JPH0566393A - Liquid crystal element and liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase the transmissivity of a display element and increase the lightness of a display, and to prevent the display quality from being spoiled by forming a reflection preventive film on at least one of a couple of glass substrates. CONSTITUTION:This liquid crystal display element has the couple of transparent substrates 14 and 15, a layer of liquid crystal 24 interposed between those transparent substrates 14 and 15, and the reflection preventive film 28 constituted by laminating at least two layers of transparent insulating films 26 and 27 which have different refractive index on at least one of the transparent substrates 14 and 15 on the side of the layer of the liquid crystal 24. A liquid crystal cell 7 in a figure has the reflection preventive film 28 formed only on the side of the glass substrate 15 where write laser light 6 is made incident. Thus, at least one of the glass substrates 14 and 15 constituting the liquid crystal cell 7 is coated with the reflection preventive film 28, so no multiple reflection is caused by the liquid crystal layer and interference fringes due to an irregularity in interference color never appears on a screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an engineer workstation (EWS), computer graphics (C
G), a liquid crystal display device or a liquid crystal display device that is useful when applied to a display device or a display device such as computer-aided design (CAD), and particularly to a liquid crystal device and a liquid crystal display device in which an antireflection film is provided in a liquid crystal cell. ..

[0002]

2. Description of the Related Art Conventionally, in EWS, CG, CAD, etc., a display element or display device having a resolution exceeding that of a CRT has been rare. And liquid crystal display devices are known. As such a laser thermal writing type liquid crystal element and liquid crystal display device, for example, a smectic liquid crystal is used as a liquid crystal element to irradiate a liquid crystal cell with laser light, and a thermoelectrooptic effect is used to display a thermally written image on a screen. 2. Description of the Related Art Projection-type displays that perform projection display are known.

FIG. 5 shows an outline of an optical system of a projection type liquid crystal display device using the laser thermal writing type liquid crystal display element described above. In the figure, a laser beam emitted from a laser diode 1 passes through a collimation lens 2 and a galvano-scanner mirror 3 which is scanned in the X-axis as well as the Y-axis direction of a liquid crystal cell 7, which will be described later, and passes through a first condenser lens 4. Then, the writing laser light 6 is reflected by the dichroic mirror 5 and is irradiated so as to focus on the liquid crystal surface of the liquid crystal cell 7. The writing point with which the liquid crystal cell 7 is irradiated with the writing laser beam 6 is held as it is.

Further, the writing laser beam 6 projected on the liquid crystal cell surface is scanned by the two galvano-scanner mirrors 3 for the X-axis and the Y-axis, and a figure or the like can be drawn at an arbitrary position on the liquid crystal surface. ..

A figure or the like drawn on the liquid crystal surface of the liquid crystal cell 7 is projected onto the screen 9 by the projection light 10 from the projection lamp 8.
Projected on. That is, the projection light 10 of the projection lamp 8 is collected by the second condenser lens 11 and applied to the liquid crystal cell 7 from the back via the dichroic mirror 5, and the figure on the liquid crystal surface is projected onto the projection lens 12 and the folding mirror. Screen 9 through 13
Projected on.

Although the transmission type projection liquid crystal display device has been described in the above configuration, a reflection type projection liquid crystal display device for projecting the reflected light from the liquid crystal cell 7 on the screen is also known.

In the reflection type liquid crystal element of such a reflection type projection liquid crystal display device, a transparent electrode is formed on the inner surface of one glass substrate.
It is known that the inner surface of the other glass substrate is provided with a metal thin film that absorbs laser light in contact with the liquid crystal layer (JP-A-57-165820).

Further, a method is also known in which a light-to-heat conversion dye having a large absorption in the wavelength range of a laser beam used for writing is added to a liquid crystal layer and a smectic A liquid crystal is sandwiched between two glass substrates. (JP-A-58-42372)

The principle of thermal writing of the liquid crystal cell 7 will be described with reference to FIGS. 6A, 6B, 6C and 6D. In the figure, the liquid crystal cell 7 is composed of two glass substrates 14 and 15. These glass substrates 14 have ITO (Indium-Tin-Oxid).
The transparent electrode films 16 and 17 such as e) and the insulating films 18 and 19 such as SiO ₂ (silicon dioxide) are coated, and the glass substrate 1 on the reflection side on which the writing laser beam 6 is incident.
A laser mirror 20 is formed at 4. This laser mirror 20 is composed of a dielectric optical multilayer film.

