JP2008073911A - Screen printing method, screen printing machine and manufacturing method of organic thin-film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an excellent ink pattern which is free from blurring even when ink of low viscosity is used. <P>SOLUTION: A squeegee disposed on a printing object by the medium of a screen mask is moved in contact with the ink and the ink pattern corresponding to a printing pattern provided on the screen mask is formed on the printing object. In this printing method, an ink-philic treatment is given to the printing object through the medium of the screen mask, prior to the process for forming the ink pattern by moving the squeegee. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screen printing method, a screen printer, and an organic thin film transistor manufacturing method.

  The merit of organic thin-film transistors (hereinafter referred to as organic TFTs) is that they can be produced at low cost by directly forming patterns using expensive equipment such as vacuum film formation and photolithography processes and processes such as simple coating without the need for complicated processes. This is a possible point. However, it is still difficult to use organic materials in all of the production of organic TFTs.

  Under such circumstances, a method for directly forming a pattern on an organic semiconductor film has been studied. One of the direct patterning methods is a screen printing method.

  The screen printing method has a merit that the printing speed is faster than other direct patterning methods such as an ink jet method, and the manufacturing time can be shortened. On the other hand, it is necessary to use ink having a higher viscosity than other printing methods.

  However, each component of the organic TFT has a small thickness, and the ink used as each component is generally low in viscosity. For this reason, when an organic TFT is produced using a screen printing method, bleeding occurs in the printed portion and it is difficult to perform good patterning. In addition, it is possible to adjust the viscosity of ink constituting each component such as a gate electrode, a source electrode, a drain electrode, an insulating film, and an organic semiconductor film constituting an organic TFT to a viscosity suitable for screen printing. It is necessary to add an additive for adjusting the ink to the ink. For this reason, the basic performance of the material to be printed is lowered, and there is a problem that desired characteristics cannot be obtained.

  In order to solve the above-described bleeding, in a screen printing plate composed of at least a plate frame, a wrinkle, and a plate film that forms a printing pattern, the plate film is made of metal, and the surface of the metal to be printed is water-repellent and repellent. There is a screen printing plate provided with an oily film (for example, Patent Document 1).

On the other hand, there is a technique for forming a highly accurate pattern using a coating method such as ink jet after forming a lyophilic / repellent pattern. For example, there is a manufacturing method of an organic semiconductor or an optoelectronic device in which a fluorinated photoresist layer is stacked on a substrate, the fluorinated photoresist layer is patterned to form a relief pattern, and a semiconductor or a conductive material is stacked on the substrate. There is (for example, Patent Document 2). This relief pattern prevents the organic material from spreading into unnecessary areas.
JP 2004-358830 A JP 2005-522000 Gazette

  However, although the screen printing plate described in Patent Document 1 increases the water repellency of the screen printing plate, the problem of ink entering between the screen printing plate and the work is reduced but not fully solved.

  Moreover, although the relief pattern of the fluorinated photoresist layer described in Patent Document 2 can be formed to achieve high resolution by the ink jet method, the ink jet method is not sufficiently fast in printing speed. When the screen printing method is used instead of the ink jet method, it is necessary to precisely align the screen printing plate in order to apply ink in accordance with the relief pattern. Therefore, an expensive high-precision alignment apparatus for performing precise alignment is required, and there is a problem that the manufacturing cost increases.

  The present invention has been made in view of the above problems, and the object of the present invention is to provide a screen printing method and a screen that can form a good ink pattern without bleeding even when ink having a low viscosity is used. It is providing the manufacturing method of the organic thin-film transistor using a printing machine and this screen printing method.

  Said subject is solved by the following structures.

1. Screen printing for forming an ink pattern according to a printing pattern provided on the screen mask on the printing material by moving a squeegee arranged on the printing material via a screen mask in contact with ink In the method
Prior to the step of moving the squeegee to form the ink pattern,
A screen printing method, wherein an ink-philic treatment is performed on the substrate to be printed through the screen mask.

  2. 2. The screen printing method according to 1, wherein the ink-philic process is performed in a state where the screen mask is in close contact with the substrate.

  3. 3. The screen printing method according to 1 or 2, wherein the screen mask is a metal mask.

  4). The screen printing method according to any one of claims 1 to 3, wherein the printed material is provided with an undercoat layer on a surface on which the ink pattern is formed.

  5. 5. The screen printing method according to 4, wherein the undercoat layer is a self-assembled monolayer.

  6). 6. The screen printing method according to any one of claims 1 to 5, wherein the lye ink treatment irradiates the printed material with ultraviolet rays through the screen mask.

