JPWO2020170874A1 - Optical laminate and its manufacturing method - Google Patents

Abstract

Provided are an optical laminate capable of setting an arbitrary axis and a method for manufacturing the same. In the optical laminate (100), a first optically anisotropic layer (30) made of a double refraction-inducing material and a second optically anisotropic layer (40) made of a polymerizable liquid crystal material are adjacent to each other. The first optically anisotropic layer (30) is composed of a surface layer (32) and an inner layer (31) having different slow axes, and the surface layer (30) is formed. 32) and the second optically anisotropic layer (40) are in contact with each other, and the slow axial direction of the inner layer (31) of the first optically anisotropic layer and the second optically anisotropic layer (40) are in contact with each other. ) Crosses the slow axis direction.

Description

Related application

This application claims the priority of Japanese Patent Application No. 2019-030471 filed on February 22, 2019, which is cited in its entirety as part of this application by reference.

The present invention relates to an optical laminate capable of setting an arbitrary axis and a method for manufacturing the same.

Various retardation plates are used in thin display devices such as liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs) in order to improve display quality. For example, in an OLED such as an organic EL display device, a wideband circularly polarizing plate is used to suppress reflection.

As a retardation film used for such a broadband circular polarizing plate, Patent Document 1 (Japanese Unexamined Patent Publication No. 2016-184013) describes a first optically anisotropic layer made of a birefringence-inducing material and a polymerizable liquid crystal. A retardation film in which a second optically anisotropic layer is directly laminated without an adhesive layer is disclosed. Further, as a method for producing the same, a step of applying a birefringence-inducing material on a supporting base material to form a birefringence-inducing material layer, and a step of irradiating the birefringence-inducing material layer with the first polarized light. In one light irradiation step, a polymerizable liquid crystal is applied onto the birefringence-induced material layer irradiated with the first polarized light, and the polymerizable liquid crystal material layer is laminated on the birefringence-induced material layer. The step of forming the laminated body and the second light irradiation step of irradiating the laminated body with the second polarized light are included, and the polarization axis direction of the first polarized light and the polarization axis direction of the second polarized light. However, a method for producing a retardation film, which is characterized by being different from each other, is described.

Japanese Unexamined Patent Publication No. 2016-184013

However, in the method for producing a retardation film described in Patent Document 1, the polymerizable liquid crystal material layer that is oriented in the second light irradiation step of irradiating the second polarized light for orienting the birefringence-induced material layer. Since the second polarized light is irradiated through the light, and the polarization state of the second polarized light is changed when passing through the oriented polymerizable liquid crystal material layer, the desired polarized light is applied to the birefringence-induced material layer. It was difficult to irradiate. Therefore, it is difficult to establish the intended slow-phase axis relationship between the birefringence-induced material layer and the polymerizable liquid crystal material layer.

Therefore, an object of the present invention is to provide an optical laminate and a manufacturing method that can be set to an arbitrary slow phase axis in each optically anisotropic layer.

As a result of diligent research to solve the above problems, the present inventor irradiates the birefringence-induced material layer with the first polarization to form the oriented first optically anisotropic layer, and then first. By orienting the surface of the optically anisotropic layer of No. 1 so as to have an orientation different from that of the inner layer, and applying a polymerizable liquid crystal material to the surface to form a second optically anisotropic layer. i) The optical orientation of the inner layer composed of the birefringence-inducing material is not affected by another layer, and the inner layer can be given a desired orientation, and (ii) serves as an alignment film. Since the orientation of the surface layer to be achieved can be adjusted independently of the inner layer, it has been found that the desired orientation can be imparted to the second optically anisotropic layer in consideration of the relationship with the orientation of the inner layer. rice field. Then, they have found that the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer can be arbitrarily set in the obtained optical laminate, and completed the present invention. rice field.

That is, the present invention can be configured in the following aspects.
[Aspect 1]
A first optically anisotropic layer made of a birefringence-inducing material,
The second optically anisotropic layer made of a polymerizable liquid crystal material is an optically laminated body laminated adjacent to each other.
The first optically anisotropic layer is composed of a surface layer and an inner layer having different slow phases, and the surface layer and the second optically anisotropic layer are in contact with each other.
An optical laminate in which the slow-phase axial direction of the inner layer of the first optically anisotropic layer and the slow-phase axial direction of the second optically anisotropic layer intersect.
[Aspect 2]
In the optical laminate according to the first aspect, the slow axis direction of the inner layer of the first optically anisotropic layer and the slow axis direction of the second optically anisotropic layer are non-parallel and non-orthogonal. Optical laminates that intersect at an angle.
[Aspect 3]
The optical laminate according to the first or second aspect, wherein the polymerizable liquid crystal material contains a cross-linking agent having a functional group capable of forming a cross-linking bond with the birefringence-inducing material.
[Aspect 4]
A method for producing an optical laminate according to any one of aspects 1 to 3.
A first light irradiation step of irradiating a birefringence-inducing material layer made of a birefringence-inducing material with first polarized light for expressing a phase difference to form a first optically anisotropic layer.
A surface orientation step of aligning the surface of the first optically anisotropic layer so as to give an orientation different from that of the inner layer to form a surface layer on the first optically anisotropic layer.
A method for producing an optical laminate, comprising a step of applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has been subjected to orientation treatment to form a second optically anisotropic layer.
[Aspect 5]
In the manufacturing method according to the fourth aspect, in the surface orientation step, the surface of the first optically anisotropic layer is irradiated with a second polarized light having a polarization axis direction different from that of the first polarized light. A method for manufacturing an optical laminate, which is a second light irradiation step of forming a surface layer on the first optically anisotropic layer.
[Aspect 6]
The production method according to the fifth aspect, which is a surface treatment step of treating the surface of the first optically anisotropic layer with a solvent between the first light irradiation step and the second light irradiation step. A method for manufacturing an optical laminate.
[Aspect 7]
A circularly polarizing plate in which the optical laminate according to any one of aspects 1 to 3 and a linear polarizing plate are laminated.
[Aspect 8]
The optical laminate according to any one of aspects 1 to 3.
A first optically anisotropic layer formed by irradiating a birefringence-inducing material with a first polarized light for expressing a phase difference,
The surface layer of the first optically anisotropic layer is oriented so as to be oriented differently from the inner layer thereof, and the surface layer formed on the first optically anisotropic layer is formed.
An optical laminate comprising a second optically anisotropic layer formed by applying a polymerizable liquid crystal material on the surface layer.

It should be noted that any combination of claims and / or at least two components disclosed in the specification and / or drawings is included in the present invention. In particular, any combination of two or more of the claims described in the claims is included in the present invention.

According to the optical laminate of the present invention and the method for producing the same, the first optically anisotropic layer and the second optically anisotropic layer can have a desired combination of slow axes, so that the two layers are slow to each other. The angle at which the axes intersect can be set arbitrarily, and for example, it can be used as a circularly polarizing plate by laminating it with a linear polarizing plate.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily shown at a constant scale and are exaggerated to show the principles of the present invention. However, the embodiments and drawings are for illustration and description purposes only and should not be used to define the scope of the invention. The scope of the present invention is determined by the appended claims.
It is schematic cross-sectional view before the first light irradiation step in one Embodiment of the manufacturing method of the optical laminate of this invention. It is a schematic cross-sectional view after the first light irradiation step in one Embodiment of the manufacturing method of the optical laminate of this invention. It is a schematic cross-sectional view after the surface orientation process in one Embodiment of the manufacturing method of the optical laminate of this invention. It is a schematic cross-sectional view after the second optically anisotropic layer forming step in one Embodiment of the manufacturing method of the optical laminate of this invention.

[Manufacturing method of optical laminate]
In the method for producing an optical laminate of the present invention, a birefringence-inducing material layer made of a birefringence-inducing material is irradiated with the first polarization for expressing a phase difference, and the first optical anisotropy is oriented. The first light irradiation step of forming the layer and the surface of the first optically anisotropic layer are oriented so as to be oriented differently from the inner layer thereof, and the surface of the first optically anisotropic layer is surfaced. It includes a surface alignment step of forming a layer and a step of applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has been subjected to the alignment treatment to form a second optically anisotropic layer.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. 1A to 1D are schematic cross-sectional views for explaining an embodiment of the method for manufacturing an optical laminate of the present invention. Although the cross sections of each layer are shown in FIGS. 1A-1D, they do not show the actual thickness ratio.

