KR102645532B1 - Optical laminate and manufacturing method thereof - Google Patents

Abstract

An optical laminate capable of arbitrarily setting an axis and a method for manufacturing the same are provided. The optical laminate 100 is an optical laminate in which a first optically anisotropic layer 30 made of a birefringence inducing material and a second optically anisotropic layer 40 made of a polymeric liquid crystal material are stacked adjacently, wherein the first optical layer 30 is made of a birefringence inducing material. The anisotropic layer 30 is composed of a surface layer 32 and an inner layer 31 having different slow axes, and the surface layer 32 and the second optically anisotropic layer 40 are in contact with each other. The slow axis direction of the inner layer 31 of the first optically anisotropic layer and the slow axis direction of the second optically anisotropic layer 40 intersect.

Description

Optical laminate and manufacturing method thereof

This application claims priority of Japanese Patent Application No. 2019-030471, dated February 22, 2019, and is incorporated herein by reference in its entirety.

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

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

As a retardation film used in such a broadband circularly polarizing plate, Patent Document 1 (Japanese Patent Laid-Open No. 2016-184013) describes a first optically anisotropic layer made of a birefringence inducing material, and a second optically anisotropic layer made of polymeric liquid crystal. A retardation film is disclosed in which the layers are directly laminated without an adhesive layer interposed therebetween. In addition, the manufacturing method includes the steps of applying a birefringence inducing material to a support substrate and forming a birefringence inducing material layer, and irradiating first polarized light onto the birefringence inducing material layer. , a first light irradiation process, and applying a polymerizable liquid crystal on the birefringence inducing material layer irradiated with the first polarized light, thereby forming a laminate in which the polymerizable liquid crystal material layer is laminated on the birefringence inducing material layer. and a second light irradiation step of irradiating second polarized light to the laminate, wherein the polarization axis direction of the first polarized light and the polarization axis direction of the second polarized light are different. The method is described.

Japanese Patent Publication No. 2016-184013

However, in the method for manufacturing the retardation film described in Patent Document 1, in the second light irradiation step of irradiating the second polarized light to orient the birefringence inducing material layer, the second polarized light is irradiated through the aligned polymerizable liquid crystal material layer. When irradiated, the polarization state of the second polarized light is changed when it passes through the aligned polymeric liquid crystal material layer, so it was difficult to irradiate the desired polarized light to the birefringence inducing material layer. For this reason, it was difficult to create the intended slow axis relationship between the birefringence inducing material layer and the polymerizable liquid crystal material layer.

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

The present inventor conducted careful research to solve the above problem, and as a result, after forming a first optically anisotropic layer oriented by irradiating the first polarized light to the birefringence inducing material layer, the surface of the first optically anisotropic layer was formed. By orienting the inner layer to have a different orientation from that of the inner layer and applying a polymerizable liquid crystal material to its surface to form a second optically anisotropic layer, (i) a layer that is different in the photo-orientation of the inner layer composed of the birefringence inducing material. Without this influence, a desired orientation can be given to the inner layer, and (ii) the orientation of the surface layer, which serves as an orientation film, can be adjusted independently of the inner layer, taking into account the relationship with the orientation of the inner layer. , it was discovered that a desired orientation could be imparted to the second optically anisotropic layer. Then, it was discovered that in the obtained optical laminate, the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer could be arbitrarily set, and the present invention was completed.

That is, the present invention can be configured by the following aspects.

[Sun 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 stacked adjacently,

The first optically anisotropic layer is composed of a surface layer and an inner layer with 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.

[Sun 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 intersect at a non-parallel and non-orthogonal angle.

[Sun 3]

The optical laminate according to aspect 1 or 2, wherein the polymerizable liquid crystal material contains a birefringence inducing material and a crosslinking agent having a functional group capable of forming a crosslink.

[Sun 4]

A method for manufacturing the optical laminate according to any one of aspects 1 to 3, comprising:

A first light irradiation step of forming a first optically anisotropic layer by irradiating first polarized light for expressing a phase difference onto a birefringence inducing material layer made of a birefringence inducing material;

A surface alignment process of forming a surface layer on the first optically anisotropic layer by orienting the surface of the first optically anisotropic layer to have an orientation different from that of the inner layer;

A method of manufacturing an optical laminate, comprising the step of forming a second optically anisotropic layer by applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has undergone alignment treatment.

[Sun 5]

The manufacturing method according to aspect 4, wherein the surface alignment process irradiates the surface of the first optically anisotropic layer with second polarized light having a polarization axis direction different from the first polarized light, and forms a surface layer on the first optically anisotropic layer. A method of manufacturing an optical laminate, which is a second light irradiation process for forming.

[Sun 6]

The manufacturing method according to aspect 5, further comprising a surface treatment process of treating the surface of the first optically anisotropic layer with a solvent between the first light irradiation process and the second light irradiation process. .

[Taeyang 7]

A circularly polarizing plate in which the optical laminate according to any one of aspects 1 to 3 and a linear polarizing plate are laminated.

[Sun 8]

An optical laminate according to any one of aspects 1 to 3, comprising:

A first optically anisotropic layer formed by irradiating a birefringence inducing material with first polarized light to generate a phase difference;

A surface layer formed on the first optically anisotropic layer by orienting the surface of the first optically anisotropic layer to have 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.

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

According to the optical laminate and its manufacturing method of the present invention, a desired combination of slow axes can be achieved in the first optically anisotropic layer and the second optically anisotropic layer, so the angle at which the slow axes intersect with each other can be arbitrarily set, for example, It can be used as a circularly polarizing plate by laminating it with a linear polarizing plate.

The present invention can be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily to scale and are exaggerated in illustrating the principles of the invention. However, the embodiments and drawings are for illustrative and illustrative purposes only and should not be used to define the scope of the invention. The scope of the present invention is defined by the appended claims.
Figure 1A is a schematic cross-sectional view before the first light irradiation process in one embodiment of the method for manufacturing an optical laminate of the present invention.
Figure 1B is a schematic cross-sectional view after the first light irradiation process in one embodiment of the method for manufacturing an optical laminate of the present invention.
1C is a schematic cross-sectional view after the surface alignment process in one embodiment of the method for manufacturing an optical laminate of the present invention.
Figure 1D is a schematic cross-sectional view after the second optically anisotropic layer forming process in one embodiment of the method for manufacturing an optical laminate of the present invention.