7). The screen printing method according to claim 1, wherein the following conditional expression is satisfied by performing the parent ink treatment.
γm <γt
However,
γm: surface free energy of screen mask γt: surface free energy of substrate to be treated with ink for ink 8. The squeegee is a sealed head that pushes out ink from a print pattern of the screen mask while supplying ink that is shielded from air to the screen mask. Screen printing method.

  9. A screen printing machine capable of the screen printing method according to any one of 1 to 8.

10. In a method for manufacturing an organic thin film transistor, including a step of forming at least a gate electrode on a substrate, a step of forming an insulating film, a step of forming a drain electrode, a step of forming a source electrode, and a step of forming an organic semiconductor layer.
9. The method of manufacturing an organic thin film transistor, wherein at least one of the steps uses the screen printing method according to any one of 1 to 8.

  According to the screen printing method and the screen printing machine of the present invention, an ink-philic process corresponding to a printing pattern is performed on a printing medium through a screen mask. Thereafter, an ink pattern corresponding to the printing pattern is formed on the printing medium through the same screen mask.

  The place where the ink pattern of the printing medium is formed is the same as the place where the parent ink process is performed. Therefore, it is possible to form an ink pattern on the substrate to be ink-treated according to the print pattern.

  Therefore, it is possible to provide a screen printing method and a screen printing machine capable of forming a good ink pattern without bleeding even when using an ink having a low viscosity.

  In addition, at least one of a step of forming a gate electrode, a step of forming an insulating film, a step of forming a drain electrode, a step of forming a source electrode, and a step of forming an organic semiconductor layer is formed using the above-described screen printing method. To do.

  Therefore, at least one of a gate electrode, an insulating film, a drain electrode, a source electrode, and an organic semiconductor film constituting an organic thin film transistor can be formed on the substrate by the above-described screen printing method.

  Therefore, it is possible to provide a method for producing an organic thin film transistor using a screen printing method capable of forming a good ink pattern without bleeding even when an ink having a low viscosity is used.

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  In the screen printing method according to the present invention, prior to the known screen printing method, an ink-philic process is performed on the printing medium. The parent ink process performed on the printing medium refers to a process for increasing the affinity between the ink and the printing medium. The affinity of the printing medium means that, depending on the ink material, the surface of the printing medium may have good water repellency or hydrophilicity, but it may have good wettability to the printing medium. Represents good ink affinity. Specific examples of the method for treating the surface of the printing medium with the ink-friendly treatment include ultraviolet irradiation, plasma irradiation, electron beam irradiation, corona discharge irradiation, and laser light irradiation. These ink-friendly ink treatment methods are appropriately selected depending on the material of the printing medium and performed on the surface of the printing medium.

  A known screen printing method will be briefly described using a screen printing machine schematically shown in FIG. 51 is a substrate to be printed, 52 is a mounting table on which this is placed, and a screen plate 53 is disposed above it. The screen plate 53 includes a screen mask (hereinafter referred to as a mask) 54 and a plate frame 55 that holds the screen mask. Reference numeral 56 denotes a squeegee for performing printing by moving the ink 57 (or paste) placed on the print pattern on the mask 54 from the print start end to the print end end. The squeegee 56 moves in a state of contacting the mask 54 in the direction of the arrow in the figure, and returns to the screen 54 in a non-contact state when returning.

  Further, a scraper (sliding plate for ink coating, not shown) or the like that moves in a non-contact state on the mask 54 together with the squeegee 56 and scoops and scrapes the ink 57 is provided. With this scraper, ink is placed on the printing start end of the printing pattern on the mask 54, and the squeegee 56 is slidably moved against the mask 55 from the printing start end to the printing end end. An ink pattern 58 is formed on the arranged printing medium 51.

  In the known screen printing machine shown in FIG. 6 above, the known ultraviolet irradiation that enables the above-described ultraviolet irradiation, plasma irradiation, electron beam irradiation, corona discharge irradiation, and laser light irradiation to the substrate 51 through the mask 54. At least one of an apparatus, a plasma irradiation apparatus, an electron beam irradiation apparatus, a corona discharge irradiation apparatus, and a laser beam irradiation apparatus is provided in a screen printing machine as a parent ink processing means. In the parent ink processing method, the entire print pattern range of the mask may be irradiated at the same time, or in the case of an irradiation apparatus having a large printing medium or a small irradiation area, it may be irradiated by scanning sequentially. What is necessary is just to select and use suitably in an apparatus.

