KR20230113511A - Optical laminate and image display device - Google Patents

Abstract

(Problem) To provide an optical laminate excellent in crack resistance even if it has a mold release processing part.
(Solution) The optical layered body of the present invention has a release processing part, and is provided with an adhesive layer, a polarizer, an adhesive layer, a brightness enhancing film, and a surface treatment layer having a thickness of 2.5 μm or less in this order.

Description

Optical laminate and image display device {OPTICAL LAMINATE AND IMAGE DISPLAY DEVICE}

The present invention relates to an optical laminate and an image display device. More specifically, it relates to an optical laminate having a release-processed portion (eg, notch, opening) and an image display device including the optical laminate.

BACKGROUND OF THE INVENTION Optical laminates such as polarizers are used in various image display devices such as mobile phones and notebook personal computers (PCs). Depending on the application, the optical laminate can be subjected to mold release processing such as notches and openings. For example, in an image display device in which a camera is mounted, it is known to form an opening in a portion corresponding to the camera (Patent Document 1). However, there is a problem that stress concentration occurs in the mold release processing part when the mold release process is performed on the optical laminate, and cracks are likely to occur.

Various optical films are used for the optical layered body depending on the use. For example, a luminance enhancing film is used for the purpose of enhancing luminance of an image display device. The brightness enhancement film is composed of a stretched film or a liquid crystal layer, and thus is a mechanically fragile film. Therefore, in an optical laminate comprising a brightness enhancing film, the problem of crack generation due to release processing tends to become more remarkable.

Japanese Unexamined Patent Publication No. 2014-112238

The present invention has been made in order to solve the above conventional problems, and its main object is to provide an optical laminate having excellent crack resistance even if it has a mold release processing part.

The optical layered body of the present invention has a release processing portion, and is provided with an adhesive layer, a polarizer, an adhesive layer, a brightness enhancing film, and a surface treatment layer having a thickness of 2.5 μm or less in this order.

In one embodiment, the thickness of the said adhesive layer is 20 micrometers or less.

In one embodiment, the surface treatment layer is a hard coat layer.

In one embodiment, the thickness of the said polarizer is 30 micrometers or less.

In another aspect of the present invention, an image display device is provided. This image display device includes the optical laminate.

ADVANTAGE OF THE INVENTION According to this invention, even if it has a mold release processing part, the optical laminated body excellent in crack resistance can be provided. The optical layered body of the present invention has a release processing portion, and is provided with an adhesive layer, a polarizer, an adhesive layer, a brightness enhancing film, and a surface treatment layer having a thickness of 2.5 μm or less in this order. In the release-processed optical laminate, stress concentration occurs in the release-processed portion, which may locally generate film bending stress. Therefore, cracks tend to occur particularly in the brightness enhancing film. By making the thickness of the surface treatment layer thin (more specifically, to 2.5 μm or less), the bending moment can be reduced and the bending stress applied to the brightness enhancement film can be alleviated. Therefore, the crack resistance of an optical laminated body can be improved.

1 is a schematic cross-sectional view of an optical laminate in one embodiment of the present invention.
2 is a schematic plan view of an optical laminate in one embodiment of the present invention, FIG. 2 (a) is a schematic plan view of an optical laminate having a circular opening as a release processing part, and FIG. 2 (b) is It is a schematic plan view of the optical laminated body which has a notch part as a release processing part.
3 is a schematic plan view of an optical laminate in another embodiment of the present invention.
4 is a schematic perspective view of an example of a linearly polarized light separating type luminance enhancing film that can be used in the optical laminate of the present invention.
Fig. 5 is a schematic plan view illustrating a release processing part of an optical laminate having a release processing unit produced in an example.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

A. Optical stack

1 is a schematic cross-sectional view of an optical laminate in one embodiment of the present invention. The optical laminate 100 in the illustrated example includes an adhesive layer 10, a polarizer 20, an adhesive layer 30, a brightness enhancing film 40, and a surface treatment layer 50 having a thickness of 2.5 μm or less in this order. provided with When the thickness of the surface treatment layer 50 is 2.5 μm or less, the bending stress applied to the brightness enhancement film is alleviated, and an optical laminate having excellent crack resistance can be provided even when the mold release portion is provided. Examples of the surface treatment layer include a hard coat layer, an antireflection layer, an antiglare layer, and an antiglare layer. The surface treatment layer is preferably a hard coat layer. In addition, although not shown, in addition to the pressure-sensitive adhesive layer 10, the polarizer 20, the adhesive layer 30, the brightness improving film 40, and the surface treatment layer 50, any appropriate other layer may be further provided. . As another layer, protective layers, such as a polarizer, are mentioned. In addition, in order to protect the adhesive layer 10 appropriately until use practically, a separator is temporarily affixed so that peeling is possible.

