JPH1028916A - Coating method and coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform coating film without causing any streak on the surface of the coating film. SOLUTION: A reservoir 41 for uniformly pressuring a coating liq. B is provided in the inside of a coating head 5, and a liq. reservoir communicated with the reservoir 41 is formed on the upper surface of the coating head 5. The coating liq. B is extruded from the reservoir 41 to the liq. reservoir by pressure, and the coating liq. B is highly bulged on the liq. reservoir by surface tension. When a matter A to be coated is moved while rubbing the surface of the bulged coating liq. B, the coating liq. is stuck to the back surface of the matter A by tackiness power to form the coating film D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a coating apparatus.
In particular, the present invention relates to a coating apparatus for uniformly applying various liquid coating liquids such as a resist liquid used for a flat coating target object such as a liquid crystal display panel or a wafer to a flat coating target object such as a glass substrate.

[0002]

2. Description of the Related Art A spin coating method is generally used as a method for applying a coating liquid such as a resist liquid to a glass substrate or the like used for a liquid crystal display panel, a wafer or other flat object to be coated. However, in the spin coating method,
The amount of the coating liquid applied to the surface of the coating target is only a few percent of the coating liquid supplied to the surface of the coating target, and the remaining 90% is discarded, and the yield of the coating liquid is extremely low. Had the problem of being bad.

In order to improve the yield of the coating solution,
Japanese Patent Application Laid-Open No. Hei 6-339656 proposes a slot type coating apparatus. In the slot type coating apparatus, a coating liquid is formed into a thin shape in a slot provided in the coating head, flows out from a discharge port of the coating head, and is coated on the surface of a coating target. At this time, since the moving speed of the application target is larger than the outflow speed of the coating liquid discharged from the coating head, the coating liquid is thinly stretched when being applied to the surface of the application target, and A very thin coating film is formed.

[0004]

In the above-described slot type coating apparatus, when the coating is started, a liquid droplet is placed on the lower end (slot discharge port) of the coating head located above the object to be coated. , The liquid ball is crushed between the coating head and the surface of the object to be applied, so that the coating start end of the coating is fixed to the surface of the object to be applied, and the film which is thinly stretched on the surface of the object to be applied Is formed.

However, at the start of coating, a very small and uniform liquid ball is formed on the lower surface of the coating head and crushed between the liquid and the object to be coated. In some cases, a streak of liquid droplets remained in the starting area. If streaks remain in the coating film, the coated product must be discarded as a defective product. Alternatively, the remaining part of the streak is cut off and only the part without the streak is used, so that the initial size of the object to be coated becomes larger than the required dimension, making it difficult to handle the object to be coated, and The yield of the object and the coating solution will be reduced.

Further, since the application liquid is applied to the object to be applied from above, the application liquid is easily dripped from the application head, and a countermeasure has been a problem.

Further, the flatness of a coating film formed by a conventional slot type coating apparatus is determined by how uniform and fine liquid droplets are formed at the tip of the coating head at the start of coating in the slot length direction. It depends on factors such as how to discharge a fixed amount of coating liquid from the tip of the coating head. Therefore, in order to ensure the flatness of the coating film, it is necessary to obtain a uniform and constant discharge amount over the entire length in the slot length direction, and the fine processing surface from the liquid injection port to the discharge port at the time of manufacturing the coating head is required. Processing and fine adjustment of the interval of the slot width (gap) of the coating head are required, and there are great difficulties both in manufacturing the coating head and in the coating operation by the coating device.

In the conventional slot type coating apparatus for coating on the upper surface of the object to be coated, the start and the end of the coating operation are performed by opening and shutting off the flow of the coating liquid by a fluid valve or the like. According to this method, at the start and end of the application, the flatness of the applied film is deteriorated due to the leakage of the application liquid, and streaking occurs, often resulting in defective products. As described above, in the conventional slot type coating apparatus which applies the liquid from the upper surface of the object to be coated, since it is difficult to solve the problem of the liquid leakage at the start and the end of the application, a uniform film thickness is obtained by a smooth continuous applying operation. It was difficult to obtain a coating.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a coating apparatus capable of forming a coating film having a flat and uniform film thickness over the whole. To provide.

