JP2000098363A - Liquid crystal display device - Google Patents

Abstract

(57) [Problem] To provide a reflection type liquid crystal display element which can achieve sufficient screen luminance and contrast ratio and can realize high-quality image display. SOLUTION: Spectral / reflection film 6 for dispersing surrounding white light incident through a glass substrate 1 on a viewing side into three color lights of red, green and blue and reflecting the separated three color lights to a viewing side. To
It is provided on the glass substrate 2 on the back side. The color forming function (spectral function) and the reflecting function are performed by one spectral / reflective film 6.
Light incident on the liquid crystal layer 10 from outside via the polarizing film 3, the glass substrate 1, the transparent electrode 4 and the alignment film 5 enters the liquid crystal layer 10 and then passes through the liquid crystal layer 10 as it is. The color is reflected and reflected by the spectral / reflection film 6, and the color / reflected light is visually recognized from the glass substrate 1 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which performs color display using ambient white light as a light source.

[0002]

2. Description of the Related Art With the progress of so-called office automation (OA) in recent years, OA equipment typified by word processors, personal computers and the like has been widely used. Furthermore, O in such an office
The spread of the A devices has generated demand for portable OA devices that can be used both in offices and outdoors, and there has been a demand for reductions in their size and weight. A liquid crystal display device is widely used as one of means for achieving such an object. In particular, a liquid crystal display device is an indispensable technology not only for reducing the size and weight but also for reducing the power consumption of a portable OA device driven by a battery.

[0003] The liquid crystal display devices are roughly classified into a reflection type and a transmission type. The reflection type liquid crystal display device is configured to reflect surrounding light rays incident from the front side of the liquid crystal panel on the back side of the liquid crystal panel and visually recognize an image with the reflected light, and the transmission type liquid crystal display device is arranged on the back side of the liquid crystal panel. In this configuration, the image is visually recognized by the transmitted light from the provided light source (backlight).

As described above, as portable OA equipment is used, there is a strong demand for liquid crystal display devices to save power. Since a portable liquid crystal display device is driven by a battery, it is not applicable to a transmission type liquid crystal display device requiring a special light source (backlight) because the power consumption of the backlight is too large. Therefore, a reflective liquid crystal display device that does not use such a backlight is required. In order to cope with the increase and diversification of display information, the following characteristics are required as information display media in future reflective liquid crystal display devices.

(1) Low power consumption (2) High-quality color display (3) High-definition display (160 dpi or more) (4) Large-capacity display (1024 × 768 pixels or more) (5) High-luminance display screen (6) Wide Viewing angle (more than ± 40 degrees) (7) Low price

[0006] Among these characteristics, high-quality color display has become a major issue in the technical development of reflective liquid crystal display devices. In a transmission type liquid crystal display device, high quality color display comparable to a CRT display device can be realized at least for a still image by combining a micro color filter and a backlight. However, in a reflection type liquid crystal display device that does not use a backlight, the absolute luminance of the screen is low and sufficient color formation cannot be obtained, and it is difficult to realize high-quality color display.

In the prior art, the following four types of configurations are known as configurations of a reflection type liquid crystal display element for obtaining a color display.

(Conventional Example 1) A structure in which a reflection layer for reflecting incident light from the surroundings is provided on the back surface of a liquid crystal panel with a microfilter used in a transmission type color liquid crystal display element.

(Conventional example 2) A micro color filter and one polarizing film are provided on the viewing side where one electrode disposed on the back side is a reflection electrode and the other electrode which is a transparent electrode is disposed, and a birefringence control is performed. Configuration that adopts the method.

FIG. 16 is a schematic cross-sectional view of such a reflection type liquid crystal display element of Conventional Example 2. In FIG. 16, 41,
Reference numeral 42 denotes two glass substrates. A polarizing film 43 is provided on the outer surface of the glass substrate 41 on the front side (viewing side). On the inner surface of the glass substrate 41, a micro color filter 44 for selectively passing light components of the three primary colors, a transparent electrode 45 for applying an electric field to the pixel portion, and an alignment film 46 having a rubbed surface are laminated in this order. Is formed. On the other hand, on the inner surface of the rear glass substrate 42, for example, a reflective electrode 47 made of aluminum for reflecting incident light and applying an electric field to each pixel, and an alignment film 48 having a rubbed surface are laminated in this order. A TFT (Thin Film Transistor) 49 which is formed and controls ON / OFF of the reflection electrode 47 is provided. Then, a liquid crystal material is sealed between the alignment films 46 and 48 to form a liquid crystal layer 50.

In this liquid crystal display device, external light incident through the glass substrate 41 on the viewing side as white light is split in advance by the micro color filter 44, and then red light and green light are reflected by the reflective electrode 47 on the rear side. Light and blue light are reflected to form an image of each color.

(Conventional example 3) One electrode disposed on the back side is used as a reflection electrode, a micro color filter is provided on the viewing side where the other electrode which is a transparent electrode is disposed, and light is mixed with a liquid crystal mixed with a black dye. Switching configuration.

(Conventional Example 4) A birefringence effect and a color transmission / absorption effect of a dichroic dye are used to make at least 2
A configuration in which liquid crystal panels having color selectivity of colors are stacked and a multicolor display is obtained by color reduction mixing.

[0014]

Each of the above-mentioned conventional reflection type liquid crystal display elements has the following technical problems.

The liquid crystal display device of the prior art 1 has the simplest structure and is advantageous in cost, but since two polarizing films are used, the incident light passes through the polarizing layer four times by the reflection optical system. As a result, the screen luminance is significantly reduced.

In the liquid crystal display element of the second conventional example, the light can be switched only by passing through the polarizing layer twice, so that the screen luminance is improved as compared with the first conventional example. However, the light passes through the micro color filter 44 twice at the same time. Since the light reflected by the reflective electrode 47 has already been split, a certain amount of decrease in the amount of light when passing through the micro color filter 44 for the second time is inevitable. Also, the light component scattered and reflected by the reflective electrode 47 must pass through any of the red, green, and blue color filters in accordance with the scattering angle, so that the color purity is increased, but the white scattered light is reflected. No improvement in screen luminance due to light is expected, and the effect of improving color purity is offset by a decrease in screen luminance.

