JP2002341126A - Selective reflection film and liquid crystal color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a selective reflection film without uneven reflectance and chrominance non-uniformity of selectively reflected light and a liquid crystal color filter containing the same. SOLUTION: The selective reflection film is constructed by containing an organic substance with a helical structure of which the helical axis is fixed by polymerization, cross-linking or transition into a vitreous state in the aligned state in parallel with the normal and exhibits selective reflection ranging from the ultraviolet rays to the infrared rays region. In the selective reflection film the optical path length of the film thickness difference between the thickest part and the thinnest part is a half of the selective reflection wavelength or less. The optical path lengths of the film thickness differences are preferably a quarter of the selective reflection wavelength.

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 used for a circularly polarized light reflection plate and the like, and a liquid crystal color filter.

[0002]

2. Description of the Related Art In recent years, liquid crystal materials such as cholesteric liquid crystals having a helical structure and exhibiting various selective reflection colors due to the twisting force (twist angle) of the spiral have attracted attention. Because of its excellent color purity of reflected light, it is widely used for optical films, liquid crystal color filters, recording media, and the like. For example, a color filter used for a color liquid crystal display or the like generally includes red (R), green (G), and blue (B) pixels, and a black matrix for the purpose of improving display contrast is formed between the pixels. It is composed. Conventionally, such a color filter is mainly one in which a pigment is dispersed in a resin or a dye is dyed, and the manufacturing method is also to apply a colored resin liquid onto a glass substrate by spin coating or the like. Forming a colored resist layer and patterning by photolithography to form color filter pixels,
A method of printing colored pixels directly on a substrate has been common.

[0003] However, for example, the manufacturing method by the printing method has a disadvantage that it is difficult to form a high-definition image pattern with a low pixel resolution, and the manufacturing method by the spin coating method causes a large material loss and a large loss. There is a drawback that coating unevenness when coating on a substrate having a large area is large. Further, according to the production method by the electrodeposition method, it is possible to obtain a color filter having relatively high resolution and less unevenness of the colored layer, but has a disadvantage that the production process is complicated and liquid management is difficult. As described above, as a process for manufacturing a color filter, a manufacturing method capable of easily and easily manufacturing a high-quality color filter with little material loss has been demanded.

On the other hand, the performance of a color filter is as follows.
High transmittance and high color purity are required.In recent years, the method using dyes has improved the above-mentioned requirements by optimizing the type of dye and the dyeing resin, and using the pigments by using finely dispersed pigments. Has been planned. However, in recent liquid crystal display (LCD) panels, there is an extremely high demand for the transmittance and color purity of a color filter. In particular, in a color filter for a reflective LCD, compatibility between white display of paper white, contrast, and color reproducibility is high. On the other hand, in the conventional manufacturing method, the color filter manufactured by dyeing the dye in the resin or dispersing the pigment is a light absorption type color filter. The improvement of color purity by the improvement has almost reached the limit.

[0005] Under such circumstances, a polarization type color filter (cholesteric film) mainly composed of cholesteric liquid crystal is known. This color filter using polarized light reflects a certain amount of light and transmits the rest to display an image, so that the light use efficiency is high, the transmittance,
In terms of color purity, it has more excellent performance than light absorption type color filters. On the other hand, in the manufacturing method, from the viewpoint of obtaining a uniform thickness, a method of forming a film on a substrate by using a spin coating method or the like has been generally performed. Was disadvantageous.

A method using a photoreactive chiral compound is useful as a means for solving the above problems, ensuring uniformity of the color purity and the like of the color filter film, and reducing the number of manufacturing steps. It is. In this method, when a liquid crystal composition containing a photoreactive chiral compound is irradiated with light having a reaction wavelength of the chiral compound in a pattern, the reaction of the chiral compound proceeds according to the intensity of the irradiation energy, and Since the helical pitch (helical twist angle) changes, the principle is used that a selective reflection color is formed for each pixel only by pattern exposure with a light amount difference. That is, there is an advantage that the number of times of patterning at the time of forming the color filter can be completed by one mask exposure using masks having different transmitted light amounts. Therefore, a film functioning as a color filter can be formed by immobilizing the patterned cholesteric liquid crystal compound after patterning by imagewise light irradiation. this is,
It can also be applied to optical films and image recording.

The shape of the selective reflection spectrum of the cholesteric film as described above increases as the film thickness increases, and the selective reflection intensity increases, and this tendency continues up to a certain film thickness. After that, the spectral shape does not change even when the film thickness increases. The constant film thickness becomes smaller as the liquid crystal has larger anisotropy of the refractive index. Therefore, in theory, when a cholesteric film is applied to a color filter or the like, if the cholesteric film is used at a certain film thickness or more, the optical characteristics are excellent in being hardly affected by unevenness in the thickness. However, in practice, even when the cholesteric film is used at a certain film thickness or more, many color unevenness may appear on the cholesteric film, and in some cases, the color unevenness appears in a striped pattern and the display quality is significantly deteriorated. May be invited. This color unevenness is difficult to see with vertically incident circularly polarized light, and is more easily seen with obliquely incident circularly polarized light or natural light. Further, even when this cholesteric is observed with a polarizing microscope in a crossed Nicols state, the color unevenness can be recognized.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a selective reflection film having no reflectance unevenness or color unevenness of selectively reflected light, and a selective reflection film including the same. It is to provide a liquid crystal color filter.

