JP2020052170A - Optical laminate - Google Patents

Abstract

To provide an optical laminate suppressing generation of wrinkles.SOLUTION: The optical laminate has an optical film, an adhesive layer disposed on one surface side of the optical film, and a release film laminated in contact with the adhesive layer, in which the optical film includes a polarizer; the release film has a thickness of 30 μm or more and less than 45 μm; and the optical film shows a maximum reach displacement of 1 mm or less determined by the following test method. (Test method): the adhesive layer having a width of 10 mm and a thickness of 20 μm is disposed at one end of the optical film in a strip form having a width of 10 mm, and the release film in a strip form having a width of 10 mm is laminated on the adhesive layer to prepare a test piece; the portion where the optical film, the adhesive layer and the release film overlap has a width of 10 mm and a length of 15 mm in a plan view; while either the optical film or the release film of the test piece is fixed, the other is moved at a moving speed of 1 mm/min parallel to the contact plane between the adhesive layer and the release film to measure a stress; and a moving distance from the position at the start of the test to a position where the stress reaches the maximum is defined as a maximum reach displacement.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical laminate.

  A polarizing plate is used as one of optical components constituting a liquid crystal display device. As a liquid crystal display device, a laminated structure in which a polarizing plate is bonded to both surfaces of a liquid crystal panel via an adhesive layer is known.

  In addition, an image display device represented by a liquid crystal display device or an organic electroluminescence display device is used as a display surface of a portable device intended for outdoor use. A so-called antireflection film is attached to the display surface of such an image display device as an optical film for suppressing reflection of external light. The antireflection film is a laminate having a polarizing plate and a retardation layer. A configuration is known in which an antireflection film is attached to a display surface of an image display device via an adhesive layer (for example, see Patent Document 1).

  In the following description, a laminate having a polarizing plate and an adhesive layer used when the polarizing plate is bonded to a liquid crystal panel or the like may be referred to as an “optical laminate”.

JP-A-2017-54093

  In the conventional optical laminated body as described above, each member is laminated on each other in a roll-to-roll system, and after a release film is further laminated on the pressure-sensitive adhesive layer, it is cut into a predetermined shape and manufactured as a sheet. . When the pressure-sensitive adhesive layer is used, the release film is peeled off while leaving the pressure-sensitive adhesive layer on the polarizing plate side.

  In the optical laminate manufactured in this manner, streaky “wrinkles” may be generated in the adhesive layer at the interface between the release film and the adhesive layer. The "wrinkles" that occur cause image distortion of the image display device. Therefore, an optical laminate in which generation of "wrinkles" is suppressed has been demanded.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical laminate in which generation of wrinkles is suppressed.

In order to solve the above-described problem, one embodiment of the present invention includes an optical film, an adhesive layer provided on one surface side of the optical film, and a release film stacked in contact with the adhesive layer. The optical film includes a polarizer, the release film has a thickness of 30 μm or more and less than 45 μm, and provides an optical laminate having a maximum attainable displacement of 1 mm or less measured by the following test method.
(Test method)
A test piece is prepared in which an adhesive layer having a width of 10 mm and a thickness of 20 μm is disposed at one end of the strip-shaped optical film having a width of 10 mm, and a strip-shaped release film having a width of 10 mm is further laminated on the adhesive layer. .
The portion where the optical film, the adhesive layer and the release film overlap has a width of 10 mm and a length of 15 mm in plan view.
One of the optical film and the release film provided on the test piece is fixed, and the other is moved at a moving speed of 1 mm / min in parallel with the contact surface between the pressure-sensitive adhesive layer and the release film, and the stress is measured.
The other moving distance from the position at the start of the test until the measured stress shows the maximum value is defined as a maximum reaching displacement.

  In one embodiment of the present invention, the surface of the release film on the side of the pressure-sensitive adhesive layer may have a contact angle of oleic acid of 60 ° or more.

  In one embodiment of the present invention, the optical film may have a thickness of 30 μm or more.

  According to the present invention, it is possible to provide an optical laminate in which the generation of wrinkles is suppressed.

FIG. 2 is a schematic cross-sectional view illustrating the optical laminate 1. It is explanatory drawing which shows the measuring method of the creep force between the peeling film 40 and the adhesive layer 30. It is explanatory drawing which shows the measuring method of the creep force between the peeling film 40 and the adhesive layer 30.

  Hereinafter, the optical laminate according to the present embodiment will be described with reference to FIGS. 1 to 3. In all of the following drawings, dimensions, ratios, and the like of the components are appropriately changed in order to make the drawings easy to see.

[Optical laminate]
FIG. 1 is a schematic sectional view showing an optical laminate 1 of the present embodiment.

  As shown in FIG. 1, the optical laminate 1 includes an optical film 10, a surface protection film 20, an adhesive layer 30, and a release film 40.

(Optical film)
The optical film 10 has a polarizer 11 and protective films 12 and 13. The optical film 10 shown in the figure is a polarizing plate.

  The curl amount of the optical film 10 measured by a method described later is preferably 10 mm or less, and more preferably 8 mm or less. According to the study by the inventor, it has been found that when the curl amount of the optical film 10 is small, “wrinkles” of the pressure-sensitive adhesive layer 30 are less likely to occur. Also, it was found that when the curl amount exceeded 10 mm, wrinkles were likely to occur in the pressure-sensitive adhesive layer 30. The curl amount of the optical film 10 is preferably as small as possible, and the curl amount is ideally 0 mm.

