JP3073145B2 - Electric field treatment method for optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field processing method for improving the withstand voltage of an insulating film in an optical element such as a liquid crystal optical element, an AC type plasma display, a light emitting element, and a light adjusting element. .

[0002]

2. Description of the Related Art Some optical elements, such as liquid crystal elements, which adjust transmitted light, reflected light or light emission amount by applying an electric field, require an insulating layer on an electrode surface of the element. .

These insulating film layers are made of, for example, MgO, SiO ₂ , T
A thin film of iO ₂ , Al ₂ O ₃ or the like is formed by a method such as sputtering, or a compound solution prepared by heating MgO, SiO ₂ , TiO ₂ , Al ₂ O ₃ alone or a mixture thereof, or by chemical treatment, etc. It is formed by such a method.

However, microscopic projections on the order of microns or submicrons are present on the surface of glass substrates used in many current devices. These protrusions have various origins, such as those generated during the production of the glass substrate itself and those present on the electrodes formed on the glass substrate. These protrusions also form protrusions on the insulating film formed thereon, thereby deteriorating the insulation and deteriorating the withstand voltage.

In other words, a higher voltage is applied to these projections between the electrodes than to the surroundings.
A local discharge phenomenon occurs, and dielectric breakdown proceeds in that portion. When the voltage is continuously applied, a large dielectric breakdown occurs. As a matter of course, this tendency becomes more remarkable as the distance between the electrodes becomes shorter.

At present, methods for preventing dielectric breakdown due to this cause include a method of forming an insulating layer sufficiently thick and a method of polishing all element substrates on which projections are considered to exist, such as glass substrates and electrodes. Have been.

[0007]

However, the formation of a thick insulating film requires a reduction in display quality and light emission amount for various devices, for example, in order to reduce an effective voltage applied to a liquid crystal layer, a luminescent gas layer, and the like. However, there are many disadvantages such as a decrease in switching speed and an increase in manufacturing cost. In addition, the method of polishing an element substrate adds to the difficulty of the operation itself, increases the manufacturing process and the cost, and is not a good method.

An object of the present invention is to provide a method for treating an electric field of an optical element, which improves the withstand voltage of an insulating film of the optical element.

[0009]

According to the present invention, a pulse voltage is applied to an electrode on an optical element using a transparent substrate on which an electrode and an insulating film covering the electrode are formed. This is an electric field processing method for an optical element that destroys the upper minute projection.

The pulse voltage is applied at a voltage of 0.1 to 1.2 times the drive voltage of the optical element, and is applied for 1 μsec to 1 sec.
A voltage which is a repetition of a voltage application time of c and a pause time longer than the voltage application time is preferable.

Further, the pulse voltage may be changed from a lower voltage to a higher voltage stepwise or with time within an applied voltage of 0.1 to 1.2 times the drive voltage of the optical element. .

[0012]

In the dielectric breakdown between the device electrodes, as described in the related art, since a higher voltage is applied to the protruding portion than in the periphery, a local discharge phenomenon occurs, and the dielectric breakdown of the protruding portion proceeds. Therefore, in the present invention, by performing an electric field treatment of applying a pulse voltage with the time width and timing of the applied voltage adjusted to the electrode, it is possible to realize a state in which only the protruding portion is broken, and to have an insulating film layer without the protruding portion. An element can be created. This makes it possible to realize an optical element in which the withstand voltage of a subsequently applied electric field is higher than that before the electric field treatment.

The pulse voltage obtained by adjusting the time width and timing of the applied voltage may vary depending on the type of optical element to be actually subjected to electric field processing, the driving voltage, the shape of the electrodes, the distance between the electrodes, and the like. Conceivable. The applied voltage is 0.1 to 1.2 times the drive voltage of the optical element, and 1 μs
Within a pulse voltage consisting of a repetition of a voltage application time of ec to 1 sec and a rest time longer than the voltage application time, or within an application voltage of 0.1 to 1.2 times the drive voltage of the optical element,
By applying a pulse voltage consisting of a repetition of a voltage application time of 1 μsec to 1 sec, which changes stepwise or with time from a lower voltage to a higher voltage, and a pause time longer than the voltage application time, the resistance of the optical element is increased. It has been confirmed that the voltage property is improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing the structure of a liquid crystal cell using the electric field processing method according to the present invention. In this liquid crystal cell, two glass substrates 1a and 1b are arranged to face each other, a gap is provided therebetween with a spacer 4 for controlling a cell gap therebetween, and a liquid crystal 5 is injected into the gap and sealed. Structure.

On a surface of one glass substrate 1a, a plurality of transparent signal electrodes S made of indium tin oxide (hereinafter abbreviated as ITO) are arranged in parallel with each other, and the signal electrodes S are coated with an insulating film 2a. Have been. The other glass substrate 1
b, a plurality of transparent scanning electrodes L made of ITO are arranged in parallel with each other in a direction perpendicular to the signal electrodes S, and the scanning electrodes L are made of an insulating film 2b made of the same material as the insulating film 2a.
It is coated with. An alignment film 3 is formed on each of the insulating films 2a and 2b.
a, 3b are formed, and the alignment films 3a, 3b are subjected to a uniaxial alignment treatment by rubbing.

The two glass substrates 1a and 1b are provided with a liquid crystal injection port in a part thereof and bonded together. From the injection port, the two glass substrates 1a and 1b are sandwiched by alignment films 3a and 3b, and are placed in a space 5 provided by a spacer 4. After the liquid crystal is injected, the injection port is sealed with a sealant 6.

