JP2002350641A - Selective reflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a selective reflection film which is subjected to preferable aligning treatment and is excellent in the image characteristics and optical characteristics required for color images and particularly excellent in heat resistance and scratch resistance. SOLUTION: The selective reflective film is formed by using a liquid crystal composition. The liquid crystal composition contains a rod-like liquid crystal compound having at least three polymerizable groups in one molecule, a chiral compound and a polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective reflection film such as a retardation film, a color filter, and a circularly polarized light reflection plate used for a display device such as an LCD. The present invention relates to a selective reflection film having high reproducibility and display image quality.

[0002]

2. Description of the Related Art For example, a color filter used in a color liquid crystal display or the like generally includes red (R), green (G), and blue (B) pixels, and black spaces between the pixels for improving display contrast. And a matrix. In recent years, as a method for manufacturing such a color filter, a manufacturing method capable of easily manufacturing a high-quality color filter with low material loss and high efficiency has been demanded,
In addition, color filters having a liquid crystal material (particularly, cholesteric liquid crystal) as a main component have been widely studied in recent years from the viewpoint that the transmittance and color purity of the color filters are required to be high.

A color filter using a liquid crystal composition containing a cholesteric liquid crystal as a main component is a polarization-based color filter that reflects an image of a certain wavelength and transmits the other wavelength to display an image. High utilization efficiency, transmittance,
Excellent in color purity. In manufacturing, since a uniform thickness can be easily formed, a method of forming a film using a spin coating method or the like was generally used. However, material loss is disadvantageous in terms of cost, and from such a viewpoint, A production method using a photoreactive chiral compound is useful. That is, when a liquid crystalline composition containing a photoreactive chiral compound is used, when light having a wavelength sensitive to the chiral compound is irradiated in a pattern, isomerization of the chiral compound is caused according to the intensity (illuminance) of the irradiation energy. As a result, the helical pitch of the liquid crystal compound (the helical twist angle) changes. As a result, a desired selective reflection color can be easily formed for each pixel only by pattern exposure with a light amount difference, and material loss can be reduced. In addition, the number of steps and cost can be reduced.

The color filter obtained as described above has high hue purity and excellent clarity displayed by selective reflection, and can have image characteristics required for a color image. Properties) and scratch resistance. Further, not only the above-mentioned color filter but also other selective reflection films (films) such as a retardation film and a circularly polarized light reflection plate have good optical characteristics such as a large intrinsic birefringence (Δn) of the film itself. At the same time, it is indispensable that it has excellent high-temperature durability and scratch resistance, and can maintain constant optical characteristics stably for a long period of time.

On the other hand, when a film (layer) containing a liquid crystalline composition (for example, a color filter film, a retardation film, or the like) is formed by coating, especially in the case of a low-molecular liquid crystal, the liquid crystal molecules are aligned horizontally (with the substrate) on the substrate side. Even if the alignment treatment is performed, since one side of the color filter forming layer is at the air interface, the liquid crystal molecules stand vertically on the air interface side, and the tilt angle (pretilt angle) of the liquid crystal molecules toward the thickness direction of the layer is increased. A continuously changing state occurs. For this reason, it is usually necessary to sandwich both sides of the layer with an alignment film. However, when the liquid crystal composition is polymerized and used as an optical film, at least one side of the alignment is required after polymerization to reduce the weight and thickness. There is also a problem that the film needs to be peeled off, which leads to an increase in steps such as installation and removal of the alignment film and an increase in waste material.

[0006]

As described above, favorable orientation treatment is easily performed, and excellent image characteristics and optical characteristics required for a color image, and durability (heat resistance) and scratch resistance at high temperatures are obtained. At present, selective reflection films such as color filters, retardation films, and circularly polarized light reflection plates that are stable and have high reliability for a long time have not yet been provided. Therefore, the present invention solves the above-mentioned problems in the related art, is subjected to favorable alignment processing, and has image characteristics (a wide selective reflection area, high color purity, high resolution, and high transmittance) required for a color image, and It is an object of the present invention to provide a selective reflection film which is excellent in optical characteristics (intrinsic birefringence Δn, selective reflection peak) and particularly excellent in heat resistance and scratch resistance.

[0007]

Means for solving the above problems are as follows. <1> A selective reflection film formed using a liquid crystal composition, wherein the liquid crystal composition is a rod-shaped liquid crystal compound having at least three polymerizable groups in the same molecule, and a chiral compound. And a polymerization initiator. Here, the selective reflection film according to <1>,
The liquid crystal compound has a helical structure, and the helical axis is polymerized or cross-linked in a state where it is oriented so as to be substantially parallel to the normal direction of the surface of the selective reflection film, and the helical structure is fixed. It is an optical film showing a selective reflection wavelength (color) belonging to a wavelength region of infrared rays.

<2> The selective reflection film according to <1>, wherein the chiral compound is a photoreactive chiral compound. Hereinafter, the liquid crystal composition in this case may be referred to as a “photoreactive liquid crystal composition”. <3> The liquid crystal composition according to the item <1>, further comprising an air interface alignment agent.
> Or <2>. <4> The content of the rod-shaped liquid crystalline compound having at least three polymerizable groups in the same molecule is at least 40% by mass of the total solid content (mass) of the liquid crystalline composition. >
The selective reflection film according to any one of the above.

