JP2005111665A - Offset printing blanket and printing method for electrode pattern using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an offset printing blanket for performing continuous printing of conductive patterns such as electrodes for a plasma display (PDP) or the like with excellent printability and stably, and a printing method for electrode pattern using the same. <P>SOLUTION: The offset printing blanket produced by laminating a surface rubber layer on a support layer is provided with two layers comprising an upper layer having a thickness of 5 to 600 μm composed of a rubber material (silicone rubber or the like) having excellent ink releasability as its surface rubber layer, and an underlayer having a thickness of 100 to 800 μm composed of a rubber material (a low molecular weight silicone oil such as a fluorosilicone rubber is added) having an excellent solvent resistance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a blanket for offset printing and an electrode pattern printing method using the same, and particularly provides a blanket suitable for continuous printing of high-resolution and high-precision patterns required in electronic circuits and image forming apparatuses. To do.

  Conventionally, as a method of forming a pattern such as an electronic circuit in an integrated circuit or a color filter of a liquid crystal display, for example, in the case of an electrode pattern of a PDP electrode substrate, a photosensitive silver paste is applied to a glass surface, and the electrical conductivity is applied thereon. It is mainly formed by a method called a photolithographic method (photolithographic method) in which a photosensitive silver paste having a good conductivity for compensation is coated to a certain thickness, and after exposure, development is performed after drying. However, in this method, a large amount of expensive photosensitive black paste and silver paste that are not exposed are washed away during development, and disposal processing and high cost are problems.

  In recent years, a printing method has been studied as a method for forming an electrode at a low cost. In particular, intaglio offset printing has been promoted from the viewpoint of printing accuracy and ink film thickness, and it has attracted attention as a method that can solve problems caused by the photolithography method. Has been. Intaglio offset printing is performed in the order of ink filling to the intaglio, transfer to the blanket, and transfer to the substrate, and the blanket is usually a laminate in which a rubber layer (surface printing layer) is laminated on the support layer. It is used by attaching it to a blanket cylinder of a printing press. In offset printing of a fine pattern such as a PDP electrode pattern, it is required for industrial production that an electrode pattern forming ink can be used to accurately and continuously print on a substrate such as a glass plate as a substrate to be printed.

  When a fine pattern is continuously printed using a blanket, the organic solvent in the ink accumulates in the ink-receiving layer of the blanket mainly composed of silicone rubber as the number of times of printing increases, and the surface of the blanket swells, It has been pointed out that the print quality deteriorates, such as a decrease in print line width, print shape disorder, and linearity deterioration (see Patent Document 1). In order to solve this problem, a support made of a polymer material having low stretchability and excellent solvent resistance, a solvent absorption layer (sponge-like) formed on the support, and formed on the solvent absorption layer It has been proposed to perform pattern printing using a blanket containing an ink receiving layer and containing silicone oil.

  On the other hand, when applying intaglio offset printing to fine pattern printing, the solvent in the electrode pattern forming ink permeates into the rubber constituting the surface printing layer of the blanket during continuous printing and causes the rubber to swell. It is known that the wettability of ink changes, the printing line width changes, and the printing performance deteriorates. For this reason, in manufacturing an electrode substrate for PDP by offset printing, a printing method has been developed in which the blanket surface is heated to sufficiently dry the solvent and then cooled so that the surface temperature does not rise above a predetermined temperature after drying. (See Patent Document 2).

  The pattern printing of the electrode substrate for PDP in Patent Document 2 includes (i) a step of transferring the conductive ink composition from the concave portion of the intaglio to the surface of the printing blanket, and (ii) the conductive ink composition of the printing blanket. After passing through the step of transferring from the surface to the surface of the glass substrate, the step of heating the surface of the printing blanket and evaporating and removing the solvent of the ink from the surface printing layer is performed. At this time, examples of a simple method of heating the printing blanket include a method of blowing hot air or hot air from the outside of the printing blanket or heating the surface printing layer. As the heating element, for example, an infrared heater or a lamp that can be heated / not heated from the outside is conveniently used.

So far, in order to reduce the ink depositability of the printing blanket, a blanket configured so that the degree of swelling of the rubber material forming the surface printing layer is gradually lowered from the outer surface to the inside has been proposed. (See Patent Document 3). As this blanket, a surface printed layer is composed of two layers for an inner layer and an outer layer, and the amount of vulcanizing agent in a rubber material (NBR, etc.) is increased in the inner layer and decreased in the outer layer (surface side). Yes.
JP-A-8-252990 (Claims 1-3, FIG. 1, etc.) JP 2002-245931 A (Claims 1 and 2 etc.) JP 2002-234274 A (Claims 1 and 2 etc.)

  When printing a fine pattern such as a PDP electrode by offset printing, it is required for industrial production that electrode pattern forming ink can be continuously printed using a substrate such as a glass plate as a printing medium. For this purpose, it is necessary to improve the performance of the printing blanket to be more suitable than that for printing on normal paper and ink.

  In order to solve the above problems, the present inventors examined the relationship between the configuration of the surface rubber layer in the printing blanket and the printing performance. As a result, the rubber layer was divided into two layers from the viewpoints of ink releasability and solvent resistance. In other words, the present inventors have found that the printing performance does not deteriorate even when the electrode pattern is continuously printed, and have further studied and completed the following offset printing blanket and electrode pattern printing method of the present invention.

