JP3436655B2 - Substrate cleaning method - Google Patents

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 various substrates, and more particularly to a method for cleaning a plastic substrate for electronic equipment, particularly a substrate suitable for cleaning a plastic substrate for a liquid crystal display device.

[0002]

2. Description of the Related Art In a substrate with electrodes for a liquid crystal display device, a resist residue generated in an electrode patterning process by a photolithography technique and dust from a manufacturing environment adhere to the electrode surface of the substrate. These impede the uniformization of the distance between the substrates at the time of manufacturing the liquid crystal display element and cause display defects. For example, these foreign substances have a height of several μm to several tens of μm, and have a TN (Twisted Nema).
tic) cells and STN (Super Twisted)
In the Nematic) cell, the height of the foreign matter exceeds the distance between the substrates, which causes a display defect, which is a serious problem.

Further, in a liquid crystal display device using a ferroelectric liquid crystal, it is necessary to set a substrate interval to about 2 μm, and it is very difficult to manufacture a liquid crystal display device having no display defect unless these foreign substances are completely removed. Has become difficult.

Therefore, various cleaning methods have been proposed as methods for removing these foreign substances. Among them, brush cleaning is drawing attention as a method with high foreign matter removal efficiency (cleaning efficiency). Brush cleaning is a method in which a rotating brush is pressed against the substrate surface to remove foreign matter by friction (Japanese Patent Laid-Open No. 5-297336).

However, although the brush cleaning has a great effect on the glass substrate, the adhesion between the transparent electrode, which is generally used, such as ITO, and the substrate is generally weaker in the plastic substrate than that of the glass substrate. Since the hardness of the electrode itself is small, the electrode is damaged by the friction of the brush or the like and the wire is broken.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the foreign matter attached to the surface of a plastic substrate having an electrode on at least one surface used for a liquid crystal display device or the like is attached to the electrode. An object of the present invention is to provide a cleaning method that removes uniformly and efficiently without causing scratches or disconnection.

[0007]

In order to achieve the above object, as a result of a study by the present inventor, as a result, a rod-shaped member having a surface having a wall surface that is not parallel to the rotation direction is partially immersed in a liquid. , The rod-shaped member is rotated so that a film of this liquid is formed on the surface of the exposed portion of the liquid of the rod-shaped member, and the film is used as a protective film to prevent damage to the substrate electrode. Furthermore, it was found that by transporting the substrate while bringing the substrate surface into contact with this coating, the uneven wall surface only contacts the foreign substances having a height, and the foreign substances can be removed by scraping. The present inventor has completed the present invention based on this finding.

That is, the present invention is a method for cleaning a substrate for removing foreign matter adhering to the surface of the substrate, which has a rod shape having a central axis extending in the length direction through the center of a cross section perpendicular to the length direction. A member having a convex portion having a wall surface that is not parallel to the rotation direction of the rod-shaped member when the rod-shaped member is rotated about the central axis, and a liquid is used on the surface of the rod-shaped member. Forming a coating, rotating the rod about the central axis so that the surface of the substrate comes into contact with the liquid coating but not the rod, and the relative position between the substrate and the rod. A method for cleaning a substrate, which is characterized in that a foreign matter is removed by moving a position.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION There is no particular limitation on the material of the substrate to be cleaned in the present invention. There is also no particular limitation on the plastic substrate for liquid crystal display element considered to be particularly useful, for example, uniaxial polyester film, polyethylene film, polypropylene film, polycarbonate film, polyether sulfone film,
Examples thereof include polyarylate film. Further, a material in which an organic substance such as a gas barrier layer or an undercoat layer is laminated is also applicable.

In the case of cleaning a substrate with electrodes for a liquid crystal display element or the like, the material of the electrodes for driving the liquid crystal on the substrate is not particularly limited as long as it is a material having conductivity, and a known vapor deposition method or sputtering method is used. Indium oxide electrode formed by, for example, ITO composed of indium oxide and tin oxide
Examples include electrodes. Further, it is also applicable to a layer in which an insulating film layer such as SiO _x or polyamide is coated or laminated on a layer of a transparent conductive material such as ITO.

