JP2003131365A - Photocurable composition and plasma display panel having electrode formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable composition having excellent long-term storage stability and satisfying the requirements for sufficient conductivity and black color after calcining without losing excellent adhesion property with the substrate, resolution and calcination property in each step of drying, exposure, development and calcination and to provide a plasma display panel (PDP) having a black layer (lower layer) electrode circuit in the electrode having a black and white double-layer structure by using the above composition. SOLUTION: A first basic embodiment of the photocurable composition contains (A) black inorganic fine particles of ruthenium oxide, ruthenium compound, copper - chromium black double oxide, copper - iron black double oxide or cobalt oxide coated with an inorganic binder, (B) an organic binder, (C) a photopolymerizable monomer and (D) a photopolymerizable initiator. The photocurable composition is applied on the transparent electrode of a front glass substrate, exposed according to a specified pattern, developed and calcined to form the black layer (lower layer) electrode circuit of the electrode having a black and white double-layer structure of the PDP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkali-developable and photocurable composition useful for forming a fine electrode circuit on a front substrate of a plasma display panel (hereinafter abbreviated as PDP) and a composition thereof. PD in which an electrode, particularly a black layer (lower layer) in a black and white double-layer bus electrode, is formed
It is related to P.

[0002]

2. Description of the Related Art A PDP is a flat panel display for displaying images and information by utilizing light emission by plasma discharge.
They are classified into DC type and AC type depending on the panel structure and driving method. The principle of color display by PDP is rib (partition)
A gas such as He or Xe enclosed in each cell space is caused to generate plasma discharge in the cell space (discharge space) between the opposing electrodes formed on the front glass substrate and the back glass substrate separated by The fluorescent substance formed on the inner surface of the rear glass substrate is excited by the ultraviolet rays generated by the discharge of 1 to generate visible light of the three primary colors. Each cell space is D
In the C-type PDP, the cells are partitioned by grid-like ribs, while in the AC-type PDP, the cells are partitioned by ribs arranged in parallel to the substrate surface. In each case, the cell space is partitioned by the ribs. . Hereinafter, a brief description will be given with reference to the accompanying drawings.

FIG. 1 partially shows a structural example of a surface discharge PDP having a three-electrode structure for full color display. On the lower surface of the front glass substrate 1, there are a large number of a pair of display electrodes 2a, 2b, which are composed of a transparent electrode 3a or 3b for discharging and a bus electrode 4a or 4b for reducing the line resistance of the transparent electrode, at a predetermined pitch. It is lined up. These display electrodes 2
A transparent dielectric layer 5 (low melting point glass) for accumulating charges is formed on a and 2b by printing and firing, and a protective layer (MgO) 6 is vapor-deposited thereon. Protective layer 6
Has a role of protecting the display electrode and maintaining a discharge state. On the other hand, on the rear glass substrate 11, a large number of stripe-shaped ribs (partition walls) 12 for partitioning the discharge space and address electrodes (data electrodes) 13 arranged in each discharge space are arranged at a predetermined pitch. There is. In addition, on the inner surface of each discharge space, 3 of red (14a), blue (14b) and green (14c) are provided.
Colored phosphor films are regularly arranged. In full-color display, one pixel is composed of the phosphor films 14a, 14b, and 14c of the three primary colors of red, blue, and green as described above.
Further, a pair of display electrodes 2a and 2b forming a discharge space.
Stripe-shaped black matrixes 10 are similarly formed on both sides of the same in order to further enhance the contrast of the image. In the PDP having the above structure, an AC pulse voltage is applied between the pair of display electrodes 2a and 2b,
"Surface discharge method" because it discharges between electrodes on the same substrate
It is called. Further, in the PDP having the above structure, the ultraviolet rays generated by the discharge are generated by the phosphor film 14a of the rear substrate 11,
The visible light generated by exciting 14 b and 14 c is generated by the front substrate 1.
The transparent electrodes 3a and 3b are seen through.

In the PDP having such a structure, the formation of the bus electrodes 4a and 4b is conventionally performed by using Cr--Cu--Cr.
A method of patterning by photolithography method after forming the three layers by vapor deposition or sputtering. However, since the number of steps is large and the cost is high, recently, a method in which a conductive paste such as a silver paste is screen-printed and then baked or a photosensitive conductive paste is applied in order to obtain a line width of 150 μm or less. Then, after exposing through a pattern mask, developing, and then baking.

In the front substrate of the PDP in which the bus electrodes 4a and 4b are formed in this way, in recent years, in order to improve the contrast of the screen, a lower layer (transparent electrode) on the display side is formed when the bus electrodes are formed. It is practiced to print a black layer of black paste on the side of 3a, 3b in contact with) and a white layer of conductive silver paste on the black layer to form an electrode having a black and white two-layer structure. . In this case, as the black paste, a resin composition containing a heat-resistant black pigment such as a copper-iron type or a copper-chromium type is used.

However, when the black layer (lower layer) in the above-mentioned two-layer structure bus electrode is formed using a resin composition containing a heat-resistant black pigment such as a copper-iron system or a copper-chromium system,
When fired, it turns reddish and it is not possible to obtain sufficient blackness for improving the contrast of the screen. Further, the resin composition containing a heat-resistant black pigment such as copper-iron-based, copper-chromium-based, when the photocurable composition is compounded with a photopolymerizable monomer and a photopolymerization initiator, Polymerization of the reactive monomer starts and gels. Therefore, there is a problem that storage stability as a paste is poor and it is necessary to store at a low temperature, and coating workability is poor due to gelation and deterioration of fluidity, and mass productivity cannot be supported. Furthermore, if the blending amount of the heat resistant black pigment is increased in order to increase the blackness, there is a problem in that light transmission is impeded and sufficient photocurability cannot be obtained. Moreover, there arises a problem that the adhesion to the base material after firing is deteriorated. Furthermore, even if the heat-resistant black pigment is blended while balancing the adhesion and the blackness after firing, the problem remains that the long-term storage stability of the paste cannot be obtained.

