JPH06338448A - Hard-substrate coating method - Google Patents

Abstract

PURPOSE:To prevent a thin coating part from being caused near the tip of a hard substrate and to enhance the yield of products in a hard-substrate coating method in which the rear surface of the hard substrate is coated with a coating liquid by feeling the hard substrate while the hard substrate is sandwiched between a microrod bar whose lower part has been immersed in a coating liquid tank and a nip roller which is arranged so as to face the upper part of the microrod bar. CONSTITUTION:The tip speed of a microrod bar 16 is relatively decelerated below the feed speed of a hard substrate 10 until a prescribed time elapses after the tip of the hart substrate 10 has come into contact with the microrod bar 16. Reservoirs R1, R2 for a coating liquid in a nearly definite quantity are formed at an angle which is sandwiched between the microrod bar 16 and the rear surface of the hard substrate 10 which has passed the bar. After that, the tip speed of the microrod bar 16 is controlled so as to correspond to the feed speed of the hard substrate 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a hard substrate, which is used for manufacturing a liquid crystal display panel or the like using a glass substrate and applies a coating liquid such as a photoresist thinly and uniformly to a hard substrate. is there.

[0002]

2. Description of the Related Art In the process of manufacturing a liquid crystal plate, there is a process of coating a hard substrate such as a glass substrate with a coating solution such as photoresist in a thin and uniform thickness. For example, in the manufacture of a color liquid crystal plate, a glass substrate on which a transparent electrode is preformed,
A red color mosaic liquid having a photoresist function is uniformly applied, and then exposed to cure the color mosaic corresponding to red, and the excess liquid is removed to form a red color mosaic. . Then, the same processing is repeated for other colors such as green and blue.

In the case of applying a coating liquid which becomes a photoresist as described above, this liquid has a uniform thickness (for example, 2 μ ± 5%).
It is necessary to strictly control the degree) and apply thinly. This is because if the thickness of the coating is non-uniform, the light transmittance will be uneven and the quality will be deteriorated.

Conventionally, a spin coater has been used for this coating. This spin coater is one in which a coating liquid is dropped near the center of rotation of a rotated substrate and the liquid is scattered by utilizing centrifugal force to apply the liquid. However, in the method using this spin coater, not only the labor efficiency for replacing the substrate is deteriorated but also the amount of the liquid scattered and discarded increases. Therefore, there is a problem that the cost is increased.

Therefore, it has been considered to use an apparatus (so-called Geeser) for sandwiching and applying the substrate between a pair of upper and lower rollers arranged horizontally. In this device, the lower part of the micro rod bar, which serves as the lower roller, is immersed in the coating solution, and the substrate is sandwiched between the micro rod bar and the nip roller located above the micro rod bar, and the lower surface of the substrate is moved by the micro rod bar. It is to be applied.

In this case, however, the amount of the coating liquid adhering to the substrate is small for a short period of time after the tip of the substrate comes into contact with the microrod bar and coating is started. It turns out that it has the property of being painted. This thinly coated part has a higher light transmittance after various processing steps such as exposure and cleaning compared to the part with a regular coating thickness, which may lead to product quality deterioration and cause defective products. Was there. Therefore, there is a problem that the yield of the product is reduced.

On the other hand, in Japanese Utility Model Publication No. 63-8439, in order to apply the coating liquid uniformly, the conveyance drive is stopped for a certain period of time with the front end of the substrate in contact with the coating roller, and the gap between the substrate and the coating roller is reduced. Describes a device for transferring the substrate again when the amount of the coating liquid accumulated reaches a predetermined amount. That is, the transfer of the substrate is restarted after a liquid pool is formed in a predetermined amount at the corner between the coating roller and the lower surface of the substrate that has not passed through.

[0008]

However, as a result of experiments, even in such an apparatus, the film thickness becomes unstable in a certain range on the front end side of the substrate due to the influence of the liquid pool at the beginning of the movement of the substrate. found. Therefore, the problem that the quality of the product is deteriorated and the yield is deteriorated cannot be solved.