<5> The liquid crystalline composition is formed by patterning by imagewise exposing (preferably in a non-liquid crystal state) with a first light, followed by photopolymerization with a second light and curing. The selective reflection film according to any one of <1> to <4> above. <6> The selective reflection film according to any one of <1> to <5>, wherein the selective reflection film is provided on a substrate and has two or more types of regions having different selective reflection wavelengths.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the selective reflection film of the present invention,
A liquid crystal composition containing a rod-shaped liquid crystal compound having at least three polymerizable groups in the same molecule is used. Hereinafter, the selective reflection film of the present invention will be described in detail.

The selective reflection film of the present invention is formed by using a liquid crystal composition, and the liquid crystal composition is obtained by polymerizing a rod-shaped liquid crystal compound having at least three polymerizable groups in the same molecule with a chiral compound. And at least an initiator, preferably comprising an air interface alignment agent and a polymerizable monomer,
Further components may be included as needed.

The form of the selective reflection film of the present invention is not particularly limited, and may be a sheet composed only of the liquid crystal composition, a liquid crystal composition on a desired support or a temporary support, or the like. For example, the layer may be provided as a layer (liquid crystal layer), and another layer (film) such as an alignment film or a protective film may be provided adjacently. The thickness of the selective reflection film is preferably 1 to 6 μm, and 1.5 to 4 μm.
μm is more preferred.

Next, each component of the liquid crystalline composition will be described in detail. (Rod-shaped liquid crystalline compound having at least three polymerizable groups in the same molecule) In the present invention, as the liquid crystalline compound, a rod-shaped liquid crystalline compound having at least three polymerizable groups in the same molecule (hereinafter, referred to as “ Polymerizable liquid crystal compound "). By containing a liquid crystal compound having at least three polymerizable groups in the same molecule,
As will be described later, it is possible to increase the degree of curing due to the polymerization reaction when curing the oriented structure, and to improve the durability (heat resistance) of the formed selective reflection film at high temperatures and the scratch resistance. it can. In addition, since a rod-shaped compound is used, the helical pitch of the polymerizable liquid crystal compound can be greatly changed (the twist change rate is large) accompanying the isomerization of a chiral compound described later, and the optical characteristics (intrinsic birefringence Δn, (Reflection peak), exhibiting a wide range of selective reflection colors, and in particular, a selective reflection film capable of displaying three primary colors (B, G, R) with high color purity can be formed.

The polymerizable liquid crystal compound is appropriately selected from rod-shaped liquid crystal compounds (rod-shaped liquid crystal compounds) having three or more polymerizable groups in the same molecule (that is, having three or more functional groups). Can be. Specifically, a rod-shaped nematic liquid crystal compound having three or more polymerizable groups in the same molecule is exemplified.

The nematic liquid crystal compound can be appropriately selected from a liquid crystal compound having a refractive index anisotropy Δn of 0.10 to 0.40, a polymer liquid crystal compound, and a polymerizable liquid crystal compound. A cholesteric liquid crystal composition (cholesteric liquid crystal phase) can be obtained by using a (photoreactive) chiral compound in combination with a nematic liquid crystal compound. In addition, the nematic liquid crystal compound can be aligned while being in a liquid crystal state at the time of melting, for example, by using an alignment substrate that has been subjected to an alignment process such as a rubbing process. In the case where the liquid crystal state is solid phase and immobilized, means such as cooling and polymerization can be used. That is,
Since the liquid crystalline compound according to the present invention has at least three polymerizable groups and has extremely high reactivity, a tough film can be formed when polymerized efficiently in an aligned state.

Among the above trifunctional or higher functional nematic liquid crystal compounds, bifunctional (having two polymerizable groups in the same molecule)
Are highly miscible in the nematic state with the rod-shaped liquid crystal compound of the formula (1). Here, the miscibility means that no phase separation occurs and that the thermal stability of the nematic phase is not significantly impaired by mixing. Further, for example, a liquid crystal compound in which a UV-curable functional group (for example, an acrylate group) that polymerizes and cures in response to ultraviolet light, etc., is introduced in the same molecule is preferable. If this is cured by irradiating it with ultraviolet light,
It is possible to produce a color filter having high film strength at the following low temperatures.

Preferred examples of the nematic liquid crystal compound include the following compounds. However, the present invention is not limited to these.

[0018]

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For each n in each of the above compounds, n is independently preferably an integer of 2 to 8, preferably 3 to 6
Is more preferable. If n is too small, the melting temperature of the crystal may increase, and if n is too large, the smecticity may increase and the nematicity may decrease.

The polymerizable liquid crystal compound may be used alone or in combination of two or more. Further, together with a rod-shaped liquid crystal compound having at least three polymerizable groups in the same molecule (polymerizable liquid crystal compound), the polymerizability of two or less,
Alternatively, a liquid crystal compound having no polymerizable group may be used in combination.

The content of the polymerizable liquid crystal compound is as follows:
It is preferably at least 40% by mass of the total solid content (mass) of the liquid crystalline composition, more preferably at least 50% by mass, particularly preferably from 50 to 70% by mass. When the content is less than 40% by mass, durability (heat resistance) and scratch resistance at high temperatures become insufficient, and a selective reflection film that is stable and has high reliability for a long time may not be formed.