[0007]

Therefore, the present invention has been made in order to solve the problems of the prior art, and its main purpose is to preserve the photocurable composition in a paste state for a long period of time. In addition to being excellent in stability, satisfactory adhesion and blackness are simultaneously satisfied after baking without impairing excellent adhesion, resolution and baking properties to the substrate in each process of drying, exposure, development and baking. To provide a photocurable composition. Another object of the present invention is to obtain a high-definition electrode circuit from such a photocurable composition,
Particularly, it is to provide a PDP in which a black layer (lower layer) electrode circuit capable of simultaneously satisfying sufficient adhesion and blackness is formed in a black and white two-layer structure bus electrode formed on a front substrate.

[0008]

In order to achieve the above object, the first basic aspect of the photocurable composition of the present invention is
(A) Black inorganic fine particles coated with an inorganic binder,
It is characterized by containing (B) an organic binder, (C) a photopolymerizable monomer, and (D) a photopolymerization initiator,
The second aspect is characterized by containing (E) conductive powder and / or (F) silica powder in addition to the above components. Here, the black inorganic fine particles (A) coated with the inorganic binder are preferably those obtained by pulverizing a melt of the black inorganic fine particles and the inorganic binder, and the black inorganic fine particles (A) coated with the inorganic binder. The blending ratio of the black inorganic fine particles / inorganic binder in is preferably 30 to 400 parts by mass of the inorganic binder with respect to 100 parts by mass of the black inorganic fine particles. The black inorganic fine particles are preferably at least one of ruthenium oxide, ruthenium compound, copper-chromium black composite oxide, copper-iron black composite oxide, and cobalt oxide. The average particle size of the black inorganic fine particles is preferably smaller than 0.1 μm. Such a photocurable composition of the present invention may be in a paste form or a dry film formed in advance into a film form. Further, according to the present invention, there is provided a PDP in which an electrode circuit of a front substrate is formed from a fired product of such a photocurable composition.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of intensive research aimed at realizing the above-mentioned object, the inventor of the present invention coated black inorganic fine particles having a large specific surface area and high catalytic activity with an inorganic binder such as glass to obtain black inorganic fine particles. It has been found that the activity of the paste is suppressed, gelation of the paste and deterioration of fluidity are prevented, and long-term storage stability of the paste can be achieved without deteriorating coating workability. Further, it was found that an inorganic binder such as glass is melted in a state of covering the black inorganic fine particles during firing, so that a black film capable of simultaneously satisfying sufficient adhesion and blackness can be formed. Furthermore, when the average particle size of the black inorganic fine particles (A) is smaller than 0.1 μm, the formed coating film becomes dense, and even a thin film can exhibit sufficient blackness and adhesiveness. It has been found that when conductive particles are used, they are dense and therefore have excellent conductivity even when they are made thin. With such a configuration, sufficient blackness and adhesion can be satisfied at the same time after firing without impairing the excellent adhesion, resolution, and firing properties to the substrate in each process of drying, exposure, development, and firing. It was found that a fired film capable of being obtained was obtained, and the present invention was completed.

Therefore, the photocurable composition of the present invention is excellent in storage stability as described above and sufficient contrast can be obtained with a thin film thickness, which is extremely useful for mass production and cost reduction of PDPs. It is useful. Moreover, when the photocurable composition of the present invention is used as the material of the black layer (lower layer) in the black and white two-layer structure bus electrode formed on the PDP front substrate, the black black layer of the bus electrode is transparent such as ITO or Nesa. Since it has a sandwich structure sandwiched between the electrode and the white layer, it is possible to ensure interlayer conduction between the transparent electrode and the white layer by densifying and thinning the black layer even when using black inorganic particles having low conductivity. , The blackness when viewed from the screen side can be fully satisfied at the same time.

The above-mentioned photocurable composition of the present invention is most characterized in that it contains black inorganic fine particles (A) coated with an inorganic binder. Thereby, since the black inorganic fine particles are coated on the glass film, the activity is suppressed and the storage stability of the paste is excellent. The black inorganic fine particles (A) coated with this inorganic binder are obtained by pulverizing a melt of the black inorganic fine particles and the inorganic binder, and specifically, a mixture of the black inorganic fine particles and an inorganic binder such as glass powder at 400 ° C. It is preferable that the material is melted at 1200 ° C., the melt is cooled and then crushed. When such a coating treatment is performed, the blackness of the obtained pulverized powder may be lowered depending on the combination of the inorganic binder and the black inorganic fine particles, which may have an advantageous effect on the optical characteristics. Moreover, it has been found that the lowered blackness is recovered after sintering in addition to the black and white bilayer structure electrode, and a sufficiently satisfactory black film can be formed. This effect is particularly remarkable in the combination of low melting point glass and cobalt trioxide, and the melt turned blue. The reason for using the pulverized powder of the melt of the black inorganic fine particles and the inorganic binder is that the black inorganic fine particles are coated with the inorganic binder, the activity of the black inorganic fine particles is suppressed, and the storage stability of the paste is improved. Because. On the other hand, in the conventional method using the black inorganic fine particles as they are, as will be apparent from the examples described later, the catalytic activity of the black inorganic fine particles is high, which adversely affects the storage stability of the paste, resulting in long-term storage stability. I can't get it. In particular, the average particle size is 0.1
When black inorganic fine particles smaller than μm are used, the activity of the black inorganic fine particles is higher and the effect is remarkable.
The blending amount of the pulverized powder is preferably 0.1 to 300 parts by mass per 100 parts by mass of the organic binder (B).
The reason for this is that if the blending amount of the pulverized powder is less than 0.1 parts by mass, sufficient conductivity and blackness cannot be obtained after firing. This is because it is not preferable because the cost is high in addition to the deterioration. From the viewpoint of resolution, it is preferable that the pulverized powder has an average particle size of 20 μm or less, preferably 5 μm or less.

