WO2005073809A1

WO2005073809A1 - Photosensitive inorganic paste composition, sheet-shaped unbaked body, and method of producing plasma display front plate

Info

Publication number: WO2005073809A1
Application number: PCT/JP2005/001556
Authority: WO
Inventors: Hiroyuki Obiya; Kiminori Oshio; Akira Kumazawa; Hitoshi Setsuda
Original assignee: Tokyo Ohka Kogyo Co., Ltd.
Priority date: 2004-01-28
Filing date: 2005-01-27
Publication date: 2005-08-11
Also published as: JP4271048B2; CN100587598C; KR100818222B1; TWI342981B; CN1910518A; JP2005215134A; KR20060105885A; TW200535564A

Abstract

A photosensitive inorganic paste composition capable of improving pattern accuracy to such an extent to be sufficiently adapted to fine patterning required of plasma displays, a sheet-shaped unbaked body for production of a plasma display front plate using the same, and a method of producing a plasma display front plate. A Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator are used in combination as a photopolymerization initiator in a photosensitive inorganic paste composition comprising at least a photopolymerization initiator, a photopolymerizable monomer and inorganic powders.

Description

DESCRIPTION

PHOTOSENSITIVE INORGANIC PASTE COMPOSITION, SHEET-SHAPED UNBAKED BODY, AND METHOD OF PRODUCING PLASMA DISPLAY FRONT PLATE

TECHNICAL FIELD The present invention relates to a photosensitive inorganic paste composition which gives an excellent shape of patterns by photolithography, a sheet-shaped unbaked body for production of a plasma display front plate using the same, and a method of producing a plasma display front plate.

BACKGROUND ART A plasma display forming an image by self-emission of a large number of fine cells by utilizing an electronic discharge phenomenon has excellent characteristics that it is a large, thin, lightweight and flat display, which has never been realized by conventional displays, and its spread has been attempted. The conventional plasma display is composed mainly of cells of a straight structure having a rib in the vertical direction of the display. In recent years, however, a cell of a waffle structure having a rib not only in the vertical direction but also in the horizontal direction has been developed in order to attempt efficient guiding of light from an emitting site to the front of a plasma display. The waffle structure of the cell can realize very efficient guiding of light to the front by preventing light from leaking from an adjacent cell. A perspective view of a disintegrated essential part of a plasma display having waffle cells is shown in Fig. 1. The plasma display is provided with a front plate 1 on which combined electrodes 11 each consisting of transparent electrode 110 and bus electrode 112 were formed parallel to one another, and with a back plate 2 on which address electrodes 21 were formed parallel to one another in the cross direction with respect to the combined electrodes 11. The front plate 1 and the back plate 2 are disposed so as to face each other and integrated to thereby constitute a display element. The front plate 1 has a transparent glass substrate 10 serving as a display plane, and the combined electrodes 11 are disposed on the inner side of the glass substrate 10, that is, on the side thereof facing the back plate 2. A dielectric layer 12 is formed so as to cover the combined electrodes 11 , and the dielectric layer 12 is provided thereon with a patterned spacer layer 16, and a protective film 19 made of MgO etc. is formed on the spacer layer 16 and the dielectric layer 12. On the other hand, the pack plate 2 has a substrate 20, which is provided with the address electrodes 21 disposed on a side of the substrate 20 facing the front plate 1. A dielectric layer 22 is formed so as to cover the address electrodes 21 , and the light emitting portions are formed on the dielectric layer 22 as described below. The light emitting portions consist of a number of cells each of which is located in a space at which the combined electrode 11 crosses the address electrode 21. Each cell is confined by ribs 24 formed on the dielectric layer 22 along the vertical and horizontal directions of the display. A fluorescence layer 26 is provided so as to cover the sidewall of the rib 24 and the surface of the dielectric layer 22 in the rib, that is, the inner wall and bottom of each cell. In the plasma display, a predetermined voltage from an alternating power source is applied to the combined electrodes on the front plate to form an electric field thereby causing electric discharge in the cell. This discharge results in generation of ultraviolet light, which further causes light emission from the fluorescence layer 26. Fig. 2 is a perspective view of the front plate 1 in the plasma display having waffle cells, as seen from the back plate side. Fig. 3 is a cross-sectional view of the plasma display having waffle cells. As shown in Fig. 2, the plasma display of the waffle structure is provided with a large number of spacer layers 16 provided on the dielectric layer 12 so that they are arranged in a form of equally spaced lines. As shown in Fig. 3, the spacer layer 16 in the front panel 1 is brought into contact with the rib 24, thus forming gap X in an upper part of each cell enclosed by rib 24, and a rare gas can be introduced through the gap X into each cell. A production method using screen printing is known as the method of producing the front plate. The production method using screen printing involves forming a glass paste film on the glass substrate 10, baking it at 400 to 700°C to form a dielectric layer 12 and then laminating a glass paste composition in a pattern by screen printing on the electric layer 12, followed by the secondary baking at 400 to 700°C, to form a spacer layer 16. However, the production method using screen printing requires two baking steps, thus increasing production costs. The method also has a problem of poor accuracy in pattern position. The aforementioned prior art is described in, e.g., Patent Document 1 (Japanese Patent Application Laid-open No. 2002-150949) and Patent Document 2 (Japanese Patent Application Laid-open No. 2002-328467). As a method of solving the problem in the screen printing method, a new method of producing a plasma display front plate by using photolithography has been proposed. A production process utilizing photolithography will be described with reference to Figs. 4Ato 4C. First, an unbaked dielectric layer 12A consisting of a non-photosensitive glass paste film and a photosensitive light-unexposed unbaked spacer material layer 16A consisting of a photosensitive glass paste film are formed on a glass substrate 10. The spacer material layer 16A is irradiated via a photomask 3 with ultraviolet rays etc. (Fig. 4A). The layer is then developed so that a resist pattern 16A' appears (Fig. 4B). The resulting product is baked at 400 to 700°C, to form a dielectric layer 12 and spacer layer 16 are simultaneously (Fig. 4C). The production method using photolithography is advantageous in that the dielectric layer 12 and spacer 16 can be simultaneously baked by conducting only one baking step. Thus, the production cost can be reduced as compared with the production method using screen printing. In the production method described above, a photosensitive glass paste composition containing glass frit, a photopolymerization initiator, a photopolymerizable monomer and a binder resin is used as a material for forming the spacer material layer 16A. As the photopolymerization initiator used in this photosensitive glass paste composition, a so-called Norish type I photopolymerization initiator which is cleaved at the position of carbon to generate a radical has been used. The Norish type I photopolymerization initiator is characterized by high curing speed and excellent internal curing properties. By using the Norish type I photopolymerization initiator excellent in internal curing properties, curing of the photosensitive glass paste film proceeds sufficiently to its bottom, to give a highly stable pattern having a shape whose cross section is in a form of a slight trapezoid. In recent years, however, there is an increasing demand for finer patterning than ever, and there arises a problem that the conventional photosensitive glass paste composition cannot sufficiently cope with the fine patterning required for plasma displays. For example, when the photosensitive glass paste film is exposed to light to form a pattern in Fig. 4A, exposure light enters at a right angle with respect to the surface of the photosensitive glass paste film. However, the exposure light is reflected by glass frit contained in the photosensitive glass paste film to cause halation so that the exposure light reaches a broader region. Accordingly, a cross-section of the resulting pattern 16A is in a form of trapezoid as shown in Fig. 5. Hence, there arises a problem that as the interval of a pattern is narrowed. due to finer patterning required for plasma displays, the influence of such trapezoid shape becomes more significant to deteriorate pattern accuracy. Particularly in the above production method using photolithography, the unbaked dielectric layer 12A consisting of a non-photosensitive glass paste film is arranged as a lower layer beneath the photosensitive glass paste film 16A and exposed to light. Accordingly, the influence of halation therein is made more significant not only by light reflected by glass frit contained in the photosensitive glass paste film, but also by light reflected by glass frit contained in the unbaked dielectric layer 12A as a lower layer. Accordingly, the tendency to broaden the pattern bottom width W_btm relative to the top width Wtop is more significant. By a later baking treatment, the patterned spacer material layer 16A and unbaked dielectric layer 12A are slightly shrunk. When the contact area between the pattern and the unbaked dielectric layer 12A (that is, the area of the bottom of the patterned spacer material layer 16A') is large, the dielectric layer 12 as a lower layer is pulled owing to shrinkage of the individual patterned spacer materials 16A so that as shown in Fig. 6A, the dielectric layer 12 in the patterned region is raised to cause uneven thickness of the dielectric layer 12. There is also a problem that shrinkage of the patterned spacer material layer 16A causes opposite tension to be applied to the dielectric layer 12 between the patterns so that as shown in Fig. 6B, the dielectric layer 12 positioned between the pattern lines is cracked. Although the Norish type I photopolymerization initiator is excellent in internal curing properties, the curing thereof may be inhibited by oxygen, which may impede curing reaction on the surface area that is directly in contact with oxygen. Accordingly, the light exposure is usually performed with the surface of the photosensitive glass paste being covered with a transparent film 180 such as polyethylene terephthalate in order to shield it against oxygen, as shown in Fig. 5. However, even if the surface is covered with the polyethylene terephthalate film, the film is thin so that slight oxygen permeates through the film. Accordingly, the surface part of the pattern may still remain in an uncured state after exposure to light, and thus washed away with a developing solution, to disturb the flatness of the surface of the pattern. There arises a problem that when the pattern is baked in such a state, the glass frit component is melted by the baking treatment to make the surface flat to some extent, but the surface still remains uneven, to make the thickness of the pattern uneven. The present invention has been achieved in view of the problems in the prior art, and relates to a photosensitive inorganic paste composition with pattern accuracy improved to such an extent as to be sufficiently adapted to fine patterning required for plasma displays, a sheet-shaped unbaked body for production of a plasma display front plate using the same, and a method of producing a plasma display front plate.