[Method for manufacturing optical layer]

The method for manufacturing an optical laminate of the present invention includes a first light irradiation step of forming an oriented first optically anisotropic layer by irradiating first polarized light for expressing a phase difference onto a birefringence inducing material layer made of a birefringence inducing material; , a surface alignment process of forming a surface layer on the first optically anisotropic layer by aligning the surface of the first optically anisotropic layer so as to have an orientation different from that of the inner layer, and forming a surface layer on the first optically anisotropic layer, and the alignment treatment of the first optically anisotropic layer. and forming a second optically anisotropic layer on the surface by applying a polymerizable liquid crystal material.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1A to 1D are schematic cross-sectional views for explaining an embodiment of the method for manufacturing an optical laminate of the present invention. In Figures 1A to 1D, cross sections of each layer are shown, but these do not show the actual thickness ratio.

A in FIG. 1 is a schematic cross-sectional view showing a laminate of the substrate 10 and the birefringence inducing material layer 20. FIG. 1B shows the state after the first light irradiation process, and is a stack of the substrate 10 and the first optically anisotropic layer 30 formed by aligning the molecules of the birefringence inducing material layer 20 by irradiation of the first polarized light. This is a schematic cross-sectional view showing the sieve. C in FIG. 1 shows the state after the surface alignment process, including the substrate 10, the inner layer 31 having the same orientation as the first optically anisotropic layer 30, and the surface on the opposite side from the substrate 10. This is a schematic cross-sectional view showing a laminate of the first optically anisotropic layer 30 consisting of a surface layer 32 that has been oriented differently from the inner layer 31 by an orientation treatment. D in FIG. 1 represents the state after the second optically anisotropic layer forming process, and includes a substrate 10, a first optically anisotropic layer 30 consisting of an inner layer 31 and a surface layer 32, and a polymerizable liquid crystal material. This is a schematic cross-sectional view showing the optical laminate 100 of the second optically anisotropic layer 40 formed by applying .

By irradiating the first polarized light for generating a phase difference onto the birefringence inducing material layer 20 made of the birefringence inducing material shown in A of FIG. 1, the molecular orientation of the birefringence inducing material can be induced. As a result, as shown in FIG. 1B, a first optically anisotropic layer 30 oriented to have a predetermined slow axis is formed from the optically isotropic birefringence inducing material layer 20. In the first light irradiation process, 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 desired polarization can be irradiated to the birefringence inducing material layer 20. .

Next, the surface of the first optically anisotropic layer 30 shown in B in FIG. 1 is subjected to orientation treatment to achieve an orientation different from the orientation imparted in the first light irradiation process, thereby forming the first optically anisotropic layer 30. A surface layer 32 can be formed. Accordingly, as shown in FIG. 1C, the first optically anisotropic layer 30 is composed of two layers: an inner layer 31 having the originally formed orientation and a surface layer 32 having a different orientation. is formed

And, when a polymerizable liquid crystal material is applied on the surface layer 32 shown in C of FIG. 1, the surface layer 32 acts as an alignment film, and a second optically anisotropic layer ( 40) can be formed. As a result, as shown in FIG. 1D, a second optically anisotropic layer 40 oriented to have a different slow axis from that of the inner layer 31 is formed on the surface layer 32. Since the inner layer 31 and the surface layer 32 can independently adjust their orientation, a desired orientation can be given to the second optically anisotropic layer 40 by considering the relationship with the orientation of the inner layer 31, They can intersect each other at any desired ground axis.

According to the method for manufacturing an optical laminate of the present invention, there is no need to cut a plurality of films at a predetermined angle and precisely join them, so the intersection angle of the slow axes can be easily adjusted. Additionally, since it is possible to manufacture in a long form, an optical laminated body can be obtained efficiently.

(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 that can induce birefringence in an axis-selective manner by 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 include a liquid crystalline polymer that has a photosensitive group and a side chain structure capable of forming a liquid crystal structure at the same time, and may have a property in which molecular orientation is induced by photoreaction of the photosensitive group in the side chain. do. Examples of photoreactions include photodimerization reaction, photoisomerization reaction, and optical Fries rearrangement reaction.

When a 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 portion that exhibits liquid crystallinity, in the side chain structure, or by using another polymer or another side chain of the same polymer, etc. It has a structure capable of forming a dimer by hydrogen bonding, and may express liquid crystallinity by forming a mesogenic structure through dimerization.

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 aromatic rings include benzene rings, naphthalene rings, heterocycles (for example, oxygen-containing heterocycles such as furan rings and pyran rings; nitrogen-containing heterocycles such as pyrrole rings and imidazole rings), and aliphatic rings. Examples of the ring include a cyclohexane ring. In addition, these aromatic rings or aliphatic rings may have a substituent, and examples of the substituent include 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 _1-4 alkyl group) _-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (for example, C _1-6 alkenyl group, preferably C _1-4 alkenyl group), alkynyl group (for example, Examples include a C _1-6 alkynyl group (preferably a C _1-4 alkynyl group) and a halogen atom. As a linking group, in the case of a covalent bond, a single bond, -O-, -COO-, -OCO-, -N=N-, -NO=N-, -C=C-, -C≡C-, -CO- Examples include C=C-, -CH=N-, and alkylene groups. In the case of hydrogen bonding, examples include a side chain structure having a carboxyl group at the terminal, and in this case, a hydrogen bond is formed between carboxyl groups.

The photosensitive group is not particularly limited as long as it is a functional group capable of causing a photoreaction by light energy, and examples include chalcone group, coumarin group, cinnamoyl group, cinnamic acid group, cinnamylydenacetic acid group, biphenylacryloyl group, These include furyl acryloyl group, naphthylacryloyl group, azobenzene group, benzylidene aniline group, and derivatives thereof, and preferably, cinnamoyl group.

The liquid crystalline polymer has at least a side chain structure in the repeating unit that has both a photosensitive group and a structure capable of forming a liquid crystal structure. However, the photosensitive group may exist independently of the mesogenic group or mesogenic structure in the side chain structure. Alternatively, they may share a chemical structure and exist in a complex manner.

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).

(In the formula, t is an integer of 1 to 3, and 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, a 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. , C _1-6 alkynyl group, preferably C _1-4 alkynyl group), and halogen atom.)

(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, C1-3 alkylene group, -C= C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; W is coumarin group, cinnamoyl group, cinnamylidene acetic acid group, biphenylacryloyl group, furylacryloyl group, naphthylacryloyl group, or a derivative group thereof; R ₂ and R ₃ are each the same or different, and are each a hydrogen atom, an alkyl group (for example, a C _1-6 alkyl group, preferably C _{1 -4} alkyl group), alkyloxy group (for example, C _1-6 alkyloxy group, preferably C _1-4 alkyloxy group), alkenyl group (for example, C _1-6 alkenyl group, preferably C _1-4 alkenyl group), an alkynyl group (for example, a C _1-6 alkynyl group, preferably a C _1-4 alkynyl group), a carboxyl group, and a halogen atom.