When the optical film 10 is a polarizing plate, the curl amount of the optical film 10 is controlled by adjusting the tension at the time of bonding the protective films 12 and 13 to the polarizer 11. By adjusting the tension at the time of bonding the protective films 12 and 13, the internal stress of the protective films 12 and 13 after bonding to the polarizer 11 can be controlled.
When the optical film 10 is a polarizing plate, the curl amount of the optical film 10 can also be adjusted by adjusting the water content of the entire optical film 10, for example, the water content of the polarizer 11 and the water content of the protective films 12 and 13. It can be controlled.

The curl amount of the optical film 10 is calculated as follows.
The optical film 10 is cut into a rectangular sheet of 110 m × 60 mm with the absorption axis direction of the polarizer as a long side. The sheet is left to bend (curl) in an environment of a temperature of 23 ° C. and a relative humidity of 55% for 24 hours. After standing for 24 hours, the curved sheet is placed on a horizontal table so as to project downward. The height from the platform to the four corners of the single-leaf body is measured with a ruler, and the arithmetic average of the obtained four points is determined. The obtained average value is defined as the curl amount of the optical film 10.

(Polarizer)
The polarizer 11 transmits linearly polarized light having a plane of polarization in a specific direction. Light that has passed through the polarizer 11 becomes linearly polarized light that vibrates in the transmission axis direction of the polarizer. The thickness of the polarizer 11 is, for example, about 1 μm to 80 μm, and preferably 2 μm to 15 μm.

  Examples of the polarizer 11 include a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, and a dipolar dye such as iodine or a dichroic dye. Those that have been subjected to a coloring treatment and a stretching treatment with a coloring substance can be used. Further, as the polarizer 11, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride can be used. Among these, the polarizer 11 obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching is preferable because of excellent optical characteristics.

  Dyeing with iodine is performed, for example, by immersing a polyvinyl alcohol-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye after extending | stretching.

  The polyvinyl alcohol-based film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, and the like, as necessary. For example, by immersing the polyvinyl alcohol-based film in water and washing with water before dyeing, not only can the dirt and the antiblocking agent on the surface of the polyvinyl alcohol-based film be washed, but also the swelling and dyeing of the polyvinyl alcohol-based film can be performed. Unevenness and the like can be prevented.

  As described in, for example, JP-A-2006-170368, a polarizer 11 in which a dichroic dye is oriented in a cured film in which a liquid crystal compound is polymerized may be used. As the dichroic dye, those having absorption in a wavelength range of 380 to 800 nm can be used, and it is preferable to use an organic dye. An example of the dichroic dye is an azo compound. The liquid crystal compound is a liquid crystal compound that can be polymerized while being aligned, and can have a polymerizable group in the molecule.

(Protective film)
The protective films 12 and 13 are films bonded to both surfaces of the polarizer 11 to protect the polarizer 11, respectively. The protective films 12 and 13 are bonded to one surface of the polarizer 11 via an adhesive layer or a pressure-sensitive adhesive layer (not shown). Although the optical film 10 of the present embodiment has the protective films 12 and 13 bonded to both surfaces of the polarizer 11, the optical film 10 may have a protective film on only one surface of the polarizer 11.

  As the protective films 12 and 13, a resin film having light transmittance with respect to visible light can be suitably used.

  As a material for forming the protective films 12 and 13, for example, triacetyl cellulose (TAC) resin, polycarbonate resin, polyvinyl alcohol resin, polystyrene resin, (meth) acrylate resin, polyolefin resin, polyarylate resin , A polyimide resin, a polyamide resin and the like. Examples of the polyolefin resin include a cyclic polyolefin resin and a polypropylene resin.

  Further, the protective films 12 and 13 may have a hard coat layer on the surface.

  The same film may be used for the protective films 12 and 13, or different films may be used.

  The thickness of the optical film 10 is preferably 30 μm or more, and more preferably 33 μm or more. When the thickness of the optical film 10 is 30 μm or more, the durability is improved. The thickness of the optical film 10 is preferably 100 μm or less.

  In the present embodiment, the optical film 10 is a polarizing plate having the polarizer 11 and the protective films 12 and 13, but is not limited thereto. For example, the optical film may have a retardation layer such as a λ / 2 plate or a λ / 4 plate.

  When the optical laminate 1 includes a layer having another optical function such as a retardation layer in addition to the polarizing plate, the optical laminate 1 is obtained by removing the surface protective film 20, the adhesive layer 30, and the release film 40. The entire layer corresponds to the optical film 10. In this case, the thickness of the “remaining layer” is preferably 30 μm or more, and more preferably 33 μm or more.

(Surface protection film)
The surface protection film 20 is a film for protecting the surface of the optical film 10, and is bonded to the surface 10a of the optical film 10 on the side of the protection film 13 via an adhesive layer (not shown). The surface protection film 20 is peeled off after the optical laminate 1 is bonded to the display surface of a liquid crystal panel or an image display device.

  The surface protection film 20 uses a thermoplastic resin as a forming material. The material for forming the surface protective film 20 is, for example, a polyolefin resin such as a polyethylene resin, a polypropylene resin, or a cyclic polyolefin resin; a polyester resin such as polyethylene terephthalate or polyethylene naphthalate; a polycarbonate resin; Resins and the like can be mentioned.

