JP2006344590A - Photosensitive black conductive paste composition for display electrode formation, as well as black conductive thick film for display electrode, and its forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive black conductive paste for display electrode formation for forming a black conductive thick film having high conductivity, low lightness, and low yellowness, and provide the black conductive thick film for the display electrode formation, and provide a forming method of the black conductive thick film for the display electrode. <P>SOLUTION: In the photosensitive black conductive paste for forming the black conductive thick film 40, silver powder contained as a conductive component is so fine as to have a specific surface area of around 1.0 or 2.0 (m<SP>2</SP>/g), and a black pigment 46 has high photosensitivity, and consequently high resolution because it 46 is constituted of Co<SB>3</SB>O<SB>4</SB>powder in which a specific surface area is within a range of around 3 to 13 (m<SP>2</SP>/g). The black conductive thick film which has sufficiently high conductivity and sufficiently low lightness and yellowness is obtained because the black conductive thick film 40 formed from that photosensitive black conductive paste is constituted by bonding sliver 44 to the black pigment 46 composed of Co<SB>3</SB>O<SB>4</SB>by using glass 48. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photosensitive black conductive paste composition for forming display electrodes, a black conductive thick film for display electrodes, and a method for forming the same.

  For example, in a hermetic space formed between a pair of parallel flat plates, a plurality of light emitting sections provided in a matrix along one direction and another direction orthogonal thereto, and discharge is selectively performed in the plurality of light emitting sections. A plurality of pairs of discharge electrodes are provided so that a pair is positioned for each light emitting section to generate light, and a desired image such as a character, symbol, figure or the like is displayed by emitting light using the discharge. There are known discharge display devices of the type. For example, the light emission of neon orange or the like accompanying the generation of plasma generated by gas discharge is directly used, or the light emission of the phosphor excited by the ultraviolet light generated by the plasma is provided in the light emitting section. For example, a plasma display panel (hereinafter referred to as PDP). Such a PDP is considered to be an image display device that replaces a cathode ray tube because it is relatively easy to make a thin and large display surface and has a wide viewing angle and a fast response speed comparable to those of a cathode ray tube. For example, a wall-mounted television is made possible by constructing one pixel from three to four light emitting sections provided with three color phosphors of red (RED), green (GREEN), and blue (BULE) to enable multicolor display. Such a thin full-color display device is expected to be realized.

FIGS. 1A and 1B are examples of the above-described PDP, and are diagrams showing a configuration of an AC type surface discharge PDP 8 having a three-electrode structure described in Patent Document 1, for example. In the figure, in a hermetic space formed between a front plate 10 and a back plate 12 positioned in parallel to each other, a plurality of light emitting elements are formed in the longitudinal direction by being partitioned by a longitudinal partition 14 along one direction. While a plurality of discharge spaces 16 including partitions are provided, a plurality of write electrodes 18 passing between the barrier ribs 14 along one direction on the back plate 12 are provided so as to be covered with an overcoat 32. On the front plate 10, a plurality of dielectric layers 20 made of a low softening point glass such as borosilicate glass and a protective film 22 made of magnesium oxide (MgO) along the other direction orthogonal to the one direction. A pair of display discharge electrodes (sustain electrodes) 24 a and 24 b are provided, and phosphor layers 26 are provided separately for each discharge space 16 on the inner surface of the back plate 12 and the surface of the barrier ribs 14. In the figure, the display discharge electrode 24 generates surface discharge over a wide range and minimizes the shielding of the display light emitted through the front plate 10, so that ITO (Indium) formed by a thin film process or the like is used. A transparent electrode 28 made of Tin Oxide (indium tin oxide), ATO (Antimon Tin Oxide: antimony tin oxide) or the like, and on the transparent electrode 28 at the outer end position in the width direction for each pair in order to supplement the conductivity. And a bus electrode 30 formed of a thin film conductor or a thick film conductor. In the figure, reference numeral 34 denotes an undercoat for suppressing the reaction between the write electrode 18 and the back plate 12 made of soda, lime and glass.
JP-A-3-78936

By the way, in any case where the bus electrode 30 is supplementarily used for the purpose of supplementing the conductivity of the transparent electrode 28 or used alone, the voltage drop in the longitudinal direction of the bus electrode 30 is minimized. Therefore, while low resistance is required, low reflectivity is also desired at the same time. In the PDP 8 configured as described above, light transmitted through the front plate 10 is viewed on the surface 38 side opposite to the inner surface 36 of the front plate 10 on which the bus electrode 30 is provided. This is because the reflection of external light at 38 is suppressed and a high display contrast is obtained. Therefore, when forming a thin film, for example, after forming a black Cr (chromium) layer on the front plate 10 (precisely on the transparent electrode 28), Al (aluminum), Cu (copper), etc. A highly conductive metal layer is provided. In the case of forming a thick film, RuO ₂ (ruthenium oxide) or Fe— in Ag—Pd (silver-palladium) paste, Ag—Cu (silver-copper) alloyed paste, or Ag (silver) paste. Thick film screen printing method using black conductive paste containing pyrochlore oxide typified by Cr-Mn (iron-chromium-manganese) pigment and Cu-Cr-Mn (copper-chromium-manganese) pigment as black pigment Etc. are applied on the front plate 10 by using the above. The bus electrode 30 can be formed by either the thin film method or the thick film method, but the thick film method is advantageous in terms of manufacturing cost. In addition, said black pigment is added in order to reduce the reflectance, ie, brightness, of a thick film conductor. Here, “brightness” is a measure of the reflectance of the object surface and means the brightness of the color. For example, ideal black and white are displayed as L values that are digitized as 0 and 100, respectively. Is done.

However, since the black pigment as described above has low conductivity, the resistance value of the thick film conductor is remarkably increased when it is added to such an extent that the brightness is sufficiently low. Therefore, since the addition amount of the black pigment is limited to a small amount that can satisfy the high conductivity required for the bus electrode 30 (display discharge electrode 24), the brightness of the bus electrode 30 becomes relatively high, There was a problem that a high contrast of the display of the PDP 8 could not be obtained. This is particularly a problem with alloyed pastes that are inherently high in resistance. On the other hand, among the above thick film conductors, those produced from Ag paste have a relatively low resistance, so a large amount of black pigment is added to maintain a relatively high conductivity while maintaining a relatively low brightness. Can do. However, it is difficult to say that the brightness obtained in this case is sufficient, and for example, as shown in FIG. 2, one or both of the display discharge electrode pairs 24a and 24b (one in the figure) are directly on the front plate 10. In the case where only the bus electrode 30 formed with a film is formed, since Ag diffuses into the front plate 10 and yellows, there is a problem that the yellowness increases and the contrast may decrease. It is known that this yellowing can be suppressed as the amount of black pigment added increases. However, for thick film conductors where it is desired to reduce the brightness and yellowness while maintaining high conductivity, the above-mentioned allowable addition Yellowing cannot be sufficiently suppressed within the range of the amount. Of the above black pigments, RuO ₂ fine powder [for example, having a specific surface area of about 35 (m ² / g)] is relatively excellent in each of the above characteristics, but is expensive and fine. It is difficult to handle. Incidentally, in the structure shown in FIG. 1, the display discharge electrode 24 is composed of the transparent electrode 28 and the bus electrode 30 formed thereon. However, a lower luminance is suppressed by suppressing the translucency due to the transparent electrode 28. Therefore, it is desired that at least one of the display discharge electrodes 24a and 24b is constituted only by the relatively narrow bus electrode 30, and even if so, it is confirmed that there is no problem in terms of discharge characteristics. ing.

  As one method for forming the bus electrode 30 on the front plate 10 using the black conductive paste as described above, there is a method using a photolithography method. In this method, for example, a photosensitive conductive paste is applied to the entire inner surface 36 of the front plate 10 and dried to form a paste film having a predetermined thickness, and the paste film is exposed by exposure through a mask having a predetermined pattern. After being selectively cured, the unexposed portion is washed away with a developer and further baked to form a thick film conductor. Therefore, it is easy to form a large-area and high-definition pattern compared to a direct printing method such as a thick film screen printing method that can cause a pattern shift due to screen distortion. However, in this conductor forming method, it is necessary to selectively sensitize and cure the paste film as described above. Therefore, if a large amount of black pigment is mixed in the paste for the purpose of reducing the lightness of the thick film conductor, the light irradiated during exposure will not reach the inside of the paste film and resolution will be reduced. However, there is a problem in that only a thick film conductor having higher brightness can be obtained because the amount of the black pigment that can be mixed is limited to be smaller than when the thick film screen printing method is used. That is, even in the thick film conductor formed by the photolithography method in this way, it has been desired to further reduce the brightness, yellowness, and resistance value while maintaining high resolution. Here, the “resolution” represents the degree of the minimum distance at which two different points can be identified. The above problem is not limited to the PDP bus electrode, as long as it is a thick film conductor that has high conductivity and low lightness and yellowness, and other electrodes provided on the front plate in the PDP, It can occur in the same manner for other display electrodes.

  The present invention has been made in the background of the above circumstances, and its purpose is to form a photosensitive black conductive film for forming a display electrode for forming a black conductive thick film having high conductivity and low brightness and low yellowness. The object is to provide a paste, a black conductive thick film for display electrodes, and a method for forming a black conductive thick film for display electrodes.

The gist of the first invention for achieving such an object is to include a silver powder, a glass powder, an organic binder, an organic solvent, a photosensitive composition, and a black pigment. A photosensitive black conductive paste composition for forming a display electrode, which is used to form a thick conductive black film that functions as a display electrode by exposure and development, and (a) the black pigment is It consists of a Co ₃ O ₄ (tricobalt tetroxide) powder having a specific surface area of 1 to 20 (m ² / g).

Further, the gist of the second invention for achieving the above object is a black conductive thick film for a display electrode, which is provided in a predetermined pattern on a predetermined substrate and formed by combining silver and a black pigment with glass. And (a) the black pigment is made of Co ₃ O ₄ having a specific surface area of 1 to 20 (m ² / g), and (b) a photosensitive conductive paste containing a photocurable compound. The pattern is formed by exposure and development.