2 is a schematic plan view of an optical laminate in one embodiment of the present invention. The optical layered body of the present invention has any appropriate mold release processing part depending on the application or the like. For example, the mold release part 11 (Fig. 2 (a)) which is a circular opening (through hole) as shown in the illustration, the mold release part 11 (Fig. 2 (b)) which is a notch (notch), etc. can be heard In the illustrated example, only one mold release processing part is formed, but two or more mold release processing parts may be formed as needed. In addition, as will be described later, the shape of the optical laminate itself may be a release process, that is, the entire outer edge of the optical laminate may be a release processing part.

The optical stack 100 may be designed in any appropriate shape depending on the purpose for which it is used. In one embodiment, it may be processed so that the shape itself of an optical laminated body may be molded. As a shape of the optical layered body 100, a rectangle, a circular shape, a diamond shape, a different shape etc. are mentioned, for example.

3 is a schematic plan view of an optical laminate in another embodiment of the present invention. The optical laminate 100 in the illustrated example is suitably used for an automobile instrument panel. The optical laminate 100 is configured by connecting and installing the first display unit 60 and the second display unit 70, and through-holes 61 and 71 for fixing various meter needles are formed near the center of each display unit, respectively. has been The diameter of the through hole is, for example, 0.5 mm to 100 mm. The outer edges of the display units 60 and 70 are formed in an arc shape along the direction of rotation of the meter needle.

The release processing portion may be formed by any suitable method. Examples include punching blades such as Thomson blades and Pinnacle blades, cutting processing by spindles, etc., processing by cutters, or lasers. Processing conditions at the time of forming the release processing portion may be set to any appropriate conditions depending on the forming means used, the thickness of each layer, and the like.

Hereinafter, the pressure-sensitive adhesive layer 10, the polarizer 20, the adhesive layer 30, the brightness enhancing film 40, and the surface treatment layer 50 will be described in detail.

B. Adhesive layer

The thickness of the pressure-sensitive adhesive layer 10 can be set to any suitable thickness. For example, it is about 1 μm to 100 μm, preferably 2 μm to 50 μm, more preferably 2 μm to 40 μm, still more preferably 5 μm to 35 μm.

The pressure-sensitive adhesive layer 10 may be formed using any suitable pressure-sensitive adhesive. Examples of the adhesive include rubber-based adhesives, acrylic adhesives, silicone-based adhesives, urethane-based adhesives, vinylalkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. there is. Preferably, those having excellent optical transparency, exhibiting appropriate adhesive properties such as wettability, cohesion, and adhesiveness, and having excellent weather resistance, heat resistance, and the like are used. Specifically, an acrylic pressure-sensitive adhesive is preferably used.

The pressure-sensitive adhesive layer may be formed by any suitable method. For example, a method in which the adhesive is applied to a separator or the like subjected to peeling treatment and dried to remove the polymerization solvent, etc. to form an adhesive layer, followed by transfer, or a method in which the adhesive is coated and dried to remove the polymerization solvent, etc. A method of forming a layer on a polarizer, etc. are mentioned. As the separator subjected to the peeling treatment, a silicone peeling liner is preferably used. Moreover, when applying an adhesive, you may further add 1 or more types of solvents other than a polymerization solvent as needed.

Arbitrary suitable methods are used as a formation method (coating method) of an adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Methods, such as an extrusion coating method, are mentioned.

As a method of drying the adhesive, any suitable method can be used depending on the purpose. Preferably, a method of heating and drying is used. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, still more preferably 70°C to 170°C. By setting the heating temperature within the above range, a pressure-sensitive adhesive layer having excellent adhesive properties can be formed. Any suitable time may be employed for the drying time. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, still more preferably 10 seconds to 5 minutes.

