KR20250018125A - Optical laminate and organic el display device comprising the same - Google Patents

Abstract

[Task] The purpose is to provide an optical laminate that can suppress the occurrence of periodic static curl and suppress the mixing of minute bubbles at the end of the optical laminate when bonded to a display element.
[Solution] An optical laminate in which a third protective film is laminated on the side of the first polarizer protective film of a circular polarizing plate, which has a first polarizer protective film, a first adhesive layer, a polyvinyl alcohol-based polarizing film, a second adhesive layer, a second polarizer protective film, a first adhesive layer, and a phase contrast film composed of a polymer of a polymerizable liquid crystal compound, which are adjacent to each other in this order, through a second adhesive layer,
The thickness of the above phase contrast film is 0.5 to 10 ㎛,
After 48 hours in an environment of a temperature of 40°C and a relative humidity of 60%, the dimensional strain (H1) of the first polarizer protective film, the dimensional strain (H2) of the second polarizer protective film, and the dimensional strain (H3) of the third protective film are expressed by the following equations (1) and (2):
-0.300 ≤ H1-H2 ≤ -0.001 (1)
-0.040 ≤ (H3+H1)-H2 ≤ 0.100 (2)
An optical laminate satisfying .

Description

OPTICAL LAMINATE AND ORGANIC EL DISPLAY DEVICE COMPRISING THE SAME

The present invention relates to an optical laminate and a display device including the optical laminate.

A circular polarizing plate is an optical member in which a polarizing plate and a phase difference plate are laminated, and is used, for example, in a device that displays an image, such as an organic EL image display device, to cut reflected light from an electrode constituting the device and improve visibility. Conventionally, a circular polarizing plate formed by laminating a phase difference plate via an adhesive layer on a polarizing plate in which a polarizer protective film is laminated on both sides of a polarizer has been widely used, and an optical laminate in which an adhesive layer is formed on the phase difference plate side in order to laminate such a circular polarizing plate on a display element is known (e.g., Patent Document 1).

Patent Document 1: Japanese Patent Publication No. 2022-96970

As a polarizer protective film arranged on both sides of a polarizer, there are cases where different materials or thicknesses are combined and used from the same viewpoint of desired function or handleability. In an optical laminate in which different polarizer protective films are laminated on both sides of a polarizer, even in an environment maintained at relatively constant temperature and humidity, such as a clean room environment, the phase difference plate side may become convex and warp over time, which is called static curl, in some cases. In an optical laminate in which such static curl occurs, air is likely to be engulfed when bonding to a display element, easily generating microscopic bubbles at the end of the laminate, and this may lead to display defects in an image display device.

The present invention aims to provide an optical laminate capable of suppressing the occurrence of periodic static curl and suppressing the mixing of minute bubbles at an end of the optical laminate when bonded to a display element.

The inventors of the present invention have conducted thorough studies to solve the above problems and have completed the present invention. That is, the present invention includes the following aspects.

[1] An optical laminate in which a third protective film is laminated on the side of the first polarizer protective film of a circular polarizing plate, which has a first polarizer protective film, a first adhesive layer, a polyvinyl alcohol-based polarizing film, a second adhesive layer, a second polarizer protective film, a first adhesive layer, and a phase contrast film made of a polymer of a polymerizable liquid crystal compound, adjacent to each other in this order, through a second adhesive layer,

The thickness of the above phase contrast film is 0.5 to 10 ㎛,

After 48 hours in an environment of a temperature of 40°C and a relative humidity of 60%, the dimensional strain (H1) of the first polarizer protective film, the dimensional strain (H2) of the second polarizer protective film, and the dimensional strain (H3) of the third protective film are expressed by the following equations (1) and (2):

-0.300 ≤ H1-H2 ≤ -0.001 (1)

-0.040 ≤ (H3+H1)-H2 ≤ 0.100 (2)

An optical laminate satisfying .

[2] The thickness of the second polarizer protective film (T2) and the thickness of the third protective film (T3) are expressed by the following formula (3):

45 ≤ (T3/T2)×100 ≤ 350 (3)

An optical laminate as described in [1] above, satisfying .

[3] An optical laminate as described in [1] or [2], wherein the thickness of the third protective film is 10 to 100 ㎛.

[4] An optical laminate according to any one of [1] to [3], further comprising a cured resin layer on the side opposite to the circular polarizing plate side of the third protective film.

[5] The optical laminate according to any one of [1] to [4], wherein the third protective film is a triacetyl cellulose film or a polymethyl methacrylate polymer film.

[6] An optical laminate according to any one of [1] to [5], wherein the peeling force when peeling the third protective film from the optical laminate is 1 N/25 mm or more.

[7] An organic EL display device including the optical laminate described in [1] above.

According to the present invention, it is possible to provide an optical laminate capable of suppressing the occurrence of periodic static curl and suppressing the mixing of minute bubbles at an end of the optical laminate when bonded to a display element.

Figure 1 is a schematic cross-sectional view showing an example of the layer configuration of the optical laminate of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. In addition, the scope of the present invention is not limited to the embodiments described herein, and various changes can be made within a range that does not harm the spirit of the present invention.

<Optical laminate>

As illustrated in FIG. 1, the optical laminate (13) of the present invention includes a circular polarizing plate (12) in which a first adhesive layer (6) and a phase contrast film (7) composed of a polymer of a polymerizable liquid crystal compound are laminated adjacent to each other in this order on a polarizing plate (11) including a first polarizer protective film (1), a first adhesive layer (2), a polyvinyl alcohol-based polarizing film (3), a second adhesive layer (4), and a second polarizer protective film (5). In addition, the circular polarizing plate (12) has a third protective film (9) via a second adhesive layer (8) on the first polarizer protective film (1) side. The second adhesive layer and the third protective film are usually positioned adjacent to each other. The optical laminate of the present invention comprises a third protective film, separately from the first polarizer protective film and the second polarizer protective film, formed on both sides of the polarizing film in order to protect the polyvinyl alcohol-based polarizing film (hereinafter also simply referred to as a “polarizing film”), and by controlling the dimensional deformation of these three protective films, the occurrence of warping of the optical laminate over time can be suppressed. When the optical laminate of the present invention is incorporated into an image display device or the like, the third protective film (9) is usually inserted into the image display device or the like as a component of the optical laminate (13) without being peeled off from the optical laminate (13). For example, a front plate or the like can be laminated via a pressure-sensitive adhesive layer on the surface of the third protective film opposite to the first adhesive layer.

The optical laminate of the present invention may include, in addition to a first polarizer protective film (hereinafter also referred to as a “first protective film”), a first adhesive layer, a polarizing film, a second adhesive layer, a second polarizer protective film (hereinafter also referred to as a “second protective film”), a first adhesive layer, a phase contrast film composed of a polymer of a polymerizable liquid crystal compound (hereinafter also referred to simply as a “phase contrast film”), a second adhesive layer, and a third protective film, other layers for forming the optical laminate may be included as long as they do not affect the effects of the present invention. Other layers are layers that can be laminated, for example, on the outer side of the third protective film (the side opposite to the second adhesive layer) and/or the outer side of the phase contrast film (the side opposite to the first adhesive layer), and examples thereof include a cured resin layer (hard coat layer, etc.) for protecting a polarizing film or an optical laminate, an optical compensation layer, a second phase contrast layer, an additional adhesive layer other than the first (adhesive) layer and the second (adhesive) layer, a substrate layer, and the like.

In the present invention, when the dimensional deformation rate of the first protective film is H1 and the dimensional deformation rate of the second protective film is H2 after 48 hours in an environment of a temperature of 40°C and a relative humidity of 60%, H1 and H2 are expressed by the following formula (1):

-0.300 ≤ H1-H2 ≤ -0.001 (1)

If the dimensional change rate H1 of the first protective film and the dimensional change rate H2 of the second protective film satisfy the above formula (1), there is a slight difference between the dimensional change rate of the first protective film and the dimensional change rate of the second protective film. If there is such a difference in the dimensional change rates of the two protective films positioned on both sides of the polarizing film via the adhesive layer, warping (curling) that makes the second protective film side convex is likely to occur. Such warping often occurs over time, and may occur even in a relatively constant temperature and humidity environment such as a clean room. For example, if warping occurs during storage, when inserting into an image display device, etc., air may be wrapped around when joining the display element, etc., which may cause a display defect in the image display device.

Typically, in the range of equation (1), the smaller the value of H1-H2, the larger the difference in the rate of dimensional change between the first protective film and the second protective film. Therefore, it is thought that the closer the value of H1-H2 is to -0.300, the more likely it is that curl will occur over time. In the present invention, by providing a third protective film satisfying specific conditions to such a polarizing plate which is prone to curl over time, as described later, the effect of suppressing the occurrence of the curl is excellent. In the present invention, the value of H1-H2 may be, for example, -0.300 or more and -0.005 or less, or -0.300 or more and -0.01 or less, and when such a polarizing plate is included, the effect of the present invention can be more significantly exhibited.

In the present invention, when the dimensional deformation rate of the third protective film after 48 hours in an environment of a temperature of 40°C and a relative humidity of 60% is set to H3, H1, H2 and H3 are expressed by the following formula (2):

-0.040 ≤ (H3+H1)-H2 ≤ 0.100 (2)

As described above, a polarizing plate satisfying equation (1) is prone to causing curl over time due to the difference in the dimensional change rates of the two protective films positioned on both sides of the polarizing film. Equation (2) means that the sum of the dimensional change rates (H3 + H1) of the two protective films (the first protective film and the third protective film) laminated on one side of the polarizer and the dimensional change rate (H2) of the second protective film laminated on the other side of the polarizer are equal. The optical laminate of the present invention is configured so that the dimensional change rates of the respective protective films positioned on both sides of the polarizer satisfy the above relationship, and thus has a high suppression effect against the occurrence of the dimensional curl over time.

When the sum of the dimensional change rates of the first protective film and the third protective film and the dimensional change rate of the second protective film are equal, the occurrence of permanent curling can be effectively suppressed. Accordingly, even after long-term storage of, for example, 6 months or more, the mixing of microscopic bubbles at the end of the optical laminate when bonding to the display element can be suppressed. The value of (H3+H1)-H2 is preferably -0.030 or more and 0.080 or less, more preferably -0.030 or more and 0.060 or less, and even more preferably -0.020 or more and 0.040 or less.

In the present invention, the dimensional change rate H1 of the first protective film is calculated according to the following equation.

Dimensional change rate (H1) = (H1 ₄₈ -H1 ₀ )/H1 ₄₈ × 100 (i)

[In the formula, H1 ₄₈ means a dimension of the first protective film in a predetermined direction after the first protective film has been left to stand alone in an environment of a temperature of 40°C and a relative humidity of 60% for 48 hours, and H1 ₀ means an initial dimension of the first protective film in a predetermined direction before being left to stand in an environment of a temperature of 40°C and a relative humidity of 60% for 48 hours.]

Here, in the present invention, the initial dimension (H1 ₀ ) of the first protective film refers to the dimension at the time when the first protective film, which is the target for obtaining the dimensional change rate, is left in an environment of a temperature of 25°C and a relative humidity of 55% for 168 hours. By performing such pretreatment, it is possible to suppress the occurrence of measurement errors due to storage conditions of the laminate or protective film before measurement. In addition, the "predetermined direction" in the dimension measurement of H1 ₄₈ and H1 ₀ means the same direction. For example, when the first protective film is cut and the initial dimension (H1 ₀ ) in the longitudinal direction is measured, the dimension (H1 ₄₈ ) of the film in the longitudinal direction is measured even after leaving it in a state of 48 hours at 40°C and 60% RH, and the dimensional change rate is calculated. That is, the dimensional change rate H1 is

(1) After the first protective film for which the dimensional change rate is to be obtained is left to stand for 168 hours in an environment of 25℃ and 55% RH, the dimension of the first protective film in a predetermined direction is measured as the initial dimension H1 ₀ .

(2) Then, the first film, whose initial dimensions were measured, was left to stand for 48 hours in an environment of 40°C and 60% RH, and then the dimension H1 ₄₈ in the same direction as the initial dimensions was measured.

This is a value calculated based on the formula (i) from the initial dimension H1 ₀ and dimension H1 ₄₈ obtained in the measurements of (1) and (2) above. The dimensional change rate H1 calculated in this way may represent either a positive value (i.e., elongation or expansion) or a negative value (i.e., shrinkage). In addition, the dimensional change rate may be an average value obtained by measuring each initial dimension H1 ₀ in different plural directions of the film as the measurement target, storing it under the specific storage conditions, and then measuring the dimension H1 ₄₈ in the same direction as each direction in which the initial dimension was measured, and calculating the values based on the formula (i) from the initial dimension H1 ₀ and dimension H1 ₄₈ in the same direction.