FIG. 1A is a schematic cross-sectional view showing a laminate of the base material 10 and the birefringence-induced material layer 20. FIG. 1B shows a state after the first light irradiation step, in which the base material 10 and the first optical anisotropy formed by orienting the molecules of the birefringence-induced material layer 20 by irradiation with the first polarized light are shown. It is a schematic cross-sectional view which shows the laminated body with a layer 30. FIG. 1C shows the state after the surface orientation step, in which the base material 10, the inner layer 31 having the same orientation as the first optically anisotropic layer 30, and the surface opposite to the base material 10 are oriented. It is a schematic cross-sectional view which shows the laminated body with the 1st optically anisotropic layer 30 which consists of the surface layer 32 which was oriented differently from the inner layer 31. FIG. 1D shows the state after the second optically anisotropic layer forming step, in which the base material 10, the first optically anisotropic layer 30 composed of the inner layer 31 and the surface layer 32, and the polymerizable liquid crystal material are attached. It is a schematic cross-sectional view which shows the optical laminated body 100 with the 2nd optically anisotropic layer 40 formed by application.

By irradiating the birefringence-inducing material layer 20 made of the birefringence-inducing material shown in FIG. 1A with the first polarized light for expressing the phase difference, the molecular orientation of the birefringence-inducing material can be induced. As a result, as shown in FIG. 1B, a first optically anisotropic layer 30 oriented so as to have a predetermined slow-phase axis is formed from the optically isotropic birefringence-induced material layer 20. In the first light irradiation step, since there is no other layer on the birefringence-induced material layer 20, the birefringence-induced material layer 20 is desired without converting the polarization state of the irradiated first polarized light. It is possible to irradiate the polarized light of.

Next, the surface of the first optically anisotropic layer 30 shown in FIG. 1B is oriented so as to be oriented differently from the orientation given in the first light irradiation step, thereby causing the first optical anisotropic layer. The surface layer 32 can be formed on the sex layer 30. As a result, as shown in FIG. 1C, the first optically anisotropic layer 30 is formed with two layers, an inner layer 31 having an originally formed orientation and a surface layer 32 having a different orientation. NS.

Then, when the polymerizable liquid crystal material is applied on the surface layer 32 shown in FIG. 1C, the surface layer 32 acts as an alignment film, and the second optical anisotropy is oriented corresponding to the orientation of the surface layer 32. The layer 40 can be formed. As a result, as shown in FIG. 1D, a second optically anisotropic layer 40 oriented so as to have a slow phase axis different from that of the inner layer 31 is formed on the surface layer 32. Since the orientation of the inner layer 31 and the surface layer 32 can be adjusted independently, it is possible to impart a desired orientation to the second optically anisotropic layer 40 in consideration of the relationship with the orientation of the inner layer 31. And can intersect each other on the desired slow axis.

According to the method for producing an optical laminate of the present invention, it is not necessary to cut a plurality of films at a predetermined angle and precisely bond them together, so that the crossing angle of the slow axis can be easily adjusted. Further, since it can be manufactured in a long shape, an optical laminate can be efficiently obtained.

(Birefringence induced material layer)
The birefringence-induced material layer is formed from the birefringence-induced material. In the present invention, the birefringence-inducing material refers to a material capable of inducing birefringence axially selectively by molecular motion due to light irradiation (preferably light irradiation and heat-cooling treatment) and molecular orientation based on the molecular motion.

For example, the birefringence-inducing material may contain a liquid crystal polymer having a photosensitive group and having a side chain structure capable of forming a liquid crystal structure, and the molecule may be produced by the photoreaction of the photosensitive group having the side chain. It may have the property of inducing orientation. Examples of the photoreaction include a photodimerization reaction, a photoisomerization reaction, and a photofries rearrangement reaction.

When the liquid crystal polymer can form a liquid crystal structure, the liquid crystal property may be exhibited by having a mesogen group which is a rigid site exhibiting the liquid crystal property in the side chain structure, or other weights may be exhibited. It has a structure capable of forming a dimer by hydrogen bonding with other side chains of the same polymer or a coalescence, and even if it exhibits liquid crystallinity by forming a mesogen structure by dimerization thereof. good.

A mesogen group or mesogen structure is composed of two or more aromatic or aliphatic rings and a linking group that binds them, and the linking group may be a covalent bond or a hydrogen bond.
Examples of the aromatic ring include a benzene ring, a naphthalene ring, a heterocycle (for example, an oxygen-containing heterocycle such as a furan ring and a pyran ring; a nitrogen-containing heterocycle such as a pyrrole ring and an imidazole ring), and examples thereof include an aliphatic ring. Examples include a cyclohexane ring. In addition, these aromatic rings or aliphatic rings may have a substituent, and as the substituent, an alkyl group (for example, C _1-6 alkyl group, preferably C _1-4 alkyl group), Alkyloxy group (eg, C _1-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (eg, C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group (eg, C 1-4 alkenyl group) For example, C _1-6 alkynyl group, preferably C _1-4 alkynyl group), halogen atom and the like can be mentioned.
When the linking group is a covalent bond, a single bond, -O-, -COO-, -OCO-, -N = N-, -NO = N-, -C = C-, -C≡C-, Examples thereof include -CO-C = C-, -CH = N-, and an alkylene group. In the case of a hydrogen bond, a side chain structure having a carboxy group at the end may be mentioned. In this case, a hydrogen bond is formed between the carboxy groups.

The photosensitive group is not particularly limited as long as it is a functional group capable of causing a photoreaction by light energy. Examples thereof include a frillacryloyl group, a naphthylacryloyl group, an azobenzene group, a benzylideneaniline group or a derivative thereof, and a cinnamoyl group may be preferable.

The liquidaceous polymer has at least a side chain structure having both a photosensitive group and a structure capable of forming a liquid crystal structure in the repeating unit, whereas the photosensitive group is a mesogen group or a mesogen structure. It may exist independently in the side chain structure, or it may exist in a complex manner by sharing the chemical structure.

The birefringence-inducing material of the present invention may contain a liquid crystal polymer having at least one structure selected from the group consisting of side chain structures represented by the following formulas (1) and (2).

(In the formula, t is an integer of 1 to 3, and R ₁ is a hydrogen atom, an alkyl group (for example, C _1-6 alkyl group, preferably C _1-4 alkyl group), and an alkyloxy group (for example, C _{1). -6} alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (eg, C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group (eg, C _1-6 alkynyl group) , Preferably C _1-4 alkynyl group), and one or more selected from halogen atoms.)

(In the formula, k is 0 or 1, when k is 0, l is 0, when k is 1, l is an integer of 1 to 12; X is a single bond, C _1-3 alkylene group, − C = C-, -C≡C-, -O-, -N = N-, -COO-, or -OCO-; W is a coumarin group, a cinnamoyl group, a cinnamidene acetate group, a biphenylacryloyl group, a frillacrylloyl group. , Naftylacryloyl group, or derivative groups thereof; R ₂ and R ₃ are the same or different, respectively, hydrogen atom, alkyl group (eg, C _1-6 alkyl group, preferably C _1-4 alkyl group), alkyl. Oxy group (eg, C _1-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (eg, C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group (eg, C 1-4 alkenyl group) , C _1-6 alkynyl group, preferably C _1-4 alkynyl group), carboxy group and one or more selected from halogen atoms.)

The side chain structures represented by the above formulas (1) and (2) represent the chemical structure of the end of the side chain in the repeating unit, and these side chain structures are not impaired to the extent that the effects of the present invention are not impaired. Various chemical structures may be included between the main chain structure and the main chain structure.

The liquid crystal polymer may be a homopolymer composed of the same repeating unit containing the side chain structure or a copolymer containing a repeating unit containing a side chain structure having a different structure in addition to the repeating unit containing the side chain structure. good. Examples of the main chain structure include a structure formed by polymerizing hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, N-phenylmaleimides and the like.

When the liquid crystal polymer is a copolymer, it may have a repeating unit that does not have a photosensitive group and / or a structure capable of forming a liquid crystal structure.

