WO2024070440A1

WO2024070440A1 - Optical laminate

Info

Publication number: WO2024070440A1
Application number: PCT/JP2023/031427
Authority: WO
Inventors: 哲生坂口; 光敬佐▲瀬▼; 雄亮仲西; 和雅関; 昇祐李; 由紀西上
Original assignee: 住友化学株式会社
Priority date: 2022-09-29
Filing date: 2023-08-30
Publication date: 2024-04-04
Also published as: JP2024050177A

Abstract

(Abstract) (Problem) To provide an optical laminate in which a release film can be satisfactorily released from an adhesive layer. (Solution) This optical laminate includes an optical film, an adhesive layer, and a release film in the stated order. The release film has a release treatment surface containing a siloxane compound on a side where the release film makes contact with the adhesive layer. The release treatment surface of the release film satisfies the relationship indicated by formula (1).　(1): Ys/Xs × 100 ≤ 3.5 [In formula (1), Xs represents the intensity of the maximum peak Ps in a binding energy range of 96-108 eV of an XPS spectrum (Sr) of the release treatment surface, and Ys represents the intensity of the XPS spectrum (Sr) at a binding energy of (Es + 2) eV, when the binding energy at the peak PS is Es [eV].] (Selected figure) FIG. 1

Description

Optical laminate

The present invention relates to an optical laminate.

It is known that optical films such as polarizing plates are used in displays such as liquid crystal displays and organic EL displays. The optical film is incorporated into the display device by being attached to a display panel or the like of the display device using an adhesive layer. For this reason, it is known that when manufacturing a display device, a laminate is prepared in which an adhesive layer and a release film are laminated in this order on one surface of the optical film, and the separator is peeled off from this laminate to expose the adhesive layer, and the optical film is attached to the display panel or the like.

The laminate can be obtained, for example, by laminating an optical film and an adhesive layer with a release film in which an adhesive layer is formed on a release film. The adhesive layer with a release film can be obtained by forming an adhesive layer on a release film, and peeling off one release film from an adhesive sheet in which another release film is laminated on the adhesive layer. Patent Document 1 discloses an adhesive sheet with release films on both sides of an adhesive layer used for bonding optical components.

JP 2015-52073 A

In the adhesive sheet, the peel force between one release film and the adhesive layer is relatively small, and the peel force between the other release film and the adhesive layer is relatively large. This allows the release films on both sides to be easily peeled off from the adhesive layer in order, and prevents the adhesive layer from breaking when the release film is peeled off. Therefore, when the adhesive layer and release film contained in the adhesive sheet are laminated on an optical film to obtain a laminate, the release film with a release film, which has an adhesive layer and a release film with a relatively large release force (hereinafter sometimes referred to as a "heavy release film") obtained by peeling and removing the release film with a relatively small release force (hereinafter sometimes referred to as a "light release film") from the adhesive sheet, is laminated on the optical film.

When applying a polarizing plate to a display device, the heavy release film may be peeled off from the laminate, with the laminate having an adhesive layer with a release film fixed onto an adsorption plate. When attempting to peel off the heavy release film using this method, the laminate may lift up from the adsorption plate, making it impossible to peel the heavy release film from the adhesive layer.

The present invention aims to provide an optical laminate that allows the release film to be easily peeled off from the adhesive layer.

The present invention provides the following optical laminate.
[1] An optical laminate comprising an optical film, a pressure-sensitive adhesive layer, and a release film in this order,
the release film has a release-treated surface containing a siloxane compound on a side in contact with the pressure-sensitive adhesive layer,
The release-treated surface of the release film satisfies the following formula (1):
Ys/Xs×100≦3.5 (1)
[In formula (1),
Xs represents the intensity of the maximum peak Ps in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sr) of the release treated surface,
Ys represents the intensity of the XPS spectrum (Sr) at a binding energy of (Es+2) eV, where Es [eV] is the binding energy at the peak Ps.
[2] The optical laminate according to [1], wherein the surface of the pressure-sensitive adhesive layer on the release film side satisfies the relationship of the following formula (2):
Ya / Xa × 100 ≧ 2.0 (2)
[In formula (2),
Xa represents the intensity of the maximum peak Pa in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sa) of the surface of the pressure-sensitive adhesive layer on the release film side,
Ya represents the intensity of the XPS spectrum (Sa) at a binding energy of (Ea+2) eV, where Ea [eV] is the binding energy at the peak Pa.
[3] The optical laminate according to [1] or [2], wherein the optical film has a thickness of 120 μm or less.
[4] The optical laminate according to any one of [1] to [3], wherein the optical film is a polarizing plate including at least a linear polarizing layer.
[5] The optical laminate according to [4], wherein the polarizing plate further includes a retardation layer.
[6] The optical laminate according to [4] or [5], wherein the optical film includes a surface protection film provided releasably on the polarizing plate.

The optical laminate of the present invention allows the release film to be easily peeled off from the pressure-sensitive adhesive layer.

FIG. 1 is a schematic cross-sectional view showing an optical laminate according to one embodiment of the present invention. 1 is a schematic cross-sectional view showing a method for producing an optical laminate according to one embodiment of the present invention.

　Below, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment.

(Optical laminate)
1 is a schematic cross-sectional view showing an optical laminate according to one embodiment of the present invention. The optical laminate 1 has an optical film 11, a first pressure-sensitive adhesive layer 12 (pressure-sensitive adhesive layer), and a first release film 15 (release film) in this order. The first pressure-sensitive adhesive layer 12 is usually in direct contact with the optical film 11 and the first release film 15.

The optical film 11 may be a polarizing plate including at least a linear polarizing layer, or may be a polarizing plate including a polarizing plate and a retardation layer. The optical film 11 may include a surface protection film that is provided so as to be peelable from the polarizing plate.

The first release film 15 has a release-treated surface containing a siloxane compound on the side in contact with the first pressure-sensitive adhesive layer 12. The release-treated surface of the first release film 15 satisfies the relationship of the following formula (1).
Ys/Xs×100≦3.5 (1)
[In formula (1),
Xs represents the intensity of the maximum peak Ps in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sr) of the release-treated surface,
Ys represents the intensity of the XPS spectrum (Sr) at a binding energy of (Es+2) eV, where Es [eV] is the binding energy at peak Ps.

The binding energy (Es+2) eV refers to the binding energy at a position 2 eV shifted toward higher energy from the position of the binding energy Es at peak Ps in the XPS spectrum (Sr).

The maximum peak Ps in the range of bond energy 96 eV to 108 eV is considered to be mainly derived from structure (I) in which two O atoms are bonded to the Si atom of the siloxane compound contained in the release treatment surface. The intensity Ys of the XPS spectrum (Sr) at the bond energy (Es+2) eV is considered to be mainly derived from structure (II) in which three or more O atoms are bonded to the Si atom of the siloxane compound contained in the release treatment surface. Structure (I) is considered to be a structure derived from the siloxane compound that is the main agent of the release agent composition used to form the release treatment surface (release treatment layer) of the release film. Structure (II) is considered to be a structure derived from the siloxane compound as an additive added to the release agent composition to obtain a release film with a relatively large release force. Therefore, it can be said that the left side (Ys/Xs×100) in formula (1) represents the ratio of the content of the siloxane compound that is the additive to the content of the siloxane compound that is the main agent among the siloxane compounds on the release treatment surface of the first release film 15.

As described below, the optical laminate 1 can be manufactured, for example, by [i] laminating a first adhesive layer 12 formed on a second release film 25 (FIG. 2) onto an optical film 11, then peeling off the second release film 25, and [ii] laminating a first release film 15 having a smaller peel strength than the second release film 25 onto the first adhesive layer 12 exposed by the peeling off of the second release film 25. In the optical laminate 1 obtained through such a process, when the release film is replaced, a small amount of the siloxane compound constituting the release treatment surface (release treatment layer) of the second release film 25 adheres to the first adhesive layer 12, and it is believed that the siloxane compound adhered to the first adhesive layer 12 also adheres to the release treatment surface of the first release film 15. Therefore, for example, even if the release treatment surface (release treatment layer) of the first release film 15 does not contain a siloxane compound having structure (II) that provides a relatively large release force to the release film, if the release treatment surface (release treatment layer) of the second release film 25 is formed from a release agent composition containing a siloxane compound having structure (II), it is considered that the siloxane compound having structure (II) contained in the release treatment surface of the second release film 25 will adhere to the release treatment surface of the first release film 15 by replacing the second release film 25 with the first release film 15. Therefore, for example, in the optical laminate 1 manufactured with the replacement of the release film as described above, it is considered that the release treatment surface of the first release film 15 satisfies the relationship of the above formula (1).