The shape of the rod-shaped member is preferably such that it can be partially immersed in a liquid and rotated to form a liquid film having a uniform thickness on the surface of the rod-shaped member in a direction perpendicular to the rotation direction. A roll-shaped outer peripheral surface having a plurality of protrusions is preferably used. The diameter of the roll shape is not particularly limited, but is usually 20 to 20.
0 mm is preferable, and 50 to 150 mm is more preferable.
The material of the rod-shaped member is not particularly limited, but a metal material, for example, a stainless material is preferable in consideration of the ease of forming the convex portion on the surface, the durability, and the like.

The shape of the convex portion is not particularly limited as long as it has a wall surface that is not parallel to the rotation direction of the rod-shaped member. In order to make the film thickness uniform and prevent damage to the substrate, make the height of the convex parts from the outer peripheral surface of the roll shape uniform, and curve the upper surface of each convex part parallel to the outer peripheral surface of the roll shape. It is preferable to form it. The convex portions may be continuously formed in a lattice shape or the like, or may be formed in a plurality of island shapes or band shapes. In the case of a strip-shaped convex portion, it may extend parallel to the length direction of the rod-shaped member,
As long as it is not perpendicular to the longitudinal direction of the rod-shaped member, it may extend spirally with a helix angle, and may be bent or curved.

Among the wall surfaces of each convex portion which are not parallel to the rotation direction of the rod-shaped member, at least the wall surface facing the rotation direction of the rod-shaped member is approximately 90 °, preferably 45 to 90.
It is preferable to have a rake angle of °. When the rod-shaped member is rotated, this wall surface serves as a rake face and scrapes off the foreign matter adhering to the substrate surface.

The groove width between the convex portions, that is, the interval between the adjacent convex portions must be equal to or larger than the size of the target foreign matter,
Further, the upper limit differs depending on the relationship between the transport speed of the substrate and the peripheral speed of the rod-shaped member, and therefore cannot be specified as a whole, but normally,
The minimum width is preferably 100 μm or more, and 100
More preferably, it is set to μm to 10 mm. In the case of a lattice-shaped convex portion, the groove width between the convex portions means the groove width between the convex portions that face each other in one lattice.

If the height of the convex portion is too high, bubbles are generated in the liquid due to the difference in viscosity of the liquid coating film and the rotation speed of the rod-shaped member, which makes it difficult to form a uniform coating film.
The thickness is preferably mm, and more preferably 100 μm to 500 μm.

The convex portion on the surface of the rod-shaped member is, for example, engraved on a rod-shaped member material such as a roll-shaped material, grooved
It can be formed by sticking a material forming the convex portion, for example, a plate-shaped laminate.

As the grooved rod-shaped member, it is simple and suitable to use a commercially available gravure roll.

When the material for forming the convex portion is attached, examples of the material of the material include plastic materials such as polyether, acrylic resin, and Teflon resin, rubber materials, metal materials such as aluminum and SUS, and ceramics. It is suitable.

The formation of the convex portion by sticking the plate-shaped laminated body is not parallel to the rotation direction, for example, by cutting a plastic substrate into strips and using an adhesive or the like on the surface of the rod-shaped member while keeping an interval therebetween. It can be done by fixing it so that it has a wall surface. A double-sided adhesive tape may be used instead of the adhesive.

The liquid used for forming the liquid film on the surface of the rod-shaped member may be any general cleaning liquid such as ultrapure water or organic solvent without particular limitation.
The viscosity range is preferably about 0.2 to 100 cPs, preferably 0.3 to 10 cPs, and more preferably 0.3 to 5 cPs. Specific examples of the organic solvent suitable for the method of the present invention include methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, acetone and the like.

In order to prevent the foreign matter from reattaching to the substrate, it is preferable to replace the foreign matter regularly or continuously before the suspension occurs.

The liquid coating on the surface of the rod-shaped member can be formed, for example, by rotating the rod-shaped member while partially immersing the rod-shaped member in the liquid in the cleaning tank while making the rod-shaped member horizontal. Alternatively, the entire rod-shaped member may be immersed in the liquid, and the liquid may be interposed between the convex portion of the rod-shaped member and the base material to rotate the rod-shaped member. It can also be formed by rotating the rod-shaped member while supplying the liquid to the rod-shaped member by spraying or spraying it with a shower rinse or the like.

The optimum rotation speed of the rod-shaped member cannot be unconditionally specified because the optimum value varies depending on the transfer speed of the substrate, the viscosity of the liquid, etc., but it is preferably 10 rpm or more, and preferably 10 rpm to 500 rpm. Is more preferable.

