JPH09258226A - Color liquid crystal element and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal element having a wide visual field angle adequate for TVs, etc., without using a color filter by providing the element with repetitive units of plural pixels varying in the hues of a color developed state, executing the control by the electric field of the pixels between the non- color developed state and a prescribed color developed state and utilizing an additive mixture of colors. SOLUTION: A liquid crystal layer 13 is arranged between transparent substrates 12 and 14 which may have a pair of polarizers 11, 15 and transparent or comb-shaped opaque electrodes, etc. This liquid crystal layer 13 has the repetitive units consisting of plural liquid regions 13A to 13C varying in the retardation corresponding to the pixels exhibiting the color development varying by double refraction. The liquid regions 13A to 13C varying in the retardation are so regulated that the retardation is varied by a difference in the refractive index anisotropy and thickness under a specified or nearly specified electric field condition including an electric field nonimpression state. The control to the different hues by the electric fields of the pixels is not executed in this constitution and the color display is executed by utilizing the additive mixture of colors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal element and a display device suitable for personal computers, TVs, portable information devices and the like.

[0002]

2. Description of the Related Art Liquid crystal displays have become mainstream in the field of flat high-density color displays utilizing additive color mixture in personal computers and the like because of their thinness and lightness. In this field, a color liquid crystal device in which a color filter is combined with a TN device such as a normally-white mode is used, but due to the following difficulties, there is a limit in application to family applications such as TVs and portable information devices. , Difficulties of conventional elements 1) The viewing angle is narrow. In particular, there are difficulties in the vertical direction, and it is difficult to secure a viewing angle of 60 degrees from the normal in the horizontal direction. 2) In the middle tone, the hue tends to become cloudy. Further, the hue is likely to be inverted depending on the viewing angle. 3) Material cost is high because a color filter is used. 4) It becomes dark because a color filter is used, and it is particularly difficult to realize a reflective display that does not use a backlight.

On the other hand, as a conventional method which does not use a color filter, a method generally known as an electric field controlled birefringence (ECB) method such as a DAP type utilizing color development by birefringence is known. Since this method can change the hue of the pixel itself to produce the primary color without using additive color mixing, it has the advantage of being able to perform color display with a simple structure, but on the other hand, compared to the normal TN type etc. in terms of the viewing angle and halftone above. In general, there are no advantages. More specifically, the conventional ECB method has a narrow viewing angle, and the hues are completely different depending on the angle. In principle, halftone display is almost impossible. The color hue is easily affected by temperature. Since it passes through different hues in the process of turning on or off, it often causes an unpleasant afterimage and is not suitable for displaying moving images. That is, the TN type is more unsuitable for the field where it was insufficient. Conversely, the conventional E
Since the CB method has too many problems, a color liquid crystal element in which a color filter is combined with the above TN element is used.

An object of the present invention is to solve the above problems by drastically reconstructing a conventional color element by birefringence, and to use a transmission type with a wide viewing angle suitable for TVs without using a color filter. It is an object of the present invention to provide a color liquid crystal element, a reflective color liquid crystal element suitable for portable information equipment, and a display device.

[0005]

[Means for Solving the Problems]
The following means are used to achieve the above object.

A liquid crystal layer is disposed between the pair of polarizers,
Alternatively, in a color liquid crystal device that utilizes a color due to birefringence by arranging a liquid crystal layer between a polarizer and a liquid crystal layer, and a reflective layer between a pair of polarizers, the liquid crystal layer is Due to the difference in retardation determined by the refractive index anisotropy Δn and the thickness d, there is a repeating unit of a plurality of pixels having different hues in the colored state. Control by the electric field of the pixel is performed between the non-colored state and a specific colored state. The color liquid crystal element that uses the additive color mixture.

The above-mentioned color liquid crystal device in which the retardation of the liquid crystal layer is different because the refractive index anisotropy Δn of the liquid crystal material is different.

Any one of the above color liquid crystal devices in which the retardation of the liquid crystal layer is different due to the different thickness d of the liquid crystal layer.

In the repeating unit, at least one chromatic color may be included, and an achromatic color may be included. In the case where the additive color mixture is performed in a coloring state under a constant electric field condition by using pixels forming the repeating unit. The color liquid crystal device according to any one of the above, which is a repeating unit of achromatic combination.

In the non-coloring state, the liquid crystal molecules are perpendicular to or substantially perpendicular to the substrate, or in a parallel or substantially parallel state without twist, and in the coloring state, the liquid crystal molecules are parallel or even tilted with respect to the substrate. The color liquid crystal element according to any one of the above, which is in the open state or the bend state.

In the non-coloring state, the liquid crystal molecules are perpendicular to or substantially perpendicular to the substrate, or in the parallel or substantially parallel state without twist, and the liquid crystal molecules in the coloring state are parallel to or substantially parallel to the substrate without twist. A color liquid crystal device according to any one of the above.

[0012] The color liquid crystal device according to any one of the above, wherein the liquid crystal molecules in the colored state and the liquid crystal molecules in the non-colored state are both in a state of being substantially or substantially parallel to the substrate without any twist.

The color liquid crystal element is an electro-optical element that applies an electric field in the direction perpendicular to the substrate, and in the non-color-developing state, the liquid crystal molecules are perpendicular or almost perpendicular to the substrate, and a viewing angle improving means such as a birefringent film is provided. You may use N in the liquid crystal layer.
A mode in which liquid crystal molecules are aligned in a state in which no electric field is applied using p liquid crystal is parallel or substantially parallel to the substrate, or N in the liquid crystal layer.
n liquid crystal is used, and the mode of liquid crystal molecules in which no electric field is applied is perpendicular to the substrate or almost perpendicular to the substrate, or N is applied to the liquid crystal layer.
Any one of the above-described color liquid crystal elements, which is in a hybrid state in which the arrangement of liquid crystal molecules in the no-electric field state using p liquid crystal transits from a state that is parallel or approximately parallel to the substrate to a state that is vertical or approximately vertical.

