JP3508393B2 - Reflective liquid crystal device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal element suitable for displaying and recording various information.

[0002]

2. Description of the Related Art There is a demand for a flat high-density color display device which replaces a conventional CRT, and in recent years, a color liquid crystal using a backlight by combining a TN device using a polarizing plate with a color filter. The display is the mainstream. However, this method is difficult to use as a reflective color element with low power consumption required for mobile information devices by removing the backlight due to its low light utilization efficiency, and the brightness of printed matter,
It is far from white.

The cause of this is mainly to use the additive color mixing system using a polarizing plate and a color filter.
In other words, the theoretical limit of the light utilization efficiency of the current method using the color filters of the normal additive three-color mixture is 50% due to the polarizing plate, and the limit of the additive color-mixing method using the color filters of the additive three-color mixture. Is 33.3%
Therefore, 16.6% obtained by multiplying these is the theoretical limit of this method. In the case of actual devices, in addition to the light utilization efficiency below the theoretical values of actual polarizing plates and color filters, the aperture ratio of active devices such as TFT is also added,
Unless special measures are added to the reflective layer or the like, it is difficult to achieve a total utilization efficiency, that is, a reflectance of more than 10% in the case of a reflective type. On the other hand, the immediate target of brightness and whiteness is the reflectance of about 60% of the level of newspaper, but since this target value greatly exceeds the theoretical limit of the above-mentioned current method, It is clear that a fundamental modal change is needed, including removal of the board. For this reason, various methods have been proposed, but there are very few reflective methods that can achieve both whiteness and colorization.

In Japanese Unexamined Patent Publication (Kokai) No. 8-29618, an optical film having a plurality of regions having different retardations in optical parallel is used without using a conventional color filter, and two nematic liquid crystal layers having a twist of 90 degrees are provided. , A liquid crystal element arranged between the polarizing films. This method can be expected to improve against the decrease in light utilization efficiency due to the low transmittance of the actual color filter. However, the element of this configuration does not have sufficient basic color display characteristics required for high-density color display using the color mixing principle, and it is not possible to improve the large brightness and whiteness required for reflective elements. Far from principle.

That is, in order to use as a high-density color display utilizing the principle of color mixing, each pixel must be able to control between an achromatic color such as white or black and a chromatic color such as three primary colors. The configuration is only hue conversion between chromatic colors, and does not meet the basic requirements for high-density color display and recording by using additive color mixture. Further, in the above element, the means for displaying an achromatic color such as white is not necessarily clear, but if the comparison is made assuming that additive color mixing is performed using the three primary colors of additive color mixing, the above disclosed method shows that the polarizing plate The light utilization rate or reflectance of 16.6%, which is the theoretical limit of the conventional additive color mixing method using, cannot be exceeded. It is an object of the present invention to provide a reflective color liquid crystal device having a novel basic configuration, which is suitable for portable information display, rewritable recording, etc. and has a significantly improved brightness.

[0006]

[Means for solving the problems]
The following means are used to achieve the above object.

At least one of the alignment states of liquid crystal molecules, which changes depending on whether or not an electric field, heat is applied, is different from the guest-host liquid crystal layer in which the alignment state does not have twist other than the alignment state perpendicular to the substrate. an optical film having a plurality of regions in an optical parallel with edition, the conductive reflective layer such as metal and organic as basic optical components
Color, and the hue to be developed is a complementary color, such as an additive color mixture such as three primary colors.
Therefore, the combination of achromatic color pixels and the hue
Contains pixels that are themselves achromatic, such as black,
These are reflective type color liquid crystal elements in which repetitive patterns are formed .

[0008]

It is any one of the above reflective color liquid crystal elements having a diffuse transmission layer.

Any one of the above-mentioned guest-host liquid crystal modes in which at least one of the alignment states of liquid crystal molecules which changes depending on whether an electric field, heat is applied, or not is a guest-host liquid crystal mode in which the alignment state is parallel to the substrate, such as a homogeneous alignment state. It is a reflective color liquid crystal element.

At least one of the alignment states of the liquid crystal molecules, which changes depending on whether or not an electric field, heat is applied, is a guest-host liquid crystal mode in which the liquid crystal molecules are in a hybrid alignment state.

