JP3379427B2 - Liquid crystal devices and electronic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal device and electronic equipment using this liquid crystal device.

[0002]

2. Description of the Related Art Conventionally, as a reflection type liquid crystal device, a device in which a reflection plate is disposed on the back side of a liquid crystal cell in which a liquid crystal layer is sealed between two transparent substrates is often used. In such a reflective liquid crystal device, depending on the type of liquid crystal layer, driving method, etc., polarizing plates may be arranged in front of and behind the liquid crystal cell, or polarizing plates may be arranged only on the front side of the liquid crystal device. Sometimes you don't need a board at all.

In the reflection type liquid crystal device of this type, external light is incident on the liquid crystal layer through the front transparent substrate,
After passing through the transparent substrate on the back side and being reflected by the reflector,
It is visible again through the transparent substrate on the back side, the liquid crystal layer, and the transparent substrate on the front side. In this case, since there is a gap between the liquid crystal layer and the reflecting surface of the reflector by the thickness of the transparent substrate on the back side, depending on the incident angle of external light, the pixel area or dots of the liquid crystal layer that passes through at the time of incidence Since the area is different from the pixel area or the dot area of the liquid crystal layer that passes after reflection, there is a problem that a display blur or double image due to so-called parallax occurs.

As a method for solving the above problems, Japanese Patent Laid-Open No. 5-323371 and Japanese Patent Laid-Open No. 9-113 are available.
As described in Japanese Patent No. 893, there is a method in which a reflector for reflecting external light is provided on the inner surface of the liquid crystal cell to eliminate parallax.

[0005]

However, Japanese Unexamined Patent Publication No.
In the reflective liquid crystal device described in Japanese Patent No. 323371, since the reflective electrode is provided with unevenness so as to have a light diffusing property, there is a problem that the process becomes complicated and the cost increases. In order to eliminate the metallic feeling and the mirror-like feeling of the reflective electrode, a very complicated design such as the height, spacing, and arrangement of the unevenness is required. If the height of the unevenness is made too strong, the liquid crystal alignment is disturbed due to this.

One means for solving the above problems is Japanese Patent Laid-Open No. 9-113893. According to this publication, the reflective electrode is in a mirror surface state and the light diffusivity depends on the light control film on the front surface of the liquid crystal cell. However, in the reflection type liquid crystal device described in Japanese Patent Laid-Open No. 9-113893, a liquid crystal device having a different refractive index is used.
Since the light control film composed of minute regions of various kinds is arranged on the front surface of the liquid crystal cell, there is a direction that there is no diffused light at all and the viewing angle is narrow. This is because the incident light from a specific direction is scattered, but the light from other directions is not scattered. Furthermore, when the light diffusion property of the light control film is increased to achieve a wide viewing angle, there is a problem in that display blurring occurs. This light control film is used to eliminate the specular and metallic feeling of the reflector and to obtain a bright display even in the direction of regular reflection of external light, but the light diffusion property of this light control film is too large. Then, different information in different pixels are mixed by the time the human eyes recognize. That is, if white display and black display are performed by the adjacent pixels, the boundary between the white display and the black display becomes difficult to understand due to the light control film, and the display is blurred. If the light diffusing property of the light control film is too strong, display bleeding (blurring) becomes noticeable, while if it is too weak, the mirror-like feeling and metallic feeling of the reflector remain and the viewing angle of the liquid crystal device becomes narrow.

Further, with the recent development of portable equipment and OA equipment, colorization of liquid crystal display has been required, and even in equipment using a reflection type liquid crystal device, colorization may be required. Many. However, JP-A-9-113
In the method of combining the liquid crystal device and the color filter described in Japanese Patent No. 893, the viewing angle is narrow, and further the display is blurred due to scattering by the light control film.
Occurs, and it is not possible to obtain sufficient color development.

In addition, as described in JP-A-7-28055 and JP-A-7-36060, a diffusion plate is also formed on the inner surface of the liquid crystal cell to cause display blurring (blur).
Although a method of suppressing the above has been proposed, it has not been put to practical use because of problems such as high cost, reduced reliability, and difficulty in obtaining desired scattering characteristics.

