CN113474691A - Optical layered body and method for producing same - Google Patents

Optical layered body and method for producing same Download PDF

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CN113474691A
CN113474691A CN202080014310.2A CN202080014310A CN113474691A CN 113474691 A CN113474691 A CN 113474691A CN 202080014310 A CN202080014310 A CN 202080014310A CN 113474691 A CN113474691 A CN 113474691A
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optically anisotropic
anisotropic layer
layer
polarized light
liquid crystal
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CN113474691B (en
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酒井丈也
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Hayashi Telempu Corp
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/08—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of polarising materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3016—Polarising elements involving passive liquid crystal elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid

Abstract

Provided are an optical layered body capable of arbitrary axis setting and a method for manufacturing the same. The optical layered body (100) is formed by adjacently laminating a first optical anisotropic layer (30) made of a birefringence-inducing material and a second optical anisotropic layer (40) made of a polymerizable liquid crystal material, wherein the first optical anisotropic layer (30) is formed of a surface layer (32) and an internal layer (31) having different slow axes, the surface layer (32) and the second optical anisotropic layer (40) are in contact with each other, and the slow axis direction of the internal layer (31) of the first optical anisotropic layer and the slow axis direction of the second optical anisotropic layer (40) intersect each other.

Description

Optical layered body and method for producing same
RELATED APPLICATIONS
Priority of japanese patent application 2019-.
Technical Field
The present invention relates to an optical layered body capable of arbitrary axis setting and a method for manufacturing the same.
Background
In a thin display device represented by a Liquid Crystal Display (LCD) or an Organic Light Emitting Diode (OLED), various retardation plates are used to improve display quality. For example, in OLEDs such as organic EL display devices, a broadband circular polarizing plate is used to suppress reflection.
As a retardation film used for such a broadband circular polarizing plate, patent document 1 (japanese patent application laid-open No. 2016-. Further, as a method for producing the retardation film, there is described a method for producing a retardation film, comprising: a step of forming a birefringence-inducing material layer by coating a birefringence-inducing material on a support base material; a first light irradiation step of irradiating the birefringence-inducing material layer with first polarized light; applying a polymerizable liquid crystal to the birefringence-inducing material layer irradiated with the first polarized light to form a laminate in which a polymerizable liquid crystal material layer is laminated on the birefringence-inducing material layer; and a second light irradiation step of irradiating the laminate with a second polarized light; the direction of the polarization axis of the first polarized light is different from the direction of the polarization axis of the second polarized light.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2016-
Disclosure of Invention
Technical problem to be solved by the invention
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 to align the birefringence-inducing material layer, the second polarized light is irradiated through the oriented polymerizable liquid crystal material layer, and when the second polarized light passes through the oriented polymerizable liquid crystal material layer, the polarization state of the second polarized light is switched, so that it is difficult to irradiate the birefringence-inducing material layer with a desired polarized light. Therefore, it is difficult to set a desired relationship of the slow axis in the birefringence-inducing material layer and the polymerizable liquid crystal material layer.
The object of the invention is therefore: provided are an optical layered body and a manufacturing method thereof, wherein the optical anisotropic layer can be set to any slow axis.
Means for solving the problems
The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that: by (i) performing photo-alignment of the internal layer made of the birefringence-inducing material, in which the surface of the first optically anisotropic layer is aligned so as to have a different alignment from the internal layer, and (ii) the alignment of the surface layer functioning as an alignment film can be adjusted independently of the internal layer, the second optically anisotropic layer can be provided with a desired alignment in consideration of the relationship with the alignment of the internal layer. Further, it was found that the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer can be arbitrarily set with respect to the obtained optical layered body, and the present invention was completed.
That is, the present invention may be configured as follows.
[ means 1]
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 different slow axes from each other, the surface layer and the second optically anisotropic layer being 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 cross.
[ means 2]
The optical layered body described in mode 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.
[ means 3]
The optical layered body according to the aspect 1 or 2, wherein the polymerizable liquid crystal material contains a crosslinking agent having a functional group capable of forming a crosslinking bond with the birefringence-inducing material.
[ means 4]
A method for producing an optical layered body according to any one of the aspects 1 to 3, comprising:
a first light irradiation step of irradiating a first polarized light for developing a phase difference onto a birefringence-inducing material layer made of a birefringence-inducing material to form a first optically anisotropic layer;
a surface orientation step of subjecting the surface of the first optically anisotropic layer to orientation treatment to impart orientation different from that of the internal layer thereof, thereby forming a surface layer on the first optically anisotropic layer; and
and forming a second optically anisotropic layer by applying a polymerizable liquid crystal material to the surface of the first optically anisotropic layer subjected to the alignment treatment.
[ means 5]
The method of manufacturing an optical layered body according to mode 4, wherein the surface alignment step is a second light irradiation step of irradiating a surface of the first optically anisotropic layer with 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.
[ means 6]
The method of manufacturing an optical layered body according to mode 5, further comprising a surface treatment step of treating a surface of the first optically anisotropic layer with a solvent between the first light irradiation step and the second light irradiation step.
[ means 7]
A circularly polarizing plate comprising the optical layered body according to any one of the aspects 1 to 3 and a linearly polarizing plate layered together.
[ means 8]
The optical layered body according to any one of the aspects 1 to 3, comprising:
a first optically anisotropic layer formed by irradiating a birefringence-inducing material with first polarized light for developing a phase difference;
a surface layer formed on the first optically anisotropic layer by subjecting the surface of the first optically anisotropic layer to an orientation treatment to impart an orientation different from that of the internal layer; and
and a second optically anisotropic layer formed by applying a polymerizable liquid crystal material to the surface layer.
It is to be noted that any combination of at least 2 constituent elements disclosed in the claims and/or the specification and/or the drawings is included in the present invention. In particular, any combination of 2 or more claims described in the claims is included in the present invention.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the optical layered body and the method for producing the same of the present invention, since a desired combination of slow axes can be set in the first optically anisotropic layer and the second optically anisotropic layer, the angle at which the slow axes intersect with each other can be arbitrarily set, and the optical layered body can be laminated with a linear polarizing plate, for example, to be used as a circular polarizing plate.
Drawings
The invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. However, the embodiments and the drawings are only for illustration and description and should not be used to determine the scope of the invention. The scope of the invention is determined by the appended claims.
Fig. 1A is a schematic cross-sectional view of an optical layered body according to an embodiment of the present invention before a first light irradiation step.
Fig. 1B 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.
Fig. 1C is a schematic cross-sectional view after the surface alignment step in one embodiment of the method for producing an optical layered body of the present invention.
Fig. 1D is a schematic cross-sectional view after the second optically anisotropic layer forming step in one embodiment of the method for producing an optical layered body of the present invention.
Detailed Description
[ method for producing optical layered body ]
The method for producing an optical layered body of the present invention comprises: a first light irradiation step of irradiating a first polarized light for developing a phase difference on a birefringence-inducing material layer made of a birefringence-inducing material to form an oriented first optically anisotropic layer; a surface orientation step of subjecting the surface of the first optically anisotropic layer to orientation treatment to impart orientation different from that of the internal layer thereof, thereby forming a surface layer on the first optically anisotropic layer; and a step of applying a polymerizable liquid crystal material to the surface of the first optically anisotropic layer after 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. Fig. 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. Fig. 1A to 1D show cross sections of the respective layers, but these do not represent an actual thickness ratio.
