JP7406977B2 - Method for manufacturing optical laminates - Google Patents

Description

The present invention relates to a method for manufacturing an optical laminate, and also relates to an optical laminate.

In image display devices such as organic EL display devices, an optical laminate (elliptically polarizing plate) that combines a polarizer (linear polarizer) and a retardation layer is used for the purpose of preventing reflection of external light by metal electrodes. Sometimes. For example, in JP-A No. 2018-017996 (Patent Document 1), a polarizer and a retardation layer formed from a polymerizable liquid crystal compound are laminated via an ultraviolet curable adhesive layer, and the adhesive is cured by ultraviolet irradiation. It is described that the layers are cured to produce an elliptically polarizing plate.

JP2018-017996A

Conventional optical laminates produced by bonding optical films containing polarizers and retardation layers formed from polymerizable liquid crystal compounds using active energy ray-curable adhesives or pressure-sensitive adhesives have a radius of curvature. When the retardation layer is gradually curved to become smaller, fine wrinkles (hereinafter also referred to as "wrinkle defects") tend to occur in the retardation layer even at a relatively large radius of curvature. . When considering application to a bendable or even foldable image display device, the optical laminate is required to be resistant to wrinkle defects even when curved with a small radius of curvature.

The present invention relates to an optical laminate comprising an optical film and a retardation layer including a layer of a cured product of a polymerizable liquid crystal compound, the optical laminate being less likely to cause wrinkle defects even when curved with a small radius of curvature, and a method for producing the same. Our goal is to provide the following.

The present invention provides a method for manufacturing an optical laminate and an optical laminate as shown below.
[1] A method for manufacturing an optical laminate, comprising:
The optical laminate includes, in this order, an optical film, a cured adhesive layer that is a cured layer of an active energy ray-curable adhesive, and a retardation layer that includes a cured layer of a polymerizable liquid crystal compound,
The manufacturing method includes:
Laminating the optical film, the active energy ray curable adhesive layer, and the retardation layer so that the active energy ray curable adhesive layer and the retardation layer are in contact with each other;
Below (1) to (3):
(1) Hold at a temperature of 30°C or higher for 2 hours or more,
(2) Holding under vibration conditions for more than 2 hours,
(3) holding under conditions that satisfy at least one of the following: holding for 48 hours or more;
curing the active energy ray-curable adhesive layer to form the cured adhesive layer;
A method for producing an optical laminate, comprising: in this order.
[2] A method for manufacturing an optical laminate, comprising:
The optical laminate includes, in this order, an optical film, a cured adhesive layer that is a cured layer of an active energy ray-curable adhesive, and a retardation layer that includes a cured layer of a polymerizable liquid crystal compound,
The manufacturing method includes:
preparing a laminate including a base film and the retardation layer laminated in contact with the base film;
Peeling the base film from the retardation layer at a peeling speed of 50 m/min or more;
Laminating an optical film on the peeled surface of the retardation layer after peeling off the base film via an active energy ray-curable adhesive layer;
curing the active energy ray-curable adhesive layer to form the cured adhesive layer;
A method for producing an optical laminate, comprising: in this order.
[3] The method for producing an optical laminate according to [1] or [2], wherein the optical film includes a linear polarizer.
[4] In the lamination step, the optical film, the active energy ray-curable adhesive layer, and the retardation layer are laminated such that the linear polarizer and the active energy ray-curable adhesive layer are in contact with each other. The method for producing an optical laminate according to [3].
[5] An optical film, a cured adhesive layer which is a cured product layer of an active energy ray-curable adhesive, and a retardation layer including a cured product layer of a polymerizable liquid crystal compound, in this order,
The cured adhesive layer and the retardation layer are in contact with each other,
The surface of the retardation layer on the cured adhesive layer side has the following (a) to (d):
(a) the arithmetic mean roughness Sa is 0.065 μm or more;
(b) the root mean square height Sq is 0.085 μm or more;
(c) the developed area ratio Sdr of the interface is 0.2% or more;
(d) An optical laminate that satisfies one or more of the following: the bimodal root mean square slope Sdq is 0.065 or more.
[6] The optical laminate according to [5], wherein the optical film includes a linear polarizer.
[7] The optical laminate according to [6], wherein the linear polarizer and the cured adhesive layer are in contact with each other.

To provide an optical laminate comprising an optical film and a retardation layer including a layer of a cured product of a polymerizable liquid crystal compound, which hardly causes wrinkle defects even when curved with a small radius of curvature, and to provide a method for producing the same. Can be done.

2 is a schematic cross-sectional view showing an example of the layer structure of a laminate obtained by a lamination process in Embodiment 1. FIG. It is a schematic sectional view showing an example of the layer composition of an optical layered product. FIG. 7 is a schematic cross-sectional view showing an example of the layer structure of a laminate prepared in a preparation step in Embodiment 2. FIG. FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a linearly polarizing plate. It is a schematic sectional view showing an example of the layer composition of a retardation layered product. FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the optical laminate. FIG. 7 is a schematic cross-sectional view showing still another example of the layer structure of the optical laminate. It is a schematic diagram explaining the evaluation method of a wrinkle defect. It is a schematic diagram explaining the direction of an absorption axis and a slow axis in an optical laminate.

<Method for manufacturing optical laminate>
The optical laminate produced by the production method according to the present invention includes an optical film and a cured adhesive layer (hereinafter also simply referred to as "cured adhesive layer") which is a cured layer of an active energy ray-curable adhesive. and a retardation layer (hereinafter also simply referred to as "retardation layer") including a layer of a cured product of a polymerizable liquid crystal compound, in this order.
The optical laminate manufactured by the manufacturing method according to the present invention can be suitably applied to image display devices such as organic EL display devices.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a method for manufacturing an optical laminate according to the present invention will be described with reference to the drawings. Each embodiment shown below may be combined arbitrarily. All drawings are schematic illustrations and may not represent actual dimensions.
In each of the embodiments shown below, a long film or layer may be used in each step, and each step may be performed continuously, or a sheet film or layer may be used in each step, and each step may be performed continuously. may be performed discontinuously. The sheet material may be cut from a long material.

[Embodiment 1]
The method for manufacturing an optical laminate according to this embodiment includes the following steps in the order described.
A step of laminating an optical film, an active energy ray-curable adhesive layer, and a retardation layer containing a cured product layer of a polymerizable liquid crystal compound such that the active energy ray-curable adhesive layer and the retardation layer are in contact with each other. [Lamination process]
Below (1) to (3):
(1) Hold at a temperature of 30°C or higher for 2 hours or more,
(2) Holding under vibration conditions for more than 2 hours,
(3) A step of holding under conditions that satisfy at least one of the following: holding for 48 hours or more [holding step], and a step of curing the active energy ray-curable adhesive layer to form a cured adhesive layer [curing step] ].

[1] Lamination process FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a laminate obtained by the lamination process in this embodiment. The lamination process is a process of laminating the optical film 10 and the retardation layer 30 via the active energy ray-curable adhesive layer 20 (hereinafter also simply referred to as "adhesive layer"). In this specification, the active energy ray curable adhesive layer refers to a layer composed of an active energy ray curable adhesive. As the active energy ray-curable adhesive, one having the ability to bond the retardation layer 30 and the optical film 10 is used.

In the lamination process, the optical film 10, the adhesive layer 20, and the retardation layer 30 are laminated so that the adhesive layer 20 and the retardation layer 30 are in contact with each other. Moreover, the optical film 10, the adhesive layer 20, and the retardation layer 30 are preferably laminated so that the optical film 10 and the adhesive layer 20 are in contact with each other.