In addition, the side chain structure represented by the formula (1) and formula (2) represents the chemical structure of the end of the side chain in the repeating unit, and within the range that does not impair the effect of the present invention, this side chain structure and the main chain Various chemical structures may be included between structures.

The liquid crystalline polymer may be a homopolymer composed of identical repeating units including the above-mentioned side chain structure, or a copolymer including repeating units including side chain structures with different structures in addition to the repeating units including the above-mentioned side chain structure. Examples of the main chain structure include structures formed by polymerizing hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, N-phenylmaleimides, etc.

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

In addition, the birefringence inducing material of the present invention has a side chain structure having a crosslinkable functional group 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. A liquid crystalline polymer 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 the crosslinking agent described later, and examples include hydroxyl group, carboxyl group, amino group, and thiol group. The side chain structure having a crosslinkable functional group may be included in a repeating unit that has the photosensitive group described above and includes a side chain structure capable of forming a liquid crystal structure, or may have a crosslinkable functional group in repeating units other than the above repeating unit.

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, -(CH ₂ ) _n -OH (where n is an integer of 1 to 6), and It may have at least one structure selected from the group consisting of -Ph-COOH (where Ph is divalent phenyl). These side chain structures represent at least part of the chemical structure of the side chain in the repeating unit, and various chemical structures may be included between the side chain structure and the main chain structure within a range that does not impair the effect of the present invention.

Additionally, 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. As low-molecular-weight compounds, they have substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are known as mesogenic components, and include such substituents, allyl, acrylate, methacrylate, cinnamic acid group (or derivative thereof), etc. It is preferable to have liquid crystallinity in which a functional group of is bonded through 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, etc.). It is used. These low molecular compounds may be used individually or in combination of two or more types.

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 using a substrate, the substrate may be an optically isotropic substrate, or, for example, a transparent substrate may be optically isotropic, such as glass or a triacetylcellulose film (TAC film). Additionally, as a base material, for example, a base material made of a material with low adhesion to the birefringence inducing material layer (first optically anisotropic layer), such as a general-purpose polyester film, can also be used as a base material for mold release. When using a release substrate, it is possible to peel after forming the optical laminate of the present invention, so there is no need to consider the optical properties of the substrate itself, and an opaque substrate can also be used. For example, after forming the optical laminate of the present invention on a substrate, it is bonded to another optical member (e.g., a polarizing plate, etc.) through an adhesive or the like, and then the mold release substrate is peeled off and used to form an optical laminate, It can be made into a thin optical member that does not have a base material and whose thickness is substantially comprised only of the film thickness of the optically anisotropic layer.

As described above, the birefringence inducing material layer made of the birefringence inducing material may be formed by using a pre-formed birefringence inducing material film (which may or may not be laminated on the substrate) or by coating it on the substrate. You can form it. When forming a coating film of a birefringence inducing material, the birefringence inducing material is dissolved in a solvent to form a solution as described above, and this solution is applied onto the substrate. The solvent can be appropriately selected depending on the type of birefringence inducing material, for example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, Ethylene glycol derivatives (e.g., ethylene glycol 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., and these solvents may be used individually or in combination of two or more types.

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, and more preferably 10 to 25% by weight. To apply the solution to the substrate, known application methods such as spin coating and roll coating can be used. After application, if necessary, the coating film may be dried by heating to form a laminate having a base material and a birefringence inducing material layer.

Before the first light irradiation process, the birefringence inducing material layer is preferably substantially optically isotropic, that is, the liquid crystal polymer is preferably not substantially oriented.

(First light irradiation process)

In the first light irradiation process, first polarized light for developing a phase difference is irradiated onto the birefringence inducing material layer. By performing the first light irradiation process, selective photoreaction of molecules occurs not only on the surface but also inside the birefringence inducing material layer, the orientation of the molecules is induced, and a first optically anisotropic layer is formed. In the method for manufacturing an optical laminate of the present invention, the first polarized light can be directly irradiated onto the birefringence inducing material layer without intervening another layer, and thus the intended slow axis can be formed by the irradiated polarized light.

The first polarized light is an infrared ray, visible ray, ultraviolet ray (e.g., near-ultraviolet ray, far-ultraviolet ray, etc.), There is no particular limitation as to the wavelength of light, and although it varies depending on the type of side chain structure of the liquid crystal polymer, the wavelength of the light may be 200 to 500 nm. The first polarized light may be, for example, linearly polarized ultraviolet light. In this case, for example, the polarization may be converted into linearly polarized light through a Glenn-Taylor prism using an ultraviolet irradiation device such as a high-pressure mercury lamp as a light source. .

Additionally, 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 to 1 J/cm , from the viewpoint of orienting not only the surface but also the inside of the birefringence inducing material layer. cm ² , more preferably 100 mJ/cm ² to 500 mJ/cm ² .

In the method for producing an optical laminate of the present invention, if necessary, a heating step of heating the formed first optically anisotropic layer may be provided 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 process, and unoriented molecules are also oriented according to the oriented molecules, but subsequent heating causes molecular movement of the liquid crystalline polymer. This makes it possible to promote the orientation of unoriented molecules. After heating, it may be cooled to room temperature, for example, by leaving it to stand.

The heating temperature in the heating process is not particularly limited as long as the orientation of the unoriented molecules is induced along the side chain where the liquid crystalline polymer undergoes a photoreaction due to molecular motion, but is above the liquid crystal phase transition temperature of the birefringence inducing material and isotropic phase transition temperature. It is desirable to set it below. For example, the temperature may be 100 to 200°C, preferably 110 to 180°C, and more preferably 120 to 160°C.

In addition, the heating time is not particularly limited as long as the orientation of the unoriented molecules is induced along the side chain where the liquid crystal polymer undergoes a photo reaction due to molecular motion, but can be set appropriately depending on the type of liquid crystal polymer, heating temperature, etc. For example, it may be performed for 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. The upper limit is not particularly limited, but from the viewpoint of economic efficiency, it may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes).

(Surface orientation process)

In the surface alignment process, the surface of the first optically anisotropic layer is aligned so as to have a different orientation from that of the inner layer. By performing surface alignment treatment, a surface layer is formed on the first optically anisotropic layer, and two layers, an inner layer and a surface layer, which are made of the same birefringence inducing material but have different orientation states, are formed within the first optically anisotropic layer. Additionally, the internal layer may represent a portion of the first optically anisotropic layer other than the surface layer.