(Chiral Compound) The liquid crystal composition according to the present invention contains a chiral compound. The chiral compound is a compound capable of changing the helical pitch induced in the cholesteric liquid crystal composition, and depending on the purpose or the like, a chiral compound having a large twisting property due to light or a chiral compound having a large temperature dependence of the twisting property and not reacting with light. It can be appropriately selected from known compounds such as compounds. Among them, a photoreactive chiral compound capable of changing the helical pitch by light irradiation (ultraviolet light to visible light to infrared light) is particularly preferable. And a site that causes a change. These sites are preferably contained in one molecule. In the present invention, a photoreactive chiral compound may be used in combination with a chiral compound which has a large temperature dependence of torsion and does not react with light.

The photoreactive chiral compound preferably has a light-sensitive peak wavelength longer than the light-sensitive peak wavelength of the polymerization initiator in order to improve patterning sensitivity. In addition, the photoreactive chiral compound preferably has a large force for inducing the helical structure of the cholesteric liquid crystal composition. For this purpose, the chiral site is located at the center of the molecule, and the periphery thereof has a rigid structure. Preferably, the molecular weight is 300 or more. In order to increase the induction force of the helical structure by light irradiation, it is preferable to use a material having a large degree of structural change by light irradiation, and to make a chiral part and a part that causes structural change by light irradiation close to each other.

Further, a compound having high solubility in a nematic liquid crystal compound is preferable.
Those close to liquid crystal polymerizable monomers are more preferable. When the structure of the chiral compound is a structure in which one or more polymerizable bonding groups are introduced, the heat resistance of the formed selective reflection film can be further improved.

Examples of the structure of the photoreactive portion whose structure is changed by light irradiation include a photochromic compound (Kingo Uchida,
Masahiro Irie, Chemical Industry, vol. 64, p. 640, 1
999, Kingo Uchida, Masahiro Irie, Fine Chemical, v
ol. 28 (9), p.15, 1999). Hereinafter, specific examples will be described, but the present invention is not limited thereto.

[0026]

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In the formula, R ¹ and R ² represent an alkyl group, an alkoxy group, an anenyl group or an acryloyloxy group.

The chiral site may be one that undergoes decomposition, addition reaction, isomerization, dimerization reaction, or the like upon irradiation with light, resulting in an irreversible structural change. Further, as the chiral site, for example, an asymmetric carbon in which different groups are bonded to four bonds, such as a carbon atom marked with * in the compounds exemplified below, corresponds to (the chemistry of liquid crystal,
No. 22, Hiroyuki Nohira, Chemistry Review, p. 73, 199
4).

[0029]

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As the photoreactive chiral compound having both a chiral moiety and a photoisomerization unit, the following compounds can be mentioned as examples.

[0031]

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Further, a photoreactive chiral compound represented by the following general formula (I) or (II) is also preferable.

[0033]

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In the general formulas (I) and (II), R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, a total of 3 to 3 carbon atoms.
15 represents an acryloyloxyalkyloxy group and a methacryloyloxyalkyloxy group having 4 to 15 carbon atoms in total.

Hereinafter, as specific examples of the compound represented by the general formula (I), examples of the R group (exemplified compounds (1) to (1)
5))), but the present invention is not limited to these.

[0036]

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The content of the (photoreactive) chiral compound in the liquid crystal composition (cholesteric liquid crystal composition) is not particularly limited and can be appropriately selected, but is preferably about 2 to 30% by mass.

(Polymerization Initiator) The liquid crystalline composition according to the present invention contains a polymerization initiator. The polymerization initiator promotes a polymerization reaction based on a polymerizable group (unsaturated bond), polymerizes and cures the liquid crystal composition, and further improves the strength of the liquid crystal composition after the fixation. .

The polymerization initiator can be appropriately selected from known compounds such as photoreactivity and thermal reactivity, and among them, a photopolymerization initiator capable of accelerating the reaction by light irradiation is preferable. For example, the polymerization and curing reaction of a liquid crystalline composition such as a cholesteric liquid crystal composition can be rapidly performed, and a large intrinsic birefringence (Δn) and a selective reflection color with high color purity can be stably obtained.

The polymerization initiator can be appropriately selected from known ones, for example, p-methoxyphenyl-2,4-bis (trichloromethyl) -s-triazine, 2- (p-butoxystyryl) ) -5-Trichloromethyl 1,3,4-oxadiazole, 9-phenylacridine, 9,10-dimethylbenzphenazine, benzophenone / Michler's ketone, hexaarylbiimidazole / mercaptobenzimidazole, benzyldimethylketal, thioxanthon / amine, etc. Is mentioned.

The amount of the polymerization initiator to be added is preferably from 0.1 to 20% by mass, more preferably from 0.5 to 5% by mass, based on the solid content (mass) of the liquid crystal composition. The addition amount is,
If the amount is less than 0.1% by mass, the curing efficiency is low, so that a long time may be required. If the amount exceeds 20% by mass, for example, in the case of a photopolymerization initiator, the light transmittance from the ultraviolet region to the visible light region is reduced. May be inferior.

(Air Interface Orienting Agent)
A surfactant having an excluded volume effect. Here, having the excluded volume effect means controlling the alignment of the liquid crystal (molecule) on the air interface side, that is, the liquid crystal at the air interface on the layer surface when, for example, a layer containing the liquid crystal composition is formed by coating. Is to control the spatial orientation state of the three-dimensionally. Specifically, this means controlling the pretilt angle of liquid crystal molecules on the air interface side.