In JP-A-2-258085, the coating liquid is supplied so that a liquid pool is formed in the same coating method, and the rotation speed of the bar is equal to the moving speed of the substrate.
It is disclosed that the coating amount is adjusted by changing within 15%. However, since this method changes the rotation speed of the bar in the state where the liquid pool is formed in a steady shape, it is not sufficiently effective for the tip portion of the substrate where the liquid pool is not regularly formed. It was not obtained, and the thin coating phenomenon at the tip portion of the substrate as described above could not be solved.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when a coating liquid is applied using a Giesser, it is possible to prevent a thin coating portion from being generated near the tip of a hard substrate, It is an object of the present invention to provide a hard substrate coating method capable of improving the yield of.

[0011]

According to the present invention, for this purpose, a hard substrate is sandwiched between a microrod bar whose lower portion is immersed in a coating liquid tank and a nip roller which is arranged above the microrod bar so as to be fed. Thus, in the hard substrate coating method of applying the coating liquid to the lower surface of the hard substrate, the peripheral speed of the microrod bar is a period until a predetermined time elapses after the tip of the hard substrate contacts the microrod bar. Relative to the feeding speed of the hard substrate, to form a substantially constant amount of coating liquid pool at the angle between the microrod bar and the lower surface of the hard substrate that has passed through the microrod bar. This is achieved by a method for coating a hard substrate, characterized in that the peripheral speed of the rod bar is controlled so as to match the feed speed of the hard substrate.

Here, the period in which the peripheral speed of the microrod bar is kept lower than the feeding speed of the substrate starts from the time when the leading edge of the substrate comes into contact with the microrod bar at the latest, and the lower surface of the substrate after passing through the microrod bar. It is desirable to set the end point when the amount of liquid in the liquid pool (downstream liquid pool) generated at the angle sandwiched by the microrod bar becomes substantially equal to the liquid amount in the steady state.

The starting point of this period is not limited to the time when the tip of the substrate contacts the microrod bar.
Including before this. Also, within this period, as the liquid amount in the downstream liquid pool approaches the liquid amount in the steady state,
The peripheral speed of the microrod bar may be continuously changed so that the peripheral speed gradually approaches the substrate feed speed.

[0014]

The coating liquid is conveyed to the lower surface of the substrate by the rotation of the microrod bar, and accumulates at the angle between the lower surface of the substrate and the microrod bar before passing through the microrod bar. ) Is formed.

When the substrate moves and its tip passes through the microrod bar, the liquid pools (downstream liquid pool) at the corner between the lower surface of the substrate and the microrod bar after the passing.
Is formed. From the liquid pool on the downstream side of the microrod bar, the coating liquid is distributed to the lower surface of the substrate and the surface of the microrod bar and flows out. That is, a part of the coating liquid in the downstream side liquid pool adheres to the lower surface of the substrate being transferred and flows out, and a part adheres to the surface of the microrod bar and is returned to the coating liquid tank.

Therefore, during coating at a constant speed, the coating thickness on the lower surface of the substrate becomes constant if the amount of coating liquid in the liquid pool on the downstream side of the microrod bar is constant. However, immediately after the tip of the substrate comes into contact with the microrod bar, a sufficient amount of the coating liquid is not accumulated in the liquid reservoir on the downstream side. Therefore, it is considered that the coating thickness of the substrate is thin until a certain amount of coating liquid is accumulated in the downstream side liquid reservoir.

In the present invention, the peripheral speed of the microrod bar is set lower than the feeding speed of the substrate until a predetermined time elapses after the tip of the substrate comes into contact with the microrod bar.
Therefore, the amount of the liquid that is attached to the surface of the microrod bar from the liquid pool on the downstream side and is returned to the coating liquid tank is reduced. Therefore, the amount of liquid distributed to the substrate is relatively increased, and thin coating of the substrate is prevented.

At this time, the amount of liquid remaining in the downstream liquid pool increases, and the amount of liquid in this liquid pool increases rapidly. After the liquid amount reaches a predetermined amount, the micro rod bar may be applied at a constant speed for coating. As a result, the coating can be accurately performed while the coating thickness is controlled to be constant, thin coating on the front end side of the substrate can be prevented, or the range of thin coating can be extremely narrowed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall layout view of an embodiment of the present invention, FIG.
4 is a sectional view of the coating apparatus, FIG. 3 is a front sectional view thereof, and FIG.
Is a sectional view taken along line VI-VI in FIG. 3, and FIG. 5 is an operation explanatory diagram.

