JP2010184196A - Method of forming thin film and method of forming oriented film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a thin film which can form a thin film stably almost free from coating irregularities by applying a liquid to the surface of a substrate, as well as a method of forming an oriented film. <P>SOLUTION: This method of forming the thin film comprises a first coating process to discharge a liquid containing a functional material from the nozzle through relatively scanning a mother substrate 110, with a discharge head 50 having a nozzle array 52c composed of a plurality of nozzles, and thereby coat at least a film-forming region AE on the mother substrate 110. Further, the method comprises: a first drying process to dry the applied liquid; a second coating process to discharge the liquid from the nozzle and coat at least the film-forming region AE therewith through relatively scanning the mother substrate 110, with the discharge head 50 in a different scanning direction from the scanning direction in the first coating process; and a second drying process to dry the applied liquid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming a thin film and a method for forming an alignment film, in which a thin film is formed by applying a liquid to the surface of a substrate.

  As a method for forming a thin film by applying a liquid, a method for forming a multilayer film including at least a first film and a second film formed on the first film is known (Patent Document 1).

  In the multilayer film forming method, the first liquid material is applied onto the substrate to form the first coating film, and the solvent is removed from the first coating film. A multilayer film composed of a first film and a second film laminated is formed by applying a liquid material and heating and / or performing an optical treatment. Further, as a method for applying the first liquid material, a droplet discharge method using an ink jet head is employed, and it is mentioned that patterning of the first film is easier than photolithography.

  However, when a liquid material is applied using an inkjet head having a plurality of nozzles, the liquid material discharged from the nozzles arranged at intervals is spread on the substrate, but the viscosity of the liquid material and the surface of the substrate Due to the wettability, there is a possibility that the coating unevenness in which the liquid material does not spread in the portion corresponding to the space between the nozzles may occur.

  In order to improve such coating unevenness, in the film forming method of Patent Document 2 and the film forming method of Patent Document 3, the application direction when applying the liquid material by relatively moving the substrate and the inkjet head is changed. A method of changing and repainting is disclosed. In addition, a method for forming an alignment film is disclosed as an example to which this method is applied.

JP 2005-235852 A JP 2005-118633 A JP 2005-296854 A

However, in the method of Patent Document 2 or Patent Document 3, since the liquid film obtained by being applied almost continuously is dried to form a film, the liquid film is formed at the periphery of the film forming region where the liquid material is applied. There is a problem that the blotting that occurs with the drying of the water becomes conspicuous.
In addition, it is possible to improve application unevenness in which the liquid material does not spread partially, but it has been difficult to improve subtle application unevenness due to variations in the discharge amount of the liquid material between the nozzles.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] In the thin film forming method of this application example, a nozzle is scanned relative to a substrate, and a liquid material containing a functional material is discharged from the nozzle to at least a film formation region on the substrate. A first application step of applying, a first drying step of drying the applied liquid material, and scanning the substrate and the nozzle relatively in a different scanning direction with respect to the scanning direction in the first application step. And a second application step of discharging the liquid material from the nozzle and applying it to at least the film forming region, and a second drying step of drying the applied liquid material.

  According to this method, since the scanning direction of the substrate and the nozzle is different in the first coating step and the second coating step, uneven coating due to the wettability of the liquid material discharged from the nozzle on the substrate is reduced. be able to. In addition, since the first drying process is performed in the middle of the process, the number of drying processes is increased as compared with the case where the first coating process and the second coating process are continuously performed. Since the amount is small, it is possible to reduce the oozing-up state generated at the peripheral edge of the region where the liquid material is applied by drying. That is, after drying, a thin film made of a functional material with little coating unevenness can be formed.

Application Example 2 In the thin film forming method according to the application example described above, it is preferable that a first surface treatment step of making at least the film formation region lyophilic is provided before the first coating step.
According to this method, since the wettability in the film forming region is improved in the first surface treatment step, the coating unevenness due to the wettability on the substrate in the first coating step is further reduced. In addition, since the leveling property of the applied liquid material is improved, it is possible to improve unevenness in application due to variations in the discharge amount of the liquid material discharged from the nozzles.

Application Example 3 In the thin film forming method according to the application example described above, it is preferable that a second surface treatment step of making at least the film formation region lyophilic is provided before the second coating step.
According to this method, even if the wettability of the surface of the thin film obtained after the first drying step is reduced, the wettability is improved by performing the second surface treatment step, and uneven coating occurs after the second drying step. A small number of thin films can be formed.

Application Example 4 In the thin film forming method according to the application example described above, the liquid material is discharged using a discharge head having a plurality of the nozzles in at least one of the first coating step and the second coating step. It is characterized by that.
According to this method, it is possible to improve coating unevenness due to variations in the discharge amount of the liquid material between the nozzles of the discharge head.

