JPH08243476A - Method for coating of glass substrate by die coater - Google Patents

Abstract

PURPOSE: To simply apply a predetermined membrane to a substrate having undulation, warpage or thickness irregularity by holding a glass substrate on a table having a suction mechanism and a specific degree of flatness under suction and relatively moving a die coater and the table to coat the substrate. CONSTITUTION: The degree of flatness of the upper surface of a moving table 6 is set to 2μm or less and lattice like grooves 8 are provided to the upper surface of the table 6 to be allowed to coommunicate with a vacuum pump through through-holes 7. A glass substrate W is held on the moving table 6 under suction by a vacuum pump. A photoresist soln. is allowed to flow out of the slit 3 of the die head 2 of a die cone 1 while the moving table 6 is moved in the direction shown by an arrow to coat the glass substrate W. At this time, the die coater 1 is arranged so as to provide the gap obtained from a region where a capillary number calculated from the viscosity, surface tension and a coating speed of a coating soln. becomes 0.1 or less. By this constitution, a membrane with a thickness of 10μm or less is simply applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coating a glass substrate with a die coater, and more particularly to a method of coating a thin film of 10 μm or less with a die coater on a relatively thin glass substrate of 2.00 mm or less. .

[0002]

2. Description of the Related Art Conventionally, as a method of applying a coating material such as a photoresist liquid on a glass substrate, there is a spin coater method in which the coating material is applied by rotating a glass substrate. However, this method is very economically disadvantageous because about 95% of the paint is discarded without being reused. Therefore, a coating method using a die coater has attracted attention as a coating method for effectively using a coating liquid.

On the other hand, a glass substrate is provided with a "undulation", "sludge" and "thickness unevenness" of the substrate itself, and "undulations" of a table. Therefore, a thin film of 10 μm or less is formed on such a glass substrate by a die coater. When applying
A change in the gap due to the above-mentioned "warp" or the like has caused light and shade stripes in the coating film.

On the other hand, if a pressure difference is provided between an upstream side and a downstream side in the glass substrate transport direction of a bead formed between the lower end of the die coater and the glass substrate, the thickness of the coating film is reduced by the lower end of the die coater and the glass. 1/2 to 1 of gap with substrate
It is known that it can be / 7. That is,
By making the gap 2 to 7 times the coating thickness and widening the gap, the gap change due to the "waviness" or the like is substantially reduced, and the effect of the gap change on the uniformity of the coating film thickness is mitigated. I am trying to do it. Then, in order to generate the pressure difference, the means shown in FIGS. 3 and 4 is adopted.

That is, in FIG. 3, the die coater a
An air chamber c is attached to the upstream side in the transport direction of the glass substrate W, and a pressure difference is provided between the air chamber c and the downstream side of the die coater a by sucking the inside of the air chamber c. In FIG. In this method, a nozzle d is attached to the downstream side of the glass substrate W in the transport direction of a, and a gas is blown from the nozzle d to the application portion to provide a pressure difference. In the above description, the glass substrate W is moved, but the die coater may be moved on the contrary.

[0006]

However, in the former case, since the air chamber c is provided outside the die coater a, the distance L between the paint nozzle b of the die coater a and the rear end of the air chamber c is reduced. Inevitably grows. Therefore, when the rear end portion of the glass substrate W conveyed in the direction of the arrow approaches the die coater a, the lower part of the air chamber c is largely opened, and the sealability at this portion cannot be maintained, so that a sufficient pressure difference does not occur. At that portion, the coating film becomes thick and the predetermined thickness cannot be maintained. Therefore, there is a problem that the range in which the chamber c can secure a sealing property and a sufficient pressure difference can be extremely narrowed, and it is difficult to form a desired film thickness over the entire glass substrate W. .

On the other hand, in the latter case, a predetermined film thickness cannot be obtained at the tip of the glass substrate W because the airflow from the nozzle d is disturbed by a step due to the thickness of the glass substrate W.
Further, if the spray pressure from the nozzle d is increased to increase the pressure difference in order to reduce the film thickness, the paint may be interrupted or the coating surface may become wavy, resulting in coating failure. Further, when the coating material has a low viscosity (about 20 CPS or less), there is a problem that the coating liquid is scattered and the coating becomes difficult. In this method, since the dynamic pressure of the gas supplied from the nozzle d is used, it is very difficult to apply pressure uniformly over the entire width of the bead formed on the coating nozzle b. Had.

As a result of various studies to solve the problems in the coating method using the die coater, the present inventors found that the number of capillaries Ca and the dimensionless minimum coating film thickness (dimensionalless coating film thickness ratio) t shown in FIG. From the relationship, the number of capillaries Ca
It was found that the capillary number Ca and the dimensionless minimum coating film thickness t are in a proportional relationship in a range of 0.1 or less, which is a critical value. When the capillary number Ca is in the proportional range,
The dimensionless minimum coating film thickness t determined from the capillary number Ca determined by applying the physical properties and the coating speed of the coating liquid to (Equation 1), the maximum gap determined by applying (Equation 2) to the critical value of the capillary number Ca A gap setting value including a gap variation due to warpage or uneven thickness of the glass substrate exists between the dimensionless minimum coating film thickness t determined from 0.1 and the minimum gap obtained by applying the equation (2). It has been found that the coating can be performed at a predetermined coating film thickness without providing a chamber as in the related art.