Fig. 1A is a schematic cross-sectional view showing a laminate of a substrate 10 and a birefringence-inducing material layer 20. Fig. 1B is a schematic cross-sectional view showing a laminated body of the substrate 10 and the first optically anisotropic layer 30, showing a state after the first light irradiation step; the first optically anisotropic layer 30 is formed by aligning the molecules of the birefringence-inducing material layer 20 by irradiation of the first polarized light. Fig. 1C is a schematic cross-sectional view showing a state after the surface alignment step, and showing a laminated body of the substrate 10 and the first optically anisotropic layer 30 composed of the internal layer 31 and the surface layer 32; wherein the internal layer 31 has the same orientation as the first optically anisotropic layer 30 described above; the surface layer 32 is a surface on the side opposite to the base material 10, and is subjected to an orientation different from that of the internal layer 31 by an orientation treatment. Fig. 1D is a schematic cross-sectional view showing the state after the second optically anisotropic layer forming step, and shows an optical layered body 100 of the substrate 10, the first optically anisotropic layer 30 composed of the internal layer 31 and the surface layer 32, and the second optically anisotropic layer 40 formed by applying a polymerizable liquid crystal material.
By irradiating the birefringence-inducing material layer 20 made of the birefringence-inducing material shown in fig. 1A with first polarized light for developing a phase difference, the molecular orientation of the birefringence-inducing material can be induced. 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 can be irradiated with a desired polarized light.
Next, the surface layer 32 can be formed on the first optically anisotropic layer 30 by subjecting the surface of the first optically anisotropic layer 30 shown in fig. 1B to an orientation treatment to impart an orientation different from the orientation imparted in the first light irradiation step. Thus, as shown in fig. 1C, the first optically anisotropic layer 30 is formed as 2 layers of an internal layer 31 having an orientation originally formed and a surface layer 32 having an orientation different from that of the internal layer.
Further, when a polymerizable liquid crystal material is applied to the surface layer 32 shown in fig. 1C, the surface layer 32 functions as an alignment film, and the second optically anisotropic layer 40 aligned in accordance with the alignment of the surface layer 32 can be formed. Thereby, as shown in fig. 1D, the second optically anisotropic layer 40 oriented to have a slow axis different from that of the internal layer 31 is formed on the surface layer 32. Since the orientations of the internal layer 31 and the surface layer 32 can be independently adjusted, a desired orientation can be imparted to the second optically anisotropic layer 40 in consideration of the relationship with the orientation of the internal layer 31, and the desired slow axes can intersect with each other.
According to the method for producing an optical layered body of the present invention, since it is not necessary to cut 2 or more films at a predetermined angle and precisely bond the films, the crossing angle of the slow axis can be easily adjusted. Further, since the optical layered body can be manufactured in a long shape, the optical layered body can be efficiently obtained.
(birefringent-inducing Material layer)
The birefringence-inducing material layer is formed of a birefringence-inducing material. In the present invention, the birefringence inducing material means: a material capable of axially selectively inducing birefringence by utilizing molecular motion caused by light irradiation (preferably light irradiation and heat cooling treatment) and molecular orientation based thereon.
For example, the birefringence inducing material may include a liquid crystalline polymer having a side chain structure which has a photosensitive group and is capable of forming a liquid crystal structure, and may have a property of inducing molecular alignment by photoreaction of the photosensitive group of the side chain. Examples of the photoreaction include photodimerization, photoisomerization, photo-fries rearrangement, and the like.
When the liquid crystalline polymer can form a liquid crystal structure, the liquid crystalline polymer may exhibit liquid crystallinity by having a mesogen group, which is a rigid site exhibiting liquid crystallinity, in a side chain structure, or may exhibit liquid crystallinity by having a structure capable of forming a dimer by hydrogen bonding with another polymer or another side chain of the same polymer or the like, and forming a mesogen structure by dimerization thereof.
The mesogenic group or mesogenic structure is composed of 2 or more aromatic or aliphatic rings and a linking group for bonding the aromatic or aliphatic rings, and the linking group may be a covalent bond or a hydrogen bond.
Examples of the aromatic ring include a benzene ring, a naphthalene ring, a heterocyclic ring (for example, an oxygen-containing heterocyclic ring such as a furan ring or a pyran ring; a nitrogen-containing heterocyclic ring such as a pyrrole ring or an imidazole ring), and the like; examples of the alicyclic ring include a cyclohexane ring and the like. These aromatic rings or aliphatic rings may have a substituent, and examples of the substituent include an alkyl group (e.g., C)1-6Alkyl, preferably C1-4Alkyl), alkyloxy (e.g. C)1-6Alkyloxy, preferably C1-4Alkyloxy), alkenyl (e.g., C)1-6Alkenyl, preferably C1-4Alkenyl), alkynyl (e.g., C)1-6Alkynyl, preferably C1-4Alkynyl group), a halogen atom, etc.
Examples of the linking group include, in the case of a covalent bond, a single bond, -O-, -COO-, -OCO-, -N-, -NO-N-, -C-, -C.ident.C-, -CO-C-, -CH-N-, and an alkylene group. In the case of a hydrogen bond, a side chain structure having a carboxyl group at the terminal may be mentioned, 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 inducing a luminescence reaction by light energy, and examples thereof include a chalcone group, a coumarin group, a cinnamoyl group, a cinnamylidene acetate group, a biphenylacryloyl group, a furanylacryloyl group, a naphthylacryloyl group, an azophenyl group, a benzylideneanilino group, and derivatives thereof, and a cinnamoyl group may be preferable.
The liquid crystalline polymer has at least a side chain structure having both a photosensitive group and a structure capable of forming a liquid crystal structure in a repeating unit, and the photosensitive group may be present independently of a mesogen group or a mesogen structure in the side chain structure or may be present in a complex state 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 formulae (1) and (2).
[ solution 1]
Figure BDA0003210626130000071
(wherein t is an integer of 1 to 3, R1Represents a hydrogen atom, an alkyl group (e.g., C)1-6Alkyl, preferably C1-4Alkyl), alkyloxy (e.g. C)1-6Alkyloxy, preferably C1-4Alkyloxy), alkenyl (e.g., C)1-6Alkenyl, preferably C1-4Alkenyl), alkynyl (e.g., C)1-6Alkynyl, preferably C1-4Alkynyl group), and 1 or 2 or more halogen atoms. )
[ solution 2]
Figure BDA0003210626130000072
(wherein k is 0 or 1, l is 0 in the case of k being 0; l is an integer of 1 to 12 in the case of k being 1; X is a single bond; C1-3Alkylene, -C ≡ C-, -O-, -N ≡ N-, -COO-, or-OCO-; w is a coumarinyl group, cinnamoyl group, cinnamylidene acetoxy group, biphenylacryloyl group, furyl acryloyl group, naphthyl acryloyl group, or a derivative group thereof; r2And R3Each of which is the same or different and represents a hydrogen atom or an alkyl group (e.g., C)1-6Alkyl, preferably C1-4Alkyl), alkyloxy (e.g. C)1-6Alkyloxy, preferably C1-4Alkyloxy), alkenyl (e.g., C)1-6Alkenyl, preferably C1-4Alkenyl), alkynyl (e.g., C)1-6Alkynyl, preferably C1-4Alkynyl), carboxyl and 1 or 2 or more halogen atoms. )
The side chain structures represented by the above formulae (1) and (2) represent chemical structures at the ends of the side chains in the repeating units, and various chemical structures may be included between the side chain structures and the main chain structure within a range not impairing the effect of the present invention.