In the black inorganic fine particles (A) coated with this inorganic binder, the mixing ratio of black inorganic fine particles / inorganic binder is preferably 30 to 400 parts by mass of inorganic binder with respect to 100 parts by mass of black inorganic fine particles.
The reason for this is that if the amount of the inorganic binder blended is less than 30 parts by mass, the black inorganic fine particles are not sufficiently covered with the inorganic binder and the storage stability of the paste cannot be obtained. On the other hand, if the blending amount exceeds 400 parts by mass. This is because sufficient electrical conductivity and blackness cannot be obtained when the paste is fired.

In the present invention, a pulverized powder of a melt obtained by mixing black inorganic fine particles having an average particle size of less than 0.1 μm, more preferably 0.01 to 0.1 μm with an inorganic binder and melting the mixture is used. It is preferable. The average particle size is 0.
The reason for using the black inorganic fine particles smaller than 1 μm is that the black inorganic fine particles coated with the inorganic binder are exposed to the black inorganic fine particles because the inorganic coating is melted during firing and the black inorganic fine particles are greatly affected by the original particle size of the black inorganic fine particles. Is. That is, if the average particle size of the black inorganic fine particles is smaller than 0.1 μm, a dense baked film can be formed without impairing the adhesiveness even if added in a small amount, and sufficient interlayer conductivity and blackness can be satisfied at the same time. This is because the composition for the obtained black layer (lower layer) electrode can be provided. On the other hand, the average particle size is 0.
When the black inorganic fine particles having a size of 1 μm or more are used, the denseness of the fired film deteriorates, and as is clear from the examples described later, the adhesion of the black layer (lower layer) electrode film formed is deteriorated and the blackness is deteriorated. Moreover, the resistance value is likely to increase. Moreover, if the blending amount of the black inorganic fine particles is increased in order to increase the degree of blackness, the transmission of light is hindered and sufficient photocurability cannot be obtained. Therefore, the average particle size is 0.1μ
It is preferable to use black inorganic fine particles smaller than m.

As such black inorganic fine particles, ruthenium oxides, ruthenium compounds, copper-chromium black composite oxides, copper-iron black composite oxides, cobalt oxides and the like are preferably used. In particular, cobalt-based oxides are most suitable because they are extremely excellent in paste stability and cost.

Specifically, RuO ₂ is preferable as the ruthenium oxide. As a ruthenium compound,
Ru ⁴⁺ , Ir ^4+, or a mixture thereof (M ² ), which is a multi-component compound, is a ruthenium polyoxide which is one of the pyrochlore oxides represented by the following general formula: (M _X Bi _2-X ) In the formula (M ¹ _y M ² _2-y ) O _7-Z , M is selected from the group consisting of yttrium, thallium, indium, cadmium, lead, copper and rare earth metals,
M ¹ is selected from the group consisting of platinum, titanium, chromium, rhodium and antimony, M ² is ruthenium, iridium or a mixture thereof, x is 0 to 2, but for monovalent copper x is ≦ 1 and y is 0 to 0.5,
M ¹ is rhodium, or platinum, titanium, chromium,
When a plurality of rhodium and antimony are selected, y is 0 to 1 and z is 0 to 1, but when M is divalent lead or cadmium, this is at least about x / 2. Are equal. These ruthenium-based pyrochlore oxides are described in detail in US Pat. No. 3,583,931. The above ruthenium oxides and ruthenium compounds may be used alone or in combination of two or more.

The copper-chromium black composite oxide includes CuO-Cr ₂ O ₃ and CuO-Cr ₂ O ₃ -Mn ₂ O ₃ , and the copper-iron black composite oxide includes Cu.
O-Fe ₂ O ₃ and _{CuO-Fe 2 O 3 -Mn 2} O 3, CuO-
And the like _{Fe 2 O 3 -Mn 2 O 3} -Al 2 O 3. Further, examples of the cobalt-based oxides include cobalt oxide and cobalt trioxide.

Various shapes such as a spherical shape, a flake shape, and a dendrite shape can be used as the shape of such black inorganic fine particles, but in view of optical characteristics and dispersibility, it is preferable to use a spherical shape.

Examples of the inorganic binder for coating such black inorganic fine particles include low melting point ceramics and the like, which have a low melting point of glass transition point (Tg) of 300 to 500 ° C. and glass softening point (Ts) of 400 to 600 ° C. Glass powder is preferred. The reason for this is that in the composition of the present invention, an organic binder having good flammability is used and the organic binder is completed before the inorganic binder is melted. However, when the softening point of the glass powder is lower than 400 ° C., the glass is melted before the debinding is completed and the organic binder is easily wrapped, and the remaining organic binder is decomposed to cause blisters in the composition. It is not preferable because it becomes easy. As described above, according to the crushed powder of the black conductive fine particles / low melting point glass melt using the low melting point glass powder as the inorganic binder, the film after exposure and development can be easily baked at 600 ° C. or lower, Particularly, it is useful for forming electrodes of PDP.

As the low melting point glass powder, glass powder containing lead oxide, bismuth oxide or zinc oxide as a main component can be preferably used. Preferable examples of the glass powder containing lead oxide as a main component include P in mass% based on oxide.
bO is 48 to 82%, B ₂ O ₃ is 0.5 to 22%, SiO
₂ is ₃ to 32%, Al ₂ O ₃ is 0 to 12%, BaO is 0 to
10%, ZnO 0-15%, TiO ₂ 0-2.5
%, Bi ₂ O ₃ has a composition of 0 to 25%, and has a softening point of 42.
The amorphous frit which is 0-590 degreeC is mentioned.

A preferred example of the glass powder containing bismuth oxide as a main component is Bi ₂ O _{3 in} mass% based on oxide.
Of 35 to 88%, B ₂ O ₃ of 5 to 30%, and SiO ₂ of 0
20%, Al ₂ O ₃ 0-5%, BaO 1-25%, Z
nO has a composition of 1 to 20% and has a softening point of 420 to 59.
An amorphous frit that is 0 ° C. may be mentioned.

As a preferred example of the glass powder containing zinc oxide as a main component, ZnO is 25% by mass based on the oxide.
〜60%, K ₂ O ₂ ~ 15%, B ₂ O ₃ 25 ~ 45
%, SiO ₂ is 1 to 7%, Al ₂ O ₃ is 0 to 10%, Ba
An amorphous frit having a composition of O of 0 to 20% and MgO of 0 to 10% and a softening point of 420 to 590 ° C can be mentioned.

