WO2025205114A1 - Laminate - Google Patents

Abstract

The present invention addresses the problem of providing a laminate with which there is little effect on a liquid crystal layer when a protective film is peeled, and the protective film can be easily peeled in a desired order.　This laminate includes a peelable protective film A, a liquid crystal layer, and a peelable protective film B in the stated order, the protective film A including a base material and an adhesive layer, the adhesive layer and the liquid crystal layer being in contact with each other, the peeling force FA of the protective film A being 1.00 N/25 mm or less, the absolute value of the difference between the peeling force FB of the protective film B and the peeling force FA being 0.10 N/25 mm or more, and, when the protective film B is in contact with the liquid crystal layer, the variation rate VFB of the peeling force FB obtained by a predetermined method from the peeling force measured by performing a 90-degree peeling process of peeling the protective film B from the liquid crystal layer being 12% or less.

Description

Laminate

The present invention relates to a laminate.

Optical elements that control the direction of light are used in various optical devices or systems, and optical elements having polarizing plates are used as such optical elements that control the direction of light.
An optical element having such a polarizing plate is manufactured, for example, by peeling off the release film from an optical laminate having a protective film, a polarizing plate, and a release film in this order, and bonding the polarizing plate to an optical member via an adhesive layer.

Patent Document 1 describes a method for producing an optical laminate having, in this order, a surface protection film, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a release film, as well as technology related to the optical laminate.

JP 2018-120120 A

The above-mentioned patent document discloses an embodiment in which protective films are disposed on both sides of a polarizer.
On the other hand, recently, a liquid crystal optical element having a liquid crystal layer formed using a liquid crystal composition containing a liquid crystal compound has been proposed as an optical element for controlling the direction of light. In order to be used in the production of such a liquid crystal optical element, a laminate in which both sides of the liquid crystal layer are protected by protective films is required.
As the inventors continued to study these laminates, they discovered that, depending on the type of protective film, damage to the liquid crystal layer may occur, such as wrinkles forming in the liquid crystal layer when peeled off, or uneven polarization of the liquid crystal layer after peeling.
Furthermore, when the laminate is used in the production of a liquid crystal optical element, it is also required that the order in which the protective films are peeled off can be specified.

In view of the above circumstances, the present invention aims to provide a laminate that has minimal impact on the liquid crystal layer when the protective film is peeled off, and that allows the protective film to be easily peeled off in the desired order.

The inventors conducted extensive research to resolve the above-mentioned issues and discovered that the following configuration can resolve the above-mentioned issues.

[1]
A laminate having a peelable protective film A, a liquid crystal layer, and a peelable protective film B in this order, wherein the protective film A includes a substrate and an adhesive layer, and the adhesive layer is in contact with the liquid crystal layer, the peel force FA of the protective film A is 1.00 N/25 mm or less, the absolute value of the difference between the peel force FB of the protective film B and the peel force FA is 0.10 N/25 mm or more, the variability VFA of the peel force FA, determined by a specified method from the peel force measured when a 90-degree peeling process is performed to peel the protective film A from the liquid crystal layer, is 12% or less, and when the protective film B is in contact with the liquid crystal layer, the variability VFB of the peel force FB, determined by a specified method from the peel force measured when a 90-degree peeling process is performed to peel the protective film B from the liquid crystal layer, is 12% or less.
[2]
The laminate according to [1], wherein the liquid crystal layer includes a region having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound is continuously rotated along at least one direction in the plane.
[3]
The laminate according to [1] or [2], wherein the thickness of the substrate is 5 to 60 μm.
[4]
The laminate according to any one of [1] to [3], wherein the elastic modulus of the substrate is 3.0 to 5.0 GPa.
[5]
The laminate according to any one of [1] to [4], wherein the protective film B is in contact with the liquid crystal layer.
[6]
The laminate according to any one of [1] to [5], wherein protrusions having a height of 30 nm or more are formed at a rate of 10,000 or more per ^mm2 on at least one of the surfaces of the protective film A opposite to the liquid crystal layer side and the surface of the protective film B opposite to the liquid crystal layer side.

The present invention provides a laminate that has minimal impact on the liquid crystal layer when the protective film is peeled off, and allows the protective film to be easily peeled off in the desired order.

1 is a schematic cross-sectional view showing one embodiment of a laminate of the present invention. FIG. 2 is a diagram conceptually illustrating an example of a liquid crystal layer. FIG. 3 is a plan view of the liquid crystal layer shown in FIG. 2.

The present invention will be described in detail below.
The following description of the components may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the drawings, the scale of the components may differ from the actual scale for easier viewing and explanation.

In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In the numerical ranges described in stages in this specification, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.
In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.

In this specification, Re(λ) and Rth(λ) respectively represent the in-plane retardation and the thickness direction retardation at a wavelength λ, which is 550 nm unless otherwise specified.
In this specification, Re(λ) and Rth(λ) are values measured at a wavelength λ using an AxoScan (manufactured by Axometrics). By inputting the average refractive index ((nx+ny+nz)/3) and film thickness (d (μm)) into AxoScan,
Slow axis direction (°)
Re(λ)=R0(λ)
Rth(λ)=((nx+ny)/2-nz)×d
is calculated.
Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

In this specification, the refractive indices nx, ny, and nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ=589 nm) as a light source. When measuring wavelength dependency, measurements can be made using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter.
Alternatively, values from the Polymer Handbook (John Wiley & Sons, Inc.) and catalog values for various optical films can be used. Examples of average refractive index values for major optical films are listed below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

Furthermore, unless otherwise specified, the in-plane slow axis and in-plane fast axis are defined at a wavelength of 550 nm. In other words, unless otherwise specified, for example, when referring to the in-plane slow axis direction, it means the direction of the in-plane slow axis at a wavelength of 550 nm.

In this specification, the terms "all,""any,""entirety," etc., include not only 100% but also a generally acceptable error range in the technical field, such as 99% or more, 95% or more, or 90% or more.
Furthermore, with regard to angles, "orthogonal" or "perpendicular" means a range of 90°±5°, and "parallel" means a range of 0°±5°. Similarly, unless otherwise specified, angles mean that the difference from the exact angle is within a range of 5 degrees. The difference in the above angles is preferably within 4 degrees, and more preferably within 3 degrees.
In this specification, "(meth)acrylic" is used to mean "either one or both of acrylic and methacrylic."