The color liquid crystal element is an electro-optical element that applies an electric field in the direction perpendicular to the substrate, and the liquid crystal molecules in the non-coloring state are perpendicular to or substantially perpendicular to the substrate, and in the coloring state are parallel or substantially parallel to the substrate. , A mode in which Np liquid crystal is used for the liquid crystal layer and the alignment of liquid crystal molecules in the non-electric field is parallel or almost parallel to the substrate, or the alignment of liquid crystal molecules in the non-electric field is formed on the substrate by using Nn liquid crystal in the liquid crystal layer. Any of the above color liquid crystal devices in a mode that is vertical or nearly vertical.

The color liquid crystal element is an electro-optical element which applies an electric field in a direction perpendicular to the substrate, and the liquid crystal layer is made of Nn liquid crystal and the arrangement of liquid crystal molecules without an electric field is perpendicular or almost perpendicular to the substrate. The color liquid crystal device according to any one of the above, which is a mode in which liquid crystal molecules are tilted in a specific direction by an electric field by utilizing an effect of a lateral electric field due to a fringe electric field as a staggered structure.

Np liquid crystal or Nn liquid crystal is used for the liquid crystal layer,
Any one of the above color liquid crystal devices in a mode in which an electric field is applied in the same in-plane direction as the substrate.

The above-mentioned color liquid crystal element which controls gradation by controlling the intensity of transmitted light by an applied electric field without changing the hue of color development due to birefringence.

On the back surface of any of the above-mentioned transmission type color liquid crystal elements having a repeating unit having a pixel which becomes achromatic in a colored state, such as three primary colors of additive color and black, and a pair of polarizers being parallel to each other. The reflective color liquid crystal device according to any one of the above, which has a reflective layer, or has one polarizer and a liquid crystal layer, and a white metal reflective layer.

In any one of the above reflective color liquid crystal devices having one polarizer, a liquid crystal layer and a white metal reflective layer,
A reflective color liquid crystal device in which Δn · d of the liquid crystal layer is 0.1 to 2.

In any one of the above-mentioned transmission type color liquid crystal elements in which a pair of polarizers are orthogonal to each other, the transmission type color liquid crystal element in which Δn · d of the liquid crystal layer is 0.4 to 4.

A light guide plate and a reflection plate having a fluorescent tube having a high color rendering property such as a three-wavelength fluorescent tube as a light source are provided on the back surface of any of the transmission type color liquid crystal elements in which a pair of polarizers are orthogonal to each other. A color display device configured by arranging a backlight unit such as a surface light source type.

[0022]

According to the present invention, a conventional color element using birefringence will be fundamentally eliminated by fundamentally modifying and reconstructing electro-optical control and steady-state optical configuration by going back to the optical principle. However, in order to avoid the abstract difficulty that tends to fall into the explanation of the principle, a specific example corresponding to the embodiment will be appropriately described.

A color element that does not use a color filter can be formed by utilizing the color development by birefringence, and the conventional ECB element that performs color display by utilizing the color development by birefringence is a liquid crystal device handbook ( 142nd Committee, Japan Society for the Promotion of Science) p473-477
Although various methods such as the DAP type described in 1) are known, they have the above-mentioned problems or problems to be solved.

The present invention is based on the viewpoint that the drawbacks of the conventional ECB method are unavoidable based on the common electro-optical control and steady optical configuration described below. In other words, EC using conventional color development by birefringence
B mode is the following electro-optical control, steady optical configuration 1) Color hue is controlled by electrically controlling the angle of inclination of the same pixel or liquid crystal molecules of the same pixel from the substrate surface. The hue (representing the hue in the Munsell color system) is changed between chromatic colors by changing the retardation of. That is, the electro-optical control between chromatic colors generated by birefringence is fundamental. 2) Coloring due to birefringence is used when liquid crystal molecules have an angle with respect to the substrate surface. That is, a state in which liquid crystal molecules have an angle with respect to the substrate surface is a stationary optical configuration during operation. And have common difficulties derived from it. The points to be noted here are E
Unlike the TN method, the CB method is not characterized by the structural configuration of the cell such as the alignment state in which no electric field is applied, but mainly the electro-optical control of the hue and the steady optical operation during the operation. The present invention has a similar character in this respect.

That is, according to 1), since the hue control between chromatic colors is a feature, a high light shielding state or dark black,
Alternatively, the control is not focused on achromatic color such as realization of bright white required for the reflective element, and therefore, the contrast is insufficient for displaying information such as characters. Further, since electrical control is used for hue control, there is no control means for gradation display, and therefore a direction for solving gradation display cannot be found, and there is no satisfactory mode for image display. Further, due to 2), the viewing angle becomes narrow, and the hue is likely to change depending on the angle. Since the angle of the liquid crystal molecules is changed by 1), it is difficult to apply the technique for improving the viewing angle by using a birefringent film or the like in which it is desirable that the molecular arrangement is constant. Further, a hue change due to a temperature change is likely to occur. Together, these are insufficient for highly visible information display, image display, and the like.

