JP2010181674A - Deposition method of alignment layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deposition method by which an alignment layer having a uniform film thickness can be deposited on a substrate by preventing a variation in the film thickness of a material liquid when the material liquid including an alignment layer material is applied to a substrate using a liquid droplet ejecting means. <P>SOLUTION: A first material liquid L1 having a low alignment layer material concentration is applied to a substrate P and a second material liquid L2 having a high alignment layer material concentration is applied to the substrate P to which the first material liquid L1 has been applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming an alignment film.

  Conventionally, a film forming method capable of forming a thin film with a uniform film thickness on the surface of a substrate is known. This film-forming method is a coating method in which a solution is sprayed from a plurality of nozzles arranged in parallel to a head, and the solution is applied to the surface of the substrate that is transported below the substrate. After the first application step of spraying and applying the solution from the nozzle and the first application step, the substrate is rotated by a predetermined angle, and the direction thereof is relative to the parallel arrangement direction of the nozzles. A rotating step of changing, and a second coating step of transporting the substrate again after the end of the rotating step and spray-coating the solution from the nozzle on the surface thereof (see, for example, Patent Document 1). .

  In addition, a step of ejecting the solution from each nozzle to the substrate with a dot, and a portion between a pair of dots that are first ejected from a pair of nozzles at a predetermined interval by relatively moving the head and the substrate in a predetermined direction A portion between a pair of dots first sprayed on the substrate at a predetermined interval is adjacent to a dot sprayed and applied last. There is disclosed a method of painting with a plurality of dots in an order without any reference (for example, see Patent Document 2).

  Further, in a solution coating method for applying a solution to a substrate by an inkjet method, a step of exciting a plate surface of the substrate on which the solution is applied, and an inkjet method of applying the solution to the excited plate surface of the substrate And a step of applying by the above (for example, see Patent Document 3).

JP 2005-193232 A JP-A-2005-721 JP 2004-255316 A

  However, in the conventional film forming method, in order to form an alignment film used in a liquid crystal device, when applying a relatively high viscosity liquid such as a solution in which polyimide is dissolved, the following problems are encountered. is there.

  In Patent Document 1 and Patent Document 2, as shown in FIG. 11A, the droplets ejected from the droplet ejection head 34 onto the substrate P are not sufficiently wetted and spread on the substrate P. There is a problem that the alignment film material liquid L is applied in a discontinuous manner in the form of dots, resulting in non-uniform film thickness of the alignment film.

  Further, since the applied material liquid L does not spread on the substrate P, for example, as shown in FIG. 11B, by using a line feed of the droplet discharge head 34 or a plurality of droplet discharge heads 34, A region X1 is generated in which droplets overlap and are disposed in a region X2 where the end 34e of the droplet discharge head 34 overlaps. Therefore, there is a problem that the film thickness of the material liquid L varies in the region X1 and streaky unevenness occurs in the alignment film.

  In Patent Document 3, droplets discharged onto a substrate spread out, but there is a problem that a substrate excitation process is required and a special apparatus for substrate excitation process such as a chamber is required.

  Therefore, the present invention can use a film forming apparatus for forming an alignment film by a droplet discharge means, and forms an alignment film having a uniform film thickness by spreading the discharged droplets on the substrate. The present invention provides a method for forming an alignment film that can be used.

  In order to solve the above-described problems, an alignment film forming method of the present invention includes an alignment film that forms an alignment film by applying a material liquid containing an alignment film material and a solvent onto a substrate using a droplet discharge unit. A first application step of applying a first material liquid on the substrate, and applying a second material liquid on the first material liquid applied on the substrate. And a concentration of the alignment film material in the first material liquid is lower than a concentration of the alignment film material in the second material liquid.