  In this specification, “(meth) acrylic resin” refers to at least one selected from the group consisting of acrylic resins and methacrylic resins. The same applies to other terms with “(meta)”.

  The thickness of the surface protective film 20 is preferably from 5 to 200 μm, more preferably from 10 to 150 μm, further preferably from 20 to 120 μm, and still more preferably from 25 to 100 μm.

(Adhesive layer)
The pressure-sensitive adhesive layer 30 is provided on the surface 10 b of the optical film 10 on the side of the protective film 12. The optical laminate 1 of the present embodiment is bonded to a liquid crystal panel or an image display device via an adhesive layer 30.

  The pressure-sensitive adhesive layer 30 is made of a cured product of a pressure-sensitive adhesive composition containing a resin such as (meth) acrylic, rubber, urethane, ester, silicone, or polyvinyl ether as a main component (base polymer). be able to. Above all, the pressure-sensitive adhesive layer 30 is preferably a cured product of a pressure-sensitive adhesive composition containing a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer.

  The pressure-sensitive adhesive layer 30 can be formed by applying the pressure-sensitive adhesive composition to the surface 10 b of the optical film 10 on the side of the protective film 12 and curing the same.

  The pressure-sensitive adhesive composition may be an active energy ray-curable type such as an ultraviolet-curable type or a thermosetting type, but is preferably a thermosetting type.

  Examples of the (meth) acrylic resin used in the pressure-sensitive adhesive composition include butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Examples thereof include polymers in which one or more (meth) acrylic acid esters are polymerized.

  It is preferable that a polar monomer is copolymerized with the (meth) acrylic resin. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl ( Examples thereof include monomers having a carboxy group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylate.

The pressure-sensitive adhesive composition may be the base polymer alone, but preferably contains a crosslinking agent. As a crosslinking agent,
(1) A compound which is a divalent or higher valent metal ion and forms a carboxylate metal salt with a carboxy group. (2) A polyamine compound which forms an amide bond with a carboxy group. Compounds that are epoxy compounds or polyols that form an ester bond with a carboxy group (4) Compounds that are polyisocyanate compounds and form an amide bond with a carboxy group are exemplified. Among them, a polyisocyanate compound is preferable.

  The pressure-sensitive adhesive composition further contains, in addition to the base polymer and the crosslinking agent, a compound that is polymerized by heating in addition to the base polymer. The pressure-sensitive adhesive composition may contain a photopolymerization initiator, a photosensitizer, and the like, if necessary.

  The pressure-sensitive adhesive composition is a fine particle for imparting light scattering property, resin beads, beads such as glass beads, glass fiber, a resin other than the base polymer, a tackifier, metal powder within a range not impairing the effects of the invention. And other fillers such as inorganic powders, and additives such as antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

  The thickness of the pressure-sensitive adhesive layer 30 is preferably 1 μm or more and 40 μm or less, more preferably 3 μm or more and 25 μm or less. When the thickness of the pressure-sensitive adhesive layer 30 is 3 μm or more and 25 μm or less, the optical laminate 1 can be thinned while having a sufficient adhesive force as the pressure-sensitive adhesive layer 30.

  When the release film 40 is released from the optical laminate 1, the exposed surface of the adhesive layer 30 preferably has a contact angle of oleic acid of 0 ° or more and 90 ° or less. The exposed surface of the pressure-sensitive adhesive layer 30 has a contact angle of oleic acid of preferably 10 ° or more, more preferably 15 ° or more. The exposed surface of the pressure-sensitive adhesive layer 30 has a contact angle of oleic acid of preferably 80 ° or less, more preferably 70 ° or less. The upper limit and the lower limit of the contact angle can be arbitrarily combined.

  The contact angle of oleic acid is measured by dropping 1 μL of oleic acid onto the exposed surface of the pressure-sensitive adhesive layer 30 by the θ / 2 method.

  When the affinity between the pressure-sensitive adhesive layer 30 and the release film 40 is high, the release film 40 is difficult to peel off from the optical laminate 1, and the surface of the pressure-sensitive adhesive layer 30 after the release film 40 is peeled is likely to be roughened. When the surface of the pressure-sensitive adhesive layer 30 is rough, the contact angle tends to be small.

(Release film)
The release film 40 is a film that protects the surface of the pressure-sensitive adhesive layer 30 until the optical laminate 1 is bonded to the adherend via the pressure-sensitive adhesive layer 30.

  The thickness of the release film 40 is 30 μm or more. Further, the thickness of the release film 40 is preferably less than 45 μm.

  The release film 40 is preferably composed of a resin film and a release layer.

  As the resin film, for example, a film using a material such as polyester such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, or a polyolefin such as polyethylene and polypropylene can be used. Among them, a polyethylene terephthalate film is preferable as the resin film because of high light transmittance, and a biaxially stretched polyethylene terephthalate film is more preferable because of excellent dimensional stability.

The release layer can be formed using a composition containing a silicone resin, an alkyd resin, an acrylic resin, or a long-chain alkyl resin. The composition used for forming the release layer may be referred to as a “composition for forming a release layer” in the following description.