The method of alignment treatment is not particularly limited as long as an alignment layer that is different from the inner layer can be formed on the surface of the first optically anisotropic layer, for example, rubbing treatment, photo-alignment treatment by second polarized light irradiation, etc. There is. In the rubbing treatment, the orientation direction can be controlled by rubbing the surface of the first optically anisotropic layer in a certain direction by rotating a roller wound with a cloth such as cellulose, nylon, or polyester while pressing it at a certain pressure, so that the desired orientation direction can be achieved by rubbing the surface of the first optically anisotropic layer in a certain direction. Although a surface layer can be formed, the method of alignment treatment is preferably photo-alignment treatment by polarized light irradiation.

The surface alignment process may be a second light irradiation process of irradiating second polarized light having a polarization axis direction different from the first polarized light to the surface of the first optically anisotropic layer to form a surface layer on the first optically anisotropic layer. In the second light irradiation process, even after the molecules are aligned by the first light irradiation process (preferably, the first light irradiation process and the heating process), second polarized light having a polarization axis direction different from the first polarized light is irradiated, Perhaps because an axis-selective photoreaction occurs selectively near the surface centered on the unreacted birefringence inducing material of the first optically anisotropic layer, an orientation different from that of the inner layer can be imparted to the vicinity of the surface. On the other hand, perhaps because the molecules of the inner layer of the first optically anisotropic layer are already highly oriented, the orientation itself of the inner layer of the first optically anisotropic layer is not changed even after the second light irradiation process.

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

The second polarized light may have a different polarization axis direction from the first polarized light, for example, the axis angle may be different from the polarization axis of the first polarized light by 5 to 85°, preferably 10 to 80°, more preferably. In other words, it may be different by 20 to 70 degrees. Here, the difference in axis angle between the polarization axis of the second polarized light and the polarization axis of the first polarized light takes into account the orientation state (presence ratio of unreacted birefringence inducing material, etc.) near the surface of the first optically anisotropic layer after the first light irradiation process. By adjusting this, the slow axis of the second optically anisotropic layer formed later can be arbitrarily set.

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

If necessary, the method for manufacturing 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 process, it is preferable to perform a surface alignment process such as second polarized light irradiation or rubbing treatment, for example. Additionally, 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 process, by applying a solvent to the surface of the first optically anisotropic layer to dissolve the surface portion, the molecular orientation achieved by the first light irradiation process can be relaxed and made random, possibly because the first polarized light The orientation of the surface portion of the first optically anisotropic layer once formed can be eliminated, and the orientation of the surface layer of the first optically anisotropic layer can be made isotropic. In the surface treatment process, the solvent may be applied to the surface of the first optically anisotropic layer and then dried. The drying method is not particularly limited as long as the applied solvent can be evaporated, but for example, it may be left to dry naturally. Only the surface to which the solvent is applied can be made isotropic.

When the surface becomes isotropic, photo-alignment of the surface becomes easier in the subsequent second light irradiation step, so the irradiation amount of the second polarized light can be reduced. When the surface treatment process is performed, the irradiation amount 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 , and more preferably 1 mJ. /cm ² ~100mJ/cm ² is also acceptable.

In addition, when the surface treatment process 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) may be 1.5/1 to 100/1, and preferably 2/1 to 2/1. It may be 80/1, more preferably 2.5/1 to 50/1.

Since the surface becomes isotropic, there is no need to consider the orientation state of the surface layer of the first optically anisotropic layer in the subsequent second light irradiation process, so the axial angle of the polarization axis of the second polarized light is set to the slow axis of the second optically anisotropic layer. It can be reflected directly in . For this reason, the axis angle of the polarization axis of the second polarized light can be easily selected with respect to setting the slow axis of the second optically anisotropic layer 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 may be a good solvent or a poor solvent for the birefringence inducing material. The solvent used in the surface treatment process is, for example, a good solvent and a poor solvent for the birefringence inducing material from the viewpoint of making the surface of the first optically anisotropic layer isotropic and suppressing its orientation by dissolving to the inside. A mixed solvent may be used. When using a mixed solvent containing a good solvent and a poor solvent of the birefringence inducing material, it can be adjusted appropriately depending on the solubility of the used solvent in the birefringence inducing material. For example, this mixing weight ratio (good solvent/poor solvent) may be 1/100 to 100/1, preferably 1/50 to 50/1, and more preferably 1/10 to 10/1.

Solvents used in the surface treatment process include, for example, water; Alcohol-based solvents such as methanol, ethanol, propanol, isopropyl alcohol, pentanol, and hexanol; Aliphatic or alicyclic hydrocarbon solvents such as hexane, heptane, octane, and cyclohexane; Aromatic hydrocarbon solvents such as benzene, toluene, and xylene; Ketone-based solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, isopropyl methyl ketone, methyl isobutyl ketone, and cyclohexanone; Ether-based solvents such as ethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, tetrahydrofuran, and dioxane; Nitrile-based solvents such as acetonitrile and propionitrile; Sulfoxide-based solvents such as dimethyl sulfoxide; Amide-based solvents such as N,N-dimethylformamide; Ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; Glycol-based solvents such as ethylene glycol and propylene glycol; Glycol ether-based solvents such as glycol monoethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol 1-monomethyl ether 2-acetate; Halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, and dichlorobenzene; etc. These solvents may be used individually or in combination of two or more types. Since the solubility of these solvents varies depending on the type of birefringence inducing material, they can be used after considering whether they are good solvents or poor solvents depending on the birefringence inducing material used.

In the present invention, a good solvent refers to a solvent that has a solubility of a solute of 1% by mass or more at 25°C, and a poor solvent refers to a solvent that has a solubility of a solute of less than 1% by mass at 25°C. .

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

(Second optical anisotropic layer formation process)

In the second optically anisotropic layer forming process, a polymerizable liquid crystal material is applied on the surface layer of the alignment-treated first optically anisotropic layer to form a second optically anisotropic layer. By performing the second optically anisotropic layer forming process, since the surface layer oriented in the surface alignment process serves as an alignment film, the second optically anisotropic layer oriented can be formed using the orientation direction.

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 is formed into a crosslinked structure by polymerization by light or heat or by reaction with a crosslinking agent. It includes the composition after forming.