In the lamination step, an adhesive layer 20 is formed on one or more surfaces selected from the adhesive surface of the optical film 10 and the adhesive surface of the retardation layer 30, and the optical film 10 and the retardation layer 30 are bonded via the adhesive layer 20. This can be carried out by laminating them. The adhesive layer 20 can be formed by applying an active energy ray-curable adhesive to the adhesive surface using a known coating method.
In the laminate obtained by the lamination process, the thickness of the adhesive layer 20 is usually 0.5 μm or more and 50 μm or less, from the viewpoint of suppressing wrinkle defects and from the viewpoint of adhesiveness between the optical film 10 and the retardation layer 30. From the viewpoint of reducing the thickness of the resulting optical laminate, the thickness is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less.

One or more surfaces selected from the adhesive surface of the optical film 10 and the adhesive surface of the retardation layer 30 are subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, and flame (flame) treatment in advance before forming the adhesive layer 20. A surface activation treatment such as a saponification treatment or a saponification treatment may be performed. This surface activation treatment can improve the adhesiveness between the optical film 10 and the retardation layer 30.

The optical film 10 may be a film with a single layer structure or a film with a multilayer structure. Examples of the optical film 10 include a linear polarizing plate. In this specification, a linear polarizing plate is an optical element that includes at least a linear polarizer, and may include a linear polarizer and a thermoplastic resin film bonded to at least one surface of the linear polarizer.
When the optical film 10 is a linearly polarizing plate, preferably the linear polarizer included in the linearly polarizing plate and the adhesive layer 20 are in contact with each other in the laminate obtained by the lamination process.
The optical film 10 and the active energy ray-curable adhesive will be described in more detail in the <Optical laminate> section below.

The retardation layer 30 includes a layer of a cured product of a polymerizable liquid crystal compound, and exhibits optical anisotropy depending on the type of liquid crystal compound used to form the layer. Hereinafter, this cured layer of the polymerizable liquid crystal compound will also be referred to as a "retardation layer".
In this specification, the retardation layer 30 may be made of a retardation layer, or may include a retardation layer and an alignment layer.

In the lamination process, the retardation layer 30 that is bonded to the optical film 10 via the adhesive layer 20 may have one or more other layers laminated in advance before the lamination process. For example, a retardation layer laminate including the retardation layer 30 and other retardation layers may be prepared in advance, and this retardation layer laminate may be bonded to the optical film 10 via the adhesive layer 20. good.
The retardation layer, retardation expression layer, alignment layer, retardation layer laminate, etc. will be described in more detail in the section <Optical laminate> below.

[2] Holding process The holding process is a process of holding the laminate obtained by the laminating process under specific conditions. Although the specific mode of holding is not particularly limited, an example of this is to leave the laminate still under the specific conditions described above.

The above specific conditions are as follows (1) to (3):
(1) Hold at a temperature of 30°C or higher for 2 hours or more,
(2) Holding under vibration conditions for more than 2 hours,
(3) Conditions that satisfy at least one of the following: 48 hours or more.

According to the manufacturing method according to this embodiment, which includes the above-described laminating step and holding step, it is possible to manufacture an optical laminate that is less likely to cause wrinkle defects even when curved with a small radius of curvature. This is presumed to be due to the following reasons.
In the lamination process, the retardation layer 30 comes into contact with the adhesive layer 20 before curing, and this state is maintained under the above-mentioned specific conditions in the subsequent holding process. Since the active energy ray-curable adhesive before curing exhibits adhesive force to the retardation layer 30 after curing, it is recognized that an interaction occurs between the active energy ray curable adhesive and the retardation layer 30 . When the active energy ray-curable adhesive that interacts with the retardation layer 30 continues to be in contact with the retardation layer 30 under the above specific conditions, the contact surface of the retardation layer 30 with the adhesive (Surface X shown in FIG. 1) is considered to be roughened. Such roughness on the surface of the retardation layer 30 improves its adhesion to the adhesive layer 20.
When the adhesion is improved, the cured adhesive layer (adhesive layer after curing) and the retardation layer 30 deform as one when the optical laminate is curved, thereby suppressing the occurrence of wrinkle defects. It is thought that this will make it easier to do so.
The manufacturing method according to the present embodiment is also advantageous in suppressing rainbow unevenness, which will be described later, in the resulting optical laminate.

The holding temperature under the above condition (1) is 30°C or higher, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, it is preferably 35°C or higher, more preferably 38°C or higher, and still more preferably 40°C or higher. ℃ or higher. The holding temperature is usually 55° C. or lower, and is preferably 50° C. or lower because it can reduce the change in water content after the holding step is completed.

The holding time under the above condition (1) depends on the holding temperature, but is usually 2 hours or more, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, is preferably 3 hours or more, more preferably It is 4 hours or more, more preferably 5 hours or more. The holding time depends on the holding temperature, but usually less than 48 hours is sufficient. Note that the holding time may be 48 hours or more, but in this case, the holding step satisfies conditions (1) and (3).

The application of vibration to the laminate under the above condition (2) can be performed, for example, by placing the laminate on a vibration source. The vibration source is not particularly limited as long as it can vibrate at a constant frequency and constant amplitude, and a vibration generator may be used, or for example, it can rotate at a constant rotation speed. A rotary device such as an electric motor that can be used may be used, or a transformer or the like that can conduct alternating current may be used.
The frequency of the vibration is preferably 5 Hz or more, more preferably 10 Hz or more, from the viewpoint of suppressing the occurrence of wrinkle defects. The frequency of the vibration is preferably 50 Hz or less, more preferably 40 Hz or less, from the viewpoint of suppressing the occurrence of so-called floating, in which the layers constituting the laminate are partially peeled from each other.
The amplitude of the vibration is preferably 0.5 mm or more, more preferably 1 mm or more, from the viewpoint of suppressing the occurrence of wrinkle defects. The amplitude of the vibration is preferably 30 mm or less, more preferably 10 mm or less, from the viewpoint of suppressing the occurrence of so-called floating, in which the layers constituting the laminate are partially peeled from each other.

The holding temperature in the above condition (2) is not particularly limited, but is usually 5°C or higher, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, is preferably 10°C or higher, more preferably 15°C or higher. The temperature is more preferably 20°C or higher. The holding temperature may be 30° C. or higher; in this case, the holding step satisfies conditions (1) and (2). The holding temperature is usually 55° C. or lower, and is preferably 50° C. or lower because it can reduce the change in water content even after the holding step is finished.

The holding time in the above condition (2) depends on the holding temperature, but is usually 2 hours or more, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, is preferably 3 hours or more, more preferably It is 4 hours or more, more preferably 5 hours or more. The holding time depends on the holding temperature, but usually less than 48 hours is sufficient. Note that the holding time may be 48 hours or more, but in this case, the holding step satisfies conditions (2) and (3).

The holding temperature in the above condition (3) is not particularly limited, but is usually 5°C or higher, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, is preferably 10°C or higher, more preferably 15°C or higher. The temperature is more preferably 20°C or higher. The holding temperature may be 30° C. or higher; in this case, the holding step satisfies conditions (1) and (3). The holding temperature is usually 55° C. or lower, and preferably 50° C. or lower from the viewpoint of reducing the change in water content even after the holding step is finished.

The holding time in the above condition (3) depends on the holding temperature, but is usually 48 hours or more, and from the viewpoint of more effectively suppressing the occurrence of wrinkle defects, is preferably 54 hours or more, more preferably It is 66 hours or more, more preferably 72 hours or more. The holding time depends on the holding temperature, but usually 120 hours or less is sufficient.

