JP2007095513A - Method of manufacturing optical display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical display device, in which when forming a functional thin film included in the optical display device by the letterpress printing method, the quantity of ink held on a printing plate is controlled to make the thickness of the functional thin film uniform, thereby enabling display without unevenness. <P>SOLUTION: In the method of manufacturing an organic EL display device 9 as an optical display device having an organic light emitting layer 5 as a functional thin film layer by the letterpress printing method, the surface energy of a projection part of the letterpress printing plate is 50-80 mN/m<SP>2</SP>and the surface energy of a recess part thereof is 20-50 mN/m<SP>2</SP>, wherein the UV-ozone treatment or the low temperature plasma treatment is applied to the projection part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical display device that displays a visually recognizable image, and more particularly to a method for forming an organic light emitting layer of an organic electroluminescence display device (hereinafter referred to as an organic EL display device).

  In an organic EL element, a light emitting layer made of an organic light emitting material is formed between two opposing electrodes, and light is emitted by passing a current through the light emitting layer. Is important, and a thin film of about 100 nm is required. Further, in order to make this a display, it is necessary to pattern it with high definition.

  The organic light emitting material for forming the light emitting layer includes a low molecular material and a high molecular material. Generally, a low molecular material is formed into a thin film by resistance heating vapor deposition or the like, and is patterned using a fine pattern mask at this time. In this method, there is a problem that the patterning accuracy is less likely as the substrate becomes larger.

  Therefore, recently, a method of forming a thin film by a wet coating method, in which a polymer material is dissolved in a solvent to form a coating solution, has been tried. As a wet coating method for forming a thin film, there are a spin coating method, a bar coating method, a coating coating method, a dip coating method, and the like. These wet coating methods are difficult, and it is thought that thin film formation by a printing method that is good at coating and patterning is most effective.

  Furthermore, among various printing methods, in an optical display device such as an organic EL display device or a liquid crystal display device using a glass substrate, a method of using a hard plate such as a metal printing plate such as a gravure printing method is used. An offset printing method using an unsuitable elastic rubber blanket and a relief printing method using an elastic rubber plate or resin plate are also appropriate. Actually, as an attempt by these printing methods, a method by offset printing (for example, see Patent Document 1), a method by letterpress printing (for example, see Patent Document 2), and the like have been proposed.

  On the other hand, polymeric organic light-emitting materials are poorly soluble in alcohol and aliphatic organic solvents, and are dissolved in aromatic organic solvents such as toluene and xylene to make a coating liquid (hereinafter referred to as ink). Therefore, the organic organic light-emitting material ink (hereinafter referred to as organic EL ink) is an aromatic organic solvent ink. However, a rubber blanket used for offset printing has a problem that it is easily swollen or deformed by an aromatic organic solvent such as toluene or xylene. Offset printing is a system in which ink is applied to a plate on which image lines are formed, the ink is transferred to an elastic blanket, and the ink is transferred from the blanket to a printing substrate. The blanket that mediates the transition is required to have elasticity, and rubber is generally used. The types of rubbers used range from olefin rubbers to silicone rubbers, but none of these rubbers are resistant to toluene or xylene solvents and are prone to swelling and deformation. It is inappropriate for printing.

In any case, when the organic EL ink is printed, it is necessary to control the surface property of the plate in order to ensure the transfer amount of the ink. This is because the type of solvent in which the organic EL material dissolves is limited and the solubility is small, so that the solvent, solid content, viscosity, and the like are naturally determined. In addition, methods such as adding additives to alleviate such restrictions on the ink side, increase viscosity, and improve leveling properties are also conceivable. However, if foreign substances are mixed in the organic EL material, the light emission efficiency and lifetime are increased. It is difficult to use an additive. That is, since there are restrictions on the ink side as described above, it is necessary to control the transfer amount of ink, the uniformity of film thickness, and the like by controlling the surface properties of the plate. In addition, the limitation of these solvents and additives is a common problem even in the case of forming a conductive pattern typified by a color filter and an electrode constituting an optical display device.

The above prior art documents are shown below.
JP 2001-93668 A JP 2001-155858 A

  The present invention solves the problems of the prior art, and the problem is that the printing plate retains the functional thin film included in the optical display device by the relief printing method. An object of the present invention is to provide a method of manufacturing an optical display device capable of displaying without unevenness by controlling the amount of ink and making the thickness of a functional thin film uniform.