As a method of moving the relative position between the substrate and the rod-shaped member, a method of fixing the position of the rod-shaped member and moving the substrate, a method of fixing the position of the substrate and moving the rod-shaped member, and a rod-shaped member There is a method of moving both the substrate and the substrate, and either method may be used. At this time, the relative moving speed of the rod-shaped member and the substrate varies depending on the degree of adhesion of foreign matter, the rotation speed of the rod-shaped member, etc., and cannot be specified unconditionally, but usually 0.1 to 1
It is preferably 00 m / min, and more preferably 0.3 to 10 m / min.

It is preferable that the rotating direction of the rod-shaped member is usually opposite to the substrate conveying direction or the same as the moving direction of the rod-shaped member.

The method of transporting the substrate is not particularly limited as long as it can transport the substrate by bringing the substrate into contact with the liquid coating on the surface of the partial member with uniform tension. For example, in the case of a flexible long substrate, for example, a plastic substrate, a transporting means of a coating device such as a kiss coater or a gravure coater, which has a substrate unwinding part and a winding up part is used. By this, it is possible to perform efficient cleaning.

FIG. 1 is an explanatory sectional view showing an embodiment of the method of the present invention. In this embodiment, the flexible long plastic substrate 1 is conveyed by two rolls 5 being oriented in a fixed direction indicated by an arrow. On the other hand, the round bar-shaped bar-shaped member 3 is rotated in the direction of the arrow while being horizontally immersed in the liquid 4 in the cleaning tank 6 and partially immersed therein.
At a portion of the rod-shaped member 3 that is higher than the surface of the liquid 4, the liquid coating 41 is formed on the surface of the rod-shaped member 3 by the rotation of the rod-shaped member 3. The rod-shaped member 3 has a plurality of convex portions 31 each having a wall surface 311 that is not parallel to the rotation direction of the rod-shaped member 3. At the upper portion of the rod-shaped member 3, the substrate 1 comes into contact with the liquid coating film 41 on the convex portions 31 and is conveyed. Has been done.

FIG. 2 shows the plastic substrate 1 shown in FIG.
The vicinity of the contact area between the liquid coating 41 and the liquid coating 41 is shown enlarged. On the surface of the rod-shaped member 3, plate-shaped laminates are attached at intervals to form a plurality of convex portions 31 of height b having wall surfaces 311 that are not parallel to the rotation direction. When the plate-shaped laminate is attached in parallel with the length direction of the rod-shaped member 3, c is the minimum groove width between the convex portions. In this embodiment, the rake angle of the wall surface 311 that is not parallel to the rotation direction of the rod-shaped member 3 is about 90 °. The thickness of the coating film when the plastic substrate 1 is in contact with the liquid coating film 41 is a, and the foreign matter 22 attached to the plastic substrate 1 is 22.
The height of a is d, the foreign matter 22 having a height of a <d
Are scraped off by the convex portion 31. That is, in the method of the present invention, the surface of the plastic substrate is protected by the liquid film, and foreign substances can be removed and cleaned without damaging the substrate.

As described above, the thickness of the liquid coating film is determined by adjusting the rotation speed of the rod-shaped member and the viscosity of the liquid.
As an example, as a rod-shaped member, 12 strips of a polyether film having a width of 2.5 mm and a thickness of 100 μm were attached to the surface of a stainless round bar having a diameter of 20 mm at equal intervals in parallel with the length direction of the stainless round bar. Of the liquid coating film, using ultrapure water having a viscosity of 0.9 cPs as the liquid and rotating the rod-shaped member by immersing the rod-shaped member horizontally in the ultrapure water up to 10 mm in the vertical direction. Table 1 shows the results of examining the relationship with the thickness.

[0030]

[Table 1] After the cleaning, the substrate is preferably dried by blowing clean air or nitrogen gas onto the substrate with an air knife or the like to blow off the droplets and then heat-drying with a hot air dryer or the like. The drying temperature is preferably below the glass transition temperature of the substrate material.

[0031]

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

Example 1 On the surface of a stainless steel round bar having a diameter of 20 mm, a length of 360 m
m, width 2.5 mm, thickness 100 μm 12 strips of polyether film were fixed at equal intervals with double-sided tape so that the wall surface of the film was orthogonal to the direction of rotation of the stainless round bar, to produce a rod-shaped member. , Attached to the gravure coater.

As the object to be cleaned, a polyether sulfone (PES) substrate with an ITO pattern electrode (PES: Sumitomo Bakelite FST: width 360 mm, thickness 100 μ)
m, length 50 m, ITO electrode: width 1 mm, thickness 0.08
A long film substrate having a stripe shape (μm, gap 0.07 mm, pitch 1.07 mm) was set on this gravure coater. Then, as shown in FIG. 1, the rod-shaped member was placed under the water 10 in an overflow type cleaning tank to which ultrapure water (viscosity: 0.9 cPs) was supplied at 100 cc / min.
The film substrate was partially dipped to a depth of 10 mm and rotated at 100 rpm, and the film substrate was transported at a speed of 100 m / min so as to come into contact with the ultrapure water coating on the rod-shaped member and washed. The thickness of the coating was 1.7 μm. Further, the water attached to the substrate was removed by an air knife.

After that, a liquid crystal panel was manufactured by the following method.

A liquid crystal material shown below was dissolved in toluene (concentration: 25% by weight), and a microgravure coater was used on the electrode surface of the washed film substrate to apply a coating speed of 2 m / m.
in, to form a film of liquid crystal material having a thickness of 3 μm. Then, the similarly washed film substrate with ITO was laminated by using a pair of pressure rolls, and while applying a DC voltage of 40 V between the upper and lower substrates at room temperature, a bending deformation in a certain direction was given to the entire panel for orientation treatment. It was When this panel was placed between orthogonal polarizing plates and driven and displayed, the display defect due to the foreign matter adhering to the substrate was 300 mm × 600 m.
It was 0 in m size. In addition, the number of defective display lines due to the disconnection of the electrodes was zero.

The number of display defects is the number of defective parts which are visually recognized and are not normally displayed.
Such a display defect is caused by a substrate gap (3 μm) between the upper and lower substrates.
It has been confirmed that this occurs when a foreign substance having a thickness of m) or more is present.

Example 2 In the same manner as in Example 1, as an article to be cleaned, a polyether sulfone (PES) substrate (PES) with an ITO pattern electrode was used.
ES: Sumitomo Bakelite FST: width 360 mm, thickness 100 μm, length 50 m, ITO electrode: width 1 mm, thickness 0.08 μm, gap 0.07 mm, pitch 1.0
A 7 mm striped long film substrate was set on this gravure coater. Then, as shown in FIG. 1, methyl ethyl ketone (viscosity: 0.3 cPs) is 30
A micro gravure rod with a diameter of 20 mm and a slanted line number 45 (manufactured by Yasui Seiki Co., Ltd.) with a diameter of 20 mm is provided in an overflow type washing tank supplied at cc / min.
m, thickness 50 μm, twist angle of about 40 °, rake angle of wall surface of about 90 °, groove width of 0.7 mm) was dipped to 10 mm below the liquid surface and rotated at 40 rpm to make the film substrate 0.
It was conveyed at a speed of 3 m / min so as to come into contact with the film of methyl ethyl ketone on the micro gravure rod, and washed. The coating thickness was 1 μm. Further, the methyl ethyl ketone attached to the substrate was removed by hot air drying.

After that, a liquid crystal panel was manufactured by the following method.

The liquid crystal material used in Example 1 was dissolved in toluene (concentration: 25% by weight), and a microgravure coater was used on the electrode surface of the washed film substrate, and the coating speed was 2
It was applied at m / min to form a film of liquid crystal material having a thickness of 3 μm.

Then, the similarly washed film substrate with ITO was laminated by using a pair of pressure rolls, and while applying a DC voltage of 40 V at room temperature between the upper and lower substrates, the entire panel was flexibly deformed and oriented. Processed.
When this panel was placed between orthogonal polarizing plates and driven and displayed, the display defect due to the foreign matter adhering to the substrate was 300 m.
There were 0 pieces of m × 600 mm size. In addition, the number of defective display lines due to the disconnection of the electrodes was zero.