The liquid crystal cell is subjected to an electric field treatment using a pulse voltage. This pulse voltage is applied at a voltage of 0.1 to 1.2 times the drive voltage of the optical element, and applied for 1 μsec to 1 sec.
The voltage is a voltage obtained by repeating the voltage application time c and the pause time longer than the voltage application time. By performing this process, minute projections on the insulating film are broken, and the withstand voltage is improved. That is, as described in the related art, since there is no protruding portion to which a higher voltage is applied compared to the periphery, the dielectric breakdown of the insulating film does not proceed from that portion, and the withstand voltage improves.

Whether or not the above-mentioned effects were obtained was confirmed by performing an electric field treatment using a pulse voltage shown in FIG.
As shown in FIG. 2, this pulse voltage is applied to + and-every 1 second with a voltage application time of 500 μsec.
The applied voltage is sequentially increased to 2, 4, 6, 8, and 10 V, and the application time for each voltage is 5 minutes. The liquid crystal cell was subjected to electric field treatment with the following five types of pulse voltages. Here, OCD TYPE2 P-59310-SG manufactured by Tokyo Ohka Co., Ltd. was used as the insulating film material of the liquid crystal cell, the insulating film thickness was about 100 nm, and the film was fired at 450 ° C. before use. In addition, this liquid crystal cell includes an alignment film material P manufactured by Chisso Corporation.
SI-A-X007-S01 and ferroelectric liquid crystal SCE8 manufactured by Merck were used. Pulse 1: applied voltage is 2, 4, 6, 8, 10 V Pulse 2: applied voltage is 2, 4, 6, 8, 10, 20 V Pulse 3: applied voltage is 2, 4, 6, 8, 10 , 20,
30, 40V ・ Pulse 4: applied voltage is 2, 4, 6, 8, 10, 20,
30, 50, 60 V ・ Pulse 5: applied voltage is 2, 4, 6, 8, 10, 20,
40,60,80V

Thereafter, a rectangular wave of 60 V, 50 kHz was applied to the liquid crystal cell for 5 seconds to measure the withstand voltage. The results shown in Table 1 were obtained. Each cell had a withstand voltage of 60 V or more in terms of a cell gap of 1.5 μm. Here, a liquid crystal cell that did not undergo dielectric breakdown even at an applied voltage of 60 V is represented by 、, a liquid crystal cell that has undergone dielectric breakdown is represented by x, the numerical value in parentheses indicates the cell gap of the liquid crystal cell, and the applied voltage is 1.5 μm. It has been converted to.

[0020]

[Table 1]

Further, a liquid crystal cell was prepared under the same conditions as in Example 1 (the sintering temperature of the insulating film was set at 350 ° C. and 450 ° C.).
Hz rectangular wave was applied for 5 seconds to measure the withstand voltage. As shown in Table 2, the results showed lower withstand voltage than those subjected to the electric field treatment. From this, it was confirmed that by performing the electric field treatment using the pulse voltage, the withstand voltage was clearly improved.

[0022]

[Table 2]

A DC electric field insulating property of the insulating unit alone was measured by attaching an Al counter electrode to the insulating film formed on the ITO by vapor deposition. While insulation breakdown occurred at 40 V, the insulation film subjected to the electric field treatment described above
The effectiveness of the electric field treatment was confirmed without causing dielectric breakdown up to V. Accordingly, the electric field treatment is not limited to improving the withstand voltage characteristics of not only the liquid crystal optical element having the configuration described in this embodiment but also a liquid crystal optical element having an insulating film, an AC plasma display, a liquid crystal optical shutter, and an EL element. Is effective in

As described above, since the withstand voltage is improved by the electric field treatment using the pulse voltage, the insulation of the optical element can be improved without thickening the insulating film or polishing the transparent substrate. Therefore, it is possible to prevent a decrease in function of the element and an increase in cost.

The pulse voltage used in the electric field processing changes from a lower voltage to a higher voltage stepwise or with time within an applied voltage of 0.1 to 1.2 times the driving voltage of the optical element. However, the same effect can be obtained.

[0026]

According to the present invention, by subjecting an optical element to an electric field treatment using a pulse voltage, it is possible to destroy minute projections on the insulating film. It is possible to improve the insulating properties of the optical element without performing the steps, and to prevent the function of the element from deteriorating and prevent the cost from increasing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a liquid crystal cell using electric field processing of an optical element according to the present invention.

FIG. 2 is a waveform diagram showing a pulse voltage for the electric field processing.

[Explanation of symbols]

 1a, 1b Glass substrate 2a, 2b Insulating film

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1333 505

Claims (3)

(57) [Claims] 1. An optical element using a transparent substrate on which an electrode and an insulating film covering the electrode are formed, wherein a pulse voltage is applied to the electrode to break a minute protrusion on the insulating film. An electric field treatment method for a device. 2. The pulse voltage is applied at a voltage of 0.1 to 1.2 times the drive voltage of the optical element, and applied for 1 μsec to 1 sec.
2. The electric field processing method for an optical element according to claim 1, wherein the voltage application time of c and the pause time longer than the voltage application time are repeated. 3. The pulse voltage changes stepwise or from time to time from a lower voltage to a higher voltage within an applied voltage of 0.1 to 1.2 times the drive voltage of the optical element. The electric field processing method for an optical element according to claim 2.