TWI868174B - Optical laminate - Google Patents

Abstract

The present invention provides an optical laminate having a thin polarizing element, and the optical laminate has excellent transmission performance, and the surface protection film and the separation element have excellent peeling performance. The optical laminate of the present invention comprises: a polarizing plate; an adhesive layer disposed on one side of the polarizing plate; a separating piece temporarily adhered to the side of the adhesive layer opposite to the polarizing plate in a removable manner; and a surface protection film temporarily adhered to the side of the polarizing plate opposite to the adhesive layer in a removable manner; the thickness of the polarizing plate is less than 60µm; the thickness of the surface protection film is greater than 40µm, the peeling force of the surface protection film is 0.10N/25mm~0.50N/25mm, and the elastic modulus of the surface protection film is 2.00×10 ⁹ Pa or above; the thickness of the separation piece is 35µm~80µm, and the peeling force of the separation piece is less than 0.28N/25mm.

Description

Optical laminate

The present invention relates to optical laminates.

In a liquid crystal display device, which is a representative image display device, polarizers are arranged on both sides of the liquid crystal unit according to its image formation method. Polarizers can be typically manufactured by dyeing a polyvinyl alcohol (PVA) resin film with a dichroic substance such as iodine (for example, patent documents 1 and 2). In recent years, the demand for thinner image display devices has increased greatly. Therefore, polarizers are also required to be further thinned. A thin polarizer (in actual application, a polarizing plate including the polarizer) can be provided, for example, by laminating an adhesive layer, a surface protection film, and a separator to form an optical laminate. However, this optical laminate has problems such as insufficient transportability and insufficient releasability of the surface protection film and the separator. Prior art literature Patent literature

Patent document 1: Japanese Patent No. 5048120 Patent document 2: Japanese Patent Publication No. 2013-156391

Problem to be solved by the invention This invention is made to solve the above-mentioned previous problems. Its main purpose is to provide an optical laminate having a thin polarizing plate, a surface protection film and a separator. The optical laminate has excellent transport properties, and the surface protection film and the separator have excellent peeling properties. Means for solving the problem

The optical laminate of the present invention comprises: a polarizing plate; an adhesive layer disposed on one side of the polarizing plate; a separating piece temporarily adhered to the side of the adhesive layer opposite to the polarizing plate in a removable manner; and a surface protection film temporarily adhered to the side of the polarizing plate opposite to the adhesive layer in a removable manner; the thickness of the polarizing plate is less than 60µm; the thickness of the surface protection film is greater than 40µm, the peeling force of the surface protection film is 0.10N/25mm~0.50N/25mm, and the elastic modulus of the surface protection film is 2.00×10 ⁹ Pa or more; the thickness of the separation piece is 35µm~80µm, and the peeling force of the separation piece is less than 0.28N/25mm. In one embodiment, the polarizer comprises a polarizer formed of a polyvinyl alcohol-based resin film containing iodine. In one embodiment, the thickness of the polarizer is less than 10μm. In one embodiment, the iodine content of the polarizer is 10 wt%~25 wt%. Effect of the Invention

According to the present invention, for an optical laminate including a thin polarizing plate, a surface protection film and a separator, by optimizing the thickness, peeling force and elastic modulus of the surface protection film, and the thickness and peeling force of the separator, an optical laminate with excellent transportability and excellent peeling properties of the surface protection film and the separator can be achieved.

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

A. Overall Structure of Optical Laminated Body FIG1 is a schematic cross-sectional view of an optical laminated body in one embodiment of the present invention. The optical laminated body 100 of the illustrated example comprises a surface protection film 10, a polarizing plate 20, an adhesive layer 30 and a separator 40. The thickness of the polarizing plate 20 is less than 60µm. Furthermore, the thickness of the surface protection film 10 is greater than 40µm, the peeling force thereof is 0.10N/25mm~0.50N/25mm, and the elastic modulus thereof is greater than 2.00×10 ⁹ Pa. Furthermore, the thickness of the separator 40 is 35µm~80µm, and the peeling force thereof is less than 0.28N/25mm. The following is a more detailed description of the components of optical multilayers.