1) A blanket for offset printing formed by laminating a surface rubber layer on a support layer, wherein the surface rubber layer is made of a rubber material having a good ink releasability and has a thickness of 5 to 600 μm, and a solvent-resistant A blanket for offset printing, comprising two lower layers having a thickness of 100 to 800 μm made of a good rubber material.
2) The rubber material having good ink releasability is silicone rubber or fluorine rubber, and the rubber material having good solvent resistance is fluorosilicone rubber, urethane rubber, acrylonitrile-butadiene copolymer rubber (NBR), fluorine rubber, The blanket for offset printing according to the above item 1), which is one rubber selected from the group consisting of acrylic rubber and chloroprene rubber or two or more blend rubbers.

3) The upper layer made of the rubber material with good ink releasability has a JIS-A hardness of 30 to 80 °, and the lower layer made of a rubber material with good solvent resistance has a JIS-A hardness of 20 to 70 °. The blanket for offset printing as described in 1) or 2) above.
4) The blanket for offset printing according to any one of 1) to 3) above, wherein the lower layer made of a rubber material having good solvent resistance contains low molecular weight silicone oil.

5) The blanket for offset printing according to 4) above, wherein the low molecular weight silicone oil is contained in a proportion of 5 to 300 parts by weight with respect to 100 parts by weight of rubber.
6) The support layer is composed of a synthetic resin film or a metal film having a breaking elongation of 5 to 200% and a breaking strength of 150 to 1000 MPa when measured by a method specified in JIS C2151. The blanket for offset printing as described in 1) to 5) above.

  7) A step of filling a concave portion of the intaglio with a conductive ink composition in which a metal powder and a binder resin are dispersed or dissolved in a solvent when performing offset printing of the electrode pattern, and the concave portion of the intaglio plate with the conductive ink composition And a step of transferring the conductive ink composition from the surface of the blanket to the surface of the electrode substrate, and the blanket according to any one of 1) to 6) above A method for printing an electrode pattern, characterized in that

In the present invention, the upper layer constituting the surface rubber layer is located on the outermost layer of the blanket, and the lower layer is located on the support layer side in contact with the upper layer.
In the blanket for offset printing of the present invention, the upper layer of the surface rubber layer needs to have a thickness of 5 to 600 μm. In this range, the ink solvent diffused in the rubber volatilizes as soon as it is dried, which is good. The wettability is maintained. If the thickness is smaller than this, the apparent hardness of the surface rubber becomes high, and it becomes impossible to cope with the case where the surface of the printing medium has undulations, and the ink cannot be transferred sufficiently. In addition, the deformation of the rubber layer inside the intaglio cannot be followed, and the transfer of ink does not succeed, causing pinholes during printing. The thickness of the upper layer is more preferably in the range of 30 to 400 μm.

On the other hand, the lower layer of the surface rubber layer needs to have a thickness of 100 to 800 μm so that the surface of the substrate can be swelled or the rubber can be deformed and tracked even inside the intaglio. A more preferable thickness is in the range of 200 to 600 μm.
In the present invention, the ink releasability in the “upper layer of a thickness of 5 to 600 μm made of a rubber material having good ink releasability” refers to how much the ink received in the blanket can be transferred to the printing medium. Good moldability means that 100% or almost 100% of the ink is transferred. From the viewpoint of physical properties, the surface free energy of the upper layer is preferably in the range of 10 dyn / cm (mN / m) to 25 dyn / cm (mN / m). Examples of the rubber material forming the upper layer include silicone rubber and fluorine rubber. If the surface free energy exceeds 25 dyn / cm, the wettability of the blanket surface is too good and the ink releasability is deteriorated. As a result, the transferability to the printing medium is reduced, causing pinholes and shape deterioration. Cheap. On the other hand, if it is less than 10 dyn / cm, the wettability of the surface is poor, and the tendency that the ink repels on the surface of the blanket and the shape set on the intaglio cannot be maintained becomes strong.

In the present invention, “solvent resistance in a lower layer having a thickness of 80 to 100 μm made of a rubber material having good solvent resistance” means that the swelling property with respect to an organic solvent is small. When expressed by a specific index, a rubber material having a volume change rate in the range of 0 to 100% when the rubber material is immersed in toluene for 24 hours is suitable. Here, the volume change rate is a value in which the difference ΔV is expressed as a percentage with respect to V ₀ when the volume before immersing the rubber material in toluene is V ₀ and the volume after the immersion is V ₁ . When the volume change rate exceeds 100%, the ink solvent absorbed in the upper layer penetrates and accumulates in the lower layer, and since the accumulated ink solvent is difficult to be discharged, it gradually diffuses into the upper layer rubber and its ink releasability This is not preferable. Furthermore, the lower layer rubber is softened (increase in volume) and the hardness is reduced, leading to a decrease in printing accuracy.

  The blanket for offset printing of the present invention (hereinafter sometimes simply referred to as a blanket) has a surface rubber layer composed of the two layers described above, and the lower layer uses a rubber material that is less swelled by a solvent. The solvent in the ink is mainly absorbed by the upper layer and can be easily removed by drying. Therefore, an electrode pattern with high printing accuracy can be stably produced even if continuous printing is performed using conductive ink.

