JP6925808B2 - Manufacturing method of optical laminate and manufacturing method of image display device - Google Patents

Description

The present invention relates to a method for manufacturing an optical laminate and a method for manufacturing an image display device.

The polarizing plate is bonded to an optical member such as a liquid crystal cell, and is widely used in an image display device such as a liquid crystal display device. In the step of attaching the polarizing plate to the optical member, for example, the release film is peeled from the optical laminate having the surface protective film, the polarizing plate, and the release film in this order, and the polarizing plate is attached to the optical member via the pressure-sensitive adhesive layer. I can match. As such an optical laminate, Patent Document 1 describes a polarizing plate with a surface protective film having a surface protective film, a thin polarizing plate, and a release film in this order.

Japanese Unexamined Patent Publication No. 2016-118771

In the manufacturing process of the optical laminate, sufficient adhesion between the release film and the polarizing plate is required. On the other hand, in the step of attaching the polarizing plate to another optical member using the optical laminate, the release film is required to be easily peeled (peeled). The polarizing plate with a surface protective film of Patent Document 1 has low peelability of the release film in the step of bonding to another optical member, and the polarizing plate is peeled off from the surface protective film when the release film is peeled off. It may end up.

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to manufacture an optical laminate in which the polarizing plate is suppressed from being peeled from the surface protective film when the release film is peeled off. It is an object of the present invention to provide a method and a method for manufacturing an image display device.

The method for producing an optical laminate of the present invention is a method for producing an optical laminate having a surface protective film, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a release film in this order. The surface protection includes a peeling step of peeling the release film from the second pressure-sensitive adhesive layer and a re-bonding step of re-bonding the peeled release film to the second pressure-sensitive adhesive layer. The trigger peeling force of the film is X (N / 50 mm), the trigger peeling force of the peeling film before the peeling step is Y1 (N / 50 mm), and the trigger peeling of the peeling film after the re-bonding step is When the force is Y2 (N / 50 mm), Y2 <X ≦ Y1 is satisfied, and preferably XY2> 0.1 is satisfied.
One embodiment includes a foreign matter inspection step of inspecting the presence or absence of foreign matter in at least one of the polarizing plate and the second adhesive layer after the peeling step and before the reattachment step.
In one embodiment, the product of the tensile elastic modulus and the thickness of the surface protective film is A, the product of the tensile elastic modulus and the thickness of the polarizing plate is B, and the tensile elastic modulus and the thickness of the release film are When the product of is C, A> B + C is satisfied.
In one embodiment, A ≦ B + C + 25550 is satisfied.
In one embodiment, the total thickness of the surface protective film and the thickness of the first pressure-sensitive adhesive layer is 75 μm or more, and the thickness of the release film is 38 μm or less.
In one embodiment, the polarizing plate has a polarizing element and a protective layer laminated on the surface protective film side of the polarizing element, and the thickness of the polarizing element is 12 μm or less.
According to another aspect of the present invention, there is provided a method of manufacturing an image display device. In the manufacturing method of this image display device, the release film of the optical laminate obtained by the manufacturing method of the optical laminate is peeled off, and the polarizing plate is attached to the optical member via the second pressure-sensitive adhesive layer. Including the process of matching.

According to the present invention, it is possible to provide a method for manufacturing an optical laminate in which the polarizing plate is suppressed from being peeled from the surface protective film when the release film is peeled off, and a method for manufacturing an image display device.

It is schematic cross-sectional view of the optical laminated body obtained by the manufacturing method of the optical laminated body which concerns on one Embodiment of this invention. It is the schematic sectional drawing of the optical laminated body which shows the manufacturing method of the optical laminated body which concerns on one Embodiment of this invention in process order. It is a schematic cross-sectional view which shows the state that the release film is peeled off from an optical laminate. It is a schematic cross-sectional view which shows how the surface protection film is peeled off from an optical laminate. It is a schematic cross-sectional view of the optical laminate obtained by the manufacturing method which concerns on another Embodiment of this invention.

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

A. Method for Manufacturing Optical Laminates FIG. 1 is a schematic cross-sectional view of an optical laminate obtained by the method for manufacturing an optical laminate according to one embodiment of the present invention. The optical laminate 100 has a surface protective film 10, a first pressure-sensitive adhesive layer 20, a polarizing plate 30, a second pressure-sensitive adhesive layer 40, and a release film 50 in this order. In one embodiment, the polarizing plate 30 has a polarizer 31 and a first protective layer 32 laminated on the surface protective film 10 side of the polarizer 31.