As described above, in the liquid crystal display device including the micro color filter 44 and the polarizing film 43, the contrast ratio is high, but the efficiency of using reflected light is low, so that there is a limit in improving the screen brightness. In particular, since the micro color filter 44 is provided on the viewing side, even if the reflection is sufficiently performed by the reflective electrode 47, the micro color filter
At 44 the light intensity is limited. Further, some scattered reflected light which preferably works as a reflection type liquid crystal display element is blocked or monochromatic by the micro color filter 44, so that a gloss effect like gravure printing paper cannot be expected. Only a dark screen can be obtained.

In the liquid crystal display device of the third conventional example, since no polarizing film is used, the screen brightness is greatly improved as compared with the liquid crystal display devices of the first and second conventional examples. However, Conventional Example 2 employs a birefringence control method having a high light-shielding property, so that a high contrast ratio can be realized as a result, whereas Conventional Example 3 using wavelength selective absorption of a black dye has Sufficient light shielding cannot be obtained, and the contrast ratio is generally low.

In the liquid crystal display device of Conventional Example 4, since two or three liquid crystal panels are stacked, there is a disadvantage in cost.
In addition, surface reflection occurs on the surface of each substrate of the liquid crystal panel to be laminated, and as a result, the screen luminance and the contrast ratio are reduced, and a sufficient image quality cannot be obtained.

As described above, in the conventional reflection type liquid crystal display device, the polarizing film and the micro color filter are used to utilize the birefringence effect of the liquid crystal, or to select the wavelength of the liquid crystal and the dichroic dye (dye). Multicolor display is realized by using absorption, but the former has a high contrast ratio but a low screen luminance, and the latter has a relatively high screen luminance but a low contrast ratio. Lacks the ability to achieve high image quality.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a reflective liquid crystal display device capable of achieving a sufficient screen luminance and contrast ratio and realizing high-quality image display. I do.

[0022]

According to a first aspect of the present invention, there is provided a liquid crystal display device in which a liquid crystal is sandwiched between a pair of opposing substrates, and a white light incident through one of the substrates is split and reflected. A reflection film is provided on the other substrate, so that the separated and reflected light can be observed through the liquid crystal and the one substrate, respectively.

In the liquid crystal display device according to the present invention, a plurality of liquid crystal pixels are arranged in a matrix between a transparent substrate on the viewing side and a substrate on the back side, and each pixel of the back side substrate is formed. A plurality of spectroscopic / reflective films for spectroscopically / reflecting white light incident through the viewing-side substrate in a region to be viewed, and the spectroscopic / reflected light is applied to a liquid crystal pixel and the viewing-side substrate, respectively. Which can be observed through

According to a third aspect of the present invention, there is provided a liquid crystal display device.
(2) In the method (2), the spectral / reflective film is configured to be separated into color components of at least each color including red, blue, and green.

The liquid crystal display device according to the fourth aspect is the first aspect.
In any one of the first to third aspects, the spectral / reflective film is a film in which an inorganic pigment is dispersed.

The liquid crystal display device according to the fifth aspect is the fourth aspect.
Wherein the spectral / reflective film is formed by applying a paste-like substance containing the inorganic pigment, a binder resin and a solvent by printing and drying the paste-like substance.

[0027] The liquid crystal display device according to claim 6 is the liquid crystal display device according to claim 1.
In any one of the first to third aspects, the spectral / reflective film is a film in which an organic pigment is dispersed.

The liquid crystal display device according to claim 7 is the liquid crystal display device according to claim 4.
In any one of (a) to (d), the thickness of the spectral / reflective film is 10
μm or less, preferably 1 to 3 μm.

[0029] The liquid crystal display element according to claim 8 is the liquid crystal display element according to claim 4.
In any one of the above items 6, the size of the particles of the inorganic pigment or the organic pigment is 0.1 μm or more.

The liquid crystal display device according to the ninth aspect is the fourth aspect of the invention.
The average particle size of the inorganic pigment or the organic pigment is 10 μm or less, preferably 1 μm or less.
２2 μm.

The liquid crystal display device according to claim 10 is the liquid crystal display device according to claim 4.
In any one of the above items 6, the volume ratio of the inorganic pigment or the organic pigment in the spectral / reflective film is 40% or more.

[0032] The liquid crystal display device according to claim 11 is the liquid crystal display device according to claim 4.
In any one of the above, the mixed weight ratio of the inorganic pigment or the organic pigment in the spectral / reflective film is 30 to 70% by weight, preferably 35 to 55% by weight.

The liquid crystal display device according to the twelfth aspect is the fourth aspect.
In any one of the first to sixth aspects, the spectral / reflective film contains titanium oxide.

The liquid crystal display device according to claim 13 is the liquid crystal display device according to claim 12
, Wherein the mixing weight ratio of the titanium oxide in the spectral / reflective film is 1 to 5% by weight.

The liquid crystal display device according to the fourteenth aspect is the first aspect.
In any one of the above, the active matrix driving type is provided, and the active driving element is provided on the substrate provided with the spectral / reflection film.

The liquid crystal display device according to the fifteenth aspect is the first aspect.
In any of the above-mentioned, the active matrix driving type is provided, and the active driving element is provided on the substrate on the white light incident side.

The liquid crystal display device according to the sixteenth aspect is the first aspect.
In any one of the above-described embodiments, a light-transmitting electrode for applying an electric field to the liquid crystal is provided on the surface of the spectral / reflective film.

In order to realize a liquid crystal display element which satisfies the above-mentioned characteristics (1) to (7) required for a reflection type liquid crystal display device in the future and solves the problems of the conventional example described above, The inventors have proposed the following improvement policy (A)-
(D) was set up.