  Further, the gist of the third invention for achieving the above object is to function as an electrode of a display on the other surface opposite to the one surface of the translucent substrate observed from a predetermined one surface side. A method of forming a black conductive thick film for a display electrode in a predetermined pattern, comprising: (a) a photosensitive black conductive paste composition for forming a display electrode according to any one of claims 1 to 3 on the other surface of the translucent substrate. A photosensitive black paste film forming step of forming a photosensitive black conductive paste film by applying an object, and (b) a film having higher brightness and higher conductivity than that produced from the photosensitive black conductive paste film. A photosensitive conductive paste having a predetermined thickness is formed by applying a photosensitive high brightness high conductive paste composition on the photosensitive black conductive paste film to form a photosensitive high brightness high conductive paste film. Shape the membrane A photosensitive high-lightness paste film forming step to be formed; (c) an exposure step of selectively exposing the photosensitive conductive paste film through a shielding film having a predetermined opening pattern; and (d) the exposure step after the exposure step. A development step of washing and removing a non-cured portion of the photosensitive conductive paste film with a predetermined developer; and (e) a baking step of baking the photosensitive conductive paste film to generate a black conductive thick film of a predetermined pattern; Is to include.

According to the first invention, the photosensitive black conductive paste composition for forming display electrodes contains Co ₃ O ₄ powder having a specific surface area of 1 to 20 (m ² / g) as a black pigment. In addition to having high resolution, the black conductive thick film formed from this paste composition is composed of silver and a black pigment composed of Co ₃ O ₄ combined with glass. Is obtained, and a black conductive thick film having sufficiently high brightness and yellowness is obtained. That is, when a black pigment is added to the conductive paste as described above, the lightness and yellowness of the conductive thick film generated from the paste are reduced, while the resistance value of the conductive thick film is increased and the photosensitivity is increased. The resolution is lowered. In this case, the effect is not clear, but according to the results of the inventors' evaluation of these properties for various pigments, when Co ₃ O ₄ powder was added as a black pigment, it was compared with other black pigments. Accordingly, the decrease in brightness and yellowness is remarkably large, and the increase in resistance value and the decrease in resolution are suppressed. In addition, since the specific surface area of the black pigment is sufficiently large as long as the conductivity of the black conductive thick film is kept sufficiently high and the resolution is also kept sufficiently high, a black color can be obtained satisfactorily. As a result, the brightness is sufficiently reduced. In addition, if it is less than 1 (m ² / g), the lightness is not sufficiently lowered. On the other hand, if it exceeds 20 (m ² / g), the resistance value is increased and the resolution is remarkably lowered. By the above, the photosensitive black electrically conductive paste composition for display electrode formation which can form black electroconductive thick film with high electroconductivity and low brightness and yellowness can be obtained. The range of the specific surface area is more preferably 2 to 15 (m ² / g).

According to the second aspect of the invention, the black conductive thick film is composed of Co ₃ O ₄ having a specific surface area of 1 to 20 (m ² / g), and a conductive paste containing a photocurable compound. A pattern is formed by exposure and development using Therefore, as explained in the effect of the first invention, Co ₃ O ₄ has a large effect of lowering the brightness and yellowness of the black conductive thick film as compared with other black pigments, and its resistance value is reduced so much. Do not raise. In addition, when the black conductive thick film is patterned by the so-called photolithography method by exposure and development, the resolution at the time of exposure and development is not greatly reduced. In addition, since the specific surface area of the black pigment is sufficiently large as long as the conductivity of the black conductive thick film is kept sufficiently high and the resolution is also kept sufficiently high, a black color can be obtained satisfactorily. As a result, the brightness is sufficiently reduced. In addition, if it is less than 1 (m ² / g), the lightness is not sufficiently lowered. On the other hand, if it exceeds 20 (m ² / g), the resistance value is increased and the resolution is significantly lowered. With the above, a black conductive thick film for display electrodes having sufficiently high conductivity and sufficiently low brightness and yellowness can be obtained. The range of the specific surface area is more preferably 2 to 15 (m ² / g).

  According to the third aspect of the invention, when forming the black conductive thick film, in the black paste film forming step, the photosensitive black for display electrode formation according to any one of the first aspect of the invention is formed on the other surface of the translucent substrate. The conductive paste composition is applied to form a photosensitive black conductive paste film, and in the photosensitive high-lightness paste film forming step, the lightness is higher and the conductivity is higher than that produced from the photosensitive black conductive paste film A photosensitive high brightness high conductive paste composition for forming a film is applied on the photosensitive black conductive paste film, and a photosensitive high brightness high conductive paste film is laminated to form a photosensitive film having a predetermined thickness. A conductive paste film is formed, and in the exposure process, the photosensitive conductive paste film is selectively exposed through a shielding film having a predetermined opening pattern, and after the exposure process, in the development process. Then, the non-cured portion of the photosensitive conductive paste film is washed and removed with a predetermined developer, and further, in the baking process, the photosensitive conductive paste film is baked to generate a black conductive thick film with a predetermined pattern. The Therefore, the black conductive thick film is patterned by the so-called photolithographic method using the photosensitive black conductive paste composition for forming the display electrode, so that it is easier than the pattern forming by the thick film screen printing method. An accurate pattern is obtained. Also, the black conductive thick film is formed by laminating a black conductive layer generated from the photosensitive black conductive paste film and a high brightness high conductive layer generated from the photosensitive high brightness high conductive paste film. The overall conductivity is sufficiently enhanced by the high brightness and high conductivity layer. On the other hand, since the black conductive layer of the two types of laminated conductive layers is observed through the light transmissive substrate on one surface side of the light transmissive substrate on the viewing side, the black conductive thickness The color tone of the film is substantially determined by the black conductive layer. At this time, since the conductivity of the black conductive thick film is ensured by the high brightness and high conductivity layer, the conductivity of the black conductive layer may be relatively low. Moreover, since the high-lightness and high-conductivity paste film is easier to expose than the black paste film containing the black pigment, the black paste film is harder to be exposed than when the whole is produced from the black paste film. In addition, sufficient exposure can be ensured for the entire conductive paste film. Therefore, it is possible to sufficiently reduce the brightness and yellowness of the black conductive thick film by extending the black conductive layer by sufficiently increasing the amount of the black pigment contained in the black paste film. As described above, a black conductive thick film having high conductivity and low brightness and yellowness can be formed while maintaining high resolution.

Here, preferably, the specific surface area of the silver powder is 0.4 to 2.5 (m ² / g). In this way, the photosensitive black conductive paste composition for forming a display electrode has a fine specific surface area of 0.4 to 2.5 (m ² / g) of silver powder contained as a conductive component and a black pigment. Since it is Co ₃ O ₄ powder, it has high photosensitivity and high resolution, and the black conductive thick film formed from the photosensitive black conductive paste composition for forming display electrodes has silver and Co. _{Since the} black pigment composed of ₃ O ₄ is combined with glass, a black conductive thick film having sufficiently high conductivity and sufficiently low brightness and yellowness can be obtained. If the specific surface area of the silver powder is less than 0.4 (m ² / g), it becomes difficult to form a continuous film during firing, while if it exceeds 2.5 (m ² / g), it becomes difficult to form a paste and the paste film contains In this case, since the organic binder necessary for holding the silver powder increases, the thickness of the conductive thick film after firing becomes thin, so that the resistance value increases in any case. On the other hand, if it exceeds 2.5 (m ² / g), exposure becomes difficult and the resolution deteriorates. More preferably, the range of the specific surface area of the silver powder is 0.8 to 2.0 (m ² / g).

  Preferably, the silver powder has a spherical shape. In this way, when compared with similar particle sizes, spherical particles have a small specific surface area and a large particle size per surface area, so the amount of organic binder required to form a paste film is reduced. Thus, conductivity can be increased. Moreover, since the spherical particles are less likely to cause scattering of the irradiated light inside the paste film as compared with the plate-like and irregular shapes with many irregularities, the resolution is also improved. Accordingly, a photosensitive black conductive paste composition for forming a display electrode capable of forming a conductive thick film having higher conductivity while maintaining higher resolution can be obtained.

  Preferably, the silver powder is contained in a range of 40 to 80 (wt%) as a percentage of the whole paste composition. In this way, the content of the silver powder is sufficiently increased within the range that can be easily pasted and easily exposed, so that the film thickness after drying and baking can be sufficiently increased, so that higher conductivity is achieved. Is obtained. If it exceeds 80 (wt%), the irradiated light does not sufficiently reach the inside of the paste film, so that the resolution is remarkably lowered.

Preferably, the glass powder has a specific surface area of 0.5 to 10 (m ² / g). If it is less than 0.5 (m ² / g), the resistance value increases and the particle size is large, so the printability deteriorates (for example, line and edge defects after development occur), and on the contrary, it exceeds 10 (m ² / g). Dispersibility becomes worse and pasting becomes difficult. Further, as the glass powder, for example, a low softening point glass mainly composed of lead borosilicate glass having a softening point of 600 (° C.) or less, that is, PbO—SiO ₂ —B ₂ O ₃ glass, PbO—SiO ₂ -B ₂ O ₃ -Al ₂ O ₃ glass, PbO-SiO ₂ -B ₂ O ₃ -ZnO glass, PbO-SiO ₂ -B ₂ O ₃ -Al ₂ O ₃ -ZnO glass, Bi ₂ O ₃ -SiO ₂ -B ₂ O ₃ glass, ZnO-SiO ₂ -B ₂ O ₃ glass, R ₂ O-ZnO-SiO ₂ -B ₂ O ₃ glass (R ₂ O is an alkali metal oxide), etc. Preferably used. In the case of glass powder having a softening point exceeding 600 (° C.), the glass powder cannot give a sufficient anchor effect when firing a paste film formed on a predetermined substrate or the like. There is a problem that a high fixing strength cannot be obtained and the resistance value increases. In order to increase the water resistance and adhesion of the glass, the softening point of the glass powder is preferably 350 (° C.) or higher.

  Preferably, the content of the glass powder is in the range of 0.5 to 10 (wt%) with respect to the entire paste. If it is less than 0.5 (wt%), the adhesion strength between the conductive thick film and the substrate becomes insufficient, and if it exceeds 10 (wt%), the resistance value increases remarkably and the resolution also decreases.