  By forming the film in this way, when the first material liquid is applied onto the substrate in the first application step, a part of the solvent contained in the first material liquid evaporates, and the substrate is solvent-borne. It becomes a state covered with steam. When a droplet of the second material liquid is ejected onto the substrate in this state, the droplet lands on the first material liquid applied on the substrate. Here, since the first material liquid has a lower concentration of the alignment film material in the material liquid than the second material liquid, the concentration of the alignment film material in the droplet of the second material liquid in contact with the first material liquid Will decline. That is, the viscosity of the second material liquid is lowered. Further, since the substrate is covered with the vapor of the solvent, drying of the second material liquid applied on the substrate is prevented. As a result, the liquid droplets that have landed on the substrate can be easily wetted and spread to form a film of a material liquid with a uniform film thickness, thereby preventing the occurrence of streaky irregularities and an alignment film with a uniform film thickness. Can be formed. In addition, a deposition apparatus that forms an alignment film by a droplet discharge unit can be used, and a chamber or the like is not necessary.

  In the alignment film forming method of the present invention, the total amount of the first material liquid discharged in the first application step is greater than the total amount of the second material liquid discharged in the second application step. Featuring few.

  By forming the film in this way, the thickness of the first material liquid is reduced, and the entire film is easily dried. Therefore, the entire film is uniformly dried. For this reason, an increase in the film thickness of the peripheral portion due to the movement of the alignment film material (so-called “smearing”) can be prevented.

  The alignment film forming method of the present invention is characterized in that the center positions of the discharged droplets are different in the first application step and the second application step.

  The alignment film forming method of the present invention is characterized in that the second application step is performed in a state where a predetermined amount of the solvent of the first material liquid applied on the substrate remains. Here, the predetermined amount refers to an amount by which the second material liquid L2 that has landed on the first material liquid L1 can easily spread.

  In the alignment film forming method of the present invention, the first application region to which the first material solution is applied in the first application step is the second material solution in the second application step. Is equal to or included in the second application area to be applied.

  By forming the film in this way, it is possible to prevent the second material liquid applied on the substrate in the second application step from spreading out to the outside of the second application region.

  Further, the film forming method of the present invention is characterized in that the droplet is applied onto the substrate by relatively scanning the droplet discharge means and the substrate.

  The film forming method of the present invention is characterized in that the droplet discharge means is a droplet discharge head group having a plurality of droplet discharge heads.

  By forming the film in this way, the time required for film formation can be shortened, and the dry state of the entire film can be made uniform.

  In the film forming method of the present invention, the length of the droplet discharge head group is longer than the maximum width in the direction intersecting the scanning direction of the second application region.

  By forming the film in this manner, the first coating process and the second coating process can be completed with one scan. Therefore, by using a plurality of heads, the time required for film formation can be shortened, and the dry state of the entire film can be made uniform.

  In the film forming method of the present invention, the material solution is a solution in which polyimide is dissolved.

The schematic diagram which shows schematic structure of the film-forming apparatus which concerns on embodiment of this invention. FIG. 3 is a cross-sectional view illustrating a configuration of a droplet discharge head according to an embodiment of the invention. FIG. 3 is a cross-sectional view of a main part of the droplet discharge head. The bottom view of the droplet discharge head. (A)-(c) is sectional drawing which shows a mode that a droplet is apply | coated on a board | substrate in a 1st application | coating process. The top view which shows the mode of the board | substrate which apply | coated the droplet in the 1st application | coating process. Sectional drawing which shows the mode of the board | substrate which apply | coated the droplet in the 2nd application | coating process. The top view which shows the mode of the board | substrate which apply | coated the droplet in the 2nd application | coating process. Sectional drawing which shows the mode of the board | substrate which apply | coated the droplet in the 2nd application | coating process. The top view which shows the mode of the board | substrate which apply | coated the droplet in the 1st application | coating process. (A) And (c) is sectional drawing which shows the film-forming process of the conventional alignment film.

  Next, embodiments of the present invention will be described with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size.