The method for manufacturing the optical laminate 100 includes a peeling step of peeling the release film 50 from the second pressure-sensitive adhesive layer 40 and a re-bonding step of re-bonding the peeled release film 50 to the second pressure-sensitive adhesive layer 40. include. FIG. 2 is a schematic cross-sectional view of the optical laminate showing the manufacturing method of the optical laminate according to one embodiment in the order of processes. In the method for producing an optical laminate of the present embodiment, first, a polarizing plate 30 is produced as shown in (a). Next, as shown in (b), the release film 50 is laminated on one surface of the polarizing plate 30 via the second pressure-sensitive adhesive layer 40. Next, as shown in (c), the release film 50 is peeled from the second pressure-sensitive adhesive layer 40 (peeling step). Next, as shown in (d), at least one of the polarizing plate 30 and the second adhesive layer 40 is inspected for foreign matter (foreign matter inspection step). Then, as shown in (e), the peeled release film 50 is reattached to the second pressure-sensitive adhesive layer 40 (reattachment step). Next, as shown in (f), the optical laminate 100 is obtained by laminating the surface protective film 10 on the side of the polarizing plate 30 opposite to the release film 50 via the first pressure-sensitive adhesive layer 20.

The trigger peeling force of the surface protective film 10 is X (N / 50 mm), the trigger peeling force of the peeling film 50 before the peeling step is Y1 (N / 50 mm), and the trigger peeling force of the peeling film 50 after the re-bonding step is When the peeling force is Y2 (N / 50 mm), Y2 <X ≦ Y1 is satisfied, and preferably XY2> 0.1 is satisfied. Generally, when the film is peeled from the edge at a constant peeling rate, the peeling force of the film increases according to the peeling length immediately after the start of peeling, reaches a peak and decreases, and becomes constant after a lapse of a predetermined time. Stabilize with value. In the present specification, the trigger peeling force of the film means the peak value (maximum value) of the peeling force immediately after the start of peeling, and the normal peeling force of the film means the stabilized peeling force after a lapse of a predetermined time from the start of peeling. It shall mean. The optical laminate 100 is used when the release film 50 is peeled off as shown in FIG. 3 and the polarizing plate 30 is attached to another optical member (for example, a liquid crystal cell) via the second pressure-sensitive adhesive layer 40. obtain. For example, an optical laminate having a surface protective film having a high tensile elasticity, or an optical laminate in which the trigger peeling force of the release film is larger than the trigger peeling force of the surface protective film, when the release film 50 is attempted to be peeled from the end. As shown in FIG. 4, the surface protective film 10 and the first pressure-sensitive adhesive layer 20 are peeled off from the polarizing plate 30 without peeling off the release film 50 (the release film 50 is the first together with the polarizing plate 30). It may be peeled off from the pressure-sensitive adhesive layer 20), resulting in poor peeling. On the other hand, in the method for producing the optical laminate 100 of the present invention, as described above, the peeling step of peeling the release film 50 from the second pressure-sensitive adhesive layer 40 and the peeling film 50 being peeled off as the second pressure-sensitive adhesive. The trigger peeling force (Y2) of the release film 50 after the re-bonding step includes the re-bonding step of re-bonding to the layer 40, and is smaller than the trigger peeling force (X) of the surface protective film 10. Therefore, as shown in FIG. 3, the release film 50 can be peeled from the second pressure-sensitive adhesive layer 40 without the surface protection film 10 and the first pressure-sensitive adhesive layer 20 being peeled off from the polarizing plate 30. Further, in the method for producing the optical laminate 100 of the present invention, the trigger peeling force (Y1) of the peeling film 50 before the peeling step is equal to or higher than the trigger peeling force (X) of the surface protective film 10. Therefore, after the release film 50 is laminated on the polarizing plate 30 via the second pressure-sensitive adhesive layer 40, the adhesion between the release film 50 and the polarizing plate 30 is sufficiently high until the release step. As a result, when the optical laminate 100 is manufactured by laminating each layer while transporting, peeling of the release film 50 due to transport can be suppressed. As shown in FIG. 2D, the method for producing the optical laminate 100 preferably includes a foreign matter inspection step after the peeling step and before the re-bonding step.

FIG. 5 is a schematic cross-sectional view of an optical laminate obtained by the method for manufacturing an optical laminate according to another embodiment of the present invention. In the present embodiment, the polarizing plate 30 is laminated on the surface protective film 10 side of the polarizer 31 and the polarizer 31 and the second protective layer 32 laminated on the release film 50 side of the polarizer 31. It has a protective layer 33. Like the optical laminate 101 of the present embodiment, the polarizing plate 30 may have protective layers on both sides of the polarizer 31.