DISCLOSURE OF INVENTION As a result of extensive studies for solving the problem described above, the present inventors have found that in a photosensitive inorganic paste composition comprising at least a photopolymerization initiator, a photopolymerizable monomer and inorganic powders, employment of both a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator as the photopolymerization initiator results in obtaining an excellent shape of a pattern sufficiently adapted to fine patterning required of plasma displays. On the basis of this finding, the present invention has been achieved. According to preferable embodiments of the photosensitive inorganic paste composition of the present invention, the Norish type I photopolymerization initiator used is preferably at least one kind of compound selected from the group consisting of a benzoin ether compound, a benzyl ketal compound, an α-hydroxy acetophenone compound, an α-aminoacetophenone compound, a bisacyl phosphine oxide compound, an acyl phosphine oxide compound, a phenyl dicarbonyl compound and a phenyl acyl oxime compound. The hydrogen-withdrawing polymerization initiator used is preferably at least one kind of compound selected from the group consisting of an aromatic ketone compound, a thioxanthone compound, an anthraquinone compound and an amine compound. It is preferable that the containing ratio of the Norish type I photopolymerization initiator is 10 to 99 parts by weight, and the containing ratio of the hydrogen-withdrawing photopolymerization initiator is 1 to 90 parts by weight, per 100 parts by weight of the total amount of the photopolymerization initiators that are to be contained in the photosensitive inorganic paste composition. The present sheet-shaped unbaked body for production of a plasma display front plate is an unbaked body wherein a spacer material layer consisting of the photosensitive inorganic paste composition of the present invention is formed on a removable support film. In the present specification, the "sheet-shaped unbaked body for production of a plasma display front plate" means a sheet-shaped material having layers formed on the removable support film, the layers being released from the removable support film and transferred onto a glass substrate, upon producing a plasma display front plate. In the present method of producing a plasma display front plate, the photosensitive inorganic paste composition of the present invention is used for forming a spacer material layer. The light exposure treatment and subsequent treatments may be carried out in a conventional manner. According to a preferable embodiment of the method of producing a plasma display front plate according to the present invention, the softening point of the inorganic powders contained in the spacer material layer is preferably higher than the softening point of the inorganic powders contained in the unbaked dielectric layer, and preferably higher by 5°C or more than the softening point of the inorganic powders contained in the unbaked dielectric layer. A photosensitive inorganic paste film formed by using the photosensitive inorganic paste composition of the present invention provides a pattern with a surface in an excellent cured state formed after exposure to light. Accordingly, there can be brought about an effect that unlike the prior art, the uncured photosensitive inorganic paste material on the surface of a pattern can be prevented from being washed away with a developing solution, thus preventing a reduction in the thickness of the patterned film to give a pattern having uniform thickness. By using the Norish type I photopolymerization initiator in combination with the hydrogen-withdrawing photopolymerization initiator, a cross-section of the pattern after exposure to light can be controlled to be nearly rectangular as shown in Fig. 7A or to be trapezoid wherein the bottom width Wbtm of the pattern is slightly shorter than the top width W_t0p, as shown in Fig. 7B. There has been a problem that the bottom width W_btm is broadened particularly in the method of producing a plasma display front plate by utilizing photolithography wherein formation of the spacer layer is easily influenced by light reflected by the lower layer upon exposure to light, but this problem can be solved by the present invention. The contact area with the unbaked dielectric layer can thereby be reduced so that upon shrinkage of the pattern, the dielectric layer can be prevented from being cracked or deformed thus preventing uneven thickness. According to the sheet-shaped unbaked body for production of a plasma display front plate in the present invention, at least a spacer material layer consisting of the photosensitive inorganic paste composition of the present invention may be previously formed on a removable support film, and this unbaked body is laminated on a substrate at the time of manufacturing, whereby a spacer layer of uniform thickness excellent in surface smoothness can be formed on the glass substrate. The photosensitive insulating paste composition of the present invention may be used as a material for forming multi-layer circuits and various displays such as plasma display, plasma address liquid crystal display, field emission display etc., and may preferably be used in production of a spacer material layer in a plasma display front plate requiring particularly high accuracy. According to the method of producing a plasma display front plate in the present invention, two layers, that is, an unbaked dielectric layer consisting of a non-photosensitive inorganic paste composition and a spacer material layer consisting of the photosensitive inorganic paste composition of the present invention, are formed on a glass substrate, and thereafter, light exposure treatment and subsequent treatments may be carried out in a conventional manner, whereby pattern accuracy can be improved, and the dielectric layer can be prevented from being deformed and cracked upon baking. In the method of producing a plasma display front plate according to the present invention, the softening point of the inorganic powders contained in the spacer material layer may be set higher than the softening point of the inorganic powders contained in the unbaked dielectric layer, whereby a side wall of the pattern can be prevented from sagging upon baking.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a disintegrated view of a plasma display having cells of a waffle structure. Fig. 2 is a perspective view of the back of a plasma display front plate. Fig. 3 is a cross-sectional view of a plasma display having cells of the waffle structure. Fig. 4A is an illustration of a step (light exposure step) of producing a plasma display front plate by utilizing photolithography. Fig. 4B is an illustration of a step (development step) of producing a plasma display front plate by utilizing photolithography. Fig. 4C is an illustration of a step (baking step) of producing a plasma display front plate by utilizing photolithography. Fig. 5 is a cross-sectional view of a pattern after development, which is obtained by a method of producing a plasma display front plate in the prior art. Fig. 6A is a cross-sectional view of a pattern after baking, which is obtained by a method of producing a plasma display front plate in the prior art. Fig. 6B is a cross-sectional view of another pattern after baking, which is obtained by a method of producing a plasma display front plate in the prior art. Fig. 7A is a cross-sectional view of a pattern after development, which is obtained by the method of producing a plasma display front plate according to the present invention. Fig. 7B is a cross-sectional view of another pattern after development, which is obtained by the method of producing a plasma display front plate according to the present invention. Fig. 8A is an illustration of a process of producing a plasma display front plate by using the sheet-shaped baked body for production of a plasma display front plate. Fig. 8B is an illustration of a process of producing a plasma display front plate by using the sheet-shaped baked body for production of a plasma display front plate. In Figs. 8A and 8B, the numeral 18 refers to a removable film (support film 180 or protective film 182).

BEST MODE FOR CARRYING OUT THE INVENTION The photosensitive inorganic paste composition according to the present invention is a composition containing at least inorganic powders, a photopolymerization initiator and a photopolymerizable monomer, wherein a combination of a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator is used as the photopolymerization initiator. In conventional production of a plasma display front plate, a Norish type I photopolymerization initiator has been used alone as the photopolymerization initiator, and thus the curing properties on the surface of a pattern have not been sufficient, and an uncured photosensitive inorganic paste material on the surface has been washed away with a developing solution, thus giving rise to a problem of a reduction in the thickness of the patterned film. However, by using the combination of the Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator, the curing properties on the surface of a pattern may be improved, thereby preventing a reduction in the thickness of the patterned film, thus making the thickness of the patterned film uniform. By using the Norish type I photopolymerization initiator in combination with the hydrogen-withdrawing photopolymerization initiator, a cross-section of the pattern may be made nearly rectangular or trapezoid wherein the bottom width W_bt of the pattern is slightly shorter than the top width W_t0p. Accordingly, the dielectric layer may be prevented from being cracked or deformed, thus achieving uniform thickness. In the field of photolithography, the bottom width W_btm shorter than the top width W_top is generally considered not preferable because the stability of a pattern is lowered, but in the photosensitive inorganic paste film, the inorganic powders are melted by baking treatment to make the bottom width W_bt_m broader than before baking. Accordingly, in the case of a trapezoid having the bottom width W tm slightly shorter than the top width Wt_op, the bottom width Wbtm is broadened during baking thereby increasing the bottom width W_btm nearly to the top width W_t0p so that after baking, there is no problem with the stability of the pattern. Exemplary embodiments of the present invention will be explained below in detail with the following order.

(A) Photosensitive inorganic paste composition

(B) Sheet-shaped unbaked body for producing a plasma display front plate

(C) Method of producing a plasma display front plate (A) Photosensitive inorganic paste composition The photosensitive inorganic paste composition of the present invention is a composition comprising at least inorganic powders, a photopolymerization initiator and a photopolymerizable monomer, wherein a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator are contained as the photopolymerization initiator. The photosensitive inorganic paste composition of the present invention has transparency required for light exposure treatment with UV rays, an excimer laser, X rays and electron rays (hereinafter referred to as light rays), which is a composition capable of forming a highly accurate pattern by photolithographic means and usable preferably in production of plasma displays.

