JP2002268056A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device which has high contrast, high color purity and satisfactory brightness and which can be manufactured at low cost. SOLUTION: The reflection type liquid crystal display device is characteristically provided with a color filter having a cholesteric polarization element and a light absorbing layer provided on the backside of a selective reflection surface of the color filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device utilizing the wavelength selectivity of a cholesteric deflection element.

[0002]

2. Description of the Related Art A display device using a liquid crystal has the advantages of low power consumption and thinness, and various electronic devices other than a portable information terminal, a personal computer, a word processor, an amusement device, a television device, and the like. Applications such as display panels are increasingly expanding.

[0003] These liquid crystal display devices are roughly classified into a transmission type liquid crystal display device having a backlight light source and a front light type reflection type liquid crystal display device having no light source or using a light guide plate on the entire surface. Usually, a color filter using a resin colored with a pigment or a dye is used for a liquid crystal display device capable of full color display.
In principle, only about 1/3 of the light from the light source can be transmitted, so it cannot be said that the brightness is sufficient. To compensate for this drawback, for example, in a reflection type liquid crystal display device of a transmission type or a front light type, it is conceivable to increase the brightness of a backlight or a front light. The problem of damage occurs. Further, with respect to a reflection type liquid crystal display device having no light source, the brightness of the light cannot be increased. Further, such a color filter has a problem that it is very costly to form pixels by liquid development after photolithography for each color.

[0004] "T. utida et al: Japan
n Display, P.E. 312, 1986 "proposes a reflective liquid crystal display device in which a reflective electrode is formed on a TFT element via a contact hole with an insulating film interposed therebetween. Such a liquid crystal display device can improve the aperture ratio and obtain a somewhat bright image, but cannot be said to have sufficient brightness.

On the other hand, Japanese Patent No. 2999317 discloses that a phosphor is further provided on the reflection electrode of the above-mentioned reflection type liquid crystal display device, and visible light is emitted by UV in the incident light to further increase the brightness. The cost is increased by providing the phosphor.

To solve these problems, US Pat.
No. 614 proposes a color filter using a cholesteric polarizing element which does not require a liquid developing step. The cholesteric polarizing element selectively reflects circularly polarized light of a specific wavelength, and has the property of transmitting circularly polarized light of other wavelengths. This can increase the light use efficiency. Therefore, it is possible to form a substantially bright color filter. Further, since a pattern having different selective reflection wavelengths can be formed in the same layer without the need for a developing step, it is advantageous in terms of cost.

A color filter using the above cholesteric polarizing element can be suitably used for a reflection type liquid crystal display device. For this purpose, for example, incident light passing through the color filter is applied to a TFT element or its wiring. It is necessary to optimally design the members other than the color filters and their positional relationship in order to prevent the light from being reflected by the light source and resulting in leakage light emitted to the observer side. In particular, the leaked light lowers the dark level and thus lowers the contrast and color purity. At present, there is no practically usable liquid crystal display device that has solved such a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to use a color filter utilizing the wavelength selectivity of a cholesteric polarizing element, to achieve high contrast and color purity. Another object of the present invention is to provide a liquid crystal display device having sufficient brightness and capable of being manufactured at low cost.

[0009]

The object of the present invention is solved by the following means.

<1> A liquid crystal display device comprising: a color filter having a cholesteric polarizing element; and a light absorbing layer provided on a back side of a selective reflection surface of the color filter.

According to the liquid crystal display device of the above <1>, the incident light passing through the color filter can be absorbed by the light absorbing layer. For this reason, it is possible to prevent the incident light that has passed through the color filter from being reflected on the active element and its wiring and the like, and as a result, leaked light emitted to the observer side and the contrast and color purity from being lowered.

<2> The liquid crystal display device according to <1>, wherein an active element is provided on a side of the light absorbing layer not facing the color filter.

<3> The liquid crystal display device according to <1> or <2>, wherein the light absorbing layer partially has an opening.

<4> There is provided a pixel electrode connected to the active element, and the pixel electrode is electrically connected to the active element through an opening in the light absorbing layer. <3>> The liquid crystal display device.

<5> The liquid crystal display device according to any one of <1> to <4>, wherein the light absorbing layer has an insulating property.

<6> The liquid crystal display device according to any one of <1> to <5>, wherein the color filter has an opening in a pixel.