  Preferably, the organic binder is water-soluble. In this way, since the organic binder contained in the conductive paste has water solubility in order to hold the paste film in a predetermined shape on a predetermined substrate or the like, it can be used as a developer in the development processing for pattern formation. Water can be used. Therefore, regardless of the material such as the substrate on which the black conductive thick film is provided, direct damage such as erosion or alteration, such as when an alkaline aqueous solution is used as the developer, or foaming during firing due to the residue of the developer, etc. Indirect damage to the substrate or the like is suppressed.

  Also preferably, the organic binder is a cellulose derivative. In this way, since the cellulose derivative has a good water solubility, there is an advantage that water can be used as a developer in the development processing for forming a pattern.

  Preferably, the cellulose derivative is composed of one or more kinds of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, and salts thereof. Since all of these have particularly good water solubility among cellulose derivatives, the advantage that development processing with water is easier than when other cellulose derivatives such as methyl cellulose, ethyl cellulose, and ethyl hydroxyethyl cellulose are used. There is. In addition, they are highly compatible with silver powder and black pigment, and have low reactivity with metal ions present on the surface of the glass powder. Since it is excellent, high storage stability is also obtained.

  Preferably, the content of the organic binder is in the range of 5 to 20 (wt%) as a percentage of the whole paste. If it is less than 5 (wt%), the holding power of the silver powder or glass powder in the paste film is insufficient, and the pattern portion is liable to peel off during development. On the other hand, if it exceeds 20 (wt%), the content of silver powder is relatively lowered, so that the thickness of the black conductive thick film after firing becomes thin and the resistance value increases.

  Preferably, the photosensitive composition is composed of a photopolymerizable compound and a photopolymerization initiator. In this way, the photosensitive black conductive paste composition for forming a display electrode is formed by exposing and developing the paste film formed therefrom to form a pattern, whereby the exposed portion is cured and thereby the black conductive film is formed. It becomes a so-called negative type in which a thick film pattern is formed.

  In addition, said photopolymerizable compound is suitably contained in the range of 3-20 (wt%) in the ratio with respect to the whole paste. If it is less than 3 (wt%), the exposure failure, that is, the pattern portion is not sufficiently cured, and if it exceeds 20 (wt%), the conductivity of the produced black conductive thick film is remarkably lowered. Examples of the photopolymerizable compound include acrylic acid, methacrylic acid, fumaric acid, maleic acid, monomethyl fumarate, monoethyl fumarate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol monomethyl ether acrylate, and ethylene. Glycol monomethyl ether methacrylate, ethylene glycol monoethyl ether acrylate, ethylene glycol monoethyl ether methacrylate, glycerol acrylate, glycerol methacrylate, acrylic amide, methacrylic acid amide, acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate , Isobutyl acrylate, isobutyl methacrylate, 2-ethyl Monofunctional monomers such as xyl acrylate, 2-ethylhexyl methacrylate, benzyl acrylate, benzyl methacrylate, ethylene glycol diacrylate, ethylene glycol monomethacrylate, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, nonaethylene glycol monoacrylate, polyethylene glycol mono Acrylate, polyethylene glycol monomethacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, nonaethylene glycol monomethacrylate, dipropylene glycol monoacrylate, tripropylene glycol monoacrylate, tetrapropylene glycol monoacrylate, dipropylene glycol Monomethacrylate, tripropylene glycol monomethacrylate, butylene glycol monomethacrylate, propylene glycol monoacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, nonaethylene glycol diacrylate, triethylene glycol Dimethacrylate, tetraethylene glycol dimethacrylate, nonaethylene glycol dimethacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tetrapropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, butylene glycol Dimethacrylate, propylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolpropane tetraacrylate, tetramethylolpropane tetramethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetra Methacrylate, dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, cardo epoxy diacrylate, etc. Many A functional monomer can be mentioned, and in particular, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate are preferably used. Since these are easily decomposed and volatilized at the time of firing, it is difficult to reduce the electrical characteristics of the black conductive thick film produced, and it can constitute a highly sensitive photosensitive black conductive paste composition for forming display electrodes.

  Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, and 2-methyl-1- [4- (methylthio) phenyl. ] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-hydroxy-2-methyl-1-phenylpropane- 1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2,4- Diethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 3,3-dimethyl-4-methoxybenzophenone, benzophenone, 1-chloro-4-propoxythioxanthone, 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropan-1-one, 1- (4-dodecylpheny ) -2-Hydroxy-2-methylpropan-1-one, 4-benzoyl-4'-methyldimethylsulfide, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, 4 -Butyl dimethylaminobenzoate, 2-dimethylhexyl 4-dimethylaminobenzoate, 2-isoamyl 4-dimethylaminobenzoate, 2,2-diethoxyacetophenone, benzyldimethyl ketal, benzyl-β-methoxyethyl acetal, 1 -Phenyl-1,2-propanedione-2- (ο-ethoxycarbonyl) oxime, methyl ο-benzoylbenzoate, bis (4-dimethylaminophenyl) ketone, 4,4'-bisdiethylaminobenzophenone, 4,4 ' -Dichlorobenzophenone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, ben In-n-butyl ether, benzoin isobutyl ether, benzoin butyl ether, p-dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, dibenzosuberone , Α, α-dichloro-4-phenoxyacetophenone, pentyl-4-dimethylaminobenzoate, and the like. The photopolymerization initiator is preferably contained in the range of 0.05 to 10 (wt%) as a percentage of the whole paste. If it is less than 0.05 (wt%), the exposure failure, that is, the polymerization of the photopolymerizable compound does not proceed sufficiently, and the effect of the pattern portion becomes insufficient. On the other hand, if it exceeds 10 (wt%), the conductivity of the resulting black conductive thick film will be significantly reduced.

  Preferably, the black pigment is contained in a range of 0.5 to 20 (wt%) as a percentage of the whole paste composition. In this way, the black pigment content is sufficiently large so that the conductivity of the black conductive thick film is sufficiently high and the resolution is also sufficiently high. Is obtained satisfactorily and the brightness is sufficiently reduced. In addition, if it is less than 0.5 (wt%), the lightness is not sufficiently lowered. On the other hand, if it exceeds 20 (wt%), the resistance value is increased and the resolution is remarkably lowered. Moreover, the range of the said content rate is 1-8 (wt%) more suitably.

  In the second invention, preferably, the black conductive thick film is provided on the other surface opposite to the one surface of the translucent substrate observed from a predetermined one surface side, and the black pigment is provided. And a high-lightness and high-conductivity layer that has a higher brightness and higher conductivity than the black conductive layer and is provided on the upper side of the black conductive layer. In this way, the black conductive thick film is formed by laminating the black conductive layer containing the black pigment and the high brightness and high conductivity layer having higher brightness and higher conductivity. The conductivity of the entire film is sufficiently enhanced by the high brightness and high conductivity layer. On the other hand, since the black conductive layer of the two types of laminated conductive layers is observed through the light transmissive substrate on one surface side of the light transmissive substrate on the viewing side, the black conductive thickness The color tone of the film is substantially determined by the black conductive layer. At this time, since the conductivity of the black conductive thick film is ensured by the high brightness and high conductivity layer, the conductivity of the black conductive layer may be relatively low. Thus, the brightness and yellowness of the black conductive layer and the black conductive thick film can be sufficiently lowered. Therefore, a black conductive thick film having high conductivity and low brightness and yellowness can be obtained. In addition, since the black conductive layer also has a certain degree of conductivity, even when the bus electrode 30 used to overlap the transparent electrode 28 in the above-described PDP 8 is configured with such a black conductive film, there is a gap between them. The brightness when viewed from the one surface side can be sufficiently lowered while ensuring the electrical conductivity.

  In addition, when the black conductive thick film is composed of a black conductive layer and a high-lightness high-conductive layer, one of the high-lightness and high-conductive layers has higher brightness than the black conductive layer, so exposure is easy. Compared with the case where the entire black conductive thick film is composed of the black conductive layer, even if the black conductive paste for forming the black conductive layer is difficult to be exposed, sufficient exposure can be ensured as a whole. Therefore, since the amount of black pigment contained in the black conductive layer has little effect on the conductivity and exposure of the entire conductive thick film, the amount of black pigment contained in the black conductive layer is sufficiently increased to extend the black conductive layer. The brightness and yellowness of the black conductive thick film can be sufficiently lowered. Therefore, it is possible to obtain a black conductive thick film with low brightness and low yellowness while maintaining high conductivity and resolution during film formation.

In the second invention, preferably, the black pigment has a specific surface area of 1 to 20 (m ² / g). In this way, the specific surface area of the black pigment contained in the black conductive thick film is such that the conductivity of the film is kept sufficiently high and the resolution is sufficient when patterning is performed through exposure and development processing. Therefore, the black color is satisfactorily obtained and the brightness is sufficiently lowered. In addition, if it is less than 1 (m ² / g), the lightness is not sufficiently lowered. On the other hand, if it exceeds 20 (m ² / g), the resistance value is increased and the resolution is remarkably lowered. The range of the specific surface area is more preferably 2 to 15 (m ² / g).

  In the second aspect of the invention, preferably, the black pigment is contained in a range of 0.5 to 20 (wt%) as a ratio to the whole of the black conductive thick film. In this way, the content of the black pigment is within a range in which the conductivity of the black conductive thick film is kept sufficiently high and the resolution when the pattern is formed through exposure and development processing is also kept sufficiently high. Therefore, the black color is satisfactorily obtained and the brightness is sufficiently lowered. In addition, if it is less than 0.5 (wt%), the lightness is not sufficiently lowered. On the other hand, if it exceeds 20 (wt%), the resistance value is increased and the resolution is remarkably lowered. Moreover, the range of the said content rate is 1-8 (wt%) more suitably.