The liquid crystalline polymer may be a homopolymer composed of the same repeating unit having the side chain structure, or a copolymer including a repeating unit having a side chain structure different in structure in addition to the repeating unit having the side chain structure. Examples of the main chain structure include those formed by polymerizing hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, N-phenylmaleimides, and the like.
When the liquid crystalline polymer is a copolymer, the liquid crystalline polymer may have a repeating unit having no photosensitive group and/or a structure capable of forming a liquid crystal structure.
In addition, when the polymerizable liquid crystal material contains a crosslinking agent, the birefringence-inducing material of the present invention may further contain a liquid crystal polymer having 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. The crosslinkable functional group is not particularly limited as long as it is a functional group which 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 mercapto group. The side chain structure having a crosslinkable functional group may be contained in a repeating unit having the photosensitive group and containing a side chain structure capable of forming a liquid crystal structure, or may have a crosslinkable functional group in a repeating unit other than the repeating unit.
For example, a hydroxyl group or a carboxyl group is preferable as the crosslinkable functional group, and the liquid crystalline polymer may have a side chain structure selected from- (CH) s2)nAt least one structure selected from the group consisting of-OH (wherein 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 structures of the side chains in the repeating units, and various chemical structures may be included between these side chain structures and the main chain structure within a range not impairing the effect of the present invention.
In addition, the birefringence inducing material of the present invention may contain both a liquid crystalline polymer and a low molecular compound in order to promote the orientation of the side chain of the liquid crystalline polymer. As the low-molecular compound, the following are preferably used: a liquid crystalline substance having a substituent known as a mesogenic component, such as biphenyl, terphenyl, phenyl benzoate, or azobenzene, and having liquid crystallinity, in which such substituent is bonded to a functional group such as allyl, acrylate, methacrylate, or cinnamate (or a derivative thereof) via a spacer (for example, an (oxy) alkylene group having 1 to 15 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms). These low-molecular compounds may be used alone or in combination of two or more.
In fig. 1A, the birefringence-inducing material layer 20 is laminated on the substrate 10, but the substrate 10 may be omitted. When a substrate is used, the substrate may be an optically isotropic substrate, and may be a transparent substrate made of an optically isotropic phase such as glass or triacetyl cellulose film (TAC film). Further, 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 may be used as the release substrate. When a release substrate is used, the optical layered body of the present invention may be peeled off after formation, and therefore, an opaque substrate may be used without considering the optical characteristics of the substrate itself. For example, the optical layered body of the present invention is formed on a substrate, and then bonded to another optical member (for example, a polarizing plate) with an adhesive or the like, and then the release substrate is peeled off and used, whereby the optical layered body can be configured without a substrate, and a thin optical member having a thickness substantially equal to only the thickness of the optically anisotropic layer can be manufactured.
The birefringence-inducing material layer composed of the birefringence-inducing material as described above may be formed by using a pre-formed birefringence-inducing material film (which may or may not be laminated on a substrate), or by coating the film on a substrate. In the case of 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 the solution is applied to a substrate. The solvent is suitably selected depending on the kind of the birefringence-inducing material, and examples thereof include 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.), and the like, and these solvents may be used alone or in combination of two or more kinds.
The concentration of the solvent is not particularly limited, and may be, for example, 5 to 50% by weight, or preferably 8 to 40% by weight, more preferably 10 to 25% by weight. For coating the solution on the substrate, a known coating method such as spin coating or roll coating can be used.
After the coating, the coating film may be heated and dried as necessary 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 not aligned.
(first light irradiation step)
In the first light irradiation step, first polarized light for developing a phase difference is irradiated onto the birefringence-inducing material layer. 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 up to the inside thereof, and the orientation of the molecules is induced to form the first optically anisotropic layer. In the method for producing an optical layered body of the present invention, since the first polarized light can be directly irradiated onto the birefringence-inducing material layer without passing through another layer, a desired slow axis can be formed by using the irradiated polarized light.
The first polarized light is not particularly limited as long as it is a light having a wavelength at which a photoreaction occurs in a photosensitive group of a liquid crystalline polymer such as infrared light, visible light, ultraviolet light (e.g., near ultraviolet light, far ultraviolet light, etc.), X-ray, charged particle light (e.g., electron beam, etc.), etc., and the wavelength of the light may be 200 to 500nm depending on the kind of a side chain structure of the liquid crystalline polymer. The first polarized light may be linearly polarized light of ultraviolet light, for example, and in this case, for example, an ultraviolet irradiation device such as a high-pressure mercury lamp is used as a light source, and the polarized light is converted into linearly polarized light via a glantylor prism.
In addition, birefringence is never the only thingThe irradiation amount of the first polarized light may be, for example, 10mJ/cm in view of the angle at which the surface of the inducing material layer is oriented and also the inside thereof2～10J/cm2It is preferably 50mJ/cm2～1J/cm2More preferably 100mJ/cm2～500mJ/cm2。
The method for producing an optical layered body of the present invention may further include a heating step of heating the formed first optically anisotropic layer after the first light irradiation step, if necessary. Depending on the irradiation direction and the vibration direction of the first polarized light irradiated in the first light irradiation step, molecular alignment is induced, and non-aligned molecules are aligned following the already aligned molecules, and the liquid crystalline polymer can be subjected to molecular motion by subsequent heating, thereby promoting alignment of the non-aligned molecules. After heating, the mixture may be cooled to room temperature, for example, by leaving it.
The heating temperature in the heating step is not particularly limited as long as the liquid crystalline polymer induces the alignment of the non-aligned molecules along the photoreactive side chains by molecular motion, and is preferably set to a temperature equal to or higher than the liquid crystal phase transition temperature and equal to or lower than the isotropic phase transition temperature of the birefringence-inducing material. For example, the temperature may be 100 to 200 ℃, preferably 110 to 180 ℃, and more preferably 120 to 160 ℃.
The heating time is not particularly limited as long as the liquid crystalline polymer induces the alignment of the unoriented molecules along the photoreactive side chains by molecular motion, and may be appropriately set according to the type of the liquid crystalline polymer, the heating temperature, and the like, and may be, for example, 1 minute or more, preferably 3 minutes or more, and more preferably 5 minutes or more. The upper limit is not particularly limited, but may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes) from the viewpoint of economy.
(surface alignment Process)
In the surface alignment process, the surface of the first optically anisotropic layer is subjected to an alignment treatment to apply an alignment different from that of the internal layer thereof. By performing the surface alignment treatment, a surface layer is formed in the first optically anisotropic layer, and 2 layers of an internal layer and a surface layer, which are composed of the same birefringence-inducing material but have different alignment states, are formed in the first optically anisotropic layer. The internal layer may represent a portion other than the surface layer in the first optically anisotropic layer.
The method of the alignment treatment is not particularly limited as long as an alignment layer different from the internal layer can be formed on the surface of the first optically anisotropic layer, and examples thereof include rubbing treatment, photo-alignment treatment by irradiation with second polarized light, and the like. In the rubbing treatment, the surface layer in a desired orientation direction can be formed because the orientation direction can be controlled by rotating a roll around which a cloth such as cellulose, nylon, or polyester is wound while pressing the roll with a constant pressure and rubbing the surface of the first optically anisotropic layer in a certain direction, but the method of the orientation treatment is preferably a photo-orientation treatment using polarized light irradiation.