<7> The liquid crystal display according to <6>, wherein the pixel electrode has a light-transmitting property and is electrically connected to the active element through an opening of the color filter. Device.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the liquid crystal display of the present invention will be described in detail. A liquid crystal display device according to the present invention includes a color filter having a cholesteric polarizing element, and a light absorbing layer provided on a back side of a selective reflection surface of the color filter. Here, “the back side of the selective reflection surface of the color filter” is the back side of the surface (selective reflection surface) of the color filter that selectively reflects light incident on the liquid crystal display device, that is, the color filter without being selectively reflected. Refers to the side from which the incident light that has passed through exits. . In the liquid crystal display device of the present invention, the incident light passing through the color filter can be absorbed by the light absorbing layer. For this reason, the incident light that has passed through the color filter is reflected on the active element such as the TFT element or the wiring thereof, and as a result, the light leaks to the observer side and the contrast and color purity are reduced. Can be prevented. Further, the liquid crystal display device of the present invention has sufficient brightness and can be manufactured at low cost.
When an active matrix type liquid crystal display device is used for the reflection type display device of the present invention, an active element is provided on a side of the light absorbing layer which is not opposed to the color filter. In other words, the light absorption layer is provided between the color filter and the active matrix layer (for example, on the active element substrate).

The configuration of the liquid crystal display device of the present invention will be described with reference to FIG. Note that the present invention is not limited to these configurations. FIG. 1 is a schematic sectional view showing an example of the liquid crystal display device of the present invention. In FIG. 1, a liquid crystal display device 10 is an active matrix type liquid crystal display device. As shown in FIG.
Assuming that the upper side of the paper of FIG. 1 is the viewer side, a 波長 wavelength plate 14, a transparent substrate 16, a transparent common electrode 18, an electrically drivable liquid crystal layer 20, an optically transparent (Display electrode; hereinafter, sometimes referred to as “transparent pixel electrode”) 22, a color filter composed of cholesteric polarizing elements (hereinafter, sometimes simply referred to as “color filter”) 24, and color filter 24. The opening (contact hole) 26 provided, the light absorbing layer 28, the opening (contact hole) 30 provided in the light absorbing layer 28, T
Active element 32 such as FT (thin film transistor), and metal wiring 3 for electrically connecting active element 32
4. The configuration is such that the support substrates 36 are sequentially arranged. When MIM is used as the active element 32, a stripe-shaped transparent electrode is formed as a scanning line on the transparent substrate 16 side. In the liquid crystal display device 10, a liquid crystal alignment film, a spacer, a sealant, and the like are usually used.
These are omitted in FIG.

Although a glass substrate is suitable for the transparent substrate 16 and the supporting substrate 36, a plastic substrate can be used instead of the glass substrate in order to obtain a light-weight and hard-to-break liquid crystal display device 10. An ITO film is preferably used for the transparent electrodes (the common electrode 18, the transparent pixel electrode 22, the scanning lines, etc.). In the configuration shown in FIG.
Since the transparent pixel electrode 22 is provided on the light incident side of the color filter 24, the transparent pixel electrode 22 needs to have light transmissivity, but the transparent pixel electrode 22 is disposed on the light exit side (light transmission side) of the color filter 24. When provided, it is not necessary to have light transmittance.

The polarizing plate 12 and the quarter-wave plate 14 are
The polarizing plate 1 is configured such that the light h1 incident from the observer side is emitted toward the transparent substrate 16 as clockwise or counterclockwise circularly polarized light.
The two polarization planes and the 軸 wavelength plate 14 are arranged such that the slow axis maintains an angle of approximately 45 degrees. In FIG. 1, they are arranged so as to be clockwise circularly polarized light. 1/4 used here
More preferably, the wave plate 14 has a wide band that generates a quarter-wave phase modulation over the entire wavelength of visible light.

The liquid crystal layer 20 has an optically isotropic phase when the drive voltage is in the OFF state, and has a retardation of 波長 wavelength in the ON state.

The transparent pixel electrode 22 for applying a voltage to the liquid crystal layer 20 has a metal wiring 34 via openings (contact holes) 26 and 30 provided in the color filter 24 and the light absorbing layer 28. Active element (TFT)
32. Openings (contact holes) 26, 30 of color filter 24 and light absorbing layer 28
Is provided for making electrical connection between the transparent pixel electrode 22 and the active element 32. Therefore, the openings 26 and 30 are usually formed between the color filter 24 and the light absorbing layer 2.
8, the transparent pixel electrode 22 and the active element 32
Is provided at a location where In particular, the opening 26 provided in the color filter 24 is preferably provided in a pixel of the color filter. The shape of the openings 26 and 30 is not particularly limited, and may be a notch. The openings 26 and 30 have a radius of 1 μm to 10 in circle conversion.
μm is preferred, and 3 μm to 5 μm is preferred.

As a method of forming openings (contact holes) 26 and 30 in the pixels of the color filter 24 or in the light absorbing layer 28, for example, a cholesteric liquid crystal polarizing element layer or a light absorbing layer is formed by a usual photolithography method. In other words, after applying a photoresist material on the layer, it can be formed by performing exposure, development and etching, and ablation for directly removing portions to be openings 26 and 30 by infrared laser or the like. It can be performed by a method or the like. This method uses a TFT
In the case of manufacturing a liquid crystal display device using an element, an opening can be provided in the same place with respect to a layer such as an alignment layer, a substrate, and a light absorbing layer together with a cholesteric liquid crystal polarizing element layer by a plasma etching method or the like. Can be used as a contact hole, which is an advantageous method from the viewpoint of manufacturing cost.