As the organic binder (B), a resin having a carboxyl group, specifically, a carboxyl group-containing photosensitive resin which itself has an ethylenically unsaturated double bond, and an ethylenically unsaturated double bond are used. Any carboxyl group-containing resin that does not exist can be used. Examples of the resin (which may be either an oligomer or a polymer) which can be suitably used include the following. (1) Carboxyl group-containing resin obtained by copolymerizing (a) unsaturated carboxylic acid and (b) compound having unsaturated double bond (2) (a) unsaturated carboxylic acid and (b) unsaturated A carboxyl group-containing photosensitive resin (3) (c) obtained by adding an ethylenically unsaturated group as a pendant to a copolymer of a compound having a double bond and a compound having an unsaturated double bond ( b) a carboxyl group obtained by reacting (a) an unsaturated carboxylic acid with a copolymer of a compound having an unsaturated double bond, and (d) a polybasic acid anhydride with the generated secondary hydroxyl group. Containing photosensitive resin (4) (e) an acid anhydride having an unsaturated double bond, and (b)
A carboxyl group-containing resin (5) obtained by reacting a compound having an unsaturated double bond with a compound having a hydroxyl group (f) (e) an acid anhydride having an unsaturated double bond and (b) )
A carboxyl group-containing photosensitive resin (6) (g) epoxy compound (h) obtained by reacting a copolymer of a compound having an unsaturated double bond with (f) a compound having a hydroxyl group and an unsaturated double bond, and (h) ) A carboxyl group-containing photosensitive resin (7) (b) having an unsaturated double bond, which is obtained by reacting an unsaturated monocarboxylic acid and reacting a secondary hydroxyl group formed with (d) a polybasic acid anhydride In the epoxy group of the copolymer of the compound and glycidyl (meth) acrylate,
(I) Obtained by reacting an organic acid having one carboxyl group in one molecule and not having an ethylenically unsaturated bond, and reacting the generated secondary hydroxyl group with (d) a polybasic acid anhydride. Carboxyl group-containing resin (8) (j) Hydroxyl group-containing polymer (d) Polycarboxylic acid anhydride obtained by reacting (d) Polybasic acid anhydride (9) (j) Hydroxyl group-containing polymer (d) Polybasic acid anhydride To the carboxyl group-containing resin obtained by reacting
(C) Carboxyl group-containing photosensitive resin obtained by further reacting a compound having an epoxy group with an unsaturated double bond

The above-mentioned carboxyl group-containing photosensitive resin and carboxyl group-containing resin may be used alone or as a mixture, but in any case, they are 10 to 80% by mass of the total amount of the composition. It is preferable to mix them in a ratio. If the blending amount of these resins is less than the above range, the distribution of the resin in the film to be formed tends to be non-uniform, and it is difficult to obtain sufficient photocurability and photocuring depth, selective exposure and development. Patterning becomes difficult. On the other hand, if the amount is more than the above range, it is not preferable because the pattern is apt to be warped during firing and the line width is easily contracted.

The above-mentioned carboxyl group-containing photosensitive resin and carboxyl group-containing resin each have a weight average molecular weight of 1,000 to 100,000, preferably 5,
000 to 50,000, and acid value 20 to 150 mg KO
H / g, preferably 40 to 120 mgKOH / g, and in the case of a carboxyl group-containing photosensitive resin, its double bond equivalent is 350 to 2,000, preferably 400.
-1,500 can be preferably used. When the molecular weight of the above resin is lower than 1,000, it adversely affects the adhesion of the conductive film during development, while
If it is higher than the above range, defective development tends to occur, which is not preferable. Further, when the acid value is lower than 20 mgKOH / g, the solubility in an alkaline aqueous solution is insufficient and the development failure is liable to occur. This is not preferable because dissolution of (exposed portion) occurs. Furthermore, in the case of a carboxyl group-containing photosensitive resin, if the double bond equivalent of the photosensitive resin is less than 350, a residue tends to remain during firing,
On the other hand, if it is larger than 2,000, the work margin at the time of development is narrow and a high exposure amount is required at the time of photocuring, which is not preferable.

In the present invention, the photopolymerizable monomer (C)
Is used to accelerate the photocurability and improve the developability of the composition. Examples of the photopolymerizable monomer (C) include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, polyurethane diacrylate, trimethylolpropane triacrylate, penta. Erythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane ethylene oxide modified triacrylate, trimethylolpropane propylene oxide modified triacrylate, dipentaerythritol pentaacrylate,
Dipentaerythritol hexaacrylate and each methacrylate corresponding to the above acrylates; phthalic acid,
Mono-, di-, tri- of polybasic acids such as adipic acid, maleic acid, itaconic acid, succinic acid, trimellitic acid, terephthalic acid and hydroxyalkyl (meth) acrylate
Examples thereof include polyesters and the like, but the polyesters are not limited to specific ones, and these may be used alone or in combination of two or more kinds. Among these photopolymerizable monomers, a polyfunctional monomer having two or more acryloyl groups or methacryloyl groups in one molecule is preferable.

The amount of the photopolymerizable monomer (C) blended is 100% of the organic binder (carboxyl group-containing photosensitive resin and / or carboxyl group-containing resin) (B) 100.
20 to 100 parts by weight per part by weight is suitable. When the compounding amount of the photopolymerizable monomer (C) is less than the above range,
It becomes difficult to obtain sufficient photocurability of the composition. On the other hand, when the amount exceeds the above range, the photocuring of the surface portion becomes faster than the deep portion of the film, and thus uneven curing is likely to occur.

