JP2002143795A - Method for cleaning glass substrate for liquid crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a glass substrate for a liquid crystal which is capable of in-line setting, large area processing, and high-speed processing. SOLUTION: In the method, a solid dielectric is fitted to at least one of facing electrodes of a pair under atmospheric pressure in an atmosphere containing at least 4 vol.% of oxygen, and the glass substrate is brought into contact with discharge plasma generated by applying a pulse electric field between the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a glass substrate for liquid crystal, and more particularly to a method for cleaning a liquid crystal glass substrate by discharge plasma using a pulsed electric field near atmospheric pressure.

[0002]

2. Description of the Related Art In recent years, in the electronics industry, there has been an increasing demand for miniaturization of devices, which is centered on the manufacture of VLSI and liquid crystal displays. Therefore, ultra-precision cleaning technology is required. In the manufacturing process of the liquid crystal panel, cleaning of the glass substrate is indispensable, and is generally performed by a wet method. For example, shower cleaning with pure water, brush cleaning using a surfactant or the like, pure water brush cleaning, pure water brush cleaning, and the like. The steps of water rinsing, pure water ultrasonic cleaning, air blow draining and drying, and dehydration baking by an infrared heating method are sequentially performed. However, this method has to go through many steps and is very complicated. Due to the nature of the wet method, it is a one-by-one processing and cannot be inlined.

[0003] On the other hand, plasma cleaning, which is a dry cleaning method, has attracted attention ("Monthly Eco-Industry").
Published by CMC, August 2000, pp. 45-54). The gas excited in the plasma state is used for cleaning, and the excited medium serves to volatilize the pollutant by chemically changing it. This plasma cleaning is classified into a vacuum plasma method and an atmospheric pressure plasma method.

The vacuum plasma method is 1.333 × 10 ⁴
Discharge can be stably continued with low-pressure plasma of Pa or less, but processing at low pressure is required, so a vacuum chamber, a vacuum exhaust device, and the like must be installed, and a surface treatment device is expensive. When a large-area substrate is processed by this method, a large-capacity vacuum vessel and a large-output vacuum evacuation apparatus are required, so that the surface treatment apparatus becomes more expensive.

[0005] In addition, with normal pressure plasma at 6 × 10 ⁴ Pa to near atmospheric pressure, large-area processing and high-speed processing can be supported, but the atmosphere is limited and the discharge is not stable. .

[0006] Japanese Patent Application Laid-Open No. Hei 5-275193 discloses that a mixed gas composed of a rare gas and a processing gas is maintained in a unidirectional flow state between electrodes provided with a solid dielectric and discharge plasma is generated. An apparatus for treating a substrate surface to be generated is disclosed.
However, since this surface treatment apparatus is an apparatus that generates discharge plasma in an open-system atmospheric pressure state, in the case where a desired surface treatment is performed by eliminating the influence of the outside air and bringing the discharge plasma into contact with the substrate surface. It is necessary to flow the mixed gas at a high speed, and it is necessary to keep flowing a large flow of gas, which is not a satisfactory surface treatment apparatus.

Further, a processing method using atmospheric pressure plasma using helium has been proposed (for example, Japanese Patent Application Laid-Open No. 7-99182). However, helium gas has a very small amount in nature and is expensive. In addition, since helium must be used at a high rate for stable discharge, the rate of addition of oxygen-based gas necessary for the reaction is small, and sufficient processing rate efficiency cannot be obtained.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a method for cleaning a glass substrate for a liquid crystal, which can be in-lined, can perform a large area processing and can speed up the processing.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a stable discharge plasma is generated under a specific gas atmosphere under atmospheric pressure conditions, and a glass substrate for a liquid crystal is formed. Finding that washing can be done,
The present invention has been completed.

That is, a first aspect of the present invention is to provide a solid dielectric on at least one of the opposing surfaces of a pair of electrodes facing each other in an atmosphere containing at least 4% by volume of oxygen at a pressure near atmospheric pressure. A method for cleaning a glass substrate for a liquid crystal, comprising: disposing a discharge plasma generated by applying a pulsed electric field between the pair of opposed electrodes to the glass substrate for a liquid crystal.

[0011] The second invention of the present invention relates to a method in which
The method for cleaning a glass substrate for a liquid crystal according to the first invention, wherein a discharge plasma generated in an atmosphere containing about 30% by volume is contacted.