Any one of the above-mentioned guest-host liquid crystal modes in which at least one of the alignment states of liquid crystal molecules that changes depending on whether an electric field, heat is applied, or not is a guest-host liquid crystal mode in which the alignment state is perpendicular to the substrate, such as a homeotropic alignment state. Is a reflective color liquid crystal device.

It is any one of the above reflective color liquid crystal elements in which an active element such as a TFT is arranged on the back surface of the reflective layer to increase the aperture ratio.

[0014]

The present invention provides a guest-host liquid crystal layer in which at least one of the liquid crystal molecule alignment states that changes depending on whether an electric field, heat is applied or not is applied, has a molecular alignment state having no twist other than the vertical alignment, that is, , A guest-host liquid crystal layer in which transmitted light in at least one of the states becomes linearly polarized due to the dichroic absorption of a dichroic dye such as black is selected from various guest-host liquid crystal layers, and this is adopted. Since a birefringent optical film and a conductive reflective layer such as a metal are used as basic optical constituents, a reflective color liquid crystal element or a birefringent color liquid crystal element that is significantly superior in brightness and whiteness to conventional elements or A reflective color liquid crystal device capable of realizing gradation, which is a general difficulty of a color mode utilizing refraction, can be realized.

That is, the transmittance can be improved by utilizing the color development by birefringence as a color-developing mechanism in place of the color filter, such as the element described in JP-A-8-29618, that is, a mere approximation to the theoretical value can be achieved. It is not the main purpose of the present invention, but is to bring about a leap in principle to the improvement of whiteness, which is a problem of the reflection type.
Specifically, instead of a polarizing plate as a polarization functional layer, a guest-host liquid crystal layer that can control the polarization function by an electric field or heat is selectively adopted, so that a guest-host liquid crystal layer that can control transmitted light between polarized and non-polarized states is used. In this case, the unpolarized state can be utilized to bring it into the white state. For this reason, it is not necessary to produce white color by the principle of color mixing, and since the birefringent optical film does not cause a decrease in the light utilization ratio in principle like non-polarized plates as with a normal transparent plate, in the case of white display. In addition, it is possible to remove the theoretical limit in the case of the conventional device due to the color mixture of the three additive primary colors, and the theoretical limit of the reflectance for white display is improved to three times that of the conventional device. In addition, although the deviation from the theoretical limit due to the actual dichroic dye cannot be ignored, the theoretical limit of whiteness due to the use of polarized light using a polarizing plate can be removed by making it a non-polarized state, The theoretical limit is doubled.

When a guest-host liquid crystal layer capable of controlling the polarization direction of transmitted light is used, the birefringent optics is subject to the limitation of theoretical limit due to the use of polarized light as in the case of using the above polarizing plate. Since the film does not cause a theoretical loss of light due to coloring in polarized light in the optical axis direction or in the direction orthogonal to the optical axis, it is possible to remove the above-mentioned restriction due to additive color mixing by using this for white display. is there. That is, the first essence of the present invention is the above-mentioned JP-A-8-296.
It is not to utilize the color development by birefringence as a color-developing mechanism instead of the color filter like the element described in 18, but to realize the additive color mixture which is difficult with the above-mentioned element to enable high density display, Furthermore, it is possible to overcome the theoretical limit of the conventional additive color mixture method by utilizing the condition that color development due to birefringence is eliminated, and by using this, the difficulty of whiteness of the conventional reflective color element can be solved. The idea is that it can be solved in principle.

In the case of the element of the present invention by changing the polarization direction, there is an advantage that the gradation of color development due to birefringence, which is difficult to realize conventionally, can be realized. As described above, according to the structure of the present invention, the theoretical limit of the brightness of the white state is three times or six times that of the conventional device in which the color mixture is used for the additive color mixture and the polarizing plate restricts the brightness. A color element can be realized.

When the three basic color pixels are applied to the above basic structure as in the case of a normal transmissive color element, each pixel can be controlled between bright white and chromatic colors, but black can also be obtained by mixing colors. The problem arises that it is difficult to realize. For this reason, it is difficult to display and record characters such as characters and numbers that are desirable in black. In order to solve this, the method of the present invention, that is, a pixel which can be controlled to white and black is added to make it suitable for information display. That is, since the reflective color liquid crystal element has the above-described reflective color liquid crystal element having a combination in which the hue to be formed is an achromatic color due to additive color mixture such as complementary colors and three primary colors, and a repeating pattern including pixels in which the hue to be black is black, However, it is possible to display and record with excellent visibility of characters such as letters and numbers by using a pixel configuration such as complementary color + black or 3 primary colors + black as compared to the configuration of only complementary colors or 3 primary colors. And
It is suitable for portable information devices. Black pixels can be realized by setting the corresponding region of the birefringent optical film to have a retardation of λ / 4. A known pattern such as a stripe pattern or a mosaic pattern can be used as the repeating pattern.