<Laminate>
The laminate of the present invention comprises, in this order, a peelable protective film A, a liquid crystal layer, and a peelable protective film B. The protective film A includes a substrate and an adhesive layer, and the adhesive layer of the protective film A is in contact with the liquid crystal layer.
Furthermore, the laminate of the present invention satisfies the following requirements 1 to 3, and when the protective film B30 is in contact with the liquid crystal layer 40, it also satisfies the following requirement 4.
(Requirement 1) The peel strength FA of the protective film A is 1.00 N/25 mm or less.
(Requirement 2) The absolute value of the difference between the peel strength FB and the peel strength FA of the protective film B is 0.10 N/25 mm or more.
(Requirement 3) A 90-degree peeling process is performed to peel protective film A from the liquid crystal layer, and the peel force is measured at 100 positions every 0.1 mm in the peel distance. The average value of the peel force at each position is calculated, and the absolute value of the difference between the peel force at each position and the average peel force is calculated. The absolute values of the differences at the largest 10 positions are extracted, and the average value of the extracted absolute values of the differences is calculated. The ratio of the average value of the calculated absolute values of the differences to the average peel force is 12% or less.
(Requirement 4) (When protective film B is in contact with the liquid crystal layer) A 90-degree peeling process is performed to peel protective film B from the liquid crystal layer, and the peel force is measured at 100 positions every 0.1 mm in the peel distance. The average value of the peel force at each position is calculated, and the absolute value of the difference between the peel force at each position and the average peel force is calculated. The absolute values of the differences at the largest 10 positions are extracted from the absolute values of the differences calculated at each position, and the average value of the extracted absolute values of the differences is calculated. The ratio obtained by determining the ratio of the average value of the calculated absolute values of the differences to the average peel force is 12% or less.

After extensive research, the inventors have investigated a laminate having protective films on both sides of a liquid crystal layer and have discovered that by satisfying the above requirements regarding the peeling force when peeling the protective film from the laminate, the impact on the liquid crystal layer when peeling the protective film can be reduced, and the protective film can be easily peeled off in the desired order.
In this specification, matters referred to simply using the term "protective film" are meant to be applicable to both protective film A and protective film B.

The peel force FA of protective film A in the above requirements 1 and 2 is the peel force measured by peeling protective film A from the laminate, and the peel force FB of protective film B in requirement 2 is the peel force measured by peeling protective film B from the laminate.
The peel test for measuring the peel force FA and the peel force FB is carried out according to the procedure described in JIS Z 0237:2009 (ISO29862:2007), by peeling the protective film to be measured from a laminate sample at a peel angle of 90° and a peel speed of 300 mm/min, and measuring the peel force between them. The peel test and the measurement of the peel force are carried out, for example, using a Tensilon universal testing machine (manufactured by A&D Co., Ltd.). The detailed method of the peel test will be described in the examples below.

If the absolute value of the difference between the peeling force FB of the protective film B and the peeling force FA of the protective film A is "ΔF", requirement 2 is expressed by the following formula (1).
ΔF=｜FB-FA｜≧0.10 (N/25mm) (1)
In other words, requirement 2 is met when the peel strength FA of protective film A is greater than the peel strength FB of protective film B by 0.10 N/25 mm or more, or when the peel strength FA is less than the peel strength FB of protective film B by 0.10 N/25 mm or more.

When a laminate having a peelable protective film A, a liquid crystal layer, and a peelable protective film B in this order, with protective film A in contact with the liquid crystal layer, satisfies the above-mentioned requirement 3, it is thought that there will be little fluctuation in the peel force when peeling off protective film A. Similarly, when a laminate having a peelable protective film A, a liquid crystal layer, and a peelable protective film B in this order, with protective film B in contact with the liquid crystal layer, satisfies the above-mentioned requirement 4, it is thought that there will be little fluctuation in the peel force when peeling off protective film B. As a result, it is presumed that the laminate of the present invention, which satisfies the above-mentioned requirements, will more stabilize the load on the liquid crystal layer when peeling the protective film from the liquid crystal layer, thereby suppressing the occurrence of damage such as wrinkles and tears in the liquid crystal layer.
Hereinafter, in order to determine whether requirement 3 or requirement 4 is satisfied, the "ratio of the average value of the calculated absolute values of the differences to the average value of the peel force" calculated from the peel force measured at each measurement position when peeling the protective film will also be referred to as the "variation rate VFA of the peel force FA" or the "variation rate VFB of the peel force FB." Both the variation rates VFA and VFB are expressed as a percentage (%).

FIG. 1 shows a schematic cross-sectional view of one embodiment of the laminate of the present invention.
In FIG. 1, the laminate 10 has a peelable protective film A 20, a liquid crystal layer 40, and a peelable protective film B 30 in this order.
The illustrated protective film A20 includes a substrate 22 and an adhesive layer 24, and the adhesive layer 24 is in contact with the liquid crystal layer 40. The illustrated protective film B30 includes a substrate 32 and an adhesive layer 34, and the adhesive layer 34 is in contact with the liquid crystal layer 40.

In the laminate 10, the protective film A20 and the protective film B30 are disposed on both surfaces of the liquid crystal layer 40, which prevents the liquid crystal layer 40 from being scratched and also improves the handleability of the liquid crystal layer 40.
Furthermore, since the protective films A20 and B30 of the laminate 10 satisfy the above requirements 1 to 4, there is little impact on the liquid crystal layer 40 when the protective films A20 and B30 are peeled off from the laminate 10, and the protective films A20 and B30 can be easily peeled off in the desired order.

The laminate 10 shown in FIG. 1 is merely one example of a laminate of the present invention, and the laminate of the present invention is not limited to the embodiment shown in FIG.
1, the protective film B30 is in contact with the liquid crystal layer 40, but an intermediate layer may be disposed between the protective film B30 and the liquid crystal layer. The intermediate layer may be, for example, an optical adhesive (OCA) layer or a substrate with an OCA layer.
1, the protective film B 30 has a substrate 32 and an adhesive layer 34, but the configuration of the protective film B is not limited as long as it can be peeled off from the laminate. The protective film B may be, for example, a substrate having one surface subjected to a release treatment.
Furthermore, each of the protective film A and the protective film B may have a plurality of substrates.

(liquid crystal layer)
The type of the liquid crystal layer is not particularly limited, and examples thereof include known liquid crystal layers.
The liquid crystal layer is preferably formed using a liquid crystal compound and includes a region having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound is continuously rotated along at least one direction in the plane. The liquid crystal layer including the region having the liquid crystal orientation pattern is thin and has low mechanical strength when used alone, but the mechanical strength can be improved by laminating the protective films A and B.
The liquid crystal layer will be described in detail below.

Fig. 2 is a side view conceptually showing an example of a liquid crystal layer, and Fig. 3 is a plan view of the liquid crystal layer shown in Fig. 2. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 3.
The plan view is a view of the liquid crystal layer 40 seen from above in Fig. 2. That is, Fig. 2 is a view of the liquid crystal layer 40 seen from the thickness direction (i.e., the stacking direction of each layer (film)). In other words, Fig. 3 is a view of the liquid crystal layer 40 seen from a direction perpendicular to the main surface.
3, in order to clearly show the configuration of the liquid crystal layer 40, only the liquid crystal compound 42 on the surface side of the liquid crystal layer 40 is shown. However, the liquid crystal layer 40 has a structure in which the liquid crystal compound 42 is stacked in the thickness direction, as shown in FIG.