(A) In order to obtain a high contrast ratio, a liquid crystal drive mode employs a birefringence control system or a transmission / absorption system based on dye improvement. (B) When employing the birefringence control method, one polarizing film is used as a means for securing high screen luminance. (C) In order to secure a high screen luminance, a micro color filter as in the conventional example is not used. (D) In order to secure a high screen luminance, the coloring function and the reflecting function are achieved by a single member.

In the present invention, a color developing function and a reflecting function are performed by a single member so that the image quality of the liquid crystal display approaches the image quality of the information medium made of paper such as gravure printing, and a high contrast ratio is secured. That is, in the reflection type liquid crystal display device of the present invention, two contradictory characteristics, that is, improvement of screen luminance and securing of a high contrast ratio, are realized with a high level of balance.

According to the present invention, there is provided a spectral / reflective film that performs both a function of separating and a function of reflecting white light incident from the viewing side. In the present invention, the color is formed by reflecting only a specific color by the spectral / reflection film and absorbing other colors, instead of forming the color by a filter function using a color filter as in the related art. At this time, it is desirable to perform reflection with appropriate scattering.
As described above, in the present invention, the color-forming function (spectral function) and the reflecting function are performed by a single spectral / reflective film.
As in the conventional color filter, extra light absorption after coloring and reflection can be eliminated, and the screen brightness can be improved and a high contrast ratio can be secured.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. (First Embodiment) FIG. 1 is a schematic sectional view of an example of the liquid crystal display device of the present invention. In FIG. 1, reference numerals 1 and 2 denote two glass substrates. Glass substrate 1 on front side (viewing side)
Is provided with a polarizing film 3 on its outer surface. On the inner surface of the glass substrate 1, a transparent electrode 4 for applying an electric field to a plurality of pixels in common and an alignment film 5 whose surface is rubbed are laminated in this order. On the other hand, on the inner surface of the glass substrate 2 on the back side (reflection side), red and red for performing both the spectral function and the reflective function, which are characteristic parts of the present invention, are provided.
Spectral / reflective film 6 configured by arranging a plurality of individual films of green and blue in stripes, a plurality of transparent electrodes (pixel electrodes) 7 for individually applying an electric field to each pixel, and a rubbing treatment on the surface The formed alignment films 8 are laminated in this order, and a plurality of TFTs 9 for controlling on / off of the transparent electrode 7 for each pixel are provided. Then, a liquid crystal material is sealed between the alignment films 5 and 8 to form a liquid crystal layer 10. With such a configuration, a plurality of liquid crystal pixels are arranged in a matrix between the glass substrate 1 on the viewing side and the glass substrate 2 on the back side.

The transparent electrodes 4, 7 and the alignment films 5, 8 are made of ITO (Indium Tin Oxide) and polyimide, respectively. The liquid crystal material constituting the liquid crystal layer 10 is TN
(Twisted nematic) type liquid crystal, STN (super twisted nematic) type liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, homeotropic liquid crystal, polymer dispersed type liquid crystal, guest host type liquid crystal, etc. are used.

The material of the spectral / reflective film 6 is as follows.
It is effective to use a “color tile” -like substance. Specifically, it is prepared by firing an inorganic pigment or an organic pigment in a paste form at an appropriate temperature. The spectral / reflective film 6 functionally has a color developing property and a high reflective property with appropriate scattering, similarly to gravure printing paper.

In the liquid crystal display device having such a configuration, light incident on the liquid crystal layer 10 from the outside via the polarizing film 3, the glass substrate 1, the transparent electrode 4, and the alignment film 5 can be used.
When the light passes through the liquid crystal layer 10 as it is, the light is developed and reflected by the spectral / reflective film 6, and the developed / reflected light is visually recognized from the glass substrate 1 side. On the other hand, due to the birefringence effect of the liquid crystal layer 10 or absorption by a dye, etc.
If the color does not develop, or if the color does not come out of the liquid crystal panel again through the liquid crystal layer 10, it is visually recognized from the glass substrate 1 side as a “black” state.

FIG. 2 is a schematic sectional view showing the procedure for manufacturing the liquid crystal display device of the first embodiment having the structure shown in FIG. First, a 2.5 μm-thick striped spectral / reflective film 6 having a thickness of 2.5 μm is formed by color paste printing on the pixel electrode formation region of the glass substrate 2 on the back side (reflection side) in which the TFTs 9 for each pixel are arranged in a matrix. Are formed so as to extend in the column direction of the matrix (FIG. 2).
(A)). The color paste used is 45 parts of each of the red, green and blue raw materials, 10 parts of ethyl cellulose, and acrylic resin.
10 parts and 35 parts of butyl cellosolve as a solvent were mixed, kneaded with a planetary mill, and then finished and kneaded with a three-roll mill. On a predetermined portion of the glass substrate 2,
After printing each color paste in stripes,
After drying in a clean oven at 60 ° C. for 60 minutes, the spectral / reflective film 6 is formed.

Next, ITO is vapor-deposited, and a transparent electrode 7 is formed in a pixel-like pattern in each pixel forming region on the striped spectral / reflective film 6 by a photo process (FIG. 2).
(B)). In addition, a polyimide for liquid crystal alignment is applied to substantially the entire surface of the substrate, and a process for uniaxially aligning the liquid crystal in a certain direction by rubbing is performed to form an alignment film 8 (FIG. 2).
(C)).

On the other hand, a flat transparent electrode 4 common to each pixel made of ITO and an alignment film 5 made of polyimide for liquid crystal alignment are formed on one surface of the glass substrate 1 on the front side (viewing side).
Is formed (FIG. 2D). At this time, a rubbing process is performed on the alignment film 5 so that the liquid crystal has a 90 degree direction with respect to the rubbing direction of the alignment film 8 so that the liquid crystal has a twisted nematic alignment. Then, a panel is prepared according to a normal liquid crystal panel preparation process, and the polarizing film 3 is attached to the other surface of the glass substrate 1. Such two glass substrates 1 and 2
Are overlapped via a predetermined gap, and liquid crystal is sealed in the gap to complete a liquid crystal display device (FIG. 2).
(E)).

The liquid crystal has a birefringence of 0.11 and a panel gap of 4 μm. The liquid crystal is doped with a small amount of a chiral dopant to prevent reverse twist in twisted nematic alignment. The pretilt value of the alignment films 5 and 8 is about 4 degrees.

(Second Embodiment) As in the first embodiment, a TFT 9, a spectral / reflective film 6,
The transparent electrode 7 and the alignment film 8 are formed, and the transparent electrode 4 and the alignment film 5 are formed on the other glass substrate 1. On this occasion,
Rubbing treatment is performed on both alignment films 5 and 8 so that the rubbing directions are parallel to each other, so that a so-called homogeneous alignment state is obtained. Then, a panel is prepared according to a normal liquid crystal panel preparation process, and a liquid crystal in which 93 parts of nematic liquid crystal and 7 parts of black dye are compatible is sealed in the prepared panel. The black dye is once sufficiently dissolved in a solvent such as acetone, mixed with a nematic liquid crystal, and then heated to evaporate and dissolve only the solvent such as acetone. The gap of the liquid crystal panel is 8 μm, and the pretilt value is 3 degrees. No polarizing film 3 was attached to this liquid crystal display element.

(Third Embodiment) FIG. 3 is a schematic sectional view of another example of the liquid crystal display device of the present invention. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals. The liquid crystal display element shown in FIG. 3 is an active drive type liquid crystal display element in which a TFT 9 is provided for each pixel, similarly to the above-described liquid crystal display element shown in FIG. 1, but the liquid crystal display element shown in FIG. These TFTs 9 are provided on the glass substrate 2 on the side, and in the liquid crystal display element shown in FIG. 3, the TFTs 9 on the glass substrate 1 on the viewing side are provided. The glass substrate 1 has a transparent electrode (IT) facing the spectral / reflective film 6 of each color.
An electrode pad 11 made of O) is provided.

FIG. 4 is a schematic cross-sectional view showing a manufacturing procedure of the liquid crystal display device of the third embodiment having the configuration shown in FIG. A spectral / reflective film 6 of each color is formed on a predetermined portion of the glass substrate 2 on the back side in the same procedure as in the first embodiment (FIG. 4A). Next, ITO is vapor-deposited, a planar transparent electrode 7 common to each pixel is pattern-formed on the spectral / reflective film 6 by a photo process, and a polyimide for liquid crystal alignment is applied. Then, a process for uniaxially aligning the liquid crystal is performed to form an alignment film 8 (FIG. 4B).

An ITO electrode pad 11 serving as a pixel electrode is provided on the viewing side glass substrate 1 provided with a TFT 9 for each pixel at a position facing the spectral / reflection film 6 of each color. Is formed (FIG. 4C).
At this time, a rubbing process is performed so that the orientation of the liquid crystal is 90 degrees with respect to the rubbing direction of the alignment film 8 so that the liquid crystal has a twisted nematic orientation. Then, a panel is prepared according to a normal liquid crystal panel preparation process, and after attaching the polarizing film 3 to the other surface of the glass substrate 1, the liquid crystal is sealed (FIG. 4D). The birefringence of the liquid crystal is 0.11, and the panel gap is 4 μm.

(Fourth Embodiment) A color paste similar to that of the first embodiment is used, and a color paste similar to that of the third embodiment is used.
A spectroscopic / reflective film 6, a transparent electrode 7 and an alignment film 8 are formed on a glass substrate 2 on the back side, and an electrode pad 11 and an alignment film are formed on the glass substrate 1 on the viewing side provided with the TFT 9 as in the third embodiment. A film 5 is formed. At this time, a rubbing treatment is performed on each of the alignment films 5 and 8 so as to be parallel to each other, so that a so-called homogeneous alignment state is obtained. Then, a panel is created according to a normal liquid crystal panel creation process, and liquid crystal is sealed in the created panel in the same procedure as in the second embodiment. The gap of the liquid crystal panel is 8 μm, and the pretilt value is 3
Degree. No polarizing film 3 was attached to this liquid crystal display element.

The TFT 9 is installed on the rear side (FIG. 1).
(See FIG. 3) and the viewing side (see FIG. 3), and what is essential in the present invention is a coloring function (spectral function).
And the point that the spectral / reflective film 6 performing the reflection function is provided on the back side.

The liquid crystal display device shown in FIGS.
Although the liquid crystal display device is of an active matrix drive system, the present invention can be applied to a liquid crystal display device of a simple matrix drive system.

In the above-described embodiment, the spectral / reflective film 6 is formed in a stripe shape. However, the spectral / reflective film 6 may be formed in a dot shape for each liquid crystal pixel. Further, a configuration in which the liquid crystal layer 10 is divided for each liquid crystal pixel is also possible.

The pigment used for the spectral / reflective film 6 may be either an inorganic pigment or an organic pigment as long as sufficient color development and reflectance as described later can be obtained.

(Conventional example) A high transmittance micro color filter 44 having a peak intensity of a spectrum corresponding to each of the center wavelengths of red, green and blue of 60 to 70% is provided on a glass substrate 41 on the viewing side. A conventional liquid crystal display device having a configuration shown in FIG. 16 in which a reflective electrode 47 made of aluminum is provided on a glass substrate 42 with a TFT on the side is prepared as a comparative example. Note that the liquid crystal molecular orientation of this comparative example is a twisted nematic mode as in Examples 1 and 3, and the conditions such as the panel gap, the liquid crystal material birefringence, and the polarizing film are the same as in Example 1.

