JP2761820B2 - Spacer spraying device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for uniformly dispersing spacers on a substrate for a liquid crystal electro-optical device.

[0002]

2. Description of the Related Art In recent years, displays utilizing the electro-optic effect of liquid crystals have been applied to various fields such as watches, calculators, word processors, and the like. Ordinary liquid crystal electro-optical devices usually have a basic structure of a liquid crystal cell in which a liquid crystal material is sandwiched between a pair of substrates. In order to make the distance between the pair of substrates uniform, glass fibers or spherical particles are used. , Spacers.

[0003] In a spacer dispersing step in producing a liquid crystal cell, there is a spin coating method as one of conventionally used methods. In this method, a certain amount of a mixture of one or more types of spacers mixed in a solvent such as alcohol or chlorofluorocarbon is dropped on a substrate, and the spacer is rotated on the entire surface of the substrate by rotating the substrate. It is a way to make it exist. However, when the spin coating method is used, a lump of the spacer (several to several tens) often remains on the substrate because the substrate is once immersed in the mixed solution and then dried. In this case, the thickness of the portion where the spacer mass exists and the cell thickness around the portion are larger than the surrounding portion. As a result, it has been clarified that the electric field intensity when a voltage is applied between the electrodes formed on the substrate becomes smaller than that of the other parts, which adversely affects the switching of the liquid crystal. Further, when a display is performed utilizing the refractive index anisotropy of the liquid crystal as in a display device using an STN type or ferroelectric liquid crystal, color unevenness is also caused.

In general, a liquid crystal misalignment region is generated around the spacer. However, when spraying is performed by a spin coating method, centrifugal force due to rotation is used to spread the spacer over the entire surface of the substrate. They are arranged radially from the center, and the poorly-aligned regions continue radially and are recognized at the time of display, so that the display quality is greatly reduced. In addition, when a plurality of types of spacers are sprayed by the spin coating method, the ratio of the spacers in the central portion and the peripheral portion of the substrate changes due to the difference in the weight of the spacers, and as a result, the substrate spacing becomes non-uniform.

As another method for spraying the spacer, there is a method in which the spacer is mixed with an appropriate organic solvent, and the mixed solution is sprayed using a nozzle. When this method is used, the distance between the nozzle and the substrate is adjusted so that all the organic solvent components evaporate before the mixture reaches the substrate, or a heater is embedded in the inner wall of the spraying device. By using a method such as raising the temperature of the apparatus, the amount of spacer lumps on the substrate can be reduced as compared with the spin coating method.

However, the organic solvent used in this method is generally a chlorofluorocarbon-based solvent or IPA (isopropyl alcohol). However, the destruction of the ozone layer in the sky due to the use of chlorofluorocarbon gas is a problem. It seems that CFC gas will not be usable. Also, when IPA is used, the inside of the spraying device is
Filled with PA vapors, explosion hazard is very high.

[0007] Further, at the time of spraying, stirring or application of ultrasonic waves is performed to disperse the spacers. However, it is difficult to reduce the mass of the spacers by stirring, and it is difficult to slightly reduce the mass of the spacers by applying ultrasonic waves. Although it is possible, the temperature of the mixed solution is increased by the application of ultrasonic waves. Therefore, vaporization of the organic solvent is promoted, the spacer concentration of the mixed solution gradually increases, and the amount of spacers on the substrate increases as the spraying proceeds even if the spraying is performed under the same conditions.

[0008] For the above reasons, a fluorocarbon solvent or I
A method of spraying without using PA, preferably a dry method using no solvent has been desired. As means for solving such a problem, a dry spacer dispersing method using an electrostatic field has been proposed, for example, in Japanese Patent Application Laid-Open No. 3-232420 filed by the same applicant as the present invention.

The method of dispersing spacers using this electrostatic field is to disperse the spacers in a carrier gas such as air or nitrogen on a substrate installed in the spacer dispersing chamber,
When spraying, the spacers are charged, and the spacers are dispersed and dispersed on the liquid crystal substrate without being associated with each other due to the charged charges.