A third invention of the present invention is characterized in that a discharge plasma generated in an atmosphere consisting of oxygen-containing nitrogen and / or air is brought into contact with the discharge plasma.
A method for cleaning a glass substrate for liquid crystal according to the invention.

According to a fourth aspect of the present invention, the pulsed electric field has a rise time and a fall time of 4 times.
0 ns to 100 μs, electric field intensity is 0.5 to 250 kV /
cm. The method for cleaning a glass substrate for a liquid crystal according to any one of the first to third inventions, wherein

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention is directed to a pair of opposing counterparts in an atmosphere containing 4% by volume or more of oxygen at a pressure near atmospheric pressure, preferably in an atmosphere containing 4 to 30% by volume of oxygen in an inert gas. A solid dielectric is placed on at least one of the opposing surfaces of the electrodes, and a pulsed electric field between the pair of electrodes, preferably, a rise time and a fall time are 40 ns or more.
This is a method in which discharge plasma generated by applying an electric field having an electric field strength of 0.5 to 250 kV / cm for 100 μs is brought into contact with a glass substrate for a liquid crystal, and high-speed cleaning of organic stains and the like on the glass substrate for a liquid crystal.

In the present invention, the above-mentioned pressure near the atmospheric pressure means a pressure of 1.333 × 10 ^{4 to} 10.4 × 10 ⁴ Pa. Above all, the pressure is preferably in the range of 9.3 × 10 ^{4 to} 10.4 × 10 ⁴ Pa where the pressure can be easily adjusted and the apparatus can be simplified.

The atmosphere for generating the discharge plasma is as follows:
High-density plasma can be generated at a pressure close to the atmospheric pressure and by containing oxygen in an amount of 4% by volume or more, preferably 4 to 30% by volume, and more preferably 20 to 30% by volume. Processing can be performed. If the oxygen content is less than 4% by volume, high-concentration plasma cannot be realized. Further, even if it exceeds 30% by volume, the treatment effect is not so improved, and it is uneconomical.

In the method of the present invention, a gas which generates oxygen radicals may be used as the oxygen gas. Examples of the oxygen radical include an oxygen molecule, an excited oxygen molecule, an oxygen molecule ion, an oxygen atom, an oxygen atom ion, an excited ozone molecule, and an ozone molecule ion. As a source of these, any oxygen-containing gas may be used, and in addition to oxygen, carbon monoxide, carbon dioxide, air, water vapor, and the like can also be used. When the oxygen-containing gas as described above is introduced into the plasma, very active and strong oxidizing radicals are generated, and it is also effective in removing unnecessary resin by an oxidizing process such as ashing which is known for removing resist. It is.

The treatment in an oxygen gas atmosphere is preferably performed in an atmosphere diluted with an inert gas. As the atmospheric gas other than oxygen, argon, neon, xenon, helium, nitrogen, air and the like can be used, and these may be used alone or in combination of two or more. Among these, an atmosphere composed of oxygen, nitrogen, and / or air is preferable in consideration of the balance between the processing effect, economy, and handleability. Conventionally, the treatment in the presence of helium has been performed under a pressure near the atmospheric pressure. However, according to the method of applying a pulsed electric field of the present invention, nitrogen and argon are inexpensive compared to helium. Stable processing inside is possible. However, the oxygen content when air is used is a value including oxygen in the air.

A solid dielectric is provided on at least one opposing surface of the pair of opposing electrodes, and a discharge plasma generated by applying a pulsed electric field between the pair of electrodes is stabilized. If an electric field is applied without using a solid dielectric or an electric field that is not pulsed is used, the electric discharge shifts to an arc, so that the treatment cannot be continued and the substrate may be damaged.

The electrodes include, for example, those composed of a simple metal such as copper and aluminum, alloys such as stainless steel and brass, and intermetallic compounds. The shape of the electrodes is not particularly limited, but is preferably a structure in which the distance between the opposed electrodes is constant in order to avoid the occurrence of arc discharge due to electric field concentration. Examples of the electrode structure that satisfies this condition include a parallel plate type, a cylindrical opposed plate type, a spherical opposed plate type, a hyperbolic opposed plate type, and a coaxial cylindrical structure.

In addition, other than a substantially constant structure, a cylindrically opposed cylindrical type having a large cylindrical curvature can be used as a counter electrode because the degree of electric field concentration causing arc discharge is small. The curvature is preferably at least 20 mm in radius. Although it depends on the dielectric constant of the solid dielectric, at a curvature smaller than that, arc discharge due to electric field concentration tends to concentrate. If the respective curvatures are greater than this, the curvatures of the opposing electrodes may be different. The larger the curvature, the closer to the flat plate, the more stable the discharge can be obtained. Therefore, the radius is more preferably 40 mm or more.

Further, the electrodes for generating plasma only need to have a solid dielectric disposed on at least one of the pair. Even if the pair of electrodes face each other at an appropriate distance so as not to cause a short circuit. Well, they may be orthogonal.

The solid dielectric is placed on one or both of the opposing surfaces of the electrodes. At this time, the solid dielectric and the electrode on the side on which it is installed are in close contact with each other, and the opposing surface of the contacting electrode is completely covered. If there is a portion where the electrodes directly face each other without being covered by the solid dielectric, an arc discharge is likely to occur therefrom.

Examples of the material of the solid dielectric include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and double oxides such as barium titanate. Objects and the like. These two types may be laminated and used.

The solid dielectric may be in the form of a sheet or a film, and preferably has a thickness of 0.05 to 4 mm. If it is too thick, a high voltage may be required to generate discharge plasma, and if it is too thin, dielectric breakdown may occur when a voltage is applied, and arc discharge may occur. Further, the shape of the solid dielectric may be a container shape.

The distance between the electrodes is determined by the thickness of the solid dielectric,
It is appropriately determined in consideration of the magnitude of the applied voltage, the purpose of utilizing the plasma, and the like, and is preferably 1 to 50 mm. If it is less than 1 mm, it may not be sufficient to place the electrodes at intervals, and if it is more than 50 mm, it is difficult to generate uniform discharge plasma.

FIG. 1 shows an example of the voltage waveform of the pulse electric field used in the present invention. Waveforms (a) and (b) in FIG. 1 are impulse waveforms, waveform (c) is a pulse waveform, and waveform (d) is a modulation waveform. Although FIG. 1 shows a case where the voltage application is repeated positive and negative, a pulse of a type that applies a voltage to either the positive or negative polarity side may be used. The pulse voltage waveform in the present invention is not limited to the above-mentioned waveforms, but the shorter the rise time and the fall time of the pulse, the more efficiently the gas is ionized during the generation of plasma.

The rise time and fall time of the pulse electric field are preferably 40 ns to 100 μs. If it is less than 40 ns, it is not realistic in equipment, and 100
When the time exceeds μs, the discharge state easily shifts to an arc and becomes unstable. More preferably, it is 50 ns to 5 μs. Here, the rise time refers to the time during which the voltage change is continuously positive, and the fall time refers to the time during which the voltage change is continuously negative.

Further, modulation may be performed using pulses having different pulse waveforms, rise times, and frequencies.

The frequency of the pulse electric field is 1 to 100 k
Hz is preferable. If it is less than 1 kHz, it takes too much time for the treatment, and if it exceeds 100 kHz, arc discharge is likely to occur.

The time for applying one pulsed electric field is preferably 1 to 1000 μs. 1 μs
When the discharge time is less than 1,000 μs, the discharge becomes unstable.
When it exceeds, it is easy to shift to arc discharge. More preferably, it is 3 to 200 μs. Here, the time during which the one pulse electric field is applied, as shown in FIG. 1 as an example, refers to a continuous ON time of one pulse in a pulse electric field composed of repetition of ON and OFF.

The above discharge is performed by applying a voltage. The magnitude of the voltage is determined as appropriate, but is preferably in a range where the electric field strength when applied to the electrode is 0.5 to 250 kV / cm. If the electric field strength is less than 0.5 kV / cm, it takes too much time for the treatment, and 250 kV / c.
If m is exceeded, arc discharge is likely to occur. In applying the pulse voltage, a direct current may be superimposed.

The glass substrate for a liquid crystal as a substrate to be treated according to the present invention is not particularly limited as long as it is used for manufacturing a liquid crystal panel. ADVANTAGE OF THE INVENTION According to the method of this invention, the organic dirt of a glass substrate can be cleaned at high speed and efficiently, and it can respond also to a large area board | substrate.

The cleaning method of the present invention can be incorporated without particular limitation as long as cleaning is required in a liquid crystal panel manufacturing process. In particular, it is suitable for a cleaning process for a raw plate at the time of receiving a glass substrate. Also, if necessary,
It may be combined with a chemical solution treatment, a wiping process using a nonwoven fabric, or the like, a substrate overheating cooling process, or the like.

As means for irradiating the object to be treated with plasma, there are, for example, a method of arranging the object to be treated in plasma generated between opposing electrodes, a method of arranging the plasma generated in the container in a gas flow, an electric field arrangement, or a magnetic field. Method (remote plasma) by blowing toward the object to be processed by a typical action.

FIG. 2 shows an example of an apparatus using parallel plate electrodes as a specific example of the apparatus used in the present invention. In FIG.
Reference numeral 1 denotes a power source, 2 denotes an upper electrode, 3 denotes a lower electrode, 4 denotes a solid dielectric, and 6 denotes a substrate to be processed. The apparatus shown in FIG. 2 is contained in a container (not shown), and the inside of the container is filled with a processing gas. In FIG. 2, both opposing surfaces of upper and lower parallel plate type discharge electrodes having a length exceeding the width of the glass substrate are covered with a solid dielectric, and an electric field is applied between the upper electrode 2 and the lower electrode 3. As a result, discharge plasma is generated, and the glass substrate for a liquid crystal is transported during this period, whereby the front and back surfaces of the glass substrate are cleaned.

FIG. 3 shows an example of an apparatus using a roll type electrode. In FIG. 3, 1 is a power supply, 2 is an upper roll electrode,
3 is a lower roll electrode / conveyance roll, 4 is a solid dielectric, 6
Represents a substrate to be treated, respectively. In FIG. 3, the upper roll electrode is covered with a solid dielectric in a state where the processing gas is introduced into the discharge space between the electrodes, and discharge is performed by applying an electric field between the upper electrode 2 and the lower electrode 3. Plasma is generated, and the glass substrate for liquid crystal is transported by the lower roll electrode / transport roll 3 during this time, whereby the surface of the glass substrate is cleaned.

Next, FIG. 4 shows an example of a remote plasma apparatus using parallel plate electrodes. In FIG. 4, 1 is a power source, 2
Reference numerals 3 and 3 denote electrodes, 4 is a solid dielectric, 5 is a gas outlet, 6 is a substrate to be treated, 7 is a gas inlet tube, and 8 is a transport roll. In FIG. 4, the processing gas is introduced into the discharge space between the electrodes 2 and 3 from the gas introduction tube in the direction of the arrow, and a discharge plasma is generated by applying an electric field between the electrodes.
The discharge plasma is sprayed from the gas discharge port 5 onto the glass substrate 6 for liquid crystal, and the surface of the glass substrate is cleaned by moving the remote plasma device itself or by moving the substrate 6 by the transport roll 8.

In the processing method of the present invention, in order to prevent the organic substance removed from the substrate surface from reattaching, an exhaust mechanism may be provided near the substrate to perform the processing while performing the exhaust.

In the atmospheric pressure discharge cleaning process using a pulsed electric field according to the present invention, a discharge can be directly generated between the electrodes under the atmospheric pressure. High-speed processing can be realized with the device and the processing method. The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage, the substrate to be treated, the composition of the mixed gas, and the like. Further, processing parameters such as a cleaning rate can be adjusted by parameters such as a pulse frequency, a voltage, and an electrode interval.

Further, the glass substrate for a liquid crystal after cleaning according to the present invention is efficiently removed of organic dirt by contacting with oxygen plasma, and the surface to be treated of the substrate is made hydrophilic.

[0042]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The processing apparatus shown in FIG. 4 was used. In FIG. 4, the application electrode 2 and the ground electrode 3 are made of stainless steel (SUS304) having a height of 30 cm and a width of 100 cm, and the distance between the electrodes is 1 mm.
It is. The solid dielectric 4 is a 1 mm thick alumina-based dielectric, and the discharge port 5 is a 1 mm slit. The distance between the glass substrate transported by the transport roll 8 and the discharge port 5 is 8 mm. A mixed gas of 25% by volume of oxygen and 75% by volume of nitrogen is introduced into the discharge space between the electrodes 2 and 3 from the gas introduction tube 7 at a flow rate of 10 SLM. Plasma treatment was performed.