(Deposition system)
FIG. 1 is a schematic diagram showing a schematic configuration of a film forming apparatus 10 that forms a film on a substrate P by a droplet discharge method. As shown in FIG. 1, the film forming apparatus 10 includes a base 31, a substrate moving unit 32, a head moving unit 33, a droplet discharge head 34, a liquid supply unit 35, and a control device 40. Has been. A substrate moving means 32 and a head moving means 33 are installed on the base 31. The film forming apparatus 10 includes a cleaning unit (not shown) and a capping unit.

  The substrate moving means 32 has a guide rail 36 provided on the base 31 and arranged along the Y-axis direction. The substrate moving means 32 is configured to move the slider 37 along the guide rail 36 by, for example, a linear motor (not shown).

  A stage 39 is fixed on the slider 37, and this stage 39 is for positioning and holding the substrate P. That is, the stage 39 has a known suction holding means (not shown), and is configured to suck and hold the substrate P on the stage 39 by operating the suction holding means. The substrate P is accurately positioned and held at a predetermined position on the stage 39 by a positioning pin (not shown) of the stage 39, for example.

  The head moving means 33 includes a pair of mounts 33a and 33a standing on the rear side of the base 31 and a travel path 33b provided on the mounts 33a and 33a. The substrate moving means 32 is arranged along a direction orthogonal to the Y-axis direction. The travel path 33b includes a holding plate 33c passed between the gantry 33a and 33a and a pair of guide rails 33d and 33d provided on the holding plate 33c, and a liquid is provided in the length direction of the guide rails 33d and 33d. A carriage 42 on which the droplet discharge head 34 is mounted is movably held. The carriage 42 is configured to move on the guide rails 33d and 33d by operation of a linear motor (not shown) or the like, thereby moving the droplet discharge head 34 in the X-axis direction.

  Here, the carriage 42 is movable in the length direction of the guide rails 33d, 33d, that is, in the X-axis direction, for example, in units of 1 μm. Such movement of the carriage 42 is configured to be controllable by a control device 40 including a computer or the like.

  The control device 40 detects the position information of the droplet discharge head 34, that is, the position (X coordinate) of the droplet discharge head 34 on the guide rails 33d and 33d and the position of each nozzle (X coordinate) at that time. To remember.

  The droplet discharge head 34 is rotatably attached to the carriage 42 via an attachment portion 43. The mounting portion 43 is provided with a motor 44, and the droplet discharge head 34 has a support shaft (not shown) connected to the motor 44. Based on such a configuration, the droplet discharge head 34 is rotatable in the circumferential direction. Further, the motor 44 is also connected to the control device 40, so that the rotation of the droplet discharge head 34 in the circumferential direction is controlled by the control device 40.

  The liquid supply unit 35 supplies ink (material liquid) to the droplet discharge head 34. The material liquid supplied to the droplet discharge head 34 is a solution in which a material for an alignment film that regulates the alignment of liquid crystal molecules is dissolved in a solvent. For example, polyimide is used as a material for the alignment film, and an organic solvent such as butyl cellosolve can be used as a solvent capable of dissolving the alignment film material.

  The liquid supply unit 35 includes a liquid supply container 45A filled with the first material liquid L1 having a low solid content concentration of the alignment film material, and a second material liquid L2 having a high solid content concentration of the alignment film material. A liquid supply container 45B filled with liquid, a liquid supply tube 46A for sending the first material liquid L1 from the liquid supply container 45A and the liquid supply container 45B to the droplet discharge head 34, and a second material liquid L2. And a liquid supply tube 46B for feeding.

FIG. 2 is a cross-sectional view illustrating the configuration of the droplet discharge head 34, and FIG. 3 is a cross-sectional view of the main part of the droplet discharge head 34.
The droplet discharge head 34 in this embodiment includes an introduction needle unit 117, a head case 118, a flow path unit 119, and actuator units 120A and 120B as main components.

  Two liquid introduction needles 122A and 122B are mounted side by side on the upper surface of the introduction needle unit 117 with the filters 121A and 121B interposed therebetween. The sub tanks 102A and 102B are attached to the liquid introduction needles 122A and 122B, respectively. In addition, liquid introduction paths 123A and 123B corresponding to the liquid introduction needles 122A and 122B are formed inside the introduction needle unit 117, respectively.