  In the third aspect of the invention, preferably, the photosensitive high-lightness high-conductivity paste composition contains silver powder in a range of 50 to 80 (wt%) as a percentage of the total paste composition. In this way, since the content of the silver powder of the photosensitive high-lightness high-conductivity paste exclusively contributing to ensuring conductivity is sufficiently increased, the resulting black conductive thick film is sufficiently high as a whole. Conductivity is imparted. If the content of silver powder is less than 50 (wt%), the conductivity will be insufficient, while if it exceeds 80 (wt%), pasting will be difficult and the irradiated light will enter the paste film. Therefore, the resolution is remarkably deteriorated.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 3A is a perspective view showing a state in which the black conductive thick film 40 according to one embodiment of the present invention is formed on the substrate 42, and FIG. 3B is a cross-sectional view taken along line bb of FIG. It is a figure which shows typically the structure of the black conductive thick film 40 in. The black conductive thick film 40 is a thick film conductor formed by firing a photosensitive black conductive paste, which is a kind of thick film conductive paste, as will be described later, and has a thickness of about 10 (μm) and a width of 50 (μm As shown in the figure, the silver 44 as the conductive component and the black pigment 46 as the coloring component are combined by the glass 48. The substrate 42 is a flat glass plate made of soda, lime, glass, etc. and having high translucency. The glass 48 also has a function of fixing the black conductive thick film 40 to the substrate 42. Yes. The thick black conductive film 40 constitutes, for example, the bus electrode 30 of the PDP 8 shown in FIG. 1 or FIG. 2, and the substrate 42 corresponds to the front plate 10 in FIG. 3 shows the case where the black conductive thick film 40 constituting the bus electrode 30 is directly provided on the substrate 42, the black conductive thick film 40 is formed as shown in FIG. 1 or FIG. It may be provided on the transparent electrode 28.

The black pigment 46 is made of, for example, Co ₃ O ₄ exhibiting a black color having a specific surface area measured by the BET specific surface area measurement method of about ₃ to 13 (m ² / g). Is dispersed. Therefore, the black conductive thick film 40 has a relatively low blackness of about 35 to 55 when observed through the transparent substrate 42 from the viewing direction indicated by the arrow in FIG. On the other hand, the resistance value is a value between two points of a pattern having a width of about 100 (μm) with an interval of about 80 (mm) along the longitudinal direction thereof (for example, about 10 to 15 (Ω)) It has a low conductivity and high conductivity. Therefore, when used for the bus electrode 30 or the like of the PDP 8 as described above, good optical characteristics and electrical characteristics are exhibited. The “blackness” is a value obtained by measuring an L value representing brightness with a color difference meter (for example, manufactured by Minolta). Further, in the following description, when simply referred to as “resistance value”, the width of about 100 (μm) separated from each other by 80 (mm) along the longitudinal direction of the black conductive thick film 40 and the like including other embodiments. It means the resistance value between two points of the pattern.

  Hereinafter, a method of forming the black conductive thick film 40 will be described with reference to FIG. 4 showing the main part of the process and FIG. 5 showing the cross-sectional shape at each stage of the forming process. In the case where the black conductive film 40 functioning as the bus electrode 30 is provided on the front plate 10 shown in FIGS. 1 and 2, the transparent electrode 28 is first provided in an appropriate shape as described above. This is omitted in the following description.

First, in the photosensitive black conductive paste printing step S1, the surface of the substrate 42 (in the case where the transparent electrode 28 is provided, the substrate 42 and the transparent electrode 28, for example, by thick film screen printing or bar coater coating). However, for the sake of convenience, the following description will be given as “substrate 42”.) A photosensitive black conductive paste is applied to the entire surface. This photosensitive black conductive paste is made of, for example, spherical silver powder having a specific surface area of about 1.0 to 2.0 (m ² / g) and PbO having a specific surface area of about 1 to 2 (m ² / g). About 4 (wt%) of glass powder (glass frit) made of -SiO ₂ -B ₂ O ₃ glass and 5 water-soluble organic binder (polymer binder) such as carboxymethyl cellulose and hydroxypropyl cellulose (wt%), about 2 to 6 (wt%) of the black pigment 46 (Co ₃ O ₄ ), about 5 (wt%) of a photopolymerizable compound such as pentaerythritol triacrylate, and 2-benzyl -2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one and other photopolymerization initiators with about 0.5 (wt%) and the remaining organic solvent such as 3-methyl-3-methoxybutanol Are mixed so that the total amount becomes 100 (wt%), and, for example, is kneaded using a three-roll mill or the like to form a paste. The viscosity of the paste after kneading is, for example, about 100 (Pa · s).

  Next, in the paste drying step S2, for example, a photosensitive black conductive paste applied on the substrate 42 by performing a drying process for about 15 (minutes) at a temperature of about 80 (° C.) using a far-infrared dryer. Then, the organic solvent is volatilized and a black conductive paste film 52 is formed. FIG. 5 (a) shows this state. At this time, the thickness of the black conductive paste film 52 after drying is, for example, about 10 (μm).

In the subsequent exposure step S3, the black conductive paste film 52 is selectively exposed through a negative mask 54 having a predetermined size. FIG. 5 (b) shows this state. In the figure, a negative mask 54 is provided with a plurality of openings 56 parallel to each other and having a width of about w0 = 50 (μm) at regular intervals of about ws = 100 (μm). It is arranged above the paste film 52 at a slight distance. The length of the opening 56 is set according to the length of the black conductive thick film 40 formed on the substrate 42. In addition, the above-described exposure processing was performed by irradiating ultraviolet rays having a wavelength of about 350 (nm) with an energy dose of about 300 (mJ / cm ² ) using, for example, an ultrahigh pressure mercury lamp. As a result, a portion 58 indicated by oblique lines in the drawing located directly below the opening 56 is selectively exposed, and the photopolymerizable compound contained in the black conductive paste film is polymerized only in the exposed portion 58 by a polymerization reaction. Cured and firmly fixed to the surface of the substrate 42. On the other hand, the unexposed part except the exposed part 58 is not changed at all.

In the development step S4, for example, the development process is performed by spraying water as a developer at a discharge pressure of about 2 (kgf / cm ² ) for about 20 (seconds). That is, a cleaning process is performed on the substrate 42 that has been subjected to the exposure process. As a result, the unexposed portion of the paste film 52 is selectively removed by dissolving and washing away with water, leaving only the exposed portion 58 on the substrate 42. FIG. 5 (c) shows this state. Then, in the drying step S5, the substrate 42 (and the black conductive paste film 52) is dried, and in the conductor firing step S6, for example, a firing process is performed using an electric furnace under conditions of about 550 (° C.) × 2 (hr). Apply. Thereby, organic components such as a polymer binder, a photopolymerizable compound, and a photopolymerization initiator are decomposed and removed by heating from the black conductive paste film 52, and at the same time, the glass 48 in which the glass powder is melted. As a result, the silver 44 and the black pigment 46 are combined to produce the black conductive thick film 40.

  Here, Table 1 shows the characteristics of the black conductive thick film 40 formed as described above, together with the comparative example, together with the test conditions, with various formation conditions changed. In the table below, the numerical value of 100 to 1000 in the “Resolution” column is the energy dose irradiated in the exposure step S3, and “◯” indicates that the black conductive thick film 40 is in accordance with the pattern of the negative mask 54. “△” indicates that the black conductive thick film 40 was formed temporarily, but thinning of the lines, rattling of the pattern edge, etc. occurred, “×” indicates that the paste film was not cured at the time of exposure, This represents that the paste film 52 was peeled off during development and the black conductive thick film 40 could not be formed. In the “Organic binder type” column, “CMC” and “HPC” are carboxymethylcellulose and hydroxypropylcellulose, respectively. The other conditions not listed in the table are all in accordance with the above-described process description in any of Example E and Comparative Example R, and the method for measuring the blackness and the resistance value is as described above.

As is apparent from Table 1 (Examples) above, if Co ₃ O ₄ is used as the black pigment 46 and the ultraviolet ray irradiation dose in the exposure step S3 is set appropriately, the opening pattern of the negative mask 54 is set. Accordingly, the black conductive paste film 52 is cured to obtain the black conductive thick film 40 having a predetermined pattern. In particular, according to Examples E1 to E4 in which Co ₃ O ₄ having a specific surface area of about ₃ to 13 (m ² / g) was used as the black pigment 46, the energy dose of ultraviolet rays was 300 (mJ / cm ² ) or more. As a result, a black color with a sufficiently low blackness of 35 to 55 and a good black color can be obtained, and a black conductive thick film 40 having a sufficiently high resistance of about 10 to 15 (Ω) is obtained. be able to.

However, in any of the above Examples E1 to E5, the black conductive paste film 52 cannot be cured at an energy dose of about 100 (mJ / cm ² ) because the reaction of the photopolymerizable compound becomes insufficient. In Examples E1 and E4, overexposure is performed with an energy dose of about 1000 (mJ / cm ² ), and the width that can be cured from the opening 56 of the negative mask 54 is widened. The black conductive thick film 40 cannot be obtained. In Example E2, curing is not sufficient even with an energy dose of about 300 (mJ / cm ² ), and pattern width narrowing or rattling occurs. For this reason, high resolution cannot be obtained in any case. In general, as the amount of the black pigment 46 added increases, exposure tends to be difficult, so in Examples E1 and E4 where the amount added is as low as 2 (wt%), the energy dose for overexposure becomes relatively low. On the contrary, in Example E2 where the addition amount is as high as about 6 (wt%), it is estimated that the lower limit of the energy dose necessary for proper exposure has increased. In Example E5 in which the specific surface area of Co ₃ O ₄ is about 25 (m ² / g), excellent values of both blackness and resistance can be obtained. However, in order to obtain good resolution, irradiation energy is required. The amount needs to be very high. The characteristic values shown in the table are evaluated with the black conductive thick film 40 having sufficient resolution.

On the other hand, since the comparative example R1 does not include the black pigment 46, high resolution is obtained and the resistance value is extremely low, while the blackness (L value) is as high as about 70. In Comparative Examples R2 to R7, other materials such as RuO ₂ , Fe—Cr—Mn, and Cu—Cr—Mn are used as the black pigment 46. Exposure was extremely difficult within the range of the amount of addition that provided a blackness of about 60, and none of the black conductive thick films 40 having a predetermined pattern could be obtained. In Comparative Examples R8 and R9, Co ₃ O ₄ is used as the black pigment. In Comparative Example R8, the specific surface area of the silver powder is as small as about 0.3 (m ² / g) and is coarse. Although high resolution was obtained, the conductivity was insufficient. On the other hand, in Comparative Example R9, the specific surface area of the silver powder is as large as about 3.0 (m ² / g) and is too fine, so the resistance value is high and high resolution cannot be obtained. That is, if the specific surface area of the silver powder becomes coarser than 0.4 (m ² / g), it becomes difficult to form a continuous film during firing, whereas if it exceeds 2.5 (m ² / g), paste formation becomes difficult and the paste becomes difficult. Since the organic binder necessary to hold the silver powder in the film increases, the thickness of the conductive thick film after baking becomes thin, and the resistance value increases in any case.

In Comparative Examples R11 and R12, Co ₂ O ₃ which is a kind of cobalt oxide is used as a black pigment. In Comparative Example R11 having a small amount of addition, the L value is too large, but the amount of addition is large. In Comparative Example R12, even at a relatively high energy dose, the black conductive paste film was not sufficiently cured, resulting in pattern thinning and backlash, and sufficient resolution could not be obtained. That is, in Co ₂ O ₃ , an appropriate addition amount range cannot be set, and only Co ₃ O _{4 in} cobalt oxide can achieve both resolution and blackness.

In Examples E1 to E5, a silver powder having a specific surface area of about 1.0 or 2.0 (m ² / g) is a glass powder having a specific surface area of about 60 (wt%) and a specific surface area of about 1 or 2 (m ² / g). As shown in Table 1, good results can be obtained at any specific surface area. Therefore, the range of 0.4 to 2.5 (m ² / g) is suitable for the silver powder. In addition, although the experimental results are not particularly shown, the glass powder is less than 0.5 (m ² / g), and the resistance value increases and becomes coarse, so the printability decreases, and conversely, 10 (m ² / g) It has been confirmed that dispersibility becomes poor and pasting becomes difficult when the content exceeds.

In short, in this embodiment, in the photosensitive black conductive paste for forming the black conductive thick film 40, the silver powder contained as the conductive component has a specific surface area of about 1.0 or 2.0 (m ² / g). In addition, since the black pigment 46 is composed of Co ₃ O ₄ powder, it has high photosensitivity and high resolution, and the black conductive thick film 40 formed from the photosensitive black conductive paste contains silver. And a black pigment 46 made of Co ₃ O ₄ are combined by a glass 48, and as shown in Table 1, a black conductive thick film having sufficiently high conductivity and sufficiently low brightness and yellowness. Is obtained.

  In this embodiment, a spherical powder is used as the silver powder constituting the photosensitive black conductive paste. Therefore, when compared with the same particle size, since the spherical particles have a small specific surface area and a large particle size per surface area, the amount of the organic binder necessary for forming the black conductive paste film 52 is reduced. The conductivity of the black conductive thick film 40 can be further increased. In addition, since the spherical particles are less likely to cause scattering of the irradiated light inside the paste film 52 as compared with the plate shape and the indefinite shape, the resolution is also improved. Accordingly, it is possible to obtain a photosensitive black conductive paste capable of forming the black conductive thick film 40 having higher conductivity while maintaining higher resolution.

  In this example, the silver powder constituting the photosensitive black conductive paste is contained in an amount of about 60 (wt%) with respect to the total paste composition. Therefore, the content of the silver powder is sufficiently increased within a range that can be easily pasted and exposed easily, so that the film thickness after drying and baking can be sufficiently increased, and thus higher conductivity can be obtained.

In this embodiment, the glass powder constituting the photosensitive black conductive paste has a specific surface area of 1 or 2 (m ² / g). Therefore, good printability of the paste can be obtained while ensuring sufficient dispersibility. In addition, in this example, glass made of PbO—SiO ₂ —B ₂ O ₃ having a softening point of about 550 (° C.) is used as the glass powder, so that the firing temperature in the conductor firing step S6 is relatively low. Glass powder can be sufficiently melted. Therefore, high adhesion strength between the black conductive thick film 40 and the substrate 42 is ensured.

  In this example, the content of the glass powder is about 4 (wt%) with respect to the entire paste. Therefore, the fixing strength between the black conductive thick film 40 and the substrate 42 can be further increased while suppressing an increase in resistance value and a decrease in resolution.

  In this embodiment, CMC or HPC having water solubility is used as the organic binder constituting the photosensitive black conductive paste. Therefore, since the organic binder for maintaining the shape of the black conductive paste film 52 on the substrate 42 is water-soluble, in the developing step S4 for forming a pattern, water is used as the developer as described above. it can. Therefore, direct damage such as erosion and alteration of the substrate 42 by the developer, and indirect damage such as foaming during baking due to the residue of the developer are suppressed from occurring on the substrate 42. In addition, since HPC is particularly compatible with silver powder and black pigment 46 and has low reactivity with metal ions present on the surface of the glass powder, silver powder as shown in Example E4 in Table 1 above, Even when the specific surface areas of the glass powder and the black pigment 46 are relatively large, the change in viscosity and gelation of the black conductive paste are suppressed, and the storage stability is improved.

  In this example, the content of the organic binder (CMC or HPC) is about 5 (wt%) as a percentage of the whole paste. Therefore, while ensuring sufficient holding power of silver powder and glass powder in the paste film and suppressing pattern peeling in the development step S4, the film thickness of the black conductive thick film 40 after firing is secured and the resistance value thereof is increased. The rise can be suppressed.

  Further, in this example, the photosensitive composition for imparting photosensitivity to the photosensitive black conductive paste includes a photopolymerizable compound such as pentaerythritol triacrylate, 2-benzyl-2-dimethylamino-1- And a photopolymerization initiator such as (4-morpholinophenyl) -butan-1-one. Therefore, the photosensitive black conductive paste is formed by patterning the black conductive paste film 52 formed thereon through the exposure step S4 and the development step S5, so that the exposed portion is cured, thereby forming the black conductive thick film 40. It becomes a so-called negative type in which the pattern is formed.

  The photopolymerizable compound is contained in an amount of about 5 (wt%) with respect to the entire paste, and the photopolymerization initiator is contained in an amount of about 0.5 (wt%). Therefore, since the respective addition amounts are reduced within a range where the pattern portion can be easily and sufficiently cured by exposure, the black conductive thick film 40 having high conductivity and excellent pattern accuracy can be obtained. Moreover, in this example, pentaerythritol triacrylate, which is easily decomposed and volatilized at the time of firing, is used as the photopolymerizable compound, so that the sensitivity of the photosensitive black conductive paste is increased and the black color produced therefrom is used. The electrical characteristics of the conductive thick film 40 are further enhanced.

In this example, the specific surface area of the black pigment 46 is about 3 to 25 (m ² / g), and in a range where particularly favorable results are obtained, it is about 13 (m ² / g) or less, The black conductive thick film 40 is sufficiently large as long as the conductivity is kept sufficiently high and the resolution of the photosensitive black conductive paste is kept sufficiently high. Therefore, a black color is satisfactorily obtained and the brightness of the black conductive thick film 40 is sufficiently reduced.

  In the present embodiment, the black pigment 46 is about 2 to 6 (wt%) as a percentage of the total paste composition, and the conductivity of the black conductive thick film 40 is kept sufficiently high and the resolution is also high. It is large enough to keep it high enough. For this reason, a black color is satisfactorily obtained without greatly increasing the resistance value, and the brightness of the black conductive thick film 40 is sufficiently reduced.

  Next, another embodiment of the present invention will be described. In the following embodiments, description of portions common to the above-described embodiments is omitted.

  Table 2 below shows the preparation conditions and the characteristic evaluation results when the black conductive thick film 40 is formed using a 0.3 (%) sodium carbonate aqueous solution that is an alkaline aqueous solution in the development step S4 together with a comparative example. Is. In Table 2 below, “EMA” and “EA” in the “Organic binder type” column represent polymers of ethyl methacrylate and ethyl acrylate, respectively. The other formulation conditions except for the type of organic binder are the same as those in Table 1 for Examples E6 to E10 and Comparative Examples R12 to R18. The manufacturing process is the same as that shown in FIG. It is the same. As is apparent from Table 2 below, when an organic binder soluble in an alkaline aqueous solution is used, the same results as in Table 1 in which a water-soluble organic binder is used are obtained.

  FIG. 6 is a diagram schematically showing the structure of another black conductive thick film 60 that can constitute the bus electrode 30 of the PDP 8 shown in FIG. 1 or FIG. In the figure, the black conductive thick film 60 is composed of a black black conductive layer 62 formed directly on the substrate 42 and a light yellow yellow conductive layer 64 laminated on the black conductive layer 62. It has dimensions of about 50 (μm) in width and about 5 to 6 (μm) in thickness, and has a high conductivity with a resistance of about 6 (Ω) or less, and the viewing direction indicated by the arrows in the figure That is, the blackness in the state observed through the substrate 42 from the surface 66 side has a low brightness of about 40. Therefore, the bus electrode 30 or the like that requires conductivity and blackness is used more suitably than the black conductive thick film 40 as shown in Table 1 or Table 2. In a discharge display device such as a PDP 8, the viewing direction is generally on the side of the surface 66 exposed to the external space on the side opposite to the back surface (inner surface) 68 provided in the discharge space 16 with the electrodes 30 and the like. . In the present embodiment, the substrate 42 corresponds to a translucent substrate, the front surface 66 corresponds to a predetermined surface, and the back surface 68 corresponds to the other surface on the opposite side.

The black conductive layer 62 includes the black pigment 46 made of silver 44 and Co ₃ O _4, etc., like the black conductive thick film 40, and has a thickness of about tB = 3 (μm), for example. It has dimensions, its resistance value is about 20 (Ω), and its blackness is about 40. For this reason, since the blackness of the black conductive layer 62 located on the viewing direction side is sufficiently low, the blackness in the viewing direction of the entire black conductive thick film 60 is determined by the black conductive layer 62. The brightness is extremely low. On the other hand, the yellow conductive layer 64 contains silver 44 as a conductive component but does not contain any black pigment 46, and has a thickness dimension of about tY = 4 (μm), for example, and its resistance value is Although it is as low as 8 (Ω), the blackness is as high as 70. For this reason, since the resistance value of the yellow conductive layer 64 constituting a part of the black conductive thick film 60 in the thickness direction is sufficiently low, the conductivity of the black conductive thick film 60 as a whole is enhanced, as described above. The resistance value is low. Although the black conductive layer 62 is relatively thin as described above, the blackness, that is, the lightness is extremely low. Therefore, the color tone of the upper yellow conductive layer 64 passes through the black conductive layer 62 to the viewing direction side of the figure. Will not be observed from. The color tone in the case of directly observing the surface of the black conductive thick film 60 without passing through the substrate 42 is light yellow and blackness is about 70 according to the color tone of the yellow conductive layer 64 located on the upper side. The yellow conductive layer 64 cannot be viewed directly from the viewing direction. Therefore, the color tone (yellow or lightness) has no influence on the display quality of the PDP 8 or the like. In the present embodiment, the yellow conductive layer 64 corresponds to a high brightness high conductive layer.

  By the way, the black conductive thick film 60 is provided on the substrate 42 in accordance with, for example, the process shown in FIG. FIG. 7 shows only the part corresponding to steps S1 to S3 in the process chart shown in FIG. 4, and the steps after S4 follow the process chart of FIG. Hereinafter, a method for forming the black conductive thick film 60 will be described with reference to FIG. 7 and FIG. 8 showing a cross-sectional structure of the substrate 42 in the middle of the process. First, in the photosensitive black conductive paste printing step S1, a photosensitive black conductive paste is applied to the entire surface of the substrate 42 (and on the transparent electrode 28) using, for example, a thick film screen printing method, and in the paste drying step S2. For example, using a far-infrared dryer, a drying process is performed at a temperature of about 80 (° C.) for about 15 (min). As a result, the organic solvent is volatilized from the photosensitive black conductive paste applied on the substrate 42, and a black conductive paste film 70 similar to the black conductive paste film 52 shown in FIG. 5 is formed. At this time, the composition (type and amount) of the photosensitive black conductive paste was the same as that of Example E1 shown in Table 1 except for the amount of the material shown in the upper part of Table 3 below. 1. The amount of silver powder is smaller than that shown in Table 2, and the amount of glass powder, the amount of black pigment, and the amount of organic binder are increased. Further, the thickness of the black conductive paste film 70 after drying is, for example, about 6 (μm). In this embodiment, the photosensitive black conductive paste printing step S1 and the paste drying step S2 correspond to the black paste film forming step.

  In the subsequent photosensitive conductive paste printing step S1-2 and paste drying step S2-2, the photosensitive silver paste not containing the black pigment 46 is applied to the entire surface of the black conductive paste film 70 in the same manner as the black conductive paste. And is dried at a temperature of about 80 (° C.) for about 15 (minutes). As a result, the silver paste film 72 is laminated on the black conductive paste film 70 to form a conductive paste film 74 having a dry film thickness of about 14 to 15 (μm) as a whole. FIG. 8 (a) shows this state. The preparation composition of the silver paste film 72 is the same as that of the black paste for forming the black conductive paste film 70 except that the preparation amount of the material shown in the lower part of Table 3 above is excluded, that is, the implementation shown in Table 1 above. It is the same as the photosensitive black conductive paste of Example E1, and the film thickness after drying is about 8 (μm). Then, in the exposure step S3, as in the case shown in FIG. 4, the conductive paste film 74 is selectively passed through the negative mask 54 having a predetermined size from the silver paste film 72 side (that is, passed through the substrate 42). Exposure directly) That is, the black conductive paste film 70 and the silver paste film 72 are integrally exposed. FIG. 8B shows this state. In the present embodiment, the photosensitive conductive paste printing step S1-2 and the paste drying step S2-2 correspond to the high-lightness paste film forming step.

  At this time, the black conductive paste film 70 is irradiated with ultraviolet rays through the silver paste film 72. However, the silver paste film 72 contains a black pigment 46 that significantly impedes transmission of irradiation light such as ultraviolet rays. In addition, the film thickness of the black conductive paste film 70 itself is reduced as described above. Therefore, not only the silver paste film 72 directly irradiated with ultraviolet rays or the like, but also the black conductive paste film 70 located therebelow is suitably exposed. As a result, a portion 78 of the black conductive paste film 70 and the silver paste film 72 indicated by hatching in the same shape according to the opening pattern of the negative mask 54 is selectively cured. That is, a negative image is formed on the black conductive paste film 70. Therefore, a conductive paste film 74 having a predetermined pattern in which the black conductive paste film 70 and the silver paste film 72 are laminated is obtained by subsequent development processing (development step S4 shown in FIG. 4), and this is baked (the conductor of FIG. 4). By performing the firing step S6), as shown in FIG. 6, the black conductive thick film 60 having a two-layer structure having both high conductivity and low brightness (blackness) is formed. In this embodiment, since the same water-soluble organic binder as that used in Example E1 is used, water is used as the developer in the developing step S4.

Here, Table 4 below shows the results of evaluating the resolution in the process of forming the black conductive thick film 60 of the present example (Example E11) when a black pigment made of a different material is used (Comparative Example R19). , R20). The comparative examples were all evaluated under the same conditions as in Example E11 except that the type and specific surface area of the black pigment were different. That is, the silver paste film 72 is provided on a black paste film formed by applying a photosensitive black conductive paste containing the following black pigment, and has a two-layer structure similar to that shown in FIG. A conductive paste film was formed, and the resolution and the blackness and resistance value of the black conductive thick film having a two-layer structure obtained by firing the conductive paste film were evaluated. As is clear from the table, according to this example, fine pattern formation is possible by irradiating ultraviolet rays with an energy dose of about 300 to 500 (mJ / cm ² ), whereas in the comparative example, In addition, the addition amount of the black pigment as in this example not only increases the lightness (that is, the lightness is inferior), but also the cured paste film peels from the substrate 42, or the paste film hardly cures. In either case, a black conductive thick film having a predetermined pattern could not be obtained.

  In short, according to the present embodiment, the black conductive thick film 60 is laminated on the black conductive layer 62 including the black pigment 46 provided on the back surface 68 of the substrate 42 observed from the front surface 66 side. Since the yellow conductive layer 64 is provided with the yellow conductive layer 64 having higher brightness and higher conductivity than that, the overall conductivity of the black conductive thick film 60 is sufficiently enhanced by the yellow conductive layer 64. On the other hand, on the surface 66 side of the substrate 42 that is the viewing side, the black conductive layer 62 of the two conductive layers 62 and 64 that are laminated is observed through the substrate 42, so that the black conductive thickness is increased. The color tone of the film 60 is substantially determined by the black conductive layer 62. At this time, since the conductivity of the black conductive thick film 60 is ensured by the yellow conductive layer 64, there is no problem in electrical characteristics even if the conductivity of the black conductive layer 62 is relatively low. In addition, since the yellow conductive layer 64 patterned by exposure and development in the same manner as the black conductive layer 62 has higher brightness than the black conductive layer 62, exposure is easy. Compared to the case where the black conductive layer 62 is used, sufficient exposure can be ensured as a whole even if the black conductive paste for forming the black conductive layer 62 is difficult to be exposed. From these facts, the amount of the black pigment 46 contained in the black conductive layer 62 hardly affects the conductivity and exposure of the entire black conductive thick film 60, so the amount of the black pigment 46 contained therein is sufficiently increased. Thus, the brightness and yellowness of the black conductive layer 62 and the black conductive thick film 60 can be sufficiently lowered. Therefore, the black conductive thick film 60 having low brightness and low yellowness can be obtained while maintaining high conductivity and resolution during film formation.

  In this embodiment, when forming the black conductive thick film 60, the photosensitive black conductive paste is applied to the back surface 68 of the substrate 42 and dried in the photosensitive black conductive paste printing step S1 and the paste drying step S2. The black conductive paste film 70 is formed, and in the photosensitive conductive paste printing step S1-2 and the paste drying step S2-2, the lightness is higher than that of the black conductive layer 62 generated from the black conductive paste film 70 and the conductive property is high. A photosensitive silver paste for forming a high yellow conductive layer 64 is applied on the black conductive paste film 70 and a silver paste film 72 is laminated to form a conductive paste film 74 having a predetermined thickness. Further, in the conductor firing step S4, the conductive paste film 74 is fired to produce a black conductive thick film 60 having a predetermined pattern.Therefore, the black conductive thick film 60 is configured by laminating the black conductive layer 62 generated from the black conductive paste film 70 and the yellow conductive layer 64 generated from the silver paste film 72. In addition, the thick black conductive film 60 having high conductivity and low brightness and yellowness can be formed.

  Further, in this embodiment, after the photosensitive conductive paste printing step S1-2 and paste drying step S2-2 corresponding to the high-lightness paste film forming step, in the exposure step S3, the mask 54 having a predetermined opening pattern is interposed. The conductive paste film 74 is selectively exposed, and after the exposure step S3, the uncured portion of the conductive paste film 74 is removed by washing in the development step S4, and then the conductor baking step S6 is performed. Is done. Therefore, since the black conductive thick film 60 is patterned by exposure and development processing using a photosensitive paste, a highly accurate pattern can be obtained more easily than when the pattern is formed by the thick film screen printing method. At this time, the conductive paste film 74 generated on the black conductive thick film 60 is formed by laminating a black conductive paste film 70 and a silver paste film 72, and among these, the silver paste film 72 is a black containing the black pigment 46. Exposure is easier than that of the conductive paste film 70. Therefore, in addition to ensuring the conductivity of the black conductive thick film 60 generated as described above by the yellow conductive layer 64, the black conductive film 60 is compared with the case where the whole is generated from the black conductive paste film 70. Even if the paste film 70 is difficult to be exposed, the conductive paste film 74 as a whole can be sufficiently exposed, so that the amount of the black pigment 46 contained therein can be relatively large. As described above, when the black conductive thick film 60 is formed through the exposure and development processing using the photosensitive black conductive paste, the brightness and the yellowness are further increased while keeping the resolution and the conductivity of the generated film 60 high. Can be lowered.