Application Example 5 In the method for forming a thin film according to the application example, the liquid material containing different types of the functional material may be applied in the first application step and the second application step.
According to this method, a multi-layered thin film made of different types of functional materials can be formed with little coating unevenness.

Application Example 6 The alignment film forming method of this application example uses the thin film forming method of the above application example, and the liquid containing the alignment film forming material is discharged from the nozzle to align the film in the film forming region. A film is formed.
According to this method, it is possible to form an alignment film with less coating unevenness due to wettability on the substrate, oozing at the time of drying, and the like. Further, when a liquid crystal device is manufactured using a substrate including such an alignment film, for example, a liquid crystal device having excellent display quality can be manufactured with little alignment unevenness due to uneven coating of the alignment film. .

(A) is a schematic plan view which shows the structure of a liquid crystal device, The same figure (b) is the schematic sectional drawing cut | disconnected by the H-H 'line | wire of (a). The schematic plan view which shows a mother board | substrate. The schematic perspective view which shows the structure of a droplet discharge apparatus. (A) is a schematic perspective view which shows the structure of a discharge head, (b) is a schematic plan view which shows arrangement | positioning of the several nozzle in a nozzle surface. The flowchart which shows the formation method of alignment film. The schematic sectional drawing which shows the formation method of alignment film. (A) And (b) is the schematic explaining the scanning method. (A)-(c) Schematic explaining the generation | occurrence | production state of oozing. (A) And (b) is the schematic which shows the formation method of the thin film of the modification 5. FIG. FIG. 10 is a schematic cross-sectional view illustrating a method for forming a thin film according to Modification 6.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced so that the part to be described can be recognized.

<Liquid crystal device>
First, a liquid crystal device as an electro-optical device to which the thin film forming method of this embodiment can be applied will be described with reference to FIGS. 1A is a schematic plan view showing the configuration of the liquid crystal device, FIG. 1B is a schematic cross-sectional view taken along line HH ′ of FIG. 1A, and FIG. 2 is a schematic plan view showing a mother substrate. .

  As shown in FIGS. 1A and 1B, the liquid crystal device 100 is sandwiched between the element substrate 10 and the counter substrate 20 as a pair of substrates arranged opposite to each other, and the element substrate 10 and the counter substrate 20. And a liquid crystal layer 40. The element substrate 10 and the counter substrate 20 are substrates such as transparent quartz, for example, and are bonded together by a sealing material 42 made of, for example, a thermosetting or ultraviolet curable adhesive.

  The liquid crystal device 100 includes a plurality of pixels 103 arranged in a matrix in the display area 10a. On the element substrate 10, the pixel 103 constituting the pixel 103, for example, a transparent electrode such as ITO (Indium Tin Oxide), and a thin film transistor (TFT) as a switching element for driving and controlling the pixel electrode 9 are provided. 30 is provided. In addition, an alignment film 16 made of, for example, a polyimide resin is provided which covers the pixel electrodes 9 and the like and is subjected to an alignment process such as rubbing.

  On the side of the counter substrate 20 facing the liquid crystal layer 40, the counter electrode 21 made of a transparent electrode such as ITO, for example, and the counter electrode 21 covering the counter electrode 21 and subjected to an alignment treatment such as rubbing are applied on the almost entire surface. An alignment film 22 is provided.

  The counter substrate 20 includes a light-shielding film 23 that partitions the pixels 103 in a lattice pattern below the counter electrode 21 (upward in the drawing) toward the liquid crystal layer 40, and a light-shielding film disposed in the periphery of the display region 10a. 24 is provided. For the light shielding films 23 and 24, for example, a light shielding metal such as Cr or an inorganic compound such as a metal oxide or a light shielding organic compound is used.

  The sealing material 42 that joins the element substrate 10 and the counter substrate 20 has an injection port 108 in which a part of a side portion provided in a frame shape is missing. Liquid crystal is injected into the gap between the element substrate 10 and the counter substrate 20 from the injection port 108 and sealed with a sealing material 109.

The element substrate 10 is slightly larger than the counter substrate 20, and a data line driving circuit 101 and a plurality of external connection terminals 102 are provided on one side protruding from the counter substrate 20.
Inside the sealing material 42 of the element substrate 10, a pair of scanning line driving circuits 104 and a wiring 105 connecting the display area 10 a are provided. The light shielding film 24 of the counter substrate 20 is provided so as to overlap the scanning line driving circuit 104 in a plan view.

  Between the element substrate 10 and the counter substrate 20, vertical conduction members 106 are arranged at four corners of the sealing material 42, and vertical conduction terminals 107 are also arranged corresponding to the vertical conduction members 106. Thus, the counter electrode 21 on the counter substrate 20 side is electrically guided to the element substrate 10 side, and is connected to a designated terminal among the plurality of external connection terminals 102.

