JP7196278B2 - Optical layered body and manufacturing method thereof - Google Patents

Description

Related application

This application claims priority from Japanese Patent Application No. 2019-030471 filed on February 22, 2019, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD The present invention relates to an optical layered body that allows arbitrary axis setting and a method for manufacturing the same.

Various retardation plates are used in thin display devices represented by liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs) in order to improve display quality. For example, in OLEDs such as organic EL display devices, broadband circularly polarizing plates are used to suppress reflection.

As a retardation film used for such a broadband circularly polarizing plate, Patent Document 1 (Japanese Patent Application Laid-Open No. 2016-184013) discloses a first optically anisotropic layer made of a birefringence inducing material and a polymerizable liquid crystal. and a second optically anisotropic layer are directly laminated without an adhesive layer interposed therebetween. Further, as a method for producing the same, a step of applying a birefringence inducing material on a supporting substrate to form a birefringence inducing material layer; a step of irradiating a light, applying a polymerizable liquid crystal onto the birefringence inducing material layer irradiated with the first polarized light, and stacking a polymerizable liquid crystal material layer on the birefringence inducing material layer; and a second light irradiation step of irradiating the laminate with a second polarized light, wherein the polarization axis direction of the first polarized light and the polarization axis direction of the second polarized light A method for producing a retardation film is described, which is characterized in that

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 orienting the birefringence inducing material layer, the oriented polymerizable liquid crystal material layer , and the polarization state of the second polarized light is converted when it passes through the aligned polymerizable liquid crystal material layer. was difficult to irradiate. Therefore, it has been difficult to achieve the intended slow axis relationship between the birefringence inducing material layer and the polymerizable liquid crystal material layer.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical layered body and a manufacturing method, in which each optically anisotropic layer can be set to an arbitrary slow axis.

As a result of intensive research to solve the above problems, the present inventors have found that after forming a first optically anisotropic layer aligned by irradiating a birefringence inducing material layer with a first polarized light, a first By subjecting the surface of the optically anisotropic layer of ( i) can impart a desired orientation to the inner layer without affecting the photo-alignment of the inner layer composed of a birefringence-inducing material by another layer, and (ii) play a role as an alignment film. Since the orientation of the surface layer can be adjusted independently of the inner layer, the second optically anisotropic layer can be given a desired orientation in consideration of the relationship with the orientation of the inner layer. rice field. Then, the inventors found that the obtained optical layered body can 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. 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;
an optical laminate in which a second optically anisotropic layer made of a polymerizable liquid crystal material is laminated adjacently,
the first optically anisotropic layer is composed of a surface layer and an internal layer having mutually different slow axes, the surface layer and the second optically anisotropic layer being in contact,
An optical laminate, 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 intersect.
[Aspect 2]
In the optical laminate according to aspect 1, 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. The optical stack intersects at an angle of .
[Aspect 3]
3. The optical laminate according to aspect 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.
[Aspect 4]
A method for producing an optical laminate according to any one of aspects 1 to 3, comprising:
a first light irradiation step of irradiating a birefringence inducing material layer made of a birefringence inducing material with a first polarized light for developing a retardation to form a first optically anisotropic layer;
a surface orientation step of subjecting the surface of the first optically anisotropic layer to orientation treatment so as to give an orientation different from that of the inner layer to form a surface layer on the first optically anisotropic layer;
forming a second optically anisotropic layer by applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has been subjected to orientation treatment.
[Aspect 5]
The production method according to aspect 4, wherein the surface orientation 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.
[Aspect 6]
The production method according to aspect 5, wherein between the first light irradiation step and the second light irradiation step, the surface of the first optically anisotropic layer is treated with a solvent. A method for manufacturing an optical laminate, further comprising:
[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 Embodiments 1 to 3,
a first optically anisotropic layer formed by irradiating a birefringence inducing material with a first polarized light for producing a retardation;
a surface layer formed on the first optically anisotropic layer by subjecting the surface of the first optically anisotropic layer to orientation treatment so as to give an orientation different from that of the inner layer;
An optical laminate comprising a second optically anisotropic layer formed by applying a polymerizable liquid crystal material on the surface layer.

Any combination of at least two components disclosed in the claims and/or the specification and/or the drawings is included in the present invention. In particular, any combination of two or more of the claimed claims is included in the invention.

According to the optical layered body and the method for producing the same of the present invention, a desired slow axis combination can be obtained for the first optically anisotropic layer and the second optically anisotropic layer. The angle at which the axes intersect can be arbitrarily set, 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 more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily drawn to scale and are exaggerated to illustrate the principles of the invention. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the 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 laminated body of this invention. FIG. 2 is a schematic cross-sectional view after the first light irradiation step in one embodiment of the method for producing an optical layered body of the present invention; It is a schematic sectional view after the surface orientation process in one embodiment of the manufacturing method of the optical laminated body of this invention. FIG. 4 is a schematic cross-sectional view after the second optically anisotropic layer forming step in one embodiment of the method for producing the optical layered body of the present invention.

[Method for producing an 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 a first polarized light for exhibiting a retardation to produce an oriented first optically anisotropic layer. a first light irradiation step for forming a layer; 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 undergone the alignment treatment to form a second optically anisotropic layer.

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 the method for producing an optical layered body of the present invention. Although FIGS. 1A-1D show cross-sections of each layer, they do not represent actual thickness ratios.

FIG. 1A is a schematic cross-sectional view showing a laminate of a substrate 10 and a birefringence inducing material layer 20. FIG. FIG. 1B shows the state after the first light irradiation step, and the substrate 10 and the first optically anisotropic layer formed by aligning the molecules of the birefringence inducing material layer 20 by irradiation with the first polarized light. 3 is a schematic cross-sectional view showing a laminate with a layer 30; FIG. FIG. 1C shows the state after the surface orientation process, in which the substrate 10, the inner layer 31 having the same orientation as the first optically anisotropic layer 30, and the surface opposite to the substrate 10 are oriented. 1 is a schematic cross-sectional view showing a laminate with a first optically anisotropic layer 30 comprising a surface layer 32 having a different orientation from that of an inner layer 31 by . FIG. 1D shows the state after the second optically anisotropic layer forming step, in which the substrate 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 combined. FIG. 3 is a schematic cross-sectional view showing an optical layered body 100 with a second optically anisotropic layer 40 formed by application.

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 developing a phase difference. As a result, as shown in FIG. 1B, the first optically anisotropic layer 30 oriented 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 polarization state of the irradiated first polarized light is not converted, and the birefringence inducing material layer 20 is exposed to the desired light. It is possible to irradiate with polarized light of

Next, the surface of the first optically anisotropic layer 30 shown in FIG. A surface layer 32 may be formed on the conductive layer 30 . As a result, as shown in FIG. 1C, the first optically anisotropic layer 30 is formed of two layers, the inner layer 31 having the originally formed orientation and the surface layer 32 having a different orientation. be.

Then, when a polymerizable liquid crystal material is applied on the surface layer 32 shown in FIG. A layer 40 can be formed. As a result, as shown in FIG. 1D, a second optically anisotropic layer 40 is formed on the surface layer 32 so as to have a slow axis different from that of the inner layer 31 . 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 cross each other at the desired slow axis.

According to the method for producing an optical layered body of the present invention, it is not necessary to cut a plurality of films at a predetermined angle and precisely bond them together, so the crossing angle of the slow axes can be easily adjusted. Moreover, since it is possible to manufacture in a long shape, an optical layered body can be efficiently obtained.

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

For example, the birefringence inducing material may contain a liquid crystalline polymer having a photosensitive group and a side chain structure capable of forming a liquid crystal structure. It may have the property of inducing orientation. The photoreaction includes photodimerization reaction, photoisomerization reaction, photofries rearrangement reaction, and the like.

When the liquid crystalline polymer is capable of forming a liquid crystal structure, it may exhibit liquid crystallinity by having a mesogenic group, which is a rigid site that exhibits liquid crystallinity, in the side chain structure, or may exhibit liquid crystallinity. It has a structure that can form a dimer by coalescence or hydrogen bonding with other side chains of the same polymer, and by forming a mesogenic structure through dimerization, even if it exhibits liquid crystallinity good.

A mesogenic group or mesogenic structure is composed of two or more aromatic 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 benzene ring, naphthalene ring, heterocyclic ring (e.g., oxygen-containing heterocyclic ring such as furan ring and pyran ring; nitrogen-containing heterocyclic ring such as pyrrole ring and imidazole ring). includes a cyclohexane ring and the like. These aromatic rings or aliphatic rings may have substituents, and the substituents include alkyl groups (eg, C _1-6 alkyl groups, preferably C _1-4 alkyl groups), alkyloxy group (e.g., C _1-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (e.g., C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group ( Examples thereof include C _1-6 alkynyl groups, preferably C _1-4 alkynyl groups), halogen atoms and the like.
As the linking group, when it is a covalent bond, a single bond, -O-, -COO-, -OCO-, -N=N-, -NO=N-, -C=C-, -C≡C-, -CO-C=C-, -CH=N-, alkylene group and the like. In the case of a hydrogen bond, a side chain structure having a carboxyl group at the end can be mentioned, and in this case, the carboxyl 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. Examples include a furylacryloyl group, a naphthylacryloyl group, an azobenzene group, a benzylideneaniline group, derivatives thereof, and the like, preferably a cinnamoyl group.

A 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 a 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 while sharing a chemical structure.

The birefringence inducing material of the present invention may contain 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).

(Wherein, t is an integer of 1 to 3, R ₁ is a hydrogen atom, an alkyl group (eg, C _1-6 alkyl group, preferably C _1-4 alkyl group), an 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 _1-6 alkynyl group , preferably a C _1-4 alkynyl group), and one or more selected from halogen atoms.)