  In this example, the photosensitive silver paste composition contains silver powder in the range of 60 (wt%) as a percentage of the total paste composition. In this way, since the content of the silver powder of the photosensitive silver paste that contributes exclusively to ensuring conductivity is sufficiently increased, the resulting black conductive thick film 60 has a sufficiently high conductivity as a whole. Is granted.

  Table 5 below shows the evaluation results of the black conductive thick film of still another example, and is shown in FIG. 3 using a black conductive paste in which the type and addition amount of the black pigment are variously changed. The result of forming and evaluating a black conductive thick film similar to the black conductive thick film 40 using, for example, a thick film screen printing method is shown together with the preparation conditions of the black pigment together with a comparative example. In the table, the “black pigment” column indicates the type of black pigment added to the paste, the “specific surface area” and the “addition amount” columns indicate the specific surface area and addition amount of the black pigment, “sheet resistance value”, “L value”. "And" b value "represent the characteristics of the formed black conductive thick film, respectively. The “sheet resistance value” is a value obtained by converting the thickness of the black conductive thick film to 10 (μm). The “b value” represents the degree of yellowness, and the higher the value, the more yellow. The L value and b value were measured with a color difference meter in the same manner as in the above-described Examples.

The paste constituents not shown in Table 5 above, that is, constituents other than the black pigment are all the same in the examples and comparative examples. That is, in all cases, a silver powder having a specific surface area of about 2 (m ² / g) as a conductive component is about 60 (wt%), and a glass powder having a softening point of about 400 (° C.) and a specific surface area of about 2 (m ² / g). (For example, PbO—SiO ₂ —B ₂ O ₃ ) is about 5 wt%, ethyl cellulose is about 5 wt% as an organic binder, and butyl carbitol acetate (BCA) is 30 wt% as an organic solvent. Contains a common component consisting of a degree. The black pigments contained in the black conductive paste are those listed in the respective “black pigment” column in the above table, and are listed in each “addition amount” column for the total of 100 (wt%) of the above common elements. The amount is added.

  Further, the method of forming the black conductive thick film is the same in both the examples and the comparative examples, and is as follows, for example. That is, first, paste components (described later) are mixed and then kneaded by a three-roll mill to produce a black conductive paste. Next, a predetermined pattern is printed on the substrate 42 using a screen having an opening pattern similar to the mask 54. And a black conductive thick film is formed by performing a drying and baking process. Therefore, in this embodiment, a pattern is formed in advance at the time of printing without performing the exposure and development processing as described above. That is, this example is outside the scope of the present invention that requires photosensitivity, but shows the relationship between the type of black pigment, the specific surface area, the amount added, and the characteristics. The printing surface is a top surface (non-tin surface) of the substrate 42 made of, for example, soda, lime, glass, or the like, that is, a surface positioned on the upper side when a glass plate is produced by the float process. In addition, the firing was performed in a cycle of 1.5 (hours) using a belt furnace while maintaining a temperature of 550 (° C.) × 10 (minutes).

9 and 10 are graphs that summarize the results shown in Table 5 above. FIG. 9 shows the relationship between the L value (lightness) and the sheet resistance value, and FIG. 10 shows the relationship between the L value and the b value (yellowness). As is apparent from Table 5 and FIGS. 9 and 10, when any black pigment is used, the L value decreases as the amount added increases. These L value, b value, and sheet resistance value are characteristic values that are desired to be as low as possible in the black conductive thick film used for the bus electrode 30 and the like. It can be said that the characteristics are excellent. Therefore, it can be seen from both figures that when Co ₃ O ₄ is used as the black pigment 46 (Examples E12 to E19), a black conductive thick film having the above three characteristics can be obtained. In particular, in Examples E12 to E15 using Co ₃ O ₄ having a specific surface area of 7 (m ² / g), all the other black pigments have the same b value and sheet resistance value for the same L value. It is clear that it is more suitable for the bus electrode 30 and the like because it is lower than the case where it is used (that is, the curve connecting the measured values is located at the lower left). That is, it is preferable to use Co ₃ O ₄ having a specific surface area larger than 2 (m ² / g). Comparative Examples R25 to R28 show relatively good characteristics, but RuO ₂ is a fine powder with a specific surface area of about 35 (m ² / g), and is difficult to handle and expensive. There's a problem.

Note that in the PDP 8 or the like, the bus electrode 30 or the like is in the range indicated by the oblique lines in FIG. 9 where the L value is 42 or less and the sheet resistance value is 10 (mΩ / □) or less. Desirable to facilitate driving. Therefore, as is clear from the results of Examples E12 to E15, when 7 (m ² / g) of Co ₃ O ₄ is used, the sheet resistance value is 10 (mΩ / □) From the following, it can be seen that the selection range of the L value and the sheet resistance value is widened.

  As mentioned above, although one Example of this invention was described in detail with reference to drawings, this invention is implemented also in another aspect.

  For example, in the embodiment, the case where the present invention is applied to the bus electrode 30 or the like of the PDP 8 has been described. However, the present invention is required to have low lightness (L value) and low resistance value (that is, high conductivity). If it is a thick film conductor, it can be used in the same manner for other display electrodes.

  Further, the specific surface area of the silver powder, glass powder, black pigment 46, etc., the content in the paste, etc. are not limited to the ranges shown in the examples, but the L value required for the black conductive thick films 40, 60, etc., b The value is appropriately changed according to the characteristics such as the value and conductivity and the fixing strength with the substrate 42. However, in any case, it is desirable to set within the preferred range described above.

  Further, the types and amounts of the organic binder, organic solvent, photopolymerizable compound, photopolymerization initiator, etc. for preparing the paste are required for the strength required for the paste films 52 and 70, the conductive thick film 40, etc. It is appropriately changed in consideration of conductivity, resolution and the like.

  For example, as the organic binder, in addition to water-soluble CMC, HPC and ethyl cellulose, polymers of EMA and EA soluble in an alkaline aqueous solution as shown in the examples, cellulose derivatives and alkali-soluble acrylic polymers One type or a plurality of types are appropriately used. However, in the case where the black conductive thick film 40 or the like is formed using a photosensitive black conductive paste, a cellulose derivative is more preferable because the development treatment can be performed with water. The amount of the organic binder added is preferably in the range of about 5 to 20 (wt%) with respect to the total weight of the paste. If it is less than 5 (wt%), the retention of silver powder or glass powder is weak and peeling during development can occur. On the other hand, if it exceeds 20 (wt%), the silver powder content decreases and the film thickness becomes thin. This is because the conductivity decreases. In addition, when an alkali-soluble acrylic polymer is used, an alkyd resin, a rosin resin, or the like may be further added.

  Examples of the cellulose derivative include cellulose, ethyl cellulose, methyl cellulose, ethyl hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, and salts thereof. However, since the photosensitive paste is preferably water-soluble so that it can be developed with water, among the above, other water-soluble cellulose derivatives other than ethylcellulose and ethylhydroxyethylcellulose are preferably used.

  Examples of the alkali-soluble acrylic polymer include [monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, cyanocinnamic acid, cinnamic acid, maleic acid, fumaric acid, itaconic acid] and [methyl acrylate, acrylic Ethyl acetate, methyl methacrylate, ethyl methacrylate, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, monomethyl fumarate, monoethyl fumarate, ethylene glycol monomethyl ether acrylate, ethylene glycol monomethyl ether methacrylate, ethylene glycol monoethyl ether acrylate, Ethylene glycol monoethyl ether methacrylate, glycerol (mono) acrylate, glycerol (mono) methacrylate, acrylic acid amide, methacrylic acid amide , Acrylonitrile, methacrylonitrile, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, benzyl acrylate, benzyl methacrylate, and other monomers] are preferably used. When this alkali-soluble acrylic polymer is used, the acid value is preferably about 50 to 250. If it is less than 50, development with an aqueous alkali solution becomes difficult. On the other hand, if it exceeds 250, the coating properties and dispersibility deteriorate. The organic binder preferably has a weight average molecular weight of about 1000 to 200,000, more preferably about 5000 to 150,000. If it is less than 1000, the adhesion to the substrate 42 becomes insufficient and the retention of the silver powder and the black pigment 46 is lowered. On the other hand, if it exceeds 200,000, the development time becomes long or development may become impossible. .

  Photopolymerizable compounds include acrylic acid, methacrylic acid, fumaric acid, maleic acid, monomethyl fumarate, monoethyl fumarate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol monomethyl ether acrylate, ethylene glycol monomethyl. Ether methacrylate, ethylene glycol monoethyl ether acrylate, ethylene glycol monoethyl ether methacrylate, glycerol acrylate, glycerol methacrylate, acrylic acid amide, methacrylic acid amide, acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isobutyl Acrylate, isobutyl methacrylate, 2-ethylhexyl Monofunctional monomers such as acrylate, 2-ethylhexyl methacrylate, benzyl acrylate, benzyl methacrylate, ethylene glycol diacrylate, ethylene glycol monomethacrylate, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, nonaethylene glycol monoacrylate, polyethylene glycol monoacrylate , Polyethylene glycol monomethacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, nonaethylene glycol monomethacrylate, dipropylene glycol monoacrylate, tripropylene glycol monoacrylate, tetrapropylene glycol monoacrylate, dipropylene glycol monomethyl Tacrylate, tripropylene glycol monomethacrylate, butylene glycol monomethacrylate, propylene glycol monoacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, nonaethylene glycol diacrylate, triethylene glycol diacrylate Methacrylate, tetraethylene glycol dimethacrylate, nonaethylene glycol dimethacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tetrapropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, butylene glycol dimethyl ester Chryrate, propylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolpropane tetraacrylate, tetramethylolpropane tetramethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate , Dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, cardo epoxy diacrylate, etc. Sensuality A mer may be used.

  Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2- Morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2,4-diethylthioxanthone, 2 -Chlorothioxanthone, 2,4-dimethylthioxanthone, 3,3-dimethyl-4-methoxybenzophenone, benzophenone, 1-chloro-4-propoxythioxanthone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane -1-one, 1- (4-dodecylphenyl) -2-hydroxy- 2-methylpropan-1-one, 4-benzoyl-4'-methyldimethylsulfide, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, butyl 4-dimethylaminobenzoate 2-ethylhexyl 4-dimethylaminobenzoate, 2-isoamyl 4-dimethylaminobenzoate, 2,2-diethoxyacetophenone, benzyldimethyl ketal, benzyl-β-methoxyethyl acetal, 1-phenyl-1,2 -Propanedione-2- (ο-ethoxycarbonyl) oxime, methyl ο-benzoylbenzoate, bis (4-dimethylaminophenyl) ketone, 4,4'-bisdiethylaminobenzophenone, 4,4'-dichlorobenzophenone, benzyl, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl Ether, benzoin isobutyl ether, benzoin butyl ether, p-dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, dibenzosuberone, α, α -Dichloro-4-phenoxyacetophenone, pentyl-4-dimethylaminobenzoate and the like may be used.

  As the organic solvent, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monophenyl ether, diethylene glycol Dimethyl ether, diethylene glycol diethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, Diethylene glycol monopropyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monophenyl ether acetate, propylene glycol monomethyl ether acetate, proprene glycol monoethyl ether acetate, proprene Recall monopropyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 2-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3- Methoxybutyl acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, tetrahydrofuran, Rhohexane, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, 2-hydroxy-2-methyl, methyl-3-methoxypropionate, ethyl -3-methoxypropionate, ethyl-3-ethoxypropionate, ethyl-3-propoxypropionate, propyl-3-methoxypropionate, isopropyl-3-methoxypropionate, ethyl ethoxyacetate, oxyacetic acid Ethyl, methyl 2-hydroxy-3-methylbutanoate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isoamyl methyl carbonate, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, pyruvine Propyl acid, butyl pyruvate, Methyl acetoacetate, ethyl acetoacetate, benzyl methyl ether, benzyl ethyl ether, dihexyl ether, benzyl acetate, benzyl benzoate, diethyl oxalate, diethyl maleate, γ-butyrolactone, benzene, toluene, xylene, cyclohexane, methanol, ethanol, propanol Butanol, 3-methyl-3-methoxybutanol, hexanol, cyclohexanol, ethylene glycol, diethylene glycol, glycerin, terpineol, dihydroterpineol and the like may be used. Of the above, 3-methyl-3-methoxybutanol can reduce the reactivity between metal ions present on the surface of inorganic materials such as silver powder and glass powder and organic binders soluble in alkaline aqueous solutions. Therefore, the viscosity change and gelation of the paste are suppressed, and high storage stability is obtained. The content of the organic solvent in the paste is preferably about 1 to 40 (wt%). If it is less than 1 (wt%), uniform coating and contact exposure in the exposure step S6 are difficult. Conversely, if it exceeds 40 (wt%), the viscosity decreases and sedimentation tends to occur.

  The conductive paste may further contain other additives such as dyes, plasticizers, surfactants, antifoaming agents, thermal polymerization inhibitors. As the dye, for example, cyanine green can be used. As the plasticizer, dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerin and the like are preferably used. In addition, these plasticizers can also be used as an organic solvent. Moreover, as an antifoamer, various things, such as a silicone type and a fluorine type, can be used.

  In the embodiment, the photosensitive black conductive paste was applied on the substrate 42 by the thick film screen printing method or the bar coater and exposed and developed. However, the method for forming the black conductive thick film 40 and the like is not limited thereto. It is not limited. For example, the present invention is similarly applied when the black conductive thick film 40 and the like are formed by a sand blast method, a lift-off method, or the like.

  In the examples, the black conductive paste was prepared to have a viscosity of about 100 (Pa · s), but the viscosity is appropriately changed according to the thickness of the paste film to be formed. However, in order to print the entire surface with a uniform thickness, it is preferably in the range of about 5 to 200 (Pa · s), more preferably in the range of about 10 to 150 (Pa · s).

  In the embodiment, after drying, the black conductive paste film 52 is formed to have a thickness of about 10 (μm) and the conductive paste film 74 has a thickness of about 5 to 6 (μm). The thickness is appropriately changed within a range of, for example, about 5 to 20 (μm) according to the required film thickness of the black conductive thick films 40 and 60. When the required film thickness cannot be obtained by a single application, such as when a dry thickness exceeding 20 (μm) is required, the paste may be repeatedly applied until the required film thickness is reached.

  In the example, the paste drying step S2 was dried at a temperature of about 80 (° C.) for about 15 (minutes), and the conductor firing step S6 was performed at a temperature of about 550 (° C.). The drying temperature and time are appropriately changed according to the thickness of the paste film, the type of the organic solvent, the thermal polymerization start temperature of the monomer, and the like, and the firing temperature is appropriately changed according to the type of the glass powder. The preferable ranges are the drying temperature and time, for example, about 70 to 200 (° C.) and about 5 to 60 (min), respectively, and the firing temperature is about the heat deformation temperature of the substrate 42 or about 400 to 450 (° C.). Considering thermal deformation of the black conductive films 40 and 60 in the sealing process to be processed, the temperature is about 500 to 600 (° C.).

In the embodiment, the exposure process S3 is performed using ultraviolet rays having a wavelength of about 350 (nm), but the wavelength of the irradiation light is appropriately changed according to the type of the photopolymerizable compound. In the embodiment, an ultra-high pressure mercury lamp is used as a generation source of ultraviolet rays. However, a low-pressure mercury lamp, a high-pressure mercury lamp, a chemical lamp, or the like can be used. Depending on the exposure property, it is appropriately changed within a range of, for example, about 20 to 1000 (mJ / cm ² ).

  In the example, the photopolymerizable compound is contained in the photosensitive black conductive paste, so that the portion 58 exposed in the exposure step S3 is cured to form a pattern. By using a compound or the like that is decomposed by being exposed, a pattern such as the black conductive thick film 40 may be formed in a portion that is not exposed. That is, the photosensitive composition is not limited to a photopolymerizable compound, but undergoes a chemical reaction such as polymerization, decomposition, addition, dimerization, oxidation, reduction, etc. when irradiated with light, and changes in solubility and hardness. Various compositions can be used as long as they do. When a compound that decomposes by exposure is used, it is necessary to use a positive mask in which the opening 56 and the non-opening are reversed instead of the negative mask 54 in the exposure step S3.

  In addition, although not illustrated one by one, the present invention can be variously modified without departing from the gist thereof.

(a) is a perspective view showing a configuration of an example of a PDP in which the black conductive thick film of the present invention can be provided, with a part cut away, and (b) is a longitudinal direction of a write electrode in (a) It is a figure which shows the cross section along line. It is a figure which shows the cross-sectional structure in case the display discharge electrode forms a film | membrane directly on a front plate in PDP of FIG. (a) is a perspective view which shows the black conductive thick film of one Example of this invention, (b) is a figure which expands and shows the bb cross section in (a) typically. It is process drawing explaining the formation method of the black conductive thick film of FIG. (a)-(c) is a figure which shows the cross-section of a board | substrate in each step of the film | membrane formation process of FIG. It is a perspective view which shows the black conductive thick film of the other Example of this invention. It is process drawing explaining the principal part of the formation process of the black conductive thick film of FIG. (a), (b) is a figure which shows the cross-section of a board | substrate in each step of the film | membrane formation process of FIG. It is a graph which shows the relationship between L value and sheet resistance value of the black conductive thick film of the other Example of this invention. It is a graph which shows the relationship between L value and b value of the black conductive thick film of FIG.

Explanation of symbols

40: black conductive thick film, 42: substrate, 44: silver, 46: black pigment, 48: glass

Claims (6)

It contains silver powder, glass powder, organic binder, organic solvent, photosensitive composition, and black pigment, has photosensitivity, and exhibits a black color that functions as a display electrode by exposure and development processing. A photosensitive black conductive paste composition for forming a display electrode used for forming a conductive thick film,
A photosensitive black conductive paste composition for forming a display electrode, wherein the black pigment is made of Co ₃ O ₄ (tricobalt tetroxide) powder having a specific surface area of 1 to 20 (m ² / g).   The photosensitive black conductive paste composition for forming a display electrode according to claim 1, wherein the organic binder is a cellulose derivative.   The photosensitive black conductive paste composition for forming a display electrode according to claim 1 or 2, wherein the black pigment is contained in a range of 0.5 to 20 (wt%) with respect to the whole paste composition. A black conductive thick film for a display electrode, which is provided in a predetermined pattern on a predetermined substrate and formed by combining silver and a black pigment with glass,
The black pigment is made of Co ₃ O ₄ having a specific surface area of 1 to 20 (m ² / g),
A black conductive thick film for a display electrode, which is patterned by exposure and development using a photosensitive conductive paste containing a photocurable compound.   The black conductive thick film is provided on the other surface opposite to the one surface of the translucent substrate observed from a predetermined one surface side, and includes a black conductive layer containing the black pigment, and more than the black conductive layer. The black conductive thick film for a display electrode according to claim 4, comprising a high-lightness and high-conductivity layer provided on the upper side of the lightness and high conductivity. A method of forming a black conductive thick film for a display electrode functioning as an electrode of a display in a predetermined pattern on the other surface opposite to the one surface of the translucent substrate observed from a predetermined one surface side,
A photosensitive black paste film forming step of forming a photosensitive black conductive paste film by applying the photosensitive black conductive paste composition for forming a display electrode according to any one of claims 1 to 3 on the other surface of the translucent substrate. When,
A photosensitive high-lightness and high-conductivity paste composition for producing a film having higher brightness and higher conductivity than that produced from the photosensitive black conductive paste film is applied onto the photosensitive black conductive paste film. A photosensitive high-lightness paste film forming step of forming a photosensitive conductive paste film having a predetermined thickness by laminating and forming a photosensitive high-lightness high-conductive paste film;
An exposure step of selectively exposing the photosensitive conductive paste film through a shielding film having a predetermined opening pattern;
A development step of washing and removing a non-cured portion of the photosensitive conductive paste film with a predetermined developer after the exposure step;
A method of forming a black conductive thick film for display electrodes, comprising: baking the photosensitive conductive paste film to generate a black conductive thick film having a predetermined pattern.

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