  When the printed material is irradiated with ultraviolet rays, for example, by an ultraviolet irradiation device through a mask having a screen printing pattern, the printed material is exposed according to the printing pattern. Therefore, the exposed surface of the printing medium is subjected to ink affinity treatment, and the surface of the printing body not exposed is not subjected to ink affinity treatment. Next, the same mask is used as an original screen printing mask instead of an exposure mask, and an ink pattern is formed on the printing medium through the mask printing pattern. Since the surface of the printing medium to which the ink is applied by being pushed out of the printing pattern has good ink-philicity by the ink-philic treatment, the ink is well adapted to the printing medium. On the other hand, the area around the portion where the ink is applied is in a state where ink is repelled because the ink affinity is inferior because the ink affinity treatment is not performed. Accordingly, a good ink pattern without ink bleeding can be formed on the printing medium.

The surface of the printing medium is brought into the following state as an example by the above-described ink-philic treatment.
(1) Increase the surface roughness.
(2) Change the surface free energy.
(3) A film (undercoat layer) is provided in advance on the surface of the substrate to be printed, and the film of the portion that has been subjected to the parent ink treatment is removed.
In the above (1) and (2), the target to be treated with the ink may be the printing medium itself or a film provided in advance on the surface of the printing medium. Specific examples include a polyimide film and a self-assembled monolayer (SAM).

  Regarding (1), the method for increasing the surface roughness of the printing medium is not particularly limited. For example, the surface roughness can be increased by providing a polymer film such as polyimide on the surface of the printing medium and subjecting the polymer film to laser light irradiation, corona treatment, or plasma treatment.

With respect to (2), the surface free energy of the surface of the printing medium is increased by the ink affinity treatment to change from ink repellency to ink affinity. For example, the surface free energy can be increased by irradiating the surface of the printing medium with ultraviolet rays. Also, the surface free energy can be increased by providing a polymer film on the surface of the printing medium and irradiating the film with ultraviolet rays or the like. The greater the surface free energy, the better the ink affinity. The following equation (1) shows the relationship of the surface free energy of the printing medium by the ink-philic treatment such as ultraviolet exposure using a mask.
γn <γt (1)
However,
γn: surface free energy of the printing medium not subjected to the parent ink treatment γt: surface free energy of the printing body subjected to the parent ink treatment Here, when the surface free energy of the mask irradiated with ultraviolet rays is γm, It is preferable to satisfy the conditional expression (2) shown.
γm <γt (2)
However,
γm: surface free energy of the screen mask γt: surface free energy of the printing medium subjected to the ink treatment When the conditional expression (2) is satisfied, the difference in the degree of ink affinity on the surface of the printing medium depending on whether or not the ink treatment is performed In addition to improving the ink bleeding due to the ink, there are the following additional effects. By making the surface free energy of the printing medium subjected to the parent ink treatment larger than the surface free energy of the screen mask, the ink which tries to enter the gap between the printing body and the mask is the printing medium subjected to the parent ink treatment of the printing body. Be drawn to the body part. This makes it difficult for ink to enter the gap between the mask and the substrate. Accordingly, when screen printing is performed on a printing medium that has been subjected to ink affinity treatment, it is difficult for bleeding to occur in the print pattern, and a better ink pattern can be formed. However, the surface free energy (γt) of the portion of the printing material subjected to the parent ink treatment by the mask exposure or the like is obtained from the surface free energy (γn) of the portion of the printing body not subjected to the parent ink treatment using the mask. Although it can be increased, the surface free energy (γm) of the mask cannot be changed. For this reason, it is necessary to appropriately select and combine the printing material, the film provided on the surface of the printing material, the mask material, and the parent ink treatment method so as to wait for the conditional expression (2). The surface free energy can be calculated by measuring the contact angle using three kinds of solvents.

  Regarding (3), a self-assembled monomolecular film (SAM), for example, is preferably used as a film that is provided in advance on the substrate and removed by the ink-philic treatment. Specifically, there are silane coupling films, and examples include octadecyltrichlorosilane (OTS) and hexamethyldisilane (HMDS) thin films. Since these SAMs can be easily removed by irradiation with ultraviolet rays, they are suitable for pattern formation using a mask.

  For example, when a SAM having a highly ink-repellent substituent is used, the surface free energy of the SAM provided on the surface of the printing medium is smaller than that in a place where no SAM is provided. Accordingly, the ink repellency of the printing medium provided with the SAM is increased. When the surface of the printing material having the SAM is exposed to a mask using, for example, ultraviolet rays, the SAM is removed from the exposed region. Therefore, the surface free energy of the region from which the SAM has been removed becomes larger than that before the SAM is removed. Therefore, when the ink pattern is formed using the mask used for the mask exposure in the same manner as described above, in the area where the ink is applied through the print pattern, the wettability is good and the print medium is well-accommodated. Since the ink treatment is not performed, the wettability is not improved and the ink is repelled.