The pressure-sensitive adhesive layer 10 may be protected with a peeled sheet (separator) until it is put into practical use. Arbitrary appropriate materials can be used as the constituent material of the separator. For example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, nets, foam sheets, and metal foils, and thin sheets such as laminates thereof, and the like can be heard From the viewpoint of excellent surface smoothness, it is preferably a plastic film.

As the plastic film, any film capable of protecting the pressure-sensitive adhesive layer may be used. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film , an ethylene-vinyl acetate copolymer film, and the like.

The thickness of the separator can be set to any suitable thickness. The thickness of the separator is usually 5 μm to 200 μm, preferably 5 μm to 100 μm. The separator may be subjected to release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder, or the like, and antistatic treatment such as coating, kneading, or vapor deposition, as necessary. Releasability from the pressure-sensitive adhesive layer can be improved by subjecting the surface of the separator to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment.

C. Polarizer

A polarizer is comprised by the resin film containing a dichroic substance typically. As the resin film, any suitable resin film that can be used as a polarizer can be employed. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

As the PVA-based resin forming the PVA-based resin film, any suitable resin may be used. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined according to JIS K 6726-1994. A polarizer excellent in durability can be obtained by using PVA-type resin of such a degree of saponification. When the degree of saponification is too high, there is a possibility of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. In addition, the average degree of polymerization can be obtained according to JIS K 6726-1994.

Examples of the dichroic substance contained in the resin film include iodine and organic dyes. These can be used individually or in combination of 2 or more types. Preferably iodine is used.

The resin film may be a single-layer resin film or a laminate of two or more layers.

As a specific example of the polarizer comprised from the resin film of a single layer, the thing to which the dyeing process by iodine and the extending|stretching process (typically uniaxial stretching) were given to the PVA system resin film is mentioned. Dyeing with the said iodine is performed by immersing a PVA-type resin film in iodine aqueous solution, for example. The draw ratio of the said uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment, or may be performed while dyeing. Moreover, you may dye|dye it after extending|stretching. Swelling treatment, crosslinking treatment, washing treatment, drying treatment and the like are given to the PVA-based resin film as necessary. For example, by immersing and washing the PVA-based resin film in water before dyeing, it is possible to clean the surface of the PVA-based resin film of stains and anti-blocking agents, as well as to swell the PVA-based resin film to prevent staining and the like. there is.

As a specific example of a polarizer obtained using a laminate, a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a PVA-based resin layer coated and formed on the resin substrate. A polarizer obtained using a layered product is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate, for example, by applying a PVA-based resin solution to the resin substrate, drying it, forming a PVA-based resin layer on the resin substrate, Obtaining a laminated body of a resin substrate and a PVA-based resin layer; Stretching and dyeing the laminate to make the PVA-based resin layer a polarizer; can be produced by. In this embodiment, extending|stretching typically includes immersing a layered product in boric acid aqueous solution and extending|stretching. In addition, if necessary, stretching may further include air-stretching the layered product at a high temperature (for example, 95° C. or higher) before stretching in a boric acid aqueous solution. The obtained laminate of the resin substrate/polarizer may be used as it is (that is, the resin substrate may be used as a protective film for the polarizer), and the resin substrate is peeled from the laminate of the resin substrate/polarizer, and the peeling surface is disposed according to the purpose. You may use it by laminating|stacking the suitable protective film of. The detail of the manufacturing method of such a polarizer is described in Unexamined-Japanese-Patent No. 2012-73580, for example. The entire description of the above publication is incorporated herein by reference.

The polarizer preferably exhibits absorption dichroism at any one of the wavelengths of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, still more preferably 99.9% or more.

The thickness of the polarizer can be set to any suitable value. The thickness is typically 0.5 μm or more and 80 μm or less, preferably 30 μm or less, more preferably 25 μm or less, still more preferably 18 μm or less, particularly preferably 12 μm or less, and further Particularly preferably, it is less than 8 μm. The thickness of the polarizer is preferably 1 μm or more.