Hereinafter, the configuration of the blanket of the present invention and the materials used will be described.
The surface rubber layer of the blanket of the present invention is composed of two upper and lower layers as described above. The upper layer is formed of a rubber material having good ink releasability, and the surface energy value, which is an index showing the ink ink releasability, is 10 to 25 dyn / cm in a dry state not containing the ink solvent. A certain rubber material is preferably used. The thickness of the upper layer is in the range of 5 to 600 μm. The rubber hardness is preferably 30 to 80 ° as JIS-A hardness, and more preferably 40 to 60 °. By forming the upper layer in this way, the ink transferred from the intaglio can be transferred 100% or almost 100%.

  Silicone rubber or fluororubber is suitable as the rubber material. Examples of the silicone rubber include various types of silicone rubbers such as a heat curable type (HTV) and a room temperature curable type (RTV). In particular, a room temperature curable addition type silicone rubber does not generate any by-product during curing. Since it is excellent in dimensional accuracy, it is preferably used. Specific examples of such silicone rubber include dimethyl silicone rubber, methylphenyl silicone rubber, trifluoropropylmethyl silicone rubber and the like.

  Fluororubber includes (1) fluorinated silicone rubber (FE series product manufactured by Shin-Etsu Chemical Co., Ltd.), which is a copolymer of methyltrifluoropropylenesiloxane and vinylmethylsiloxane, and (2) vinylidene fluoride and 6 fluorine. (3) Copolymer of vinylidene fluoride and propylene pentafluoride (trade name “Technoflon” manufactured by Nippon Zeon Co., Ltd.), (4) Copolymer of vinylidene fluoride and ethylene trifluoride (Kellog), (5) copolymer of tetrafluoroethylene and propylene (trade name “Macras” manufactured by Asahi Glass Co., Ltd.), (6) tetrafluoroethylene Copolymer of perfluoromethyl vinyl ether (trade name “Kalrez” manufactured by DuPont) or (7) Dimer of dichlorophosphonitrile And the reaction of the fluorine-containing alcoholate (from Ethyl Co manufactured "EYPEL-F"), and the like.

It is preferable that the surface of the upper layer is extremely smooth from the viewpoint of printing accuracy and the like, and the unevenness of the surface does not affect the printing. Specifically, the ten-point average roughness (Rz) of the surface is preferably 1.0 μm or less, and more preferably 0.5 μm or less.
Next, the lower layer which comprises a surface rubber layer is comprised so that it may become the range of 100-800 micrometers in thickness using the rubber material which has oil resistance. This lower layer is bonded to the upper layer and has a solvent resistance, so it has a function of suppressing the penetration of the ink solvent to the inside as much as possible, and gives the surface rubber layer an appropriate thickness to improve the stability. . The rubber hardness of the lower layer is preferably 20 to 60 ° in terms of JIS-A hardness, and more preferably 30 to 50 °.

In consideration of solvent resistance, etc., as the rubber material constituting the lower layer, fluorosilicone rubber, urethane rubber, acrylonitrile-butadiene copolymer rubber (NBR), fluorine rubber, acrylic rubber or chloroprene rubber are suitable. You may use these rubber materials as 2 or more types of blend rubber.
By constituting the surface rubber layer into two upper and lower layers as described above, it is suppressed that the ink solvent penetrates to the inside, so that during continuous printing, the solvent is easily removed by drying from the surface layer side, Printing performance is well maintained. When drying is repeated at this time, the low-molecular silicon oil contained in the silicone rubber constituting the upper layer is gradually volatilized to change the wettability of the surface. In order to prevent this, if a low molecular weight silicone oil is previously contained in the ink, the silicone oil is replenished during printing, and stable printing can be continued. However, in order to print a desired electrode pattern, it is important that the degree of freedom in designing the ink is not limited as much as possible. From this point of view, it is desirable that the silicon oil content be as low as possible.

  Therefore, in the blanket of the present invention, it is desirable that low molecular weight silicon oil is previously contained in the lower layer of the surface rubber layer, and that the silicon oil gradually shifts to the upper rubber layer and replenishes it. This makes it possible to suppress the amount of silicon oil added to the ink as much as possible. The low molecular weight silicone oil to be contained in the lower layer is preferably added at a rate of 5 to 300 parts by weight, more preferably 10 to 150 parts by weight, relative to 100 parts by weight of the rubber content of the lower layer.

  Examples of the low molecular weight silicone oil include cyclic polydimethylsiloxane, and an example of the trimer is shown in the following formula (1).

As this cyclic polydimethylsiloxane, a dimethylsiloxane having a 3-30 mer can be used, and a 5-20 mer is particularly preferable.
By adjusting the upper and lower layers to the thickness and hardness as described above, the surface rubber layer is not sufficiently press-fitted into the recess even if the blanket is pressed against the intaglio, and as a result, There is a possibility that the filled conductive ink composition cannot be sufficiently transferred and printing with high accuracy cannot be performed. On the other hand, if it falls below the above range (if the blanket is too soft), there is a risk that when the blanket is pressed against the intaglio or glass substrate, the deformation of the surface rubber layer becomes too large and printing with high accuracy cannot be performed. The layer thickness of the surface rubber layer is preferably in the range of 200 to 1000 μm.