[0009]

The present inventors have found from the detailed observation of the phase transition temperature that the above-mentioned color unevenness is not due to the unevenness of the pitch of the cholesteric liquid crystal. The inventors have found that the color unevenness is related to the unevenness of the film thickness (optical thickness) of the cholesteric film, and have reached the present invention. That is, the present invention provides <1> an organic substance having a helical structure, in a state in which the helical axis of the helical structure is oriented so as to be substantially parallel to the normal line, in a polymerized or crosslinked state or in a glassy state. It is a selective reflection film that is fixed by being transferred and exhibits selective reflection in a range from ultraviolet light to infrared light, and in the selective reflection film,
The selective reflection film is characterized in that the optical distance of the difference in film thickness between the maximum film thickness part and the minimum film thickness part is １ ／ or less of the selective reflection wavelength.

<2> In the selective reflection film, the optical distance of the difference in film thickness between the maximum film thickness part and the minimum film thickness part is １ ／ or less of the selective reflection wavelength. > Is a selective reflection film. <3> The selective reflection film according to <1> or <2>, wherein the organic substance is a liquid crystal compound or a liquid crystal composition. <4> The selective reflection film according to <3>, wherein the liquid crystal composition contains a liquid crystal compound having at least one polymerizable group, a chiral compound, and a polymerization initiator. <5> The selective reflection film according to <3>, wherein the liquid crystal composition contains a liquid crystal compound having at least one polymerizable group, a photoreactive chiral compound, and a polymerization initiator. <6> The selective reflection film according to any one of <3> to <5>, wherein the liquid crystal composition further contains a surfactant having an excluded volume effect distributed on the air interface side. It is.

<7> A liquid crystal color filter comprising the selective reflection film according to any one of <1> to <6>.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a selective reflection film and a liquid crystal color filter according to the present invention will be described. The selective reflection film of the present invention comprises an organic substance having a helical structure, and the helical axis of the helical structure is oriented so as to be substantially parallel to the normal line of the selective reflection film, so that polymerization or crosslinking or It is fixed by transition to a glass state and exhibits selective reflection in the range from ultraviolet light to infrared light. In the selective reflection film, the optical distance of the difference in film thickness between the maximum film thickness portion and the minimum film thickness portion (each film thickness) Of the selective reflection film, hereinafter referred to as “thickness unevenness”) is １ ／ or less of the selective reflection wavelength.

FIG. 1 is a graph showing the value of x on the chromaticity diagram of the reflection color of a cholesteric film having the same helical pitch (about 0.39 μm) as a function of the thickness of the cholesteric film. In this case, right-handed cholesteric liquid crystal is irradiated with right-handed circularly polarized light at an incident angle of 35 degrees. From FIG. 1, the value of x increases and decreases in a cycle of the film thickness of about 0.2 μm, which indicates that the selective reflection spectrum of the cholesteric film changes with the film thickness. Similarly, since the brightness varies depending on the film thickness, if the cholesteric film has uneven thickness, a bright and dark stripe pattern appears correspondingly. For unknown reasons, this cycle is
Considering that the peak of the selective reflection in this case is about 530 nm, it is about 1/2 of the thickness unevenness. Therefore, in the present invention, in order to eliminate the appearance of the striped pattern, the thickness unevenness is set to １ ／ or less of the selective reflection wavelength. The thickness unevenness is more preferably １ ／ or less of the selective reflection wavelength.

In the selective reflection film of the present invention, the organic substance is preferably a liquid crystal compound or a liquid crystal composition. In the case of the liquid crystal composition, a liquid crystal compound having at least one polymerizable group, a chiral compound, It preferably contains a compound or a photoreactive chiral compound and a polymerization initiator.

The liquid crystal composition preferably further contains a surfactant having an excluded volume effect distributed on the air interface side. For example, in the case of applying a liquid crystal composition in the form of a coating liquid to form a layer, the alignment state at the air interface on the layer surface can be controlled three-dimensionally. Obtainable. Details of this surfactant will be described later.

(Photoreactive Chiral Compound) The photoreactive chiral compound contained in the liquid crystal composition can control the orientation of the liquid crystal compound and change the helical pitch of the liquid crystal by light irradiation. More specifically, the photoreactive chiral compound is a liquid crystal,
Preferably, when used in combination with a nematic liquid crystal compound, the helical structure of the liquid crystal is changed, and when light of a certain wavelength is irradiated, a photoreactive chiral compound having a wavelength sensitive to the wavelength region is sensitive to the liquid crystal. Compound twisting force (HT)
P: helical twisting power). That is, it is a compound that causes a change in the twisting force of the helical structure induced in the liquid crystal phase by light irradiation (ultraviolet light to visible light to infrared light), and a chiral part and a part that undergoes structural change by light irradiation within the same molecule. Prepare.

In addition, when the liquid crystal phase is a cholesteric liquid crystal phase, the selective reflection of the liquid crystal can be arbitrarily changed according to the HTP of the photoreactive chiral compound, and B (blue), G (green) ) And R (red) can be selectively reflected over a wide wavelength range including the three primary colors. The selective reflection characteristic of the light wavelength is determined by the torsion angle of the helical structure of the liquid crystal molecules. As the angle changes greatly, the color width of the selective reflection becomes wider and useful.

The HTP represents the twisting force of the helical structure of the liquid crystal, that is, HTP = 1 / (pitch × concentration of chiral compound [mass fraction]). For example, the helical pitch of liquid crystal molecules at a certain temperature (HTP) One period of the helical structure; μm) is measured, and this value can be calculated by converting [μm ⁻¹ ] from the concentration of the chiral compound. In the case where a selective reflection color is formed by illuminance of light using a photoreactive chiral compound, the rate of change of HTP (= HTP before irradiation / HTP after irradiation) is as follows. 5 or more is preferable, and 2.5 or more is more preferable.
Is preferably 0.7 or less, more preferably 0.4 or less.

When the photoreactive chiral compound has a structure in which one or more polymerizable bonding groups are introduced in the same molecule, a liquid crystal composition containing the photoreactive chiral compound, for example, a liquid crystal Heat resistance of a color filter, an optical film, and the like can be improved.

Hereinafter, specific examples of the photoreactive chiral compound will be shown, but the present invention is not limited thereto.

[0021]

Embedded image

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 which undergoes a decomposition, an addition reaction, an isomerization, a dimerization reaction, or the like upon irradiation with light and undergoes 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).

[0024]

Embedded image

As the photoreactive chiral compound having both a chiral moiety and a photoisomerizable moiety, the following compounds can be exemplified.

[0026]

Embedded image

The addition amount of the photoreactive chiral compound is preferably 5 to 20% by mass based on the solid content of the liquid crystal composition.

(Chiral compound) As the chiral compound, from the viewpoint of improving the hue and color purity of the liquid crystal compound, there can be mentioned isomanide, catechin, isosorbide, fencon, carvone and the like. In addition, for example,
JP-A-00-44451, JP-T-10-509726, WO98 / 00428, JP-T-2000-5068
No. 73, Japanese Patent Application Laid-Open No. 9-506088, Liqu
id Crystals 1996, 21, 327, L
liquid Crystals 1998, 24, 21
9 and the like.

The amount of the chiral compound is preferably 5 to 30% by mass based on the solid content of the liquid crystal composition.

The above-mentioned chiral compounds can be used in combination with the above-mentioned photoreactive chiral compounds.

(Liquid Crystal Compound) The liquid crystal compound is appropriately selected from low molecular liquid crystal compounds, high molecular liquid crystal compounds and polymerizable liquid crystal compounds having a refractive index anisotropy Δn of 0.10 to 0.40. can do. Among them, a nematic liquid crystal compound is preferable. These liquid crystalline compounds can be aligned while in a liquid crystal state at the time of melting, for example, by using an alignment substrate that has been subjected to an alignment treatment such as a rubbing treatment. In the case where the liquid crystal state is solid phase and immobilized, means such as cooling and polymerization can be used.

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

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

In the above formula, n represents an integer of 1 to 1000. In each of the above exemplified compounds, those in which the connecting group of the aromatic ring is changed to the following structure can also be mentioned as suitable compounds.

[0037]

Embedded image

Among the above, as the liquid crystal compound, from the viewpoint of ensuring sufficient curability and ensuring the heat resistance of the layer,
Liquid crystalline compounds having at least one polymerizable group or crosslinkable group in the molecule are preferred.

The content of the liquid crystal compound is preferably from 30 to 99.9% by mass, more preferably from 50 to 95% by mass, based on the solid content of the liquid crystal composition.

(Photopolymerization Initiator) In order to fix the helical structure of the liquid crystal after changing the torsional force by light irradiation, when a polymerization reaction by a liquid crystal compound having a polymerizable group is used, photopolymerization is required. It is preferred to add an initiator. Also,
After the formation of the desired helical structure, the polymerization and curing reaction of the liquid crystal composition is preferably rapid in order to fix the structure.

The photopolymerization initiator can be appropriately selected from known ones, for example, p-methoxyphenyl-2,4-bis (trichloromethyl) -s-triazine, 2- (p-butoxy) (Styryl) -5-trichloromethyl-1,3,4-oxadiazole, 9-phenylacridine, 9,10-dimethylbenzphenazine, benzophenone / Michler's ketone, hexaarylbiimidazole / mercaptobenzimidazole, benzyldimethylketal, thioxanthone / Amines, triarylsulfonium hexafluorophosphate,
Bisacylphosphine oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide described in JP-A-10-29997; Luci;
acyl phosphine oxides described in DE 4230555 of rin TPO and the like.