B. Polarizing plate The polarizing plate 20 has a polarizing element 22 and a protective layer disposed on one side or both sides thereof. Preferably, as shown in the figure, in the polarizing plate 20, the protective layer 21 is disposed on one side of the polarizing element 22. The thickness of the polarizing plate is less than 60µm, preferably less than 40µm, and more preferably less than 35µm. The lower limit of the thickness of the polarizing plate can be, for example, 20µm.

B-1. Polarizer The polarizer 22 is represented by a polyvinyl alcohol (PVA) resin film containing iodine.

The upper limit of the thickness of the polarizer is 10 μm in one embodiment, and 3 μm in another embodiment. The lower limit of the thickness is 1 μm in one embodiment.

The iodine content of the polarizer can be appropriately set to take into account both sufficient polarization performance and optimal single body transmittance. The iodine content is preferably 10% to 25% by weight, and more preferably 15% to 25% by weight. Even if the polarizer used in the embodiment of the present invention has an extremely high iodine content as described above, it can still achieve very excellent heat resistance that has been difficult to achieve in the past. In more detail, in a polarizer with an extremely high iodine content, the change of optical properties in a high temperature environment can be significantly suppressed. The "iodine content" in this specification refers to the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine exists in the polarizer in the form of iodine ions ( ^I- ), polyiodine ions ( _I3- , _I5- ⁾ , etc., and the iodine content in this specification refers to the amount of iodine including all such ^forms . The iodine content can be calculated using, for example, the calibration curve method of fluorescent X-ray analysis. In addition, polyiodine ions exist in the polarizer in the form of a PVA-iodine complex. By forming the complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA・I ₃ ^- ) has an absorption peak near 470nm; the complex of PVA and pentaiodide ion (PVA・I ₅ ^- ) has an absorption peak near 600nm. As a result, polyiodine ions can absorb light in a wide range of visible light depending on their form. On the other hand, iodine ion (I ^- ) has an absorption peak near 230nm, which has no substantial correlation with the absorption of visible light. Therefore, the polyiodine ions existing in the complex state with PVA are mainly related to the absorption performance of the polarizer.

The single body transmittance (Ts) of the polarizer is preferably 30.0%~43.0%, preferably 35.0%~41.0%. The polarization degree of the polarizer is preferably above 99.9%, preferably above 99.95%, and even more preferably above 99.98%. By setting the single body transmittance lower and the polarization degree higher, the contrast can be improved, and the black display can be made darker, so that an image display device with excellent image quality can be realized. In addition, the single body transmittance is a value measured by a spectrophotometer with an integrating sphere. The single body transmittance is measured with a 2 degree field of view (C light source) of JIS Z8701 and the Y value obtained by performing a visual sensitivity correction. For example, it can be measured using a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, product name: V7100).

B-2. PVA resin film PVA resins used to form PVA resin films include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The saponification degree of PVA resins is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be obtained in accordance with JIS K 6726-1994. By using a PVA resin having the above saponification degree, a polarizer having excellent durability can be obtained. When the saponification degree is too high, there is a risk of gelling.

The thickness of the PVA resin film is not particularly limited and can be set according to the desired thickness of the polarizer. The thickness of the PVA resin film is, for example, 10 μm to 200 μm.

In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on a substrate. The laminate of the substrate and the PVA-based resin layer may be obtained by, for example, the following methods: a method of applying a coating liquid containing the above-mentioned PVA-based resin to the substrate, a method of laminating the PVA-based resin film on the substrate. The substrate may be any appropriate resin substrate, for example, a thermoplastic resin substrate.

B-3. Protective layer Any appropriate resin film can be used for the protective layer. The material forming the resin film can include (meth) acrylic resin, cellulose resins such as cellulose diacetate and cellulose triacetate, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. In addition, "(meth) acrylic resin" means acrylic resin and/or methacrylic resin.