The surface alignment step may be a second light irradiation step of irradiating 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 to form a surface layer on the first optically anisotropic layer. In the second light irradiation step, even after the molecular orientation is performed in the first light irradiation step (preferably, in the first light irradiation step and the heating step), by irradiating the second polarized light having a polarization axis direction different from that of the first polarized light, it is possible that the axis-selective photoreaction centered on the unreacted birefringence-inducing material of the first optically anisotropic layer occurs selectively in the vicinity of the surface, and therefore, the vicinity of the surface can be given an orientation different from that of the internal layer. On the other hand, it may be that the orientation itself of the internal layer of the first optically anisotropic layer is not switched even after the second light irradiation process, since the molecules of the internal layer of the first optically anisotropic layer are already oriented with a high degree of orientation.
The second polarized light may be light of the above-described various wavelengths as the first polarized light, and for example, linearly polarized light of ultraviolet rays may be used. The second polarized light may be a light of a different type 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 polarization axis direction different from that of the first polarized light, and for example, may be different from an axis angle of the polarization axis of the first polarized light by 5 to 85 °, may also be preferably different from 10 to 80 °, and more preferably different from 20 to 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 can be adjusted by taking into account the orientation state (the presence ratio of unreacted birefringence-inducing material, etc.) in the vicinity of the surface of the first optically anisotropic layer after the first light irradiation step, and the slow axis of the second optically anisotropic layer to be formed thereafter can be arbitrarily set.
The irradiation amount of the second polarized light may be, for example, 50mJ/cm from the viewpoint of reorienting the surface of the first optically anisotropic layer which has been oriented2～20J/cm2It is also preferably 100mJ/cm2～10J/cm2More preferably 150mJ/cm2～1J/cm2。
The method for producing an optical layered body according to 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, a surface alignment step such as second polarized light irradiation or rubbing treatment is preferably performed. In the case where the heating step is performed after the first light irradiation step, the surface treatment step may be performed after the heating step.
In the surface treatment step, the solvent is applied to the surface of the first optically anisotropic layer to dissolve the surface portion, and it is possible to relax the molecular orientation applied in the first light irradiation step and form the surface portion in a random state, so that the orientation of the surface portion of the first optically anisotropic layer temporarily formed by the first polarized light can be eliminated, and the orientation of the surface layer of the first optically anisotropic layer can be made isotropic. 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 solvent to be applied can be evaporated, and for example, the solvent may be left to dry naturally. Only the surface to which the solvent is applied can be made isotropic.
By making the surface isotropic, the light orientation of the surface becomes easy in the subsequent second light irradiation step, and therefore the irradiation amount of the second polarized light can be reduced. In the case of performing the surface treatment step, the irradiation amount of the second polarized light may be, for example, 0.1mJ/cm2～200mJ/cm2Further, it is preferably 0.5mJ/cm2～150mJ/cm2More preferably 1mJ/cm2～100mJ/cm2。
In the case of performing the surface treatment step, the ratio of the irradiation amount of the first polarized light to the irradiation amount of the second polarized light (first polarized light/second polarized light) may be 1.5/1 to 100/1, preferably 2/1 to 80/1, and more preferably 2.5/1 to 50/1.
Since the surface is isotropic, it is not necessary to consider the orientation state of the surface layer of the first optically anisotropic layer in the subsequent second light irradiation step, and therefore the axial angle of the polarization axis of the second polarized light can be directly reflected on the slow axis of the second optically anisotropic layer. Therefore, the axis angle of the polarization optical 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 may be a good solvent or a poor solvent for the birefringence-inducing material. The solvent used in the surface treatment step may be, for example, a mixed solvent in which a good solvent and a poor solvent for the birefringence-inducing material are mixed, from the viewpoint of making the surface of the first optically anisotropic layer isotropic and suppressing dissolution into the inside to disturb the orientation thereof. When a mixed solvent of a good solvent and a poor solvent containing a birefringence-inducing material is used, the solvent can be suitably adjusted depending on the solubility of the solvent used in the birefringence-inducing material, and the weight ratio (good solvent/poor solvent) of the mixed solvent may be, for example, 1/100 to 100/1, preferably 1/50 to 50/1, and more preferably 1/10 to 10/1.
Examples of the solvent used in the surface treatment step include water; alcohol solvents such as methanol, ethanol, propanol, isopropanol, 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 solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, isopropyl methyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as diethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, tetrahydrofuran, dioxane, etc.; nitrile solvents such as acetonitrile and propionitrile; sulfoxide solvents such as dimethyl sulfoxide; amide solvents such as N, N-dimethylformamide; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; glycol solvents such as ethylene glycol and propylene glycol; glycol ether 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, dichlorobenzene, and the like; and the like. These solvents may be used alone or in combination of two or more. Since these solvents have different solubilities depending on the type of the birefringence-inducing material, they can be used in consideration of whether they are good solvents or poor solvents depending on the birefringence-inducing material used.
In the present invention, the good solvent means a solvent having a solubility in the solute of 1 mass% or more at 25 ℃, and the poor solvent means a solvent having a solubility in the solute of less than 1 mass% at 25 ℃.
For example, dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, etc. can be used as a good solvent for the birefringence-inducing material, and ethanol, methanol, n-hexane, etc. can be used as a poor solvent for the birefringence-inducing material. These good solvents and poor solvents are mixed at the above-mentioned mixing weight ratio and used as a mixed solvent.
(second optically anisotropic layer Forming Process)
In the second optically anisotropic layer forming step, a polymerizable liquid crystal material is applied to the surface layer of the first optically anisotropic layer after the alignment treatment, thereby forming a second optically anisotropic layer. By performing the second optically anisotropic layer forming step, the surface layer oriented in the surface orientation step functions as an orientation film, and thus the oriented second optically anisotropic layer can be formed by utilizing the orientation direction thereof.
In the present invention, the polymerizable liquid crystal material includes a composition containing a monofunctional or bifunctional polymerizable liquid crystal compound containing at least a reactive functional group and a mesogenic group, and having a crosslinked structure formed by polymerization using light or heat or reaction with a crosslinking agent.
The polymerizable liquid crystal compound may be a liquid crystal monomer or a liquid crystal polymer. Examples of the polymerizable liquid crystal compound include a polymerizable liquid crystal monomer and/or a polymerizable liquid crystal polymer having a polymerizable functional group that is polymerizable by light or heat, and a crosslinkable liquid crystal monomer and/or a crosslinkable liquid crystal polymer having a crosslinkable functional group capable of introducing a crosslinked structure by a reaction with a crosslinking agent.
The polymerizable liquid crystal compound is not particularly limited as long as it is a monomer having a mesogenic group or a polymer having a unit composed of a mesogenic group, can form a liquid crystal structure, and has polymerizability and/or crosslinkability, and various polymerizable liquid crystal compounds can be used. Examples of the polymerizable liquid crystal compound include liquid crystal compounds having a molecular skeleton of schiff base, biphenyl, terphenyl, ester, thioester, stilbene, tolyene, azoxy, azo, phenylcyclohexane, pyrimidine, cyclohexylcyclohexane, trimesic acid, triphenylene, terpene, phthalocyanine, porphyrin, or a mixture thereof, and any compound may be used as long as it shows a nematic, cholesteric, or smectic liquid crystal phase. As an example, a photopolymerizable nematic liquid crystal monomer can be used as the polymerizable liquid crystal compound.
The unit composed of a mesogenic group may be in the main chain or in the side chain of the liquid crystal polymer. Examples of the main chain type liquid crystal polymer include polyester type, polyamide type, polycarbonate type, polyimide type, polyurethane type, polybenzimidazole type, polybenzoxazole type, polybenzothiazole type, polyazomethine type, polyesteramide type, polyestercarbonate type, polyesterimide type liquid crystal polymer, and a mixture thereof. Examples of the side chain type liquid crystalline polymer include liquid crystalline polymers having mesogenic groups bonded as side chains to macromolecules having linear or cyclic skeleton chains such as polyacrylate, polymethacrylate, polyvinyl, polysiloxane, polyether, and polyacrylate, and mixtures thereof.