The optical laminate 100 and the optical laminate 101 may have a single-wafer shape or a long shape. The thickness of the polarizer 31 is typically 12 μm or less. The total thickness of the surface protective film 10 and the thickness of the first pressure-sensitive adhesive layer 20 is preferably 75 μm or more, and the thickness of the release film 50 is preferably 38 μm or less. In the optical laminate 100 and the optical laminate 101, the product of the tensile elastic modulus and the thickness of the surface protective film 10 is A, the product of the tensile elastic modulus of the polarizing plate 30 and the thickness is B, and the tensile elasticity of the release film 50. When the product of the rate and the thickness is C, preferably A> B + C is satisfied, and more preferably A ≦ B + C + 25550 is satisfied. The product B of the tensile elastic modulus and the thickness of the polarizing plate 30 is the product B1 of the tensile elastic modulus and the thickness of the polarizer 31 and the product B2 of the tensile elastic modulus and the thickness of the first protective layer 32. It is calculated by the sum of the product B3 (when the second protective layer is present) of the tensile elastic modulus of the second protective layer 33 and the thickness.

B. Surface Protective Film The surface protective film is laminated on one surface of the polarizing plate via a first pressure-sensitive adhesive layer, and can function as a protective film for the polarizing plate. The surface protective film is typically a transparent film having isotropic properties. The surface protective film can be peeled off and removed at any suitable time after the polarizing plate is attached to another optical member via the second pressure-sensitive adhesive layer.

The thickness of the surface protective film is preferably 25 μm to 250 μm, more preferably 50 μm to 200 μm, and particularly preferably 70 μm to 150 μm. By using a surface protective film having sufficient thickness and rigidity, it is possible to suppress the occurrence of curl in the process of attaching the polarizing plate to an optical member such as a liquid crystal cell, and further, each layer constituting the optical laminate is conveyed. However, in the case of laminating, the transportability of the laminated body is improved, and as a result, the manufacturing efficiency of the optical laminated body can be improved.

The tensile elastic modulus of the surface protective film is preferably 2000 MPa to 5000 MPa, more preferably 2500 MPa to 4500 MPa, and particularly preferably 3000 MPa to 4000 MPa.

Examples of the material constituting the surface protective film include polyester resin such as polyethylene terephthalate film, cellulose resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, and polyolefin resin. Examples include resins and acrylic resins. Of these, polyester-based resins are preferable.

C. Polarizing plate The polarizing plate contains at least a polarizer. Preferably, the polarizing plate has a protective layer on at least one side of the polarizer.

C-1. Polarizer The thickness of the polarizer is preferably 12 μm or less, more preferably 1 μm to 10 μm, and further preferably 3 μm to 8 μm as described above. The tensile elastic modulus of the polarizer is preferably 300 MPa to 1000 MPa, more preferably 400 MPa to 900 MPa, and particularly preferably 500 MPa to 800 MPa.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. In one embodiment, the transmittance of the polarizer at a wavelength of 589 nm (also referred to as single transmittance) is preferably 42.0% to 46.0%, more preferably 44.5% to 46.0%. Is. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more. In another embodiment, the polarizer preferably has a degree of polarization P greater than − (10 ^{0.929T-42.4-1} ) × 100% when the transmittance T is less than 42.3% and is transparent. When the rate T is 42.3% or more, the degree of polarization P is 99.9% or more.

As the polarizer, any suitable polarizer can be adopted. For example, the resin film forming the polarizer may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer system partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine or a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical properties, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or while dyeing. Alternatively, it may be stretched and then dyed. If necessary, the PVA-based film is subjected to a swelling treatment, a cross-linking treatment, a washing treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt on the surface of the PVA-based film and the blocking inhibitor, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizer obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer).

C-2. Protective Layer The protective layer (first protective layer and second protective layer) is formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition. The constituent material of the first protective layer and the constituent material of the second protective layer may be the same as or different from each other.

If necessary, the protective layer may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment.

The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. When the surface treatment is applied, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer. The thickness of the first protective layer and the thickness of the second protective layer may be the same as or different from each other. The tensile elastic modulus of the protective film constituting the protective layer is preferably 1500 MPa to 3800 MPa, more preferably 2000 MPa to 3300 MPa, and particularly preferably 2300 MPa to 3000 MPa.

D. Release film The release film is laminated on the side opposite to the surface protective film of the polarizing plate via the second pressure-sensitive adhesive layer, and when the polarizing plate is attached to another optical member via the second pressure-sensitive adhesive layer. It is peeled off and removed.

The thickness of the release film is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 20 to 50 μm. The tensile elastic modulus of the release film is preferably 2000 MPa to 5000 MPa, more preferably 2500 MPa to 4500 MPa, and particularly preferably 3000 MPa to 4000 MPa.

The release film is typically composed of a plastic film and a release-imparting layer provided on one side of the plastic film. Examples of the plastic film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film such as polyethylene terephthalate film, polybutylene terephthalate film, and polyurethane. Examples thereof include a film and an ethylene-vinyl acetate copolymer film. Of these, polyester film is preferable. The release-imparting layer may be a layer coated with any suitable release agent such as silicone-based, long-chain alkyl-based, and fluorine-based.

