JP2007095425A - Film formation method, functional film and electrooptical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functional film having an excellent profile; to provide its film formation method; and to provide an electrooptical device equipped with the functional film. <P>SOLUTION: This electrooptical device (organic EL display device) 10 is provided, in partitioned areas 19 partitioned by banks 20, with luminescent elements 25 each including a hole transport film 22 and an organic EL film 23. In this case, each partitioned area 19 is formed into a tapered shape where its cross-sectional area is reduced toward an opening 19a from an element substrate 11; and the hole transport film 22 and the organic EL film 23 are formed by arranging a predetermined functional liquid in the partitioned area 19 by a droplet jetting method and thereafter passing through a drying process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film forming method by a liquid phase method, a functional film formed by a liquid phase method, and an electro-optical device.

  In recent years, film formation techniques using a droplet discharge method (inkjet method) have been used in the formation of conductive wiring and functional elements. In this film forming technique, a liquid (functional liquid) containing a functional material is patterned on a substrate using a drawing apparatus such as an ink jet printer, and the arranged functional liquid is dried to form a film. It is said to be very effective, such as being able to handle a variety of small-volume production. For example, Patent Document 1 discloses an example in which a light emitting element of an organic electroluminescence (hereinafter referred to as organic EL) display device is formed using a droplet discharge method.

JP 2004-63138 A

  The light emitting element is formed by forming a bank with a photosensitive resin or the like on a substrate, disposing a functional liquid containing an organic EL material in a partition region partitioned by the bank by a droplet discharge method, and then performing a drying process. . In this drying step, the surface of the functional liquid has a curved surface due to the surface tension and the liquid repellency in the bank. Therefore, there is a difference in the evaporation speed of the functional liquid between the central portion and the outer edge portion of the partition region. This is because, at the outer edge portion, the liquid surface is inclined with respect to the substrate surface, thereby substantially increasing the surface area. Such unevenness of the evaporation rate disturbs the profile of the functional film to be formed into a film and causes a bad influence on the functional characteristics of the functional film.

  SUMMARY An advantage of some aspects of the invention is that it provides a functional film having a good profile, a method for forming the functional film, and an electro-optical device including the functional film.

  The present invention is a film forming method comprising: placing a functional liquid in a partitioned area partitioned by banks on a substrate; and drying the placed functional liquid, wherein the partitioned area comprises: It has a tapered shape that reduces the cross-sectional area from the substrate toward the opening.

  According to the film forming method of the present invention, the evaporation of the functional liquid in the outer edge portion is suppressed by the inner wall of the bank formed so as to protrude toward the center portion of the partition region. Is alleviated. Thus, a functional film having a good profile can be provided.

Preferably, in the step of disposing the functional liquid in the partition region in the film forming method, the liquid level of the functional liquid is set lower than the opening surface of the partition region.
According to the film forming method of the present invention, the effect of suppressing evaporation at the outer edge portion described above can be suitably exhibited.

The present invention is a functional film formed by a liquid phase method in a partitioned area partitioned by banks on a substrate, and the partitioned area has a tapered shape that reduces a cross-sectional area from the substrate toward the opening. It is characterized by that.
In the functional film of the present invention, evaporation of the functional liquid at the outer edge is suppressed by the inner wall of the bank formed so as to protrude toward the center of the partition region, and unevenness of the evaporation rate in the partition region is alleviated. In this state, the film is formed. For this reason, it has a favorable profile.

The electro-optical device of the present invention includes the functional film.
The electro-optical device according to the present invention is of high quality because it includes the functional film having a good profile.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms. In the drawings referred to in the following description, the scales of the layers and the members are shown to be different from the actual ones in order to make each layer and each member recognizable on the drawings.

(Electro-optical device)
First, the electro-optical device according to the present invention will be described with reference to FIG. 1 by taking an organic electroluminescence (hereinafter referred to as organic EL) display device as an example. FIG. 1 is a cross-sectional view of an essential part showing a schematic configuration of an organic EL display device.