  In the liquid crystal device 100, the alignment films 16 and 22 are formed by an alignment film forming method to which a thin film forming method of the present embodiment described later is applied. As will be described in detail later, the liquid material containing the alignment film forming material is discharged from the nozzles of the discharge head onto the substrate surface, and the applied liquid material is dried.

  As a method for manufacturing the liquid crystal device 100, for example, a plurality of element substrates 10 and mother substrates each provided with an opposing substrate 20 are bonded to each other, and liquid crystal is injected and sealed between the mother substrates. A method of taking out the individual liquid crystal device 100 by cutting at the position of the above.

  FIG. 2 shows a mother substrate 110 on which a plurality of element substrates 10 are provided. The mother substrate 110 is, for example, a quartz substrate having a wafer shape of 8 inches and a thickness of 1.2 mm. The quadrangular (rectangular) element substrate 10 is applied to the surface of the mother substrate 110 in a matrix. One element substrate 10 has a diagonal length of about 1 inch. In this case, the number of impositions is 40. Under such design conditions, the pixel electrode 9 and the TFT 30, the data line driving circuit 101, the scanning line driving circuit 104, and the wiring connecting these are formed on the surface of the mother substrate 110. Further, the alignment film 16 covering these components is provided in a film formation region AE set corresponding to each element substrate 10.

<Droplet ejection device>
Next, a droplet discharge device capable of discharging and drawing a liquid as droplets on a work will be described with reference to FIGS. 3 is a schematic perspective view showing the configuration of the droplet discharge device, FIG. 4A is a schematic perspective view showing the structure of the discharge head, and FIG. 3B is a schematic plan view showing the arrangement of a plurality of nozzles on the nozzle surface. It is.

  As shown in FIG. 3, the droplet discharge device 200 discharges a liquid material as droplets onto a workpiece W as an object to be discharged, and forms a coating film made of the liquid material. A stage 204 on which the workpiece W is placed and a head unit 201 on which a plurality of ejection heads 50 (see FIG. 4) for ejecting a liquid material as droplets onto the placed workpiece W are mounted.

  An X-direction guide shaft 202 for driving the head unit 201 in the sub-scanning direction (X direction) and an X-direction drive motor 203 that rotates the X-direction guide shaft 202 are provided. In addition, a Y-direction guide shaft 205 for guiding the stage 204 in the main scanning direction (Y direction) orthogonal to the sub-scanning direction, and a Y-direction drive motor 206 that rotates by engaging with the Y-direction guide shaft 205. It has. The X-direction guide shaft 202 and the Y-direction guide shaft 205 have a base 207 disposed in the upper part, and a control device 208 is provided in the lower part of the base 207.

  Further, in order to clean (recovery) the plurality of ejection heads 50 of the head unit 201, the cleaning mechanism 209 that moves along the Y-direction guide shaft 205 and the ejected liquid material are heated to evaporate and dry the solvent. Heater 211 is provided. The cleaning mechanism 209 has a Y-direction drive motor 210 that rotates by engaging with the Y-direction guide shaft 205.

  The stage 204 has a structure that can fix the work W by vacuum suction at the center of the placement surface. Moreover, the structure (illustration omitted) which can rotate the workpiece | work W to (theta) direction centering | focusing on the said center in the surface parallel to a mounting surface is provided.

  The head unit 201 includes a discharge head 50 (see FIG. 4) that applies a liquid material to the workpiece W. Then, the liquid material can be discharged by the discharge head 50 in accordance with a discharge control signal supplied from the control device 208.

  The X-direction drive motor 203 is not limited to this, but is a stepping motor, for example. When a drive pulse signal is supplied from the control device 208, the X-direction guide shaft 202 is rotated and the X-direction guide shaft 202 is rotated. The head unit 201 engaged with is moved in the X direction.

  Similarly, the Y-direction drive motors 206 and 210 are not limited thereto, but are, for example, stepping motors. When a drive pulse signal is supplied from the control device 208, the Y-direction drive motors 206 and 210 are engaged with the Y-direction guide shaft 205. The stage 204 that rotates and moves the stage 204 including the Y-direction drive motors 206 and 210 and the cleaning mechanism 209 in the Y direction.

  When cleaning the ejection head 50, the cleaning mechanism 209 moves to a position facing the head unit 201, and adheres to the nozzle surface of the ejection head 50, and capping, suctioning the liquid material, and the like adhere to the nozzle surface. Wiping to wipe the nozzle surface, preliminary discharge for discharging the liquid material from all nozzles of the discharge head 50, or processing for receiving and discharging the liquid material that is no longer necessary. Details of the cleaning mechanism 209 are omitted.

  Although not limited to this, the heater 211 is means for heat-treating the workpiece W by, for example, lamp annealing, and heats the liquid material discharged onto the workpiece W to evaporate the solvent and convert it into a film. Heat treatment is performed. The control device 208 also controls turning on and off the power of the heater 211.