  Next, in the blanket of the present invention, the support layer constituting the lower layer of the surface print layer is required to be made of a material having as little elongation as possible and high strength and a smooth surface. In general, a cotton cloth is often used for the support layer of the offset printing blanket. However, in the case of precision printing such as a PDP electrode pattern, the cotton cloth generates fibrous dust during printing, and the printing performance is improved. It is desirable not to use it because it lowers. In the present invention, the support layer is preferably composed of a synthetic resin film or a metal film having a breaking elongation of 5 to 200% and a breaking strength of 150 to 1000 MPa when measured by the method defined in JIS C2151. .

  The synthetic resin film is preferably made of one or more mixed resins selected from the group consisting of polyester resin, polycarbonate resin, polyimide resin, acrylic resin, urethane resin, polyamideimide resin and polyethersulfone resin. Used. As the material of the metal film, stainless steel, nickel, iron, aluminum or the like is used.

  When the film is used as a blanket support layer, its thickness depends on the strength of the material, but it is preferably about 50 to 1000 μm as a practically small thickness. If it is thinner than this, it will be stretched when it is attached to the blanket cylinder or during printing, and if it is thicker than this, it will become hard and the attachment to the blanket cylinder will be poor. For example, in the blanket of Patent Document 1, a base film having a thickness of 5 to 50 μm is supposed to be used. It is not suitable for performing intaglio offset printing intended for use. The total thickness of the blanket of the present invention is preferably in the range of 100 to 500 μm, more preferably in the range of 200 to 400 μm.

  The blanket of the present invention is constituted by laminating the above-mentioned surface rubber layer on a support layer, and can be produced, for example, by performing a casting method using a mold. The process sequence is as follows: (1) A film to be a support layer is adsorbed and placed in advance in a mirror-finished mold. (2) Liquid silicone rubber (containing a main agent and a curing agent in a desired quantity ratio) , Stirring and degassing treatment) are injected from the casting port, (3) allowed to stand at room temperature for 12 to 24 hours and cured, and (4) removed from the mold.

Next, an intaglio offset printing method using the blanket of the present invention will be described. This blanket is suitable for continuous printing of high-resolution and high-precision patterns required in electronic circuits and image forming apparatuses. As a representative example, a case where pattern printing is performed on an electrode substrate for a PDP electrode will be described as an example.
For example, as shown in FIG. 1, the PDP includes a back substrate (rear substrate) 11 provided with an address electrode (Ag) 10, a dielectric layer (glass) 16 ′ and a protective layer (MgO) 17 ′, a transparent electrode 14, and a bus. The electrode 15, the transparent dielectric layer 16, and a front substrate (front substrate) 18 having a protective layer (MgO) 17 are faced to each other. On the back substrate 11, ribs (partition walls) 12 and phosphors 13 (R, G, B) are formed on the surface of the protective layer 17 ′.

  In manufacturing the electrode substrate for PDP, the blanket of the present invention is prepared by filling the concave portion of the intaglio with a conductive ink composition in which a metal powder and a binder resin are dispersed or dissolved in a solvent. In order to offset print the electrode pattern by the step of transferring the ink composition from the concave portion of the intaglio to the surface of the blanket, and (ii) transferring the conductive ink composition from the surface of the blanket to the surface of the glass substrate, It is advantageously used for accuracy and industrial production. In this offset printing, by applying a heat treatment at a predetermined temperature to the blanket, a fine pattern required for the electrode substrate for PDP can be formed with high accuracy, and by the heat treatment, Deterioration of printed shape and pinholes due to blanket swelling can be prevented. As a result, high productivity can be exhibited when manufacturing an electrode substrate for PDP. Further, after the heat treatment, the surface of the intaglio Since the printing blanket is cooled so that the temperature does not rise above a predetermined range with respect to the temperature, the intaglio is expanded by the heat remaining in the printing blanket, and accordingly the printed shape of the pattern is reduced and pinholes Can be prevented.

When the blanket of the present invention is used, the heat treatment and the cooling treatment can be performed in a short time, and the heat energy can be used effectively. A pattern made of a conductive ink composition formed on the surface of the glass substrate is baked by a conventional method, and the binder resin content of the pattern is removed to produce a target PDP electrode.
The intaglio used as an original plate at the time of printing and forming a conductive pattern has a concave portion corresponding to the electrode pattern formed on the surface thereof, a flat plate, or a flat plate wound around a cylinder, A cylindrical thing, a cylindrical thing, etc. are mentioned. In the intaglio, the smoothness of the surface is extremely important. If the surface of the intaglio plate is not smooth enough, when the conductive ink composition is filled into the recesses with a doctor blade, ink scraps are generated on the surface of the intaglio plate (other than the recesses), and stains on the non-image area (ground) Smudges), and the printing accuracy is significantly reduced.