  As shown in FIG. 1, the electro-optical device 10 includes an element substrate 11 as a substrate, a drive circuit unit 12 formed on the element substrate 11, a light emitting element unit 13 formed on the drive circuit unit 12, A sealing substrate 14 for sealing the drive circuit portion 12 and the light emitting element portion 13 is provided opposite to the element substrate 11. As the element substrate 11, a transparent glass substrate is preferably used. A drive element such as a TFT and a drive wiring are formed in the drive circuit unit 12 that is partially omitted in the drawing. The sealed space 15 sealed by the sealing substrate 14 is filled with an inert gas.

  The light emitting element section 13 has a plurality of partitioned areas 19 partitioned by the banks 20, and each of the light emitting elements 25 formed in the partitioned areas 19 constitutes a gradation element for forming an image. is doing. Further, a light shielding film 26 for preventing interference between gradation elements is formed between the bank 20 and the drive circuit unit 12 with chromium, oxide thereof, or the like.

  The bank 20 is a partition structure formed using acrylic resin, polyimide resin, or the like, and the partition region 19 forms a predetermined arrangement when viewed from the normal direction of the substrate surface (vertical direction in the drawing). It is formed with a pattern. Further, the bank 20 is formed so that the partition region 19 has a tapered shape in which the cross-sectional area decreases from the element substrate 11 toward the opening 19a when viewed from the cross-sectional direction (the illustrated direction).

  The light emitting element 25 includes a hole transport film 22 as a functional film and a functional film as a functional film between a segment electrode (anode) 21 that is an output terminal of the drive circuit unit 12 and a common electrode (cathode) 24. The organic EL film 23 is laminated.

  The segment electrode 21 is made of a light-transmitting conductive material such as indium tin oxide (ITO), and the common electrode 24 is made of a three-layer film of a calcium metal layer and a silver-magnesium alloy layer that protects the calcium metal layer. ing. The hole transport film 22 is a functional film for injecting holes into the organic EL film 23, and is formed of a polymer conductor such as a polythiophene derivative doped body (hereinafter referred to as PEDOT). For the organic EL film 23, a known organic EL material capable of emitting fluorescence or phosphorescence, for example, a polyfluorene derivative, a (poly) paraphenylene vinylene derivative, a polyphenylene derivative, or the like is used.

  In the above configuration, when a voltage is applied between the segment electrode 21 and the common electrode 24 by drive control via the drive circuit unit 12, holes are injected from the hole transport film 22 into the organic EL film 23, The holes combine with electrons from the common electrode 24 side to emit light. This light emission occurs near the interface between the hole transport film 22 and the organic EL film 23.

  In addition to the structure of the light emitting element 25 shown in FIG. 1, an electron transport film made of an oxadiazole derivative or the like may be provided between the organic EL film 23 and the segment electrode 21. This electron transport film is for injecting electrons into the organic EL film 23.

(Droplet discharge device)
Next, with reference to FIG. 2, a droplet discharge apparatus used in the droplet discharge method will be described. FIG. 2 is a schematic diagram illustrating an example of the configuration of the droplet discharge device.

  In FIG. 2, the droplet discharge device 200 includes a discharge head 201 having a plurality of nozzles 212 arranged on one surface, and a mounting table 203 for mounting a substrate 202 at a position facing the discharge head 201. Further, a scanning unit 204 that moves (scans) the ejection head 201 vertically and horizontally while maintaining a distance from the substrate 202, a functional liquid supply unit 205 that supplies functional liquid to the ejection head 201, and ejection control of the ejection head 201. And a discharge control means 206 for performing the above.