2, the liquid crystal layer 40 has a liquid crystal orientation pattern in which the direction of the optical axis 42A derived from the liquid crystal compound 42 changes while continuously rotating counterclockwise in one direction indicated by the arrow X within the plane of the liquid crystal layer 40. Although the direction of the optical axis 42A derived from the liquid crystal compound 42 rotates counterclockwise in FIG. 2, the present invention is not limited to this embodiment, and the direction may also rotate clockwise.
The optical axis 42A derived from the liquid crystal compound 42 is the axis along which the refractive index is highest in the liquid crystal compound 42. For example, when the liquid crystal compound 42 is a rod-shaped liquid crystal compound, the optical axis 42A is aligned with the long axis direction of the rod shape.
In the following description, the "direction indicated by arrow X" will also be simply referred to as the "arrow X direction." Furthermore, in the following description, the optical axis 42A originating from the liquid crystal compound 42 will also be referred to as the "optical axis 42A of the liquid crystal compound 42" or the "optical axis 42A."
In the liquid crystal layer 40, the liquid crystal compounds 42 are two-dimensionally aligned in a plane parallel to the direction of arrow X and the direction of Y perpendicular to the direction of arrow X. In FIG. 2, the Y direction is perpendicular to the paper surface.

FIG. 3 conceptually shows a plan view of the liquid crystal layer 40. As shown in FIG.
The liquid crystal layer 40 has a liquid crystal orientation pattern in which the direction of the optical axis 42A derived from the liquid crystal compound 42 changes while continuously rotating along the direction of the arrow X within the plane of the liquid crystal layer 40.
The expression "the orientation of the optical axis 42A of the liquid crystal compound 42 changes while continuously rotating in the direction of the arrow X (one predetermined direction)" specifically means that the angle formed between the optical axis 42A of the liquid crystal compound 42 aligned along the direction of the arrow X and the direction of the arrow X differs depending on the position in the direction of the arrow X, and that the angle formed between the optical axis 42A and the direction of the arrow X changes sequentially from θ to θ+180° or θ−180° along the direction of the arrow X.
The difference in angle between the optical axes 42A of the liquid crystal compounds 42 adjacent to each other in the direction of the arrow X is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

On the other hand, the liquid crystal compounds 42 forming the liquid crystal layer 40 are arranged at equal intervals in the Y direction perpendicular to the direction of the arrow X, i.e., in the Y direction perpendicular to the direction in which the optical axis 42A continuously rotates.
In other words, among the liquid crystal compounds 42 forming the liquid crystal layer 40, the angles formed by the direction of the optical axis 42A and the direction of the arrow X are equal among the liquid crystal compounds 42 aligned in the Y direction.

In such a liquid crystal orientation pattern of the liquid crystal compound 42, the length (distance) over which the optical axis 42A of the liquid crystal compound 42 rotates 180° in the direction of arrow X, in which the orientation of the optical axis 42A continuously rotates and changes in plane, is defined as the length Λ of one period of the liquid crystal orientation pattern. In other words, the length of one period of the liquid crystal orientation pattern is defined as the distance from when the angle between the optical axis 42A of the liquid crystal compound 42 and the direction of arrow X changes from θ to θ+180°.
That is, the distance between the centers of two liquid crystal compounds 42 in the direction of arrow X that are at the same angle with respect to the direction of arrow X is defined as the length Λ of one period. Specifically, as shown in Fig. 3, the distance between the centers of two liquid crystal compounds 42 in the direction of arrow X that are aligned with the direction of arrow X and the direction of their optical axes 42A is defined as the length Λ of one period. In the following description, this length Λ of one period is also referred to as "one period Λ."
The liquid crystal alignment pattern of the liquid crystal layer 40 repeats this one period Λ in the direction of the arrow X, that is, in one direction in which the direction of the optical axis 42A continuously rotates and changes.

As described above, in the liquid crystal layer 40, the liquid crystal compounds 42 aligned in the Y direction have the same angle between their optical axes 42A and the direction of the arrow X (one direction in which the orientation of the optical axes of the liquid crystal compounds 42 rotates). A region R is defined as a region in which the liquid crystal compounds 42 aligned in the Y direction have the same angle between their optical axes 42A and the direction of the arrow X.
In this case, the in-plane retardation (Re) value in each region R is preferably half the wavelength, i.e., λ/2. These in-plane retardations are calculated by the product of the refractive index difference Δn associated with the refractive index anisotropy of region R and the thickness of the liquid crystal layer. Here, the refractive index difference associated with the refractive index anisotropy of region R in the liquid crystal layer is a refractive index difference defined by the difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction perpendicular to the slow axis. In other words, the refractive index difference Δn associated with the refractive index anisotropy of region R is equal to the difference between the refractive index of liquid crystal compound 42 in the direction of optical axis 42A and the refractive index of liquid crystal compound 42 in the direction perpendicular to the optical axis 42A in the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

The 180° rotation period in the liquid crystal layer does not need to be uniform over the entire surface, that is, there may be regions within the plane where the length of the 180° rotation period (length Λ of one period) is different.
The minimum value of the length of one period, which is the length of the in-plane rotation of the optical axis derived from the liquid crystal compound by 180°, is preferably 20 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less. The lower limit is not particularly limited, but is often 0.5 μm or more.
Furthermore, it is sufficient that the liquid crystal layer has a liquid crystal orientation pattern in which the direction of the optical axis is rotated in at least one direction in the plane of the liquid crystal layer, and the liquid crystal layer may have a portion in which the direction of the optical axis is constant.

The thickness of the liquid crystal layer is not particularly limited, but is preferably greater than ¼ of the minimum length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane. The upper limit is not particularly limited, but is often equal to or less than twice the minimum length of one period.
The thickness of the liquid crystal layer is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.5 μm or more. The upper limit is not particularly limited, but is preferably 20 μm or less, and more preferably 15 μm or less.

The orientation of the optical axis 42A of the liquid crystal compound 42 in the liquid crystal alignment pattern of the liquid crystal layer 40 shown in FIGS. 2 and 3 rotates continuously only along the direction of the arrow X.
The present invention is not limited to the above embodiment, and various configurations can be used as long as the orientation of the optical axis of the liquid crystal compound in the liquid crystal layer rotates continuously along one direction.

Liquid crystal compounds used to form liquid crystal layers can generally be classified into rod-shaped and discotic types based on their shape. Each of these can further be divided into low-molecular-weight and high-molecular-weight types. High-molecular-weight compounds generally refer to those with a degree of polymerization of 100 or more (Polymer Physics/Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992). While either type of liquid crystal compound can be used in the present invention, rod-shaped or discotic liquid crystal compounds are preferred.

The method for manufacturing the liquid crystal layer is not particularly limited, and known methods can be used. For example, the method for manufacturing an optically anisotropic layer using an alignment film described in JP-A-2022-095795 can be used.

(Protective film A)
The protective film A includes a substrate and an adhesive layer in contact with the liquid crystal layer.