(a) Photopolymerization initiator In the present invention, a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator are used together as the photopolymerization initiator. The Norish type I photopolymerization initiator is a photopolymerization initiator which is cleavable at the position of α carbon to form a radical as shown in scheme (1) below. On one hand, the hydrogen-withdrawing photopolymerization initiator is a photopolymerization initiator which withdraws hydrogen of a hydrogen donor (RH) to form a radical as shown in scheme (2) below. d o II X— C—Y II X — c- + -Y ( 1 )

O OH II I X — C—Y + RH *- X — C—Y + - R ^{• • •} ( 2 )

wherein X is a substituted or unsubstituted aromatic group which is an organic group composed of at least one member selected from C, H, O, N, and S. There are some radical photopolymerization initiators which are cleaved at the position of α carbon to form a radical of Norish type I (-Y) which then withdraws hydrogen of a hydrogen donor (RH) to form a radical ( R) of hydrogen withdrawal type. In the present invention, however, such radical photopolymerization initiators are defined as belonging to the Norish type I photopolymerization initiator insofar as they are cleaved at the position of α carbon to form radicals. In the present invention, therefore, the photopolymerization initiator forming radicals of both Norish type I and hydrogen withdrawal type is classified into the Norish type I photopolymerization initiator. (I) Norish type I photopolymerization initiator The Norish type I photopolymerization initiator used in the present invention is preferably a compound represented by the following general formulae (1-1) to (I-3):

wherein R-|₀ to R₁₃ each represent an organic group composed of at least one member selected from C, H, O, N, and S, and when there are a plurality of Rios, they may be the same or different from one another, and two of Rn to R₁3 may be bound to each other to form a ring structure, and n1 is an integer of 0 to 5.

wherein R₂o to R₂₂ each represent an organic group composed of at least one member selected from C, H, O, N, and S, and when there are a plurality of R₂os, they may be the same or different from one another, and n2 is an integer of 0 to 5.

wherein X is O or N, R₃₀ and R3₁ each represent an organic group composed of at least one member selected from C, H, O, N, and S, and when there are a plurality of R₃0S, they may be the same or different from one another, R32 represents an organic group composed of at least one member selected from

C, H, O, N, and S, and n3 is an integer of 0 to 5. The Norish type I photopolymerization initiator may preferably be at least one kind of compound selected from the group consisting of a benzoin ether compound, a benzyl ketal compound, an α-hydroxy acetophenone compound, an α-aminoacetophenone compound, a bisacyl phosphine oxide compound, an acyl phosphine oxide compound, a phenyl dicarbonyl compound and a phenyl acyl oxime compound, among which the benzyl ketal compound, bisacyl phosphine oxide compound and acyl phosphine oxide are preferable, and the benzyl ketal compound is more preferable. Hereinafter, examples of the Norish type I photopolymerization initiators represented by the general formulae (1-1) to (I-3) will be illustrated, but the Norish type I photopolymerization initiator for use in the present invention is not limited thereto. As a matter of course, analogues of these compounds may also be used as the Norish type I photopolymerization initiator in the present invention. (1) Benzoin ether compound

O OC4H9 fΛ II I c— c H -

Benzoin methyl ether Benzoin ethyl ether Benzoin isopropyl ether

(2) Benzyl ketal compound

(3) α-Hydroxy acetophenone compound

1 -(4-lsopropylphenyl)-2-hydroxy-2-methylpropane-1 -one 1 -(4-Dodecylpheny!)-2-hydroxy-2-methylpropane-1 -one (4) α-Aminoacetophenone compound

(5) Bisacyl phosphine oxide compound

(6) Acyl phosphine oxide compound

(7) Phenyl dicarbonyl compound

o o ^X II II / V— C— C— OCH₃

(8) Phenyl acyl oxime compound

(II) Hydrogen-withdrawing photopolymerization initiator The hydrogen-withdrawing photopolymerization initiator used in the present invention is preferably a compound represented by the following general formula (11-1) or (II-2):

wherein R₄0 and R₄₁ each represent an organic group composed of at least one member selected from C, H, O, N, and S, and when there are a plurality of R₄₀S and R₄1S, they may be the same or different from one another, and two of R40S and R41S may be bound to each other to form a ring structure, and n40 and n41 each is an integer of 0 to 5.

wherein R₅0 and R₅₁ each represent a hydrocarbon group, and R₅₂ is an organic group composed of at least one member selected from C, H, O, N, and S. The hydrogen-withdrawing photopolymerization initiator may preferably be at least one kind of compound selected from the group consisting of an aromatic ketone compound, a thioxanthone compound, an anthraquinone compound and an amine compound (aromatic compound having a dialkylamino group, alkyl alkanol amine etc.), more preferably a thioxanthone compound and an aromatic compound having a dialkylamino group, still more preferably a thioxanthone compound. Hereinafter, examples of the hydrogen-withdrawing photopolymerization initiator represented by the general formula (11-1) or (II-2) will be illustrated, but the hydrogen-withdrawing photopolymerization initiator for use in the present invention is not limited thereto. As a matter of course, analogues of these compounds may also be used as the hydrogen-withdrawing photopolymerization initiator in the present invention.

(1 ) Aromatic ketone compound

3,3-dimethyl-4-methoxybenzophenone benzophenone

(2) Thioxanthone compound

thioxanthone 2-methylthioxanthone 2-isoproylthioxanthone 2,4-dimethylthioxanthone 2-chlorothioxanthone 1 -chloro-4-propoxythioxanthone (3) Anthraquinone compound

(4) Amine compound

(i) Aromatic compound having a dialkylamino group

4,4-bis(dimethylamino)-benzophenone (Michler's ketone) pentyl-4-dimethylaminobenzoate

N-butoxyethyl-4-dimethylaminobenzoate

2-(dimethylamino)ethyl benzoate

4-dimethylaminobenzoic acid methyl 4-dimethylaminobenzoate ethyl 4-dimethylaminobenzoate butyl 4-dimethylaminobenzoate

2-ethylhexyl 4-dimethylaminobenzoate

2-isoamyl 4-dimethylaminobenzoate pentyl 4-dimethylaminobenzoate

(ii) Alkyl alkanol amine monoethanol amine diethanol amine triethanol amine

N-methyl ethanoi amine

N-methyl diethanol amine

2-diethyl ethanoi amine triisopropanol amine

(b) Photopolymerizable monomer The photopolymerizable monomer may be a known photopolymerizable monomer and is not particularly limited, and examples thereof may include benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxy polyethylene glycol acrylate, phenoxy polyethylene glycol methacrylate, styrene, nonyl phenoxy polyethylene glycol monoacrylate, nonyl phenoxy polyethylene glycol monomethacrylate, nonyl phenoxy polypropylene glycol monoacrylate, nonyl phenoxy polypropylene glycol monomethacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl phthalate,

2-acryloyloxyethyl-2-hydroxyethyl phthalate,

2-methacryloyloxyethyl-2-hydroxypropy! phthalate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxy ethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, ethylene glycol monoacrylate, ethylene glycol monomethacrylate, glycerol acrylate, glycerol methacrylate, dipentaerythritol monoacrylate, dipentaerythritol monomethacrylate, dimethyl aminoethyl acrylate, dimethyl aminoethyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, phthalic acid-modified monoacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate, trimethylol ethane triacrylate, trimethylol ethane trimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetraacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, glycerol acrylate, glycerol methacrylate, cardoepoxy diacrylate, and those fumarates, itaconates and maleates wherein in these illustrated compounds, (meth)acrylate is replaced by fumarate, itaconate and maleate, respectively.

(c) Inorganic powders The inorganic powders contained in the photosensitive inorganic paste composition of the present invention are not particularly limited insofar as it satisfies transparency necessary for a light source for light exposure, and examples thereof may include glass, ceramics (cordierite etc.), metal etc. Specifically, glass powders such as borosilicate lead glass, borosilicate zinc glass, borosilicate bismuth glass based on PbO-SiO₂₎ PbO-B₂O₃-SiO₂, ZnO-SiO₂, ZnO-B₂O₃-SiO₂, BiO-SiO₂, BiO-B₂O₃-SiO₂ etc., oxides of Na, K, Mg, Ca, Ba, Ti, Zr, Al etc. such as cobalt oxide, iron oxide, chrome oxide, nickel oxide, copper oxide, manganese oxide, neodymium oxide, vanadium oxide, cerium oxide tipaque yellow, cadmium oxide, ruthenium oxide, silica, magnesia, spinel etc., fluorescent powders such as ZnO:Zn, Zn₃(PO₄)₂:Mn, Y₂SiO₅:Ce, CaWO₄:Pb, BaMgAlι₄O₂₃:Eu, ZnS:(Ag, Cd), Y₂O₃:Eu, Y₂SiO₅:Eu, Y₃AI₅O₁₂:Eu, YBO₃:Eu, (Y, Gd)BO₃:Eu, GdBO₃:Eu, ScBO₃:Eu, LuBO₃:Eu, Zn₂SiO₄:Mn, BaAlι₂Oι₉:Mn, SrAlι₃O₁₉:Mn, CaAI₁₂O₁₉:Mn, YBO₃:Tb, BaMgAlι₄O₂₃:Mn, LuBO₃:Tb, GdBO:Tb, ScBO₃Tb, Sr₆Si₃O₃CI₄:Eu, ZnS:(Cu, Al), ZnS:Ag, Y₂O₂S:Eu, ZnS:Zn, (Y, Cd)BO₃:Eu, BaMgAlι₂O₂₃:Eu, etc., and metallic powders such as iron, nickel, palladium, tungsten, copper, aluminum, silver, gold, platinum etc. In particular, glass, ceramics etc. are preferable because of excellent transparency. Especially, glass powders (glass frit) may be used to bring about the most significant effect. When the inorganic powders contain silicon oxide, aluminum oxide or titanium oxide, it turns opaque to reduce light transmittance, and thus the inorganic powders may desirably be free from such component. The particle diameter of the inorganic powders depends on the shape of a pattern to be formed, but the inorganic powders having an average particle diameter of 0.1 to 10 μm, more preferably 0.5 to 8 μm, are preferably used. An average particle diameter of greater than 10 μm is not preferable because of formation of an uneven surface upon forming a highly accurate pattern, while an average particle diameter of smaller than 0.1 μm is not preferable either because of formation fine pores upon baking to cause insulation deficiency and insufficient dispersibility. The inorganic powders may be in the forms of sphere, block, flake and dendrite, and one of these forms or a combination of two or more thereof may be used. The inorganic powders may contain inorganic pigments emitting e.g. red, blue and green lights in addition to black ones. A photosensitive insulating paste composition containing the pigments may be used to form a pattern of various colors, and is suitable for preparation of e.g. a color filter in a plasma display panel. Further, the inorganic powders may be a mixture of fine particles different in physical properties. In particular, glass powders and ceramic powders different in their thermal softening points may be used to inhibit shrinkage during baking. The inorganic powders may be compounded so as to change the shape and a combination of physical values etc. depending on the properties of a partition wall etc. As described above, the inorganic powders have an average particle diameter of 1 to 10 μm, i.e., 10 μm or less. Thus, in order to prevent secondary aggregation thereof and to improved dispersibility, its surface may be previously treated with a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, a surfactant etc. to such an extent that the properties of the inorganic powders are not deteriorated. In a method for this treatment, a treating agent may be dissolved in an organic solvent or water, and then the inorganic powders may be added thereto and stirred, and the solvent may be distilled away, followed by heat treatment at about 50 to 200°C for 2 hours or more. The treating agent may be added at the time of converting the photosensitive composition into a paste.

(d) Binder resin Usually, a binder resin may be added to the photosensitive inorganic paste composition in order to improve coating properties and film form ability. In the present invention, the binder resin may be a known binder resin, and is not particularly limited, and acrylic resin, cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, urethane resin and melamine resin may be used. Acrylic resin, particularly acrylic resin having a hydroxyl group, is preferably contained to form an image excellent in accuracy with improved development resistance. In the photosensitive inorganic paste composition of the present invention, acrylic resin having a hydroxyl group and a water-soluble cellulose derivative are preferably used in combination because the transmittance of active rays such as UV rays, an excimer laser, X-rays, electron rays etc. may be improved thereby for forming a pattern having an excellent accuracy. The acrylic resin having a hydroxyl group may include a copolymer obtained by polymerizing a hydroxyl-containing monomer as a main copolymerizable monomer and if necessary another monomer copolymerizable therewith. The hydroxyl-containing monomer may preferably be an alkylene-oxide adduct having alkylene oxide added to acrylic acid or methacrylic acid, specifically an adduct of ethylene oxide, propylene oxide or butylene oxide, or a mixture of these adducts, and examples thereof may include hydroxymethyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxy butyl acrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxy butyl acrylate, 4-hydroxybuty I methacrylate etc., as well as epoxylated ester compounds such as monoesters of acrylic acid or methacrylic acid and C1 to C10 glycol, glycerol acrylate, glycerol methacrylate, dipentaerythritol monoacrylate, dipentaerythritol monomethacrylate, ε-caprolactone-modified hydroxyethyl acrylate, ε-caprolactone-modified hydroxyethyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate etc. Preferable examples of the other monomer copolymerizable with the hydroxyl-containing monomer may include, for example, α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, citraconic acid, itaconic acid, maleic acid, fumaric acid etc. and anhydrides or half-esters thereof; α,β-unsaturated carboxylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, sec-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, 2,2,2-trifluoromethyl acrylate, 2,2,2-trifluoromethyl methacrylate etc.; styrene and styrene derivatives such as α-methyl styrene, p-vinyl toluene etc. Further, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, glycidyl acrylate, glycidyl methacrylate etc. may also be used. These may be used singly or as a mixture of two or more thereof. The water-soluble cellulose derivative used may be a known one and is not particularly limited, and examples thereof may include carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, ethylhydroxy ethyl cellulose, carboxymethyl ethyl cellulose, hydroxypropyl methyl cellulose etc. These may be used singly or as a mixture of two or more thereof.

(e) Compounding ratio of each component In the photosensitive inorganic paste composition of the present invention, the ratio of the Norish type I photopolymerization initiator and the hydrogen-withdrawing photopolymerization initiator may be as follows. The ratio of the Norish type I photopolymerization initiator may be in the range of 1 to 90 parts by weight, and the ratio of the hydrogen-withdrawing photopolymerization initiator may be 10 to 99 parts by weight. Preferably the ratio of the Norish type I photopolymerization initiator may be 10 to 50 parts by weight, and the ratio of the hydrogen-withdrawing photopolymerization initiator may be 50 to 90 parts by weight. More preferably the ratio of the Norish type I photopolymerization initiator may be 20 to 40 parts by weight, and the ratio of the hydrogen-withdrawing photopolymerization initiator may be 60 to 80 parts by weight, all based on 100 parts by weight of the two components in total. Particularly when the photosensitive inorganic paste composition of the present invention is used as a spacer material layer in a plasma display front plate, it is preferable that the ratio of the hydrogen-withdrawing photopolymerization initiator in the photopolymerization initiator in the photosensitive inorganic paste composition is determined to be relatively high. Specifically, the ratio of the Norish type I photopolymerization initiator may be 10 to 90 parts by weight and the ratio of the hydrogen-withdrawing photopolymerization may be 10 to 90 parts by weight. Preferably the ratio of the Norish type I photopolymerization initiator may be 20 to 50 parts by weight, and the ratio of the hydrogen-withdrawing polymerization initiator may be 50 to 80 parts by weight. More preferably the ratio of the Norish type I photopolymerization initiator may be 30 to 40 parts by weight and the ratio of the hydrogen-withdrawing photopolymerization initiator may be 60 to 70 parts by weight, all based on 100 parts by weight of the photopolymerization initiators in total in the photosensitive inorganic paste composition. In production of the plasma display front plate, the unbaked dielectric layer 12A consisting of a non-photosensitive inorganic paste layer is provided as a lower layer beneath the photosensitive inorganic paste film 16A and exposed to light. Accordingly, the influence of halation may be made significant not only by light reflected by the inorganic powders contained in the photosensitive inorganic paste film, but also by light reflected by the inorganic powders contained in the unbaked dielectric layer 12A as a lower layer, and thus there is a tendency to broaden the bottom width W_bt of the pattern after exposure to light. However, when the compounding ratio of the Norish type I photopolymerization initiator to the hydrogen-withdrawing photopolymerization initiator is set in the above range, a cross-section of the pattern after exposure to light may be made nearly rectangular or trapezoid wherein the bottom width W tm of the pattern is slightly shorter than the top width W_top, and the deformation and cracking of the dielectric layer caused by shrinkage of the pattern upon baking may thereby be prevented. In the photosensitive inorganic paste composition of the present invention, the ratio of the water-soluble cellulose derivative and the acrylic resin having a hydroxyl group may be as follows. Based on 100 parts by weight of the two components in total, the ratio of the water-soluble cellulose derivative may be in the range of 50 to 90 parts by weight, and the ratio of the acrylic resin having a hydroxyl group may be 50 to 10 parts by weight. Preferably the ratio of the water-soluble cellulose derivative may be 60 to 80 parts by weight, and the ratio of the acrylic resin having a hydroxyl group may be 40 to 20 parts by weight. More preferably the ratio of the water-soluble cellulose derivative may be 60 to 70 parts by weight, and the ratio of the acrylic resin having a hydroxyl group may be 40 to 30 parts by weight. The photopolymerization initiator may be used in the range of preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the water-soluble cellulose derivative and the photopolymerizable monomer in total. When the ratio of the photopolymerization initiator is lower than 0.1 part by weight, curing properties may be lowered. When the ratio of the photopolymerization initiator is higher than 10 parts by weight, insufficient curing in the bottom may occur due to absorption of the initiator. The ratio of the organic components such as the binder resin such as the water-soluble cellulose derivative and acrylic resin, the photopolymerization initiator etc. with respect to the inorganic components such as glass frit and other inorganic powders may be as follows. Based on 100 parts by weight of the photosensitive inorganic paste composition in total, the ratio of the organic components may be 10 to 40 parts by weight, and the ratio of the inorganic components may be 90 to 60 parts by weight. Preferably the ratio of the organic components may be 15 to 35 parts by weight, and the ratio of the inorganic components may be 85 to 65 parts by weight. More preferably the ratio of the organic components may be 20 to 30 parts by weight, and the ratio of the inorganic components may be 80 to 70 parts by weight. In formation of the spacer material layer, a solvent may be added if necessary in order to maintain the viscosity of the photosensitive inorganic paste composition of the present invention in a suitable range. The solvent contained in the photosensitive inorganic paste composition is not particularly limited insofar as it is sufficiently capable of dissolving organic components, capable of conferring suitable viscosity on the photosensitive inorganic paste composition, and capable of being easily evaporated and removed by drying. The solvent is particularly preferably a ketone, alcohol and ester having a boiling point of 100 to 200°C. Examples of such solvents may include ketones such as diethyl ketone, methyl butyl ketone, dipropyl ketone, cyclohexanone etc.; alcohols such as n-pentanol, 4-methyl-2-pentanol, cyclohexanol, diacetone alcohol etc.; ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether etc.; saturated alkyl aliphatic monocarboxylates such as n-butyl acetate, amyl acetate etc.; lactates such as ethyl lactate, n-butyl lactate etc.; and ether-based esters such as methyl Cellosolve acetate, ethyl Cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl-3-ethoxypropionate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 2-methyl~3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl~3-methoxy butyl acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate etc. and these may be used singly or as a mixture of two or more thereof. The content of the solvent may preferably be 300 parts by weight or less, more preferably 10 to 70 parts by weight, most preferably 25 to 35 parts by weight, based on 100 parts by weight of the inorganic component and organic component in total. In addition to those described above, additive components such as UV absorber, a sensitizer, a polymerization inhibitor, a plasticizer, a thickening agent, an organic solvent, a dispersant, a defoaming agent, and an organic or inorganic suspending agent may be added if necessary. The polymerization inhibitor may be added to improve heat stability during storage, and specific examples thereof may include hydroquinone, a hydroquinone monoester, N-nitrosodiphenyl amine, phenothiazine, p-t-butyl catechol, N-phenyl naphthyl amine, 2,6-di-t-butyl-p-methyl phenol, chloranil, pyrogallol etc. The plasticizer for improving plasticizing properties on a substrate may include phthalates, specifically dibutyl phthalate (DBP), dioctyl phthalate (DOP), polyethylene glycol, glycerin, tartaric diesters, specifically diethyl tartrate, dibutyl tartrate etc., and citrates, specifically triethyl citrate, tributyl citrate etc. Specific examples of the defoaming agent may include defoaming agents based on alkylene glycols such as polyethylene glycol (molecular weight 400 to 800), silicone and higher alcohols, by which bubbles in a paste or film may be reduced and pores after baking may be reduced. (B) Sheet-shaped unbaked body for production of a plasma display front plate The sheet-shaped unbaked body for production of a plasma display front plate according to the present invention is an unbaked body wherein at least a spacer material layer consisting of a coating film of the photosensitive inorganic paste composition of the present invention is formed on a removable support film. It is considered that the sheet-shaped unbaked body according to the present invention may be provided mainly in the form of one-layer constitution consisting of only the spacer material layer, two-layer constitution consisting of the spacer material layer and the unbaked dielectric layer or a burnable intermediate layer, or three-layer constitution consisting of the spacer material layer, the unbaked dielectric layer and the burnable intermediate layer. Both surfaces of these one- to three-layer constitutions may be protected by a removable support film which is easily peelable, by which the unbaked body may be easily stored, conveyed and handled. The sheet-shaped unbaked body of the present invention may be stored for a predetermined period within usable life after production, and may be immediately used upon producing a plasma display front plate, to thereby increase the efficiency of production of a plasma display front plate. Hereinafter, specific examples for providing the sheet-shaped unbaked body of the present invention will be described in detail. One is a sheet-shaped unbaked body having a coating film of the photosensitive inorganic paste composition of the present invention formed on a removable support film. By applying and drying the photosensitive inorganic paste composition of the invention diluted with a solvent to a concentration suitable for application onto a peelable support film, the spacer material layer is formed. The spacer material layer is then covered with a protective film as a protective layer. Another example is a sheet-shaped unbaked body having a spacer material layer and an unbaked dielectric body. A spacer material layer consisting of the photosensitive inorganic paste composition of the present invention is formed on a peelable support film. An unbaked dielectric layer consisting of a non-photosensitive inorganic paste composition is then formed on the spacer material layer and covered with a protective film as a protective layer. Still another example is a sheet-shaped unbaked body having a burnable intermediate layer formed on a spacer material layer. A spacer material layer consisting of a coating film of the photosensitive inorganic paste composition of the present invention is formed on a peelable support film. A water-soluble or water-swellable burnable intermediate layer is formed on the spacer material layer and covered with a protective film as a protective layer. Still another example is a sheet-shaped unbaked body having a burnable intermediate layer and an unbaked dielectric layer on a spacer material layer. In Fig. 8A, a spacer material layer 16A consisting of a coating film of the photosensitive inorganic paste composition of the present invention is formed on a peelable support film 180. On the spacer material layer 16A, a water-soluble or water-swellable burnable intermediate layer 14 is formed, and an unbaked dielectric layer 12A consisting of a non-photosensitive inorganic paste film is formed thereon. The unbaked dielectric layer 12A is covered with a protective film 182 as a protective layer. Among these examples, the sheet-shaped unbaked body wherein a coating film of the photosensitive inorganic paste composition of the present invention is formed on a removable support film and covered with a protective film may be used most preferably. Hereinafter, the respective layers constituting the sheet-shaped unbaked body of the present invention will be described, and then the method of producing a sheet-shaped unbaked body according to the present invention will be described in detail.

