JP2007219328A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that when a display of a color liquid crystal display device is observed by reflection, parallax or color mixture in a display occurs, display contrast decreases and interference light occurs. <P>SOLUTION: A color filter is prepared by mixing a pigment and light-scattering fine particles having a particle size larger than wavelengths of visible light. The color filter thus obtained acts as a functional layer having both of a coloring function and a scattering function, and the scattering function layer is disposed close to a reflection film, which eliminates parallax. By varying the particle size and a mixing ratio, scattering degrees can be easily controlled. That is, the method is effective to improve the display quality of a reflective liquid crystal display which uses external light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device used in an electronic device such as a mobile phone. In detail, it is related with the improvement of the visibility of the reflection type display using the external light which is the light of use environment.

  A reflective liquid crystal display device using a color filter requires a reflective material such as a reflective film that reflects incident light from the outside to the observer side. As the reflective film, a metal thin film in which a metal such as aluminum or silver is formed by a method such as vacuum deposition or sputtering is usually used. However, the metal thin film formed in this way generally has a specular gloss, and an extremely strong reflected light can be obtained only in a predetermined angle region with respect to the incident light. Therefore, there is a problem of lack of practicality. Therefore, this problem is solved by providing a light scattering layer such as a transparent resin layer mixed with fine particles that scatter light.

The conventional liquid crystal display device has various derived configurations, but is roughly configured as follows. A reflective film is formed on the glass substrate, and a color filter is formed on the reflective film. The color filter is flattened by an overcoat layer or the like, and a transparent electrode is formed thereon. A counter transparent electrode is formed on the counter substrate facing the glass substrate with the nematic liquid crystal interposed therebetween. Optical elements such as a scattering plate, a retardation plate, and a polarizing plate are appropriately arranged on the observer side of the counter substrate. Here, the scattering plate is on the side of observing the display on the counter substrate, and the reflective film on the mirror surface is disposed behind the color filter. Therefore, the distance between the scattering plate and the reflecting film is large, and the light reflected by the reflecting film after the incident light is scattered by the scattering plate and the light scattered by the scattering plate after being reflected by the reflecting film are simultaneously The shadow appears on the display. This is called parallax. In addition, scattering and reflection are repeated between the scattering plate and the reflection film, and light passing through one color filter passes through another color filter, resulting in color mixing and a decrease in color purity and display contrast. . Therefore, a method of forming irregularities on the surface of the reflective film has been studied (for example, see Patent Document 1).
JP-A-4-243226

  However, in the method of forming irregularities on the surface of the reflective film, it is difficult to control the degree of scattering, and since irregularities are artificially formed, regularity occurs in the arrangement of irregularities, and interference light according to regularity is generated. The problem of being observed arises. There are also problems such as an increase in the number of steps for forming the organic film.

  Therefore, an object of the present invention is to eliminate the occurrence of display parallax and color mixing and the reduction of display contrast with a simple configuration.

  The liquid crystal display device of the present invention includes a substrate on which a colored layer is formed, a counter substrate, a liquid crystal provided between the substrate and the counter substrate, and a back side of the colored layer, which is incident from an observation direction. The mirror layer is provided with a specular reflection layer that reflects the incident light, and the colored layer also has a scattering function for scattering incident light. In order to have such a scattering function, the colored layer contains light scattering fine particles that scatter incident light. Here, the light-scattering fine particles have a particle size larger than the visible light wavelength, for example, a particle size of 1000 nm to 3000 nm.

  The colored layer includes a photosensitive resin, and the light scattering fine particles have a refractive index different from that of the photosensitive resin.

  The reflective layer is formed between the substrate and the colored layer. Therefore, parallax can be eliminated. Further, the reflective layer may have a function of transmitting a part of incident light. In this case, a transflective liquid crystal display device is obtained.

  Specifically, in addition to the red (R), green (G), and blue (B) color pigments in the photosensitive resist of the color filter, light scattering fine particles having a particle size larger than the visible light wavelength are mixed, and photo A color filter is formed by an ordinary pigment dispersion method color filter manufacturing method using lithography. Thereby, the color filter becomes a functional layer having both a coloring function and a scattering function, and the reflection film and the scattering functional layer are close to each other, so that parallax can be eliminated. Further, the scattering degree can be easily controlled by changing the particle diameter and the mixing ratio.

  The reflective liquid crystal device according to the present invention eliminates the occurrence of display parallax and color mixing and the decrease in display contrast in the reflective liquid crystal display without increasing the number of steps, and does not cause interference light and can control the degree of scattering. It becomes easy. That is, there is an effect of improving the display quality of the reflective liquid crystal display using external light.

  The liquid crystal display device of the present invention includes a substrate on which a reflective film is formed on a glass substrate and a color filter formed thereon, a counter substrate provided to face the substrate, and a gap between the substrate and the counter substrate. The liquid crystal layer is provided, and fine particles that scatter light contained in the color filter are provided. With such a configuration, the color filter becomes a functional layer having both a coloring function and a scattering function, and since the reflective film and the scattering functional layer are close to each other, parallax can be eliminated. Further, the scattering degree can be easily controlled by changing the particle diameter and the mixing ratio.

  Any fine particles can be used regardless of whether they are organic or inorganic, as long as the difference in refractive index from the photosensitive resin is large. The diameter of the granular resin is preferably 780 nm or more. Furthermore, it is possible to easily control the scattering degree by controlling the particle diameter and the mixing ratio.