-Base material-
The substrate may be made of an organic material or an inorganic material, and is preferably a resin substrate.
Examples of materials for the resin substrate include cellulose-based polymers, (meth)acrylic polymers, polyester-based polymers, styrene-based polymers, and olefin-based polymers (including cycloolefin-based polymers). Among these, cellulose-based polymers, (meth)acrylic polymers, and cycloolefin-based polymers are preferred as materials for the resin substrate, and triacetyl cellulose (TAC) is more preferred.

There are no particular restrictions on the thickness of the substrate, but from the standpoints of ease of handling and thinness, a thickness of 5 to 200 μm is preferred, 10 to 100 μm is more preferred, and 15 to 60 μm is even more preferred.

The elastic modulus of the substrate is preferably 2.0 to 6.0 GPa, and more preferably 3.0 to 5.0 GPa, in terms of better effects of the present invention and better protection performance when handling the liquid crystal layer, specifically better performance in preventing deformation of the liquid crystal layer when sheets of the laminate are stacked and adhesion or the like occurs.
Here, the modulus of elasticity of the substrate is the tensile modulus of elasticity at room temperature (25°C) in accordance with Japanese Industrial Standards JIS K7161:2014.
The elastic modulus of the substrate can be measured, for example, by a tensile test using a Tensilon universal material testing machine (manufactured by A&D Co., Ltd.) in which the substrate is stretched at a temperature of 25°C, a relative humidity of 60%, a chuck length of 100 mm, and a tensile speed of 200 mm/min, and the strains at elongations of 0.1% and 0.5% are measured, and the elastic modulus of each substrate is calculated from the slopes of the strain at two points.

-Adhesive layer-
The adhesive layer is a layer formed using an adhesive. Any known adhesive can be used as the adhesive. It is preferable to select an appropriate adhesive taking into consideration the peel strength and fluctuation rate between the liquid crystal layer and the adhesive layer in contact with the liquid crystal layer in the present invention.
Examples of the adhesive include (meth)acrylic adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, cellulose adhesives, and vinyl alkyl ether adhesives. Among these, (meth)acrylic adhesives are preferred.

Examples of the (meth)acrylic polymer used in the (meth)acrylic pressure-sensitive adhesive include copolymers made of a (meth)acrylic acid ester and a hydrophilic component such as a vinyl monomer having a hydroxyl group and a (meth)acrylic acid derivative.
The (meth)acrylic acid ester preferably has an ester moiety that is an alkyl group having 1 to 18 carbon atoms. Specific examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, and hexadecyl (meth)acrylate.

Examples of vinyl monomers and (meth)acrylic acid derivatives having a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, as well as hydroxyl group-containing monomers such as vinyl alcohol and allyl alcohol.
The ratio of the hydrophilic component to the (meth)acrylic acid ester is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester. From the viewpoints of adhesive strength and cohesive strength, the amount of the hydrophilic component having a hydroxyl group is preferably 50 parts by mass or less per 100 parts by mass of the (meth)acrylic acid ester.
The (meth)acrylic polymer may be a copolymer having structural units derived from other vinyl monomers and/or polar group-containing monomers.

The (meth)acrylic polymer is also preferably a crosslinked product obtained by crosslinking using a crosslinking agent.
Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, and an aziridine crosslinking agent, and an isocyanate crosslinking agent having two or more isocyanate groups in the molecule is preferred. Examples of the isocyanate crosslinking agent include tolylene diisocyanate (sometimes referred to as TDI), chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate, and hexamethylene diisocyanate or diphenylmethane diisocyanate is preferred.
The amount of the crosslinking agent is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 2 to 10 parts by mass, per 100 parts by mass of the (meth)acrylic polymer.

The adhesive layer may contain various additives to the extent that they do not impair the desired performance, such as transparency, depending on the intended application. Such additives include tackifiers such as rosin derivative resins, polyterpene resins, and oil-soluble phenolic resins, plasticizers, fillers, antioxidants, surfactants, colorants, silane coupling agents, inorganic curing promoters, and ultraviolet absorbers.

The adhesive layer preferably does not have optical anisotropy.
Specifically, the in-plane retardation of the adhesive layer at a wavelength of 550 nm is preferably 5 nm or less, and more preferably 0 nm.
The retardation of the adhesive layer in the thickness direction at a wavelength of 550 nm is preferably −5 to 5 nm, more preferably 0 nm.

The thickness of the adhesive layer is not particularly limited, and is preferably 5 to 30 μm, more preferably 5 to 15 μm, from the viewpoint of adhesiveness to optical elements and thinning.
The thickness of the adhesive layer is an arithmetic average of thicknesses measured at 10 arbitrary points on the adhesive layer using a constant pressure thickness measuring instrument PG-18J (manufactured by Teclock Corporation).

The protective film A may have multiple substrates. For example, the protective film A may be a protective film having, in this order, a substrate, an adhesive layer, a substrate, and an adhesive layer in contact with the liquid crystal layer. In the protective film A having multiple substrates, specific examples and preferred aspects of each substrate and adhesive layer may be the same as those described above.
The protective film A may include components other than the substrate and the adhesive layer, but it is preferred that the protective film A does not include components other than the substrate and the adhesive layer.

--Properties of Protective Film A--
In order to obtain a more excellent effect of the present invention, the peel strength FA of the protective film A is preferably 0.80 N/25 mm or less, and more preferably 0.60 N/25 mm or less. Although there is no particular lower limit for the peel strength FA, it is often 0.10 N/25 mm or more.

Furthermore, the variation rate VFA of the peel force FA when peeling off protective film A is preferably 11% or less, and more preferably 9% or less, in order to achieve better effects of the present invention. There is no particular lower limit for the variation rate VFA, and it may be 0%.

It is preferable that a plurality of protrusions protruding from the surface by a certain height or more are formed on the surface opposite the liquid crystal layer side of the protective film A. This reduces adhesion between layers of the laminate and has a significant effect of increasing the slipperiness, thereby further enhancing the effect of protecting the liquid crystal layer.
The height of the protrusions is preferably 30 nm or more, as this provides a more excellent effect. The upper limit of the height of the protrusions is not particularly limited, but is preferably 100 nm or less. Here, the height of the protrusions is defined as the distance between the surface and the protruding top of the protrusions in the thickness direction.
In order to obtain the above-mentioned effects more effectively, the number density of protrusions having a height of 30 nm or more per area of the surface is preferably 3,000 pieces/ ^mm2 or more, and more preferably 10,000 pieces/ ^mm2 or more. There is no particular upper limit, but a density of 1,000,000 pieces/ ^mm2 or less is preferred.

The number density of protrusions can be measured by observing the surface of the protective film A from a direction approximately perpendicular to the surface and using the observed image. More specifically, a scanning probe microscope (SPA400, manufactured by SII NanoTechnology Inc.) is used to observe the surface of the protective film A in an area of 100 μm × 100 μm in AFM (Atomic Force Microscope) mode, and an observation image (AFM image) is obtained. In the AFM image, the brightness of the pixel corresponding to the observed location is displayed higher depending on the protrusion height from the surface at that location. Based on this property, if a predetermined brightness is set as a threshold value in the AFM image and a binarization process is performed, locations above a predetermined height from the surface can be separated and extracted. Utilizing this, the number density of protrusions above 30 nm can be determined by performing a binarization process on the AFM image, separating areas protruding 30 nm or more from the surface as bright and other areas as dark.
When determining the number density of the above protrusions, three observation areas were arbitrarily selected on the surface of protective film A, and the arithmetic mean value of the number densities obtained from each observation area was calculated, which was used as the number density of protrusions with a height of 30 nm or more per surface of protective film A.