(a) Spacer material layer The spacer material layer 16A is a layer forming a spacer layer 16A by subjecting the same to a patterning with photolithography and then removing organic materials and simultaneously baking the inorganic powders in a baking step. In the present invention, the spacer material layer 16A is produced by using the photosensitive inorganic paste composition of the present invention. In the present invention, the Norish type I photopolymerization initiator and the hydrogen-withdrawing photopolymerization initiator are used in combination, whereby a cross-section of the resulting pattern after exposure to light may be made nearly rectangular or trapezoid wherein the bottom width W_bt of the pattern may be slightly shorter than the top width Wtop. The patterned spacer material layer 16A may be shrunk by a later baking treatment. However, by slightly narrowing the bottom width Wbtm of the pattern, deformation or cracking upon shrinkage of the pattern may be prevented. When glass frit contained in the patterned spacer material layer is melted in the baking treatment which will be described later, a side wall of the pattern may sag. When the pattern is in the form of a trapezoid wherein the bottom width W_btm of the pattern is slightly shorter than the top width W_t0p, it is preferable that the bottom width W_btm is increased to some extent by consciously causing sagging by baking treatment, in order to improve the stability of the pattern. On one hand, when a cross-section of the resulting pattern is in a nearly rectangular form, it is preferable that this rectangular shape is maintained even after baking treatment, and thus it is preferable to prevent the side wall of the pattern from sagging during baking treatment. To prevent the side wall of the pattern from sagging during baking treatment, the softening point of the glass frit contained in the spacer material layer is preferably set higher than the softening point of the glass frit contained in the unbaked dielectric layer. Particularly, sagging of the side wall of the pattern during baking treatment may be prevented to a negligible degree by adjusting the softening point of the glass frit contained in the spacer material layer to be set higher by at least 5°C, preferably at least 7°C, more preferably at least 10°C, than the softening point of the glass frit contained in the unbaked dielectric layer. The thickness of the spacer material layer obtained by drying a coating film of the photosensitive inorganic paste composition of the present invention may be 10 to 50 μm, preferably 15 to 40 μm.

(b) Unbaked dielectric layer The unbaked dielectric layer 12A consists of an inorganic paste film prepared by drying a coating film formed from a non-photosensitive inorganic paste composition. The unbaked dielectric layer 12A is a layer which will be the dielectric layer 12 in a baking step in which organic materials are removed and simultaneously the inorganic powders are baked. The inorganic paste composition for forming the unbaked dielectric layer 12A contains inorganic powders and a binder resin as essential components. As the inorganic powders contained in the non-photosensitive inorganic paste composition for forming the unbaked dielectric layer, the same inorganic powders as described in the item (A) Photosensitive inorganic paste composition may be used. The binder resin contained in the non-photosensitive inorganic paste composition may be a known binder resin and is not particularly limited, and acrylic resin, cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyester resin, urethane resin etc. may be used. Acrylic resin, particularly acrylic resin having a hydroxyl group, is preferably contained to exhibit excellent thermal adhesion to a glass substrate. As the acrylic resin having a hydroxyl group, the same acrylic resin as described in the item (A) Photosensitive inorganic paste composition may be used. The ratio of the inorganic components in total, that is, glass frit and inorganic particles, and the organic components such as binder resin etc. may be as follows. Based on 100 parts by weight of the inorganic components and organic components in total, the ratio of the organic components are 10 to 40 parts by weight, and the ratio of the inorganic powders is 90 to 60 parts by weight. Preferably the ratio of the organic components is 15 to 35 parts by weight, and the ratio of the inorganic powders is 85 to 65 parts by weight. More preferably the ratio of the organic components is 20 to 30 parts by weight, and the ratio of the inorganic powders is 80 to 70 parts by weight. An amount outside the above range is not preferable because when the ratio of the organic components is less than 10 parts by weight, a film may not be formed, while when the organic components are higher than 40 parts by weight, significant shrinkage may occur after baking. In formation of the unbaked dielectric layer, a solvent may be added if necessary in order to maintain the viscosity of the non-photosensitive inorganic paste composition in a suitable range. As the solvent contained in the non-photosensitive inorganic paste composition, the same solvent as described in the item (A) Photosensitive inorganic paste composition may be used. In order to maintain the viscosity of the non-photosensitive inorganic paste composition in a suitable range, the content of the solvent is preferably 300 parts by weight or less, based on 100 parts by weight of the inorganic components and organic components in total, or more preferably the solvent is in such an amount to achieve a viscosity of 3000 cps or more, most preferably 5000 cps or more. The non-photosensitive inorganic paste composition may contain various additives such as a plasticizer, a dispersant, a tackifier, a surface tension regulator, a stabilizer, and a deforming agent as optional components in addition to the inorganic powders, binder resin and solvent. The unbaked dielectric layer may be formed by forming a coating film of the non-photosensitive inorganic paste composition and then drying the coating film to remove the solvent. The thickness of the unbaked dielectric layer after drying may be 10 to 100 μm, preferably 25 to 70 μm. (c) Burnable intermediate layer The burnable intermediate layer 14 is a water-soluble or water-swellable layer which is dissolved or swollen by washing with water thereby raising and removing the spacer material layer remaining on a site that has already been subjected to the removal treatment by development. The burnable intermediate layer 14 is a layer which may be provided optionally on the spacer material layer 16A. This burnable intermediate layer is to be located between the unbaked dielectric layer and the spacer material layer upon producing a plasma display front plate, as will be described later in detail in the production method. When the spacer material layer in such laminated state is irradiated with patterning light and developed for patterning of the spacer material layer, residues of the spacer material may remain on the exposed surface of the burnable intermediate layer between pattern convexes. The residues of the spacer material remaining between the pattern convexes have been melted by baking treatment, by which the exposed surface of the dielectric layer which should be a uniform smooth surface has been deteriorated to form an uneven surface. Against this problem, the burnable intermediate layer is provided between the unbaked dielectric layer and the spacer material layer, whereby residues of the spacer material are formed on the surface of the burnable intermediate layer, and when the burnable intermediate layer is water-soluble, the residues of the spacer material together with the burnable intermediate layer in the exposed region are washed away with a developing solution (water or an aqueous solution). When the burnable intermediate layer is water-swellable, the intermediate layer is swollen with a developing solution to raise residues of the spacer material present on the surface thereof, and the residues may be easily washed away with the developing solution. Having finished its role, the burnable intermediate layer enabling removal of residues of the spacer material with a development solution is completely burned out by baking treatment of the unbaked dielectric layer and the unbaked spacer material layer. As a result, a dielectric layer and spacer layer having the same constitution and size as in the prior art are formed on the glass substrate as a front plate. The difference between the resulting present front plate and the front plate in the prior art is that the exposed surface of the dielectric layer between the spacer layer and its adjacent spacer layer is uneven in the prior art, while the exposed surface in the front plate produced by the present invention is smooth. This is a particularly significant effect obtainable by providing the water-soluble or water-swellable burnable intermediate layer between the unbaked dielectric layer and the spacer material layer. Insofar as the burnable intermediate layer 14 is water-soluble or water-swellable and decomposed and burned out by baking at 400 to 700°C, the intermediate layer is not particularly limited, but consists preferably of at least one kind of water-soluble resin and water-swellable resin. The burnable intermediate layer is formed preferably by using a burnable intermediate layer composition containing a solvent and at least one of water-soluble resin and water-swellable resin. As the water-soluble resin, polyvinyl alcohol, polyvinyl alcohol derivatives, water-soluble cellulose etc. may be preferably used. As the water-swellable resin, a partially cross-linked product of the water-soluble resin may be used. These may be used singly or as a mixture of two or more thereof. Specific examples of the polyvinyl alcohol derivatives may include, for example, silanol-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, mercapto group-containing polyvinyl alcohol, butyral resin etc. Specific examples of the water-soluble cellulose may include, for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, ethylhydroxy ethyl cellulose, carboxymethyl ethyl cellulose, hydroxypropyl methyl cellulose etc. Among these, polyvinyl alcohol and hydroxymethyl cellulose are preferable from the viewpoint of water solubility, thermal degradability, and solvent resistance (resistance to the solvent in the dielectric layer). The solvent used in forming the burnable intermediate layer is not particularly limited insofar as it is sufficiently capable of dissolving the water-soluble resin or water-swellable resin, capable of conferring viscosity suitable for coating, and capable of being evaporated and removed by drying, and water and an organic solvent such as propyl alcohol etc. may be used. The burnable intermediate layer may be formed by diluting the water-soluble resin or water-swellable resin with a solvent to a concentration suitable for coating, then forming a coating film of the composition, and removing the solvent by drying. The ratio of the water-soluble resin or water-swellable resin in the burnable intermediate layer composition for forming the burnable intermediate layer is preferably 50 wt% or less, more preferably 30 wt% or less, most preferably 0.1 to 20 wt%. The thickness of the burnable intermediate layer is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less. It is not preferable for the burnable intermediate layer to be too thick because the pattern of the photosensitive light-unexposed unbaked spacer material layer may also be washed away in a later development step. The optimum thickness of the burnable intermediate layer is 0.1 to 3 μm.

