JP7387361B2 - Optical laminates and image display devices - Google Patents

Description

The present invention relates to an optical laminate and an image display device. More specifically, the present invention relates to an optical laminate having a shaped portion (for example, a cutout, an opening) and an image display device including the optical laminate.

Optical laminates such as polarizers are used in various image display devices such as mobile phones and notebook personal computers (PCs). The optical laminate may be processed into irregular shapes, such as cutouts and openings, depending on the intended use. For example, in an image display device equipped with a camera, it is known to form an opening in a portion corresponding to the camera (Patent Document 1). However, when the optical laminate is shaped into a different shape, stress concentration occurs in the shaped part, which causes cracks to easily occur.

Various optical films are used in the optical laminate depending on the purpose. For example, a brightness enhancement film is used for the purpose of improving the brightness of an image display device. The brightness enhancement film is composed of a stretched film or a liquid crystal layer, and is a mechanically fragile film. Therefore, in an optical laminate including a brightness-enhancing film, the problem of crack generation due to irregular processing tends to become more prominent.

Japanese Patent Application Publication No. 2014-112238

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide an optical laminate that has excellent crack resistance even if it has irregularly shaped portions.

The optical laminate of the present invention has a modified section and includes, in this order, an adhesive layer, a polarizer, an adhesive layer, a brightness enhancement film, and a surface treatment layer having a thickness of 2.5 μm or less.
In one embodiment, the thickness of the adhesive layer is 20 μm or less.
In one embodiment, the surface treatment layer is a hard coat layer.
In one embodiment, the thickness of the polarizer is 30 μm or less.
In another aspect of the invention, an image display device is provided. This image display device includes the optical laminate described above.

According to the present invention, it is possible to provide an optical laminate having excellent crack resistance even if it has irregularly shaped portions. The optical laminate of the present invention has a modified section and includes, in this order, an adhesive layer, a polarizer, an adhesive layer, a brightness enhancement film, and a surface treatment layer having a thickness of 2.5 μm or less. In an optical laminate that has been processed into a irregular shape, stress concentration occurs in the irregularly processed portion, and film bending stress may be generated locally. Therefore, cracks tend to occur particularly in the brightness enhancement film. By reducing the thickness of the surface treatment layer (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 the optical laminate can be improved.

FIG. 1 is a schematic cross-sectional view of an optical laminate in one embodiment of the present invention. 2A is a schematic plan view of an optical laminate according to an embodiment of the present invention, FIG. FIG. 2 is a schematic plan view of an optical laminate having a cutout portion as a modified portion. FIG. 3 is a schematic plan view of an optical laminate in another embodiment of the present invention. FIG. 1 is a schematic perspective view of an example of a linearly polarized light separating type brightness enhancement film that can be used in the optical laminate of the present invention. FIG. 3 is a schematic plan view illustrating a modified shaped part of an optical laminate having a modified shaped part produced in an example.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate in one embodiment of the present invention. The illustrated optical laminate 100 includes an adhesive layer 10, a polarizer 20, an adhesive layer 30, a brightness enhancement film 40, and a surface treatment layer 50 having a thickness of 2.5 μm or less in this order. To provide an optical laminate having a thickness of 2.5 μm or less for the surface treatment layer 50, which relieves bending stress applied to the brightness enhancement film and has excellent crack resistance even when it has irregularly shaped parts. Can be done. 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. Further, although not shown in the drawings, any suitable other layer may be further provided in addition to the adhesive layer 10, polarizer 20, adhesive layer 30, brightness enhancement film 40, and surface treatment layer 50. Other layers include protective layers such as polarizers. Moreover, in practical use, in order to properly protect the adhesive layer 10 until use, a separator is temporarily attached in a releasable manner.

FIG. 2 is a schematic plan view of an optical laminate in one embodiment of the present invention. The optical laminate of the present invention has any appropriate irregularly shaped portion depending on the use and the like. For example, the irregularly shaped part 11 (FIG. 2(a)), which is a circular opening (through hole) as shown in the illustration, the irregularly shaped part 11 (FIG. 2(b)), which is a notch, etc. Can be mentioned. In the illustrated example, only one irregularly shaped part is formed, but two or more irregularly shaped parts may be formed as necessary. Furthermore, as will be described later, the shape of the optical laminate itself may be irregular, that is, the entire outer edge of the optical laminate may be a modified portion.

The optical laminate 100 can be designed into any suitable shape depending on the intended use. In one embodiment, the optical laminate itself may be processed to have an irregular shape. Examples of the shape of the optical laminate 100 include a rectangle, a circle, a diamond, and an irregular shape.

FIG. 3 is a schematic plan view of an optical laminate in another embodiment of the present invention. The illustrated optical laminate 100 is suitably used in an automobile instrument panel. The optical laminate 100 is composed of a first display section 60 and a second display section 70 arranged in series, and near the center of each display section there are through holes 61, 71 for fixing various meter needles. are formed respectively. The diameter of the through hole is, for example, 0.5 mm to 100 mm. The outer edges of the display sections 60 and 70 are formed in an arc shape along the rotation direction of the meter needle.

The contoured portion may be formed by any suitable method. Examples include cutting with a punching blade such as a Thomson blade and a pinnacle blade, a spindle, a cutter, a laser, or the like. The processing conditions for forming the irregularly shaped part may be set to any appropriate conditions depending on the forming means used, the thickness of each layer, and the like.

Hereinafter, the adhesive layer 10, polarizer 20, adhesive layer 30, brightness enhancement film 40, and surface treatment layer 50 will be explained in detail.

B. Adhesive Layer The thickness of the adhesive layer 10 can be set to any appropriate thickness. For example, it is about 1 μm to 100 μm, preferably 2 μm to 50 μm, more preferably 2 μm to 40 μm, and even more preferably 5 μm to 35 μm.

Adhesive layer 10 may be formed using any suitable adhesive. Examples of adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, and polyacrylamide adhesives. and cellulose-based adhesives. Preferably, those having excellent optical transparency, exhibiting appropriate adhesive properties such as wettability, cohesiveness, and adhesiveness, and having excellent weather resistance, heat resistance, etc. are used. Specifically, an acrylic adhesive is preferably used.

The adhesive layer may be formed by any suitable method. For example, a method of applying the above-mentioned adhesive to a separator etc. that has been subjected to a release treatment and drying it to remove the polymerization solvent etc. to form an adhesive layer, and then transferring it, or a method of applying the above-mentioned adhesive to a separator etc. that has been dried and then transferring it. Examples include a method of forming an adhesive layer on a polarizer by removing a polymerization solvent and the like. As the release-treated separator, preferably a silicone release liner is used. Note that when applying the adhesive, one or more solvents other than the polymerization solvent may be further added as necessary.

Any suitable method can be used as the method for forming the adhesive layer (coating method). 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. Examples include methods such as extrusion coating.

Any suitable method can be used to dry the adhesive depending on the purpose. Preferably, a heating drying method is used. The heat drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, even 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 drying time may be employed. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, even more preferably 10 seconds to 5 minutes.

The adhesive layer 10 may be protected with a release-treated sheet (separator) until it is put into practical use. Any suitable material can be used as a constituent material of the separator. Examples include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, nets, foam sheets, metal foils, and thin sheets such as laminates thereof. Preferred is a plastic film because of its excellent surface smoothness.

The plastic film may be any film that can protect the adhesive layer. 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, ethylene-vinyl acetate copolymer. Examples include films.

The thickness of the separator can be set to any appropriate thickness. The thickness of the separator is usually 5 μm to 200 μm, preferably 5 μm to 100 μm. The separator may be treated with silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agents, silica powder, etc., as well as antifouling treatment, as well as coated, kneaded, or vapor-deposited types. The antistatic treatment may be applied. By performing a peeling treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the separator, the peelability from the adhesive layer can be improved.

C. Polarizer A polarizer is typically composed of a resin film containing a dichroic substance. 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 resin (hereinafter referred to as "PVA resin") film.