SUMMARY OF THE INVENTION Therefore, the present invention solves the above problems and provides a reflection type liquid crystal device which is bright in a wide viewing angle and has no display blurring or color mixture.
Another object is to provide electronic equipment using this liquid crystal device.

[0010]

[Means for Solving the Problems] Means taken by the present invention for solving the above problems are as follows.

In the liquid crystal device of the present invention, the liquid crystal layer is sandwiched between the two substrates, and the outer surface of one of the two substrates has a light diffusing property for scattering incident light from all directions. In a liquid crystal device in which different first scattering layers and second scattering layers are arranged and a reflecting layer is provided on the other substrate side, a polarizing plate is arranged between the first scattering layer and the second scattering layer. The second scattering layer of the first scattering layer and the second scattering layer is disposed on the liquid crystal layer side, and the light diffusivity of the first scattering layer is the same as that of the second scattering layer. It is characterized by being weaker than light diffusivity.

According to this means, since the first scattering layer having a weak light diffusing property is disposed on the surface side, specular reflection on the surface of the liquid crystal cell can be suppressed, and at the same time, it is bright in a wide viewing angle and has a display blur. It is possible to realize a reflective display without (blurring) or color mixture. Further, since the polarizing plate is arranged between the first scattering layer and the second scattering layer, and the second scattering layer having a light diffusivity higher than that of the first scattering layer is arranged on the liquid crystal layer side, the mirror surface of the reflecting layer is obtained. Feeling and metallic feeling are made cloudy, and bright display is possible even in a direction other than the regular reflection direction of external light. About half of the backscattered light from the second scattering layer is absorbed by the polarizing plate, so that the contrast due to backscattering is reduced. You can suppress the decline,
It is possible to obtain a reflection type color display which is clear and has high contrast and good color development.

Further, the scattering plates do not have to be individual units, but may be ones in which the retardation plate and the scatterer are integrated. Further, the light-diffusing material may be used for the pressure-sensitive adhesive layer of the retardation plate or the polarizing plate.

A reflective layer may be formed on the liquid crystal side surface of the other substrate, in which case the reflective layer may also serve as the pixel electrode. By doing so, it is not necessary to newly form a pixel electrode, and the liquid crystal device can be manufactured at low cost. A color filter may be formed between the reflective layer and the first substrate. By doing so, reflective color display can be realized.

The scattering layer is made of Asia Displa.
Scattering to the incident light side (backscattering) as announced by Professor Uchida and others at Tohoku University at y95, pp599-pp602.
It is more preferable that there is no light and the main part is forward scattering.

Next, the scattering layer used in the present invention will be described. The scattering layer suppresses the blurring of the display by appropriately selecting the haze value, which is calculated by the ratio of the total light transmittance measured by the integrating sphere light transmittance measuring device and the scattered light transmittance. can do. If the haze is too small, the specular and metallic feeling of the reflective layer remains, and a bright, high-quality display cannot be obtained. On the other hand, if the haze is too large, it becomes difficult to suppress display bleeding (blur), and a clear, high-contrast, high-quality display cannot be obtained. According to the experiment, the preferable haze range was 3% or more and 50% or less for each scattering layer alone.

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

Electronic equipment of the present invention is characterized by being equipped with the above liquid crystal device.

According to this means, it is possible to realize an electronic apparatus using a liquid crystal device which is bright in a wide viewing angle and is capable of a reflection type display without display blurring (blurring) and color mixture.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a schematic vertical sectional view showing a structure of a first embodiment of a liquid crystal device according to the present invention.
Although this embodiment basically relates to a simple matrix type liquid crystal display device, it can also be applied to an active matrix type device, another segment type device, and other liquid crystal devices with the same configuration. .