In the above-mentioned basic structure of the present invention, the coloring efficiency, that is, the contrast is high when the reflection layer is a specular reflection layer. However, in this case, there are problems such as the appearance of the outside scene where the surroundings or the user himself / herself is reflected on the liquid crystal element,
The viewing angle is narrow. In order to solve this, unevenness may be provided in the reflective layer to give diffuse reflectivity, but there is a drawback that the process becomes complicated. This difficulty can be solved by the method of the present invention, that is, by adding a diffusion transmission layer to the surface or the like.
That is, since the present invention is any one of the above reflective color liquid crystal elements having a diffuse transmission layer, it is possible to use a specular reflection layer such as an aluminum vapor-deposited film that has high reflection efficiency and is easy to manufacture. Therefore, it is possible to improve the difficulty such as the appearance of the outside scene when the specular reflection layer is used by the diffuse transmission layer.

The diffusion / transmission layer is of a type that utilizes the difference in refractive index between internal minute regions such as a method of adding fine particles of a white inorganic pigment or organic fine particles to a polymer material base, or an uneven interface such as an uneven surface. A type that utilizes the difference in refractive index of The diffusion transmission layer may be provided between the reflection layer and the guest-host liquid crystal layer, but it can be suitably implemented by providing it on the outside of the guest-host liquid crystal layer such as the device surface. In this case, an ultraviolet absorber, a fluorescent whitening agent or the like may be added, and a film which also serves as a protective film can be obtained. It may also serve as an input device on the surface of an element such as a touch panel type.

Next, the guest-host liquid crystal layer will be described. As the guest host layer used in the present invention among various guest host layers, a guest host liquid crystal in which at least one of the alignment states of liquid crystal molecules which changes depending on whether an electric field, heat is applied or not is applied, has no twist. Layers, ie
A guest-host liquid crystal layer in which transmitted light in at least one state that changes depending on whether an electric field, heat is applied or not is linearly polarized can be used, but a phase transition including twist due to addition of a chiral agent, etc. Guest host layers such as modes are unsuitable. Specific examples of the array state corresponding to the above include an array having no clear twist parallel or almost parallel to the substrate such as a homogeneous array, an array uniformly inclined with respect to the substrate, a bend or hybrid array, etc. .

Of these, by using a guest-host liquid crystal mode capable of taking an array state such as a homogeneous array state parallel to the substrate, a guest-host liquid crystal mode is brought into a colored state,
Since light having a good degree of polarization can be incident on the optical film, it is possible to obtain an element having good color development due to birefringence. That is, the direction of the absorption axis of the guest-host liquid crystal layer in the above-described array state or the direction of the transmission axis orthogonal thereto,
By setting the angle formed by the optical axis direction of the optical film to be an angle other than parallel and orthogonal, preferably 45 degrees, it is possible to obtain an element having a good coloring property in a coloring state.

As a concrete example of the guest-host liquid crystal mode in which a twist-free alignment state parallel to the substrate, such as a homogeneous alignment state, is taken, first, the present invention is selected from the guest-host liquid crystal modes of the type in which an electric field is applied perpendicularly to the substrate. List the preferred modes. Among these types, a guest-host liquid crystal mode using a smectic liquid crystal known as a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal, a Np liquid crystal having a homogeneous initial alignment, a Nn liquid crystal having a homeotropic initial alignment. The guest-host liquid crystal mode using an Nn liquid crystal having an alignment state, a bend orientation or a hybrid orientation and having no or little twist may be mentioned. When a guest-host layer made of a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal is used, a tilt angle of 4 is well known when the guest-host mode is made by using these liquid crystals.
A guest host liquid crystal layer of 5 degrees is not preferred in the present invention. For use in the present invention, a dichroic dye is preferably added to a ferroelectric liquid crystal or antiferroelectric liquid crystal used in a normal birefringence mode having an inclination angle of 22.5 degrees.