  The upper ends of the liquid introduction paths 123A and 123B communicate with the liquid introduction needles 122A and 122B via the filters 121A and 121B, and the lower ends communicate with case flow paths 125A and 125B formed inside the head case 118 via the packing 124. To do.

  The filters 121A and 121B are arranged to remove foreign substances contained in the first material liquid L1 and the second material liquid L2, and the material thereof is, for example, stainless steel and is formed in a mesh shape. Yes.

  The sub tanks 102A and 102B are molded from a resin material such as polypropylene. The sub tanks 102A and 102B are formed with recesses to be the liquid chambers 127A and 127B, and the elastic chambers 126A and 126B are attached to the opening surfaces of the recesses to partition the liquid chambers 127A and 127B.

  In addition, needle connecting portions 128A and 128B into which the liquid introduction needles 122A and 122B are inserted project downward from the sub tanks 102A and 102B. The liquid chambers 127A and 127B in the sub tanks 102A and 102B have a mortar shape with a shallow bottom. The upstream openings of the connection flow paths 129A and 129B communicating with the needle connecting portions 128A and 128B face the positions slightly below the vertical center on the side surfaces of the liquid chambers 127A and 127B. Are attached with tank part filters 130A and 130B for filtering the first material liquid L1 and the second material liquid L2, respectively.

  Seal members 131A and 131B into which the liquid introduction needles 122A and 122B are liquid-tightly fitted are fitted in the internal spaces of the needle connection portions 128A and 128B. A liquid supply tube 46A and a liquid supply tube 46B are connected to the sub tanks 102A and 102B, respectively. The liquid supply tube 46A supplies the first material liquid L1 stored in the liquid supply container 45A of the liquid supply unit 35. The liquid supply tube 46 </ b> B supplies the second material liquid L <b> 2 stored in the liquid supply container 45 </ b> B of the liquid supply unit 35. Accordingly, the first material liquid L1 and the second material liquid L2 that have passed through the liquid supply tube 46A and the liquid supply tube 46B flow into the liquid chamber 127A and the liquid chamber 127B, respectively.

  The elastic sheets 126A and 126B can be deformed in a direction in which the liquid chambers 127A and 127B are contracted and expanded. The pressure fluctuations of the first material liquid L1 and the second material liquid L2 are absorbed by the damper function due to the deformation of the elastic sheets 126A and 126B. That is, the sub tanks 102A and 102B function as pressure dampers by the action of the elastic sheets 126A and 126B. Accordingly, the first material liquid L1 and the second material liquid L2 are supplied to the droplet discharge head 34 side in a state where pressure fluctuation is absorbed in the sub tanks 102A and 102B.

  The head case 118 is a synthetic resin hollow box-like member, and a flow path unit 119 is joined to the lower end surface via an adhesive, and the actuator units 120A, 137B are formed in the housing empty portions 137A, 137B formed inside. 120B is accommodated, and the introduction needle unit 117 is attached with the packing 124 interposed on the upper end surface opposite to the flow path unit 119 side.

  Inside the head case 118, case flow paths 125A and 125B are provided through the height direction. The upper ends of the case flow paths 125A and 125B communicate with the liquid introduction paths 123A and 123B of the introduction needle unit 117 through the packing 124, respectively.

  The lower ends of the case flow paths 125A and 125B communicate with the common liquid chamber 144A and the common liquid chamber 144B in the flow path unit 119. Therefore, the first material liquid L1 and the second material liquid L2 introduced from the liquid introduction needles 122A and 122B are common liquid chamber 144A and common liquid chamber 144B through the liquid introduction paths 123A and 123B and the case flow paths 125A and 125B. Supplied to each side.