  The discharge head 201 is formed with a plurality of minute flow paths that branch into a pressure chamber (cavity) 211 and a nozzle 212. One surface of the outer wall of the pressure chamber 211 can be deformed by the piezoelectric element 210, and a droplet 213 is discharged from the nozzle 212 by generating pressure in the pressure chamber 211 by a drive signal from the discharge control means 206. The In addition to the electromechanical system as in this example, the discharge technique includes a so-called thermal system in which an electric signal is converted into heat to generate pressure.

  In the above configuration, by performing ejection control for each nozzle 212 in synchronization with the scanning of the ejection head 201, it is possible to dispose the functional liquid in a desired pattern on the substrate 202. The droplet discharge device 200 can also be configured to discharge a plurality of types of functional liquids during one scan.

(Method for forming light emitting element)
Next, a method for forming a light emitting element will be described along the flowchart of FIG. 3 with reference to FIG. FIG. 3 is a flowchart showing a process related to formation of the light emitting element. FIG. 4 is a cross-sectional view of the main part showing one process in the formation of the light emitting element.

  First, prior to the formation of the light emitting element, functional liquids corresponding to the respective functional films are prepared. Specifically, a functional liquid (hereinafter referred to as PEDOT liquid) containing Vitron-P (manufactured by Bayer), which is a type of PEDOT, contains an organic EL material for the hole transport film 22 (see FIG. 1). A functional liquid (hereinafter referred to as an organic EL liquid) is prepared for the organic EL film 23 (see FIG. 1). These functional liquids are appropriately adjusted for use in the droplet discharge device 200 (see FIG. 2) by adding a surfactant, a viscosity modifier, a humectant, and the like.

  Next, as shown in FIG. 4A, the light shielding film 26 is formed on the element substrate 11 on which the drive circuit section 12 and the segment electrode 21 are formed by using a vapor phase method, a photolithography method, and the like. (Step S1 in FIG. 3).

  Next, the bank 20 is formed on the light shielding film 26 (step S2 in FIG. 3). Specifically, a photosensitive resin film is formed on the entire surface of the element substrate 11 by using a spin coating method, and patterning is performed through exposure and development processes. At this time, the positive / negative of the photosensitive resin to be used is selected and the exposure conditions are optimized so that the tapered shape of the partition region 19 is obtained.

  Next, a lyophilic process is performed on the side of the element substrate 11 on which the bank 20 is formed by an oxygen plasma process or the like (step S3 in FIG. 3). By this treatment, the exposed surface of the segment electrode 21 in the partition region 19 is uniformly cleaned, so that the wettability unevenness is reduced and the wettability itself is improved.

Next, a liquid repellency process is performed on the side of the element substrate 11 on which the bank 20 is formed by a tetrafluoromethane (CF ₄ ) plasma process or the like (step S4 in FIG. 3). By this treatment, a fluorine group is introduced on the surface of the bank 20 made of an organic material, so that it has liquid repellency. At this time, the exposed surface of the segment electrode 21 made of an inorganic material is also somewhat affected by the plasma treatment, but not so much as to affect the lyophilicity. Note that the liquid repellent treatment described above may be omitted by using a resin material having liquid repellency (for example, a fluororesin such as hexafluoropolypropylene) as a resin material for forming the bank 20.

  Next, as shown in FIG. 4B, the PEDOT liquid 30 is arranged in the partition region 19 by using a droplet discharge method (step S5 in FIG. 3), and the element substrate 11 is placed in a vacuum dryer or the like. Or leave it to dry (step S6 in FIG. 3). Thereby, as shown by the arrow, the vapor | steam of a volatile component (water, an organic solvent, etc.) evaporates from the PEDOT liquid 30. FIG.

  In step S <b> 6, evaporation of volatile components in the vicinity of the outer edge of the partition region 19 is suppressed to some extent by the inner wall 20 a of the bank 20 formed so as to protrude toward the center of the partition region 19. As a result, the evaporation rate is balanced between the outer edge portion and the center portion having a relatively large surface area, and the PEDOT liquid 30 is uniformly formed throughout the partition region 19. Then, as shown in FIG. 4C, the hole transport film 22 having a good profile is formed.