In order to achieve the above object in the present invention, first, the invention of claim 1 is a method of manufacturing an optical display device in which a functional thin film is formed by a relief printing method, and is a printing plate used in the relief printing method. The surface energy of the convex part is 50 to 80 mN / m ² , and the surface energy of the concave part is 20 to 50 mN / m ² .

  According to a second aspect of the present invention, there is provided the method for manufacturing an optical display device according to the first aspect, wherein the convex portions of the printing plate are subjected to UV ozone treatment.

  According to a second aspect of the present invention, there is provided the method for manufacturing an optical display device according to the first aspect, wherein the convex portion of the printing plate is subjected to a low temperature plasma treatment.

  According to a third aspect of the present invention, there is provided the method for manufacturing an optical display device according to any one of the first to third aspects, wherein the printing plate is made of a water developable resin.

  According to a fourth aspect of the present invention, the optical display device is an organic electroluminescence display device in which a functional thin film is formed. The optical display according to any one of the first to fourth aspects, This is a device manufacturing method.

  According to a fifth aspect of the present invention, the functional thin film is an organic light emitting layer constituting the organic electroluminescent display device. The method for manufacturing an optical display device according to the fifth aspect is provided. .

  The optical display device in the above claims refers to a device capable of displaying a visible image regardless of a still image or a moving image, and examples thereof include an organic EL display device and a liquid crystal display device.

A functional thin film refers to a thin film that performs a function necessary for optical display. In an organic EL display device, an electrode, a thin film transistor, a hole transport / injection layer, an organic light emitting layer, and a liquid crystal display device. Can include electrodes, thin film transistors, and color filter layers. Here, a case where an organic light emitting layer of an organic electroluminescence display device (organic EL display device) is formed will be described. The organic EL display device includes at least an organic light emitting layer and a pair of electrodes sandwiching the organic light emitting layer.

  In addition, the letterpress printing method is a printing method in which the image portion has a convex shape, that is, any printing method using a letterpress, but the letterpress printing method described in this specification is composed of a rubber plate or a resin plate. A printing method using a letterpress will be shown. In the printing industry, the one using rubber letterpress is called flexographic printing, and the one using resin letterpress is distinguished from resin letterpress printing. And Currently, photosensitive rubber plates and resin plates are used in the relief printing system, but the material of the plates is diversified, and the distinction between photosensitive rubber plates and photosensitive resin plates is unclear. In this specification, this distinction is not particularly provided, and both are referred to as photosensitive resin plates. The photosensitive resin relief plate is a plate that forms a relief plate by exposing the photosensitive resin using a mask that transmits light only to the image area, curing the image area, and washing away the uncured portion with a solvent or the like. There are two types: a solvent development type in which washing is mainly carried out with a solvent and a water development type in which washing is carried out with water, depending on whether the plate material comprises a hydrophilic component or a hydrophobic component.

  Since this invention is the above structure, there exist the following effects.

That is, according to the first aspect of the invention, in the method of manufacturing an optical display device in which the functional thin film is formed by the relief printing method, the ink for forming the functional thin film is a solvent in order not to impair the functionality. Although there are many restrictions on additives, the surface energy of the convex part of the printing plate used in the above-mentioned relief printing method is 50 to 80 mN / m ² , and the surface energy of the concave part is in the range of ²⁰ to 50 mN / m ^2. The amount of ink transferred to the printed circuit board can be kept within an appropriate range, and the film thickness of the printed pattern can be kept uniform.

  Further, according to the inventions according to claims 2 and 3, the ink for forming the functional thin film on the surface energy of the printing plate by treating the convex portions of the printing plate by UV ozone treatment or by low temperature plasma. Can be adjusted so as to be an appropriate amount, and can be modified so as to be transferred to the substrate to be printed.

  According to the fourth aspect of the present invention, the printing plate is made from a water-developable resin and a method for producing an optical display device, whereby the water-developable resin becomes a solvent having a high SP (Solubility parameter) value. Since the resistance is high, an ink for forming a functional thin film often using a solvent having a high SP value can be suitably printed.