  As shown in FIG. 3, the actuator units 120A and 120B accommodated in the accommodating empty portions 137A and 137B of the head case 118 include a plurality of piezoelectric vibrators 138A and 138B arranged in a comb shape, and the piezoelectric vibrations. The fixed plates 139A and 139B to which the children 138A and 138B are joined, and flexible cables 140A and 140B as wiring members for supplying a drive signal from the control device 40 to the piezoelectric vibrators 138A and 138B, are configured. Each piezoelectric vibrator 138A, 138B has a fixed end portion joined to the fixed plates 139A, 139B, and a free end portion protruding outward from the front end surfaces of the fixed plates 139A, 139B. That is, the piezoelectric vibrators 138A and 138B are mounted on the fixing plates 139A and 139B in a so-called cantilever state.

  The fixing plates 139A and 139B that support the piezoelectric vibrators 138A and 138B are made of, for example, stainless steel having a thickness of about 1 mm. The actuator units 120A and 120B are housed and fixed in the housing cavities 137A and 137B by bonding the back surfaces of the fixing plates 139A and 139B to the inner wall surface of the case that partitions the housing cavities 137A and 137B, respectively. .

  The flow path unit 119 is manufactured by joining and integrating with an adhesive in a state where the flow path unit constituent members including the vibration plate 141, the flow path substrate 142, and the nozzle substrate 143 are stacked. These are a series of first liquid flow paths from the common liquid chamber 144A through the liquid supply port 145A and the pressure chamber 146A to the nozzle 147A, and from the common liquid chamber 144B through the liquid supply port 145B and the pressure chamber 146B to the nozzle 147B. This is a member that forms a series of second liquid flow paths up to.

  The pressure chambers 146A and 146B are formed as elongated chambers in a direction orthogonal to the direction in which the nozzles 147A and 147B are arranged.

  The common liquid chamber 144A and the common liquid chamber 144B communicate with the case flow paths 125A and 125B, and the first material liquid L1 and the second material liquid L2 are introduced from the liquid introduction needles 122A and 122B, respectively. It is a room. The first material liquid L1 and the second material liquid L2 introduced into the common liquid chamber 144A and the common liquid chamber 144B are distributed and supplied to the pressure chambers 146A and 146B through the liquid supply port 145A and the liquid supply port 145B, respectively. Is done.

  As shown in FIG. 4, the nozzle substrate 143 disposed at the bottom of the flow path unit 119 is a thin metal plate in which a plurality of nozzles 147A and 147B are opened in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. It is a board material. The nozzle substrate 143 of the present embodiment is made of a stainless steel plate, and in this embodiment, a plurality of rows of nozzles 147A and nozzles 147B are formed corresponding to the sub tank 102A and the sub tank 102B, respectively (FIG. 4 is not shown).

  The flow path substrate 142 disposed between the nozzle substrate 143 and the vibration plate 141 is a flow path portion that becomes the first liquid flow path and the second liquid flow path, specifically, the common liquid chamber 144A, the common liquid chamber. 144B is a plate-like member in which empty portions that become the liquid supply port 145A, the liquid supply port 145B, and the pressure chambers 146A and 146B are partitioned.

  In the present embodiment, the flow path substrate 142 is manufactured by performing an anisotropic etching process on a Si wafer which is a base material having crystallinity. The vibration plate 141 is a composite plate material having a double structure in which an elastic film is laminated on a metal support plate such as stainless steel. At portions corresponding to the pressure chambers 146A and 146B of the vibration plate 141, island portions 148A and 148B to which the tip surfaces of the piezoelectric vibrators 138A and 138B are joined are formed by removing the support plate in an annular shape by etching or the like. This part functions as a diaphragm part. That is, the diaphragm 141 is configured such that the elastic film around the island portions 148A and 148B is elastically deformed in accordance with the operation of the piezoelectric vibrators 138A and 138B. The vibration plate 141 also seals one opening surface of the flow path substrate 142 and functions as the compliance portions 149A and 149B. As for the portions corresponding to the compliance portions 149A and 149B, the support plate is removed by etching or the like in the same manner as the diaphragm portion to make only the elastic film.

