JPH0566394A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal panel which stably controls a cell gap and eliminates a coloring phenomenon. CONSTITUTION:The liquid crystal panel is constituted by charging liquid crystal 31 which makes a bright-dark display in birefringent mode between a couple of transparent substrates 11 and 12 and an uneven part which make light, transmitted through or reflected by this liquid crystal panel, white is formed on an one opposite surface of at least one of said transparent substrates. For the formation of the uneven part, a transparent member of glass, etc., having an uneven opposite surface made smooth by etching, a flattening member which is formed on the transparent member of glass, etc., having an uneven opposite surface to make the unevenness of the transparent member smooth, or a mixed member which is formed on the transparent member of glass, etc., by mixing granular insulating members with a resin member is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device which performs bright and dark display by a birefringence mode.

[0002]

2. Description of the Related Art In recent years, research and development of a liquid crystal display device using a ferroelectric liquid crystal has been actively conducted. In this, polarizing plates are installed on both sides of a liquid crystal cell filled with a ferroelectric liquid crystal so that their polarization axes are 90 degrees (this is called a crossed Nicol position), and an electric field applied to the liquid crystal is controlled. This changes the direction of the molecular axis of the ferroelectric liquid crystal, and the birefringence effect causes the dark state to be changed when the molecular axis of the ferroelectric liquid crystal is parallel or perpendicular to the polarization axis of one polarizing plate. The vertical state represents the bright state. The angle difference between the two states of the molecular axis in the above-mentioned bright and dark states is usually called a switching angle and is represented by the symbol 2θ.

Since a liquid crystal display device using a ferroelectric liquid crystal performs bright and dark display by a birefringence mode, there is a problem in that transmitted light or reflected light in the bright state is colored and display quality is deteriorated. is there. Particularly when color display is performed in combination with a color filter or the like, it is difficult to obtain a good color display due to this coloring phenomenon.

Generally, the transmittance or reflectance of a liquid crystal panel is related to the product Δnd of the refractive index anisotropy Δn of the liquid crystal and the cell gap d of the liquid crystal cell. It also depends on the wavelength λ.

FIG. 8 shows the transmittance T of the liquid crystal panel in the bright state.
3 shows the result of simulation performed by the inventors of the present application in order to investigate the wavelength λ dependency of the. here,
The intensity of the linearly polarized light incident on the liquid crystal layer is 100 percent, and the loss of light in the substrate, electrodes, liquid crystal layer, etc. is not considered. Each parameter has a switching angle 2θ = 45 degrees, a refractive index anisotropy Δn = 0.13, and a cell gap d = 6, 7, 8 μm. As can be seen from the figure, the transmittance T greatly differs depending on the wavelength λ, which causes the above-described coloring phenomenon.

To eliminate the coloring phenomenon, the visible region (38
It is necessary to average the transmittance over the entire range (0 to 780 nm). In order to average the transmittance over the entire visible region, the product of the refractive index anisotropy Δn and the cell gap d Δn ·
It is known that the value of d must be close to 0.28 μm. However, since the refractive index anisotropy Δn of the ferroelectric liquid crystal currently manufactured can take only a value in a narrow range of about 0.13 to 0.18, the value of the cell gap d must be changed. .. According to the calculation, the optimum value of the cell gap d is about 2 μm.

Conventionally, in order to average the transmittance over the entire visible region and eliminate the coloring phenomenon, the liquid crystal cell is formed by setting the value of the cell gap d to about 2 μm.

[0008]

Controlling the cell gap is very important in forming a liquid crystal panel, but the cell gap d needs to be 4 to 6 μm or more to stably control the cell gap. Is. Therefore, it is extremely difficult to form a liquid crystal cell with a cell gap d of about 2 μm as in the conventional case, and it is not suitable for mass production.

An object of the present invention is to provide a liquid crystal panel which can stably control the cell gap and can eliminate the coloring phenomenon.

