JP2005144409A - Slit coater die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slit coater die by which a thin film can be formed uniformly at a high speed by adopting a die coater system and forming the lip surface of the slit coater die into a proper shape regardless of a surface-treated state of the lip surface. <P>SOLUTION: This slit coater die 1 is constituted so that a coating liquid 10 is applied to the substrate 9 to be coated by discharging the coating liquid 10 from a slit 4 and moving the slit coater die relatively to the substrate 9 to be coated while keeping a predetermined gap between the slit coater die and the substrate 9 to be coated. At least one groove 8 extending along the longitudinal direction of the slit 4 is formed on the rear lip surface 7 which is one of two surfaces formed by halving the lip surface by the slit 4 for discharging the coating liquid 10 and is positioned on the downstream side of a stream of the discharged coating liquid 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention applies a photoresist or the like on a glass substrate used for manufacturing a flat panel display such as a liquid crystal display or a plasma display, or a flat substrate having a single wafer shape such as a wafer for semiconductor manufacturing. The present invention relates to a slit coater die for applying a liquid.

  Conventionally, a coating solution such as a photoresist solution is uniformly applied on a flat and single-wafer substrate such as a glass substrate used for manufacturing a flat panel display such as a liquid crystal display or a plasma display or a wafer related to semiconductor manufacturing. As a method of applying to the substrate, a spin coater method, a bar coater method, and a roll coater method are widely used.

  The spin coater method is widely used when applying a photoresist solution on a wafer involved in semiconductor manufacturing. The photoresist solution is dropped onto the center of a rotating (spinning) wafer and applied using centrifugal force. It is a method to do.

  However, in recent years, glass substrates used for the production of flat panel displays such as liquid crystal displays and plasma displays have been increasing in size. Spinning such a large glass substrate requires a huge device and large power, and is difficult to adapt. Furthermore, most of the photoresist solution dropped on the wafer is scattered by centrifugal force, and all the scattered photoresist solution becomes a waste solution, so that the yield is very poor. Furthermore, since the drying proceeds from the outer peripheral direction of the wafer, there is a problem that the film thickness of the coating film is not uniform.

  The bar coater method is a method in which a wire or the like is wound around the outer periphery of a bar and applied to a substrate to be coated.

  However, when coating is performed using the bar coater method, when the state of coating on the substrate to be coated is observed, scaly cloud-like or satin-like dry spots are frequently generated. Furthermore, the wire wound around the outer periphery of the bar may come into contact with the substrate to be coated and damage the substrate to be coated.

  The roll coater method is a method in which a roller immersed in a bath filled with a coating solution is applied to a substrate to be coated through one or more rollers.

  However, when applied using the roll coater method, the coating solution is exposed to the atmosphere for a relatively long time until it is applied from the bathtub to the substrate to be coated, so that the physical properties of the coating solution change, and foreign matter May be mixed.

  In recent years, a die coater method has been proposed in order to eliminate such defects in coating quality. The die coater method uses a base called a slit coater die. The slit coater die spreads the coating liquid supplied from the supply port in the lateral width direction by a manifold formed inside, and discharges the coating liquid uniformly in a thin film through the slit communicated with the manifold. At this time, the discharged coating liquid forms a liquid pool, that is, a meniscus, between the pair of lip surfaces forming the slit and the substrate to be coated. That is, the die coater method is a method of forming a coating film on a substrate to be coated by relatively moving the slit coater die and the substrate to be coated while holding the meniscus.

  At the time of coating by the die coater method, it is an important issue to always keep the meniscus formed by the coating solution in a stable state.

  For the purpose of solving such problems, in order to keep the meniscus formed by the coating liquid always stable and to form a coating film, the surface treatment of both lip surfaces sandwiching the slit is performed upstream of the discharge flow of the coating liquid. The lip surface located on the side (hereinafter referred to as “front lip surface”) is coated with a water repellent material, and the lip surface located on the downstream side of the discharge flow of the coating liquid (hereinafter referred to as “rear lip surface”). .) Is known as a slit coater die coated with a hydrophilic material (for example, Patent Document 1).

  Further, a step is provided so that the gap between the rear lip surface and the substrate to be coated is narrower than the gap between the front lip surface and the substrate to be coated, and the gap between the front lip surface and the rear lip surface is provided. There is known a slit coater die that suppresses thickening at the start of coating by forming a pool of coating liquid (for example, Patent Document 2).

Further, contrary to the above case, at least a part of the gap between the rear lip surface and the substrate is made larger than the gap between the front lip surface and the substrate, and the capillary pressure of the upstream meniscus is set at the downstream meniscus. By maintaining the capillary pressure at a higher rate than the sum of the pressure difference in the coating direction due to the flow of the coating liquid between the downstream lip and the substrate, streak defects (liquid breakage) can be obtained even in high-speed coating. A slit coater die that is prevented from being generated is known (for example, Patent Document 3).
JP-A-11-145043 JP 2002-45763 A JP 2003-10773 A

  However, in the slit coater die described in Patent Document 1, when the front lip surface is coated with a water-repellent material, the wet state of the coating solution varies in the front lip surface during coating, and the meniscus shape becomes unstable. Furthermore, when the coating speed is high (for example, 100 mm / second or more; the same applies hereinafter), air may flow from the gap between the front lip surface and the substrate to be coated, resulting in a liquid breakage phenomenon.

  Also, in the slit coater die described in Patent Document 2, if the coating speed is increased, the meniscus shape becomes unstable and is not suitable for high-speed coating.

  Furthermore, even with the slit coater die described in Patent Document 3, there is a limit to precision processing, and depending on the surface treatment state of the rear lip surface, the wet state of the coating film changes in the portion in the coating film width direction. As a result, unevenness in the flow rate may occur, and problems such as uneven color and running out of liquid may occur.

  Therefore, the present invention adopts a die coater method and optimizes the lip surface shape of the slit coater die, thereby enabling the slit to be applied uniformly and at high speed regardless of the surface processing state of the lip surface. The purpose is to provide a coater die.

  In order to achieve the above object, the slit coater die according to the present invention applies a coating to a substrate to be coated by relative movement with the substrate to be coated while discharging a coating liquid from the slit while maintaining a predetermined distance from the substrate to be coated. A slit coater die to be applied, wherein at least one of the lip surfaces divided by the slit for discharging the coating liquid extends along a length direction of the slit to a lip surface positioned on the downstream side of the discharge flow of the coating liquid One groove is formed.

  Moreover, it is preferable that the protrusion which restrict | squeezes the internal flow-path cross section of the said slit is formed in the slit inner wall face.

  Furthermore, of the lip surfaces divided into two by the slit, it is preferable that the lip surface located on the downstream side of the discharge flow of the coating liquid has a larger surface area than the lip surface located on the upstream side.

  Furthermore, among the lip surfaces divided by the slit, a rear lip surface located downstream of the discharge flow of the coating liquid is formed on the same surface as a front lip surface located upstream. It is preferable that the distance from the substrate to be coated is smaller than the front lip surface.

  In the slit coater die according to the present invention, a groove extending along the slit is formed on the rear lip surface, so that the groove becomes a liquid pool for the coating liquid, and the thin film can be uniformly and rapidly formed regardless of the surface treatment state of the lip surface. Can be applied.

  Embodiments of a slit coater die according to the present invention will be described below with reference to FIGS. In addition, the same code | symbol was attached | subjected to the same component through the whole figure.

  FIG. 1 is a perspective view showing a state in which the slit coater die according to an embodiment of the present invention is applied, and FIG. 2 is an enlarged longitudinal side view showing a lip surface of the slit coater die in FIG. It is.

In FIG. 1, 1 is a slit coater die, 2 is a supply port, 3 is a manifold, 4 is a slit, 4a is a protrusion that narrows the cross section of the internal flow path of the slit 4, 5 is a discharge port, and 6 is a discharge flow of the coating liquid 10. , A front lip surface located upstream, a rear lip surface located downstream of the discharge flow of the coating liquid 10, and a groove formed along the length direction of the slit 4 formed on the rear lip surface. , 9 is the substrate to be coated, 10 is the coating liquid, t _f is the length of the front lip surface (vertical width), _tr is the length of the rear lip surface (vertical width), and g _f is the front lip surface and the substrate to be coated. , G _r is the gap between the rear lip surface 7 and the substrate 9 to be coated, and the arrow X is the slit coater die when the slit coater die travels with the substrate 9 being fixed when forming the coating liquid film. The traveling directions are respectively shown.

  First, the coating method using the slit coater die 1 of FIG. 1 will be briefly described. The coating solution 10 flows into the supply port 2 of the slit coater die 1 and is spread in the lateral width direction by the manifold 3. Then, it flows into the slit 4 communicating with the space of the manifold 3, is discharged from the discharge port 5, and is applied to the substrate 9 to be coated while forming a meniscus.

  In order to make the film thickness uniform, the pressure in the manifold 3 is assumed to be constant. Here, if the space of the manifold 3 is sufficiently wide and the gap between the slits 4 is sufficiently narrow, the pressure in the manifold 3 approaches a constant pressure. However, if the gap between the slits 4 is too narrow, the overall pressure becomes too high, which is not preferable. Moreover, if the space of the manifold 3 is excessively widened, the die itself becomes large, which is not preferable. Therefore, a protrusion 4a extending in the length direction of the slit 4 is formed on the inner wall surface of the slit 4 so that the flow passage cross section of the slit 4 is narrowed, so that even if the space of the manifold 3 is somewhat small, It is preferable to make the pressure uniform. This is because by increasing the back pressure by narrowing the gap of the slit 4 by the protrusion 4a, the flow of the coating liquid upstream of the protrusion 4a can be expanded in the coating film width direction of the slit coater die 1. . The protrusion 4a may be either a fixed type in which the slit gap is constant or a movable type in which the slit gap is variable.

Thereafter, the coating liquid flowing into the slit 4 from the manifold 3 is discharged from the discharge port 5, and the gap g _f between the front lip surface 6 and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 and the substrate 9 to be coated. To form a meniscus.

  The meniscus shape when the slit coater die 1 is stopped is determined by the surface tension between the coating liquid 10 and the substrate 9 or the solid of the slit coater die 1 and the liquid, and is always stable.

  It is considered that it is necessary to always keep the meniscus shape stable in order to prevent problems such as liquid breakage, uneven color, and streaks during the running of the slit coater die 1.

  For that purpose, the uniformity of the flow distribution of the coating liquid discharged from the discharge port 5 is required as a premise. Since the flow rate of the coating liquid is quantitatively supplied by a gear pump or the like, the flow rate distribution can be uniform to some extent, but the protrusion 4a also contributes to further improving the uniformity of the flow rate distribution.

  The groove 8 running in the width direction (the length direction of the slit) on the rear lip surface 7 makes the wet state of the coating film in the coating film width direction uniform regardless of the surface treatment state of the rear lip surface 7 and uneven flow rate. Prevents the occurrence of defects such as uneven color and running out of liquid. This is because the coating liquid discharged from the discharge port 5 is held and stored in the groove 8 by capillary action from the upstream side of the groove 8 during application, that is, while the slit coater die 1 is running, and the rear lip surface 7 is considered to prevent liquid breakage and the like by being extruded on the downstream side of the groove 8.

  Further, the cross-sectional shape of the groove 8 is set to a shape that does not cause a dead space such as a stay portion during convection, and is formed by an arc or an elliptical arc, or a circular or elliptical arc and a straight line or a curve are smoothly formed A connected shape is preferred. In this way, it is considered that a part or all of the cross-sectional shape of the groove 8 is an arc or an elliptical arc, thereby generating a vortex along the arc surface in the groove 8, which also contributes to prevention of liquid breakage. Conceivable. Thus, the meniscus shape is always more stable, and a more stable coating liquid film can be formed even at high speeds. FIG. 4 shows another embodiment of the cross-sectional shape of the groove 8, FIG. 4 (a) is a semi-tearing shape and an arc is formed on the downstream side, and FIG. 4 (b) is a streamlined type and the arc is on the upstream side. Is formed.

Further, as described above, in order to keep the meniscus shape more stable, it is preferable that the longitudinal width of the rear lip surface 7 is short. In addition, it is preferable to make the meniscus shape as small as possible for the purpose of reducing the amount of coating solution used. If the vertical width of the rear lip surface 7 is shortened, the meniscus shape can be reduced. From this point of view, it is preferable that the longitudinal width of the rear lip surface 7, that is, the rear lip surface length _tr is short, and further, as shown in FIG. 5, a plurality of grooves 8 running in the width direction of the rear lip surface 7 are provided. Is preferred. In addition, as shown in FIG.5 (b), the longitudinal cross-sectional area of the groove | channel 8 provided with two or more may not be all the same.

Furthermore, when comparing the front lip surface length t _f and the rear lip surface length t _r of the slit coater die, in order to avoid the time of application, in particular in the coating start, the to extra supply coating liquid to the rear , the vertical width or the front lip surface length t _f of the front lip surface is preferably less than the vertical width or the rear lip surface of the rear lip surface length t _r.

Further, as described above, the rear lip surface 7 has an effect of forming the coating liquid film 10 more uniformly. Therefore, when comparing the gap g _f between the front lip surface 6 and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 and the substrate 9 to be coated, the gap g between the rear lip surface 7 and the substrate 9 to be coated. against gap g _f of _r is the front lip surface 6 and the substrate to be coated 9, is preferably equal to or narrow gap. In particular, since the action of leveling the meniscus formed on the front lip surface 6 with the rear lip surface 7 is large, as shown in FIGS. 3, 5 (c) and 5 (d), a narrower gap is more preferable. preferable.

  The relationship of d / 2 ≦ W ≦ 60d and d / 4 ≦ H ≦ 30d among the vertical width (W) of the groove 8, the depth (H) of the groove, and the vertical width (d) of the slit. (See FIGS. 3 and 4A). This is because when W <d / 2 or H <d / 4, it is difficult to process, and even if it can be processed, the effect of the high-speed coating performance is small. This is because the lip surface becomes longer, the meniscus shape becomes larger, and the amount of the coating liquid used also increases. When H> 30d, depending on the width dimension (W) of the groove 8, a stagnant portion is generated and the coating liquid is used. This is because it causes deterioration.

  A comparative evaluation for confirming the usefulness of the implementation of the present invention was performed and will be described below.

  As a coating method, first, a pump for quantitatively supplying the coating liquid is installed, and the coating liquid is injected into the pump. The pipe connected to the pump is connected to a filter which is mainly used to remove impurities such as a coating liquid gel substance located downstream of the pump. Further, a slit coater die located downstream of the filter is connected by a pipe connected to the filter. By operating the pump, the coating liquid flows through the pipe and flows into the filter downstream of the pump. Further, the coating liquid flows from the filter through the pipe to the slit coater die and is applied onto the substrate to be coated placed on the surface plate. The slit coater die is fixed to a portion called a gate-like arm, and the arm travels on a surface plate, and forms a coating liquid film on the substrate to be coated. The slit coater die had an effective width of 1000 mm and the material used was heat-treated with SUS630. In addition, the area coated on the substrate to be coated was 1000 mm × 1100 mm, the total discharge amount was 60 cc, and the viscosity of the coating liquid was 10 mPa · s.

  In the examples and comparative examples of the present invention, the same apparatus and piping up to the slit coater die were used. That is, the difference in the shape in the slit coater die flow path, the difference in the shape of the lip tip, the difference in coating speed, and the difference in the amount of coating liquid used were evaluated.

Example 1
Example 1 is equivalent to the slit coater die shown in FIG. 2, and one semicircular groove 8 is formed on the rear lip surface 7, and the radius of the sectional shape of the groove 8 is 0.5 mm. Regarding the gap of the slit 4, the slit gap of the narrow gap due to the protrusion 4a was 0.1 mm, and the slit gap of other relatively wide gaps was 0.2 mm. Further, the gap g _f between the front lip surface 6 of the slit coater die and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 and the substrate 9 to be coated are 0.2 mm, respectively, and the length of the front lip surface t _f was 0.3 mm, and the rear lip surface length _tr was 3 mm. The coating speed was evaluated under two conditions of 100 mm / second and 200 mm / second.

Example 2
Example 2 is equivalent to the slit coater die shown in FIG. 5 (a), in which two semicircular grooves 8 are formed on the rear lip surface 7, and the radius of the sectional shape of the groove 8 is 0.3 mm. It was. Regarding the gap of the slit 4, the slit gap of the narrow gap due to the protrusion 4 a was 0.1 mm, and the slit gap of the other wide gap was 0.2 mm. Further, the gap g _f between the front lip surface 6 and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 and the substrate 9 to be coated are 0.2 mm, respectively, and the front lip surface length t _f is 0. .3mm, and the rear lip surface length t _r and 3mm. The coating speed was evaluated under two conditions of 100 mm / second and 200 mm / second.

Example 3
Example 3 is equivalent to the slit coater die shown in FIG. 5B, and two semicircular grooves 8 are formed on the rear lip surface 7, and the radius of the cross-sectional shape of the groove 8 is set to the discharge port 5. The thickness was set to 0.4 mm and 0.2 mm in order from the vicinity. Regarding the gap of the slit 4, the slit gap of the narrow gap due to the protrusion 4 a was 0.1 mm, and the slit gap of the other wide gap was 0.2 mm. Further, the gap g _f between the front lip surface 6 and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 and the substrate 9 to be coated are 0.2 mm, respectively, and the front lip surface length t _f is 0. .3mm, and the rear lip surface length t _r and 3mm. The coating speed was evaluated under two conditions of 100 mm / second and 200 mm / second.

Example 4
Example 4 has the same shape as the slit coater die shown in FIG. 5 (c). Two semicircular grooves 8 are formed on the rear lip surface 7, and the radius of the sectional shape of the groove 8 is 0.3 mm. It was. The slit 4 has a narrow gap of 0.1 mm due to the protrusion 4a, and the other wide gap has a slit gap of 0.2 mm. Further, the gap g _f between the front lip surface 6 and the substrate 9 to be coated is 0.3 mm, the gap g _r between the rear lip surface 7 and the substrate 9 to be coated is 0.2 mm, and the front lip surface length t _{f is set.} Was 0.3 mm, and the rear lip surface length _tr was 4 mm. The coating speed was evaluated under two conditions of 100 mm / second and 200 mm / second.

Comparative Example The comparative example has the same shape as the conventional slit coater die shown in FIG. 6, and has no groove on the rear lip surface. The gap of the slit 4 was 0.1 mm from the manifold connection part to the discharge port. Further, the gap g _f between the front lip surface 6 of the slit coater die and the substrate 9 to be coated and the gap g _r between the rear lip surface 7 of the slit coater die and the substrate 9 to be coated are 0.2 mm, respectively. the lip surface length t _f and the rear lip surface length t _r was 0.3mm, respectively. The coating speed was evaluated under two conditions of 100 mm / second and 200 mm / second.

<Evaluation details>
(Double-circle): The application | coating state is very favorable.
○: Application state is relatively good.
X: A lot of liquid running out phenomenon occurs and it is NG.

  As can be seen from Table 1, in any of Examples 1 to 4, when the coating speed was 100 mm / second, the meniscus shape of the coating solution was always stable even during coating, and the coating state was very high. Even when the coating speed was 200 mm / sec, the coating state was relatively good.

  In Comparative Example 1 with respect to Examples 1 to 4 described above, when the coating speed is 100 mm / second, the meniscus shape of the coating liquid becomes unstable during coating, and a partial liquid drainage phenomenon occurs and the coating is performed. It could not be applied to the entire surface of the substrate. Even when the coating speed was 200 mm / second, the same result as that obtained when the coating speed was 100 mm / second was obtained, and the level of the liquid breakage phenomenon was very poor.

It is a perspective view which shows the state currently apply | coated using the slit coater die which concerns on this invention. It is a longitudinal cross-sectional view which expands and shows the lip | rip part of the slit coater die of FIG. It is a longitudinal cross-sectional view which expands and shows the other lip shape of the slit coater die | dye which concerns on this invention. It is an expanded sectional view which shows the example of the cross-sectional shape of the groove | channel which is a component of this invention. It is an expanded sectional view which shows the variation of the cross-sectional shape of the groove | channel which is a component of this invention. It is a longitudinal cross-sectional view which expands and shows the lip | rip part of the conventional slit coater die.

Explanation of symbols

1: a slit coater die 2: supply port 3: Manifold 4: slit 4a: projecting 5: discharge port 6: front lip surface 7: Rear lip surface 8: Groove 9: the substrate to be coated 10: coating liquid t _f: Before part lip surface length t _r: rear lip surface length g _f: gap g _r of the front lip face and the substrate to be coated in a slit coater die: rear lip surface of the slit coater die and a gap between the substrate to be coated

Claims (4)

A slit coater die that applies a coating to a substrate to be coated by relative movement with the substrate to be coated while discharging a coating liquid from the slit while maintaining a predetermined distance from the substrate to be coated, and the slit that discharges the coating liquid. Of the bisected lip surfaces, a slit is characterized in that at least one groove extending along the length direction of the slit is formed on the rear lip surface located on the downstream side of the discharge flow of the coating liquid. Coater die. The slit coater die according to claim 1, wherein a projecting shape for narrowing an inner channel cross section of the slit is formed on an inner wall surface of the slit. Of the lip surfaces divided by the slit, the longitudinal width of the rear lip surface located on the downstream side of the discharge flow of the coating liquid is longer than the longitudinal width of the front lip surface located on the upstream side. The slit coater die according to claim 1 or 2. 2. The rear lip surface is formed on the same surface as the front lip surface, or is formed at a position where the distance from the substrate to be coated becomes smaller than the front lip surface. The slit coater die according to any one of?

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