(Wherein, 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 are each a hydrogen atom, an alkyl group (eg, a C _1-6 alkyl group, preferably a C _1-4 alkyl group), an alkyl oxy group (e.g. C _1-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (e.g. C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group (e.g. , 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 structures of the terminals of the side chains in the repeating unit, and these side chain structures are used within the range that does not impair the effects of the present invention. and the main chain structure may contain various chemical structures.

The liquid crystalline polymer may be a homopolymer consisting 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 structures formed by polymerization of hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, N-phenylmaleimides, and the like.

When the liquid crystalline 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 used from the viewpoint of improving adhesion between the first optically anisotropic layer and the second optically anisotropic layer when the polymerizable liquid crystal material contains a cross-linking agent. , may contain a liquid crystalline polymer having a side chain structure having a crosslinkable functional group. 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 later, and examples thereof include a hydroxyl group, a carboxyl group, an amino group, and a thiol group. The side chain structure having a crosslinkable functional group may be contained in the repeating unit containing the side chain structure having a 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, the crosslinkable functional group is preferably a hydroxyl group or a carboxyl 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 (wherein Ph is a divalent phenyl group). These side chain structures represent at least a part of the chemical structure of the side chains in the repeating unit, and there are various structures between these side chain structures and the main chain structure within the range that does not impair the effects of the present invention. may contain the chemical structure of

In addition, 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. Low-molecular-weight compounds have substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are known as mesogenic components. group) via a spacer (e.g., an (oxy)alkylene group having 1 to 15 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms), etc.). is preferably used. These low-molecular-weight compounds may be used alone or in combination of two or more.

Although the birefringence inducing material layer 20 is laminated on the base material 10 in FIG. 1A, the base material 10 may be omitted. When a substrate is used, it may be an optically isotropic substrate. For example, it may be a transparent substrate having an optically isotropic phase such as glass or a triacetyl cellulose film (TAC film). good. As the substrate, for example, a substrate 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 a release substrate. may When a release substrate is used, it can be peeled off after forming the optical layered body of the present invention, so the optical properties of the substrate itself need not be considered, and an opaque substrate may be used. For example, after the optical laminate of the present invention is formed on a base material, it is bonded to another optical member (for example, a polarizing plate, etc.) via an adhesive or the like, and then the release base material is peeled off for use. As a result, the optical layered body can be a thin optical member that does not have a substrate and has a thickness substantially equal to only the thickness of the optically anisotropic layer.

The birefringence inducing material layer made of the birefringence inducing material as described above may be a birefringence inducing material film formed in advance (which may or may not be laminated on the substrate). Alternatively, it may be formed by coating the base material. 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. Solvents can be appropriately selected according to the type of birefringence inducing material. monoethyl ether, diethylene glycol monoethyl ether, etc.), propylene glycol derivatives (e.g., propylene glycol monomethyl ether, propylene glycol 1-monomethyl ether 2-acetate, etc.), etc. These solvents may be used alone or in combination of two or more. may be used as
The concentration of the solvent is not particularly limited, but for example, it may contain 5 to 50% by weight of the birefringence inducing material, preferably 8 to 40% by weight, more preferably 10 to 25% by weight. good too. 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, the liquid crystal polymer is preferably substantially non-oriented.

(First light irradiation step)
In the first light irradiation step, the birefringence inducing material layer is irradiated with a first polarized light for developing a retardation. By performing the first light irradiation step, a selective photoreaction of molecules occurs not only on the surface of the birefringence-inducing material layer but also on the inside of the layer, thereby inducing orientation of the molecules and providing the first optical anisotropy. A layer is formed. In the method for producing the optical laminate of the present invention, the birefringence inducing material layer can be directly irradiated with the first polarized light without passing through another layer, so that the irradiated polarized light forms the intended slow axis. can do.

The first polarized light is infrared rays, visible rays, ultraviolet rays (e.g., near ultraviolet rays, far ultraviolet rays, etc.), X-rays, charged particle beams (e.g., electron beams, etc.). The wavelength of the light may be 200 to 500 nm, although it may vary depending on the type of side chain structure of the liquid crystalline polymer. The first polarized light may be, for example, linearly polarized ultraviolet light. 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 into linearly polarized light via a Glan-Taylor prism. good.
Further, the irradiation amount of the first polarized light may be, for example, 10 mJ/cm ² to 10 J/cm ² , preferably 50 mJ/cm ² from the viewpoint of aligning not only the surface of the birefringence inducing material layer but also the inside thereof. ˜1 J/cm ² , more preferably 100 mJ/cm ² to 500 mJ/cm ² .

The method for producing the 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. Depending on the irradiation direction and vibration direction of the first polarized light irradiated in the first light irradiation step, molecular orientation is induced, and the unoriented molecules are also oriented according to the oriented molecules, but the liquid crystallinity is enhanced by subsequent heating. Molecules are allowed to perform molecular motion, and orientation of unoriented molecules can be promoted. After heating, it may be cooled to about room temperature by, for example, standing.