In addition, when the polymerizable liquid crystal compound has a polymerizable functional group, the polymerizable liquid crystal material may contain a photopolymerization initiator and/or a thermal polymerization initiator.
As the photopolymerization initiator, commercially available photopolymerization initiators such as Irgacure (Irgacure)907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all of which are available from Ciba Japan, Inc.), SEIKUOL BZ, SEIKUOL Z, SEIKUOL BEE (all of which are available from Seiko Chemicals, Ltd.), Kayakure (Kayakure) BP100 (available from Nippon Chemicals, Ltd.), Kayakure UVI-6992 (available from Dow Co., Ltd.), Adekaoptomer SP-152 and Adekaoptomer SP-170 (all of which are available from Adeka, Ltd.), TAZ-A, TAZ-PP (available from Nippon シイベルヘグナー Co., Ltd.) and TAZ-104 (available from Sanwa Co., Ltd.) can be used.
Examples of the thermal polymerization initiator include azo compounds such as azobisisobutyronitrile; peroxides such as hydrogen peroxide, persulfate, and benzoyl peroxide.
The content of the polymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.03 to 10% by weight, and still more preferably 0.05 to 8% by weight, based on the total weight of the polymerizable liquid crystal material. When the amount is within the above range, the polymerizable liquid crystal compound can be polymerized without disturbing the orientation thereof.
When a photopolymerization initiator is used as the polymerization initiator, it may be used in combination with a photosensitizer. Examples of the photosensitizer include xanthone compounds such as xanthone and thioxanthone (e.g., 2, 4-diethylthioxanthone and 2-isopropylthioxanthone); anthracene compounds such as anthracene and alkoxy-containing anthracene (e.g., dibutoxyanthracene); phenothiazine; rubrene, and the like.
When the polymerizable liquid crystal compound has a crosslinkable functional group, the polymerizable liquid crystal material may contain an appropriate crosslinking agent. In this case, the polymerizable liquid crystal compound may be a liquid crystal compound capable of fixing the alignment by means of crosslinking (thermal crosslinking or photo-crosslinking) or the like in a liquid crystal state or a state cooled to a liquid crystal transition temperature or lower.
Examples of the crosslinkable functional group include a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxirane group, and an oxetanyl group. Among them, acryloxy, methacryloxy, vinyloxy, oxirane and oxetanyl groups are preferable, and acryloxy groups are particularly more preferable.
When the polymerizable liquid crystal material contains a crosslinking agent, the liquid crystal polymer of the birefringence inducing material can form a crosslinking bond when the liquid crystal polymer has a crosslinkable functional group in addition to forming a crosslink with the polymerizable liquid crystal compound having a crosslinkable functional group. In this case, since a crosslink can be formed between the first optically anisotropic layer made of the birefringence-inducing material and the second optically anisotropic layer containing a crosslinking agent, the adhesiveness between the layers can be improved.
Examples of the crosslinking agent include polyfunctional compounds having 2 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 crosslinking bond with the liquid crystalline polymer, and examples thereof include compounds having an isocyanate group, a carbodiimide group, an aziridine group, an azetidine group, an oxazoline group, an epoxy group, and the like, when the liquid crystalline polymer has a crosslinkable functional group which is a hydroxyl group or a carboxyl group. Among these crosslinking agents, polyisocyanate compounds that are polyfunctional compounds having 2 or more isocyanate groups in the molecule are preferable from the viewpoint of reactivity with the crosslinkable functional group of the liquid crystalline polymer under relatively mild reaction conditions, and known polyisocyanate compounds can be used. Examples of the polyisocyanate compound include a diisocyanate compound and a triisocyanate compound. Examples of the diisocyanate compound include phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, methylcyclohexylene diisocyanate, bis (isocyanatomethyl) cyclohexane, methylenebis (cyclohexyl isocyanate), isophorone diisocyanate, and condensation compounds of hexamethylene diisocyanate and diol. Examples of the triisocyanate compound include isocyanurates of diisocyanates such as hexamethylene diisocyanate, biurets, and adducts of diisocyanates such as hexamethylene diisocyanate and methylolpropane. Among these crosslinking agents, triisocyanate compounds can be preferably used.
When the crosslinking agent is a polyisocyanate compound, the liquid crystalline polymer may have an active hydrogen group as a crosslinkable functional group. Examples of the active hydrogen group include a hydroxyl group, a carboxyl group, an amino group, and a mercapto group. When the active hydrogen group is a hydroxyl group, a urethane bond (-NH-CO-O-) is formed, when the active hydrogen group is a carboxyl group, an amide bond (-NH-CO-) is formed, when the active hydrogen group is an amino group, a urea bond (-NH-CO-NH-) is formed, and when the active hydrogen group is a mercapto group, a thiocarbamate bond (-NH-CO-S-) is formed. The active hydrogen group of the liquid crystalline polymer is preferably a hydroxyl group or a carboxyl group.
In the present invention, the content of the crosslinking agent in the polymerizable liquid crystal material 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 polymerizable liquid crystal material, from the viewpoint of suppressing the decrease in alignment properties and optical characteristics of the second optically anisotropic layer due to the reaction with the liquid crystal polymer.
In the second optically anisotropic layer forming step, the polymerizable liquid crystal material as described above is applied to the surface layer of the first optically anisotropic layer. In application, the polymerizable liquid crystal material dissolved in a solvent is dissolved in a solution and applied by a known coating method such as spin coating or roll coating. The solvent is suitably selected depending on the type of the polymerizable liquid crystal material, and examples thereof include dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, 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), and the like, and these solvents may be used alone or in combination of two or more.
The solvent for the polymerizable liquid crystal material may be selected not only according to the combination of the kinds of the birefringence-inducing material and the polymerizable liquid crystal material but also according to the alignment state of the surface layer. For example, in the case where most of the molecules of the surface layer have a desired orientation (for example, in the case of performing a surface treatment step, in the case of performing a rubbing treatment as an orientation treatment, or the like), the solvent of the polymerizable liquid crystal material is preferably a poor solvent of the birefringence-inducing material from the viewpoint of imparting the orientation of the surface layer to the second optically anisotropic layer and suppressing disturbance of the orientation of the first optically anisotropic layer. On the other hand, when only a part of the molecules of the surface layer have a desired orientation, the solvent of the polymerizable liquid crystal material is preferably a mixed solvent in which a good solvent and a poor solvent for the birefringence-inducing material are mixed. The mechanism in this case is not clear, but when a poor solvent for the birefringence-inducing material is contained as a solvent for the polymerizable liquid crystal material, the poor solvent does not penetrate into the first optically anisotropic layer, and the alignment can be prevented from being disturbed. On the other hand, when a good solvent containing a birefringence-inducing material is used as the solvent for the polymerizable liquid crystal material, the wettability of the solution to the surface layer is improved, and the molecules of the polymerizable liquid crystal material can be aligned along the alignment of only a part of the molecules of the surface layer, and as a result, the second optically anisotropic layer can be aligned. The solvent of the polymerizable liquid crystal material may be appropriately adjusted depending on the combination of the kinds of the birefringence-inducing material and the polymerizable liquid crystal material and the alignment state of the surface layer, but from the viewpoint of maintaining the alignment of the first optically anisotropic layer, it is preferable to contain a poor solvent with respect to the birefringence-inducing material so as not to intrude into the surface layer, and for example, the mixing weight ratio (good solvent/poor solvent) of the good solvent and the poor solvent of the birefringence-inducing material may be 0/100 to 100/1, and may be 0/100 to 50/1, and more preferably 0/100 to 10/1. As the solvent for the polymerizable liquid crystal material, a general solvent can be used according to the purpose, and for example, toluene, an ethylene glycol derivative, a propylene glycol derivative, and the like can be contained.