  Examples of the film whose surface state changes from ink repellency to ink affinity due to the ink affinity treatment include various polymer thin films. It is possible to change the water-repellent material to hydrophilic by irradiating with ultraviolet rays, cutting the bond of the polymer material or the alkyl group on the surface, and revealing the carboxyl group or hydroxyl group on the surface.

(mask)
The mask used for screen printing is not particularly limited, and may be a known one. For example, there are a mask provided with a photosensitive emulsion for masking on a mesh made of a fibrous material such as resin or metal and a metal mask provided with a hole through which ink passes through a thin metal plate. When the surface of the printing medium is subjected to the parent ink treatment through the mask, it is preferable that the surface of the printing body at the masked portion is not subjected to the parent ink treatment at all. For this purpose, a mask capable of sufficiently blocking the influence of the parent ink treatment, for example, having a high light shielding property is preferable. In addition, in the screen plate using a mesh, there is a possibility that the ink-philic process may be hindered because there is a net-like fine line made of metal or resin at the opening of the print pattern. From these viewpoints, a metal mask is preferable.

  The material of the metal mask is not particularly limited, and a material having a thickness of about 50 μm to 200 μm can be used. Examples of the manufacturing method include a laser processing method, an etching method, and an additive method. Among these, a more precise pattern can be formed by using the additive method.

  Further, it is preferable that the mask is brought into close contact with the substrate to be printed during the ink treatment. By being in close contact with each other, it is possible to perform the ink-philic treatment on the printing medium more faithfully by the printing pattern of the mask as compared with the case where there is a gap between the mask and the printing medium. When an ink pattern is formed on a printing medium via a mask printing pattern, the interval (clearance) between the mask and the printing medium needs to be set to a value that is generally determined by the size and material of the mask. This is because if there is no such clearance, it will be difficult to remove ink after printing or to separate the mask from the substrate. A clearance is provided between the printing medium and the mask, and an ink pattern is formed on the printing medium placed under the mask by sliding the squeegee in pressure contact with the mask from the printing start edge to the printing end edge. Is done. At this time, the mask is pressed from above with a squeegee and deformed into a convex state downward. For this reason, the ink pattern formed on the printing medium is displaced from the original print pattern of the mask. However, since the ink-philic pattern is formed on the printing medium by the ink-philic process, the ink pushed out from the mask printing pattern forms an ink pattern following the ink-philic pattern. Therefore, an ink pattern that is more faithful to the printing pattern of the mask can be formed on the printing medium.

(ink)
The ink applied by screen printing is not particularly limited. As the ink, for example, when manufacturing an organic thin film transistor (TFT) to be described later, there are inks in which conductive ink, insulating ink, and organic semiconductor are dissolved in a solvent. As the conductive ink, silver paste, metal nano ink using metal nanoparticles, PEDOT / PSS (complex of polyethylene dioxythiophene and polystyrene sulfonic acid) which is a conductive polymer, carbon nanotube dispersion liquid, and the like can be used. . Examples of the insulating ink include a liquid in which fine particles of an insulating material are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as necessary, or a solution of an oxide precursor, for example, an alkoxide body. is there. As the insulating material, an inorganic oxide, an inorganic nitride, a polymer, or the like can be used. In particular, an inorganic oxide having a high relative dielectric constant is preferable. Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. The ink in which the organic semiconductor is dissolved in the solvent may be a polymer, an oligomer, or a precursor, and any organic semiconductor that is generally used as a coating type can be used and is not particularly limited.

  In the case of the ink-philic treatment for increasing the surface roughness, all of the inks listed above can be used. Some inks have photosensitivity. In this case, if ink is accumulated on the mask surface, it will be exposed and deteriorated. In order to cope with this, a sealed head 59 which serves as a squeegee is provided with an ink supply path 59-1 for storing the ink shown in FIG. 5 in an ink tank (not shown) and supplying an amount of ink necessary for printing. Is preferred. By using the sealed head 59, it is possible to satisfactorily form the ink pattern 58-1 on the substrate 51 without degrading the photosensitive ink 57-1. In FIG. 5, the same reference numerals as those in FIG. 6 indicate the same or the same functions.

