WO2020170874A1

WO2020170874A1 - Optical layered body and method for manufacturing same

Info

Publication number: WO2020170874A1
Application number: PCT/JP2020/004976
Authority: WO
Inventors: 丈也酒井
Original assignee: 林テレンプ株式会社
Priority date: 2019-02-22
Filing date: 2020-02-07
Publication date: 2020-08-27
Also published as: JPWO2020170874A1; CN113474691B; KR20210123290A; JP7196278B2; KR102645532B1; CN113474691A

Abstract

Provided are an optical layered body which can have an arbitrary axis setting, and a method for manufacturing the same. In the optical layered body (100), a first optically anisotropic layer (30) comprising a birefringence inducing material and a second optically anisotropic layer (40) comprising a polymerizable liquid crystal material are layered adjacent to each other, the first optically anisotropic layer (30) being constituted from a surface layer (32) and an internal layer (31) having mutually different slow axes, the surface layer (32) and the second optically anisotropic layer (40) being in contact with each other, and the slow-axis direction of the internal layer (31) of the first optically anisotropic layer and the slow-axis direction of the second optically anisotropic layer (40) intersecting with each other.

Description

Optical layered body and manufacturing method thereof

Related application

The present application claims the priority of Japanese Patent Application No. 2019-030471 filed on February 22, 2019, and is hereby incorporated by reference in its entirety as a part of the present application.

The present invention relates to an optical layered body in which arbitrary axes can be set and a manufacturing method thereof.

A variety of retardation plates are used in thin display devices such as liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs) to improve display quality. For example, in an OLED such as an organic EL display device, a broadband circular polarization plate is used to suppress reflection.

As a retardation film used for such a broadband circularly polarizing plate, Patent Document 1 (JP-A-2016-184013) discloses a first optically anisotropic layer made of a birefringence inducing material and a polymerizable liquid crystal. A second retardation film in which the second optically anisotropic layer is directly laminated without an adhesive layer is disclosed. Further, as its manufacturing method, a step of applying a birefringence inducing material on a supporting substrate to form a birefringence inducing material layer, and irradiating the birefringence inducing material layer with a first polarized light, One light irradiation step, the polymerizable liquid crystal is applied to the birefringence induction material layer irradiated with the first polarized light, and the polymerizable liquid crystal material layer is laminated on the birefringence induction material layer. And a second light irradiation step of irradiating the laminated body with second polarized light, the polarization axis direction of the first polarized light, and the polarization axis direction of the second polarized light. And are different from each other, a method for producing a retardation film is described.

JP, 2016-184013, A

However, in the method for producing a retardation film described in Patent Document 1, in the second light irradiation step of irradiating the second polarized light for aligning the birefringence inducing material layer, the polymerizable liquid crystal material layer that is aligned is aligned. The second polarized light is radiated through, and the polarization state of the second polarized light is converted when passing through the oriented polymerizable liquid crystal material layer, so that the desired polarization in the birefringence inducing material layer is changed. Was difficult to irradiate. Therefore, it was difficult to establish the intended slow axis relationship between the birefringence inducing material layer and the polymerizable liquid crystal material layer.

Therefore, an object of the present invention is to provide an optical layered body and a manufacturing method capable of setting an arbitrary slow axis in each optically anisotropic layer.

The present inventor, as a result of earnest research to solve the above problems, after forming a first optically anisotropic layer oriented by irradiating the birefringence inducing material layer with a first polarized light, By subjecting the surface of the optically anisotropic layer of 1 to 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 made of the birefringence-inducing material is not affected by another layer, the desired orientation can be imparted to the inner layer, and (ii) the role as the orientation film. Since the orientation of the surface layer to be achieved can be adjusted independently of the inner layer, it has been found that a desired orientation can be given to the second optically anisotropic layer in consideration of the relation with the orientation of the inner layer. It was Then, the obtained optical laminate was found to be able to arbitrarily set the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer, and completed the present invention. It was

That is, the present invention can be configured in the following modes.
[Aspect 1]
A first optically anisotropic layer made of a birefringence inducing material,
A second optically anisotropic layer made of a polymerizable liquid crystal material, which is an optical laminate 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,
An optical laminate in which 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 intersect.
[Aspect 2]
The optical laminate according to Aspect 1, wherein 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. An optical stack that intersects at an angle.
[Aspect 3]
The optical laminate according to Aspect 1 or 2, wherein the polymerizable liquid crystal material contains a crosslinking agent having a functional group capable of forming a crosslink with the birefringence inducing material.
[Mode 4]
A method for manufacturing the optical laminate according to any one of aspects 1 to 3,
On a birefringence inducing material layer made of a birefringence inducing material, irradiating a first polarized light for expressing a phase difference, a first light irradiation step of forming a first optically anisotropic layer,
The surface of the first optically anisotropic layer is subjected to an alignment treatment so as to give an orientation different from that of the inner layer, and a surface alignment step of forming a surface layer on the first optically anisotropic layer,
And a step of applying a polymerizable liquid crystal material to form a second optically anisotropic layer on the surface of the first optically anisotropic layer that has been subjected to the alignment treatment.
[Aspect 5]
The production method according to Aspect 4, wherein the surface alignment step irradiates the surface of the first optically anisotropic layer with second polarized light having a polarization axis direction different from that of the first polarized light. And a second light irradiation step of forming a surface layer on the first optically anisotropic layer, the method for producing an optical laminate.
[Aspect 6]
The manufacturing method according to Aspect 5, wherein 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. The manufacturing method of an optical laminated body further provided with.
[Aspect 7]
A circularly polarizing plate in which the optical laminate according to any one of aspects 1 to 3 and a linearly polarizing plate are laminated.
[Aspect 8]
The optical laminate according to any one of aspects 1 to 3, wherein
The birefringence inducing material, a first optically anisotropic layer formed by irradiating a first polarized light for expressing a phase difference,
The surface of the first optically anisotropic layer is subjected to an alignment treatment so as to give an orientation different from that of the inner layer, and a surface layer formed on the first optically anisotropic layer,
An optical layered body comprising a second optically anisotropic layer formed by applying a polymerizable liquid crystal material on the surface layer.