  The degree of smoothness of the intaglio surface is preferably about 1 μm or less, more preferably about 0.5 μm or less in terms of ten-point average roughness (Rz). Examples of intaglio substrates include glass substrates such as soda lime glass, non-alkali glass, quartz glass, low alkali glass, and low expansion glass; fluororesin, polycarbonate (PC), polyethersulfone (PES), polyester, Resin plates such as polymethacrylic resin; metal substrates such as stainless steel, copper, nickel, and low expansion alloy amber. Among them, a glass substrate is preferably used because an intaglio having excellent surface smoothness can be produced most inexpensively and the pattern edge shape can be made extremely sharp. Among the above-mentioned intaglio plates, non-alkali glass is one of the most excellent materials that can meet the requirements for extremely high dimensional accuracy, but is very expensive. For example, soda lime glass is sufficient to achieve the dimensional accuracy required for a normal PDP.

  The concave portion of the intaglio is formed by a photolithographic method, an etching method, an electroforming method, a sand blast method (shot blast method), or the like. As described above, the depth of the concave portion may be appropriately set according to the thickness of the target print pattern. However, the ink remaining in the concave portion (usually about half the amount of ink with respect to the depth of the concave portion). In consideration of a decrease in thickness after printing due to evaporation of the solvent, etc., it is preferably about 1 to 50 μm, particularly about 3 to 20 μm.

  Therefore, in performing offset printing, (i) a step of transferring the conductive ink composition from the concave portion of the intaglio to the surface of the printing blanket; and (ii) the conductive ink composition from the surface of the printing blanket to the glass substrate. And a step of transferring the surface to the surface of the blanket, the surface of the blanket is heated, and the step of evaporating and removing the ink solvent from the surface rubber layer (surface printed layer) is performed.

Since the solvent that has penetrated into the surface print layer of the blanket is evaporated and removed by heating the surface print layer, it can be completely returned to the original dry surface state. The easiness of evaporation and drying of the surface print layer is related to the heating temperature, the characteristics of the solvent of the conductive ink composition (particularly the boiling point), and the thickness of the surface print layer. If it heats so that it may become 40-200 degreeC, it can dry sufficiently effectively.

Blanket surface temperature during heating When the temperature is lower than 40 ° C., the effect of evaporating and removing the solvent that has permeated the surface print layer becomes insufficient. Meanwhile, blanket surface temperature during heating When the temperature exceeds 200 ° C., the rubber constituting the surface print layer is thermally deteriorated and modified. Blanket surface temperature during heating Is particularly preferably 60 to 150 ° C., more preferably 80 to 120 ° C. in the above range.

  Conventionally, the blanket is heated by placing a heating device inside the blanket cylinder to heat the entire printing blanket, blowing hot air or hot air from the outside of the blanket, or under the blanket itself or the blanket and blanket. For example, a heating element layer may be disposed between the body and the surface printing layer may be heated from the heating element layer. When the blanket of the present invention is used, a simple method of irradiating and drying the surface printed layer is adopted as the heating element, for example, using a flexible infrared heater or lamp capable of external heating / non-heating operation. Sometimes, since the heat rays can be used effectively, shortening of the heating time and energy consumption can be suppressed.

  The heat treatment of the blanket can be always performed while the conductive pattern is printed, but it may be performed periodically after repeating the above steps (i) and (ii) several times. Alternatively, it may be performed irregularly depending on the degree to which the blanket is swollen by the solvent of the conductive ink composition. The degree of the heat treatment of the blanket is not particularly limited, but the rate of change in the surface tension of the surface treatment layer is adjusted to be -30 to 30% with respect to the dry state (initial state). Is preferred. By adjusting in this way, the extent to which the blanket absorbs the solvent of the ink can be kept almost constant at a state close to the initial state at all times, preventing deterioration of the pattern shape over time, and excellent for a long time It becomes possible to demonstrate printing accuracy.

Blanket surface temperature Is maintained in the state of being raised by the heat treatment, there is a problem in that the thermal expansion of the intaglio is caused by the contact between the blanket and the intaglio in the printing process, leading to a decrease in printing accuracy. . Intaglio surface temperature Usually, it is necessary to keep the temperature change within ± 1 ℃, and the blanket surface temperature It is necessary to keep the change in a predetermined range.

A method for cooling the surface of the blanket is not particularly limited, but it is most effective to forcibly cool the surface of the printing blanket with cold air. Generally, the blanket cylinder is made of metal and has a large heat capacity. In the conventional blanket, heat transfer to the lanquet cylinder is large, and this cooling takes time.
As described above, the conductive ink composition used for offset printing is a paste in which metal powder and a resin binder are dispersed or dissolved in a solvent. As the ink composition of the PDP electrode, it is necessary to consider the printability and the blackness particularly in the case of the front electrode. Examples of the metal powder include silver, copper, gold, platinum, nickel, aluminum, iron, and palladium. These metal powders can be used alone or in combination of two or more. Moreover, it can also be used as a plating composite (for example, silver plating copper) or an alloy body. Further, as black metals, ruthenium oxide (RuO ₂ ), manganese oxide (MnO ₂ ), molybdenum oxide (MoO ₂ ), chromium oxide (Cr ₂ O ₃ ), copper oxide (CuO), titanium oxide (TiO) or oxide Black metal oxide such as palladium (PdO), Cr—Co—Mn—Fe, Cr—Cu, Cr—Cu—Mn, Mn—Fe—Cu, Cr—Co—Fe, Co—Ni—Cr—Fe, etc. The composite alloy of these is mentioned.