The color filter 24 has a red reflection area,
It is divided into a green reflection region and a blue reflection region, and each region has a helical pitch that selectively reflects the corresponding reflection color.

In the liquid crystal device of the present invention, the light absorbing layer 28
Are those having a sufficient optical density so as to absorb all the light transmitted through the color filter 24, the color filter 24, the active element (TFT) 32 and the metal wiring 3.
4 between them. By arranging in this way,
When no voltage is applied to the liquid crystal layer 20, the circularly polarized light (for example, counterclockwise circularly polarized light) transmitted through the color filter 24 is re-reflected by the metal wiring 34 or the like connecting the active elements 32, and the circularly polarized light (for example, counterclockwise circularly polarized light). (Circularly polarized light) can be prevented from passing through the color filter 24 and reaching the observer side. In addition, it is necessary to maintain electrical insulation between the active elements 32. However, it is preferable that the light absorption layer 28 has insulation because the light absorption layer and the insulation layer can be combined. When the light absorbing layer 28 is not made insulating, the light absorbing layer 28 and the active element 32
It is necessary to provide an insulating layer between the metal wiring and the metal wiring. In order to give the light absorbing layer 28 an insulating property, for example, polyacetal, polyamide, acrylic resin, polycarbonate or the like may be used as the binder polymer.

The light absorbing layer 28 is preferably a layer that absorbs all light having a wavelength in the visible region. For example, carbon black particles can be used as a pigment. Further, an insulating resin is preferably used as a binder polymer of the light absorbing layer, and examples thereof include those described above. Light absorbing layer 2
The thickness of 8 is not particularly limited as long as it can exhibit a sufficient optical density so as to absorb all transmitted light, but is 0.1 μm to 1 μm in consideration of the structure of the liquid crystal display device.
0 μm is preferable, and 1 μm to 5 μm is particularly preferable. In addition, as a method for forming the light absorbing layer 28, a known coating method or the like can be appropriately selected, and specific examples include a bar coating method, a slit coating method, a spin coating method, and a blade coating method.

Next, a display operation by the liquid crystal display device having the above configuration will be described with reference to FIG. In FIG. 1, the driving voltage is OFF on the left side and the driving voltage O is on the right side with respect to the center broken line.
N state.

As shown in FIG. 1, the observer side (upper side of the paper)
The light beam h1 incident from the
Is converted into clockwise circularly polarized light. When the clockwise circularly polarized light passes through the transparent substrate 16 and the transparent common electrode 18, the clockwise circularly polarized light enters the liquid crystal layer 20 where no voltage is applied as clockwise circularly polarized light without any modulation. . The liquid crystal layer 20 is in an optically isotropic state when no voltage is applied, so that the liquid crystal layer 20 transmits light without being modulated and then passes through the transparent pixel electrode 22 in the right circularly polarized state. Color filter 2
Go to 4. At this time, assuming that the cholesteric polarizing element of the color filter 24 has a helical direction and a pitch determined so as to exhibit selective reflection in the red wavelength region, for example, of clockwise circularly polarized light, the incoming right circularly polarized light h1
Among them, the light h2 of a color other than red passes through the color filter 24, reaches the light absorbing layer 28, and is absorbed. On the other hand, of the right circularly polarized light that has entered, the red light is
Cannot be transmitted, is reflected as clockwise circularly polarized light h3, and travels toward the observer. The reflected red right circularly polarized light h3 is １ ／ without being modulated for any of the above reasons.
The light reaches the wave plate 14, and the polarization axis is observed as linearly polarized light parallel to the polarization plane of the polarizing plate 12 by the action of the ４ wave plate 14 and the polarizing plate 12.

When a voltage is applied to the liquid crystal layer 20, the incident light h4 enters the liquid crystal layer 20 as clockwise circularly polarized light in the same manner as described above. When the voltage is applied, the liquid crystal layer 20 has a half-wave retardation,
The right-handed circularly polarized light is modulated to the left-handed circularly polarized light to form a liquid crystal layer 2.
Since the light is emitted from 0, it passes through all the color filters 24 that exhibit selective reflection only for clockwise circularly polarized light.
Since all the transmitted light is absorbed by the light absorbing layer 28, no light is reflected to the observer as a result.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic sectional view showing another example of the liquid crystal display device of the present invention. In FIG. 2, a liquid crystal display device 38 is a simple matrix type liquid crystal display device.
As shown in FIG. 2, the liquid crystal display element 38 has a 波長 wavelength plate 42 under a polarizing plate 40,
A transparent substrate 44, a transparent scanning electrode 46, an electrically drivable liquid crystal layer 48, a transparent pixel electrode 50, a color filter 52 composed of a cholesteric polarizing element, an opening 53 provided between pixels of the layer, a transparent support substrate 54, The light absorbing layers 56 are sequentially arranged.