In any of the conditions (1) to (3) above, the relative humidity of the environment in which the laminate is held is, for example, 20% RH or more and 80% RH or less, preferably 30% RH or more and 70% RH or less. be.

[3] Curing Step Referring to FIG. 2, in this step, an optical laminate can be obtained by curing adhesive layer 20 by irradiating active energy rays to form a cured adhesive layer 20a. The type of active energy ray to be irradiated is appropriately selected depending on the sensitive wavelength of the curable component contained in the active energy ray-curable adhesive constituting the adhesive layer 20. The active energy rays are preferably ultraviolet rays.

[Embodiment 2]
The method for manufacturing an optical laminate according to this embodiment includes the following steps in the order described.
A step of preparing a laminate including a base film and a retardation layer laminated in contact with the base film [preparation step];
A step of peeling the base film from the retardation layer at a peeling speed of 50 m/min or more [peeling step],
a step of laminating an optical film on the peeled surface of the retardation layer after peeling off the base film via an active energy ray-curable adhesive layer [lamination step];
A process of curing the active energy ray-curable adhesive layer to form a cured adhesive layer [curing process].

[1] Preparation process As mentioned above, the retardation layer 30 includes a retardation developing layer (a layer of a cured product of a polymerizable liquid crystal compound), and may be composed of a retardation developing layer, or a retardation developing layer. It may include a layer and an alignment layer. Therefore, the laminate prepared in this step, which includes a base film and a retardation layer laminated in contact with the base film, has, for example, a layer configuration of base film/alignment layer/retardation layer. It may have a layer structure of base film/retardation expressing layer.

FIG. 3 is a schematic cross-sectional view showing an example of the layer structure of the laminate prepared in the preparation step in this embodiment. The laminate shown in FIG. 3 has a layer structure of base film 41/alignment layer 32/retardation layer 31, and is an example in which the retardation layer 30 is composed of the retardation layer 31 and the alignment layer 32. It is. As the laminate prepared in this step, one commercially available product or a combination of multiple commercially available products may be used.

The laminate prepared in this step may include a base film and a retardation layer laminated in contact with the base film, and is not limited to the example shown in FIG. 3. One or more layers other than the base film 41 and the retardation layer 30 may be laminated on the laminate. For example, a retardation layer laminate including the base film 41, the retardation layer 30, and other retardation layers may be prepared in this step.
The base film, retardation layer, retardation expression layer, alignment layer, retardation layer laminate, etc. will be explained in more detail in the section <Optical laminate> below.

[2] Peeling process This process is a process of peeling the base film 41 from the retardation layer 30 at a peeling speed of 50 m/min or more.
The peeling speed is preferably 60 m/min or more, more preferably 70 m/min or more, still more preferably 80 m/min or more, and particularly preferably The speed is 90m/min or more. The peeling speed is usually 150 m/min or less, and preferably 120 m/min or less from the viewpoint of preventing breakage of the base film.

The peeling angle of the base film 41 with respect to the laminate from which the base film 41 is peeled is usually greater than 90 degrees and less than 180 degrees. From the viewpoint of making peeling of the base film 41 easier, the peeling angle is preferably 120 degrees or more and 180 degrees or less.
The peeling angle refers to the angle between the surface direction or transport direction of the laminate when the base film 41 is peeled and the surface direction or transport direction of the base film 41 to be peeled.

In the case where the laminate prepared in the preparation step has a base film 41, an alignment layer 32, and a retardation layer 31, when the base film 41 is peeled off, the alignment layer 32 is peeled off together with the base film 41. In this case, the surface of the retardation expressing layer 31 is exposed on the surface of the laminate through this step. When the alignment layer 32 remains on the laminate without being peeled off, the surface of the alignment layer 32 is exposed on the surface of the laminate.
In the case where the laminate prepared in the preparation step has the base film 41 and the retardation layer 31 but does not have the alignment layer 32, the surface of the retardation layer 31 is added to the surface of the laminate in this step. is exposed.

[3] Lamination process In this process, an optical film is applied to the peeled surface (exposed surface) of the retardation layer 30 after peeling off the base film 41 via an active energy ray-curable adhesive layer (adhesive layer) 20. This is the process of laminating 10 layers. Through this step, a layer structure similar to that shown in FIG. 1 is obtained. The peeling surface may be the surface of the alignment layer 32 or the surface of the retardation layer 31. As the active energy ray-curable adhesive, one having the ability to bond the retardation layer 30 and the optical film 10 is used.

In the lamination process, the optical film 10, the adhesive layer 20, and the retardation layer 30 are laminated so that the adhesive layer 20 and the retardation layer 30 are in contact with each other. Moreover, the optical film 10, the adhesive layer 20, and the retardation layer 30 are preferably laminated so that the optical film 10 and the adhesive layer 20 are in contact with each other.

In the lamination process, an adhesive layer 20 is formed on one or more surfaces selected from the adhesive surface of the optical film 10 and the adhesive surface (peeling surface) of the retardation layer 30, and the adhesive layer 20 is formed on the optical film 10 via the adhesive layer 20. This can be implemented by laminating the retardation layer 30. The adhesive layer 20 can be formed by applying an active energy ray-curable adhesive to the adhesive surface using a known coating method.
In the laminate obtained by the lamination process, the thickness of the adhesive layer 20 is usually 0.5 μm or more and 50 μm or less, from the viewpoint of suppressing wrinkle defects and from the viewpoint of adhesiveness between the optical film 10 and the retardation layer 30. From the viewpoint of reducing the thickness of the resulting optical laminate, the thickness is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less.

One or more surfaces selected from the adhesive surface of the optical film 10 and the adhesive surface (peeling surface) of the retardation layer 30 are subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, etc. before forming the adhesive layer 20. Surface activation treatments such as flame treatment and saponification treatment may also be performed. This surface activation treatment can improve the adhesiveness between the optical film 10 and the retardation layer 30.

The optical film 10 may be a film with a single layer structure or a film with a multilayer structure. Examples of the optical film 10 include a linear polarizing plate. When the optical film 10 is a linearly polarizing plate, preferably the linear polarizer included in the linearly polarizing plate and the adhesive layer 20 are in contact with each other in the laminate obtained by the lamination process.
The optical film 10 and the active energy ray-curable adhesive will be described in more detail in the <Optical laminate> section below.

According to the manufacturing method according to the present embodiment, which includes the above-described peeling step and lamination step, it is possible to manufacture an optical laminate that is less likely to cause wrinkle defects even when curved with a small radius of curvature. This is presumed to be due to the following reasons.
When the base film 41 is peeled from the retardation layer 30 at a peeling speed of 50 m/min or more in the peeling process, the surface (peeled surface) of the retardation layer 30 after peeling becomes rough. Such roughness on the surface of the retardation layer 30 improves the adhesion with the adhesive layer 20 when the adhesive layer 20 is laminated and brought into contact with the surface in the subsequent lamination step.
When the adhesion is improved, the cured adhesive layer (adhesive layer after curing) and the retardation layer 30 deform as one when the optical laminate is curved, thereby suppressing the occurrence of wrinkle defects. It is thought that this will make it easier to do so.
The manufacturing method according to the present embodiment is also advantageous in suppressing rainbow unevenness, which will be described later, in the resulting optical laminate.

In this embodiment, the peeling speed of the base film 41 is controlled as a means for roughening the surface of the retardation layer 30. As another means for roughening, for example, a base film whose at least one surface has been roughened in advance is used, and the retardation layer 30 is formed on this roughened surface. It may also be a laminate prepared in the process.
The surface of the base film 41 can be roughened by a method such as rubbing the surface.

[4] Curing step In this step, an optical laminate having a layer structure similar to that shown in FIG. 2 can be obtained by curing the adhesive layer 20 by irradiating active energy rays to form a cured adhesive layer 20a. can. Regarding this step, the description regarding the curing step of Embodiment 1 is cited.

<Optical laminate>
Referring to FIG. 2, the optical laminate according to the present invention (hereinafter also simply referred to as "optical laminate") includes an optical film 10 and a cured adhesive that is a cured layer of an active energy ray-curable adhesive. The layer 20a and a retardation layer 30 including a retardation developing layer (a layer of a cured product of a polymerizable liquid crystal compound) are provided in this order.
The optical laminate can be suitably applied to image display devices such as organic EL display devices.

In the optical laminate, the cured adhesive layer 20a and the retardation layer 30 are in contact with each other. In the optical laminate, preferably the optical film 10 and the cured adhesive layer 20a are in contact with each other.

In the optical laminate, the surface of the retardation layer 30 on the cured adhesive layer 20a side (surface Xa in FIG. 2) has the following (a) to (d):
(a) the arithmetic mean roughness Sa is 0.065 μm or more;
(b) the root mean square height Sq is 0.085 μm or more;
(c) the developed area ratio Sdr of the interface is 0.2% or more;
(d) One or more of the following conditions is satisfied: the bimodal root mean square slope Sdq is 0.065 or more.

The arithmetic mean roughness Sa, the root mean square height Sq, the developed area ratio Sdr of the interface, and the bimodal root mean square slope Sdq are all indicators of surface roughness, and according to ISO 25178, [Example] Measured by the method described in section.

Since the optical laminate according to the present invention satisfies any one or more of the above (a) to (d), wrinkle defects are unlikely to occur even when curved with a small radius of curvature. This is because the adhesion between the cured adhesive layer 20a and the retardation layer 30 is improved due to the roughness of the surface of the retardation layer 30 on the side of the cured adhesive layer 20a. This is believed to be because the layer 30 deforms as one when the optical laminate is bent.

Further, an optical laminate that satisfies any one or more of the above (a) to (d) is advantageous in that rainbow unevenness can be suppressed in reflected light when viewed from the surface on the optical film 10 side. Being able to suppress rainbow unevenness is advantageous in improving the visibility of an image display device such as an organic EL display device when the optical laminate is applied to the device.
An optical laminate that satisfies any one or more of the above (a) to (d) can suppress rainbow unevenness because the light incident on the inside of the optical laminate is reflected at the interface between each layer, resulting in a difference between the reflected lights. This is thought to be because interference can be suppressed.

An optical laminate that satisfies any one or more of the above (a) to (d) can be suitably manufactured by the manufacturing method according to the present invention described in the section <Method for manufacturing an optical laminate> above.

From the viewpoint of more effectively suppressing the occurrence of wrinkle defects and rainbow unevenness, the optical laminate preferably satisfies any two or more of the above (a) to (d), and more preferably satisfies any two or more of the above (a) to (d). Any three or more of (d) are satisfied, and more preferably all of the above (a) to (d) are satisfied.

The arithmetic mean roughness Sa in the above (a) is preferably 0.067 μm or more, more preferably 0.070 μm or more, from the viewpoint of more effectively suppressing the occurrence of wrinkle defects and rainbow unevenness. The arithmetic mean roughness Sa is usually 0.200 μm or less, and preferably 0.150 μm or less from the viewpoint of reducing the internal haze of the optical laminate, ensuring transparency, and maintaining light transmittance.

The root mean square height Sq in the above (b) is preferably 0.087 μm or more, more preferably 0.090 μm or more, from the viewpoint of more effectively suppressing the occurrence of wrinkle defects and rainbow unevenness. The root mean square height Sq is usually 0.250 μm or less, and preferably 0.200 μm or less from the viewpoint of reducing the internal haze of the optical laminate, ensuring transparency, and maintaining light transmittance.

The developed area ratio Sdr of the interface in (c) above is preferably 0.25% or more, more preferably 0.3% or more, from the viewpoint of more effectively suppressing the occurrence of wrinkle defects and rainbow unevenness. . The developed area ratio Sdr of the interface is usually 1.20% or less, and is preferably 1.10% or less from the viewpoint of reducing the internal haze of the optical laminate, ensuring transparency, and maintaining light transmittance. be.

The bimodal root mean square slope Sdq in the above (d) is preferably 0.070 or more, more preferably 0.072 or more, from the viewpoint of more effectively suppressing the occurrence of wrinkle defects and rainbow unevenness. The bimodal mean square slope Sdq is usually 0.180 or less, and is preferably 0.160 or less from the viewpoint of reducing the internal haze of the optical laminate, ensuring transparency, and maintaining light transmittance.

Elements that constitute or can constitute the optical laminate will be described below.
[1] Optical Film As described above, the optical film 10 may be a film with a single layer structure or a film with a multilayer structure.
Examples of the optical film 10 include a linear polarizing plate, a linear polarizer, and the like.

[2] Linear polarizing plate A linear polarizing plate is an optical element that includes at least a linear polarizer, and may further include a thermoplastic resin film bonded to at least one surface of the linear polarizer. A linear polarizer is an optical element that has the property of transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis when unpolarized light is incident thereon.

The linear polarizer may be, for example, one in which a dichroic dye such as iodine is adsorbed and oriented on an oriented polyvinyl alcohol resin film. The linear polarizer may be a single-layer polyvinyl alcohol resin film (orientated polyvinyl alcohol molecules contained in the polyvinyl alcohol resin film) in which a dichroic dye is adsorbed and oriented. It may be a laminated film of two or more layers provided with a polyvinyl alcohol resin layer in which a color dye is adsorbed and oriented. Such linear polarizers can be manufactured by various methods known in the art.
The thickness of a linear polarizer formed by adsorbing and aligning a dichroic dye to a single layer polyvinyl alcohol resin film is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

The linear polarizer may be a cured film obtained by aligning a dichroic dye to a polymerizable liquid crystal compound and polymerizing the polymerizable liquid crystal compound. The linear polarizer is usually produced by coating a composition containing a polymerizable liquid crystal compound and a dichroic dye on a base film made of a thermoplastic resin film or the like, or on an alignment layer provided thereon, and then drying the composition. However, it can be obtained by polymerizing and curing the polymerizable liquid crystal compound contained in the coating film by irradiating active energy rays such as ultraviolet rays. The thus obtained laminate of the base film and the linear polarizer (cured film) can be used as a linear polarizing plate.

The thickness of the base film for forming the above-mentioned cured film is not particularly limited, but generally from the viewpoint of workability such as strength and handleability, it is preferably 1 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less. and more preferably 30 μm or more and 120 μm or less.

In the linear polarizing plate, the thermoplastic resin film bonded to at least one surface of the linear polarizer includes, for example, polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene polymers; polyethylene terephthalate, polyethylene Polyester resins such as naphthalate; (meth)acrylic acid resins such as methyl poly(meth)acrylate; Cellulose ester resins such as triacetyl cellulose, diacetyl cellulose and cellulose acetate propionate; polyvinyl alcohol and polyvinyl acetate Vinyl alcohol resins such as; polycarbonate resins; polystyrene resins; polyarylate resins; polysulfone resins; polyethersulfone resins; polyamide resins; polyimide resins; polyetherketone resins; polyphenylene sulfide resins; polyphenylene Examples include resin films made of oxide resins, mixtures thereof, copolymers, and the like.
Among the above resins, it is preferable to use any one of a cyclic polyolefin resin, a polyester resin, a cellulose ester resin, and a (meth)acrylic acid resin, or a mixture thereof.
Note that "(meth)acrylic acid" means "at least one of acrylic acid and methacrylic acid."