  As the silicone resin used as a material for forming the release layer, a curable silicone resin having dimethylpolysiloxane as a basic skeleton can be given. Examples of the curable silicone resin include addition reaction type, condensation reaction type, and radical polymerization type. Above all, the addition reaction type silicone resin is preferable because it has advantages such as high reactivity, excellent productivity, and a small change in peeling force after production and no cure shrinkage as compared with the condensation reaction type silicone resin.

  Specific examples of the addition reaction type silicone resin include a mixture of a polysiloxane having two or more alkenyl groups having 2 to 10 carbon atoms in a molecule and a polysiloxane having two or more H-Si bonds in a molecule. Can be mentioned. The addition reaction type silicone resin is converted to a high molecular weight by a hydrosilylation reaction which is an addition reaction in the presence of a metal catalyst.

  Examples of the metal catalyst include fine-particle platinum, fine-particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, and metal compounds of white metals such as palladium and rhodium. Is mentioned. By using such a catalyst, the curing reaction of the composition for forming a release layer can be advanced more efficiently.

  Additives such as a release controlling agent (described later), a dye, and a dispersant may be appropriately added to the composition for forming a release layer.

  Further, the composition for forming a release layer may appropriately contain a dispersion medium or a solvent in order to control the viscosity at the time of application to an appropriate range. Examples of the dispersion medium or the solvent include aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone (hereinafter, MEK), and aliphatic hydrocarbons such as hexane and heptane.

These dispersion media or solvents may be used alone or as a mixture of two or more.
For example, when a silicone resin is used as a material for forming the release layer, a mixed solvent of toluene and MEK is preferably used. The mixing ratio of toluene and MEK is preferably such that toluene is 20 to 50% by mass based on the entire mixed solvent of MEK and toluene.

  The release film 40 can be produced, for example, by applying a release layer forming composition diluted with a solvent to one surface of a resin film, heating and drying, and reacting a release layer forming material.

  The application of the composition for forming a release layer is performed, for example, by a gravure coating method, a bar coating method, a spray coating method, a spin coating method, an air knife coating method, a roll coating method, a blade coating method, a gate roll coating method and a die coating method. Do. Among these, the gravure coating method and the bar coating method are preferable, and the gravure coating method is more preferable.

  As a method for heating and drying the composition for forming a release layer, for example, a method of heat drying in a hot air drying furnace or the like may be used. The drying temperature is preferably, for example, 50 ° C. or more and 150 ° C. or less. The drying time is preferably, for example, 10 seconds to 5 minutes.

  The thickness of the release film 40 can be controlled by the thickness of the resin film and the thickness of the release layer. Above all, the thickness of the resin film is dominant and can be controlled by selecting a polyester film having a target thickness.

  The thickness of the resin film is preferably 30 μm or more. Although the upper limit of the thickness of the resin film is not particularly limited, it is more preferably less than 45 μm.

  The dry thickness of the release layer is preferably from 40 nm to 300 nm, more preferably from 50 nm to 200 nm, even more preferably from 80 nm to 150 nm. By setting the thickness of the release layer to 40 nm or more, variation in physical properties due to variation in the application amount of the composition for forming a release layer can be suppressed. In addition, by setting the thickness of the release layer to 300 μm or less, blocking of the release film can be suppressed.

The optical laminate 1 of the present embodiment described above measures the creep force of the interface between the release film 40 and the pressure-sensitive adhesive layer 30 by the following test method, and based on the moving distance when the creep force is measured, a non-defective product. Can be determined.
(Test method)
A test piece is prepared in which an adhesive layer having a width of 10 mm and a thickness of 20 μm is disposed at one end of the strip-shaped optical film having a width of 10 mm, and a strip-shaped release film having a width of 10 mm is further laminated on the adhesive layer. .
The portion where the optical film, the adhesive layer and the release film overlap has a width of 10 mm and a length of 15 mm in plan view.
One of the optical film and the release film provided on the test piece is fixed, and the other is moved at a speed of 1 mm / min in parallel with the contact surface between the pressure-sensitive adhesive layer and the release film, and the stress is measured. The maximum value of the measured stress is measured as the creep force.

An example of a method for producing a test piece will be described in more detail.
First, on one side of an optical film having a size of 110 mm × 60 mm, 110 mm × 60 mm
A pressure-sensitive adhesive layer having a thickness of 20 μm is disposed, and a release film of 110 mm × 60 mm is further laminated on the pressure-sensitive adhesive layer. Thereafter, the obtained laminate is cut into a size of 110 mm × 10 mm to prepare a test piece.

  2 and 3 are explanatory diagrams showing a specific method for measuring the creep force between the release film 40 and the pressure-sensitive adhesive layer 30. FIG.

  First, as shown in FIG. 2, a rectangular test piece TP having a long side of 110 mm and a short side of 10 mm is cut out from the optical laminate 1. Next, the release film 40 is cut at a position of 7.5 mm from the center in the long side direction of the test piece TP to one end side to form a cut C1. Similarly, the other laminated portion except the release film 40 is cut at a position of 7.5 mm from the center in the long side direction of the test piece TP to the other end to form a cut C2.

  Among the obtained test pieces TP, the part 40x of the release film 40 divided by the cut C1, the part 10x of the optical film 10 divided by the cut C2, and the pressure-sensitive adhesive layer 30 divided by the cut C2. Part 30x corresponds to the test piece in the test method described above. The optical film 10x, the release film 40x, and the pressure-sensitive adhesive layer 30x overlap each other with a width of 10 mm and a length of 15 mm in plan view.