  In the droplet discharge head 34, when a drive signal is supplied to the piezoelectric vibrators 138A and 138B through the flexible cables 140A and 140B, the piezoelectric vibrators 138A and 138B expand and contract in the longitudinal direction of the element. The island portions 148A and 148B move in a direction close to or away from the pressure chambers 146A and 146B. As a result, the volumes of the pressure chambers 146A and 146B change, and pressure fluctuations occur in the first material liquid L1 and the second material liquid L2 in the pressure chambers 146A and 146B. Due to this pressure fluctuation, the first material liquid L1 and the second material liquid L2 that are in the form of droplets are ejected from the nozzles 147A and 147B, respectively.

(Method for forming alignment film)
Next, the film forming method of this embodiment will be described. In the present embodiment, an element substrate of a liquid crystal device in which an insulating film, a TFT, an electrode, a wiring, and the like are formed on a transparent substrate as a substrate P is prepared, and the above-described material liquid is applied onto the substrate P using the film forming apparatus 10. A method for forming an alignment film by discharging will be described.

  First, as shown in FIG. 1, the substrate P is positioned on the stage 39 by positioning pins, and is sucked and held by the suction holding means. As a result, the substrate P is held in a state of being accurately positioned on the stage 39.

  Next, the first application process will be described. The droplet discharge head 34 is moved by the substrate moving means 32 and the head moving means 33 and the motor 44 of the mounting portion 43 is operated to bring the droplet discharge head 34 into the initial position with respect to the substrate P as shown in FIG. Deploy.

  In the first application step, the first material liquid L1 is applied to the first application region A included in the second application region B as shown in FIG. In this embodiment, a solution in which polyimide is dissolved in N-methyl-2-pyrrolidone (NMP) so as to have a solid content concentration of 1% is used as the first material liquid. Here, when a solvent capable of dissolving the alignment film material is used as the first material liquid L1, when the second material liquid L2 is applied, the first material liquid L1 and the second material liquid L2 Therefore, the solid content is not uniformly dispersed, resulting in uneven density. Further, when the solid content concentration is high, when applied on the substrate P, the film does not easily spread and the film thickness becomes uneven. For this reason, it is desirable that the solid content concentration of the first material liquid is in the range of 0.5% to 1.5%.

  The first application area A where the first material liquid L1 is applied is an area smaller than the second application area B by 0.5 mm in both the X-axis direction and the Y-axis direction. If it does in this way, it can prevent that the material liquid apply | coated on the board | substrate P in a 2nd application | coating process spreads outside the 2nd application | coating area | region B.

  Next, the stage 39 is moved in the positive Y-axis direction by the substrate moving means 32, so that the droplet discharge head 34 is moved in the negative Y-axis direction relative to the substrate P, while the droplet discharge head 34 is moved. As shown in FIG. 5A, the first material liquid L1 is ejected and applied as droplets from the nozzle 147 onto the substrate P. Here, the distance C between the centers of the droplets of the first material liquid L1 is set so that the droplets of the first material liquid L1 land on the substrate P as shown in FIG. 5B, and FIG. As shown in FIG. 5, by adjusting the droplet diameter D so as to be substantially equal to that when expanded on the substrate P, a very thin film is formed so that adjacent droplets are barely connected to each other. By forming the film in this way, the thickness of the first material liquid is reduced, and the entire film is easily dried. Therefore, the entire film is uniformly dried. For this reason, an increase in the film thickness of the peripheral portion due to the movement of the alignment film material (so-called “smearing”) can be prevented.

  The distance C between the droplet centers can be adjusted using a known technique. For example, the droplet center distance C can be adjusted by rotating the droplet discharge head 34 and adjusting the nozzle interval in the direction orthogonal to the scanning direction. Moreover, the distance C between droplet centers can also be adjusted by selectively using nozzles and changing the discharge interval.