Comparative Example 1 A liquid crystal panel was prepared in the same manner as in Example 1, except that the same substrate with ITO pattern electrodes used in Example 1 was used without cleaning. When drive display was performed on this liquid crystal panel in the same manner as in Example 1, there were 20 display defects of 360 mm × 600 mm size, which were caused by foreign substances adhering to the substrate. However, the number of defective display lines due to the disconnection of the electrodes was zero.

Comparative Example 2 The same substrate with an ITO pattern electrode as used in Example 1 was washed by using the method described in JP-A-2-297336. That is, while the substrate is being conveyed at a rate of 0.3 m / min in one direction, it is arranged on both sides of the substrate and the rotation speed is 100 r
A pair of roller-shaped cleaning brushes (brush material: diameter 100 μm, length 30 m) that rotate in the direction opposite to the substrate transport direction at pm
m nylon material), and brush cleaning was performed.
During the brush cleaning, ultrapure water was sprayed on both the substrate and the cleaning brush to rinse the substrate simultaneously with the cleaning with the brush. After brush cleaning, the substrate is cleaned by spraying cleaning water, and then ultrasonically cleaned in an ultrasonic cleaning tank containing ultrapure water.
After rinsing by jetting ultrapure water again, water was dried with an air knife.

A liquid crystal panel was produced in the same manner as in Example 1 using the substrate thus washed. Then, the liquid crystal panel thus obtained was driven and displayed in the same manner as in Example 1, and as a result, there were 5 display defects of 360 mm × 600 mm size, which were caused by the foreign matter adhering to the substrate.
When the height of the foreign matter that became the display defect was measured, it was 3 μm.
It was a very small foreign substance of about 10 μm. Also,
There were 18 defective display lines due to electrode breakage.

As described above, when the brush cleaning is used, the effect of removing very small foreign matter is low, and the electrode is broken.

[0045]

According to the method of the present invention, it is possible to efficiently remove foreign substances and complete the cleaning step without causing damage or scratching of the object to be cleaned due to cleaning. In particular, it is possible to efficiently remove and clean foreign matter attached to the plastic substrate with electrodes, which is likely to cause disconnection of the electrodes, and is suitable as a method for cleaning substrates used for liquid crystal display elements and the like.
In addition, the method of the present invention includes rotating a rod-shaped member having a convex portion having a wall surface that is not parallel to the rotation direction on the surface by partially immersing the rod-shaped member in a liquid to form a film on the surface of the rod-shaped member. It can be carried out by an extremely simple operation of transferring while contacting the liquid coating, and is also a method suitable for continuous large-scale cleaning.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing one embodiment of the method of the present invention.

FIG. 2 is a partially enlarged explanatory view of the embodiment shown in FIG.

[Explanation of symbols]

1 plastic substrate 2 Surface with foreign matter 22 foreign matter 3 Rod-shaped members 31 convex 4 liquid 41 Liquid coating 5 rolls 6 cleaning tank

Claims (8)

(57) [Claims] 1. A method for cleaning a substrate for removing foreign matter adhering to the surface of the substrate, comprising a rod-shaped member having a central axis extending in the length direction through the center of a cross section perpendicular to the length direction. Forming a liquid film on the surface of the rod-shaped member by using a rod-shaped member having a convex portion having a wall surface that is not parallel to the rotation direction when the rod-shaped member is rotated about the central axis as the surface , The surface of the substrate is in contact with the liquid coating but not the rod-shaped member, the rod-shaped member is rotated about the central axis, and the relative position of the substrate and the rod-shaped member is moved. A method of cleaning a substrate, characterized by removing foreign matter. 2. The method according to claim 1, wherein the thickness of the liquid coating between the convex portion of the rod-shaped member and the surface of the substrate is 0.1 to 100 μm. 3. The method according to claim 1, wherein the liquid has a viscosity of 0.3 to 10 cPs. 4. The liquid film is formed by rotating the rod-shaped member while partially immersing it in the liquid.
The method described in either. 5. While immersing the entire rod-shaped member in the liquid,
Alternatively, the method according to claim 1, wherein the liquid film is formed by rotating the rod member while supplying the liquid to the surface of the rod member by spraying. 6. The method according to claim 1, wherein a relative moving speed between the rod-shaped member and the substrate is 0.1 to 100 m / min. 7. The method according to claim 6, wherein the position of the rod-shaped member is fixed, and the substrate is moved. 8. The method according to claim 6, wherein the position of the substrate is fixed, and the rod-shaped member is moved.