The invention resides in realizing an improved color display due to birefringence, starting from the above recognition. The basic idea or solution procedure of the present invention is based on the following 1) as a base: 1) Hue control between chromatic colors is not performed by birefringence control using an electric field, and each pixel has a unique primary color such as three primary colors. Hue is assigned, and control by the electric field of the pixel is performed between the non-coloring state of the achromatic color and the coloring state of the hue unique to the pixel, and the hue is controlled by using additive color mixture. As a result, the molecular alignment of the liquid crystal in the colored state becomes constant with respect to the substrate, so that it is easy to improve the viewing angle with a birefringent film or the like. 2) As a combination in which the repeating unit of a pixel becomes an achromatic color when its constituent pixels are subjected to additive colors such as complementary colors and three primary colors, in particular, a combination which may include an achromatic pixel such as three primary colors + black When the reflection type element is used, the visibility of character display such as characters and numbers is enhanced, and the element is suitable for portable information devices and the like. 3) Non-coloring state (refers to an achromatic state such as a black light-shielding state or a white transmitting state. When an achromatic pixel is present in a state where the three primary colors + black are present, it produces a chromatic color under the same electric field conditions. The state in which there are no active pixels) means that the liquid crystal molecules are aligned so that a wide viewing angle, high light-shielding properties, and high whiteness can be obtained. 4) The color alignment of the liquid crystal molecules is set to a wide viewing angle. 5) Realize gradation control of color development by birefringence. It is to realize a bright reflective display or image display by constructing a color element by birefringence as in 2) to 5).

That is, as an alternative to the conventional hue control by the birefringence control by the electric field of 1), the liquid crystal is produced by the two means of the present invention under a constant electric field condition, that is, a condition that the molecular arrangement is almost constant. Due to the difference in retardation determined by the layer refractive index anisotropy Δn and the thickness d, a plurality of pixels having different hues are formed, a unique hue is assigned to each pixel, and hue control using additive color mixture is performed. .

The first means is the refractive index anisotropy Δ of the liquid crystal material.
This is a method of selecting a specific color hue by selecting n, and by using a liquid crystal material of Δn that differs depending on the pixel,
In this method, Δn of the liquid crystal layer of the pixel is adjusted to individually fill the pixels partitioned by the partition wall or the like to realize different hues.

The second means is a method of determining a specific color hue according to the thickness d of the liquid crystal layer, in which unevenness having different heights or depths with flat tops or bottoms is provided and the other substrate is bonded. This is a method in which the thickness d of the liquid crystal layer of each pixel is different depending on the method described above. Providing the above-mentioned unevenness of the level required for the present invention on the flat substrate is the basis of the thin film processing technique, and can be carried out by combining various known elemental techniques. As an example in which the thickness d of the liquid crystal layer is specifically changed for each pixel, there is an application example to a TN device described in JP-A-60-202423. The above-mentioned coloring state may be applied with an electric field or not applied.

In addition, the structure of the pixel having a repeating unit is not limited to a combination of only chromatic colors such as complementary colors, three additive primary colors, and three subtractive primary colors, as long as the combination produces an achromatic color by the additive color mixture in the color-developed state. A combination of three primary colors of red, green, and blue and four colors including an achromatic color such as black may be used. When the above-mentioned four colors including black are set to the colored state, the non-colored state is set to white, whereby a reflective element capable of displaying black characters in a white background with good contrast can be obtained.

In the hue control, the conventional ECB element changes the hue of a single pixel and expresses primary colors such as three additive primary colors and three subtractive primary colors in one pixel, whereas the present invention constitutes a repeating unit. It is performed by additive color mixture of pixels. For example, as in the case of expressing the subtractive color primary color yellow by using the pixels of the additive color primary colors red and green, color mixture is controlled and other primary colors are expressed.

As a means for realizing black or moderate white having a high light-shielding property and simultaneously enlarging the viewing angle as described in 3) above, the non-coloring state is such that the liquid crystal molecules are perpendicular or nearly perpendicular to the substrate, or parallel to each other. It is used by controlling the orientation or drive in a substantially parallel state with no twist.

The expansion of the viewing angle in 4) above is achieved by orienting or controlling the coloring state such that the liquid crystal molecules are parallel to the substrate surface or have as little angle as possible.
This eliminates the need for a viewing angle expanding means such as a birefringent film.

To realize gradation display by birefringence in 5) above, a mode is selected in which liquid crystal molecules are operated in a state in which there is no twist parallel to the substrate surface in the process of coloring, non-coloring and its response. Will be realized.

Next, the color display by birefringence will be described in detail from the optical side. The coloring state can be used in the present invention if the direction of the average director of the liquid crystal layer or the projection component of the director on the substrate is an angle other than parallel or orthogonal to the polarization direction of the incident light, but preferably 45 degrees. Set and use the condition that maximizes the coloring effect by birefringence.

The molecular arrangement of the liquid crystal layer is typically a homogeneous state in which the direction of the director is parallel to the substrate, which is preferable in terms of viewing angle, but the liquid crystal molecules are uniformly tilted with respect to the substrate. The average director direction may be angled with respect to the substrate, such as a bent state or a bent state such as a hybrid arrangement. In this case, it is effective to improve the viewing angle with a birefringent film or the like.

The non-coloring state is preferably oriented or controlled so that the alignment of liquid crystal molecules is perpendicular to or substantially perpendicular to the substrate, or parallel to or substantially parallel to the twist-free state. In the case of this parallel or substantially parallel twist-free state, the polarizer is set so that the direction of the director and the polarization direction of the incident light are parallel or orthogonal to each other, and the non-coloring state is set. The pair of polarizers may be orthogonal or parallel. When the pair of polarizers are parallel to each other, the hue in the coloring state becomes a complementary hue in the orthogonal state, and an element capable of controlling the transmission state or the non-coloring state of white and the above-mentioned coloring state can be obtained.

The black coloring state may be set to retardation of λ / 2 when the angle between the director and the polarization direction is 45 degrees. The color-developed state and the non-color-developed state may be applied or not applied with an electric field. By setting and driving in this way, a high light-shielding property or a non-coloring state having a moderate white color and a wide viewing angle is achieved.