Specific examples of the photopolymerization initiator (D) include benzoin and benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenylacetophenone. , 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone and other acetophenones; 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl 2-Aminoacetophenones such as 2-dimethylamino-1- (4-morpholinophenyl) -butanone-1;
Anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone and 1-chloroanthraquinone; 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropyl Thioxanthones such as thioxanthone; Ketals such as acetophenone dimethyl ketal, benzyl dimethyl ketal;
Benzophenones such as benzophenone; or xanthones; (2,6-dimethoxybenzoyl) -2,4,4-
Pentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl-2,4,6-trimethylbenzoylphenylphosphineate, etc. Phosphine oxides; various peroxides and the like,
These known and commonly used photopolymerization initiators can be used alone or in combination of two or more kinds. The mixing ratio of these photopolymerization initiators (D) is appropriately 1 to 30 parts by weight, preferably 100 parts by weight of the organic binder (carboxyl group-containing photosensitive resin and / or carboxyl group-containing resin) (B). Is 5 to 20 parts by weight.

Further, the photopolymerization initiator (D) as described above
Is N, N-dimethylaminobenzoic acid ethyl ester,
N, N-dimethylaminobenzoic acid isoamyl ester,
It can be used in combination with one or more photosensitizers such as tertiary amines such as pentyl-4-dimethylaminobenzoate, triethylamine and triethanolamine. Further, when a deeper photocuring depth is required, a titanocene-based photopolymerization initiator such as Irgacure 784 manufactured by Ciba Specialty Chemicals, which initiates radical polymerization in the visible region, and a leuco dye are cured, if necessary. It can be used in combination as an auxiliary agent.

Further, when a deeper photocuring depth is required, a thermal polymerization catalyst can be used in combination with the photopolymerization initiator (D), if necessary. This thermal polymerization catalyst is capable of reacting an uncured photopolymerizable monomer by aging at a high temperature for several minutes to about 1 hour, and specifically, a peroxide such as benzoyl peroxide or azoisobutyronitrile. There are azo compounds such as
Preferably 2,2'-azobisisobutyronitrile,
2,2'-azobis-2-methylbutyronitrile, 2,
2'-azobis-2,4-divaleronitrile, 1'-azobis-1-cyclohexanecarbonitrile, dimethyl-2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid , 2-methyl-
2,2′-azobispropane nitrile, 2,4-dimethyl-2,2,2 ′, 2′-azobispentanenitrile,
1,1′-azobis (1-acetoxy-1-phenylethane), 2,2,2 ′, 2′-azobis (2-methylbutanamide oxime) dihydrochloride and the like,
More preferable environment friendly non-cyan,
Non-halogen type 1,1′-azobis (1-acetoxy-1-phenylethane) may be mentioned.

In the composition of the present invention, an inorganic binder such as a low-melting glass powder, a conductive powder (E), a silica powder (F) and the like are blended, if necessary, within a range that does not impair the conductivity and blackness. be able to.

The conductive powder (E) has a specific resistance value of 1
It can be widely used as long as it is a conductive powder of 10 ³ Ω · cm or less, and silver (Ag), gold (Au), nickel (N
i), copper (Cu), aluminum (Al), tin (S
n), lead (Pb), zinc (Zn), iron (Fe), platinum (Pt), iridium (Ir), osmium (Os),
In addition to simple substances such as palladium (Pd), rhodium (Rh), ruthenium (Ru), tungsten (W), and molybdenum (Mo) and their alloys, tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), ITO (Indium Tin Oxide) or the like can be used. These can be used alone or as a mixed powder of two or more kinds.

The conductive powder (E) may have various shapes such as spherical shape, flake shape and dendrite shape, but it is preferable to use spherical shape in consideration of optical characteristics and dispersibility. From the viewpoint of resolution, the average particle size is preferably 20 μm or less, more preferably 5 μm or less. Further, in order to prevent the oxidation of the conductive powder, improve the dispersibility in the composition, and stabilize the developability, it is preferable to treat Ag, Ni, and Al with a fatty acid. As fatty acids, oleic acid,
Examples thereof include linoleic acid, linolenic acid and stearic acid.

The amount of the conductive powder (E) to be blended is appropriately 100 parts by weight or less per 100 parts by weight of the organic binder (B). When it is blended in a large amount in excess of 100 parts by weight, light transmission is impaired, and it becomes difficult to obtain sufficient photocurability of the composition. In addition, when a conductive powder that does not exhibit black color is added, it becomes impossible to obtain a conductive composition for a black layer electrode that can satisfy sufficient blackness.

As the silica powder (F), synthetic amorphous silica fine powder is particularly preferable, and specific examples thereof include AEROSIL (registered trademark) 50, 130, 200, 200V, 200CF manufactured by Nippon Aerosil Co., Ltd., 2
00FAD, 300, 300CF, 380, OX50,
TT600, MOX80, MOX170, COK84,
Nisil (registered trademark) A manufactured by Nippon Silica Industry Co., Ltd.
Q, AQ-S, VN3, LP, L300, N-300
A, ER-R, ER, RS-150, ES, NS, NS
-T, NS-P, NS-KR, NS-K, NA, KQ,
Examples thereof include KM and DS, and these can be used alone or in combination of two or more kinds. Among these,
Primary particle size is 5 to 50 nm, specific surface area is 50 to 500 m
² / g is preferable.

When the synthetic amorphous silica fine powder having a silanol group as described above is added to a photocurable composition containing a combination of a resin having a carboxyl group and black inorganic fine particles as described above, drying, exposure and development are carried out. ,
It shows stable adhesion to the substrate in each firing process, and can suppress the occurrence of peeling and curling between the substrate and the black layer and between the black layer and the white layer in the firing process for manufacturing the bus electrode. . The reason why such an effect is exerted has not been sufficiently clarified yet, but before firing, the hydrogen atom of the silanol group on the surface of the synthetic amorphous silica and the oxygen atom of the carboxyl group of the glass substrate or resin used as the substrate Due to hydrogen bonding and the Coulomb force between the electrically negative oxygen atom of the silanol group and the electrically positive metal of the conductive powder, a dense coating film with excellent adhesion to the substrate is formed and baked. It is speculated that the synthetic amorphous silica fine particles later enter the gaps between the glass substrate and the conductive particles and the gaps between the conductive particles to increase their adhesive strength.