Note that any combination of at least two components disclosed in the claims and/or the description and/or the drawings is included in the present invention. In particular, any combination of two or more claims recited in the claims is included in the present invention.

According to the optical layered body and the method for producing the same of the present invention, a desired combination of slow axis can be formed in the first optically anisotropic layer and the second optically anisotropic layer, so that the slow phase of each other is delayed. 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 linearly polarizing plate.

The present invention will be understood more clearly from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily shown to scale and are exaggerated to illustrate the principles of the invention. However, the embodiments and drawings are for illustration and description purposes only, and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims.
It is a schematic sectional drawing before the 1st light irradiation process in one embodiment of the manufacturing method of the optical layered product of the present invention. It is a schematic sectional drawing after the 1st light irradiation process in one embodiment of the manufacturing method of the optical layered product of the present invention. It is a schematic sectional drawing after the surface alignment process in one embodiment of a manufacturing method of an optical layered product of the present invention. It is a schematic sectional drawing after the 2nd optically anisotropic layer formation process in one embodiment of a manufacturing method of an optical layered product of the present invention.

[Method for producing optical laminate]
The method for producing an optical layered body of the present invention comprises irradiating a birefringence inducing material layer made of a birefringence inducing material with a first polarized light for expressing a retardation, and orienting the first optical anisotropy. A first light irradiation step of forming a layer, and the surface of the first optically anisotropic layer is subjected to an alignment treatment so as to give an orientation different from that of the internal layer, and the surface of the first optically anisotropic layer is formed. The method includes a surface alignment step of forming a layer, and a step of applying a polymerizable liquid crystal material to form a second optically anisotropic layer on the surface of the first optically anisotropic layer subjected to the alignment treatment.

An embodiment of the present invention will be described below with reference to the drawings. 1A to 1D are schematic cross-sectional views for explaining one embodiment of a method for manufacturing an optical layered body of the present invention. Although cross-sections of each layer are shown in FIGS. 1A-1D, these do not represent actual thickness ratios.

FIG. 1A is a schematic cross-sectional view showing a laminate of a base material 10 and a birefringence inducing material layer 20. FIG. 1B shows a state after the first light irradiation step, and shows the substrate 10 and the first optical anisotropy formed by orienting the molecules of the birefringence inducing material layer 20 by irradiation of the first polarized light. It is a schematic sectional drawing which shows the laminated body with the layer 30. FIG. 1C shows a state after the surface alignment step, in which the substrate 10, the inner layer 31 having the same orientation as the first optically anisotropic layer 30, and the alignment treatment on the surface opposite to the substrate 10 are performed. 3 is a schematic cross-sectional view showing a laminated body with the first optically anisotropic layer 30 formed of a surface layer 32 having an orientation different from that of the inner layer 31. FIG. FIG. 1D shows a state after the second optically anisotropic layer forming step, in which the base material 10, the first optically anisotropic layer 30 including the inner layer 31 and the surface layer 32, and the polymerizable liquid crystal material are shown. It is a schematic sectional drawing which shows the optical laminated body 100 with the 2nd optical anisotropic layer 40 formed by applying.

The molecular orientation of the birefringence inducing material can be induced 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 retardation. Thereby, as shown in FIG. 1B, the first optically anisotropic layer 30 oriented so as to have a predetermined slow axis is formed from the optically isotropic birefringence inducing material layer 20. In the first light irradiation step, since there is no other layer on the birefringence inducing material layer 20, the birefringence inducing material layer 20 is not converted without changing 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 subjected to an alignment treatment so as to be oriented differently from the orientation given in the first light irradiation step, whereby the first optically anisotropic layer is obtained. The surface layer 32 can be formed on the functional layer 30. As a result, as shown in FIG. 1C, the first optically anisotropic layer 30 is formed into two layers, that is, the inner layer 31 having the originally formed orientation and the surface layer 32 having the orientation different from that. It

Then, when a polymerizable liquid crystal material is applied on the surface layer 32 shown in FIG. 1C, the surface layer 32 functions as an alignment film, and the second optical anisotropy aligned corresponding to the alignment of the surface layer 32 is applied. The layer 40 can be formed. As a result, as shown in FIG. 1D, the second optically anisotropic layer 40 oriented so as to have a slow axis different from that of the inner layer 31 is formed on the surface layer 32. Since the orientations 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. Yes, they can cross each other at 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 axes can be easily adjusted. Further, since it can be manufactured in a long shape, an optical layered body can be efficiently obtained.

(Birefringence inducing material layer)
The birefringence inducing material layer is formed of a birefringence inducing material. In the present invention, the birefringence-inducing material refers to a material capable of inducing birefringence in an axis-selective manner by molecular motion by light irradiation (preferably light irradiation and heating/cooling treatment) and molecular orientation based on the motion.

For example, the birefringence inducing material may have a photosensitive group and may include a liquid crystalline polymer having a side chain structure capable of forming a liquid crystal structure. It may have the property of inducing orientation. Examples of the photoreaction include a photodimerization reaction, a photoisomerization reaction, and a photo-Fries rearrangement reaction.

When the liquid crystalline polymer is capable of forming a liquid crystal structure, it may have liquid crystallinity by having a mesogenic group that is a rigid site that exhibits liquid crystallinity in the side chain structure, or may have other liquid crystals. It has a structure capable of forming a dimer by a hydrogen bond with a polymer or other side chains of the same polymer, and even if it exhibits liquid crystallinity by forming a mesogenic structure by its dimerization. Good.

