JPH09244005A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device which is ameliorated in surface reflection, temp. rise, unequal temp. distribution and coloring. SOLUTION: A medium (liquid) 10 having the refractive index nearly equal to the refractive index of a protective plate 12 for protecting the surface of a liquid crystal panel 1A and the substrate 5 of the liquid crystal panel 1A is enclosed into the space formed between the liquid crystal panel 1A and the protective plate 1, by which the surface reflection is suppressed and a high contrast is obtd. The medium (liquid) 10 having the thermal conductivity higher than the thermal conductivity of the air is enclosed between the liquid crystal panel 1A and the protective plate 1 and the heat generated in the liquid crystal panel 1A is radiated by this medium (liquid) 10, by which the temp. rise and the unequal temp. distribution are ameliorated and the unequal display is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device,
In particular, the present invention relates to a liquid crystal panel in which the display surface is protected by a protective plate arranged in front of the liquid crystal panel.

[0002]

2. Description of the Related Art Today, a liquid crystal device is widely used as a display device for various office automation equipment such as a television and a notebook computer. The liquid crystal device is formed by sandwiching a liquid crystal between a pair of opposed substrates. There is a configuration including a liquid crystal panel and a protective plate that protects the display surface of the liquid crystal panel.

FIG. 8 is a schematic view of a direct-view type liquid crystal device which is an example of such a liquid crystal device. In FIG.
0 is a protective plate for protecting the liquid crystal panel 100A, 10
Reference numerals 1 and 102 denote polarizing plates for converting incident light into linearly polarized light.
5 is a liquid crystal layer, 103 and 104 sandwich the liquid crystal layer 105,
Also, a liquid crystal cell substrate coated with various functional films such as a color filter (not shown), a transparent electrode (not shown) for driving pixels, and an alignment film (not shown) for aligning liquid crystal molecules, 106 Is the backlight.

By the way, in the liquid crystal device having such a structure, the observer can see the liquid crystal layer 105, the liquid crystal cell substrate 103,
The reflection from 104, the polarizing plates 101 and 102, and the protective plate 100 is observed as surface reflection. However, generally, due to the relationship between the refractive index of each medium and the absorption of the polarizing plate and the color filter, the reflection inside the outer polarizing plate 101 is rarely observed. Therefore, for the surface reflection, the protection plate surface 11
1, reflection from the inner surface 112 of the protective plate and the surface 113 of the polarizing plate greatly contributes.

Here, the refractive indexes of the polarizing plate 101 and the protective plate 100 are about 1.5, and the outside of the display device and the hollow portion l1.
Since the air that fills 0 has a refractive index of 1.0, the difference in refractive index causes about 4% reflection from each surface, which significantly impairs the appearance of the device.

By the way, since the liquid crystal device is required to secure a sufficient contrast at the time of display, conventionally, in order to suppress surface reflection which hinders the securing of such a contrast, the reflectance is conventionally reduced by an antireflection film. A method (generally called anti-reflection), a method of roughening the surface and scattering reflected light (generally called anti-glare), etc. have been adopted.

On the other hand, in recent years, there is a tendency that the temperature rise or the temperature distribution unevenness of the liquid crystal panel increases due to the reasons such as the large screen of the liquid crystal device, the load of the peripheral circuit accompanying the increase in the driving speed, the increase in the number of times of switching and the like. Furthermore, depending on the case, a temperature distribution of ten and a few degrees may occur in the panel surface, which causes a difference in the operating environment at each point on the liquid crystal panel surface, resulting in display unevenness or a display exceeding the operating range due to a temperature rise. It may be impossible.

In particular, in the case of a liquid crystal device using a ferroelectric liquid crystal, higher voltage driving is required than nematic liquid crystals such as normal twist nematic and super twist nematic, so that temperature rise and temperature distribution unevenness are caused. More serious. In the conventional liquid crystal device, heat is radiated from the hollow portion 110 or the peripheral portion of the panel.

[0009]

However, in such a conventional liquid crystal device, the antireflection which suppresses the surface reflection is a very expensive process, so that the cost is high, and the antiglare process causes the display to be blurred and the image quality to be improved. However, there was a problem that

Further, since the thermal conductivity of the hollow portion 110 is extremely poor and no convection is generated, the heat radiation effect of the hollow portion 110 hardly occurs in reality, and it is impossible to suppress the temperature rise and the uneven temperature distribution. There was a problem.