The polymerizable liquid crystal compound may be a liquid crystalline monomer or a liquid crystalline polymer. For example, polymerizable liquid crystal compounds include polymerizable liquid crystal monomers and/or polymerizable liquid crystal polymers that have a polymerizable functional group that polymerizes by light or heat, or polymerizable liquid crystal compounds that have a crosslinkable functional group that can introduce a crosslinked structure by reaction with a crosslinking agent. Examples include crosslinkable liquid crystal monomer and/or crosslinkable liquid crystal polymer.

The polymerizable liquid crystal compound is a monomer having a mesogenic group or a polymer having a unit composed of a mesogenic group, and is not particularly limited as long as it is capable of forming a liquid crystal structure and has polymerizability and/or crosslinking properties, and may include various polymerizable liquid crystal compounds. can be used. Polymerizable liquid crystal compounds include, for example, Schiff base-based, biphenyl-based, terphenyl-based, ester-based, thioester-based, stilbene-based, tran-based, azoxy-based, azo-based, phenylcyclohexane-based, pyrimidine-based, There are liquid crystal compounds having cyclohexylcyclohexane-based, trimesic acid-based, triphenylene-based, torcene-based, phthalocyanine-based, porphyrin-based molecular skeletons, or mixtures of these compounds, and nematic, cholesteric, or smectic liquid crystals. Any compound that represents a phase may be used. As an example, a photopolymerizable nematic liquid crystal monomer may be used as the polymerizable liquid crystal compound.

The unit constituted by the mesogenic group may be in the main chain of the liquid crystal polymer or in the side chain. Main chain liquid crystal polymers include polyester-based, polyamide-based, polycarbonate-based, polyimide-based, polyurethane-based, polybenzimidazole-based, polybenzoxazole-based, polybenzthiazole-based, polyazomethine-based, and polyesteramide-based. , polyester carbonate-based, polyesterimide-based liquid crystal polymer, or mixtures thereof. In addition, as the side-chain liquid crystalline polymer, polymers having a straight or cyclic skeletal chain, such as polyacrylate-based, polymethacrylate-based, polyvinyl-based, polysiloxane-based, polyether-based, and polymalonate-based polymers with side chains. Examples include liquid crystal polymers to which mesogenic groups are bonded, or mixtures thereof.

Additionally, 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 a photopolymerization initiator, Irgacure 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all manufactured by Chiba Japan Co., Ltd.), Sei Kuol BZ, Seikuol Z, Seikuol BEE (all manufactured by Seiko Chemical Co., Ltd.), Kayacure BP100 (manufactured by Nippon Kayaku Co., Ltd.), Kayacure UVI -6992 (manufactured by Dow Corporation), ADEKA Optomer ADEKA OPTOMERSP-152 or ADEKA OPTOMERSP-170 (above, all manufactured by ADEKA Co., Ltd.), TAZ-A, TAZ-PP (above, Nippon Shiberuhe) Commercially available photopolymerization initiators such as (manufactured by Kunasa) and TAZ-104 (manufactured by Sanwa Chemical) can be used.

Examples of the thermal polymerization initiator include azo compounds such as azobisisobutyronitrile; Peroxides such as hydrogen peroxide, persulfate, and benzoyl (Il) peroxide can be mentioned.

The content of the polymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.03 to 10% by weight, and still more preferably 0.05 to 8% by weight, based on the total weight of the polymerizable liquid crystal material. If it is within the above range, it is possible to polymerize the polymerizable liquid crystal compound without disturbing its orientation.

In addition, when using a photopolymerization initiator as a polymerization initiator, a photosensitizer may be used together. Examples of the photosensitizer include xanthone compounds such as xanthone and thioxanthone (for example, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); Anthracene compounds such as anthracene and alkoxy group-containing anthracene (for example, dibutoxyanthracene, etc.); phenothiazine; Rubren, etc.

Additionally, 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 whose orientation can be fixed by means such as crosslinking (thermal crosslinking or photocrosslinking) in a liquid crystal state or in a state cooled to the liquid crystal potential 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. there is. 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 more preferable.

When the polymerizable liquid crystal material contains a crosslinking agent, in addition to forming crosslinks with the polymerizable liquid crystal compound having a crosslinkable functional group, when the liquid crystalline polymer of the birefringence inducing material has a crosslinkable functional group, the liquid crystalline polymer is crosslinked. bonds can be formed. In this case, it becomes possible to form crosslinking between the first optically anisotropic layer composed of a birefringence inducing material and the second optically anisotropic layer including a crosslinking agent, and thus the adhesion between the layers can be improved.

Examples of the crosslinking agent include polyfunctional compounds having two or more functional groups in the molecule. When forming a crosslink in a liquid crystalline polymer, the multifunctional compound is not particularly limited as long as it has a functional group capable of forming a crosslink with the liquid crystalline polymer. For example, the liquid crystalline polymer has a crosslinkable functional group, When the crosslinkable functional group is a hydroxyl group or a carboxyl group, there are compounds having an isocyanate group, carbodiimide group, aziridine group, azetidine group, oxazoline group, epoxy group, etc. Among these crosslinking agents, polyisocyanate-based compounds, which are polyfunctional compounds having two or more isocyanate groups in the molecule, are preferred from the viewpoint of reactivity that reacts with the crosslinkable functional group of the liquid crystalline polymer under relatively mild reaction conditions, and polyisocyanate-based compounds are Known ones can be used. For example, polyisocyanate-based compounds include diisocyanate compounds and triisocyanate compounds. Examples of diisocyanate compounds include phenylene diisocyanate, trilene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, methylcyclohexylene diisocyanate, bis(isocyanatomethyl)cyclohexane, These include methylenebis(cyclohexylisocyanate), isophorone diisocyanate, and condensation compounds of hexamethylene diisocyanate and thiol. In addition, the triisocyanate compound includes an isocyanurate form of diisocyanate such as hexamethylene diisocyanate, a biuret form, and an adduct form which is an adduct between a diisocyanate such as hexamethylene diisocyanate and methylolpropane. Among these crosslinking agents, triisocyanate compounds can be preferably used.

When the crosslinking agent is a polyisocyanate-based compound, the liquid crystalline polymer may have an active hydrogen group as a crosslinking functional group. Examples of the active hydrogen group include hydroxyl group, carboxy group, amino group, and thiol group. If the active hydrogen group is a hydroxyl group, a urethane bond (-NH-CO-O-) is formed, if the active hydrogen group is a carboxyl group, an amide bond (-NH-CO-) is formed, and if the active hydrogen group is an amino group, a urethane bond (-NH-CO-O-) is formed. A bond (-NH-CO-NH-) is formed, and if the active hydrogen group is a thiol group, a thiourethane bond (-NH-CO-S-) is formed. As the active hydrogen group contained in the liquid crystalline polymer, hydroxyl group and carboxy group are preferable.