The mesogenic group or mesogenic structure is composed of two or more aromatic rings or aliphatic rings and a linking group connecting 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 pyrrole ring, a nitrogen-containing heterocycle such as an imidazole ring), and the like. Include a cyclohexane ring and the like. In addition, these aromatic rings or aliphatic rings may have a substituent, and as the substituent, an alkyl group (for example, a C _1-6 alkyl group, preferably a C _1-4 alkyl group), An alkyloxy group (for example, a C _1-6 alkyloxy group, preferably a C _1-4 alkyloxy group), an alkenyl group (for example, a C _1-6 alkenyl group, preferably a C _1-4 alkenyl group), an alkynyl group ( For example, a C _1-6 alkynyl group, preferably a C _1-4 alkynyl group), a 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—, -CO-C=C-, -CH=N-, an alkylene group and the like can be mentioned. In the case of a hydrogen bond, a side chain structure having a carboxy group at the terminal and the like can be mentioned. In this case, the carboxy groups form a hydrogen bond.

The photosensitive group is not particularly limited as long as it is a functional group capable of causing a photoreaction with light energy, for example, a chalcone group, a coumarin group, a cinnamoyl group, a cinnamic acid group, a cinnamylidene acetic acid group, a biphenylacryloyl group, Examples thereof include a furyl acryloyl group, a naphthyl acryloyl group, an azobenzene group, a benzylidene aniline group and derivatives thereof, and a cinnamoyl group is preferable.

The liquid crystalline 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, and the photosensitive group is a mesogenic group or a mesogenic structure. May exist independently in the side chain structure, or may exist in a complex manner by sharing a chemical structure.

The birefringence inducing material of the present invention may include a liquid crystalline 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, R ₁ is a hydrogen atom, an alkyl group (for example, a C _1-6 alkyl group, preferably a C _1-4 alkyl group), 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 a 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, a C _1-3 alkylene group, C=C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; W is a coumarin group, a cinnamoyl group, a cinnamylideneacetic acid group, a biphenylacryloyl group, a furylacryloyl group. , A naphthylacryloyl group, or a derivative group thereof; R ₂ and R ₃ are the same or different and each represents a hydrogen atom, an alkyl group (for example, a C _1-6 alkyl group, preferably a C _1-4 alkyl group), an alkyl group. An oxy group (for example, a C _1-6 alkyloxy group, preferably a C _1-4 alkyloxy group), an alkenyl group (for example, a C _1-6 alkenyl group, preferably a C _1-4 alkenyl group), an alkynyl group (for example, , A C _1-6 alkynyl group, preferably a C _1-4 alkynyl group), a carboxy group and a halogen atom.

The side chain structures represented by the above formulas (1) and (2) represent the chemical structure of the terminal of the side chain in the repeating unit, and these side chain structures are within a range that does not impair the effects of the present invention. Various chemical structures may be included between the main chain structure and the main chain structure.

The liquid crystalline polymer may be a homopolymer consisting of the same repeating unit containing the side chain structure or a copolymer containing repeating units containing side chain structures of different structures in addition to the repeating unit containing the side chain structure. Good. Examples of the main chain structure include structures formed by polymerizing hydrocarbon, acrylate, methacrylate, siloxane, maleimide, N-phenylmaleimide and the like.

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

Further, the birefringence inducing material of the present invention, 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 crosslinking agent. Alternatively, a liquid crystal polymer having a side chain structure having a crosslinkable functional group may be included. The crosslinkable functional group is not particularly limited as long as it is a functional group that causes a crosslinking reaction with a crosslinking agent described below, 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 has the above-mentioned photosensitive group, and may be contained in a repeating unit containing a side chain structure capable of forming a liquid crystal structure, and a repeating unit other than the repeating unit. It may have a crosslinkable functional group therein.

For example, a hydroxyl group or a carboxy group is preferable as the crosslinkable functional group, and the liquid crystalline polymer has a side chain structure having a crosslinkable functional group of —(CH ₂ ) _n —OH (where n is an integer of 1 to 6). And -Ph-COOH (in the formula, Ph is a divalent phenyl group), and may have at least one structure selected from the group consisting of: In addition, these side chain structures represent at least a part of the chemical structure of the side chain in the repeating unit, and within a range that does not impair the effects of the present invention, various side chain structures are present between the side chain structure and the main chain structure. The chemical structure of

The birefringence inducing material of the present invention may contain a low molecular weight compound together with the liquid crystalline polymer in order to promote the orientation of the side chains of the liquid crystalline polymer. The low molecular weight compound has a substituent such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are known as mesogen components, and such a substituent and allyl, acrylate, methacrylate, cinnamic acid group (or a derivative thereof). A liquid crystallinity in which a functional group such as a 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 are preferably used. These low molecular weight compounds may be used alone or in combination of two or more.

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

The birefringence inducing material layer formed of the birefringence inducing material as described above may use a previously formed birefringence inducing material film (may or may not be laminated on the base material). Well, 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 form a solution, and this solution is applied onto a substrate. The solvent can be appropriately selected depending on the type of the birefringence inducing material, and examples thereof include dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, and ethylene glycol derivatives (eg, ethylene glycol). Monoethyl ether, diethylene glycol monoethyl ether, etc.), propylene glycol derivatives (eg, propylene glycol monomethyl ether, propylene glycol 1-monomethyl ether 2-acetate, etc.), etc., and these solvents may be used alone or in combination of two or more kinds. You may use it.
The concentration of the solvent is not particularly limited, and may be, for example, one containing 5 to 50% by weight of the birefringence inducing material, preferably 8 to 40% by weight, more preferably 10 to 25% by weight. Good. A known coating method such as spin coating or roll coating can be used to apply the solution to the substrate.
After coating, if necessary, the coating film may be dried by heating to form a laminate having a substrate and a birefringence inducing material layer.

Before the first light irradiation step, the birefringence inducing material layer is preferably substantially optically isotropic, that is, it is preferable that the liquid crystal polymer is not substantially aligned.