(d) Method of producing the sheet-shaped unbaked body As the support film 180 used in producing the sheet-shaped unbaked body of the present invention, a removable film capable of permitting each layer formed thereon to be easily released therefrom and transferring the unbaked layer onto a glass substrate may be used without particular limitation. Examples thereof may include a flexible film of 15 to 125 μm in thickness consisting of synthetic resin film such as polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyvinyl chloride etc. The support film is preferably subjected to release treatment so as to facilitate transfer. For forming the spacer material layer 16A, burnable intermediate layer

14 and unbaked dielectric layer 12A on the support film, compositions for forming the respective layers may be prepared and then applied onto the support film 180 by an applicator, bar coater, wire bar coater, slit coater, curtain flow coater etc. In particular, the roll coater is preferable because a thick film of excellent uniform thickness may be efficiently formed. After the coating film is dried, this dried coating film may be coated with another composition for a next layer thereby laminating each layer to prepare the sheet-shaped unbaked body of the present invention. A protective film 182 may preferably be stuck to the surface opposite to the support film 180 in order to stably protect the photosensitive paste composition layer etc. before use. This protective film is preferably a polyethylene terephthalate film, polypropylene film or polyethylene film of about 15 to 125 μm in thickness on which silicone was coated or baked.

(C) Method of producing a plasma display front plate The method of producing a plasma display front plate according to the present invention comprises laminating an unbaked dielectric layer and a spacer material layer in this order on the surface of a glass substrate on which electrodes were formed, then irradiating the spacer material layer with patterning light, developing it thereby patterning the spacer material layer, and subjecting the unbaked dielectric layer and the patterned spacer material layer on the glass substrate simultaneously to baking treatment thereby simultaneously forming the dielectric layer and the spacer layer on the glass substrate. In the present invention, a water-soluble or water-swellable burnable intermediate layer may be optionally provided between the unbaked dielectric layer and the spacer material layer. A material layer capable of being dissolved or swollen with an aqueous solution or developing liquid for giving a spacer layer and capable of being burned out by baking treatment is preferably laminated as an intermediate layer between the unbaked dielectric layer and the spacer material layer formed thereon. The following light exposure treatment and subsequent treatments may be carried out in a conventional way, whereby residues of the spacer material remaining in concaves between patterns may be removed before baking treatment, and the intermediate layer disappears by being burned out by baking treatment, and the structure of the laminate after baking is made the same as in the prior art.

(a) Formation of each layer on a glass substrate The method of laminating the unbaked dielectric layer and the spacer material layer on a glass substrate is not particularly limited, and each layer may be laminated by known means such as, for example, a coating method, a screen printing method etc. However, the method of forming the respective layers by using the above-described sheet-shaped unbaked body of the present invention is most preferable from the viewpoint of formability of a layer of uniform thickness excellent in surface smoothness. An example of the process of producing a plasma display front plate by using the sheet-shaped unbaked body of the present invention will be described in detail. First, the sheet-shaped unbaked body having a support film, a spacer material layer and a protective layer laminated in this order is prepared. Separately, an unbaked dielectric layer is formed on the surface of a glass substrate on which electrodes have been formed. The method of forming the unbaked dielectric layer is not particularly limited, but it is preferable that a non-photosensitive inorganic paste composition is applied onto a support film and dried to form an unbaked dielectric layer, and if necessary a burnable intermediate layer is formed by coating and drying, followed by lamination thereof on a glass substrate such that the unbaked dielectric layer is contacted with the surface of the glass substrate on which electrodes have been formed, and the unbaked dielectric layer is transferred onto the glass substrate by moving a heated roller to the support film. Then, the protective film is removed from the sheet-shaped unbaked body, and the revealed spacer material layer is attached to the unbaked dielectric layer. A heat roller is then moved over the support film, thereby the spacer material layer is hot-pressed on the surface of the unbaked dielectric layer. The hot-press may preferably be carried out at a roll pressure in the range of 1 to 5 kg/cm² and a speed of travel of 0.1 to 10.0 m/min. while the surface temperature of glass substrate 10 is heated at 80 to 140°C. The glass substrate may be preheated, and the preheat temperature is selected for example in the range of 40 to 120°C. Subsequently, another example of production of a plasma display front plate by using the below-mentioned sheet-shaped unbaked body will be illustrated. First, a sheet-shaped unbaked body having a support film, a spacer material layer, an unbaked dielectric layer and a protective film laminated in this order is prepared. After removal of the protective film from the sheet-shaped unbaked body, the unbaked dielectric layer is attached to the surface of the glass substrate on which electrodes have been provided, and a heat roller is then moved over the support film thereby the unbaked dielectric layer and the spacer material layer are hot-pressed to the glass substrate. Another example of production of a plasma display front plate by using the below-mentioned sheet-shaped unbaked body will then be illustrated. First, a sheet-shaped unbaked body having a support film, a spacer material layer, a burnable intermediate layer and a protective film laminated in this order is prepared. Separately, an unbaked dielectric layer is formed on the surface of a glass substrate on which electrodes have been formed. The protective layer is removed from the sheet-shaped unbaked body to reveal the burnable intermediate layer, and this revealed burnable intermediate layer is attached to the unbaked dielectric layer formed on the surface of the glass substrate on which electrode have been provided, and a heat roll is then moved over the support film, thereby the burnable intermediate layer and the spacer material layer are hot-pressed to the surface of the glass substrate. Another example of production of a plasma display front plate by using the below-mentioned sheet-shaped unbaked body will then be described in detail with reference to Fig. 8A and Fig. 8B. First, a sheet-shaped unbaked body having a support film 180, a spacer material layer 16A, a burnable intermediate layer 14, an unbaked dielectric layer 12Aand a protective film 182 laminated in this order is prepared (Fig. 8A). The protective layer 182 is removed from the sheet-shaped unbaked body to reveal the unbaked dielectric layer 12A, and the revealed unbaked dielectric layer 12A is attached to the surface of the glass substrate 10 on which electrodes have been provided, and a heat roll 40 is moved over the support film 180, thereby the unbaked dielectric layer 12A, the burnable intermediate layer 14 and the spacer material layer 16A are hot-pressed to the surface of the glass substrate (Fig. 8B).

(b) Light exposure/development treatment The light exposure treatment and subsequent treatments may be carried out in a conventional way. The light exposure/development treatment will be described in detail with reference to Figs. 4Ato 4C. According to the method described above, the unbaked dielectric layer 12A and spacer material layer 16A are formed on a glass substrate, and then a photomask 3 is positioned over the spacer material layer 16A which is then exposed to light thereby curing the spacer material layer in a pattern portion (Fig. 4A). In the present invention, the Norish type I photopolymerization initiator and the hydrogen-withdrawing photopolymerization initiator are simultaneously used, and thus the influence of inhibition by oxygen may be prevented.