  Therefore, the present invention can control the amount of ink retained on the printing plate when forming the functional thin film included in the optical display device by the relief printing method, and make the film thickness of the functional thin film uniform. Therefore, it is possible to provide a method of manufacturing an organic EL display device among optical display devices that are free from unevenness and short-circuited.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

Formation of the light emitting layer of the organic EL element in the present invention is performed by a relief printing method. Printing can be performed using a letterpress printing method using a resin letterpress, or a rubber-type flexographic plate, but the organic EL material is soluble in an aromatic organic solvent and is used for high-definition displays. Is required to have high solvent resistance. The water-developable photosensitive resin improves the solvent resistance by containing many hydrophilic components, so it can be used as a printing plate for organic EL inks that use aromatic solvents such as toluene and xylene. The resin plate with a large amount of hydrophilic components shows a high value far from the SP value range of 8 to 9 of toluene / xylene, and a sufficient toluene / xylene resistance at 12 or more. Further, the solvent resistance can be directly evaluated by the expansion rate when actually immersed in toluene. When the expansion is 1% or less after immersion for 24 hours, it can be used as a plate for organic EL ink. A water-developable photosensitive resin relief is very preferable in terms of high definition and solvent resistance.

  Further, the plate surface needs to be surface-modified. This is because the higher the definition of the display is, the smaller the size of the convex portion of the printing plate on which the ink is placed, so that the amount of ink transfer decreases. Also, in photosensitive resin plates that require development, the components dissolved by development cover the projections, increasing the surface energy of the plate surface and reducing the amount of ink that is deposited. It is also necessary to perform surface modification treatment.

  As the surface modification treatment, in the present invention, UV ozone treatment or low-temperature plasma treatment for irradiating ultraviolet rays is used, and as the low-temperature plasma treatment, corona discharge treatment, glow discharge treatment, atmospheric pressure plasma treatment, or the like is used. it can.

As the surface energy, the convex portion of the printing plate may be in the range of 50 to 80 mN / m ² , preferably in the range of 65 to 75 mN / m ² , and if the surface energy is greater than 75 mN / m ² , the ink transfer The amount is remarkably reduced and an appropriate film thickness cannot be obtained. On the other hand, if it is smaller than 65 mN / m ^2, it becomes close to the surface energy of the concave portion, so that ink is taken in the concave portion and the film thickness is reduced or the shape of the concave portion is reflected, resulting in poor pattern accuracy.

  As a printing machine which prints the light emitting layer of the organic EL element in this invention, as shown in FIG. 2, the ink tank 10, the ink chamber 12, the anilox roll 14, and the letterpress 16 which have stored the ink for organic EL, for example An ink layer 14a having a wound plate cylinder 18 and supplied to the surface by rotation of the anilox roll 14 is formed in a uniform film thickness, and the ink of this ink layer 14a is a relief printing plate wound on the plate cylinder 18. On the other hand, there is a circular pressure type letterpress printing machine on which the substrate to be printed 24 is placed and moved to a printing position, and the ink is transferred to the support table 20. .

  For example, as shown in FIG. 3, a relief printing press of a type in which the ink 13 from the ink tank 10 is supplied to the die head 11 and transferred from the die head 11 to the relief plate 16 via the anilox roll 14 can be used. .

  Next, the structure of the organic EL element in the present invention is exemplified, but the structure is not limited to this structure. For example, as shown in the side sectional view of FIG. 1, the organic EL display device 9 in the present invention is formed. An indium-tin oxide (ITO) film is formed as a transparent pixel electrode (2) on a glass substrate (1) and is formed into a pattern as an electrode, and a polymer is formed thereon by wet coating. Hole transport layer (4) is formed.

  On top of this, the organic light emitting layer (5) is formed in a pattern by the printing method described above, and further, a cathode (6) made of a metal thin film is formed in a pattern on the organic light emitting layer (5) by these vapor deposition methods. Is hermetically sealed with a glass cap (7) to protect it from external oxygen and moisture.

  Specific examples of the present invention will be described below.

As for the printing conditions, the printing machine has an anilox roll for supplying ink to the printing plate, a cylindrical plate cylinder, and a flat table on which the substrate is placed, and the cylindrical plate cylinder rotates on the flat table. Printing was performed using a flatbed printing machine that prints on the substrate. As the printing plate, a printing plate of a type in which various prepressed sheet-like relief plates are wound around a cylindrical plate cylinder was used.

  As the organic light emitting material ink, a solution in which a polyphenylene vinylene derivative, which is a polymeric fluorescent substance, was dissolved in tetralin was used. In addition, as a substrate on which the organic light emitting layer is printed, a glass substrate in which an indium-tin oxide (ITO) film, which is a transparent electrode, is patterned according to the pixel of the EL element, and a hole is formed thereon A substrate having a transport layer coated on the entire surface was used. As the hole transport material, a polymer material composed of a polythiophene derivative and polystyrene sulfonic acid was used.