The heating temperature in the heating step is not particularly limited as long as the alignment of the unaligned molecules is induced along the side chains of the liquid crystalline polymer that have undergone photoreaction due to molecular motion. 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, more preferably 120 to 160°C.

In addition, the heating time is not particularly limited as long as the alignment of the unaligned molecules is induced along the side chains of the liquid crystalline polymer that caused the photoreaction due to the molecular motion, but the type of the liquid crystalline polymer, the heating temperature, etc. For example, the time may be 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. Although the upper limit is not particularly limited, it may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes) from the viewpoint of economy.

(Surface orientation step)
In the surface orientation step, the surface of the first optically anisotropic layer is oriented so as to be oriented differently from the inner layers. By performing surface orientation treatment, a surface layer is formed on the first optically anisotropic layer, and two layers, an inner layer and a surface layer, which are composed of the same birefringence inducing material but have different orientation states are formed. It is formed in the first optically anisotropic layer. The internal layer may refer to 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 orientation layer different from the inner layer can be formed on the surface of the first optically anisotropic layer. mentioned. In the rubbing treatment, the orientation direction can be controlled by rubbing the surface of the first optically anisotropic layer in a given direction with a roller wound with a cloth of cellulose, nylon, polyester, or the like, which is pressed under a given pressure and rotated. Therefore, it is possible to form a surface layer in a desired orientation direction, and the orientation treatment method is preferably a photo-alignment treatment using polarized light 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 to form a surface layer on the first optically anisotropic layer. It may be a second light irradiation step for forming. In the second light irradiation step, a polarization axis direction different from that of the first polarized light is obtained even after the molecular orientation is performed in the first light irradiation step (preferably the first light irradiation step and the heating step). By irradiating the second polarized light having can be given an orientation different from that of the inner layer. On the other hand, the molecules in the inner layer of the first optically anisotropic layer are already oriented with a high degree of orientation. The layer orientation itself is not transformed.

As the second polarized light, light of various wavelengths described above as the first polarized light can be used. For example, linearly polarized ultraviolet light may be used. Moreover, the second polarized light may be a different type of light from the first polarized light irradiated in the first light irradiation step, or may be the same type of light.

The second polarized light may have a different polarization axis direction than the first polarized light, for example, may differ from the polarization axis of the first polarized light by an axis angle of 5-85°, preferably 10°. They may differ by ~80°, more preferably between 20 and 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 is the alignment state (until The slow axis of the second optically anisotropic layer to be formed later can be arbitrarily set by adjusting it in consideration of the existence ratio of the birefringence inducing material for 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 2 from the viewpoint of reorienting the surface of the first optically anisotropic layer. 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 inducing material layer with a solvent after the first light irradiation step. After the surface treatment step, for example, it is preferable to carry out a surface orientation step such as a second polarized light irradiation or a rubbing treatment. Moreover, when the heating process is performed after the first light irradiation process, the surface treatment process may be performed after the heating process.

In the surface treatment step, a solvent is applied to the surface of the first optically anisotropic layer to dissolve the surface portion, thereby relaxing the molecular orientation applied in the first light irradiation step to a random state. Because the orientation of the surface portion of the first optically anisotropic layer once formed by the first polarized light can be eliminated, the orientation of the surface layer of the first optically anisotropic layer can be made 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. For example, the coating may be left to dry naturally. Only surfaces to which solvent is applied can be made isotropic.

By making the surface isotropic, it becomes easier to align the surface with light 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 dose of the second polarized light 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 1 mJ/cm ² to 100 mJ/cm ² .
Further, when the surface treatment step is performed, the ratio of the irradiation amount of the first polarized light and the irradiation amount of the second polarized light (first polarized light/second polarized light) is 1.5/1 to 100/1. , preferably 2/1 to 80/1, more preferably 2.5/1 to 50/1.

Since the surface becomes isotropic, there is no need to consider the alignment state of the surface layer of the first optically anisotropic layer in the subsequent second light irradiation step, so the polarization axis of the second polarized light is The axis angle can be directly reflected in 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 for setting 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 constituting the first optically anisotropic layer, and is a good solvent for the birefringence inducing material. or a poor solvent. From the viewpoint of making the surface of the first optically anisotropic layer isotropic and preventing it from dissolving into the inside and disturbing its orientation, the solvent used in the surface treatment step is, for example, a good birefringence inducing material. A mixed solvent in which a solvent and a poor solvent are mixed may be used. When using a mixed solvent containing a good solvent and a poor solvent for the birefringence inducing material, the solubility of the solvent used in the birefringence inducing material can be appropriately adjusted. / poor solvent) may be 1/100 to 100/1, preferably 1/50 to 50/1, more preferably 1/10 to 10/1.