[0010]

In a liquid crystal display device of the present invention, a liquid crystal panel is formed by filling a pair of transparent substrates with a liquid crystal that performs bright and dark display by a birefringent mode, and is transmitted through the liquid crystal panel. It is a configuration in which convex and concave portions for whitening reflected light are formed on at least one of the opposing surfaces of the transparent substrate, and a transparent member such as glass smoothed by etching the convex and concave opposing surfaces is used. Forming a convex or concave portion, or forming the convex or concave portion by using a flattening member which is formed on a transparent member such as glass whose opposing surface is concave and convex and smooths the convex or concave portion of the transparent member; or It is characterized in that the projections and depressions are formed by using a mixing member formed on the transparent member and containing a granular insulating member mixed in a resinous member.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration example of a liquid crystal display device of the present invention.

In the figure, reference numerals 11 and 12 denote transparent substrates, and convex and concave portions are formed on the surface of one transparent substrate 12. The transparent substrates 11 and 12 are formed of a transparent member, a transparent electrode, an alignment layer and the like. Two
Reference numerals 1 and 22 denote polarizing plates, which are arranged such that their polarization axes are in the crossed Nicols position. Reference numeral 31 is a liquid crystal that performs bright and dark display by a birefringent mode such as a ferroelectric liquid crystal. The transparent substrates 11 and 12, the polarizing plates 21 and 22, and the liquid crystal 31 shown above constitute a liquid crystal panel.

In the above structure, the height, size, shape, density, etc. of the projections and depressions are appropriately determined so as to whiten the light transmitted or reflected by the liquid crystal panel. The term "whitening" used herein means to appropriately mix the cell gap d formed by the convex and concave portions so that lights having different transmission or reflection characteristics are mixed with each other at a resolution equal to or lower than the resolution of human eyes so that light of a specific color is obtained. Means not to be emphasized. Therefore, it is preferable that the projections and depressions are formed as densely as possible. From the viewpoint of the resolution of human eyes, the average distance between adjacent convex portions and convex portions or concave portions and concave portions is 0.
It is preferably 1 mm or less. In addition, in the case of a large display which is viewed away from the display surface, this is not limited to 0.1
mm or more, and the viewing angle may be 1 minute or less.

The liquid crystal used in the present invention may be any liquid crystal that displays bright and dark by a birefringence mode controlled by an electric field. For example, a nematic liquid crystal may be used, but the present invention is a ferroelectric liquid crystal. Since a remarkable effect can be exhibited by using, the following description will be made on the assumption that the ferroelectric liquid crystal is used unless otherwise specified.

5. It is easy to manufacture the distance between the facing surfaces of the transparent substrates 11 and 12, that is, the average cell gap d '.
When it is set to about 3 μm, the product Δn · d of the refractive index anisotropy Δn and the cell gap d is changed continuously or intermittently in the range of 0.5 to 1.15 μm to transmit each wavelength. The rates can be averaged over the visible range (380-780 nm) and the light transmitted or reflected by the liquid crystal panel can be whitened. The product Δn · d of the refractive index anisotropy Δn and the cell gap d is 0.5 to 1.15 μm.
Assuming that the refractive index anisotropy Δn of the liquid crystal is 0.13, which is the standard value of the ferroelectric liquid crystal, the variation of the cell gap d due to the projections and depressions is 3.8 to 8.8 μm. Therefore, when the average cell gap d ′ is about 6.3 μm,
The maximum height difference L between the convex and concave portions is 5 μm.

FIGS. 2 and 3 show the transmittance T with respect to the wavelength λ when the convex and concave portions are formed on the surface of the one transparent substrate 12.
3 shows the simulation result of. In both figures, each parameter has a switching angle 2θ = 45 degrees and a refractive index anisotropy Δn = 0.13.

In the simulation shown in FIG. 2, the average cell gap d ′ is 6.3 μm, and the maximum height difference L between the convex and concave portions is 0, 2 and 5 μm. L = 5μ
In the case of m, the transmittance T is averaged over the entire visible region (380 to 780 nm), compared to the case of L = 0, that is, no projections and depressions and the case of L = 2 μm. It can be seen that the one provided with the projections and depressions is extremely effective for whitening.

In the simulation shown in FIG. 3, the maximum height difference L between the convex and concave portions is set to 4 μm, and the average cell gap d ′ is set.
Was changed to 5.8, 6.2 and 6.6 μm. As can be seen from the figure, the transmittance T is averaged over the entire visible region (380 to 780 nm) even if the average cell gap d'changes to some extent, and there is no great difference in the effect on whitening. Therefore, the control of the cell gap does not have to be so strict when manufacturing a liquid crystal panel,
The manufacturing process can be simplified or the yield can be improved.

As can be seen from the above simulation results, in the present invention, by forming the convex and concave portions on the surface of the transparent substrate, even if the average cell gap d'is set within the range where the liquid crystal cell can be easily manufactured. The light transmitted or reflected by the liquid crystal panel can be whitened.

Next, a more specific embodiment will be described based on the basic configuration example of the liquid crystal display device described above.

Embodiment 1 FIG. 4 shows a first embodiment of the present invention.

In the figure, transparent substrates 11 and 12
Are transparent members 11a, 12a such as glass, transparent electrode 11
b, 12b and the alignment layers 11c, 12c. The polarizing plates 21 and 22 and the liquid crystal 31 are as shown in FIG.
It is similar to the basic configuration shown in. Above, the transparent substrate 1
A liquid crystal panel is composed of 1 and 12, polarizing plates 21 and 22, and liquid crystal 31. That is, the transparent member 12a
The surface of the transparent substrate 12 is made uneven, and the unevenness is formed on the surface of the transparent substrate 12.

By using # 500 to # 1000 polished glass for the transparent member 12a, the average distance between adjacent convex portions and convex portions or concave portions and concave portions can be set to about 50 μm. Generally, the irregularities on the surface of the polished glass are not uniform, and the irregularities on the surface are not smooth. Therefore, it is preferable that the surface of the polished glass is etched with hydrofluoric acid or the like to make the irregularities uniform and smooth. This makes it possible to prevent disconnection or poor adhesion of the transparent electrode 12b, and to further prevent the alignment layer (thickness is usually 100 nm).
Can be reliably formed.

When the surface of the transparent member 12a is formed to be uneven, glass having a flat surface may be used for the transparent member 12a, and the glass surface may be etched with hydrofluoric acid or the like to form the unevenness.

Embodiment 2 FIG. 5 shows a second embodiment of the present invention. In this example, a transparent smoothing member 12d is provided on the surface of the transparent member 12a in order to smooth the unevenness of the surface of the transparent member 12a made of glass or the like. This makes it possible to prevent disconnection or poor adhesion of the transparent electrode 12b, and to further prevent the alignment layer (thickness is usually 100 nm).
Can be reliably formed. An acrylic resin or the like can be used for the smoothing member 12d.

Embodiment 3 FIG. 6 shows a third embodiment of the present invention. In this example, a transparent intermediate member (mixing member) 12e is formed on the surface of a transparent member 12a made of glass or the like, and projections and depressions are provided on the surface of this intermediate member (mixing member) 12e. As the intermediate member (mixing member) 12e, an acrylic resin mixed with a spherical insulating member 12f made of alumina or glass may be used. Insulating member 1
By mixing 2f in an appropriate ratio, it is possible to form projections and depressions on the surface of the intermediate member (mixing member) 12e. When forming the intermediate member (mixing member) 12e, a liquid resin or the like mixed with the insulating member 12f may be sprayed onto the surface of the transparent member 12a, and then dried and solidified.

Embodiment 4 FIG. 7 shows a fourth embodiment of the present invention. As can be seen from FIG. 9A, in this example, as in the third embodiment, the transparent intermediate member 12e made of acrylic resin or the like is formed on the surface of the transparent member 12a made of glass or the like. The surface of the intermediate member 12e is provided with convex and concave portions. In order to form the projections and depressions on the surface of the intermediate member 12e, as shown in FIG. 6B, after applying the acrylic resin or the like to the transparent member 12a, before completely hardening it,
It suffices to press the intermediate member 12e by the molding means 40 having a surface with an uneven shape, and then dry and solidify the intermediate member 12e. It is effective to use an ultraviolet curing type acrylic resin because the resin can be cured in a short time.