The preferred molecular structure of the air interface alignment agent includes a flexible hydrophobic portion and a molecularly rigid unit having one or more cyclic units (hereinafter referred to as a rigid portion). That is. Note that, depending on the type of the liquid crystalline compound used, the flexible hydrophobic portion can be a perfluoro chain or a long alkyl chain. Since the hydrophobic portion is flexible, the hydrophobic portion can be effectively arranged on the air side. Further, the air interface alignment agent may be a short molecule having a number of molecules of about several hundreds, or may be a polymer or an oligomer in which the molecules are linked. It is also possible to add a polymerizable functional group depending on the purpose.

When such an air interface aligning agent is contained, the flexible hydrophobic portion of the air interface aligning agent exists in the air interface direction, the rigid portion exists in the liquid crystal molecule direction, and the rigid portion further exists. Are planar and are arranged parallel to the air interface, so that the liquid crystal molecules can be arranged parallel to the air interface. On the other hand, if the rigid portions are arranged perpendicular to the air interface, it becomes possible to arrange the liquid crystal molecules perpendicular to the air interface. Specifically, nonionic surfactants are preferable, and for example, the following compounds are preferable.

[0045]

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[0046]

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The amount of the air interface aligning agent added is preferably such that it covers the surface of the layer containing the liquid crystal composition on the air interface side by about one molecule, and is preferably based on the solid content (mass) of the liquid crystal composition. 0.05-5 mass% is preferred, and 0.1-1.0
% Is more preferred. The addition amount is 0.05% by mass.
If the amount is less than 5%, the effect may not be exhibited. If the amount is more than 5% by mass, the air interface alignment agent itself may cause association and phase separation with the liquid crystal. Although the surface tension is reduced by containing the air interface alignment agent,
Further, for the purpose of lowering the surface tension and improving the coating property, a surfactant other than the air interface alignment agent may be used in combination.

The surfactant can three-dimensionally control the orientation state of liquid crystal molecules at the air interface on the surface of the layer, for example, when a cholesteric liquid crystal phase in a coating liquid is applied to form a layer. In this case, a selective reflection wavelength having higher color purity can be obtained.

(Polymerizable Monomer) A polymerizable monomer may be used in combination with the liquid crystal composition. When the polymerizable monomer is used in combination, after patterning (in the case of a cholesteric liquid crystal phase, the distribution of the selective reflection wavelength is formed by changing the torsional force of the liquid crystal by light irradiation), its helical structure (selective reflectivity)
And the strength of the liquid crystal layer (liquid crystal composition) after the fixation can be further improved. However, when the nematic liquid crystal compound has an unsaturated bond in the same molecule,
It is not always necessary to add.

Examples of the polymerizable monomer include a monomer having an ethylenically unsaturated bond, and specific examples thereof include polyfunctional monomers such as pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate. Specific examples of the monomer having an ethylenically unsaturated bond include the following compounds, but are not limited to these in the present invention.

[0051]

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The amount of the polymerizable monomer to be added is preferably 0.5 to 50% by mass of the total solid content (mass) of the liquid crystal composition. If the amount is less than 0.5% by mass, sufficient curability may not be obtained. If the amount exceeds 50% by mass, the alignment of liquid crystal molecules is inhibited, and sufficient color formation cannot be obtained. Sometimes.

(Other Components) Further, other components include a binder resin, a polymerization inhibitor, a solvent, a thickener, a dye, a pigment,
An ultraviolet absorber, a gelling agent and the like can be added. As the other components, those having excellent compatibility with the nematic liquid crystal compound are preferable because they affect the strength of the color filter film cured by ultraviolet curing.

If these components can move in the cured color filter film, the released components lower the film strength and cause changes in various characteristics of the color filter. Therefore, it is preferable to use, as another component to be added, a component having a functional group of the same type as the polymerizable functional group introduced into the nematic liquid crystal compound. That is, the other components are fixed in the liquid crystal compound by polymerization and curing without being released in the film, so that the film strength and various characteristics are not impaired. Further, the content of the other components excluding the binder resin and the surfactant is preferably 10% by mass or less based on the total solid content (mass) of the liquid crystal composition. When the content exceeds 10% by mass, the strength of the selective reflection film may be reduced.

Examples of the binder resin include polystyrene compounds such as polystyrene and poly-α-methylstyrene, cellulose resins such as methylcellulose, ethylcellulose and acetylcellulose, acidic cellulose derivatives having a carboxyl group in the side chain, polyvinylformal, Acetal resins such as polyvinyl butyral, JP-A-59-44615, JP-B-54-34327,
JP-B-58-12577, JP-B-54-25957
JP-A-59-53836, JP-A-59-7104
No. 8, methacrylic acid copolymer, acrylic acid copolymer, itaconic acid copolymer, crotonic acid copolymer, maleic acid copolymer, partially esterified maleic acid copolymer and the like. Further, a homopolymer of an alkyl acrylate and a homopolymer of an alkyl methacrylate may also be mentioned. Of these, the alkyl group is particularly preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an iso-butyl group. , N-hexyl, cyclohexyl, 2-ethylhexyl and the like are preferred. In addition, a polymer having a hydroxyl group to which an acid anhydride is added, a benzyl (meth) acrylate / (homopolymer of methacrylic acid) acrylic acid copolymer or benzyl (meth) acrylate / (meth) acrylic acid / other monomer And the like.