A space between the two glass substrates 14 and 15 is sealed with a sealing material 21 composed of an adhesive layer such as a thermosetting resin.

A smectic liquid crystal 24 or the like is filled in the empty cell container sealed with the sealing material 21. This liquid crystal 2
For No. 4, a material that changes its phase from SmA (smectic A) liquid crystal phase to N liquid crystal phase to isotropic liquid crystal phase (Iso phase) by thermal writing with a laser or the like is used. Of course, it may be a cholesteric liquid crystal that undergoes a phase transition between a cholesteric phase and an Iso phase.

Heat such as a laser is applied to the liquid crystal 24 as described above to cause S
The original SmA after a single phase transition from the mA phase to the Iso phase
When returning to the phase, the random orientation in the Iso phase is retained in the SmA phase, a light scattering state is formed, and the memory state is retained. To erase this state, a voltage may be applied to restore the uniformly oriented SmA phase.

That is, the transparent electrode films 16 and 17 are formed to apply a voltage when the screen is erased, and the insulating film 1
8 and 19 are transparent electrodes 16 and 1 due to impurities in the liquid crystal.
It is formed to prevent short-circuiting between the seven.
Further, the laser mirror 20 reflects the writing laser light incident from the laser diode 30 and is coated to effectively use the energy of the laser beam.

The transparent electrode film 16 of the liquid crystal cell 7 as described above,
A switch 22 and an AC power supply 23 are connected in series between 17 and 17.

In the state shown in FIG. 6A, the switch 22 is in the off state and the liquid crystal 24 is in the uniformly aligned SmA phase.

Next, as shown in FIG. 6B, the writing laser beam 6
Is incident from the glass substrate 15 side, the writing laser light 6
Only the liquid crystal 24a in the hit portion is in the light scattering state.
As shown in C, the pixel becomes 25, and a predetermined image can be drawn.

Next, as shown in FIG. 6D, when the switch 22 is turned on and a voltage is applied from the AC power source 23 to the transparent electrodes 16 and 17, the Iso phase of the liquid crystal 24a (pixel 25) becomes the original Sm.
It is returned to the uniform arrangement of phase A.

Particularly, in such a liquid crystal panel 7,
The thickness value of the standard cell gap t (see FIG. 6D) is 1
At 0 μm, the pixel size is about 10 μm ² , so 1
When a spacer such as a glass fiber having a diameter of 0 μm is dispersed in the display area, the screen is crushed by the glass fiber, so that the thickness of the cell gap t is held by the glass fiber mixed in the sealing material 21. ..

[0019]

As described above, since the laser thermal writing type liquid crystal cell 7 has an extremely small pixel size, it is possible to use the liquid crystal cell 7 like an ordinary XY matrix type liquid crystal display device.
There is a problem that the spacers cannot be uniformly dispersed in the display screen to keep the thickness of the cell gap t uniform.

When such a liquid crystal cell 7 is used, for example, as a direct-viewing type liquid crystal display device, light from a backlight is used. When it is used as a projection type liquid crystal display device as in the above example, a light source from a projection light source is used. When the projected light hits the liquid crystal cell 7, an interference color is generated along the uneven thickness of the cell gap t. This interference color usually appears as a red-and-green striped pattern, which impairs the display quality.

The cause of such interference fringes can be explained with reference to FIG. The figure schematically shows the basic structure of a conventional liquid crystal cell 7, and in reality, transparent electrodes, color filters and the like necessary for the function and operation of a liquid crystal element are arranged.

With the above-mentioned structure, the light of the backlight or the projection light 1 for projection is applied from one glass substrate 14 side of the liquid crystal cell 7.
When 0 is incident, the incident light undergoes multiple reflection 26 between the layers of the liquid crystal 24, a specific wavelength is emphasized to generate an interference color, and unevenness of the interference color is generated due to the nonuniform thickness of the cell gap t in the display region. Will be done. When this liquid crystal cell 7 is projected onto the screen 9 by the projection light 10, interference fringes are generated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal element and a liquid crystal display device in which interference fringes do not occur and display quality is improved. Is.