Further, the birefringence-inducing material of the present invention is from the viewpoint of improving the adhesion between the first optically anisotropic layer and the second optically anisotropic layer when the polymerizable liquid crystal material contains a cross-linking agent. , A liquid crystal polymer having a side chain structure having a crosslinkable functional group may be contained. The crosslinkable functional group is not particularly limited as long as it is a functional group that causes a crosslink reaction with a crosslinking agent described later, and examples thereof include a hydroxyl group, a carboxy group, an amino group, and a thiol group. The side chain structure having a crosslinkable functional group may be included in a repeating unit including the side chain structure having the above-mentioned photosensitive group and capable of forming a liquid crystal structure, and a repeating unit other than the repeating unit. It may have a crosslinkable functional group inside.

For example, a hydroxyl group and a carboxy group are preferable as the crosslinkable functional group, and the liquid crystal polymer has a side chain structure having a crosslinkable functional group _{of-(CH 2} ) _n- OH (in the formula, n is an integer of 1 to 6). It may have at least one structure selected from the group consisting of -Ph-COOH (in the formula, Ph is a divalent phenyl group). It should be noted that these side chain structures represent at least a part of the chemical structure of the side chain in the repeating unit, and there are various types between these side chain structures and the main chain structure as long as the effects of the present invention are not impaired. May contain the chemical structure of.

Further, the birefringence-inducing material of the present invention may contain a low molecular weight compound together with the liquid crystal polymer in order to promote the orientation of the side chains of the liquid crystal polymer. The low molecular weight compound has substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene known as mesogen components, and such substituents and allyl, acrylate, methacrylate, and cinnamic acid groups (or derivatives thereof) are included. A liquidity in which a functional group such as (group) is bonded via a spacer (for example, an (oxy) alkylene group having 1 to 15 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms)). Those having the above are preferably used. These small molecule compounds may be used alone or in combination of two or more.

In FIG. 1A, the birefringence-induced material layer 20 is laminated on the base material 10, but the base material 10 may be omitted. When a base material is used, it may be a base material made of an optically isotropic body, and may be a transparent base material made of an optically isotropic phase such as glass or a triacetyl cellulose film (TAC film). good. Further, as the base material, for example, a base material made of a material having low adhesion to the birefringence-inducing material layer (first optically anisotropic layer) such as a general-purpose polyester film is used as the base material for mold release. You may. When a release base material is used, it can be peeled off after forming the optical laminate of the present invention. Therefore, it is not necessary to consider the optical characteristics of the base material itself, and an opaque base material may be used. For example, after forming the optical laminate of the present invention on a base material, it is bonded to another optical member (for example, a polarizing plate) via an adhesive or the like, and then the release base material is peeled off and used. As a result, the optical laminate can be made into a thin optical member having a structure having no base material and having a thickness substantially only the thickness of the optically anisotropic layer.

As the birefringence-inducing material layer made of the birefringence-inducing material as described above, a pre-formed birefringence-inducing material film (which may or may not be laminated on the base material) may be used. It may be formed by coating the substrate. When forming a coating film of a birefringence-inducing material, the birefringence-inducing material as described above is dissolved in a solvent to prepare a solution, and this solution is applied onto a substrate. The solvent can be appropriately selected depending on the type of the compound refraction-inducing material, for example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol derivative (for example, ethylene glycol). Examples thereof include monoethyl ether, diethylene glycol monoethyl ether, etc.), propylene glycol derivatives (for example, propylene glycol monomethyl ether, propylene glycol 1-monomethyl ether 2-acetylate, etc.), and these solvents may be used alone or in combination of two or more. May be used.
The concentration of the solvent is not particularly limited, but may be, for example, 5 to 50% by weight of the birefringence-inducing material, preferably 8 to 40% by weight, and more preferably 10 to 25% by weight. May be good. For coating the solution on the base material, a known coating method such as spin coating or roll coating can be used.
After coating, if necessary, the coating film may be dried by heating to form a laminate having a base material and a birefringence-induced material layer.

Prior to the first light irradiation step, the birefringence-induced material layer is preferably substantially optically isotropic, that is, the liquid crystal polymer is not substantially oriented.

(First light irradiation step)
In the first light irradiation step, the birefringence-induced material layer is irradiated with the first polarized light for developing a phase difference. By performing the first light irradiation step, a selective photoreaction of molecules occurs not only on the surface of the birefringence-induced material layer but also inside, the orientation of the molecules is induced, and the first optical anisotropy is induced. Layers are formed. In the method for producing an optical laminate of the present invention, the first polarized light can be directly irradiated on the birefringence-induced material layer without interposing another layer, so that the intended slow-phase axis is formed by the irradiated polarized light. can do.

In the first polarization, the photosensitive group of a liquid crystal polymer such as infrared rays, visible rays, ultraviolet rays (for example, near ultraviolet rays, far ultraviolet rays, etc.), X-rays, charged particle rays (for example, electron beams, etc.) undergoes a photoreaction. The wavelength of light is not particularly limited as long as it is generated, and the wavelength of light may be 200 to 500 nm, although it depends on the type of side chain structure of the liquid crystal polymer. The first polarized light may be, for example, linearly polarized light of ultraviolet rays. In this case, for example, using an ultraviolet irradiation device such as a high-pressure mercury lamp as a light source, the polarized light may be converted to linearly polarized light via a Grantailer prism. good.
Further, the irradiation amount of the first polarized light may be, for example, 10 mJ / cm ^{2 to} 10 J / cm ² from the viewpoint of orienting not only the surface of the birefringence-induced material layer but also the inside, preferably 50 mJ / cm ^2. ~1J / cm ^2, more preferably it may be ^{100mJ / cm 2 ~500mJ / cm 2} .

If necessary, the method for producing an optical laminate of the present invention may include a heating step of heating the formed first optically anisotropic layer after the first light irradiation step. Molecular orientation is induced depending on the irradiation direction and vibration direction of the first polarized light irradiated in the first light irradiation step, and unaligned molecules are also oriented according to the oriented molecules, but the liquid crystallinity is increased by subsequent heating. Molecules can move, and the orientation of unaligned molecules can be promoted. After heating, it may be cooled to about room temperature by, for example, leaving it to stand.

The heating temperature in the heating step is not particularly limited as long as the orientation of the unaligned molecules is induced along the side chain in which the liquid crystal polymer causes a photoreaction by molecular motion, but the liquid crystal phase transition temperature of the birefringence-inducing material is not particularly limited. With the above, it is preferable to set the temperature to be equal to or lower than the isotropic phase transition temperature. For example, it may be 100 to 200 ° C., preferably 110 to 180 ° C., and more preferably 120 to 160 ° C.

The heating time is not particularly limited as long as the orientation of the unaligned molecules is induced along the side chain in which the liquid crystal polymer causes a photoreaction by molecular motion, but the type of the liquid crystal polymer, the heating temperature, etc. It may be appropriately set according to the above, and may be carried out for, for example, 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. The upper limit is not particularly limited, but from the viewpoint of economy, it may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes).

(Surface orientation process)
In the surface orientation step, the surface of the first optically anisotropic layer is oriented so as to be oriented differently from the inner layer thereof. By performing the surface orientation treatment, a surface layer is formed on the first optically anisotropic layer and is composed of the same birefringence-inducing materials, but two layers, an inner layer and a surface layer having different orientation states, are formed. It is formed in the first optically anisotropic layer. The inner layer may indicate a portion of the first optically anisotropic layer other than the surface layer.

The method of orientation treatment is not particularly limited as long as the surface of the first optically anisotropic layer can form an orientation layer different from the inner layer thereof, and examples thereof include rubbing treatment and photoalignment treatment by second polarization irradiation. Can be mentioned. In the rubbing process, the orientation direction can be controlled by rubbing the surface of the first optically anisotropic layer in a certain direction by rotating a roller wrapped with a cloth such as cellulose, nylon, or polyester while pushing it at a constant pressure. Therefore, a surface layer in a desired orientation direction can be formed, but the method of alignment treatment is preferably photoalignment treatment by polarization irradiation.

