JP2000225765A - Method and device for offset printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an offset printing method and an offset printing device thereof for continuously carrying out the offset printing of fine and minute patterns with good accuracy for a long period of time. SOLUTION: An offset printing method includes a process of holding a plate in atmosphere of a solvent contained in ink for the purpose of preventing the drying of ink remaining on the plate, and if required, includes a process of retaining at least a part of a blanket in atmosphere not containing the solvent contained in ink for the purpose of removing the solvent absorbed into the blanket.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset printing method and an offset printing apparatus suitable for printing, for example, a color pattern of a liquid crystal color filter or an electrode pattern of a plasma display.

[0002]

2. Description of the Related Art In recent years, it has been attempted to employ various printing methods as means for forming a colored pattern on a glass substrate of a liquid crystal color filter or means for forming an electrode pattern for a plasma display. One of the printing methods is offset printing.

[0003] Offset printing is a method in which ink is originally supplied onto a metal or resin rugged plate, which is once transferred to a blanket and then printed on a paper or plastic support. This method is generally used as a method for inexpensively mass printing. FIG. 1 schematically shows a general method of offset printing. As shown in FIG. 1A, a concave portion (5) formed in a predetermined ink pattern
When the blanket (3) is pressed against the intaglio (1) filled with the ink (2a) and rotated, the ink (2a) is transferred to the blanket (3). When the blanket (3) is pressed against the support (4) and rotated as shown in FIG. 1 (b), the ink (2a) transferred to the blanket (3) is transferred from the blanket (3) to paper or the like. It is sequentially transferred to the support (4), and printing is achieved.

[0004]

A coloring pattern of a liquid crystal color filter and an electrode pattern of a plasma display are generally formed on a glass substrate surface. That is, when these patterns are formed by printing, the support is a glass substrate. The transfer condition to the glass substrate is significantly different from the transfer condition to paper or plastic used for general printing, and therefore, transfer failure is likely to occur.

Further, the coloring pattern of the liquid crystal color filter and the electrode pattern of the plasma display are fine patterns, and are required to be uniform in shape, film thickness and the like. For example, when an electrode pattern of a plasma display is formed of silver paste, the width of a line forming the pattern is about 100 μm, and the maximum allowable error is ± 10 μm.

When these patterns are formed by using the conventional offset printing technique, the thickness and line width of the printed ink pattern vary greatly, and the fine and precise pattern as described above must be formed stably. Was difficult. The reasons are as follows.

[0007] The first reason is a transfer failure caused by drying of the ink remaining on the plate. In offset printing, when transferring ink from the plate to the blanket, not all the ink supplied to the plate is necessarily transferred,
Some ink remains on the plate. This is schematically shown in FIG. FIG. 1A shows that a part of the ink (2a) filled in the recess (5) of the intaglio (1) is transferred to the blanket (3) and a part remains in the recess (5). ing.

[0008] The ink remaining on the plate gradually dries during printing and increases in tackiness, so that it becomes easier to adsorb newly supplied ink. As a result, the ink newly supplied to the intaglio is not sufficiently transferred to the blanket, resulting in a decrease in printing accuracy. To deal with this problem, cleaning of the printing plate can be performed, but printing cannot be performed during cleaning of the printing plate.

[0009] The second reason is the "repelling" of ink by a blanket. The present inventors use the silicone rubber blanket with good releasability when printing the ink on the glass substrate surface, that is, when transferring the ink to the glass substrate surface, almost the entire amount of the ink on the blanket is printed on the glass substrate surface. Have already found it to be transcribed.
However, a silicone rubber blanket having good releasability inherently has a property of easily repelling ink. This property becomes more noticeable as the silicone rubber blanket absorbs the solvent contained in the ink.
Therefore, as printing continues, it becomes difficult to transfer ink from the plate to the blanket, and as a result, printing accuracy decreases. To address this problem, it is conceivable to wash the blanket with water, or to wash the blanket with a solvent compatible with the solvent contained in the ink. is not.

In view of the above problems, an object of the present invention is to provide an offset printing method and an offset printing apparatus capable of continuously performing fine pattern offset printing with good accuracy for a long time.

[0011]

In order to solve the above-mentioned problems, the offset printing method according to the present invention is characterized by including a step of holding a plate in an atmosphere of a solvent contained in ink. This step prevents or suppresses the drying of the ink remaining on the plate and thus prevents the remaining ink from becoming more sticky and adsorbing newly supplied ink. As a result, the transferability from the plate to the blanket is not deteriorated, and the ink pattern having a predetermined line width and film thickness can be repeatedly transferred to the blanket, so that stable printing can be performed for a long time.