Further, a guest-host liquid crystal layer using a p-type liquid crystal exhibiting a smectic A phase may be used for the substrate subjected to the parallel alignment treatment and the base paper. can do. For example, a guest-host liquid crystal layer having a narrow nematic phase on a smectic A phase is formed on a parallel alignment-treated alignment layer, and the optical axis of the birefringent optical film forms an angle of 45 degrees. The guest-host liquid crystal layer, the birefringent optical film, and the reflective layer are arranged in optical series. When this is heated so as to be an isotropic phase and then gradually cooled and passed through the nematic phase, the guest host layers are aligned in parallel and the pixels are in a colored state. In this case, when the guest host layer is cooled while applying an electric field, the guest host layer has a vertical orientation and the pixel becomes transparent or white. When the material is rapidly cooled from the isotropic phase, the guest host layer has a random orientation and the pixel becomes black. As described above, when the smectic liquid crystal is used, it is possible to display and record with a memory property. Further, a polymer liquid crystal may be used, or a polymer dispersion type may be used.

Examples of the mode in which an electric field is applied in the direction parallel to the substrate surface include a guest-host liquid crystal mode in which the initial alignment is homogeneous alignment and Np liquid crystal or Nn liquid crystal is used. For example, it can be realized by applying the guest-host liquid crystal composition to the mode described in JP-A-7-225388. In this case, if the direction of the molecule or the director is controlled at an angle of up to 45 degrees, and the direction of the director in the initial alignment state and the direction of the optical axis of the optical film are set to be parallel, no electric field is applied. It is possible to obtain an element that develops white color in the state and chromatic color in the applied state.

Among the guest-host modes that can be used in the present invention, at least one of the alignment states of liquid crystal molecules which changes depending on whether an electric field, heat is applied or not, is an alignment state perpendicular to the substrate such as a homeotropic alignment state. By using the guest-host liquid crystal mode that takes the light, the light whose polarization state has been canceled can be incident on the optical film.
By making this a non-coloring state, it is possible to realize a reflective element having excellent brightness and whiteness as compared with the method using a polarizing plate, although it depends on the dichroism of the guest-host composition. Specifically, among guest-host liquid crystal modes of a type in which an electric field is applied perpendicularly to the substrate, those using Np liquid crystal and having an initial alignment of homogeneous alignment, those using Nn liquid crystal and having an initial alignment of homeotropic alignment, and bends A guest-host liquid crystal mode using Np liquid crystal having no or little twist, which may be an alignment or a hybrid alignment, may be mentioned.

Among the above, the use of Nn liquid crystal with the initial alignment in the homeotropic alignment state makes it possible to construct an element having particularly high whiteness. In addition, the bend orientation or the hybrid orientation may be N with no or little twist.
When the guest-host liquid crystal mode using p-liquid crystal is used, the difficulty of high driving voltage, which is a general difficulty of the guest-host mode, is alleviated.

The optical film used in the present invention has a refractive index anisotropy Δ.
An optical film that has retardation (Δn · d) that differs depending on the region defined by n and thickness d, and that has a plurality of regions that have different hues due to birefringence and that are optically parallel, and that polymerizes with a liquid crystalline mesogen group. It can be produced by a method of polymerizing a monomer or oligomer having a functional group on an alignment-treated substrate. For example, it can be formed by the method described in JP-A-8-29618 by a photopolymerization method.

The optical design of the optical film of different retardation used in the present invention varies depending on the region caused by birefringence when the optical film is arranged between parallel polarizers and white natural light is incident. The transmitted light of the coloring hue is red,
In the case of the present invention, considering the retardation condition of the combination of the additive primary colors of green and blue or the additive primary colors of subtractive color mixture, the complementary color pair and the like, which becomes an achromatic color as a reference, it is reflected by a reflecting mirror. , Part 1
A retardation of / 2 provides an optical film suitable for color display.

A liquid crystal material is disclosed in Japanese Patent Laid-Open No. 22538/1995.
8 or those having further substituents, or Liquid Crystal Device Handbook (edited by Japan Society for the Promotion of Science, 142nd Committee: 1989), P116 to P192.
Biphenyl having a cyano group having a P-type or N-type dielectric anisotropy such as those described in JP-A-7-225388 or further having a substituent, a fluorine atom, a chlorine atom, etc. In addition to various nematic liquid crystals having skeleton of phenylcyclohexane or its derivatives, or smectic A liquid crystals, smectic liquid crystals such as ferroelectric liquid crystals having an optically active center and antiferroelectric liquid crystals, or these via a spacer group or the like. It can be selected from pendant polymer liquid crystals linked to polymer chains. As the guest-host liquid crystal, various dichroic dyes such as azo and anthraquinone compounds are mixed, and preferably the black compounded dye is dissolved in the above Np liquid crystal, Nn liquid crystal, ferroelectric liquid crystal, polymer liquid crystal and the like. Can be prepared. The dichroic dye may be linked to the polymer chain via a spacer group or the like.