In one embodiment, the (meth)acrylic resin is a (meth)acrylic resin having a glutarimide structure. The (meth)acrylic resin having a glutarimide structure (hereinafter also referred to as a glutarimide resin) is described in, for example, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. 2006-328329, Japanese Patent Laid-Open No. 2006-328334, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. 2006-328329, Japanese Patent Laid-Open No. 2006-328334, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. 2006-328329, Japanese Patent Laid-Open No. 2006-328334, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. 2006-328334 ... 6-337491, Japanese Patent Publication No. 2006-337492, Japanese Patent Publication No. 2006-337493, Japanese Patent Publication No. 2006-337569, Japanese Patent Publication No. 2007-009182, Japanese Patent Publication No. 2009-161744 and Japanese Patent Publication No. 2010-284840. These descriptions are incorporated herein by reference.

When a laminate of a substrate and a PVA-based resin layer is used to manufacture a polarizer, the substrate can be used directly as a protective layer without peeling off the substrate. Alternatively, the protective layer can be attached to the polarizer after peeling off the substrate.

The thickness of the protective layer is preferably less than 5 mm, more preferably less than 1 mm, more preferably 1µm to 500µm, and most preferably 5µm to 150µm. In addition, when surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

The protective layer is attached to the polarizer through any appropriate bonding layer (bonding agent layer, adhesive layer).

C. Surface protection film As shown in the example of the figure, the surface protection film 10 is temporarily adhered to the side of the polarizing plate 20 opposite to the adhesive layer 30 in a removable manner. More specifically, the surface protection film 10 includes a base film and an adhesive layer, and the surface protection film 10 and the polarizing plate 20 are bonded through the adhesive layer.

C-1. Base film The base film of the surface protection film can be made of any appropriate resin film. The forming material of the resin film can include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Ester resins (especially polyethylene terephthalate resins) are more desirable. As long as it is the above-mentioned material, it has the advantages of having a high elastic modulus and not easily deforming even when tension is applied during transportation and/or bonding.

The thickness of the substrate film is preferably 38 μm or more, more preferably 48 μm or more. The upper limit of the thickness of the substrate film may be, for example, 128 μm. As long as the thickness is the above, it has the advantage that it is not easy to deform even when tension is applied during transportation and/or lamination.

C-2. Adhesive layer Any appropriate adhesive may be used as the adhesive forming the adhesive layer in the surface protection film. Examples of the base resin of the adhesive include acrylic resins, styrene resins, and silicone resins. From the viewpoints of chemical resistance, adhesion to prevent the treatment liquid from penetrating during immersion, and the degree of freedom for the adherend, acrylic resins are preferred. Examples of crosslinking agents that may be contained in the adhesive include isocyanate compounds, epoxy compounds, The adhesive may also contain, for example, a silane coupling agent. The mixing formula of the adhesive may be appropriately set according to the purpose.

The thickness of the adhesive layer is preferably 2µm or more, more preferably 5µm or more. The upper limit of the thickness is, for example, 40µm.

C-3. Characteristics of surface protection film The thickness of the surface protection film is 40µm or more, preferably 50µm or more. The upper limit of the thickness of the surface protection film may be, for example, 130µm. In addition, the thickness of the surface protection film refers to the total thickness of the base film and the adhesive layer. When the thickness of the surface protection film is within the above range, an optical laminate with excellent transport properties can be obtained. If the thickness of the surface protection film is thinner than 40µm, the transport properties will become insufficient.

The peeling force of the surface protection film is 0.10N/25mm~0.50N/25mm, and preferably 0.10N/25mm~0.35N/25mm. When the peeling force of the surface protection film is within the above range, an optical laminate with excellent peeling properties of the surface protection film and the separation piece can be obtained. If the peeling force of the surface protection film is less than 0.10N/25mm, the surface protection film will be embossed when the separation piece is peeled off. Furthermore, if it is greater than 0.50N/25mm, delamination will occur when the surface protection film is peeled off.

The elastic modulus of the surface protection film is 2.00×10 ⁹ Pa or more, and preferably 2.50×10 ⁹ Pa or more. The upper limit of the elastic modulus of the surface protection film may be 8.00×10 ⁹ Pa. When the elastic modulus of the surface protection film is within the above range, an optical laminate having excellent transportability can be obtained. If the elastic modulus of the surface protection film is less than 2.00×10 ⁹ Pa, wrinkles and bends of the film may occur during transport.

D. Adhesive layer The adhesive layer 30 may be composed of an acrylic adhesive. As shown in the figure, the adhesive layer 30 is formed on one side of the polarizing plate 20 and is provided for attaching the liquid crystal panel to the polarizing plate 20.

The thickness of the adhesive layer is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. The lower limit of the thickness may be, for example, 1 μm.

E. Separation piece As shown in the figure, the separation piece 40 is temporarily adhered to the side of the adhesive layer 30 opposite to the polarizing plate 20 in a removable manner. The separation piece can protect the adhesive layer until it is actually used and can be formed into a roll of polarizing plate.

The material for forming the separation element includes, for example, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins and copolymer resins thereof. Preferably, ester resins (especially polyethylene terephthalate resins) are used.

The thickness of the separation piece is 35µm to 80µm, and preferably 40µm to 60µm. By making the thickness of the separation piece within the above range, an optical laminate having excellent transportability and excellent peeling property of the separation piece can be obtained. If the thickness of the separation piece is thinner than 35µm, the transportability becomes insufficient. Furthermore, if the thickness of the separation piece is thicker than 80µm, poor picking occurs when the separation piece is peeled off.

The peeling force of the separation piece is less than 0.28N/25mm, and preferably less than 0.10N/25mm. When the peeling force of the separation piece is within the above range, an optical laminate having excellent peeling property of the separation piece can be obtained. If the peeling force of the separation piece is greater than 0.28N/25mm, poor picking will occur when the separation piece is peeled.

F. Method for manufacturing optical laminates F-1. Polarizer The method for manufacturing a polarizer in an embodiment of the present invention includes at least stretching and dyeing a PVA-based resin film. Typically, the manufacturing method includes a step of preparing a PVA-based resin film, a stretching step, a dyeing step, a cross-linking step, a washing step, and a drying step. In addition, a swelling step may be provided before the stretching step as required. The steps of providing the PVA-based resin film may be performed in any appropriate order and timing. Therefore, each step may be performed in the above order or in a different order from the above order. One step may also be performed multiple times as required. In addition, steps other than the above (such as the insolubilization step) can be performed at any appropriate time sequence. In addition, when the PVA-based resin film is a PVA-based resin layer formed on a substrate, the laminate of the substrate and the PVA-based resin layer can be provided to the above steps.

The following describes each step, but as mentioned above, each step can be performed in any appropriate order and is not limited to the order in which it is described.

(Stretching step) In the stretching step, the PVA resin film is typically uniaxially stretched to 3 to 7 times. The stretching direction can be the long side direction (MD direction) of the film or the width direction (TD direction) of the film. The stretching method can be dry stretching or wet stretching, or a combination of these. In addition, the PVA resin film can be stretched during the crosslinking step, swelling step, dyeing step, etc. In addition, the stretching direction can correspond to the absorption axis direction of the obtained polarizer.

(Swelling step) The swelling step is usually performed before the dyeing step. The swelling step can be performed, for example, by immersing the PVA resin film in a swelling bath. The swelling bath can usually be water such as distilled water or pure water. The swelling bath can also contain any other appropriate components other than water. Other components can include solvents such as alcohols, additives such as surfactants, and iodides. Iodides can include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Potassium iodide is preferably used. The temperature of the swelling bath is, for example, 20°C to 45°C. In addition, the immersion time is, for example, 10 seconds to 300 seconds.