[0024]

As shown in FIG. 1, the liquid crystal device of the present invention has a pair of transparent substrates 14 and 15 and a liquid crystal 24 sandwiched between the transparent substrates 14 and 15. And at least two transparent and insulative films 26 and 27 having different refractive indexes, which are provided on the liquid crystal 24 layer side of at least one of the transparent substrates 14 and 15 and are laminated. And an antireflection film 28.

[0025]

According to the present invention, the antireflection film 28 is formed on at least one of the pair of glass substrates 14 and 15 constituting the liquid crystal cell.
Thus, a liquid crystal element and a liquid crystal display device can be obtained in which multiple reflection does not occur in the liquid crystal layer and interference fringes due to uneven interference colors do not appear on the screen 9.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal element and the liquid crystal display device of the present invention will be described below with reference to FIGS.

FIG. 1 shows one mode of the liquid crystal cell 7 of this example, which is a laser thermal writing liquid crystal element similar to that described with reference to FIG. 6 and is used as, for example, a projection type liquid crystal display device for CAD. This is the case.

In FIG. 1, the portions corresponding to those in FIG. 6 are designated by the same reference numerals and duplicate description is omitted, but in this example, only the glass substrate 15 side on which the writing laser beam 6 is incident in the liquid crystal cell 7 in FIG. Then, an antireflection film 28 is coated.

That is, since the laser mirror 20 is disposed on the glass substrate 14 on the screen 9 side, this is used as an antireflection film, and the glass substrate 14 on this side is not coated with the antireflection film 28.

After cleaning the glass substrate 15, an alumina (Al ₂ O ₃ ) film 27 is vapor-deposited or sputtered, and a titanium dioxide (TiO ₂ ) film 2 is further formed on the Al ₂ O ₃ film 27.
The antireflection film 28 having a predetermined thickness is formed by vapor-depositing or sputtering 6.

Next, the TiO which constitutes this antireflection film 28.
_{2 The} conductive film is formed in a solid pattern on the film 26. The conductive film is I
A transparent electrode 17 (16) such as TO, and if necessary, an insulating film 19 such as SiO ₂ on the transparent electrode 17 (16).
(18) is vapor deposited.

The insulating film 19 (18) is formed on the glass substrate 15
It was formed in order to prevent the alkaline component in (14) from dissolving in the liquid crystal 24 through the pinholes of the transparent electrode 17 (16). If there is no such an adverse effect, the insulating film 1
It is not necessary to provide 7 (18).

An orientation layer is formed on the insulating film 19 (18) formed in this way, and the pair of glass substrates 15 and 14 are bonded to each other with the sealing material 21 interposed therebetween.

At the time of bonding, as described above, in order to maintain the cell gap t at a predetermined thickness, a glass fiber having a diameter of about 10 μm is mixed in the adhesive of thermosetting resin as the sealing material 21 to form the liquid crystal cell 7. The thickness of the cell gap t is kept constant. However, spacers such as glass fibers cannot be dispersed in the display area for the above-mentioned reason.

A glass substrate 1 having a pair of electrodes thus formed
Numerals 5 and 14 are sealed after the empty cell containers made by pasting are put into a vacuum chamber after being heated and cured, and smectic liquid crystal or the like is injected as the liquid crystal material 24.

The liquid crystal cell shown in FIG. 1 has an antireflection film 28.
Only one of the glass substrates 15 was vapor-deposited.
In the liquid crystal cell 7 as shown in FIG.
Antireflection films 28 and 28 are provided on the pair of glass substrates 14 and 15, respectively.
It is made to form. This antireflection film 28, 28
Is at least Al as in FIG.₂O₃Membrane 27 and TiO ₂
It is composed of two layers of membrane 26.

The liquid crystal cell after the formation of such an antireflection film can be manufactured by the same steps as in FIG.

In the above-mentioned embodiment, A is used as the antireflection film 28.
l₂O₃Membrane 27 and TiO₂The film 26 is overlaid to form an antireflection film.
Although it is configured, it is not limited to this, and a film having a different refractive index is appropriately used.
It can be combined to form an antireflection film. High refractive index
As the material of TiO 2, the refractive index n is about 2.3₂, Middle bend
As a material having a folding ratio, Al having a refractive index n of about 1.6
₂O ₃, A low refractive index material has a refractive index n of about 1.4
Degree of SiO₂Transparent oxides, etc., but not limited to this
However, it may be made of an organic material or the like. Transparent
As a method for forming the oxide film, vacuum deposition or the like is used.
If so, it is easy to control the layer thickness.

In the configuration of FIG. 1, since the laser mirror 20 is formed on the glass substrate 14 on the screen 9 side, the glass substrate 1 on the incident side of the writing laser beam 6 is left untouched.
Although the antireflection film 28 was formed on No. 5, since the transparent electrode 16 and the insulating film 18 have already been vapor-deposited on the glass substrate 14 side, the optical characteristics such as the thickness of the antireflection film 28 including these layers can be determined. Need to be determined.

In FIGS. 3A and 3B, the membrane breaks of the main parts of FIGS.
The calculation results of surface thickness and reflectance are shown below. Transparent electrode film 16 (1
7) ITO (refractive index n = 1.9) is used as the insulating film 18
(19) as SiO₂(Refractive index n = 1.46)
Al as the protection film 28₂O₃(Refractive index n = 1.6)
To TiO₂(Refractive index n = 2.3) and the liquid crystal 24
Considering the film structure as shown in FIG.
Then, change the thickness of each film to Al ₂O₃= 94 nm, TiO₂=
130 nm, ITO = 79 nm, SiO₂= 205 nm
Then, the glass substrate 15 on the incident side of the writing laser beam 6
Reflectance (of the intensity of the reflected light 31 relative to the intensity of the incident light 30)
It is determined by the ratio and considered under the vertical incidence condition. ) Is the figure
3B is plotted and sufficient reflectance is obtained.

FIGS. 4A and 4B show the film structure of transparent electrodes 16 and 1.
ITO of 7 to 79 nm and 205 of insulating films 18 and 19
The calculation result of the reflectance when nm is selected is shown.
It can be seen that the one without the antireflection film 28 like this structure has a high reflectance and cannot be used as the antireflection film 28 as compared with FIGS. 3A and 3B.

According to the liquid crystal element and the liquid crystal display device of the present invention, by providing the antireflection film, the interference fringes caused by the uneven thickness of the cell gap t become invisible, and the transmittance as the display element is increased to improve the display brightness. It is possible to obtain a display device that does not impair the display quality.

Although the laser thermal writing liquid crystal element has been described in each of the above-mentioned embodiments, it is obvious that this example can be applied to a liquid crystal element for various ordinary display devices.

[0044]

According to the liquid crystal element and the liquid crystal display device of the present invention, it is possible to obtain a liquid crystal device in which interference fringes are not conspicuous and the display quality is not impaired.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a liquid crystal element of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the liquid crystal element of the present invention.

FIG. 3 is an explanatory diagram showing an example of the reflectance of the liquid crystal element of the present invention.

FIG. 4 is an explanatory diagram showing a comparative example of the reflectance of the liquid crystal element of the present invention.

FIG. 5 is a system configuration diagram of a conventional thermal writing projection type liquid crystal cell.

FIG. 6 is an explanatory diagram of an operating principle of a conventional thermal writing projection type liquid crystal cell.

FIG. 7 is a diagram illustrating the cause of interference fringes.

[Explanation of symbols]

1 Laser Diode 7 Liquid Crystal Cell 8 Projection Lamp 9 Screen 14, 15 Glass Substrate 21 Sealing Material 24 Liquid Crystal 26 TiO ₂ Film 27 Al ₂ O ₃ Film 28 Antireflection Film

Claims (2)

[Claims] 1. A pair of transparent substrates, a liquid crystal layer sandwiched between the transparent substrates, and a transparent and insulating material having a different refractive index provided on the liquid crystal layer side of at least one transparent substrate of the transparent substrates. A liquid crystal element, comprising: an antireflection film obtained by laminating at least two layers of the film. 2. A liquid crystal display device in which an optical image is recorded on a liquid crystal element by a phase change of liquid crystal due to heat generated by laser light irradiation, and the optical image is projected and displayed by light from a light source. At least two layers of a transparent substrate, a liquid crystal layer sandwiched between the transparent substrates, and a transparent and insulating film having a different refractive index provided on the liquid crystal layer side of at least one transparent substrate of the transparent substrates. A liquid crystal display device having the above antireflection film.