The dimensions of the protective film can be measured using an image dimension measuring device such as Nikon NEXIV (VMZ-R4540).

The dimensional change rate H2 of the second protective film and the dimensional change rate H3 of the third protective film can also be measured and calculated in the same manner as H1. In that case, in the measuring method and formula (i) of the dimensional change rate H1 of the first protective film, H1 is read as H2 or H3, H1 ₀ is read as H2 ₀ or H3 ₀ , and H1 ₄₈ is read as H2 ₄₈ or H3 ₄₈ , respectively.

In addition, in the present invention, a cured resin layer such as a hard coat layer or an optical functional layer capable of imparting various optical functions may be formed on the surface of the first to third protective films, as described later. When such a cured resin layer is formed directly on the surface of the protective film, the dimensional change rate is measured and calculated by integrating the cured resin layer and the protective film.

In the present invention, the dimensional change rate of each protective film is not particularly limited as long as it satisfies the relationship of the above formulas (1) and (2), but if the dimensional change rate of the protective film (as an absolute value) becomes large, it becomes difficult to control the relationship of the dimensional change rates among the three protective films. Therefore, in one embodiment of the present invention, the dimensional change rate H1 of the first protective film may be, for example, -0.3 to 0.1, preferably -0.2 to 0.05. In addition, the dimensional change rate H2 of the second protective film may be, for example, -0.1 to 0.3, preferably -0.05 to 0.2. Furthermore, the dimensional change rate H3 of the third protective film may be, for example, -0.1 to 0.3, preferably -0.05 to 0.2. In addition, when the dimensional change rate of each protective film is within the above range, it is advantageous in that the overall dimensional change of the laminate can be suppressed during long-term storage, etc.

In one embodiment of the present invention, the difference between the dimensional change rate H2 of the second protective film and the dimensional change rate H3 of the third protective film is preferably 0.1 or less, preferably 0.06 or less, and more preferably 0.03 or less in absolute value. When the second protective film and the third protective film exhibit the same dimensional change behavior, the static-suppression effect tends to be enhanced.

The dimensional change rate of each protective film varies depending on, for example, the type of material constituting the protective film, the thickness of the protective film, the presence or absence of surface treatment for the protective film, the moisture permeability, etc. That is, by appropriately selecting and combining, for example, the type of material constituting the protective film, the thickness of the protective film, the presence or absence of surface treatment for the protective film, the moisture permeability, etc., the dimensional change rate of the protective film can be controlled within a desired range. For example, when the protective film is composed of a hydrophobic resin, for example, a polyolefin-based resin such as a chain-like polyolefin-based resin and a cyclic polyolefin-based resin; a polyester-based resin such as polyethylene terephthalate; the dimensional change rate tends to show a negative value (i.e., shrinkage). On the other hand, when the protective film is composed of a hydrophilic resin, for example, a cellulose-based resin such as triacetyl cellulose; a polymethyl methacrylate resin (PMMA), etc., the dimensional change rate tends to show a positive value (i.e., elongation or expansion). In addition, for example, when the thickness of the protective film increases, the dimensional change rate also generally tends to increase.

In the laminate of the present invention, the thickness (T2) of the second protective film and the thickness (T3) of the third protective film are as follows:

45 ≤ (T3/T2)×100 ≤ 350 (3)

It is preferable that T2 and T3 satisfy the relationship satisfying Equation (3). When T2 and T3 are in a relationship satisfying Equation (3), the effect of suppressing the occurrence of static curl over time is more excellent, and the effect of suppressing bubble mixing when bonding to a display element, etc. can be further improved. The value of (T3/T2) × 100 is more preferably 80 or more, still more preferably 100 or more, and further more preferably 300 or less, still more preferably 250 or less, and may be, for example, 80 or more and 200 or less, or 80 or more and 190 or less.

In one embodiment of the present invention, the thickness of the third protective film is preferably 10 to 100 µm. When the thickness of the third protective film is within the above range, it is easy to control the value of (H3 + H1) - H2 in formula (2) or the value of (T3 / T2) × 100 in formula (3) to a desired range, and the effect of suppressing the occurrence of static curl over time can be enhanced. In addition, it is advantageous in that a thin optical laminate can be obtained while suppressing the occurrence of static curl. The thickness of the third protective film is preferably 10 to 100 µm, more preferably 10 to 60 µm, even more preferably 10 to 40 µm, and particularly preferably 10 to 25 µm.

The thickness of the third protective film can be measured using a laser microscope or a film thickness meter, and the same applies to the measurement of the thickness of each layer or film constituting the optical laminate, such as the first protective film or the second protective film.

In one embodiment of the present invention, the thickness of the first protective film is preferably 10 to 60 μm, more preferably 20 to 50 μm, and even more preferably 25 to 40 μm. When the thickness of the first protective film is within the above range, the occurrence of periodic curl can be effectively suppressed while also reducing the thickness of the optical laminate.

It is preferable that the first protective film be thinner than the third protective film. If the first protective film is thinner than the third protective film, it is easy to balance the thickness and dimensional change rate in relation to the second protective film located on the opposite side with the polarizer in between, so that it is easy to control the value of (H3+H1)-H2 in equation (2). Accordingly, an improvement in the effect of suppressing the occurrence of static curl over time can be expected.

In one embodiment of the present invention, the thickness of the second protective film is preferably 5 to 60 μm, more preferably 20 to 50 μm, and even more preferably 20 to 40 μm. When the thickness of the second protective film is within the above range, the occurrence of periodic curl can be effectively suppressed while also reducing the thickness of the optical laminate.

The thickness of the second protective film may be the same as or different from the thickness of the first protective film, but in one embodiment of the present invention, it is preferable that the thickness of the first protective film and the thickness of the second protective film are the same. The same thickness of the first protective film and the second protective film means, for example, that the difference in the thickness of these two protective films is 15 μm or less, preferably 10 μm or less. When the thickness of the first protective film and the second protective film is the same, it becomes easy to balance the thickness or dimensional change rate of each protective film positioned on both sides of the polarizer, and it becomes easy to control the value of (H3+H1)-H2 in equation (2). Accordingly, further improvement in the effect of suppressing the occurrence of static curl over time can be expected.

Hereinafter, each component of the optical laminate of the present invention will be described in detail.

(Protective film)

For the first protective film, the second protective film and the third protective film (hereinafter, when simply referred to as “protective film”, it refers to all of the first protective film, the second protective film and the third protective film), for example, a resin film or the like conventionally known in the optical film field can be used, and the material of each protective film can be appropriately selected so as to satisfy the relationship of the above formulas (1) and (2). As the resin constituting the protective film, for example, chain or cyclic polyolefin resins such as polyethylene, polypropylene and norbornene polymers; cellulose resins such as triacetyl cellulose, diacetyl cellulose and cellulose acetate propionate; polyvinyl alcohol; polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; (meth)acrylic resins selected from polymethyl methacrylate resins; polycarbonate; polysulfone; polyether sulfone; polyether ketone; Examples thereof include polyphenylene sulfide and polyphenylene oxide. Among them, from the viewpoints of strength and permeability, a resin selected from a cyclic polyolefin resin, a cellulose resin, and a (meth)acrylic resin is preferable. These may be used alone or in combination of two or more. Such a resin can be formed into a resin film by a known means such as a solvent casting method or a melt extrusion method. As a protective film, a cyclic polyolefin resin film, a cellulose resin film, and an acrylic resin film are preferable.

Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefins as polymerization units. Specifically, examples thereof include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of chain olefins such as ethylene and propylene and cyclic olefins, graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrogenates thereof. Among them, norbornene resins that use norbornene monomers such as norbornene or polycyclic norbornene monomers as the cyclic olefin are preferably used.

A commercially available product may also be used as a cyclic olefin resin film. Examples of commercially available cyclic olefin resin films include "ES-CINA" (registered trademark), "SCA40" (registered trademark) (all manufactured by Sekisui Chemical Co., Ltd.), "ZEONOA FILM" (registered trademark) (manufactured by Offes Co., Ltd.), and "ATON FILM" (registered trademark) (manufactured by JSR Co., Ltd.).

The cellulose-based resin is preferably a cellulose ester-based resin, and is usually an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include triacetyl cellulose, diacetyl cellulose, cellulose tripropionate, and cellulose dipropionate. In addition, a copolymerized product thereof or a product in which some of the hydroxyl groups are modified with other substituents may be used. Among these, triacetyl cellulose (TAC) is preferable.

A commercially available product may also be used as a cellulose-based resin film. Examples of commercially available cellulose-based resin films include "Fujitak Film" (manufactured by Fujifilm Co., Ltd.), "KC8UX2M", "KC8UY", and "KC4UY" (all manufactured by Konica Minolta Co., Ltd.).

As the (meth)acrylic resin, examples thereof include homopolymers of methacrylic acid alkyl esters or acrylic acid alkyl esters, copolymers of methacrylic acid alkyl esters and acrylic acid alkyl esters, etc. Specific examples of the methacrylic acid alkyl esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, etc., and specific examples of the acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, propyl acrylate, etc. As these (meth)acrylic resins, those commercially available as general-purpose (meth)acrylic resins can be used. The (meth)acrylic resin is a polymer of a monofunctional acrylic monomer, and preferably exhibits a glass transition temperature of 25°C or lower, more preferably 0°C or lower. Examples of such a (meth)acrylic resin include polymethyl methacrylate.

In one embodiment of the present invention, it is preferable to use, as the first protective film, a resin film composed of a resin whose dimensional change rate H1 tends to not change or to show a negative value (i.e., shrinkage). Examples of such a resin film include a polyolefin-based resin film, a polyester-based resin film, and the like. Among them, a cyclic polyolefin-based resin film is preferable.

In one embodiment of the present invention, it is preferable to use, as the second protective film, a resin film composed of a resin whose dimensional change rate H2 tends to show a positive value (i.e., elongation or expansion). Examples of such resin films include a cellulose-based resin film, a (meth)acrylic-based resin film, and the like. Among them, a cellulose-based resin film is preferable, and a triacetylcellulose film is particularly preferable.

In one embodiment of the present invention, it is preferable to use, as the third protective film, a resin film composed of a resin whose dimensional change rate H3 tends to show a positive value (i.e., elongation or expansion). Examples of such a resin film include a cellulose-based resin film, a (meth)acrylic-based resin film, and the like. Among them, a cellulose-based resin film or a (meth)acrylic-based resin film is preferable, and a triacetylcellulose film or a polymethyl methacrylate polymer film is preferable.

In the present invention, the combination of the first protective film, the second protective film, and the third protective film can be appropriately determined so that the dimensional change rate of each protective film satisfies the relationship satisfying the above formulas (1) and (2). The first protective film, the second protective film, and the third protective film may be the same or different from each other. When the first protective film is a resin film formed of a different resin from the second protective film and/or the third protective film, the above-mentioned curl suppression effect can be obtained even though it has a configuration that is originally prone to causing curl, and the effect of the present invention tends to be remarkable. In addition, from the viewpoint of easy curl control, it is preferable that the first protective film or the second protective film and the third protective film are films formed of the same resin.

As a combination in which the dimensional change rate of each protective film is easy to control by the relationship expressed by Equations (1) and (2), and the effect of suppressing the occurrence of permanent curl over time can be expected, for example, the following combinations can be mentioned. In addition, the combinations according to the lamination order of the third protective film/first protective film/second protective film are shown below.

Cellulose-based resin film/cyclic polyolefin-based resin film (hereinafter, COP)/cellulose-based resin film, (meth)acrylic-based resin film/COP/cellulose-based resin film, more preferably triacetylcellulose film (hereinafter, TAC)/COP/TAC, polymethyl methacrylate resin (hereinafter, PMMA)/COP/TAC.

In order to provide surface adhesion to the protective film, depending on the configuration of adjacent layers, etc., the film surface may be modified by corona treatment, plasma treatment, flame treatment, etc. In addition, hard coat treatment, anti-reflection treatment, anti-static treatment, etc. may be performed.

In the present invention, the third protective film is inserted into an image display device, etc. as a component of the optical laminate without being peeled off from the optical laminate. For example, a protective film provided to temporarily protect a polarizing plate, etc. before the optical laminate is inserted into the display device is laminated so as to be finally peelable from the optical laminate. If the film is laminated so as to be peelable, it may be difficult to secure sufficient support force to suppress deformation (curl) of the optical laminate in the relationship between the first protective film and the second protective film. Therefore, it is preferable that the third protective film is laminated with a certain or higher adhesive force via the second adhesive layer so as not to be peeled off from other components such as the polarizing plate that constitute the optical laminate. In one embodiment of the present invention, the peeling force when peeling the protective film from the optical laminate is preferably 1 N/25 mm or more. The upper limit thereof is not particularly limited, and it may be firmly bonded to the extent that material destruction, i.e., destruction of the optical laminate, the third protective film, or the second adhesive layer, occurs when attempting to peel it. When the peeling force of the third protective film is equal to or higher than the lower limit, peeling from the optical laminate can be suppressed, and the third protective film can sufficiently function in preventing curl suppression.

The peeling force of the third protective film is a value measured as the peeling force required to peel a layer (for example, the first protective film in Fig. 1) of an optical laminate as a measurement target that is bonded to the third protective film, whose peeling force is measured, via a second adhesive layer. For example, in a test piece in which a surface of the optical laminate as a measurement target, opposite to the third protective film, whose peeling force is measured (for example, the side opposite to the first adhesive layer of the phase contrast film), is bonded or otherwise fixed to a glass plate with an adhesive, the peeling force is measured as the peeling force required to peel the third protective film, whose peeling force is measured, from the optical laminate of the test piece. When the third protective film is peeled, the peeling surface may be between the third protective film and the second adhesive layer, or may be between the layer to which the third protective film is bonded via the second adhesive layer and the second adhesive layer. The above peel strength can be measured according to the 90° peel test method specified in JIS K 6854-1:1999.

The peeling force of the third protective film can be controlled by, for example, the type and thickness of the third protective film, the surface treatment state, the composition and thickness of the layer laminated through the third protective film and the second adhesive layer, the surface treatment state, the type and thickness of the second adhesive layer, etc.

When inserted into a display device, etc., the third protective film positioned on the viewing side may function for image display (display screen, etc.) (for example, to make the image easier to see), and may have optical functions such as a phase difference function (1/4 wavelength plate, etc.), brightness enhancement function, anti-glare function, anti-reflection function, diffusion function, and light gathering function. In that case, the third protective film itself may be a single layer having these optical functions, or may have a multilayer structure in which optical functional layers having various optical functions are formed on a resin film such as the one described above.

In one embodiment of the present invention, the optical laminate of the present invention preferably further comprises a cured resin layer on the side opposite to the circular polarizing plate of the third protective film from the viewpoint of being able to obtain surface scratch prevention and dimensional change rate adjustment functions. The cured resin layer may be, for example, a hard coat layer positioned on the outermost layer of the optical laminate to protect and reinforce the optical laminate, or may be a layer having various optical functions described above (for example, an antiglare layer or an antireflection layer). When the optical laminate includes the cured resin layer, the thickness of the cured resin layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm, and even more preferably 2 to 5 μm. When the thickness of the cured resin layer is within the above range, not only can the desired function of the cured resin layer be exhibited without affecting the function that the third protective film can achieve in the present invention, but also the dimensional change of the third protective film can be adjusted, so that it becomes easy to achieve accurate curl control in the present invention.

(Polyvinyl alcohol polarizing film)

The polyvinyl alcohol-based polarizing film constituting the optical laminate of the present invention is a film having a polarizing function. Such a polarizing film is typically a stretched film having adsorbed a dichroic dye having absorption anisotropy, and can be produced, for example, through a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to thereby adsorb the dichroic dye, a process of treating the polyvinyl alcohol-based resin film having adsorbed the dichroic dye with a boric acid aqueous solution, and a process of washing the film after the treatment with the boric acid aqueous solution.

Polyvinyl alcohol resins can be obtained by saponifying polyvinyl acetate resins. As polyvinyl acetate resins, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith are exemplified. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having ammonium groups.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably about 90 mol% or more, more preferably about 98 mol% or more. The polyvinyl alcohol-based resin may be a partially modified polyvinyl alcohol, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, and preferably in the range of 1,500 to 5,000.

The film formed from such polyvinyl alcohol-based resin is used as the raw film of a polarizing film. The method for forming a film of the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. The film thickness of the polyvinyl alcohol-based raw film can be, for example, about 10 to 150 ㎛.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with a dichroic dye, or may be performed simultaneously with or after dyeing. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment, or may be performed during the boric acid treatment. Furthermore, the uniaxial stretching may be performed in a plurality of these stages. In the uniaxial stretching, the stretching may be performed uniaxially between rolls having different peripheral speeds, or the stretching may be performed uniaxially using a hot roll. Furthermore, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol-based resin film is swollen using a solvent. The stretching ratio is usually about 3 to 8 times.

Dyeing of a polyvinyl alcohol-based resin film with a dichroic dye is accomplished, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye.

As a dichroic dye, specifically, iodine or a dichroic organic dye is used. As a dichroic organic dye, a dichroic direct dye including a disazo compound such as C.I. DIRECT RED 39 and a dichroic direct dye including a compound such as trisazo or tetrakisazo can be mentioned. It is preferable to immerse the polyvinyl alcohol-based resin film in water before dyeing.

When iodine is used as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually adopted. The iodine content in this aqueous solution is usually about 0.01 to 1 part by mass per 100 parts by mass of water. In addition, the potassium iodide content is usually about 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40°C. In addition, the immersion time in this aqueous solution (dyeing time) is usually about 20 to 1,800 seconds.

Meanwhile, when a dichroic organic dye is used as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually adopted. The content of the dichroic organic dye in this aqueous solution is usually about 1×10 ^-4 to 10 parts by mass, preferably about 1×10 ^-3 to 1 part by mass, and more preferably about 1×10 ^-3 to 1×10 ^-2 parts by mass, per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing agent. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80°C. In addition, the immersion time in this aqueous solution (dyeing time) is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can usually be carried out by a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid aqueous solution. The content of boric acid in the boric acid aqueous solution is usually about 2 to 15 parts by mass per 100 parts by mass of water, and preferably about 5 to 12 parts by mass. When iodine is used as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide, and in that case, the content of potassium iodide is usually about 0.1 to 15 parts by mass per 100 parts by mass of water, and preferably about 5 to 12 parts by mass. The immersion time in the boric acid aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature for boric acid treatment is usually 50℃ or higher, preferably 50 to 85℃, and more preferably 60 to 80℃.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be performed, for example, by a method of immersing the polyvinyl alcohol-based resin film treated with boric acid in water. The temperature of the water in the water washing treatment is usually about 5 to 40°C. In addition, the immersion time is usually about 1 to 120 seconds.

After washing, a drying process is performed to obtain a polarizer. The drying process can be performed, for example, using a hot air dryer or a far-infrared heater. The temperature of the drying process is usually about 30 to 100°C, preferably about 50 to 80°C. The time of the drying process is usually about 60 to 600 seconds, preferably about 120 to 600 seconds. By the drying process, the moisture content of the polarizing film is reduced to a practical level. The moisture content is usually about 5 to 20 mass%, preferably about 8 to 15 mass%. When the moisture content is within the above range, a polarizing film having appropriate flexibility and excellent heat stability can be obtained.

In the present invention, the thickness of the polarizing film is preferably 5 to 40 ㎛, more preferably 5 to 30 ㎛, even more preferably 5 to 20 ㎛, and particularly preferably 5 to 15 ㎛.

(First adhesive layer and second adhesive layer)

In the optical laminate of the present invention, a first protective film is laminated on one side of a polarizing film via a first adhesive layer, and a second protective film is laminated on the other side of the polarizing film via a second adhesive layer. These layers are laminated adjacent to each other to form a laminate that functions as a polarizing plate. The first adhesive layer and the second adhesive layer (hereinafter, when simply referred to as an “adhesive layer,” the first adhesive layer and the second adhesive layer are intended) are layers formed of an adhesive. The adhesive layer can be formed of a known adhesive as long as it can function as a layer that bonds the polarizing film and the protective film. As such an adhesive, any conventionally known adhesive can be used without particular limitation, and can be appropriately selected according to the type of the protective film to be bonded, the characteristics required for the optical laminate, or the intended use. As an adhesive that can form the first adhesive layer and the second adhesive layer, for example, an active energy ray-curable adhesive, a water-based adhesive, an organic solvent-based adhesive, and a solvent-free adhesive can be mentioned. Among them, a water-based adhesive or an active energy ray-curable adhesive is preferable.

As a water-based adhesive, it is common to use a composition that uses, for example, a polyvinyl alcohol-based resin or a urethane resin as the main component and, in order to improve adhesiveness, mixes a crosslinking agent or a curing compound, such as an isocyanate-based compound or an epoxy compound.

When a polyvinyl alcohol-based resin is used as the main component of an aqueous adhesive, in addition to partially saponified polyvinyl alcohol and completely saponified polyvinyl alcohol, a modified polyvinyl alcohol-based resin such as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol may be used. An aqueous solution of such a polyvinyl alcohol-based resin is used as the aqueous adhesive. The concentration of the polyvinyl alcohol-based resin in the aqueous adhesive is usually 1 to 10 parts by mass, and preferably 1 to 5 parts by mass, per 100 parts by mass of water.

In an aqueous adhesive containing an aqueous solution of a polyvinyl alcohol-based resin, a curable compound such as a polyhydric aldehyde, a water-soluble epoxy resin, a melamine-based compound, a zirconia-based compound, or a zinc compound can be blended in order to improve adhesiveness. As a water-soluble epoxy resin, there is a water-soluble polyamide-epoxy resin obtained by reacting epichlorohydrin with a polyamide-polyamine obtained by the reaction of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. Commercial products of such polyamide-epoxy resins include, for example, "Sumirezu Resin 650" and "Sumirezu Resin 675" sold by Sumika ChemteX Co., Ltd., and "WS-525" sold by Nippon PMC Co., Ltd. When mixing a water-soluble epoxy resin, the amount added is usually about 1 to 100 parts by mass, and preferably 1 to 50 parts by mass, per 100 parts by mass of the polyvinyl alcohol-based resin.

In addition, when using a urethane resin as the main component of an aqueous adhesive, it is effective to use a polyester ionomer type urethane resin as the main component of the aqueous adhesive. The polyester ionomer type urethane resin referred to here is a urethane resin having a polyester skeleton into which a small amount of ionic components (hydrophilic components) are introduced. Since such an ionomer type urethane resin is emulsified directly in water without using an emulsifier to form an emulsion, it can be used as an aqueous adhesive. When using a polyester ionomer type urethane resin, it is effective to mix a water-soluble epoxy compound as a crosslinking agent.

Each of these components that make up the water-based adhesive is usually used in a state of being dissolved in water. The adhesive layer can be obtained by applying the water-based adhesive to the surface forming the adhesive layer and drying it. Components that do not dissolve in water can be dispersed within the system.

As a method for forming an adhesive layer on a polarizing film using a water-based adhesive, a method of directly applying the adhesive composition described above to the surface of the polarizing film and drying the same may be exemplified. The thickness of the adhesive layer is usually about 0.001 to 5 ㎛, preferably 0.01 ㎛ or more, further preferably 2 ㎛ or less, and more preferably 1 ㎛ or less. When the adhesive layer is within the above range, the necessary adhesiveness can be secured without affecting the static suppression effect obtained by controlling the dimensional change rate of each protective film, or the optical characteristics and/or appearance of the polarizing plate.

An active energy ray-curable adhesive is an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays. Examples of the active energy ray-curable adhesive include a cationic polymerizable adhesive containing an epoxy compound and a cationic polymerization initiator, a radical polymerizable adhesive containing an acrylic curing component and a radical polymerization initiator, an adhesive containing both a cationic polymerizable curing component such as an epoxy compound and a radical polymerization curing component such as an acrylic compound, and further containing a cationic polymerization initiator and a radical polymerization initiator, and an adhesive that does not contain any of these polymerization initiators and is cured by irradiation with an electron beam.

Among these, a radical polymerizable active energy ray-curable adhesive containing an acrylic curing component and a photoradical polymerization initiator, and a cationic polymerizable active energy ray-curable adhesive containing an epoxy compound and a photocationic polymerization initiator are preferable. Examples of the acrylic curing component include (meth)acrylates such as methyl (meth)acrylate and hydroxyethyl (meth)acrylate, and (meth)acrylic acid. The active energy ray-curable adhesive containing an epoxy compound may further contain a compound other than the epoxy compound. Examples of the compound other than the epoxy compound include an oxetane compound and an acrylic compound.