Accordingly, even if the surface of the spacer material layer 16A is not covered with a transparent film, the curing of the surface may proceed. However, when dust etc. adhere by static electricity to the surface of the spacer material layer 16A, qualities may be deteriorated. Thus, if a transparent film is used as the support film 180 in the sheet-shaped unbaked body of the present invention, it is preferable that the light exposure is performed with the support film 180 left attached to the spacer layer 16A after laminating the layers on the glass substrate, and after light exposure, the support film 180 may then be removed. As the device for irradiation of radiations used in light exposure, it is possible to employ an ultraviolet irradiation device used generally in photolithography and a light exposure device used in production of semiconductors and liquid crystal displays. Then, the uncured part 16A of the photosensitive light-unexposed unbaked spacer material layer is removed by development so that the resist pattern 16A' appears (see Fig. 4B). In the development treatment, a general-purpose alkali developing solution or water may be used. The alkali components in the alkali developing solution may include hydroxides, carbonates, bicarbonates, phosphates, and pyrophosphates of alkali metals such as lithium, sodium, potassium, etc., primary amines such as benzyl amine, butyl amine etc., secondary amines such as dimethyl amine, dibenzyl amine, diethanol amine etc., tertiary amines such as trimethylamine, triethylamine, triethanolamine etc., cyclic amines such as morpholine, piperazine, pyridine etc., polyamines such as ethylenediamine, hexamethylenediamine etc., ammonium hydroxides such as tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, trimethyl benzyl ammonium hydroxide, trimethyl phenyl benzyl ammonium hydroxide etc., trimethyl sulfonium hydroxides, sulfonium hydroxides such as trimethyl sulfonium hydroxide, diethylmethyl sulfonium hydroxide, dimethyl benzyl sulfonium hydroxide etc., choline, silicate-containing buffers, among which water is preferable in consideration of damage to frit caused by alkali components. A cross-section of the resulting pattern obtained by using the Norish type I photopolymerization initiator in combination with the hydrogen-withdrawing photopolymerization initiator may be made nearly rectangular as shown in Fig. 7A or trapezoid wherein the bottom width Wbtm of the pattern is slightly narrower than the top width W_t0p as shown in Fig. 7B. Accordingly, the dielectric layer may be prevented from being deformed or cracked upon baking treatment. (c) Baking The laminate having the pattern formed thereon may be baked, whereby the glass frit contained in the unbaked dielectric layer 12A and in the photosensitive light-unexposed unbaked spacer material layer 16A' is baked thereby converting the layers into a dielectric layer 12 and a spacer layer 16 respectively. The plasma display front plate of the invention comprising the spacer layer 16 patterned on the dielectric layer 12 is thus obtained (see Fig. 4C). The temperature used in this baking may be a temperature at which the organic materials in the photosensitive inorganic paste composition disappear by burning and the inorganic powders are baked, and baking at 400 to 700°C for 10 to 90 minutes may be selected. When the softening point of the inorganic powders contained in the space material layer is made higher than the softening point of the inorganic powders contained in the unbaked dielectric layer in order to prevent a side wall of the pattern from sagging during baking treatment, the baking temperature may be made preferably not higher than the softening point Ti (°C) of the inorganic powders contained in the spacer material layer and not lower than the softening point T₂ (°C) of the inorganic powders contained in the unbaked dielectric layer (T₂<Tι). Particularly, baking at a baking temperature slightly lower than the softening point Ti of the inorganic powders contained in the spacer material layer is preferable. The baking temperature may preferably be T₂°C or more and Tι°C or less, more preferably (Ti - 5)°C or more and Tι°C or less, still more preferably (Ti - 7)°C or more and Tι°C or less, particularly preferably around (Ti -10)°C. After producing the plasma display front plate having a patterned spacer layer formed on the dielectric layer formed on the glass substrate having electrodes formed thereon in this manner, the uncovered dielectric layer and the spacer layer may preferably be covered with a protective layer 19 such as MgO etc.

EXAMPLES The present invention will be described in more detail with reference to the Examples below. However, the present invention is not limited thereto.

Experimental Example 1 >

(Preparation of a photosensitive inorganic paste composition) As a water-soluble cellulose derivative, 22 parts by weight of hydroxypropyl cellulose, 14 parts by weight of styrene/hydroxyethyl methacrylate=55/45 (wt%) copolymer (Mw=40000) as acrylic resin having a hydroxy group, 60 parts by weight of 2-methacryloyloxyethyl-2-hydroxypropyl phthalate (trade name: HO-MPP, manufactured by Kyoeisha Chemical Co., Ltd.) as a photopolymerizable monomer, 0.9 part by weight of 2,2-dimethoxy-2-phenyl acetophenone (trade name: IR-651 , Norish type I, manufactured by Chiba-Geigy) and 1.8 parts by weight of 2,4-diethyl thioxanthone (trade name: DETX-S, hydrogen-withdrawing type, manufactured by Nippon Kayaku Co., Ltd.) as photopolymerization initiators, 3.9 parts by weight of butyl tartrate as a plasticizer, 0.1 part by weight of an azo dyestuff (trade name: Dye SS, manufactured by Daito Chemix Corporation) as an UV absorber and 100 parts by weight of 3-methoxy-3-methyl butanol as solvent were mixed by a mixer for 3 hours to prepare an organic component solution. Then, 40 parts by weight of this organic component solution (solids content 50%) were kneaded with 80 parts by weight of glass frit having a softening point of 581 °C as an inorganic component, to prepare a photosensitive inorganic paste composition.

Experimental Example 2>

(Preparation of a non-photosensitive inorganic paste composition) 45 parts by weight of isobutyl methacrylate/hydroxyethyl methacrylate = 60/40 (wt%) copolymer (Mw=70000) as acrylic resin having a hydroxyl group, 5 parts by weight of dibutyl phthalate as a plasticizer and 50 parts by weight of 3-methoxy-3-m ethyl butanol as solvent were stirred in a stirring machine equipped with a water bath at 80°C for 2 hours to prepare an organic component solution. Then, 40 parts by weight of this organic component solution (solids content 50%) was kneaded with 80 parts by weight of glass frit having a softening point of 574°C, to prepare a non-photosensitive inorganic paste composition.

Experimental Example 3> (Preparation of a composition for- forming a burnable intermediate layer) 4 parts by weight of polyvinyl alcohol (trade name: PVA-235, manufactured by Kuraray Co., Ltd.), and 53 parts by weight of water and 43 parts by weight of isopropyl alcohol as solvents were mixed by a mixer for 12 hours to prepare a permeation-preventing layer composition. Example 1 > The non-photosensitive inorganic paste composition of Experimental Example 2 was applied onto a support film made of polyethylene terephthalate such that the thickness of the resulting coating film after drying was 60 μm, to form a coating film thereon. This coating film was then laminated on a glass preheated at 80°C at a lamination temperature of 100°C, a lamination pressure of 2.5 kg/cm² and a lamination speed of 1.0 m/min., to form an unbaked dielectric layer. The photosensitive inorganic paste composition prepared in the above was then applied onto the unbaked dielectric layer such that the thickness of the film after drying was 40 μm, followed by exposure thereof via a test square pattern mask to ultraviolet rays at an irradiation of 400 mJ/cm² from an ultra high pressure mercury lamp. Then, spray development with water at a liquid temperature of 30°C at a jetting pressure of 3.0 kg/cm² for 30 seconds was performed to form a pattern. The resulting pattern was evaluated for adhesiveness, and it was found out that the width of the remaining minimum line was 60 μm, and the minimum formed space was 60 μm. A cross-section of the resulting pattern was trapezoid wherein the bottom width W_btm was narrower than the top width Wt_op> and Wtop.'Wbtm was 1 :0.9. To evaluate the shape stability of the pattern after baking, a pattern of a mask line width of 200 μm was formed in accordance with the method described above, and baking treatment wherein the sample was heated at an increasing temperature of 10°C/min. and then kept at 580°C for 30 minutes was conducted. As a result, a good baked pattern was maintained. A cross-section of the pattern after baking was rectangular wherein Wt_op:W tm was almost 1 :1.

Example 2> The non-photosensitive inorganic paste composition of Experimental Example 2 was applied by a lip coater onto a support film consisting of removable polyethylene terephthalate (trade name: PurexA24, manufactured by Teijin DuPont Films Japan Limited), and the resulting coating film was dried at 100°C for 6 minutes to remove the solvent completely, whereby an unbaked dielectric layer of 60 μm in thickeness was formed on the support film. The burnable intermediate layer-forming composition of Experimental

Example 3 was then applied by a lip coater onto the unbaked dielectric layer formed on the support film, and the coating film was dried at 100°C for 6 minutes to remove the solvent completely, thereby forming a burnable intermediate layer of 0.5 μm in thickness on the unbaked dielectric layer. The photosensitive inorganic paste composition of Experimental

Example 1 was applied by a lip coater onto the burnable intermediate layer formed on the support film, and the coating film was dried at 100°C for 6 minutes to remove the solvent completely, thereby forming a photosensitive light-unexposed unbaked spacer material layer of 40 μm in thickness. Then, a protective film consisting of removable polyethylene terephthalate (trade name; Purex A53, manufactured by Teijin DuPont Film) was stacked on the photosensitive light-unexposed unbaked spacer material layer, to produce a water-developable photosensitive film of a 5-layer structure. The removable polyethylene terephthalate (trade name: Purex A24, manufactured by Teijin DuPont Film) that was a support film of the water-developable photosensitive film prepared above was peeled off, while the photosensitive film was laminated by hot roll laminatior at 150°C on a glass substrate having bus electrodes formed thereon that had previously been heated at 80°C. The air pressure was 3 kg/cm² and the lamination speed was 1.0 m/min. The photosensitive film layer was exposed via a test square pattern mask to ultraviolet rays at an irradiation amount of 300 mJ/cm² from an ultra high pressure mercury lamp. After the protective film of polyethylene terephthalate was removed, spray development with water at a liquid temperature of 30°C at a jetting pressure of 3 kg/cm² for 30 seconds was performed, to form a pattern. The resulting pattern was evaluated for adhesiveness and pattern shape, and it was found out that the width of the remaining minimum line was 60 μm, and the minimum formed space was 60 μm, which is a good pattern shape. A cross-section of the resulting pattern was trapezoid wherein the bottom width Wbtm was narrower than the top width Wtop, and Wto_P:Wbtm was 1 :0.9. To evaluate the shape stability of the pattern after baking, a pattern of a mask line width of 200 μm was formed in accordance with the method described above, and baking treatment wherein the sample was heated at an increasing temperature of 10°C/min. and then kept at 580°C for 30 minutes was conducted. As a result, a good baked pattern was maintained. A cross-section of the pattern after baking was rectangular wherein Wt_o :W tm was almost 1:1.