(Dyeing step) The dyeing step is a step of dyeing the PVA resin film with a dichroic substance. It is preferably performed by making it adsorb the dichroic substance. The adsorption method includes: a method of immersing the PVA resin film in a dyeing liquid containing the dichroic substance, a method of applying the dyeing liquid on the PVA resin film, and a method of spraying the dyeing liquid on the PVA resin film. The method of immersing the PVA resin film in the dyeing liquid is ideal because the dichroic substance can be well adsorbed.

The above-mentioned dichroic substance can be iodine and dichroic dyes. Iodine is preferred. When iodine is used as the dichroic substance, an iodine aqueous solution is preferably used as the dyeing liquid. The iodine content of the iodine aqueous solution is preferably 0.04 to 5.0 parts by weight relative to 100 parts by weight of water. In order to increase the solubility of iodine in water, iodide is preferably mixed in the iodine aqueous solution. Potassium iodide is preferably used as the iodide. The iodide content is preferably 0.3 to 15 parts by weight relative to 100 parts by weight of water.

The temperature of the dyeing solution during dyeing can be set to any appropriate value, for example, 20° C. to 50° C. When the PVA resin film is immersed in the dyeing solution, the immersion time is, for example, 5 seconds to 5 minutes.

(Crosslinking step) In the crosslinking step, a boron compound is usually used as a crosslinking agent. Examples of the boron compound include boric acid and borax. Boric acid is preferred. In the crosslinking step, the boron compound is usually used in the form of an aqueous solution.

When a boric acid aqueous solution is used, the boric acid concentration of the boric acid aqueous solution is, for example, 1% to 15% by weight, preferably 1% to 10% by weight. The boric acid aqueous solution may further contain iodides such as potassium iodide, zinc compounds such as zinc sulfate and zinc chloride.

The crosslinking step can be performed by any appropriate method. For example, the method of immersing the PVA resin film in an aqueous solution of a boron compound, the method of applying the aqueous solution of a boron compound to the PVA resin film, or the method of spraying the aqueous solution of a boron compound to the PVA resin film. Preferably, the method of immersing the film in an aqueous solution of a boron compound is performed.

The temperature of the solution used for crosslinking is, for example, above 25° C., preferably 30° C. to 85° C., more preferably 40° C. to 70° C. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.

(Washing step) The washing step is typically performed after the crosslinking step. The washing step is typically performed by immersing the PVA-based resin film in a washing solution. A typical example of the washing solution is pure water. Potassium iodide may also be added to pure water.

The cleaning liquid temperature is, for example, 5°C to 50°C. The immersion time is, for example, 1 second to 300 seconds.

(Drying step) The drying step can be performed by any appropriate method. Examples of drying methods include natural drying, air drying, reduced pressure drying, and heating drying. Heating drying is preferably used. From the perspective of shortening the drying time, when performing heating drying, the heating temperature is, for example, 30°C to 100°C. In another embodiment, it is preferably below 50°C, more preferably below 45°C, and more preferably below 40°C. The lower limit of the heating temperature is not particularly limited, but is a lower limit temperature that can be set in the heating drying device. For example, it is 30°C. By setting the heating temperature of the drying step to the above range, the free boric acid content of the polarizer can be adjusted to within a predetermined range. In addition, the drying time is, for example, 20 seconds to 10 minutes. In one embodiment, the heat drying is performed in two or more stages. At this time, it is preferred that the heating temperature of at least one stage is within the above range. When the heat drying is performed, the heating temperature is set within the above range, and a polarizer with excellent heat resistance can be obtained.

F-2. Polarizing plate A resin film as a protective layer is bonded to the surface of the polarizing element obtained in F-1 (the surface opposite to the resin substrate). Then, by peeling off the resin substrate, a polarizing plate having a protective layer/polarizing element structure can be obtained. Alternatively, a resin film as another protective layer can be bonded to the peeled surface as required.