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 in the lower portion functions as an alignment film (alignment imparting film) to cause alignment of the liquid crystal molecules. Thereby forming a second optically anisotropic layer in which liquid crystals are aligned in a predetermined direction.
The second optically anisotropic layer forming step may further include a heating step and/or a light irradiation step (for example, a non-polarized light irradiation step) as necessary after the formation of the coating film of the polymerizable liquid crystal material. The polymerizable liquid crystal material is already aligned in a predetermined direction in accordance with the alignment of the surface layer of the first optically anisotropic layer by forming a coating film, and is polymerized and/or crosslinked in the subsequent heating step and/or light irradiation step (for example, unpolarized light irradiation step), thereby fixing the alignment properties.
Specifically, when the polymerizable liquid crystal material is made of a thermopolymerizing material, the polymerizable liquid crystal material is polymerized by heating to fix the orientation. When the photo-polymerizable material is used, polymerization occurs when light is irradiated, and the orientation is fixed. When the material is made of a crosslinkable material, crosslinking occurs upon heating and/or light irradiation, and the orientation is fixed.
In addition, when the polymerizable liquid crystal material contains a crosslinking agent and the crosslinking agent has a functional group capable of forming a crosslink with the birefringence-inducing material, a crosslink can be formed between the first optically anisotropic layer and the second optically anisotropic layer by applying thermal energy and/or optical energy.
In the heating step in the second optically-anisotropic layer forming step, the polymerization and/or crosslinking reaction is not particularly limited as long as it proceeds, but it is preferably performed at a heating temperature equal to or lower than the isotropic phase transition temperature of the birefringence-inducing material, from the viewpoint of suppressing the disturbance of the orientation of the internal layer of the first optically-anisotropic layer. For example, the temperature may be 70 to 180 ℃, preferably 80 to 150 ℃, and more preferably 100 to 140 ℃. The heating time may be, for example, 1 minute or more, preferably 3 minutes or more, and more preferably 5 minutes or more. The upper limit is not particularly limited, but may be about 60 minutes (preferably about 40 minutes, more preferably about 30 minutes) from the viewpoint of economy.
In the light irradiation step in the second optically anisotropic layer forming step, the light irradiation is not particularly limited as long as the polymerization and/or crosslinking reaction proceeds, but unpolarized light is preferable as the irradiation light. As the unpolarized light, the light having the above-described various wavelengths as the first polarized light and the second polarized light can be used, and for example, unpolarized ultraviolet rays can be used. The irradiation amount of light may be 10mJ/cm2～10J/cm2It is also preferably 50mJ/cm2～1J/cm2More preferably 100mJ/cm2～500mJ/cm2。
[ optical layered body ]
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, wherein the first optically anisotropic layer is composed of a surface layer and an internal layer having different slow axes, and the surface layer and the second optically anisotropic layer are in contact with each other.
The first optically anisotropic layer is composed of a surface layer and an internal layer, which 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 in the vicinity of 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 an orientation treatment to apply a different orientation from that of the internal layer. Here, the alignment treatment may be performed by the surface alignment step in the above-described manufacturing method.
The polymerizable liquid crystal material constituting the second optically anisotropic layer may also 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 can improve the adhesion between the first optically anisotropic layer and the second optically anisotropic layer by forming a crosslinking bond with the birefringence-inducing material of the first optically anisotropic layer. Thus, since an adhesive layer is not required to be provided between the first optically anisotropic layer and the second optically anisotropic layer, the optical layered body can be made thin, and a structure in which the surface layer of the first optically anisotropic layer is in contact with the second optically anisotropic layer can be formed. The adhesion between the first optically anisotropic layer and the second optically anisotropic layer can be confirmed by a cross-cut test described in examples described later.
The thickness of the second optically anisotropic layer may be 0.1 to 20 μm, preferably 0.3 to 15 μm, and more preferably 0.5 to 10 μm. The thickness ratio of the first optically anisotropic layer to the second optically anisotropic layer (first optically anisotropic layer/second optically anisotropic layer) may be 1/10 to 10/1, preferably 1/8 to 8/1, and more preferably 1/5 to 5/1. For example, the second optically anisotropic layer may be formed by applying a polymerizable liquid crystal material to the surface layer of the first optically anisotropic layer after the alignment treatment. Here, the application of the polymerizable liquid crystal material may be performed by the second optically anisotropic layer forming step in the above-described manufacturing method.
The thickness of the optical layered body of the present invention may be, for example, 1 to 40 μm, preferably 2 to 30 μm, and more preferably 3 to 20 μm.
In the optical layered body of the present invention, the slow axis direction of the inner layer of the first optically anisotropic layer and the slow axis direction of the second optically anisotropic layer intersect. The optical layered body of the present invention is produced by the above-described production method, and the angle formed by the slow axis of the first optically anisotropic layer (internal 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 (internal layer) and the slow axis direction of the second optically anisotropic layer may cross 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 to 75 °. The slow axis of the inner layer of the first optically anisotropic layer can be measured as the slow axis of the entire first optically anisotropic layer because the influence of the orientation in the surface layer can be regarded as extremely small.
In the optical layered body of the present invention, particularly in the first optically anisotropic layer, the slow axis direction is preferably constant in the plane. In the present invention, since the lower layer is irradiated with polarized light through the alignment layer and the polarization state is not converted (for example, from linearly polarized light to elliptically polarized light), the slow axis direction can be made constant without disturbing the molecular alignment.
The optical layered body of the present invention can exhibit desired optical characteristics by the above-described production method. Examples of the optical properties include retardation (e.g., in-plane retardation: Re). The range shown below of these optical properties may be a range of measured values of the optical layered body, or may be a range of measured values of the first optically anisotropic layer or the second optically anisotropic layer.
The in-plane retardation value (Re) means: a parameter defined by the product (Δ Nxy × d) of the anisotropy (Δ Nxy ═ nx-ny |) of the refractive index (nx, ny) of each of the biaxial axes orthogonal to the film and the film thickness d (nm) represents the optical isotropy and the anisotropy. The in-plane retardation (Re) of the optical layered body of the present invention may be, for example, 1 to 600nm, preferably 3 to 500nm, and more preferably 5 to 400 nm. The in-plane retardation (Re) is a measured value with respect to light having a wavelength of 550 nm.
The optical layered body of the present invention can be used as, for example, a retardation film, and can be used for various optical members (an antireflection film, an optical compensation film, and the like). The optical layered body of the present invention can be used as a circularly polarizing plate used as an antireflection film in an OLED such as an organic EL display device, for example, by being laminated with a linearly polarizing plate as a retardation film.
Examples
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples at all.
(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 was added a large excess of methacrylic acid in the presence of p-toluenesulfonic acid to conduct esterification reaction, and monomer 1 represented by the following chemical formula was synthesized.
[ solution 3]
Figure BDA0003210626130000201
(monomer 2)
4- (6-hydroxyhexyloxy) benzoic acid was synthesized by heating 4-hydroxybenzoic acid and 6-chloro-1-hexanol under basic conditions. Subsequently, a large excess of methacrylic acid was added to the product in the presence of p-toluenesulfonic acid to conduct esterification reaction, thereby synthesizing monomer 2 represented by the following chemical formula.