Further, driving is performed by a triode element such as TFT, TF
A bipolar element such as D or an active element such as a plasma element may be used. By constructing these active elements on the back surface of the reflective layer that also serves as an electrode, the element aperture ratio is increased to improve brightness and whiteness. Can be made.

Incidentally, Japanese Unexamined Patent Publication (Kokai) No. 8-29618 describes that a guest-host mode is combined with an optical film having different retardation depending on the region. However, the optical configuration and characteristics of the reflection type are clear. is not. In a broad sense, the guest-host mode means a mode in which a so-called guest-host effect is used in which a dichroic dye is added to liquid crystal and the dichroic absorption is utilized. If a liquid crystal composition containing a dichroic dye is used instead of, the guest-host effect can be easily utilized. That is, it can be widely applied from TN and STN modes to PDLC mode or ferroelectric liquid crystal, and has two polarizing plates, one polarizing plate or no polarizing plate. It is no exaggeration to say that there is no liquid crystal display mode that cannot be changed. For this reason, its specific configuration is extremely diverse.

On the other hand, the guest-host mode is, in a narrow sense or a typical mode, a mode known as a Heilmeier system using a single polarizing plate and a white Taylor system in which a chiral agent is added to cause twisting. The phase transition guest-host mode and the two-layer mode of Uchida et al. Are known, but the constitution of the present invention is distinctly different from them.

Further, as is clear from the application example to the TN device shown in the embodiment of the above-mentioned Japanese Patent Laid-Open No. 8-29618,
The birefringent optical film is completely different from the conventional pigmented color filter that develops color regardless of whether it is polarized light or non-polarized light, and since it develops color only under a specific polarization condition, it has no compatibility with each other. For this reason, it is extremely difficult to apply it to an existing liquid crystal element as it is, and a special device that has been optically examined is indispensable for application to the element. For example, PD
It is not easy to effectively apply the characteristics of PDLC to a liquid crystal mode, which is characterized by brightness by not using polarized light like LC. Under such circumstances, the guest host mode is merely described in Japanese Patent Laid-Open No. 8-29.
From 618 it is clear that the basic features of the invention and the salient features of the reflective type are not readily conceivable.

EXAMPLE FIG. 1 is a schematic cross-sectional view of a reflective element of the present invention having an optical film having a region where retardation differs from that of a guest-host liquid crystal layer, and a conductive reflective layer. 11 is a diffuse transmission layer, 1
2 is a transparent substrate which may have electrodes, 13 and 15 are alignment layers for aligning guest-host liquid crystals, 14 is a guest-host liquid crystal layer, and 16 is a birefringent layer having regions with different retardations. An optical film, 17 is an alignment layer for orienting the optical film, 18 is a reflection layer also serving as an electrode, 19 is an insulating layer, 20 is an active element such as TFT, and 21 is a substrate. In this figure, an example in which the liquid crystal and dye molecules are parallel to the substrate is shown, but the mode in which the projection component of the transition moment vector of the absorption of the dichroic dye onto the substrate is theoretically zero, such as vertical alignment. With the exception of, any mode having a substantially linear constant value can be used.

As an example of the method of constructing the device of the present invention, a TFT device 20 is formed on a substrate 21, an insulating layer 19 having a through hole is formed, and a metal reflection layer 18 such as aluminum is vapor-deposited thereon. Then, an electrically conductive coupling portion with the TFT element is simultaneously formed in the through hole. Next, an alignment layer 17 for the optical film is formed, and an optical film material having a mesogenic group such as biphenyl is applied on this,
The film is exposed and cured through a photomask to form the optical film 16. An alignment film is applied to this and alignment treatment is carried out to form one liquid crystal element substrate, which is attached to the other alignment treatment substrate which may have an electrode, and a guest-host liquid crystal composition is injected into this to form the element of the present invention. To do. Further, the birefringent optical film is configured such that regions having different retardations determined by the product of the refractive index anisotropy Δn and the thickness d have repeating units such as stripes and mosaics.