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

In the second optically anisotropic layer forming process, the polymerizable liquid crystal material as described above is applied on the surface layer of the first optically anisotropic layer. In application, the polymerizable liquid crystal material dissolved in a solvent may be applied as a solution using a known coating method such as spin coating or roll coating. The solvent can be appropriately selected depending on the type of polymerizable liquid crystal material, for example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, and methyl isobutyl ketone. , ethylene glycol derivatives (e.g., 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) Tato) etc. can be mentioned as examples, and these solvents may be used individually or in combination of two or more types.

The solvent for the polymerizable liquid crystal material can be selected not only according to the combination of the types of the birefringence inducing material and the polymerizable liquid crystal material, but also according to the orientation state of the surface layer. For example, when most of the molecules of the surface layer have the desired orientation (for example, when a surface treatment process is performed or when a rubbing treatment is performed as an orientation treatment, etc.), the orientation of the surface layer is given to the second optically anisotropic layer. From the viewpoint of suppressing disruption of the orientation of the first optically anisotropic layer, it is preferable that the solvent for the polymerizable liquid crystal material is a poor solvent for the birefringence inducing material. On the other hand, when only a portion of the molecules of the surface layer have 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 of the birefringence inducing material are mixed. Although the mechanism in this case is not clear, if a poor solvent of the birefringence inducing material is contained as a solvent of the polymerizable liquid crystal material, it can be suppressed from invading the first optically anisotropic layer and disturbing its orientation. On the other hand, if a good solvent of the birefringence inducing material is contained as a solvent for the polymerizable liquid crystal material, is it because the wettability of the solution to the surface layer is improved, or is it possible to make the molecules of the polymerizable liquid crystal material follow the orientation that only some of the molecules in the surface layer have? and, as a result, the second optically anisotropic layer can be oriented. The solvent for the polymerizable liquid crystal material can be appropriately adjusted depending on the combination of the types of birefringence inducing material and the polymerizable liquid crystal material and the orientation state of the surface layer, but does not invade the surface layer from the viewpoint of maintaining the orientation of the first optically anisotropic layer. It is preferable to include a poor solvent for the birefringence inducing material. For example, the mixed weight ratio (good solvent/poor solvent) of the good solvent and poor solvent of the birefringence inducing material may be 0/100 to 100/1. , preferably 0/100 to 50/1, more preferably 0/100 to 10/1. As a solvent for the polymerizable liquid crystal material, general solvents can be used depending on the purpose, and may include, for example, toluene, ethylene glycol derivatives, propylene glycol derivatives, etc.

A coating film is formed by applying the solution, and the coating film is dried by heating as necessary. At this time, the surface layer of the first optically anisotropic layer present at the bottom functions as an alignment film (orientation imparting film), and alignment of the liquid crystal molecules occurs. As a result, a second optically anisotropic layer in which the liquid crystal is oriented in a predetermined direction is formed.

In the second optically anisotropic layer forming process, a heating process and/or a light irradiation process (for example, a non-polarized light irradiation process) may be provided after formation of the coating film of the polymerizable liquid crystal material, as needed. 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, and the subsequent heating process and/or light irradiation process (e.g., non-polarized irradiation process) ), the polymerizable liquid crystal material polymerizes and/or crosslinks, thereby fixing the orientation.

Specifically, when the polymerizable liquid crystal material is made of a thermally polymerizable material, the orientation is fixed by polymerization by heating.

When made of a photopolymerizable material, polymerization occurs upon irradiation of light, and the orientation is fixed. When made of a crosslinkable material, crosslinking occurs upon heating and/or irradiation of light, and the orientation is fixed.

Additionally, 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-link with the birefringence inducing material, the first optically anisotropic layer and the second optically anisotropic layer are formed by applying heat energy and/or light energy. 2 Crosslinking can be formed between the optically anisotropic layers.

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 from the viewpoint of suppressing disturbance of the orientation of the inner layer of the first optically anisotropic layer, birefringence is induced. It is preferable to carry out the heating temperature below the isotropic phase transition temperature of the material. For example, it may be 70 to 180°C, preferably 80 to 150°C, and more preferably 100 to 140°C. Additionally, the heating time may be, for example, 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. The upper limit is not particularly limited, but from the viewpoint of economic efficiency, it may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes).

In the light irradiation step in the second optically anisotropic layer forming step, there is no particular limitation as long as the polymerization and/or crosslinking reaction proceeds, but non-polarized light is preferable as the light to be irradiated. As the non-polarized light, light of the various wavelengths described above can be used as the first polarized light or the second polarized light. For example, non-polarized ultraviolet rays may be used. The amount of light irradiated 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 layer]

The optical laminate of the present invention is an optical laminate in which a first optically anisotropic layer made of a birefringence inducing material and a second optically anisotropic layer made of a polymerizable liquid crystal material are laminated adjacently, and the first optically anisotropic layers have mutually slow axes. It is composed of another surface layer and an inner layer, and the surface layer is in contact with the second optically anisotropic layer.

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 have a different orientation from that of the inner layer. Here, the orientation treatment may be performed by the surface alignment process aspect in the above-described manufacturing method.

The polymerizable liquid crystal material constituting the second optically anisotropic layer may contain a crosslinking agent having a functional group capable of forming a crosslinking bond with the birefringence inducing material. The crosslinking agent contained in the polymerizable liquid crystal material forms a crosslinking bond with the birefringence inducing material of the first optically anisotropic layer, thereby improving the adhesion between the first optically anisotropic layer and the second optically anisotropic layer. As a result, there is no need to form an adhesive layer between the first optically anisotropic layer and the second optically anisotropic layer, so the optical laminate can be thinned, and the surface layer of the first optically anisotropic layer and the second optically anisotropic layer can be separated. It can be made into a structure where the layers are in contact. And, the adhesion between the first optically anisotropic layer and the second optically anisotropic layer can be confirmed by a crosscut test described in the Examples described later.

The thickness of the second optically anisotropic layer may be 0.1 to 20 μm, preferably 0.3 to 15 μm, and more preferably 0.5 to 10 μm. Additionally, the ratio of the thicknesses of the first optically anisotropic layer and the second optically anisotropic layer (first optically anisotropic layer/second optically anisotropic layer) may be 1/10 to 10/1, and is 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 surface layer of the first optically anisotropic layer that has undergone alignment treatment. Here, the application of the polymerizable liquid crystal material may be carried out according to the second optically anisotropic layer forming process aspect in the above-described manufacturing method.