Example 3> The burnable intermediate layer-forming composition of Experimental Example 3 was applied onto a support film made of polyethylene terephthalate to form a coating film such that the thickness of the coating film after drying was 0.5 μm, and then this coating film was dried at 100°C for 6 minutes to remove the solvent, thereby forming a burnable intermediate layer. Then, the non-photosensitive inorganic paste composition of Experimental Example 2 was applied thereon and dried to form a coating film such that the thickness of the coating film after drying was 60 μm. The surface of the coating film was attached to a glass preheated, and lamination was performed at 80°C at a lamination temperature of 100°C, a lamination pressure of 2.5 kg/cm² and a lamination speed of 1.0 m/min., to form an unbaked dielectric layer having the burnable intermediate layer formed thereon. Subsequently, the support film was removed. The photosensitive inorganic paste composition prepared in the above was then applied onto the unbaked dielectric layer such that the thickness of the resulting coating film after drying was 40 μm, followed by exposure thereof via a test square pattern mask to ultraviolet rays at an irradiation amount of 400 mJ/cm² from an ultra high pressure mercury lamp. Spray development with water at a liquid temperature of 30°C at a jetting pressure of 3.0 kg/cm² for 30 seconds was then performed, to form a pattern. The resulting pattern was evaluated for adhesiveness, and it was found out that the width of the remaining minimum line was 60 μm, and the minimum formed space was 60 μm . A cross-section of the resulting pattern was trapezoid wherein the bottom width W tm was narrower than the top width Wt_o , and Wt_op:Wbt_m was 1 :0.9. To evaluate the shape stability of the pattern after baking, a pattern of a mask line width of 200 μm was formed in accordance with the method described above, and baking treatment wherein the sample was heated at an increasing temperature of 10°C/min. and kept at 580°C for 30 minutes was conducted. As a result, a good baked pattern was maintained. A cross-section of the pattern after baking was rectangular wherein W_top:W t_m was almost 1:1.

^•Comparative Example 1> A photosensitive inorganic paste composition and an insulating sheet composition were prepared in the same manner as in Example 1 except that 0.9 part by weight of a Norish type I photpolymerization initiator 2,2-dimethoxy-2-phenyl acetophenone (trade name: IR-651 , manufactured by Ciba-Geigy) was used alone as the photopolymerization initiator in the photosensitive inorganic paste composition, and the adhesiveness was evaluated in the same manner as the above. As a result, the width of the remaining minimum line was 60 μm, although the minimum formed space was 100 μm. A cross-section of the resulting pattern was trapezoid wherein the bottom width Wbt was broader than the top width W_t0p, and Wt_op:Wbtm was 0.6:1. Comparative Example 2> A photosensitive inorganic paste composition and an insulating sheet composition were prepared in the same manner as in the above Example except that 1.8 parts by weight of hydrogen-withdrawing 2,4-dimethyl thioxanthone (trade name: DETX-S, manufactured by Nippon Kayaku Co., Ltd.) was used alone as the photopolymerization initiator in the photosensitive inorganic paste composition, and spray development for 30 seconds was conducted in the same manner as the above. As a result, the pattern was washed away and unable to be cured.

INDUSTRIAL APPLICABILITY As described above, the photosensitive inorganic paste composition of the present invention may give a good pattern shape by combining the Norish type I photopolymerization initiator with the hydrogen-withdrawing photopolymerization initiator, and may thus be used preferably as a material forming multi-layer circuits and various displays such as plasma display, plasma address liquid crystal display etc., particularly preferably in production of a spacer material layer in a plasma display front plate requiring high accuracy.

Claims

1. A photosensitive inorganic paste composition comprising a photopolymerization initiator, a photopolymerizable monomer and inorganic powders, wherein said photopolymerization initiator contains both a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator.

2. The photosensitive inorganic paste composition according to claim 1 , wherein said Norish type I photopolymerization initiator is a compound selected from the group consisting of a benzoin ether compound, a benzyl ketal compound, an α-hydroxy acetophenone compound, an α-aminoacetophenone compound, a bisacyl phosphine oxide compound, an acyl phosphine oxide compound, a phenyl dicarbonyl compound, a phenyl acyl oxime compound, and mixtures thereof.

3. The photosensitive inorganic paste composition according to claim 1 or

2, wherein said hydrogen-withdrawing polymerization initiator is a compound selected from the group consisting of an aromatic ketone compound, a thioxanthone compound, an anthraquinone compound, an aromatic compound having a dialkylamino group, alkyl alkanol amine, and mixtures thereof.

4. The photosensitive inorganic paste composition according to claim 1 , wherein said Norish type I photopolymerization initiator is a benzyl ketal compound, and said hydrogen-withdrawing photopolymerization initiator is a thioxanthone compound.

5. The photosensitive inorganic paste composition according to any one of claims 1 to 4, wherein content of said Norish type I photopolymerization initiator is 10 to 99 parts by weight, and content of said hydrogen-withdrawing photopolymerization initiator is 90 to 1 part by weight, relative to 100 parts by weight of the total amount of said Norish type I photopolymerization initiator and said hydrogen-withdrawing photopolymerization initiator in the photosensitive inorganic paste composition.

6. A sheet-shaped unbaked body for production of a plasma display front plate comprising a glass substrate having a plurality of electrodes formed on a surface thereof, a dielectric layer formed on said substrate, and a plurality of spacer layers of uniform thickness formed on said dielectric layer, said unbaked body comprising: a removable support film, and a photosensitive light-unexposed unbaked spacer material layer provided thereon, said spacer material layer containing a photopolymerization initiator containing both a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator, a photopolymerizable monomer, and inorganic powders.

7. The sheet-shaped unbaked body for production of a plasma display front plate according to claim 6, further comprising an unbaked dielectric layer provided on said spacer material layer, said unbaked dielectric layer containing inorganic powders and a binder resin.

8. The sheet-shaped unbaked body for production of a plasma display front plate according to claim 7, wherein the softening point of said inorganic powders contained in said spacer material layer is higher than the softening point of the inorganic powders contained in said unbaked dielectric layer.

9. The sheet-shaped unbaked body for production of a plasma display front plate according to claim 8, wherein the softening point of the inorganic powders contained in said spacer material layer is higher by at least 5°C than the softening point of said inorganic powders contained in said unbaked dielectric layer.

10. The sheet-shaped unbaked body for production of a plasma display front plate according to claim 6, comprising a water-soluble or water-swellable burnable intermediate layer on said spacer material layer.

11. A method of producing a plasma display front plate comprising a glass substrate having a plurality of electrodes formed on a surface thereof, a dielectric layer formed on said substrate, and a plurality of spacer layers of uniform thickness formed on said dielectric layer, said method comprising: (a) forming an unbaked dielectric layer and a photosensitive light-unexposed unbaked spacer material layer in this order on said surface of said glass substrate having said electrodes, wherein said unbaked dielectric layer contains inorganic powders and a binder resin, and wherein said photosensitive light-unexposed unbaked spacer material layer contains a photopolymerization initiator containing both a Norish type I photopolymerization initiator and a hydrogen-withdrawing photopolymerization initiator, a photopolymerizable monomer, and inorganic powders, (b) irradiating said spacer material layer with patterning light and developing it, thereby patterning said spacer material layer, and (c) baking said unbaked dielectric layer and said patterned spacer material layer on said glass substrate simultaneously, thereby forming said dielectric layer and said spacer layer simultaneously on said glass substrate.

12. The method of producing a plasma display front plate according to claim 11 , wherein the softening point of said inorganic powders contained in said spacer material layer is higher by at least 5°C than the softening point of said inorganic powders contained in said unbaked dielectric layer.

13. The method of producing a plasma display front plate according to claim 12, wherein in the step (c), the baking temperature is a temperature which is not lower than the softening point of said inorganic powders contained in said unbaked dielectric layer and not higher than the softening point of said inorganic powders contained in said spacer material layer.

14. The method of producing a plasma display front plate according to claim 11 , wherein in the step (a), said unbaked dielectric layer is formed on said glass substrate, and then the sheet-shaped unbaked body for production of a plasma display front plate according to claim 6 or 10 is laminated thereon such that said spacer material layer is positioned on said unbaked dielectric layer.

15. The method of producing a plasma display front plate according to claim 11 , wherein in the step (a), the sheet-shaped unbaked body for production of a plasma display front plate according to any one of claims 7 to 9 is laminated such that said unbaked dielectric layer is positioned on said glass substrate.