In the present invention, an organic solvent can be added as a diluent in order to adjust the viscosity of the paste in the coating step and to enable film formation by drying and contact exposure. Specifically, ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene; cellosolve, methyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, diether. Propylene glycol monomethyl ether, dipropylene glycol monoethyl ether,
Glycol ethers such as triethylene glycol monoethyl ether; acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate Alcohols such as ethanol, propanol, ethylene glycol, propylene glycol; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, solvent naphtha, etc. Or two or more kinds can be used in combination.

When a large amount of black inorganic fine particles and low melting point glass powder are blended in the photocurable composition, the resulting composition has poor storage stability and poor coating workability due to gelation and fluidity deterioration. Tends to become. Therefore, for the purpose of improving the storage stability of the composition, it is known to add, as a stabilizer, a compound having an effect of complexing with a metal or oxide powder which is a component of black inorganic fine particles or glass or forming a salt. Has been. However, since the stabilizers effective for the black inorganic fine particles and the metal or oxide powder as the component of the glass are different components, it is very difficult to stabilize the paste composed of the two components. In this respect, in the photocurable composition of the present invention, since the black inorganic fine particles coated with an inorganic binder such as low-melting glass are used, only a stabilizer effective for the inorganic binder such as a glass component may be considered. It became easier to stabilize the storage of the paste. Examples of the stabilizer include acids such as inorganic acids, organic acids, and phosphoric acid compounds (inorganic phosphoric acid, organic phosphoric acid). Such a stabilizer is preferably added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the glass powder or conductive powder.

When the photocurable composition is blended with a photopolymerizable monomer, the resulting composition has poor storage stability,
The coating workability tends to deteriorate due to gelation and deterioration of fluidity. Therefore, in the composition of the present invention, a thermal polymerization inhibitor of a photopolymerizable monomer can be added as necessary to improve the storage stability of the composition. Examples of the thermal polymerization inhibitor include phenothiazine, 2-ethylanthraquinone, hydroquinone, N-phenylnaphthylamine, chloranil, pyrogallol, benzoquinone, and t-butylcatechol, which may be used alone or in combination of two or more. . Such a stabilizer may be added in an amount of 0.01 to 1 per 100 parts by mass of the organic binder (B).
It can be added in a proportion of parts by mass.

The photocurable composition of the present invention may further contain other additives such as a silicone-based or acrylic-based defoaming / leveling agent and a silane coupling agent for improving the adhesion of the film, if necessary. Agents can also be included. Furthermore, if necessary, a known conventional antioxidant for preventing the oxidation of the conductive metal powder, a thermal polymerization inhibitor for improving the thermal stability during storage, and a substrate during baking. It is also possible to add fine particles such as metal oxides, silicon oxides, and boron oxides as a binding component.

The photocurable composition of the present invention may be laminated on a substrate when it is previously formed into a film, but in the case of a paste composition, a screen printing method,
A substrate, for example, a glass substrate to be a front substrate of a PDP, is coated by an appropriate coating method such as a bar coater or a blade coater, and then a hot air circulation type drying furnace is used to obtain touch dryness.
For example, in a far-infrared ray drying oven at about 60 to 120 ° C. for 5 to 40
After drying for about a minute, the organic solvent is evaporated to obtain a tack-free coating film. After that, selective exposure, development, and baking are performed to form an electrode circuit having a predetermined pattern.

As the exposure step, contact exposure and non-contact exposure using a negative mask having a predetermined exposure pattern are possible, but contact exposure is preferable from the viewpoint of resolution. As the exposure light source, a halogen lamp, a high pressure mercury lamp, a laser beam, a metal halide lamp, a black lamp, an electrodeless lamp or the like is used. The exposure amount is 50-100
About 0 mJ / cm ² is preferable.

As the developing process, a spray method, a dipping method or the like is used. As the developing solution, an aqueous solution of a metal alkali such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate or the like, an aqueous solution of an amine such as monoethanolamine, diethanolamine, triethanolamine or the like, particularly about 1.5% by weight or less A dilute alkaline aqueous solution having a concentration of is preferably used, but it is sufficient that the carboxyl group of the carboxyl group-containing resin in the composition is saponified and the uncured portion (unexposed portion) is removed. It is not limited to. Further, it is preferable to carry out washing with water or acid neutralization after the development in order to remove unnecessary developer.

In the firing step, the substrate after development is subjected to a heat treatment at about 400 to 600 ° C. in air or a nitrogen atmosphere to form a desired conductor pattern. The rate of temperature increase at this time is preferably set to 15 ° C./minute or less.

In forming the bus electrode, first,
As shown in FIG. 2 (A), the front glass substrate 1 on which the transparent electrode 3 is formed in advance by ITO, SnO ₂ or the like by a conventionally known appropriate means such as sputtering, ion plating, chemical vapor deposition, or electrodeposition, A photocurable composition containing the above-mentioned black inorganic fine particles is applied and dried to form a tack-free black layer (lower layer) 20. Next, FIG. 2 (B)
As shown in, the black inorganic fine particles in the composition are Ag,
A tack-free white conductive layer (upper layer) 21 is obtained by applying a composition similar to the photocurable composition except that it is replaced with the above-mentioned conductive powder such as Au, Al, Pt, or Pd, and drying. To form. Then, as shown in FIG. 2C, a photomask 2 having a predetermined exposure pattern is formed on the photomask 2.
2 are overlaid and exposed. Then, it is developed with an alkaline aqueous solution to remove the non-exposed portion, and a predetermined electrode pattern as shown in FIG. 2 (D) is formed. Then, by firing, a black layer (lower layer) electrode 20a and a white layer (upper layer) electrode 2 are formed on the transparent electrode 3 as shown in FIG.
A bus electrode 4 composed of 1a is formed. Incidentally, in the case of a dry film in which the black photocurable composition and the white photocurable composition are previously formed into a film shape, they are exposed to heat and pressure, and then sequentially laminated on the front glass substrate, and then exposed and developed. And each process of baking may be performed. Moreover, after coating the above-mentioned photocurable composition on the front glass substrate and performing the steps of drying, exposing, developing and baking to form a black layer (lower black) electrode, a white photocurable composition It is also possible to employ a method in which a white layer (upper layer) electrode is formed by applying a material and performing each step of drying, exposing, developing and baking.

[0045]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited to the following Examples. The terms “part” and “%” are based on mass unless otherwise specified.

Synthesis Example 1 A flask equipped with a thermometer, a stirrer, a dropping funnel, and a reflux condenser was charged with methyl methacrylate and methacrylic acid at a molar ratio of 0.76: 0.24, and dipropylene glycol was used as a solvent. Monomethyl ether and azobisisobutyronitrile as a catalyst were added, and the mixture was stirred under a nitrogen atmosphere at 80 ° C. for 2 to 6 hours to obtain a resin solution. This resin solution was cooled, methyl hydroquinone as a polymerization inhibitor, tetrabutylphosphonium bromide as a catalyst, glycidyl methacrylate,
Under conditions of 95 to 105 ° C. for 16 hours, the addition reaction was carried out at an addition molar ratio of 0.12 mol to 1 mol of the carboxyl group of the resin, and after cooling, it was taken out to prepare an organic binder A. The resin of this organic binder A had a weight average molecular weight of about 10,000, an acid value of 59 mgKOH / g, and a double bond equivalent of 950. The weight average molecular weight of the obtained copolymer resin was measured by Shimadzu Corporation pump LC-6AD and Showa Denko column Shodex.
(Registered trademark) KF-804, KF-803, KF-80
The measurement was carried out by high performance liquid chromatography in which 2 of 3 were connected.

(Example 1 of component (A)) 100 parts of cobalt tetraoxide having an average particle size of 0.1 μm was added to a platinum (Pt) crucible.
Parts, average particle size 10 μm, glass transition point (Tg) 400
200 parts of low melting glass powder having a glass softening point (Ts) of 500 ° C. was charged and melted at 900 ° C. in a firing furnace. Next, the obtained melt was cooled and then pulverized with a pulverizer to an average particle size of 10 μm to prepare a glass trioxide cobalt oxide powder coated with the glass.

(Example 2 of component (A)) 100 parts of ruthenium oxide having an average particle size of 0.1 μm was added to a platinum (Pt) crucible,
20 low melting point glass powders having an average particle size of 10 μm, a glass transition point (Tg) of 400 ° C. and a glass softening point (Ts) of 500 ° C.
0 part was charged and melted at 900 ° C. in a firing furnace. Then
After cooling the obtained melt, the average particle size is 10 with a pulverizer.
The ruthenium oxide powder coated with the glass was prepared by grinding to a particle size of μm.

Using the organic binder A, the component example 1 of (A) and the component example 2 of (A) prepared as described above, the components were blended in the following composition ratios, stirred with a stirrer, and then kneaded with a three-roll mill. And made into a paste. In this example, as the low melting point glass powder, PbO 6 was used.
0%, B ₂ O ₃ 20%, SiO ₂ 15%, and Al ₂ O ₃ 5% were crushed, and the thermal expansion coefficient α ₃₀₀ = 70 × 10 ⁻⁷ / ° C., glass transition point 445 ° C., average particle size 1. The one having a size of 6 μm was used.

[0050]  Conductive paste for white layer electrode (upper layer);     Organic binder A 100.0 parts     Pentaerythritol triacrylate 50.0 parts     2-benzyl-2-dimethylamino-1-           (4-morpholinophenyl) butan-1-one 5.0 parts     Dipropylene glycol monomethyl ether 80.0 parts     Silver powder 450.0 parts     Low melting point glass powder 22.0 parts     Phosphate ester 1.0 part

[0051]  Black layer electrode (lower layer) paste:  (Composition example 1)     Organic binder A 100.0 parts     Pentaerythritol triacrylate 50.0 parts     2-benzyl-2-dimethylamino-1-           (4-morpholinophenyl) butan-1-one 5.0 parts     Dipropylene glycol monomethyl ether 80.0 parts     Phosphate ester 1.0 part     (A) Component Example 1 (glass-coated trisodium cobalt oxide powder) 30.0 parts

[0052]   (Composition example 2)     Organic binder A 100.0 parts     Pentaerythritol triacrylate 50.0 parts     2-Methyl-1- [4- (methylthio) phenyl]- 2-morpholinopropan-1-one 7.0 parts 2,4-diethylthioxanthone 1.0 part     Dipropylene glycol monomethyl ether 80.0 parts     Phosphate ester 1.0 part     (A) Component example 2 (glass-coated ruthenium oxide powder) 30.0 parts

[0053] (Comparative composition example 1)     Organic binder A 100.0 parts     Pentaerythritol triacrylate 50.0 parts     2-Methyl-1- [4- (methylthio) phenyl]- 2-morpholinopropan-1-one 7.0 parts 2,4-diethylthioxanthone 1.0 part     Dipropylene glycol monomethyl ether 80.0 parts     Low melting point glass (average particle size 10 μm, glass transition point (Tg) 400 ° C, glass softening point (Ts) 500 ° C) 20.0 parts     Cobalt trioxide (average particle size 0.1 μm) 10.0 parts     Phosphate ester 1.0 part

[0054] (Comparative composition example 2)     Organic binder A 100.0 parts     Pentaerythritol triacrylate 50.0 parts     2-benzyl-2-dimethylamino-1-           (4-morpholinophenyl) butan-1-one 5.0 parts     Dipropylene glycol monomethyl ether 80.0 parts     Low melting point glass (average particle size 10 μm, glass transition point (Tg) 400 ° C, glass softening point (Ts) 500 ° C) 20.0 parts     Ruthenium oxide (average particle size 0.1 μm) 10.0 parts     Phosphate ester 1.0 part