The release film is obtained by applying the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer on the release-imparting layer, drying the film, and then attaching the release film to a polarizing plate.

E. Adhesive layer As the adhesive constituting the adhesive layer, any suitable adhesive can be used. Examples of such adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, and polyacrylamide adhesives. Examples include adhesives and cellulose-based adhesives. Among these adhesives, those having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesiveness, and excellent weather resistance and heat resistance are preferably used. An acrylic pressure-sensitive adhesive is preferably used to exhibit such characteristics. The pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer and the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer may be the same as or different from each other.

The thickness of the pressure-sensitive adhesive layer is preferably 7 μm to 30 μm, more preferably 10 μm to 25 μm. The thickness of the first pressure-sensitive adhesive layer and the thickness of the second pressure-sensitive adhesive layer may be the same as or different from each other.

F. Image display device The optical laminate according to items A to E can be used when a polarizing plate is attached to an optical member included in an image display device such as a liquid crystal display device and an organic EL display device. Therefore, the method for manufacturing an optical laminate of the present invention includes a method for manufacturing an image display device using the above-mentioned polarizing plate. The method for manufacturing an image display device of the present invention includes a step of peeling a release film of an optical laminate obtained by the manufacturing method of the present invention and attaching a polarizing plate to an optical member via a second pressure-sensitive adhesive layer. ..

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method and evaluation method for each characteristic are as follows.

(1) Thickness Measured using a digital micrometer (KC-351C manufactured by Anritsu Co., Ltd.).
(2) Tensile elastic modulus The film or polarizing plate to be measured is formed into a tensile test dumbbell having a parallel portion width of 10 mm and a length of 40 mm based on JIS K6734: 2000, and a tensile test is performed in accordance with JIS K7161: 1994. The tensile elastic modulus was determined.
(3) Normal peeling force of surface protective film The size of the end of the long optical laminate on the long side is 50 mm x 100 mm so that the long side of the optical laminate corresponds to the short side of the measurement sample. It was cut into a sample for measurement. The release film was peeled off from the measurement sample, and the adhesive layer on the peeled surface was attached to a flat plate-shaped peeling jig.
Next, the polarizing plate interface and the first pressure-sensitive adhesive layer are peeled off from the short side of the measurement sample, the surface protective film and the first pressure-sensitive adhesive layer are chucked, and the tensile strength (N / 50 mm) is pulled by using a tensile tester. (Tensile direction: 180 ° with respect to the surface of the optical laminate, tensile speed: 300 mm / min). The peeling force was measured for five measuring samples, and the average value of the measured values of each measuring sample was adopted as the normal peeling force of the surface protective film.
(4) Trigger peeling force of surface protective film The size of the end of the long optical laminate on the long side is 50 mm x 100 mm so that the long side of the optical laminate corresponds to the short side of the measurement sample. It was cut into a sample for measurement. The release film was peeled off from the measurement sample, and the adhesive layer on the peeled surface was attached to a flat plate-shaped peeling jig.
Next, a 19 mm wide polyester adhesive tape (manufactured by Nitto Denko KK, product name "No. 31B") corresponds to the short side (long side of the optical laminate) of the measurement sample so as not to come into contact with the peeling jig. It was attached to the surface protective film at the end on the side) side, and further, a polyester base material adhesive tape (manufactured by Nitto Denko KK, product name "No. 343B") was attached to the polyester adhesive tape.
Next, the polyester base material adhesive tape is chucked, pulled using a tensile tester, and the peeling force (N / 50 mm) is measured (tensile direction: 90 ° with respect to the surface of the optical laminate, tensile speed: 300 mm). / Min, tensile distance: 60 mm), peak value (maximum value) of peeling force was defined as "trigger peeling force (N / 50 mm)" of the surface protective film. The trigger peeling force was measured for five measurement samples, and the average value of the measured values of each measurement sample was adopted as the trigger peeling force of the surface protective film. In the measurement of the trigger peeling force of the surface protective film, the surface protective film peels off between the first pressure-sensitive adhesive layer and the polarizing plate as a peeling interface (the surface protection film and the first pressure-sensitive adhesive layer are polarizing plates. Peel off from).
(5) Normal peeling force of release film The end of the long optical laminate on the long side is 50 mm x 100 mm so that the long side of the optical laminate corresponds to the short side of the measurement sample. It was cut into a sample for measurement. The measurement sample was attached to a flat plate-shaped peeling jig via an acrylic adhesive with the surface protective film side facing down.
Next, the peeling film interface and the second pressure-sensitive adhesive layer were peeled off from the short side of the measurement sample, the peeling film was chucked, and the peeling force (N / 50 mm) was measured by pulling using a tensile tester. Direction: 180 ° with respect to the surface of the optical laminate, tensile speed: 300 mm / min). The peeling force was measured for five measuring samples, and the average value of the measured values of each measuring sample was adopted as the normal peeling force of the peeling film.
(6) Trigger peeling force of release film The end of the long optical laminate on the long side is 50 mm x 100 mm so that the long side of the optical laminate corresponds to the short side of the measurement sample. It was cut into a sample for measurement. The measurement sample was attached to a flat plate-shaped peeling jig via an acrylic adhesive with the surface protective film side facing down.
Next, a 19 mm wide polyester adhesive tape (manufactured by Nitto Denko KK, product name "No. 31B") corresponds to the short side (long side of the optical laminate) of the measurement sample so as not to come into contact with the peeling jig. It was attached to the release film at the end on the side) side, and further, a polyester base material adhesive tape (manufactured by Nitto Denko KK, product name "No. 343B") was attached to the polyester adhesive tape.
Next, the polyester base material adhesive tape is chucked, pulled using a tensile tester, and the peeling force (N / 50 mm) is measured (tensile direction: 90 ° with respect to the surface of the optical laminate, tensile speed: 300 mm). / Min, tensile distance: 60 mm), peak value (maximum value) of peeling force was defined as "trigger peeling force (N / 50 mm)" of the peeling film. The trigger peeling force was measured for five measurement samples, and the average value of the measured values of each measurement sample was adopted as the trigger peeling force of the release film.
In Examples 1 to 6, the trigger peeling force of the peeling film was measured for each of the optical laminate before the peeling step and the optical laminate after the re-bonding step.
(7) Peeling Test of Peeling Film A long optical laminate was cut into a size of 1215 mm × 684 mm to prepare a sample for a peeling test. The peeling test sample was placed and fixed on a suction table having a suction pad with the surface protective film side facing down. Next, a peeling roll having a diameter of 20 mm was applied to the apex of the peeling test sample, and the peeling film was peeled off by rotating the peeling roll (peeling direction: 180 ° with respect to the surface of the optical laminate and the measurement sample. 45 ° to the long and short sides of the, peeling speed: 300 mm / min).
If only the release film can be peeled off without the polarizing plate peeling from the surface protection film when the release film is peeled off, the peeling is successful, and if the polarizing plate is peeled off from the surface protection film when the release film is peeled off, the peeling is successful. Peeling failed.
The peeling film was peeled off from 10 peeling test samples, and the peelability of the peeling film was evaluated according to the following criteria.
⊚: The peeling was successful for 90% or more of the peeling test samples.
◯: The peeling was successful for the peeling test sample of 60% or more and less than 90%.
Δ: The peeling test sample of 30% or more and less than 60% was successfully peeled.
X ... Peeling was successful for a peeling test sample of less than 30%.