D. Adhesive layer

The adhesive layer is composed of an adhesive or pressure-sensitive adhesive. As the adhesive or pressure sensitive adhesive, any suitable adhesive or pressure sensitive adhesive may be used. Examples of the adhesive include rubber-based adhesives, acrylic adhesives, silicone-based adhesives, urethane-based adhesives, vinylalkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. there is. Preferably, those having excellent optical transparency, exhibiting appropriate adhesive properties such as wettability, cohesion, and adhesiveness, and having excellent weather resistance, heat resistance, and the like are used. Specifically, an acrylic pressure-sensitive adhesive is preferably used.

As the adhesive, any suitable adhesive may be used as long as it is optically transparent. For example, those of various forms such as solvent type, hot melt type, and active energy ray curing type can be used. Preferably, an active energy ray curable adhesive is used.

The thickness of the adhesive layer is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 12 μm or less. The thickness of the adhesive layer is preferably 2 μm or more. When the thickness of the adhesive layer is within this range, the laminated state of the polarizer and the luminance enhancing film can be maintained in good condition. In addition, bending stress applied to the luminance enhancing film can be more alleviated.

Details of the pressure-sensitive adhesive constituting the adhesive layer are disclosed in, for example, Japanese Unexamined Patent Publication No. 2008-46147. The entire description of the above publication is incorporated herein by reference.

E. Brightness enhancement film

The brightness enhancement film is a film that separates polarized light to improve brightness, and may be a linear polarization separation type or a circular polarization separation type. Examples of the brightness enhancing film include a film composed of a stretched film and a film composed of a liquid crystal layer. When natural light (for example, light from a backlight of an image display device) is incident, the brightness enhancing film separates the light into two polarization components, transmits linearly polarized light of a predetermined polarization axis or circularly polarized light in a predetermined direction, and transmits the light. It has a function to reflect undesirable polarized light. By passing the non-transmitting polarized light through a reflector or the like and re-injecting depolarized light into the luminance enhancing film, the efficiency of using predetermined polarized light can be improved. Hereinafter, as an example, a linear polarization separation type luminance enhancing film (reflection type polarizer) will be described.

The linear polarization separation type luminance enhancing film has a function of separating incident light into two orthogonal polarization components, transmitting one polarization component and reflecting the other polarization component. 4 is a schematic perspective view of an example of a luminance enhancing film of a linear polarization separation type. The linearly polarized light separation-type luminance enhancing film in the illustrated example is a multilayer laminate in which a layer A having birefringence and a layer B having substantially no birefringence are alternately laminated. The total number of layers of such a multilayer laminate may be, for example, 50 to 1000. In the illustrated example, the refractive index (nx) of the layer A in the x-axis direction is greater than the refractive index (ny) in the y-axis direction, and the refractive index (nx) of the layer B in the x-axis direction and the refractive index (ny) in the y-axis direction are substantially same. Therefore, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis and the y-axis direction becomes the transmission axis. The refractive index difference between the A layer and the B layer in the x-axis direction is preferably 0.2 to 0.3. In addition, the x-axis direction corresponds to the stretching direction of the brightness enhancing film.

The A layer is preferably composed of a material that exhibits birefringence by stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyester (eg, polyethylene naphthalate), polycarbonate, and acrylic resin (eg, polymethyl methacrylate). Polyethylene naphthalate is preferred. The layer B is preferably made of a material that does not substantially exhibit birefringence even when stretched. Representative examples of such materials include copolyesters of naphthalenedicarboxylic acid and terephthalic acid.

The linear polarization separation type luminance enhancing film transmits light (eg, p-wave) having a first polarization direction at the interface between the A layer and the B layer, and has a second polarization direction orthogonal to the first polarization direction. It reflects light (e.g., s-waves). At the interface between the A layer and the B layer, a part of the reflected light is transmitted as light having a first polarization direction, and a part of the reflected light is reflected as light having a second polarization direction. In the inside of the luminance enhancing film, the use efficiency of light can be increased by repeating such reflection and transmission many times.

In one embodiment, the linear polarization separation-type luminance enhancing film may include a reflective layer R as an outermost layer on the opposite side to the polarizer, as shown in FIG. 4 . By forming the reflective layer R, the light utilization efficiency can be further increased because the light returned to the outermost portion of the luminance enhancing film without being finally used can be further utilized. The reflective layer R typically exhibits a reflective function due to the multilayer structure of the polyester resin layer.