In the case of such a spraying method, if the flow of the carrier gas containing the spacer is too strong, the distribution of the spacers on the substrate is affected. If the flow is too weak, the spacers cannot reach the substrate, or the spacers cannot reach the substrate properly. There is a problem that cannot be dispersed. Furthermore, from the inner wall around the spacer spray room,
The spacer once adhered comes off and adheres again on the substrate. Since such a spacer has a small or no charge amount, it easily associates and adheres again on the substrate in a lump state.

In addition, in any of the above methods, the spacers attached to portions other than the substrate are not effectively used and are discarded as they are, which is contrary to the use of resources and the reduction of the manufacturing cost of the liquid crystal device. Was.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a spacer dispersing method for preventing the aggregation of spacers by charging the spacers when dispersing the spacers on the substrate. And a means for reducing the dispersion of the spacers in the area other than the substrate and collecting the spacers dispersed in the area other than the substrate.

That is, according to the present invention, after being sprayed from the nozzle, the charged spacer flies in the direction of the side wall of the spraying device, and in order to prevent the spacer from adhering to the side wall, the charge is applied to the side wall or the vicinity of the side wall. A charge of the same polarity as that of the spacer is applied to prevent the spacer from adhering to the side wall. In addition, near the back of the substrate to be sprayed,
By providing a collecting means having a polarity opposite to the charge applied to the spacer, the unused spacer can be easily collected.

The spacers sprayed from the nozzles are carried and sprayed by a carrier gas such as dry air or dry nitrogen. Therefore, the strength of the gas flow affects the spacers already dispersed on the substrate. In order to eliminate this, a means to adjust the kinetic energy of this spacer is provided in the space between the spray nozzle and the substrate to be sprayed, so that the influence of the flow of the carrier gas does not appear near the substrate. As a means for adjusting the kinetic energy, a net-like object is installed in a scatter space, a plurality of the net-like objects are installed and the aperture ratio of the net is changed, and baffles are provided at appropriate intervals. That is, the baffle plate is provided in a plurality of stages and the interval is changed. Furthermore, a charge is applied to the mesh-like object or the baffle plate, and the kinetic energy can be adjusted by the polarity of the charge and its potential.

In the present invention, as a method of charging the spacer, a known method such as corona discharge conventionally used for electrostatic coating or the like can be used. However, in the conventional electrostatic coating, in order to perform the coating uniformly and without unevenness, it is necessary to release the charge after the charged coating particles reach the target object to make the particles electrically neutral. Because, in the charged state, after the paint particles at a certain point on the object (charged state) arrive, even if the next particles try to reach the vicinity of the point, they are repulsed by Coulomb force, This is because it is impossible to perform uniform coating. However, in the present invention, since a certain distance is required between the spacers, this Coulomb repulsion can be used. Therefore, during the spraying, the substrate (object) is kept in an electrically floating state, and after the spraying is completed, the substrate is connected to the ground, or is electrically neutralized by ion blow, so that the electric charge is later obtained. It is possible to prevent foreign matter, such as dust, having dust from being drawn.

By using the present invention, the spacers can be sprayed without using a solvent such as chlorofluorocarbon or IPA, and in addition, the spacers can be sprayed without forming spacer lumps on the substrate. In addition, the spacer that has reached the area other than the substrate can be repelled by applying a charge of opposite polarity to the side wall or the vicinity of the side wall of the spraying device, and can be returned to the vicinity of the substrate, thereby preventing the spacer from adhering to the side wall. .

Further, by providing an electrode having a charge having the opposite polarity to the charge given to the spacer near the back surface of the substrate,
Unused spacers can be electrically collected, and the spacers can be effectively used. Furthermore, a baffle plate or the like can be installed in the spraying area to adjust the flow of the carrier gas. At the same time, the spacers can be more evenly dispersed, and the influence of the flow of the carrier gas can be reduced. Hereinafter, the present invention will be described with reference to examples.