As the photoradical polymerization initiator and the cationic polymerization initiator, an initiator known in the field of active energy ray-curable adhesives can be appropriately selected and used. The content of the photoradical polymerization initiator and the cationic polymerization initiator is usually 0.5 to 20 parts by mass, and preferably 1 to 15 parts by mass, per 100 parts by mass of the active energy ray-curable adhesive.

As a method for forming an adhesive layer on a polarizing film using an active energy ray-curable adhesive, an example thereof includes a method of applying the above-described adhesive composition to the surface of the polarizing film, drying the solvent if necessary, and then irradiating the film with active energy rays to form an adhesive layer. The thickness of the adhesive layer is usually about 0.001 to 5 µm, preferably 0.01 µm or more, more preferably 2 µm or less, and even more preferably 1 µm or less. When the adhesive layer is within the above range, the necessary adhesiveness can be secured without affecting the static-suppressing effect obtained by controlling the dimensional change rate of each protective film, or the optical characteristics and/or appearance of the polarizing plate.

In the optical laminate of the present invention, the first adhesive layer and the second adhesive layer may be the same or different in terms of their composition or thickness, etc.

(First adhesive layer and second adhesive layer)

In the optical laminate of the present invention, a phase contrast film is laminated via a first adhesive layer on a side of the second protective film opposite to the polarizing film. The layers from the first protective film to the phase contrast film are laminated adjacent to each other to form a laminate that functions as a circularly polarizing plate. In addition, a third protective film is laminated via a second adhesive layer on the first protective film side of the circularly polarizing plate. The first adhesive layer and the second adhesive layer (hereinafter, when simply described as a “adhesive layer,” the first adhesive layer and the second adhesive layer are intended) are layers formed with an adhesive (meaning an adhesive, an adhesive, or an agent having these properties). The adhesive layer can be formed with a known adhesive as long as it can function as a layer that bonds the third protective film and the circularly polarizing plate, and the second protective film and the phase contrast film. As such a pressure-sensitive adhesive, any conventionally known pressure-sensitive adhesive can be used without particular limitation, and can be appropriately selected in accordance with the type of protective film or phase-shift film to be bonded, or the characteristics or purpose required for the optical laminate.

As the adhesive that can form the first adhesive layer and the second adhesive layer, examples thereof include the adhesives described above that can form the first adhesive layer, etc., and adhesives whose main component is a resin such as a (meth)acrylic type, a rubber type, a urethane type, an ester type, a silicone type, or a polyvinyl ether type. The adhesive may be an active energy ray-curable adhesive, a heat-curable adhesive, or the like. As the adhesive that forms the first adhesive layer and the second adhesive layer, an adhesive is preferable, and among them, an adhesive that uses a (meth)acrylic resin as a base polymer that is excellent in transparency, weather resistance, heat resistance, etc. is preferable.

The (meth)acrylic resin (base polymer) used in the adhesive may be a polymer or copolymer having as a monomer component one or more types of (meth)acrylic acid esters, such as butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate. Furthermore, the (meth)acrylic resin may be one obtained by copolymerizing a polar monomer. As polar monomers, examples thereof include monomers having a carboxylic acid group, a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

In one embodiment of the present invention, the structural unit derived from the (meth)acrylic acid ester in the (meth)acrylic resin constituting the adhesive is preferably 80 to 100 mass%, more preferably 85 mass% or more, and even more preferably 90 mass% or more, relative to the total mass of all structural units constituting the (meth)acrylic resin. In addition, when the (meth)acrylic resin includes a structural unit derived from a polar monomer, the structural unit derived from the polar monomer is preferably 0.1 to 10 mass%, more preferably 0.5 mass% or more, even more preferably 1 mass% or more, and further more preferably 8 mass% or less.

The weight average molecular weight (hereinafter also simply referred to as "Mw") of the (meth)acrylic resin is preferably 500,000 to 2.5 million. When the weight average molecular weight is 500,000 or more, the durability of the first adhesive layer under a high temperature and high humidity environment can be improved. When the weight average molecular weight is 2.5 million or less, the operability when applying the adhesive becomes good. The molecular weight distribution (Mw/Mn) expressed by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (hereinafter also simply referred to as "Mn") is usually 2 to 10. The weight average molecular weight and the number average molecular weight in this specification are polystyrene conversion values measured by the gel permeation chromatography (GPC) method.

The adhesive may contain only the acrylic resin, but may also use a crosslinking agent in combination. Examples of the crosslinking agent include a divalent or higher metal ion that forms a carboxylic acid metal salt with the carboxyl group; a polyamine compound that forms an amide bond with the carboxyl group; a polyepoxy compound or polyol that forms an ester bond with the carboxyl group; and a polyisocyanate compound that forms an amide bond with the carboxyl group. Among them, a polyisocyanate compound is preferable from the viewpoints of crosslinking speed and durability.

When a crosslinking agent is included, the ratio is, for example, 0.01 to 10 parts by mass, preferably 0.1 to 3 parts by mass, and more preferably 0.1 to 1 part by mass, with respect to 100 parts by mass of the base polymer.

The pressure-sensitive adhesive may further contain a silane compound as needed. By containing the silane compound, the adhesion between the pressure-sensitive adhesive layer formed with the pressure-sensitive adhesive and the laminated layer can be improved. Examples of the silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylethoxydimethylsilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and the like. These can be used alone or in combination of two or more.

When a silane compound is included, its content in the adhesive is usually 0.01 to 10 parts by mass, preferably 0.03 to 5 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, per 100 parts by mass of the base polymer.

In this specification, an active energy ray-curable pressure-sensitive adhesive means an adhesive that has a property of being cured when irradiated with active energy rays such as ultraviolet rays or electron rays, can adhere to an adherend such as a film with adhesiveness even before irradiation with active energy rays, and can be cured by irradiation with active energy rays to adjust adhesion, etc. It is preferable that the active energy ray-curable pressure-sensitive adhesive is an ultraviolet ray-curable pressure-sensitive adhesive.

The active energy ray-curable adhesive is generally composed of a base polymer such as (meth)acrylic resin and a crosslinking agent as described above, in addition to an energy ray polymerizable compound. In addition, a photopolymerization initiator or a photosensitizer may be included as needed.

Examples of the active energy ray polymerizable compound include (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule; (meth)acrylic compounds such as (meth)acrylate oligomers obtained by reacting two or more functional group-containing compounds and having at least two (meth)acryloyloxy groups in the molecule; and the like.

The adhesive may further contain conventional components as components that constitute the adhesive. Such components include, for example, additives such as resins other than the base polymer, tackifiers, fillers (such as metal powders or other inorganic powders), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoamers, and corrosion inhibitors.

In one embodiment of the present invention, the first adhesive layer and the second adhesive layer may be composed of a reaction product of an adhesive including a base polymer such as a (meth)acrylic resin, a crosslinking agent, and a silane compound as described above. Such an adhesive layer may be formed by applying, for example, an organic solvent dilution of an adhesive including the above components, to a surface on which the adhesive layer is to be formed, and drying the same.

In addition, in one embodiment of the present invention, the first adhesive layer and the second adhesive layer may be layers formed of an active energy ray-curable adhesive. When the adhesive layer is formed of an active energy ray-curable adhesive, for example, an organic solvent dilution of an adhesive comprising the components described above is applied to a surface on which the adhesive layer is formed, and the adhesive layer formed by drying is irradiated with an active energy ray, thereby forming a cured layer having a desired degree of curing.

The first adhesive layer and the second adhesive layer may be the same or different in terms of composition, thickness, and configuration.

The thickness of the first adhesive layer can be appropriately determined depending on the composition of the adhesive, the configuration or size of the optical laminate, etc. In one embodiment of the present invention, the thickness of the first adhesive layer is usually 1 to 30 µm, preferably 5 to 25 µm, and more preferably 5 to 20 µm. When the thickness of the first adhesive layer is within the above range, the phase contrast film can be bonded with high adhesion, and a thin laminate structure having an excellent effect of suppressing the occurrence of static curl over time can be formed.

The thickness of the second adhesive layer can be appropriately determined depending on the composition of the adhesive, the configuration or size of the optical laminate, etc. In one embodiment of the present invention, the thickness of the second adhesive layer is preferably 1 to 50 μm, more preferably 3 to 25 μm, and even more preferably 5 to 15 μm. When the thickness of the second adhesive layer is within the above range, the third protective film can be bonded to the first protective film side of the polarizing plate with high adhesion, and a laminate structure having an excellent effect of suppressing the occurrence of static curl over time can be formed.

The water vapor permeability of the first adhesive layer and the second adhesive layer at a temperature of 40°C and a relative humidity of 90% is preferably 1,000 to 10,000 g/m ² ·24h, more preferably 2,000 to 9,000 g/m ² ·24h, respectively. When the water vapor permeability of the adhesive layer is within the above range, deformation is unlikely to occur even in a high-temperature and high-humidity environment, and the effect of suppressing the occurrence of static curl over time can be improved. The water vapor permeability of the adhesive layer can be controlled within a desired range depending on the composition, thickness, etc. of the adhesive forming the adhesive layer.

The water vapor permeability of the adhesive layer can be measured using a water vapor permeability meter. In cases where it is difficult to measure the water vapor permeability of the adhesive layer alone, the adhesive may be bonded to a highly moisture-permeable substrate, and then the water vapor permeability may be calculated from the ratio to the highly moisture-permeable substrate.

In the optical laminate of the present invention, the storage elastic moduli of the first adhesive layer and the second adhesive layer are preferably 0.01 MPa or more, more preferably 0.05 MPa or more, particularly preferably 0.07 MPa or more, and 0.5 MPa or less, more preferably 0.2 MPa or less, particularly preferably 0.15 MPa or less. When the storage elastic moduli of the adhesive layers are within the above range, misalignment is unlikely to occur between layers bonded via the adhesive layers, and the effect of suppressing curling can be improved. The storage elastic modulus of the adhesive layer can be controlled within a desired range depending on the composition of the adhesive forming the adhesive layer, etc. In the adhesive layer formed with an active energy ray-curable adhesive, the storage elastic modulus can often be increased.

The storage elastic modulus of the adhesive layer can be measured using a viscoelasticity measuring device. Specifically, it can be measured by, for example, the method described in the examples described below.

The glass transition temperature (Tg) of the first adhesive layer and the second adhesive layer is preferably room temperature (25°C) or lower, more preferably 0°C or lower, and usually -40°C or higher. When the glass transition temperature of the adhesive layer is within the above range, sufficient adhesive strength can be exerted. The glass transition temperature of the adhesive layer can be controlled within a desired range depending on the type or amount of the base polymer, etc. included in the adhesive forming the adhesive layer, the type or amount of the monomer used to form the polymer, the combination, etc.

The glass transition temperature of the adhesive layer can be measured, for example, by the method described in the examples described below.

(phase barrier)

In the optical laminate of the present invention, the phase contrast film laminated adjacent to the first adhesive layer is composed of a polymer of a polymerizable liquid crystal compound. If the phase contrast film bonded to the polarizing plate via the first adhesive layer is a cured layer (cured film) of a polymerizable liquid crystal compound, a thin circularly polarizing plate can be formed compared to a case where the layer having the phase contrast includes a stretched film; however, since the phase contrast film is a thin film (e.g., 5 µm or less), curling is likely to occur over time. In the optical laminate of the present invention, by forming a third protective film on the surface opposite to the phase contrast film of the circularly polarizing plate, and controlling the third dimensional change rate in the relationship between the first protective film and the second protective film, the occurrence of curling, which is likely to occur originally, can be effectively suppressed by utilizing a thin-film phase contrast film.

From the viewpoint that the above effect is likely to become remarkable, in one embodiment of the present invention, the thickness of the phase contrast film laminated adjacent to the first adhesive layer is 0.5 to 5 µm, preferably 0.5 to 3.0 µm, and more preferably 1.0 to 3.0 µm. Furthermore, in the present invention, the phase contrast film is a film showing a phase difference in the plane or in the thickness direction, and may be a single layer containing a polymer of a polymerizable liquid crystal compound, or, when a layer containing the polymer and an alignment film for forming the same exist adjacent to each other, the alignment film may be included. When the phase contrast film includes an alignment film, a thickness of 0.1 to 5 µm is further added.

In the present specification, the phase contrast film may be included in one or two or more. When two or more phase contrast films are included, the thickness of each phase contrast film can be appropriately determined according to the optical characteristics required for each phase contrast film, the configuration or use of the optical laminate, etc., and the thicknesses may be the same or different. Hereinafter, when the optical laminate includes two or more phase contrast films, a plurality of phase contrast films laminated via an adhesive layer may be referred to as a composite phase contrast film. The total thickness of the composite phase contrast film, that is, two or more phase contrast films and an adhesive layer interposed therebetween, is preferably 15 µm or less, more preferably 10 µm or less, even more preferably 8 µm or less, and particularly preferably 6 µm or less.