In FIG. 1, reference numeral 10 is a glass substrate, and 12 is a glass substrate.
Is a roller conveyor, and the glass substrate 10 is fed from the left to the right in the figure with the left and right edges of the lower surface of the glass substrate 10 placed on the rollers of the conveyor 12. Gieser 1 in the middle of conveyor 12
4 are provided. The Geeser 14 has a micro rod bar 16 having a small diameter and a circular cross section, a large diameter nip roller 18 facing the micro rod bar 16 above the micro rod bar 16, and a coating liquid tank 20 into which almost the entire micro rod bar 16 is left except for the upper portion.

Here, the micro rod bar 16 is formed by winding a thin metal wire on the surface of a rod having a circular cross section so as to be in close contact with the rod, and applies the coating liquid by utilizing the capillary phenomenon by the groove between the metal wires. Is.

As shown in FIGS. 2 and 3, the coating liquid tank 20 has a long and shallow liquid reservoir 22 in a direction orthogonal to the substrate 10 feeding direction, and the liquid reservoir 22 has a liquid supply pipe 2 in the reservoir 22.
While the new liquid is supplied from No. 4, the coating liquid is discharged from the liquid discharge port 26. The liquid supply pipe 24 is desired near one end of the liquid reservoir 22, and the drainage port 26 opens at the bottom near the other end. Therefore, the coating liquid is suitable for flowing in the liquid reservoir 22 in its longitudinal direction to homogenize the liquid. The depth of the coating liquid is monitored by a liquid level sensor (not shown) and is constantly controlled.

The microrod bar 16 is held horizontally so that its upper portion is exposed from the liquid. That is, bearing portions 30, 32 having recesses that open upward in a semicircular arc shape are provided at both ends of the liquid reservoir portion 22, and the bearing portions 30, 32 are provided.
The microrod bar 16 is rotatably held between the cap and the caps 34 and 36 which are covered from above. The intermediate portion of the microrod bar 16 is supported by the backup member 38 from below.

The backup member 38 is made of a hard synthetic resin having excellent slidability, and a semicircular groove formed along the longitudinal direction on the upper surface of the backup member 38 abuts the micro rod bar 16 from below to make it micro. The rod bar 16 is prevented from bending. The height of the backup member 38 can be finely adjusted from the lower surface of the coating liquid tank 20 by a large number of adjusting screws 40 arranged below the backup member 38.

One end (the end on the far side in FIG. 1) of the microrod bar 16 projects rearward from the coating liquid tank 20, and this projecting end is connected to an electric motor 44 by a removable joint 42. The electric motor 44 is a glass substrate 10.
The rotation thereof is controlled so that the feeding speed of the same becomes equal to that of the conveyor 12. The surface of the nip roller 18 is made of conductive rubber, and is held so as to apply a predetermined pinching pressure to the glass substrate 10 while sandwiching the glass substrate 10 with the microrod bar 16.

Next, the operation of this embodiment will be described. The glass substrate 10 sent from the left side to the right side in FIG. 1 by the roller conveyor 12 includes the micro rod bar 16 and the nip roller 1.
Enter between 8 and. Since the coating liquid of the liquid reservoir 22 is attached to the surface of the microrod bar 16 by its rotation, the coating liquid is coated on the lower surface of the glass substrate 10 as the microrod bar 16 rotates.

FIG. 5A shows a state in which the leading edge 10A of the substrate 10 is in contact with the upper edge of the microrod bar 16.
At this time, a part of the liquid 16A attached to the surface of the microrod bar 16 and lifted is started to be collected by the tip edge 10A, and the upstream side liquid pool R ₁₀ is formed.

FIG. 5B shows a state in which the substrate 10 is slightly moved thereafter. In this state, the liquid pool R ₁ on the upstream side of the microrod bar 16 grows and the liquid pool R ₂₀ starts to be formed on the downstream side.