[0018]

【Example】

[Embodiment 1] In this embodiment, the case where the device of the present invention is used in manufacturing an STN liquid crystal display device will be described.
An ITO thin film was formed on two glass substrates by using a known DC magnetron sputtering method, and electrodes were formed by a photolithography process. Then, a polyamic acid was applied by a printing method on the electrode forming surface of the substrate, and a heat treatment was performed to obtain a polyimide thin film. Thereafter, a rubbing step was performed on both substrates using a cotton cloth. At this time, pay attention to the rubbing angle.

The rubbing angle of the two substrates is set to an angle of 240 ° C. in the bonding step performed after the next spacer dispersing step. Next, spherical particles of 6.2 μm in diameter made of SiO ₂ were sprayed on the surface of one of the substrates on which the polyimide thin film was formed, using a spacer sprayer as shown in FIG.
The spraying method at this time is as follows. The substrate (1) is placed on the table (2), dry air is introduced into the spacer tank (4) from the dry air inlet (3), and the spacer (5) also serves as a nozzle serving as an electrode. The spacer is sprayed on the substrate (1) by blowing out from (6). At this time, about 100c
A voltage of 15 kV is applied using a power source (8) between the electrodes (6) and (7) that are m apart from each other to charge the spacer. The nozzle (6) also serves as an electrode, and the inner diameter of the nozzle is
The thing of 12 μm was used. Further, near the back surface of the table (2), an electrode for collecting the spacer was provided as an electrode for charging the spacer. Further, a metal plate, for example, aluminum (9) is provided along the side wall so that the spacer does not adhere near the side wall of the spraying device. After giving a polar charge, the spacer is sprayed from the nozzle,
The spacer was pushed again to the center of the spray area by repelling with electric charge so as to fly toward the side wall and not adhere. By using such a dispersing device, since each spacer is charged to the same polarity, the spacers dispersed on the substrate can be present at a certain distance or more, and the number of spacers on the substrate can be reduced. Also, compared to the related art, there is almost no difference depending on the place, and the spray can be evenly distributed.

Thereafter, an epoxy-based adhesive was seal-printed on the other substrate (no spacer was sprayed) by a screen printing method, and bonding was performed. Then, when the actually scattered spacers were observed using a microscope, the clumped spacers were not confirmed in one visual field even after 100 times of observation. Thereafter, the liquid crystal was injected using a known vacuum injection method. The state of the cell after liquid crystal injection was such that the central portion of the cell was swollen, and pressure was applied to the cell here to drive out excess liquid crystal out of the cell. Thereafter, the inlet of the cell was sealed.

Then, display was performed by attaching two polarizing plates. In the case of spraying using the conventional spin coating method, color unevenness is conspicuous, especially in the central part of the cell, the background color changes from yellow to red, and there are cells in which the purple part is conspicuous. In the case of the present embodiment, color unevenness was not confirmed, and good display was realized. Further, as the dry air used in this example, air containing about 2 ppm of water was used. If air with a high water content is used, the spacers will not be easily charged, and water will remain on the substrate. If the liquid crystal is later injected and displayed, the display will be spotted and affect the display. I found out. Therefore, the moisture content in the dry air needs to be 1% or less.

[Embodiment 2] FIG. 2 is a schematic view of an electrostatic spraying apparatus according to the present embodiment. In the figure, the basic configuration is the same as the device used in the first embodiment. In addition to that configuration,
In the present embodiment, two kinds of kinetic energy adjusting means (11) (1) are provided in the spray area between the spray nozzle (6) and the substrate (1).
2) is provided. Among them, (11) is an arrangement in which five elongated metal baffles whose surfaces are covered with an insulating material are arranged at intervals, and these five baffles are floating in potential in the spray area. It is installed as follows. Therefore, the baffle plate (11) simply blocks the flow of the gas blown out from the nozzle (6), and does not affect the electric charge of the spacer.