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

In the optical laminate of the present invention, the slow 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 laminate of the present invention is manufactured by the above-described manufacturing method, so that 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 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 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 to 80 °, and more preferably 10 °. It can be ∼75°. And, since the slow axis of the inner layer of the first optically anisotropic layer can be considered to have an extremely small influence of the orientation in the surface layer, it may be measured as the slow axis of the entire first optically anisotropic layer.

In the optical laminate of the present invention, especially in the first optically anisotropic layer, it is preferable that the slow axis direction is constant in the plane. In the present invention, the polarization state is not changed (for example, from linear polarization to elliptically polarized light) by irradiating polarized light through the alignment layer to the lower layer, so the molecular orientation is not disturbed and the slow axis direction is oriented. can be kept constant.

The optical laminate of the present invention can exhibit desired optical properties by using the above-described manufacturing method. Optical characteristics include, for example, retardation value (for example, in-plane retardation value: Re). The ranges shown below for these optical properties may be the range of the measured values of the optical laminate or the range of the measured values of the first optically anisotropic layer or the second optically anisotropic layer.

The in-plane retardation value (Re) is the product (△xy It is a defined parameter 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, and more preferably 5 to 400 nm. In addition, 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 as a retardation film, for example, and can be used for various optical members (anti-reflection film, optical compensation film, etc.). The optical laminate of the present invention can be used as a circular polarizer used as an anti-reflection film in OLEDs such as organic EL displays, for example, by laminating it with a linear polarizer as a retardation film.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited at all 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. To this product, a large excess of methacrylic acid was added in the presence of p-toluenesulfonic acid to carry out an esterification reaction, thereby synthesizing monomer 1 represented by the following formula.

(Monomer 2)

4-(6-hydroxyhexyloxy)benzoic acid was synthesized by heating 4-hydroxybenzoic acid and 6-chloro-1-hexanol under alkaline conditions. Next, a large excess of methacrylic acid was added to this product in the presence of p-toluene sulfonic acid to carry out an esterification reaction, thereby synthesizing monomer 2 represented by the following formula.

(Copolymer 1)

Monomer 1 and monomer 2 were dissolved in dioxane so that the molar ratio of monomer 1 and monomer 2 was monomer 1:monomer 2 = 3:7, AIBN (azobisisobutyronitrile) was added as a reaction initiator, and the mixture was heated to 70°C. Copolymer 1 was obtained by polymerization for 24 hours. This copolymer 1 exhibited liquid crystallinity.

(Copolymer 2)

Monomer 1, monomer 2, and HEMA were dissolved in dioxane so that the molar ratio of monomer 1, monomer 2, and 2-hydroxyethyl methacrylate (HEMA) was monomer 1:monomer 2:HEMA=3:7:2; Copolymer 2 was obtained by 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 laminate were measured using a birefringence measuring device (AxoScan, manufactured by AXOMETRICS), and the thickness was measured using a film thickness measuring meter (F20, manufactured by FILMETRICS). It was measured using .

(Example 1)

Copolymer 1 was dissolved in tetrahydrofuran (THF) to prepare a solution. This solution was applied to a cover glass substrate to a thickness of 2.4 μm using a spin coater and dried at 25°C. To the dried coating film, ultraviolet rays from a high-pressure mercury lamp were irradiated perpendicularly to the coating film with polarized light (first polarization) converted to linearly polarized light using a Glenn-Taylor prism for 200 seconds (irradiation dose 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. The optical properties of the obtained coating film were such that the axial direction of the in-plane phase difference was 90° with respect to the irradiated polarization axis direction.

Afterwards, ultraviolet rays from a high-pressure mercury lamp were converted to linearly polarized light (second polarized light) whose polarization axis direction is 45° different from the polarization axis direction of the previously irradiated polarized light using a Glenn-Taylor prism, and irradiated on the coating film for 300 seconds. (Irradiation amount: 300 mJ/cm ² ), a surface layer was formed on the first optically anisotropic layer.

100 parts by weight of polymerizable liquid crystal compound (LC-242, manufactured by BASF) and 5 parts by weight of photopolymerization initiator (Irgacure 907, manufactured by Chiba Specialty Chemicals) are mixed, THF and propylene glycol 1-monomethyl ether 2- Acetate (PGMEA) was dissolved in a mixed solvent with a volume ratio (THF:PGMEA) of 1:1 to prepare a solution. This solution was applied to the coating film obtained after the second polarized light irradiation to a thickness of 0.9 μm using a spin coater, heated to 70°C, and then cooled to room temperature to form a second optically anisotropic layer. Additionally, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount of 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 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 and second optically anisotropic layers were measured, respectively. 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. In the irradiation of the second polarized light, since the first optically anisotropic layer itself was already oriented, 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, the polarization axis direction was selected in consideration of the orientation state near the surface of the first optically anisotropic layer, and as a result, the desired slow axis direction of the second optically anisotropic layer could be set. As a result, it was confirmed that it was an optical laminate in which two optically anisotropic layers were laminated, and the angle formed by the slow axis of each layer was 13°. Additionally, the slow axis direction within the plane of the first optically anisotropic layer was constant.

(Example 2)

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

Afterwards, a mixed solvent of THF and ethanol (THF:ethanol) in a volume ratio of 1:6 was applied to the obtained coating film using a spin coater, and left to dry. In addition, ultraviolet rays from a high-pressure mercury lamp were converted to linearly polarized light (second polarized light) whose polarization axis direction is 60° different from the polarization axis direction of the previously irradiated polarized light using a Glenn-Taylor prism, and irradiated on the coating film for 70 seconds ( At an irradiation dose of 70 mJ/cm ² ), a surface layer was formed on the first optically anisotropic layer.

100 parts by weight of polymerizable liquid crystal compound (LC-242, manufactured by BASF) and 5 parts by weight of photopolymerization initiator (Irgacure 907, manufactured by Chiba 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 to a thickness of 0.9 μm using a spin coater, heated to 70°C, and then cooled to room temperature to form a second optically anisotropic layer. Additionally, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount of 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 laminate were calculated using analysis software (Multi-Layer Analysis) of a birefringence measurement device (AxoScan, manufactured by AXOMETRICS). 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 the slow axis direction was 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 laminate composed of two optically anisotropic layers, and the angle formed by the slow axis of each layer was 61.5°. Additionally, the slow axis direction within the plane of the first optically anisotropic layer was constant.

(Example 3)

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

Afterwards, ultraviolet rays from a high-pressure mercury lamp were converted to linearly polarized light (second polarized light) whose polarization axis direction is 45° different from the polarization axis direction of the previously irradiated polarized light using a Glenn-Taylor prism, and irradiated on the coating film for 300 seconds. (Irradiation amount: 300 mJ/cm ² ), a surface layer was formed on the first optically anisotropic layer.