The linearly polarized light separation-type luminance enhancing film can be typically produced by combining coextrusion and transverse stretching. Co-extrusion can be done in any suitable way. For example, a feed block system or a multi-manifold system may be used. For example, the material constituting the A layer and the material constituting the B layer are extruded from the feed block, and then multilayered using a multiplier. In addition, such a multi-layering device is known to those skilled in the art. Next, the obtained elongated multilayer laminate is typically stretched in a direction (TD) orthogonal to the transport direction. The refractive index of the material constituting the layer A (for example, polyethylene naphthalate) increases only in the stretching direction by the transverse stretching, and consequently exhibits birefringence. The refractive index of the material constituting the layer B (for example, copolyester of naphthalene dicarboxylic acid and terephthalic acid) does not increase in any direction even by the transverse stretching. As a result, a luminance enhancing film (reflection type polarizer) having a reflection axis in the stretching direction (TD) and a transmission axis in the conveying direction (MD) can be obtained (TD corresponds to the x-axis direction in FIG. 4 and MD corresponds to the y-axis direction). corresponding to the axial direction). Also, the stretching operation can be performed using any appropriate device.

As the brightness enhancing film, one described in, for example, Japanese Patent Publication No. Hei 9-507308 can be used. A commercially available product may be used as it is, or a commercially available product may be used after secondary processing (for example, stretching) of the brightness enhancing film. As a commercial item, the brand name APCF by Nitto Denko Co., Ltd., the brand name DBEF by 3M Corporation, and the brand name APF by 3M Corporation are mentioned, for example.

F. Surface treatment layer

As the surface treatment layer 50, any suitable surface treatment layer is formed depending on the use of the optical laminate. The thickness of the surface treatment layer is 2.5 μm or less, preferably 2 μm or less, and more preferably 1.5 μm or less. In addition, the thickness of the surface treatment layer is preferably 0.5 μm or more. By setting the thickness of the surface treatment layer within the above range, the bending moment to the optical laminate can be reduced even when the release process is performed. Therefore, the bending stress to the brightness enhancement film included in the optical laminate is alleviated, and the crack resistance (more specifically, the crack resistance of the brightness enhancement film) of the optical laminate can be improved.

Examples of the surface treatment layer include a hard coat layer, an antireflection layer, an antiglare layer, and an antiglare layer. Preferably, the surface treatment layer is a hard coat layer. Since the hard coat layer is a layer with high hardness, it can generate a larger bending stress. When the thickness of the surface treatment layer is 2.5 μm or less, even when the surface treatment layer is made into a hard coat layer, the crack resistance of the optical laminate can be improved. Also, the crack resistance of the surface treatment layer itself can be improved.

The hard coat layer is preferably a cured layer of any appropriate ultraviolet curing resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain any suitable additive as needed. Representative examples of the additive include inorganic fine particles and/or organic fine particles. By including fine particles, for example, an appropriate refractive index can be provided.

The hard coat layer is typically provided to the optical laminate in a state in which a laminate is formed by subjecting a base material to a hard code process in advance. Any appropriate resin film can be employed as the substrate. Examples of the resin constituting the resin film include polyester-based resins, cellulose-based resins, polycarbonate-based resins, and (meth)acrylic-based resins. In addition, in this specification, "(meth)acrylic resin" refers to acrylic resin and/or methacrylic resin.

G. Other floors

The optical laminate may include any appropriate other layer in addition to the pressure-sensitive adhesive layer, the polarizer, the adhesive layer, the brightness enhancing film, and the surface treatment layer. For example, a protective layer is mentioned. Examples of the material for forming the protective layer include cellulose resins such as diacetyl cellulose and triacetyl cellulose, (meth)acrylic resins, cycloolefin resins, olefin resins such as polypropylene, and esters such as polyethylene terephthalate resins. based resins, polyamide-based resins, polycarbonate-based resins, copolymer resins thereof, and the like.

The thickness of the protective layer is preferably 10 μm to 100 μm. A protective film is typically laminated|stacked on a polarizer through arbitrary adhesive layers (specifically, an adhesive bond layer and an adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activated energy ray curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive.