[ solution 4]
Figure BDA0003210626130000202
(copolymer 1)
Dissolving monomer 1 and monomer 2 in dioxane to make the molar ratio of monomer 1 to monomer 2 be monomer 1: monomer 2 ═ 3: 7, AIBN (azobisisobutyronitrile) was added as a reaction initiator, and polymerization was carried out at 70 ℃ for 24 hours to obtain copolymer 1. The copolymer 1 exhibits liquid crystallinity.
(copolymer 2)
Dissolving monomer 1, monomer 2 and 2-hydroxyethyl methacrylate (HEMA) in dioxane to ensure that the molar ratio of monomer 1 to monomer 2 to HEMA is monomer 1: monomer 2: HEMA ═ 3: 7: 2, AIBN (azobisisobutyronitrile) was added as a reaction initiator, and polymerization was carried out at 70 ℃ for 24 hours to obtain copolymer 2. The copolymer 2 exhibits liquid crystallinity.
In the following examples and comparative examples, the optical properties (retardation value Re, etc.) of the obtained optical layered body were measured using a birefringence measurement device (AxoScan, manufactured by axome rics) and the thickness was measured using a film thickness meter (F20, manufactured by FILMETRICS).
(example 1)
The copolymer 1 was dissolved in Tetrahydrofuran (THF) to prepare a solution. The solution was coated on a glass cover substrate to a thickness of 2.4 μm by a spin coater, and dried at 25 ℃. The dried coating film was irradiated perpendicularly for 200 seconds (irradiation dose 200 mJ/cm) with polarized light (first polarized light) obtained by converting ultraviolet light from a high-pressure mercury lamp into linearly polarized light using a Glan Taylor prism2) And forming a first optically anisotropic layer. After irradiation with the first polarized light, the plate was heated at 130 ℃ for 3 minutes, and orientation was induced by cooling to room temperature. With respect to the optical characteristics of the obtained coating film, the axial direction of the in-plane retardation was 90 ° with respect to the polarization optical axis direction of the irradiation.
Thereafter, the ultraviolet light from the high-pressure mercury lamp was converted into polarized light of linear polarization whose polarization axis direction was different by 45 ° from that of the polarized light irradiated before (second polarized light) using a Glan Taylor prism, and the polarized light was irradiated to the coating film for 300 seconds (irradiation amount 300 mJ/cm)2) A surface layer is formed on the first optically anisotropic layer.
100 parts by weight of a polymerizable liquid crystal compound (LC-242 manufactured by BASF Co., Ltd.) and 5 parts by weight of a photopolymerization initiator (Irgacure 907 manufactured by Ciba Specialty Chemicals) were mixed, and dissolved in THF and propylene glycol 1-monomethyl ether 2-acetate (PGMEA) at a volume ratio (THF: PGMEA) of 1: 1 to prepare a solution. By rotatingThe solution was applied to the coating film obtained after the irradiation of the second polarized light to a thickness of 0.9 μm by a coater, heated to 70 ℃, and cooled to room temperature to form a second optically anisotropic layer. Further, 100 seconds of unpolarized ultraviolet light was irradiated (irradiation dose: 400 mJ/cm)2) The polymerizable liquid crystal compound is polymerized. The in-plane retardation value of the resulting optical layered body was 242nm (Linear retardation): 228nm, Circular retardation (Circular retardation): 78 nm).
In order to examine the optical properties of each layer of the obtained optical layered body, only the second optically anisotropic layer was transferred to the optically isotropic film with an adhesive. Further, optical characteristics of the first optically anisotropic layer and the second optically anisotropic layer after peeling were measured, respectively. The in-plane retardation Re of the first optically anisotropic layer was 135nm, and the slow axis direction was 90 ° with respect to the polarization optical axis direction of the irradiated first polarized light irradiation. In the second polarized light irradiation, since the first optically anisotropic layer itself is already oriented, the orientation itself is not greatly affected and the axial direction is maintained. The in-plane retardation Re of the second optically anisotropic layer was 115.3nm, and the slow axis direction was 77 ° with respect to the polarization optical axis direction of the irradiated first polarized light irradiation. In the second polarized light irradiation, the polarization axis direction is selected in consideration of the orientation state in the vicinity of the surface of the first optically anisotropic layer, and as a result, the slow axis direction of the second optically anisotropic layer can be set to a desired direction. Thus, it was confirmed that the optical layered body was formed by stacking 2 optically anisotropic layers, and the angle formed by the slow axes of the respective layers was 13 °. In addition, the slow axis direction is constant in the plane of the first optically anisotropic layer.
(example 2)
Copolymer 1 was dissolved in THF to prepare a solution. The solution was coated on a glass cover substrate to a thickness of 2.4 μm by a spin coater, and dried at 25 ℃. Ultraviolet rays from a high-pressure mercury lamp were converted into polarized light of linear polarization (first polarized light) using a Glan Taylor prism, and the dried coating film was irradiated with the polarized light for 200 seconds (irradiation dose 200 mJ/cm)2) And forming a first optically anisotropic layer. After irradiating with polarized light, heating at 130 deg.COrientation was induced by cooling to room temperature for 3 minutes. With respect to the optical characteristics of the obtained coating film, the axial direction of the in-plane retardation was 90 ° with respect to the polarization optical axis direction of the irradiation.
Thereafter, the obtained coating film was coated with a volume ratio of THF to ethanol (THF: ethanol) of 1: 6, and drying the resultant mixture by leaving it to stand. Further, ultraviolet rays from the high-pressure mercury lamp were converted into polarized light of linear polarization whose polarization axis direction was different by 60 ° from that of the polarized light irradiated before (second polarized light) using a Glan Taylor prism, and the polarized light was irradiated to the coating film for 70 seconds (irradiation amount 70 mJ/cm)2) A surface layer is formed on the first optically anisotropic layer.
100 parts by weight of a polymerizable liquid crystal compound (LC-242, manufactured by BASF corporation) and 5 parts by weight of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Specialty Chemicals) were mixed and dissolved in toluene to prepare a solution. The solution was applied to the coating film obtained after irradiation with the second polarized light by a spin coater to a thickness of 0.9 μm, heated to 70 ℃, and then cooled to room temperature to form a second optically anisotropic layer. Further, 100 seconds of unpolarized ultraviolet light was irradiated (irradiation dose: 400 mJ/cm)2) The polymerizable liquid crystal compound is polymerized. The in-plane retardation value of the resulting optical layered body was 142.7nm (Linear retardation): 114.8nm, and Circular retardation (Circular retardation): 84.5 nm).
The optical properties of each Layer of the obtained optical layered body were calculated by using Analysis software (Multi-Layer Analysis) of a birefringence measurement apparatus (AXOMETRICS, inc.). The in-plane retardation Re of the first optically anisotropic layer was 100nm, and the slow axis direction was 90 ° with respect to the polarization optical axis direction of the irradiated first polarized light irradiation. The in-plane retardation Re of the second optically anisotropic layer was 180nm, and the slow axis direction was 28.5 ° with respect to the polarization optical axis direction of the irradiated first polarized light irradiation. Thus, it was confirmed that the angle formed by the slow axes of the respective layers was 61.5 ° in an optical layered body in which 2 optically anisotropic layers were laminated. In addition, the slow axis direction is constant in the plane of the first optically anisotropic layer.