An example of an organic TFT manufacturing method using the screen printing method described so far will be described. FIG. 1 shows an example of the configuration of the organic TFT. The organic TFT 10 includes a substrate 1, a gate electrode 2, an insulating film 3, a source electrode 4s, a drain electrode 4d, and an organic semiconductor film 5. In the organic TFT 10, a gate electrode 2 is provided on a substrate 1, and an insulating film 3 is provided so as to cover the gate electrode 2. On the insulating film 3, a source electrode 4 s and a drain electrode 4 d are provided by providing a space serving as a channel formation portion made of an organic semiconductor. These are connected by providing an organic semiconductor 5 in a space between the source electrode 4s and the drain electrode 4d. In such an organic TFT element 10, for example, a transparent pixel electrode made of ITO or the like is provided on the drain electrode 4d, and these are arranged in a matrix to form a display circuit of a display device. One pixel portion arranged in a matrix is shown in FIG. In addition to the organic TFT portion described above, 7 is a source bus electrode, 8 is a gate bus electrode, and 9 is a transparent pixel electrode.
The formation of the source electrode 4s and the drain electrode 4d of the organic TFT 10 shown in FIG. 1 by a screen printing method will be described with reference to FIG.

  First, the 1st member A provided with the gate electrode 2 and the insulating film 3 on the board | substrate 1 used as the to-be-printed body for forming the source electrode 4s and the drain electrode 4d with a screen printing method is prepared (FIG. 3 (a )).

  The substrate 1 is made of glass or a flexible resin sheet. For example, a plastic film can be used as the sheet. Examples of the plastic film include films made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES) polycarbonate (PC), cellulose triacetate (TAC), and the like.

  Next, the gate electrode 2 is provided. As a method for forming the gate electrode 2, first, a conductive thin film to be the gate electrode 2 is formed on the substrate 1. The conductive thin film is not particularly limited as long as it is a conductive material, and a metal material that can sufficiently secure conductivity is preferable. For example, Au, Al, Cr, Ag, Mo, a material obtained by adding doping to these, and the like can be given.

  As a method for forming the above-described conductive thin film, a known method such as vapor deposition or sputtering can be used using the above-described materials as raw materials. Thereafter, the gate electrode 2 can be formed by patterning the conductive thin film using a known photolithography process (resist application, exposure, development) and an etching process. The screen printing method described above can also be used.

  Next, an insulating film 3 is provided. The insulating film 3 is not particularly limited, and various insulating films can be used. In particular, an inorganic oxide film having a high relative dielectric constant is preferable. Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used. The screen printing method described above can also be used.

  As a method for forming the insulating film 3, there are a dry process and a wet process. Examples of the dry process include a vacuum deposition method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and the like. Examples of the wet process include a method by coating, a method by patterning such as printing or inkjet, and the screen printing method described above can also be used. Thus, the first member A can be prepared.

  Next, a self-assembled monomolecular film (SAM) 20 is provided on the insulating film 3 as a film to be treated for ink affinity (FIG. 3B). The SAM 20 includes a film having an ink repellency with respect to ink that forms the source electrode 4s and the drain electrode 4d by screen printing to be performed later, for example, OTS.

  Next, the mask 30 is brought into close contact with the first member A on which the SAM 20 is the uppermost layer, and the SAM 20 is exposed with ultraviolet rays L (FIG. 3C). The mask 30 has a printed pattern for forming the source electrode 4s and the drain electrode 4d. The mask 30 is preferably a metal mask with good light shielding properties. The SAM 30 exposed through the mask 30 is subjected to a parent ink process, and the exposed SAM is removed from the first member A. Accordingly, the SAM pattern 20a according to the print pattern of the mask 30 is formed on the first member A. Since the SAM pattern 20a is formed by exposure in a state where the mask 30 is in close contact with the SAM 20, the SAM pattern 20a has a shape faithful to the print pattern of the mask 30.

  Next, the same mask 30 as that used for the parent ink process is set as a mask for screen printing so as to have a predetermined distance from the first member A (FIG. 3D). Therefore, it is preferable to change the interval between the mask 30 and the first member A between the case of using for the parent ink processing and the case of using for the screen printing. For this reason, for example, the first member A is moved up and down as an interval setting means that can be set by changing the distance between the mask 30 and the first member A by moving the mask 30 in the up and down direction. It is preferable that the screen printer has the mechanism. Specifically, a vertical movement mechanism may be provided on a member (not shown) that holds the mask 30 or a mounting table 52 on which the printing material 51 shown in FIG. The vertical movement mechanism only needs to satisfy the required accuracy and can be moved up and down. For example, a mechanism for setting a clearance during screen printing may be used, or a vertical movement mechanism may be provided according to the required accuracy. Here, the required accuracy means the setting accuracy of the vertical position and the horizontal shift deviation when moving up and down. It depends on the size of the ink pattern to be printed. The vertical position setting accuracy is preferably 5 μm or less, and the horizontal shift deviation is preferably ± 5 μm or less.

  Thereafter, the source electrode 4s and the drain electrode 4d, which are ink patterns, are formed on the first member A by a known screen printing method in which the ink 45 is pushed out from the print pattern of the mask 30 by the squeegee 40 (FIG. 3E). The ink 45 to be used is a conductive ink, for example, a water-soluble PEDOT / PSS aqueous dispersion.