On the other hand, the retardation Δnd of the liquid crystal layer used in the liquid crystal device (Δn: the difference in refractive index between normal light and extraordinary light, d:
Although the layer thickness) is given Δnd so as to suppress the coloring of white, if the thickness of the liquid crystal layer changes and Δnd changes even slightly, the spectral transmittance becomes different. When the spectral transmittances are different in this way, there is a problem that, for example, white display becomes yellowish, that is, so-called coloring occurs.

In order to suppress such coloring, conventionally, the thickness of the liquid crystal layer has been strictly controlled.
In this case, since liquid crystal panels having different Δnd are defective products, another problem arises that the yield is deteriorated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal device in which surface reflection, temperature rise, uneven temperature distribution, and coloring are improved. is there.

[0014]

According to the present invention, a display surface of a liquid crystal panel formed by sandwiching a liquid crystal between a pair of opposed substrates is protected by a protective plate provided in front of the liquid crystal panel. In the liquid crystal device, a medium having a refractive index different from that of air is sealed in a space formed between the liquid crystal panel and the protective plate.

The present invention is also characterized in that the medium has substantially the same refractive index as that of the protective plate and the substrate.

The present invention is also characterized in that the medium has a thermal conductivity higher than that of air.

Further, the present invention is characterized in that the medium is transparent.

The present invention is also characterized in that the medium is colored with a predetermined pigment.

Further, the present invention is characterized in that the pigment for coloring the medium is an inorganic pigment.

Further, the present invention is characterized in that the medium is ethylene glycol, or a mixture of ethylene glycol and glycerin or pure water.

According to the present invention, the space for enclosing the medium is formed by the liquid crystal panel, the protective plate and the housing member, and the housing member absorbs expansion of the medium caused by heat generation of the liquid crystal panel. It is characterized in that a void portion is formed.

Further, the invention is characterized in that the void portion is an air reservoir formed between a medium filling port formed in the housing member and the medium.

Further, the present invention is characterized in that the liquid crystal used in the liquid crystal panel is a ferroelectric liquid crystal.

Further, the present invention is characterized in that the ferroelectric liquid crystal is a chiral smectic liquid crystal.

A liquid crystal panel formed by sandwiching liquid crystal between a pair of substrates facing each other in this way and a protective plate provided in front of the liquid crystal panel for protecting the display surface of the liquid crystal panel. By constructing a medium in which the refractive index of air is different from that of air and is substantially the same as the refractive index of the protective plate and the substrate, surface reflection is suppressed and high contrast is obtained.

Further, by enclosing a medium having a thermal conductivity higher than that of air in a space formed between the liquid crystal panel and the protective plate, the heat generated in the liquid crystal panel is radiated to raise the temperature. Also, the uneven temperature distribution is improved to eliminate the uneven display.

Further, by forming a space for absorbing the expansion of the medium generated by the heat generation of the liquid crystal panel in the housing member forming the space for enclosing the medium together with the liquid crystal panel and the protective plate, the device by the expansion of the medium is formed. Try to prevent the destruction of.

Further, by coloring the medium with a predetermined pigment, coloring is suppressed, and by using an inorganic pigment as the pigment, light resistance and heat resistance are increased.

Further, by using a chiral smectic liquid crystal which is a ferroelectric liquid crystal for the liquid crystal panel, it is possible to improve the high speed and memory property of the device.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a liquid crystal device according to an embodiment of the present invention. In FIG. 1, 1 is a protective plate for protecting the liquid crystal panel 1A, 2 and 3 are polarizing plates for converting incident light into linearly polarized light, 4 is a liquid crystal layer, and 5 and 6 are liquid crystal layers 4.
And a liquid crystal having various functional films such as a color filter (not shown), a transparent electrode (not shown) for driving pixels, and an alignment film (not shown) for aligning liquid crystal molecules. A cell substrate, 7 is a backlight.

It should be noted that the protective plate 1 is such that the user does not directly touch the display surface of the liquid crystal panel 1A when the liquid crystal having poor impact resistance such as chiral smectic liquid crystal is used, or the display surface is rough. The display surface is scratched by cleaning etc.
Prevents poor visibility (even if the protective plate 1 is scratched,
It can be easily replaced).

As the liquid crystal used for the liquid crystal panel 1A, nematic liquid crystal, chiral smectic liquid crystal, guest-host liquid crystal and the like are used, but generally, ferroelectric liquid crystal having bistability, for example, chiral smectic, in a particular temperature range. When liquid crystal is used, it is possible to provide a liquid crystal device having excellent performance such as high-speed display and memory property.

In the liquid crystal device configured as described above, the light emitted from the backlight 7 is converted into linearly polarized light by the polarizing plate 2, transmitted through the liquid crystal cell substrate 5, and the liquid crystal molecule alignment in the liquid crystal layer 4 is performed. Due to the birefringence or optical rotatory power, the light is converted into a specific elliptically polarized light or linearly polarized light. Further, the light transmitted through the liquid crystal layer 4 is transmitted through the liquid crystal cell substrate 6, converted into linearly polarized light by the polarizing plate 3, and light corresponding to the signal given to each pixel is emitted to form an image. Has become.

On the other hand, in the figure, 10 is an optical coupling liquid (hereinafter O) which is ethylene glycol or a mixture of ethylene glycol and glycerin or pure water.
OC liquid 10 which is an example of this medium.
Is a protective plate 1, a polarizing plate 2 and an OC liquid 1 as shown in FIG.
It is enclosed in a space (corresponding to the hollow portion 110 in FIG. 8) surrounded by the OC housing 23 for preventing 0 leakage. In addition, in this embodiment, the OC liquid 10 is a transparent liquid.

Here, when the OC liquid 10 is sealed, first, the OC housing 2 is provided between the protective plate 1 and the polarizing plate 2.
Protective plate 1, polarizing plate 2, OC housing 2 with 3 interposed
3 is airtightly fixed, and then the OC liquid 10 is filled through the medium filling port 23a formed in the OC housing 23. After filling the OC liquid 10 in this way,
The medium filling port 23a is sealed with a diaphragm 24 so that the OC liquid 10 does not leak.

By the way, the refractive index of the OC liquid 10 is different from the refractive index of air so as to minimize reflections occurring at the boundary surfaces between the protective plate 1 and the OC liquid 10 and between the polarizing plate 2 and the OC liquid 10. The refractive indices of the protective plate 1 and the polarizing plate 2 are close to each other. In this embodiment, the protective plate 1 and the polarizing plate 2 have a refractive index of about 1.5, and the OC liquid has a refractive index of 1.4 to 1.5.

In this way, the refractive index of the OC liquid and the refractive index of the protective plate 1 and the polarizing plate 2 are brought close to each other to suppress reflection as much as possible, thereby obtaining a high contrast and improving the image quality of the display image. I am trying.

Incidentally, FIG. 3 schematically shows the reflected light generated from each surface from the protective plate 1 to the polarizing plate 2 in the liquid crystal device having such a structure, and the reflected light is shown in the same figure. Reflection from the surface of the protective plate 1, the protective plate 1
And the reflection 13 from the OC liquid 10, the reflection 14 from the surface of the OC liquid 10 and the polarizing plate 2, and the reflection 15 of the liquid crystal layer and the like.

Here, the reflectance Rot from the polarizing plate 2 to the liquid crystal layer 4 on the backlight side and the others is about 1% or less. The reflectance (vertical incidence) of the surface of the protective plate 1, the surface of the protective plate 1 and the OC liquid 10, and the surface of the OC liquid 10 and the polarizing plate 2 are such that the refractive index of the external air is 1.0, Assuming that the refractive index is 1.5, the OC liquid 10 has a refractive index of 1.4, and the polarizing plate has a refractive index of 1.5, the Fresnel formula shows that the reflectance Rp from the surface of the protective plate 1 is 4%, 1 and the reflectance Rfo from the OC liquid 10 is 0.12%,
The reflectance Rbo from the surfaces of the OC liquid 10 and the polarizing plate 2 is 0.
12%.

As a result, the reflectance Roc of this embodiment is
(= Rot + Rp + Rfo + Rbo) is 5.24%
(= 1 + 4 + 0.12 + 0.12). Here, in the conventional liquid crystal device, the protective plate 10 shown in FIG.
0 and the hollow portion 110, and the hollow portion 110 and the polarizing plate 102 have reflectances of 4%, respectively, so that the reflectance Roc of the conventional liquid crystal device is 13% (= 1 + 4 + 4 + 4). Is suppressed to about 40% compared to the conventional one.

By suppressing the surface reflection in this way, it is possible to obtain a high-contrast, high-quality image without display unevenness.

On the other hand, when the liquid crystal device is driven, the liquid crystal panel 1
The display surface of A generates heat, and this heat is conducted to the protective plate 1 through the OC liquid 10 and escapes to the outside, so that a heat radiation effect is also obtained.
Here, ethylene glycol, which is a component of the OC liquid 10,
The thermal conductivity of glycerin is about 3 × 10 ⁻³ W / mK and that of water is about 6 × 10 ⁻³ W / mK, and the thermal conductivity of air filling the hollow portion 110 of the conventional liquid crystal device is About 3 × 10 ^-4
Since it is W / mK, the heat dissipation effect of the OC liquid 10 is considerably improved by these media.

When heat passes through the OC liquid 10 as described above, the OC liquid 10 expands due to the heat generated by the liquid crystal panel 1A, but the housing 23 has a filling port 23a and a liquid crystal layer 4 as shown in FIG. Since the air reservoir 25 as a void portion for absorbing the expansion of the OC liquid 10 is formed between and, the extreme increase of the internal pressure is prevented. As a result, it is possible to prevent the device from breaking, leaking, deforming or the like.

Although the OC liquid 10 has been described as a liquid in the above description, the present invention is not limited to this.
Even if the OC liquid 10 is solid or gel, the same operation and effect can be obtained.

In the above description, the OC liquid 1
Although 0 has been described as being transparent, the present invention is not limited to this, and by coloring the OC liquid, a coloring preventing effect can be provided.

FIG. 4 is a schematic sectional view of such a liquid crystal device according to a second embodiment of the invention. In the figure, the same reference numerals as those in FIG. 1 denote the same parts.

In the figure, 20 is an OC liquid colored with a pigment. Here, as a pigment for coloring the OC liquid 20, an inorganic pigment, specifically, an oxide such as red iron oxide, a sulfide such as cadmium yellow, a chromate salt such as chromium yellow, a ferrocyanide such as dark blue, and ultramarine. Etc. and organic pigments such as yellow to red azo, blue to green phthalocyanine, metal complex salts, triphenylmethane, quinacridone and isoindolinone.

By dispersing one or several kinds of these pigments in the OC liquid 20, the OC liquid 20 can be colored and a desired spectral transmittance distribution can be obtained. In addition,
Even when the OC liquid 20 is colored in this way, it is possible to obtain the antireflection effect, heat dissipation, and uniform temperature distribution effect in the above-described first embodiment. Moreover, if an inorganic pigment is used as the pigment, the light resistance and heat resistance of the OC liquid 20 can be increased.

5 and 6 are diagrams showing the relationship between the transmittance and the wavelength. In FIG. 5, the transmittance 1 is the ideal spectral transmittance distribution of the liquid crystal device, and the transmittance 2 is the color. 3 schematically shows a spectral transmittance distribution of a liquid crystal device having a problem.

In the figure, when an ideal spectral transmittance distribution having a peak at the wavelength A is shown, the white display is correctly recognized as white, and the transmittance of an ideal liquid crystal device is 1 Indicates such an ideal spectral transmittance distribution. On the other hand, the transmittance 2 of the liquid crystal device having a problem with coloring shows a spectral transmittance distribution having a peak at the wavelength B, and in this case, the spectral transmittance distribution is shifted to the long wavelength side, so that white display Will become yellowish.

On the other hand, in FIG. 6, the transmittance 3 is OC liquid 2
The spectral transmittance distribution of 0 and the transmittance 4 represent the spectral transmittance distribution of the transmittance 2 corrected by the OC liquid 20. That is, in the liquid crystal device having the transmittance of 2, the spectral transmittance distribution is changed by using the OC liquid 20 having the spectral transmittance distribution like that of the transmittance 3, and the spectral transmittance distribution of the entire liquid crystal device is changed. The transmittance is 4 with the wavelength A as the peak. Therefore, the liquid crystal device is close to the transmittance 1 of the ideal spectral transmittance distribution, and the coloring is improved.

Finally, the structure of the information transmission device provided with such a liquid crystal device will be briefly described with reference to FIG.

In an information transmission device such as a color display of an office automation equipment such as a television or a notebook computer equipped with the liquid crystal device according to the present invention, as shown in FIG.
0 is a scanning signal application circuit 402 and an information signal application circuit 4
03 is connected to the scanning signal applying circuit 40.
2 and the information signal application circuit 403 includes a drive control circuit 404.
And the graphic controller 405 is connected in order.

The graphic controller 405
Data and a scanning method signal from the drive control circuit 404.
The signal is transmitted to the scanning signal control circuit 406 and the information signal control circuit 407 via the.

The data among these is converted into scanning line address data and display data by the scanning signal control circuit 406 and the information signal control circuit 407, and the other scanning method signal is directly applied to the scanning signal application circuit 402 and the information. The signal is applied to the signal application circuit 403.

Further, the scanning signal application circuit 402 applies a scanning signal having a waveform determined by the scanning method signal to the scanning electrodes determined by the scanning line address data, and the information signal application circuit 403 applies white or black transmitted by the display data. It is configured to apply an information signal having a waveform determined by two of the display content and the scanning method signal.

[0058]

As described above, according to the present invention, a medium having a refractive index substantially equal to that of the protective plate and the substrate is enclosed in the space formed between the liquid crystal panel and the protective plate. As a result, surface reflection can be improved and high contrast can be obtained.

By enclosing a medium having a thermal conductivity higher than that of air in the space between the liquid crystal panel and the protective plate, the heat generated in the liquid crystal panel is radiated to increase the temperature and the temperature distribution. The unevenness can be improved and the uneven display can be eliminated. Furthermore, by coloring the medium with a predetermined pigment, coloring can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal device according to a first embodiment of the invention.

FIG. 2 is a side sectional view showing the OC liquid filling portion of the embodiment.

FIG. 3 is a diagram showing light reflection in the front portion of the liquid crystal device of the above embodiment.

FIG. 4 is a schematic cross-sectional view of a liquid crystal device according to a second embodiment of the invention.

FIG. 5 is a diagram showing a spectral transmittance distribution of the liquid crystal device.

FIG. 6 is a diagram showing a spectral transmittance distribution of the liquid crystal device using a colored OC liquid.

FIG. 7 is a diagram showing a configuration of an information transmission device including a liquid crystal device.

FIG. 8 is a schematic cross-sectional view of a conventional liquid crystal device.

[Explanation of symbols]

 1,100 Protective plate 1A, 100A Liquid crystal panel 4,105 Liquid crystal layer 5,6,103,104 Liquid crystal cell substrate 10,20 OC liquid 23 OC housing 23a Medium filling port 25 Air reservoir 110 Hollow part

Claims (11)

[Claims] 1. A liquid crystal device in which a display surface of a liquid crystal panel formed by sandwiching liquid crystal between a pair of opposed substrates is protected by a protective plate provided in front of the liquid crystal panel. A liquid crystal device, characterized in that a medium having a refractive index different from that of air is enclosed in a space formed between the protective plate and the protective plate. 2. The liquid crystal device according to claim 1, wherein the refractive index of the medium is substantially the same as the refractive indexes of the protective plate and the substrate. 3. The liquid crystal device according to claim 1, wherein the medium has a thermal conductivity higher than that of air. 4. The liquid crystal device according to claim 1, wherein the medium is transparent. 5. The liquid crystal device according to claim 1, wherein the medium is colored with a predetermined pigment. 6. The liquid crystal device according to claim 5, wherein the pigment for coloring the medium is an inorganic pigment. 7. The liquid crystal device according to claim 1, wherein the medium is ethylene glycol, or a mixture of ethylene glycol and glycerin or pure water. 8. A space for enclosing the medium is formed by the liquid crystal panel, a protective plate and a housing member,
2. The liquid crystal device according to claim 1, wherein the housing member is provided with a void portion for absorbing expansion of the medium caused by heat generation of the liquid crystal panel. 9. The liquid crystal device according to claim 8, wherein the void portion is an air reservoir formed between the medium filling port formed in the housing member and the medium. 10. The liquid crystal device according to claim 1, wherein the liquid crystal used in the liquid crystal panel is a ferroelectric liquid crystal. 11. The liquid crystal device according to claim 10, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal.