JPH10104638A - Method for spraying spacer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly spray spacers with good reproducibility by forming electric fields between electrodes and wirings and adhering the spacers suspended in a medium between the electrodes and the wirings onto the wirings of the substrate. SOLUTION: The substrate 3 made of glass and the electrodes 7 made of platinum having a large area facing the substrate 3 are immersed into the soln. 5 in a vessel 4. The electric fields are formed between the electrodes 7 and video lines 6, by which the spacers 2 of the negative polarity dispersed in the soln. 5 are adhered onto the video lines 6 of the positive polarity on the substrate 3. Namely, the spacers which are electrified to the negative polarity among the spacers 2 in the soln. 5 by impressing the voltage of the positive polarity to the video lines 6 on the substrate 3 and the voltage of the negative polarity on the electrodes 7 facing the video lines 6 are adhered to the oriented films on the video lines 6 for the specified time by electrophoresis. As a result, the spacers 2 may be adhered out of the soln. 5 only to the necessary parts existing in the limited occupying area on the one substrate 3 of the liquid crystal display panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for disposing spacers between substrates of a liquid crystal display device, for example.

[0002]

2. Description of the Related Art In a liquid crystal display device, although the distance between a pair of substrates is about several μm, the vertical and horizontal dimensions of the substrates are several cm or more, and the display dimensions of the substrates are much larger than the distance between the substrates. Normally, a resin seal is provided around the substrate to enclose the liquid crystal. However, with the above-described configuration, the seal around the substrate alone causes the center of the substrate to bend due to the weight of the substrate, and interference fringes unfavorable to the liquid crystal display device are generated. Is caused.

[0003] Therefore, it is necessary to disperse spacers against the deformation of the substrate on the substrate on which the alignment film is formed in order to keep the distance between the substrates. FIG. 5 is a cross-sectional view of a conventional spraying device that sprays spacers on one substrate of a liquid crystal display device on which an alignment film is formed. As shown in FIG. 5, the spacer 2 ejected from the ejection port 1 sinks in the direction of the substrate 3 below according to gravity.

[0004] However, in this method, the dispersion density of the spacers tends to be uneven, and it has been difficult to uniformly distribute the spacers. Therefore, as an improved spraying method, a method in which the spacer is dispersed in a solution at the time of descent and sprayed in a mist state,
A method of avoiding concentration by giving electric charges to each other has been proposed.

[0005]

However, in these techniques, repulsion acts when the polarity of each part of the substrate on which the spacers are scattered and the settling spacers are the same, and attraction acts when the polarity is different. For this reason, the density of the spacers changes depending on the charged state of each part of the substrate, and the spacers dispersed in the solution gather again in the air as the solvent evaporates. Therefore, it was difficult to uniformly disperse and spray the spacer.

In addition, since the spacers are scattered over the entire surface of the liquid crystal display panel, the spacers are also present in the pixels, causing light leakage, defective alignment of the liquid crystal, and damage to the transistor, which is a factor alienating improvement in display quality. I was The present invention is to perform spacer spraying uniformly and with good reproducibility,
Spray only on the necessary parts of the panel, high quality, LC
It is an object of the present invention to provide a technique for manufacturing a panel including a pair of substrates, such as D (liquid crystal display), DMD, and FED (field emission display).

[0007]

The spacer dispersing method of the present invention is characterized in that spacers are attached to a substrate by electrophoresis. In addition, the spacer spraying method of the present invention,
An electrode, a wiring formed on a substrate facing the electrode, and a spacer floating in a medium between the electrode and the wiring, by forming an electric field between the electrode and the wiring,
A spacer floating in a medium between the electrode and the wiring is attached to the wiring on the substrate.

[0008] The spacer dispersing method of the present invention is characterized in that the medium is a liquid or a gas. Further, the spacer dispersing method of the present invention is characterized in that the substrate is a substrate of a liquid crystal display device having an alignment film on a wiring. That is,
According to the spacer dispersing method of the present invention, the charged spacer is attracted to a wiring having a polarity opposite to that of the spacer disposed on a specific portion of the substrate by electromagnetic force, and is selectively fixed on the substrate.

Further, by using a gas having a lower viscosity than a liquid as a medium or by using a spacer having a lower density, the spacer can be attached to the substrate faster. Then, since the spacer is attached only on the alignment film of the wiring of the liquid crystal display device, the spacer does not adhere to the pixel, and the accuracy of the interval between the pair of substrates of the liquid crystal display device and the display quality are improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention.
It will be described based on. FIG. 1 is a perspective view illustrating a distribution of spacers on a substrate according to the first embodiment. As shown in FIG. 1, the TFT on the substrate first has a polycrystalline semiconductor layer 8 on a transparent glass substrate 3 as an operation layer.

The surface of the semiconductor layer 8 is cleaned by RCA, and then ion-assisted low-temperature oxidation at 450 ° C. in a mixed gas of O ₂ and Ar and a chemical oxide film formed using heated H ₂ O _2. And the oxide film 9 formed in this way.
Further, a gate 10 made of a polycrystalline semiconductor and a gate made of WSix or TaSi ₂ are separated by an oxide film 9 on the surface of the semiconductor layer 8.
And a gate electrode 11 are laminated on the oxide film 9.

An insulating film A12 is formed mainly on the substrate 3 in order to reduce the level difference between the place where the semiconductor layer 8 exists and the place where the semiconductor layer 8 does not exist. Also, the gate electrode 11 and the image line 6
And the insulating film B13 is formed of an insulating film A1.
2 is deposited. By partially removing the oxide film 9 on the semiconductor layer 8, the image line 6 made of Al and the semiconductor film 8 are removed.
Also, the display electrode 14 made of ITO and the semiconductor film 8 are in electrical contact.

The surface of such a TFT structure is covered with a rubbed polyimide alignment film 15. Next, as shown in the figure, the spacer 2 is attached only on the alignment film 15 above the thick video line 6. The characteristic thing is
An almost spherical spacer 2 is applied only to the alignment film 15 above the image line 6 to which an external potential is applied due to the attraction based on the different polarity.
Is to be fixed.

FIG. 2 is a perspective view of the spacer spraying apparatus according to the first embodiment. As shown in FIG. 2, by forming an electric field between the electrode 7 and the image line 6, the negative spacer 2 dispersed in the solution 5 is attached to the positive image line 6 on the substrate. . Then, in order to reduce the specific resistance of the solution while suppressing contamination by the alkali metal in the container 4, distilled water or ethyl alcohol + butyl acetate (volume ratio 1:
A specific gravity of 3.0 was added to a solution 5 in which a quaternary ammonium salt (R ₄ NX, where R was an alkyl group and X was a halogen) was dissolved in 2).
A spacer 2 made of alumina 7 or 2.20 silica is dispersed.

At this time, when ultrasonic waves are externally applied to the solution, the spacers are uniformly dispersed in the solution. When the medium is liquid, the density is higher than that of gas, so that the buoyancy acting on the spacer is large, and the time for which the spacer floats against gravity is longer than that of gas. Furthermore, if the medium is water,
As compared with chlorofluorocarbon and alcohol, the resistance of the solution is easily reduced by the solute, the IR drop is small, and an electric field is easily applied to the spacer.

Next, a glass substrate 3 on the TFT (thin film transistor) side of the liquid crystal display device, on which an alignment film made of polyimide is formed on the surface and an image line 6 made of Al is formed thereunder, A platinum electrode 7 having a large opposing area is immersed in the solution 5 in the container 4. At this time, it is desirable that the surface of the substrate 3 on which the image lines 6 are formed be angled so that the image line 6 is vertical or the attached surface is downward so that the spacer in the solution does not settle by gravity on the substrate surface.

Subsequently, a positive voltage is applied to the image line 6 on the substrate 3 and a negative voltage is applied to the electrode 7 facing the image line, and the spacer 2 in the solution 5 is charged to the negative polarity. It adheres to the alignment film on the image line 6 for a certain period of time by electrophoresis.
Since the amount of the spacer adhering per unit time is determined by the current value at this time, it is preferable to use a constant current source for performing a process with good reproducibility.

Further, after the voltage for electrophoresis is cut off, the substrate 3 is taken out of the solution 5 while a washing solution without a quaternary ammonium salt but without a spacer flows down on both surfaces of the glass substrate. Then, water as a solvent is evaporated in an atmosphere in which dust does not fall on the substrate. By the above-described processing, the spacer can be attached from the solution only to a necessary portion located in a limited occupied area on one substrate of the liquid crystal display panel.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view of a spacer spraying apparatus using a two-frequency excitation plasma processing apparatus according to the second embodiment. As shown in FIG. 3, the two-frequency excitation plasma processing apparatus is surrounded by a metal apparatus wall 22, receives Ar gas and a positive voltage supply from the left apparatus wall 22, and An exhaust port connected to a molecular pump and a negative voltage supply source are provided.

Also, the power A23 having the frequency f1 is received from the upper device wall 22, and plasma is generated in the device. Further, the frequency f
In response to the second power B24, the plasma potential is adjusted. The low-pass filter and the LPF 25 connected to the upper and lower powers remove the AC component of the power and convert it to a DC component.

The bias 26 connected to the LPF 25 is a circuit for providing a DC component to each electrode. The electric power A23 described above is connected to the excitation electrode 16 in the device while being insulated from the upper device wall 22 and the device wall. The power B24 is connected from the lower device wall 22 to the substrate electrode 17 in the device while being insulated from the device wall.

A bandpass filter 27 using LC series resonance is attached to the upper and lower excitation electrodes 16 and the substrate electrode 17. The phase component of the power generated by the shape of the device wall and the wiring of each power is adjusted by the bandpass filter 27. The Ar gas introduced into the apparatus, which has been depressurized from the left apparatus wall 22 described above, moves inside the apparatus from left to right.

Then, Ar is introduced from the gas inlet on the left side of the apparatus.
After supplying the gas so that the inside of the apparatus becomes several mTorr,
When f1 is supplied to the excitation electrode 16, plasma is generated in the apparatus. Here, when the medium is a depressurized gas, the viscosity is lower than that of the gas at normal pressure, and the spacer is easily accelerated.

The excitation electrode 16 and the substrate electrode 17 are supported by a ceramic 28 while being insulated. In general, when it is considered that a plasma is composed of two types of particles, electrons and ions, ions tend to stay at the center of the plasma due to their large mass, and conversely electrons tend to dissipate around the plasma.

Therefore, the potential inside the plasma, that is, the plasma potential Vp is more likely to be a positive potential than that around the plasma. When a positive potential is applied to the substrate electrode, electrons around the plasma are more likely to flow into the substrate electrode. Then, under the condition that the plasma is neutral or because the number of electrons in the plasma inside decreases, the plasma potential Vp
Is raised to a more positive potential.

The DC voltage (average voltage) of the substrate electrode which fluctuates at the frequency f2 is called a self-bias voltage Vdc, and it is experimentally known that the amplitude of f2 is approximately | Vdc | + 2Vp. The acceleration voltage of the ion is | Vdc |
+ Vp, so that f2 applied to the substrate electrode 17
Is increased, the kinetic energy of the ions increases, and the speed of the ions can be adjusted by the substrate electrode.

Therefore, the substrate electrode 17 is connected to the excitation electrode 16.
Frequency f1 for generating high-density plasma in the space between
And a power B24 of frequency f2 for controlling the self-bias is applied to the substrate electrode 17. The spacer is introduced into the plasma generated between the upper and lower electrodes together with the gas from the inlet 18 of the spacer.

Excess spacers are removed from the apparatus through the spacer outlet 19 located on the right side of the inlet.
The substrate 3 is provided on the left side of the space formed by the excitation electrode 16 and the substrate electrode 17 arranged like a parallel capacitor, and the electrode 7 is provided on the right side of the space. At this time, the spacer around the substrate located around the plasma is negatively charged due to the nature of the plasma.

A bandpass filter 27 using LC series resonance is attached to the upper and lower excitation electrodes 16 and the substrate electrode 17. L and C of the band-pass filter are set so that the impedance becomes small with respect to the high frequency voltage above and below. The magnet 29 disposed on the excitation electrode 16 applies a DC magnetic field in parallel to the surface of the excitation electrode 16 to improve ionization efficiency.

The molecular pump connected to the gas outlet on the right side of the apparatus gives momentum to the gas molecules moving from left to right in a direction perpendicular to the gas molecules, and sends the gas to the auxiliary pump side arranged in that direction. It is a pump for removing. As described above, the spacer around the plasma is likely to be negatively charged due to collision with electrons.

In such an apparatus, as shown in FIG.
Excitation electrode 1 in an atmosphere decompressed to about several tens mTorr
The spacer 2 negatively charged by the plasma generated between the substrate 6 and the substrate electrode 17 is accelerated between the negative electrode 7 and the positive image line on the substrate 2. In the second embodiment using a gas, it is possible to increase the attachment speed of the spacer to the substrate compared to the first embodiment using a liquid.

For example, the radius of the spacer r = 3 × 10
^-6 m, density of alumina spacer ρ = 3.97 × 10 ³
kg / m ³ , the distance d between the electrode and the image line d = 1 × 10
^-2 m, voltage difference between electrode and image line V = 1 × 10 ² V, number of charged spacer spacers n = 1, quantity of electron e = 1.6
022 × 10 ⁻¹⁹ C, viscosity of water at normal pressure of 20 ° C., ηW = 1.002 × 10 ⁻³ Nsm ⁻² , viscosity of argon under normal pressure of 20 ° C., ηA = 2.215 × 10 ⁻⁵ N
When sm ^-2, the electric field E = V / d = 1 × 10 2/1 × 1
0 ⁻² = 1 × 10 ⁴ V / m, and the frictional force generated by the viscous flow having the viscosity η is Stok for a macroscopic sphere having a radius r.
By es, the frictional force = 6πrηv (where v is the moving speed of the spacer).

The electromagnetic force applied by the electric field is electromagnetic force = neE. When the electromagnetic force and the friction force match, the spacer stops, and the minimum velocity v0 in each medium is reduced.
It is thought that it becomes. By substituting the above values, the minimum speed v0W in the aqueous solution of the first embodiment is v0W = 2.77.
2 × 10 ⁻⁸ ms ⁻¹ , the minimum velocity v0A in the argon gas of the second embodiment is v0A = 1.279 × 10 ⁻⁶ ms
^-1 and the lowest speed is 2 in argon compared to in aqueous solution.
Digits also increase.

Therefore, m, which is considered to be the maximum speed vM,
(VM) obtained from the ^2/2 = ^neV vM = 8.45
From the average value of × 10 ⁻³ ms ⁻¹ and the minimum speed v0, the second embodiment using gas has a higher spacer attachment speed than in the second embodiment. Here, in the second embodiment, since the pressure is reduced, the viscosity is lower than the normal pressure, so the minimum speed is further increased, and the spacer can be attached at a high speed.

The material has a density of 2.20 × 10 ³ kg / m ^3.
When amorphous silica is used, maximum speed vM (silica)
= 1.13 × 10 ⁻² ms ⁻¹ and the density is 3.97 × 10
Maximum speed of ³ kg / m ³ alumina vM (alumina) =
8.45 × greater than 10 ^-3 ms ^-1, preferable to use a small spacer density is improved throughput to be changed is the gap between the pair of substrates.

This means that spacers made of an organic polymer having a smaller specific gravity than spacers made of an inorganic oxide can disperse spacers on a substrate more quickly. For example, the density of a polymer spacer such as a benzogamine / melamine / formaldehyde condensate, a styrene / divinylbenzene copolymer, or a styrene polymer is 1.2 × 10
^{Since it is 3} kg / m ^3, the organic polymer spacer adheres to the substrate faster than alumina or silica.

FIG. 4 is a process chart of the spacer spraying method according to the second embodiment. As shown in FIG. 4a, the upper excitation electrode 16
, A high-frequency voltage of 100 W and a power of 100 W, a ground connected to the lower substrate electrode 17, and an Ar gas pressure of 7 mT.
Under orr, plasma 20 is generated between the electrodes. Next, as shown in FIG. 4B, the spacer is introduced into the plasma 20 through the inlet 18 to be charged, and the extra spacer is discharged from the outlet 19.

Subsequently, as shown in FIG. 4C, in order to avoid damage to the semiconductor device by the plasma, the voltage applied between the electrodes is eliminated, and smoke 21 made of a charged spacer is produced. If the pressure in the apparatus is reduced to several Torr or less at room temperature, the water becomes almost water vapor and is almost exhausted, so that the static electricity is not lost due to the water passing through the apparatus wall during acceleration.

Further, as shown in FIG. 4D, a substrate 3 having an image line from the left and an electrode 7 from the right are inserted into the gap between the upper and lower electrodes such that their surfaces are parallel to the direction of gravity. Alternatively, earth substrates may be arranged on the left and right sides of the upper and lower excitation electrodes and the substrate electrode, and the earth plate may be slid back and forth to expose the substrate and the electrodes previously arranged on the back surface of the earth plate. .

Thereafter, as shown in FIG. 4E, a positive polarity is applied to the substrate 3 located on the left side, and a negative polarity is applied to the electrode 7 located on the right side, so that the negatively charged spacer 2 is moved to a specific position on the substrate. To the alignment film on the image line. By the above-described processing, the spacer can be attached to only a necessary portion on one substrate of the liquid crystal display panel from the gas.

Incidentally, the parallel plate type two-frequency excitation plasma apparatus used in the present embodiment can realize all semiconductor processes including the sputtering technique with the same design apparatus, and can easily integrate various kinds of apparatuses to reduce the occupied area of the apparatus. Can be smaller. The present invention is not limited to the active matrix type liquid crystal display device. The present invention is also applicable to a simple matrix type liquid crystal display device in which a BM (black matrix) such as metal Cr is formed on ITO, that is, on the side closer to the liquid crystal side. be able to.

In this embodiment, the liquid crystal display panel has been described as an example. However, it goes without saying that the present invention may be applied to a DMD whose reflectance changes depending on the strength of an electric field and an FED whose brightness changes. Further, the spacer attached to the substrate may be heated or melted to control the distance between the pair of substrates and to seal the unit cells.

[0043]

As described above, according to the spacer dispersing method of the present invention in which the spacer is fixed to the substrate by electrophoresis,
Good reproducibility and selective spacer spraying are possible. In addition, since only a necessary amount of spacers are required for spraying, the economic efficiency is improved as compared with the conventional case.

Further, since the spacers can be scattered only on the wirings, the scatter density can be improved as compared with the prior art, and further, for example, the gap (interval) accuracy of the liquid crystal display panel can be increased within the surface of one panel. And uniformity among a plurality of panels. Further, since the medium is a liquid, the floating time of the spacer is longer due to the difference in buoyancy than the gas, and the sprayable time can be longer.

Alternatively, since the medium is a gas, the viscosity is smaller than that of a liquid, and the spacers can be easily accelerated and sprayed at a high speed. Further, since the substrate is a substrate of a liquid crystal display device having an alignment film on a wiring, a display defect of a liquid crystal which occurs when a spacer is fixed to a display electrode does not occur, and a high quality of the liquid crystal display device can be achieved. .

[Brief description of the drawings]

FIG. 1 is a distribution perspective view of spacers fixed by the spacer dispersing method of the present invention.

FIG. 2 is a perspective view of a spacer dispersing device for accelerating a spacer in a liquid according to the present invention.

FIG. 3 is a cross-sectional view of a spacer spraying apparatus for accelerating a spacer in a gas according to the present invention.

FIG. 4 is a cross-sectional process diagram of a spacer spraying method for spraying spacers in a gas according to the present invention.

FIG. 5 is a cross-sectional view of a conventional spacer spraying apparatus for spraying spacers in gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spout 2 Spacer 3 Substrate 4 Container 5 Solution 6 Image line 7 Electrode 8 Semiconductor layer 9 Oxide film 10 Gate 11 Gate electrode 12 Insulating film A 13 Insulating film B 14 Display electrode 15 Alignment film 16 Excitation electrode 17 Substrate electrode 18 Inlet DESCRIPTION OF SYMBOLS 19 Outlet 20 Plasma 21 Smoke 22 Device wall 23 Power A 24 Power B 25 LPF 26 Bias 27 Bandpass filter 28 Ceramic 29 Magnet

Claims (4)

[Claims] 1. A spacer dispersing method, wherein a spacer is attached to a substrate by electrophoresis. 2. An electrode, a wiring formed on a substrate facing the electrode, and a spacer floating in a medium between the electrode and the wiring, forming an electric field between the electrode and the wiring. A spacer dispersing method, wherein a spacer floating in a medium between an electrode and a wiring is attached to the wiring on the substrate. 3. The method according to claim 2, wherein the medium is a liquid or a gas. 4. The method according to claim 2, wherein the substrate is a substrate of a liquid crystal display having an alignment film on a wiring.