As the photopolymerization initiator, it is preferable to select a photopolymerization initiator having a photosensitive wavelength range different from the photosensitive wavelength range of a photoreactive chiral compound described later. Here, having different photosensitive wavelengths means that the photosensitive central wavelengths of the two do not overlap and, for example, the liquid crystals are not mutually exposed at the time of image exposure or polymerization curing so as not to cause a decrease in hue purity due to image display characteristics and selective reflection. This means that the orientation is not changed. In order to prevent the photosensitive central wavelengths from overlapping each other, the wavelengths of light irradiated through a band-pass filter or the like may be controlled in addition to the molecular structures of the two.

The amount of the photopolymerization 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 of the liquid crystal composition.

(Polymerizable monomer) The liquid crystal composition includes:
A polymerizable monomer may be used in combination. When the polymerizable monomer is used in combination, the distribution of the selective reflection wavelength is formed (patterned) by changing the torsional force of the liquid crystal by light irradiation, and then the helical structure (selective reflectivity) is fixed, and the liquid crystal composition after fixing is fixed. The strength of the object can be further improved. However, when the nematic liquid crystalline compound has an unsaturated bond in the same molecule, it is not always necessary to add the compound.

The polymerizable monomer includes, for example, a monomer having an ethylenically unsaturated bond, and specifically, a polyfunctional monomer 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.

[0046]

Embedded image

The amount of the polymerizable monomer to be added is preferably 0.5 to 50% by mass based on the weight of the solid content of the liquid crystal composition.

(Other Components) Further, other components include a binder resin, a solvent, a surfactant, a polymerization inhibitor, a thickener,
Dyes, pigments, ultraviolet absorbers, gelling agents and the like can also be added. Examples of the binder resin include polystyrene, polystyrene compounds such as poly-α-methylstyrene, cellulose resins such as methyl cellulose, ethyl cellulose and acetyl cellulose, acidic cellulose derivatives having a carboxyl group in a side chain, polyvinyl formal, polyvinyl butyral, and the like. Acetal resin of JP-A-59-44615, JP-B-54-34327, JP-B-58-12577, JP-B-54-25957,
Methacrylic acid copolymers and acrylic acid copolymers described in JP-A-59-53836 and JP-A-59-71048;
Examples include an itaconic acid copolymer, a crotonic acid copolymer, a maleic acid copolymer, a partially esterified maleic acid copolymer, and the like.

The homopolymer of an alkyl acrylate and the homopolymer of an alkyl methacrylate are also mentioned. In these, the alkyl group is a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an
-Butyl group, n-hexyl group, cyclohexyl group, 2-
Examples thereof include an ethylhexyl group. 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.

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

In the liquid crystal composition, it is preferable to use a surfactant together with a photoreactive chiral compound and a liquid crystal, preferably a nematic liquid crystal compound. As the surfactant, a surfactant having an excluded volume effect is preferable. Here, exerting the excluded volume effect means, for example, when a layer containing a liquid crystal composition is formed by coating, three-dimensionally controlling the spatial alignment state at the air interface on the surface of the layer. Specifically, a nonionic surfactant is preferable, and a nonionic surfactant can be appropriately selected from known nonionic surfactants.

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 the above-mentioned components in an appropriate solvent. The liquid crystal composition can be formed into an arbitrary shape or formed on a support or the like. Here, examples of the solvent include 2-butanone, cyclohexanone, methylene chloride, chloroform and the like.

The selective reflection film of the present invention is formed by applying a coating solution of the above liquid crystal composition on the substrate surface. To make the thickness unevenness less than 以下 of the selective reflection wavelength, for example, A coating solution may be prepared and applied by selecting a solvent having an appropriate viscosity. In addition, if the coating liquid has a boiling point of
A method of adjusting the drying rate by using a solvent at 0 ° C. or higher is used. In this case, the drying speed is reduced to reduce the thickness unevenness.

<Change in Helical Structure of Liquid Crystal> As described above, the liquid crystal composition of the present invention contains a photoreactive chiral compound, and the liquid crystal composition of the present invention is irradiated with light in a pattern by changing the amount of light. By changing the twisting force of the liquid crystal, it is possible to form a twisted structure of the liquid crystal, that is, regions having different degrees of twisting of the spiral (twisting force; HTP).