Protective film A having a number density of protrusions having a height of 30 nm or more per surface within the above range can be obtained, for example, by using a mixture in which fine particles are added to the raw material resin of the substrate when producing the substrate.
As the fine particles, for example, organic particles such as resin particles, and inorganic particles can be used. The material, size, and content of the fine particles in the substrate are appropriately selected depending on the height and number density of the protrusions, the thickness of the substrate, and the like.

-Method for manufacturing protective film A-
The protective film A can be produced by known methods, such as a method of preparing an adhesive layer on a temporary support using a composition containing an adhesive and transferring the prepared adhesive layer to a substrate, or a method of applying a composition containing an adhesive directly to the surface of a substrate to form an adhesive layer.
The method for producing the protective film A will be specifically described below, but the method for producing the protective film A is not limited to the following method.

First, a coating liquid for forming an adhesive layer (hereinafter also referred to as an adhesive layer coating liquid) containing an adhesive is prepared. The adhesive layer coating liquid may further contain a solvent. Examples of the solvent include acetate esters, ketones, toluene, alcohols, and water.
A long separator film (e.g., a PET film having a release layer) is conveyed in the longitudinal direction, and a coating liquid for an adhesive layer is applied to the surface of the separator film, and then this coating film is dried. The method for applying the coating liquid for an adhesive layer is not particularly limited, and examples include known coating methods using devices such as a die coater and a gravure coater. The drying process can be carried out, for example, by passing the coated separator film through a drying device equipped with a chamber into which a dry gas (e.g., air) is supplied. The dry gas may be heated, for example, to a temperature of around 80°C.

A substrate such as a TAC film is superimposed on the adhesive layer formed after drying the coating film while being transported in the longitudinal direction. The superposition is performed by guiding the substrate and the separator film with the adhesive layer between a pair of nip rollers arranged opposite each other and pressing the substrate and the separator film with the adhesive layer with the outer peripheral surfaces of the pair of nip rollers.
After the substrate and the separator film with the adhesive layer are superimposed, the laminated member comprising the separator film, the adhesive layer, and the TAC film is wound into a roll, thereby obtaining a roll body.
The obtained roll body is preferably subjected to an aging step, which is a step for stably developing the adhesive strength of the adhesive layer, for example, a step of leaving the roll body in an atmosphere at a temperature of 40° C. Thereafter, if necessary, a cutting step may be performed in which each side portion is cut off to a predetermined width.

(Protective film B)
The configuration of the protective film B is not particularly limited as long as it is a member that satisfies the above requirement 2 and, in some cases, requirement 4.
The protective film B may be in contact with the liquid crystal layer or the intermediate layer, but is preferably in contact with the liquid crystal layer.

An example of the configuration of the protective film B is one including a substrate and an adhesive layer.
When protective film B includes a substrate and an adhesive layer, the adhesive layer of protective film B is preferably disposed between the substrate and the liquid crystal layer of protective film B. In this case, the adhesive layer of protective film B may be in contact with the liquid crystal layer, or the intermediate layer may be disposed between the adhesive layer of protective film B and the liquid crystal layer.
When protective film B comprises a substrate and an adhesive layer, the material constituting the substrate, the adhesive contained in the adhesive layer, and the manufacturing method of protective film B, including their preferred variations, may be the same as those described for protective film A.

The protective film B may have a substrate with one surface subjected to a release treatment, or may consist solely of a substrate with one surface subjected to a release treatment. Examples of the release treatment include treatment using a treatment agent such as a silicone treatment agent, and surface treatments such as corona treatment and plasma treatment.
When a substrate having one surface subjected to a release treatment is used as the protective film B, it is preferable that the release-treated surface is disposed so as to face the liquid crystal layer. The release-treated surface may be in contact with the liquid crystal layer or the intermediate layer.

The protective film B may have a plurality of substrates. The protective film B may be, for example, a protective film in which, from the side farther from the liquid crystal layer to the side closer to the liquid crystal layer, a substrate, an adhesive layer, a substrate, and an adhesive layer are arranged in this order. The protective film B may also be, for example, a protective film in which, from the side farther from the liquid crystal layer to the side closer to the liquid crystal layer, a substrate, an adhesive layer, and a substrate whose surface on the liquid crystal layer side has been subjected to a release treatment are arranged in this order. In the protective film B having a plurality of substrates, the specific examples and preferred aspects of each substrate and adhesive layer may be the same as those described above.
The protective film B may include components other than the substrate and the adhesive layer, but it is preferred that the protective film B does not include components other than the substrate and the adhesive layer.

-Properties of Protective Film B-
The peel strength FB of the protective film B is preferably 0.60 N/25 mm or less, more preferably 0.40 N/25 mm or less. There is no particular lower limit to the peel strength FB, but it is often 0.01 N/25 mm or more.

The absolute value ΔF of the difference between the peel strength FB of protective film B and the peel strength FA of protective film A is not particularly limited as long as it is 0.10 N/25 mm or more, but is preferably 0.15 N/25 mm or more, and more preferably 0.20 N/25 mm or more.
There is no particular upper limit to ΔF, but the higher the peel strength of the protective film, the easier it is to peel, so it is preferably 0.60 N/25 mm or less.

When protective film B is in contact with the liquid crystal layer, the variation rate VFB of the peel force FB when peeling protective film B is preferably 11% or less, and more preferably 9% or less, in order to achieve better effects of the present invention. There is no particular lower limit for the variation rate VFB, and it may be 0%.

As with protective film A, it is preferable that a plurality of protrusions protruding from the surface of protective film B to a certain height or more are formed on the surface opposite the liquid crystal layer side. The specific and preferred range of the protrusion height is the same as for protective film A.
In particular, in terms of reducing adhesion between laminates, increasing slipperiness, and providing a more excellent effect of protecting the liquid crystal layer, the number density of protrusions having a height of 30 nm or more per area of the surface of protective film B opposite the liquid crystal layer side is preferably 3,000/ ^mm2 or more, and more preferably 10,000/ ^mm2 or more. There is no particular upper limit, but a value of 1,000,000/ ^mm2 or less is preferred.
In order to further enhance the above-mentioned effects, it is particularly preferable that the number density of protrusions having a height of 30 nm or more per surface opposite to the liquid crystal layer side in both protective film A and protective film B of the laminate is within the above-mentioned range.