Among these, a binder resin containing a carboxyl group is preferable from the viewpoint of alkali developability after patterning and mass productivity. When forming a liquid crystal layer on a plastic substrate (coating, transfer, etc.), when a binder resin containing a carboxyl group is used as a binder component in a cholesteric liquid crystal composition prepared as a coating liquid,
Alkaline development is possible, and patterning can be easily performed by alkali development after light irradiation.

The content of the binder resin in the liquid crystal composition is preferably from 0 to 50% by mass,
% Is more preferred. If the content exceeds 50% by mass, the orientation of the nematic liquid crystal compound may be insufficient.

The polymerization inhibitor may be added for the purpose of improving the storage stability. Examples include hydroquinone, hydroquinone monomethyl ether, phenothiazine, benzoquinone, and derivatives thereof. The addition amount of the polymerization inhibitor is 0 to 1 with respect to the polymerizable monomer.
0 mass% is preferable, and 0 to 5 mass% is more preferable.

The liquid crystal composition can be prepared by dissolving and dispersing each of the above-mentioned components in an appropriate solvent, and can be used by molding it into an arbitrary shape or forming it on a support or the like. Here, examples of the solvent include 2-butanone, cyclohexanone, methylene chloride, chloroform and the like.

-Production of Selective Reflection Film- The selective reflection film of the present invention comprises a polymerizable liquid crystal compound and a chiral compound.
Product, polymerization initiator and preferably air interface alignment agent, etc.
If necessary, use a liquid crystalline composition containing other components as needed.
It can be manufactured by an appropriately selected method. Among them, the photoreactive key
Using photoreactive liquid crystalline compositions containing ral compounds
More preferably, the photoreactive liquid crystal composition is prepared by adding (preferably, a non-liquid crystal
State) first light (wavelength λ¹) By imagewise exposure
After patterning, the second light (in the liquid crystal state) (wavelength λ
^Two(≠ λ¹)) To cure by photopolymerization (hereinafter referred to as
Is sometimes referred to as an “exposure step”. By)
It can be suitably formed. That is, for example, the non-liquid crystal state
Of the liquid crystalline composition of the formula¹The light of
After irradiating and patterning to the desired image, heat
By maintaining the liquid crystal phase formation temperature, the desired liquid crystal state
(State showing selective reflection)
The second light source is used so that the helical pitch of the liquid crystal is more fixed.
Wavelength λ ^TwoOf light.

By repeating the exposure step a plurality of times, it is possible to obtain a selective reflection film (for example, a color filter) having two or more types of regions having different selective reflection wavelengths and exhibiting selective reflection of a plurality of colors. Can be. Further, the liquid crystal composition may be laminated in two or more layers (for example, as a brightness enhancement film of a transmission type LCD, a color filter for a transmission type LCD, a circularly polarizing mirror, etc.). A plurality of steps are provided. Further, in the production of the selective reflection film, depending on the specific production mode to be selected,
A step of providing a liquid crystal composition on a substrate (forming a liquid crystal layer) (coating step, etc.); a step of subjecting a surface in contact with the liquid crystal composition to an alignment treatment (alignment treatment step); A step (transfer step) of transferring an object (liquid crystal layer) or the like is appropriately included.

When the light having the wavelength λ ¹ is irradiated on the whole or a part including the desired region in which coloring is to be obtained, the photoreactive chiral compound responds to the light in accordance with the illuminance, and the trans-cis A state showing desired selective reflection (hue), that is, an image pattern showing a selective reflection color is formed by the isomerization and a change in the helical pitch of the liquid crystal. Therefore, if light irradiation is performed with the irradiation intensity changed for each desired region, a plurality of colors are presented in accordance with the irradiation intensity, for example, exposure is performed through an exposure mask created by changing the light transmittance like an image. Thus, an image, that is, a colored region having different selective reflection can be simultaneously formed by one light irradiation.

The wavelength λ ¹ of the first light may be set to a light-sensitive wavelength region of the photoreactive chiral agent, particularly to a wavelength close to the light-sensitive peak wavelength, in that sufficient patterning sensitivity can be obtained. preferable. Further, it is preferable that the wavelength λ ² of the second light be set in a light-sensitive wavelength range of the polymerization initiator, in particular, a wavelength close to a light-sensitive peak wavelength, in that sufficient photopolymerization sensitivity can be obtained. The illuminance (irradiation intensity) of the first and second lights is not particularly limited, and can be appropriately selected depending on the material to be used so that sufficient photosensitivity can be obtained during patterning and polymerization curing.

The light source used for irradiating the first and second light is preferably a light source which emits ultraviolet light because it has a high energy, a structural change of a liquid crystal compound and a polymerization reaction can be carried out quickly. , Metal halide lamps, Hg-Xe lamps and the like. Further, it is preferable to have a light quantity variable function. Hereinafter, a method of manufacturing a cholesteric liquid crystal color filter will be described in detail as an example of manufacturing the selective reflection film of the present invention.