  As shown in FIG. 4, after the first material liquid L1 is applied from the edge on the initial position side to the edge on the opposite side to the discharge start position, the liquid droplet discharge head 34 is moved in the positive X-axis direction by the head moving means 33. The stage 39 is moved in the negative direction of the Y axis by the substrate moving means 32. Then, the first material liquid L1 is ejected and applied onto the substrate P from the nozzle 147 of the droplet ejection head 34 while moving the droplet ejection head 34 in the positive Y-axis direction relative to the substrate P. . In this manner, while repeating the line feed in the positive direction of the X axis at the outer edge of the first coating region A of the alignment film, the droplet discharge head 34 is reciprocated in the Y axis direction, and the first coating region is entirely covered with the first coating region A. The material liquid L1 is applied (first application process).

  When applied in this manner, as shown in FIG. 6, the first material liquid L1 is disposed on the substrate P to such an extent that the adjacent droplets are barely connected to each other, and is thinly applied. However, in this state, it is conceivable that a portion to which the first material liquid L1 is not applied as shown by the shaded portion in FIG. 6 remains. However, due to the surface tension of the droplets on the substrate, the droplets are connected to fill the gap, and a continuous film can be formed, and the first material liquid L1 is thinly applied.

  Then, the solvent of the first material liquid L1 evaporates on the substrate P to generate the vapor, and the substrate P is covered with the solvent vapor of the first material liquid L1.

  Next, the second application process will be described. The second application step is performed in a state where a predetermined amount of the solvent contained in the first material liquid L1 applied on the substrate P remains. Here, the predetermined amount refers to an amount by which the second material liquid L2 that has landed on the first material liquid L1 can easily spread.

  First, the droplet discharge head 34 is moved to the initial position in the second coating process. The initial position in the second coating step is shifted from the initial position in the first coating step in order to shift the center of the droplet applied in the first coating step from the center of the droplet applied in the second coating step. A fixed offset is set in a direction crossing the scanning direction. In general, since the central portion of the droplet is thicker than the outer edge portion, an alignment film having a more uniform thickness can be obtained by shifting the center of the droplet than when the central portions of the droplet overlap. .

  Next, the stage 39 is moved in the positive Y-axis direction by the substrate moving means 32, so that the droplet discharge head 34 is moved in the negative Y-axis direction relative to the substrate P, while the droplet discharge head 34 is moved. As shown in FIG. 7, the second material liquid L2 is ejected as droplets from the nozzle 147 onto the substrate P and applied to the second application region B. As the second material liquid L2, in this embodiment, a solution in which polyimide is dissolved in N-methyl-2-pyrrolidone so as to have a solid content concentration of 5% is used.

  As shown in FIG. 7, the total amount of liquid droplets ejected in the second application process is applied so as to be larger than the total amount of liquid droplets ejected in the first application process.

  Then, as shown in FIG. 8, the first material liquid applied on the substrate P from the nozzle 147 of the droplet discharge head 34 while moving the droplet discharge head 34 in the negative Y-axis direction with respect to the substrate P. A droplet of the second material liquid L2 is ejected and applied onto L1. Then, as in the first application step, the droplet discharge head 34 is reciprocated in the Y-axis direction while repeating the line feed in the X-axis positive direction at the outer edge of the second application region B, and the first application step is performed as shown in FIG. The second material liquid L2 is applied to the entire area of the second application region B (alignment film formation region) (second application step).

  At this time, as shown in FIG. 7, the film of the first material liquid L1 is applied on the substrate P with a uniform film thickness and is covered with the vapor of the solvent of the first material liquid L1. ing. Therefore, the droplet of the second material liquid L2 discharged in the second application process is prevented from drying after landing on the substrate P. In addition, since the first material liquid L1 has a lower solid content concentration of polyimide than the second material liquid L2, when the droplet of the second material liquid comes into contact with the first material liquid L1, the solid content of the liquid droplet The concentration decreases and the viscosity decreases. For this reason, as shown in FIG. 9, the droplets easily wet and spread in the region X1 where the droplets generated in the region X2 through which the droplet discharge heads 34 repeatedly pass are arranged to have a uniform film thickness. An alignment film is formed.