In particular, when the liquid crystal phase is a cholesteric liquid crystal phase, the selective reflection color of the liquid crystal can be arbitrarily changed according to the twisting force. When the change rate of the twisting force (torsion change rate) is large, the color width of the selective reflection color that the liquid crystal can selectively reflect is widened, and the selective reflection in a wide wavelength range including the three primary colors (B, G, R) is performed. It is possible to obtain

Specifically, it can be performed as follows. That is, when the liquid crystal composition is irradiated with light of a certain wavelength, the co-existing photoreactive chiral compound responds to the irradiation intensity to change the helical structure (twist angle) of the liquid crystal, and this selective change causes a different selective reflection. An image-like pattern showing a color is formed (patterning). Therefore, if light irradiation is performed while changing the irradiation intensity 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. This light irradiation can be performed without any particular limitation as long as the irradiation intensity can be changed for each desired region, in addition to the method using an exposure mask. In the case of forming a liquid crystal color filter, an optical film, or the like described below, after patterning by exposing the light of a certain wavelength imagewise as described above, the polymerizable group in the liquid crystal composition is further irradiated with light. The polymer is cured by photopolymerization, and the helical structure of the liquid crystal is fixed to a desired selective reflection color. Details of these forming methods will be described later.

The light source used for light irradiation is preferably a light source that emits ultraviolet light because it has a high energy and can rapidly change the structure of a liquid crystal compound and rapidly perform a polymerization reaction. Examples thereof include a high-pressure mercury lamp, a metal halide lamp, and an Hg-Xe lamp. And the like. Further, it is preferable to have a light quantity variable function.

<Immobilization of spiral structure of liquid crystal>
By irradiating light of a specific wavelength to the photoreactive chiral compound, the twisting force of the coexisting liquid crystal can be changed to change the helical structure. The liquid crystal composition of the present invention comprises at least one liquid crystal compound having a polymerizable group, a photopolymerization initiator, and a photoreactive chiral compound. Then, by polymerizing or cross-linking the liquid crystal compound, the changed helical structure can be fixed, and the strength of the liquid crystal composition after the fixing can be further improved. It is preferable that the photopolymerization initiator and the photoreactive chiral compound have different sensitive wavelength ranges.

Specifically, it can be performed as follows. That is, first, the above-mentioned “change in the helical structure of liquid crystal”
As in the case of the patterning described in 1 above, light in the photosensitive wavelength region of the optically active compound in the liquid crystal composition is irradiated imagewise. By this light irradiation, the optically active compound responds and changes the helical structure of the liquid crystal to form an image-like pattern (patterning). After this patterning, light in the sensitive wavelength region of the photopolymerization initiator in the liquid crystal composition is irradiated. Then, the liquid crystal compound is polymerized by the photopolymerization initiator, and is fixed while maintaining the changed helical structure. Before this step, for example, a step such as nitrogen substitution may be provided.

When the photosensitive wavelength region of the optically active compound is different from the photosensitive wavelength region of the photopolymerization initiator, light irradiation for changing HTP and light irradiation for photopolymerization do not affect each other. . Therefore, when imagewise exposed to change the HTP, photopolymerization does not proceed, so that patterning with the HTP change rate as set becomes possible, while photopolymerization to fix the helical structure is performed. The optically active compound does not react to light, and the formed HTP change pattern can be reliably immobilized.

In the case of forming a liquid crystal color filter, an optical film or the like to be described later, after light is imagewise exposed to light having a wavelength to which the optically active compound is sensitive as described above, a photopolymerization initiator is further added. The polymerizable group in the liquid crystal composition is photopolymerized and cured by irradiation with light having a sensitive wavelength, and the helical structure of the liquid crystal is fixed to a desired selective reflection color. Details of these forming methods will be described later.

The light source used for light irradiation is the same as the light source exemplified in the above description of the “change in the helical structure of the liquid crystal”.

The above is a method of immobilization by polymerization. For example, it may be immobilized by crosslinking by vulcanization or by transition to a glassy state.

<Liquid Crystal Color Filter> The liquid crystal color filter of the present invention has the above-mentioned structure of the present invention. It can be manufactured by irradiating light with a desired pattern and light amount appropriately selected based on the above-mentioned “change of the helical structure of the liquid crystal” or “fixation of the helical structure of the liquid crystal”.

Hereinafter, the liquid crystal color filter of the present invention will be described in detail through the description of the method of manufacturing the liquid crystal color filter. The liquid crystal color filter of the present invention can be produced from the above-mentioned liquid crystal composition of the present invention, and has the above-mentioned selective reflection film of the present invention.

The method for producing the liquid crystal color filter is not particularly limited. For example, a step of imagewise exposing with a first light and patterning, followed by photopolymerization with a second light and curing (hereinafter, referred to as a step). The manufacturing method may include at least one step of “exposure step”. In addition, a step of appropriately subjecting the contact surface with the liquid crystal composition to an alignment treatment (alignment treatment step), a step of transferring and forming a liquid crystal layer by adhesion / peeling (transfer step), and a nematic liquid crystal composition according to a selected production mode. May be formed through a step of applying a liquid crystal layer to form a liquid crystal layer (coating step).

Hereinafter, a specific embodiment will be described as an example of the manufacturing method including the above-mentioned exposure step. -Exposure Step- In the exposure step, both patterning and fixing (polymerization curing) of the liquid crystalline compound are performed by light irradiation. That is, after the photoreactive chiral compound is imagewise exposed and patterned by the first light having a wavelength sensitive to high sensitivity,
The polymerization initiator is photopolymerized and cured by the second light which can be sensitively sensitive, and the helical structure of the liquid crystal compound is fixed to a desired selective reflection color.

When the liquid crystal composition is irradiated with the first light, the coexisting photoreactive chiral compound responds to the illuminance to change the helical structure of the liquid crystal. A color-like image-like pattern is formed. Therefore, if light irradiation is performed while changing the irradiation intensity 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. By doing so, the image can be
That is, colored regions that perform different selective reflections can be formed simultaneously. Further, a liquid crystal color filter can be manufactured by irradiating second light and curing (fixing) the second light.

The wavelength of the first light is preferably set in the light-sensitive wavelength range of the photoreactive chiral compound, particularly in a wavelength close to the light-sensitive peak wavelength, in that sufficient patterning sensitivity can be obtained. Further, it is preferable that the wavelength of the second light be set in a light-sensitive wavelength range of the polymerization initiator, in particular, a wavelength close to the 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. As the light source used for the irradiation of the first and second lights, the same light sources as those usable for the light irradiation of the liquid crystal composition can be used.

More specifically, the manufacturing method according to the first and second embodiments described below may be used, and the manufacturing method can be more suitably performed according to these two embodiments. [First Embodiment] (1) A step of providing a coating liquid crystal composition on a temporary support to form a transfer material having at least a liquid crystal layer. The liquid crystal composition in the coating liquid can be prepared by dissolving and dispersing each component in an appropriate solvent. Here, as the solvent,
For example, 2-butanone, cyclohexanone, methylene chloride, chloroform and the like can be mentioned. 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. Preferably, the surface of the cushion layer or the like is preferably subjected to an orientation treatment (orientation treatment step) such as a rubbing treatment. (2) a step of laminating the transfer material on a light transmissive substrate; In addition to the light transmitting substrate, an image receiving material having an image receiving layer on a base may be used. Further, the liquid crystal composition may be formed directly on the substrate without using the transfer material (coating step). Coating can be appropriately selected from known coating methods using a bar coater, a spin coater, or the like. However, the transfer method is preferable in terms of material loss and cost.

(3) A step of removing the transfer material from the light-transmitting substrate to form a cholesteric liquid crystal layer on the substrate (transfer step). The liquid crystal layer may be formed of a plurality of layers by further laminating after the following (4). (4) A step of irradiating the cholesteric liquid crystal layer with an imagewise ultraviolet ray through an exposure mask to form a pixel pattern showing a selective reflection color through an exposure mask, and further irradiating the pixel pattern with an ultraviolet ray of illuminance ν2 to cure the layer ( Exposure step).

[Second Aspect] (1) A step of providing a liquid crystal composition directly on a support constituting a color filter to form a liquid crystal layer. Here, the liquid crystal layer can be formed by applying a liquid crystal composition 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 temporary support. The surface of the alignment film or the like is preferably subjected to an alignment treatment (alignment treatment step) such as a rubbing treatment.

(2) An exposure step similar to step (4) of the first embodiment. The thickness of the liquid crystal layer (sheet-like liquid crystal composition) functioning as a liquid crystal color filter is preferably 1.5 to 4 μm.

Further, a description will be given below with reference to FIGS. 2 to 4 are schematic views showing one embodiment of a process for manufacturing the liquid crystal color filter of the present invention. First, the components described above are dissolved in an appropriate solvent to prepare a coating liquid cholesteric liquid crystal composition. Here, each component and solvent are as described above.

As shown in FIG. 2A, a support 10 (hereinafter, also referred to as a “temporary support”) is prepared, and an acrylic resin, polyester, polyurethane, or the like is formed on the support 10 by coating. Cushion layer (thermoplastic resin layer) 12
And an alignment film 1 made of polyvinyl alcohol or the like.
4 is laminated. The alignment film is subjected to a rubbing treatment as shown in FIG. This rubbing treatment is not always necessary, but the rubbing treatment can further improve the orientation. Next, FIG.
As shown in (C), a coating liquid cholesteric liquid crystal composition is applied on the alignment film 14 and dried to form a cholesteric liquid crystal layer 16, and then a cover film 18 is provided on the cholesteric liquid crystal layer 16, Create a transfer material. Hereinafter, the transfer material is referred to as a transfer sheet 20.

On the other hand, as shown in FIG. 2D, another support 22 is prepared, an alignment film 24 is formed on the support in the same manner as described above, and the surface is subjected to a rubbing treatment. Hereinafter, this is referred to as a color filter substrate 26.