Although the basic configuration example of the liquid crystal display device of the present invention and Examples 1 to 4 have been described above, in the present invention, the convex and concave portions are not formed only on one opposing surface of the transparent substrate, and the transparent substrate is transparent. It may be formed on both facing surfaces of the substrate.

[0030]

According to the present invention, by forming convexes and concaves on the surface of the transparent substrate, even if the average cell gap of the liquid crystal cell is set within a range where the liquid crystal cell can be easily manufactured, the transmittance of each wavelength is increased. Can be averaged over the entire visible region (380 to 780 nm), and light transmitted or reflected by the liquid crystal panel can be whitened. This is extremely effective especially when a color display is performed by combining a liquid crystal panel and a color filter.

Especially when a ferroelectric liquid crystal is used, it is not necessary to narrow the cell gap to about 2 μm as in the conventional case, so that the cell gap can be easily controlled, and the manufacturing process can be simplified and the manufacturing cost can be reduced. You can measure.

Further, even if the average cell gap is changed to some extent, the transmittances of the respective wavelengths are averaged over the entire visible region (380 to 780 nm), and there is no great difference in the whitening effect. Therefore, the control of the cell gap does not have to be so strict when manufacturing the liquid crystal panel, and the manufacturing process can be simplified and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a basic configuration example of a liquid crystal display device according to the present invention.

FIG. 2 is a characteristic diagram showing a characteristic of a liquid crystal display device according to the present invention by simulation.

FIG. 3 is a characteristic diagram showing characteristics of a liquid crystal display device according to the present invention by simulation.

FIG. 4 is a cross-sectional view showing a first embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view showing a second embodiment of the liquid crystal display device of the present invention.

FIG. 6 is a cross-sectional view showing a third embodiment of the liquid crystal display device of the present invention.

FIG. 7 is a cross-sectional view showing a fourth embodiment of the liquid crystal display device of the present invention.

FIG. 8 is a characteristic diagram showing a characteristic of a conventional liquid crystal display device by simulation.

[Explanation of symbols]

 11, 12 ...... Transparent substrate 31 ...... Liquid crystal 12a ...... Transparent member 12d ...... Flattening member 12e ...... Intermediate member (mixing member) 12f ...... Insulating member

Claims (3)

[Claims] 1. A liquid crystal panel is constructed by filling a pair of transparent substrates with liquid crystal for displaying light and dark by a birefringent mode, and convex and concave portions for whitening light transmitted through or reflected by the liquid crystal panel. A liquid crystal display device, characterized in that the convex and concave portions are formed by using a transparent member such as glass, which is formed on at least one of the opposing surfaces of the transparent substrate, and the convex and concave opposing surfaces are subjected to etching treatment and smoothed. 2. A liquid crystal panel is constructed by filling a pair of transparent substrates with liquid crystal for displaying light and dark by a birefringent mode, and convex and concave portions for whitening light transmitted through or reflected by the liquid crystal panel. The uneven surface is formed on at least one of the facing surfaces of the transparent substrate, and the facing surface is formed on a transparent member such as glass having unevenness, and the unevenness is formed by using a flattening member that smoothes the unevenness of the transparent member. Liquid crystal display device characterized by. 3. A liquid crystal panel is constructed by filling a pair of transparent substrates with liquid crystal for displaying light and dark by a birefringence mode, and convex and concave portions for whitening light transmitted through or reflected by the liquid crystal panel. It is characterized in that the convex and concave portions are formed by using a mixing member formed on at least one opposing surface of the transparent substrate and formed on a transparent member such as glass, and a granular insulating member mixed with a resinous member. Liquid crystal display device.