In this embodiment, two substrates 101, 1
A liquid crystal cell in which the liquid crystal layer 105 is sealed by a frame-shaped sealing material 104 is formed between the two. Liquid crystal layer 105
Is composed of a nematic liquid crystal having a predetermined twist angle. A color filter 110 is formed on the inner surface of the upper transparent substrate 101.
Colored layers of three colors (red), G (green), and B (blue) are arranged in a predetermined pattern. A transparent protective film 111 is coated on the surface of the color filter, and a plurality of stripe-shaped transparent electrodes 112 are formed of ITO or the like on the surface of the protective film. An alignment film is formed on the surface of the transparent electrode 112, and a rubbing process is performed in a predetermined direction. In addition, the polarizing plate 10 is provided on the outer surface of the upper transparent substrate 101.
6, retardation plate 107, first scattering plate 108, second scattering plate 1
09 is arranged.

On the other hand, on the inner surface of the lower substrate 102, a plurality of stripe-shaped reflective electrodes 103 formed for each colored layer of the color filter are arranged so as to intersect with the transparent electrodes 112. In the case of an active matrix type device including a MIM element or a TFT element, each reflective electrode 103 is formed in a rectangular shape and connected to a wiring via the active element. The reflective electrode 103 is made of Cr or Al.
And the like, and the surface thereof is a reflecting surface that reflects light incident from the transparent substrate 101 side. An alignment film similar to the above is formed on the surface of the reflective electrode 103.

First, the first scattering plate 108 and the second scattering plate 10
9 will be described. To investigate the light diffusivity of the scattering plate,
A measurement system as shown in FIG. 4 was used. The parallel light was made incident on the scattering plate 403 from the light source 401, and the transmitted light traveling straight through the scattering plate 403 was detected by the light receiving section 404. At this time, the scattering plate 403 was rotated 402 and the intensity of the transmitted light was measured. The result measured by the measurement system of FIG. 4 is shown in FIG. The horizontal axis represents the rotation angle of the diffusion plate, and 0 ° is defined when the parallel light from the light source is vertically incident on the scattering plate. Clockwise is negative and counterclockwise is positive. The vertical axis represents the transmitted light intensity. 501 in the figure
Is a characteristic of a transparent acrylic plate having no light diffusion property. 5
02 is a characteristic of a scattering plate having a weak light diffusion property,
Is a characteristic of a scattering plate having a strong light diffusion property. Furthermore, 5
Reference numeral 04 is the characteristic of the scattering plate having a strong light diffusing property in the range of −30 ° to + 30 °, and 505 is the characteristic of the scattering plate having a strong light diffusing property in the range of −60 ° to 0 °. In the present embodiment, the first scattering plate 108 is a scattering plate having a light diffusing property of 502 in FIG. 5, and the second scattering plate 109 is a scattering plate having a light diffusing property of 505 in FIG. Using.

Next, the reflective display will be described. External light passes through the polarizing plate 106, the retardation plate 107, the first scattering plate 108, the second scattering plate 109, and the color filter 110 in FIG. 1, passes through the liquid crystal layer 105, and is reflected by the reflective electrode 103 in a mirror state. Then, the light is again emitted from the polarizing plate 106 to the outside of the liquid crystal cell. At this time, the polarization state of the incident light is changed by the voltage applied to the liquid crystal layer 105, and the bright state, the dark state, and the brightness between them are controlled. The first scattering plate 108 and the second scattering plate 109 have an effect of making the mirror-like feeling and the metallic feeling of the reflective electrode 103 cloudy, and enabling a bright display to be recognized even in a direction other than the regular reflection direction of external light. At this time, by using not only one scattering plate but two layers as in the present embodiment, it is possible to realize a reflection type liquid crystal device which is bright in a wide viewing angle and has no display blurring (blurring) or color mixture. We were able to. The second scattering plate 109 enables a very bright display with directivity, and the first scattering plate 108 can widen the viewing angle. The second scattering plate 109 is often formed by periodically forming materials having different refractive indexes in order to have directivity, like a light control film (trade name: Lumisty) manufactured by Sumitomo Chemical Co., Ltd. When such a film is used alone as a scattering plate, coloring or glare due to light interference peculiar to the light control film is observed. To alleviate this, the first scattering plate 108 is very effective, and this has been confirmed in this embodiment.