  Since the ink 45 pushed out according to the printing pattern on the SAM pattern 20a of the first member A uses the same mask 30, an ink pattern is formed almost at the position where the OTS film is removed by the parent ink process. At this time, the SAM is liquid repellent, and the removed place shows ink affinity compared to the place where the SAM is located. Therefore, the ink pushed out onto the first member A is easy to become familiar in the area where the SAM is not present, that is, the area where the parent ink is processed, and the ink is easily repelled in the area where the SAM is present, ie, the area where the parent ink is not processed. For this reason, a good ink pattern without ink bleeding is formed (FIG. 3F).

Also. When the ink 45 is pushed out from the print pattern of the mask 30 by the squeegee 40, the mask 30 is deformed into a convex state downward because the squeegee 40 is brought into pressure contact with the mask 30 for sliding operation. For this reason, a deviation from the printing pattern shape originally possessed by the mask 30 occurs, and the ink 45 is pushed out of the printing pattern onto the substrate 1 in this deviation state. Here, the ink 45 is applied to a region where the SAM has been removed, and an ink repellent OTS film is provided around this region. Therefore, the ink 45 pushed out on the first member A forms an ink pattern in accordance with the region where the SAM has been removed by the parent ink treatment. Accordingly, the source electrode 4s and the drain electrode 4d that are faithful to the printing pattern of the mask 30 can be provided on the substrate 1. Thereafter, the organic semiconductor layer 5 that connects the source electrode 4s and the drain electrode 4d is formed. Thus, the organic TFT is completed (FIG. 3 (g)). The material constituting the organic semiconductor is not particularly limited, and various condensed polycyclic aromatic compounds and conjugated compounds are applicable. Moreover, the method for forming the organic semiconductor may be a known method, for example, mask deposition by vacuum deposition.

  As an example in which the screen printing method is used in the manufacture of the organic TFT described so far, the source electrode 4s and the drain electrode 4d are formed as an example. However, the gate electrode 2 and the source bus electrode 7 shown in FIGS. Similarly, members constituting the organic TFT such as the gate bus electrode 8, the pixel electrode 9 and the organic semiconductor layer 5 are also appropriately selected from a parent ink processing method and, if necessary, a target film (undercoat layer) for the parent ink processing. Can be formed.

(Comparative Example 1)
Blue glass was used as the substrate. As for the dimensions, the outer shape was 150 mm wide × 150 mm long × 1.0 mm thick. An OTS thin film was previously formed as a water-repellent layer on the blue plate glass. As the ink, a polyvinyl alcohol (PVA) 2 mass% aqueous solution was used. The apparatus used for the screen printing was a screen printing machine (manufactured by Microtech, model MT-750). A metal mask (manufactured by Kyushu Hitachi Maxell Co., Ltd.) having a thickness of about 65 μm and a printing pattern in which round holes of φ50 μm were arranged in a pitch of 263 × vertical × 199 with a pitch of 429 μm. Using these members and apparatus, screen printing was performed according to the following procedure.
(1) The printing medium is fixed to the stage of the printing press by vacuum suction.
(2) A stage on which a printing medium is fixed is disposed on a metal mask.
(3) The clearance between the substrate to be printed and the metal mask necessary for screen printing is set. This clearance is appropriately determined from the mask material, the size of the plate, and the like. In this example, it was 1 mm.
(4) Ink is supplied to one end of the metal mask.
(5) The squeegee is pressed against the mask at a squeegee angle of 60 degrees and a pressure of 0.2 MPa.
(6) The ink was pushed out from the metal mask by moving the squeegee at a speed of 15 mm / s to form an ink pattern on the substrate.

(Example 1)
Using the same members and devices as in Comparative Example 1, printing was performed according to the procedure shown below.
(1) The printing medium is fixed to the stage of the printing press by vacuum suction.
(2) A stage on which a printing medium is fixed is disposed on a metal mask.
(3) Raise the stage and bring the metal mask into close contact with the blue plate glass.
(4) Irradiate UV light (wavelength 254 nm).
(5) The clearance between the printing medium and the metal mask necessary for printing is set.
(6) Ink is supplied to one end of the metal mask.
(7) The squeegee is pressed against the metal mask at a squeegee angle of 60 degrees and a pressure of 0.2 MPa.
(8) The ink was pushed out from the metal mask by moving the squeegee at a speed of 15 mm / s to form an ink pattern on the substrate.
(9) The printed material was dried at 80 degrees in an oven in order to completely evaporate the solvent.