FIG. 2 is a model plan view showing the colored and non-colored states of the color liquid crystal element utilizing the color development by birefringence of the present invention. Figure (2-A) shows the color development state,
(2-B) and (2-C) show a non-coloring state, that is, a white state of the present invention. 21A to 21C are the transmission axis direction of the guest host layer, 22 is the optical axis direction of the birefringent optical film, 23A to 23C are liquid crystal molecules corresponding to colored and non-colored states, and 24A to 24C are corresponding dichroisms. Indicates a dye molecule. The color-developed state and the non-color-developed state may be applied with electric field, applied with heat, or not applied.

First, the coloring state due to birefringence will be described with reference to FIG. (2-A) which is a model diagram of the coloring state. In a state where the direction of the optical axis of the optical film and the direction of the transmission axis of the guest host layer have an angle other than parallel or orthogonal to each other, linearly polarized light passing through the guest host layer is elliptically polarized due to the refractive index anisotropy of the optical film, The light passes through the optical film while changing to circularly polarized light, linearly polarized light, etc., is reflected by the reflective layer, passes through the optical film again, then becomes light in either state, and re-enters the guest host layer. . The light emitted from the guest host layer may be achromatic light, and in many cases, colored light. The coloring of the emitted light is maximum when the direction of the optical axis of the optical film and the direction of the transmission axis of the guest host layer form an angle of 45 degrees with each other. Therefore, this condition is usually set, but from this angle It can be used with a deviation of about ± 15 degrees. The hue of the emitted light differs depending on Δn and the thickness d of the optical film, and in the case of the present invention, it is folded back by the reflection layer, so that Δn · d is effective.
It will be twice the retardation. The retardation of the optical film of the black pixel used in the present invention is achieved by setting the retardation condition that the incident polarized light to the optical film returns as orthogonal polarized light, that is, λ / 4. .

The non-coloring state, that is, the white state is (2-
B) and two states shown in (2-C) are possible.
A guest-host mode capable of controlling the colored state of -A) and the state of (2-B) or (2-C) can be preferably used in the present invention. That is, the (2-B) non-coloring state is configured such that the absorption axis of the guest host layer or the transmission axis orthogonal thereto is parallel or orthogonal to the optical axis of the optical film.
In both of the above two types of non-color-developing states, that is, in the white state, it is not necessary to create white by the principle of color mixing such as complementary colors or color mixing of three primary colors as in the conventional mode. It is possible to remove the theoretical limit in the case of, and the theoretical limit of the reflectance of white display is improved to three times that of the conventional device. this house,
In the case of the mode that takes the non-colored state of the non-polarized state shown in (2-C), the theoretical limit of the whiteness due to the use of conventional polarization can be removed, and therefore the theoretical limit of the reflectance of white display is It will be further doubled.

In the non-colored state of the non-polarized state shown in the above (2-C), in the case where a nematic liquid crystal is used among the modes in which an electric field is applied perpendicularly to the liquid crystal layer, parallel alignment treatment is performed. A non-electric field-imparted state obtained by filling a liquid crystal in the above-described cell is a homogeneous alignment state which may have a pretilt or a substantially homogeneous alignment state, and N
First, a mode using p liquid crystal is given. An orientation state having a large pretilt and a certain inclination may be used.

Further, a mode in which Nn liquid crystal is used in a vertically-aligned cell and homeotropic alignment or substantially homeotropic alignment in a state where no electric field is applied is also a mode useful in the present invention. The molecules are arranged so that the molecules are oriented in one direction, parallel or almost parallel to each other, without twisting, and a colored state is obtained. As a means for arranging molecules in one direction in an electric field-applied state, an orientation with a tilt in one direction or the effect of a lateral electric field component such as a tilted electric field in the fringe portion is formed by staggering the upper and lower electrodes. , A. Lien, R .; A. John: Euro. Di
Known methods such as the method described in spray '93, p22 (1993) can be applied.