Ys/Xs x 100 in formula (1) may be 3.50 or less, 3.45 or less, or 3.40 or less. Ys/Xs x 100 in formula (1) is usually 0.1 or more, 1.0 or more, 2.0 or more, or 2.6 or more. The strengths Xs and Ys can be measured by the method described in the examples below.

It is believed that the optical laminate 1 is provided with a release film with a small peeling force because the release-treated surface of the first release film 15 satisfies the relationship of formula (1). Therefore, when the first release film 15 is peeled off from the optical laminate 1 with the optical film 11 side of the optical laminate 1 fixed to an adsorption plate, it becomes easier to separate the first release film 15 between the first adhesive layer 12 and the first release film 15.

In the optical laminate 1, the surface of the first pressure-sensitive adhesive layer 12 on the side of the first release film 15 preferably satisfies the relationship of the following formula (2).
Ya / Xa × 100 ≧ 2.0 (2)
[In formula (2),
Xa represents the intensity of the maximum peak Pa in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sa) of the surface of the first pressure-sensitive adhesive layer 12 on the side of the first release film 15,
Ya represents the intensity of the XPS spectrum (Sa) at a binding energy of (Ea+2) eV, where Ea [eV] is the binding energy at peak Pa.

The bond energy (Ea+2) eV refers to the bond energy at a position 2 eV higher than the bond energy Ea at peak Pa in the XPS spectrum (Sa).

The maximum peak Pa in the bond energy range of 96 eV to 108 eV is believed to be mainly due to structure (I) in which two O atoms are bonded to the Si atom of the siloxane compound attached to the surface of the first adhesive layer 12 facing the first release film 15. The intensity of the XPS spectrum (Sa) at a bond energy of (Ea+2) eV is believed to be mainly due to structure (II) in which three or more O atoms are bonded to the Si atom of the siloxane compound attached to the surface of the first adhesive layer 12 facing the first release film 15. The siloxane compounds that result in structure (I) and structure (II) are as described above.

It is believed that a small amount of the siloxane compound contained in the release treatment surface (release treatment layer) of the release film laminated on the surface during the manufacturing process of the optical laminate 1 adheres to the surface of the first adhesive layer 12 on the first release film 15 side. As described above, when the optical laminate 1 is manufactured with the replacement of the release film, it is believed that the siloxane compound constituting the release treatment surface (release treatment layer) of the second release film 25 (FIG. 2) that was laminated before the replacement also adheres to the surface of the first adhesive layer 12 on the first release film 15 side. Therefore, when the release treatment surface of the second release film 25 is formed from a release agent composition containing a siloxane compound having structure (II), even if the second release film 25 is replaced with the first release film 15, it is believed that the siloxane compound having structure (II) contained in the release treatment surface of the second release film 25 remains on the surface of the first adhesive layer 12 on the first release film 15 side. Therefore, for example, in the optical laminate 1 manufactured with the above-described replacement of the release film, it is considered that the surface of the first adhesive layer 12 on the side of the first release film 15 satisfies the relationship of the above formula (2).

Ya/Xa×100 in formula (2) may be 2.0 or more, 2.5 or more, 3.0 or more, or 3.4 or more. Ya/Xa×100 in formula (2) is usually 20 or less, 15 or less, 10 or less, or 6.6 or less. The strengths Xa and Ya can be measured by the method described in the examples below.

When the surface of the first adhesive layer 12 on the side of the first release film 15 satisfies the relationship of formula (2), it can be considered that the optical laminate 1 is manufactured by replacing the release film as described above. Therefore, when the first release film 15 is peeled off from the optical laminate 1 with the optical film 11 side of the optical laminate 1 fixed to the suction plate, it becomes easier to separate the first release film 15 between the first adhesive layer 12 and the first release film 15.

The optical laminate 1 can be attached to the display element of a display device by peeling off the first release film 15 and using the exposed first adhesive layer 12 to bond the optical film 11. The display device is not particularly limited, but examples include liquid crystal display devices and organic EL display devices. The display device may be a mobile terminal such as a smartphone or tablet, or may be a television, digital photo frame, electronic signboard, measuring device or gauge, office equipment, medical equipment, computing equipment, etc.

(Method for producing optical laminate)
2 is a schematic cross-sectional view showing a method for producing an optical laminate according to one embodiment of the present invention. The method for producing an optical laminate according to this embodiment is a method for producing an optical laminate 1 including an optical film 11, a first pressure-sensitive adhesive layer 12, and a first release film 15 in this order. Hereinafter, a method for producing the optical laminate 1 described above will be described, but the optical laminate produced by this method is not limited thereto.

The method for producing the optical laminate 1 includes the steps of:
a step of bonding the first pressure-sensitive adhesive layer 12 side of a pressure-sensitive adhesive layer 21 with a release film, the first pressure-sensitive adhesive layer 12 being provided on a second release-treated surface of a second release film 25, to the optical film 11 to obtain a first laminate 2 ((c) of FIG. 2);
a step of peeling off the second release film 25 from the first laminate 2 (FIG. 2(d));
The method includes a step of peeling off the second release film 25 and bonding the first release treated surface of the first release film 15 to the first adhesive layer 12 exposed thereby to obtain a second laminate 3 (FIG. 2 (e)).

In the manufacturing method of the optical laminate 1, both the first release treatment surface and the second release treatment surface contain a polysiloxane compound.

In the above-mentioned method for producing the optical laminate 1, it is preferable that the peeling force between the first release film 15 and the first adhesive layer 12 is smaller than the peeling force between the second release film 25 and the first adhesive layer 12. This makes it easier to obtain an optical laminate 1 from which the first release film 15 can be easily peeled off while the optical film 11 side of the optical laminate 1 is fixed to the suction plate.

The method for producing the optical laminate 1 includes the steps of:
The second release treatment surface of the second release film 25 peeled off from the first laminate 2, and the first release treatment surface of the first release film 15 peeled off from the second laminate 3 may satisfy the relationships of the following formulas (3) and (4).
Ys2/Xs2>Ys1/Xs1 (3)
Ys1/Xs1×100≦3.5 (4)
[In formula (3) and formula (4),
Xs2 represents the intensity of the maximum peak Ps2 in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sr2) of the second release treatment surface,
Ys2 represents the intensity of the XPS spectrum (Sr2) at a binding energy (Es2+2) [eV] when the binding energy at peak Ps2 is Es2 [eV],
Xs1 represents the intensity of the maximum peak Ps1 in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sr1) of the first release treatment surface,
Ys1 represents the intensity of the XPS spectrum (Sr1) at a binding energy of (Es1+2) [eV] when the binding energy at peak Ps1 is Es1 [eV].

The binding energy (Es2+2) eV refers to the binding energy at a position 2 eV shifted toward higher energy from the position of the binding energy Es2 at peak Ps2 in the XPS spectrum (Sr2).

In the above formula (3), the maximum peak Ps2 in the range of bond energies of 96 eV to 108 eV is believed to be mainly derived from structure (I) in which two O atoms are bonded to the Si atom of the siloxane compound attached to the second release treatment surface of the second release film 25. The intensity of the XPS spectrum (Sr2) at the bond energy (Es2+2) eV is believed to be mainly derived from structure (II) in which three or more O atoms are bonded to the Si atom of the siloxane compound attached to the second release treatment surface of the second release film 25. The siloxane compounds that provide structures (I) and (II) are as described above. The second release treatment surface that satisfies the above formula (3) is believed to be formed by a release agent composition that includes, in addition to a siloxane compound having structure (I), a siloxane compound having structure (II) that provides a relatively large release force to the release film.