In the surface orientation step, the surface of the first optically anisotropic layer is irradiated with a second polarized light having a polarization axis direction different from that of the first polarized light, and the surface layer is formed on the first optically anisotropic layer. It may be the second light irradiation step to form. In the second light irradiation step, even after the molecular orientation is performed by the first light irradiation step (preferably, the first light irradiation step and the heating step), the polarization axis direction different from that of the first polarization is obtained. By irradiating the second polarized light having, an axis-selective photoreaction is selectively generated in the vicinity of the surface centering on the unreacted birefringence-inducing material of the first optically anisotropic layer, or in the vicinity of the surface. It is possible to impart an orientation different from that of the inner layer. On the other hand, probably because the molecules in the inner layer of the first optically anisotropic layer are already oriented with a high degree of orientation, the inside of the first optically anisotropic layer even after the second light irradiation step. The layer orientation itself is not transformed.

As the second polarized light, light having various wavelengths described above can be used as the first polarized light, and for example, linearly polarized light of ultraviolet rays may be used. Further, as the second polarized light, a type of light different from that of the first polarized light irradiated in the first light irradiation step may be used, or a similar type of light may be used.

The second polarized light may have a polarization axis direction different from that of the first polarized light, and for example, the axis angle may differ from the polarization axis of the first polarized light by 5 to 85 °, preferably 10. It may differ by ~ 80 °, more preferably 20 ~ 70 °. Here, the difference in the axis angle between the polarization axis of the second polarization and the polarization axis of the first polarization is the orientation state near the surface of the first optically anisotropic layer after the first light irradiation step (not yet). The slow axis of the second optically anisotropic layer to be formed later can be arbitrarily set by adjusting in consideration of the abundance ratio of the birefringence-inducing material in the reaction.

^{The irradiation amount of the second polarized light may be, for example, 50 mJ / cm 2 to 20} J / cm ² , preferably 100 mJ / cm, from the viewpoint of reorientating the surface of the first optically anisotropic layer that is oriented. It may be ^{cm 2 to} 10 J / cm ² , more preferably 150 mJ / cm ^{2 to 1} J / cm ^2.

If necessary, the method for producing an optical laminate of the present invention may further include a surface treatment step of treating the surface of the birefringence-induced material layer with a solvent after the first light irradiation step. After the surface treatment step, it is preferable to perform a surface orientation step such as a second polarization irradiation and a rubbing treatment. Further, when the heating step is performed after the first light irradiation step, the surface treatment step may be performed after the heating step.

In the surface treatment step, a solvent is applied to the surface of the first optically anisotropic layer to dissolve the surface portion, whereby the molecular orientation given by the first light irradiation step is relaxed and a random state is obtained. Perhaps because it is possible, the orientation of the surface portion of the first optically anisotropic layer once formed by the first polarization can be eliminated, and the orientation of the surface layer of the first optically anisotropic layer is isotropic. Can be. In the surface treatment step, the solvent may be applied to the surface of the first optically anisotropic layer and then dried. The drying method is not particularly limited as long as the applied solvent can be evaporated, but for example, it may be left to dry naturally. Only the surface to which the solvent is applied can be isotropic.

Since the surface becomes isotropic, the light orientation of the surface becomes easy in the subsequent second light irradiation step, so that the irradiation amount of the second polarized light can be reduced. When the surface treatment step is performed, the irradiation amount of the second polarization may be, for example, 0.1 mJ / cm ^{2 to} 200 mJ / cm ² , preferably 0.5 mJ / cm ^{2 to} 150 mJ / cm ² . more preferably it may be a ^{1mJ / cm 2 ~100mJ / cm 2} .
When the surface treatment step is performed, the ratio of the irradiation amount of the first polarized light to the irradiation amount of the second polarized light (first polarized light / second polarized light) is 1.5 / 1 to 100/1. It may be 2/1 to 80/1, more preferably 2.5 / 1 to 50/1.

Since the surface becomes isotropic, it is not necessary to consider the orientation state of the surface layer of the first optically anisotropic layer in the subsequent second light irradiation step, so that the polarization axis of the second polarized light is used. The axial angle can be directly reflected on the slow axis of the second optically anisotropic layer. Therefore, the axis angle of the polarization axis of the second polarized light can be easily selected with respect to the setting of the slow phase axis of the second optically anisotropic layer to be formed later.

The solvent used in the surface treatment step is not particularly limited as long as it can dissolve the birefringence-inducing material constituting the first optically anisotropic layer, and is a good solvent for the birefringence-inducing material. It may be a poor solvent. The solvent used in the surface treatment step is, for example, a good birefringence-inducing material from the viewpoint of making the surface of the first optically anisotropic layer isotropic and suppressing the dissolution to the inside to disturb the orientation. It may be a mixed solvent in which a solvent and a poor solvent are mixed. When a mixed solvent containing a good solvent and a poor solvent of the compound refraction-inducing material is used, it can be appropriately adjusted according to the solubility of the solvent used in the compound refraction-inducing material. / Poor solvent) may be 1/100 to 100/1, preferably 1/50 to 50/1, and more preferably 1/10 to 10/1.

The solvent used in the surface treatment step is, for example, water; an alcohol solvent such as methanol, ethanol, propanol, isopropyl alcohol, pentanol, hexanol; an aliphatic or alicyclic solvent such as hexane, heptane, octane, cyclohexane. Aromatic hydrocarbon solvents such as benzene, toluene and xylene; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, isopropyl methyl ketone, methyl isobutyl ketone and cyclohexanone; ethyl ether and propyl Ether solvents such as ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, tetrahydrofuran, dioxane; nitrile solvents such as acetonitrile and propionitrile; sulfoxide solvents such as dimethyl sulfoxide; amides such as N, N-dimethylformamide System solvent; Ester solvent such as methyl acetate, ethyl acetate, butyl acetate; Glycol solvent such as ethylene glycol and propylene glycol; Glycol monoethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol 1-monomethyl ether 2 -Glycol ether-based solvents such as acetate; halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, and dichlorobenzene; and the like. These solvents may be used alone or in combination of two or more. Since these solvents have different solubilities depending on the type of birefringence-inducing material, it is necessary to consider whether the solvent is a good solvent or a poor solvent depending on the birefringence-inducing material used. can.
In the present invention, a good solvent means a solvent having a solubility in a solute of 1% by mass or more at 25 ° C., and a poor solvent means a solvent having a solubility in a solute of less than 1% by mass at 25 ° C.

For example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene or the like may be used as a good solvent for the birefringence-inducing material, and ethanol, methanol, n-hexane or the like may be used as a poor solvent for the birefringence-inducing material. You may use it. These good solvents and poor solvents may be mixed at the above-mentioned mixed weight ratio and used as a mixed solvent.

(Second optically anisotropic layer forming step)
In the second optically anisotropic layer forming step, a polymerizable liquid crystal material is applied on the surface layer of the first optically anisotropic layer that has been oriented to form a second optically anisotropic layer. By performing the second optical anisotropy layer forming step, the surface layer oriented in the surface orientation step acts as an alignment film, and therefore the second optical anisotropy oriented using the orientation direction. Layers can be formed.

In the present invention, the polymerizable liquid crystal material is a composition containing a monofunctional or bifunctional polymerizable liquid crystal compound containing at least a reactive functional group and a mesogen group, and is polymerized by light or heat or reacted with a cross-linking agent. Contains the composition after forming a crosslinked structure with.

The polymerizable liquid crystal compound may be a liquid crystal monomer or a liquid crystal polymer. For example, as the polymerizable liquid crystal compound, a polymerizable liquid crystal monomer having a polymerizable functional group that polymerizes by light or heat and / or a polymerizable liquid crystal polymer, or a cross-linking functional group capable of introducing a cross-linked structure by reaction with a cross-linking agent. Examples thereof include a crosslinkable liquid crystal monomer and / or a crosslinkable liquid crystal polymer having a crosslinkable liquid crystal polymer.

The polymerizable liquid crystal compound is a monomer having a mesogen group or a polymer having a unit composed of a mesogen group, and is not particularly limited as long as it can form a liquid crystal structure and has polymerizable and / or crosslinkability. Various polymerizable liquid crystal compounds can be used. Examples of the polymerizable liquid crystal compound include Schiff base-based, biphenyl-based, terphenyl-based, ester-based, thioester-based, stillben-based, trans-based, azoxy-based, azo-based, phenylcyclohexane-based, pyrimidine-based, cyclohexylcyclohexane-based, and trimesin. Liquid crystal compounds having an acid-based, triphenylene-based, Torxene-based, phthalocyanine-based, porphyrin-based molecular skeleton, or a mixture of these compounds can be mentioned, and any compound exhibiting a nematic, cholesteric, or smectic liquid crystal phase. It may be. As an example, a photopolymerizable nematic liquid crystal monomer may be used as the polymerizable liquid crystal compound.