The transparent substrate 44, the transparent support substrate 54, the transparent (scanning / pixel) electrodes 46 and 50, the polarizing plates 40 and 1/4
Wave plate 42, liquid crystal layer 48 and color filter 52
Is similar to that shown in FIG. 1 and functions similarly.

A transparent pixel electrode 50 for applying a voltage to the liquid crystal layer 48 is disposed between the color filter 52 and the liquid crystal layer 48.

The light absorbing layer 56 has a sufficient optical density so as to absorb all the light transmitted through the color filter 52 and the transparent support substrate 54. Place on the surface.

The liquid crystal display device 38 shown in FIG.
The light ray h1 when no voltage is applied to 8 and the light ray h4 when voltage is applied are reflected or absorbed as in the case of the liquid crystal display device 10 in FIG. 1, and h1 is reflected by the color filter 52 as h3. On the other hand, h4 passes through the color filter, passes through the transparent substrate 54, is entirely absorbed by the light absorbing layer 56, and the light is not reflected toward the observer.

(Color Filter) Next, the color filter used in the present invention will be described in detail. The color filter used in the present invention has a cholesteric liquid crystal polarizing element layer composed of a cholesteric liquid crystal polarizing element. In the following, the cholesteric liquid crystal polarizing element layer may be simply referred to as a color filter. As an example of the method for producing the color filter (cholesteric liquid crystal polarizing element layer) of the present invention, a liquid crystal layer formed on a substrate and containing at least a liquid crystalline compound having at least one polymerizable group and a photoreactive chiral agent, The method includes a step of image-wise irradiating light in the photosensitive wavelength region of the photoreactive chiral agent imagewise, and a step of photopolymerizing a liquid crystalline compound having at least one polymerizable group.

First, a liquid crystal composition used for preparing a liquid crystal layer containing at least a liquid crystalline compound having at least one polymerizable group and a photoreactive chiral agent will be described. [Liquid crystal composition] The liquid crystal composition used for producing the color filter of the present invention contains at least a liquid crystalline compound having at least one polymerizable group and a photoreactive chiral agent. Further, it is preferable to further add a polymerization initiator to the liquid crystal composition.

In the liquid crystal composition, the liquid crystal compound having a polymerizable group is preferably a nematic liquid crystal compound having a polymerizable group. Depending on the polymerizable group of the liquid crystal compound,
Sufficient curability is ensured, and the heat resistance of the layer is improved.

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

[0040]

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[0041]

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[0042]

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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.

[0044]

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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. When the content is less than 30% by mass, the orientation is insufficient and a desired selective reflection color may not be obtained.

(Photoreactive Chiral Agent) Next, the photoreactive chiral agent will be described. The photoreactive chiral agent has a chiral site and a photoreactive site that undergoes a structural change upon irradiation with light,
For example, the torsional force (H
TP). In order to increase the helical structure inducing force by light irradiation, it is preferable that the degree of structural change by light irradiation is large. Further, as the photoreactive chiral agent, those having a solubility parameter SP value close to that of a liquid crystalline compound are desirable. Further, when the photoreactive chiral agent has a structure in which one or more polymerizable bonding groups are introduced into the molecule, the heat resistance of the liquid crystal phase is improved.

Examples of photoreactive sites whose structure is changed by light irradiation include photochromic compounds (Kingo Uchida, Masahiro Irie, Chemical Industries, vol. 64, 640p, 1999,
Kingo Uchida, Masahiro Irie, Fine Chemical, vol. 28
(9), 15p, 1999).
Further, the structural change means a decomposition or addition reaction, isomerization, dimerization reaction, or the like caused by light irradiation on a photoreactive site, and the structural change may be irreversible. Examples of the chiral moiety include, for example, Hiroyuki Nohira, Chemical Review, N
o. The asymmetric carbon described in 22 Chemistry of Liquid Crystals, 73p: 1994, and the like correspond thereto.

The photoreactive chiral agent used in the present invention includes, for example, Japanese Patent Application No. 11-3 previously provided by the present applicant.
No. 43666, paragraphs [0044] to [0047], photoreactive chiral agents, Japanese Patent Application No. 2000-193142.
In addition to the photoreactive chiral agents described in paragraphs [0021] to [0029], optically active compounds described in paragraphs [0019] to [0043] of Japanese Patent Application No. 2000-380919 and Japanese Patent Application No. 2000-381001. Paragraph [0020]
To [0044], Japanese Patent Application 2000
-381002, optically active compounds described in paragraphs [0016] to [0040], Japanese Patent Application No. 2000-381003, paragraphs [0015] to [0036], optically active compounds described in Japanese Patent Application No. 2000-381966, paragraph [ 001
7] to [0050], the optically active compound described in Japanese Patent Application No.
Paragraphs [0018] to [004] of 00-381967
4], an optically active compound described in Japanese Patent Application No. 2000-3825.
The optically active compounds described in paragraphs [0020] to [0049] of No. 15 can be used as a photoreactive chiral agent.

In the liquid crystal composition of the present invention, in addition to the low molecular weight liquid crystal compound having a polymerizable group and the photoreactive chiral agent, a polymerizable monomer, a polymerization initiator, a binder resin, a solvent, , Surfactants, polymerization inhibitors, thickeners,
Other components such as dyes, pigments, ultraviolet absorbers, and gelling agents can be included. In the liquid crystal composition of the present invention, it is particularly preferable to use a surfactant in combination. For example, when applying a liquid crystal composition in the form of a coating liquid to form a layer, the alignment state at the air interface of the layer surface can be controlled three-dimensionally, and in particular, in the case of a cholesteric liquid crystal phase, a selective reflection wavelength having higher color purity can be obtained. Obtainable.

(Polymerizable monomer) A polymerizable monomer may be used in combination with the liquid crystal composition of the present invention. When the polymerizable monomer is used in combination, the distribution of the selective reflection wavelength is formed (patterned) by changing the twisting force of the liquid crystal due to light irradiation,
The helical structure (selective reflectivity) can be fixed, and the strength of the liquid crystal composition after fixing can be further improved. However,
When the 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. Specifically, in addition to polyfunctional monomers such as pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate, Compounds shown can be mentioned,
However, the present invention is not limited to these.

[0052]

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The amount of the polymerizable monomer to be added is preferably 0.5 to 50% by mass based on the mass of the solid content of the liquid crystal composition. When the addition amount is less than 0.5% by mass,
In some cases, sufficient curability cannot be obtained, and when it exceeds 50% by mass, the alignment of liquid crystal molecules is hindered, and sufficient color formation may not be obtained.

(Photopolymerization Initiator) In order to fix the helical structure after changing the torsional force of the liquid crystal by light irradiation and to further improve the strength of the liquid crystal composition after the fixation, polymerization with a polymerizable liquid crystal compound is performed. When utilizing a reaction, it is preferable to add a photopolymerization initiator. Further, the photosensitive wavelength region of the photopolymerization initiator is preferably different from the photosensitive wavelength region of the photoreactive chiral agent. Here, having different photosensitive wavelengths means that both photosensitive central wavelengths do not overlap. When the photosensitive wavelength region of the photoreactive chiral agent is different from the photosensitive wavelength region of the photopolymerization initiator, the irradiation of light for changing HTP and the irradiation of light 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. Indicates that the photoreactive chiral agent does not react to light and the HT formed
The P change pattern can be reliably fixed, and selective reflection according to the setting is achieved.

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 and triarylsulfonium hexafluorophosphate. In addition, bisacylphosphine oxides such as bis- (2,4,6-trimethylbenzoyl) phenylphosphine oxide described in JP-A-10-29997 and the like, and DE4 such as Lucirin TPO and the like.
Acylphosphine oxides described in JP 230555 and the like.

The addition amount of the photopolymerization initiator is preferably from 0.1 to 20% by mass, more preferably from 0.5 to 5% by mass, based on the mass of the solid content of the liquid crystal composition. If the amount is less than 0.1% by mass, the curing efficiency at the time of light irradiation is low, so that it may take a long time. If the amount exceeds 20% by mass, the light transmittance from the ultraviolet region to the visible light region may be required. May be inferior.

[Production of Color Filter] A color filter having a cholesteric polarizing element used in the present invention can be produced from the above liquid crystal composition. The color filter used in the present invention may be in the form of a sheet in which the color filter layer is composed of only the liquid crystal composition, or in the form in which the color filter layer is provided on a desired support or substrate. May be
Further, another layer such as an alignment film or a protective film may be provided. Two or more liquid crystal layers can be stacked.

The method for producing the color filter is not particularly limited, and at least the step of forming a liquid crystal layer on the color filter substrate, the light in the photosensitive wavelength region of the photoreactive chiral agent of the liquid crystal layer is imagewise formed. Irradiating and photopolymerizing the liquid crystalline compound having at least one polymerizable group. In addition, in addition to the above-described steps, the step of producing the color filter of the present invention may include a step of subjecting the contact surface between the liquid crystal layer and the color filter substrate or the temporary support to an alignment treatment as described below. .

The formation of the liquid crystal layer can be carried out by directly applying the liquid crystal composition of the present invention to a color filter substrate or by peeling the liquid crystal layer once formed on a temporary support into close contact with the color filter substrate and then removing the temporary support. This is performed by a transfer method.

When the photoreactive chiral agent used in the present invention is irradiated with light in the photosensitive wavelength range, a photoreaction (isomerization, decomposition, addition, dimerization, etc.) occurs according to the amount of light. Change the pitch of the spiral structure. Therefore, if the light irradiation intensity is changed for each desired region of the liquid crystal layer and light irradiation is performed, a change in the pitch of the helical structure occurs in accordance with the irradiation intensity, and selective reflection of light having a wavelength corresponding to the pitch occurs. Presents multiple colors. In order to irradiate different light amounts to different regions, for example, a method of exposing through an exposure mask manufactured by changing the light transmittance imagewise is preferably used. In this method, the degree of photoreaction differs imagewise by a single light irradiation (as a result, the helical pitch of the liquid crystal phase can be changed imagewise).
This is a preferable method because a liquid crystal layer can be formed.

Thereafter, the entire liquid crystal layer is irradiated with light to be photopolymerized (cured), thereby fixing the changed helical pitch of the liquid crystal phase. In this case, as described above, the wavelength range of light that causes a photoreaction to the photoreactive chiral agent (the photosensitive wavelength range of the photoreactive chiral agent) and the wavelength range of light to be photopolymerized (when a polymerization initiator is used, (A photosensitive wavelength region) are preferably different.

The wavelength of the light that causes the photoreactive chiral agent to undergo a photoreaction may be set in the light-sensitive wavelength region of the photoreactive chiral agent, particularly a wavelength close to the light-sensitive peak wavelength, so that sufficient patterning sensitivity is obtained. It is preferable in that it can be obtained. Also,
The wavelength of the light to be photopolymerized is preferably set to a light sensitive wavelength range of the polymerization initiator, particularly to a wavelength close to the light sensitive peak wavelength, in that sufficient photopolymerization sensitivity can be obtained. The irradiation intensity of these lights can be appropriately selected so as to obtain sufficient light sensitivity.

The following is a more specific description. [First Embodiment] The first embodiment is a method using a transfer method for forming a liquid crystal layer on a color filter substrate. (1) A step of providing a layer of the liquid crystal composition of the present invention on a temporary support to form a transfer material having at least a liquid crystal layer. The liquid crystal layer is formed by applying the liquid crystal composition of the present invention to a temporary support using a bar coater, a spin coater, or the like. Between the liquid crystal layer and the temporary support, a thermoplastic resin (acrylic resin, polyester, urethane resin, or the like) is used 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 possible to provide a cushion layer. In addition, it is preferable to perform an alignment treatment (formation of an alignment film and a rubbing treatment) on the surface of the temporary support or the cushion layer. Further, a cover film for protection can be provided on the liquid crystal layer. (2) a step of laminating the transfer material on a light transmissive substrate; The substrate may be provided with an image receiving layer. Also,
It is preferable to perform the same alignment treatment as in the above (1) on the substrate or the image receiving layer. (3) A step of transferring the liquid crystal layer to the light transmitting substrate and peeling off the temporary support (transfer step). After passing through the following (4), a plurality of liquid crystal layers can be formed by further stacking transfer materials in the same manner. (4) A step of irradiating the liquid crystal layer imagewise with light through an exposure mask to form a pixel pattern showing a selective reflection color, and further irradiating light to cure the liquid crystal layer (exposure step).

Hereinafter, a method of manufacturing the color filter according to the first embodiment will be described with reference to the drawings. First, Figure 3-
As shown in (A), a cushion layer 62 is provided on a temporary support 60, and an orientation film 64 such as polyvinyl alcohol is further provided.
Are laminated. Next, as shown in FIG. 3B, a rubbing process is performed on the alignment film. This rubbing treatment is not always necessary, but the rubbing treatment can further improve the orientation. Next, as shown in FIG. 3C, a liquid crystal composition is applied on the alignment film 64 and dried to form a liquid crystal layer 66, and then a cover film 68 is provided on the liquid crystal layer 66. A transfer material 70 is prepared.

On the other hand, as shown in FIG. 3D, an alignment film 74 is formed on another substrate 72 in the same manner as in FIG. 3B, and the surface is subjected to a rubbing process. Hereinafter, this is referred to as a color filter substrate 76. Next, after peeling off the cover film 68 of the transfer sheet material 70, FIG.
As shown in (E), the surface of the liquid crystal layer 66 of the transfer sheet 70 and the surface of the alignment film 74 of the color filter substrate 76 are overlapped so as to be in contact with each other, and passed through a roll rotating in the direction of the arrow in the figure. Laminated. Then, FIG.
As shown in (F), the liquid crystal layer 66 is transferred together with the alignment film 64 onto the color filter substrate 76 by being peeled off between the alignment film 64 of the transfer material 70 and the cushion layer 62. In this case, the cushion layer 62 does not necessarily have to be peeled off together with the temporary support 60.

After the transfer, as shown in FIG. 5G, an exposure mask 78 having a plurality of regions having different light transmittances and a band-pass filter (not shown) above the alignment film 64.
Is arranged and irradiated with ultraviolet rays through the mask 78 to cause a photoreaction to the photoreactive chiral agent.

Next, as shown in FIG. 5H, a light source similar to that in the above step (G) (without using a band-pass filter) is used for the liquid crystal layer 66, and the above-mentioned step (G) is performed. The pattern is fixed by irradiating with ultraviolet light at an irradiation intensity different from that of the light irradiation of (1). Thereafter, unnecessary portions (for example, remaining portions of the cushion layer, the intermediate layer, and the like, and unexposed portions) on the liquid crystal layer 66 are removed using 2-butanone, chloroform, or the like, so as to be illustrated in FIG. So, BGR
A liquid crystal layer having a reflective area of

[Second Aspect] The second aspect is a method for forming a liquid crystal layer directly on a substrate constituting a color filter. This is a method of performing the same exposure step as in the above.

The thickness of the liquid crystal layer functioning as a color filter is preferably 1.5 to 4 μm.

These steps and materials to be used, such as a transfer material and a 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.

As described above, when a liquid crystal composition containing a photoreactive chiral agent is used, the rate of change of the twisting force of the helical structure of the liquid crystal with respect to the amount of light is large, so that the color width of the selective reflection color that can be exhibited by the liquid crystal is widened. Blue (B), Green (G), Red with excellent color purity
A color filter consisting of the three primary colors (R) can be obtained.

[0072]

[Embodiment 1] An example of a color filter of the present invention and a liquid crystal display device using the color filter will be described. The liquid crystal display had a structure as shown in FIG. 1. Preparation of Liquid Crystal Composition A liquid crystal composition having the following composition was prepared.

[0073]

Embedded image

Incidentally, the isotropi of the liquid crystal compound
The point c is 120 ° C. and the nematic point is 85 ° C.

2. Preparation of Color Filter (1) Preparation of Transparent Support Substrate After washing commercially available alkali-free glass (thickness 0.75 mm) using an alkaline detergent while applying ultrasonic waves,
Dry at 0 ° C. for 20 minutes. (2) Formation of TFT element, light absorption layer, color filter, contact hole, transparent pixel electrode and alignment film on transparent support substrate Formation of TFT element and light absorption layer TFT element on transparent support substrate prepared in (1) above It was formed by a conventional method. Next, a solution for a light absorbing layer containing carbon black and an insulating resin (polyvinyl butyral) (30% by mass of carbon black added to the insulating resin) containing the black was spun on the spin-coating liquid so that the dry thickness became 2 μm. A light absorbing layer was formed by coating and drying by a coating method.

Alignment treatment of light absorbing layer A polyimide alignment film coating solution [LX-1400
(A 2% by mass solution of (Hitachi Chemical DuPont) in a 1: 1: 1 mixed solvent of N-methyl-2-pyrrolidone: 2-butoxyethanol: diethylene glycol monoethyl ether) using a spin coater. , 1000
The solution was applied at rpm, dried in an oven at 100 ° C. for 30 minutes, and cured in an oven at 250 ° C. for 30 minutes to form an alignment film. Further, the surface of the film was subjected to an alignment treatment by a rubbing treatment.

Formation of Cholesteric Liquid Crystal Polarizing Element Layer The above-mentioned 1. Was applied using a spin coater at 600 rpm so that the coating layer became approximately 2 μm, and dried in an oven at 100 ° C. for 30 minutes to form a liquid crystal layer. On the liquid crystal layer, the transmittance varies in three stages (0%, 46%, 92%).
%), A photomask in which each region is arranged corresponding to a red pixel, a green pixel, and a blue pixel and a 350 nm
An ultra-high pressure mercury lamp was arranged via a band pass filter having a center at the center, and irradiation was performed with the ultra high pressure mercury lamp through this photomask and the band pass filter to perform patterning.
The irradiation energy at this time is 84 m for the blue pixel.
J / cm ² , and the irradiation intensity was 4.2 mW / cm ² . The irradiation time was 20 seconds. Thereafter, the photomask and the bandpass filter were removed, and the liquid crystal layer was heated by a hot plate and kept at the iso point of 120 ° C. for 30 seconds. Thereafter, the liquid crystal layer was cooled to 85 ° C., which is the N point, by a hot plate kept at 85 ° C., and kept at that temperature for 30 seconds. Next, while maintaining the liquid crystal layer at 85 ° C., an irradiation intensity of 11.4 mW / c was applied by an ultra-high pressure mercury lamp through a band-pass filter centered at 320 nm.
The entire surface was exposed for 20 seconds at m ² to polymerize and cure the liquid crystal layer. Further, in order to accelerate the curing of the color filter layer, baking is performed for 20 minutes in an oven at 220 ° C.
A cholesteric liquid crystal polarizing element layer in which green pixel and blue pixel patterns were formed was obtained.

Formation of Openings in Pixels of Cholesteric Liquid Crystal Polarizing Element Layer Next, a commercially available photoresist material (negative type) was applied on the cholesteric liquid crystal polarizing element layer to form a resist layer. Next, using a normal photolithography method, a portion excluding a portion where an opening (contact hole) to be formed in the pixel is to be formed (contact hole) is exposed, and then the non-exposed portion is removed in an alkali developing solution. For 1 hour to cure the remaining resist film. Next, using a dry etching apparatus (reactive ion etching apparatus DEA-506 manufactured by Nidec Anelva) and CF ₄ gas, T
An opening communicating with the FT element was formed. Subsequently, the resist layer remaining on the exposed part of the cholesteric liquid crystal polarizing element layer was removed.

Formation of Contact Hole and Pixel Electrode Thereafter, an opening for a contact hole reaching the TFT element through the alignment film and the light absorbing layer through a part of the opening formed above by a conventional method. Form a part,
Thereafter, a contact hole for electrical connection between the TFT element and the transparent pixel electrode was formed by a conventional method. Next, a transparent pixel electrode was formed. Next, a coating liquid of a polyimide alignment film (LX-1400, manufactured by Hitachi Chemical DuPont) is applied onto the pixel electrode by a spin coater.
After drying in an oven at 00 ° C. for 5 minutes, it was baked in an oven at 250 ° C. for 1 hour to form an alignment film, and the surface of the film was subjected to an alignment treatment by rubbing.

3. 1. Preparation of Liquid Crystal Display (1) Preparation of Transparent Substrate (Counter Substrate) On a counter glass substrate having a thickness of 1.1 mm, an ITO film (common electrode) was formed to a thickness of 0.1 μm by a sputtering method. The orientation treatment was performed by the method. (2) Preparation of Liquid Crystal Display Device After bonding the alignment-treated surface of the transparent support substrate provided with the color filters and the like and the alignment-treated surface of the counter substrate with a space of 2 μm, liquid crystal was injected. The liquid crystal used had a homeotropic alignment when the voltage was ON, and had a retardation of １ ／ wavelength when the voltage was OFF. A 波長 wavelength plate (manufactured by Sumikalite Sumitomo Chemical Co., Ltd.) and a polarizing plate (manufactured by Sumitomo Chemical Co., Ltd., SH-1832AW) were adhered to the counter substrate side of the liquid crystal cell via an adhesive. The color filter having the cholesteric liquid crystal polarizing element layer having the opening thus produced was excellent in resolution. The liquid crystal display device incorporating the color filter was excellent in brightness and color purity.

Comparative Example 1 A color filter and a liquid crystal display device were produced in the same manner as in Example 1 except that the light absorbing layer was not provided in the production of the color filter and the liquid crystal display device of Example 1 described above. Contrast and color purity were inferior to those of Example 1.

[0082]

According to the liquid crystal display of the present invention, there is provided a color filter having a cholesteric polarizing element, and a light absorbing layer provided on the back side of the selective reflection surface of the color filter.
Is provided, the incident light that has passed through the color filter can be absorbed. Thereby, it is possible to prevent the incident light that has passed through the color filter from being reflected on the active element and its wiring, thereby preventing the light from leaking to the observer side.
A sufficiently bright liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one example of a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view showing another example of the liquid crystal display device of the present invention.

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

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

FIG. 5 is a schematic view showing a part of a process of manufacturing a liquid crystal color filter used in the present invention.

[Explanation of symbols]

10, 38 Liquid crystal display device 12, 40 Polarizing plate 14, 42 1/2 wavelength plate 16, 44 Transparent substrate 18 Transparent common electrode 20, 48 Liquid crystal layer 22 Transparent pixel electrode 24, 52 Color filter having cholesteric liquid crystal polarizing element 26, 53 Opening or contact hole provided in cholesteric liquid crystal polarizing element layer 28, 56 Light absorbing layer 30 Opening or contact hole provided in light absorbing layer 32 Active element 34 Metal wiring 36, 54 Support substrate 46 Transparent scanning electrode 50 Transparent pixel electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA05 BA06 BA07 BA18 BA43 BB03 BB62 BB63 BC22 2H091 FA02Y FA08X FA09Y FA14Y FA34Y FD24 GA03 GA07 GA13 LA12 LA15 LA17 2H092 GA28 JA24 NA01 PA08 PA09

Claims (7)

[Claims] 1. A liquid crystal display device comprising: a color filter having a cholesteric polarizing element; and a light absorbing layer provided on a back side of a selective reflection surface of the color filter. 2. The liquid crystal display device according to claim 1, wherein an active element is provided on a side of the light absorbing layer that does not face the color filter. 3. The liquid crystal display device according to claim 1, wherein the light absorbing layer partially has an opening. 4. The device according to claim 3, further comprising a pixel electrode connected to the active element, wherein the pixel electrode is electrically connected to the active element via an opening in the light absorbing layer. 3. The liquid crystal display device according to 1. 5. The liquid crystal display device according to claim 1, wherein the light absorbing layer has an insulating property. 6. The liquid crystal display device according to claim 1, wherein the color filter has an opening in a pixel. 7. The liquid crystal according to claim 6, wherein the pixel electrode has a light transmitting property and is electrically connected to the active element through an opening of the color filter. Display device.