In this embodiment, the one-polarizing plate type reflective liquid crystal device has been described. However, a polymer scattering type liquid crystal or a dichroic dye which does not require a polarizing plate is added to the liquid crystal layer. Guest-host liquid crystal may be used. At this time, the polarizing plate and the retardation plate used in this embodiment are unnecessary.

According to the configuration of this embodiment as described above,
We have realized a reflective liquid crystal device that is bright with a wide viewing angle and has no display blurring or color mixing.

Further, in this embodiment, the reflective layer also serves as the pixel electrode, but a transparent electrode such as ITO may be formed after forming a protective film or an insulating film on the reflective layer to form a pixel electrode. Good.

(Second Embodiment) FIG. 2 is a schematic vertical sectional view showing the structure of a second embodiment of the liquid crystal device according to the present invention.
Although this embodiment basically relates to a simple matrix type liquid crystal display device, it can also be applied to an active matrix type device, another segment type device, and other liquid crystal devices with the same configuration. .

In this embodiment, two substrates 201, 2
A liquid crystal cell in which the liquid crystal layer 205 is sealed by a frame-shaped sealing material 204 is formed between the two. Liquid crystal layer 205
Is composed of a nematic liquid crystal having a negative dielectric anisotropy. A color filter 210 is formed on the inner surface of the upper transparent substrate 201.
Colored layers of three colors (red), G (green), and B (blue) are arranged in a predetermined pattern. A transparent protective film 211 is coated on the surface of the color filter 210, and a plurality of stripe-shaped transparent electrodes 212 are formed on the surface of the protective film 211.
Are formed of ITO or the like. An alignment film for vertically aligning liquid crystals is formed on the surface of the transparent electrode 212,
The rubbing process is performed in a predetermined direction. By this rubbing treatment, the liquid crystal molecules have a pretilt angle of about 85 degrees in the rubbing direction.

On the other hand, on the inner surface of the lower substrate 202, a plurality of stripe-shaped reflective electrodes 203 formed for each colored layer of the color filter are arranged so as to intersect with the transparent electrodes 212. In the case of an active matrix type device including an MIM element or a TFT element, each reflective electrode 203 is formed in a rectangular shape and connected to a wiring via the active element. This reflective electrode 203 is made of Cr or A.
1 and the like, the surface of which is a reflecting surface in a mirror surface state that reflects light incident from the transparent substrate 201 side. An alignment film similar to the above is formed on the surface of the reflective electrode 203. Note that this alignment film was not subjected to rubbing treatment.

The reflective electrode 203 contains 1.0% by weight of Nd.
A metal film formed by sputtering Al added with a thickness of 500 angstrom was used. A first scattering plate 208 and a polarizing plate 206 are arranged on the outer surface of the upper transparent substrate 201, and a retardation plate (1/4 wavelength plate) 207 and a second scattering plate 209 are provided between the polarizing plate 206 and the transparent substrate 201. Are arranged. At this time, the first diffusing plate 208 is a diffusing plate having the light diffusing property 502 in FIG. 5 and the second diffusing plate 209 is 50 in FIG.
A scattering plate having a light diffusing property of 3 was used. First scattering plate 208
Since is located on the outermost surface of the reflective liquid crystal device, it can also serve as an anti-glare effect.

External light passes through the first scattering plate 208, the polarizing plate 206, the retardation plate 207, the second scattering plate 209, and the color filter 210 in FIG. 2, passes through the liquid crystal layer 205, and is reflected by the reflection electrode 203. Then, the light is emitted again from the first scattering plate 208 to the outside of the liquid crystal cell. At this time, the polarization state of the incident light is changed by the voltage applied to the liquid crystal layer 205, and the bright state, the dark state, and the intermediate brightness are controlled.

In this embodiment, by disposing the first scattering plate 208 having a weak light diffusing property (haze: about 3% to 10%) in front of the liquid crystal cell, specular reflection on the liquid crystal cell surface can be suppressed. it can. In this liquid crystal device, a scattering plate with a strong light diffusing property is placed below the polarizing plate, so that half of the scattering (backscattering) to the incident light side is absorbed by the polarizing plate, so the contrast is clear and the contrast is high. It was possible to obtain a reflective color display with good color development.