(First light irradiation step)
In the first light irradiation step, the birefringence inducing material layer is irradiated with the first polarized light for expressing the phase difference. By performing the first light irradiation step, a selective photoreaction of the molecules occurs not only on the surface of the birefringence inducing material layer but also inside the layer, and the orientation of the molecules is induced, which results in the first optical anisotropy. A layer is formed. In the method for producing an optical layered body of the present invention, since the first polarized light can be directly irradiated onto the birefringence inducing material layer without passing through another layer, an intended slow axis is formed by the irradiated polarized light. can do.

The first polarized light is the infrared, visible light, ultraviolet rays (eg, near ultraviolet rays, far ultraviolet rays, etc.), X-rays, charged particle beams (eg, electron beams, etc.), etc. The wavelength of the light may be 200 to 500 nm, though it is not particularly limited as long as it is the wavelength of the generated light and varies depending on the kind of the side chain structure of the liquid crystalline polymer. The first polarized light may be, for example, a linearly polarized light of ultraviolet rays. In this case, for example, an ultraviolet irradiation device such as a high-pressure mercury lamp may be used as a light source and converted into linearly polarized light via a Glan-Taylor prism. Good.
The irradiation amount of the first polarized light may be, for example, 10 mJ/cm ² to 10 J/cm ² , and preferably 50 mJ/cm ² from the viewpoint of aligning not only the surface but also the inside of the birefringence inducing material layer. It may be ˜1 J/cm ² , more preferably 100 mJ/cm ² to 500 mJ/cm ² .

The method for producing an optical layered body of the present invention may optionally 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 aligned according to the aligned molecules. It is possible for the molecules to carry out molecular motion, and it is possible to promote the orientation of unoriented molecules. After heating, it may be cooled down to about room temperature, for example, by leaving it standing.

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 chains where the liquid crystalline polymer undergoes a photoreaction due to molecular motion, but the liquid crystal phase transition temperature of the birefringence inducing material It is above, and it is preferable to set below 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 chains where the liquid crystalline polymer undergoes a photoreaction due to molecular motion, but the type of the liquid crystalline polymer, the heating temperature, etc. The time may be appropriately set depending on the above conditions, and 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 may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes) from the viewpoint of economy.

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

The method of the alignment treatment is not particularly limited as long as the surface of the first optically anisotropic layer can form an alignment layer different from the inner layer thereof, for example, a rubbing treatment, a photo-alignment treatment by the second polarized light irradiation, etc. Can be mentioned. In the rubbing treatment, the orientation direction can be controlled by rotating a roller wrapped with a cloth such as cellulose, nylon or polyester while pressing it at a constant pressure and rubbing the surface of the first optically anisotropic layer in a constant direction. Therefore, the surface layer having a desired alignment direction can be formed, but the method of alignment treatment is preferably photo-alignment treatment by polarized light irradiation.

In the surface alignment 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 to form a surface layer on the first optically anisotropic layer. It may be the second light irradiation step of forming. In the second light irradiation step, even after the molecular orientation in the first light irradiation step (preferably the first light irradiation step and the heating step), a polarization axis direction different from that of the first polarized light is set. By irradiating with the second polarized light, the axial-selective photoreaction centering on the unreacted birefringence-inducing material of the first optically anisotropic layer selectively occurs near the surface. Can be provided with a different orientation from that of the inner layer. On the other hand, probably because the molecules of the inner layer of the first optically anisotropic layer are already oriented with a high degree of orientation, even after the second light irradiation step, the inside of the first optically anisotropic layer is 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, linear polarized light of ultraviolet rays may be used. Further, as the second polarized light, a different kind of light from the first polarized light irradiated in the first light irradiation step may be used, or the same kind of light may be used.

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

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

If necessary, the method for producing an optical layered body of the present invention may further include a surface treatment step of treating the surface of the birefringence inducing material layer with a solvent after the first light irradiation step. After the surface treatment step, it is preferable to perform a surface alignment step such as a second irradiation of polarized light and a rubbing treatment. 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, by applying a solvent to the surface of the first optically anisotropic layer to dissolve the surface portion, the molecular orientation performed by the first light irradiation step is relaxed to a random state. Probably because it is possible, it is possible to eliminate the orientation of the surface portion of the first optically anisotropic layer once formed by the first polarized light, 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 standing and naturally dried. Only the surface to which the solvent is applied can be made isotropic.

When the surface is isotropic, the photo-alignment of the surface is facilitated in the subsequent second light irradiation step, so that the irradiation amount of the second polarized light can be reduced. When performing the surface treatment step, the dose of the second polarization, for ^example, may be 0.1mJ / cm 2 ~ 200mJ / cm 2, preferably from ^{^{0.5mJ / cm 2 ~ 150mJ / cm}} 2, More preferably, it may be 1 mJ/cm ² to 100 mJ/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. May be, preferably 2/1 to 80/1, and more preferably 2.5/1 to 50/1.

Since the surface is 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, and thus the polarization axis of the second polarized light 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 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 forming the first optically anisotropic layer, and is a good solvent for the birefringence inducing material. Or a poor solvent may be used. 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 dissolution of the first optically anisotropic layer to disturb the orientation thereof. 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 for the birefringence inducing material is used, it can be appropriately adjusted depending on the solubility of the solvent used in the birefringence 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, or hexanol; an aliphatic or alicyclic group such as hexane, heptane, octane, cyclohexane Aromatic hydrocarbon solvents such as benzene, toluene, xylene; Ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, isopropyl methyl ketone, methyl isobutyl ketone, cyclohexanone; ethyl ether, propyl Ether-based solvents such as ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, tetrahydrofuran, dioxane; nitrile-based solvents such as acetonitrile and propionitrile; sulfoxide-based solvents such as dimethyl sulfoxide; amides such as N,N-dimethylformamide System solvents; ester solvents such as methyl acetate, ethyl acetate, butyl acetate; glycol solvents 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 solvents such as acetate; halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, dichlorobenzene; and the like. You may use these solvent individually or in combination of 2 or more types. Since these solvents have different solubilities depending on the type of the 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. it can.
In the present invention, the good solvent means a solvent having a solubility of 1 mass% or more at 25°C, and the poor solvent means a solvent having a solubility 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. These good solvents and poor solvents may be mixed at the above mixing weight ratio and used as a mixed solvent.