  Among the metal powders exemplified above, silver powder is most preferable from the viewpoints of conductivity, cost, oxidation resistance (characteristic that hardly generates an oxide having high insulating properties), and the like. The average particle size of the metal powder is preferably about 0.05 to 20 μm, more preferably about 0.1 to 10 μm, considering the printability of the conductive ink composition. The shape of the metal powder is not particularly limited, but it is more preferably a scaly shape than a spherical shape from the viewpoint of increasing the contact area of the powder and enabling a reduction in resistance. In order to close-pack the metal powder, it is also effective to use a mixture of flaky particles and spherical particles.

  The packing density of the metal powder in the conductive ink composition can suppress the volume change when the conductive pattern is baked into an electrode pattern as much as possible, and the content ratio of the metal powder in the baked electrode pattern can be achieved. From the viewpoint of increasing the amount as much as possible, it is desired that the conductive ink composition be made higher if it is within a range where the printability of the conductive ink composition can be sufficiently maintained. The amount of the metal powder added to the conductive ink composition is not particularly limited, but is preferably about 60 to 95% by weight, preferably 80 to 90% by weight based on the total amount of the conductive ink composition. More preferably, it is about%. When the addition amount of the metal powder is below the above range, there arises a problem that the packing density of the metal powder after firing does not increase and the resistance of the conductive pattern does not decrease. Conversely, if the amount of the metal powder added exceeds the above range, the binding strength of the binder resin that bonds the metal powders is weakened, and the printability of the conductive ink composition is reduced, resulting in deterioration of the printing shape and printing. There is a risk of lowering the transferability from the blanket to the glass substrate.

  Any of various resins such as a thermosetting resin, an ultraviolet curable resin, and a thermoplastic resin can be used as the binder resin constituting the conductive ink composition. Examples of the thermosetting binder resin include polyester-melamine resin, melamine resin, epoxy-melamine resin, phenol resin, polyimide resin, thermosetting acrylic resin, and the like. Examples of the ultraviolet curable binder resin include an acrylic resin. Examples of the thermoplastic binder resin include polyester resin, polyvinyl butyral resin, cellulose resin, and acrylic resin. The above exemplified resins can be used alone or in combination of two or more.

Among the resins exemplified above, a resin that is completely decomposed into carbon dioxide (CO ₂ ) and water (H ₂ O) when fired at a high temperature of 300 ° C. or higher is preferably used. Examples of such a resin include thermoplastic polyvinyl butyral resin, cellulose resin (ethyl cellulose), and acrylic resin. The amount of the binder resin added to the conductive ink composition is preferably about 0.5 to 50% by weight, and about 1 to 30% by weight, expressed as a percentage of the total amount of the conductive ink composition. Is more preferable. If the added amount of the binder resin is less than the above range, the binding power of the binder resin for bonding metal powders is weakened, and the printability of the conductive ink composition (transfer of ink from the pattern printing shape, printing blanket, etc.) May be reduced. On the contrary, when the addition amount of the binder resin exceeds the above range, there arises a problem that the electric resistance of the electrode pattern after firing cannot be lowered.

  The solvent constituting the conductive ink composition is an important factor that governs the printability in intaglio offset printing. In particular, as already mentioned, the ink solvent always comes into contact with the surface printing layer of the blanket during printing, so that the surface printing layer swells with the solvent and changes the wetting properties of its surface. In general, when the degree of swelling by the ink solvent is small, there is little change in the wettability of the surface of the blanket, and as a result, stable printing is possible.

  The solvent of the conductive ink composition is appropriately set according to the type of the surface print layer of the printing blanket used for printing the conductive pattern. The solvent used in the conductive ink composition is not limited to this, but the volume of the rubber increases when the rubber constituting the surface printing layer of the printing blanket is immersed at room temperature (23 ° C.) for 24 hours. It is preferable that the rate (swelling rate) is 20% or less, preferably 10% or less.

  Other requirements required for the solvent used in the conductive ink composition are not limited thereto, but for example, those having a boiling point of 150 ° C. or higher are preferable. When the boiling point of the solvent is lower than 150 ° C., it becomes easy to dry on a glass substrate or the like at the time of printing, and the printing characteristics may be changed. Moreover, there is a possibility that the conductive ink composition is likely to change with time. Specific examples of such solvents include alcohols (hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, bentadecanol, stearyl alcohol, seryl alcohol, cyclohexanol, terpineol, etc.), alkyl ethers, and the like. [Ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol monophenyl ether, diethylene glycol, diethylene glycol monobutyl ether (butyl carbitol), cellosolve acetate, butyl cellosolve acetate, strong lupitol acetate or butyl carbitol acetate, etc. 1 type or 2 types or more are appropriately selected in consideration of printability and workability.