100 parts by weight of polymerizable liquid crystal compound (LC-242, manufactured by BASF), 5 parts by weight of photopolymerization initiator (Irgacure 907, manufactured by Chiba Specialty Chemicals), and polyisocyanate (Duranate TKA, manufactured by Asahi Chemical Co., Ltd.) -100) 0.6 parts by weight was mixed and dissolved in a mixed solvent with 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 to a thickness of 0.9 μm using a spin coater, heated to 70°C, and then cooled to room temperature to form a second optically anisotropic layer. Additionally, non-polarizing ultraviolet rays were irradiated for 100 seconds (irradiation amount of 400 mJ/cm ² ) to polymerize the polymerizable liquid crystal compound and crosslink Copolymer 2. The obtained optical laminate had an in-plane retardation value of 202 nm (Linear Retardance: 185 nm, Circular Retardance: 81 nm). Additionally, a crosscut 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, peeling of the second optically anisotropic layer was not observed, and it was confirmed that it had good adhesion.

The optical properties of each layer of the obtained optical laminate exhibit optical properties similar to those of Example 1.

(Comparative Example 1)

Copolymer 1 was dissolved in tetrahydrofuran (THF) to prepare a solution. This solution was applied to a cover glass substrate to a thickness of 2.6 μm using a spin coater and dried at 25°C. The dried coating film was irradiated with ultraviolet rays from a high-pressure mercury lamp, polarized light converted to linear polarization using a Glenn-Taylor prism, for 30 seconds (irradiation dose of 30 mJ/cm ² ).

Then, on the obtained coating film, 100 parts by weight of polymerizable liquid crystal compound (LC-242, manufactured by BASF) and 5 parts by weight of photopolymerization initiator (Irgacure 907, manufactured by Chiba Specialty Chemicals) were mixed, and the solution was dissolved in toluene. The solution was applied to a thickness of 1.2 μm using a spin coater, 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 direction of the irradiated polarization axis.

Afterwards, ultraviolet rays from a high-pressure mercury lamp were converted to linearly polarized light using a Glenn-Taylor prism, the polarization axis of which was 60° different from the polarization axis of the previously irradiated polarized light, and the coating film was irradiated for 100 seconds (irradiation dose: 100 mJ/cm). ² ).

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

In order to investigate the optical properties of each layer of the obtained optical laminate, only the second optically anisotropic layer was peeled. 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 it was an optical laminate in which two optically anisotropic layers were laminated, but the angle formed by the slow axis of each layer was 50.2°, which was significantly different from the polarization axis direction (=60°) during the second polarization irradiation. . In addition, it was confirmed that the slow axis direction was not constant in the plane, and that the orientation was disturbed and haze occurred due to the generation of microdomains. This means that, due to the second polarization irradiation through the oriented second optical anisotropy, when polarized light is incident on the first optical anisotropy made of Copolymer 1, it changes from linear polarization to elliptical polarization, and changes in the direction of the polarization axis (of elliptically polarized light). It is believed that this is because the direction of the long axis also changes. Therefore, in Comparative Example 1, it was difficult to produce the desired optical laminate.

Since the optical laminates of Examples 1 to 3 were manufactured by a specific method, it was possible to arbitrarily adjust the slow axis of each layer of the first optically anisotropic layer and the second optically anisotropic layer. In particular, in Example 2, since the surface was treated with a solvent before irradiation with the second polarized light, it was possible to align the surface more easily. In addition, in Example 3, since polyisocyanate having an isocyanate group capable of forming a cross-link with the hydroxy group of Copolymer 2 was contained together with the polymerizable liquid crystal compound, the adhesion between the first optically anisotropic layer and the second optically anisotropic layer was improved. This was good.

On the other hand, in the optical laminate of Comparative Example 1, since polarized light for orienting the birefringence inducing material layer was irradiated through the layer made of polymeric liquid crystal material, the polarized light is converted by the layer made of polymeric liquid crystal material, and each layer It was not possible to adjust the ground axis to what was desired.

According to the present invention, it is possible to provide an optical laminate in which the intersecting angles of the slow axes can be arbitrarily set. Such an optical laminate can be used for purposes such as polarizing plates and optical compensation films used in liquid crystal display devices and organic EL display devices. In particular, it is possible to use it as a circularly polarizing plate for use in an organic EL display device by laminating it with a linear polarizing plate.

As described above, preferred embodiments of the present invention have been described with reference to the drawings, but those skilled in the art will be able to easily assume various changes and modifications within the scope of the obvious by looking at the specification. Accordingly, such changes and modifications are construed as being within the scope of the invention as defined by the claims.

10… write
20… Birefringence inducing material layer
30… First optically anisotropic layer
31… inner 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 stacked adjacently,
The first optically anisotropic layer is composed of a surface layer and an inner layer with different slow axes, and the surface layer and the second optically anisotropic layer are in contact with each other,
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 birefringence inducing material includes a liquid crystalline polymer having a photosensitive group and a side chain structure capable of forming a liquid crystal structure. According to paragraph 1,
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 at a non-parallel and non-orthogonal angle. According to paragraph 1,
An optical laminate wherein the polymerizable liquid crystal material contains a birefringence inducing material and a cross-linking agent having a functional group capable of forming a cross-link. A method for manufacturing the optical laminate according to any one of claims 1 to 3, comprising:
A first light irradiation step of forming a first optically anisotropic layer by irradiating first polarized light for expressing a phase difference onto a birefringence inducing material layer made of a birefringence inducing material;
A surface alignment process of forming a surface layer on the first optically anisotropic layer by orienting the surface of the first optically anisotropic layer to have a different orientation from that of the inner layer;
A method of manufacturing an optical laminate, comprising the step of forming a second optically anisotropic layer by applying a polymerizable liquid crystal material on the surface of the first optically anisotropic layer that has undergone alignment treatment. According to paragraph 4,
The surface alignment process is a second light irradiation process of forming a surface layer on the first optically anisotropic layer by irradiating second polarized light having a polarization axis direction different from the first polarized light to the surface of the first optically anisotropic layer. , Method for manufacturing optical laminates. According to clause 5,
Between the first light irradiation process and the second light irradiation process, the method of manufacturing an optical laminate further comprising a surface treatment process of treating the surface of the first optically anisotropic layer with a solvent. A circularly polarizing plate in which the optical laminate according to any one of claims 1 to 3 and a linear polarizing plate are laminated.