JP2002122862A - Reflective display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective display device capable of obtaining a sufficiently bright screen under such a surrounding that the intensity of incident light is low and further, capable of displaying a screen with excellent contrast when used under such a surrounding that the intensity of external light made incident thereon is high. SOLUTION: In the reflective liquid crystal display device comprising a reflection film 12 arranged on the rear side, light transmission adjusting films 7, exhibiting high transmittance when the intensity of the incident light is low and exhibiting low transmittance when the intensity of the incident light is high, is arranged on the inner surface of the front side, i.e., the display observer' s side, of a substrate 2 out of a pair of front and rear substrates 2, 3 opposed to each other across a liquid crystal layer 1 while corresponding to regions (b) between a plurality of pixel regions (a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective display device.

[0002]

2. Description of the Related Art For example, as a display device such as a liquid crystal display device which controls transmission of light and displays the light, external light (natural light, indoor light, etc.) which is light of the use environment is used, and a display side of the display is used. There is a reflection type in which light incident from a certain front side is reflected at the rear side to display.

This reflective display device has a plurality of front and rear substrates opposed to each other with an electro-optical material layer such as a liquid crystal layer therebetween, and a plurality of substrates provided on at least one inner surface of the pair of substrates and facing each other. It comprises a plurality of electrodes forming a pixel area, and a reflection means for reflecting light that has entered from the front side, which is the display observation side, and has passed through the electro-optical material layer.

[0004] Since the above-mentioned reflection type display device uses an external light which is the light of the usage environment, the screen is bright when used in a bright environment where high-intensity external light is incident. However, the screen becomes darker as the intensity of the incident light decreases.

Therefore, in the reflective display device, the black mask provided on the inner surface of the front substrate so as to correspond to the region between the plurality of pixel regions in the transmissive display device using the illumination light from the backlight is omitted. The external light is also incident from the area between the pixel areas, and the reflected light is also emitted from the area between the pixel areas, whereby a screen with sufficient brightness can be obtained even in an environment where the intensity of the incident light is low. I am trying to be.

[0006]

However, the reflective display device in which the black mask is omitted can provide a screen having a certain brightness even in an environment where the intensity of incident light is low.
When used in an environment where high-intensity external light is incident, high-intensity reflected light is emitted from a region between pixel regions, and the contrast of a displayed image is significantly reduced.

According to the present invention, it is possible to obtain a screen with sufficient brightness even in an environment where the intensity of incident light is low, and to display an image with good contrast when used in an environment where high-intensity external light is incident. It is an object of the present invention to provide a reflection type display device which can perform the following.

[0008]

A reflection type display device according to the present invention is provided on a pair of front and rear substrates opposed to each other with an electro-optical material layer interposed therebetween, and provided on at least one inner surface of the pair of substrates and opposed to each other. A plurality of electrodes forming a plurality of pixel regions by the region, provided on the inner surface of the substrate on the front side which is the display observation side, corresponding to the region between the plurality of pixel regions, when the intensity of incident light is weak It is characterized by comprising a light transmission adjusting film showing a high transmittance and showing a low transmittance when the intensity of the incident light is high, and a reflecting means for reflecting light incident from the front side and transmitted through the electro-optical material layer. It is assumed that.

According to this reflection type display device, when the intensity of the incident light is low, the light transmission adjusting film provided corresponding to the region between the plurality of pixel regions has a high transmittance. External light enters from the region between the pixel regions, and reflected light also exits from the region between the pixel regions. Therefore, when the intensity of the incident light is low, the incident light and the outgoing light increase, and a screen with sufficient brightness can be obtained.

When the intensity of the incident light is high, the light transmission adjusting film exhibits a low transmittance, so that light is hardly emitted from a region between the pixel regions, and an image with good contrast is displayed. be able to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a reflection type display device of the present invention is provided on an inner surface of a front substrate, which is a display observation side, of a pair of front and rear substrates facing each other with an electro-optical material layer interposed therebetween. Corresponding to the region between the plurality of pixel regions, by providing a light transmittance adjustment film that shows a high transmittance when the intensity of the incident light is low and a low transmittance when the intensity of the incident light is high, A screen with sufficient brightness can be obtained even in an environment where the intensity of incident light is low, and a high-contrast image can be displayed when used in an environment where high-intensity external light is incident. is there.

In the liquid crystal display device according to the present invention, it is preferable that the light transmission adjusting film is formed of a photochromic material which is substantially transparent in a dark place and darkens under strong light.

Further, in the reflective display device according to the present invention, when a plurality of color filters are provided on one of the inner surfaces of the pair of substrates so as to correspond to the plurality of pixel regions, respectively. Forming at least a color filter having the lowest light transmittance in an area smaller than the area of the pixel region, and defining a region corresponding to the color filter in the pixel region as an emission region of colored light; It is preferable that a region that does not correspond to the filter be an emission region of non-colored light.

For example, when the color filters of the plurality of colors are a red filter, a green filter, and a blue filter, at least the green filter among these color filters is smaller than the area of the pixel region. It is preferable to form the area.

[0015]

1 to 3 show one embodiment of the present invention. FIG. 1 is a sectional view of a part of a reflection type display device, and FIGS. 2 and 3 show light provided on the reflection type display device. FIG. 3 is a plan view of a part of a transmission adjustment film and a color filter.

The reflective display device of this embodiment is a TN (twisted nematic) liquid crystal display device for displaying a color image. As shown in FIG. A plurality of transparent electrodes 2, 5 provided on the inner surfaces of the pair of substrates 2 and 3, respectively, and forming a plurality of pixel regions a by regions facing each other; For example, a plurality of color filters, for example, three color filters of red, green, and blue are provided on the inner surface of the substrate 2 on the front side (upper side in FIG. 1) which is the display observation side, respectively, corresponding to the plurality of pixel areas a. 6R,
6G and 6B, a light transmission adjusting film 7 provided on the inner surface of the front substrate 2 so as to correspond to the region b between the plurality of pixel regions a, and an outer surface of the pair of substrates 2 and 3 respectively. And a reflection means 12 for reflecting light that has entered from the front side, which is the display observation side, and has passed through the liquid crystal layer 1.

The liquid crystal display device of this embodiment is of a simple matrix type, and the electrodes 4 provided on one substrate, for example, the inner surface of the front substrate 2, are arranged along the row direction (the horizontal direction of the screen). The plurality of scanning electrodes formed in parallel with each other, and the electrodes 5 provided on the inner surface of the rear substrate 3, which is the other substrate, are formed in parallel with each other along the column direction (vertical direction of the screen). There are a plurality of signal electrodes.

A plurality of pixel areas a are formed on the inner surface of the front substrate 2.
(Hereinafter, referred to as an inter-pixel region) b, the light transmission adjusting film 7 provided has a high transmittance when the intensity of the incident light is low, and shows a high transmittance when the intensity of the incident light is high. It is formed of a substance exhibiting low transmittance, for example, a photochromic substance that is almost transparent in a dark place and darkens under strong light.

As shown in FIGS. 1 and 2, the light transmission adjusting film 7 is formed in a lattice pattern corresponding to an inter-pixel region b between a plurality of pixel regions a arranged in a row direction and a column direction. Each of the portions corresponding to the inter-pixel regions b has a width such that both side edges thereof slightly enter both adjacent pixel regions a.

In this embodiment, as shown in FIGS. 1 and 3, the red, green,
Among the three blue color filters 6R, 6G, 6B, the green filter 6G having the lowest light transmittance is formed in an area smaller than the area of the pixel region a.
A region corresponding to the green filter 6G in the pixel region a corresponding to the green filter 6G is defined as an emission region of colored light.
A region not corresponding to G is defined as a non-colored light emission region.

That is, in this embodiment, the green filter 6G is formed in a shape corresponding to the area of the pixel area a except for the peripheral edge of the area corresponding to the area surrounded by the light transmission adjusting film 7. The central region of the region surrounded by the light transmission adjusting film 7 is a colored light emitting region, and the peripheral region is a non-colored light emitting region.

On the other hand, the red filter 6R and the blue filter 6B, which have higher light transmittance than the green filter 6G,
The red filter 6R and the blue filter 6B each have an area corresponding to the entire pixel region a, and are formed in a continuous band shape over all the pixel regions a arranged in the column direction.

The color filters 6R, 6G, 6
B and the light transmission adjusting film 7 are formed on the inner surface of the front substrate 2, and the scanning electrode 4 is formed thereon.

The pair of substrates 2 and 3 are joined at their peripheral edges via a frame-shaped sealing material (not shown), and are surrounded by the sealing material between the substrates 2 and 3. The liquid crystal layer 1 is provided in the region that is separated.

The alignment direction of the liquid crystal molecules of the liquid crystal layer 1 in the vicinity of the substrates 2 and 3 is controlled by alignment films 8 and 9 provided on the inside of the pair of substrates 2 and 3 so as to cover the electrodes 4 and 5. It is regulated and twisted at a predetermined twist angle (for example, approximately 90 degrees) between the pair of substrates 2 and 3. The front polarizing plate 10 and the rear polarizing plate 11 move their transmission axes in a predetermined direction. It is arranged facing.

The reflection means 12 is a reflection plate made of a metal film such as aluminum, and the reflection means (hereinafter, referred to as a reflection plate) 12 is arranged behind the rear polarizing plate 11.

This liquid crystal display device performs reflection display using external light which is light in the environment in which the liquid crystal display device is used.
0 absorbs light of the polarization component along the absorption axis,
The light enters the liquid crystal layer 1 as linearly polarized light along the transmission axis of the front polarizing plate 10.

The light incident on the liquid crystal layer 1 is subjected to a birefringence effect in accordance with the orientation state of the liquid crystal molecules, which is changed by the electric field applied between the electrodes 4 and 5 while passing through the liquid crystal layer 1, and thereafter The incident light is incident on the side polarizing plate 11, and of the light, the light of the polarization component along the absorption axis of the rear polarizing plate 11 is absorbed by the rear polarizing plate 11, and is transmitted to the transmission axis of the rear polarizing plate 11. The light of the polarized component along the light passes through the rear polarizing plate 11.

The light transmitted through the rear polarizer 11 is reflected by a reflector 12, and the reflected light is transmitted through the rear polarizer 11, the liquid crystal layer 1, and the front polarizer 10 to the front. Emit.

In this liquid crystal display device, red, green, and blue color filters 6 corresponding to a plurality of pixel areas a, respectively.
R, 6G, and 6B, the light emitted from the plurality of pixel areas a is absorbed by the red, green, and blue color filters 6R, 6G, and 6B to absorb the wavelength light in the absorption wavelength band. These are red, green, and blue lights colored in the colors of the color filters 6R, 6G, and 6B, and a full-color image is displayed by emitted lights of these colors.

Since this liquid crystal display device uses external light for display, when used in a bright environment, high-intensity external light is incident. Accordingly, the intensity of the incident external light decreases.

However, when the intensity of the incident light is low, the transmission adjusting film 7 provided on the inner surface of the front substrate 2 so as to correspond to the inter-pixel region b between the plurality of pixel regions a exhibits a high transmittance. , External light is also incident from the inter-pixel region b, and the reflected light reflected by the reflection plate 12 is reflected by the inter-pixel region b.
Also emitted from.

Therefore, according to this liquid crystal display device, when the intensity of the incident light is low, the amount of light entering from the inter-pixel region b increases, and the amount of outgoing light also increases, thereby obtaining a screen with sufficient brightness. be able to.

When the intensity of the incident light is high, since the light transmission adjusting film 7 has a low transmittance, the incidence of external light from the inter-pixel region b is almost eliminated, and the inter-pixel region b There is almost no emission of reflected light.

Therefore, according to this liquid crystal display device, when the intensity of incident light is high, an image with good contrast can be displayed as in the case where the black mask is provided corresponding to the inter-pixel region.

In this embodiment, the light transmission adjusting film 7 is
Since it is formed of a photochromic substance that is almost transparent in a dark place and darkens under strong light, when the intensity of incident light is low, light transmits through the inter-pixel region b with a high transmittance, and the incident light Is high, light hardly transmits through the inter-pixel region b, and the inter-pixel region b becomes almost black.

Therefore, the brightness of the screen in an environment where the intensity of incident light is low can be made brighter, and the contrast when used in an environment where high-intensity external light is incident can be made higher.

In this embodiment, a plurality of pixel areas a
Of the three color filters 6R, 6G, and 6B of three colors of red, green, and blue provided correspondingly to each other, a green filter 6G having the lowest light transmittance is formed in an area smaller than the area of the pixel region a. Since the area corresponding to the green filter 6G in the pixel area a is set as the emission area of the colored light and the area not corresponding to the green filter 6G is set as the emission area of the non-colored light, the green filter having a low light transmittance is used. The brightness of the green light emitted from the colored light emission region of the pixel region a corresponding to 6G can be raised by the high-luminance non-colored light emitted from the non-colored light emission region of the pixel region a.

Therefore, according to this liquid crystal display device,
The brightnesses of the red, green, and blue emission lights emitted from the respective pixel areas a corresponding to the color filters 6R, 6G, 6G of the red, green, and blue colors are balanced, and a color image with good color quality is displayed. be able to.

When the red filter 6R and the blue filter 6B are formed in an area corresponding to the entire area of the pixel area a as in this embodiment, the green filter 6G is surrounded by the light transmission adjusting film 7 in the pixel area a. About 80 to 9 of the area of
It is preferable to form the green filter 6G in such an area so that green light of a sufficient density is emitted from the pixel region a corresponding to the green filter 6G, The brightness of the emitted light of green and blue is almost evenly balanced, and a color image with better color quality can be displayed.

In the above embodiment, the green filter 6G
Is formed in a shape corresponding to a region of the pixel region a except for a peripheral portion of the region surrounded by the light transmission adjusting film 7, and a central region of the region surrounded by the light transmission adjusting film 7 is formed as a colored light emitting region. And the surrounding area is an uncolored light emitting area,
The green filter 6G may be formed in another shape as long as it has a smaller area than the area of the pixel area a surrounded by the light transmission adjusting film 7.

In the above embodiment, among the red, green, and blue color filters 6R, 6G, 6G, only the green filter 6G having the lowest light transmittance is formed in an area smaller than the area of the pixel area a. The color filter 6
All of R, 6G, and 6G may be formed to have an area smaller than the area of the pixel region a, and by doing so, each of the red, green, and blue color filters 6R, 6G, and 6G corresponds to each other. Red emitted from the colored light emission area of the pixel area a,
The brightness of green and blue light is raised by the high-luminance non-colored light emitted from the non-colored light emission area of each pixel area a, so that a brighter color image can be displayed.

In this case, the red, green, and blue color filters 6R, 6G, and 6G have an area of the red filter 6R of 90 to 90% of the area of the pixel area a surrounded by the light transmission adjusting film 7. 95%, the area of the green filter 6G is 70-
It is preferable that the area of the blue filter 6B is 80 to 90% and the area of the blue filter 6B is 85 to 90%.
By forming the green and blue color filters 6R, 6G, and 6G, it is possible to make the brightness of the red, green, and blue emitted lights substantially uniform, and to display a color image with good color quality.

Note that the liquid crystal display device of the above embodiment has red,
Although the color filters are provided with green and blue color filters 6R, 6G, and 6G, the color filters are not limited to red, green, and blue, and may be, for example, three color filters of magenta, yellow, and cyan.

Also in this case, among the three color filters, at least a color filter having the lowest light transmittance is formed in an area smaller than the area of the pixel region, and the color filter corresponding to the color filter in the pixel region is formed. It is preferable that the region is an emission region of colored light, and a region not corresponding to the color filter is an emission region of non-colored light. In this way, light is emitted from each pixel region corresponding to the color filter of each color. The brightness of the emitted light of each color can be balanced, and a color image with good color quality can be displayed.

In the above embodiment, the reflecting plate 1 is used as a reflecting means for reflecting the light incident from the front side and transmitted through the liquid crystal layer 1.
2, but the reflecting means is a semi-transmissive reflecting plate,
A backlight may be arranged as an auxiliary light source behind the semi-transmissive reflection plate, and by adopting such a configuration, a reflective display using external light in an environment where external light of sufficient brightness can be obtained. When the device is used in an environment where external light of sufficient brightness cannot be obtained, illumination light can be emitted from the backlight, and transmissive display using the illumination light can be performed.

Further, the reflecting means may be provided on the inner surface of the rear substrate 2, and in this case, an electrode provided on the inner surface of the rear substrate 2 is formed of a metal film such as aluminum and the like. The reflecting means may also be used.

When the reflecting means is provided on the inner surface of the rear substrate 2 as described above, light incident from the front side and transmitted through the front polarizing plate 10 and the liquid crystal layer 1 is reflected on the inner surface of the rear substrate 2 by the reflecting means. The reflected light is transmitted through the liquid crystal layer 1 again and is incident on the front polarizing plate 10.
The light of the polarization component along the absorption axis of the front-side polarizing plate 10 is absorbed by the polarizing plate 10, and the light of the polarization component along the transmission axis of the front-side polarizing plate 10 is transmitted through the polarizing plate 10 to the front side. Since the light is emitted, reflection display can be performed only by providing one polarizing plate 10 on the front side.