(Second optical 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 subjected to the alignment treatment to form the second optically anisotropic layer. By performing the second optically anisotropic layer forming step, the surface layer oriented in the surface orientation step plays a role of an orientation film, and thus the second optical anisotropy oriented by utilizing the orientation direction is used. Layers can be formed.

In the present invention, the polymerizable liquid crystal material is a composition containing a monofunctional or difunctional polymerizable liquid crystal compound containing at least a reactive functional group and a mesogenic group, and reacts with a polymerization or crosslinking agent by light or heat. The composition after the formation of the crosslinked structure is included.

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 and/or a polymerizable liquid crystal polymer having a polymerizable functional group which is polymerized by light or heat, or a crosslinkable functional group capable of introducing a crosslinked structure by a reaction with a crosslinking agent The crosslinkable liquid crystal monomer and/or the crosslinkable liquid crystal polymer having

The polymerizable liquid crystal compound is not particularly limited as long as it is a monomer having a mesogen group or a polymer having a unit composed of a mesogen group and capable of forming a liquid crystal structure and having polymerizability and/or crosslinkability. Various polymerizable liquid crystal compounds can be used. Examples of the polymerizable liquid crystal compound include Schiff base type, biphenyl type, terphenyl type, ester type, thioester type, stilbene type, tolan type, azoxy type, azo type, phenylcyclohexane type, pyrimidine type, cyclohexylcyclohexane type, trimesine type. Examples include acid-based, triphenylene-based, torquecene-based, phthalocyanine-based, porphyrin-based liquid crystal compounds having a molecular skeleton, or a mixture of these compounds, and any compound that exhibits a nematic, cholesteric, or smectic liquid crystal phase. But it is okay. 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 side chain of the liquid crystal polymer. The main chain type liquid crystal polymer, polyester, polyamide, polycarbonate, polyimide, polyurethane, polybenzimidazole, polybenzoxazole, polybenzthiazole, polyazomethine, polyesteramide, polyester carbonate, Examples thereof include a polyesterimide-based liquid crystal polymer or a mixture thereof. The side chain type liquid crystalline polymer may be a side chain of a polymer having a linear or cyclic skeleton chain such as polyacrylate type, polymethacrylate type, polyvinyl type, polysiloxane type, polyether type, polymalonate type. Examples thereof include a liquid crystal polymer having a mesogen group bonded thereto, or a mixture thereof.

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.

As the photopolymerization initiator, Irgacure 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all manufactured by Ciba Japan Co., Ltd.), Sequol BZ, Sequol Z, Sequol BEE (or more) , All manufactured by Seiko Chemical Co., Ltd., kayacure BP100 (manufactured by Nippon Kayaku Co., Ltd.), Kayacure UVI-6992 (manufactured by Dow), Adeka Optomer SP-152 or Adeka Optomer SP-170 (or more) , All commercially available from ADEKA, TAZ-A, TAZ-PP (all manufactured by Nippon Siber Hegner Co., Ltd.) and TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.) can be used.

Examples of the thermal polymerization initiator include azo compounds such as azobisisobutyronitrile; peroxides such as hydrogen peroxide, persulfates 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, further preferably 0.05 to 8% by weight, based on the total weight of the polymerizable liquid crystal material. .. Within the above range, polymerization can be carried out without disturbing the orientation of the polymerizable liquid crystal compound.

When using a photopolymerization initiator as the polymerization initiator, a photosensitizer may be used together. Examples of the photosensitizer include xanthone compounds such as xanthone and thioxanthone (eg, 2,4-diethylthioxanthone and 2-isopropylthioxanthone); anthracenes such as anthracene and alkoxy group-containing anthracene (eg, dibutoxyanthracene). Compounds; phenothiazine; rubrene and the like.

Also, the polymerizable liquid crystal material may contain an appropriate crosslinking agent when the polymerizable liquid crystal compound has a crosslinkable functional group. In this case, the polymerizable liquid crystal compound may be a liquid crystal compound which can be orientation-fixed by a means such as cross-linking (thermal cross-linking or photo-cross-linking) in a liquid crystal state or in a state cooled to a liquid crystal transition temperature or lower.

Examples of the crosslinkable functional group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferable, and an acryloyloxy group is particularly 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-linkable functional group, when the liquid crystal polymer of the birefringence inducing material has a cross-linkable functional group The liquid crystalline polymer can form cross-links. In this case, since it becomes possible to form a cross-linking bond between the first optically anisotropic layer composed of the birefringence inducing material and the second optically anisotropic layer containing the cross-linking agent, The adhesion between layers can be improved.

As the cross-linking agent, a polyfunctional compound having two or more functional groups in the molecule can be mentioned. When a cross-linking bond is formed in the liquid crystalline polymer, the polyfunctional compound is not particularly limited as long as it has a functional group capable of forming a cross-linking bond with the liquid crystalline polymer. In the case where 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, or the like can be given. Among these cross-linking agents, from the viewpoint of reactivity to react with the cross-linkable functional group of the liquid crystalline polymer under a relatively mild reaction condition, it is a polyfunctional compound having two or more isocyanate groups in the molecule. A polyisocyanate compound is preferable, and known polyisocyanate compounds can be used. Examples of polyisocyanate compounds include diisocyanate compounds and triisocyanate compounds. Examples of the diisocyanate compound include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, methylcyclohexylene diisocyanate, bis(isocyanatomethyl)cyclohexane, methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, hexamethylene diisocyanate. And a condensation compound of diol. Examples of the triisocyanate compound include an isocyanurate body of diisocyanate such as hexamethylene diisocyanate, a biuret body, and an adduct body which is an adduct of diisocyanate such as hexamethylene diisocyanate and methylolpropane. Of these crosslinking 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-linkable functional group. Examples of the active hydrogen group include a hydroxyl group, a carboxy group, an amino group, and a thiol group. 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 an 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. The active hydrogen group contained in the liquid crystal polymer is preferably a hydroxyl group or a carboxy group.

In the present invention, the content of the cross-linking agent in the polymerizable liquid crystal material is a polymerizable liquid crystal material from the viewpoint of suppressing the deterioration of the orientation and the optical properties of the second optically anisotropic layer due to the reaction with the liquid crystalline polymer. 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.

In the second optically anisotropic layer forming step, the polymerizable liquid crystal material as described above 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, and examples thereof include dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, and ethylene glycol derivatives (eg 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-acetate), etc., and these solvents may be used alone or You may use it in combination of 2 or more types.

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 alignment state of the surface layer. For example, when most of the molecules of the surface layer have a desired orientation (for example, when the surface treatment step is performed or when the rubbing treatment is performed as the orientation treatment), the orientation of the surface layer is set to the second orientation. The solvent of the polymerizable liquid crystal material is preferably a poor solvent for the birefringence inducing material, from the viewpoint of suppressing the disturbance of the orientation of the first optically anisotropic layer while imparting it to the optically anisotropic layer. On the other hand, when only a part of the molecules of the surface layer have a desired orientation, the solvent of the polymerizable liquid crystal material is preferably a mixed solvent obtained by mixing a good solvent and a poor solvent of the birefringence inducing material. Although the mechanism in this case is not clear, when the poor solvent of the birefringence inducing material is contained as the solvent of the polymerizable liquid crystal material, the first optically anisotropic layer is prevented from being disturbed and the orientation thereof is suppressed. can do. On the other hand, if a good solvent for the birefringence inducing material is contained as the solvent for the polymerizable liquid crystal material, the wettability of the solution with respect to the surface layer may be improved. The molecules of the liquid crystal material can be aligned, and as a result, the second optically anisotropic layer can be aligned. 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 alignment state of the surface layer, but maintains the alignment of the first optically anisotropic layer. In view of the above, it is preferable to include a poor solvent for the birefringence inducing material so as not to damage the surface layer. For example, a mixed weight ratio of the good solvent and the poor solvent of the birefringence inducing material (good solvent/poor solvent). 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 according to the purpose, but it may contain, for example, toluene, an ethylene glycol derivative, a propylene glycol derivative or the like.

-Form a coating film by applying the solution, and heat to dry the coating film if necessary. At that time, the surface layer of the first optically anisotropic layer existing below functions as an alignment film (alignment property imparting film), and alignment of liquid crystal molecules occurs. As a result, the second optically anisotropic layer in which the liquid crystal is aligned in the predetermined direction is formed.

The second optically anisotropic layer forming step may optionally include a heating step and/or a light irradiation step (for example, a non-polarized light irradiation step) after forming the coating film of the polymerizable liquid crystal material. The polymerizable liquid crystal material is already aligned in a predetermined direction corresponding to the orientation of the surface layer of the first optically anisotropic layer by forming a coating film, and the subsequent heating step and/or light irradiation. In the step (for example, a non-polarized light irradiation step), the polymerizable liquid crystal material is polymerized and/or cross-linked to fix the orientation.
Specifically, when the polymerizable liquid crystal material is a thermally polymerizable material, the orientation is fixed by polymerization by heating. In the case of using a photopolymerizable material, polymerization occurs upon irradiation with light and the orientation is fixed. When the material is a crosslinkable material, crosslinkage occurs during heating and/or irradiation with light, and the orientation is fixed.

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-linkage with the birefringence inducing material, the first optical difference is caused by the application of heat energy and/or light energy. Crosslinking bonds can be formed between the layers of the anisotropic 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 polymerization and/or crosslinking reaction proceeds, but it suppresses disturbing the orientation of the inner layer of the first optically anisotropic layer. From the viewpoint, it is preferable to perform the heating at a temperature not higher 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 may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes) from the viewpoint of economy.

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

[Optical layered product]
The optical layered body of the present invention is an optical layered body 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 adjacently laminated. The first optically anisotropic layer is composed of a surface layer and an inner layer having mutually 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 that is in contact with the second optically anisotropic layer. For example, the surface layer may be formed by subjecting the surface of the first optically anisotropic layer to an orientation treatment 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 alignment step in the above-described manufacturing method.

The polymerizable liquid crystal material forming the second optically anisotropic layer may contain a crosslinking agent having a functional group capable of forming a crosslink 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. The adhesion with is improved. Thereby, since it is not necessary to provide an adhesive layer between the first optically anisotropic layer and the second optically anisotropic layer, the optical layered body can be made thin and the first optical anisotropic layer can be formed. It is possible to have a structure in which 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 a cross cut test described in Examples below.

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. Further, the thickness ratio of the first optically anisotropic layer and the second optically anisotropic layer (first optically anisotropic layer/second optically anisotropic layer) is from 1/10 to 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 subjected to the alignment treatment. Here, the application of the polymerizable liquid crystal material may be performed according to the aspect of the second optically anisotropic layer forming step in the above-described manufacturing method.

The thickness of the optical layered body 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 layered body of the present invention, 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 intersect. The optical layered body of the present invention is produced by the above-mentioned production method, whereby the slow axis of the first optically anisotropic layer (inner layer) and the slow axis of the second optically anisotropic layer are formed. The angle formed can be set to an arbitrary angle. The slow axis direction of the first optically anisotropic layer (inner layer) and the slow axis 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 the orientation in the surface layer can be considered to be negligible. May be.

In the optical layered body of the present invention, it is particularly preferable that the slow axis direction is constant in the plane in the first optically anisotropic layer. In the present invention, because the polarization state is not converted by irradiating the lower layer with polarized light through the alignment layer (for example, from linearly polarized light to elliptically polarized light), without disturbing the molecular orientation, It is possible to keep the slow axis direction constant.

The optical layered body of the present invention can exhibit desired optical characteristics according to the above-mentioned manufacturing method. Examples of the optical characteristics include a retardation value (for example, in-plane retardation value: Re). The range shown below of these optical properties 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. Good.

The in-plane retardation value (Re) means the anisotropy (ΔNxy=|nx-ny|) of the biaxial refractive indexes (nx, ny) orthogonal to each other 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 isotropy and anisotropy. The optical layered body of the present invention may have an in-plane retardation value (Re) of, 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 layered body of the present invention can be used as a circularly 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.

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

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

(Copolymer 1)
The monomer 1 and the monomer 2 were dissolved in dioxane so that the molar ratio of the monomer 1 and the monomer 2 was monomer 1:monomer 2=3:7. AIBN (azobisisobutyronitrile) was added and polymerized at 70° C. for 24 hours to obtain a copolymer 1. This copolymer 1 exhibited liquid crystallinity.

(Copolymer 2)
Monomer 1 and monomer 2 are mixed so that the molar ratio of Monomer 1, Monomer 2 and 2-hydroxyethyl methacrylate (HEMA) is Monomer 1: Monomer 2: HEMA = 3:7:2. The copolymer 2 was obtained by dissolving the monomer 2 and HEMA in dioxane, adding AIBN (azobisisobutyronitrile) as a reaction initiator, and polymerizing at 70° C. for 24 hours. This copolymer 2 exhibited liquid crystallinity.

In the following examples and comparative examples, the optical properties (retardation value Re, etc.) of the obtained optical layered body were measured by using a birefringence measuring device (AxoScan, AxoScan), and the thickness was measured by a film thickness meter (FILMETRICS, It was measured using F20).

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

Then, using a Glan-Taylor prism, the ultraviolet rays from the high-pressure mercury lamp are converted into linearly polarized light whose polarization axis direction is different by 45° from the polarization axis direction of the previously irradiated polarized light (second polarized light). For 300 seconds (irradiation dose 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 (LC-242 manufactured by BASF) and 5 parts by weight of a photopolymerization initiator (Igarcure 907 manufactured by Ciba Specialty Chemicals) were 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 is applied on the coating film obtained after the second polarized light irradiation by using a spin coater so as to have a thickness of 0.9 μm, heated to 70° C., and then cooled to room temperature. An anisotropic layer was formed. Furthermore, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ/cm ² ) to polymerize the polymerizable liquid crystal compound. The in-plane retardation value of the obtained optical layered body was 242 nm (Linear Retardance: 228 nm, Circular Retardance: -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 properties of the peeled first optically anisotropic layer and second optical anisotropic layer were measured. The in-plane retardation value Re of the first optically anisotropic layer was 135 nm, and the slow axis direction was 90° with respect to the polarization axis direction of the irradiated first polarized light. Upon irradiation with the second polarized light, since the first optically anisotropic layer itself had already been oriented, the orientation itself was not significantly affected and the axial direction was maintained. The in-plane retardation value Re of the second optically anisotropic layer was 115.3 nm, and the slow axis direction was 77° with respect to the polarization axis direction of the irradiated first polarized light. In the irradiation of the second polarized light, as a result of selecting the polarization axis direction in consideration of the alignment state near the surface of the first optically anisotropic layer, the desired slow axis direction of the second optically anisotropic layer We were able to. From this, it was confirmed that the optical laminate was a laminate of two optically anisotropic layers, and the angle formed by the slow axis of each layer was 13°. The slow axis 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 on a cover glass substrate with a spin coater to a thickness of 2.4 μm and dried at 25° C. The coating film after drying was irradiated with polarized light (first polarized light) obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Glan-Taylor prism for 200 seconds (irradiation amount 200 mJ/cm ² ). An optically anisotropic layer was formed. After irradiation with polarized light, the alignment was induced by heating at 130° C. for 3 minutes and cooling to room temperature. The optical properties of the obtained coating film were 90° with respect to the direction of the polarized axis of irradiation, in which the axial direction of the in-plane retardation was.

After that, a mixed solvent having a volume ratio of THF and ethanol (THF:ethanol) of 1:6 was applied to the obtained coating film by a spin coater and left to dry. Further, the polarized light (second polarized light) obtained by converting the ultraviolet light from the high-pressure mercury lamp into a linearly polarized light whose polarization axis direction is 60° different from the polarization axis direction of the polarized light previously irradiated by using the Glan-Taylor prism is applied. For 70 seconds (irradiation dose 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 (LC-242 manufactured by BASF) and 5 parts by weight of a photopolymerization initiator (Igarcure 907 manufactured by Ciba Specialty Chemicals) were mixed and dissolved in toluene to prepare a solution. This solution is applied on the coating film obtained after the second polarized light irradiation by using a spin coater so as to have a thickness of 0.9 μm, heated to 70° C., and then cooled to room temperature. An anisotropic layer was formed. Furthermore, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ/cm ² ) to polymerize the polymerizable liquid crystal compound. The obtained optical layered body 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 layered product were calculated by the analysis software (Multi-Layer Analysis) of the birefringence measuring device (AxoScan, manufactured by AXOMETRICS). The in-plane retardation value Re of the first optically anisotropic layer was 100 nm, and the slow axis direction was 90° with respect to the polarization axis direction of the irradiated first polarized light. The in-plane retardation value Re of the second optically anisotropic layer was 180 nm, and the slow axis direction was 28.5° with respect to the polarization axis direction of the irradiated first polarized light. From this, it was confirmed that the optical laminate was a laminate of two optically anisotropic layers, and the angle formed by the slow axis of each layer was 61.5°. The slow axis 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 on a cover glass substrate with a spin coater to a thickness of 2.4 μm and dried at 25° C. The coating film after drying was irradiated with polarized light (first polarized light) obtained by converting ultraviolet rays from a high-pressure mercury lamp into linearly polarized light using a Glan-Taylor prism for 200 seconds (irradiation amount 200 mJ/cm ² ). An optically anisotropic layer was formed. After irradiation of the first polarized light, the alignment was induced by heating at 130° C. for 3 minutes and cooling to room temperature. The optical properties of the obtained coating film were 90° with respect to the direction of the polarized axis of irradiation, in which the axial direction of the in-plane retardation was.

100 parts by weight of a polymerizable liquid crystal compound (LC-242 manufactured by BASF), 5 parts by weight of a photopolymerization initiator (Igarcure 907 manufactured by Ciba Specialty Chemicals), and polyisocyanate (Duranate TKA-100 manufactured by 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 is applied on the coating film obtained after the second polarized light irradiation by using a spin coater so as to have a thickness of 0.9 μm, heated to 70° C., and then cooled to room temperature. An anisotropic layer was formed. Furthermore, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount 400 mJ/cm ² ) to polymerize the polymerizable liquid crystal compound and to crosslink the copolymer 2. The obtained optical layered body had an in-plane retardation value of 202 nm (Linear Retardance: 185 nm, Circular Retardance: 81 nm). Furthermore, in order to confirm the adhesiveness of the interface between the first optically anisotropic layer and the second optically anisotropic layer, a cross cut test was performed. As a result of performing the test according to JIS K 5600, peeling of the second optically anisotropic layer was not observed, and it was confirmed that the film had good adhesion.

The optical characteristics of each layer of the obtained optical layered body 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 on a cover glass substrate with a spin coater to a thickness of 2.6 μm and dried at 25° C. The dried coating film was irradiated with ultraviolet rays from a high-pressure mercury lamp for 30 seconds with polarized light converted into linearly polarized light using a Glan-Taylor prism (irradiation amount 30 mJ/cm ² ).

Thereafter, 100 parts by weight of a polymerizable liquid crystal compound (LC-242, manufactured by BASF) and 5 parts by weight of a photopolymerization initiator (Igarcure 907, manufactured by Ciba Specialty Chemicals) 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.

Then, using a Glan-Taylor prism, the ultraviolet rays from the high-pressure mercury lamp were converted into linearly polarized light whose polarization axis direction was 60° different from the polarization axis direction of the previously irradiated polarized light, and the coating film was irradiated with the polarized light for 100 seconds ( Irradiation amount 100 mJ/cm ² ).

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

Only the second optically anisotropic layer was peeled off in order to investigate the optical properties of each layer of the obtained optical laminate. The second optically anisotropic layer had an in-plane retardation value Re of 116.8 nm at any point, and the slow axis direction was 39.8° with respect to the polarization axis direction of the previously irradiated polarized light. .. As a result, it was confirmed that the optical laminated body was formed by laminating two optically anisotropic layers, but the angle formed by the slow axes of the layers was 50.2°. It is significantly different from the polarization axis direction of (=60°). Furthermore, it was confirmed that the slow axis direction was not constant in the plane and that the orientation was disturbed and the haze was caused by the generation of microdomains. This is because when polarized light is incident on the first optical anisotropy composed of the copolymer 1 by irradiating the second polarized light through the oriented second optical anisotropy, the linear polarized light is changed. It is considered that elliptically polarized light is obtained and the polarization axis direction (the major axis direction of elliptically polarized light) is also changed. Therefore, in Comparative Example 1, it was difficult to produce a desired optical laminate.

Since the optical laminates of Examples 1 to 3 were manufactured by a specific method, the slow axes of the first optically anisotropic layer and the second optically anisotropic layer can be adjusted arbitrarily. there were. In particular, in Example 2, since the surface treatment with the solvent was performed before the irradiation with the second polarized light, it was possible to more easily orient the surface. Moreover, in Example 3, since the polyisocyanate having an isocyanate group capable of forming a cross-link 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 mixed. The adhesion to the anisotropic layer was good.

On the other hand, in the optical layered body of Comparative Example 1, polarized light for orienting the birefringence inducing 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. However, the slow axis of each layer could not be adjusted to a desired one.

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

As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, those skilled in the art can easily envision various changes and modifications within the obvious scope by viewing the present specification. Ah Therefore, such changes and modifications are construed as being within the scope of the invention defined by the claims.

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

Claims

A first optically anisotropic layer made of a birefringence inducing material,
A second optically anisotropic layer made of a polymerizable liquid crystal material, which is an optical laminate 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,
An optical laminate in which 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 intersect.
The optical layered body according to claim 1, wherein 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-parallel. Optical stacks that intersect at an angle that is orthogonal.
The optical laminate according to claim 1 or 2, wherein the polymerizable liquid crystal material contains a crosslinking agent having a functional group capable of forming a crosslink with the birefringence inducing material.
A method for producing the optical laminate according to any one of claims 1 to 3, comprising:
On a birefringence inducing material layer made of a birefringence inducing material, irradiating a first polarized light for expressing a phase difference, a first light irradiation step of forming a first optically anisotropic layer,
The surface of the first optically anisotropic layer is subjected to an alignment treatment so as to give an orientation different from that of the inner layer, and a surface alignment step of forming a surface layer on the first optically anisotropic layer,
And a step of applying a polymerizable liquid crystal material to form a second optically anisotropic layer on the surface of the first optically anisotropic layer that has been subjected to the alignment treatment.
The manufacturing method according to claim 4, wherein the surface alignment step irradiates the surface of the first optically anisotropic layer with second polarized light having a polarization axis direction different from that of the first polarized light. Then, the method for producing an optical layered body, which is the second light irradiation step of forming a surface layer on the first optically anisotropic layer.
The manufacturing method according to claim 5, wherein the surface treatment 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. The manufacturing method of an optical laminated body which further comprises a process.
A circularly polarizing plate in which the optical layered body according to any one of claims 1 to 3 and a linearly polarizing plate are laminated.