(middle class)
The laminate of the present invention may have an intermediate layer between the liquid crystal layer and the protective film B.
Examples of the intermediate layer include an optical clear adhesive (OCA) layer and an OCA layer-attached substrate formed by laminating an OCA layer and a substrate. The OCA layer may be a known layer formed using an optical pressure-sensitive adhesive. The substrate used in the OCA layer-attached substrate can be the same as the substrate of the protective film A, and the same preferred embodiments apply.
When the protective film B is peeled from the laminate having the intermediate layer, the protective film B is peeled at the interface between the protective film B and the intermediate layer.

<Method of manufacturing laminate>
The method for producing the laminate is not particularly limited, and any known method can be used.
For example, the laminate of the present invention can be produced by laminating the liquid crystal layer and protective film A together, with one surface of the liquid crystal layer facing the adhesive layer of protective film A, which comprises a substrate and an adhesive layer, and then laminating the other surface of the liquid crystal layer in the resulting laminate with protective film B.

The laminate of the present invention has little effect on the liquid crystal layer when the protective film is peeled off, and the protective film can be easily peeled off in the desired order, making it suitable for use in the production of liquid crystal optical elements having a liquid crystal layer.
When the liquid crystal layer of the laminate is to be bonded to another component to produce a liquid crystal optical element, the protective film having the smaller peel strength of either protective film A or B is peeled off from the laminate, and the exposed liquid crystal layer (or intermediate layer) is bonded to another optical component via an adhesive or the like, and then the remaining protective film is peeled off, thereby transferring the liquid crystal layer to the other optical component.

Liquid crystal optical elements manufactured using the laminate can be used as optical elements that control the direction of light in optical devices such as backlights for liquid crystal display devices; head-mounted displays (HMDs) such as AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses that display virtual images and various types of information superimposed on the actual scene; head-up displays (HUDs); projectors; beam steering; and sensors for detecting objects and measuring the distance to objects.

The present invention will be explained in more detail below based on examples. The materials, amounts used, ratios, processing details, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[Production of laminate]
<Preparation of substrate>
As the substrate used for producing the protective film A or B, the following films were prepared.
"TAC40": low retardation TAC (triacetyl cellulose) film (manufactured by Fujifilm Corporation, product name: ZRG40).
"TAC20": low retardation TAC film (manufactured by Fujifilm Corporation, product name: ZRG20).
"TAC60": TAC film (manufactured by Fujifilm Corporation, product name: TG60).
"TAC80": TAC film (manufactured by Fujifilm Corporation, product name: TG80).
"TAC40R": A release-treated film obtained by subjecting one surface of the above TAC40 to a release treatment using a silicone treatment agent.
"COP40": COP (cycloolefin polymer) film (manufactured by JSR Corporation, trade name: ARTON film).
"COP20": COP film (manufactured by JSR Corporation, trade name: ARTON film).
"Acrylic": Acrylic polymer film (manufactured by Okura Kogyo Co., Ltd., product name: OXIS-PMMA)
Table 1 below shows the thickness (μm), modulus of elasticity (GPa), number density of protrusions 30 nm or more in height per surface area (pieces/mm ² ), and whether or not each film was subjected to a release treatment.

<Preparation of Coating Solution for Adhesive Layer>
(Synthesis of Acrylic Polymer A)
A reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer, and a stirrer was charged with isobutyl acrylate (80 parts by mass), 4-hydroxybutyl acrylate (20 parts by mass), and ethyl acetate (170 parts by mass) to prepare a mixed solution. Subsequently, a solution of 2,2'-azobisisobutyroninitrile (0.4 parts by mass) as a polymerization initiator dissolved in ethyl acetate (10 parts by mass) was added to the reaction vessel, and the mixed solution was stirred while blowing nitrogen gas into the reaction vessel. The reaction was carried out at 60°C for 4 hours, thereby synthesizing acrylic polymer A. The weight-average molecular weight Mw of the resulting acrylic polymer A was 600,000.

(Synthesis of Acrylic Polymer B)
Acrylic polymer B was synthesized in the same manner as in the synthesis of acrylic polymer A, except that isobutyl acrylate (85 parts by mass), 4-hydroxybutyl acrylate (15 parts by mass), acrylic acid (0.1 parts by mass), and ethyl acetate (170 parts by mass) were charged to prepare a mixed solution. The weight average molecular weight Mw of the obtained acrylic polymer B was 700,000.

(Synthesis of Acrylic Polymer C)
Acrylic polymer C was synthesized in the same manner as in the synthesis of acrylic polymer A, except that isobutyl acrylate (50 parts by mass), 2-ethylhexyl acrylate (20 parts by mass), 4-hydroxyethyl methacrylate (30 parts by mass), and ethyl acetate (170 parts by mass) were charged to prepare a mixed solution. The weight average molecular weight Mw of the obtained acrylic polymer C was 800,000.

An isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate (registered trademark) HX"), a crosslinking agent whose main component is a compound having an isocyanate group, was blended into the solution containing the above acrylic polymer A, and toluene was further added to adjust the solid content concentration to 30% by mass, thereby preparing a coating liquid for the adhesive layer.
When preparing the adhesive layer coating liquid, the amount of crosslinking agent relative to the acrylic polymer A was adjusted to prepare adhesive layer coating liquids A-1 to A-5 with different adhesive strengths.

Acrylic polymer B was used instead of acrylic polymer A, but the adhesive layer coating liquid preparation method described above was followed to prepare adhesive layer coating liquids B-1 to B-3, which differ in the amount of crosslinker relative to acrylic polymer B and have different adhesive strengths.

Acrylic polymer C was used instead of acrylic polymer A, and a crosslinking agent (manufactured by AICA Corporation) whose main component is a trimethylolpropane adduct of toluene diisocyanate was used as the crosslinking agent. Following the same method for preparing the adhesive layer coating solution as above, adhesive layer coating solutions C-1 to C-3 were prepared, each with different amounts of crosslinking agent relative to acrylic polymer C and different adhesive strengths.

<Preparation of protective film>
The adhesive layer coating solution A-1 was applied to the release-treated surface of a PET (polyethylene terephthalate) film, one surface of which had been subjected to a release treatment, and the resulting coating film was dried to form an adhesive layer A-1 having a thickness of 10 μm. Next, the above-mentioned substrate TAC40 was attached to the surface of the adhesive layer-attached film on which the adhesive layer A-1 had been formed, thereby obtaining a laminated film A1 having a protective film A1 composed of the substrate TAC40 and the adhesive layer A-1, and a PET film.
Next, a laminated film B1 having a protective film B1 consisting of a substrate TAC40 and an adhesive layer A-4 (thickness 10 μm) and a PET film was obtained in the same manner as the protective film A1, except that adhesive layer coating liquid A-4 was used instead of adhesive layer coating liquid A-1.