In order for the optical laminate of the present invention to function as a circular polarizing plate, the optical laminate is composed of the following formula (4):

120 nm ≤ Re(550) ≤ 170 nm (4)

〔In the formula, Re(λ) represents the in-plane phase difference value of the phase difference film at wavelength λ nm〕

It is preferable to include a phase contrast film satisfying the above equation (4). That is, when the optical laminate of the present invention includes only one phase contrast film, it is preferable that the phase contrast film satisfies the above equation (4).

When the in-plane phase difference Re(550) of the phase difference film is within the range of equation (4), the phase difference film becomes a phase difference film that functions as a 1/4 wavelength plate, and when an optical laminate (circular polarizing plate) including the phase difference film is applied to an organic EL display device or the like, the effect of improving the front reflection color (the effect of suppressing coloring) is likely to be enhanced. A more preferable range of the in-plane phase difference value is 130 nm ≤ Re(550) ≤ 150 nm.

In addition, the phase difference film is added to equation (4) by the following equations (5) and (6):

Re(450)/Re(550) ≤ 1.00 (5)

1.00 ≤ Re(650)/Re(550) (6)

〔In the formula, Re(λ) represents the in-plane phase difference value of the phase difference film at wavelength λ nm〕

It is preferable that the phase contrast film satisfies equations (5) and (6). When the phase contrast film satisfies equations (5) and (6), the phase contrast film exhibits so-called reverse wavelength dispersion, in which the in-plane phase difference value at a short wavelength is smaller than the in-plane phase difference value at a long wavelength. An optical laminate (circular polarizing plate) having such a phase contrast film tends to have excellent frontal color when inserted into an organic EL display device, etc. From the viewpoint that the reverse wavelength dispersion is improved and the effect of improving the reflection color in the frontal direction can be further enhanced, Re(450)/Re(550) is preferably 0.70 or more, more preferably 0.78 or more, and further preferably 0.92 or less, more preferably 0.90 or less, even more preferably 0.87 or less, particularly preferably 0.86 or less, and further particularly preferably 0.85 or less. In addition, Re(650)/Re(550) is preferably 1.01 or more, more preferably 1.02 or more.

The above in-plane retardation value can be adjusted by the film thickness (dA) of the retardation film. The in-plane retardation value is determined by the formula ReA(λ) = (nxA(λ)-nyA(λ))×dA [wherein nxA(λ) represents the principal refractive index at wavelength λ nm in the in-plane of the retardation film, nyA(λ) represents the refractive index at wavelength λ nm in the direction orthogonal to the direction of nxA in the same plane as nxA, and dA represents the film thickness of the retardation film]. Therefore, in order to obtain a desired in-plane retardation value (ReA(λ): in-plane retardation value of the retardation film at wavelength λ (nm)), the three-dimensional refractive index and the film thickness (dA) can be adjusted.

The optical laminate of the present invention preferably includes a phase contrast film including a "horizontal alignment liquid crystal cured film" in which a polymerizable liquid crystal compound is cured in a state in which the polymerizable liquid crystal compound is aligned in a horizontal direction with respect to the phase contrast film plane. When the optical laminate of the present invention includes only one phase contrast film, the phase contrast film is usually a "horizontal alignment liquid crystal cured film" and preferably satisfies the above formulas (4) to (6).

The optical laminate of the present invention may further include, in addition to the phase contrast film having a quarter-wave plate function, a phase contrast film which is a positive C plate (nx≒ny < nz). The phase contrast film which is a positive C plate is a "vertical alignment liquid crystal cured film" in which a polymerizable liquid crystal compound is cured in a state in which it is aligned in a direction perpendicular to the phase contrast film plane. By including a combination of the phase contrast film having a quarter-wave plate function and the phase contrast film which is a positive C plate, when the optical laminate is applied to an organic EL display device or the like, in addition to an improvement in the front reflection color, an improvement in the oblique reflection color can also be expected.

When the optical laminate of the present invention includes a phase contrast film that is a positive C plate, it is preferable that the phase contrast film (hereinafter also referred to as a “vertical alignment liquid crystal cured film”) satisfies equations (7) to (9).

Rth(450)/Rth(550) ≤ 1.00 (7)

1.00 ≤ Rth(650)/Rth(550) (8)

-100 nm ≤ Rth(550) ≤ -40 nm (9)

〔In the formula, Rth(λ) represents a thickness direction phase difference value at a wavelength λnm of the vertically aligned liquid crystal cured film, and RthC = ((nxC(λ)+nyC(λ))/2-nzC)×dC (in the formula, dC represents a thickness of the vertically aligned liquid crystal cured film, nxC represents a principal refractive index at a wavelength λnm in a direction parallel to a plane of the vertically aligned liquid crystal cured film, in a refractive index ellipsoid formed by the vertically aligned liquid crystal cured film, nyC represents a refractive index at a wavelength λnm in a direction parallel to the plane of the vertically aligned liquid crystal cured film and also orthogonal to the direction of nxC, in the refractive index ellipsoid formed by the vertically aligned liquid crystal cured film, and nzC represents a refractive index at a wavelength λnm in a direction perpendicular to the plane of the vertically aligned liquid crystal cured film, in the refractive index ellipsoid formed by the vertically aligned liquid crystal cured film).〕

When the vertical alignment liquid crystal curing film satisfies equations (7) and (8), in a circular polarizing plate including the phase difference film (vertical alignment liquid crystal curing film), the decrease in ellipticity on the short wavelength side can be suppressed, thereby improving the all-round reflection color. The value of Rth(450)/Rth(550) in the vertical alignment liquid crystal curing film is preferably 0.70 or more, more preferably 0.78 or more, and further preferably 0.92 or less, more preferably 0.90 or less, even more preferably 0.87 or less, particularly preferably 0.86 or less, and further particularly preferably 0.85 or less. Furthermore, Rth(650)/Rth(550) is preferably 1.01 or more, more preferably 1.02 or more.

In addition, when the phase contrast film, which is a positive C plate, satisfies equation (9), the all-round reflection color can be improved when an optical laminate (circular polarizing plate) including the phase contrast film is applied to an organic EL display device. The phase contrast value Rth(550) in the film thickness direction of the phase contrast film (vertically aligned liquid crystal cured film) is more preferably -90 nm or more, even more preferably -80 nm or more, and further, more preferably -50 nm or less.

The optical laminate of the present invention may further include a phase contrast film having a 1/2 wavelength plate function in addition to a phase contrast film having a 1/4 wavelength plate function. In this case, examples of the phase contrast film functioning as a 1/4 wavelength plate include those satisfying the following equations (10), (12), and (13). In addition, examples of the phase contrast film functioning as a 1/2 wavelength plate include those satisfying the following equations (11), (12), and (13).

100 nm < Re(550) < 160 nm (10)

200 nm < Re(550) < 320 nm (11)

Re(450)/Re(550) ≥ 1.00 (12)

1.00 ≥ Re(650)/Re(550) (13)

By laminating a phase shift film having a 1/4 wavelength plate function and a phase shift film having a 1/2 wavelength plate function so that their primary axes intersect each other at an angle of approximately 60 degrees, the film can function as a 1/4 wavelength plate over a wide range (broadband) spanning approximately the entire visible light spectrum.

As a method for obtaining a composite phase contrast film further including a phase contrast film having a 1/2 wavelength plate function in addition to a phase contrast film having a 1/4 wavelength plate function, there can be mentioned, for example, the methods described in Japanese Patent Application Laid-Open No. 2015-163935 and WO2013/137464. From the viewpoint of viewing angle compensation that provides the same field of view as when viewed from the front even in an oblique direction, it is preferable that the phase contrast film having a 1/2 wavelength plate function is a phase contrast film formed of a disc-shaped liquid crystal compound, and the phase contrast film having a 1/4 wavelength plate function is a phase contrast film formed of a rod-shaped liquid crystal compound.

The above-mentioned phase-shift film having a 1/4 wavelength plate function, the phase-shift film functioning as a positive C layer, and the phase-shift film having a 1/2 wavelength plate function may each be tilt-aligned, cholesterically aligned, or nematically aligned.

In the present invention, the polymerizable liquid crystal compound capable of forming a phase contrast film can be appropriately selected from polymerizable liquid crystal compounds conventionally known in the field of phase contrast films, depending on the desired optical properties. The polymerizable liquid crystal compounds usable in the present invention can be classified, for example, based on their shapes, into rod-shaped types (rod-shaped liquid crystal compounds) and disc-shaped types (disco-shaped liquid crystal compounds, discotic liquid crystal compounds), and any liquid crystal compound can be used. In addition, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds may be used.

A polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable group. As the polymerizable liquid crystal compound, a polymer (cured product) obtained by polymerizing the polymerizable liquid crystal compound alone while being oriented in a specific direction can be exemplified, a polymerizable liquid crystal compound exhibiting forward wavelength dispersion and a polymerizable liquid crystal compound exhibiting reverse wavelength dispersion. In the present invention, only one type of the polymerizable liquid crystal compound may be used, or both types of the polymerizable liquid crystal compounds may be mixed and used. In addition, when the optical laminate includes a phase contrast film having a quarter wavelength plate function and a phase contrast film including a liquid crystal cured film that is a positive C plate, the polymerizable liquid crystal compounds constituting them may be the same or different. For example, when the phase contrast film having a quarter wavelength plate function and/or the phase contrast film including the liquid crystal cured film that is a positive C plate are cured films of a polymerizable liquid crystal composition including a polymerizable liquid crystal compound exhibiting so-called reverse wavelength dispersion, the optical properties as the optical laminate are likely to be improved.

In the present invention, the polymerizable group of the polymerizable liquid crystal compound forming the phase contrast film is preferably a photopolymerizable group. The photopolymerizable group is a polymerizable group and refers to a group that can participate in a polymerization reaction by a reactive species generated from a photopolymerization initiator, such as an active radical or an acid. Examples of the photopolymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, a (meth)acryloyl group, an oxiranyl group, and an oxetanyl group. Among them, a (meth)acryloyl group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyl group is more preferable.

The liquid crystal properties exhibited by the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, but thermotropic liquid crystal is preferable because it allows for tight film thickness control. In addition, as for the phase order structure in the thermotropic liquid crystal, nematic liquid crystal, smectic liquid crystal, or discotic liquid crystal may be used. The polymerizable liquid crystal compounds may be used alone or in combination of two or more.

In the present invention, the phase contrast film may be configured to include an alignment film. The alignment film has an alignment regulating power that aligns the polymerizable liquid crystal compound in a desired direction, and by applying a polymerizable liquid crystal composition onto the alignment film, it is easy to obtain a phase contrast film that is precisely aligned. As the alignment film, it is preferable to have solvent resistance that does not dissolve due to application of a polymerizable liquid crystal composition, and further, heat resistance in the removal of the solvent or heat treatment for orientation of the polymerizable liquid crystal compound. As the alignment film, examples thereof include an alignment film containing an aligning polymer, a photoalignment film, a groove alignment film having an uneven pattern or a plurality of grooves on the surface, and a stretched film stretched in the alignment direction. These various alignment films can be appropriately selected from those known in the art according to the desired alignment regulating power.

In one embodiment of the present invention, as a horizontal alignment film having an alignment control force for horizontally orienting a polymerizable liquid crystal compound, a photo-alignment film is preferable from the viewpoints of alignment angle precision and quality. The photo-alignment film is also advantageous in that the direction of the alignment control force can be arbitrarily controlled by selecting the polarization direction of the polarized light to be irradiated.

The photoalignment film can be obtained by applying a composition containing a polymer, oligomer or monomer having a photoreactive group and a solvent (hereinafter also referred to as a “photoalignment film-forming composition”) onto a substrate or the like and irradiating it with polarized light (preferably polarized UV). If the polymer or the like included in the photoalignment film-forming composition has a reactive group (e.g., a (meth)acryloyl group) that is the same as a functional group of a polymerizable group of a polymerizable liquid crystal compound forming a phase contrast film, the adhesion between the cured layer of the polymerizable liquid crystal compound and the alignment film tends to be improved.