For example, the production method of the following embodiments a or b may be used, and the production can be more suitably performed by these two embodiments. <Aspect a> (Step 1): A step of preparing a transfer material. A liquid crystal composition in a coating liquid state is applied on a temporary support to prepare a transfer material having at least a cholesteric liquid crystal layer. The cholesteric liquid crystal phase (liquid crystalline composition) in the coating liquid can be prepared by dissolving and dispersing each component in an appropriate solvent. Examples of the solvent include 2-butanone, cyclohexanone, methylene chloride, chloroform and the like. Can be Between the liquid crystal layer and the temporary support, a cushion layer containing a thermoplastic resin or the like may be provided from the viewpoint of ensuring adhesion during transfer, such as when there is a foreign substance or the like on the transfer target. It is also preferable that the surface of the cushion layer or the like is subjected to an alignment treatment such as a rubbing treatment (an alignment treatment step). (Step 2): a step of transferring and forming a cholesteric liquid crystal layer. The transfer material is laminated on a light-transmitting substrate, and the transfer material is peeled from the substrate to form a cholesteric liquid crystal layer on the substrate (transfer step). The liquid crystal layer can be formed of a plurality of layers by further laminating after the following step 3. In addition to the light-transmitting substrate, an image-receiving material having an image-receiving layer on the substrate may be used. Although a liquid crystal layer may be applied and formed as in the embodiment b described later, a transfer method is preferable in terms of material loss and cost.

(Step 3): The above-mentioned exposure step according to the present invention. Against the cholesteric liquid crystal layer on the substrate, desired selective reflection region is formed, desired selective reflection wavelength and the pattern by irradiating a further wavelength lambda ² of light to the area by irradiating light of wavelength lambda ¹ And at least one step of curing and fixing. The details of each of these steps and the materials used, such as a transfer material and a substrate, are described in detail in the specifications of Japanese Patent Application Nos. 11-342896 and 11-343665 filed by the present inventors. Has been described.

<Aspect b> (Step 1): A step of applying and forming a cholesteric liquid crystal layer. A cholesteric liquid crystal layer is formed by directly providing a liquid crystal composition (cholesteric liquid crystal phase) on a substrate (support) constituting a color filter. The liquid crystal layer can be formed by applying a liquid crystal phase prepared as a coating liquid in the same manner as described above by a known coating method using a bar coater, a spin coater or the like. Further, an alignment film similar to the above may be formed between the cholesteric liquid crystal layer and the substrate. It is also preferable to perform an alignment treatment such as a rubbing treatment on the surface of the alignment film or the like (alignment treatment step). (Step 2): An exposure step according to the present invention similar to (Step 3) of the above-described embodiment a.

Further, a specific description will be given with reference to FIGS. FIGS. 1 to 3 are schematic diagrams showing a selective reflection film (cholesteric liquid crystal layer) of the present invention formed on a substrate. First, at least a polymerizable liquid crystal compound, a chiral compound, and a polymerization initiator are dissolved in an appropriate solvent to prepare a coating liquid crystal composition (cholesteric liquid crystal composition).
As shown in FIG. 1- (A), a temporary support 10 is prepared, and an acrylic resin, polyester,
A cushion layer (thermoplastic resin layer) 12 is provided by applying and forming polyurethane or the like, and an alignment film 14 made of polyvinyl alcohol or the like is further laminated. In this alignment film, FIG.
A rubbing treatment is performed as shown in FIG. This rubbing treatment is not always necessary, but the rubbing treatment can further improve the orientation. Next, as shown in FIG. 1- (C), a liquid crystal composition in a coating liquid state is applied on the alignment film 14 and dried to form a cholesteric liquid crystal layer 16, and a cover is formed on the cholesteric liquid crystal layer 16. The transfer material is prepared by providing the film 18. Hereinafter, the transfer material is referred to as a transfer sheet 20.

On the other hand, as shown in FIG. 1- (D), another base material 22 is prepared, an alignment film 24 is formed on the base material 22 in the same manner as described above, and the surface is subjected to a rubbing treatment. (Orientation treatment step). Hereinafter, this is referred to as a color filter substrate 26. Subsequently, after the cover film 18 of the transfer sheet 20 was peeled off, as shown in FIG.
The cholesteric liquid crystal layer 16 is overlapped with the surface of the alignment film 24 of the color filter substrate 26 so as to be in contact with the surface of the cholesteric liquid crystal layer 16, and laminated through a roll rotating in the direction of the arrow in the figure. Thereafter, as shown in FIG. 1- (F), when the transfer film 20 is peeled between the alignment film 14 and the cushion layer 12, the cholesteric liquid crystal layer is transferred onto the color filter substrate together with the alignment film 14 ( Transfer step). In this case, the cushion layer 12 does not necessarily have to be peeled off together with the temporary support 10.

After the transfer, 7
The color is developed by heating to a temperature of 0 to 120 ° C. As shown in FIG. 3G, an exposure mask 28 having a plurality of regions having different light transmittances is disposed above the alignment film 14, and the first light is transmitted through the mask 28 through the cholesteric liquid crystal layer. 16
Is irradiated in a pattern. After the irradiation, the material is heated to a temperature capable of forming a liquid crystal state exhibiting a selective reflection wavelength corresponding to the photoreactive chiral compound isomerized according to the light irradiation amount. In the cholesteric liquid crystal layer 16, regions having different helical pitches depending on the light irradiation amount reflect, for example, green (G), blue (B) and red (R), and blue (B). A region for transmitting green (G) and red (R),
It is formed so as to form a region that reflects red (R) and transmits green (G) and blue (B).

Next, as shown in FIG. 5H, the cholesteric liquid crystal layer 16 is further irradiated with ultraviolet rays at an irradiation intensity different from the light irradiation in the step (G) to fix the pattern. Thereafter, unnecessary portions on the cholesteric liquid crystal layer 16 (for example, remaining portions such as a cushion layer and an intermediate layer, and unexposed portions) are removed by alkali development using 2-butanone, chloroform, or the like.
As shown in (I), a cholesteric liquid crystal layer (selective reflection film) having a BGR reflection region can be formed.

The method shown in FIGS. 1 to 3 is an embodiment of a method for manufacturing a color filter by a lamination method, but may be a method by a coating method in which a liquid crystal layer is directly formed on a color filter substrate. . In this case, when applied to the above embodiment, the cholesteric liquid crystal composition is applied on the alignment film 24 of the color filter substrate 26 shown in FIG. The steps shown in I) are sequentially performed. Regarding these steps and materials such as a transfer material and a support to be used, Japanese Patent Application No. 11-342896 and Japanese Patent Application No.
It is described in detail in each specification of JP-343665.

The selective reflection film of the present invention can be used for a display device such as an LCD, for example, a retardation film, a color filter, a laminated color filter, a circularly polarized light reflection plate, and a transmission type LCD
It can be suitably used for a brightness enhancement film for use.

[0074]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (Example 1) (1) Preparation of filter substrate A polyimide alignment film (LX-1400, manufactured by Hitachi Chemical DuPont) was applied on a glass substrate by a spin coater and dried in an oven at 100 ° C for 5 minutes. , 25
The alignment film was formed by baking for 1 hour in an oven at 0 ° C. Further, the surface of the film was subjected to an orientation treatment by a rubbing treatment to produce a glass substrate with an orientation film.

(2) Formation of Filter Layer On the alignment film of the glass substrate provided with the alignment film obtained above, a coating liquid (1) for a photosensitive liquid crystal layer prepared according to the following formulation was applied by a spin coater. In an oven at 100 ° C for 2
After drying for a minute, a photosensitive liquid crystal layer was formed. The clear point (Iso point) of the photosensitive liquid crystal layer after drying was 108 ° C. When the layer thickness was measured with a confocal microscope, it was 2.2 μm.

[0076]

Embedded image

Next, contact is made on the surface of the glass substrate.
Hold on a hot plate at 80 ° C for 3 minutes.
The crystal layer was oriented (colored). At this temperature, the photosensitive liquid crystal
The layer becomes a liquid crystal phase and shows selective reflection at a center wavelength of 540 nm.
did. Subsequently, an opening of 80 μm was formed on the photosensitive liquid crystal layer.
Photomask with width and transmission center wavelength at 365nm
An ultra-high pressure mercury lamp is placed via an interference filter, and this
With ultra-high pressure mercury lamp through photomask and interference filter
3 seconds (irradiation intensity 15 mW / cm^Two) Shi Patani
I did. At this time (80 ° C.), the light irradiation part of the photosensitive liquid crystal layer
Showed selective red reflection. After irradiation, the alignment state becomes uniform
After holding at 80 ° C for 3 minutes under nitrogen atmosphere
Through an interference filter having a transmission center wavelength at 312 nm.
And irradiate with an ultra-high pressure mercury lamp for 10 seconds (irradiation intensity 100
mW / cm ^Two) And cured. As described above,
A selective reflection film was formed on a substrate.

The film strength of the cured selective reflection film (photosensitive liquid crystal layer) was measured using a pencil photometer, and the scratch resistance was evaluated. The hardness was 3H. Further, when this selective reflection film was further heated at 250 ° C. for 1 hour and subjected to a high-temperature heat resistance test (heat resistance evaluation), the selective reflection wavelength changed only by 10 nm to the short wavelength side.

Example 2 First, a glass substrate with an alignment film was produced in the same manner as in Example 1. Subsequently, a filter layer was formed as shown below. A photosensitive liquid crystal layer coating solution (2) prepared according to the following formulation was applied on the alignment film of the glass substrate with an alignment film by a spin coater, and dried in a 100 ° C. oven for 2 minutes to obtain a photosensitive liquid crystal layer. A liquid crystal layer was formed. In addition, of the photosensitive liquid crystal layer after drying,
The point was 107.5 ° C. When the layer thickness was measured with a confocal microscope, it was 2.1 μm.

[0080]

Embedded image

Next, the substrate was kept on a hot plate at 80 ° C. for 3 minutes so as to be in contact with the surface of the glass substrate, and the photosensitive liquid crystal layer was oriented (colored). At this temperature, the photosensitive liquid crystal layer became a liquid crystal phase and exhibited selective reflection at a center wavelength of 465 nm. Subsequently, an opening is formed on the photosensitive liquid crystal layer with a line width of 80.
An ultra-high pressure mercury lamp is arranged via a striped photomask having an aperture pitch of 270 μm and an interference filter having a transmission center wavelength at 365 nm, and irradiation is performed for 1 second by the ultrahigh pressure mercury lamp through the photomask and the interference filter (irradiation intensity). 15 mW / cm ² ) and patterned. At this time (80 ° C.), the light-irradiated portion of the photosensitive liquid crystal layer showed green selective reflection. Subsequently, the photomask was moved in the line width direction by 90 μm steps, and irradiated in the same manner as described above (using the interference filter and the ultra-high pressure mercury lamp) for 3 seconds. Then, the light-irradiated part of the photosensitive liquid crystal layer showed red selective reflection. The unirradiated part of the photosensitive liquid crystal layer showed blue selective reflection (alignment step). As described above, a multi-color selective reflection film showing selective reflection in green, red, and blue was formed on the glass substrate. After the irradiation, the film is kept at 80 ° C. for 3 minutes so that the alignment state becomes uniform, and then, under a nitrogen atmosphere, 312 n
m for 10 seconds with an ultra-high pressure mercury lamp through an interference filter having a transmission center wavelength at m (irradiation intensity 100 mW / c
m ² ) and cured.