H. Image display device

The image display device of the present invention includes the optical laminate. As an image display device, a liquid crystal display device and an organic electroluminescent device are mentioned, for example. In the image display device, the optical laminate is preferably disposed on the backlight side. As described above, the optical laminate of the present invention is excellent in crack resistance even when subjected to release processing. Therefore, it can be suitably used also for an image display device having a heterogeneous image display unit represented by an automobile instrument panel and a smart watch.

(Example)

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples.

[Production Example 1] Production of polarizer

As the substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption of 0.75% and a Tg of 75° C. was used. Corona treatment was performed on one side of the substrate, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl denaturation degree 4.6%, saponification degree 99.0 mol% or more) were applied to the corona-treated surface. , manufactured by Nippon Kosei Kagaku Kogyo Co., Ltd., trade name "Gosefamer Z200") at a ratio of 9:1 is applied and dried at 25°C to form a PVA-based resin layer having a thickness of 11 µm to prepare a laminate. did.

The obtained layered product was uniaxially stretched at the free end by 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in a 120°C oven (air assisted stretching).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment).

Next, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30°C while adjusting the iodine concentration and the immersion time so as to have a predetermined transmittance. In this example, 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide were mixed with 100 parts by weight of water, and immersed in an iodine aqueous solution for 60 seconds (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a solution temperature of 30°C for 30 seconds (crosslinking treatment).

After that, while immersing the layered product in an aqueous solution of boric acid at a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water), In the longitudinal direction), uniaxial stretching was performed so that the total stretching ratio was 5.5 times (submerged stretching).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30°C (washing treatment).

Subsequently, an ultraviolet curable adhesive was applied to the surface of the PVA-based resin layer of the laminate so that the thickness of the cured adhesive layer was 0.5 μm, and a protective film (20 μm thick, TAC film) was bonded. Subsequently, ultraviolet rays were irradiated as active energy rays to cure the adhesive, and a polarizing plate (polarizer (transmittance: 42.3%, thickness: 5 μm)/protective film) having a total thickness of 25.5 μm was obtained.

[Production Example 2] Preparation of adhesive layer forming composition

91 parts of butyl acrylate, 6 parts of N-acryloylmorpholine, 2.7 parts of acrylic acid, 0.3 part of 2-hydroxybutyl acrylate, polymerization in a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet pipe, and condenser As an initiator, 0.1 parts by weight of 2,2'-azobisisobutyronitrile and 200 parts by weight of ethyl acetate were introduced, and nitrogen gas was introduced and substituted with nitrogen while gently stirring. Next, while maintaining the liquid temperature in the flask at around 55°C, a polymerization reaction was performed for 8 hours to prepare an acrylic polymer solution. The weight average molecular weight of the acrylic polymer was 2,200,000.

[Production Example 3] Preparation of hard coat layer forming composition

A coating solution for forming a hard coat layer was prepared by adding 0.5% by weight of a leveling agent to an acrylic resin raw material (manufactured by Dainippon Ink Co., Ltd., trade name: GRANDIC PC1071) and further diluting with ethyl acetate so that the solid content concentration was 50% by weight did. In addition, the leveling agent is a copolymer copolymerized at a molar ratio of dimethylsiloxane:hydroxypropylsiloxane:6-isocyanatehexylisocyanuric acid:aliphatic polyester = 6.3:1.0:2.2:1.0.

[Production Example 4] Preparation of pressure-sensitive adhesive composition

100 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, 0.1 part by weight of 2-hydroxybutyl acrylate, 2,2'- 0.1 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate were introduced, and nitrogen gas was introduced and nitrogen-substituted, stirring gently. Subsequently, while maintaining the liquid temperature in the flask at around 55°C, a polymerization reaction was performed for 8 hours to prepare an acrylic polymer solution. The weight average molecular weight of the acrylic polymer was 1,920,000. 0.6 part by weight of a polyisocyanate-based crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Kogyo Co., Ltd.) composed of a trimethylolpropane adduct of tolylene diisocyanate as a crosslinking agent was blended with respect to 100 parts of solid content of the obtained acrylic polymer solution, and the acrylic adhesive solution prepared

[Example 1]

The pressure-sensitive adhesive composition obtained in Production Example 4 was applied to one side of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., thickness: 38 μm) subjected to silicone treatment to a thickness of 20 μm, and was incubated at 130° C. for 3 minutes. It was dried to form an adhesive layer. The formed pressure-sensitive adhesive layer was transferred to the polarizer-side surface of the polarizing plate obtained in Production Example 1.