(Third Embodiment) FIG. 3 is a schematic vertical sectional view showing the structure of a third embodiment of the liquid crystal device according to the present invention.
Although this embodiment basically relates to a simple matrix type liquid crystal display device, it can also be applied to an active matrix type device, another segment type device, and other liquid crystal devices with the same configuration. .

In this embodiment, two substrates 301 and 3 are used.
A liquid crystal cell in which the liquid crystal layer 305 is sealed by a frame-shaped sealing material 304 is formed between the two. Liquid crystal layer 305
Is composed of a nematic liquid crystal having a predetermined twist angle. A color filter 310 is formed on the inner surface of the upper transparent substrate 301.
Colored layers of three colors (red), G (green), and B (blue) are arranged in a predetermined pattern. A transparent protective film 311 is coated on the surface of the color filter, and a plurality of stripe-shaped transparent electrodes 312 are formed of ITO or the like on the surface of the protective film. An alignment film is formed on the surface of the transparent electrode 312, and is rubbed in a predetermined direction. In addition, the polarizing plate 30 is formed on the outer surface of the upper transparent substrate 301.
6, first scattering plate 308, retardation plate 307, second scattering plate 3
09 is arranged.

On the other hand, on the inner surface of the lower substrate 302, a plurality of stripe-shaped reflective electrodes 303 formed for each colored layer of the color filter are arranged so as to intersect with the transparent electrodes 312. In the case of an active matrix type device including a MIM element or a TFT element, each reflective electrode 303 is formed in a rectangular shape and connected to a wiring via the active element. The reflective electrode 303 is made of Cr or Al.
And the like, and the surface thereof is a reflecting surface in a mirror surface state that reflects light incident from the transparent substrate 301 side. An alignment film similar to the above is formed on the surface of the reflective electrode 303. As the first scattering plate 308, a scattering plate having a light diffusing property 504 in FIG. 5 was used, and as the second scattering plate 309, a scattering plate having a light diffusing property 502 in FIG. 5 was used.

The reflective display will be described. External light is obtained by polarizing plate 306, first scattering plate 308, and phase difference plate 30 in FIG.
7, the second scattering plate 309, and the color filter 310, respectively, and after passing through the liquid crystal layer 305, the light is reflected by the reflection electrode 303 in a mirror state and again emitted from the polarizing plate 306 to the outside of the liquid crystal cell. At this time, the polarization state of the incident light is changed by the voltage applied to the liquid crystal layer 305, and the bright state, the dark state, and the brightness between them are controlled. First scattering plate 30
8 and the second scattering plate 309 have an effect of making the mirror-like feeling and metallic feeling of the reflective electrode 303 cloudy, and enabling a bright display to be recognized even in a direction other than the regular reflection direction of external light. At this time, by using not only one scattering plate but two layers as in the present embodiment, it is possible to realize a reflection type liquid crystal device which is bright in a wide viewing angle and has no display blurring (blurring) or color mixture. We were able to. The first scattering plate 308 enables a very bright display with directivity, and the second scattering plate 309 can widen the viewing angle. In addition, the first scattering plate 308 is a light control film (trade name: Lumisty) manufactured by Sumitomo Chemical Co., Ltd. in which materials having different refractive indexes are periodically formed to have directivity. Many. When such a film is used alone as a scattering plate, coloring or glare due to light interference peculiar to the light control film is observed. To alleviate this, the second scattering plate 309 is very effective, and this has been confirmed in this embodiment.

According to the configuration of this embodiment as described above,
We have realized a reflective liquid crystal device that is bright with a wide viewing angle and has no display blurring or color mixing.

In the present embodiment, the reflective layer also serves as the pixel electrode, but a transparent electrode such as ITO may be formed after forming a protective film or an insulating film on the reflective layer to form a pixel electrode. Good.

Finally, the colored layer of the color filter used in each of the above embodiments will be described. In each embodiment, in the case of performing a reflective display, after the incident light once passes through one of the color layers of the color filter, it passes through the liquid crystal layer, is reflected by the reflective electrode, and then passes through the color layer again. Is released. Therefore, unlike a normal transmissive liquid crystal device, since the light passes through the color filter twice, the display becomes dark with the normal color filter. Therefore, in each embodiment, the R, G, and B colored layers of the color filter are lightened so that the minimum transmittance in the visible region is 30 to 50%. The lightening of the colored layer is performed by reducing the film thickness of the colored layer or decreasing the concentration of the pigment or dye mixed in the colored layer. This makes it possible to prevent the display brightness from being lowered when the reflective display is performed.

In each of the above embodiments, the scattering plate is a single unit, but a film in which the retardation plate and the scatterer are integrated may be used. Further, a light diffusing material may be used for the diffusion layer of the retardation plate or the polarizing plate.

Fourth Embodiment Three examples of the electronic equipment of the present invention will be shown. Since the liquid crystal device of the present invention is of a reflective type, it is suitable for portable devices that are used in various environments and require low power consumption. For example, FIG. 6A shows a mobile phone, FIG. 6B shows a wristwatch, and FIG. 6C shows a portable information device. Since the liquid crystal device of the present invention has high display quality without display blurring or the like,
It is most suitable when high-definition display is required. recent years,
Due to the increase in information volume and the development of information infrastructure, many electronic devices that are frequently carried are manufactured and sold. The liquid crystal device of the present invention is most suitable for the display portion of such an electronic device, and particularly when color display is required, it is very bright, has a wide viewing angle, and enables display with good color development.

[0052]

As described above, according to the present invention, it is possible to realize a reflection type liquid crystal device which is bright in a wide viewing angle and has no display blurring or color mixture.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a schematic structure of a first embodiment of a liquid crystal device according to the present invention.

FIG. 2 is a schematic vertical sectional view showing a schematic structure of a second embodiment of a liquid crystal device according to the present invention.

FIG. 3 is a schematic vertical sectional view showing a schematic structure of a third embodiment of a liquid crystal device according to the present invention.

FIG. 4 is a schematic diagram of a measurement system for measuring the light diffusivity of a scattering plate.

5 is a diagram showing the characteristics of the scattering plate measured by the measurement system of FIG.

FIG. 6 is a schematic view of an electronic device equipped with a liquid crystal device according to the present invention.

[Explanation of symbols]

101, 102, 201, 202, 301, 302 Transparent substrates 103, 203, 303 Reflective electrodes 104, 204, 304 Sealing materials 105, 205, 305 Liquid crystal layers 106, 206, 306 Polarizing plates 107, 207, 307 Phase difference plate 108 , 208, 308 First scattering plates 109, 209, 309 Second scattering plates 110, 210, 310 Color filters 111, 211, 311 Protective films 112, 212, 312 Transparent electrode 401 Light source 402 Rotation axis 403 Scattering plate 404 Light receiving part 501 Characteristics of transparent acrylic plate without light diffusion 502 Characteristics of scattering plate with weak light diffusion 503 Characteristics of scattering plate with strong light diffusion 504 Scattering with strong light diffusion in the range of -30 ° to + 30 ° Characteristics of plate 505 Characteristics of scattering plate having strong light diffusivity in the range of -60 ° to 0 °

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-9-230345 (JP, A) JP-A-8-201802 (JP, A) JP-A-9-318934 (JP, A) JP-A-8- 122755 (JP, A) JP 61-120121 (JP, A) JP 11-119215 (JP, A) JP 11-7007 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/1335 G02F 1/1343 G02F 1/13 505

Claims (2)

(57) [Claims] 1. A first scattering layer in which a liquid crystal layer is sandwiched between two substrates, and the outer surface of one of the two substrates has a different light diffusivity for scattering incident light from all directions. And the second
In a liquid crystal device in which a scattering layer is disposed and a reflective layer is provided on the other substrate side, a polarizing plate is disposed between the first scattering layer and the second scattering layer, and the first scattering layer and the second scattering layer are disposed. The second scattering layer of the two scattering layers is disposed closer to the liquid crystal layer, and the light diffusivity of the first scattering layer is weaker than that of the second scattering layer. And liquid crystal device. 2. An electronic device equipped with the liquid crystal device according to claim 1.