Plasma processing conditions Processing gas: mixed gas 10 SLM of 25 vol% oxygen + 75 vol% nitrogen Discharge conditions: waveform (a), rise / fall time 5
μs, output 300W, frequency 10KHz, peak value 25k
V _PP , treatment time 20 sec; generated plasma was a uniform discharge with no arc pillars.

The processing effect of the plasma-irradiated portion was confirmed by measuring C / Si by ESCA before and after processing the surface of the glass substrate for liquid crystal. C / Si is 10% to 0.5%
It was confirmed that the organic components on the surface of the glass substrate for liquid crystal had disappeared.

Example 2 A surface of a glass substrate for liquid crystal was processed in the same manner as in Example 1 except that dry air was used as a processing gas. The processing effect of the plasma-irradiated portion was confirmed by measuring C / Si by ESCA before and after processing the surface of the liquid crystal glass substrate. C / Si was reduced from 10% to 0.42%, and it was confirmed that the organic components on the surface of the glass substrate for liquid crystal had disappeared.

Comparative Example 1 Instead of a pulsed electric field, a peak value of 8.4 k
The surface treatment of the liquid crystal glass substrate was performed in the same manner as in Example 1 except that the discharge was performed using an AC voltage having a sin waveform of V _PP and a frequency of 2.4 kHz. An uneven discharge state where a large number of streamers were observed was confirmed, and processing unevenness occurred.

Comparative Example 2 A liquid crystal glass substrate was prepared in the same manner as in Example 1 except that a mixed gas of 2% by volume of oxygen and 98% by volume of argon was used as a processing gas, and the discharge conditions were V _PP : 10 kV. Surface treatment was performed. When the treatment effect was confirmed by ESCA, C / Si was reduced from 10% to 2%. Example 1
To obtain a result equivalent to
sec.

[0049]

From the above characteristics, the method of the present invention can be carried out under atmospheric pressure, so that it can be easily in-lined and the organic substances adhering during the manufacturing process of the liquid crystal panel are subjected to normal pressure plasma treatment. It is effective as a method of removing by.
Further, by using the method of the present invention, it is possible to prevent a reduction in the speed of the entire processing step. In addition, it can be used for dry etching of semiconductor elements, cleaning of organic contaminants and the like present on the surface of the object to be processed, stripping of resist, improvement of adhesion of organic films, reduction of metal oxides, surface modification, etc. .

[Brief description of the drawings]

FIG. 1 is a diagram of a voltage waveform showing an example of a pulsed electric field.

FIG. 2 is a diagram showing an example of a cleaning apparatus using a parallel plate type electrode.

FIG. 3 is a diagram showing an example of a cleaning apparatus using a roll-type electrode.

FIG. 4 is a diagram showing an example of a remote plasma device using parallel plate electrodes.

[Explanation of symbols]

 Reference Signs List 1 power supply (high-voltage pulse power supply) 2 applied electrode 3 ground electrode 4 solid dielectric 5 gas discharge port 6 glass substrate 7 gas introduction pipe 8 transport roll

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Motokazu Yuasa 2-1 Shimomotocho, Mishima-gun, Osaka Prefecture Sekisui Chemical Co., Ltd. (72) Inventor Takaharu Honma 2-703 Tateno Higashiyamato-shi Tokyo F term in Chemtronics (reference) 2H088 FA21 FA24 FA30 MA20 2H090 JC09 JC19 3B116 AA02 AB14 BB62 BB89 BC01 CC05

Claims (4)

[Claims] 1. At a pressure near atmospheric pressure, oxygen is added at 4% by volume.
In an atmosphere containing the above, a solid dielectric is placed on at least one of the opposing surfaces of a pair of opposing electrodes, and a discharge plasma generated by applying a pulsed electric field between the pair of opposing electrodes is used as a liquid crystal. A method for cleaning a glass substrate for a liquid crystal, comprising contacting the glass substrate for a liquid crystal. 2. The method for cleaning a glass substrate for a liquid crystal according to claim 1, wherein a discharge plasma generated in an atmosphere containing 20 to 30% by volume of oxygen is contacted. 3. The method for cleaning a glass substrate for a liquid crystal according to claim 1, wherein a discharge plasma generated in an atmosphere comprising oxygen-containing nitrogen and / or air is contacted. 4. The pulsed electric field according to claim 1, wherein the rise time and the fall time are 40 ns to 100 μs, and the electric field strength is 0.5 to 250 kV / cm. The method for cleaning a glass substrate for a liquid crystal according to the above item.