Solvents used in the surface treatment step include, for example, water; alcoholic solvents such as methanol, ethanol, propanol, isopropyl alcohol, pentanol, and hexanol; 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, propyl Ether solvents such as ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, tetrahydrofuran and dioxane; nitrile solvents such as acetonitrile and propionitrile; sulfoxide solvents such as dimethyl sulfoxide; amides such as N,N-dimethylformamide Ester-based solvents such as methyl acetate, ethyl acetate and butyl acetate; Glycol-based 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; These solvents may be used alone or in combination of two or more. Note that these solvents have different solubility depending on the type of birefringence inducing material, so depending on the birefringence inducing material to be used, it is necessary to consider whether it is a good solvent or a poor solvent before use. can.
In the present invention, a good solvent refers to a solvent having a solubility of 1% by mass or more in a solute at 25°C, and a poor solvent refers to a solvent having a solubility of less than 1% by mass in a solute at 25°C.

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

(Second optically anisotropic layer forming step)
In the second optically anisotropic layer forming step, a second optically anisotropic layer is formed by applying a polymerizable liquid crystal material on the surface layer of the first optically anisotropic layer that has undergone alignment treatment. By performing the second optically anisotropic layer forming step, the surface layer oriented in the surface orientation step serves as an orientation film, so that the second optically anisotropic layer oriented using 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 bifunctional polymerizable liquid crystal compound containing at least a reactive functional group and a mesogenic group, and is polymerized by light or heat or reacted with a cross-linking agent. including the composition after forming a crosslinked structure by.

The polymerizable liquid crystal compound may be a liquid crystalline monomer or a liquid crystalline 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 that polymerizes by light or heat, or a crosslinkable functional group capable of introducing a crosslinked structure by reaction with a crosslinker. crosslinkable liquid crystal monomers and/or crosslinkable liquid crystal polymers having

The polymerizable liquid crystal compound is a monomer having a mesogenic group or a polymer having a unit composed of mesogenic groups, and is not particularly limited as long as it can form a liquid crystal structure and has polymerizability and/or crosslinkability. Various polymerizable liquid crystal compounds can be used. Examples of polymerizable liquid crystal compounds include Schiff base, biphenyl, terphenyl, ester, thioester, stilbene, tolan, azoxy, azo, phenylcyclohexane, pyrimidine, cyclohexylcyclohexane, and trimesin. Acid-based, triphenylene-based, torxene-based, phthalocyanine-based, porphyrin-based liquid crystal compounds having a molecular skeleton, or mixtures of these compounds, and the like, any compound exhibiting a nematic, cholesteric or smectic liquid crystal phase. It's okay. As an example, a photopolymerizable nematic liquid crystal monomer may be used as the polymerizable liquid crystal compound.

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

Moreover, 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.

Examples of photopolymerization initiators include Irgacure 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all manufactured by Ciba Japan Co., Ltd.), Seikuol BZ, Seikuol Z, Seikuol BEE (all , 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 (above , all manufactured by ADEKA Co., Ltd.), TAZ-A, TAZ-PP (manufactured by Nihon SiberHegner Co., Ltd.), and TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.).

Examples of thermal polymerization initiators include azo compounds such as azobisisobutyronitrile; hydrogen peroxide, persulfates, and peroxides such as benzoyl peroxide.

The content of the polymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.03 to 10% by weight, even more preferably 0.05 to 8% by weight, relative to 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.

In addition, when using a photoinitiator as a polymerization initiator, you may use a photosensitizer together. Examples of photosensitizers include xanthone and xanthone compounds such as thioxanthone (eg, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); compounds; phenothiazine; rubrene and the like.

Moreover, the polymerizable liquid crystal material may contain an appropriate cross-linking agent when the polymerizable liquid crystal compound has a cross-linkable functional group. In this case, the polymerizable liquid crystal compound may be a liquid crystal compound that can be aligned and fixed by cross-linking (thermal cross-linking or photo-cross-linking) or the like in a liquid crystal state or in a state cooled to a liquid crystal transition temperature or lower.

Examples of crosslinkable functional groups 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 preferred, and an acryloyloxy group is particularly preferred.

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

Cross-linking agents include polyfunctional compounds having two or more functional groups in the molecule. When the liquid crystalline polymer is crosslinked, the polyfunctional compound is not particularly limited as long as it has a functional group capable of forming a crosslinked bond with the liquid crystalline polymer. When the crosslinkable functional group is a hydroxyl group or a carboxyl group, compounds 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, polyfunctional compounds having two or more isocyanate groups in the molecule are preferred from the viewpoint of the reactivity of reacting with the cross-linking functional groups of the liquid crystalline polymer under relatively mild reaction conditions. Polyisocyanate-based compounds are preferred, and known polyisocyanate-based compounds can be used. For example, polyisocyanate compounds include diisocyanate compounds and triisocyanate compounds. Examples of diisocyanate compounds include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, methylcyclohexylene diisocyanate, bis(isocyanatomethyl)cyclohexane, methylenebis(cyclohexylisocyanate), isophorone diisocyanate, and hexamethylene diisocyanate. and a condensed compound with a diol. Examples of triisocyanate compounds include isocyanurate compounds of diisocyanates such as hexamethylene diisocyanate, biuret compounds, and adducts which are adducts of diisocyanates such as hexamethylene diisocyanate and methylolpropane. Among these cross-linking agents, triisocyanate compounds can be preferably used.

When the cross-linking agent is a polyisocyanate compound, the liquid crystalline polymer may have an active hydrogen group as a cross-linkable functional group. Active hydrogen groups include hydroxyl groups, carboxy groups, amino groups, thiol groups, 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. 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. A hydroxyl group and a carboxy group are preferable as the active hydrogen group possessed by the liquid crystalline polymer.

In the present invention, the content of the cross-linking agent in the polymerizable liquid crystal material is determined from the viewpoint of suppressing deterioration of the orientation and optical properties of the second optically anisotropic layer due to 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, based on the total weight of the

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 according to the type of the polymerizable liquid crystal material. 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). More than one species may be used in combination.

The solvent for the polymerizable liquid crystal material can be selected according to the alignment state of the surface layer as well as the combination of the types of the birefringence inducing material and the polymerizable liquid crystal material. For example, when most of the molecules in the surface layer are in a 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 changed to the second orientation. The solvent for the polymerizable liquid crystal material is preferably a poor solvent for the birefringence inducing material, from the viewpoint of suppressing disturbance of the orientation of the first optically anisotropic layer while imparting it to the optically anisotropic layer. On the other hand, when only part of the molecules in the surface layer are in the desired orientation, the solvent for the polymerizable liquid crystal material is preferably a mixed solvent in which a good solvent and a poor solvent for the birefringence inducing material are mixed. Although the mechanism in this case is not clear, if a poor solvent for the birefringence inducing material is included as the solvent for the polymerizable liquid crystal material, the first optically anisotropic layer is not damaged and the alignment is suppressed from being disturbed. 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 to the surface layer is improved, and the polymerizability to the orientation of only a part of the molecules of the surface layer is improved. The molecules of the liquid crystal material can be oriented so that the second optically anisotropic layer can be oriented. The solvent for 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 the viewpoint of improving the performance of the birefringence-inducing material, it is preferable that the solvent contains a poor solvent for the birefringence-inducing material so as not to damage the surface layer. may be from 0/100 to 100/1, preferably from 0/100 to 50/1, more preferably from 0/100 to 10/1. As a solvent for the polymerizable liquid crystal material, a general solvent can be used depending on the purpose, and for example, toluene, an ethylene glycol derivative, a propylene glycol derivative and the like may be included.

A coating film is formed by coating the solution, and the coating film is dried by heating if necessary. At that time, the surface layer of the first optically anisotropic layer existing below functions as an alignment film (orientation imparting film), and the liquid crystal molecules are oriented. This forms a second optically anisotropic layer in which the liquid crystal is oriented in a predetermined direction.

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. By forming a coating film, 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. The orientation is fixed by polymerizing and/or cross-linking the polymerizable liquid crystal material in the process (for example, the non-polarized light irradiation process).
Specifically, when the polymerizable liquid crystal material is made of a thermally polymerizable material, the orientation is fixed by polymerization by heating. When it is made of a photopolymerizable material, polymerization occurs when light is irradiated, and the orientation is fixed. When made of a crosslinkable material, crosslinkage occurs upon heating and/or irradiation of light, fixing the orientation.

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 application of heat energy and/or light energy causes the first optical difference. Crosslinking can be formed between 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 cross-linking reaction proceeds, but it prevents the orientation of the inner layers of the first optically anisotropic layer from being disturbed. From the point of view, the heating temperature is preferably 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, 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. Although the upper limit is not particularly limited, it 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, there are no particular limitations as long as the polymerization and/or cross-linking reaction proceeds, but the light to be irradiated is preferably non-polarized light. As the non-polarized light, light of various wavelengths described above as the first polarized light and the second polarized light can be used. 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 , more preferably 100 mJ/cm ² to 500 mJ/cm ² . .

[Optical laminate]
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 laminated adjacent to each other. The first optically anisotropic layer is composed of a surface layer and an internal 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 0.1-20 μm, preferably 0.3-15 μm, more preferably 0.5-10 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 subjecting the surface of the first optically anisotropic layer to orientation treatment so as to give an orientation different from that of the inner layer. Here, the orientation treatment may be performed in accordance with the aspect of the surface orientation step in the manufacturing method described above.

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 first optically anisotropic layer and the second optically anisotropic layer are formed by forming a cross-linked bond between the cross-linking agent contained in the polymerizable liquid crystal material and the birefringence inducing material of the first optically anisotropic layer. Improves adhesion with Accordingly, 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 thinner, and the first optically anisotropic layer can be A structure in which the surface layer of the optically anisotropic layer and the second optically anisotropic layer are in contact with each other can be employed. 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 below.