  Next, as shown in FIG. 4D, the organic EL liquid 31 is disposed on the hole transport film 22 in the partition region 19 by using a droplet discharge method (step S7 in FIG. 3), and the element substrate. 11 is put into a vacuum dryer or the like or left to dry (step S8 in FIG. 3). As a result, the organic EL liquid 31 is turned into a film and becomes the organic EL film 23 (see FIG. 1).

  Here, it is preferable that the amount of the organic EL liquid 31 disposed in the partition region 19 in step S7 is set so that the liquid surface 31a is lower than the opening surface 19b. This is because, in step S8, in order to balance the evaporation rate between the regions in the partition region 19, it is desirable that the liquid surface 31a at the outer edge is always blocked by the inner wall 20a. For this reason, it is preferable to form the bank 20 sufficiently high in accordance with the required amount of the organic EL liquid 31 corresponding to the design film thickness. Further, the organic EL film 31 (see FIG. 1) may be formed by multilayering by repeating the steps S7 and S8 a plurality of times without arranging the entire amount of the organic EL liquid 31 at once.

  Finally, the common electrode 24 (see FIG. 1) is formed on the organic EL film 23 (see FIG. 1) by a vapor phase method or the like (step S9 in FIG. 3), and the light emitting element 25 is completed. When the common electrode 24 (see FIG. 1) is formed by a vapor phase method, it is preferable to incline the substrate surface of the element substrate 11 in order to ensure that the electrode material adheres to the inner wall 20a of the bank 20 as well.

  As described above, the electro-optical device 10 (see FIG. 1) manufactured through the above-described steps includes the hole transport film 22 and the organic EL film 23 (see FIG. 1) having a good profile, and thus has high quality. It is.

The present invention is not limited to the above-described embodiment.
For example, as another example of the electro-optical device or the functional film according to the present invention, a color filter film in a liquid crystal display device, a fluorescent film in a plasma display device, and the like can be given.
In the above-described embodiment, the functional liquid is arranged by the droplet discharge method. However, the functional liquid may be arranged by another method (for example, a dip method).
Moreover, each structure of each embodiment can combine these suitably, can be abbreviate | omitted, or can combine with the other structure which is not shown in figure.

FIG. 2 is a cross-sectional view of a main part showing a schematic configuration of an organic EL display device. FIG. 3 is a schematic diagram illustrating an example of a configuration of a droplet discharge device. 6 is a flowchart showing a process related to formation of a light emitting element. (A)-(d) is principal part sectional drawing which shows one process in formation of a light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electro-optical apparatus, 11 ... Element board | substrate as a board | substrate, 12 ... Drive circuit part, 13 ... Light emitting element part, 14 ... Sealing board | substrate, 15 ... Sealing space, 19 ... Partition area | region, 19a ... Opening part, 19b ... Opening surface, 20 ... bank, 20a ... inner wall, 21 ... segment electrode, 22 ... hole transport film as functional film, 23 ... organic EL film as functional film, 24 ... common electrode, 25 ... light emitting element, 26 ... light shielding film, 30 ... PEDOT liquid as functional liquid, 31 ... organic EL liquid as functional liquid, 31a ... liquid surface.

Claims (4)

A film forming method comprising: placing a functional liquid in a partitioned area partitioned by banks on a substrate; and drying the placed functional liquid.
The partition region has a taper shape in which a cross-sectional area is reduced from the substrate toward the opening.   2. The film forming method according to claim 1, wherein in the step of disposing the functional liquid in the partition region, a liquid level of the functional liquid is set lower than an opening surface of the partition region. A functional film formed by a liquid phase method in a partitioned area partitioned by banks on a substrate,
The functional region is characterized in that the partition region has a tapered shape that reduces a cross-sectional area from the substrate toward the opening. An electro-optical device comprising the functional film according to claim 3.

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