The hard coat layer forming composition obtained in Production Example 3 was applied to a brightness enhancing film (manufactured by 3M, product name "APF V4", thickness: 16 µm) so that the thickness after drying was 0.5 µm to form a hard coat layer.

Through the adhesive layer forming composition obtained in Production Example 2 in which the protective film-side surface of the polarizing plate on which the pressure-sensitive adhesive layer was formed and the luminance-enhancing film-side surface of the luminance-enhancing film on which the hard coat layer was formed were applied to each thickness described in Table 1, It was joined and a laminated body was obtained.

The obtained laminate was subjected to end milling to obtain a radius of curvature (R ₁ ) of 2.5 mm, a length (W ₁ ) of 5 mm, and a maximum depth (D) of 6.5 mm, as shown in the lower part (inverted U-shaped part) of FIG. 5 . A phosphorus notch portion was formed in the laminate to obtain an optical laminate having a mold release processing portion. In addition, the absorption axis of the polarizer was made parallel to the long side (L) of the optical layered body.

[Examples 2 to 8]

An optical laminate having a mold release processing part was obtained in the same manner as in Example 1 except that the hard coat layer forming composition was applied so that the thickness of the hard coat layer became the thickness shown in Table 1.

(Comparative Examples 1 to 2)

An optical laminate having a mold release processing part was obtained in the same manner as in Example 1 except that the hard coat layer forming composition was applied so that the thickness of the hard coat layer became the thickness shown in Table 1.

The following evaluation was performed using the optical layered body obtained by Examples 1-8 and Comparative Examples 1-2. The results are shown in Table 1.

(crack resistance evaluation)

Using the optical laminates obtained in Examples and Comparative Examples, a heat cycle test was conducted 100 times in a cold/heat shocker (product name: TSA-303EL-W, manufactured by Espek Corporation). As for the heat cycle, a cycle in which the temperature was raised from -40°C to 85°C over 30 minutes and cooled down to -40°C over 30 minutes when the chamber temperature reached 85°C was set as one cycle. After the heat cycle test of 100 cycles, the presence or absence of cracks in the release processing portion was visually confirmed, and when cracks were confirmed, the length of the cracks was measured using an optical microscope. When a plurality of cracks could be confirmed, the length of the largest crack was set as the crack length.

Each optical laminate was evaluated according to the following criteria.

5: No cracks in any layer of the optical laminate

4: Cracks of less than 100 μm in any one layer of the optical laminate

3: Crack of 100 μm or more and less than 200 μm in any one layer of the optical laminate

2: There is a crack of 200 μm or more and less than 300 μm in any one layer of the optical laminate

1: Any one layer of the optical laminate has a crack exceeding 300 μm

In the optical laminates of Examples 1 to 8, it was confirmed that there were no cracks in the optical laminates even after a heat cycle test of 100 cycles, and the crack resistance was excellent.

The optical layered body of the present invention is suitably used for image display devices such as liquid crystal display devices and organic EL devices. The optical laminate of the present invention can also be suitably used for an image display device having a heterogeneous image display unit typified by an instrument panel of a vehicle and a smart watch.

10: adhesive layer
20: polarizer
30: adhesive layer
40: luminance enhancement film
50: surface treatment layer
100: optical laminate

Claims (3)

It has a mold release processing part,
An optical laminate comprising a pressure-sensitive adhesive layer, a polarizer, an adhesive layer having a thickness of 12 μm or less, a brightness enhancing film, and a surface treatment layer having a thickness of 1.5 μm or less in this order,
The optical laminate wherein the surface treatment layer is a hard coat layer. According to claim 1,
The thickness of the said polarizer is 30 micrometers or less, an optical laminated body. An image display device comprising the optical laminate according to claim 1 or 2.