The unit composed of the mesogen group may be in the main chain or the side chain of the liquid crystal polymer. As the main chain type liquid crystal polymer, polyester type, polyamide type, polycarbonate type, polyimide type, polyurethane type, polybenzimidazole type, polybenzoxazole type, polybenzthiazole type, polyazomethine type, polyesteramide type, polyester carbonate type, Examples thereof include polyesterimide-based liquid crystal polymers and mixtures thereof. The side chain type liquid crystal polymer is a polymer having a linear or cyclic skeleton chain such as polyacrylate-based, polymethacrylate-based, polyvinyl-based, polysiloxane-based, polyether-based, and polymalonate-based polymer. Examples thereof include a liquid crystal polymer to which a mesogen group is bonded, a mixture thereof, and the like.

Further, the polymerizable liquid crystal material may contain a photopolymerization initiator and / or a thermal polymerization initiator when the polymerizable liquid crystal compound has a polymerizable functional group.

Photopolymerization initiators include Irgacure 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all manufactured by Ciba Japan Co., Ltd.), Sakeol BZ, Sakeall Z, Sakeall BEE (and above). , All manufactured by Seiko Kagaku Co., Ltd., kayacure BP100 (manufactured by Nippon Kayaku Co., Ltd.), Kayacure UVI-6992 (manufactured by Dow), ADEKA PTOMER SP-152 or ADEKA PTOMER SP-170 (above) , All of which are manufactured by ADEKA Corporation, TAZ-A, TAZ-PP (all manufactured by Nihon Shibel Hegner Co., Ltd.) and TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.), and commercially available photopolymerization initiators can be used.

Examples of the thermal polymerization initiator include azo compounds such as azobisisobutyronitrile; and peroxides such as hydrogen peroxide, persulfate, and benzoyl peroxide.

The content of the polymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.03 to 10% by weight, still more preferably 0.05 to 8% by weight, based on the total weight of the polymerizable liquid crystal material. .. Within the above range, the polymerizable liquid crystal compound can be polymerized without disturbing the orientation.

When a photopolymerization initiator is used as the polymerization initiator, a photosensitizer may be used in combination. Examples of the photosensitizer include xanthone compounds such as xanthone and thioxanthone (eg, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); anthracene and anthracene such as alkoxy group-containing anthracene (eg, dibutoxyanthracene, etc.). Compounds; phenothiazines; rubrene and the like can be mentioned.

Further, the polymerizable liquid crystal material may contain an appropriate cross-linking agent when the polymerizable liquid crystal compound has a cross-linking functional group. In this case, the polymerizable liquid crystal compound may be a liquid crystal compound that can be oriented and fixed by means such as crosslinking (thermal crosslinking or photocrosslinking) in a liquid crystal state or in a state of being cooled to a liquid crystal transition temperature or lower.

Examples of the crosslinkable functional group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxylanyl group, an oxetanyl group and the like. Of these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxylanyl group and an oxetanyl group are preferable, and an acryloyloxy group is more preferable.

When the polymerizable liquid crystal material contains a cross-linking agent, in addition to forming a cross-link with the polymerizable liquid crystal compound having a cross-linking functional group, when the liquid crystal polymer of the compound refraction-inducing material has a cross-linking functional group. , The liquid crystal polymer can form a crosslinked bond. In this case, a cross-linking bond can be formed between the first optically anisotropic layer composed of the birefringence-inducing material and the second optically anisotropic layer containing a cross-linking agent. Adhesion between layers can be improved.

Examples of the cross-linking agent include polyfunctional compounds having two or more functional groups in the molecule. When a crosslink is formed on the liquid crystal polymer, the polyfunctional compound is not particularly limited as long as it has a functional group capable of forming a crosslink with the liquid crystal polymer. For example, the liquid crystal polymer is crosslinked. When the crosslinkable functional group has a sex functional group and the crosslinkable functional group is a hydroxyl group or a carboxy group, a compound having an isocyanate group, a carbodiimide group, an aziridine group, an azetidine group, an oxazoline group, an epoxy group and the like can be mentioned. Among these cross-linking agents, it is a polyfunctional compound having two or more isocyanate groups in the molecule from the viewpoint of reactivity that reacts with the cross-linking functional group of the liquid crystal polymer under relatively mild reaction conditions. Polyisocyanate-based compounds are preferable, and known polyisocyanate-based compounds can be used. For example, examples of the polyisocyanate compound include a diisocyanate compound and a triisocyanate compound. Examples of the diisocyanate compound include phenylenediocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, methylcyclohexylene diisocyanate, bis (isocyanatomethyl) cyclohexane, methylenebis (cyclohexyl isocyanate), isophorone diisocyanate, and hexamethylene diisocyanate. Examples thereof include a condensed compound of diol and diol. Examples of the triisocyanate compound include an isocyanurate compound of diisocyanate such as hexamethylene diisocyanate, a biuret compound, and an adduct compound which is an adduct of diisocyanate such as hexamethylene diisocyanate and methylolpropane. Of these cross-linking agents, a triisocyanate compound can be preferably used.

When the cross-linking agent is a polyisocyanate compound, the liquid crystal polymer may have an active hydrogen group as a cross-linking functional group. Examples of the active hydrogen group include a hydroxyl group, a carboxy group, an amino group, a thiol group and the like. When the active hydrogen group is a hydroxyl group, a urethane bond (-NH-CO-O-) is formed, and when the active hydrogen group is a carboxy group, an amide bond (-NH-CO-) is formed, and the active hydrogen group is formed. When is an amino group, a urea bond (-NH-CO-NH-) is formed, and when the active hydrogen group is a thiol group, a thiourethane bond (-NH-CO-S-) is formed. As the active hydrogen group contained in the liquid crystal polymer, a hydroxyl group and a carboxy group are preferable.

In the present invention, the content of the cross-linking agent in the polymerizable liquid crystal material is determined from the viewpoint of suppressing the orientation of the second optically anisotropic layer and the deterioration of the optical properties due to the reaction with the liquid crystal polymer. It may be 0.01 to 5% by weight, preferably 0.05 to 3% by weight, and more preferably 0.1 to 1.5% by weight based on the total weight of the above.

In the second optically anisotropic layer forming step, the above-mentioned polymerizable liquid crystal material is applied on the surface layer of the first optically anisotropic layer. The application may be carried out by applying a polymerizable liquid crystal material dissolved in a solvent as a solution by a known coating method such as spin coating or roll coating. The solvent can be appropriately selected depending on the type of the polymerizable liquid crystal material. For example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol derivative (for example, ethylene). Glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, etc.), propylene glycol derivatives (propylene glycol monomethyl ether, propylene glycol 1-monomethyl ether 2-acetylate, etc.), etc., and these solvents may be used alone or in combination of two. You may use it in combination of more than seeds.

The solvent of the polymerizable liquid crystal material can be selected according to not only the combination of the types of the birefringence-inducing material and the polymerizable liquid crystal material but also the orientation state of the surface layer. For example, if most of the molecules of the surface layer have the desired orientation (for example, when a surface treatment step is performed or when a rubbing treatment is performed as an orientation treatment), the orientation of the surface layer is second. The solvent of the polymerizable liquid crystal material is preferably a poor solvent of the birefringence-inducing material from the viewpoint of suppressing the orientation of the first optically anisotropic layer from being disturbed while imparting it to the optically anisotropic layer. On the other hand, when only a part of the molecules of the surface layer has a desired orientation, the solvent of the polymerizable liquid crystal material is preferably a mixed solvent in which a good solvent and a poor solvent of the birefringence-inducing material are mixed. Although the mechanism in this case is not clear, when a poor solvent of the birefringence-inducing material is contained as the solvent of the polymerizable liquid crystal material, the first optically anisotropic layer is not invaded and the orientation is suppressed from being disturbed. can do. On the other hand, if a good solvent of the birefringence-inducing material is contained as the solvent of the polymerizable liquid crystal material, the wettability of the solution to the surface layer is improved, or the solution is polymerizable with respect to the orientation of only a part of the molecules of the surface layer. The molecules of the liquid crystal material can be aligned so that the second optically anisotropic layer can be oriented. The solvent of the polymerizable liquid crystal material can be appropriately adjusted according to the combination of the types of the birefringence-inducing material and the polymerizable liquid crystal material and the orientation state of the surface layer, but the orientation of the first optically anisotropic layer is maintained. From this point of view, it is preferable to contain a poor solvent for the birefringence-inducing material so as not to invade the surface layer. May be 0/100 to 100/1, preferably 0/100 to 50/1, and more preferably 0/100 to 10/1. As the solvent of the polymerizable liquid crystal material, a general solvent can be used depending on the intended purpose, but for example, toluene, an ethylene glycol derivative, a propylene glycol derivative and the like may be contained.