(Example 2)
The substrate to be printed was obtained by applying a soluble polyimide material (manufactured by Nissan Chemical Co., Ltd.) in a thickness of about 500 μm to blue plate glass in advance. Except for these, printing was performed according to the procedure shown in Example 1 using the same members and apparatuses as in Example 1.

(Comparison result between Comparative Example 1 and Example 1 and Example 2)
The ink pattern shapes produced in Comparative Example 1, Example 1 and Example 2 were observed with a microscope. As a result of observation, in Comparative Example 1, bleeding was observed in the ink pattern, a large pattern was formed as compared with the printed pattern of the metal mask, and the round shape was distorted.

  In Example 1, no blur was observed in the ink pattern, and printing could be performed with a pattern size substantially the same as the metal mask print pattern.

  In Example 2, no blur was observed, and printing could be performed with a pattern size substantially the same as the printing pattern of the metal mask.

  From the above results, in Example 1, the water-repellent OTS film pattern was formed by the parent ink treatment, and in Example 2, the surface of the soluble polyimide material was roughened by the parent ink treatment, resulting in good bleeding. It was confirmed that we could do anything. Therefore, it has been confirmed that a printing pattern can be produced with a takt time faster than that of inkjet using an ink having a low viscosity that is not suitable for screen printing.

(Example 3)
The production of the source electrode 4s and the drain electrode 4d constituting the organic TFT using the screen printing method will be described with reference to FIG.
(1) Using substrate 1 as a polyethersulfone (PES) substrate made by Sumitomo Bakelite, Al having a thickness of 130 nm is formed on the top by sputtering, and patterning of Al is performed by ordinary photolithography, and gate electrode 2 is formed. Obtained.
(2) A 300 nm-thick SiO ₂ film was formed as an insulating film 3 on the gate electrode 2 of the substrate 1 using tetraethoxysilane (TEOS) as a liquid source by atmospheric pressure plasma CVD (FIG. 3A). .
(3) After immersing the substrate 1 prepared in (2) in a 0.1 mol / l toluene solution of OTS, the substrate 1 is washed with toluene and dried, followed by a self-assembled monomolecule that is an ink repellent film A film (SAM) 20 was formed (FIG. 3B).
(4) After a metal mask, which is a screen printing mask 30 having a source electrode and a drain electrode pattern, and a substrate 1 provided with a gate electrode 2 are closely aligned, a metal mask is used as a parent ink treatment. Then, the substrate 1 was irradiated with ultraviolet light L of about 150 mW / cm ² from a high-pressure mercury lamp through an optical fiber (FIG. 3C). As a result of the irradiation, the SAM in the region irradiated with the ultraviolet light L was removed, and a SAM pattern 20a according to the printing pattern of the mask 30 was formed. Specifically, the SAM in a region of about 500 μm × 100 μm corresponding to the size of each of the electrodes 4s and 4d was removed at the place where the source electrode 4s and the drain electrode 4d are formed. The size of the channel is a channel length of 50 μm and a channel width of 500 μm.
(5) The clearance between the mask 30 and the substrate 1 is generally set to perform screen printing (FIG. 3D).
(6) An aqueous dispersion 45 of PEDOT / PSS was applied with a squeegee 40 by screen printing (FIG. 3 (e)). Thereafter, baking was performed at a temperature of 200 ° C. for 30 minutes to form an organic electrode layer to be the source electrode 4s and the drain electrode 4d. At this time, when the organic electrode was observed with a microscope, an organic electrode layer with less bleeding could be formed (FIG. 3 (f)).
(7) Pentacene, which is the organic semiconductor 5, was formed on the channel portion by mask vapor deposition to complete an organic TFT (FIG. 3 (g)).

Immediately after fabrication, the mobility of the organic TFT was 0.03 cm ² / V · sec on average, and the on-off ratio was 16400. From this, it was possible to confirm the operation of the organic TFT considered to be sufficiently practical.