Then, when the substrate 10 is fed a sufficient distance,
While holding a certain amount of the liquid pool (upstream liquid pool) R ₁ of the coating liquid at the angle between the entrance side of the substrate 10 and the microrod bar 16, the passage side of the substrate 10 and the microrod bar 1 are held.
A fixed amount of the liquid pool (downstream liquid pool) R ₂ is held also in the corner sandwiched by 6 and 6 (FIG. 5 (C)). Since the level of the liquid surface of the liquid reservoir 22 and the pressure applied by the nip roller 18 are controlled to be constant, the glass substrate 10
The thickness of the liquid applied to the lower surface of the is sufficiently thin and can be controlled with high accuracy.

Since the microrod bar 16 always rotates with a fixed amount of coating liquid at a constant rotation speed,
The liquid amounts of the liquid pools R ₁ and R ₂ are kept constant in a steady state in which the transport speed of the substrate 10 and the peripheral speed of the microrod bar 16 are constant, and the coating film thickness is also kept constant. . However, at the initial stage of coating, the coating film thickness becomes thin because the liquid amount in the liquid pool R ₂ on the downstream side is insufficient. According to the present invention, the amount of liquid in the liquid pool R ₂ can be controlled by changing these relative speeds, and the coating film thickness can be controlled.

That is, the transport speed of the substrate 10 is Vp,
The peripheral speed of the microrod bar 16 is Vc, and Vp = V
When the film thickness T applied at c is To, T can be changed by changing Vc as follows. When Vp> Vc, T> To When Vp <Vc, T <To

This phenomenon is as described in the above section. That is, when the relative speed difference between the feeding speed of the substrate 10 and the peripheral speed of the microrod bar 16 is zero, the substrate 10 and the microrod bar 1 are detected from the liquid pool R _2.
A fixed amount of the coating liquid is taken away in each of 6 and 6. When the rotation speed of the microrod bar 16 is reduced from this steady state, the amount of the microrod bar 16 carried away from the liquid pool R ₂ is reduced and the amount of the coating liquid carried away by the substrate 10 is relatively increased. As a result, the coating film thickness on the substrate 10 becomes thick.

In order to prevent thin coating of the tip of the substrate by utilizing this phenomenon, speed control may be performed as follows. First, it is assumed that the speed is Vp = Vc in a steady state (a state where the coating is continuously performed) for coating the target film thickness T.

Immediately after the substrate 10 contacts the microrod bar 16, the liquid pool R ₂ begins to be formed, but immediately after this contact, a sufficient amount of liquid is not accumulated in the liquid pool R ₂ .
Therefore, the rotational speed of Vc is decreased immediately after the contact between the two until a sufficient amount of liquid is stored in the liquid pool R ₂ . By doing so, even if the liquid pool R ₂ having a sufficient amount of liquid is not formed at that stage, a large amount of the coating liquid is carried and coated on the substrate 10. Then, when a sufficient amount of the liquid pool R ₂ is likely to be formed, the peripheral speed of Vc is returned to the same as Vp to make a steady state, and then the substrate 10 can be coated with a constant coating film thickness.

At this time, the substrate 10 is the microrod bar 1
6, the peripheral velocity V of the micro rod bar 16
It is also possible to lower _C. However, in this case, the amount of the coating liquid to which the microrod bar 16 is attached and lifted up becomes small, and it takes time to form the fixed amount of the liquid pools R ₁ and R _2, which is not preferable.

On the contrary, the substrate 10 is the microrod bar 16
If a large amount of the coating liquid is lifted by increasing the peripheral speed of the microrod bar 16 immediately before coming into contact with, the fixed amounts of the liquid reservoirs R ₁ and R ₂ can be quickly formed. Therefore, in this way, before contact between the two, the micro rod bar 16
It is even more preferable to increase the peripheral speed of the micro rod bar 16 and decrease the peripheral speed of the micro rod bar 16 after the contact of both.

[0037]

[Experimental Example] Using the Giessor 10 shown in FIGS. 2 and 3,
Glass substrate 10 with a size of 450 mm x 450 mm and a thickness of 1.1 mm
A photoresist solution was applied on top. The micro rod bar 16 was made of stainless steel having a diameter of 12 mm and wound with stainless steel having a diameter of 0.15 mm.

4 and 5, the micro rod bar 1
The distance between the height of the liquid surface formed by the coating liquid supplied to the side where the liquid pool R ₁ is to be formed and the height of the apex of the bar 16 is maintained at 2 mm in a stationary state where the rotation of 6 is stopped. The transport speed of the substrate 10 was 3 m / min, and the peripheral speed of the microrod bar 16 in the steady coating part was 3 m / min, which is the same speed as the substrate 10.