A photoreactive group refers to a group that generates liquid crystal alignment ability by irradiating light. Specifically, examples thereof include groups that are involved in a photoreaction that is the origin of liquid crystal alignment ability, such as molecular alignment induction, isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction caused by irradiating light. Among these, a group that is involved in a dimerization reaction or photocrosslinking reaction is preferable in that it has excellent alignment property. As the photoreactive group, a group having an unsaturated bond, particularly a double bond, is preferable, and a group having at least one selected from the group consisting of a carbon-carbon double bond (C=C bond), a carbon-nitrogen double bond (C=N bond), a nitrogen-nitrogen double bond (N=N bond), and a carbon-oxygen double bond (C=O bond) is particularly preferable.

In order to provide an orientation control force to the alignment film, a rubbing treatment can be performed as needed (rubbing method). As a method of providing an orientation control force by a rubbing method, an example of a method is a method in which an orientation polymer composition is applied to a substrate and annealed on a rubbing roll in which a rubbing cloth is wound and rotated, thereby bringing the film of the orientation polymer formed on the surface of the substrate into contact. When masking is performed during the rubbing treatment, a plurality of regions (patterns) with different orientation directions can be formed on the alignment film.

When the optical laminate of the present invention includes a composite phase contrast film as the phase contrast film, the plurality of included phase contrast films may be respectively bonded via a pressure-sensitive adhesive layer, and a phase contrast film composed of a polymer of a polymerizable liquid crystal compound may be laminated on another phase contrast film with or without an alignment film. For example, when a phase contrast film including a phase contrast film having a quarter-wave plate function and a liquid crystal cured film that is a positive C plate is included, these phase contrast films may be bonded via a pressure-sensitive adhesive layer, and a phase contrast film including a liquid crystal cured film that is a positive C plate may be laminated on a phase contrast film having a quarter-wave plate function with or without an alignment film having a vertical alignment regulating force, or a phase contrast film having a quarter-wave plate function may be laminated on a phase contrast film including a liquid crystal cured film that is a positive C plate with or without an alignment film having a horizontal alignment regulating force. When the optical laminate includes two or more different phase contrast films on the side opposite to the polarizing film of the first adhesive layer, the order of lamination is not particularly limited. For example, even if a phase contrast film having a 1/4 wavelength plate function is adjacent to the first adhesive layer, a phase contrast film including a liquid crystal curing film that is a positive C plate or a phase contrast film having a 1/2 wavelength plate function may be adjacent to the first adhesive layer.

As a point-of-contact adhesive for bonding multiple phase-shift films, an adhesive such as the one described as an adhesive for forming the first and second adhesive layers can be used.

When laminating a phase contrast film having a 1/4 wavelength plate function on a polarizing plate, it is preferable to laminate so that the ground axis (optical axis) of the phase contrast film and the absorption axis of the polarizing film are substantially at 45°. By laminating so that the ground axis (optical axis) of the phase contrast film and the absorption axis of the polarizing film are substantially at 45°, the function as a circular polarizing plate can be obtained. In this case, substantially at 45° is usually in the range of 45±5°.

The optical laminate of the present invention can be manufactured by forming and laminating a third protective film, a second adhesive layer, a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, a second protective film, a first adhesive layer, and a phase contrast film in an appropriate order according to the manufacturing method described above for each layer so as to have a desired configuration depending on the intended use, etc.

For example, a polarizing plate is manufactured by laminating a first protective film on one side of a polarizing film and a second protective film on the other side through adhesive layers, respectively. In contrast to this, a phase contrast film formed on a substrate through an alignment film is manufactured, and the polarizing plate and the phase contrast film are bonded together by a pressure-sensitive adhesive to manufacture a circularly polarizing plate. Next, by laminating a third protective film on the first protective film side of the circularly polarizing plate through a pressure-sensitive adhesive, an optical laminate including third protective film/second pressure-sensitive adhesive layer/first protective film/first adhesive layer/polarizing film/second adhesive layer/2 protective film/first pressure-sensitive adhesive layer/phase contrast film, as illustrated in FIG. 1, can be obtained. In addition, by forming a cured resin layer on the side opposite to the second adhesive layer of the third protective film, an optical laminate including cured resin layer/third protective film/second adhesive layer/first protective film/first adhesive layer/polarizing film/second adhesive layer/second protective film/first adhesive layer/phase contrast film can be obtained. In addition, by laminating an additional phase contrast film on a circularly polarizing plate through the adhesive, an optical laminate including, for example, third protective film/second adhesive layer/first protective film/first adhesive layer/polarizing film/second adhesive layer/second protective film/first adhesive layer/phase contrast film/adhesive layer/phase contrast film can be obtained.

The optical laminate of the present invention is unlikely to cause static cracking over time and can suppress the mixing of minute bubbles at the end of the optical laminate when inserted into a display element, so high optical performance can be expected. Therefore, the optical laminate of the present invention is suitable as a component of various display devices. In addition, since long-term storage is possible, disposal of the optical laminate due to changes over time can be reduced.

A display device is a device having a display element, and includes a light-emitting element or light-emitting device as a light-emitting source. As display devices, examples thereof include liquid crystal displays, organic electroluminescence (EL) displays, inorganic electroluminescence (EL) displays, touch panel displays, electron emission displays (e.g., field emission displays (FEDs), surface field emission displays (SEDs)), electronic paper (display devices using electronic ink or electrophoretic elements, plasma displays, projection displays (e.g., diffractive light valve (GLV) displays, displays having digital micromirror devices (DMDs)), and piezoelectric ceramic displays. Liquid crystal display devices include any of transmissive liquid crystal displays, semitransmissive liquid crystal displays, reflective liquid crystal displays, direct-view liquid crystal displays, and projection liquid crystal displays. These display devices may be display devices that display two-dimensional images, or stereoscopic display devices that display three-dimensional images. In particular, the optical laminate of the present invention can be suitably used for organic electroluminescence (EL) display devices and inorganic electroluminescence (EL) display devices. It is also suitable for use in liquid crystal display devices and touch panel display devices. These display devices can exhibit good image display characteristics by having the optical laminate of the present invention, which has an excellent effect of suppressing the mixing of minute bubbles at the end of the optical laminate when inserted into a display element.

Example

Hereinafter, the present invention will be described in more detail by examples and comparative examples, but the present invention is not limited to these examples. “%” and “part” in the examples and comparative examples are “mass%” and “mass part”, unless specifically stated otherwise.

1. Production of polarizing plate

(1) Production of polarizing film

A 20 ㎛ thick polyvinyl alcohol-based resin film (average degree of polymerization about 2400, degree of saponification 99.9 mol% or more) was stretched uniaxially about 5 times by dry stretching, and further, while maintaining the tension, was immersed in pure water at a temperature of 60°C for 1 minute, and then immersed in an aqueous solution at a temperature of 28°C having a mass ratio of iodine/potassium iodide/water of 0.05/5/100 for 60 seconds. Thereafter, it was immersed in an aqueous solution at a temperature of 72°C having a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds. Subsequently, it was washed in pure water at a temperature of 26°C for 20 seconds, and then dried at a temperature of 65°C to obtain an 8 ㎛ thick polarizer in which iodine was adsorbed and aligned on the polyvinyl alcohol-based resin film.

(2) Preparation of water-based adhesive for forming first adhesive layer and second adhesive layer

3 parts by mass of carboxyl-modified polyvinyl alcohol ("KL-318" manufactured by Kuraray Co., Ltd.) was dissolved in 100 parts by mass of water to prepare a polyvinyl alcohol aqueous solution. A water-soluble polyamide epoxy resin ("Sumirezu Resin 650 (30)" manufactured by Taoka Chemical Industry Co., Ltd., solid content concentration: 30% by mass) was mixed in the obtained aqueous solution at a ratio of 1.5 parts by mass to 100 parts by mass of water to obtain an aqueous adhesive.

(3) Production of polarizing plate

On one side of the polarizing film obtained above, the aqueous adhesive obtained above was applied, and a protective film (1) ["ZEONOA FILM ZD-U" manufactured by Nippon Zeon Co., Ltd., thickness 23 μm, cyclic polyolefin-based resin film (COP film)] was laminated, and on the other side of the polarizing film, the aqueous adhesive obtained above was applied, and a protective film (2) [triacetyl cellulose film (TAC film) thickness 20 μm] was laminated. By drying the obtained laminate at a temperature of 80°C for 5 minutes, a polarizing plate having protective films via adhesive layers on both sides of the polarizing film was obtained. The layer configuration of this polarizing plate is protective film (1) (COP film)/aqueous adhesive layer/polarizing film/aqueous adhesive layer/protective film (2) (TAC film).

(4) Measurement of dimensional change rate of protective film

The protective film (1) (COP film) was cut into a longitudinal size of 150 mm x 50 mm to serve as a measurement sample, and the dimensions of the long sides and the short sides were precisely measured using an image measuring device "NEXIV (VMZ-R4540)" manufactured by Nikon Corporation, and these were used as the initial dimensions. Next, the measurement sample was maintained in an oven at 40°C and 60% RH for 48 hours, and the dimensions of the long sides and the short sides were precisely measured in the same manner as the initial dimension measurement method, and these were used as the dimensions after 48 hours. The dimensional change rates of the long sides and the short sides were obtained by the following calculation formula, and the average value was used as the dimensional change rate of the protective film (1).

Dimension change rate = (Dimension after 48 hours - Initial dimension) / (Dimension after 48 hours) × 100

The dimensional change rate of the protective film (1) (COP film) was -0.01%.

Regarding the protective film (2) (TAC film), the dimensional change rate was obtained as the average of the long side and the short side in the same manner as the protective film (1). The dimensional change rate of the protective film (2) (TAC film) was +0.02%.

2. Production of a laminate including a point-of-contact adhesive layer

(1) Production of adhesive layer (1)

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 95.0 parts of n-butyl acrylate, 4.0 parts of acrylic acid, 1.0 part of 2-hydroxyethyl acrylate, 200 parts of ethyl acetate, and 0.08 part of 2,2'-azobisisobutyronitrile were injected, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60°C while stirring under a nitrogen atmosphere, reacted for 6 hours, and then cooled to room temperature.

The weight average molecular weight of a portion of the obtained solution was measured, and the production of 1.8 million (meth)acrylic acid ester polymers was confirmed. The weight average molecular weight (Mw) of the (meth)acrylic resin is the weight average molecular weight in polystyrene conversion measured using gel permeation chromatography (GPC) under the following conditions.

〔Measurement conditions〕

·GPC measuring device: HLC-8020 manufactured by Tosoh Kabushiki Kaisha

·GPC column (passed in the following order): Manufactured by Tosoh Corporation

TSK guard column HXL-H

TSK Gel GMHXL (×2)

TSK Gel G2000HXL

·Measurement solvent: Tetrahydrofuran

·Measurement temperature: 40℃

100 parts (in terms of solid content) of the (meth)acrylic acid ester polymer obtained in the above process, 1.5 parts (in terms of solid content) of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, trade name "Corona (registered trademark) L") as an isocyanate crosslinking agent, 0.30 parts (in terms of solid content) of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM403") as a silane coupling agent, 7.5 parts (in terms of solid content) of ethoxylated isocyanuric acid triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "A-9300") as an ultraviolet-curable compound, and 1.5 parts (in terms of solid content) of a photopolymerization initiator. 0.5 part (in terms of solid content) of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (manufactured by BASF: Irgacua (registered trademark) 907) was mixed, stirred sufficiently, and diluted with ethyl acetate to obtain a coating solution of an adhesive composition (1).

The coating solution of the adhesive composition (1) obtained above was applied to the release-treated surface of a separator film (manufactured by Lintech Co., Ltd.: SP-PLR382190) having been subjected to a release treatment on one surface, by an applicator, so that the thickness after drying became 5 µm (as measured with a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.), and then dried at a temperature of 100°C for 1 minute. A separator film (manufactured by Lintech Co., Ltd.: SP-PLR381031) having been subjected to a release treatment on one surface was bonded to the release-treated surface side of the coated layer opposite to the surface on which the separator of the dried coating layer was bonded (the exposed surface of the coated layer). Next, an ultraviolet ray (irradiation intensity 500 mW/cm ^{2 , accumulated light quantity 500 mJ/cm 2} ) was irradiated beyond a separator film (SP-PLR382190) using an ultraviolet irradiation device equipped with a belt conveyor on the coating layer (manufactured by Fusion UV Systems, ^Inc. , using a D bulb as the lamp), thereby forming an adhesive layer (1), thereby obtaining an adhesive layer (1) equipped with a double-sided separator. The layer configuration of the adhesive layer (1) equipped with a double-sided separator is separator film (SP-PLR382190)/adhesive layer (1)/separator film (SP-PLR381031). The thickness of the adhesive layer (1) was 5 ㎛.