In the above formulas (3) and (4), the bond energy (Es1+2), peak Ps1, and intensity Ys2 of the XPS spectrum (Sr1) at the bond energy (Es1+2) eV are as described for the bond energy (Es+2), peak Ps, and intensity Ys in the above formula (1). When the second release film 25 is replaced with the first release film 15, a small amount of the siloxane compound (having structure (II) and serving as an additive that provides a relatively large peeling force) constituting the second release treated surface of the second release film 25 also adheres to the first release treated surface of the first release film 15. Therefore, the first release treated surface is considered to satisfy the relationship of the above formula (4), and an optical laminate 1 that satisfies the relationship of the above-described formula (1) can be manufactured.

By satisfying the relationship between formula (3) and formula (4) in the manufacturing method of the optical laminate 1, it can be considered that the optical laminate 1 is manufactured by replacing the second release film 25, which has a relatively large peeling force, with the first release film 15, which has a relatively small peeling force. Therefore, according to the manufacturing method of the optical laminate 1 described above, it is possible to manufacture an optical laminate 1 in which the first release film 15 can be easily separated and peeled off between the first adhesive layer 12 and the first release film 15 with the optical film 11 side of the optical laminate 1 fixed to the suction plate.

The value obtained by multiplying Ys2/Xs2 in formula (3) by 100 (Ys2/Xs2 x 100) may be 3.6 or more, 4.0 or more, or 5.0 or more, or 15.0 or less, 12.5 or less, or 10.0 or less. The strengths Xs2 and Ys2 can be measured by the method described in the examples below.

In formula (4), Ys1/Xs1×100 may be 3.50 or less, 3.45 or less, or 3.40 or less, and is usually 0.1 or more, 1.0 or more, 2.0 or more, or 2.6 or more. The strengths Xs1 and Ys1 can be measured by the method described in the examples below.

The method for producing the optical laminate 1 includes the steps of:
The second exposed surface, which is the surface of the first pressure-sensitive adhesive layer 12 exposed by peeling the second release film 25 from the first laminate 2, and the first exposed surface, which is the surface of the first pressure-sensitive adhesive layer 12 exposed by peeling the first release film 15 from the second laminate 3, may satisfy the relationships of the following formulas (5) and (6). The second exposed surface is the surface of the first pressure-sensitive adhesive layer 12 on the second release film 25 side, and the first exposed surface is the surface of the first pressure-sensitive adhesive layer 12 on the first release film 15 side.
Ya2/Xa2>Ya1/Xa1 (5)
Ya1 / Xa1 × 100 ≧ 2.0 (6)
[In formula (5) and formula (6),
Xa2 represents the intensity of the maximum peak Pa2 in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sa2) of the second exposed surface,
Ya2 represents the intensity of the XPS spectrum (Sa2) at a binding energy of (Ea2+2) eV, where Ea2 [eV] is the binding energy at peak Pa2.
Xa1 represents the intensity of the maximum peak Pa1 in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sa1) of the first exposed surface,
Ya1 represents the intensity of the XPS spectrum (Sa1) at a binding energy of (Ea1+2) eV, where Ea1 [eV] is the binding energy at peak Pa1.

The bond energy (Ea2+2) eV refers to the bond energy at a position 2 eV higher than the bond energy Ea2 at peak Pa2 in the XPS spectrum (Sa2).

In the above formula (5), the maximum peak Pa2 in the range of bond energies of 96 eV to 108 eV is believed to be mainly due to structure (I) in which two O atoms are bonded to the Si atom of the siloxane compound attached to the second exposed surface of the first adhesive layer 12. The intensity of the XPS spectrum (Sr2) at a bond energy of (Es2+2) eV is believed to be mainly due to structure (II) in which three or more O atoms are bonded to the Si atom of the siloxane compound attached to the second exposed surface. A small amount of the siloxane compound contained in the second release treatment surface of the second release film is believed to be attached to the second exposed surface.

In the above formulas (5) and (6), the bond energy (Ea1+2), peak Pa1, and intensity Ya1 of the XPS spectrum (Sa1) at the bond energy (Ea1+2) eV are as described for the bond energy (Ea+2), peak Pa, and intensity Ya in the above formula (2). Although the manufacturing method of the optical laminate 1 involves replacing the second release film 25 with the first release film 15, the siloxane compound (having structure (II) and serving as an additive that provides a relatively large release force) constituting the second release treatment surface of the second release film 25 remains on the first exposed surface of the first adhesive layer 12. Therefore, it is considered that by replacing the release film, the second exposed surface and the first exposed surface satisfy the relationship of formula (5), and the first exposed surface satisfies the relationship of formula (6).

By satisfying the relationship between formula (5) and formula (6) in the manufacturing method of the optical laminate 1, it can be considered that the optical laminate 1 is manufactured by replacing the second release film 25, which has a relatively large peeling force, with the first release film 15, which has a relatively small peeling force. Therefore, according to the manufacturing method of the optical laminate 1 described above, it is possible to manufacture an optical laminate 1 in which the first release film 15 can be easily separated and peeled off between the first adhesive layer 12 and the first release film 15 with the optical film 11 side of the optical laminate 1 fixed to the suction plate.

The value obtained by multiplying Ya2/Xa2 in formula (5) by 100 (Ya2/Xa2 x 100) may be, for example, 20 or less, 18 or less, 15 or less, 6.7 or more, 7.0 or more, or 8.0 or more. The strengths Xa2 and Ya2 can be measured by the method described in the examples below.

In formula (6), Ya1/Xa1×100 may be 2.0 or more, 2.5 or more, 3.0 or more, 3.4 or more, 20 or less, 15 or less, 10 or less, or 6.6 or less. The strengths Xa1 and Ya1 can be measured by the method described in the examples below.

The manufacturing method of the optical laminate 1 described above preferably further includes a step ((a) and (b) in FIG. 2) of obtaining an adhesive layer with a release film 21 by peeling off a third release film 26 from an adhesive sheet 20 in which the release treatment side of the third release film 26 is laminated on the first adhesive layer 12 side of the adhesive layer with a release film. The adhesive sheet 20 has a layer structure of the second release film 25/first adhesive layer 12/third release film 26.

In the adhesive sheet 20 used above, the peeling force between the third release film 26 and the first adhesive layer 12 is preferably smaller than the peeling force between the second release film 25 and the first adhesive layer 12. In the adhesive sheet 20, if the release films provided on both sides of the first adhesive layer 12 have the same peeling force, the first adhesive layer 12 may be torn when attempting to peel the release film, and the release film may not be peeled off properly. As described above, the peeling force is different between the second release film 25 and the third release film 26 provided on both sides of the first adhesive layer 12, so that the first adhesive layer 12 can be prevented from being torn when the third release film 26 is peeled off from the adhesive sheet 20. This allows the third release film 26 to be peeled off properly from the adhesive sheet 20, and the adhesive layer 21 with the release film can be obtained.

The first laminate 2 is obtained by laminating the adhesive layer 21 with a release film to one side of the optical film 11 (FIG. 2(c)). The first laminate 2 has a layer structure of optical film 11/first adhesive layer 12/second release film 25. The second release film 25 is peeled off from the first laminate 2 (FIG. 2(d)), and the first release treatment surface of the first release film 15 is laminated onto the exposed first adhesive layer 12 to obtain the second laminate 3 (FIG. 2(e)). The second laminate 3 has a layer structure of optical film 11/first adhesive layer 12/first release film 15. The second laminate 3 may be the optical laminate 1.

Hereinafter, each layer constituting the optical laminate will be described in detail.
(First Release Film (Release Film))
The first release film 15 is provided releasably with respect to the first pressure-sensitive adhesive layer 12 of the optical laminate 1, and covers and protects the first pressure-sensitive adhesive layer 12. The first release film 15 can have a base layer and a release treatment layer constituting a release treatment surface. The base layer may be a resin film. For example, the resin film can be a film using a resin material described as a thermoplastic resin used to form a protective film as a protective layer described later.

The release treatment layer of the first release film 15 can be formed by a release agent composition containing a siloxane compound. The release agent composition preferably contains a siloxane compound (main agent) having a structure (I) in which two O atoms are bonded to a Si atom, and does not contain a siloxane compound (additive) having a structure (II) in which three or more O atoms are bonded to a Si atom. This allows the first release film 15 to be peeled off from the first adhesive layer 12 of the optical laminate 1 with a relatively small peeling force.