  Next, the alignment film is formed on the substrate P by, for example, heating and drying the first material liquid L1 and the second material liquid L2 applied on the substrate P. In this embodiment, the film is temporarily dried on a hot plate at 80 ° C. for 10 minutes to remove the solvent, and further subjected to main baking for 60 minutes in a clean oven at 220 ° C.

  As described above, according to this embodiment, the first material liquid L1 having a low solid content concentration is applied onto the substrate P, and the second material liquid L2 having a high solid content concentration is discharged thereon. Thus, even in the region X1 where the droplets are overlapped, the droplets of the second material liquid L2 discharged on the substrate P can be easily spread and prevented from being dried, and the first X in the region X1 is prevented. The film thickness of the second material liquid L2 can be prevented from becoming large, and the film thickness can be made uniform. Therefore, the thickness of the alignment film can be made uniform.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the film forming apparatus including a single droplet discharge head has been described. However, a film forming apparatus including a plurality of droplet discharge heads may be used. When using such a film forming apparatus, the maximum width that can be applied in one scan is the sum of the dimension in the X-axis direction of the formation region and the offset amount in the X-axis direction of the initial position in the second application step. Larger is preferred. By doing in this way, the 1st application process and the 2nd application process can each be completed by one scan. Therefore, the time required for film formation can be shortened, and the dry state of the entire film can be made uniform.

  In the present embodiment, the first application region is the region in the second application region, but the first application region may be the same region as the second application region. Moreover, the magnitude | size of a 1st application area | region can be set suitably.

  In addition, since the viscosity of the second material liquid L2 discharged onto the substrate P can be reduced by bringing the second material liquid L2 into contact with the first material liquid L1, the concentration of the alignment film material in the second material liquid is increased. The viscosity of the second material liquid L2 can be increased. Thereby, the movement of the alignment film material to the peripheral edge during the drying of the second material liquid L2 can be prevented, and an increase in the film thickness (so-called soaking) of the peripheral edge of the alignment film can be prevented. Moreover, a solvent will not be specifically limited if the material of alignment film can be melt | dissolved.

  Needless to say, the film forming method of the present invention can also be applied to film formation of films other than alignment films.

  34 ... droplet ejection head, 34e ... end, A ... first coating region, B ... second coating region, C ... distance between droplet centers, D ... droplet diameter, L1 ... first material liquid, L2 ... second material liquid, P ... substrate, X1 ... region where droplets are placed overlapping each other, X2 ... region through which the head repeatedly passes.

Claims (9)

A method for forming an alignment film in which an alignment film is formed by applying a material liquid containing an alignment film material and a solvent onto a substrate using a droplet discharge means,
A first application step of applying a first material liquid on the substrate;
A second application step of applying a second material liquid on the first material liquid applied on the substrate;
A method for forming an alignment film, wherein the concentration of the alignment film material in the first material liquid is lower than the concentration of the alignment film material in the second material liquid.   2. The total amount of the first material liquid discharged in the first application step is smaller than the total amount of the second material liquid discharged in the second application step. The method for forming the alignment film.   The method for forming an alignment film according to claim 1, wherein a central position of a droplet to be discharged is different between the first application step and the second application step.   4. The second application step is performed in a state where a predetermined amount of the solvent of the first material liquid applied on the substrate remains. 5. The method for forming the alignment film.   The first application area where the first material liquid is applied in the first application process is equal to the second application area where the second material liquid is applied in the second application process, or The method for forming an alignment film according to claim 1, wherein the alignment film is included.   6. The alignment film according to claim 1, wherein the droplet is applied to the substrate by relatively scanning the droplet discharge unit and the substrate. Method.   The alignment film forming method according to claim 6, wherein the droplet discharge means is a droplet discharge head group having a plurality of droplet discharge heads.   8. The method of forming an alignment film according to claim 7, wherein a length of the droplet discharge head group is longer than a maximum width in a direction intersecting a scanning direction of the second application region.   9. The method for forming an alignment film according to claim 1, wherein the material solution is a solution in which polyimide is dissolved.

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