  Further, as the reflective film, a transflective film or a film provided with an opening can be used. In that case, it is also possible to observe a display using a light source such as a backlight by utilizing the opening and the transflective characteristics.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

  The configuration of the liquid crystal display device of this example is schematically shown in FIG. As shown in the figure, this liquid crystal display device has a configuration in which a nematic liquid crystal layer 7 is provided between a lower substrate 5 and a counter substrate 6 facing the lower substrate 5, and an optical film 8 is disposed so as to sandwich both substrates. is there. The lower substrate has a structure in which an aluminum deposition reflective film 3 having an opening 9 is formed on a glass substrate 4 and a color filter 2 is formed thereon. The color filter 2 has three colored portions of RGB per pixel and uniformly contains fine particles 1 that scatter light. The optical film 8 is obtained by sequentially laminating a polarizing plate and a retardation film. This liquid crystal display device used STN mode driven by a passive matrix system.

  In this configuration, external light incident on the liquid crystal display device passes through the optical film 8, the counter substrate 6, and the nematic liquid crystal layer 7 and reaches the color filter 2. Light is scattered by the fine particles 1 provided in the color filter 2 and reflected by the reflection film 3 provided immediately thereafter, and the reflected light passes through the color filter 2 and is again scattered by the fine particles 1 provided in the color filter 2. Is done. Therefore, scattering and reflection occur multiple times, and finally the scattered reflected light returns to the nematic liquid crystal layer 7 and is observed. At this time, since the color filter 2 having a function of scattering light and the reflection film 3 having a function of reflecting light are close to each other, there is no parallax and no reduction in contrast due to multiple scattering. Therefore, a display with high visibility in a reflective liquid crystal display using external light can be achieved.

  In addition, according to the configuration of the present embodiment, since the reflective film 3 has the opening 9, it is possible to visually recognize a display using a light source such as a backlight. At that time, since the fine particles 1 exhibit a scattering effect, a display with a wide viewing angle can be obtained.

  Specifically, since the degree of scattering depends on the wavelength of light if the particle 1 has a diameter of 380 nm to 780 nm, which is a wavelength in the visible light range, or smaller, the particle diameter is larger than the wavelength in the visible light range. Those having a thickness of 1 μm (= 1000 nm) to 3 μm were used. Any material can be used regardless of whether it is an organic or inorganic material as long as the difference in refractive index from the photosensitive resin used as the base is large. In this embodiment, aluminum oxide fine particles were used.

  The configuration of the liquid crystal display device of this example is schematically shown in FIG. In this example, a semi-transmissive film such as a dielectric multilayer film that does not have an opening is used. Since other parts are the same as those in the first embodiment, the duplicate description is omitted. As shown in the figure, the lower substrate 5 has a structure in which a dielectric multilayer film 10 is formed on a glass substrate 4 and a color filter 2 in which fine particles 1 that reflect light are uniformly included is formed thereon. is there. Here, a dielectric multilayer film 10 that reflects 50% light and transmits 50% light is used. Also with this configuration, the same reflection and scattering effects as those in the first embodiment can be obtained, so that a display with good visibility in a reflective liquid crystal display using external light can be achieved.

  In each of the embodiments described above, the STN mode that is driven by the passive matrix method is used. However, the present invention is not limited to this, and an active matrix liquid crystal panel that drives the pixel electrode by a switching element may be used. Further, any electro-optic effect mode such as a TN mode or an ECB mode can be used.

  The specular reflection film is not limited to a metal thin film or a dielectric multilayer film, but can be applied by using a reflection electrode.

  Since a good display can be visually recognized using ambient light, which is ambient light, it can be applied to electronic devices that are desired to be used in various environments such as portable information devices.

It is sectional drawing which shows typically the liquid crystal display device of this invention. It is sectional drawing which shows typically the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fine particle 2 Color filter 3 Reflective film 4 Glass substrate 5 Lower side substrate 6 Opposite substrate 7 Liquid crystal layer 8 Optical film 9 Opening part 10 Transflective film

Claims (10)

A substrate on which a colored layer is formed, a counter substrate, a liquid crystal provided between the substrate and the counter substrate, and a specular reflection layer that is provided behind the colored layer and reflects light incident from an observation direction In a liquid crystal display device comprising:
The liquid crystal display device, wherein the colored layer also has a scattering function for scattering incident light.   The liquid crystal display device according to claim 1, wherein the colored layer includes light scattering fine particles that scatter incident light so as to have the scattering function.   The liquid crystal display device according to claim 2, wherein the light-scattering fine particles have a particle size larger than a visible light wavelength.   The liquid crystal display device according to claim 3, wherein the light-scattering fine particles have a particle size of 1000 nm to 3000 nm.   The liquid crystal display device according to claim 2, wherein the light-scattering fine particles are fine particles of aluminum oxide.   The liquid crystal display device according to claim 2, wherein the colored layer includes a photosensitive resin, and the light-scattering fine particles have a refractive index different from that of the photosensitive resin.   The liquid crystal display device according to claim 2, wherein the reflective layer is formed between the substrate and the colored layer.   The liquid crystal display device according to claim 7, wherein the reflective layer has a function of transmitting a part of incident light.   The liquid crystal display device according to claim 8, wherein the reflective layer is a dielectric multilayer film.   The liquid crystal display device according to claim 8, wherein the reflective layer has an opening that transmits incident light.

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