Further, the liquid crystal display device of the above embodiment has a TN
The present invention is directed to a simple matrix liquid crystal display device of the type, in which the liquid crystal molecules are oriented at 180 to 270 degrees (usually 240 to 26 degrees).
It can be applied to a STN (super twisted nematic) type liquid crystal display device in which twist alignment is performed at a twist angle of 0 °), a liquid crystal display device in which liquid crystal molecules are homogeneously aligned in one direction, and the like. The present invention is not limited to this, and is applied to an active matrix type liquid crystal display device, and also to a liquid crystal display device of a horizontal electric field driving method in which a plurality of electrodes forming a plurality of pixel regions by opposing regions are provided on one substrate. be able to.

Further, the present invention is not limited to a liquid crystal display device, but can be applied to a reflection type display device using an electro-optical material such as electrophoresis or electrochromic.

[0051]

According to the reflection type display device of the present invention, of the pair of front and rear substrates opposed to each other with the electro-optic material layer interposed therebetween, the inner surface of the front substrate, which is the display observation side, is provided on one of the substrates. On the inner surface, corresponding to the area between the multiple pixel areas,
When the intensity of the incident light is low, it shows a high transmittance, and when the intensity of the incident light is high, it has a light transmission adjustment film that shows a low transmittance, so it is sufficient even in an environment where the intensity of the incident light is low. A bright screen can be obtained, and when used in an environment where high-intensity external light is incident, an image with good contrast can be displayed.

In the liquid crystal display device according to the present invention, it is preferable that the light transmission adjusting film is formed of a photochromic material which is substantially transparent in a dark place and darkens under strong light. By using this, the brightness of the screen in an environment where the intensity of incident light is low can be made brighter, and the contrast when used in an environment where high-intensity external light is incident can be made higher.

Further, in the reflective display device of the present invention, when a plurality of color filters are provided on one of the inner surfaces of the pair of substrates so as to correspond to the plurality of pixel regions, respectively. Forming at least a color filter having the lowest light transmittance in an area smaller than the area of the pixel region, and defining a region corresponding to the color filter in the pixel region as an emission region of colored light; It is preferable that an area not corresponding to the filter is an emission area of the non-colored light. In this way, the brightness of the emission light of each color emitted from each pixel area corresponding to the color filter of each color is balanced, It is possible to display a color image of an excellent color quality.

That is, for example, when the color filters of the plurality of colors are a red filter, a green filter, and a blue filter, among these color filters,
At least a green filter having the lowest light transmittance may be formed in an area smaller than the area of the pixel region. With this configuration, light is emitted from each pixel region corresponding to the red, green, and blue color filters. It is possible to balance the brightness of the emitted light of red, green, and blue, and display a color image with good color quality.

[Brief description of the drawings]

FIG. 1 is a sectional view of a part of a reflective display device according to an embodiment of the present invention.

FIG. 2 is a plan view of a part of a light transmission adjusting film provided in the reflective display device.

FIG. 3 is a plan view of a part of a color filter provided in the reflective display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal layer 2, 3 ... Substrate 4, 5 ... Electrode a ... Pixel area b ... Inter-pixel area 6R, 6G, 6B ... Color filter 7 ... Light transmission adjustment film 8, 9 ... Alignment film 10, 11 ... Polarizer 12 …reflector

Claims (4)

[Claims] 1. A pair of front and rear substrates facing each other with an electro-optical material layer interposed therebetween, and a plurality of electrodes provided on at least one inner surface of the pair of substrates and forming a plurality of pixel regions by regions facing each other. Provided on the inner surface of the substrate on the front side, which is the display observation side, corresponding to the region between the plurality of pixel regions, shows a high transmittance when the intensity of incident light is low,
A reflection-type display device comprising: a light transmission adjustment film exhibiting a low transmittance when the intensity of incident light is high; and reflection means for reflecting light incident from the front side and transmitted through the electro-optical material layer. . 2. The reflective display device according to claim 1, wherein the light transmission adjusting film is formed of a photochromic material. 3. A color filter of a plurality of colors is provided on one of the inner surfaces of the pair of substrates so as to correspond to the plurality of pixel regions, respectively, and among these color filters, at least the light transmittance is the lowest. A color filter is formed in an area smaller than the area of the pixel region, a region corresponding to the color filter in the pixel region is set as an emission region of colored light, and a region not corresponding to the color filter is uncolored. The reflective display device according to claim 1, wherein the reflective display device is a light emission region. 4. The color filters of a plurality of colors are a red filter, a green filter, and a blue filter, and at least the green filter is formed in an area smaller than an area of the pixel region. The reflective display device according to claim 3.