With respect to the pastes of the composition examples 1 and 2 and the comparative composition examples 1 and 2 thus obtained, the adhesiveness,
The specific resistance value, interlayer conduction, color tone after firing, L value, and paste stability were evaluated. The evaluation method is as follows. (Paste Stability) 300 g each of the pastes of Composition Examples 1 and 2 and Comparative Composition Examples 1 and 2 were placed in a closed container.
After leaving it for 1 month at ℃, the state was confirmed. (Adhesion) A black and white two-layer coating formed on a glass substrate
Pattern exposure is performed using a negative film with a line / space of 50/100 μm, and then the liquid temperature is 30 ° C.
It was developed with a wt% Na ₂ CO ₃ aqueous solution, washed with water, and then fired to form a patterned fired substrate, and then subjected to Sellotape (registered trademark) peeling, and it was evaluated whether or not the pattern was peeled. (Resistance value) A paste for evaluation was applied on the entire surface of a glass substrate using a 300-mesh polyester screen, and then dried at 90 ° C. for 20 minutes in a hot air circulation type drying oven to obtain good touch dryness. A film was formed. Then, a white conductive paste (for the white layer electrode) is applied to the surface of the coating film in an amount of 20.
It was applied to the entire surface using a 0 mesh polyester screen, and then dried at 90 ° C. for 20 minutes in a hot air circulation type drying oven to form a black and white two-layer coating having good touch dryness. After that, a metal halide lamp was used as a light source, and a negative mask with a pattern size of 100 μm × 10 cm was used.
After exposing the entire surface so that the integrated light amount on the composition becomes 500 mJ / cm ² , 0.5 wt% Na ₂ CO _{3 at} a liquid temperature of 30 ° C.
It was developed using an aqueous solution and washed with water. Finally, the temperature was raised at 5 ° C./min in an air atmosphere, and the substrate was baked at 550 ° C. for 30 minutes. The resistance value of the fired film thus obtained was measured. (Interlayer conduction) A 100 μm × 3 cm pattern was formed on the glass substrate with the ITO film by the same method as described above. The white layer (upper layer) and IT of the fired film thus obtained
A tester was applied to O to confirm continuity. (Color tone after firing) A 3 cm × 10 cm pattern was formed on the glass substrate with the ITO film by the same method as described above. The fired film thus obtained was visually observed from the glass side to confirm the color tone. (L * value) Using the color difference meter (CR-221 manufactured by Minolta Camera Co., Ltd.) using the test piece whose color tone was confirmed after firing, the value of the L * a * b * color system was determined according to JIS-Z. The measurement was performed according to -8729, and the L * value, which is an index representing lightness, was evaluated as an index of blackness. The smaller the L * value, the better the blackness.

Table 1 shows the results of these evaluations. (Table 1) As is clear from the results shown in Table 1, the paste according to the composition of the present invention has an adhesiveness, a resistance value, interlayer conduction, a color tone after firing, and an L value, which are higher than those of the paste of the comparative composition. It can be seen that the paste stability remains excellent.

With respect to the above evaluation paste, the line shape after development and the line shape after firing were evaluated, but there was no problem in either case. According to these evaluation methods, the two-layer coating formed on the glass substrate was used as line / space = 50 /
Pattern exposure is performed using a negative film having a thickness of 100 μm, then development is performed with a 1 wt% Na ₂ CO ₃ aqueous solution having a liquid temperature of 30 ° C., washing is performed with water, and then firing is performed to form a patterned firing substrate for evaluation. Other than the above, the evaluation method for the resistance value is the same as the above. The evaluation criteria, for the line shape after development, microscopic observation of the pattern completed up to development, there is no irregular variation in the line, evaluated by whether there is no wrinkles, for the line shape after firing, The pattern after firing was observed under a microscope to evaluate whether there were irregular variations in the line and whether there was any deviation.

[0058]

As described above, according to the photocurable composition of the present invention, the paste has excellent long-term storage stability, and has excellent adhesion and solution to the substrate in each step of drying, exposure, development and baking. It is possible to form a black layer (lower layer) in a PDP bus electrode having a black-and-white two-layer structure having image quality, firing property, and blackness.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view of a surface discharge type AC PDP.

FIG. 2 is a schematic cross-sectional view of a process example of forming a bus electrode of PDP using the photocurable composition of the present invention.

[Explanation of symbols]

1 Front glass substrate 2a, 2b display electrodes 3,3a, 3b Transparent electrode 4,4a, 4b Bus electrode 5 Transparent dielectric layer 6 protective layer 11 Rear glass substrate 12 ribs 13 address electrodes 14a, 14b, 14c Phosphor film 20 Black layer (lower layer) 21 White conductive layer (upper layer) 20a black layer (lower black) electrode 21a White layer (upper layer) electrode

Claims (11)

[Claims] 1. A photocurable composition, comprising: (A) black inorganic fine particles coated with an inorganic binder, (B) an organic binder, (C) a photopolymerizable monomer, and (D) a photopolymerization initiator. Sex composition. 2. The composition according to claim 1, further comprising (E) a conductive powder. 3. The composition according to claim 1, further comprising (F) silica powder. 4. The black inorganic fine particles (A) coated with an inorganic binder are obtained by crushing a melt of the black inorganic fine particles and the inorganic binder. The composition according to. 5. The black inorganic fine particles (A) coated with the inorganic binder have a blending ratio of black inorganic fine particles / inorganic binder of 30 to 400 parts by mass with respect to 100 parts by mass of the black inorganic fine particles. The composition according to claim 4. 6. The black inorganic fine particles are ruthenium oxide, ruthenium compound, copper-chromium black composite oxide,
6. The composition according to claim 1, wherein the composition is at least one of a copper-iron-based black composite oxide and a cobalt-based oxide. 7. The average particle size of the black inorganic fine particles is 0.1.
7. The composition according to claim 1, wherein the composition is smaller than μm. 8. The compounding amount of the black inorganic fine particles (A) coated with an inorganic binder is 0.1 to 300 parts by mass per 100 parts by mass of the organic binder (B). The composition according to any one of claims. 9. The softening point of the inorganic binder is 400 to 400.
It is glass powder of 600 degreeC, It is characterized by the above-mentioned.
9. The composition according to any one of items 8 to 8. 10. The composition according to claim 1, which is formed into a film. 11. A plasma display panel in which a black layer in an electrode circuit having a black and white two-layer structure is formed from a fired product of the photocurable composition according to any one of claims 1 to 10.