(2) Production of adhesive layer (2)

An adhesive layer (2) having a double-sided separator was obtained by operating in the same manner as in the production of the adhesive layer (2) except that the coating solution of the adhesive composition (2) was applied so that the thickness after drying became 15 ㎛. The layer configuration of the adhesive layer (2) having a double-sided separator was separator film (SP-PLR382190)/adhesive layer (2)/separator film (SP-PLR381031). The thickness of the adhesive layer (2) was 15 ㎛.

(3) Measurement of water vapor permeability

Under the conditions of a temperature of 40°C and a relative humidity of 90%, the water vapor permeability of the adhesive layers (1) and (2) manufactured above was measured using a water vapor permeability meter (“Lyssy-L80-5000” manufactured by Lyssy), and the results were 7600 g/(m2·24h) each.

(4) Measurement of storage elastic modulus

As a sample for measuring the storage elastic modulus G', a plurality of adhesive layers (1) and (2) were laminated to a thickness of 0.2 mm (measured with a digital micrometer "MH-15M" manufactured by Nikon Corporation), and then a cylinder having a diameter of 8 mm was punched out. Regarding this sample for measurement, measurements were made under the following conditions by the torsional shear method using a viscoelasticity measuring device (MCR300 manufactured by Physica Corporation) in accordance with JIS K7244-6.

〔Measurement conditions〕

Normal Force FN: 1 N

Strain γ: 1%

Frequency: 1 Hz

Temperature: 25℃

The storage elastic modulus G' of the adhesive layers (1) and (2) was measured and found to be 125,000 Pa (0.125 MPa) at a temperature of 25°C.

(5) Measurement of glass transition temperature

The glass transition temperatures of the adhesive layer (1) and the adhesive layer (2) were measured according to the following procedure.

First, 5 mg of the adhesive layer (1) or (2) was collected, placed in a container with an aluminum press lid, and tightly sealed to prepare a measurement sample. The container containing the measurement sample was set in a differential scanning calorimeter (DSC) ["EXSTAR-6000 DSC6220" sold by SII Nanotechnology Co., Ltd.], and while purging nitrogen gas, the temperature was lowered from 20°C to -60°C, and after reaching -60°C, it was maintained for 1 minute, and then the temperature was increased from -60°C to 150°C at a temperature increase rate of 10°C/min, and when it reached 150°C, the temperature was immediately lowered to 20°C. And, from the DSC curve when the temperature was increased from -60℃ to 150℃, the midpoint glass transition temperature specified in JIS K 7121-1987 "Method for measuring transition temperature of plastics" was obtained, and this was used as the glass transition temperature of the adhesive layers (1) and (2) of the measurement target. The results were all 25℃ or lower.

(6) Production of adhesive layer (3)

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 97.0 parts of n-butyl acrylate, 1.0 part of acrylic acid, 0.5 part of 2-hydroxyethyl acrylate, 200 parts of ethyl acetate, and 0.08 part of 2,2'-azobisisobutyronitrile were injected, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60°C while stirring under a nitrogen atmosphere, reacted for 6 hours, and then cooled to room temperature. The weight average molecular weight of a part of the obtained solution was measured in the above-described procedure, and production of a (meth)acrylic acid ester polymer having a molecular weight of 1.8 million was confirmed.

100 parts of the (meth)acrylic acid ester polymer obtained in the above process (in terms of solid content; the same applies hereinafter), 0.30 parts of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, trade name “Corona (registered trademark) L”) as an isocyanate crosslinking agent, and 0.30 parts of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM403”) as a silane coupling agent were mixed, stirred sufficiently, and diluted with ethyl acetate, thereby obtaining a coating solution of an adhesive composition (3).

The coating solution of the adhesive composition (3) obtained above was applied to the release-treated surface of a separator film (manufactured by Lintech Co., Ltd.: SP-PLR382190) having a release treatment on one side by an applicator so that the thickness after drying became 25 µm (the thickness was measured with a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.). Thereafter, the film was dried at a temperature of 100°C for 1 minute, and a separator film (manufactured by Lintech Co., Ltd. "SP-PLR381031") having a release treatment on one side was bonded to the exposed surface of the coating layer after drying (the surface opposite to the surface on which the separator film is laminated), thereby obtaining an adhesive layer (3) having a double-sided separator.

The storage elastic modulus G' of the adhesive layer (3) was measured using the above-described procedure and was 25,500 Pa (0.0255 MPa) at a temperature of 25°C. In addition, the glass transition temperature of the adhesive layer (3) was measured using the above-described procedure and was 25°C or lower.

3. Fabrication of a laminate including a phase-shift film

(1) Production of phase barrier film (1)

(i) Preparation of a composition for forming a photo-alignment film

A composition for forming a photoalignment film was obtained by mixing 2 parts of a photoalignable material having the structure shown below and 98 parts of cyclopentanone (solvent), and stirring at a temperature of 80°C for 1 hour. The photoalignable material having the structure shown below (weight average molecular weight: 50,000, m:n = 50:50) was synthesized according to the method described in Japanese Patent Application Laid-Open No. 2021-196514.

Photo-orientable materials:

(ii) Preparation of polymerizable liquid crystal composition (1)

A polymerizable liquid crystal composition (1) was prepared by mixing the polymerizable liquid crystal compound (X6), the polymerizable liquid crystal compound (X7), the leveling agent, and the photopolymerization initiator shown below, further mixing N-methyl-2-pyrrolidone (NMP) so that the solid concentration became 13%, and stirring at a temperature of 80°C for 1 hour. The polymerizable liquid crystal compound (X6) and the polymerizable liquid crystal compound (X7) have the structures shown below. The polymerizable liquid crystal compound (X6) was prepared in the same manner as the method described in Japanese Patent Application Laid-Open No. 2019-003177. The polymerizable liquid crystal compound (X7) was prepared in the same manner as the method described in Japanese Patent Application Laid-Open No. 2009-173893.

Polymerizable liquid crystal compound (X6): 90 parts

Polymerizable liquid crystal compound (X7): 10 parts

Leveling agent [BYK-361N (manufactured by BM Chemie)]: 0.1 part

Photopolymerization initiator [Irgacur OXE-03 (manufactured by BASF Japan Co., Ltd.)]: 3 parts

·Polymerizable liquid crystal compound (X6):

·Polymerizable liquid crystal compound (X7):

A solution was obtained by dissolving 1 mg of a polymerizable liquid crystal compound (X6) in 10 mL of chloroform. The obtained solution was placed in a measuring cell with an optical path length of 1 cm, and the measuring sample was set in an ultraviolet-visible spectrophotometer (“UV-2450” manufactured by Shimadzu Seisakusho Co., Ltd.) to measure the absorption spectrum. The wavelength at which the maximum absorption was obtained was read from the obtained absorption spectrum, and the maximum absorption wavelength λmax in the wavelength range of 300 to 400 nm was 356 nm.

(iii) Production of a phase-shift film (1) having a substrate layer

The composition for forming a photo-alignment film obtained above was applied to a biaxially oriented polyethylene terephthalate (PET) film (Diafoil, manufactured by Mitsubishi Jushi Co., Ltd.) by a bar coater to obtain a coating layer. The obtained coating layer was dried at a temperature of 120°C for 2 minutes, cooled to room temperature to dry the coating layer, and then, after drying, the coating layer was irradiated with 100 mJ (based on 313 nm) of polarized ultraviolet light using a UV irradiation device (SPOT CURE SP-9; manufactured by Ushio Denki Co., Ltd.) to obtain a photo-alignment film on the PET film. The thickness of the photo-alignment film, as measured using an ellipsometer M-220 manufactured by Nippon Bunko Co., Ltd., was 100 nm.

On the photoalignment film obtained on the PET film, the polymerizable liquid crystal composition (1) prepared above was applied using a bar coater to form a coating layer. The formed coating layer was dried by heating at a temperature of 120°C for 2 minutes, and then cooled to room temperature. After drying, the coating layer was irradiated with ultraviolet light at an exposure dose of 500 mJ/ ^cm2 (based on 365 nm) in a nitrogen atmosphere using a high-pressure mercury lamp (“Unicure VB-15201BY-A” manufactured by Ushio Denki Co., Ltd.), thereby forming a cured layer (1) of the polymerizable liquid crystal composition (1) in which the polymerizable liquid crystal compound was aligned within the plane of the PET film. The thickness of the cured layer (1) measured using a laser microscope LEXT OLS4100 manufactured by Olympus Corporation was 2 μm. Accordingly, a phase-shielding film (1) having a substrate layer including a first substrate layer (PET film)/phase-shielding film (1) (photo-alignment film/cured layer (1)) was obtained. Here, the thickness of the phase-shielding film (1) composed of the photo-alignment film (100 nm) and the cured layer (1) (2 ㎛) is 2.1 ㎛.

(2) Measurement of phase difference value

A first phase-shift film (1) having a substrate layer was subjected to corona treatment on the phase-shift film (1) side, and the first liquid crystal phase-shift film (1) having a substrate layer was bonded to an inorganic glass plate from the side via the adhesive layer (1), and the first substrate layer (PET film) was peeled off to obtain a test body. The layer configuration of this test body is phase-shift film (1) [photoalignment film/cured layer (1)]/adhesive layer (1)/inorganic glass plate. The in-plane phase difference value of this test body was measured using "KOBRA-WR" manufactured by Ojigeisokuki Co., Ltd. The in-plane phase difference values for light with wavelengths of 450 nm, 550 nm, and 650 nm were obtained from the Cauchy dispersion formula obtained from the measurement results of the in-plane phase difference values for light with wavelengths of 448.2 nm, 498.6 nm, 548.4 nm, 587.3 nm, 628.7 nm, and 748.6 nm. As a result, the in-plane phase difference values were Re(450)=122 nm, Re(550)=140 nm, Re(650)=144 nm, and the relationship of the in-plane phase difference values at each wavelength was as follows.

Re(450)/Re(550) = 0.87

Re(650)/Re(550) = 1.03

[In the equation, Re(450) represents the in-plane phase difference value for light with a wavelength of 450 nm, Re(550) represents the in-plane phase difference value for light with a wavelength of 550 nm, and Re(650) represents the in-plane phase difference value for light with a wavelength of 650 nm.]

In addition, the in-plane phase difference values of the inorganic glass plate were 0 nm at wavelengths of 448.2 nm, 498.6 nm, 548.4 nm, 587.3 nm, 628.7 nm, and 748.6 nm, and the in-plane phase difference values at 450 nm, 550 nm, and 650 nm were all 0 nm. In this respect, the in-plane phase difference value of this test piece is the in-plane phase difference of the phase difference film (1) (photoalignment film and cured layer (1)) constituting it.

(3) Production of phase barrier film (2)

(i) Preparation of a composition for forming a vertical alignment film

2-Phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate, and bis(2-vinyloxyethyl) ether were mixed in a ratio (mass ratio) of 1:1:4:5 to obtain a mixture, and 4 parts by mass of "LUCIRIN TPO" manufactured by Chiba Japan Co., Ltd. was added as a polymerization initiator to 100 parts by mass of the obtained mixture, thereby preparing a composition for forming a vertical alignment film.

(ii) Preparation of polymerizable liquid crystal composition (2)

The polymerizable liquid crystal composition (2) was prepared by mixing a photopolymerizable nematic liquid crystal compound (“RMM28B” manufactured by Melk Corporation) and a solvent at a solid content of 1 to 1.5 mass%. The solvent used was a mixed solvent in which methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CHN) were mixed at a mass ratio of 35:30:35 (MEK:MIBK:CHN).

(iii) Production of a phase-shift film (2) having a substrate layer

A surface opposite to the release-treated side of a polyethylene terephthalate (PET) film ("FF-50" manufactured by Yunichika Co., Ltd., support substrate (PET film (thickness 50 µm))) having one side subjected to a release treatment was subjected to corona treatment, and a composition for forming a vertical alignment film prepared above was applied to the corona-treated side using a slot die coater so that the thickness after curing became 3 µm. The applied film was irradiated with ultraviolet rays at 200 mJ/ ^cm2 to form a vertical alignment film on the PET film having one side subjected to a release treatment.

On the vertical alignment film formed on the PET film having one side treated with a release process as described above, the polymerizable liquid crystal composition (2) prepared as described above was applied using a slot die coater so that the thickness after curing became 1 ㎛ to obtain a coating layer. The coating layer was dried at a drying temperature of 75° C. and a drying time of 120 seconds, and then the polymerizable liquid crystal compound was polymerized by irradiating with ultraviolet rays to form a cured layer (2). Accordingly, a phase contrast film (2) having a substrate layer including a PET film/phase contrast film (2) having one side treated with a release process (vertical alignment film/cured layer (2)) was obtained. The phase contrast film (2) was a positive C plate.