The thermoplastic resin film may be a single layer made of one resin material or a mixture of two or more resin materials, or may have a multilayer structure of two or more layers. When having a multilayer structure, the resins constituting each layer may be the same or different.
Arbitrary additives may be added to the thermoplastic resin film. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

The thickness of the thermoplastic resin film is preferably 2 μm or more and 300 μm or less, more preferably 5 μm or more and 200 μm or less, from the viewpoint of thinning and flexibility of the optical laminate and the durability of the optical laminate. Preferably it is 5 μm or more and 100 μm or less, still more preferably 5 μm or more and 50 μm or less, particularly preferably 5 μm or more and 30 μm or less.

The thermoplastic resin film can be laminated to the linear polarizer via an adhesive layer.
Examples of the adhesive forming the adhesive layer include water-based adhesives, active energy ray-curable adhesives, and the like.
Examples of water-based adhesives include polyvinyl alcohol resin aqueous solutions, water-based two-component urethane emulsion adhesives, and the like.
Active energy ray-curable adhesives are adhesives that are cured by irradiation with active energy rays such as ultraviolet rays, and include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, and those containing a binder. Examples include those containing a resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth)acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. . Examples of the photopolymerization initiator include those containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays.

The linearly polarizing plate can further include other films or layers than those described above. Other films or layers include a protection film laminated on the surface of the linear polarizing plate; a reflective film, a transflective film, an optical compensation film, a film with an anti-glare function, which is placed at an appropriate position on the linear polarizing plate; Examples include retardation films.

The linear polarizing plate is preferably a single-protected polarizing plate, as shown in FIG. 4, in which a thermoplastic resin film is bonded to only one side of a linear polarizer. When the linear polarizing plate is a single-protection polarizing plate, its thickness is small, and as a result, the thickness of the optical laminate can be reduced. Therefore, for example, an organic EL display device including the optical laminate of the present invention can be easily applied as a flexible organic EL display device that can be bent, folded, rolled, etc.
When the optical film 10 is a single-protection polarizing plate, it is preferable that the linear polarizer in the optical laminate be in contact with the cured adhesive layer 20a.

[3] Cured adhesive layer The cured adhesive layer 20a is a cured product layer of an active energy ray-curable adhesive. The cured adhesive layer 20a can be formed by curing the active energy ray-curable adhesive layer (adhesive layer) 20 formed in the above-described lamination process in a curing process.
As the active energy ray curable adhesive, the same active energy ray curable adhesive as described in [2] above can be used.

In the optical laminate, the thickness of the cured adhesive layer 20a is usually 0.5 μm or more and 50 μm or less. From the viewpoint of making the optical laminate thinner, the thickness is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less.

[4] Retardation layer The retardation layer 30 includes a retardation expression layer 31 which is a layer of a cured product of a polymerizable liquid crystal compound, and may further include an alignment layer 32.

The retardation developing layer 31 is formed using a polymerizable liquid crystal compound, and any known polymerizable liquid crystal compound can be used. The type of polymerizable liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. The polymerizable liquid crystal compound for forming the reverse wavelength dispersive quarter-wave plate is preferably a rod-shaped liquid crystal compound, for example, the polymerizable liquid crystal compound described in JP-A No. 2011-207765.

A composition for forming a retardation layer containing a polymerizable liquid crystal compound, a solvent, and various additives as necessary is applied onto the alignment layer 32 to form a coating film, and this coating film is cured. A retardation expression layer 31, which is a cured layer of a polymerizable liquid crystal compound, can be formed. Alternatively, the retardation layer 31 may be formed by directly applying the composition for forming a retardation layer onto a base film to form a coating film, and stretching this coating film together with the base film.
The thickness of the retardation layer 31 is usually 0.1 μm or more and 10 μm or less, preferably 0.2 μm or more and 5 μm or less.

The composition for forming a retardation layer may contain a polymerization initiator, a reactive additive, a leveling agent, a polymerization inhibitor, etc. in addition to the above-mentioned polymerizable liquid crystal compound and solvent. As the polymerizable liquid crystal compound, solvent, polymerization initiator, reactive additive, leveling agent, polymerization inhibitor, etc., known ones can be used as appropriate.
Examples of the leveling agent that may be included in the composition for forming a retardation layer and the retardation layer include a leveling agent whose main component is an organically modified silicone oil, a leveling agent whose main component is a polyacrylate compound, Examples include leveling agents whose main component is a fluorine atom-containing compound such as perfluoroalkyl. The main component refers to the component that is included in the largest amount out of all the components contained in the leveling agent. The content of the leveling agent in the composition for forming a retardation layer is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.1 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound. The amount is 3 parts by mass or less.

The alignment layer 32, which may be included in the retardation layer 30, is a layer having an alignment regulating force that causes the polymerizable liquid crystal compound included in the liquid crystal layer formed thereon to align the liquid crystal in a desired direction. Examples of the alignment layer 32 include an alignment polymer layer formed of an alignment polymer, a photoalignment polymer layer formed of a photoalignment polymer, and a groove alignment layer having an uneven pattern or a plurality of grooves on the layer surface. be able to.
The thickness of the alignment layer 32 is usually 10 nm or more and 500 nm or less, preferably 10 nm or more and 200 nm or less.

The oriented polymer layer can be formed by applying a composition in which an oriented polymer is dissolved in a solvent to the base film 41, removing the solvent, and performing a rubbing treatment if necessary. In this case, the alignment regulating force can be arbitrarily adjusted depending on the surface condition of the oriented polymer and rubbing conditions.

The photo-alignable polymer layer can be formed by applying a composition containing a polymer having a photo-reactive group or a monomer and a solvent to the base film 41 and irradiating it with polarized light. In this case, the alignment regulating force in the photo-alignable polymer layer can be arbitrarily adjusted by adjusting the polarized light irradiation conditions for the photo-alignable polymer.

The groove alignment layer can be formed, for example, by exposing and developing the surface of a photosensitive polyimide film through an exposure mask having pattern-shaped slits to form a concavo-convex pattern, or by applying activation to a plate-shaped master having grooves on the surface. A method of forming an uncured layer of an energy ray curable resin, transferring this layer to a base film 41 and curing it, forming an uncured layer of an active energy ray curable resin on the base film 41, The layer can be formed by a method of forming irregularities by pressing a roll-shaped master having irregularities on the layer and curing the layer.

As the base film 41, a resin film having the same structure as the above-mentioned thermoplastic resin film can be used.
The thickness of the base film 41 is not particularly limited, but generally from the viewpoint of workability such as strength and handleability, it is preferably 1 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less, and even more preferably 30 μm or more. It is 120 μm or less.
An arbitrary additive may be added to the base film 41. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[5] Retardation layer laminate As described above, in the lamination step of the first embodiment and the preparation step of the second embodiment of the method for manufacturing an optical laminate, the retardation layer 30 and other layers are used as the retardation layer 30. A retardation layer laminate including a retardation layer and a retardation layer laminate may be used.

FIG. 5 is a schematic cross-sectional view showing an example of the layer structure of the retardation laminate. The retardation laminate shown in FIG. 5 includes a base film 41, an orientation layer 32, a retardation layer 31, an adhesive layer 61, a retardation layer 71, an orientation layer 72, and a base film 42 in this order. In the retardation laminate shown in FIG. 5, the retardation layer 31 and the alignment layer 32 can become the retardation layer 30 bonded to the optical film 10 via the cured adhesive layer 20a in the optical laminate.
The retardation laminate shown in FIG. 5 does not need to have at least one of the alignment layer 32 and the alignment layer 72.

In the retardation laminate shown in FIG. 5, the combination of the retardation layer 31 and the retardation layer 71 is, for example, a combination of a 1/2 wavelength plate and a 1/4 wavelength plate, or a reverse wavelength dispersion property. This is a combination of a 1/4 wavelength plate and a positive C plate.
In the case of a combination of a 1/2 wavelength plate and a 1/4 wavelength plate, it is preferable that the retardation developing layer 31 disposed closer to the optical film 10 in the optical laminate is a 1/2 wavelength plate.

When the retardation laminate shown in FIG. 5 is used in the lamination step of the first embodiment or the second embodiment of the method for producing an optical laminate, the retardation laminate has a structure in which the base film 41 is peeled off. After that, it is laminated to the optical film 10 via the adhesive layer 20.
FIG. 6 is an example of the layer structure of an optical laminate manufactured when the retardation laminate shown in FIG. 5 is used in the lamination step of the first embodiment or the second embodiment of the method for manufacturing an optical laminate. FIG. The optical laminate shown in FIG. 6 may not include at least one of the alignment layer 32 and the alignment layer 72.

For example, the retardation laminate shown in FIG. It can be manufactured by producing or preparing a laminate having a layer structure of 1 and bonding these laminates together via the adhesive layer 61.

Examples of the adhesive forming the adhesive layer 61 include water-based adhesives, active energy ray-curable adhesives, and the like. As these adhesives, those similar to the above-mentioned adhesives that can be used for bonding the linear polarizer and the thermoplastic resin film can be used.
An adhesive layer can also be used as the adhesive layer 61. The adhesive composition forming the adhesive layer is a composition in which a (meth)acrylic resin, styrene resin, silicone resin, etc. is used as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, an aziridine compound, etc. is added. can be mentioned.

From the viewpoint of more effectively suppressing the occurrence of wrinkle defects, the adhesive layer 61 is preferably a cured layer of an active energy ray-curable adhesive such as a UV-curable adhesive.

[6] Adhesive layer The optical laminate may further include an adhesive layer. FIG. 7 is a schematic cross-sectional view showing an example of the layer structure of an optical laminate having an adhesive layer 80.
The optical laminate shown in FIG. 7 can be manufactured, for example, by peeling off the base film 42 from the optical laminate shown in FIG. 6 and laminating an adhesive layer on the peeled surface. A separate film may be laminated on the outer surface of the adhesive layer.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Example 1>
(1) Preparation of linear polarizing plate A linear polarizer (thickness: 8 μm), which is a uniaxially stretched film made by adsorbing and orienting iodine on a polyvinyl alcohol resin film, was prepared.
A first thermoplastic resin film is laminated on one surface of the linear polarizer via a polyvinyl alcohol adhesive, and a second thermoplastic resin film is laminated on the other surface of the linear polarizer. The mixture was passed between rolls to obtain a laminate having a layer structure of first thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/second thermoplastic resin film. There is no adhesive between the linear polarizer and the second thermoplastic resin film, and the second thermoplastic resin film is removably laminated on the linear polarizer.

The following were used as the first thermoplastic resin film and the second thermoplastic resin film.
・First thermoplastic resin film: Nippon Paper Industries Co., Ltd.'s clear hard coat film, trade name "COP20ST-HC" (film in which a clear hard coat layer is formed on a cyclic polyolefin resin film, thickness: 25 μm) )
・Second thermoplastic resin film: triacetyl cellulose (TAC) film manufactured by Fujifilm Co., Ltd., product name "FujiTac" (thickness: 80 μm)

The obtained laminate was heat-treated at 80° C. for 300 seconds using a hot air dryer to dry the polyvinyl alcohol adhesive layer to obtain a linear polarizing plate.

(2) Production of retardation layer laminate Retardation films 1 and 2 and active energy ray-curable adhesive 1 shown below were prepared.
・Retardation film 1 which is a 1/2 wavelength plate: Product name "QL FILM QL AA 318" manufactured by Fuji Film Co., Ltd. (base film 1 which is a TAC film with a thickness of 80 μm and an orientation formed thereon) A retardation film with a total thickness of 2 μm consisting of layer 1 and a retardation developing layer 1 (in-plane retardation value of 235 nm) which is a cured product layer (single layer) of a polymerizable liquid crystal compound formed thereon)
・Retardation film 2 which is a quarter wavelength plate: Product name "QL FILM QL AB 318" manufactured by Fuji Film Co., Ltd. (base film 2 which is a TAC film with a thickness of 80 μm and an orientation formed thereon) A retardation film with a total thickness of 1 μm consisting of layer 2 and a retardation developing layer 2 (in-plane retardation value 120 nm) which is a cured product layer (single layer) of a polymerizable liquid crystal compound formed thereon)
・Active energy ray curable adhesive 1: Cationic polymerizable ultraviolet curable high refractive index adhesive

The surface of the retardation layer 1 of the retardation film 1 and the surface of the retardation layer 2 of the retardation film 2 were subjected to corona treatment. The active energy ray-curable adhesive 1 was applied to the corona-treated surface of each of these retardation films using a bar coater so that the total thickness of the adhesive layer after curing was 1.5 μm, and then the retardation film was applied. Film 1 and retardation film 2 are superimposed and passed between a pair of laminating rolls to form base film 1/alignment layer 1/retardation expression layer 1/layer of active energy ray-curable adhesive 1/retardation expression. A laminate having a layer structure of layer 2/alignment layer 2/base film 2 was obtained.

The obtained laminate is irradiated with ultraviolet rays using an ultraviolet irradiation device (the lamp used is "D Bulb" manufactured by Fusion UV Systems) so that the cumulative light intensity is 250 mJ/cm ² (UVB). The layer of active energy ray-curable adhesive 1 was cured to obtain a retardation layer laminate.

(3) Preparation of optical laminate 1 The second thermoplastic resin film of the linear polarizing plate obtained in (1) above is peeled off, and the base material of the retardation layer laminate obtained in (2) above is peeled off. Film 1 was peeled together with alignment layer 1 at a peeling speed of 25 m/min. The peeling angle of the base film 1 with respect to the retardation layer laminate from which the base film 1 was peeled was 180 degrees.
Corona treatment was applied to the surface of the linear polarizer exposed by peeling off the second thermoplastic resin film and the surface of retardation developing layer 1 exposed by peeling off base film 1.
Note that the alignment layer 1 was peeled and removed together with the base film 1.

After applying the active energy ray-curable adhesive 2 to the corona-treated surfaces of the linear polarizing plate and the retardation layer laminate using a bar coater so that the total thickness of the adhesive layer after curing is 2 μm, The polarizing plate and retardation layer laminate are stacked and passed between a pair of laminating rolls to form a layer of first thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/active energy ray-curable adhesive 2. A laminate having a layer structure of /Retardation layer 1/cured layer of active energy ray-curable adhesive 1/Retardation layer 2/Orientation layer 2/Substrate film 2 was obtained.

As the active energy ray curable adhesive 2, the following was used.
・Active energy ray curable adhesive 2: Cationic polymerizable ultraviolet ray curable adhesive

The obtained laminate was placed in a constant temperature and humidity chamber and held (left standing) in an environment at a temperature of 40° C. for 5 hours (holding step). The relative humidity in the holding step was 55% RH (the same applies to other Examples and Comparative Examples).

Thereafter, the laminate is irradiated with ultraviolet rays using an ultraviolet irradiation device (the lamp used is "H Bulb" manufactured by Fusion UV Systems) so that the cumulative light intensity is 400 mJ/cm ² (UVB). The layer of active energy ray-curable adhesive 2 was cured to obtain an optical laminate 1. The environment during ultraviolet irradiation was a temperature of 23° C. and a relative humidity of 55% RH (the same applies to other Examples and Comparative Examples).
In the obtained optical laminate 1, the angle of the fast axis SL1 of the retardation layer 1 (1/2 wavelength plate) with respect to the absorption axis PL of the linear polarizer is 75°, and the angle of the fast axis SL1 of the retardation layer 2 (1/2 wavelength plate) is 75°. The angle of the fast axis SL2 of the 4-wavelength plate was 15°. This optical laminate 1 functioned as a circularly polarizing plate.

(4) Preparation of optical laminate 2 (lamination of adhesive layer on optical laminate 1)
A sheet-like adhesive 1 shown below was prepared.
・Sheet-like adhesive 1: transfer type non-carrier film ((meth)acrylic adhesive layer [thickness: 15 μm], easy peelable film laminated on one side, and laminated on the other side) laminated film with heavy release film)

The base film 2 of the optical laminate 1 obtained in (3) above was peeled together with the alignment layer 2, and the easily peelable film of the sheet-like adhesive 1 was peeled off. Corona treatment was applied to the surface of the retardation layer 2 exposed by peeling off the base film 2 and the surface of the adhesive layer exposed by peeling off the easily peelable film.
Note that the alignment layer 2 was peeled off together with the base film 2.

The optical laminate 1 and the sheet-like adhesive 1 are stacked and passed between a pair of laminating rolls to form a first thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/active energy ray-curable adhesive 2. An optical laminate 2 was obtained having the following layer structure: cured layer of layer/retardation layer 1/cured layer of active energy ray curable adhesive 1/retardation layer 2/adhesive layer/heavy release film. .

<Example 2>
In the holding process, the optical laminate 1 was prepared in the same manner as in Example 1, except that the laminate was attached to the inner wall of a constant temperature and humidity chamber and held (left still) in a vibration environment with a frequency of 10 Hz and an amplitude of 1 mm for 5 hours. Created. The temperature environment in the holding step was 23°C. Further, an optical laminate 2 was produced in the same manner as in Example 1 except that this optical laminate 1 was used.

<Example 3>
In the holding step, an optical laminate 1 was produced in the same manner as in Example 1, except that the laminate was placed in a constant temperature and humidity bath and held (left standing) for 3 days in an environment at a temperature of 23°C. The relative humidity during the holding step was 55% RH. Further, an optical laminate 2 was produced in the same manner as in Example 1 except that this optical laminate 1 was used.

<Example 4>
(1) Production of linearly polarizing plate A linearly polarizing plate was produced in the same manner as in Example 1.

(2) Production of retardation layer laminate A retardation layer laminate was produced in the same manner as in Example 1.

(3) Preparation of optical laminate 1 The second thermoplastic resin film of the linearly polarizing plate obtained in (1) above is peeled together with alignment layer 1, and the retardation layer laminate obtained in (2) above is removed. The base film 1 having the following was peeled off at a peeling speed of 90 m/min. The peeling angle of the base film 1 with respect to the retardation layer laminate from which the base film 1 was peeled was 180 degrees.
After this, an optical laminate 1 was produced in the same manner as in Example 1 except that the holding step was not performed.

(4) Preparation of optical laminate 2 (lamination of adhesive layer on optical laminate 1)
An optical laminate 2 was produced in the same manner as in Example 1 except that the optical laminate 1 obtained in (3) above was used.

<Comparative example 1>
In the holding step, an optical laminate 1 was produced in the same manner as in Example 1, except that the laminate was placed in a constant temperature and humidity chamber and held (left standing) in an environment at a temperature of 23° C. for 5 hours. The relative humidity during the holding step was 55% RH. Further, an optical laminate 2 was produced in the same manner as in Example 1 except that this optical laminate 1 was used.

<Comparative example 2>
First thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/layer of active energy ray curable adhesive 2/retardation layer 1/active energy ray curable adhesive without performing a holding step. After obtaining a laminate having a layer configuration of cured product layer of agent 1/retardation expression layer 2/base film 2, the layer of active energy ray-curable adhesive 2 was immediately cured by irradiation with ultraviolet rays. Optical laminate 1 was produced in the same manner as in Example 1 except for the above. Further, an optical laminate 2 was produced in the same manner as in Example 1 except that this optical laminate 1 was used.

<Comparative example 3>
(1) Production of linearly polarizing plate with adhesive layer A linearly polarizing plate was produced in the same manner as in Example 1.
In addition, a sheet-like adhesive 2 shown below was prepared.
・Sheet-like adhesive 2: transfer type non-carrier film ((meth)acrylic adhesive layer [thickness: 5 μm], easy peelable film laminated on one side, and laminated on the other side) laminated film with heavy release film)

The second thermoplastic resin film of the linearly polarizing plate was peeled off, and the easily releasable film of the sheet-like adhesive 2 was also peeled off. Corona treatment was applied to the surface of the linear polarizer exposed by peeling off the second thermoplastic resin film and the surface of the adhesive layer exposed by peeling off the easily peelable film.
Thereafter, a sheet-like adhesive 2 with a lightly peelable film peeled off is laminated on the surface of the linear polarizer (corona-treated surface) on the corona-treated surface side, and the first thermoplastic resin film/polyvinyl alcohol adhesive layer is formed. A linear polarizing plate with an adhesive layer having a layer structure of /linear polarizer/adhesive layer/heavy release film was obtained.

(2) Production of retardation layer laminate A retardation layer laminate was produced in the same manner as in Example 1.

(3) Preparation of optical laminate 1 The heavy releasable film possessed by the linear polarizing plate with an adhesive layer obtained in the above (1) is peeled off, and the retardation layer laminate obtained in the above (2) is The base film 1 was peeled together with the alignment layer 1 at a peeling speed of 25 m/min. The peeling angle of the base film 1 with respect to the retardation layer laminate from which the base film 1 was peeled was 180 degrees.
Corona treatment was applied to the surface of the adhesive layer exposed by peeling off the heavy release film and the surface of retardation expressing layer 1 exposed by peeling off base film 1.
Note that the alignment layer 1 was peeled and removed together with the base film 1.

Thereafter, a retardation layer laminate is laminated on the corona-treated surface of the linear polarizing plate with an adhesive layer on the corona-treated side, and the first thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/adhesive An optical laminate 1 having a layer structure of layer/retardation layer 1/cured layer of active energy ray-curable adhesive 1/retardation layer 2/base film 2 was obtained.

(4) Preparation of optical laminate 2 (lamination of adhesive layer on optical laminate 1)
An optical laminate 2 was produced in the same manner as in Example 1 except that the optical laminate 1 obtained in (3) above was used.

[Measurement/Evaluation]
(1) Measurement of surface roughness A rectangular laminate piece with a length of 50 mm (long side) and a width of 15 mm with the absorption axis of the linear polarizer in the longitudinal direction was cut out from the optical laminate 2, and a heavy release film was cut out. Peel it off to expose the adhesive layer, and attach the exposed adhesive layer to an acrylic plate (black) to form a test piece [first thermoplastic resin film/polyvinyl alcohol adhesive layer/linear polarizer/active energy ray curing] The layer structure is as follows: cured layer of adhesive 2/retardation layer 1/cured layer of active energy ray curable adhesive 1/retardation layer 2/adhesive layer/acrylic plate (black). ]. This test piece was irradiated with light from the first thermoplastic resin film side, and the optical laminate 1 was measured in layer cross-section analysis mode using a scanning white interference microscope "VertScan" (manufactured by Hitachi Techscience) in accordance with ISO 25178. Measure the arithmetic mean roughness Sa, root mean square height Sq, developed area ratio Sdr of the interface, and bimodal root mean square slope Sdq of the linear polarizer side surface of the retardation layer (retardation expression layer 1). did. The results are shown in Table 1. The measurement conditions were as follows.
Camera: Sony “XCL-32”
Objective lens: 5CTI
Lens barrel: 1.0X
Zoom lens: 1X
Light source: 530White
Measurement device: Piezo Measurement mode: Wave

(2) Evaluation of wrinkle defects A test piece (rectangle) having a length of 50 mm (long side) and a width of 15 mm (short side) with the absorption axis of the linear polarizer in the length direction was cut out from the optical laminate 1.
As shown in Fig. 8, this test piece (S) is curved so that the two short sides (S1) face each other to form a curved part (C) at the center in the long side direction, and while maintaining this state, The curvature diameter (R A 10 mm bending test was conducted by repeating 10 times a reduction step in which the distance between the two glass plates was increased until the curved state was resolved, followed by an expansion step in which the distance between the two glass plates was increased until the curved state was resolved. Note that the two short sides (S1) of the test piece (S) were each fixed to a glass plate (G).
If no wrinkle defects occur in the test piece after the 10 mm bending test, the same test piece is subjected to 5 mm bending by repeating the shrinking process and expanding process 10 times in the same manner as above, except that the curvature diameter R of the bent part is set to 5 mm. The test was conducted.
If no wrinkle defects occur in the test piece after the 5 mm bending test, the same test piece is further subjected to 4 mm bending by repeating the reduction process and the expansion process 10 times in the same manner as above, except that the curvature diameter R of the bend part is set to 4 mm. The test was conducted.
If no wrinkle defects occur in the test piece after the 4 mm bending test, the same test piece is subjected to 3 mm bending by repeating the shrinking process and expanding process 10 times in the same manner as above, except that the curvature diameter R of the bent part is set to 3 mm. The test was conducted.
If no wrinkle defects occur in the test piece after the 3 mm bending test, the same test piece is further subjected to 2 mm bending by repeating the shrinking process and expanding process 10 times in the same manner as above, except that the curvature diameter R of the bent part is set to 2 mm. The test was conducted.

The part of the test piece wrapped around the mandrel was visually observed, and the resistance to wrinkle defects was evaluated according to the following criteria. The results are shown in Table 1.
A: Starting from a 10 mm bending test, no wrinkle defects are observed even after completing a 2 mm bending test.
B: Starting from the 10 mm bending test, no wrinkle defects were observed even after the 3 mm bending test was completed, but when the 2 mm bending test was subsequently performed, wrinkle defects occurred.
C: Starting from the 10 mm bending test, no wrinkle defects were observed even after the 4 mm bending test was completed, but when the 3 mm bending test was subsequently performed, wrinkle defects occurred.

The absorption axis (PL) of the linear polarizer, the fast axis (SL1) of the retardation layer 1, and the fast axis (SL2) of the retardation layer 2 in each test piece are as follows when viewed from the linear polarizer side. It was as shown in FIG. In other words, when viewed from the first thermoplastic resin film side (linear polarizer side), counterclockwise rotation is positive (+), the absorption axis (PL) is +135° with respect to the short side, and the fast axis (SL1) is relative to the short side. The fast axis (SL2) was +120° with respect to the short side. Each test piece functions as a circularly polarizing plate.

(3) Evaluation of rainbow unevenness A test piece (rectangle) with a size of 100 mm in length x 100 mm in width was cut out from the optical laminate 2. The heavy release film was peeled off from this test piece, and the exposed adhesive layer was used to bond it to a flat black acrylic board. In addition, a glass plate [alkali-free glass "Eagle It was made into a laminate.

The obtained laminate for evaluation was placed in a room lit with fluorescent lights. The fluorescent lamp was positioned at a height of 250 mm from the black acrylic board. In this state, the reflected light from the fluorescent lamp was visually observed from the surface of the evaluation laminate (the surface on the glass plate side), and the difficulty of producing rainbow unevenness was evaluated according to the following criteria. The results are shown in Table 1. The reflected light from the fluorescent lamp refers to the light that is emitted from the glass plate side when the light from the fluorescent lamp enters the inside of the optical laminate 2 and is reflected at the interface between each layer.
A: No rainbow unevenness is observed in the reflected light.
B: Very slight rainbow unevenness is observed in the reflected light.
C: Rainbow unevenness is observed in the reflected light (rainbow unevenness is observed more clearly than in B).

10 Optical film, 20 Active energy ray curable adhesive layer (adhesive layer), 20a Cured adhesive layer, 30 Retardation layer, 31, 71 Retardation expression layer, 32, 72 Orientation layer, 41, 42 Base film , 50 linear polarizer, 51, 61 adhesive layer, 52 thermoplastic resin film, 80 adhesive layer.

Claims (6)

A method for manufacturing an optical laminate, comprising:
The optical laminate includes, in this order, an optical film, a cured adhesive layer that is a cured layer of an active energy ray-curable adhesive, and a retardation layer that includes a cured layer of a polymerizable liquid crystal compound,
The manufacturing method includes:
Laminating the optical film, the active energy ray curable adhesive layer, and the retardation layer so that the active energy ray curable adhesive layer and the retardation layer are in contact with each other;
Below (1) to (2):
(1) Hold at a temperature of 30°C or higher for 2 hours or more,
(2) Holding under conditions that satisfy one or more of the following conditions: holding at a temperature of 5°C or more for 2 hours or more under vibration conditions in which the frequency of vibration is 5Hz or more and the amplitude of vibration is 0.5mm or more and,
curing the active energy ray-curable adhesive layer to form the cured adhesive layer;
A method for producing an optical laminate, comprising: in this order. The method for manufacturing an optical laminate according to claim 1, wherein the optical film includes a linear polarizer. In the lamination step, the optical film, the active energy ray-curable adhesive layer, and the retardation layer are laminated so that the linear polarizer and the active energy ray-curable adhesive layer are in contact with each other. Item 2. A method for producing an optical laminate according to item 2. An optical film, a cured adhesive layer that is a cured product layer of an active energy ray-curable adhesive, and a retardation layer containing a cured product layer of a polymerizable liquid crystal compound, in this order,
The cured adhesive layer and the retardation layer are in contact with each other,
The surface of the retardation layer on the cured adhesive layer side has the following (a) to (d):
(a) Arithmetic mean roughness Sa is 0.065 μm or more and 0.150 μm or less,
(b) the root mean square height Sq is 0.085 μm or more;
(c) the developed area ratio Sdr of the interface is 0.2% or more;
(d) An optical laminate that satisfies all of the conditions that the bimodal root mean square slope Sdq is 0.065 or more. The optical laminate according to claim 4, wherein the optical film includes a linear polarizer. The optical laminate according to claim 5, wherein the linear polarizer and the cured adhesive layer are in contact with each other.

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