In addition, a mode in which the liquid crystal array has a bend structure can also be used in the present invention. As a typical example of this, there is a mode in which the upper and lower substrates are subjected to parallel alignment and vertical alignment treatments, respectively, and are in a hybrid alignment state in which no electric field is applied and a transition is made from a homogeneous alignment to a homeotropic alignment. Np for this sequence
It is preferably used in the present invention by applying a sufficient electric field using a liquid crystal to make the alignment of liquid crystal molecules substantially vertical so that the liquid crystal molecules are in a non-coloring state. In the various modes in which an electric field is applied perpendicularly to the liquid crystal layer, the degree of polarization can generally be continuously changed over the non-polarized state, and thus gradation display of color development by birefringence can be realized.

Next, a mode in which (2-B) is in a non-coloring state will be described. Among the modes in which an electric field is applied perpendicularly to the liquid crystal layer, examples of modes using smectic liquid crystals include modes using ferroelectric liquid crystals and antiferroelectric liquid crystals, in which liquid crystal molecules are substantially parallel to the substrate. . In this case, a liquid crystal having an inclination angle of 22.5 degrees is used to perform switching at an angle of approximately 45 degrees, and the transmission axis direction of the guest host layer in one state is orthogonal or parallel to the optical axis of the optical film. To do.

Among the modes in which the electric field is applied in the direction parallel to the liquid crystal layer, the mode in which the electric field is not applied is the homogeneous state or the substantially homogeneous state, and the mode in which the electric field is applied in the direction parallel to the substrate by using a comb-shaped electrode is Useful in the present invention. This mode can also control the gradation of color development by birefringence. In this case, either Np liquid crystal or Nn liquid crystal may be used. The pair of electrodes may be provided via an insulating layer, and an example of a specific electrode structure is disclosed in JP-A-7-225388.
Examples include the structures described.

[0045]

According to the present invention, it is possible to realize a reflection type color liquid crystal element which is excellent in whiteness and brightness and which is suitable for use in portable information equipment and the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reflective color liquid crystal element that is an embodiment of the present invention.

FIG. 2 is a model diagram showing a coloring state and a non-coloring state due to birefringence of the present invention.

[Explanation of symbols] 11 Diffuse transmission layer. 12 A transparent substrate that may have electrodes. 13, 15 Alignment layer. 14 Guest-host liquid crystal layer. 16 An optical film having regions with different retardations. 17 Alignment layer of optical film. 18 Reflective layer that doubles as an electrode. 19 Insulating layer. 20 Active element such as TFT. 21 Substrate.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-333600 (JP, A) JP-A-4-225322 (JP, A) JP-A-4-371923 (JP, A) JP-A-1- 244425 (JP, A) JP 56-92520 (JP, A) JP 9-146124 (JP, A) JP 9-90431 (JP, A) JP 3-114023 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/137 G02F 1/1335 G02F 1/1343 G02F 1/1362 G02F 1/13363

Claims (6)

(57) [Claims] 1. A guest-host liquid crystal layer in which at least one of the alignment states of liquid crystal molecules which is changed by application of an electric field, heat, or no application is in an alignment state having no twist other than an alignment state perpendicular to a substrate, possess an optical film having a plurality of regions having different retardation optically parallel, the conductive reflective layer such as a metal as a basic optical components
The optical film has a complementary hue such as complementary colors, three primary colors, etc.
Of chromatic pixels that become achromatic by various additive colors
And a pixel whose coloring hue is achromatic in itself, such as black
Including and, which form a repeating pattern
A reflective color liquid crystal device characterized by: 2. A reflection type color liquid crystal device請<br/> Motomeko 1, wherein further comprising a diffuse transmission layer. 3. A guest-host liquid crystal mode in which at least one of the alignment states of liquid crystal molecules that changes with the application of an electric field, heat, or no application is a guest-host liquid crystal mode in which the alignment state is parallel to the substrate, such as a homogeneous alignment state. The reflective color liquid crystal device according to claim 1 or 2 . 4. A field, the application of heat, at least one of the alignment state of the liquid crystal molecules changes with no applied, according to claim 1 to 3, which is a guest-host liquid crystal mode that takes a hybrid alignment state The reflective color liquid crystal device according to any one of the above . 5. A field, the application of heat, at least one of the alignment state of the liquid crystal molecules changes with no application is that it is a guest-host liquid crystal mode that takes a vertical alignment state to a substrate, such as a homeotropic alignment state reflective type color liquid crystal device according to any one of請<br/> Motomeko 1-4, characterized. 6. The reflection type color liquid crystal device according to any one of claims 1 to 5, characterized in that an increased aperture ratio by arranging the active element such as TFT on the back of the reflective layer.