

(Lamination layer, other adhesive layer)
The bonding layer is an adhesive layer (hereinafter referred to as "adhesive layer [bonding layer]") or an adhesive layer.
The bonding layer in the case of the adhesive layer [bonding layer] and the other adhesive layer for bonding the composite polarizing plate to the image display element are obtained by bonding the surface-treated film and the polarizing plate described above. The one described in the pressure-sensitive adhesive layer for bonding can be mentioned.

The thickness of the pressure-sensitive adhesive layer [bonding layer] and the other pressure-sensitive adhesive layer are each independently preferably 1 μm or more and 200 μm or less, more preferably 2 μm or more and 100 μm or less, and 2 μm or more and 80 μm or less. is more preferable, and it is particularly preferable to be 3 μm or more and 50 μm or less.

Any appropriate adhesive can be used as the adhesive that constitutes the adhesive layer. As the adhesive, a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, or the like can be used, but a water-based adhesive is preferable.

The thickness of the adhesive when applied can be set to any appropriate value. For example, it is set so that an adhesive layer having a desired thickness is obtained after curing or after heating (drying). The thickness of the adhesive layer is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, still more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm. It is below.

A known water-based adhesive can be used as the water-based adhesive. As the water-based adhesive, a water-based adhesive containing a PVA-based resin (hereinafter sometimes referred to as "PVA-based adhesive") is preferably used. The average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably 100-5500, more preferably 1000-4500, from the viewpoint of adhesiveness. The average saponification degree of the PVA-based resin is preferably 85 mol % to 100 mol %, more preferably 90 mol % to 100 mol %, from the viewpoint of adhesiveness.

The PVA-based resin contained in the PVA-based adhesive used when bonding the polarizing element and the protective film preferably contains an acetoacetyl group. This is because the adhesiveness between the protective film and the PVA-based resin layer constituting the polarizing element is excellent, and the durability is excellent. A PVA-based resin containing an acetoacetyl group can be obtained, for example, by reacting a PVA-based resin with diketene by any method. The degree of modification of the acetoacetyl group of the PVA-based resin containing the acetoacetyl group is typically 0.1 mol % or more, preferably 0.1 mol % to 20 mol %.

The concentration of the PVA-based resin in the PVA-based adhesive is preferably 0.1 wt% to 15 wt%, more preferably 0.5 wt% to 10 wt%.

When the PVA-based resin contains an acetoacetyl group, the PVA-based adhesive preferably contains one or more of glyoxal, glyoxylate, and methylolmelamine as a cross-linking agent. It is preferable to contain at least one, and it is particularly preferable to contain glyoxal.

The PVA-based adhesive may contain an organic solvent. In this case, since it is miscible with water, the organic solvent is preferably an alcohol, and among the alcohols, methanol or ethanol is preferable.

From the viewpoint of improving heat resistance, the PVA-based adhesive further contains urea compounds such as urea, urea derivatives, thiourea, and thiourea derivatives; reducing agents such as ascorbic acid, erythorbic acid, thiosulfuric acid, and sulfurous acid; and dicarboxylic acids such as phthalic acid; ammonium compounds such as ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride; dextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; A blocked isocyanate compound; a nitroxy radical such as an N-oxyl compound; a compound having a nitroxide group;

Active energy ray-curable adhesives are adhesives that are cured by irradiation with active energy rays such as ultraviolet rays. For example, adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin , an adhesive containing a binder resin and a photoreactive cross-linking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy-based monomers, photocurable (meth)acrylic monomers, and photocurable urethane-based monomers, and oligomers derived from these monomers. . Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays.

(Release film)
The release film is provided so as to be peelable from another pressure-sensitive adhesive layer for bonding the composite polarizing plate to the image display element, and covers and protects the surface of the other pressure-sensitive adhesive layer. The release film has a substrate layer and a release treatment layer. The base layer may be a resin film. The resin film can be formed, for example, from the resin material used for forming the protective film described above.
The release treatment layer may be any known release treatment layer, and examples thereof include a layer formed by coating a base material layer with a release agent such as a fluorine compound or a silicone compound.

(protection film)
A protection film is provided so that peeling is possible with respect to a surface treatment film. The protective film may contain a substrate layer and an adhesive layer, and may be a self-adhesive film. The base layer may be a resin film, and the base layer can be formed from, for example, the resin material used to form the protective film described above. Examples of the pressure-sensitive adhesive layer include those described in the above-described pressure-sensitive adhesive layer [bonding layer]. Examples of the thermoplastic resin that constitutes the self-adhesive film include polypropylene-based resins and polyethylene-based resins.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Measurement of glass transition temperature]
The glass transition temperature (Tg) of the (meth)acrylic resin is measured using a differential scanning calorimeter (DSC) "EXSTAR DSC6000" manufactured by SII Nanotechnology Co., Ltd. under a nitrogen atmosphere, with a temperature range of -80 to 50. °C and a heating rate of 10°C/min.

[Measurement of stress of adhesive layer (Y)]
A release film (polyethylene terephthalate film having a thickness of 38 μm with a release treatment layer) is attached to the surface of the adhesive layer (Y) side of the adhesive sheet (Y) formed using the adhesive composition described later. In addition, a pressure-sensitive adhesive sheet with a double-sided release film having a pressure-sensitive adhesive layer (Y) with a thickness of 5 μm (layer structure: release film/adhesive layer (Y)/release film) was heated at a temperature of 23° C. and a relative humidity of 50% RH. for 2 days, 3 days, 8 days, and 10 days. Peel off one release film from each adhesive sheet with a double-sided release film after storage, remove the adhesive layer (Y) of length 150 mm × width 30 mm, and remove the adhesive layer (Y) in the length direction (direction of 150 mm ) to prepare a cylindrical sample with a diameter of about 1 mm and a height (width) of 30 mm. For each sample prepared, under the conditions of a temperature of 23 ° C. and a relative humidity of 50% RH, a material testing machine (STA-1225S, manufactured by Orientec Co., Ltd.) was used, a distance between chucks of 10 mm, and a tensile speed of 300 mm / min. measured the stress in the range of 0% to 1600% elongation.
The measurement results are shown in FIG. As shown in FIG. 2, compared to the samples stored for a short period of time (2 days, 3 days), the samples stored for a long time (8 days, 10 days) had a larger stress at 800% elongation.

[Measurement of surface hardness]
The release film was peeled off from the composite polarizing plates obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer (X) was laminated on a glass plate. In this state, from the surface treatment film side of the composite polarizing plate, JIS K 5600-5-4: 1999 "Paint general test method-Part 5: Mechanical properties of coating film-Section 4: Scratch hardness (pencil method) A pencil hardness test specified in ” was performed.

[Measurement of adhesive strength]
The composite polarizing plates obtained in Examples and Comparative Examples were cut into a size of 200 mm in length (length in the direction parallel to the absorption axis direction of the polarizing element) x 25 mm in width, and the release film was peeled off to form an adhesive layer ( X) was attached to a glass plate to obtain a test piece. This test piece was placed in an environment with a temperature of 23° C. and a relative humidity of 50% RH for 24 hours. After that, put a cutter blade between the polarizing plate and the surface treatment film of the test piece, peel off 30 mm from the end in the length direction, grasp the peeled part with the upper grip of the tester, and the lower grip with the glass plate. Grabbed. For the test piece in this state, in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55%, JIS K 6854-2: 1999 "Adhesive-Peeling adhesive strength test method-Part 2: 180 degree peel" , A peel test was performed at a grip movement speed of 300 mm / min, and the average peel force (unit: N / 25 mm) over a length of 60 mm excluding 30 mm of the grip part was obtained. and the adhesive strength of the pressure-sensitive adhesive layer (Y) between. Table 1 shows the results.

<Fabrication of polarizing element>
A polyvinyl alcohol-based resin film having a thickness of 75 μm made of polyvinyl alcohol having an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol % or more is uniaxially stretched by a dry method to about 5 times, and further while maintaining a tensioned state. , immersed in pure water at a temperature of 60°C for 1 minute, and then immersed in an aqueous solution of iodine/potassium iodide/water at a weight ratio of 0.05/5/100 at a temperature of 28°C for 60 seconds. After that, it was immersed in an aqueous solution of potassium iodide/boric acid/water at a weight ratio of 8.5/8.5/100 at a temperature of 72° C. for 300 seconds. Subsequently, after washing with pure water at a temperature of 26° C. for 20 seconds, the film was dried at a temperature of 65° C. to obtain a 28 μm thick polarizing element in which iodine was adsorbed and oriented on the polyvinyl alcohol resin film.

<Preparation of water-based adhesive>
50 g of a modified polyvinyl alcohol resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Corporation: Gohsenex Z-410) is dissolved in 950 g of pure water, heated at a temperature of 90° C. for 2 hours, cooled to room temperature, and a PVA solution is obtained. got This PVA solution, pure water, maleic acid, and glyoxal were mixed with a polyvinyl alcohol resin concentration of 3.0% by weight, a maleic acid concentration of 0.01% by weight, and a glyoxal concentration of 0.15% by weight. to obtain a water-based adhesive.

<Preparation of polarizing plate and polarizing plate with adhesive layer (X)>
(Preparation of polarizing plate)
A cellulose acylate film “TD40” (manufactured by Fuji Film Co., Ltd.: thickness 40 μm) as a protective film was immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) kept at a temperature of 55° C. for 2 minutes. was washed with water. Thereafter, the film was immersed in a 0.05 mol/L sulfuric acid aqueous solution at a temperature of 25° C. for 30 seconds and then passed through a washing bath under running water for 30 seconds to neutralize the film. After that, draining with an air knife was repeated three times. After draining, the film was held in a drying zone at a temperature of 70° C. for 15 seconds and dried to prepare a saponified protective film.

The saponified protective film is laminated on both sides of the polarizing element prepared above via the water-based adhesive prepared above using a roll laminator, and dried at a temperature of 80 ° C. for 5 minutes to form a polarizing plate. got The water-based adhesive interposed between the polarizing element and the protective film was adjusted so that the thickness of the adhesive layer after drying was 100 nm on both sides.

(Preparation of polarizing plate with adhesive layer (X))
A pressure-sensitive adhesive sheet (X) was prepared by forming a pressure-sensitive adhesive layer (X) having a thickness of 25 μm on a release film (polyethylene terephthalate film having a thickness of 38 μm with a release treatment layer). The pressure-sensitive adhesive layer (X) side of the pressure-sensitive adhesive sheet (X) was laminated on one side of the polarizing plate obtained above to obtain a polarizing plate with the pressure-sensitive adhesive layer (X). The bonding surface between the pressure-sensitive adhesive layer (X) and the polarizing plate was subjected to corona treatment. The obtained polarizing plate with adhesive layer (X) had a layer structure of protective film/adhesive layer/polarizing element/adhesive layer/protective film/adhesive layer (X)/release film.

<Preparation of surface treatment film>
(Formation of antiglare hard coat layer)
UV-curable urethane (meth)acrylate monomer (refractive index 1.51) 50 parts by weight, UV-curable (meth)acrylate monomer (refractive index 1.51) 50 parts by weight, average particle size 3.5 μm 14 parts by weight of methyl methacrylate-styrene copolymer beads (refractive index 1.55), 5 parts by weight of benzophenone-based photopolymerization initiator, and toluene were mixed with a solution having a solid content of 40% by weight. (refractive index: 1.49)) and dried at 120°C for 5 minutes. After that, curing treatment was performed by irradiating ultraviolet rays to prepare an antiglare hard-coated film in which an antiglare hard-coated layer having a concave-convex structure and a thickness of about 4 μm was formed on the base film.

(Formation of antireflection layer)
According to the examples of JP-A-2019-035969, the antiglare hard-coated film obtained above is introduced into a roll-to-roll type sputtering deposition apparatus, and the antiglare hard coat is applied while the film is running. After bombarding the layer formation surface (plasma treatment with Ar gas), a 5 nm SiOx layer (x<2) is formed as an adhesion improving layer, and a 20 nm Nb ₂ O ₅ layer and a 35 nm layer are formed thereon. A SiO ₂ layer of 35 nm, a Nb ₂ O ₅ layer of 35 nm and a SiO ₂ layer of 100 nm were sequentially deposited to form an antireflection layer having a four-layer structure and a thickness of 190 nm. A fluorine-based resin was formed as an antifouling layer on the antireflection layer so as to have a thickness of 5 nm, thereby producing a surface-treated film. The surface treatment layer of the surface treatment film had a laminated structure of an antiglare hard coat layer, an antireflection layer, and an antifouling layer.

<Preparation of adhesive sheet (Y)>
(Manufacturing of (meth)acrylic resin)
74.5 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate, and 5 parts by mass of 2-hydroxyethyl acrylate were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. 0.5 parts by mass of acrylic acid, 0.2 parts by mass of azobisisobutyronitrile, and 120 parts by mass of ethyl acetate were charged together with 120 parts by mass of ethyl acetate. A polymerization reaction was carried out for 8 hours while keeping the liquid temperature around 60° C. to obtain a solution of a (meth)acrylic resin. When the glass transition temperature Tg of the (meth)acrylic resin was measured by the method described above, it was -40°C.

(Preparation of adhesive composition)
To the solution of the (meth)acrylic resin obtained above, to 100 parts by mass of the (meth)acrylic resin, Coronate L (trimethylolpropane adduct of tolylene diisocyanate) Ethyl acetate solution: Solid content concentration 75% by mass , Tosoh Corporation) 4 parts by mass (solid content) were mixed to obtain an adhesive composition.

(Formation of adhesive layer (Y))
The pressure-sensitive adhesive composition prepared above was applied to a release film (polyethylene terephthalate film having a thickness of 38 µm with a release treatment layer) to form a pressure-sensitive adhesive layer (Y) having a thickness of 5 µm to prepare a pressure-sensitive adhesive sheet (Y). bottom.

[Example 1]
Immediately after the adhesive sheet (Y) was prepared, the adhesive layer (Y) side of the adhesive sheet (Y) was laminated to the substrate film side surface of the surface treatment film prepared above. Two days after the preparation of the pressure-sensitive adhesive sheet (Y) (substantially after lamination of the pressure-sensitive adhesive sheet (Y) on the surface-treated film), the release film on the pressure-sensitive adhesive layer (Y) is peeled off, The polarizing plate side of the polarizing plate with the pressure-sensitive adhesive layer (X) was laminated on the exposed pressure-sensitive adhesive layer (Y) to obtain a laminate. The bonding surfaces of the surface-treated film, the pressure-sensitive adhesive layer (Y), and the polarizing plate with the pressure-sensitive adhesive layer (X) were subjected to corona treatment.

The steps of preparing the pressure-sensitive adhesive sheet (Y), laminating the pressure-sensitive adhesive sheet (Y), and obtaining the laminate were all performed under an environment of a temperature of 23° C. and a relative humidity of 50% RH. The resulting laminate was stored for 6 days under an environment of 23° C. temperature and 50% RH relative humidity to obtain Composite Polarizing Plate (1). Preparation of the pressure-sensitive adhesive sheet (Y) and lamination of the pressure-sensitive adhesive sheet (Y) were performed in a state where the stress at 800% elongation of the pressure-sensitive adhesive layer (Y) was 0.6 N/mm ² or less based on the graph shown in FIG. The step of obtaining a laminate was carried out in a state where the pressure-sensitive adhesive layer (Y) had a stress of 0.6 N/mm ² at an elongation of 800%.
Moreover, the stress at elongation of 800% at a temperature of 23° C. of the adhesive layer (Y) of the composite polarizing plate (1) was 1.1 N/mm ² .

The layer structure of the composite polarizing plate (1) is: surface treatment film (surface treatment layer/base film)/adhesive layer (Y)/polarizing plate (protective film/adhesive layer/polarizing element/adhesive layer/protective film )/adhesive layer (X)/release film. The composite polarizing plate (1) is observed using a microscope (VHX-5000, manufactured by Keyence Corporation), between the surface treatment film and the adhesive layer (Y), and between the adhesive layer (Y) and the polarizing plate. The number of air bubbles (the number per 1 m ² of the composite polarizer) was counted. Further, the surface hardness and adhesive strength of the composite polarizing plate (1) were measured by the methods described above. Table 1 shows the results.

[Comparative Example 1]
8 days after laminating the adhesive sheet (Y) on the surface-treated film, the polarizing plate side of the polarizing plate with the adhesive layer (X) was laminated on the adhesive layer (Y) of the surface-treated film. A composite polarizing plate (2) was obtained in the same manner as in Example 1, except that a laminate was obtained. Preparation of the pressure-sensitive adhesive sheet (Y) and lamination of the pressure-sensitive adhesive sheet (Y) were performed in a state where the stress at 800% elongation of the pressure-sensitive adhesive layer (Y) was 0.6 N/mm ² or less based on the graph shown in FIG. However, the step of obtaining the laminate was carried out in a state where the stress at 800% elongation of the pressure-sensitive adhesive layer (Y) was 1.1 N/mm ² . Also, from the graph shown in FIG. 2, the stress at 800% elongation at a temperature of 23° C. of the adhesive layer (Y) of the composite polarizing plate (2) was 1.1 N/mm ² . In the same procedure as in Example 1, the number of air bubbles (composite The number per 1 m ² of the polarizing plate) was counted, and the surface hardness and adhesive strength were measured.
Table 1 shows the results.

1 Composite polarizing plate, 10 Polarizing plate, 11 Polarizing element, 12 Bonding layer, 13 Protective film, 20 Surface treatment film, 21 Base film, 22 Surface treatment layer, 31 Adhesive layer.

Claims

A method for manufacturing a composite polarizing plate in which a surface-treated film and a polarizing plate are laminated,
The surface-treated film has a base film and a surface-treated layer formed on the surface of the base film,
The polarizing plate includes at least a polarizing element,
The manufacturing method is
Step (a) of obtaining a laminate by bonding the surface-treated film and the polarizing plate via an adhesive layer having a stress of 0.8 N/mm 2 or less at 800% elongation;
A method for producing a composite polarizing plate, comprising the step (b) of adjusting the stress of the adhesive layer at 800% elongation at a temperature of 23° C. to 0.9 N/mm 2 or more in the laminate.
The step (a) is
A step (a1) of forming the pressure-sensitive adhesive layer on the surface-treated film;
2. The method for producing a composite polarizing plate according to claim 1, comprising a step (a2) of laminating the polarizing plate on the adhesive layer formed on the surface-treated film.
The method for producing a composite polarizing plate according to claim 2, wherein the step (a2) is performed within 6 days after the step (a1).
The method for manufacturing the composite polarizing plate according to any one of claims 1 to 3, wherein the step (b) is a step of storing the laminate.
The surface-treated film has the surface-treated layer on one side of the base film,
5. The method for producing a composite polarizing plate according to claim 1, wherein the laminate has the pressure-sensitive adhesive layer on the base film side of the surface treatment film.
The method for producing a composite polarizing plate according to any one of claims 1 to 5, wherein the polarizing plate has a protective film on one side or both sides of the polarizing element.
The method for producing a composite polarizing plate according to any one of claims 1 to 6, wherein the adhesive layer has a thickness of 10 µm or less.
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing a (meth)acrylic resin,
The method for producing a composite polarizing plate according to any one of claims 1 to 7, wherein the (meth)acrylic resin has a glass transition temperature of -30°C or lower.
The composite polarizing plate according to any one of claims 1 to 8, wherein the surface treatment layer is one or more selected from the group consisting of an antireflection layer, an antiglare layer, a hard coat layer, and an antifouling layer. manufacturing method.