  The printed pattern of the light emitting layer is a line pattern for producing a passive matrix type display having a diagonal size of 1.8 inches, and is a pattern in which 64 lines having a line width of 166 μm are formed in about 33 mm square. .

  The resin relief printing plate used for printing the light emitting layer was made as follows. Using a plate material in which a water-developable photosensitive resin layer is laminated on a PET film substrate, a film mask for forming a predetermined image line is applied to the surface of the plate material, and from above the mask Irradiate ultraviolet rays with an exposure machine to cure the image area, and then wash it with tap water to wash out the uncured area to form the image area (convex area) and non-image area (recess area). This was dried to remove moisture, and then post-exposed again with an exposure machine to obtain a resin relief plate.

The surface energy of the resin relief plate thus obtained, the convex portion at 65 mN / m ^2, the recess was also 65 mN / m ^2.

  UV irradiation with 185 nm and 254 nm as main wavelengths creates an ozone atmosphere of 5 ppm, the resin relief printing plate is exposed to the atmosphere for 5 minutes to perform UV ozone treatment, the surface energy of the convex part is 73 mN / m, the surface of the concave part The energy was 47 mN / m.

  Using the resin relief printing plate treated with UV ozone in this way, the light emitting layer was printed on the light emitting layer printing substrate under the above printing conditions. The film thickness of the light emitting layer was 80 nm which is the optimum value of the light emission efficiency. The uniformity of the film thickness was 80 nm ± 5 nm. Thereby, the light emitting layer patterned on the glass substrate which has an ITO electrode layer and a positive hole transport layer was obtained. The luminance of light emission was uniform and there was no short circuit.

  As the surface treatment of the resin relief plate produced in the same manner as in Example 1, a corona discharge treatment, which is a kind of low-temperature plasma treatment with an intensity of 8 mA, is performed at a speed of 2.5 m / min, and the surface energy of the convex portion is 71 mN / m. The surface energy of the recess was 49 mN / m.

  Using the resin relief printing plate subjected to the corona discharge treatment in this manner, the light emitting layer was printed on the light emitting layer printing substrate under the same printing condition 1 as in Example 1. The film thickness of the light emitting layer was 80 nm which is the optimum value of the light emission efficiency. The uniformity of the film thickness was 80 nm ± 5 nm. Thereby, the light emitting layer patterned on the glass substrate which has an ITO electrode layer and a positive hole transport layer was obtained. The luminance of light emission was uniform and there was no short circuit.

  Below, the comparative example of this invention is demonstrated.

Using the water-developing type resin relief plate in Example 1, the light emitting layer was printed on the light emitting layer printing substrate under the same printing conditions as in Example 1 without performing surface treatment such as UV ozone treatment. The film thickness of the light emitting layer was only 30 nm, and the uniformity of the film thickness was 40 nm ± 20 nm, resulting in uneven emission luminance and many shorts.

It is explanatory drawing which represented the example of the organic EL display element obtained by the example of the manufacturing method of the optical display apparatus of this invention with the side cross section. It is explanatory drawing which represented the example of the printing apparatus used for the manufacturing method of the optical display apparatus of this invention by the side surface. It is explanatory drawing which represented on the side the other example of the printing apparatus used for the manufacturing method of the optical display apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Pixel electrode 3 ... Insulating partition 4 ... Hole transport layer 5 ... Organic light emitting layer 6 ... Cathode 7 ... Sealing cap 8 ... Adhesive

Claims (6)

A method for manufacturing an optical display device in which a functional thin film is formed by a relief printing method, wherein the surface energy of a projection of the printing plate used in the relief printing method is 50 to 80 mN / m ² , and the surface energy of a recess is 20 to 20 50 mN / m < ² >, The manufacturing method of the optical display apparatus characterized by the above-mentioned.   2. The method of manufacturing an optical display device according to claim 1, wherein the convex portion of the printing plate is subjected to UV ozone treatment.   The method for manufacturing an optical display device according to claim 1, wherein the convex portion of the printing plate is subjected to low-temperature plasma treatment.   The method for manufacturing an optical display device according to claim 1, wherein the printing plate is made of a water-developable resin.   5. The method of manufacturing an optical display device according to claim 1, wherein the optical display device is an organic electroluminescence display device in which a functional thin film is formed.   6. The method of manufacturing an optical display device according to claim 5, wherein the functional thin film is an organic light emitting layer constituting the organic electroluminescence display device.

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