The thickness of the second optically anisotropic layer may be 0.1-20 μm, preferably 0.3-15 μm, more preferably 0.5-10 μm. Further, the thickness ratio of the first optically anisotropic layer to 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, 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 alignment-treated surface layer of the first optically anisotropic layer. 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 manufacturing method described above.

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

In the optical laminate 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 manufactured by the manufacturing method described above, so that the slow axis of the first optically anisotropic layer (inner layer) and the slow axis of the second optically anisotropic layer It is possible to set the angle to be formed to any 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 a non-parallel and non-orthogonal angle. 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 ~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, since the influence of the orientation in the surface layer can be considered to be negligible. may

In the optical layered body of the present invention, it is preferable that the slow axis direction is constant in the plane, especially in the first optically anisotropic layer. In the present invention, the polarization state is not changed by irradiating the lower layer with polarized light through the alignment layer (for example, from linearly polarized light to elliptically polarized light), or the molecular alignment is not disturbed. It is possible to keep the slow axis direction constant.

The optical layered body of the present invention can develop desired optical properties according to the aspect of the manufacturing method described above. The optical properties include, for example, a retardation value (for example, an in-plane retardation value: Re). The ranges shown below for these optical properties may be the ranges of the measured values of the optical layered body, or the ranges of the measured values of the first optically anisotropic layer or the second optically anisotropic layer. good too.

The in-plane retardation value (Re) is the difference between the anisotropy (ΔNxy=|nx−ny|) of the biaxial refractive indices (nx, ny) on the film and the film thickness d (nm). It is a parameter defined by the product (ΔNxy×d) and is a measure of optical isotropy and anisotropy. The optical laminate of the present invention may have an in-plane retardation value (Re) of, for example, 1 to 600 nm, preferably 3 to 500 nm, more preferably 5 to 400 nm. The in-plane retardation value (Re) may be a measured value for light with 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, for example, 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 linearly polarizing plate as a retardation film.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these 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 effect an esterification reaction, thereby synthesizing 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 effect an esterification reaction, thereby synthesizing a monomer 2 represented by the following chemical formula.

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

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

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

After that, 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 45° different from the polarization axis direction of the previously irradiated polarized light using a Glan-Taylor prism is applied to the coating film. for 300 seconds (irradiation amount: 300 mJ/cm ² ) to form a surface layer on the first optically anisotropic layer.

Polymerizable liquid crystal compound (manufactured by BASF, LC-242) 100 parts by weight, and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Igarcure 907) 5 parts by weight 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 was applied to the coating film obtained after the second polarized light irradiation 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. 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 Retardance: 228 nm, Circular Retardance: -78 nm).

In order to examine 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 the second optically anisotropic layer were measured. The first optically anisotropic layer had an in-plane retardation value Re of 135 nm, and the slow axis direction was 90° with respect to the polarization axis direction of the first polarized light irradiation. Since the first optically anisotropic layer itself had already been oriented by irradiation with the second polarized light, 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 axis direction was 77° with respect to the polarization axis direction of the first polarized light irradiation. 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 slow axis direction of the second optically anisotropic layer 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 axes of each layer was 13°. Also, the slow axis direction was constant within 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 using a spin coater to a thickness of 2.4 μm and dried at 25°C. After drying, the coating film 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 film was heated at 130° C. for 3 minutes and cooled to room temperature to induce orientation. As for the optical properties of the obtained coating film, the axial direction of the in-plane retardation was 90° with respect to the direction of the irradiated polarization axis.

Thereafter, 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 the coating film was left to dry. Furthermore, 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 previously irradiated polarized light using a Glan-Taylor prism is applied to the coating film. 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 (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 was applied to the coating film obtained after the second polarized light irradiation 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. 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 properties of each layer of the obtained optical layered body were calculated by analysis software (Multi-Layer Analysis) of a birefringence measuring device (manufactured by AXOMETRICS, AxoScan). The first optically anisotropic layer had an in-plane retardation value Re of 100 nm, and the slow axis direction was 90° with respect to the polarization axis direction of the first polarized light irradiation. The second optically anisotropic layer had an in-plane retardation value Re of 180 nm and a slow axis direction of 28.5° with respect to the polarization axis direction of the first polarized light irradiation. As a result, it was confirmed that it was an optical layered body in which two optically anisotropic layers were layered, and the angle formed by the slow axes of each layer was 61.5°. Also, the slow axis direction was constant within 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 using a spin coater to a thickness of 2.4 μm and dried at 25°C. After drying, the coating film 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 the first polarized light irradiation, orientation was induced by heating at 130° C. for 3 minutes and cooling to room temperature. As for the optical properties of the obtained coating film, the axial direction of the in-plane retardation was 90° with respect to the direction of the irradiated polarization axis.

After that, 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 45° different from the polarization axis direction of the previously irradiated polarized light using a Glan-Taylor prism is applied to the coating film. for 300 seconds (irradiation amount: 300 mJ/cm ² ) to form a surface layer on the first optically anisotropic layer.