  Next, as shown in FIG. 3, both ends of the test piece TP in the longitudinal direction are gripped, and the test piece TP is pulled. The creep force is measured using a tensile tester (Autograph AG-IS, manufactured by Shimadzu Corporation). Both ends in the longitudinal direction of the test piece TP are gripped by the gripper of the tester, and the test piece TP is pulled at a moving speed of 1 mm / min.

  The maximum value of the measured stress measured by the above method is defined as the creep force. Further, based on the start of the test, the moving distance of the gripper when the measured stress shows the maximum value (the moving distance of the gripper when the creep force is measured) is referred to as “maximum reaching displacement”. In the optical laminate 1 of the present embodiment, the maximum attainable displacement measured by the above-described measuring method is 1 mm or less. The maximum attainable displacement may be 0.01 mm or more, and may be 0.1 mm or more.

  As described above, the pressure-sensitive adhesive layer 30 can be formed by curing the pressure-sensitive adhesive composition. Since the pressure-sensitive adhesive composition undergoes shrinkage during curing, the resulting pressure-sensitive adhesive layer 30 has internal stress due to curing shrinkage.

  As a result of the study, the inventors have considered that the internal stress of the pressure-sensitive adhesive layer 30 is a cause of “wrinkles” as described above. That is, after the pressure-sensitive adhesive layer 30 is formed, when the pressure-sensitive adhesive layer 30 contracts little by little due to internal stress, the friction generated between the pressure-sensitive adhesive layer 30 and the release film 40 causes the pressure-sensitive adhesive near the interface between the pressure-sensitive adhesive layer 30 and the release film 40. The movement of the layer 30 is hindered. As a result, it is considered that “wrinkles” occur at the interface between the pressure-sensitive adhesive layer 30 and the release film 40.

  In the optical laminate 1 of the present embodiment, when the test piece TP manufactured from the optical laminate 1 is measured by the above-described method, the measurement is performed from the start of the test until the moving distance of the gripper reaches 1 mm. The maximum displacement reached is measured.

  The fact that this maximum displacement is "small" means that when a surface stress is applied to the interface between the release film and the pressure-sensitive adhesive layer, shearing easily occurs at the interface between the release film and the pressure-sensitive adhesive layer. I do. As described above, in the vicinity of the interface between the pressure-sensitive adhesive layer and the release film, when it is considered that “wrinkles” occur at the interface due to the inhibition of the movement of the pressure-sensitive adhesive layer, the shearing occurs at the interface between the release film and the pressure-sensitive adhesive layer. It is considered that in a laminated body in which shearing easily occurs, "wrinkles" hardly occur at the interface.

  That is, in the optical laminate 1 having the above-described properties, when the pressure-sensitive adhesive layer 30 shrinks, shear shear easily occurs at the interface between the release film 40 and the pressure-sensitive adhesive layer 30, and the generation of “wrinkles” is suppressed. It is thought that.

  From another viewpoint, it is preferable that the surface of the release layer of the release film 40, that is, the surface 40a of the release film 40 on the side of the pressure-sensitive adhesive layer 30 has a contact angle of oleic acid of 60 ° or more. The surface 40a of the release film 40 on the side of the pressure-sensitive adhesive layer 30 preferably has a contact angle of oleic acid of 180 ° or less, more preferably 90 ° or less. When the contact angle of the release film 40 is within the above range, the release film 40 easily slips at the interface with the pressure-sensitive adhesive layer 30. Therefore, generation of “wrinkles” over time due to shrinkage of the pressure-sensitive adhesive layer 30 is easily suppressed.

  In the present invention, suitable properties of the surface 40a of the release film 40 on the side of the pressure-sensitive adhesive layer 30 are determined using the contact angle of oleic acid. The contact angle of oleic acid is measured by a 1/2 method by dropping 1 μL of oleic acid onto a release film.

If the contact angle of the surface 40a (= measurement surface) of the release film 40 on the side of the adhesive layer 30 is measured using a solvent having a higher polarity than oleic acid, the affinity between the measurement surface and the solvent is high and the contact angle is high. May be too small.
Further, when the contact angle of the measurement surface of the release film 40 is measured using a solvent having a lower polarity than that of oleic acid, the affinity between the measurement surface and the solvent may be low and the contact angle may be too large.

  In any of these cases, no difference is observed in the measurement results of the contact angle for each release film 40, and it is difficult to determine the quality. Therefore, in the present invention, the quality of the release film 40 is determined using oleic acid.

  The creep force at the interface between the pressure-sensitive adhesive layer 30 and the release film 40 and the contact angle of the release film 40 can be controlled by, for example, adjusting the polarity of the surface of the release layer.

  For example, it can be controlled by adding a release adjusting agent such as a silicone resin, silica, or silicone oil to the composition for forming a release layer. If the amount used is the same, the silicone oil tends to lower the peel strength of the release film 40 as compared with the silicone resin and silica.

  The creep force at the interface between the pressure-sensitive adhesive layer 30 and the release film 40 tends to decrease as the added amount of these preparations increases.

  When a silicone resin is used as a material for forming the release layer, the mixing ratio of toluene and MEK used as a solvent for dissolving the release layer forming composition is such that toluene is 20 to 50 with respect to the entire mixed solvent of MEK and toluene. A ratio that results in mass% is preferred. If the amount of toluene contained in the mixed solvent used is too large, the solubility of the silicone resin will be high, and the release layer will be less likely to adhere. As a result, the contact angle of the release film 40 tends to be small.

  The contact angle of the release film 40 can also be controlled by adjusting the amount of the metal catalyst contained in the composition for forming a release layer.

  For example, when the metal catalyst is a platinum catalyst, the content of the platinum catalyst in the composition for forming a release layer is preferably 0.1 parts by mass or more and 7.0 parts by mass or less, and more preferably 0.5 parts by mass or more. More preferably, it is 5.0 parts by mass or less. By controlling the content of the platinum catalyst in the composition for forming a release layer in such a range, the contact angle of the release film 40 can be easily controlled in a desired range.

  When the content of the platinum catalyst in the composition for forming a release layer is reduced, the contact angle tends to decrease, and when the content of the platinum catalyst increases, the contact angle tends to increase.

  When the content of the platinum catalyst in the composition for forming a release layer is less than 0.1 part by mass, the curing reaction in the release layer to be formed becomes insufficient, and the contact angle of the release film 40 becomes smaller than 60 °. There is a tendency.

  On the other hand, when the content of the platinum catalyst in the composition for forming a release layer exceeds 7.0 parts by mass, the reactivity of the composition for forming a release layer is increased, and gel foreign matter is easily generated. As a result, there occurs a problem that a uniform release layer is not formed.

  The optical laminate 1 of the present embodiment has the above-described configuration.

  According to the optical laminated body 1 configured as described above, it is possible to suppress occurrence of wrinkles.

  As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but it is needless to say that the present invention is not limited to the embodiments. The shapes, combinations, and the like of the constituent members shown in the above-described examples are merely examples, and various changes can be made based on design requirements and the like without departing from the gist of the present invention.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

(Preparation of release film)
(1) Preparation of Release Film 1 An addition polymerization type silicone resin solution containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrosilyl group (manufactured by Dow Corning Toray Co., Ltd., BY24-561, solid (30% by mass) was diluted with a mixed solvent of 46% by mass of toluene and 54% by mass of MEK so as to have a solid content concentration of 0.8% by mass.

  Next, a platinum-based catalyst (manufactured by Dow Corning Toray Co., Ltd., SRX-212, solid content: 100% by mass) was added to the obtained diluted solution to prepare Composition 1 for forming a release layer.

  Next, the obtained composition 1 for forming a release layer was applied to one surface of a polyethylene terephthalate (PET) film (PET38R-64, manufactured by Toray Industries, Inc.) having a thickness of 38 μm. Coating was performed using a bar coater so that the thickness of the release layer obtained after drying was 0.1 μm.

  After application of the composition 1 for forming a release layer, the composition was dried to obtain a release film 1 as a release layer.

  For the obtained release film 1, the contact angle of the release layer measured by the following method was 67.6 °. The contact angle was measured by the θ / 2 method.

<Measurement method>
The film was horizontally placed on a contact angle meter (FACE CA-X type, manufactured by Kyowa Interface Science Co., Ltd.) with the surface of the release film on which the release layer was formed facing upward. 1 μL of oleic acid was dropped on the surface of the release layer, and the contact angle was measured.

(2) Preparation of Release Film 2 As a composition for forming a release layer, an addition polymerization type silicone resin solution was diluted with a mixed solvent of toluene and MEK so as to have a solid concentration of 1.0% by mass. A release film 2 was obtained in the same manner as in the production of the release film 1 except that the prepared composition 2 for forming a release layer was used.
About the obtained release film 2, the contact angle of the release layer measured by the above method was 68.8 °.

(3) Preparation of Release Film 3 Except that the addition polymerization type silicone resin solution was diluted with a mixed solvent of toluene and MEK to a solid content concentration of 2.0% by mass, Composition 3 for forming a release layer was prepared in the same manner as in the preparation.

  The obtained release layer forming composition 3 was applied to one surface of a PET film (manufactured by Mitsubishi Chemical Corporation, product name “T600E”) having a thickness of 25 μm. Coating was performed using a bar coater so that the thickness of the release layer obtained after drying was 0.1 μm.

  After application of the composition 3 for forming a release layer, the composition was dried to form a release layer, thereby obtaining a release film 3.

  About the obtained release film 3, the contact angle of the release layer measured by the above method was 80.1 °.

(Preparation of polarizing plate)
(1) Preparation of Polarizing Film A polyvinyl alcohol (PVA) film (“Kuraray Poval Film VF-PE # 3000”, manufactured by Kuraray Co., Ltd.) having an average degree of polymerization of about 2400, a degree of saponification of 99.9 mol%, and a thickness of 30 μm was prepared. It was used as a raw film. After the PVA film is immersed in pure water at 37 ° C., it is immersed in an aqueous solution containing iodine and potassium iodide (iodine / potassium iodide / water (mass ratio) = 0.04 / 1.5 / 100) at 30 ° C. And stained. During the dyeing, the PVA film was stretched in the machine direction (MD direction, film transport direction).

  Next, it was immersed in an aqueous solution containing potassium iodide and boric acid (potassium iodide / boric acid / water (mass ratio) = 12 / 3.6 / 100) at 56.5 ° C. During the immersion, the PVA film was stretched in the longitudinal direction.

  Next, the film was washed with pure water at 10 ° C. for 4 seconds, and then dried at 85 ° C. to obtain a polarizing film having a thickness of about 12 μm in which iodine was adsorbed and oriented on PVA.

  The total stretching ratio of the obtained polarizing film (PVA film) was 5.3 times based on the raw film.

(2) Preparation of water-based adhesive 3 parts by mass of carboxy-modified polyvinyl alcohol (trade name “KL-318” manufactured by Kuraray Co., Ltd.) was dissolved in 100 parts of water, and the resulting aqueous solution was dissolved in a water-soluble epoxy resin. 1.5 parts by mass of a polyamide epoxy-based additive (manufactured by Taoka Chemical Industry Co., Ltd., trade name “SUMIREZ Resin 650 (30)”, an aqueous solution having a solid content of 30%). Prepared.

(3) Production of polarizing plate A transparent protective film ("25KCHCN-TC", manufactured by Toppan Printing Co., Ltd.) obtained by applying a 7 µm thick hard coat layer to a 25 µm thick triacetyl cellulose (TAC) film. Prepared.

The TAC film side of the transparent protective film was bonded to one surface of the obtained polarizing film using the above-mentioned aqueous adhesive.
A 23 μm-thick cycloolefin-based resin (COP) film (“ZF14-023”, manufactured by Zeon Corporation) is attached to the other surface of the polarizing film using the above-mentioned water-based adhesive. Optical film).
In addition, as for each film, a film which was subjected to corona treatment in advance on the surface in contact with the aqueous adhesive was used.

  The thickness of the obtained polarizing plate was 67 μm.

(Preparation of adhesive)
(1) Preparation of pressure-sensitive adhesive 1 A urethane acrylate oligomer is blended with a copolymer of butyl acrylate and acrylic acid, and an isocyanate-based cross-linking agent and an ionic compound as an antistatic agent are added. 1 was produced.

(2) Preparation of Adhesive 2 Adhesive 2 was prepared by blending a urethane acrylate oligomer with a copolymer of butyl acrylate and acrylic acid, and further adding an isocyanate-based crosslinking agent.

(3) Preparation of Adhesive 3 To the copolymer of n-butyl acrylate, acrylic acid, and 2-hydroxyethyl acrylate, an isocyanate-based cross-linking agent and a silane coupling agent were further added to prepare Adhesive 3. .

(Preparation of optical laminate)
(1) Production of optical laminate A1 (Example 1-1)
After performing a corona treatment on the surface of the polarizing plate on the COP film side, the pressure-sensitive adhesive 1 was applied to form a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer was 20 μm.
The release film 1 was laminated on the obtained pressure-sensitive adhesive layer. Then, it was cured for 7 days to produce an optical laminate A1.

  The contact angle of the surface of the pressure-sensitive adhesive layer in the obtained optical laminate A1 was measured by a θ / 2 method after the release film was peeled to expose the pressure-sensitive adhesive layer.

<Measurement method>
The pressure-sensitive adhesive layer exposed by peeling the release film was placed horizontally on a contact angle meter (FACE CA-X type, manufactured by Kyowa Interface Science Co., Ltd.) with the surface of the adhesive layer facing upward. 1 μL of oleic acid was dropped on the surface of the pressure-sensitive adhesive layer, and the contact angle was measured.

The curl amount of the obtained polarizing plate measured by the following measurement method was 10 mm or less.
<Measurement method>
The curl amount of the polarizing plate was calculated as follows. The polarizing plate was cut out into a single sheet of 110 mm × 60 mm with the absorption axis direction of the polarizer as a long side. The sheet was allowed to stand in an environment of a temperature of 23 ° C. and a relative humidity of 55% for 24 hours to bend (curl). After standing for 24 hours, the curved sheet was placed on a horizontal table so as to project downward. The height from the platform to the four corners of the single-leaf body was measured with a ruler, respectively, and the arithmetic average of the obtained values of the four points was obtained. The obtained average value was defined as the curl amount of the optical laminate.

(2) Production of optical laminate A2 (Comparative Example 1-1)
An optical laminate A2 was produced in the same manner as the optical laminate A1, except that the release film 2 was used instead of the release film 1.

(3) Production of optical laminate A3 (Comparative Example 1-2)
An optical laminate A3 was produced in the same manner as the optical laminate A1, except that the release film 3 was used instead of the release film 1.

(4) Production of optical laminates B1 to B3 (Examples 2-1 and 2-2, Comparative Example 2-1)
Optical laminates B1 to B3 were produced in the same manner as optical laminates A1 to A3, except that adhesive 2 was used instead of adhesive 1.

(5) Production of optical laminates C1 to C3 (Examples 3-1 and 3-2, Comparative Example 3-1)
Optical laminates C1 to C3 were produced in the same manner as optical laminates A1 to A3, except that adhesive 3 was used instead of adhesive 1.

((Reference example) Production of laminate)
(1) Production of laminate D1 (Reference Example 1)
One surface of a 23 μm-thick COP film (“ZF14-023”, manufactured by Zeon Corporation) was subjected to corona treatment.
An adhesive 1 was applied to the corona-treated surface of the COP film to form an adhesive layer. The thickness of the pressure-sensitive adhesive layer was 20 μm.
The release film 1 was laminated on the obtained pressure-sensitive adhesive layer. Thereafter, the laminate was cured for 7 days to produce a laminate D1. The curl amount of the COP film was 0 mm.

  The contact angle of the surface of the pressure-sensitive adhesive layer in the obtained laminate D1 was measured by the θ / 2 method after the release film was peeled to expose the pressure-sensitive adhesive layer.

(2) Production of laminate D2 (Reference Example 2)
A laminate D2 was produced in the same manner as the laminate D1, except that the release film 2 was used instead of the release film 1.

(3) Production of laminate D3 (Reference Example 3)
A laminate D3 was produced in the same manner as the laminate D1, except that the release film 3 was used instead of the release film 1.

(4) Production of laminates E1 to E3 (Reference Examples 4 to 6)
Laminates E1 to E3 were produced in the same manner as the laminates D1 to D3, except that the pressure-sensitive adhesive 2 was used instead of the pressure-sensitive adhesive 1.

(5) Production of laminates F1 to F3 (Reference Examples 7 to 9)
Laminates F1 to F3 were produced in the same manner as laminates D1 to D3, except that pressure-sensitive adhesive 3 was used instead of pressure-sensitive adhesive 1.

<Evaluation>
(1) Appearance evaluation The produced optical laminate was cut into 110 mm x 60 mm using a continuous automatic cutting machine (Super cutter PN1-600, manufactured by Ogino Seiki Seisaku-sho, Ltd.) with the absorption axis direction of the polarizer as a long side. The obtained test piece was allowed to stand for 72 hours in an environment at a temperature of 23 ° C. and a humidity of 75% RH.

  Next, the test piece was placed on the table with the release film side facing upward, and light from a fluorescent lamp of 1200 lux or more was irradiated from above the test piece. Observe the fluorescent light image reflected on the test piece from a distance of about 30 cm to 50 cm from the test piece while illuminating with a fluorescent light, and observe the wrinkle observed overlapping with the fluorescent light image based on the following criteria. Was checked.

(Evaluation criteria)
X: Streak-shaped "wrinkles" exceeding 1 mm in length or streaks "wrinkles" exceeding 0.5 mm in width were observed.
：: The above-mentioned “wrinkle” was not confirmed.

In the above visual observation, “wrinkles” were observed as shadows overlapping the fluorescent lamp image.
Note that wrinkles having a length of 1 mm or less and a width of 0.5 mm or less were excluded from measurement.

(2) Evaluation of Maximum Achieved Displacement The optical laminated body produced by using a continuous automatic cutting machine was cut into 110 mm × 10 mm with the absorption axis direction of the polarizer as a long side, and then a test piece shown in FIG. 2 was produced.

  Next, both ends in the longitudinal direction of the test piece were gripped by gripping portions of a tensile tester (Autograph AG-IS, manufactured by Shimadzu Corporation) so that the longitudinal direction of the test piece was oriented vertically. As shown in FIG. 3, the lower grip was moved at a moving speed of 1 mm / min, and the test piece was pulled.

  The moving distance at which the measured stress showed the maximum value during the movement of the grip portion from the start of the test until it reached 5 mm was recorded as "maximum reaching displacement".

Table 1 shows the evaluation results of the optical laminates A1 to A3, B1 to B3, and C1 to C3.
Table 2 shows the evaluation results of the laminates D1 to D3, E1 to E3, and F1 to F3.

  As a result of the evaluation, from the comparison between the optical laminates A1 to A3, B1 to B3, and C1 to C3 and the laminates D1 to D3, E1 to E3, and F1 to F3, when the optical laminate does not include a polarizer, It was found that "wrinkles", which is the subject of the present invention, did not occur.

  In addition, from the results shown in Table 1, it was confirmed that no wrinkles occurred in the test piece in which the release film was 30 μm or more and the maximum displacement was 1.0 mm or less.

  From the above, it was confirmed that the present invention was useful.

  1: optical laminate, 40, 40x: release film, 30, 30x: adhesive layer, TP: test piece

Claims (3)

An optical film,
An adhesive layer provided on one side of the optical film,
Having a release film in contact with the pressure-sensitive adhesive layer,
The optical film includes a polarizer,
The thickness of the release film is 30 μm or more and less than 45 μm,
An optical laminate having a maximum attainable displacement measured by the following test method of 1 mm or less.
(Test method)
A test piece is prepared in which an adhesive layer having a width of 10 mm and a thickness of 20 μm is disposed at one end of the strip-shaped optical film having a width of 10 mm, and a strip-shaped release film having a width of 10 mm is further laminated on the adhesive layer. .
The portion where the optical film, the adhesive layer and the release film overlap has a width of 10 mm and a length of 15 mm in plan view.
One of the optical film and the release film provided on the test piece is fixed, and the other is moved at a moving speed of 1 mm / min in parallel with the contact surface between the pressure-sensitive adhesive layer and the release film, and the stress is measured.
The other moving distance from the position at the start of the test until the measured stress shows the maximum value is defined as a maximum reaching displacement.   The optical laminate according to claim 1, wherein a contact angle of oleic acid is 60 ° or more on a surface of the release film on the side of the pressure-sensitive adhesive layer.   The optical laminate according to claim 1, wherein the thickness of the optical film is 30 μm or more.

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