[0010]

DISCLOSURE OF THE INVENTION The coating method according to claim 1 of the present invention comprises:
The coating liquid is held in a liquid pool provided on the upper surface of the coating head,
Applying the coating liquid to the lower surface of the coating object by raising the coating liquid from the liquid pool by the surface tension of the coating liquid and relatively moving the coating object while making contact with the coating liquid rising from the liquid pool. Features.

According to a fourth aspect of the present invention, there is provided a coating apparatus, comprising: a coating head having a reservoir inside, and a liquid reservoir for holding a coating liquid supplied from the reservoir on an upper surface;
It is characterized by comprising a means for supplying a coating liquid to the coating head, and a transport means for moving an object to be coated so as to pass above the coating head.

The present invention is a coating method and a coating apparatus suitable for applying various liquid coating liquids such as a resist liquid to a coating target such as a glass substrate or a wafer of a liquid crystal display panel.
In the liquid pool at the tip of the coating head, the liquid surface rises due to the surface tension of the coating liquid itself, and when the object to be coated is moved while contacting the surface of the coating liquid rising horizontally in the slot direction, the viscosity of the coating liquid itself becomes high. As a result, the coating liquid adheres to the object to be coated, and a coating film is formed on the surface of the object to be coated.

Further, since the application liquid is applied to the application object from the lower surface side, the problem of liquid dripping does not occur.

Further, since the coating liquid is raised by the surface tension of the coating liquid in the liquid pool, if the liquid discharge port of the coating head and the shape of the liquid pool are uniform in the length direction, the coating liquid Swells uniformly in the length direction, and the coating film has no streak like a conventional slot type coating device, and a high quality coating film can be obtained.
Product yield is improved.

Further, when the coating liquid is supplied to the liquid pool,
Since the coating liquid spreads in the liquid pool and rises evenly due to surface tension, fine processing is not required unlike the conventional slot type coating head, so that the structure of the coating head can be simplified and the opening of the slot can be simplified. Fine adjustment of width and the like becomes unnecessary.

According to a second aspect of the present invention, in the coating method according to the first aspect, after the application liquid in the application head is pressurized to cause the application liquid to swell in the liquid reservoir, the upper surface of the application head is removed. It is characterized in that the application head is raised so that the distance from the lower surface of the object to be applied is constant, and the application of the application liquid rising in the liquid pool is brought into contact with the lower surface of the object to start application of the application liquid. And

According to this embodiment, the coating liquid is pressurized to rise in the liquid pool, and the coating head is raised in a state where the liquid level of the coating liquid is made uniform by the surface tension to apply the coating liquid to the object to be coated. , It is possible to form a uniform film thickness at the beginning of application of the coating liquid, that is, at the beginning of the coating film.

According to a third aspect of the present invention, in the coating method according to the first aspect, after the pressure of the coating liquid in the liquid pool in contact with the lower surface of the object to be coated is reduced, the coating head is lowered. Thus, the application of the application liquid is completed.

According to this embodiment, the coating liquid rises above the liquid pool and contacts the lower surface of the object to be coated, and the coating liquid is separated from the object by lowering the coating head in a state where the applied coating liquid is reduced in pressure. Since the coating liquid is applied, the coating liquid can be uniformly drained from the object to be coated, and the end of application of the coating liquid, that is, the end of the coating film can be formed with a uniform film thickness.

According to a fifth aspect of the present invention, in the coating apparatus of the fourth aspect, a means for adjusting a liquid pressure of the coating liquid in the reservoir and a means for raising and lowering the coating head are further provided. It is characterized by having.

In this embodiment, since means for adjusting the liquid pressure of the coating liquid in the reservoir is provided, it is possible to pressurize or depressurize the coating liquid.
The application liquid can be pressurized or depressurized before the application head moves up and down as in the application method described in (1).