Any suitable resin may be used as the PVA resin forming the PVA resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer with excellent durability can be obtained. If the degree of saponification is too high, there is a risk 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 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. Note that the average degree of polymerization can be determined according to JIS K 6726-1994.

Examples of dichroic substances contained in the resin film include iodine and organic dyes. These may be used alone or in combination of two or more. Preferably iodine is used.

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

A specific example of a polarizer made of a single-layer resin film includes a PVA resin film subjected to dyeing treatment with iodine and stretching treatment (typically, uniaxial stretching). The above-mentioned staining with iodine is performed, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing process or may be performed while dyeing. Alternatively, it may be dyed after being stretched. If necessary, the PVA resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA resin film in water and washing it with water before dyeing, it is possible to not only wash the dirt and anti-blocking agent on the surface of the PVA resin film, but also to swell the PVA resin film and dye it. Unevenness etc. can be prevented.

Specific examples of polarizers obtained using a laminate include a laminate of a resin base material and a PVA resin layer (PVA resin film) laminated on the resin base material, or a laminate of a resin base material and the resin Examples include polarizers obtained using a laminate with a PVA-based resin layer coated on a base material. A polarizer obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be obtained by, for example, applying a PVA-based resin solution to the resin base material and drying it. Forming a PVA-based resin layer thereon to obtain a laminate of a resin base material and the PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution, if necessary. The obtained resin base material/polarizer laminate may be used as is (that is, the resin base material may be used as a protective film for the polarizer), or the resin base material may be peeled from the resin base material/polarizer laminate. However, any appropriate protective film may be laminated on the release surface depending on the purpose. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

The polarizer preferably exhibits absorption dichroism at a wavelength 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, and 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 even more preferably is less than 8 μm. The thickness of the polarizer is preferably 1 μm or more.

D. Adhesive Layer The adhesive layer consists of adhesive or adhesive. Any suitable adhesive or pressure-sensitive adhesive can be used as the adhesive or pressure-sensitive adhesive. Examples of adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, and polyacrylamide adhesives. and cellulose-based adhesives. Preferably, those having excellent optical transparency, exhibiting appropriate adhesive properties such as wettability, cohesiveness, and adhesiveness, and having excellent weather resistance, heat resistance, etc. are used. Specifically, an acrylic adhesive is preferably used.

As the adhesive, any suitable adhesive can be used as long as it is optically transparent. For example, various forms such as a solvent type, a hot melt type, and an active energy ray curable 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, and even 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 such a range, the laminated state of the polarizer and the brightness enhancement film can be maintained well. Moreover, the bending stress applied to the brightness enhancement film can be further relaxed.

Details of the adhesive constituting such an adhesive layer are disclosed in, for example, Japanese Patent Laid-Open No. 2008-46147. The entire description of this publication is incorporated herein by reference.

E. Brightness Enhancing Film The brightness enhancing film is a film that separates polarized light to improve brightness, and may be of a linearly polarized light separating type or a circularly polarized light separating type. Examples of the brightness enhancement film include a film composed of a stretched film, a film composed of a liquid crystal layer, and the like. When natural light (for example, light from the backlight of an image display device) is incident on the brightness enhancement film, the light is separated into two polarized components, and linearly polarized light with a predetermined polarization axis or circularly polarized light in a predetermined direction is transmitted. It has the function of reflecting polarized light that does not pass through. By passing the polarized light that is not transmitted through a reflector or the like and causing the depolarized light to re-enter the brightness enhancement film, it is possible to improve the utilization efficiency of the predetermined polarized light. Hereinafter, a linearly polarized light separation type brightness enhancement film (reflection type polarizer) will be explained as an example.

A linearly polarized light separating type brightness enhancement film has a function of separating incident light into two orthogonal polarized components, transmitting one polarized component, and reflecting the other polarized component. FIG. 4 is a schematic perspective view of an example of a linearly polarized light separating type brightness enhancement film. The illustrated linearly polarized light separating type brightness enhancement film is a multilayer laminate in which layers A having birefringence and layers B having substantially no birefringence are alternately laminated. The total number of layers in such a multilayer laminate can be, for example, from 50 to 1000. In the illustrated example, the refractive index nx in the x-axis direction of the A layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of the B layer are substantially the same. be. Therefore, the refractive index difference between layer A and layer B 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 layer A and layer B in the x-axis direction is preferably 0.2 to 0.3. Note that the x-axis direction corresponds to the stretching direction of the brightness enhancement film.

The layer A is preferably made of a material that exhibits birefringence upon stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyesters (eg, polyethylene naphthalate), polycarbonates, and acrylic resins (eg, polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably made of a material that does not substantially exhibit birefringence even when stretched. A typical example of such a material is a copolyester of naphthalene dicarboxylic acid and terephthalic acid.

A linearly polarized light separation type brightness enhancement film transmits light having a first polarization direction (for example, p-wave) at the interface between layer A and layer B, and transmits light having a second polarization direction orthogonal to the first polarization direction. Reflects directional light (eg, S-wave). A portion of the reflected light is transmitted as light having the first polarization direction at the interface between the A layer and the B layer, and a portion thereof is reflected as light having the second polarization direction. By repeating such reflection and transmission many times inside the brightness enhancement film, the efficiency of light utilization can be increased.

In one embodiment, the linearly polarized light separating type brightness enhancement film may include a reflective layer R as the outermost layer on the side opposite to the polarizer, as shown in FIG. By providing the reflective layer R, it is possible to further utilize the light that is not ultimately used and has returned to the outermost part of the brightness enhancement film, thereby further increasing the light utilization efficiency. The reflective layer R typically exhibits a reflective function through a multilayer structure of polyester resin layers.

A linearly polarized light separating type brightness enhancement film can typically be produced by combining coextrusion and lateral stretching. Coextrusion may be performed in any suitable manner. For example, a feed block method or a multi-manifold method may be used. For example, a material constituting layer A and a material constituting layer B are extruded in a feedblock, and then multilayered using a multiplier. Note that such multilayering devices are known to those skilled in the art. Next, the obtained elongated multilayer laminate is typically stretched in a direction (TD) perpendicular to the transport direction. The material constituting layer A (for example, polyethylene naphthalate) has a refractive index increased only in the stretching direction by the lateral stretching, and as a result exhibits birefringence. The refractive index of the material constituting layer B (for example, a copolyester of naphthalene dicarboxylic acid and terephthalic acid) does not increase in any direction even by the lateral stretching. As a result, a brightness-enhancing film (reflective polarizer) having a reflective axis in the stretching direction (TD) and a transmission axis in the transport direction (MD) can be obtained (TD corresponds to the x-axis direction in FIG. 4). , MD corresponds to the y-axis direction). Note that the stretching operation can be performed using any suitable device.

As the brightness enhancing film, for example, those described in Japanese Patent Publication No. Hei 9-507308 can be used. As the brightness enhancement film, a commercially available product may be used as it is, or a commercially available product may be used after being subjected to secondary processing (for example, stretching). Commercially available products include, for example, APCF (trade name) manufactured by Nitto Denko Corporation, DBEF (trade name) manufactured by 3M Company, and APF (trade name) manufactured by 3M Company.

F. Surface Treatment Layer Any suitable surface treatment layer may be formed as the surface treatment layer 50 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. Moreover, 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 optical laminate is processed into a different shape. Therefore, the bending stress applied to the brightness enhancement film included in the optical laminate is relaxed, and the crack resistance of the optical laminate (more specifically, the crack resistance of the brightness improvement film) 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, larger bending stress may occur. When the thickness of the surface treatment layer is 2.5 μm or less, the crack resistance of the optical laminate can be improved even when the surface treatment layer is a hard coat layer. Furthermore, the crack resistance of the surface treatment layer itself can also be improved.

The hard coat layer is preferably a cured layer of any suitable ultraviolet curable 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 additives as necessary. 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.

Typically, the hard coat layer is provided to the optical laminate in a state in which a laminate is formed by subjecting a base material to a hard coat treatment in advance. Any suitable resin film can be used as the base material. Typical examples of the resin constituting the resin film include polyester resins, cellulose resins, polycarbonate resins, (meth)acrylic resins, and the like. Note that in this specification, "(meth)acrylic resin" refers to acrylic resin and/or methacrylic resin.

G. Other Layers The optical laminate may contain any appropriate other layers in addition to the above adhesive layer, polarizer, adhesive layer, brightness enhancement film, and surface treatment layer. For example, a protective layer may be mentioned. Examples of materials for forming the protective layer include cellulose resins such as diacetylcellulose and triacetylcellulose, (meth)acrylic resins, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. , polyamide resins, polycarbonate 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 to a polarizer via an arbitrary adhesive layer (specifically, an adhesive layer or a pressure-sensitive adhesive layer). The adhesive layer is typically formed of a PVA adhesive or an activation energy ray curable adhesive. The adhesive layer is typically formed of an acrylic adhesive.

H. Image Display Device The image display device of the present invention includes the optical laminate described above. Examples of the image display device include a liquid crystal display device and an organic EL device. In the image display device, the optical laminate is preferably placed on the backlight side. As described above, the optical laminate of the present invention has excellent crack resistance even when processed into a different shape. Therefore, it can also be suitably used for image display devices having irregularly shaped image display sections, such as automobile instrument panels and smart watches.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

[Production Example 1] Preparation of polarizer As a base material, a long, amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of 75°C was used. was used. Corona treatment was applied to one side of the base material, and polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6) was applied to the corona-treated surface. %, saponification degree of 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefimer Z200") in a ratio of 9:1 was coated and dried at 25°C to form a 11 μm thick film. A PVA-based resin layer was formed to produce a laminate.
The obtained laminate was uniaxially stretched free end to 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 120° C. (in-air assisted stretching).
Next, the laminate was immersed for 30 seconds in an insolubilization bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. (insolubilization treatment).
Next, the polarizing plate was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, 100 parts by weight of water was mixed with 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide. .
Next, it was immersed for 30 seconds in a crosslinking bath (an aqueous boric acid 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 liquid temperature of 30°C. (Crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 70°C. However, uniaxial stretching was performed between rolls having different circumferential speeds in the longitudinal direction (longitudinal direction) so that the total stretching ratio was 5.5 times (underwater stretching).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30° C. (cleaning treatment).
Next, an ultraviolet curable adhesive was applied to the surface of the PVA resin layer of the laminate so that the thickness of the adhesive layer after curing was 0.5 μm, and a protective film (thickness 20 μm, TAC film) was applied. pasted together. Next, the adhesive was cured by irradiating ultraviolet rays as active energy rays to obtain a polarizing plate (polarizer (transmittance 42.3%, thickness 5 μm)/protective film) with a total thickness of 25.5 μm.

[Production Example 2] Preparation of Adhesive Layer Forming Composition In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, 91 parts of butyl acrylate, 6 parts of N-acryloylmorpholine, and 2.0 parts of acrylic acid were placed. 7 parts, 0.3 parts of 2-hydroxybutyl acrylate, 0.1 parts by weight of 2,2'-zobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate, and nitrogen gas was introduced while stirring gently. The atmosphere was replaced with nitrogen. Next, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55° C. to prepare an acrylic polymer solution. The weight average molecular weight of the acrylic polymer was 2.2 million.

[Production Example 3] Preparation of hard coat layer forming composition 0.5% by weight of a leveling agent was added to acrylic resin raw material (manufactured by Dainippon Ink Co., Ltd., product name: GRANDIC PC1071), and further, a solid content concentration of 50% by weight was added. %, a coating solution for forming a hard coat layer was prepared. 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. It is.

[Production Example 4] Preparation of adhesive composition In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, 100 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, and 2-hydroxybutyl acrylate were added. 0.1 part by weight, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate were charged, and nitrogen gas was introduced while stirring gently to perform nitrogen substitution. Next, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55° C. to prepare an acrylic polymer solution. The weight average molecular weight of the acrylic polymer was 1.92 million. Per 100 parts of the solid content of the obtained acrylic polymer solution, 0.6 parts by weight of a polyisocyanate crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Kogyo Co., Ltd.) consisting of a trimethylolpropane adduct of tolylene diisocyanate as a crosslinking agent. were blended to prepare an acrylic adhesive solution.