Example 4
The production of the organic semiconductor layer 5 constituting the organic TFT using the screen printing method will be described with reference to FIG.
(1) Using substrate 1 as a polyethersulfone (PES) substrate made by Sumitomo Bakelite, Al having a thickness of 130 nm is formed on the top by sputtering, and patterning of Al is performed by ordinary photolithography, and gate electrode 2 is formed. Obtained.
(2) An SiO ₂ film having a thickness of 300 nm was formed as an insulating film 3 on the gate electrode 2 of the substrate 1 using tetraethoxysilane (TEOS) as a liquid material by an atmospheric pressure plasma CVD method.
(3) A tin-doped indium oxide (ITO) film having a thickness of 100 nm is formed on the entire surface by a sputtering method, and then the ITO film is patterned by a normal photolithography process to obtain a source electrode 4s, a drain electrode 4d, and a source bus line ( (Not shown) was formed (FIG. 4A). The gate length of the channel portion constituting the organic TFT was 10 μm, and the gate width was 100 μm.
(4) After immersing the substrate 1 prepared in (3) in a 0.1 mol / l toluene solution of OTS, the substrate 1 is washed with toluene and subjected to a drying process. A film (SAM) 22 was formed (FIG. 4B).
(5) The size of the organic semiconductor layer 5 formed in the next (6) is 50 μm × 120 μm. After the metal mask which is the mask 32 for screen printing having the organic semiconductor layer 5 pattern and the substrate 1 on which the source electrode 4s and the drain electrode 4d are provided are aligned in a close state, the metal mask is used as a parent ink process. Then, the substrate 1 was irradiated with ultraviolet light L of about 150 mW / cm ² from a high-pressure mercury lamp through an optical fiber (FIG. 4C). As a result of the irradiation, the SAM in the region exposed by the ultraviolet light L was removed, and a SAM pattern 20a according to the print pattern of the mask 30 was formed. In the specific droplet, the SAM in a region of approximately 50 μm × 120 μm corresponding to the size of the organic semiconductor layer 5 was removed at the place where the organic semiconductor layer 5 was formed.
(6) The clearance between the mask 32 and the substrate 1 is generally set to perform screen printing (FIG. 4D).
(7) A dichlorobenzene solution 47 of P3HT (poly-3-hexylthiophene), which is an organic semiconductor material, was applied by screen printing with a squeegee 40 by screen printing (FIG. 4E). Thereafter, the solvent was volatilized in vacuum to form the organic semiconductor layer 5 to complete the organic TFT (FIG. 4F).

When the organic semiconductor layer 5 was observed with a microscope, the organic semiconductor layer 5 free from bleeding could be formed. Immediately after fabrication, the mobility of the thin film TFT was 0.009 cm ² / V · sec on average, and the on-off ratio was 7200. As a result, it was possible to confirm the operation of the organic TFT considered to be sufficiently practical.

It is a figure which shows the example of a structure of organic TFT. It is a figure which shows the mode of an example in which organic TFT is used for the pixel of a display device. It is a figure which shows the example of the process of manufacturing organic TFT using a screen printing method. It is a figure which shows the example of the process of manufacturing organic TFT using a screen printing method. It is a figure which shows the example of a sealing type head. It is a figure which shows a screen printer typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Insulating film 4s Source electrode 4d Drain electrode 5 Semiconductor layer 7 Source bus electrode 8 Gate bus electrode 9 Pixel electrode 10 Organic TFT
20, 22 SAM (self-assembled monolayer)
20a, 22a SAM pattern 30, 32, 54 Mask 40, 56 Squeegee 45, 47, 57 Ink 51 Substrate 52 Mounting base 53 Screen plate 57-1 Photosensitive ink 58, 58-1 Ink pattern 59 Sealed head 59- 1 Ink supply path A First member

Claims (10)

Screen printing for forming an ink pattern according to a printing pattern provided on the screen mask on the printing material by moving a squeegee arranged on the printing material via a screen mask in contact with ink In the method
Prior to the step of moving the squeegee to form the ink pattern,
A screen printing method, wherein an ink-philic treatment is performed on the substrate to be printed through the screen mask. The screen printing method according to claim 1, wherein the ink-philic process is performed in a state where the screen mask is in close contact with the substrate. The screen printing method according to claim 1, wherein the screen mask is a metal mask. 4. The screen printing method according to claim 1, wherein the printed material is provided with an undercoat layer on a surface on which the ink pattern is formed. 5. The screen printing method according to claim 4, wherein the undercoat layer is a self-assembled monolayer. 6. The screen printing method according to claim 1, wherein, in the parent ink treatment, the printing material is irradiated with ultraviolet rays through the screen mask. The screen printing method according to claim 1, wherein the following conditional expression is satisfied by performing the parent ink treatment.
γm <γt
However,
γm: surface free energy of screen mask γt: surface free energy of substrate to be treated with ink for ink The squeegee is a sealed head that pushes ink from a print pattern of the screen mask while supplying ink that is shielded from air to the screen mask. The screen printing method described in 1. 9. A screen printing machine capable of the screen printing method according to claim 1. In a method for manufacturing an organic thin film transistor, including a step of forming at least a gate electrode on a substrate, a step of forming an insulating film, a step of forming a drain electrode, a step of forming a source electrode, and a step of forming an organic semiconductor layer.
9. The method of manufacturing an organic thin film transistor, wherein the screen printing method according to claim 1 is used in at least one of the steps.

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