  In the coating operation of the droplet discharge device 200, a predetermined drive pulse signal is sent from the control device 208 to the X direction drive motor 203 and the Y direction drive motor 206, the head unit 201 is moved in the sub-scanning direction (X direction), and the stage 204 is moved. Relative movement in the main scanning direction (Y direction). During this relative movement, a control signal for ejection is supplied from the control device 208, and the liquid material is ejected as droplets from each ejection head 50 to a predetermined region of the workpiece W to perform coating.

As shown in FIG. 4A, the discharge head 50 has a so-called double structure, a liquid material introduction portion 53 having two connection needles 54, a head substrate 55 laminated on the introduction portion 53, and A head body 56 disposed on the head substrate 55 and having a liquid-in-head flow path formed therein.
The connection needle 54 is connected to a liquid material supply mechanism (not shown) via a pipe, and supplies the liquid material to the flow path in the head.
The head substrate 55 is provided with two connectors 58 connected to a head driving circuit (not shown) via a flexible flat cable (not shown).

  The head main body 56 includes a pressurizing unit 57 having a cavity made of a piezoelectric element, and a nozzle plate 51 in which two nozzle rows 52a and 52b are formed in parallel to each other on the nozzle surface 51a.

  As shown in FIG. 4B, in the two nozzle rows 52a and 52b, a plurality (180) of nozzles 52 are arranged at substantially equal intervals at a pitch P1, and the pitch P2 is shifted by half of the pitch P1. In this state, the nozzle plate 51 is disposed. In this case, the pitch P1 is approximately 141 μm. Accordingly, when viewed from a direction orthogonal to the nozzle row 52c formed of the two nozzle rows 52a and 52b, 360 nozzles 52 are arranged at a nozzle pitch of about 70.5 μm. In the following description, the interval between the nozzles 52 is the nozzle pitch P2. The diameter of the nozzle 52 is approximately 27 μm.

  In the ejection head 50, when a drive signal as an electric signal is applied to the piezoelectric element from the head drive circuit, the volume of the cavity of the pressurizing unit 57 is changed, and the liquid filled in the cavity is pressurized by the pumping action. Then, the liquid material can be discharged as droplets from the nozzle 52.

The driving means in the ejection head 50 is not limited to a piezoelectric element. An electromechanical conversion element that displaces a vibration plate as an actuator by electrostatic adsorption, or an electrothermal conversion element (thermal method) that heats a liquid material and discharges it as droplets from the nozzle 52 may be used.
Further, the number of nozzle rows 52c provided in the ejection head 50 is not limited to two, and may be one.

  In the droplet discharge device 200 including such a discharge head 50, discharge data for applying a liquid material to a desired region on the work W is input to the control device 208 from an external information processing device such as a host computer. The liquid material is ejected from the nozzle 52 as droplets based on the ejection data. The discharge data includes position data relating to the desired area on the workpiece W, control data defining discharge timing, and selection (ON) / non-selection (OFF) of the plurality of nozzles 52 in the main scanning of the discharge head 50 and the workpiece W. ) Nozzle data such as data and the number of droplet ejections are included.

<Method for forming thin film>
Next, a method for forming a thin film according to the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing a method for forming an alignment film, FIGS. 6A to 6F are schematic cross-sectional views showing the method for forming the alignment film, and FIGS. 7A and 7B are scanning methods for the ejection head relative to the substrate. FIG. 8A to FIG. 8C are schematic diagrams for explaining a state of occurrence of a blot. Hereinafter, an example in which the alignment film 16 is formed in the film formation region AE (see FIG. 2) of the mother substrate 110 will be described.

  As shown in FIG. 5, the alignment film forming method of the present embodiment includes a first surface treatment step (step S <b> 1) for making the surface of the mother substrate 110 lyophilic and a liquid material containing the alignment film forming material as the mother substrate 110. First coating step (step S2) for applying to the film forming region AE, a first drying step (step S3) for drying the applied liquid, and a second surface treatment for making the surface of the mother substrate 110 lyophilic again A step (step S4), a second application step (step S5) for applying a liquid material containing an alignment film forming material to the film formation region AE of the mother substrate 110, and a second drying step (step S5) for drying the applied liquid material. Step S6) and a firing step (Step S7).

In the first surface treatment step (step S1) in FIG. 5, as shown in FIG. 6A, the surface of the mother substrate 110 (the surface on the side where the pixel electrode 9 is provided) is treated with oxygen gas (O ₂ gas). Plasma processing is performed using a processing gas. Examples of the plasma processing method include a method in which the mother substrate 110 is disposed in a chamber, oxygen gas is introduced to generate plasma, and the surface of the mother substrate 110 is exposed to the generated O ₂ plasma. By exposing the surface of the mother substrate 110 to O ₂ plasma for about 1 minute, it can be made lyophilic with respect to the liquid material described later. Note that not only the surface of the mother substrate 110 can be made lyophilic by the plasma treatment, but also dirt (which affects the application of the liquid material) made of an organic substance adhering to the surface of the substrate is converted into carbon dioxide gas and water. It can be decomposed and removed. The processing gas is not limited to oxygen gas but may be air containing oxygen. Then, the process proceeds to step S2.