[Example 1]
The adhesive composition obtained in Production Example 4 was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., thickness: 38 μm) to a thickness of 20 μm, and heated at 130°C. It was dried for 3 minutes to form an adhesive layer. The formed 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 enhancement film (manufactured by 3M Company, product name "APF V4", thickness: 16 μm) so that the thickness after drying was 0.5 μm to form a hard coat. formed a layer.
Obtained in Production Example 2 in which the protective film side surface of the polarizing plate on which the adhesive layer was formed and the brightness enhancement film side surface of the brightness enhancement film on which the hard coat layer was formed were coated to the respective thicknesses listed in Table 1. They were bonded together via the adhesive layer forming composition to obtain a laminate.
The obtained laminate was end milled to give a radius of curvature _R1 of 2.5 mm, a length _W1 of 5 mm, and a maximum depth D of 6.5 mm, as shown in the lower part (inverted U-shaped part) of FIG. A chipped part was formed in the laminate to obtain an optical laminate having a irregularly shaped part. Note that the absorption axis of the polarizer was made parallel to the long side L of the optical laminate.

[Examples 2 to 8]
An optical laminate having irregularly shaped parts was obtained in the same manner as in Example 1, except that the hard coat layer forming composition was applied so that the hard coat layer had the thickness shown in Table 1.

(Comparative Examples 1-2)
An optical laminate having irregularly shaped parts was obtained in the same manner as in Example 1, except that the hard coat layer forming composition was applied so that the hard coat layer had the thickness shown in Table 1.

The following evaluations were performed using the optical laminates obtained in Examples 1 to 8 and Comparative Examples 1 to 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 thermal shock apparatus (manufactured by ESPEC Co., Ltd., product name: TSA-303EL-W). One heat cycle consisted of raising the temperature from -40°C to 85°C over 30 minutes, and cooling the inside of the refrigerator to -40°C over 30 minutes when the temperature reached 85°C. After the 100-cycle heat cycle test, the presence or absence of cracks in the irregularly processed portion was visually confirmed, and when cracks were confirmed, the length of the cracks was measured using an optical microscope. When multiple cracks were confirmed, the length of the largest crack was defined as the crack length.
Each optical laminate was evaluated based on the following criteria.
5: No cracks in any layer of the optical laminate 4: Cracks of less than 100 μm in any layer of the optical laminate 3: Cracks of 100 μm or more and less than 200 μm in any layer of the optical laminate 2: Optical Cracks of 200 μm or more and less than 300 μm in any layer of the optical laminate 1: Cracks of more than 300 μm in any layer of the optical laminate

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

The optical laminate of the present invention is suitably used in 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 image display devices having irregularly shaped image display sections, such as automobile instrument panels and smart watches.

10 Adhesive layer 20 Polarizer 30 Adhesive layer 40 Brightness enhancement film 50 Surface treatment layer 100 Optical laminate

Claims (2)

Has an irregularly shaped part,
an adhesive layer, a polarizer having a thickness of 1 μm or more and less than 8 μm , an adhesive layer having a thickness of 2 μm to 12 μm and made of an acrylic adhesive , a layer A having birefringence, and a layer A having birefringence. It is a multilayer laminate in which layers B and layers B, which do not have the same properties, are alternately laminated, where the A layer is made of naphthalene dicarboxylic acid polyester, polycarbonate, or acrylic resin, and the B layer is made of naphthalene dicarboxylic acid and terephthalic acid. An optical laminate comprising, in this order, a brightness-enhancing film made of copolyester and a surface treatment layer having a thickness of 1.5 μm or less,
An optical laminate, wherein the surface treatment layer is a hard coat layer that is a hardened layer of acrylic resin . An image display device comprising the optical laminate according to claim 1 .

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