[Equation 1] Ca = μU / σ

T = h / H, μ: viscosity (Pa · S) U: coating speed (m / s) σ: surface tension (N / m) h: minimum coating film thickness (μm) H: gap ( μm). Therefore, an object of the present invention is to provide a method for coating a glass substrate using a die coater, which can solve the above-described problems of the die coater based on the above knowledge.

[0009]

According to the present invention, in order to achieve the above object, in claim 1, when a glass substrate is coated with a die coater, it has a suction mechanism and a flatness of 2 μm. The glass substrate is adsorbed and held on the following table, the die coater and the table are moved relative to each other, and the glass substrate is coated with the die coater. Further, in claim 2, the viscosity of the coating liquid,
A die coater is installed with a gap obtained from a region where the number of capillaries calculated from the surface tension and the coating speed of the coating liquid is 0.1 or less, and coating is performed on a glass substrate.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a die coater 1 has a die head 2
And a coating liquid supply pump 4 for supplying a photoresist liquid as a coating liquid to the head 2 and a coating liquid tank 5. Reference numeral 6 denotes a moving table on which the glass substrate W is placed. The upper surface of the moving table 6 has a flatness of 2 μm, and grooves 8 are formed in a grid on the upper surface. Through a vacuum pump (not shown). Then, the glass substrate W is placed on the moving table 6, and the glass substrate W is sucked and held on the moving table 6 by suction with a vacuum pump. It is applied by flowing out of the slit 3.

Now, the physical property value of the photoresist solution is determined by the viscosity:
0.06 Pa · S, surface tension: 30 × 10 ⁻³ N / m, precision of glass substrate “sludge”: 500 μm, thickness: 1.1
mm ± 10 μm, application conditions: application speed: 10 mm / s,
Coating thickness: 10 μm. In this case, the capillary number Ca is from the above-mentioned number 1 to 0.02, and from FIG. 2, the dimensionless minimum coating film thickness t is about 0.15. Since the coating thickness h is 10 μm according to the coating conditions, the gap H is about 66 μm from (Equation 2). In addition, since the gap H is minimized near the critical value 0.1 of the capillary number Ca as described above, the dimensionless minimum coating film thickness t when the capillary number Ca is 0.1 is about 0. The minimum gap H is about 16 μm from (Equation 2) because the coating film thickness is 10 μm. Therefore, the distance between the reference surface of the glass substrate W and the lower end of the die coater 1 is in the range of the gap 16 μm to 66 μm obtained by the above calculation, and
Even if the gap fluctuates due to uneven thickness of the glass substrate W, etc., if the gap is within the gap range, the applied film thickness is 10 μm.
m is obtained.

On the other hand, the "warp" of the substrate W is caused by the glass substrate W being attracted to the moving table 6 and corrected, so that "thickness unevenness" of ± 10 μm occurs only on the glass substrate W, and The flatness of the moving table 6 is ± 1 μm
Therefore, the upper surface of the glass substrate W is ± 1 from the reference plane.
A difference of 1 μm results. However, the distance (gap H) between the lower end of the die coater 1 and the reference surface of the glass substrate W can be adjusted in the range of 16 μm to 66 μm. 55 + 11 = 66 μm, which is within the above range even if it is far away.
11 = 44 μm, and even if the coating film thickness of 10 μm is taken into consideration, 44-1 is provided between the lower end of the die coater 1 and the coating film surface.
A space of 0 = 34 μm is formed, and there is no problem in application. Further, by setting the set value of the gap H to the maximum value within the above range, the influence of the thickness unevenness can be reduced as much as possible.

In the above description, the number of capillaries Ca
Was used to determine the gap between the die coater and the glass substrate. However, in some cases, simply holding the glass substrate on a moving table to correct the "undulation" or "sludge" of the glass substrate would cause the die coater to become capillary. A gap may be set and applied regardless of the number Ca.

[0014]

As is apparent from the above description, claim 1
According to the invention, since the glass substrate is held by suction on a table having a flatness of 2 μm or less, the “undulation” and “sludge” of the glass substrate can be ignored. It only appears as a gap change with the substrate, and since this gap change is relatively small, a desired thin film can be applied to a glass substrate without providing a pressure chamber in the die coater. According to the second aspect, the gap between the die coater and the glass substrate can be increased by setting the capillary number calculated from the viscosity of the coating solution, the surface tension of the coating solution and the coating speed to be 0.1 or less. Thus, a desired thin film can be applied to the glass substrate.

[Brief description of drawings]

FIG. 1 is a sectional view of a die coater device embodying the present invention.

FIG. 2 Capillary number Ca and dimensionless minimum coating thickness t
A graph showing the relationship with.

FIG. 3 is a sectional view showing a conventional die coater.

FIG. 4 is a sectional view showing a conventional die coater.

[Explanation of symbols]

1 ... Die coater, 2 ... Die head, 3 ... Slit, 6 ...
Moving table, 7: through hole, 8: groove, W: glass substrate.

Claims (2)

[Claims] 1. When coating a glass substrate with a die coater, the glass substrate is suction-held on a table having a suction mechanism and a flatness of 2 μm or less, and the die coater and the table are relatively held. A method of coating on a glass substrate by a die coater, which comprises moving and coating on a glass substrate by a die coater. 2. A die coater is installed with a gap obtained from a region where the number of capillaries calculated from the viscosity of the coating liquid, the surface tension of the coating liquid and the coating speed is 0.1 or less, and coating is performed on a glass substrate. A coating method for a glass substrate by the die coater according to claim 1, wherein