F-3. Optical laminate An adhesive layer is formed on the polarizing element side of the polarizing plate obtained in F-2 above, and a separation element is temporarily adhered to the surface of the adhesive layer in a releasable manner. A surface protection film is temporarily adhered to the surface of the polarizing plate opposite to the adhesive layer in a releasable manner, thereby obtaining an optical laminate 100. Example

The present invention is specifically described below with reference to the embodiments, but the present invention is not limited to the embodiments. The measuring methods of each characteristic are as follows.

(1) Transportability While transporting the polarizing plate while contacting the surface of the polarizing plate with the guide roller, check with the naked eye whether the polarizing plate is bent or scratched. The transport speed is set to 5m/min to 30m/min. ○: Transported without any problems. △: Although it is rolled into the roller during transport, no bends or scratches are generated. ×: It is rolled into the roller during transport and bends or scratches are generated. (2) Evaluation of peeling of surface protective film A starting tape (manufactured by NICHIBAN, CELLOTAPE (registered trademark) CT-24) is attached to the corner of the surface protective film, and the peeling state of the surface protective film is checked with the naked eye. ○: The surface protection film can be peeled off without any problem. △: The surface protection film rarely fails to follow the starting tape. The success rate is 80% to 100%. ×: The surface protection film fails to follow the starting tape. The success rate is less than 80%. Even if the surface protection film can be peeled off, embossing of the separation piece and delamination of the polarizing plate may occur. (3) Evaluation of separation piece peeling A starting tape (manufactured by NICHIBAN, CELLOTAPE (registered trademark) CT-24) is attached to the corner of the separation piece, and the peeling state of the separation piece is confirmed by naked eyes. ○: The separation piece can be peeled off without any problem. △: There are few cases where the separation film does not follow the starting tape. The success rate is 80%~100%. ×: The separation film does not follow the starting tape. The success rate is less than 80%. Or it is peeled between the surface protection film/polarizing film. (4) Peeling force of surface protection film The above optical laminate was cut into a size of 25mm×150mm and the separation piece was peeled off, and then bonded in such a way that the adhesive layer was in contact with the glass. The stress (N/25mm) when the surface protection film was peeled off at a speed of 300mm/min in the 90° direction was measured using an adhesive film peeling analyzer (manufactured by Kyowa Interface Science Co., Ltd., model: VPA-2). The measuring temperature was set to 25℃. (5) Peeling force of separated parts The optical laminate was cut into a size of 25 mm × 150 mm and attached to glass with double-sided tape (Nitto Denko Co., Ltd., No. 500) with the surface protection film surface in contact with the double-sided tape. The stress (N/25 mm) when the separated parts were peeled at a speed of 300 mm/min in the 90° direction was measured using an adhesive film peeling analysis device (Kyowa Interface Science Co., Ltd., model: VPA-2). The measuring temperature was set to 25°C.

[Example 1] The thermoplastic resin substrate is an amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) film (thickness: 100μm) with a water absorption rate of 0.75% and a Tg of 75℃. A corona treatment is applied to one side of the substrate, and an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") in a ratio of 9:1 is applied to the corona treated surface at 25℃ and then dried to form a PVA resin layer with a thickness of 11μm to produce a laminate. The obtained laminate was stretched in the air 4.5 times at 140°C in a direction perpendicular to the long side direction of the laminate using a tenter stretching machine (stretching treatment). Then, the laminate was immersed in a dyeing bath (an aqueous solution with an iodine concentration of 1.4% by weight and a potassium iodide concentration of 9.8% by weight) at a liquid temperature of 25°C for 12 seconds to be dyed (dyeing treatment). Next, the laminate was immersed in a cleaning bath (pure water) at a liquid temperature of 25°C for 6 seconds (first cleaning treatment). Then, it was immersed in a crosslinking bath (an aqueous solution with a boron concentration of 1% by weight and a potassium iodide concentration of 1% by weight) at a liquid temperature of 60°C for 16 seconds (crosslinking treatment). The laminate was then immersed in a cleaning bath (aqueous solution of potassium iodide with a concentration of 1% by weight) at a liquid temperature of 25°C for 3 seconds (second cleaning treatment). Then the laminate was dried in an oven at 40°C for 8 seconds (first drying treatment). Finally, the laminate was dried in an oven at 40°C for 13 seconds (second drying treatment), and a laminate (polarizing plate) having a PVA-based resin layer (polarizer) with a thickness of 1.2μm was obtained. The iodine content of the obtained polarizer was 18.6% by weight, and the single body transmittance was 39.9%. An adhesive layer is formed on the polarizer side surface of the polarizing plate obtained above, and a separation piece is temporarily adhered to the adhesive layer surface in a removable manner. A surface protection film is temporarily adhered to the side of the polarizing plate opposite to the adhesive layer in a removable manner to obtain an optical laminate. The obtained optical laminate is subjected to the evaluations of (1) to (3) above. The results are listed in Table 1.