  In the first application process (step S2) of FIG. 5, the mother substrate 110 that has been subjected to surface treatment is placed on the stage 204 of the droplet discharge device 200 described above. Then, as shown in FIG. 6B, while the ejection head 50 is relatively scanned with respect to the mother substrate 110, the liquid material 70 containing the alignment film forming material is used as droplets from the nozzles 52 of the ejection head 50. Discharge to the film formation region AE. The discharged liquid 70 lands on the surface treated with the lyophilic solution and spreads wet.

  The liquid 70 includes an alignment film forming material and a solvent for dissolving the alignment film, and a known alignment film forming material can be used as the alignment film forming material. Examples include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polysiloxane, cellulose derivative, polyacetal, polystyrene derivative, poly-styrene-phenylmaleimide derivative, poly (meth) acrylate, and the like.

  As the solvent, an aprotic polar solvent or a phenol solvent is selected and used. Examples of the aprotic polar solvent include amide solvents, sulfoxide solvents, ether solvents, and nitrile solvents. Among these, from the viewpoints of solute solubility and drying properties, it is preferable to use an amide solvent or a sulfoxide solvent.

  Examples of amide solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N, N′-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexa Examples include methyl phosphoramide and tetramethylurea.

  Examples of the sulfoxide solvent include dimethyl sulfoxide and diethyl sulfoxide.

  In addition, examples of the phenol solvent include cresols such as o-cresol, m-cresol, and p-cresol, or xylenol such as o-xylenol, m-xylenol, and p-xylenol, phenol, or o-chlorophenol, m -Halogenated phenols such as chlorophenol, o-bromophenol and m-bromophenol.

  Among these, at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N, N′-dimethyl-2-imidazolidinone, γ-butyrolactone, and propylene carbonate is preferably used.

  On the other hand, these organic solvents have a relatively large surface tension and are difficult to wet and spread on the substrate surface that forms the alignment film. Therefore, a composition containing only these organic solvents may not be able to form a sufficient film on the substrate surface. Therefore, a mixed solvent system in which another organic solvent having a low surface tension is added although the solubility in a solute is poor.

  Other organic solvents include, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), 1-methoxy-2-propanol. , Alcohol solvents such as 1-methoxy-2-acetoxypropane, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or ethylene Glycol monomethyl ether, diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol isopropyl Ether, ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol butyl methyl ether , Ether solvents such as diethylene glycol dibutyl ether, dipropylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, tetrahydrofuran, or ethyl lactate, Ester solvents such as butyl acid, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate and diethyl malonate, and further dichloromethane, 1,2-dichloroethane, 1, Halogenated hydrocarbon solvents such as 4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, aliphatic hydrocarbon solvents such as n-hexane, n-heptane, n-octane, benzene, toluene, xylene, etc. Aromatic hydrocarbon solvents and the like. These solvents can be used alone or in combination of two or more.

In the present embodiment, the composition of the liquid 70 is as follows.
Alignment film forming material; polyimide; 1 to 5 wt%
Mixed solvent: γ-butyrolactone; 85-89 wt%
NMP: 5 wt%
Butyl cellosolve; 5wt%
The liquid 70 has a viscosity in the range of 3 to 20 mPa, s, and adjusts the concentration of the alignment film forming material, which is mainly a solute, and the concentration of butyl cellosolve so that the surface tension is in the range of 30 to 45 mN / m. is doing.
Further, as the discharge conditions of the discharge head 50, the drive conditions of the piezoelectric elements provided corresponding to the nozzles 52 were set so that the discharge amount of the droplets was about 10 ng.
The total amount of the liquid 70 discharged to the film formation area AE is set in consideration of the target film thickness after film formation, the plane area of the film formation area AE, and the concentration of the solute. Then, the process proceeds to step S3.

  In the first drying step (step S3) in FIG. 5, the liquid 70 applied to the film formation region AE is dried to form the first thin film 16a as shown in FIG. 6C. As a method for drying the liquid material 70, for example, the heater 211 of the droplet discharge device 200 is used to heat the mother substrate 110 so that the surface temperature becomes 70 to 100 ° C., and is left for about 1 to 5 minutes. Thereby, the solvent component can be substantially evaporated. The method is not limited to this drying method, and a method of placing and heating the mother substrate 110 on a hot plate, a method of placing the mother substrate 110 coated with the liquid material 70 in a chamber, and drying under reduced pressure can be cited. . Then, the process proceeds to step S4.

In the second surface treatment step (step S4) in FIG. 5, as shown in FIG. 6D, the mother substrate 110 on which the first thin film 16a is formed is again subjected to plasma treatment. The plasma treatment method is the same as the first surface treatment step, but the exposure time is set to about 10 seconds in consideration of the reduction of the first thin film 16a by O ₂ plasma. Thereby, the surface of the first thin film 16a is made lyophilic. This second surface treatment step is not essential and may be omitted if the wettability of the surface of the first thin film 16a after drying is good. Examples of the method for evaluating the wettability of the surface of the first thin film 16a include a method of measuring the contact angle of the liquid 70 or a mixed solvent constituting the liquid 70. Then, the process proceeds to step S5.

  In the second application step (step S5) in FIG. 5, as shown in FIG. 6E, the liquid material 70 is dropped from the nozzle 52 of the discharge head 50 into the film formation region AE where the first thin film 16a is formed. Discharge as That is, the liquid material 70 is applied repeatedly through the first drying process. In this case, the discharge conditions such as the total amount of the liquid material 70 to be applied are the same as those in the first application process (step S2). Then, the process proceeds to step S6.

  In the second drying step (step S6) in FIG. 5, the applied liquid material 70 is dried. The drying method is the same as that in the first drying step, the heater 211 of the droplet discharge device 200 is used, and the drying conditions are the same. Thereby, as shown in FIG. 6F, a second thin film 16b laminated on the first thin film 16a is formed. Then, the process proceeds to step S7.

  In the firing step (step S7) of FIG. 5, the mother substrate 110 is heated to fire the laminated first thin film 16a and second thin film 16b, and the solvent component is completely removed to form polyimide. A polymer alignment film 16 is formed in the film formation region AE. As a firing method, for example, there is a method in which the mother substrate 110 is placed in a firing furnace in which nitrogen gas as an inert gas is sealed, the heating temperature is set to 180 to 250 ° C., and the heating is performed for about 10 minutes to 1 hour. Can be mentioned.

  In the method for forming the alignment film of the present embodiment, the mother substrate 110 and the ejection head 50 in the first application process and the second application process are relatively moved in order to form the alignment film 16 with a uniform thickness. The scanning method to be moved was as follows.

  FIG. 7A is a schematic diagram illustrating a scanning method in the first coating process. As described above, the plurality of element substrates 10 are imposed on the mother substrate 110 in a matrix. The size of the film formation region AE in one element substrate 10 is less than 1 inch in the diagonal length of the square film formation region AE. On the other hand, as described above, the ejection head 50 has 360 nozzles 52 arranged with a nozzle pitch P2 of about 70.5 μm, and therefore the length of the nozzle row 52c is about 25310 μm and about 1 inch. Therefore, it is needless to say that a plurality of ejection heads 50 are required if the liquid 70 is to be ejected simultaneously to all the film formation regions AE arranged on the mother substrate 110. However, it is difficult to make the discharge conditions between the discharge heads 50 exactly the same, and the provision of a plurality of discharge heads 50 complicates the structure and control of the droplet discharge device 200. .

  Therefore, in the present embodiment, as shown in FIG. 7A, one of the plurality of film formation areas AE arranged on the mother substrate 110 is 1 for the row of film formation areas AE arranged in a certain direction. The liquid 70 was discharged by scanning the two discharge heads 50.

  Specifically, the ejection head 50 is mounted on the head unit 201 of the droplet ejection apparatus 200 so that the nozzle row 52c and the scanning direction (the direction of the arrow in the drawing) are orthogonal to each other. The mother substrate 110 is placed on the stage 204, and the mother substrate 110 is positioned so that the longitudinal direction of the film formation region AE and the scanning direction are orthogonal to each other. Then, scanning is performed by the ejection head 50 so as to trace the rows of the film formation regions AE one by one. That is, the stage 204 is moved relative to the ejection head 50 to eject droplets from the plurality of nozzles 52, and the ejection head 50 is moved in the scanning direction corresponding to the columns of the film formation regions AE. Scanning combined with sub-scanning that moves in the orthogonal direction is performed. In the first application step, the main scanning for discharging the liquid material 70 to the rows of the film formation regions AE is performed by the forward movement in the relative movement of the mother substrate 110 (stage 204) and the discharge head 50 as shown in FIG. This will be done both in reverse and 6 times in total. The main scanning may be only forward movement.

  FIG. 7B is a schematic diagram illustrating a scanning method in the second coating process. In the second coating step, the mother substrate 110 is placed on the stage 204 at a position rotated 90 degrees with respect to the placement in the first coating step. That is, the mother substrate 110 is arranged so that the longitudinal direction of the film formation region AE matches the scanning direction. Then, in the same manner as in the first application step, main scanning is performed so that the columns of the film formation regions AE arranged along the scanning direction are traced one by one. In the second coating step, the main scanning for discharging the liquid material 70 to the rows of the film formation regions AE is performed in the forward movement in the relative movement between the mother substrate 110 (stage 204) and the discharge head 50 as shown in FIG. This is done in both backward movements, a total of 8 times. The main scanning may be only forward movement.

  In the scanning method, main scanning is performed in the direction perpendicular to the longitudinal direction of the film forming area AE in the first coating process, and main scanning is performed in the longitudinal direction of the film forming area AE in the second coating process. The main scanning method in the first coating process and the main scanning method in the second coating process may be interchanged. That is, the application direction is made different between the first application process and the second application process. Even if the application directions are different, in main scanning, the nozzle 52 that is applied to the film formation region AE is selected from the plurality of nozzles 52 that constitute the nozzle row 52c, and the liquid 70 is ejected as droplets. Needless to say, discharge conditions such as the discharge amount of droplets (about 10 ng in this case), the discharge interval in the scanning direction, and the number of discharges are set in advance so as to spread within the film formation region AE.

  Although the liquid 70 discharged from the nozzle 52 lands on the surface of the mother substrate 110 and spreads wet, application unevenness occurs due to variations in the viscosity, surface tension, wettability of the substrate surface, and the like. According to the scanning method, the application unevenness can be reduced by making the application direction different between the first application process and the second application process as compared with the case where the liquid 70 is applied in the same application direction. .

  Furthermore, since at least the surface of the film formation region AE is made lyophilic in the first surface treatment step and the second surface treatment step, the wettability with respect to the liquid material 70 is improved, and the leveling property of the applied liquid material 70 is improved. improves. Accordingly, it is possible to improve coating unevenness due to variations in the discharge amount of droplets between the nozzles 52 in the discharge head 50.

  As shown in FIG. 8A, when the applied liquid material 70 is dried, the evaporation rate of the solvent in the peripheral portion of the film formation region AE is faster than that in the central portion, and therefore toward the peripheral portion where the evaporation rate is high. Solvent migration in the liquid film occurs. Since the solute moves as the solvent moves, a squeeze (also referred to as coffee stain) occurs in which the film thickness at the peripheral edge portion becomes thicker than others after drying. The alignment film 16 formed in the film formation region AE has a squeeze that slightly varies in film thickness at the peripheral edge.

  As shown in FIG. 8B, according to the method for forming the alignment film, after the first drying process, the liquid 70 is applied onto the formed first thin film 16a and then the second drying process. To implement. Therefore, the second thin film 16b is formed so as to overlap the first thin film 16a.

  However, as shown in FIG. 8C, a thin film obtained by applying and drying all of the liquid 70 necessary to form the alignment film 16 in one application step is referred to as a third thin film 16c. Then, since the amount of the liquid material 70 to be dried is larger than that in the first drying step or the second drying step, more solute moves to the peripheral portion of the film formation region AE. Therefore, the height h2 and width d2 of the generated blot (when cut along the line BB ′ in FIG. 8A) are the height h1 of the blot in the alignment film forming method of this embodiment. It becomes larger than the width d1.

  That is, according to the method for forming an alignment film of the present embodiment, the uneven coating due to the wettability with respect to the film formation surface of the liquid 70 is improved, and the alignment film 16 having a small amount of oozing is formed. Can do.

  The alignment film forming method of this embodiment can be applied not only to forming the alignment film 16 on the element substrate 10 side but also the alignment film 22 on the counter substrate 20 side. The liquid crystal device 100 including the alignment films 16 and 22 having a stable film thickness with little coating unevenness has excellent display quality with little alignment unevenness due to coating unevenness and film thickness unevenness.

  Various modifications other than the above embodiment are conceivable. Hereinafter, a modification will be described.

  (Modification 1) In the scanning method in the alignment film forming method of the above embodiment, the nozzle row 52c and the scanning direction do not necessarily have to be orthogonal to each other. By making them orthogonal, the application range of the liquid material possessed by the nozzle row 52c can be utilized during main scanning. Substantial nozzle spacing is reduced, and droplets can be arranged at higher density in the sub-scanning direction perpendicular to the scanning direction on the film forming surface. Therefore, uneven coating due to the nozzle interval can be reduced.

  (Modification 2) In the method for forming an alignment film of the above embodiment, changing the application direction in the second application step relative to the application direction in the first application step results in a substantial scanning direction with respect to the film formation region AE. The rotation angle is not limited to 90 degrees. For example, the coating direction may be changed by rotating the mother substrate 110 relative to the arrangement of the mother substrate 110 in the first coating process at an angle of less than 90 degrees or greater than 90 degrees and less than 180 degrees. .