A coating film is formed by applying the solution, and if necessary, the coating film is heated to dry. At that time, the surface layer of the first optically anisotropic layer existing at the lower part functions as an alignment film (orientation imparting film), and the liquid crystal molecules are oriented. As a result, a second optically anisotropic layer in which the liquid crystal is oriented in a predetermined direction is formed.

The second optically anisotropic layer forming step may include a heating step and / or a light irradiation step (for example, a non-polarized light irradiation step), if necessary, after forming the coating film of the polymerizable liquid crystal material. The polymerizable liquid crystal material is already oriented in a predetermined direction corresponding to the orientation of the surface layer of the first optically anisotropic layer by forming a coating film, and is subsequently heated and / or irradiated with light. The orientation is fixed by the polymerizable liquid crystal material being polymerized and / or crosslinked in the step (for example, the non-polarized light irradiation step).
Specifically, when the polymerizable liquid crystal material is made of a heat-polymerizable material, the orientation is fixed by polymerization by heating. When it is made of a photopolymerizable material, polymerization occurs when it is irradiated with light, and the orientation is fixed. When made of a crosslinkable material, crosslinkage occurs during heating and / or irradiation with light, and the orientation is fixed.

Further, when the polymerizable liquid crystal material contains a cross-linking agent and the cross-linking agent has a functional group capable of forming a cross-linking bond with the birefringence-inducing material, the first optical difference is obtained by applying thermal energy and / or light energy. A crosslinked bond can be formed between the rectangular layer and the second optically anisotropic layer.

The heating step in the second optically anisotropic layer forming step is not particularly limited as long as the above-mentioned polymerization and / or cross-linking reaction proceeds, but suppresses disturbing the orientation of the inner layer of the first optically anisotropic layer. From the viewpoint, it is preferable to carry out at a heating temperature equal to or lower than the isotropic phase transition temperature of the birefringence-inducing material. For example, it may be 70 to 180 ° C., preferably 80 to 150 ° C., and more preferably 100 to 140 ° C. The heating time may be, for example, 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. The upper limit is not particularly limited, but from the viewpoint of economy, it may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes).

The light irradiation step in the second optically anisotropic layer forming step is not particularly limited as long as the polymerization and / or crosslinking reaction proceeds, but non-polarized light is preferable as the light to be irradiated. As the unpolarized light, light having various wavelengths described above can be used as the first polarized light or the second polarized light, and for example, unpolarized ultraviolet rays may be used. The dose of light ^may be a ^{10mJ / cm 2 ~10J / cm 2} , preferably ^{50mJ / cm 2 ~1J / cm 2} , more preferably may be 100mJ ^/ cm ² ~500mJ ^/ cm 2 ..

[Optical laminate]
The optical laminate of the present invention is an optical laminate in which a first optically anisotropic layer made of a birefringence-inducing material and a second optically anisotropic layer made of a polymerizable liquid crystal material are laminated adjacent to each other. The first optically anisotropic layer is composed of a surface layer and an inner layer having different slow axes, and the surface layer and the second optically anisotropic layer are in contact with each other.

The first optically anisotropic layer is composed of a surface layer and an inner layer, and these layers are composed of the same birefringence-inducing material. For example, the thickness of the first optically anisotropic layer may be 0.1 to 20 μm, preferably 0.3 to 15 μm, and more preferably 0.5 to 10 μm. The surface layer may be near the surface of the first optically anisotropic layer in contact with the second optically anisotropic layer. For example, the surface layer may be formed by orienting the surface of the first optically anisotropic layer so as to give an orientation different from that of the inner layer. Here, the alignment treatment may be performed according to the aspect of the surface orientation step in the above-mentioned production method.

The polymerizable liquid crystal material constituting the second optically anisotropic layer may contain a cross-linking agent having a functional group capable of forming a cross-linking bond with the birefringence-inducing material. The cross-linking agent contained in the polymerizable liquid crystal material forms a cross-linking bond with the birefringence-inducing material of the first optically anisotropic layer, whereby the first optically anisotropic layer and the second optically anisotropic layer are formed. Adhesion with is improved. As a result, it is not necessary to provide an adhesive layer between the first optically anisotropic layer and the second optically anisotropic layer, so that the optical laminate can be thinned and the first The structure can be such that the surface layer of the optically anisotropic layer and the second optically anisotropic layer are in contact with each other. The adhesion between the first optically anisotropic layer and the second optically anisotropic layer can be confirmed by the cross-cut test described in Examples described later.

The thickness of the second optically anisotropic layer may be 0.1 to 20 μm, preferably 0.3 to 15 μm, and more preferably 0.5 to 10 μm. The thickness ratio of the first optically anisotropic layer to the second optically anisotropic layer (first optically anisotropic layer / second optically anisotropic layer) is 1/10 to 10 It may be 10/1, preferably 1/8 to 8/1, and more preferably 1/5 to 5/1. For example, the second optically anisotropic layer may be formed by applying a polymerizable liquid crystal material on the surface layer of the first optically anisotropic layer that has been oriented. Here, the application of the polymerizable liquid crystal material may be applied according to the mode of the second optically anisotropic layer forming step in the above-mentioned production method.

The thickness of the optical laminate of the present invention may be, for example, 1 to 40 μm, preferably 2 to 30 μm, and more preferably 3 to 20 μm.

In the optical laminate of the present invention, the slow-phase axial direction of the inner layer of the first optically anisotropic layer and the slow-phase axial direction of the second optically anisotropic layer intersect. The optical laminate of the present invention is produced by the above-mentioned production method, so that the slow axis of the first optically anisotropic layer (inner layer) and the slow axis of the second optically anisotropic layer are It is possible to set the angle to be formed to any angle. The slow-phase axial direction of the first optically anisotropic layer (inner layer) and the slow-phase axial direction of the second optically anisotropic layer may intersect at an angle that is non-parallel and non-orthogonal. For example, the angle formed by the slow axis of the first optically anisotropic layer (inner layer) and the slow axis of the second optically anisotropic layer may be 5 to 85 °, preferably 8. It may be ~ 80 °, more preferably 10-75 °. The slow axis of the inner layer of the first optically anisotropic layer is measured as the slow axis of the entire first optically anisotropic layer because the influence of orientation on the surface layer can be considered to be negligible. You may.

In the optical laminate of the present invention, it is preferable that the slow phase axial direction is constant in the plane, particularly in the first optically anisotropic layer. In the present invention, the polarization state is not changed (for example, from linearly polarized light to elliptically polarized light) by irradiating the lower layer with polarized light via the oriented layer, or the molecular orientation is not disturbed. It is possible to keep the slow axis direction constant.

The optical laminate of the present invention can exhibit desired optical properties according to the above-mentioned aspect of the production method. Examples of the optical characteristics include a retardation value (for example, an in-plane retardation value: Re) and the like. The range shown below of these optical characteristics may be the range of the measured values of the optical laminate, and is the range of the measured values of the first optically anisotropic layer or the second optically anisotropic layer. May be good.

The in-plane retardation value (Re) is the anisotropy (ΔNxy = | nx−ny |) of the orthogonal biaxial refractive index (nx, ny) on the film and the film thickness d (nm). It is a parameter defined by the product (ΔNxy × d), and is a scale showing optical isotropic and anisotropy. In the optical laminate of the present invention, the in-plane retardation value (Re) may be, for example, 1 to 600 nm, preferably 3 to 500 nm, and more preferably 5 to 400 nm. The in-plane retardation value (Re) may be a measured value for light having a wavelength of 550 nm.