(4) Production of composite phase barrier film

(i) Preparation of active energy ray curable composition (1)

3',4'-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: CEL2021P, manufactured by Daicel Co., Ltd.): 70 parts by mass

Neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by Nagase Chemtex Co., Ltd.): 20 parts by mass,

2-Ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase Chemtex Co., Ltd.): 10 parts by mass,

Cationic polymerization initiator (trade name: CPI-100_50% solution, manufactured by San-Apro Co., Ltd.): 4.5 parts by mass (actual solid content 2.25 parts by mass) and

1,4-diethoxynaphthalene: 2 parts by mass

By mixing, an active energy ray curable composition (1) was obtained.

(ii) Production of a composite phase-shift film having a substrate layer

The phase contrast film (1) having a substrate layer and the phase contrast film (2) having a substrate layer obtained above were laminated with the phase contrast film (1) side and the phase contrast film (2) side facing each other using the active energy ray-curable composition (1) prepared above. Next, ultraviolet rays were irradiated on the phase contrast film (2) side having a substrate layer, and the active energy ray-curable composition (1) was cured to form an adhesive layer having a thickness of 2 µm, thereby obtaining a composite phase contrast film having a substrate layer. This composite phase contrast film having a substrate layer has a layer structure of first substrate layer (PET film)/phase contrast film (1) (photoalignment film/cured material layer (1))/adhesive layer (cured material layer of active energy ray-curable composition (1))/phase contrast film (2) (cured material layer (2)/vertical alignment film)/second substrate layer (PET film having one side subjected to release treatment).

4. Fabrication of an optical laminate (circular polarizing plate) equipped with a separator

From the polarizing plate obtained above, a rectangular shape was cut so that the absorption axis direction became the long side, and corona treatment was performed on the surface of the protective film (2) side (TAC film side). Next, the first substrate layer (PET film) on the phase contrast film (1) side of the composite phase contrast film having the substrate layer obtained above was peeled off to expose the photoalignment film, and corona treatment was performed on the exposed photoalignment film. The surfaces that had been subjected to the corona treatment, that is, the TAC film side and the photoalignment film side, were bonded together through the adhesive layer (2) obtained above with a thickness of 15 μm so that their long sides coincided.

Thereafter, the second substrate layer (a PET film having one side subjected to a release treatment) of the phase contrast film (2) having a substrate layer is peeled off to expose the vertical alignment film, a corona treatment is performed on the exposed surface of the vertical alignment film, and on top of that, one side of the separator from the adhesive layer (3) having a double-sided separator is peeled off, and the exposed adhesive layer (3) is bonded, thereby obtaining an optical laminate having a separator. This optical laminate having a separator has a layer structure of polarizing plate (first protective film/first adhesive layer/polarizing film (polarizer)/second adhesive layer/second protective film)/adhesive layer (2)/phase contrast film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase contrast film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. In addition, the ground axis of the cured layer (1) constituting the phase contrast film (1) intersected the absorption axis of the polarizer at 45 degrees within the plane.

5. Production of the third protective film

(1) Production of clear hard coat film

(i) Preparation of a solution for forming a cured resin layer

A solution having a solid concentration of 40 wt% was prepared by mixing 50 parts by mass of an ultraviolet-curable urethane acrylate monomer (refractive index 1.51), 50 parts by mass of an ultraviolet-curable acrylate monomer (refractive index 1.51), 5 parts by mass of a benzophenone-based photopolymerization initiator, and toluene.

(ii) Production of clear hard coat film

The solution obtained above was applied onto a long resin film and dried at 120°C for 5 minutes. Thereafter, curing was performed by ultraviolet irradiation to form a clear hard coat layer (cured resin layer) with a flat surface and a thickness of approximately 4 ㎛, thereby producing a long clear hard coat film.

As a resin film

Clear hard coat film (1) using a triacetyl cellulose film having a thickness of 25 ㎛

Clear hard coat film (2) using a triacetyl cellulose film with a thickness of 40 ㎛

Clear hard coat film (3) using a triacetyl cellulose film having a thickness of 60 ㎛.

A clear hard coat film (4) was made using a triacetyl cellulose film having a thickness of 80 ㎛.

A clear hard coat film (5) was made using an acrylic film (polymethyl methacrylate polymer film) having a thickness of 60 ㎛.

(2) Measurement of dimensional change rate

A sample sized 150 mm x 50 mm was cut from the manufactured long clear hard coat film (1). At this time, the sample was cut so that the long side (150 mm) of the sample was at a 45° angle with respect to the longitudinal direction of the long clear hard coat film (1). This was used as a measurement sample, and was set in an image measuring device "NEXIV (VMZ-R4540)" manufactured by Nikon Corporation with the clear hard coat layer side facing upward, and the dimensions of the long side and the short side were precisely measured, and these were set as the initial dimensions. Next, after maintaining it in an oven at 40°C and 60% RH for 48 hours, the dimensions of the long side and the short side were precisely measured in the same manner, and these were set as the dimensions after 48 hours. The dimensional change rate of the long side and the short side was obtained by the following calculation formula, and the average value was set as the dimensional change rate of the clear hard coat film (1).

Dimension change rate = (Dimension after 48 hours - Initial dimension) / (Dimension after 48 hours) × 100

As described above, for the clear hard coat films (2) to (5), the dimensional change rate of each long side and each short side was measured, and the dimensional change rate of each film was obtained from the average value. The results are shown in Table 1.

<Example 1>

The COP film side of the optical laminate equipped with a separator and the TAC film side of the clear hard coat film (1) were each subjected to corona treatment and bonded via an adhesive layer (2). When viewed from the cured resin layer side of the clear hard coat film (1), a sample was obtained by cutting to a size of 150 mm × 50 mm such that the optical axis of the polarizing film was arranged 45° clockwise with respect to the long side and the optical axis of the phase contrast film was arranged further 45° clockwise with respect to the optical axis of the polarizing film.

The optical laminate of Example 1 includes a clear hard coat film (1) (cured resin layer/TAC film)/adhesive layer (2)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (1) in the optical laminate of Example 1 from the optical laminate is 1 N/25 mm or more.

<Example 2>

A sample was obtained in the same manner as in Example 1, except that the adhesive layer (2) bonding the clear hard coat film (1) and the polarizing plate was changed to the adhesive layer (1).

The optical laminate of Example 2 includes a clear hard coat film (1) (cured resin layer/TAC film)/adhesive layer (1)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (1) in the optical laminate of Example 2 from the optical laminate is 1 N/25 mm or more.

<Example 3>

A sample was obtained in the same manner as in Example 2, except that the clear hard coat film (1) was changed to a clear hard coat film (2).

The optical laminate of Example 3 includes a clear hard coat film (2) (cured resin layer/TAC film)/adhesive layer (1)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (2) in the optical laminate of Example 3 from the optical laminate is 1 N/25 mm or more.

<Example 4>

A sample was obtained in the same manner as in Example 2, except that the clear hard coat film (1) was changed to a clear hard coat film (3).

The optical laminate of Example 4 includes a clear hard coat film (3) (cured resin layer/TAC film)/adhesive layer (1)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (3) in the optical laminate of Example 4 from the optical laminate is 1 N/25 mm or more.

<Example 5>

A sample was obtained in the same manner as in Example 2, except that the clear hard coat film (1) was changed to a clear hard coat film (5).

The optical laminate of Example 5 includes a clear hard coat film (5) (cured resin layer/TAC film)/adhesive layer (1)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (5) in the optical laminate of Example 5 from the optical laminate is 1 N/25 mm or more.

<Comparative Example 1>

A sample was obtained by cutting to a size of 150 mm × 50 mm so that, when viewed from the polarizing plate side of an optical laminate equipped with a separator and without laminating a clear hard coat film, the optical axis of the polarizing film is arranged at a clockwise angle of 45° with respect to the long side, and the ground axis of the phase contrast film is arranged at a further clockwise angle of 45° with respect to the absorption axis of the polarizing film.

The optical laminate of Comparative Example 1 includes a polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film.

<Comparative Example 2>

A sample was obtained in the same manner as in Example 2, except that the clear hard coat film (1) was changed to a clear hard coat film (4).

The optical laminate of Comparative Example 2 includes a clear hard coat film (4) (cured resin layer/acrylic film)/adhesive layer (1)/polarizing plate (protective film (1)/first adhesive layer/polarizing film/second adhesive layer/protective film (2))/adhesive layer (2)/phase protection film (1) (photoalignment film/cured material layer (1))/cured material layer of active energy ray-curable composition (1)/phase protection film (2) (cured material layer (2)/vertical alignment film)/adhesive layer (3)/separator film. The peeling force when peeling the clear hard coat film (5) in the optical laminate of Comparative Example 2 from the optical laminate is 1 N/25 mm or more.

<Reference example>

A sample was obtained in the same manner as in Comparative Example 1, except that the phase contrast film (1) (photoalignment film/cured material layer (1))/cured material layer of the active energy ray-curable composition (1)/phase contrast film (2) (cured material layer (2)/vertical alignment film) was changed to “Pure Ace RM” (phase contrast film) manufactured by Teijin Co., Ltd.

The optical laminate of Reference Example 1 includes a polarizing plate (first protective film/first adhesive layer/polarizing film/second adhesive layer/second protective film)/adhesive layer (2)/Pure Ace RM/adhesive layer (3)/separator film.

Evaluation of optical laminates

(1) Curl measurement

After peeling off the separator film on the adhesive layer (3) side of each chip sample, the adhesive layer (3) was placed upward, placed in an oven at 40°C and 60% RH for 48 hours, and immediately after taking it out, placed on a “silicon pot holder manufactured by Daiso” in a form in which the adhesive layer (3) was in contact.

The curl heights of the four corners of the chip sample were measured with a ruler, and the maximum curl amount was taken as the measurement value. The results are shown in Tables 2 and 3.

(2) Observation of the degree of bubble mixing

After placing in a 40℃, 60% RH oven for 48 hours, immediately after taking it out, the separator film on the adhesive layer (3) side of the chip sample was peeled off and bonded to an alkali-free glass plate ("Eagle-XG" manufactured by Corning Inc.) using a roller. After performing an autoclave treatment on this, the number of bubbles was counted at two 50 mm sides of the sample using a loupe, and the evaluation was made based on the following criteria. The results are shown in Tables 2 and 3.

〔Evaluation criteria〕

A: Less than 1 bubble larger than 50 ㎛

B: 1 or more but less than 5 bubbles larger than 50 ㎛

C: 5 or more but less than 10 bubbles larger than 50 ㎛

D: 10 or more but less than 15 bubbles larger than 50 ㎛

Claims (7)

An optical laminate in which a third protective film is laminated on the side of the first polarizer protective film of a circular polarizing plate, which has a first polarizer protective film, a first adhesive layer, a polyvinyl alcohol-based polarizing film, a second adhesive layer, a second polarizer protective film, a first adhesive layer, and a phase contrast film composed of a polymer of a polymerizable liquid crystal compound, adjacent to each other in this order, through a second adhesive layer,
The thickness of the above phase contrast film is 0.5 to 10 ㎛,
After 48 hours in an environment of a temperature of 40°C and a relative humidity of 60%, the dimensional strain (H1) of the first polarizer protective film, the dimensional strain (H2) of the second polarizer protective film, and the dimensional strain (H3) of the third protective film are expressed by the following equations (1) and (2):
-0.300 ≤ H1-H2 ≤ -0.001 (1)
-0.040 ≤ (H3+H1)-H2 ≤ 0.100 (2)
An optical laminate satisfying . In the first paragraph, the thickness (T2) of the second polarizer protective film and the thickness (T3) of the third protective film are as follows:
45 ≤ (T3/T2)×100 ≤ 350 (3)
An optical laminate satisfying . An optical laminate in claim 1, wherein the thickness of the third protective film is 10 to 100 ㎛. An optical laminate in claim 1, further comprising a cured resin layer on the side opposite to the circular polarizing plate side of the third protective film. An optical laminate in claim 1, wherein the third protective film is a triacetyl cellulose film or a polymethyl methacrylate polymer film. An optical laminate in claim 1, wherein the peeling force when peeling the third protective film from the optical laminate is 1 N/25 mm or more. An organic EL display device comprising an optical laminate as described in claim 1.