(Modification 3) In the method for forming an alignment film according to the above-described embodiment, the liquid 70 is not discharged to one discharge head 50. For example, in the first application process and the second application process, a plurality of ejection heads 50 may be arranged in parallel in the sub-scanning direction so that the nozzle row 52c intersects the scanning direction. According to this method, it is possible to expand the discharge range of the liquid 70 by one main scanning.
Further, the ejection heads 50 used in the first application process and the second application process may be different. For example, in the head unit 201 of the droplet discharge device 200, the two discharge heads 50 are mounted so that the nozzle rows 52c are orthogonal to each other. In the first application process, a nozzle row 52c orthogonal to the main scanning direction (Y direction) is used. In the second application step, there is a method in which the ejection head 50 having the nozzle row 52c along the main scanning direction (Y direction) is used, and the ejection head 50 is scanned with respect to the workpiece W in the sub scanning direction (X direction). It is done. According to this method, the same kind of liquid can be applied in different scanning directions. Also, if the two discharge heads 50 are filled with different types of functional materials and discharged, then different types of functional films can be stacked and formed with different application directions.

  (Modification 4) In the method for forming an alignment film of the above embodiment, the method for making the surface of at least the film formation region AE on the mother substrate 110 lyophilic is not limited to the plasma processing using a processing gas containing oxygen. For example, a method of generating ozone by irradiating ultraviolet rays having a specific wavelength in the atmosphere and exposing the mother substrate 110 to the ozone can be employed.

(Modification 5) In the alignment film forming method as the thin film forming method of the above embodiment, the method of discharging the liquid 70 is not limited to using the discharge head 50 having a plurality of nozzles 52. FIGS. 9A and 9B are schematic views showing a thin film forming method of Modification 5. For example, as shown in FIG. 9 (a), a so-called dispenser that fills a syringe having a nozzle with a liquid material, pressurizes the liquid material by feeding nitrogen gas or air into the syringe, and discharges the liquid material from the nozzle. A so-called quantitative discharge device may be used. By overcoating by changing the application direction, uneven application along the nozzle scanning direction can be reduced.
Further, as shown in FIG. 9B, the thin film forming method can also be applied in the case of using a coating apparatus such as a slit coater that discharges and applies a liquid material in a strip shape from a slit nozzle. That is, coating unevenness can be reduced by applying a drying process after one of the coating processes is completed, and then applying the film in a different direction.

(Modification 6) The thin film to which the thin film forming method of the above embodiment can be applied is not limited to the alignment film. FIG. 10 is a schematic cross-sectional view showing a method for forming a thin film according to Modification 6. For example, in the counter substrate 20 of the liquid crystal device 100, after forming the insulating film 25 on the counter electrode 21, the alignment film 22 may be formed so as to cover the insulating film 25. By applying the thin film forming method to the insulating film 25 forming method, the liquid material containing the insulating film forming material is applied in the first application step. After passing through the first drying process, the liquid material containing the insulating film forming material is applied again by changing the application direction in the second application process. And a 2nd drying process is performed. Further, the liquid material containing the alignment film forming material is applied over the insulating film 25 in the third application process and the fourth application process in which the application directions are changed. That is, the type of functional material contained in the liquid to be applied may be changed.
As a result, a multilayer film having different functions can be formed with reduced coating unevenness and spreading.

  (Modification 7) A device to which the thin film forming method of the above embodiment can be applied is not limited to the liquid crystal device 100. A wiring layer made of a conductive material such as metal, a thin film transistor made of the wiring layer and a semiconductor layer, or an organic EL (electroluminescence) made up of a plurality of organic functional films, which can be formed by applying a liquid material. Examples include a light emitting layer.

  DESCRIPTION OF SYMBOLS 10 ... Element substrate as a substrate, 16, 22 ... Alignment film, 20 ... Counter substrate as a substrate, 50 ... Discharge head, 52 ... Nozzle, 70 ... Liquid, 110 ... Mother substrate as a substrate, AE ... Film formation region .

Claims (6)

A first application step of scanning the nozzle relative to the substrate, discharging a liquid containing a functional material from the nozzle, and applying it to at least a film forming region on the substrate;
A first drying step of drying the applied liquid material;
A second coating step in which the substrate and the nozzle are relatively scanned in a scanning direction different from the scanning direction in the first coating step, and the liquid material is discharged from the nozzle and applied to at least the film forming region; When,
A second drying step of drying the applied liquid,
A method for forming a thin film, comprising:   The thin film forming method according to claim 1, further comprising a first surface treatment step of making at least the film formation region lyophilic before the first coating step.   3. The method for forming a thin film according to claim 1, further comprising a second surface treatment step for making at least the film formation region lyophilic before the second coating step.   4. The liquid material is ejected using an ejection head having a plurality of the nozzles in at least one of the first coating process and the second coating process. 5. A method for forming a thin film according to 1.   5. The thin film formation according to claim 1, wherein the liquid material containing different types of the functional material is applied in the first application step and the second application step. 6. Method.   5. The alignment film is formed in the film formation region by discharging the liquid containing the alignment film forming material from the nozzle using the thin film formation method according to claim 1. A method for forming an alignment film.

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