Next, after the cover film 18 of the transfer sheet 20 is peeled off, as shown in FIG. 3E, the surface of the cholesteric liquid crystal layer 16 of the transfer sheet 20 and the alignment film 24 of the color filter substrate 26 are removed. Are laminated so that they come into contact with the surface of each other, and laminated through a roll rotating in the direction of the arrow in the figure. Thereafter, as shown in FIG. 3F, the orientation film 14 of the transfer sheet 20 and the cushion layer 1 are formed.
2 and the cholesteric liquid crystal layer is transferred together with the alignment film 14 on the color filter substrate. In this case, the cushion layer 12 does not necessarily have to be peeled off together with the temporary support 10.

After the transfer, as shown in FIG. 4G, an exposure mask 28 having a plurality of regions having different light transmittances is arranged above the alignment film 14, and the first mask 28 is provided through the mask 28. The cholesteric liquid crystal layer 16 is irradiated with light in a pattern. The cholesteric liquid crystal layer 16 contains a liquid crystal compound, a chiral compound, or the like so that the helical pitch varies depending on the amount of light irradiation, and a structure having a different helical pitch reflects, for example, green (G) for each pattern. An area that transmits blue (B) and red (R), reflects blue (B),
It is formed to form a region that transmits green (G) and red (R) and a region that reflects red (R) and transmits green (G) and blue (B).

Next, as shown in FIG. 4H, 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 (for example, remaining portions of the cushion layer, the intermediate layer, and the like, and unexposed portions) on the cholesteric liquid crystal layer 16 are removed using 2-butanone, chloroform, or the like, so that the structure shown in FIG. As shown, a cholesteric liquid crystal layer having a BGR reflection region can be formed.

The method shown in FIGS. 2 to 4 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, a cholesteric liquid crystal layer is applied on the alignment film 24 of the color filter substrate 26 shown in FIG. The steps shown in ()) are sequentially performed.

These processes and materials used for the transfer material and the support are described in Japanese Patent Application Nos. 11-342896 and 11-343665 filed by the present inventors.
The details are described in each specification of the item.

On the other hand, when a layer containing a liquid crystal composition (color filter forming layer) is formed by coating in the production of a color filter, especially in the case of a low-molecular liquid crystal, the liquid crystal molecules are aligned so as to be horizontal (to the substrate) on the substrate side. Even after the treatment, one side of the color filter forming layer is at the air interface, so that the liquid crystal molecules stand vertically on the air interface side, and the tilt angle (pretilt angle) of the liquid crystal molecules is continuous toward the thickness direction of the color filter forming layer. Changes occur. 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. It is necessary to peel off the film, which entails an increase in steps such as installation and removal of the alignment film and an increase in waste material. Therefore, it is preferable to use the following surfactant having an excluded volume effect distributed on the air interface side (hereinafter, referred to as “air interface aligning agent”).

(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 molecular structure requirements of the preferred air interface aligning agent include 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.

[0087]

Embedded image

[0088]

Embedded image

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.
5 mass% is preferable, and 0.1 to 1.0 mass% is more preferable. If the amount is less than 0.05% by mass, the effect may not be exhibited. If the amount exceeds 5% by mass,
In some cases, the air interface alignment agent itself associates to cause phase separation with the liquid crystal. Although the surface tension is reduced by containing the air interface aligning agent, a surfactant other than the air interface aligning agent may be used in combination for the purpose of further lowering the surface tension and improving coating properties. Can also.

[0090]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Example 1] 1. Preparation of Substrate A polyimide alignment film (LX-1400, manufactured by Hitachi Chemical DuPont) is applied on a glass substrate by a spin coater and dried in an oven at 100 ° C. for 5 minutes.
The resultant was heated and baked in an oven at 250 ° C. for 1 hour to form an alignment film. Further, the surface of this film was subjected to an orientation treatment by a rubbing treatment to produce a glass substrate with an orientation film.

[0092] 2. Formation of Cholesteric Liquid Crystal Layer The cholesteric liquid crystal layer coating liquid 1 prepared according to the following formulation was applied to the surface on the alignment film side of the glass substrate provided with an alignment film obtained above by a spin coater. This is 10
It was dried in an oven at 0 ° C. for 3 minutes to form a cholesteric liquid crystal layer.

[0093]

Embedded image

3. Next, the glass substrate was kept on a hot plate at 100 ° C. for 3 minutes to align the cholesteric liquid crystal layer. Then, after holding at 80 ° C. for 3 minutes, irradiation was performed for 5 seconds at an irradiation intensity of 100 mW / cm ² by an ultra-high pressure mercury lamp through an interference filter having a central wavelength of transmission at 312 nm in a nitrogen atmosphere. The color of the fixed selective reflection film was green. When the film thickness of this selective reflection film was measured with a confocal microscope, it was 2.3 μm ± 0.1 μm. That is, the thickness unevenness in the selective reflection film is 0.2
μm. The selective reflection wavelength was 530 nm, and the thickness unevenness was about 2/5 of the selective reflection wavelength.

Comparative Example 1 Example 1 was repeated except that the coating solvent in Example 1 was changed from cyclohexane to chloroform.
A composition similar to the composition of was prepared, and as in Example 1,
Coating, orientation, and immobilization were performed. The color of the fixed selective reflection film was green. When the film thickness of this selective reflection film was measured by a confocal microscope, it was 2.3 μm ± 0.3 μm.
m. That is, the thickness unevenness in the selective reflection film was 0.6 μm. The selective reflection wavelength was 535 nm, and the thickness unevenness was about ／ of the selective reflection wavelength.

[0096]

[Table 1]

[Embodiment 2] Preparation of Substrate A polyimide alignment film (LX-1400, manufactured by Hitachi Chemical DuPont) is applied on a glass substrate by a spin coater and dried in an oven at 100 ° C. for 5 minutes.
The resultant was heated and baked in an oven at 250 ° C. for 1 hour to form an alignment film. Further, the surface of this film was subjected to an orientation treatment by a rubbing treatment to produce a glass substrate with an orientation film.

2. Formation of Cholesteric Liquid Crystal Layer Coating liquid 2 for cholesteric liquid crystal layer prepared according to the following formulation was applied on the alignment film of the glass substrate provided with the alignment film obtained above by a spin coater. 100 ℃
And dried in an oven for 2 minutes to form a cholesteric liquid crystal layer.

[0099]

Embedded image

Next, the glass substrate was kept at 80 ° C. for 2 minutes. At this temperature, an ultrahigh-pressure mercury lamp was applied to the cholesteric liquid crystal layer through an ultrahigh-pressure mercury lamp through a photomask having a stripe-shaped opening, a line width of 80 μm, and a pitch of the opening of 270 μm and an interference filter having a central wavelength of transmission at 365 nm. Irradiation was performed for 1.5 seconds at an irradiation intensity of cm ² . Next, the mask was moved stepwise in the line width direction of 90 μm and irradiated for 4 seconds using the same interference filter and light source. Irradiation was performed for 10 seconds at an irradiation intensity of 40 mW / cm ² by an ultra-high pressure mercury lamp under a nitrogen atmosphere at this temperature. When this film thickness was measured with a confocal microscope, it was 2.2.
μm ± 0.1 μm. That is, the thickness unevenness of the color filter was 0.2 μm. The selective reflection wavelength is 450 nm for the blue part, 535 nm for the green part, and 650 nm for the red part.
And each thickness unevenness is 4/4 of the selective reflection wavelength.
9, about 2/5, 4/13. The area where no mask exposure was performed was blue, the area where 1.5 seconds was performed was green,
The portion subjected to 4 seconds showed selective reflection of red, and it was confirmed that the portion was good as a color filter. This filter portion had no optical pattern and showed good optical characteristics.

According to the present invention, it is possible to provide a selective reflection film and a liquid crystal color filter which are free from unevenness in reflectance and color unevenness of selectively reflected light.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the value of x on a chromaticity diagram and the thickness of a cholesteric film.

FIG. 2 is a schematic view showing a part of a process of manufacturing a liquid crystal color filter of the present invention.

FIG. 3 is a schematic view showing a part of a process of manufacturing a liquid crystal color filter of the present invention.

FIG. 4 is a schematic view showing a part of a process of manufacturing a liquid crystal color filter of the present invention.

[Explanation of symbols]

 Reference Signs List 10 support (temporary support) 12 cushion layer (thermoplastic resin layer) 14 24 alignment film 16 liquid crystal layer (liquid crystal composition) 18 cover film 20 transfer sheet 22 substrate 26 substrate for color filter 28 exposure mask

Claims (7)

[Claims] 1. An organic material having a helical structure,
In a state where the helical axis of the helical structure is oriented so as to be substantially parallel to the normal, the helical structure is fixed by polymerization or crosslinking or transition to a glassy state, and is a selective reflection film showing selective reflection in a range from ultraviolet rays to infrared rays. Wherein the optical distance of the difference in film thickness between the maximum film thickness portion and the minimum film thickness portion in the selective reflection film is 以下 or less of the selective reflection wavelength. 2. The selective reflection film according to claim 1, wherein an optical distance of a difference in film thickness between a maximum thickness portion and a minimum thickness portion is equal to or less than ４ of a selective reflection wavelength. The selective reflection film according to the above. 3. The selective reflection film according to claim 1, wherein the organic substance is a liquid crystal compound or a liquid crystal composition. 4. The selective reflection film according to claim 3, wherein the liquid crystal composition contains a liquid crystal compound having at least one polymerizable group, a chiral compound, and a polymerization initiator. 5. The liquid crystal composition according to claim 1, wherein the liquid crystal composition has at least one polymerizable group, a photoreactive chiral compound,
The selective reflection film according to claim 3, further comprising: a polymerization initiator. 6. The selective reflection according to claim 3, wherein the liquid crystal composition further contains a surfactant having an excluded volume effect distributed on the air interface side. film. 7. A liquid crystal color filter comprising the selective reflection film according to claim 1. Description: