METHOD OF AND MATERIAL FOR FORMING THICK FILMY PATTERN

Abstract: Molds (2, 12, 22, 32, 42, 52, and 62) in desired patterns are formed on substrata (1, 11, 21, 31, 41, 51, and 61). Spaces in the molds are filled with ceramic materials (3, 13, 23, 33, 43, 53, and 63). The molds are removed by heating the whole of each substratum so that desired thick filmy patterns may be formed easily but accurately on the substrata. As ceramic materials, an inorganic paste material composed of an inorganic liquid vehicle constituted mainly of water-glass and powdery solid constituent dispersed in said inorganic liquid vehicle is used. Said inorganic paste material can be prevented from being broken because volumetric change thereof is small when dried and sintered.

Description: The present invention relates to a method of forming a thick film pattern in a manufacturing process of a liquid crystal display device, a display panel made of fluorescent character display tubes, a plasma display panel, a hybrid integrated circuit and the like. Conventionally, there is known a method of forming a thick film pattern by the steps of printing a paste for the conductor or insulator on a substrate made of glass or ceramic in the form of pattern by a screen printing, drying and calcinating the paste, and repeating the above steps. Recently in various fields, thick film patterns are formed on a substrate made of glass or the like using ceramic material. In this case, paste-like ceramic materials which are formed by dispersing ceramics in a binder is employed, and similarly, the thick film pattern is formed by the steps of printing the paste-like ceramic material by a screen printing, drying and calcinating the paste-like ceramic material, and repeating the above steps. US-A-4 119 480 describes inter alia a method of manufacturing a thick film circuit which comprises depositing a photosensitive resin on a substrate, exposing said photosensitive resin selectively to light, removing the unnecessary parts of said photosensitive resin, filling a paste material for thick-film circuit use into the openings from which said photosensitive resin was removed, and then removing the remaining photosensitive resin and firing the filled paste material. DE-A-1 915 756 describes a process for the preparation of thick-film structures on substrates, wherein a photopolymer is applied on the substrate, the photopolymer is subjected to a known photolithographic procedure to form spaces, e.g. a ceramic is filled into spaces, and the ceramic material is fired. In the conventional method of forming a thick film pattern on a glass substrate using a ceramic material by a screen printing, in order to attain a film pattern having a desirable thickness, it is necessary to repeat screen printing several times. That is, in this method, it is necessary to repeat the screen printing five to ten times in order to attain a thick film having a thickness of 50 to 100 µm, and a drying process is required at every time. Therefore, the productivity is extremely low and the yield rate is lowered. Further, there is the problem that the accuracy of a line width of pattern is impaired due to viscosity of the paste, thixotropy or the like. It is therefore a primary object of the present invention to provide a method of forming a thick film pattern in which ceramic material can reliably adhere to a substrate. Another object of the present invention is to provide a method of forming a thick film pattern and material for forming a thick film pattern which can prevent paste material from being broken when drying and calcinating the same and strengthen the binding force between powdery solids and the adhesive force between powder solid and a substrate, and which can form a desirable thick film pattern by a calcinating process at a low temperature. Still another object of the present invention is to provide a method of forming a thick film pattern which is improved in radiation resistance when used in a plasma display panel. According to the present invention, there is provided a method of forming a thick film pattern of ceramic material on a substrate comprising the steps of forming a female mold on said substrate comprising the steps of forming a photoresist layer on said substrate by applying more than one layer of a dry film on said substrate and performing pattern exposure to develop said photoresist layer; filling said ceramic material in the spaces formed in said female mold; and calcining to cause said female mold to vanish, wherein the step of filling said ceramic material in the spaces formed in said female mold comprises the step of filling inorganic paste material in said spaces of said female mold, said inorganic paste material containing powdery solid dispersed in inorganic liquid vehicle as a binder whose main ingredient is water glass. In a preferred embodiment of the present invention the step of forming a female mold comprises the steps of providing one photoresist layer on said substrate; performing pattern exposure and development of said photoresist layer (54a); providing upper photoresist layer of a desirable height on said one photoresist layer; performing pattern exposure and development of said upper photoresist layer. In a preferred embodiment of the present invention the step of forming a female mold comprises the steps of providing a photoresist layer having a desirable height on said substrate; performing a pattern exposure and development of said photoresist; causing a poor development portion of said photoresist layer to vanish by dry etching. In a further preferred embodiment of the present invention the inorganic paste material contains 10 to 90% by weight of said water glass. Figs. 1(a) through 1(c) are explanatory views showing a basic method concerning a method of forming a thick film pattern. Figs. 2(a) through 2(e) are explanatory views showing a specific method of forming a thick film pattern according to a first reference embodiment. Figs. 3(a) through 3(h) are explanatory views showing a method of forming a thick film pattern according to a second reference embodiment; Figs. 4(a) through 4(g) are explanatory views showing a method of forming a thick film pattern according to a third reference embodiment; and Figs. 5(a) through 5(e) are explanatory views showing a method of forming a thick film pattern according to the present invention. First, second and third reference embodiments are technical background information only and are not within the scope of the present invention. A first reference embodiment of a method of forming thick film pattern A basic method concerning the method of forming a thick film pattern is shown in Figs. 1(a) through 1(c). First, a female mold 2 having a desirable pattern is formed on a substrate 1 made of glass or the like using material such as photoresist as shown in Fig. 1(a). Then, ceramic material 3 is filled in spaces 2a defined in the female mold 2 as shown in Fig. 1(b). Thereafter, the female mold 2 is caused to vanish by chemical treatment or calcinating treatment, thereby obtaining the thick film pattern made of the ceramic materials 3 as shown in Fig. 1(c). Next, the first reference embodiment will be described with reference to Figs. 2(a) through 2(e). Figs. 2(a) through 2(e) are explanatory views showing a forming process of a female mold using photoresist. Fig. 2(a) shows a process for forming a photoresist layer on a substrate, Fig. 2(b) a process for pattern exposure, Fig. 2(c) a developing process, Fig. 2(d) a process for filling ceramic material, and Fig. 2(e) a process for calcinating. In this reference embodiment, a dry film (AP-850 manufactured by Tokyo Ouka Industry Co.) which was used in a photomechanical process was used to easily form a thick film as the photoresist. A dry film which is used in the field of electronics may be used as well. However, this choice is not restricted, that is, a suitable photoresist can be chosen in accordance with pattern size. Each process will be described in order with reference to Fig. 2. First, a dry film as a photoresist 14 on a glass substrate 11 was arranged in four layers to thereby obtain the layers having a thickness of 200 µm using a laminate roll 17 by a heating laminate method. Thereafter, a parallel light 18 was irradiated onto the dry film using a parallel light printer incorporating an ultra high-pressure mercury lamp as a light source, as shown in Fig. 2(b), thereby performing pattern exposure through a line pattern mask 15 having a line width of 100 µm and a pitch of 300 µm. The exposure conditions were an intensity of 200 µw/cm 2 and irradiation amount of 250 mJ/cm 2 when measured by wave length of 365 nm. Next, in the developing process in Fig. 2(c), spray development was carried out by aqueous solution 19 containing sodium carbonate anhydride of 1% by weight at a liquid temperature of 30 to 50°C. The termination point of development was confirmed by the naked eye. A female mold 12 having a desirable pattern having a line width of 200 µm, a pitch of 300 µm and a height of 200 µm was obtained through the above processes. In the filling process for the ceramic material in Fig. 2(d), as ceramic material 13, a paste-like mixture containing glass frit having a low melting point, heat-resistant pigment and filling agent dispersed in organic binder was used. A flat rubber plate 16 was brought into contact with a female mold 12 and moved across the pattern of the female mold 12, whereby the paste-like ceramic material 13 was filled in the spaces 12a of the female mold 12 and excessive ceramic material which was forced out was scraped. Then the substrate 11 and the ceramic material 13 filled in the spaces 12a of the female mold 12 were dried at a temperature of 80 to 120°C to remove solvent contained in the organic binder and fed to the calcinating process. Incidentally, the filling process of the paste-like ceramic material 13 may be repeated several times, if necessary. In the calcinating process in Fig. 2(e), the substrate 11 and the female mold 12 carrying the ceramic material were calcinated for 10 to 20 minutes at a peak temperature of 585°C, whereby the female mold 12 formed by the photoresist was vanished and the ceramic material 13 adhered to the glass substrate 11. The thick film pattern made of the ceramic material 13 having a line width of 100 to 200 µm, a pitch of 300 µm and a height of 150 µm was obtained through the above processes. According to the first reference embodiment, the following effects were obtained. (1) Since a pattern having a height of not less than 100 µm could be obtained by only one operation, the operating time could be shortened when compared with the laminating method used for conventional screen printing. (2) Since operations such as positioning were only once, the process was simplified. A second reference embodiment of a method of forming thick film pattern A method of forming a thick film pattern according to the second reference embodiment will be described with reference to Figs. 3(a) through 3(h). First, one layer of the photoresist 54a was provided on the glass substrate 51. That is, as photoresist, a dry film (Nopcocure F-5040 manufactured by San Nopco Limited) having a thickness of 40 µm was used, one layer was formed on the glass substrate 51 by a heating laminate method. Next, a parallel light 58 was irradiated onto the dry film using a parallel light printer incorporating an ultra high-pressure mercury lamp as a light source as shown in Fig. 3(b), thereby performing pattern exposure through a line pattern mask 55 having a line width of 100 µm and a pitch of 300 µm. The exposure condition was intensity of 200 µw/cm 2 and irradiation amount of 72 mJ/cm 2 when measuring by wave length of 365 nm. Next, in the developing process in Fig. 3(c), spray development was carried out by 1,1,1-trichloroethane 59 at liquid temperature of 25°C. In this case, the photoresist 54a had a thickness of 40 µm which was small, therefore, a desirable pattern was obtained by pattern exposure and development without the photoresist 54a remaining at the opening 57. Thereafter, three layers of dry film were placed on one layer of the photoresist 54a to thereby form the upper layers of the photoresist 54b, whereby the photoresist 54 having four layers was formed as shown in Fig. 3(d). Next, a pattern exposure was performed by a parallel light 58 through the line pattern mask 55 as shown in Fig. 3(e). The exposure condition of this case had an intensity of 200 µw/cm 2 and irradiation amount of 200 mJ/cm 2 when measuring by wave length of 365 nm. Thereafter, spray development was carried out by 1,1,1-trichloroethane 59 at liquid temperature of 25°C, whereby the female mold 52 having a desirable pattern with a line width of 200 µm, a pitch of 300 µm and a height of 160 µm was obtained, as shown in Fig. 3(f). The female mold 52 had spaces 52a. In the filling process in Fig. 3(g), as a ceramic material 53, a paste-like mixture containing glass frit having a low melting point, a heat-resisting pigment and a filling material dispersed in organic binder was used. A flat rubber plate 56 was brought into contact with the female mold 52 and moved across the pattern of the female mold 52, whereby the paste-like ceramic material 53 was filled in the spaces 52a of the female mold 52 and excessive ceramic material 53 which was forced out was scraped. Then, in order to remove the solvent contained in the organic binder in the ceramic material 53, the substrate 51 and the ceramic material 53 filled in the spaces 52a of the female mold 52 were dried at a temperature of 80 to 120°C and fed to the calcinating process. Incidentally, the filling process of the paste-like ceramic material 13 may be repeated, if necessary. Finally, calcination was performed for 10 to 20 minutes at a peak temperature of 585°C, whereby the female mold 52 formed by the photoresist vanished and the ceramic material 53 was adhered onto the glass substrate 51. The thick film pattern made of the ceramic material 53 having a line width of 100 to 120 µm, a pitch of 300 µm and a height of 150 µm was obtained through the above processes as shown in Fig. 3(h). According to the second reference embodiment, the following effect was obtained. (1) Even if the female mold had a fine pattern with a certain height, the photoresist did not remain in the space of the female mold and the ceramic material filled in the space of the female mold was reliably adhered onto the substrate by the calcinating process. A third reference embodiment of a method of forming thick film pattern A method of forming a thick film pattern according to the third reference embodiment will be described with reference to Fig. 4(a) through 4(g). First, a dry film (Nopcocure F-540 manufactured by San Nopco Limited.) having a thickness of 40 µm was arranged in four layers by a heating laminate method to thereby form the photoresist layer 64 having a thickness of 160 µm as shown in Fig. 4(a). Next, a parallel light 65 was irradiated onto the dry film using a parallel light printer incorporating a ultra high-pressure mercury lamp as a light source as shown in Fig. 4(b), thereby performing pattern exposure through a line pattern mask 65 having a line width of 100 µm and a pitch of 300 µm. The exposure condition was an intensity of 200 µw/cm 2 and an irradiation amount of 230 mJ/cm 2 when measured by a wave length of 365 nm. Next, a spray development was carried out by mixture 68 of 1,1,1-trichloroethane and dichloromethane (mixing rate 4:1) at liquid temperature of 25°C, thereby obtaining the photoresist 64 having a desirable pattern as shown in Fig. 4(c). In this case, the photoresist 64 had a thickness of 160 µm, a part 64a of photoresist remained in the concave of the pattern at the stage of developing. Therefore, the remaining part of the photoresist was removed by dry etching, for example, plasma ashing by reactive gas 69 as shown in Fig. 4(d). The condition of the plasma ashing was a reactive gas pressure of 20 mm Torr, the degree of vacuum of 9 × 10 -5 Torr, and substrate's rotational speed of 1 rpm. Furthermore, the reactive gas was oxygen (O 2 ) and the flow rate of the reactive gas was 30 SCCM. The ashing time was 30 minutes. The female mold 62 having a thick film pattern with a line width of 200 µm, a pitch of 300 µm and a height of 150 µm was obtained through the above processes. The female mold 62 had spaces 62a as shown in Fig. 4(e). Ion etching containing O 2 and CF 4 , or other dry etching was effective to remove the photoresist 64a which remained on the substrate 61. In the filling process in Fig. 4(f), as the ceramic material 63, a paste-like mixture containing glass frit having a low melting point, heat-resisting pigment and a filling material dispersed in organic binder was used. A flat rubber plate 66 was brought into contact with the female mold 52 and moved across the pattern of the female mold 62, whereby the paste-like ceramic material 63 was filled in the spaces 62a of the female mold 62 and excessive ceramic material 63 which was forced out was scraped. Then, in order to remove the solvent contained in the organic binder in the ceramic material 63, the substrate 61 and the ceramic material 63 filled in the spaces 62a of the female mold 62 were dried at a temperature of 80 to 120°C and fed to the calcinating process. Incidentally, the filling process of the paste-like ceramic material 63 may be repeated, if necessary. Finally, calcination was performed for 10 to 20 minutes at a peak temperature of 585°C, whereby the female mold 62 formed by the photoresist vanished and the ceramic material 63 adhered onto the glass substrate 61. The thick film pattern made of the ceramic material 63 having a line width of 100 to 120 µm, a pitch of 300 µm and a height of 150 µm was obtained through the above processes as shown in Fig. 4(g). According to the third reference embodiment, the following effects were attained. (1) Since the female mold on which the photoresist did not remain was formed, the ceramic material filled in the space of the female mold reliably adhered onto the substrate by calcinating process. Method of forming thick film pattern according to the present invention A method of forming a thick film pattern according to the present invention will be described below. First, a photoresist layer is formed on the substrate, and a pattern exposure and development are performed to the photoresist layer to thereby form the female mold having a desirable pattern. Thereafter, inorganic paste material containing powder solid dispersed in inorganic liquid vehicle comprising water glass as main ingredient is filled in spaces of the female mold. Next, calcination is performed to cause the female mold to vanish, and the powder solid is adhered onto the substrate to thereby obtain a desirable thick film pattern, with water glass in inorganic paste material serving as a binder. As water glass serves as the vehicle in the inorganic paste material, water glass containing sodium silicate as main ingredient is used, the molecular formula of the water glass being Na 2 O nSiO 2 mH 2 O. There are three types of water glass in standard, that is, No. 1, No. 2, No. 3 according to the ratio of Na 2 O to SiO 2 , every type can be used in this embodiment. Furthermore, the inorganic paste material containing water glass of 10 to 90% by weight is used. To be more specific, the paste material loses fluidity in the case of water glass of less than 10% by weight, and it is difficult to carry out filling process. On the contrary, in the case of water glass of above 90% by weight, the rate of powdery solid in the inorganic paste material is small, therefore, the thick film pattern cannot be formed. Taking into consideration fluidity in the form of paste, the inorganic paste material preferably contains the water glass of 20 to 50% by weight so that it is filled into the fine spaces of the female mold and so that excessive material which is forced out from the pattern is easily scraped. On the other hand, as powdery solid in the inorganic paste material, aggregate and pigment are used in a mixed state. As the aggregate, silica, alumina, zirconia, silicon carbide (SiC), boron nitoride (BN), stainless steel (SUS), mica, or the like may be used, further, as the pigment, chromium oxide, iron oxide, cobalt oxide, titanium oxide, molybdenum oxide, copper oxide, aluminum, or the like may be used. The scope of the present invention is not restricted by the choice of the above aggregate and pigment, suitable aggregate and pigment may be used in accordance with purpose. Furthermore, if necessary, curing agent, stabilizer, disperse agent or the like may be added to the inorganic paste material. An embodiment of the present invention will be described with reference to Figs. 5(a) through 5(e). First, a resist film (Nopcocure F-5040 manufactured by Sun Nopco Limited film thickness 40 µm) of original type was arranged in four layers on a glass substrate 71 which was heated at a temperature of 90°C using a laminate roll 77, thereby forming a photoresist layer 74 having a thickness of 160 µm as shown in Fig. 5(a). Next, ultraviolet rays 78 were irradiated with a irradiation amount of 250 - 300 mJ/cm 2 onto the photoresist layer 74 through a film mask 75 having a line pattern by a contacting printer from the side of the film mask 75 as shown in Fig. 5(b). Thereafter, a spray development was performed on the unexposed portions by solution 79 in which dichloromethane of 20% by volume was mixed in 1,1,1-trichloroethane, thereby forming a female mold 72 having the required pattern with line-like spaces 72a having a line width of 100 µm, a pitch of 300 µm as shown in Fig. 5(c). Next, a flat rubber plate 76 was brought in contact with the space 72a of the female mold 72 and moved parallel to the pattern of the female mold 72, whereby the inorganic paste material 73 was filled in the space 72a of the female mold 72 and excessive material 73 which was forced out was scraped as shown in Fig. 5(d). Vehicle: water glass No. 2 (sodium silicate manufactured by Toyo Keisan Soda Co.) 30% by weight Powdery solid: alumina beads (CB-AO5S manufactured by Showa Denko Co.) 60% by weight Heat resistant black pigment (Daipirokiside color #9590 manufactured by Dainichiseika) Furthermore, in order to remove water contained in the inorganic paste material 73, the inorganic paste material 73 was dried at a temperature of 80 to 90°C. Incidentally, the filling process of the paste material 73 may be repeated, if necessary. Finally, calcination was performed for 30 to 60 minutes at a peak temperature of 450°C, whereby the female mold 72 formed by photoresist was ashed and vanished and the powdery solid of the inorganic paste material 73 adhered onto the glass substrate. The thick film pattern having a line width of 100 µm, a pitch of 300 µm and a thickness of 150 µm was obtained through the above processes as shown in Fig. 5(e). The glass substrate 71 on which the thick film pattern was formed was used as a base plate having cell barriers in the plasma display panel. In this case, ultraviolet rays were generated by electric discharge between cells, but the thick film pattern 73 was not deteriorated because water glass which was binder of the thick film pattern 73 had an excellent radiation resistance. Therefore, the glass substrate 71 having the thick film pattern 73 was effective as cell barriers of the plasma display panel. According to the present invention, the following effects were attained. (1) Since the inorganic paste material in which powdery solid was dispersed in inorganic liquid vehicle made by water glass as main ingredient was used as a ceramic material filled into a female mold, the volume change of the inorganic paste material was small in the drying process and the calcinating process, and so the inorganic paste material was prevented from being broken. (2) The bonding force between the powdery solid and the adhesive force between the powdery solid and the substrate were enhanced by the existence of water glass. (3) After the calcinating process, organic material did not remain unlike the conventional paste including organic medium, so that the thick film pattern was formed by calcinating process of lower temperature than before. The present invention is widely applicable to manufacture of liquid crystal display devices, fluorescent display devices, plasma display panels, and hybrid integrated circuits or the like.