  When a higher alcohol is used as the solvent, the drying property and fluidity of the ink composition may be lowered. Therefore, butyl carbitol, butyl cellosolve, ethyl carbitol, butyl cellosolve acetate, Tall acetate or the like may be used in combination. The amount of the solvent added is preferably adjusted so that the viscosity of the conductive ink composition is about 50 to 2000 poise (P), preferably about 200 to 1000 P. If the viscosity of the conductive ink composition is below the above range or exceeds the above range, in any case, the printability of the conductive ink composition may be reduced and a fine pattern may not be formed. Because there is.

As a glass substrate which forms the printing pattern by the said conductive ink composition, soda lime glass, non-alkali glass, quartz glass, low alkali glass, low expansion glass etc. are mentioned, for example.
Moreover, it is more preferable to use a glass with a high strain point (temperature) in consideration of subjecting the pattern to a step of baking the pattern at a high temperature. Specifically, the strain point is preferably 500 ° C. or higher. Therefore, it is particularly preferable to use high strain point glass (low alkali glass) among the above exemplified glasses. Specific examples of the high strain point glass include a product number “PD200” manufactured by Asahi Glass Co., Ltd. and a product number “PP8C” manufactured by Nippon Electric Glass Co., Ltd. The thickness of the substrate is appropriately set according to the heat resistance of the substrate and is not particularly limited, but the thickness is appropriately set in the range of 1 to 10 mm.

  The line width and thickness of the conductive pattern formed by printing the conductive ink composition are set according to the size of the pixel of the PDP and the like, and taking into account the amount reduced by firing. Accordingly, although not particularly limited, in general, in the case of a back substrate, the line width is set to 40 to 100 μm, preferably 50 to 70 μm. Further, the thickness of the pattern is usually set to be 3 to 30 μm, preferably 5 to 20 μm.

  On the other hand, in the case of the front substrate, the pattern of the front electrode (bus electrode) formed by the method of the present invention is required to be thinner and finer than the address electrode formed on the back electrode. Specifically, the line width is set to 20 to 70 μm, preferably 30 to 50 μm. Further, the thickness of the pattern is usually set to be 3 to 30 μm, preferably 5 to 20 μm.

  The conductive pattern printed and formed on the back substrate is further heated to 450 to 650 ° C., preferably 500 to 600 ° C., and baked. By such firing, the solvent in the conductive ink composition evaporates, and the binder resin disappears due to thermal decomposition. Thus, an electrode pattern made of metal can be obtained according to the pattern shape of the conductive pattern.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Comparative Examples 1-5
The thickness of the silicone rubber (room temperature curable addition type silicone rubber, JIS-A hardness 45, “KE1600” manufactured by Shin-Etsu Chemical Co., Ltd.) is variously changed as shown in Table 1 to form a surface rubber layer (one layer). A blanket for printing was prepared by laminating on a polyethylene terephthalate (PET) film having a thickness of 0.3 mm as a support (breaking elongation: 150%, breaking strength: 250 MPa according to JIS C2151). In producing the blanket, a method was used in which a silicone rubber containing fine ITO powder was laminated on the support by a casting method using a mold whose surface was precisely polished. The total thickness of the blanket is represented by the thickness of the lower layer rubber (300 μm) and the thickness of each upper layer silicone in Table 1, and the surface roughness of the surface printed layer is 0.1 μm in terms of 10-point average roughness (Rz).

Examples 1-4 and Comparative Examples 6-9
The surface rubber layer is made of silicone rubber (“KE1600” manufactured by Shin-Etsu Chemical Co., Ltd., JIS-A hardness 45) as the upper layer (outermost layer), and fluorosilicone rubber (“FE61” manufactured by Shin-Etsu Chemical Co., Ltd., thickness 300 μm, JIS-A). Polyethylene terephthalate (PET) film having a hardness of 25 and a volume change rate ΔV: 50% after immersion in toluene for 24 hours as a lower layer and having a thickness of 0.3 mm as a support (according to JIS C2151 A printing blanket was prepared by laminating at a degree of 150% and a breaking strength of 250 MPa. Here, the thickness of the upper silicone rubber was changed as shown in Table 2. In producing the blanket, a method was used in which a silicone rubber containing fine ITO powder was laminated on the support by a casting method using a mold whose surface was precisely polished. The surface roughness of the surface printed layer is 0.1 μm in terms of 10-point average roughness (Rz).

[Printing of PDP electrode pattern]
Using the printing blankets obtained in the above Examples and Comparative Examples, a pattern made of conductive paste ink was formed on the front panel (42 inches diagonal) of the PDP by offset printing. Here, the line width of the intaglio was 80 μm, the pitch was 360 μm, the depth was 25 μm, and the printed material was high strain point glass for PDP (“PD200” manufactured by Asahi Glass Co., Ltd.). The conductive paste ink is blended and dispersed with acrylic resin (100 parts by weight), silver powder (1600 parts by weight), glass frit (50 parts by weight) and solvent (200 parts by weight), and kneaded using three rolls. In the final stage, a solvent (butyl carbitol acetate) was added to adjust the viscosity to 250 poise (shear rate 10 s ⁻¹ ).