The optical laminate of the present invention can be used, for example, as a retardation film, and can be used for various optical members (antireflection film, optical compensation film, etc.). The optical laminate of the present invention can be used as a circular polarizing plate used as an antireflection film in an OLED such as an organic EL display device by laminating it with a linear polarizing plate as a retardation film, for example.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the present Examples.

(Monomer 1)
4- (6-Hydroxyhexyloxy) cinnamic acid was synthesized by heating p-coumaric acid and 6-chloro-1-hexanol under alkaline conditions. In the presence of p-toluenesulfonic acid, a large excess of methacrylic acid was added to this product for an esterification reaction to synthesize monomer 1 represented by the following chemical formula.

(Monomer 2)
4- (6-Hydroxyhexyloxy) benzoic acid was synthesized by heating 4-hydroxybenzoic acid and 6-chloro-1-hexanol under alkaline conditions. Next, a large excess of methacrylic acid was added to this product in the presence of p-toluenesulfonic acid to cause an esterification reaction, and a monomer 2 represented by the following chemical formula was synthesized.

(Copolymer 1)
Monomer 1 and monomer 2 are dissolved in dioxane so that the molar ratio of monomer 1 to monomer 2 is monomer 1: monomer 2 = 3: 7, and the reaction initiator is used. Copolymer 1 was obtained by adding AIBN (azobisisobutyronitrile) and polymerizing at 70 ° C. for 24 hours. This copolymer 1 exhibited liquid crystallinity.

(Copolymer 2)
Monomer 1, simple so that the molar ratio of monomer 1, monomer 2, 2-hydroxyethyl methacrylate (HEMA) is monomer 1: monomer 2: HEMA = 3: 7: 2. Polymer 2 and HEMA were dissolved in dioxane, AIBN (azobisisobutyronitrile) was added as a reaction initiator, and the mixture was polymerized at 70 ° C. for 24 hours to obtain a copolymer 2. This copolymer 2 exhibited liquid crystallinity.

In the following examples and comparative examples, the optical characteristics (retention value Re, etc.) of the obtained optical laminate are obtained by using a birefringence measuring device (AXOMETRICS, AxoScan), and the thickness is a film thickness meter (FILMETRIS, manufactured by FILMETRICS). It was measured using F20).

(Example 1)
Copolymer 1 was dissolved in tetrahydrofuran (THF) to prepare a solution. This solution was applied onto a cover glass substrate using a spin coater to a thickness of 2.4 μm, and dried at 25 ° C. The dried coating film is irradiated with polarized light (first polarized light) obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Gran Tailor prism for 200 seconds perpendicularly to the coating film (irradiation amount 200 mJ /). cm ² ), the first optically anisotropic layer was formed. After the first polarization irradiation, the orientation was induced by heating at 130 ° C. for 3 minutes and cooling to room temperature. The optical characteristics of the obtained coating film were 90 ° with respect to the axial direction of the irradiated polarization axis in the axial direction of the in-plane phase difference.

Then, using a Gran Tailor prism, the ultraviolet rays from the high-pressure mercury lamp are converted into linearly polarized light whose polarization axis direction is 45 ° different from the polarization axis direction of the previously irradiated polarized light (second polarized light). Was irradiated for 300 seconds (irradiation amount 300 mJ / cm ² ) to form a surface layer on the first optically anisotropic layer.

100 parts by weight of a polymerizable liquid crystal compound (BASF, LC-242) and 5 parts by weight of a photopolymerization initiator (Ciba Specialty Chemicals, Igalcure 907) are mixed, and THF and propylene glycol 1-monomethyl ether 2- A solution was prepared by dissolving in a mixed solvent having a volume ratio (THF: PGMEA) of 1: 1 with acetate (PGMEA). This solution was applied onto the coating film obtained after the second polarization irradiation to a thickness of 0.9 μm using a spin coater, heated to 70 ° C., cooled to room temperature, and then cooled to room temperature for the second optical. An anisotropic layer was formed. Further, non-polarized ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ / cm ² ) to polymerize the polymerizable liquid crystal compound. The obtained optical laminate had an in-plane retardation value of 242 nm (Linear Relayance: 228 nm, Circular Relayance: −78 nm).

In order to investigate the optical properties of each layer of the obtained optical laminate, only the second optically anisotropic layer was transferred to an optically isotropic film with an adhesive. Then, the optical characteristics of the peeled first optically anisotropic layer and second optically anisotropic layer were measured, respectively. The first optically anisotropic layer had an in-plane retardation value Re of 135 nm, and the slow-phase axial direction was 90 ° with respect to the polarization axial direction of the first polarized light irradiated. In the irradiation of the second polarized light, the first optically anisotropic layer itself was already oriented, so that the orientation itself was not significantly affected, and the axial direction was maintained. The second optically anisotropic layer had an in-plane retardation value Re of 115.3 nm, and the slow phase axial direction was 77 ° with respect to the polarization axial direction of the first polarized light irradiated. In the irradiation of the second polarized light, as a result of selecting the polarization axis direction in consideration of the orientation state near the surface of the first optically anisotropic layer, the desired second optically anisotropic layer is oriented in the slow axis direction. We were able to. As a result, it was confirmed that it was an optical laminate in which two optically anisotropic layers were laminated, and the angle formed by the slow axis of each layer was 13 °. In addition, the slow-phase axial direction was constant in the plane of the first optically anisotropic layer.

(Example 2)
Copolymer 1 was dissolved in THF to prepare a solution. This solution was applied onto a cover glass substrate using a spin coater to a thickness of 2.4 μm, and dried at 25 ° C. The dried coating film is irradiated with polarized light (first polarized light) obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Gran Tailor prism for 200 seconds (irradiation amount 200 mJ / cm ² ). An optically anisotropic layer was formed. After the polarization irradiation, the orientation was induced by heating at 130 ° C. for 3 minutes and cooling to room temperature. The optical characteristics of the obtained coating film were 90 ° with respect to the axial direction of the irradiated polarization axis in the axial direction of the in-plane phase difference.

Then, a mixed solvent having a volume ratio of THF and ethanol (THF: ethanol) of 1: 6 was applied to the obtained coating film with a spin coater, and the mixture was allowed to dry. Further, using a Gran Tailor prism, the ultraviolet rays from the high-pressure mercury lamp are converted into linearly polarized light whose polarization axis direction is 60 ° different from that of the previously irradiated polarized light (second polarization). Was irradiated for 70 seconds (irradiation amount 70 mJ / cm ² ) to form a surface layer on the first optically anisotropic layer.

100 parts by weight of a polymerizable liquid crystal compound (manufactured by BASF, LC-242) and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Igalcure 907) were mixed and dissolved in toluene to prepare a solution. This solution was applied onto the coating film obtained after the second polarization irradiation to a thickness of 0.9 μm using a spin coater, heated to 70 ° C., cooled to room temperature, and then cooled to room temperature for the second optical. An anisotropic layer was formed. Further, non-polarized ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ / cm ² ) to polymerize the polymerizable liquid crystal compound. The obtained optical laminate had an in-plane retardation value of 142.7 nm (Linear Retardance: 114.8 nm, Circular Retardance: 84.5 nm).

The optical characteristics of each layer of the obtained optical laminate were calculated by analysis software (Multi-Layer Analysis) of a birefringence measuring device (AxoScan, manufactured by AXOMETRICS). The first optically anisotropic layer had an in-plane retardation value Re of 100 nm, and the slow phase axial direction was 90 ° with respect to the polarization axial direction of the first polarized light irradiated. The second optically anisotropic layer had an in-plane retardation value Re of 180 nm, and the slow-phase axial direction was 28.5 ° with respect to the polarization axial direction of the first polarized light irradiated. As a result, it was confirmed that it was an optical laminate in which two optically anisotropic layers were laminated, and the angle formed by the slow axis of each layer was 61.5 °. In addition, the slow-phase axial direction was constant in the plane of the first optically anisotropic layer.