[Examples 2 to 12 and Comparative Examples 1 to 10] As shown in Table 1, the thickness, peeling force and elastic modulus of the surface protection film, and the thickness and peeling force of the separation member were changed, and an optical laminate was obtained in the same manner as in Example 1. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are listed in Table 1. [Table 1]

As is apparent from Table 1, the optical laminate of the embodiments of the present invention (especially Embodiment 1) has excellent transportability, and has excellent peelability of the surface protection film and the peelability of the separation piece. As can be seen from Comparative Example 1, if the thickness of the surface protection film is less than 40µm, the transportability will be insufficient. As can be seen from Comparative Examples 2 and 5, if the peeling force of the surface protection film is greater than 0.50N/25mm, delamination will occur when the surface protection film is peeled off, and as can be seen from Comparative Examples 3 and 4, if the peeling force of the surface protection film is less than 0.10N/25mm, embossing of the surface protection film will occur when the separation piece is peeled off. Comparative Example 9 shows that if the elastic modulus of the surface protection film is below 2.00×10 ⁹ Pa, wrinkles will be generated during transportation. Comparative Examples 6 and 7 show that if the thickness of the separation piece is less than 35µm, the transportability will be insufficient, and Comparative Example 10 shows that if the thickness of the separation piece is greater than 80µm, poor picking will occur when the separation piece is peeled off. Comparative Example 8 shows that when the peeling force of the separation piece is greater than 0.28N/25mm, poor picking will occur when the separation piece is peeled off. Industrial Applicability

The optical multilayer body of the present invention can be applied to image display devices.

10: Surface protection film 20: Polarizing plate 21: Protective layer 22: Polarizer 30: Adhesive layer 40: Separator 100: Optical laminate

FIG1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention.

10: Surface protection film

20: Polarizing plate

21: Protective layer

22: Polarizer

30: Adhesive layer

40: Separation

100: Optical multilayer

Claims (4)

An optical laminate comprises: a polarizing plate; an adhesive layer disposed on one side of the polarizing plate; a separator temporarily adhered to the side of the adhesive layer opposite to the polarizing plate in a removable manner; and a surface protection film temporarily adhered to the side of the polarizing plate opposite to the adhesive layer in a removable manner; the thickness of the polarizing plate is less than 60 μm; the thickness of the surface protection film is more than 40 μm, the peeling force of the surface protection film is 0.10 N/25 mm to 0.50 N/25 mm, and the elastic modulus of the surface protection film is 2.00×10 ⁹ Pa or above; the thickness of the separation piece is 35μm~80μm, and the peeling force of the separation piece is less than 0.10N/25mm. As in claim 1, the optical laminate, wherein the aforementioned polarizing plate comprises a polarizing element formed of an iodine-containing polyvinyl alcohol-based resin film. As in claim 2, the optical laminate, wherein the thickness of the polarizer is less than 10 μm. As in claim 2 or 3, the iodine content of the aforementioned polarizer is 10% to 25% by weight.

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