<Preparation of Liquid Crystal Layer>
According to the method described in Example 1 of WO 2022/050319, a liquid crystal layer having a liquid crystal alignment pattern was formed on a glass substrate to obtain a glass substrate with a liquid crystal layer.
This liquid crystal layer is obtained by applying a liquid crystal composition containing a liquid crystal compound in multiple layers. Multilayer application refers to a process in which a first layer of composition is applied onto an alignment film, heated, cooled, and then cured with ultraviolet light to form a liquid crystal fixed layer. Then, subsequent layers are applied by recoating them on the liquid crystal fixed layer, and similarly heated, cooled, and then cured with ultraviolet light. By forming the layer by multilayer application, the alignment direction of the alignment film is reflected from the lower surface to the upper surface of the optically anisotropic layer, even if the total thickness of the optically anisotropic layer is increased.

Example 1
The PET film was peeled from the laminated film A1, and while transporting the resulting protective film A1, it was attached to the glass substrate with the liquid crystal layer using a 50 mmΦ rubber roller from the protective film A1 side so that the adhesive layer A-1 and the liquid crystal layer faced each other. Next, while supporting the bonded body with the rubber roller used for the lamination, it was peeled from the glass substrate, thereby transferring the liquid crystal layer to the protective film A1. The transport speed of the protective film A1 in this case was 3000 mm/min.
Next, a protective film B1 obtained by peeling the PET film from the laminate film B1 was attached to the exposed surface of the liquid crystal layer so that the adhesive layer B-1 and the liquid crystal layer faced each other, thereby obtaining a laminate of Example 1 having, in this order, a protective film A1 (substrate TAC40 and adhesive layer A-1), a liquid crystal layer, and a protective film B1 (adhesive layer A-4 and substrate TAC40).

<Examples 2 to 14 and Comparative Examples 1 to 3 and 5>
Protective films A and B having the configurations shown in Table 1 were prepared by changing at least one of the substrate and the adhesive layer coating liquid, and laminates of Examples 2 to 14 and Comparative Examples 1 to 3 and 5 were produced according to the same procedures as in Example 1 and the above-mentioned protective film preparation method, except that the obtained protective films A and B were used.

Example 15
Except for using the adhesive layer coating liquid A-3 instead of the adhesive layer coating liquid A-1, the same procedure as in the method for producing the protective film was followed to obtain a laminated film A15 having the substrate TAC40, the adhesive layer A-3, and the PET film in this order.
Except for using the adhesive layer coating liquid A-5 instead of the adhesive layer coating liquid A-1, the same procedure as in the method for producing the protective film was followed to obtain a laminated film B15 having the substrate TAC40, the adhesive layer A-5, and a PET film in this order.
The PET film was peeled off from the laminated film B15 to obtain a protective film B15 composed of the base material TAC40 and the adhesive layer A-5, and then the protective film B15 was bonded to one surface of the base material TAC 20. Next, an optical adhesive film (manufactured by Lintec Corporation, product name: NCF-D692, thickness 15 μm) was bonded to the surface of the base material TAC 20 to which the protective film B15 was not bonded.
Except for using laminate film A15 instead of laminate film A1 and laminate film B15 instead of laminate film B1, the same procedure as in Example 1 was followed to produce a laminate of Example 15 having, in this order, a protective film A15 (substrate TAC40 and adhesive layer A-3), a liquid crystal layer, an optical adhesive layer (OCA), a substrate TAC20, and a protective film B15 (adhesive layer A-5 and substrate TAC40).

Example 16
Except for using adhesive layer coating liquid B-1 instead of adhesive layer coating liquid A-5, the same procedure as in Example 15 was followed to produce a laminate of Example 16 having, in this order, a protective film A16 (substrate TAC40 and adhesive layer A-3), a liquid crystal layer, an optical adhesive layer (OCA), a substrate TAC20, and a protective film B16 (adhesive layer B-1 and substrate TAC40).

<Examples 17 to 20>
An optical adhesive film (manufactured by Lintec Corporation, trade name: NCF-D692, thickness 15 μm) was attached to the release-treated surface of the above substrate TAC40R to prepare a substrate with OCA.
The laminate of Example 17, having in this order protective film A17 (substrate TAC40 and adhesive layer A-3), liquid crystal layer, OCA, and substrate TAC40R (protective film B17), was produced according to the same procedure as in Example 15, except that the protective film A to which the liquid crystal layer had been transferred and the above-mentioned substrate with OCA were bonded together so that the liquid crystal layer and OCA faced each other.
The adhesive layer coating liquid was changed to prepare a protective film A having the configuration shown in Table 1, and the laminates of Examples 18 to 20 were produced according to the same procedure as above, except that the obtained protective film A was used.

<Comparative Example 4>
A laminated film Ac4 having a protective film Ac4 consisting of a substrate TAC40 and an adhesive layer C-2 and a PET film was obtained according to the same procedure as in the method for producing the protective film described above, except that adhesive layer coating liquid C-2 was used instead of adhesive layer coating liquid A-1.
The PET film was peeled off from the laminated film Ac4, and the obtained protective film Ac4 and a glass substrate with a liquid crystal layer were bonded together so that the adhesive layer C-2 and the liquid crystal layer faced each other. Next, the glass substrate was peeled off from the bonded body, and the liquid crystal layer was transferred to the protective film Ac4, thereby obtaining a laminate of Comparative Example 4 having, in this order, the protective film Ac4 (base material TAC40 and adhesive layer C-2) and the liquid crystal layer.

[measurement]
The laminate prepared in each example was cut to a size of 25 mm wide and 150 mm long to prepare a sample for measuring peel force, and the obtained sample was attached to the surface of a glass plate (manufactured by AGC Inc., product name: Eagle XG Glass) using a commercially available non-carrier type adhesive (NCF-D692 manufactured by Lintec Corporation, thickness 15 μm). At this time, the laminate attached to the glass plate was oriented so that the protective film to be measured was placed on the outside and the other protective film was placed on the glass plate side. If the protective film side to be measured and the liquid crystal layer were not stably peeled off and the peel force could not be measured, the measurement was performed by attaching the surface from which one of the protective films had been peeled to the adhesive, for example.
Next, according to the procedure described in JIS Z 0237:2009 (ISO29862:2007), a peel test was performed in which one end of the longitudinal direction of the protective film to be measured, which was placed on the outside, was gripped and peeled at a peel angle of 90° and a peel speed of 300 mm/min (5 mm/sec), to measure the peel force when peeling the protective film from the laminate. The peel test and the measurement of the peel force were performed using a Tensilon universal testing machine (manufactured by A&D Co., Ltd.).
In the longitudinal direction of the sample, the position at which peeling began was set to 0 mm, and the distance the protective film was peeled was within the range of 10 to 40 mm. The average value of the peel force in a 10 mm section where the peel force stabilized was taken as the peel force FA of protective film A (or the peel force FB of protective film B).

Furthermore, in the above peel test, the peel force was measured at 100 positions within the 10 mm section where the peel force stabilized. Specifically, in measuring the peel force, the measurement values were taken at intervals of 0.02 seconds. As a result, the 100 positions represent the peel force values at positions spaced 0.1 mm apart along the longitudinal direction of the sample. From the measured peel force results, the variability VFA (%) of the peel force FA when peeling protective film A from the laminate, and the variability VFB (%) of the peel force FB when peeling protective film B from the laminate were calculated according to the method described above.