(Example 3)
Copolymer 2 was dissolved in THF to prepare a solution. This solution was applied onto a cover glass substrate using a spin coater to a thickness of 2.4 μm, and dried at 25 ° C. The dried coating film is irradiated with polarized light (first polarized light) obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Gran Tailor prism for 200 seconds (irradiation amount 200 mJ / cm ² ). An optically anisotropic layer was formed. After the first polarization irradiation, the orientation was induced by heating at 130 ° C. for 3 minutes and cooling to room temperature. The optical characteristics of the obtained coating film were 90 ° with respect to the axial direction of the irradiated polarization axis in the axial direction of the in-plane phase difference.

Then, using a Gran Tailor prism, the ultraviolet rays from the high-pressure mercury lamp are converted into linearly polarized light whose polarization axis direction is 45 ° different from the polarization axis direction of the previously irradiated polarized light (second polarized light). Was irradiated for 300 seconds (irradiation amount 300 mJ / cm ² ) to form a surface layer on the first optically anisotropic layer.

100 parts by weight of polymerizable liquid crystal compound (BASF, LC-242), 5 parts by weight of photopolymerization initiator (Ciba Specialty Chemicals, Igalcure 907), and polyisocyanate (Duranate TKA-100, Asahi Kasei Co., Ltd.) 0.6 parts by weight were mixed and dissolved in a mixed solvent having a volume ratio of THF and PGMEA (THF: PGMEA) of 1: 1 to prepare a solution. This solution was applied onto the coating film obtained after the second polarization irradiation to a thickness of 0.9 μm using a spin coater, heated to 70 ° C., cooled to room temperature, and then cooled to room temperature for the second optical. An anisotropic layer was formed. Further, non-polarized ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ / cm ² ) to polymerize the polymerizable liquid crystal compound and crosslink the copolymer 2. The obtained optical laminate had an in-plane retardation value of 202 nm (Linear Retardance: 185 nm, Circular Retardance: 81 nm). Further, a cross-cut test was carried out in order to confirm the adhesion of the interface between the first optically anisotropic layer and the second optically anisotropic layer. As a result of conducting the test in accordance with JIS K 5600, no peeling of the second optically anisotropic layer was observed, and it was confirmed that the test had good adhesion.

The optical characteristics of each layer of the obtained optical laminate showed the same optical characteristics as in Example 1.

(Comparative Example 1)
Copolymer 1 was dissolved in tetrahydrofuran (THF) to prepare a solution. This solution was applied onto a cover glass substrate using a spin coater to a thickness of 2.6 μm, and dried at 25 ° C. The dried coating film was irradiated with polarized light obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Gran Tailor prism for 30 seconds (irradiation amount: 30 mJ / cm ² ).

Then, 100 parts by weight of the polymerizable liquid crystal compound (manufactured by BASF, LC-242) and 5 parts by weight of the photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Igal Cure 907) were mixed on the obtained coating film. The solution dissolved in toluene was applied using a spin coater to a thickness of 1.2 μm, heated to 70 ° C., and then cooled to room temperature. It was confirmed that the polymerizable liquid crystal compound was oriented at 90 ° with respect to the irradiated polarization axis direction.

After that, the coating film was irradiated with polarized light obtained by converting the ultraviolet rays from the high-pressure mercury lamp into a linearly polarized light whose polarization axis direction was 60 ° different from the polarization axis direction of the previously irradiated polarization using a Gran Tailor prism (for 100 seconds). Irradiation amount 100 mJ / cm ² ).

The obtained optical laminate had an in-plane retardation value of 172.9 nm (Linear Retardance: 136.8 nm, Circular Retardance: −105.7 nm) at any point.

In order to investigate the optical characteristics of each layer of the obtained optical laminate, only the second optically anisotropic layer was peeled off. The second optically anisotropic layer had an in-plane retardation value Re of 116.8 nm at an arbitrary point, and the slow phase axial direction was 39.8 ° with respect to the polarization axis direction of the previously irradiated polarized light. .. From this, it was confirmed that it was an optical laminate in which two optically anisotropic layers were laminated, but the angle formed by the slow axis of each layer was 50.2 °, and at the time of the second polarization irradiation. It is significantly different from the polarization axis direction (= 60 °) of. Furthermore, it was confirmed that the slow-phase axial direction was not constant in the plane, the orientation was disturbed, and haze was caused by the generation of microdomains. This is due to the second polarization irradiation via the oriented second optical anisotropy, so that when the polarized light is incident on the first optical anisotropy composed of the copolymer 1, the linearly polarized light is used. It is considered that the polarization becomes elliptically polarized light and the polarization axis direction (long axis direction of elliptically polarized light) also changes. Therefore, in Comparative Example 1, it was difficult to produce a desired optical laminate.

Since the optical laminates of Examples 1 to 3 were produced by a specific method, it is possible to arbitrarily adjust the slow axis of each of the first optically anisotropic layer and the second optically anisotropic layer. there were. In particular, in Example 2, since the surface treatment with a solvent was performed before irradiating the second polarized light, it was possible to more easily orient the surface. Further, in Example 3, since a polyisocyanate having an isocyanate group capable of forming a crosslink with the hydroxy group of the copolymer 2 was contained together with the polymerizable liquid crystal compound, the first optically anisotropic layer and the second optically different layer were contained. The adhesion with the square layer was good.

On the other hand, in the optical laminate of Comparative Example 1, the polarized light for orienting the birefringence-induced material layer was irradiated through the layer made of the polymerizable liquid crystal material, so that the polarized light was converted by the layer made of the polymerizable liquid crystal material. Therefore, the slow axis of each layer could not be adjusted to the desired one.

According to the present invention, it is possible to provide an optical laminate in which the angle at which the slow-phase axes intersect with each other can be arbitrarily set. Such an optical laminate can be used in applications such as a polarizing plate used in a liquid crystal display device and an organic EL display device, and an optical compensation film. In particular, it can be used as a circular polarizing plate used in an organic EL display device by laminating it with a linear polarizing plate.

As described above, a preferred embodiment of the present invention has been described with reference to the drawings, but those skilled in the art can easily assume various changes and modifications within a self-evident range by looking at the present specification. There will be. Therefore, such changes and amendments are construed as being within the scope of the invention as defined by the claims.

10 ... Base material 20 ... Birefringence-induced material layer 30 ... First optical anisotropy layer 31 ... Inner layer 32 ... Surface layer 40 ... Second optical anisotropy Layer 100 ... Optical laminate

Claims (7)

A first optically anisotropic layer made of a birefringence-inducing material,
The second optically anisotropic layer made of a polymerizable liquid crystal material is an optically laminated body laminated adjacent to each other.
The first optically anisotropic layer is composed of a surface layer and an inner layer having different slow phases, and the surface layer and the second optically anisotropic layer are in contact with each other.
An optical laminate in which the slow-phase axial direction of the inner layer of the first optically anisotropic layer and the slow-phase axial direction of the second optically anisotropic layer intersect. In the optical laminate according to claim 1, the slow-phase axial direction of the inner layer of the first optically anisotropic layer and the slow-phase axial direction of the second optically anisotropic layer are non-parallel and non-parallel. Optical laminates that intersect at orthogonal angles. The optical laminate according to claim 1 or 2, wherein the polymerizable liquid crystal material contains a cross-linking agent having a functional group capable of forming a cross-linking bond with the birefringence-inducing material. The method for producing an optical laminate according to any one of claims 1 to 3.
A first light irradiation step of irradiating a birefringence-inducing material layer made of a birefringence-inducing material with first polarized light for expressing a phase difference to form a first optically anisotropic layer.
A surface orientation step of aligning the surface of the first optically anisotropic layer so as to give an orientation different from that of the inner layer to form a surface layer on the first optically anisotropic layer.
A method for producing an optical laminate, comprising a step of applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has been subjected to orientation treatment to form a second optically anisotropic layer. The production method according to claim 4, wherein in the surface orientation step, the surface of the first optically anisotropic layer is irradiated with a second polarized light having a polarization axis direction different from that of the first polarized light. A method for manufacturing an optical laminate, which is a second light irradiation step of forming a surface layer on the first optically anisotropic layer. The production method according to claim 5, wherein the surface of the first optically anisotropic layer is treated with a solvent between the first light irradiation step and the second light irradiation step. A method for manufacturing an optical laminate, further comprising a process. A circularly polarizing plate in which the optical laminate according to any one of claims 1 to 3 and a linear polarizing plate are laminated.

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