Here, the difference between the present invention and the conventional example will be described. In the conventional example shown in FIG. 16, a micro color filter 44 that performs a coloring function is provided on the viewing side, and a reflective electrode 47 that performs a reflecting function is provided on the back side, and a layer that performs a light emitting function and a layer that performs a reflecting function are provided. Are completely separated. Then, the light incident on the liquid crystal layer 50 is colored by transmitting through the micro color filter 44, reflected by the reflective electrode 47, and passes through the micro color filter 44 again.
By this process, the intensity of the transmitted light is reduced, and even if the diffused light is appropriately reflected and reflected by the reflective electrode 47, the scattered light is reduced to a level that the human eye cannot recognize.
Therefore, it is impossible to realize a reflection type liquid crystal display element which has a good appearance after all.

On the other hand, according to the present invention, by providing the spectral / reflective film 6 having a color developing function (spectral function) and a reflecting function on the back side, it is possible to realize a reflection type liquid crystal display device with high image quality. I have.

The ideal spectral characteristics of the reflection type liquid crystal display element, that is, the ideal values of the reflectance for red light (wavelength 625 nm), green light (wavelength 550 nm) and blue light (wavelength 450 nm) are shown in the following table. It is shown in FIG.

[0063]

[Table 1]

FIG. 5 shows the reflectance characteristics of the spectral / reflective film 6 of the present invention when an inorganic pigment and an organic pigment are used as the raw materials, respectively. The data shown in FIG. 5 shows the reflectance when barium sulfate is used as the perfect diffusing substance that reflects light of any wavelength on the surface (reflectance 100%). In addition, the conventional example described above (Fig. 16)
Table 2 shows the characteristics of the reflectance at.

[0065]

[Table 2]

It is hard to say that the conventional example shown in Table 2 exhibits ideal spectral characteristics as shown in Table 1. On the other hand, in particular, in the spectral / reflective film 6 of the present invention using an inorganic pigment as a material, as shown in FIG. 5, the reflectance for each color light is selectively high (90% or more), and the reflectance is high in other wavelength regions. The ratio is low (around 5%) and exhibits ideal spectral characteristics as shown in Table 1.

Next, the spectral / reflective film 6 which performs a color developing function (spectral function) and a reflecting function, which are characteristic parts of the present invention, is described.
Will be described in detail. The color development characteristics (spectral characteristics) and the reflection characteristics of the spectral / reflective film 6 are based on the thickness of the spectral / reflective film 6, the type of the inorganic pigment or the organic pigment dispersed in the spectral / reflective film 6, and the size of the pigment particles. , The ratio of the pigment particles, and the like.

First, the thickness of the spectral / reflective film 6 will be considered. In the above-described embodiment, a liquid crystal panel in which the thickness of the spectral / reflective film 6 was changed from 1 μm to 10 μm in steps of 1 μm was manufactured, and the screen luminance was measured by a measurement system as shown in FIG. FIG. 7 shows the measurement results. Also, in FIG.
The measurement results of the screen luminance in the conventional example are also shown. As shown in FIG. 6, the measurement conditions at this time are as follows: under a white light environment illuminance of 1000 lux, almost in a diffuse scattered light state, at a distance of 30 cm from the liquid crystal panel 21 to be measured, A luminance meter (for example, BM-
5) 22 were installed, and the luminance was measured at an expected viewing angle of 0.2 degrees.

From the measurement results shown in FIG.
It can be seen that the screen brightness can be improved by increasing the thickness of the. A common layer of color paste is 20
Although it has a thickness of about μm, it is preferable that the thickness of the spectral / reflection film 6 be about several μm, preferably 1 to 3 μm in order to cause color development in the liquid crystal panel as in the present invention. Since the panel gap of the liquid crystal is about several μm and the step of the TFT 9 is 1 to 2 μm, the thickness of the spectral / reflection film 6 is 1 to 2 in order to maintain effective panel gap uniformity.
It is preferably 3 μm. Even when the thickness of the spectral / reflection film 6 is 1 to 3 μm, the screen luminance can be greatly improved as compared with the screen luminance of the conventional example (about 4 cd / m ² ).

Next, the size of the pigment particles will be considered. As shown in FIG. 8, the size of all particles of the inorganic pigment or the organic pigment dispersed in the spectral / reflection film 6 is set to 0.1 μm.
Above. By doing so, it is possible to increase the reflection of light having a desired wavelength.

The reflectance of a plurality of blue spectral / reflective films 6 prepared by changing the size of dispersed blue pigment particles to 450 nm light was measured. However, the blue spectral / reflective film 6
The ratio of the volume of this pigment to the total volume of was always 40%. FIG. 9 shows the measurement results. The reflectance greatly depends on the size of the pigment particles used, and the reflectance is small when the size of the pigment particles is small, and may increase when the size of the pigment particles is large. I understand. In particular,
Pigment particle size of 0.1 μm that can achieve 60% reflectance
The reflectance changes abruptly after the case of.
This is presumably because, when the size of the pigment particles was less than half the wavelength of visible light, light scattering and diffraction different from ordinary light reflection and refraction occurred.

As shown in Table 1, the ideal reflectance of the blue spectral / reflection film 6 for 450 nm light is 90% or more, but the minimum contrast is 60% or more when the reflectance is 60% or more. Ratio can be obtained. When the reflectance for 450 nm light is 60% for the blue spectral / reflective film 6, 5% for the green spectral / reflective film 6, and 5% for the red spectral / reflective film 6, the liquid crystal of all pixels is When displaying white in the transmission mode, the reflectance is 23%. Since the reflectance becomes 5% when black display is performed with the liquid crystal of all pixels in the absorption mode, the contrast ratio is 4.6.
Becomes Considering that the contrast ratio of newspaper is 5, a sufficient value is obtained as the contrast ratio of the reflective display.

The same reflection characteristics as those of the blue spectral / reflective film 6 were obtained with the green spectral / reflective film 6 and the red spectral / reflective film 6. Therefore, high reflectance can be obtained by setting the size of all particles of the pigment to be used to 0.1 μm or more.

By the way, considering the post-process of patterning and forming a transparent electrode on the surface of the spectral / reflective film 6, the spectral
It is necessary to flatten the surface of the reflection film 6. Further, as described above, the thickness of the spectral / reflective film 6 is preferably set to 1 to 3 μm. Therefore, the upper limit of the size of the pigment particles used is preferably set to 2 μm or less.

Next, the average size of the pigment particles will be considered. The average size of the particles of the inorganic pigment or the organic pigment dispersed in the spectral / reflective film 6 is 10 μm or less, especially 1 to 10 μm.
It is preferably 2 μm.

In the above-described embodiment, the thickness of the spectral / reflective film 6 is fixed at 5 μm, and the average size of the pigment particles contained in the color paste used for the spectral / reflective film 6 is 500 nm, 1 μm. , 2 μm, 3 μm, 4 μm, 5
A liquid crystal panel having a thickness of μm was prepared, and the screen luminance was measured using a measurement system as shown in FIG. FIG. 10 shows the measurement results.

From the measurement results shown in FIG. 10, it can be seen that the screen brightness can be improved by increasing the average of the particle size of the pigment. Since the thickness of the spectral / reflective film 6 is preferably 1 to 3 μm as described above,
According to this, the average size of pigment particles is 1-2 μm.
Is preferred. Even when the average is 1 to 2 μm, the screen luminance can be greatly improved as compared with the conventional example.

Next, the ratio (volume ratio, weight ratio) of the inorganic pigment or the organic pigment dispersed in the spectral / reflective film 6 will be considered.

As shown in FIG. 11, the ratio of the volume of the inorganic pigment or the organic pigment dispersed in the spectral / reflective film 6 to the total volume of the spectral / reflective film 6 is set to 40% or more. By doing so, it is possible to increase the reflection of light having a desired wavelength.

The reflectance of 450 nm light of a plurality of blue spectral / reflective films 6 prepared by changing the volume ratio of the blue pigment to be dispersed (the ratio of the volume to the total volume of the spectral / reflective film 6) was measured. However, the size of the blue pigment particles used is
0.08 μm or more. FIG. 12 shows the measurement results. It can be seen that the reflectance largely depends on the volume ratio of the pigment, and the reflectance is low when the volume ratio of the pigment is small, and the reflectance increases when the volume ratio of the pigment is large. This is presumably because the larger the volume ratio, the higher the ratio of light having a desired wavelength reflected by the surface of the pigment and emitted from the surface of the spectral / reflection film 6. And the volume ratio is 40%
In this case, a reflectivity of 60%, which is a sufficient value for the contrast ratio of the reflective display, is realized.

The same reflection characteristics as those of the blue spectral / reflective film 6 were obtained with the green spectral / reflective film 6 and the red spectral / reflective film 6. Therefore, a high reflectance can be obtained by setting the volume ratio of the pigment to 40% or more.

The weight ratio of the inorganic pigment or the organic pigment dispersed in the spectral / reflective film 6 (the ratio of the weight to the total weight of the spectral / reflective film 6) is related to the thickness of the spectral / reflective film 6. In the case of a thickness of 1 to 3 μm, 30 to 70% by weight, especially
35-55% by weight is preferred. If the weight ratio of the pigment is too small, the transparency of the spectral / reflective film 6 becomes too high, and the reflection characteristics are reduced. On the other hand, if the weight ratio of the pigment is too high, the scattering properties become too strong, and particularly in the case of the birefringence method, the contrast ratio is reduced.

Next, the substance added to the spectral / reflective film 6 will be considered. Although the color development characteristics of the spectral / reflection film 6 depend exclusively on the pigment, it is effective to mix fine particles of, for example, titanium oxide (SiO ₂ ) with respect to the reflectance in order to induce some scattering reflection. . When mixing such fine particles to improve the scattering reflectance,
In particular, in a birefringence control type liquid crystal display element, it is necessary to consider the balance with the contrast ratio. If the mixing ratio of the fine particles is low, there is no effect. If the mixing ratio is too high, the contrast ratio is reduced due to scattered light. The mixing ratio of the fine particles also has a relative relationship with the weight ratio of the pigment,
5% by weight is suitable. Note that a high effect can be obtained even if the mixing ratio of the fine particles exceeds 5% by weight in order to improve the screen brightness, particularly the apparent brightness due to the scattered light.

In the above embodiment, a liquid crystal panel in which titanium oxide fine particles were not mixed in the spectral / reflection film 6 and a liquid crystal panel in which titanium oxide particles were mixed were manufactured, and the screen luminance was measured using a measurement system as shown in FIG. Table 3 shows the measurement results. In each of the present inventions A and B in the table, the thickness of the spectral / reflective film 6 was 5 μm, the average size of the pigment particles used was 2 μm, and the present invention A did not contain titanium oxide fine particles. In the present invention B, 4% by weight of titanium oxide fine particles are mixed. Table 3 also shows numerical values of the screen luminance in the conventional example.

[0085]

[Table 3]

From the results shown in Table 3, it can be seen that the screen luminance was significantly improved as compared with the conventional example. Further, by adding 4% by weight of titanium oxide fine particles to the spectral / reflective film 6, the screen luminance is reduced from 23 cd / m ² to 6 cd / m ^2.
It can be seen that the height was increased only to 29 cd / m ² .

The characteristics of the specific example of the present invention will be described below. (Example 1) In the above embodiment, the thickness of the spectral / reflective film 6 was set to 5 μm, the average size of the pigment particles used was set to 2 μm, and the liquid crystal panel 21 was measured by a measuring system as shown in FIG.
Were turned on / off, the contrast ratio (on / off ratio) was measured. Table 4 shows the measurement results. Table 4 also shows similar measurement results for gravure printing paper and the conventional example.

[0088]

[Table 4]

In the present invention, the contrast ratio is greatly improved as compared with the conventional example, and a contrast ratio of more than half as compared with the gravure printing paper can be realized.

(Example 2) In the above embodiment,
The thickness of the spectral / reflective film 6 is 5 μm, the average size of the pigment particles used is 2 μm, and the angle (θ) from the normal direction of the liquid crystal panel 21 is measured using a measuring device as shown in FIG. And the luminance of the liquid crystal panel 21 were measured. FIG. 14 shows the measurement results. Similar measurement results for gravure printing paper and the conventional example are also shown in FIG. In FIG. 13,
The same parts as those in FIG. 6 are denoted by the same reference numerals.

In the conventional example, a high screen brightness (reflectance) can be obtained only when the viewing angle is narrow and the incident light is measured in the specular direction with parallel light instead of diffused light.
Since the incident light is not parallel light, in this measurement system, θ = 0 to
The screen luminance is 4 cd / m ² or less in the range of 80 °. On the other hand, in the present invention, the screen brightness does not change so much even if θ changes, and the viewing angle is widened as in the case of gravure printing paper.

(Example 3) On a glass substrate 2 of 100 mm x 100 mm, a dried film of a red, green, and blue paint ink was used as a spectral / reflective film 6 with a width of 100 µm and a pitch of 300 µm.
Each was formed in a stripe shape so as to have a thickness of 2 to 3 μm. Each color paint ink has a pigment particle size of 0.1
0.20.2 μm, and the ratio of the volume of the pigment to the entire volume of the spectral / reflective film 6 was 40%. Since the spectral / reflective film 6 has some steps, it was flattened with a transparent planarizing film, and then ITO was formed as the transparent electrode 7 and patterned so as to overlap the spectral / reflective film 6 of each color. Furthermore, a polyimide SE-7792 manufactured by Nissan Chemical Co., Ltd. is transferred and printed to a thickness of about 1000 mm to form an alignment film 8, and after drying and washing, the alignment film 8 is subjected to a predetermined rubbing treatment to obtain a liquid crystal display. A reflection-side substrate for an element was manufactured.

The reflection-side substrate is placed on a table under an environment of illuminance of 500 lux, and a luminance meter (for example, SR-1 manufactured by Topcon Corporation) is placed at a position 30 ° from the normal line of the reflection-side substrate.
Was 30 cd / m ² when the luminance was measured by using.

Example 4 The size of pigment particles was 0.5 to
A reflection-side substrate for a liquid crystal display element was manufactured under the same conditions as in Example 3 except that the thickness was 0.6 μm. This reflection side substrate,
When the luminance was measured under the same conditions as in Example 3, it was 50 cd / m ^2.
Met.

(Example 5) The size of the pigment particles was set to 1.0 to
A reflection-side substrate for a liquid crystal display device was manufactured under the same conditions as in Example 3 except that the thickness was changed to 1.2 μm. This reflection side substrate,
When the luminance was measured under the same conditions as in Example 3, 70 cd / m ²
Met.

Example 6 A reflection-side substrate for a liquid crystal display element was manufactured under the same conditions as in Example 3 except that the ratio of the volume of the pigment to the total volume of the spectral / reflective film 6 was 60%.
When the luminance of this reflection-side substrate was measured under the same conditions as in Example 3, it was 40 cd / m ² .

Example 7 A reflection-side substrate for a liquid crystal display element was manufactured under the same conditions as in Example 3 except that the ratio of the volume of the pigment to the entire volume of the spectral / reflective film 6 was 80%.
The luminance of this reflection-side substrate measured under the same conditions as in Example 3 was 45 cd / m ² .

(Example 8) The size of the pigment particles was 0.5 to
A reflection-side substrate for a liquid crystal display device was manufactured under the same conditions as in Example 3 except that the thickness was 0.6 μm and the ratio of the volume of the pigment to the entire volume of the spectral / reflection film 6 was 80%. When the luminance of this reflection-side substrate was measured under the same conditions as in Example 3, it was found to be 60%.
cd / m ² .

(Example 9) The size of the pigment particles was 1.0 to
A reflection-side substrate for a liquid crystal display device was manufactured under the same conditions as in Example 3 except that the thickness was 1.2 μm and the ratio of the volume of the pigment to the entire volume of the spectral / reflection film 6 was 80%. When the luminance of this reflection-side substrate was measured under the same conditions as in Example 3, 75
cd / m ² .

(Comparative Example 1) The size of the pigment particles was 0.5 to
A reflection-side substrate for a liquid crystal display element was manufactured under the same conditions as in Example 3 except that the thickness was 0.6 μm and the ratio of the volume of the pigment to the total volume of the spectral / reflection film 6 was 35%. When the luminance of this reflection-side substrate was measured under the same conditions as in Example 3, 10
cd / m ² . In this case, the reflector was grayish rather than a reflector for white display.

(Comparative Example 2) Under an environment of illuminance of 500 lux,
Example 3 Place white gravure printing paper on the table
When the luminance was measured under the same conditions as described above, it was 50 cd / m ² .

The measurement results in Examples 3 to 5, 7 to 9 and Comparative Examples 1 and 2 are shown in the graph of FIG. Examples 3 to 9
Let the pigment particle size be 0.1 μm or more,
By setting the ratio of the volume of the pigment to the total volume of the reflective film 6 to be 40% or more, it is possible to perform display close to the object color such as gravure printing paper, and to obtain a bright display, particularly when the liquid crystal of all pixels is set to the transmission mode. Bright white display can be realized.

From the results of the measurement of the characteristics as described above, the liquid crystal display device of the present invention can obtain a very good balance of the screen brightness, the contrast ratio, and the scattered reflection as compared with the conventional liquid crystal display device. Sufficient image quality can be obtained as a liquid crystal display device.