Further, the constitution of one polarizer, the liquid crystal layer and the reflection layer, which can be regarded as optically equivalent to the system in which the liquid crystal layer is disposed between the pair of polarizers, is excellent in the brightness of the present invention. It is important as a reflective color liquid crystal device. in this case,
The reflective layer is preferably a conductive material such as a white metal material such as aluminum. Although the reflective layer may be provided on the back surface of the substrate, providing the reflective layer close to the liquid crystal layer improves the viewing angle, double reflection, and the like. As a reference example of such a configuration, T.W. Uchida et al. , ASIA
The configuration of the monochrome element described in DISPLAY '95 p599 (1995) and the like can be mentioned.

Further, like the homogeneous state, the colored state is preferable because the molecular arrangement of the liquid crystal layer is free from twisting because it is not affected by optical rotation, but it may be twisted. When twisting is involved, such as in a twisted state, the polarizers may be set at an angle deviating from normal orthogonal or parallel.

Further, in order to easily embody the above idea of the present invention, an example of the electro-optical element used in the present invention will be described from the aspect of the alignment mode when no electric field is applied. As an example of a mode in which a nematic liquid crystal is used among the modes in which an electric field is applied perpendicularly to the liquid crystal layer, a state in which no electric field is applied is a homogeneous alignment state or a substantially homogeneous alignment state, and
A mode using p liquid crystal, a mode in which homeotropic alignment or almost homeotropic alignment is obtained in the state where no electric field is applied using Nn liquid crystal, or an intermediate state between homeotropic state and homogenous state in which no electric field is applied using Np liquid crystal A mode in which the hybrid orientation state is

In this case, since the angle of the liquid crystal molecules in the colored state falls within a certain range by the constitution and control of the present invention, the viewing angle can be easily improved by the birefringent film. As a reference example for the construction of the reflective element, the above T. Uchida et al. , ASIA DISP
LAY'95 p599 (1995) etc. are mentioned.

If the orientation mode is such that an alignment state of liquid crystal molecules parallel or substantially parallel to the substrate such as the above-mentioned homogeneous alignment state can be taken in the state where the electric field is applied or not applied, a color is formed by setting this as a coloring state. A display with an improved viewing angle in a state can be realized. Among the modes using the nematic liquid crystal described above, a mode using Np liquid crystal in which no electric field is applied is a homogeneous alignment or a substantially homogeneous alignment,
An example is a mode in which homeotropic alignment or substantially homeotropic alignment is performed in a state where no electric field is applied using n liquid crystal.

In the mode in which a nematic liquid crystal is used among the modes in which an electric field is applied perpendicularly to the liquid crystal layer, the non-coloring state is aligned or driven so that the liquid crystal molecules are aligned vertically or almost vertically to the substrate. By using
The viewing angle in the non-colored state is improved. That is, except when the liquid crystal molecules in the non-electric field applied state are already vertical,
A sufficient electric field is applied to drive the liquid crystal molecules so that the liquid crystal molecules are aligned vertically or almost vertically to the substrate, and a non-coloring state is obtained. By such a method of the present invention, a non-coloring state having a wide viewing angle, a light shielding property or a high whiteness is achieved.

As an example of the mode using the smectic liquid crystal, there is a mode in which a ferroelectric liquid crystal and an antiferroelectric liquid crystal are used, and a state in which liquid crystal molecules are almost parallel to the substrate and not twisted is used. In this case, since the arrangement of the liquid crystal molecules in the colored state and the arrangement of the liquid crystal molecules in the non-colored state are both parallel or substantially parallel to the substrate, display with a wide viewing angle can be performed.

The realization of gradation display of color development by birefringence, which is the next subject of the present invention, will be described in detail. In order to solve this problem, it is necessary to directly change the brightness of the coloring state without changing the hue. In recent years, there is no example of directly controlling the coloring brightness by birefringence, but the direction of the director of the liquid crystal layer is changed without changing the retardation of the present invention to change the angle formed by the polarization direction. To be achieved.

More specifically, an electro-optical mode in which the direction of the director can be changed in the plane of the substrate in an analog manner, for example, M.M. Oh-e et al. , ASIADIS
It can be realized by using Np liquid crystal or Nn liquid crystal described in PLAY '95p577 (1995) and using a mode in which an electric field is applied in the in-plane direction of the substrate by a comb-shaped electrode or the like. Specifically, as the angle between the direction of the director of the liquid crystal layer and the polarization direction of the incident light is parallel, that is, 0 degrees, from the non-coloring state, the polarizers are made orthogonal to each other as the angle is increased up to 45 degrees. When set, the brightness in the non-coloring state, which is a light-shielding state, increases from the non-coloring state to the maximum at 45 degrees.

Since the mode in which the electric field is applied in the in-plane direction of the substrate does not pass through another hue in the process of response, compared with the other modes using the nematic liquid crystal, an afterimage having a strange feeling in the response process is generated. It never happens. When the polarizers are set to be parallel, white light that is in a non-coloring state at 0 degree,
At 45 degrees, the hue develops with a hue determined by retardation, and at an intermediate angle, the hue develops lightly. In this case, a reflective element suitable for character display or the like can be obtained by adding a pixel that becomes black in the colored state as described above.

Next, the features of the device of the present invention will be clarified, and the significance of the application of the device such as a display device will be described. The first feature of the element of the present invention is that it is possible to easily select a hue that is free from turbidity due to birefringence without using a color filter. Therefore, whether it is a transmission type or a reflection type, a clear hue is bright. Color display is possible. Among them, the feature of brightness is particularly effective when the polarizers are set parallel to each other to form a reflective element. That is, since it is possible to control the unit pixel between the non-coloring state of white and the clear coloring state due to birefringence, a reflective plate can be added to form a reflective element having good whiteness or brightness. Even when a single polarizer, a liquid crystal layer, and a reflective layer are used, since it is possible to control between white and vivid color development due to birefringence, a reflective element with good whiteness or brightness can be obtained. In the case of the above-mentioned two types of reflective elements, by adding pixels whose coloring state is black, it is also suitable for character display.