The film strength of the cured selective reflection film (photosensitive liquid crystal layer) was measured using a pencil photometer, and the scratch resistance was evaluated. The hardness was 2H. Further, when this selective reflection film was further heated at 250 ° C. for 1 hour and subjected to a high-temperature heat resistance test (heat resistance evaluation), the selective reflection wavelength changed only by 10 nm to the short wavelength side.

Comparative Example 1 First, a glass substrate with an alignment film was manufactured in the same manner as in Example 1. Subsequently, a filter layer was formed as shown below. A photosensitive liquid crystal layer coating solution (3) prepared by the following formulation was applied on the alignment film of the glass substrate with an alignment film by a spin coater, and dried in an oven at 100 ° C. for 2 minutes to obtain a photosensitive liquid. A liquid crystal layer was formed. The clear point (Iso point) of the photosensitive liquid crystal layer after drying was 115.5 ° C. When the layer thickness was measured with a confocal microscope, it was 2.1 μm.

[0084]

Embedded image

Next, the substrate was kept on a hot plate at 80 ° C. for 3 minutes so as to be in contact with the surface of the glass substrate, and the photosensitive liquid crystal layer was oriented (colored). At this temperature, the photosensitive liquid crystal layer became a liquid crystal phase and exhibited selective reflection at a central wavelength of 515 nm. Subsequently, an opening of 80 μm was formed on the photosensitive liquid crystal layer.
An ultra-high pressure mercury lamp is arranged via a photomask having a width and an interference filter having a transmission center wavelength at 365 nm, and irradiation is performed for 3.5 seconds (irradiation intensity: 15 mW / cm ² ) by the ultra-high pressure mercury lamp through the photomask and the interference filter. And patterned. At this time (80 ° C.), the light-irradiated portion of the photosensitive liquid crystal layer showed red selective reflection. After the irradiation, the film was kept at 80 ° C. for 3 minutes so that the alignment state became uniform. Then, the film was irradiated with an ultra-high pressure mercury lamp for 10 seconds under an atmosphere of nitrogen through an interference filter having a transmission center wavelength of 312 nm (irradiation intensity of 10).
0 mW / cm ² ) and cured.

The film strength of the cured selective reflection film (photosensitive liquid crystal layer) was measured using a pencil photometer, and the scratch resistance was evaluated. The hardness H was only 1H.
Further, when the selective reflection film was further heated at 250 ° C. for 1 hour and subjected to a high-temperature heat resistance test (heat resistance evaluation), the selective reflection wavelength changed by 50 nm to the shorter wavelength side.

[0087]

According to the present invention, a good orientation treatment is performed, and the image characteristics required for a color image (a wide range of selective reflection areas, high color purity, high resolution, high transmittance) and optical characteristics (intrinsic) It is possible to provide a selective reflection film that is excellent in birefringence Δn and selective reflection peak) and particularly excellent in heat resistance and scratch resistance.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state in which a selective reflection film of the present invention is formed on a substrate.

FIG. 2 is a schematic view showing that a selective reflection film of the present invention is formed on a substrate.

FIG. 3 is a schematic view showing a state where a selective reflection film having three colors of RGB is formed like an image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Temporary support 12 ... Cushion layer (thermoplastic resin layer) 14, 24 ... Orientation film 16 ... Cholesteric liquid crystal layer 20 ... Transfer sheet 22 ... Substrate (support) 26 ... Color filter substrate 28 ... Exposure mask

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G02F 1/1335 520 G02F 1/1335 520 1/13363 1/13363 F term (Reference) 2H048 BA04 BA64 BB02 BB14 BB42 2H049 BA03 BA06 BA18 BA43 BC04 BC05 BC08 BC22 2H091 FA02X FA02Z FA08X FA08Z FA11X FA11Z FA14Z FC01 GA06 KA01 KA10 LA02 LA04

Claims (6)

[Claims] 1. A selective reflection film formed using a liquid crystal composition, wherein the liquid crystal composition is a rod-shaped liquid crystal compound having at least three polymerizable groups in the same molecule, and a chiral compound. And a polymerization initiator. 2. The selective reflection film according to claim 1, wherein the chiral compound is a photoreactive chiral compound. 3. The selective reflection film according to claim 1, wherein the liquid crystal composition contains an air interface alignment agent. 4. The content of the rod-shaped liquid crystalline compound having at least three polymerizable groups in the same molecule is 40% by mass or more of the total solid content (mass) of the liquid crystalline composition. The selective reflection film according to any one of the above. 5. The liquid crystal composition is formed by imagewise exposing the liquid crystal composition to light with a first light, patterning the liquid crystal composition, and then photopolymerizing and curing with a second light.
The selective reflection film according to any one of the above. 6. The selective reflection film according to claim 1, wherein the selective reflection film has two or more regions having different selective reflection wavelengths provided on a substrate.