The siloxane compound having structure (I) may be, for example, a siloxane compound having dimethylpolysiloxane as a basic skeleton. The siloxane compound having structure (II) may be, for example, a silicone resin. The silicone resin may be, for example, an MQ resin including an M unit which is a monofunctional siloxane unit [R ₃ SiO _1/2 ] and a Q unit which is a tetrafunctional siloxane unit [SiO _4/2 ]. Each of the three R in the M unit independently represents a hydrogen atom, a hydroxyl group, or an organic group, and at least one of the three R is preferably a hydroxyl group or a vinyl group, more preferably a vinyl group.

The release agent composition for forming the release treatment layer of the first release film 15 can contain, in addition to the siloxane compound having structure (I), a solvent such as an organic solvent, a crosslinking agent, a catalyst, various additives, etc.

The first release film 15 can be obtained by applying a release agent composition onto the substrate layer and drying it. Methods for applying the release agent composition include, for example, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

(First Pressure-Sensitive Adhesive Layer (Pressure-Sensitive Adhesive Layer))
The first pressure-sensitive adhesive layer 12 can be formed using a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition exhibits adhesive properties when attached to an adherend, and is a so-called pressure-sensitive adhesive.

The thickness of the first adhesive layer 12 is preferably 5 μm or more, may be 10 μm or more, may be 15 μm or more, or may be 20 μm or more, and is preferably 100 μm or less, may be 80 μm or less, may be 75 μm or less, or may be 70 μm or less.

The first adhesive layer 12 can be formed, for example, by applying the adhesive composition itself or a diluted solution of the adhesive composition in an organic solvent onto the release-treated surface of a release film (e.g., the second release film 25) and drying it. Methods for applying the adhesive composition or its diluted solution in an organic solvent include, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc.

The adhesive composition may be a publicly known adhesive composition having excellent optical transparency. As the publicly known adhesive composition, for example, an adhesive composition containing a base polymer such as a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a polyvinyl ether may be used. The adhesive composition may be an active energy ray curable adhesive or a heat curable adhesive. Among these, an adhesive composition having an acrylic resin as a base polymer, which is excellent in transparency, adhesive strength, removability (reworkability), weather resistance, heat resistance, etc., is preferable. The first adhesive layer is preferably composed of an adhesive composition containing a (meth)acrylic polymer, a crosslinking agent, and a silane coupling agent, and may contain other components. "(Meth)acrylic" refers to at least one of acrylic and methacrylic. The same applies to other terms with "(meth)".

The (meth)acrylic polymer preferably contains a structural unit derived from an alkyl (meth)acrylate ester (monomer) having an alkyl group with 1 to 24 carbon atoms. The alkyl group may be linear or branched. Examples of the alkyl (meth)acrylate ester having the above alkyl group include butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, and docosyl (meth)acrylate. The above alkyl (meth)acrylate esters may be used alone or in combination of two or more.

The content of the constituent units derived from the (meth)acrylic acid alkyl ester having the above alkyl group relative to the total constituent units of the (meth)acrylic polymer is preferably 30% by mass or more, may be 40% by mass or more, may be 50% by mass or more, and may be 99% by mass or less, may be 97% by mass or less, or may be 90% by mass or less.

The (meth)acrylic polymer may contain a structural unit derived from a monomer having a polar functional group. Examples of the polar functional group include a hydroxyl group, a carboxyl group, an amino group, an epoxy group, and an amide group.

Examples of monomers having a polar functional group include:
(meth)acrylates having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, 2- or 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate;
Ethylenically unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, and β-carboxyethyl (meth)acrylate;
(meth)acrylates having an amino group, such as aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and N,N-dimethylaminoethyl (meth)acrylate;
(meth)acrylates having an epoxy group, such as (3,4-epoxycyclohexyl)methyl (meth)acrylate and glycidyl (meth)acrylate;
(meth)acrylates having an amide group, such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-methylol(meth)acrylamide;
Monomers having a heterocyclic group, such as (meth)acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, and tetrahydrofurfuryl (meth)acrylate;
The monomer having a polar functional group may be used alone or in combination of two or more kinds.

The content of structural units derived from monomers having polar functional groups relative to the total structural units of the (meth)acrylic polymer is preferably 5% by mass or less, may be 2% by mass or less, or may be 1% by mass or less.

The (meth)acrylic polymer can be obtained by mixing the above-mentioned monomers, adding a polymerization initiator, etc., and polymerizing the monomers. The polymerization initiator can be selected depending on the polymerization method, and examples include cationic polymerization initiators and radical polymerization initiators. When the polymerization method is photopolymerization, a photopolymerization initiator can be used. One or more types of photopolymerization initiators can be used.

Examples of crosslinking agents that may be included in the adhesive composition include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents.

Examples of the silane coupling agent that may be contained in the pressure-sensitive adhesive include an organosilicon compound having at least one alkoxysilyl group in the molecule. Examples of the silane coupling agent include
Silicon compounds containing a polymerizable unsaturated group, such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane;
Silicon compounds having an epoxy structure, such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane;
Mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane;
Amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane;
Examples of the silane include 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane.

(Second Release Film)
The second release film 25 covers and protects the first pressure-sensitive adhesive layer 12 included in the first laminate 2 prepared when producing the optical laminate 1. The second release film 25 is included in the pressure-sensitive adhesive sheet 20, and may be a film to which a pressure-sensitive adhesive composition for forming the first pressure-sensitive adhesive layer 12 is applied when the first pressure-sensitive adhesive layer 12 is obtained.

The second release film 25 can have a base layer and a release treatment layer that forms the release treatment surface. The base layer may be a resin film. The resin film can be, for example, a film made of a resin material described as a thermoplastic resin used to form a protective film as a protective layer, which will be described later.

The release treatment layer of the second release film 25 can be formed by a release agent composition containing a siloxane compound. The release agent composition preferably contains a siloxane compound having structure (I) and a siloxane compound having structure (II). Examples of these siloxane compounds include the siloxane compounds described for the first release film. By forming the release treatment layer of the second release film 25 from the release agent composition, the peel force between the second release film 25 and the first adhesive layer 12 can be increased. This makes it possible to make the peel force between the first adhesive layer 12 and the second release film 25 in the adhesive sheet 20 greater than the peel force between the first adhesive layer 12 and the third release film 26, making it easier to peel the third release film 26 from the adhesive sheet 20.

The release agent composition for forming the release treatment layer of the second release film 25 can contain, in addition to the siloxane compound described above, a solvent such as an organic solvent, a crosslinking agent, a catalyst, various additives, etc. The second release film 25 can be obtained by applying the release agent composition onto the substrate layer and drying it. Methods for applying the release agent composition include the methods described for the first release film 15.

(Third Release Film)
The third release film 26 may be a film that is included in the pressure-sensitive adhesive sheet 20 and is laminated to the first pressure-sensitive adhesive layer 12 formed on the second release film 25 when obtaining the pressure-sensitive adhesive sheet 20. Examples of the third release film 26 include the release films described for the first release film 15.

(Adhesive sheet)
The adhesive sheet 20 can have a layer structure of second release film 25/first adhesive layer 12/third release film 26. By including the above-mentioned second release film 25 and third release film 26 in the adhesive sheet 20, the peel force between the third release film 26 and the first adhesive layer 12 can be made smaller than the peel force between the second release film 25 and the first adhesive layer 12.

The adhesive sheet 20 can be obtained, for example, by the following procedure. First, the adhesive composition itself or an organic solvent dilution of the adhesive composition for forming the first adhesive layer 12 is applied to the release treatment surface of one of the second release film 25 and the third release film 26, and a coating layer is formed by drying, etc., as necessary. Next, the other release film of the second release film 25 and the third release film 26 is laminated on this coating layer so that the release treatment surface side is the coating layer side, and an adhesive sheet is obtained by drying, etc., as necessary. The adhesive composition or its organic solvent dilution is preferably applied to the second release film 25. The coating layer formed on one release film may be the first adhesive layer 12, or the first adhesive layer 12 may be formed from the coating layer by drying treatment, etc., before or after laminating the other release film.

Methods for applying the adhesive composition or its organic solvent dilution include, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc.

(Optical film)
Examples of the optical film include a linear polarizing layer, a linear polarizing plate having a protective layer on one or both sides of the linear polarizing layer, a circular polarizing plate including a linear polarizing layer or a linear polarizing plate and one or more retardation layers, a polarizing plate having a surface protective film on one side of a polarizing plate such as a linear polarizing plate and a circular polarizing plate, a retardation layer, a retardation plate having a protective layer on one or both sides of the retardation layer, a reflective film, a semi-transmissive reflective film, a brightness improving film, and a film with an anti-glare function, and one or more of these may be used in combination. The optical film preferably includes at least a linear polarizing layer, and more preferably includes a linear polarizing plate or a circular polarizing plate. At least one of the retardation layers included in the circular polarizing plate is usually a λ/4 retardation layer.

The thickness of the optical film 11 is preferably 150 μm or less, may be 140 μm or less, may be 130 μm or less, may be 120 μm or less, and is usually 10 μm or more, and may be 20 μm or more. When the thickness of the optical film 11 is small as described above, when an attempt is made to peel the release film from the optical laminate with the optical film side fixed to the suction plate, the optical laminate may lift up from the suction plate, and separation may not be possible between the adhesive layer and the release film. According to the optical laminate of this embodiment, even when the thickness of the optical film 11 is small, the first release film 15 can be satisfactorily separated and peeled from the first adhesive layer 12 from the optical laminate.

(Linear Polarizing Layer)
The linearly polarizing layer has a property of transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis when non-polarized light is incident. The linearly polarizing layer may be a polyvinyl alcohol-based resin film (hereinafter, sometimes referred to as a "PVA-based film") in which iodine is adsorbed and oriented, or may be a film including a liquid crystal polarizing layer formed by applying a composition including a compound having absorption anisotropy and liquid crystallinity to a substrate film. The compound having absorption anisotropy and liquid crystallinity may be a mixture of a dye having absorption anisotropy and a compound having liquid crystallinity, or may be a dye having absorption anisotropy and liquid crystallinity.

The linear polarizing layer, which is a PVA-based film, may be, for example, a PVA-based film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, which has been dyed with iodine and stretched. If necessary, the PVA-based film to which iodine has been adsorbed and oriented by the dyeing process may be treated with an aqueous boric acid solution, followed by a washing process in which the aqueous boric acid solution is washed off. A known method may be used for each step.

Polyvinyl alcohol resins (hereinafter sometimes referred to as "PVA resins") can be produced by saponifying polyvinyl acetate resins. Polyvinyl acetate resins can be polyvinyl acetate, which is a homopolymer of vinyl acetate, or they can be copolymers of vinyl acetate and other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides with ammonium groups.

The degree of saponification of PVA-based resins is usually about 85 to 100 mol%, and preferably 98 mol% or more. The PVA-based resin may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of PVA-based resins is usually about 1,000 to 10,000, and preferably about 1,500 to 5,000. The degree of saponification and average degree of polymerization of PVA-based resins can be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 1,000, it is difficult to obtain favorable polarizing performance, and if it exceeds 10,000, film processability may be poor.

The manufacturing method of the linear polarizing layer, which is a PVA-based film, may include the steps of preparing a base film, applying a solution of a resin such as a PVA-based resin onto the base film, and performing drying or the like to remove the solvent to form a resin layer on the base film. A primer layer may be formed in advance on the surface of the base film on which the resin layer is to be formed. As the base film, a film using a resin material described below as a thermoplastic resin used to form a protective film as a protective layer can be used. As a material for the primer layer, a resin obtained by crosslinking a hydrophilic resin used in the linear polarizing layer can be mentioned.

Then, the amount of solvent such as water in the resin layer is adjusted as necessary, after which the base film and resin layer are uniaxially stretched, and then the resin layer is dyed with iodine to adsorb and align the iodine in the resin layer. Next, if necessary, the resin layer with iodine adsorbed and oriented is treated with an aqueous boric acid solution, followed by a washing step in which the aqueous boric acid solution is washed off. This produces a resin layer with iodine adsorbed and oriented, i.e., a PVA-based film that serves as a linear polarizing layer. Publicly known methods can be used for each step.

The amount of boric acid in the boric acid-containing aqueous solution used to treat the PVA-based film or resin layer with iodine adsorbed and oriented is usually about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. This boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by mass, preferably about 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

The uniaxial stretching of the PVA-based film, the substrate film, and the resin layer may be performed before dyeing, during dyeing, or during the boric acid treatment after dyeing. Uniaxial stretching may be performed at each of these multiple stages. The PVA-based film, the substrate film, and the resin layer may be uniaxially stretched in the MD direction (film transport direction). In this case, they may be uniaxially stretched between rolls with different peripheral speeds, or may be uniaxially stretched using a heated roll. The PVA-based film, the substrate film, and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction). In this case, the so-called tenter method can be used. The above stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state in which the PVA-based film or the resin layer is swollen with a solvent. In order to express the performance of the linearly polarizing layer, the stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit to the stretch ratio, but it is preferably 8 times or less to prevent breakage, etc.

The linearly polarizing layer produced by the manufacturing method using a substrate film can be obtained by laminating a protective layer and then peeling off the substrate film. This method makes it possible to further reduce the thickness of the linearly polarizing layer.

The thickness of the linearly polarizing layer, which is a PVA-based film, is preferably 1 μm or more, may be 2 μm or more, or may be 5 μm or more, and is preferably 30 μm or less, more preferably 15 μm or less, may be 10 μm or less, or may be 8 μm or less.

The film containing a liquid crystal linear polarizing layer may be a linear polarizing layer obtained by applying a composition containing a dye having liquid crystallinity and absorption anisotropy, or a composition containing a dye having absorption anisotropy and a polymerizable liquid crystal, to a substrate film. The liquid crystal linear polarizing layer may be a cured product of a polymerizable liquid crystal compound, and may contain an alignment layer. The alignment layer may be an alignment layer contained in a retardation layer described later. The film containing a liquid crystal linear polarizing layer may be a liquid crystal linear polarizing layer, or may have a laminated structure of a liquid crystal linear polarizing layer and a substrate film. The substrate film may be, for example, a film using a resin material described as a thermoplastic resin used to form a protective film as a protective layer described later. The film containing a liquid crystal linear polarizing layer may be, for example, a polarizing layer described in JP-A-2013-33249.

The total thickness of the substrate film and linear polarizing layer formed as described above is preferably small, but if it is too small, the strength decreases and processability tends to be poor, so it is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 to 3 μm.

(Protective Layer)
Examples of the protective layer include a protective film formed from a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture blocking properties, isotropy, stretchability, etc., and an overcoat layer formed from a composition having excellent solvent resistance, transparency, mechanical strength, thermal stability, shielding properties, isotropy, etc. The protective film is preferably laminated on the linearly polarizing layer via an attachment layer, and the overcoat layer is preferably laminated so as to be in direct contact with the linearly polarizing layer.

Specific examples of thermoplastic resins for forming the protective film include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamide; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo- and norbornene structures (also called norbornene resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins, and mixtures thereof. The thickness of the protective film is preferably 3 μm or more, more preferably 5 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less.

The overcoat layer can be formed from a composition that is excellent in solvent resistance, transparency, mechanical strength, thermal stability, shielding properties, isotropy, etc. The overcoat layer can be formed, for example, by applying the above-mentioned composition onto the linearly polarizing layer. Materials constituting the overcoat layer include, for example, photocurable resins and water-soluble polymers, and (meth)acrylic resins, polyvinyl alcohol resins, polyamide epoxy resins, etc. can be used. The thickness of the overcoat layer can be, for example, 0.1 μm or more and 10 μm or less.

The protective layer may have anti-reflection properties, anti-glare properties, hard coat properties, etc. (Hereinafter, a protective film having such properties may be referred to as a "functional protective layer"). When the protective layer is not a functional protective layer, a surface functional layer such as an anti-reflection layer, anti-glare layer, hard coat layer, etc. may be provided on one side of the linear polarizing plate. The surface functional layer is preferably provided so as to be in direct contact with the protective layer. The surface functional layer is preferably provided on the side opposite the linear polarizing layer side of the protective layer.

　In the above, a protective layer is provided on a linear polarizing layer, but the protective layer may also be provided on a retardation layer.

(Retardation Layer)
The retardation layer may be a stretched film, or may include a layer of a cured product of a polymerizable liquid crystal compound.

When the retardation layer is a stretched film, the stretched film may be a conventionally known film, and may be a resin film that has been uniaxially or biaxially stretched to give it a retardation. Examples of resin films that may be used include, but are not limited to, cellulose films such as triacetyl cellulose and diacetyl cellulose, polyester films such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, acrylic resin films such as polymethyl (meth)acrylate and polyethyl (meth)acrylate, polycarbonate films, polyethersulfone films, polysulfone films, polyimide films, polyolefin films, and polynorbornene films.

When the retardation layer includes the above-mentioned cured material layer, a known polymerizable liquid crystal compound can be used as the polymerizable liquid crystal compound. The polymerizable liquid crystal compound is a compound that has at least one polymerizable group and has liquid crystal properties.

The polymerizable group of the polymerizable liquid crystal compound means a group that participates in a polymerization reaction, and is preferably a photopolymerizable group. The photopolymerizable group means a group that can participate in a polymerization reaction by an active radical or an acid generated from a photopolymerization initiator. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, a (meth)acryloyloxy group, an oxiranyl group, an oxetanyl group, a styryl group, and an allyl group. Among them, a (meth)acryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The liquid crystal property of the polymerizable liquid crystal compound may be a thermotropic liquid crystal or a lyotropic liquid crystal, and when a thermotropic liquid crystal is classified by the degree of order, it may be a nematic liquid crystal or a smectic liquid crystal. When two or more types of polymerizable liquid crystal compounds are used in combination to form a cured layer of the polymerizable liquid crystal compound, it is preferable that at least one type has two or more polymerizable groups in the molecule.

When the retardation layer includes the above-mentioned cured material layer, the retardation layer may include an alignment layer. The alignment layer has an alignment regulating force for aligning the polymerizable liquid crystal compound in a desired direction. The alignment layer may be a vertical alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned vertically to the planar direction of the laminate, a horizontal alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally to the planar direction of the laminate, or an inclined alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned at an angle to the planar direction of the laminate.

The above-mentioned cured layer can be formed by applying a composition for forming a retardation layer, which contains a polymerizable liquid crystal compound, a solvent, and various additives as necessary, onto the alignment layer to form a coating film, and solidifying (curing) the coating film. Alternatively, the above-mentioned composition may be applied onto a substrate film to form a coating film, and the coating film may be stretched together with the substrate film to form a cured layer. In addition to the above-mentioned polymerizable liquid crystal compound and solvent, the above-mentioned composition may contain a polymerization initiator, a reactive additive, a leveling agent, a polymerization inhibitor, etc. As the polymerizable liquid crystal compound, solvent, polymerization initiator, reactive additive, leveling agent, polymerization inhibitor, etc., known ones can be appropriately used. As the substrate film, a film using the resin material described as the thermoplastic resin used to form the protective film as the above-mentioned protective layer can be used.

(Surface protection film)
The surface protective film is provided releasably with respect to the polarizing plate. The surface protective film may have a single-layer structure or a multi-layer structure. The surface protective film may include a base layer and a second pressure-sensitive adhesive layer, or may be a self-adhesive base layer.

As the base layer constituting the surface protective film, a film using the resin material described as the thermoplastic resin used to form the protective film as the protective layer above can be used. As the adhesive composition for forming the second adhesive layer, a known adhesive composition can be used. Examples of known adhesive compositions include those described above as the adhesive composition.

The surface protection film including the substrate layer and the second adhesive layer can be formed by applying the adhesive composition itself or an organic solvent dilution of the adhesive composition onto the substrate layer and drying it. Methods for applying the adhesive composition or its organic solvent dilution include, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc.

If the surface protection film has self-adhesive properties, examples of the thermoplastic resin that constitutes the self-adhesive base layer include polypropylene-based resins and polyethylene-based resins.

　In the above, a case where a surface protection film is used for a polarizing plate is described, but the surface protection film may also be laminated to a member exemplified as an optical film other than a polarizing plate.

(Laminating layer)
When the optical film has a multi-layer structure, the layers may be bonded together by a bonding layer. The bonding layer is a pressure-sensitive adhesive layer or an adhesive layer. When the bonding layer is a pressure-sensitive adhesive layer, it can be formed using a known pressure-sensitive adhesive composition. Examples of known pressure-sensitive adhesive compositions include those described above in the pressure-sensitive adhesive composition.

When the lamination layer is an adhesive layer, the adhesive layer can be formed by curing a curable component in the adhesive composition. The adhesive composition for forming the adhesive layer is an adhesive other than a pressure-sensitive adhesive (adhesive), such as a water-based adhesive or an active energy ray-curable adhesive.

An example of a water-based adhesive is an adhesive in which polyvinyl alcohol resin is dissolved or dispersed in water. There are no particular limitations on the drying method when using a water-based adhesive, but for example, a drying method using a hot air dryer or infrared dryer can be used.

Examples of active energy ray-curable adhesives include solvent-free active energy ray-curable adhesives that contain a curable compound that cures when exposed to active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. By using a solvent-free active energy ray-curable adhesive, it is possible to improve the adhesion between layers.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. "%" and "parts" in the examples and comparative examples are by mass % and parts by mass unless otherwise specified.

[Preparation of Release Film (1)]
(Preparation of Stripping Agent Composition a)
One part of a 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex (obtained from Dow Toray Industries, Inc., product name: "LTC759" (solid content concentration 30%)) was mixed as a catalyst with 100 parts of a toluene solution (manufactured by Dow Toray Industries, Inc., product name: "SRX212") The resulting mixture was mixed with a mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) to adjust the solid content concentration to 1.5%, thereby obtaining a release agent composition a.

(Preparation of Release Film (1))
A transparent polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, trade name: Diafoil T190E38, thickness 38 μm) was prepared. Next, the release agent composition a obtained above was applied to one side of the PET film with a bar coater so that the thickness after drying was 100 nm, and the film was dried at a temperature of 120 ° C. for 3 minutes to form a release treatment layer on the PET film. The film with the release treatment layer formed was stored for 5 days or more under an environment of a temperature of 23 ° C. and a relative humidity of 55%, and a release film (1) with a release treatment layer formed on the PET film was obtained.

[Preparation of Release Film (2)]
(Preparation of Stripping Agent Composition b)
100 parts of a toluene solution of a silicone resin (manufactured by Dow Toray Industries, Inc., product name: "LTC759" (solid content concentration 30%)) was mixed with 1 part of a 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex (obtained from Dow Toray Industries, Inc., product name: "SRX212") as a catalyst. Next, 10 parts of a xylene and ethylbenzene solution of a vinyl-modified silicone resin (manufactured by Dow Toray Industries, Inc., product name: "SD7292" (solid content concentration 65%, vinyl group content in the solid content is 3% by mass) was further added. A mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) was mixed with the obtained mixture to adjust the solid content concentration to 1.5%, and a release agent composition b was obtained.

(Preparation of Release Film (2))
A release film (2) was obtained in the same manner as in the production of the release film (1), except that the release agent composition b was used instead of the release agent composition a.

[Preparation of Release Film (3)]
(Preparation of Stripping Agent Composition c)
100 parts of a toluene solution of a silicone resin (manufactured by Dow Toray Industries, Inc., trade name: "LTC759" (solid content concentration 30%)) was mixed with 1 part of a 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex (obtained from Dow Toray Industries, Inc., trade name: "SRX212") as a catalyst. Next, 5 parts of a xylene and ethylbenzene solution of a vinyl-modified silicone resin (manufactured by Dow Toray Industries, Inc., trade name: "SD7292" (solid content concentration 65%, vinyl group content in the solid content is 3% by mass) were further added. A mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) was mixed with the obtained mixture to adjust the solid content concentration to 1.5%, and a release agent composition c was obtained.

(Preparation of Release Film (3))
A release film (3) was obtained in the same manner as in the preparation of the release film (1), except that the release agent composition c was used instead of the release agent composition a.

[Preparation of Pressure-Sensitive Adhesive Compositions (1) to (3)]
(Preparation of acrylic resin solution (1))
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer was charged with a mixed solution of 45 parts of ethyl acetate, 34 parts of butyl acrylate, 10 parts of methyl acrylate, 0.5 parts of 2-hydroxyethyl acrylate and 0.5 parts of acrylic acid, and the air in the vessel was replaced with nitrogen gas to make it oxygen-free, while the internal temperature was raised to 55°C. Thereafter, a solution of 0.14 parts of azobisisobutyronitrile dissolved in 9.86 parts of ethyl acetate as a polymerization initiator was added in its entirety. After the addition of the polymerization initiator, the temperature was maintained for 1 hour, and then, while maintaining the internal temperature at 54-56°C, ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts/hr, and the addition of ethyl acetate was stopped when the concentration of the acrylic resin reached 35%, and the temperature was maintained until 12 hours had elapsed from the start of the addition of ethyl acetate. Finally, ethyl acetate was added, and the concentration of the acrylic resin was adjusted to 20%, to prepare an acrylic resin solution (1). The resulting acrylic resin had a weight average molecular weight Mw of 1.3 million and a molecular weight distribution Mw/Mn of 4.2. Mw and Mn were measured in terms of standard polystyrene using two "TSKgel GMHHR-H(S)" columns manufactured by Tosoh Corporation connected in series as columns in a GPC apparatus, tetrahydrofuran as an eluent, a sample concentration of 2 mg/mL, a sample introduction amount of 100 μL, a temperature of 40° C., and a flow rate of 1 mL/min.

(Preparation of Pressure-Sensitive Adhesive Composition (1))
To 100 parts of the solid content of the acrylic resin solution (1) obtained above, 0.5 parts on an active ingredient basis of a crosslinking agent (manufactured by Tosoh Corporation: product name "Coronate L" (a solution of a trimethylolpropane adduct of tolylene diisocyanate in ethyl acetate (solid content concentration 75% by mass)) was added, and ethyl acetate was further added so that the solid content concentration became 16%, thereby obtaining a pressure-sensitive adhesive composition (1).

(Preparation of Pressure-Sensitive Adhesive Composition (2))
To 100 parts of the solid content of the acrylic resin solution (1) obtained above, 0.5 parts on an active ingredient basis of a crosslinking agent (manufactured by Mitsui Chemicals: trade name "D-103" (a solution of an ethyl acetate adduct of tolylene diisocyanate (solid content concentration 75% by mass)) was added, and 0.1 parts on an active ingredient basis of a silane compound (manufactured by Shin-Etsu Chemical Co., Ltd.: trade name "KBM-403" (3-glycidoxypropyltrimethoxysilane) was added, and ethyl acetate was further added so that the solid content concentration became 16%, thereby obtaining a pressure-sensitive adhesive composition (2).

(Preparation of Pressure-Sensitive Adhesive Composition (3))
To 100 parts of the solid content of the acrylic resin solution (1) obtained above, 0.5 parts on an active ingredient basis of a crosslinking agent (manufactured by Mitsui Chemicals: product name "D-103" (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75 mass%)) was added, and 0.1 parts on an active ingredient basis of a silane compound (manufactured by Shin-Etsu Chemical Co., Ltd.: product name "KR-519" (mercapto group-containing silicone oligomer) was added, and ethyl acetate was further added so that the solid content concentration became 16%, thereby obtaining a pressure-sensitive adhesive composition (3).

[Preparation of Adhesive Sheet (1)]
The adhesive composition (1) obtained above was applied onto the release treatment layer (release treatment surface) of the release film (2) obtained above using an applicator, and then dried at a temperature of 100° C. for 1 minute to obtain an adhesive layer (1) having a thickness of 20 μm. The release treatment layer (release treatment surface) of the release film (1) obtained above was laminated on the side of the adhesive layer (1) obtained opposite to the release film (2) side. The obtained laminate was left to stand for 7 days or more in an environment of a temperature of 23° C. and a relative humidity of 60%, to obtain an adhesive sheet (1).

[Preparation of Adhesive Sheet (2)]
The adhesive composition (2) obtained above was applied onto the release treatment layer (release treatment surface) of the release film (2) obtained above using an applicator, and then dried at a temperature of 100° C. for 1 minute to obtain an adhesive layer (2) having a thickness of 20 μm. The release treatment layer (release treatment surface) of the release film (1) obtained above was laminated on the side of the adhesive layer (2) opposite to the release film (2) side obtained. The obtained laminate was left to stand for 7 days or more in an environment of a temperature of 23° C. and a relative humidity of 60%, to obtain an adhesive sheet (2).

[Preparation of Adhesive Sheet (3)]
The adhesive composition (3) obtained above was applied onto the release treatment layer (release treatment surface) of the release film (2) obtained above using an applicator, and then dried at a temperature of 100° C. for 1 minute to obtain an adhesive layer (3) having a thickness of 20 μm. The release treatment layer (release treatment surface) of the release film (1) obtained above was laminated on the side of the adhesive layer (3) opposite to the release film (2) side. The obtained laminate was left to stand for 7 days or more in an environment of a temperature of 23° C. and a relative humidity of 60%, to obtain an adhesive sheet (3).

[Preparation of Adhesive Sheet (4)]
The adhesive composition (3) obtained above was applied onto the release treatment layer (release treatment surface) of the release film (3) obtained above using an applicator, and then dried at a temperature of 100° C. for 1 minute to obtain an adhesive layer (4) having a thickness of 20 μm. The release treatment layer (release treatment surface) of the release film (1) obtained above was laminated on the side of the adhesive layer (4) opposite to the release film (3) side. The obtained laminate was left to stand for 7 days or more in an environment at a temperature of 23° C. and a relative humidity of 60%, to obtain an adhesive sheet (4).

(Evaluation of peelability of pressure-sensitive adhesive sheet)
When the release film (1), which has a relatively weaker peeling strength than the release films (2) and (3), was peeled by hand from the pressure-sensitive adhesive sheets (1) to (4) obtained above under conditions of a temperature of 23° C. and a relative humidity of 60%, the release film (1) could be peeled off without the pressure-sensitive adhesive layer being torn. In addition, the surface of the release treatment layer side of the peeled release film (1) was observed and evaluated according to the following criteria. The results are shown in Table 1.
a: No or only slight transfer of the adhesive layer (adhesive residue) was observed on the release treated surface.
b: Transfer of the adhesive layer (adhesive residue) was observed on the release treated surface.

Comparative Example 1
(Preparation of Polarizing Plate)
A 25 μm-thick first protective film (triacetyl cellulose film) was attached to one side of a 12 μm-thick linear polarizing layer (a polarizing film in which iodine was adsorbed and oriented on a uniaxially stretched polyvinyl alcohol film), and a 20 μm-thick second protective film (triacetyl cellulose film) was attached to the other side via an adhesive to obtain a polarizing plate. Furthermore, a surface protective film was laminated on the first protective film side to obtain a polarizing plate with a surface protective film. The surface protective film has a structure in which a 15 μm-thick adhesive layer is laminated on a 38 μm-thick PET film. The thickness of the polarizing plate with the surface protective film was 110 μm.

(Preparation of optical laminate (c1))
The surface of the second protective film side of the polarizing plate with the surface protective film obtained above was subjected to a corona treatment, and the pressure-sensitive adhesive layer (1) exposed by peeling off the release film (1) of the pressure-sensitive adhesive sheet (1) obtained above was attached to this corona-treated surface to obtain an optical laminate (c1). The layer structure of the optical laminate (c1) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (1)/release film (2).

Comparative Example 2
Except for using the pressure-sensitive adhesive sheet (2) instead of the pressure-sensitive adhesive sheet (1), an optical laminate (c2) was obtained in the same manner as in Comparative Example 1. The layer structure of the optical laminate (c2) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (2)/release film (2).

Comparative Example 3
Except for using the pressure-sensitive adhesive sheet (3) instead of the pressure-sensitive adhesive sheet (1), an optical laminate (c3) was obtained in the same manner as in Comparative Example 1. The layer structure of the optical laminate (c3) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (3)/release film (2).

Comparative Example 4
Except for using the pressure-sensitive adhesive sheet (4) instead of the pressure-sensitive adhesive sheet (1), an optical laminate (c4) was obtained in the same manner as in Comparative Example 1. The layer structure of the optical laminate (c4) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (4)/release film (3).

Example 1
(Preparation of optical laminate (1))
An optical laminate (c1) was obtained by the procedure described in Comparative Example 1. The release film (2) was peeled off from the optical laminate (c1), and the release treatment layer side of the release film (1) obtained above was laminated on the exposed pressure-sensitive adhesive layer (1) to obtain an optical laminate (1). The layer structure of the optical laminate (1) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (1)/release film (1).

Example 2
(Preparation of optical laminate (2))
An optical laminate (c2) was obtained by the procedure described in Comparative Example 2. The release film (2) was peeled off from the optical laminate (c2), and the release treatment layer side of the release film (1) obtained above was laminated on the exposed pressure-sensitive adhesive layer (2) to obtain an optical laminate (2). The layer structure of the optical laminate (2) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (2)/release film (1).

Example 3
(Preparation of optical laminate (3))
An optical laminate (c3) was obtained by the procedure described in Comparative Example 3. The release film (2) was peeled off from the optical laminate (c3), and the release treatment layer side of the release film (1) obtained above was laminated on the exposed pressure-sensitive adhesive layer (3) to obtain an optical laminate (3). The layer structure of the optical laminate (3) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (3)/release film (1).

Example 4
(Preparation of optical laminate (4))
An optical laminate (c4) was obtained by the procedure described in Comparative Example 4. The release film (3) was peeled off from the optical laminate (c4), and the release treatment layer side of the release film (1) obtained above was laminated on the exposed pressure-sensitive adhesive layer (4) to obtain an optical laminate (4). The layer structure of the optical laminate (4) was a polarizing plate with a surface protective film (surface protective film/first protective film/linear polarizing layer/second protective film)/pressure-sensitive adhesive layer (4)/release film (1).

[XPS Measurement]
The release film was peeled off from the optical laminate obtained in each of the Examples and Comparative Examples, and the surface of the peeled release film on the release treatment layer side (release treatment surface) and the surface of the exposed pressure-sensitive adhesive layer on the release film side were subjected to XPS measurement under the following conditions using an XPS device (K-Alpha+, manufactured by Thermofisher Scientific). The sample size was 10 mm x 10 mm.
(XPS measurement conditions)
Irradiation X-ray: Monochromatic Al Kα (12 kV/6 mA), 400 μm
Dwell Time: 50 ms
Pass Energy: 50 eV
Orbitals of interest: C1s, O1s, Si2p

In each of the XPS spectrum (Sr) of the release treatment surface obtained by XPS measurement and the XPS spectrum (Sa) of the surface of the release film side of the pressure-sensitive adhesive layer, the intensity Xs of the maximum peak Ps and the intensity Xa of the maximum peak Pa in the range of binding energy from 96 eV to 108 eV were determined. In addition, in each of the XPS spectra (Sr) and (Sa), the intensity Ys of the XPS spectrum (Sr) at a position (binding energy (Es+2)) 2 eV higher than the binding energy Es of the peak Ps, and the intensity Ya of the XPS spectrum (Sa) at a position (binding energy (Ea+2)) 2 eV higher than the binding energy Ea of the peak Pa were determined. From the determined intensities, the value of the left side of the above formula (1) (Ys/Xs×100) and the value of the left side of the above formula (2) (Ya/Xa×100) were determined. The results are shown in Tables 1 and 2.

In addition, in Examples 1 to 4, the value (Ys2/Xs2×100) obtained by multiplying the left side of the above formula (3) of the release-treated surface of the release film (2) or (3) peeled off from the optical laminates (c1) to (c4) by 100 can be regarded as the value of the left side (Ys/Xs×100) of the above formula (1) determined in Comparative Examples 1 to 4. The value obtained by multiplying the right side of the above formula (3) of the release-treated surface of the release film (1) peeled off from the optical laminates (1) to (4) in Examples 1 to 4 by 100 and the value of the left side (Ys1/Xs1×100) of the above formula (4) can be regarded as the value of the left side (Ys/Xs×100) of the above formula (1) determined in Examples 1 to 4. In Examples 1 to 4, the value obtained by multiplying the left side of the above formula (5) by 100 (Ya2/Xa2 x 100) can be regarded as the value of the left side of the above formula (2) (Ya/Xa x 100) determined in Comparative Examples 1 to 4. In Examples 1 to 4, the value obtained by multiplying the right side of the above formula (5) by 100 and the value of the left side of the above formula (6) (Ya1/Xa1 x 100) can be regarded as the value of the left side of the above formula (2) (Ya/Xa x 100) determined in Examples 1 to 4.

[Measurement of peel strength of release film]
The optical laminates obtained in the examples and comparative examples were cut to a size of 50 mm wide x 190 mm long to obtain test samples. The release film of the test sample was chucked using an autograph (AGS-X 50N, manufactured by Shimadzu Corporation), and the peel force was measured when peeled in a 180° direction at a speed of 300 mm/min. The results are shown in Tables 1 and 2.

[Release property test of release film of optical laminate]
The optical laminates obtained in the examples and comparative examples were cut into a size of 50 mm width x 50 mm length to obtain test samples. Furthermore, the adhesive side of a double-sided tape (manufactured by Nichiban Co., Ltd., product name: Nicetack general type (width 25 mm)) was laminated on the base surface of a mending tape (manufactured by 3M, product name: Scotch mending tape (width 24 mm)) and cut into a size of 10 mm x 10 mm. The adhesive side of the mending tape of the laminate of the mending tape and the double-sided tape was attached to the center of the surface protection film side of the test sample, and after peeling off the release paper of the double-sided tape, the adhesive side of the double-sided tape was attached to a glass plate to fix the test sample to the glass plate. A Kapton tape (manufactured by Nitto Denko, product name: No. 360UL (width 13 mm)) cut to 30 mm x 13 mm was attached to one corner of the release film side surface of the test sample fixed to the glass plate so that it protruded 20 mm from the corner. The Kapton tape attached to the test sample was held by hand and the state when peeled off was judged according to the following criteria. The results are shown in Tables 1 and 2.
a: Only the release film was completely peeled off from the optical laminate.
b: The release film was not completely peeled off from the optical laminate, and the optical laminate was peeled off from the mending tape.

In the optical laminates (1) to (4) obtained in the examples in which the release film (2) or (3) was replaced with the release film (1), the peeling force of the release film (1) could be reduced, and only the release film was completely peeled off in the peelability test, so it is considered that the release film (1) can be easily peeled off from the optical laminates (1) to (4). In the optical laminates (c1) to (c4) having the release film (release film (2) or (3)) obtained in the comparative examples, the release film still had a large peeling force, and the release film was not completely peeled off in the peelability test, so it is considered that the release film is difficult to peel off from the optical laminates (c1) to (c4).

1 optical laminate, 2 first laminate, 3 second laminate, 11 optical film, 12 first adhesive layer (adhesive layer), 15 first release film (release film), 20 adhesive sheet, 21 adhesive layer with release film, 25 second release film, 26 third release film.

Claims

An optical laminate comprising an optical film, a pressure-sensitive adhesive layer, and a release film in this order,
the release film has a release-treated surface containing a siloxane compound on a side in contact with the pressure-sensitive adhesive layer,
The release-treated surface of the release film satisfies the following formula (1):
Ys/Xs×100≦3.5 (1)
[In formula (1),
Xs represents the intensity of the maximum peak Ps in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sr) of the release treated surface,
Ys represents the intensity of the XPS spectrum (Sr) at a binding energy of (Es+2) eV, where Es [eV] is the binding energy at the peak Ps.
The optical laminate according to claim 1 , wherein the surface of the pressure-sensitive adhesive layer on the release film side satisfies the following formula (2):
Ya / Xa × 100 ≧ 2.0 (2)
[In formula (2),
Xa represents the intensity of the maximum peak Pa in the binding energy range of 96 eV or more and 108 eV or less in the XPS spectrum (Sa) of the surface of the pressure-sensitive adhesive layer on the release film side,
Ya represents the intensity of the XPS spectrum (Sa) at a binding energy of (Ea+2) eV, where Ea [eV] is the binding energy at the peak Pa.
The optical laminate of claim 1, wherein the optical film has a thickness of 120 μm or less.
The optical laminate according to any one of claims 1 to 3, wherein the optical film is a polarizing plate including at least a linearly polarizing layer.
The optical laminate of claim 4, wherein the polarizing plate further includes a retardation layer.
The optical laminate according to claim 4, wherein the optical film includes a surface protection film that is peelably provided on the polarizing plate.