<Manufacturing example 1>
A polyethylene terephthalate film (MRF38CK manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of about 550 μm was stretched 3.7 times in the vertical direction at 85 ° C., stretched 3.9 times in the horizontal direction at 100 ° C., and heat-treated at 210 ° C. A biaxially stretched polyester film having a thickness of 38 μm was obtained.
On the surface of the biaxially stretched polyester film, a mold release agent having a mold release agent composition A shown below is applied by a reverse gravure coating method so ^{that the coating amount (after drying) is 0.12 g / m 2 and dried.} A conventional release film A (thickness 38 μm, tensile elastic modulus 3500 MPa) was obtained by peeling treatment with a silicone-based release agent.
(Release agent composition A)
24 parts by weight of a curable silicone resin (molecular weight 200,000) of the general formula (I) having a ratio of a1: methyl group, hexenyl group and phenyl group of 100: 1: 0.1.

・ａ２：メチル基とビニル基の比が１００：０．２である一般式（II）の硬化型シリコーン樹脂（分子量２０００００）を３３重量部

33 parts by weight of a curable silicone resin (molecular weight 200,000) of the general formula (II) in which the ratio of a2: methyl group to vinyl group is 100: 0.2.

・ａ３：メチル基とヒドロシリル基の比が１００：１．５である一般式（III）の硬化型シリコーン樹脂（分子量２０００００）を８重量部

A3: 8 parts by weight of a curable silicone resin (molecular weight 200,000) of the general formula (III) having a ratio of methyl group to hydrosilyl group of 100: 1.5.