The second feature of the device of the present invention is that the conventional EC
Compared to the B element and the TN type element, it has a high light-shielding property, a dark black color, a high contrast, and a wide viewing angle, especially when a pair of polarizers are orthogonal to each other. The viewing angle is selected so that the angle of the molecules in the colored state with respect to the substrate is constant, so that it is easy to improve the viewing angle with a birefringent film or the like. In addition, the viewing angle is remarkably improved and the viewing angle of 60 degrees or more with respect to the normal to the substrate can be easily achieved by further arranging the colored state in a molecular arrangement parallel to the substrate.

Regarding the light-shielding property and the contrast,
In particular, in the mode in which homogeneous alignment treatment is performed using Nn liquid crystal and the mode in which an electric field is applied in the in-plane direction of the substrate, the light shielding property, contrast and viewing angle are remarkably excellent. In this case, a contrast of 300: 1 or more, which is difficult for the TN type, can be easily realized. Further, the above two types are also excellent in that they are easy to use as a transmission type in that they are normally black. The third feature is that the gradation control of color development by birefringence, which has been difficult in the past, is realized by the mode in which the electric field is applied in the surface of the substrate. Therefore, a transmissive color liquid crystal device suitable for image display for family use can be obtained.

Due to these characteristics of the device of the present invention, the light source is a three-wavelength fluorescent tube having a high color rendering property, a three-primary-color LED, and the like.
By combining with a backlight unit which may have a light guide plate or a reflection plate or an organic EL element having a high color rendering property, it is possible to form a thin, flat display device or the like, and particularly in the above-mentioned substrate plane. A display device suitable for image display such as a TV can be obtained by combining with a mode in which an electric field is applied. Hereinafter, the idea and embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

Example FIG. 1 is a schematic sectional view showing an optical basic structure of a color liquid crystal device having pixels showing different colors due to birefringence according to the present invention. FIG. 1-A shows a pair of polarizers 11 and 1.
5. A liquid crystal layer 13 is arranged between transparent substrates 12, 14 which may have transparent or comb-like opaque electrodes. The liquid crystal layer has a repeating unit composed of a plurality of liquid crystal regions having different retardations corresponding to pixels which exhibit different colors due to birefringence, and the liquid crystal regions 13 having different retardations.
It is specified that A to 13C have different retardations due to different Δn and thickness d under a constant or almost constant electric field condition including no electric field applied. Transparent substrate 1
An alignment layer or a flattening layer made of polyimide or the like, an insulating dielectric layer, or the like may be provided between the liquid crystal layers 2 and 14 and the liquid crystal layer 13, and an active driving element such as a TFT may be provided. A partition may be provided at each boundary of the liquid crystal regions 13A to 13C.

Between the pixels, a black light-shielding layer may be provided on the transparent substrate corresponding to the boundary of the liquid crystal region, and a black mask for shielding the TFT element part and the boundary part may be provided. It may also serve as a black mask.
The element of FIG. 1-A is used as a transmissive element,
A reflective plate having a diffusive reflective layer or the like may be provided on the back surface to form a reflective element.

FIG. 1-B shows a reflective element having a polarizer, a liquid crystal layer, and a reflective layer as basic components.
The liquid crystal layer 13 and the reflective layer 16 are arranged between the transparent substrate 12 which may have the above-mentioned electrodes and the substrate 14 which may be opaque. The reflective layer 16 is preferably a conductive reflective layer made of a metal such as aluminum or silver having a high reflectance in the visible region and having a low whitening property. The reflective layer may also serve as an electrode, may be electrically independent for each pixel, or may be formed on an active element such as a TFT.

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.

The basic idea of the present invention is that, usually, the hue control between chromatic colors by the electric field of a single pixel is not performed, the coloring state and non-coloring state of the set hue are controlled by the electric field, and the plural pixels are used. Although there are other primary colors to be displayed by using the additive color mixture, the coloring state and non-coloring state used in the present invention will be described with reference to FIG. The figure (2-A) shows a color-developed state, and (2-B) and (2-C) show a non-colored state. Reference numerals 21 and 22 respectively indicate the transmission axis directions of the polarizer and the analyzer, and show the case where they are orthogonal to each other in the figure. 23
A to 23C are liquid crystal molecules corresponding to colored and non-colored states, 2
4A to 24C indicate the directions of the projection components of the director of the corresponding liquid crystal layer onto the substrate surface. The pair of polarizers may be either orthogonal or parallel, but the case where they are orthogonal will be described below as an example unless otherwise specified. Coloring state,
The non-colored state may be applied with an electric field or not applied.

First, the coloring state due to birefringence will be described. When the direction of the projection component of the director and the transmission axis direction of the polarizer have an angle other than parallel or orthogonal to each other, linearly polarized light passing through the polarizer is elliptically polarized or circularly polarized due to the refractive index anisotropy of the liquid crystal layer. The light passes through the liquid crystal layer while changing like linearly polarized light, becomes light in one of the states depending on Δn and the thickness d of the liquid crystal layer, and enters the analyzer. The light that has passed through the analyzer is in some cases white light and in many cases colored light.
The hue of the transmitted light is determined by the retardation determined by Δn and the thickness d of the liquid crystal layer.

A plurality of pixels having different hues are shown in FIG.
Liquid crystal regions 13A to 13A having different retardations in the colored state of A) under different electric field conditions are arranged in parallel as shown in FIG. 1 so as to have repeating units such as three primary colors. The non-coloring state of the present invention is basically as shown in FIG.
(2-C). That is, the direction of the director is parallel to or orthogonal to the polarization direction of the incident polarized light as shown in FIG.
As described above, the direction of the director is perpendicular to the polarization direction. The non-coloring state is a light-shielding state or a transmission state depending on whether the polarizers are orthogonal to each other or parallel to each other,
Alternatively, in the case of a reflective type, the state is black or white. The above-mentioned colored state and non-colored state may be applied or not applied with an electric field.

Next, from the viewpoint of the alignment state when no electric field is applied, in the mode in which the nematic liquid crystal is used among the modes in which the electric field is applied perpendicularly to the liquid crystal layer, the liquid crystal is filled in the cells subjected to the parallel alignment treatment. The first mode is a mode in which the non-applied electric field is a homogeneous alignment state or a substantially homogeneous alignment state that may have a pretilt, and uses Np liquid crystal. The pretilt angle of the upper and lower substrates may be changed, or the orientation state having a large pretilt and having a substantially constant inclination may be changed. When using the above Np liquid crystal,
The no voltage applied state is the colored state, and the voltage applied state is the non-colored state.

A mode in which Nn liquid crystal is used in a vertically-aligned cell and homeotropic alignment or substantially homeotropic alignment is obtained without application of an electric field is also a mode useful in the present invention. The molecules are arranged so that the molecules are oriented in one direction, which is parallel to or approximately parallel to, and a colored state is obtained. As a means for arranging molecules in one direction in the state of applying an electric field, orienting with an inclination in one direction,
By using the effect of a lateral electric field component such as an inclined electric field of the fringe portion as a configuration in which the upper and lower electrodes are offset, A. Li
en, R.M. A. John: Euro. Display '
93, p22 (1993) and other known methods can be applied. This alignment mode can provide a display with excellent light shielding properties.

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 the pixels are not applied with an electric field and transition from a homogeneous alignment to a homeotropic alignment is performed. To be In the case of the hybrid arrangement, there is no particular limitation in using either Nn liquid crystal or Np liquid crystal in the conventional ECB element, but the idea of the present invention is set without normally performing hue control by the electric field as described above. Since the colored state and the non-colored state of the specific hue are controlled by the electric field, it is not easy to set the colored state of the specific hue and the non-colored state having a particularly high light shielding property in the mode using the Nn liquid crystal. Not suitable. In the case of this arrangement, Np liquid crystal is used in the present invention by applying a sufficient electric field to make the arrangement of the liquid crystal molecules substantially vertical and non-coloring. In the case of this hybrid arrangement, it is effective to improve the viewing angle with a birefringent film. It is also useful as a reflective element.

By applying an electric field perpendicularly to the above liquid crystal layer, N
In the mode using either the n liquid crystal or the Np liquid crystal, according to the idea of the present invention, usually, the liquid crystal is driven between two states, that is, the no electric field applied state and the fully applied state, but locally or unsteadily. By applying an intermediate electric field, a hue other than a normal hue may be controlled by the electric field to display an abnormality.

As an example of a mode in which a smectic liquid crystal is used in a mode in which an electric field is applied perpendicularly to the liquid crystal layer, a ferroelectric liquid crystal or an antiferroelectric liquid crystal is used, and liquid crystal molecules are almost free from twist parallel to the substrate. There is a mode that uses the state. In this mode, the liquid crystal molecules in the non-coloring state and the color-forming state are both aligned in parallel with the substrate, and a display with a wide viewing angle can be obtained.

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 for invention. As a result, it becomes possible to control the gradation of the color development due to the high light-shielding property and the 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 Japanese Patent Laid-Open No.
Examples include the structure described in -225388. When the polarizers are orthogonal in this mode, the intensity of the transmitted colored light depends on the angle formed by the direction of the director and the transmission axis direction of the polarizer. The intensity increases and peaks at 45 degrees.

Next, regarding the means for producing different colors by making the retardation different for each pixel according to the present invention, the first means is that the thickness d of the liquid crystal layer is kept constant and partition walls are provided between the pixels. Or, a method is provided in which a seal portion is provided to sandwich liquid crystal materials having different refractive index anisotropies Δn. As a method of forming such an element, for example, a partition wall material made of a polymer material or the like is linearly printed on one substrate by a printing method or a resist to form partition walls, and the other substrate is formed on the partition wall material. A cell having stripe-shaped voids formed by laminating is formed. Next, the opening end other than the intended one of the void is temporarily sealed with a resist material, and a desired Δn liquid crystal material is injected,
After sealing, a method of forming the resist by repeating the process of removing the resist can be mentioned. The partition may serve as a black mask or a part thereof, or may serve as a spacer. Further, since the partition wall also has the effect of improving the mechanical strength of the entire device, the above configuration is suitable for a large-sized device such as a public display, which has a large display area and unit pixel area.

FIG. 3 shows a basic optical structure of a method of forming pixels having different retardations according to the present invention, that is, a system having pixels having different thicknesses d with a constant Δn of the liquid crystal material. FIG. In the figure, 31 and 35 are polarizers, 32 and 34 are transparent substrates that may have electrodes, 331
Is a layer of convex portions with different heights having flat tops provided on the substrate 32 to control the thickness d of the liquid crystal layer.
32 is a liquid crystal layer, and 33a, 33b and 33c are liquid crystal regions having different thicknesses d corresponding to respective pixels. Although FIG. 3 shows a method of providing a convex portion having a flat top portion and a different height on one substrate, a method of providing a concave portion having a flat bottom portion and a different depth may be adopted. You may use together. Such a convex portion or a concave portion can be implemented by using a transparent polymer material or the like and selecting and combining various element methods of known thin film processing and molding techniques. As an example of forming pixels of this kind having different thicknesses d, Japanese Patent Laid-Open No. 60-20242
3 and the like. Further, both Δn and the thickness d may be changed by combining the two types of means.

The coloring hue of each pixel is set to the target wavelength λ.
When the polarizers are set to be orthogonal to each other, Δn and d of the liquid crystal layer are expressed by the following formula λ (2m−1) / 2 = Δn · dm = 1, 2,
3, ... To set the three primary colors of red, green, and blue, the center wavelength is 0.65 μm,
When selecting 0.55μm and 0.45μm, Δn · d
Are 0.325, 0.275, and 0.225 (2
It can be selected from m-1) times.

In Japanese Patent Laid-Open No. 7-225388, the range of d.Δn is set to 0.
21 to 0.36 μm is described as being preferable. It is considered that this is because the range of m = 1, that is, λ / 2, is wide, and the above range is adopted because the present invention deals with white light and the color development depends on the color filter. Is not always preferable because the half-value width is too wide and the vividness of the hue is likely to be lost when a color display such as a transmission type is formed by utilizing the color development by the birefringence of the present invention.

On the other hand, in order to form a reflective multi-color structure having three primary colors + black pixels by providing a reflective layer on the back surface, the Δn · d condition of λ / 2 is used for black pixels. In the case of a configuration including one polarizer, a liquid crystal layer, and a reflection layer, light is reflected and reflected, so the retardation is set to 1/2 that in the case where the liquid crystal layer is arranged between the pair of polarizers. In the case of a black pixel, λ / 4, that is, Δ of 0.1 to 0.17
The n · d condition is used.

The retardation condition suitable for color display is generally m = in consideration of the half value width and the half value wavelength.
A device suitable for full-color display can be obtained by selecting from 2, 3 and the like. In this case, Δn · d is 0.675
The range is (blue = 0.45 μm; m = 2) to 3.25 (red = 0.65 μm; m = 3). Specifically, red is m = 2, green and blue are m = 3.
The condition to be is one of realistic options. In this case Δ
n · d is 0.975 to 1.375. When a backlight using a light source having a peak at a specific wavelength such as a fluorescent tube is used, good display can be performed by selecting the center wavelength and the half-value width in consideration of the wavelength characteristics.

In consideration of the visual characteristics, the infrared part and the ultraviolet region have no meaning as colors, so red,
For blue, the half-value wavelengths of the short wavelength portion and the long wavelength portion may be emphasized, respectively. From this point of view, when the center wavelength is shifted to the long wavelength and the short wavelength, respectively, the wavelength range of the light overlapping with the light of another hue is reduced. From this perspective, "Liquid Crystal (Basic)", Baifukan; p90 (198)
From the spectrum diagram described in 5), it can be seen that Δn · d = 0.4 is in the range usable as red. Further, when the above-mentioned m is increased, the full width at half maximum becomes narrower and the degree of hue separation is improved, so that the practical range of Δn · d is 0.4 or more. From the above, Δn · d of 0.4 to 4 is a practical range. An example of Δn · d of the three primary colors is shown in “Liquid Crystal Display (Edited by the Television Society)” 1985, p69-71.

When the polarizers are set parallel to each other, the transmission spectrum becomes an inverted spectrum in which the transmittance is minimum at the wavelength where the transmittance is maximum, as compared with the case where the transmission spectra are orthogonal. If expressed in terms of hue, it will be a complementary hue.

When a light source such as a backlight having a peak at a specific wavelength such as a fluorescent tube is used, good display can be performed by selecting the center wavelength and the half value width in consideration of the wavelength characteristics. An infrared or ultraviolet cut filter may be used. In consideration of the visual characteristics, the infrared part and the ultraviolet part have no meaning as colors. Therefore, for red and blue, the half-value wavelengths of the short wavelength part and the long wavelength part should be emphasized, respectively. From this point of view, when the center wavelength is shifted to the long wavelength and the short wavelength, respectively, the wavelength range of the light overlapping with the light of another hue is reduced. In addition, it is necessary to consider the wavelength dispersion of the birefringence of the liquid crystal material from the viewpoint of the coloring hue.

In order to select the liquid crystal material, if a fast response is required, it is advisable to select a material having a large Δn and reduce the thickness d. When a fast response is not required, a material having a small Δn can be used to reduce the accuracy of cell assembly such as uneven thickness. As a liquid crystal material, Japanese Patent Application Laid-Open No. 7-22
5388 or those further having a substituent, or Liquid Crystal Device Handbook (edited by the 142nd Committee of Japan Society for the Promotion of Science: 1989) P116 to P
192, 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., It can be selected from various nematic liquid crystals having biphenyl, phenylcyclohexane, cyclohexylcyclohexane or a derivative thereof as a skeleton, or smectic liquid crystals such as a ferroelectric liquid crystal having an optically active center and an antiferroelectric liquid crystal. The Δn of the liquid crystal material is generally large in those having many aromatic rings such as benzene rings, those having many triple bonds, and small those having many cyclohexane rings and those having fluorine atoms. Modern materials are relatively freely available and selectable in the 0.05 to 0.25 range. Further, an active element such as TFT or plasma may be used for driving.

FIG. 4 shows a rear surface of a color element utilizing color development by birefringence, which has liquid crystal layers 43 having different retardations between polarizers 41 and 45 and transparent substrates 42 and 44 which may have electrodes. This is an example of a flat display device by arranging a side light type flat light source in which a fluorescent tube 46 such as a cold cathode tube and a light guide plate 48 are combined. In this case, a high brightness LED of three primary colors may be used instead of the fluorescent tube. A diffusion plate, a prism sheet or the like may be combined between the color element and the light guide plate. Alternatively, a combination of a fluorescent tube known as a direct type backlight, a V-shaped reflector, and a diffuser may be used. You may combine planar light emitting elements, such as organic EL with favorable color rendering properties.

[0077]

According to the present invention, a transmissive color liquid crystal element having a good contrast and a good viewing angle, a bright reflective color liquid crystal element and a color display device using the same can be realized without using a color filter.

[Brief description of drawings]

FIG. 1 is a sectional view of a 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.

FIG. 3 is a schematic cross-sectional view of a color liquid crystal device having pixels of different thickness d according to the present invention.

FIG. 4 is a schematic sectional view of a display device using a color liquid crystal element of the present invention.

[Explanation of symbols]

 11 Polarizer. 12 A transparent substrate that may have electrodes. 13 Liquid crystal layers 13A to 13C Liquid crystal layers having different retardations. 14 A transparent substrate that may have electrodes. 15 Polarizer.

Claims (16)

[Claims] 1. A liquid crystal layer is disposed between a pair of polarizers,
Alternatively, in a color liquid crystal device that utilizes a color due to birefringence by arranging a liquid crystal layer between a polarizer and a liquid crystal layer, and a reflective layer between a pair of polarizers, the liquid crystal layer is Due to the difference in retardation determined by the refractive index anisotropy Δn and the thickness d, there is a repeating unit composed of a plurality of pixels having different hues in the colored state, and control by the electric field of the pixel is performed in the non-colored state and the specific colored state. Color liquid crystal element that uses an additive color mixture performed between. 2. The color liquid crystal element according to claim 1, wherein the retardation of the liquid crystal layer is different because the refractive index anisotropy Δn of the liquid crystal material is different. 3. The color liquid crystal element according to claim 1, wherein the retardation of the liquid crystal layer is different because the thickness d of the liquid crystal layer is different. 4. The repeating unit has at least one chromatic color and may have an achromatic color, and additive color mixture is performed in a colored state under a constant electric field condition using pixels constituting the repeating unit. The color liquid crystal device according to any one of claims 1 to 3, wherein the color liquid crystal device is a repeating unit of a combination that produces an achromatic color. 5. The non-coloring state is a state in which the liquid crystal molecules are perpendicular to or substantially perpendicular to the substrate, or is in a parallel or substantially parallel state without twist, and in the coloring state, the liquid crystal molecules are parallel to or uniform with respect to the substrate. 5. The color liquid crystal element according to claim 1, which is in a tilted state or in a bend state. 6. A liquid crystal molecule in a non-coloring state is perpendicular to or substantially perpendicular to the substrate, or in a parallel or substantially parallel state without twist, and a liquid crystal molecule in a coloring state is twisted in parallel or substantially parallel to the substrate. The color liquid crystal element according to claim 1, which is in a non-existent state. 7. The color liquid crystal device according to claim 1, wherein the liquid crystal molecules in the colored state and the liquid crystal molecules in the non-colored state are in a state in which the liquid crystal molecules are parallel or substantially parallel to the substrate and are not twisted. 8. A color liquid crystal element is an electro-optical element that applies an electric field in a direction perpendicular to a substrate, and liquid crystal molecules are perpendicular or substantially perpendicular to the substrate in a non-coloring state, and a viewing angle improving means using a birefringent film or the like. May be contained in the liquid crystal layer.
A mode in which liquid crystal molecules are aligned in a state in which no electric field is applied using p liquid crystal is parallel or substantially parallel to the substrate, or N in the liquid crystal layer.
n liquid crystal is used, and the mode of liquid crystal molecules in which no electric field is applied is perpendicular to the substrate or almost perpendicular to the substrate, or N is applied to the liquid crystal layer.
7. The color liquid crystal device according to claim 1, which is a hybrid state in which an array of liquid crystal molecules in a non-electric field applied state using p liquid crystal transits from a parallel or substantially parallel state to a vertical or substantially vertical state. 9. A color liquid crystal element is an electro-optical element that applies an electric field in a direction perpendicular to a substrate, and liquid crystal molecules in a non-coloring state are perpendicular to or substantially perpendicular to the substrate, and in a coloring state are parallel or substantially parallel to the substrate. Therefore, when Np liquid crystal is used for the liquid crystal layer and the mode of liquid crystal molecules in the non-electric field applied state is parallel or substantially parallel to the substrate, or when Nn liquid crystal is used in the liquid crystal layer The color liquid crystal element according to any one of claims 1 to 6 and 8, which is in a mode in which it is vertical or substantially vertical to the substrate. 10. A color liquid crystal device is an electro-optical device which applies an electric field in a direction perpendicular to a substrate, wherein Nn liquid crystal is used for a liquid crystal layer, and an array of liquid crystal molecules in a non-electric field applied state is perpendicular or almost perpendicular to the substrate. 10. The color liquid crystal device according to any one of claims 1 to 6, 8 and 9, which is a mode in which liquid crystal molecules are tilted in a specific direction by an electric field by utilizing an effect of a lateral electric field due to a fringe electric field or the like in a configuration in which upper and lower electrodes are offset. 11. A color liquid crystal device according to claim 1, which is a mode in which Np liquid crystal or Nn liquid crystal is used for the liquid crystal layer and an electric field is applied in the same in-plane direction as the substrate. 12. The color liquid crystal device according to claim 11, wherein gradation control is performed by controlling the intensity of transmitted light by an applied electric field without changing the hue of color development due to birefringence. 13. The transmissive color according to claim 1, wherein the pair of polarizers are parallel to each other and have a repeating unit having pixels that are achromatic in a colored state such as three primary colors of additive color mixture and black. A liquid crystal device having a reflective layer on the back surface thereof, or having a polarizer and a liquid crystal layer, and a white metal reflective layer.
2. Either of the reflective color liquid crystal elements. 14. The reflective color liquid crystal device according to claim 1, which has one polarizer, a liquid crystal layer and a white metal reflective layer, wherein the liquid crystal layer has Δn · d of 0.1 to 2. Color liquid crystal element. 15. The pair of polarizers are orthogonal to each other.
2. A transmission type color liquid crystal element, wherein Δn · d of the liquid crystal layer is 0.4 to 4 in the transmission type color liquid crystal element. 16. A pair of polarizers are orthogonal to each other.
On the back surface of the transmissive color liquid crystal element of 2 or 15,
Using a fluorescent tube with high color rendering such as a three-wavelength fluorescent tube as a light source,
A color display device in which a backlight unit such as a surface light source type which may have a light guide plate and a reflection plate is arranged.