In order to detect the time when the substrate 10 contacts the microrod bar 16, an optical sensor is provided at a position corresponding to the length of the substrate 10 before the traveling direction of the substrate 10.
A signal is obtained when the rear end of the substrate 10 passes. Upon receiving this signal, the rotation speed of the microrod bar 16 was reduced from 3 m / min to 1 m / min for 0.1 second and returned to the speed of 3 m / min again.

The results are shown in FIG. As can be seen from this figure, the microrod bar 16 at a speed of 3 mm / min.
In the case of the conventional coating method in which the coating was performed while rotating, the thin coating portion was formed from the tip of the substrate 10 to the inner side by about 25 mm. On the other hand, according to this experimental example,
It can be seen that the thinly coated portion is reduced to about 5 mm from the tip of the substrate 10.

In the above embodiment, the micro rod bar 16
Although the rotational speed (peripheral speed) of the substrate 10 is temporarily decreased, the present invention temporarily increases the feed speed of the substrate 10, or the feed speed of the substrate 10 and the peripheral speed of the microrod bar 16. Similar effects can be obtained by simultaneously changing and to relatively reduce the peripheral speed of the microrod bar 16. Further, instead of the micro rod bar 16, another coating bar may be used.

[0042]

As described above, according to the first aspect of the present invention, the rotational speed of the microrod bar is temporarily reduced during the period from the time when the substrate contacts the microrod bar to the elapse of a predetermined time. Since an appropriate amount of coating liquid is stored in the liquid pool (downstream liquid pool) formed between the bar and the substrate that has passed through it, during this period, the micro liquid flows from the downstream liquid pool. The amount of liquid carried away by the rod bar decreases, and conversely the amount of liquid applied to the substrate increases. Therefore, it is possible to prevent the occurrence of a thinly coated portion near the tip of the substrate or to reduce the range of the thinly coated portion. Therefore, the thickness of the coating liquid can be controlled with high accuracy, and the yield of products can be improved.

Further, according to the present invention, the peripheral speed of the microrod bar may be made relatively slower than the feeding speed of the substrate for the above period, and it is desirable to temporarily decelerate the microrod bar while keeping the feeding speed of the substrate constant ( Claim 2). However, this may be reversed to temporarily delay the substrate or change the speed of both.

[Brief description of drawings]

FIG. 1 is an overall layout diagram of an embodiment of the present invention.

FIG. 2 is a sectional view of the coating device.

FIG. 3 is a front sectional view of a coating device.

FIG. 4 is a sectional view taken along line VI-VI in FIG.

FIG. 5 is an explanatory diagram of a liquid pool generation process.

FIG. 6 is a diagram showing experimental results.

[Explanation of symbols]

10 Glass Substrate as Hard Substrate 12 Roller Conveyor 14 Geeseer 16 Micro Rod Bar 18 Nip Roller 22 Coating Liquid Layer R ₁ Coating Liquid Upstream Liquid Pool R ₂ Coating Liquid Downstream Liquid Pool

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirofumi Kumagai, Hiromi Kumagai 1005, Koen, Ayase, Kanagawa Fuji Micrographix Co., Ltd. (72) Shinya Yamazaki, 1005, Koen, Ayase, Kanagawa Fuji Micrographs, Inc. Within

Claims (2)

[Claims] 1. A hard substrate is sandwiched between a microrod bar whose lower portion is immersed in a coating liquid tank and a nip roller which is arranged above the microrod bar to face the lower surface of the hard substrate. In a hard substrate coating method of applying a coating liquid, the peripheral speed of the microrod bar is relative to the feeding speed of the hard substrate in a period until a predetermined time elapses after the tip of the hard substrate contacts the microrod bar. The peripheral speed of the microrod bar after forming a substantially constant amount of a pool of coating liquid at the angle between the microrod bar and the lower surface of the hard substrate that has passed through the microrod bar. A method for coating a hard substrate, characterized in that it is controlled so as to match the feeding speed of the. 2. The hard substrate coating method according to claim 1, wherein the feeding speed of the hard substrate is kept constant, and the microrod bar is temporarily decelerated.