[0104]

As described above, in the reflection type liquid crystal display device according to the present invention, the spectral function and the reflection function are performed by one film, so that the problems of the prior art can be solved and the screen brightness can be reduced. Conflict 2 of improvement and ensuring high contrast ratio
The two characteristics can be realized in a high level in a well-balanced manner.

The use of the reflective liquid crystal display device of the present invention, which can provide a display such as gravure printing paper, having a sufficient screen luminance, contrast ratio, and appropriate scattering reflection, enables a notebook personal computer to be used. , Etc., the continuous use time of the portable information processing device can be greatly improved. A transmissive liquid crystal display device (SV
GA (Super Video Graphics Array), about 12 inches)
The power consumption of the main body of the liquid crystal display is 300-400 m
The power consumption of the backlight is 1200 mW compared to W
It also takes. Therefore, when the same battery is used for the transmission type liquid crystal display device and the reflection type liquid crystal display device according to the present invention, even if a similar high image quality state is realized, the continuous use time is longer in the latter than in the former. Is three times or more.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of the liquid crystal display device of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a manufacturing procedure of an example of the liquid crystal display element of the present invention.

FIG. 3 is a schematic sectional view of another example of the liquid crystal display device of the present invention.

FIG. 4 is a schematic cross-sectional view showing a manufacturing procedure of another example of the liquid crystal display device of the present invention.

FIG. 5 is a graph showing the reflectance characteristics of the spectral / reflective film in the liquid crystal display device of the present invention.

FIG. 6 is a schematic diagram of a measurement system for measuring a screen luminance and a contrast ratio of a liquid crystal panel.

FIG. 7 is a graph showing the measurement results of the screen luminance of the liquid crystal panel when the thickness of the spectral / reflective film is changed.

FIG. 8 is a schematic diagram showing the size of pigment particles in a spectral / reflective film.

FIG. 9 is a graph showing the measurement results of the reflectance of the spectral / reflective film when the size of the pigment particles is changed.

FIG. 10 is a graph showing the measurement results of the screen luminance of a liquid crystal panel in which the average of the pigment particle sizes is changed.

FIG. 11 is a schematic diagram showing the ratio of the volume of a pigment to the total volume of a spectral / reflective film.

FIG. 12 is a graph showing the measurement results of the reflectance of the spectral / reflective film when the proportion of the volume of the pigment is changed.

FIG. 13 is a schematic diagram of a measurement system for measuring the relationship between the angle from the normal direction of the liquid crystal panel and the screen brightness of the liquid crystal panel.

FIG. 14 is a graph showing a measurement result of a relationship between an angle of a liquid crystal panel from a normal direction and a screen luminance of the liquid crystal panel.

FIG. 15 is a graph showing measurement results of characteristics in a specific example of the present invention.

FIG. 16 is a schematic sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 1, 2 glass substrate 3 polarizing film 4, 7 transparent electrode 5, 8 alignment film 6 spectral / reflective film 9 TFT 10 liquid crystal layer 11 electrode pad

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Makino 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Yoshinori Kiyota 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Co., Ltd. (72) Inventor Akihiro Mochizuki 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term within Fujitsu Co., Ltd. FC12 FC22 GA03 GA06 GA13 HA07 HA08 HA10 HA12 JA02 KA04 LA16 LA17

Claims (16)

[Claims] 1. A liquid crystal is sandwiched between a pair of substrates facing each other, and white light incident through one of the substrates is separated and analyzed.
A liquid crystal display device, comprising a spectral / reflective film for reflecting light on the other substrate, wherein the spectral / reflected light can be observed through a liquid crystal and the one substrate, respectively. 2. A liquid crystal display device comprising: a plurality of liquid crystal pixels arranged in a matrix between a transparent substrate on the viewing side and a substrate on the back side; A plurality of spectral / reflective films for spectrally / reflecting white light incident through the substrate are provided, and the spectrally / reflected light can be observed through the liquid crystal pixels and the substrate on the viewing side, respectively. A liquid crystal display device characterized by the above. 3. The spectroscopic / reflective film is at least red,
3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is configured to be separated into color components of each color including blue and green. 4. The liquid crystal display device according to claim 1, wherein the spectral / reflective film is a film in which an inorganic pigment is dispersed. 5. The liquid crystal display device according to claim 4, wherein the spectral / reflective film is formed by applying a paste-like substance containing the inorganic pigment, a binder resin, and a solvent by printing and drying. 6. The liquid crystal display device according to claim 1, wherein the spectral / reflective film is a film in which an organic pigment is dispersed. 7. The liquid crystal display device according to claim 4, wherein the thickness of the spectral / reflective film is 10 μm or less, preferably 1 to 3 μm. 8. The liquid crystal display device according to claim 4, wherein the size of the particles of the inorganic pigment or the organic pigment is 0.1 μm or more. 9. An average particle size of the inorganic pigment or the organic pigment is 10 μm or less, preferably 1-2 μm.
The liquid crystal display device according to any one of claims 4 to 6, wherein 10. The liquid crystal display device according to claim 4, wherein a volume ratio of the inorganic pigment or the organic pigment in the spectral / reflective film is 40% or more. 11. The mixing weight ratio of the inorganic pigment or the organic pigment in the spectral / reflective film is 30 to 70% by weight,
The liquid crystal display device according to any one of claims 4 to 6, wherein the content is preferably 35 to 55% by weight. 12. The liquid crystal display device according to claim 4, wherein said spectral / reflective film contains titanium oxide. 13. The liquid crystal display device according to claim 12, wherein a mixing weight ratio of the titanium oxide in the spectral / reflective film is 1 to 5% by weight. 14. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is of an active matrix drive type, and the active drive element is provided on the substrate provided with the spectral / reflection film. 15. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is of an active matrix drive type, and the active drive element is provided on the substrate on the white light incident side. 16. The liquid crystal display device according to claim 1, further comprising a translucent electrode for applying an electric field to the liquid crystal on the surface of the spectral / reflective film.