In (12), a mesh-like metal electrode is provided below the baffle plate (11).
2) is connected to a completely independent power supply (13), and given an arbitrary charge amount and polarity from this power supply, acts on the charge of the spacer, and determines the speed and direction in which the spacer falls. It can be adjusted to. In the apparatus shown in FIGS. 1 and 2,
Since an electrode (7) having a polarity opposite to that given to the spacer (5) is provided on the back surface of the substrate to collect the unnecessary spacer (5), the spacer existing in the spraying area is replaced with the electrode (7). By the electric field generated between (7) and the nozzle (6), it is more accelerated and moves toward the substrate. Since the energy adjusting means of this embodiment can adjust the moving speed in the spray area, it is possible to arbitrarily prevent and adjust the installation of the collecting electrode (7) so that the influence of the gas flow is further reduced. Can be.

Further, by providing a plurality of such adjusting means, a wide range of spraying conditions can be realized. By changing the positions and areas of the openings of the plurality of adjusting means, it is possible to realize a complicated gas flow from the spray nozzle (6) to the substrate (1) instead of a linear flow. Thus, a more natural fall of the spacer can be realized, and the influence of the flow of the carrier gas on the substrate can be further reduced.

In the above embodiment, the electrode for preventing adhesion is provided on the side wall of the spraying apparatus. However, the same effect can be obtained by directly applying a charge to the side wall of the spraying apparatus without providing an electrode. . In FIGS. 1 and 2, the cross-sectional shape of the spraying device is trapezoidal, and the upper bottom is wider than the lower bottom. This is because if the spacer is attached to the side wall of the spraying area. In this case, the device is devised so as to separate from the side wall again for some reason and not to fall into a substrate shape. That is, the spacer attached to the side wall falls down by gravity even if it separates from the side wall.Therefore, the spacer moves down along the side wall, so that it does not drop onto the substrate. If so, the spacers adhering to some of the side walls may be re-adhered on the substrate, affecting the distribution density and making it impossible to provide a liquid crystal electro-optical device having uniform intervals.

Further, the spacer collecting means shown in FIGS. 1 and 2 can be easily taken out of the spraying area, and the spacer can be collected outside the apparatus. Although not shown in the drawings, naturally, the substrate can be easily installed in the spraying device. If necessary, the substrate can be sprayed continuously by using a cassette system and a robot hand or a rotary table. It may be devised so that it can be done.

[0027]

As described above, by using the present invention, the spacers can be sprayed very uniformly without using a solvent such as CFCs and IPA. In addition, the application density could be adjusted over a wide range of conditions, and more uniform application could be achieved. Further, since the influence of the carrier gas carrying the spacer can be eliminated, the flow rate of the carrier gas can be increased and the spacer can be more uniformly dispersed. In addition, unused spacers can be collected and reused.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a spraying device of the present invention.

FIG. 2 is a schematic view showing another example of the spraying device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Table 3 ... Dry air introduction port 4 ... Spacer tank 5 ... Spacer 6 ... Nozzle 7 ... Recovery electrode 8 ... Power supply 9 ... Electrode for preventing adhesion 10. Spray area 11. Adjusting means (baffle plate) 12. Adjusting means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/13 101 G02F 1/1339 500

Claims (3)

(57) [Claims] 1. An apparatus for spraying a plurality of spacers on a substrate for a liquid crystal electro-optical device, a means for charging the plurality of spacers to the same polarity, a nozzle for spraying the plurality of spacers, A reticulated object or baffle disposed in a spray area between a nozzle and the substrate; and applying a positive or negative potential to the reticulated object or baffle.
Spacer spraying apparatus characterized by comprising means that, the. 2. The method according to claim 1, wherein said positive or negative potential is
Means for applying the spacer spraying apparatus, characterized in that for changing the potential. 3. An apparatus for spraying a plurality of spacers on a substrate for a liquid crystal electro-optical device, comprising: means for charging the plurality of spacers to have the same polarity;
A nozzle for dispersing the plurality of spacers; a potential-floating baffle; and a mesh-like electrode having an arbitrary potential and polarity. The baffle and the mesh-like electrode include the nozzle and the substrate. And the mesh-like electrode is provided on the substrate side of the baffle plate.