Polymerizable liquid crystal compound (manufactured by BASF, LC-242) 100 parts by weight, photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Igarcure 907) 5 parts by weight, and polyisocyanate (manufactured by Asahi Kasei Corporation, Duranate TKA-100) 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 to the coating film obtained after the second polarized light irradiation 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. 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). Furthermore, a cross-cut test was performed to confirm the adhesion of the interface between the first optically anisotropic layer and the second optically anisotropic layer. As a result of conducting a test in accordance with JIS K 5600, no peeling of the second optically anisotropic layer was observed, confirming good adhesion.

The optical properties of each layer of the obtained optical layered body showed the same optical properties 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 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 from a high-pressure mercury lamp converted into linearly polarized light using a Glan-Taylor prism for 30 seconds (irradiation amount: 30 mJ/cm ² ).

After that, on the resulting coating film, 100 parts by weight of a polymerizable liquid crystal compound (manufactured by BASF, LC-242) and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Igarcure 907) 5 parts by weight were mixed, A 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° to the irradiated polarization axis direction.

After that, the UV light from the high-pressure mercury lamp was converted to a linearly polarized light whose polarization axis direction was 60° different from the polarization axis direction of the previously irradiated polarized light using a Glan-Taylor prism, and the coating film was irradiated 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.

Only the second optically anisotropic layer was peeled off in order to investigate the optical properties of each layer of the obtained optical layered body. The second optically anisotropic layer had an in-plane retardation value Re of 116.8 nm at an arbitrary 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 it was an optical laminate in which two optically anisotropic layers were laminated. is significantly different from the polarization axis direction of (=60°). Furthermore, it was confirmed that the direction of the slow axis was not constant in the plane, and that the orientation was disturbed and the haze was caused by the occurrence of microdomains. By the second polarized light irradiation through the oriented second optical anisotropy, when the polarized light is incident on the first optical anisotropy composed of the copolymer 1, the linearly polarized light becomes This is probably because the light becomes elliptically polarized and the polarization axis direction (major axis direction of the elliptically polarized light) is also changed. Therefore, in Comparative Example 1, it was difficult to produce a desired optical layered body.

Since the optical laminates of Examples 1 to 3 were produced by a specific method, the slow axis of each layer of the first optically anisotropic layer and the second optically anisotropic layer can be arbitrarily adjusted. there were. In particular, in Example 2, surface treatment with a solvent was performed before irradiation with the second polarized light, so it was possible to more easily align the surface. Further, in Example 3, since the polyisocyanate having an isocyanate group capable of forming a cross-linking bond 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 anisotropic layer were formed. Adhesion to the tropic layer was good.

On the other hand, the optical laminate of Comparative Example 1 was irradiated with polarized light for orienting the birefringence inducing material layer through the layer made of the polymerizable liquid crystal material, so the polarized light was converted by the layer made of the polymerizable liquid crystal material. As a result, the slow axis of each layer could not be adjusted to a desired value.

ADVANTAGE OF THE INVENTION According to this invention, the optical laminated body which can set arbitrarily the angle which a mutual slow axis cross|intersects can be provided. Such an optical laminate can be used for applications such as polarizing plates and optical compensation films used in liquid crystal display devices and organic EL display devices. In particular, it can be used as a circularly polarizing plate used in an organic EL display device by laminating it with a linearly polarizing plate.

As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but those skilled in the art can easily conceive of various changes and modifications within the scope of obviousness after looking at the present specification. be. Accordingly, such changes and modifications are intended to be within the scope of the invention as defined by the appended claims.

DESCRIPTION OF SYMBOLS 10... Base material 20... Birefringence inducing material layer 30... First optically anisotropic layer 31... Internal layer 32... Surface layer 40... Second optically anisotropic Layer 100... Optical laminate

Claims (7)

a first optically anisotropic layer made of a birefringence inducing material;
an optical laminate in which a second optically anisotropic layer made of a polymerizable liquid crystal material is laminated adjacently,
the first optically anisotropic layer is composed of a surface layer and an internal layer having mutually different slow axes, the surface layer and the second optically anisotropic layer being in contact,
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 , wherein the birefringence inducing material includes a liquid crystalline polymer having a side chain structure capable of forming a liquid crystal structure and having a photosensitive group . 2. The optical laminate 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. An optical stack that intersects at an angle that is orthogonal. 3. The optical laminate according to claim 1, 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. A method for producing the 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 a first polarized light for developing a retardation to form a first optically anisotropic layer;
a surface orientation step of subjecting the surface of the first optically anisotropic layer to orientation treatment so as to give an orientation different from that of the inner layer to form a surface layer on the first optically anisotropic layer;
forming a second optically anisotropic layer by applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has been subjected to orientation treatment. 5. The manufacturing method according to claim 4, wherein the surface orientation 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. 6. The manufacturing 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 layered body, further comprising a step. A circularly polarizing plate comprising the optical layered body according to any one of claims 1 to 3 and a linearly polarizing plate.

Images