・ａ４：メチル基とヒドロシリル基の比が１００：０．４である上記一般式（III）の硬化型シリコーン樹脂（分子量２０００００）を３３重量部
・ｂ１：一般式（IV）の未反応性シリコーン樹脂（分子量８００００）を１重量部

A4: 33 parts by weight of the curable silicone resin (molecular weight 200,000) of the above general formula (III) having a ratio of methyl group to hydrosilyl group of 100: 0.4. 1 part by weight of resin (molecular weight 80000)

・ｃ１：付加型白金触媒（ＰＬ−５０Ｔ：信越化学工業製）を１重量部
ＭＥＫ／トルエン混合溶媒（混合比率は１：１）

C1: Addition type platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) in 1 part by weight MEK / toluene mixed solvent (mixing ratio is 1: 1)

<Manufacturing example 2>
A normal type release film B that has been peeled with a silicone-based release agent in the same manner as in Production Example 1 except that the draw ratio of the polyethylene terephthalate film is 5.1 times in the vertical direction and 5.3 times in the horizontal direction. (Thickness 25 μm, tensile elastic modulus 3500 MPa) was obtained.

<Manufacturing example 3>
A heavy release type release film C (thickness 38 μm) that has been peeled with a silicone-based release agent in the same manner as in Production Example 1 except that a release agent having a release agent composition B shown below is used as the release agent. , Tensile elastic modulus 3500 MPa) was obtained.
(Release agent composition B)
A1: 32 parts by weight of the curable silicone resin (molecular weight 200,000) of the above general formula (I) having a ratio of methyl group, hexenyl group and phenyl group of 100: 1: 0.1. 66 parts by weight of the curable silicone resin (molecular weight 200,000) of the general formula (II) having a ratio of 100: 0.2 b1: The unreacted silicone resin (molecular weight 80000) of the general formula (IV) is 1 Parts by weight c1: Additive platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical Industry Co., Ltd.) by weight 1 part by weight MEK / toluene mixed solvent (mixing ratio 1: 1)

<Manufacturing example 4>
A heavy-release type release film that has been peeled with a silicone-based release agent in the same manner as in Production Example 3 except that the draw ratio of the polyethylene terephthalate film was 5.1 times in the vertical direction and 5.3 times in the horizontal direction. D (thickness 25 μm, tensile elastic modulus 3500 MPa) was obtained.