[evaluation]
(1) Formation State of Liquid Crystal Layer The laminate of each example was placed between two linear polarizers arranged in a crossed Nicol state, and the laminate was rotated in the in-plane direction to observe the polarization state of the liquid crystal layer.
From the observation results, the state of formation of the liquid crystal layer in the laminate was evaluated according to the following evaluation criteria: Evaluations A and B are within desirable ranges for the quality of the liquid crystal layer.
A: There was no unevenness in the polarization state, and a uniform liquid crystal layer was formed.
B: There was some unevenness in the polarization state, but it was at an acceptable level.
C: There was a strong unevenness in part of the polarization state.
D: The liquid crystal layer was torn.
E: A liquid crystal layer could not be formed.

(2) Peelability of Protective Film The laminate produced in each example was placed on a flat plate with the protective film A side facing outwards and fixed with a commercially available non-carrier type adhesive (NCF-D692 manufactured by Lintec Corporation, thickness 15 μm). Tape (31B manufactured by Nitto Denko Corporation) was applied to the edge of the protective film located on the upper surface of the laminate, and the protective film was peeled off to confirm whether protective film A or B had separated from the liquid crystal layer.
The above protective film peeling test was carried out on three laminates, and the peelability of the protective film was evaluated based on the number of protective films separated from the liquid crystal layer, according to the following evaluation criteria. Evaluations A and B are in the desirable range.
A: Protective film A peeled off in all three laminates.
B: Protective film B peeled off in all three laminates.
C: There were both laminates in which protective film A peeled off and laminates in which protective film B peeled off.

(3) Liquid crystal layer after both surfaces were peeled off: One side of the protective film was peeled off from the laminate of each example, and the adhesive side of a glass plate with an adhesive layer was attached to the peeled surface. The other protective film was then peeled off. In the laminates of Examples 15 and 17 to 20, the OCA exposed after peeling off protective film B was used to attach the laminate to the glass plate. In cases where peeling off the protective film caused deformation or damage to the liquid crystal layer, the protective film was peeled off slowly to minimize deformation or damage.
After the two protective films were peeled off, the liquid crystal layer was visually observed, and the state of the liquid crystal layer after both sides were peeled off was evaluated based on the observation results according to the following evaluation criteria. Evaluations A and B are in the desirable range.
A: Neither wrinkles nor breaks were observed in the liquid crystal layer, and the film was uniform.
B: When peeled slowly, neither wrinkles nor tears were observed in the liquid crystal layer, and the film was uniform.
C: Even when peeled slowly, at least one of wrinkles and tears due to peeling was observed in the liquid crystal layer.

(4) Protection Performance of Liquid Crystal Layer Ten laminates of each example were stacked and placed in an aluminum packaging bag, and the bag was sealed after the pressure was reduced. The packaging bag was stored in an environment of 55°C for 72 hours, after which the laminate was removed from the packaging bag, and the adhesion of the laminate and the presence or absence of deformation in the liquid crystal layer were visually observed. Here, adhesion in the laminate refers to the appearance of the film being partially stuck together, observed when the laminate is observed in a stacked state. Furthermore, deformation in the liquid crystal layer refers to the deformation observed when the liquid crystal layer is observed alone.
The protective performance of the liquid crystal layer was evaluated based on the observation results according to the following evaluation criteria, with ratings A to C being in the desirable range.
A: No adhesion is observed in the laminate, and no deformation is observed in the liquid crystal layer.
B: Adhesion is observed in the laminate, but no deformation is observed in the liquid crystal layer.
C: Adhesion is observed in the laminate, and slight deformation is observed in the liquid crystal layer, but the deformation of the liquid crystal layer is at an acceptable level.
D: Deformation is observed in the liquid crystal layer.

The table below shows the laminate structure, measurement results of peel strength, etc., and evaluation results for each example and comparative example.

As shown in the table, it was confirmed that the desired effects were achieved when the laminate of the present invention was used.

Comparisons between Example 8 and Comparative Example 2, and between Examples 3 and 4 and Comparative Examples 4 and 5, confirmed that when the peel strengths FA and VFA of protective film A are within the ranges of the present application, the formability of the liquid crystal layer and the effect of suppressing damage to the liquid crystal layer when peeling off the protective film are better.
A comparison of Examples 4 and 5 with Comparative Examples 1 and 3 confirmed that when the difference in peel strength between protective films A and B is within the range of the present application, the peelability of the protective film can be stably set to the desired peel side.

10 Laminate 20 Protective film A
22, 32 Substrate 24 Adhesive layer 30 Protective film B
34 Adhesive layer 40 Liquid crystal layer 42 Liquid crystal compound 42A Optical axis

Claims (6)

A laminate having a peelable protective film A, a liquid crystal layer, and a peelable protective film B in this order,
The protective film A includes a substrate and an adhesive layer,
the adhesive layer and the liquid crystal layer are in contact with each other,
The peel strength FA of the protective film A is 1.00 N/25 mm or less,
the absolute value of the difference between the peel strength FB of the protective film B and the peel strength FA is 0.10 N/25 mm or more;
a 90-degree peeling process is performed to peel the protective film A from the liquid crystal layer, the peel force is measured at 100 positions every 0.1 mm in a peeling distance, the average value of the peel forces obtained at each of the positions is calculated, the absolute value of the difference between the peel force at each position and the average peel force is calculated, the absolute values of the differences at 10 points are extracted from the largest absolute values of the differences calculated at each position, the average value of the extracted absolute values of the differences is calculated, and the ratio of the average value of the calculated absolute values of the differences to the average peel force is obtained, and the ratio obtained is 12% or less;
When the protective film B is in contact with the liquid crystal layer, a 90-degree peeling process is performed to peel the protective film B from the liquid crystal layer, the peel force is measured at 100 positions every 0.1 mm in peel distance, the average value of the peel forces obtained at each of the positions is calculated, the absolute value of the difference between the peel force at each position and the average value of the peel force is calculated, the absolute values of the differences at 10 points are extracted from the largest absolute values of the differences calculated at each position, the average value of the extracted absolute values of the differences is calculated, and the ratio of the average value of the calculated absolute values of the differences to the average value of the peel forces is obtained, and the ratio obtained is 12% or less. The laminate of claim 1, wherein the liquid crystal layer includes a region having a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound is continuously rotated along at least one direction in the plane. The laminate according to claim 1 or 2, wherein the thickness of the substrate is 5 to 60 μm. The laminate according to claim 1 or 2, wherein the elastic modulus of the substrate is 3.0 to 5.0 GPa. The laminate described in claim 1 or 2, wherein the protective film B is in contact with the liquid crystal layer. 3. The laminate according to claim 1, wherein protrusions having a height of 30 nm or more are formed at a rate of 10,000 or more per ^mm2 on at least one of the surfaces of the protective film A opposite the liquid crystal layer side and the surface of the protective film B opposite the liquid crystal layer side.