Therefore, in these embodiments, it is possible to minimize the deterioration of the flatness of the coating film due to the dripping of the coating liquid at the start and end of coating. In particular, it is possible to smoothly perform an intermittent application operation on a plurality of rectangular application objects. Further, it is also possible to apply the coating liquid uniformly on the inside while leaving the frame of the object to be coated in a frame shape, which is difficult with the conventional coating apparatus.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

(Work Supply Table) FIG. 1 is a partially broken perspective view showing a coating apparatus 1 according to an embodiment of the present invention. Various tanks, controllers and the like are housed in the cabinet 2, and a control panel 3 is provided on a side surface of the cabinet 2. On the upper surface of the cabinet 2, there are provided a work supply table 4, a coating mechanism unit 6 having a coating head 5, a transfer device 8 having a suction table 7, and the like. ).

A positioning piece 10 for positioning an object to be coated such as a glass substrate is provided on the upper surface of the work supply table 4, and the object to be applied carried into the work supply table 4 is surrounded by the positioning piece 10. Is positioned so that it fits in the area where it is located. A work support pin 11 that protrudes or retracts from the work supply table 4 is provided inside a region surrounded by the positioning piece 10, and the object to be coated is applied onto the work supply table 4 in a state where the work support pin 11 is retracted. The object to be coated can be pushed up from between the positioning pieces 10 by positioning the object and then projecting the work support pin 11.

(Transporting Apparatus) The transporting apparatus 8 sucks an object to be coated and passes it over the coating head 5 and has the following structure. Sliders 13 are slidably engaged with rails 12 fixed on both sides of the upper surface of the cabinet 2, respectively.
The suction table 7 is provided on the lower surface of the bridge 14 provided between them.
Is attached. The suction table 7 is for suctioning an object to be coated by a negative pressure, and is connected to an air circuit (not shown). A drive mechanism 15 for moving the bridge 14 and the suction table 7 is provided in the cabinet 2. The drive mechanism 15 is a ball screw mechanism. When the screw shaft 17 is rotationally driven by the servo motor 16, the female screw block 18 screwed with the screw shaft 17 moves along the screw shaft 17. . Since the slider 13 is connected to the female screw block 18 of the drive mechanism 15,
When the drive mechanism 15 is driven to move the female screw block 18, the suction table 7 moves with it.

When the object to be coated is carried into the work supply table 4 and positioned between the positioning pieces 10, the transfer device 8 moves the suction table 7 onto the work supply table 4. When the suction table 7 moves directly above the work supply table 4, the work support pins 11 protrude to push the application target from between the positioning pieces 10, and further press the application target against the lower surface of the suction table 7. When the application object comes into close contact with the lower surface of the suction table 7, the suction table 7 suctions almost the entire surface of the application object to the lower surface. Next, the work support pin 11 is retracted as before. The application object sucked on the lower surface of the suction table 7 is transported by the transport device 8 so as to pass above the coating head 5.

(Coating Mechanism) The structure of the coating mechanism 6 is shown in FIG.
Shown in A pair of guide bushes 21 is fixed to a base 20 mounted on a frame 19 of the cabinet 2, and a guide shaft 22 is slidably inserted into each of the guide bushes 21. Both ends of a beam 9 erected between the upper ends of the guide shafts 22 are rotatably supported on the upper ends of the two guide shafts 22, and the upper surface of the beam 9 is coated with the liquid discharge side facing upward. The head 5 is attached. The lower end of each guide shaft 22 is in contact with the upper end surface of an output rod 24 of an NC cylinder (numerical control type cylinder) 23 and is supported from the lower surface.
Are raised and lowered so that the inclination and height of the coating head 5 can be precisely adjusted.

The NC cylinder 23 is provided with a base 2
Elevating plate 26 inserted through guide shaft 25 suspended from zero
The lifting plate 26 is supported on an upper end of an output shaft 29 of an air cylinder 28 fixed to a fixing plate 27 fixed to a lower end of a guide shaft 25. Therefore, the entire application head 5 can be moved up and down by driving the air cylinder 28 to move the elevating plate 26 up and down.

The height of the lower surface of the object to be applied which is sucked and conveyed to the lower surface of the suction table 7 varies due to the thickness variation of the object to be applied. Therefore, as shown in FIG. 3, a non-contact type for measuring the height of the lower surface of the conveyed object to be applied or the thickness of the object to be applied is provided on each of the left and right sides in front of the application head 5. A clearance measuring head 30 is provided to measure the height of the lower surface of the object to be applied immediately before the application, and transmit the measurement information to the controller. Reference numeral 31 denotes an NC cylinder 23 for adjusting the height of the clearance measuring head 30.
The controller that has received the transmission information from the clearance measuring head 30 drives the NC cylinder 23 so that the liquid discharge port 36 of the coating head 5 and the lower surface of the object to be coated are parallel to each other, and the coating head 5 The height and the inclination of the coating head 5 are adjusted so that the gap between the liquid discharge port 36 and the lower surface of the coating target becomes a predetermined value.

A coating head cover 33 held at the tip of a rotatable arm 32 is provided at the rear of the coating head 5. During standby, the coating head cover 33 is attached to a liquid discharge port 36 on the upper surface of the coating head 5. To prevent the coating liquid from drying. Further, at the time of the coating operation, the arm 32 rotates and the coating head cover 33 separates from the coating head 5 to enable the coating operation.

(Coating Head) FIG. 4 is an exploded perspective view showing the structure of the coating head 5, and FIGS. 5A and 5B are sectional views of the coating head 5 at different cross-sectional positions. The coating head 5 includes a pair of split dies 37 and 38,
The inner surfaces 7 and 38 are integrated by tightly contacting with each other and fastening with bolts. On the inner surfaces of both split dies 37, 38, semicircular groove-shaped concave portions 39, 40 are formed over substantially the entire length, and the concave portions 39, 40 face each other to form a reservoir 41 in the coating head 5. . This reservoir 41
Is to uniformly apply pressure to the coating liquid to stabilize the discharge amount of the coating liquid. As shown in FIG. 5A, one of the split dies 37 is provided with a coating liquid supply port 42 for supplying a coating liquid into the reservoir 41. A liquid discharge port 36 protrudes from the upper surface of the coating head 5, and a liquid pool 43 of a uniform shape for storing the coating liquid is formed in a straight line at the upper end of the liquid discharge port 36 over substantially the entire length. Is formed. At least one of the split dies 37 and 38 is provided with a slot 44 for communicating the reservoir 41 with the liquid reservoir 43. When pressure is applied to the coating liquid in the reservoir 41, the coating liquid in the reservoir 41 It rises to the pool 43 and rises from the liquid pool 43 due to surface tension (see FIG. 7A). The slot 44 has a relatively large gap so that the pressure loss of the coating liquid does not become too large. Although the size varies depending on the characteristics of the coating liquid, the gap is, for example, about 0.3 to 1.5 mm.

On both sides of the liquid discharge port 36 on the upper surface of the coating head 5, a waste liquid pool 45 is formed substantially over the entire length. In the waste liquid pool 45, a coating liquid overflowing from the liquid discharge port 36, a cleaning liquid (solvent) used for cleaning, and the like are stored. Therefore, the liquid discharge port 3 is formed by the solvent evaporating from the coating liquid and the cleaning liquid in the waste liquid pool 45.
The vicinity of 6 can be kept in a solvent atmosphere, and the coating liquid applied to the lower surface of the object to be coated itself can assist the function of leveling the coating film (leveling). Furthermore, as shown in FIG. 5B, discharge ports 46 that open to the side through the inside of the split dies 37 and 38 communicate with both ends of the waste liquid pool 45.

(Liquid supply / discharge system) FIG.
FIG. 3 is a diagram showing a supply / discharge system of a coating liquid to the system. A liquid discharge path 48 having a manual valve 47 is connected to a discharge port 46 of the coating head 5, and a pipe end of the liquid discharge path 48 is guided to a waste liquid tank 49 disposed below. Therefore, by closing the manual valve 47, the coating liquid and the cleaning liquid can be stored in the waste liquid pool 45, and when the manual valve 47 is opened, the coating liquid and the cleaning liquid in the waste liquid pool 45 can be discharged to the waste liquid tank 49.

A liquid supply path 51 having an opening / closing valve 50 is connected to the coating liquid supply port 42 of the coating head 5. The liquid supply path 51 is provided with a switching valve 52 and a filter 53 on the way. Cleaning liquid supply path 5 including liquid supply path 54, switching valve 55 and filter 56
7, the pipe end of the coating liquid supply path 54 is guided into the coating liquid tank 58, and the pipe end of the cleaning liquid supply path 57 is guided into the cleaning liquid tank 59. In the coating liquid tank 58,
N ₂ gas is supplied through a precision pressure reducing valve 60 and a filter 61. The supply pressure of the coating liquid B is obtained by this gas pressure, and the coating liquid is sent to the tip of the coating head 5. The gas pressure at that time is a pressure value that takes into account the amount of the coating liquid inside the coating head 5 and the pipe and the pipe resistance. Precision pressure reducing valve 60
The reason why is used is to precisely balance the pressure so as to keep the amount of the coating liquid rising at the tip of the coating head 5 constant. Also, in the cleaning liquid tank 59,
N ₂ gas is supplied through a precision pressure reducing valve 62 and a filter 63, and the cleaning pressure can be supplied by this gas pressure.

Further, a coating liquid discharge path 64 for pressure reduction branches off from the liquid supply path 51.
Is led to a recovery tank 66 via a pressure release valve 65.

(Operating Operation) The coating apparatus 1 of the present invention has the above-described configuration, and a coating liquid such as a resist liquid is applied to the lower surface of the coating object A such as a glass substrate as described below. B is applied uniformly. First, at the time of cleaning in preparation for operation start, the manual valve 47 is opened. Next, when the switching valve 52 of the coating liquid supply path 54 is closed, the switching valve 55 of the cleaning liquid supply path 57 is opened, and the opening / closing valve 50 of the liquid supply path 51 is opened, the cleaning liquid C is supplied to the coating head 5. The inside of the application head 5 is filled with the cleaning liquid C and cleaned.

Next, when the switching valve 55 of the cleaning liquid supply path 57 is closed and the switching valve 52 of the coating liquid supply path 54 is opened, the coating liquid B is supplied into the coating head 5. Flows out of the liquid discharge port 36, and the cleaning liquid C in the coating head 5 is replaced by the coating liquid B.

If the coating operation is not started immediately after this, the open / close valve 50 is closed and the pressure release valve 65 is opened to reduce the pressure inside the coating head 5. On the other hand, the manual valve 47 is closed to keep the application liquid B or the cleaning liquid C in the waste liquid pool 45. Then, the liquid discharge port 36 of the coating head 5
Then, the waste liquid pool 45 is covered with the coating head cover 33 and a standby state is set until the start of coating.

When starting the coating operation, the coating head cover 33 is opened, and the opening / closing valve 50 of the liquid supply path 51 is opened. When the application target A supplied to the work supply table 4 is adsorbed on the lower surface of the suction table 7 and transported at a set speed, the clearance measuring head 30 moves the application target A
The height (or plate thickness) of the lower surface of is measured. Each NC cylinder 23 is driven in accordance with the measurement result of the clearance measuring head 30, and the height of the coating head 5 is adjusted so that an appropriate clearance is obtained between the lower surface of the coating target and the liquid discharge port 36. Next, the opening / closing valve 50 is opened, and pressure is applied to the reservoir 41 in the coating head 5, so that the coating liquid B in the reservoir 41 rises to the liquid discharge port 36, and as shown in FIG. , The coating liquid B rises high.

Next, when the application start position of the application target A is directly above the liquid discharge port 36, the coating head 5 is raised by the air cylinder 28, and the liquid discharge port 36 of the coating head 5 is raised.
And the lower surface of the application target A are kept at a predetermined distance (for example, about 50 μm). At this time, the coating liquid B rising in the liquid pool 43 adheres to the lower surface of the coating object A. When the application target A moves in such a manner that the liquid discharge port 36 and the application target A are not in contact with each other while rubbing the rising surface of the application liquid B, as shown in FIG. Coating liquid B
The coating liquid B adheres to the lower surface of the coating object A due to the viscosity of the coating object A, and a coating film D having a uniform film thickness is formed. At this time, by applying a constant pressure to the coating liquid B, the supply amount of the coating liquid B to the coating head 5 and the coating amount to the coating target A can be balanced, and the swelling of the coating liquid B can be kept constant. it can.

Further, at this time, the coating film D just applied by the solvent vapor E evaporating from the cleaning liquid C and the coating liquid B in the waste liquid pool 45 is surrounded by the solvent atmosphere, and the surface is leveled flat.

Immediately before the end of coating, the open / close valve 50 is closed and the pressure release valve 65 is opened. As a result, the inside of the coating head 5 is decompressed, and the coating liquid B in the liquid pool 43 is applied to the end only by the remaining amount of the liquid pool 43 while being reduced by its own weight. However, a slight pressure is applied to the coating liquid B so that the liquid level does not decrease so much. When the application is completed, the application head 5 is
Is lowered. Thereafter, the coating head cover 33 covers the liquid discharge port 36 and the waste liquid pool 45, and returns to the standby state.

According to the coating apparatus 1 of the present invention, the reservoir 4
The coating liquid B in 1 is automatically supplied to the liquid pool 43 by the liquid pressure, and the coating liquid B is raised by the surface tension. Therefore, the coating liquid B is raised uniformly in the liquid pool 43 by the surface tension. Moreover, the slot 44 only supplies the coating liquid B. Therefore, unlike the conventional slot type coating apparatus, there is no need to perform fine processing and fine adjustment for obtaining a uniform discharge amount in the slot 44.

The coating liquid B is transferred to the lower surface of the coating liquid A by the adhesive force by moving the coating liquid A while contacting the surface of the coating liquid B uniformly rising in the liquid pool 43. Since it only moves, streaks do not occur in the coating film D. Further, since the application head 5 is arranged on the lower side with the liquid discharge port 36 facing upward, the problem of liquid dripping does not occur.

The thickness of the coating film D formed as described above is determined by the relative speed of the coating object A and the coating head 5 and the viscosity of the coating liquid B, and becomes thinner by increasing the speed of the coating object A. A coating can be obtained. For example, a coating film having a thickness of 5000 to several tens of μm can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing a coating apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of a coating mechanism in the coating device of the same.

FIG. 3 is a side view showing the coating mechanism and the structure around the coating mechanism;

FIG. 4 is an exploded perspective view showing a structure of a coating head.

FIGS. 5A and 5B are cross-sectional views at different cross-sectional positions of a coating head.

FIG. 6 is a schematic diagram showing a liquid supply / discharge system of the coating apparatus according to the first embodiment.

FIGS. 7 (a) and 7 (b) are partially cutaway sectional views for explaining a coating method using the coating apparatus of the above.

[Explanation of symbols]

 Reference Signs List 5 coating head 6 coating mechanism part 36 liquid discharge port 37, 38 split die 41 reservoir 43 liquid pool 44 slot 45 waste liquid pool A coating target object B coating liquid

Claims (5)

[Claims] 1. A coating liquid is held in a liquid pool provided on an upper surface of a coating head, the coating liquid is raised from the liquid pool by the surface tension of the coating liquid, and the object to be coated is brought into contact with the coating liquid raised from the liquid pool. A coating liquid is applied to the lower surface of the object to be applied by relatively moving the application liquid. 2. After the application liquid in the application head is pressurized and the application liquid is raised in the liquid pool, the application head is raised so that the distance between the upper end of the application head and the lower surface of the object to be applied is constant. The application method according to claim 1, wherein the application of the application liquid is started by bringing the application liquid rising in the liquid pool into contact with the lower surface of the object to be applied. 3. The method according to claim 1, wherein the application of the application liquid is completed by lowering the application liquid in the liquid pool in contact with the lower surface of the object to be applied and then lowering the application head. Coating method. 4. A coating head having a reservoir therein and having a reservoir on the upper surface for holding a coating liquid supplied from the reservoir, a means for supplying the coating liquid to the coating head, and passing above the coating head. And a conveying means for moving the object to be coated. 5. The coating apparatus according to claim 4, further comprising: means for adjusting a liquid pressure of the coating liquid in the reservoir; and means for moving the coating head up and down. .