(example 3)
Copolymer 2 was dissolved in THF to prepare a solution. The solution was coated on a glass cover substrate to a thickness of 2.4 μm by a spin coater, and dried at 25 ℃. Ultraviolet rays from a high-pressure mercury lamp were converted into polarized light of linear polarization (first polarized light) using a Glan Taylor prism, and the dried coating film was irradiated with the polarized light for 200 seconds (irradiation dose 200 mJ/cm)2) And forming a first optically anisotropic layer. After irradiation with the first polarized light, the plate was heated at 130 ℃ for 3 minutes, and orientation was induced by cooling to room temperature. With respect to the optical characteristics of the obtained coating film, the axial direction of the in-plane retardation was 90 ° with respect to the polarization optical axis direction of the irradiation.
Thereafter, the ultraviolet light from the high-pressure mercury lamp was converted into polarized light of linear polarization whose polarization axis direction was different by 45 ° from that of the polarized light irradiated before (second polarized light) using a Glan Taylor prism, and the polarized light was irradiated to the coating film for 300 seconds (irradiation amount 300 mJ/cm)2) A surface layer is formed on the first optically anisotropic layer.
100 parts by weight of a polymerizable liquid crystal compound (LC-242 manufactured by BASF Co., Ltd.), 5 parts by weight of a photopolymerization initiator (Irgacure 907 manufactured by Ciba Specialty Chemicals) and 0.6 part by weight of a polyisocyanate (DURANATE TKA-100 manufactured by Asahi Kasei corporation) were mixed, and the volume ratio of THF to PGMEA (THF: PGMEA) was 1: 1 to prepare a solution. The solution was applied to the coating film obtained after irradiation with the second polarized light by a spin coater to a thickness of 0.9 μm, heated to 70 ℃, and then cooled to room temperature to form a second optically anisotropic layer. Further, 100 seconds of unpolarized ultraviolet light was irradiated (irradiation dose: 400 mJ/cm)2) The polymerizable liquid crystal compound is polymerized and the copolymer 2 is crosslinked. The in-plane retardation value of the obtained optical layered body was 202nm (Linear retardation): 185 nm) and Circular retardation (Circular retardation): 81 nm). Further, in order to confirm the adhesion at the interface between the first optically anisotropic layer and the second optically anisotropic layer, a cross-cut test was performed. The test was carried out in accordance with JIS K5600, and as a result, peeling of the second optically anisotropic layer was not observed,good adhesion was confirmed.
The optical properties of each layer of the obtained optical layered body showed optical properties comparable to those of example 1.
Comparative example 1
The copolymer 1 was dissolved in Tetrahydrofuran (THF) to prepare a solution. The solution was coated on a glass cover substrate to a thickness of 2.6 μm by a spin coater, and dried at 25 ℃. Ultraviolet rays from a high-pressure mercury lamp were converted into polarized light of linear polarization by a Glan Taylor prism, and the dried coating film was irradiated with the polarized light for 30 seconds (irradiation dose 30 mJ/cm)2)。
Then, a solution obtained by mixing 100 parts by weight of a polymerizable liquid crystal compound (LC-242, manufactured by BASF) and 5 parts by weight of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Specialty Chemicals) and dissolving them in toluene was applied to the obtained coating film by a spin coater to a thickness of 1.2 μm, heated to 70 ℃, 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 polarizing optical axis.
Thereafter, the ultraviolet light from the high-pressure mercury lamp was converted into polarized light of linear polarization whose polarization axis direction was different by 60 ° from that of the polarized light irradiated before by using a Glan Taylor prism, and the polarized light was irradiated to the coating film for 100 seconds (irradiation amount 100 mJ/cm)2)。
The in-plane retardation value of the obtained optical layered body at an arbitrary point was 172.9nm (Linear retardation): 136.8nm, Circular retardation (Circular retardation): 105.7 nm).
In order to examine the optical properties of each layer of the obtained optical layered body, only the second optically anisotropic layer was peeled off. The in-plane retardation Re of the second optically anisotropic layer at an arbitrary point was 116.8nm, and the slow axis direction was 39.8 ° with respect to the polarization optical axis direction of the polarized light irradiated before. This confirmed that the optical layered body was formed by stacking 2 optically anisotropic layers, but the angle formed by the slow axes of the layers was 50.2 °, which was greatly different from the polarization axis direction (60 °) when the 2 nd polarized light was irradiated. Further, it was confirmed that the slow axis direction was not constant in the plane, the orientation was disturbed, and a domain appeared to generate haze. This is considered to be because when the polarized light is incident on the first optically anisotropic layer made of the copolymer 1 by irradiating the 2 nd polarized light through the oriented second optically anisotropic layer, the linearly polarized light is changed to elliptically polarized light, and the polarization axis direction (the long 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 layered bodies of examples 1 to 3 were produced by a specific method, the slow axis of each of the first and second optically anisotropic layers could be arbitrarily adjusted. In embodiment 2 in particular, since the surface treatment is performed with the solvent before the irradiation of the second polarized light, the orientation of the surface can be applied more easily. In example 3, since the polyisocyanate having an isocyanate group capable of forming a crosslinking bond with the hydroxyl group of the 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 good.
On the other hand, in the optical layered body of comparative example 1, since polarized light for aligning the birefringence-inducing material layer was irradiated through the layer made of the polymerizable liquid crystal material, the polarized light was converted by the layer made of the polymerizable liquid crystal material, and the slow axis of each layer could not be adjusted to a desired direction.
Industrial applicability
According to the present invention, it is possible to provide an optical layered body in which the angle at which the slow axes intersect with each other can be arbitrarily set. Such an optical layered body can be used for polarizing plates, optical compensation films, and the like used in liquid crystal display devices and organic EL display devices. In particular, the polarizing plate can be laminated with a linear polarizing plate and used as a circular polarizing plate used in an organic EL display device.
As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but it is apparent that those skilled in the art can easily make various changes and modifications within the scope of the present invention by reading the present specification. Accordingly, such changes and modifications are to be construed as being within the scope of the invention as defined by the appended claims.
Description of the symbols
10. substrate
20 birefringent inducing material layer
30. first optically anisotropic layer
31. inner layer
32. surface layer
40. second optically anisotropic layer
100. optical laminate

Claims (7)

1. 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 different slow axes from each other, 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 cross.
2. The optical layered body as claimed in 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 cross at a non-parallel and non-orthogonal angle.
3. The optical layered body according to claim 1 or 2, wherein the polymerizable liquid crystal material contains a crosslinking agent having a functional group capable of forming a crosslinking bond with the birefringence inducing material.
4. A method for producing the optical layered body according to any one of claims 1 to 3, comprising:
a first light irradiation step of irradiating a first polarized light for developing a phase difference onto a birefringence-inducing material layer made of a birefringence-inducing material to form a first optically anisotropic layer;
a surface orientation step of subjecting the surface of the first optically anisotropic layer to orientation treatment to impart orientation different from that of the internal layer thereof, thereby forming a surface layer on the first optically anisotropic layer; and
and a second optically anisotropic layer forming step of applying a polymerizable liquid crystal material to the surface of the first optically anisotropic layer subjected to the alignment treatment to form a second optically anisotropic layer.
5. The method of producing an optical layered body according to claim 4, wherein the surface alignment step is a second light irradiation step of irradiating a surface of the first optically anisotropic layer with 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.
6. The method of producing an optical layered body according to claim 5, further comprising a surface treatment step of treating a surface of the first optically anisotropic layer with a solvent between the first light irradiation step and the second light irradiation step.
7. A circularly polarizing plate comprising the optical layered body according to any one of claims 1 to 3 and a linearly polarizing plate laminated thereon.
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