<Example 1>
1. 1. Fabrication of polarizing plate A long amorphous polyethylene terephthalate (A-PET) film (manufactured by Mitsubishi Resin Co., Ltd., trade name "Novaclear", thickness: 100 μm) was prepared as a base material, and polyvinyl was applied to one side of the base material. An aqueous solution of an alcohol (PVA) resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosenol (registered trademark) NH-26") was applied and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 7 μm. The laminate thus obtained was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. for 30 seconds (insolubilization step). Then, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. for 60 seconds (dyeing step). Then, it was immersed in a cross-linking bath having a liquid temperature of 30 ° C. for 30 seconds (cross-linking step). Then, the laminate was uniaxially stretched in the longitudinal direction (long direction) between rolls having different peripheral speeds while being immersed in a boric acid aqueous solution having a liquid temperature of 60 ° C. The immersion time in the boric acid aqueous solution was 120 seconds, and the laminate was stretched until just before breaking. Then, the laminate was immersed in a washing bath and then dried with warm air at 60 ° C. (washing / drying step). In this way, a long polarizing element laminate in which a polarizer having a thickness of 5 μm was formed on the substrate was obtained.
Next, a (meth) acrylic resin film having a lactone ring structure having a thickness of 40 μm was prepared as a protective film constituting the protective layer, and the easily adhesive-treated surface of the protective film was subjected to corona treatment, and the polarizer side of the polarizing element laminate was subjected to corona treatment. A protective layer (thickness: 40 μm, tensile modulus: 2650 MPa) / polarizer (thickness: 5 μm, tensile modulus : A long polarizing plate having a layer structure of 650 MPa) was obtained.
2. Lamination of release film A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile was charged together with ethyl acetate as a polymerization initiator with respect to 100 parts of the above-mentioned monomer mixture (solid content), and nitrogen gas was introduced while gently stirring. After the nitrogen substitution, the liquid temperature in the flask was maintained at around 60 ° C. and the polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to prepare a solution of an acrylic polymer (A-1) having a weight average molecular weight of 1.4 million adjusted to a solid content concentration of 30%.
With respect to 100 parts of the solid content of the obtained acrylic polymer (A-1) solution, 0.095 parts of trimethylolpropanexylylene diisocyanate (trade name: Takenate D110N, manufactured by Mitsui Kagaku Co., Ltd.) was used as a cross-linking agent. , Dibenzoyl peroxide (trade name: Niper BMT40SV, manufactured by Nippon Oil & Fats Co., Ltd.) 0.3 part, as a thiol-based silane coupling agent (C1), an alkoxysilyl resin containing a methyl group and a mercapto group (trade name: X- 41-1810, manufactured by Shin-Etsu Chemical Industry Co., Ltd., 0.2 parts, as an acetacetyl group-containing silane coupling agent (C2), an acetacetyl group-containing silane coupling agent (trade name: A-100, Soken Kagaku Co., Ltd.) ) To prepare an acrylic pressure-sensitive adhesive solution A by blending 0.2 parts.
Next, the acrylic pressure-sensitive adhesive solution A was uniformly applied to the surface of the release film A with a fountain coater, dried in an air circulation type constant temperature oven at 155 ° C. for 2 minutes, and the surface of the release film A had a thickness of 20 μm. A pressure-sensitive adhesive layer was formed. Next, the release film A was attached to the polarizer side of the polarizing plate via the pressure-sensitive adhesive layer.
Next, the release film is peeled from the polarizing plate to which the release film is bonded (peeling step), and the peeled film is reattached to the surface of the polarizing plate on the polarizer side (rebonding step). , A long-shaped polarizing plate with a release film was prepared.
3. 3. Lamination of surface protective film In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler, 94 parts by mass of 2-ethylhexyl acrylate (2EHA) and 1 mass of N, N-diethylacrylamide (DEAA). Parts, 1 part by mass of ethoxydiethylene glycol acrylate (EDE), 4 parts by mass of 4-hydroxybutyl acrylate (HBA), 0.2 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator, 150 parts by mass of ethyl acetate. Is charged, nitrogen gas is introduced while gently stirring, the liquid temperature in the flask is maintained at around 60 ° C., and the polymerization reaction is carried out for 5 hours to prepare a solution (40% by mass) of the acrylic polymer (A-2). bottom. The weight average molecular weight of the acrylic polymer (A-2) was 570,000, and the glass transition temperature (Tg) was −68 ° C.
Acrylic polymer (A-2) solution (40% by mass) is diluted with ethyl acetate to 20% by mass, and an isocyanurate form of hexamethylene diisocyanate (Nippon Polyurethane Industry Co., Ltd.) is added to 500 parts by mass (solid content 100 parts by mass) of this solution. Co., Ltd., Coronate HX: C / HX) 2 parts by mass (solid content 2 parts by mass), dibutyltin dilaurate (1 mass% ethyl acetate solution) 2 parts by mass (solid content 0.02 parts by mass) was added as a cross-linking catalyst. , Mixing and stirring was carried out to prepare an acrylic pressure-sensitive adhesive solution B.
A transparent polyethylene terephthalate (PET) film (polyester film) having a thickness of 75 μm was prepared as a surface protective film. The acrylic pressure-sensitive adhesive solution B was applied to the PET film and heated at 130 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 15 μm. Next, a silicone-treated surface of a polyethylene terephthalate film (thickness 25 μm), which is a separator treated with silicone on one side, was bonded to the surface of the pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive sheet (surface protection film with a separator).
The separator is peeled off from the adhesive sheet, and the surface protective film (thickness: 75 μm, tensile elastic modulus: 3500 MPa) is attached to the surface of the polarizing plate with the release film opposite to the release film to form a long shape. The optical laminate 1 of the above was produced. The optical laminate 1 has a layer structure of a surface protective film / first pressure-sensitive adhesive layer / polarizing plate / second pressure-sensitive adhesive layer / release film.
The obtained optical laminate 1 was used for evaluation of peeling force and peeling test. In addition, the stiffness index (X) represented by the following formula (1) was calculated. The results are shown in Tables 1 and 2.
X = ABC (1)
A: Tension elastic modulus of surface protective film (MPa) x thickness of surface protective film (μm)
B: Tension elastic modulus of the polarizing plate (MPa) x thickness of the polarizing plate (μm)
C: Tension elastic modulus of release film (MPa) x thickness of release film (μm)
When the polarizing plate has a first protective layer and a second protective layer, the value of B in the above formula (1) shall be calculated based on the following formula (2).
B = B1 + B2 + B3 (2)
B1: Tension elastic modulus of the polarizer (MPa) x thickness of the polarizer (μm)
B2: Tension elastic modulus (MPa) of the first protective layer × thickness (μm) of the first protective layer
B3: Tension elastic modulus of the second protective layer (MPa) × thickness of the second protective layer (μm)

<Example 2>
A long optical laminate 2 was produced in the same manner as in Example 1 except that the release film B was used as the release film. The optical laminate 2 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Example 3>
A long optical laminate 3 was produced in the same manner as in Example 1 except that the release film C was used as the release film. The optical laminate 3 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Example 4>
A long optical laminate 4 was produced in the same manner as in Example 1 except that the release film D was used as the release film. The optical laminate 4 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Example 5>
A (meth) acrylic resin film having a lactone ring structure with a thickness of 20 μm is used as a protective film constituting the protective layer (first protective layer), and the easily adhesive-treated surface of the protective film is corona-treated to form a polarizer laminate. The protective film subjected to corona treatment was attached to the surface on the polarizer side of the above, and the base material was peeled off from the polarizer. Next, a (meth) acrylic resin film having a lactone ring structure with a thickness of 20 μm was used as a protective film constituting the protective layer (second protective layer), and the easily adhesive-treated surface of the protective film was subjected to corona treatment to obtain a polarizing element. The first protective layer (thickness: 20 μm, tensile elastic modulus: 2650 MPa) / polarizing element (thickness: 5 μm, tensile elastic modulus: 650 MPa) by adhering the corona-treated protective film to the peeled surface of the base material. / A polarizing plate having a layer structure of a second protective layer (thickness: 20 μm, tensile elastic modulus: 2650 MPa) was obtained.
A long optical laminate 5 was produced in the same manner as in Example 1 except that the above polarizing plate was used. The optical laminate 5 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Example 6>
A (meth) acrylic resin film having a lactone ring structure with a thickness of 25 μm was used as the protective film constituting the protective layer (first protective layer), and the protective film constituting the protective layer (second protective layer). A long optical laminate 6 was produced in the same manner as in Example 5 except that a (meth) acrylic resin film having a lactone ring structure having a thickness of 13 μm was used. The optical laminate 6 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative example 1>
The same as in Example 1 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 7 was produced. The optical laminate 7 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative example 2>
The same as in Example 2 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 8 was produced. The optical laminate 8 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative example 3>
The same as in Example 3 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 9 was produced. The optical laminate 9 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative example 4>
Same as in Example 4 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 10 was produced. The optical laminate 10 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative example 5>
The same as in Example 5 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 11 was produced. The optical laminate 11 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

<Comparative Example 6>
The same as in Example 6 except that the peeling step of peeling the peeling film and the re-sticking step of re-sticking the release film to the peeling surface were not performed after the release film was attached to the polarizer side of the polarizing plate. A long optical laminate 12 was produced. The optical laminate 12 was subjected to the same evaluation as in Example 1. The results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, the optical laminates of Examples 1 to 6 have higher peelability of the release film than the optical laminates of Comparative Examples. In particular, the optical laminates of Example 1, Example 3, Example 5, and Example 6 having a stiffness index of 25550 or less have extremely high peelability of the release film.

The manufacturing method of the present invention is suitably used for manufacturing an optical laminate used in an image display device such as a liquid crystal display device or an organic EL display device.

10 Surface protective film 20 First adhesive layer 30 Polarizing plate 31 Polarizer 32 First protective layer 33 Second protective layer 40 Second adhesive layer 50 Release film 100 Optical laminate 101 Optical laminate

Claims (6)

A method for producing an optical laminate having a surface protective film, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a release film in this order.
A peeling step of peeling the release film from the second pressure-sensitive adhesive layer,
A re-bonding step of re-bonding the peeled release film to the second pressure-sensitive adhesive layer is included.
The trigger peeling force when the surface protective film and the first pressure-sensitive adhesive layer are peeled from the polarizing plate is X (N / 50 mm), and the trigger peeling force of the release film before the peeling step is Y1 ( N / 50 mm), and when the trigger peeling force of the release film after the re-bonding step is Y2 (N / 50 mm)
Y2 <X≤Y1
Satisfied ,
When the product of the tensile elastic modulus and the thickness of the surface protective film is A, the product of the tensile elastic modulus and the thickness of the polarizing plate is B, and the product of the tensile elastic modulus and the thickness of the release film is C. ,
A> B + C
Satisfied and further
A ≤ B + C + 25550
Satisfy
A method for manufacturing an optical laminate. XY2> 0.1
The method for producing an optical laminate according to claim 1. The first or second aspect of claim 1 or 2, further comprising a foreign matter inspection step of inspecting the presence or absence of foreign matter in at least one of the polarizing plate and the second adhesive layer after the peeling step and before the reattachment step. A method for manufacturing an optical laminate. The total thickness of the surface protective film and the thickness of the first pressure-sensitive adhesive layer is 75 μm or more.
The method for producing an optical laminate according to any one of claims 1 to 3 , wherein the release film has a thickness of 38 μm or less. The polarizing plate has a polarizing element and a protective layer laminated on the surface protective film side of the polarizing element.
The method for producing an optical laminate according to any one of claims 1 to 4 , wherein the polarizing element has a thickness of 12 μm or less. The release film of the optical laminate obtained by the method for producing an optical laminate according to any one of claims 1 to 5 is peeled off, and the polarizing plate is used as an optical member via the second pressure-sensitive adhesive layer. A method of manufacturing an image display device, which includes a step of laminating.

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