Claims: A method of forming a thick film pattern of ceramic material (3, 13, 53, 63, 73) on a substrate (1, 11, 51, 61, 71) comprising the steps of: forming a female mold (2, 12, 52, 62, 72) on said substrate (1, 11, 51, 61, 71) comprising the steps of forming a photoresist layer (14, 54, 54a, 54b, 64, 74) on said substrate (1, 11, 51, 61, 71) by applying more than one layer of a dry film on said substrate (1, 11, 51, 61, 71) and performing pattern exposure to develop said photoresist layer (14, 54, 54a, 54b, 64, 74); filling said ceramic material (3, 13, 53, 63, 73) in the spaces (2a, 12a, 52a, 62a, 72a) formed in said female mold (2, 12, 52, 62, 72); and calcining to cause said female mold (2, 12, 52, 62, 72) to vanish, wherein the step of filling said ceramic material (3, 13, 53, 63, 73) in the spaces (2a, 12a, 52a, 62a, 72a) formed in said female mold (2, 12, 52, 62, 72) comprises the step of: filling inorganic paste material in said spaces (2a, 12a, 52a, 62a, 72a) of said female mold (2, 12, 52, 62, 72), said inorganic paste material containing powdery solid dispersed in inorganic liquid vehicle as a binder whose main ingredient is water glass. The method according to claim 1, wherein the step of forming a female mold (2, 12, 52, 62, 72) comprises the steps of: providing one photoresist layer (54a) on said substrate (1, 11, 51, 61, 71); performing pattern exposure and development of said photoresist layer (54a); providing upper photoresist layer (54b) of a desirable height on said one photoresist layer (54a); performing pattern exposure and development of said upper photoresist layer (54b). The method according to claim 1, wherein the step of forming a female mold (2, 12, 52, 62, 72) comprises the steps of: providing a photoresist layer (64) having a desirable height on said substrate (1, 11, 51, 61, 71); performing a pattern exposure and development of said photoresist (64); causing a poor development portion (64a) of said photoresist layer (64) to vanish by dry etching. The method according to anyone of the preceding claims 1 to 3, wherein said inorganic paste material contains 10 to 90% by weight of said water glass.

Inventors: FUJII HIDEAKI, MATSUMOTO TAKESHI, MINEO NORIKAZU, ONO NORIKATSU, SAKAI YORIHIKO, FUJII, HIDEAKI, MATSUMOTO, TAKESHI, MINEO, NORIKAZU, ONO, NORIKATSU, SAKAI, YORIHIKO, FUJII, Hideaki, c/o Dai Nippon Insatsu K.K., MATSUMOTO, Takeshi, c/o Dai Nippon Insatsu K.K., MINEO, Norikazu, c/o Dai Nippon Insatsu K.K., ONO, Norikatsu, c/o Dai Nippon Insatsu K.K., SAKAI, Yorihiko, c/o Dai Nippon Insatsu K.K.
Applicants: DAINIPPON PRINTING CO LTD, DAI NIPPON INSATSU KABUSHIKI KAISHA
Application year: 1991
Main classification: G03F7
IPC codes: G03F7, H01L21, H05K1, H05K3