The offset printing was performed in the process shown in FIG. 2 according to the method described in Patent Document 2. For each printing, the surface of the blanket 10 was heated and dried by applying hot air of 100 ° C. for 20 seconds from the air outlet 25 of the heating device 25. The clean room for printing was controlled at a room temperature of 23 ° C. ± 1 ° C., and the surface temperature of the intaglio was within this temperature range. The blanket surface after drying was cooled by forcing cold air at 10 ° C. for 20 seconds from the air outlet 26a of the cold air device 26. Under this printing condition, 10,000 PDP electrode patterns were continuously printed.
[Evaluation test]
An electrode pattern offset-printed using each of the above blankets was evaluated by the following evaluation method.

Line width variation: The line widths at 10 points in the plane were measured and expressed as an average value thereof.
A: Within ± 1 μm.
○: Within ± 2 μm.
Δ: Within ± 5 μm.
X: Variation of about ± 10 μm or more.

Pinhole and disconnection: In-plane pinholes and disconnection were inspected visually.
A: No pinholes or disconnections are observed (not allowed even with inspection equipment).
○: No pinholes or disconnections are observed (1-2 points are recognized in the inspection device).
(Triangle | delta); The pinhole of 1 or 2 points | pieces and a disconnection are recognized.
X: 5 or more pinholes and disconnection are recognized.

Print shape: The shape was observed with an optical microscope of 100 times magnification, and the disorder of the edge shape was measured.
A: Edge shape is not disturbed at all. The shape is very good.
A: Edge shape disturbance amount is about 1 to 2 μm.
Δ: Edge shape disturbance amount is about 3 to 5 μm.

X: Edge shape disturbance amount exceeds 5 μm.
Printing accuracy: The amount of shift in distance between 500 mm square alignments was measured.
A: Within ± 1 μm.
○: Within ± 2 μm.
Δ: Within ± 5 μm.

X: ± 10 μm or more.
Blanket surface temperature after printing: The surface temperature was measured with a non-contact infrared thermometer.
A: Room temperature is within ± 2 ° C.
○: Within room temperature ± 5 ° C.
Δ: Room temperature within ± 8 ° C.

X: It is room temperature +/- 10 degreeC or more.
Comprehensive evaluation:
A: Shape, pinhole / disconnection, and accuracy are all equal to or higher than those of the photolithography method.
○: Good shape, pinhole / disconnection test results. Although the accuracy is a little lower than that of photolithography, there is no problem in the practical process.

Δ: There is a slight problem with the shape, pinhole / disconnection test results.
X: There is a problem as a practical process, and improvement is difficult.

The results of each evaluation test are shown in Table 1 (Comparative Examples 1 to 5) and Table 2 (Examples 1 to 4 and Comparative Examples 6 to 9).

  As a result, when printing was performed using the blankets of Examples 1 to 4, the line width variation was within ± 5 μm, and an electrode pattern having a stable film thickness and good printability could be created. This was a level with no problem in mounting the PDP panel, and a front electrode having very good conductivity could be formed. Since the amount of ink used is small, there is no problem of waste liquid as in the photolithography method, and the printing equipment is inexpensive, so the production cost can be reduced.

  The blanket for offset printing of the present invention is suitable for continuous printing with fine printability such as PDP electrode pattern with good printability, and there is no problem of waste liquid treatment compared to the photolithography method, and greatly contributes to the reduction of production cost. can do.

It is a perspective view which shows an example of the back substrate of PDP. It is explanatory drawing which shows the printing process of an electroconductive pattern.

Claims (7)

  A blanket for offset printing formed by laminating a surface rubber layer on a support layer, wherein the surface rubber layer is made of a rubber material having a good ink releasability and has a thickness of 5 to 600 μm, and a solvent-resistant rubber A blanket for offset printing, comprising two lower layers having a thickness of 100 to 800 μm made of a material.   The rubber material having good ink releasability is silicone rubber or fluorine rubber, and the rubber material having good solvent resistance is fluorosilicone rubber, urethane rubber, acrylonitrile-butadiene copolymer rubber (NBR), fluorine rubber, acrylic rubber. The blanket for offset printing according to claim 1, wherein the blanket is one kind of rubber selected from the group consisting of chloroprene rubber and two or more kinds of blend rubber.   The upper layer made of a rubber material having good ink releasability has a JIS-A hardness of 30 to 80 °, and the lower layer made of a rubber material having a good solvent resistance has a JIS-A hardness of 20 to 70 °. The blanket for offset printing according to claim 1 or 2.   The blanket for offset printing according to any one of claims 1 to 3, wherein the lower layer made of a rubber material having good solvent resistance contains low molecular weight silicone oil.   The blanket for offset printing according to claim 4, wherein the low molecular weight silicone oil is contained in a proportion of 5 to 300 parts by weight with respect to 100 parts by weight of rubber.   The support layer is composed of a synthetic resin film or a metal film having a breaking elongation of 5 to 200% and a breaking strength of 150 to 1000 MPa when measured by a method defined in JIS C2151. The blanket for offset printing in any one of Claims 1-5.   In offset printing of the electrode pattern, a step of filling a concave portion of the intaglio with a conductive ink composition in which a metal powder and a binder resin are dispersed or dissolved in a solvent, and the blanket of the conductive ink composition from the concave portion of the intaglio And a step of transferring the conductive ink composition from the surface of the blanket to the surface of the electrode substrate, and using the blanket according to any one of claims 1 to 6 as the blanket. A method for printing an electrode pattern.

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