Further, in addition to the above steps, the offset printing method of the present invention includes a step of maintaining at least a part of the blanket in an atmosphere containing no solvent contained in the ink. By this step, the solvent absorbed in the blanket can be removed, and therefore, repelling of the ink by the blanket can be suppressed. as a result,
The ink pattern of a predetermined line width and film thickness can be repeatedly transferred to the blanket without deteriorating the transferability from the plate to the blanket, and stable printing can be performed over a long period of time.

An offset printing apparatus according to the present invention is an apparatus for performing the offset printing method according to the present invention.
It is characterized by including a means for holding the plate in an atmosphere of a solvent contained in the ink. Further, in order to prevent the blanket from repelling the ink, the apparatus of the present invention is further characterized by further comprising means for holding at least a part of the blanket in an atmosphere containing no solvent contained in the ink.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an offset printing method of the present invention will be described in detail with reference to the drawings together with an offset printing apparatus of the present invention for carrying out the method.

[0015] The offset printing method of the present invention includes a step of holding the plate in an atmosphere of a solvent contained in the ink. In the present invention, an ink is a substance to be transferred to a support by printing, and a substance (for example, silver powder) that forms a predetermined pattern on the support and a solvent (for example, butyl carbitol acetate) that disperses or dissolves the substance. Means. “Holding the plate in the atmosphere of the solvent contained in the ink” means that the plate is placed in a gas containing solvent vapor, preferably containing a large amount, more preferably containing a saturated state (eg, air, nitrogen gas, etc.). Or placing the plate in an environment where a mist-like solvent is present, such as by placing a gaseous or droplet-like solvent around the plate. This step is effective for preventing drying of the ink.

In the present invention, it is desirable to supply the ink to the plate surface in the step of holding the plate in an atmosphere of a solvent contained in the ink. That is, it is preferable to supply the ink to the plate surface in an atmosphere of a solvent contained in the ink. An example of this embodiment is shown in FIG.

FIG. 2A shows a box-shaped housing (7).
The intaglio (1) is held in the doctor blade (6)
FIG. 4 is a diagram schematically showing a state in which ink (2a) is filled in a concave portion (5) forming an ink pattern.
FIG. 2B is a schematic view showing how the intaglio (1) supplied with the ink (2a) is taken out of the housing (7) in order to perform the next step or operation, for example, transfer of the ink to a blanket. Is shown.

The housing (7) is in a closed state or a state close to the closed state. By introducing a gas containing a vapor of a solvent contained in the ink or a mist-like solvent into the housing (7), the housing (7) is filled with the ink. The plate can be kept in the atmosphere of the contained solvent. As a method of introducing the vapor of the solvent contained in the ink into the housing (7), for example, there is a method of placing cloth or paper impregnated with the solvent in the housing. This method is particularly effective when the volatility of the solvent is high. According to this method, the housing can be easily filled with the vapor of the solvent.
Alternatively, a gas (for example, air) is blown into the container containing the solvent and bubbled to contain the vapor of the solvent in the gas, which is then introduced into the housing (7) by a suitable introduction means (not shown) such as a nozzle. There is a way to send to. Further, a mist-like solvent generated by spraying or the like may be sent into the housing. In this case, it is preferable that the atomizing nozzle is located in the housing.

When two or more solvents are contained in the ink, the plate is held in an atmosphere in which the solvents are mixed, that is, in an atmosphere containing the vapor of the mixed solvent. Therefore,
In the embodiment shown in FIG. 2A, for example, a cloth impregnated with a mixed solvent composed of each solvent contained in the ink is used, or air is blown into the mixed solvent to bubble, After air is separately blown into the air and bubbled, it is necessary to mix the air containing the vapor of each solvent inside or outside the housing.

The other components shown in FIG. 2 are conventional components, and the supply of the ink (2a) to the intaglio (1) can also be carried out in a conventional manner. For example, the intaglio plate (1) used in the embodiment shown in FIG. 2 is a plate in which an ink pattern is formed by concave portions (5). For example, an intaglio plate (1) used for forming a coloring pattern of a liquid crystal filter or an electrode pattern of a plasma display can be obtained by performing a photoetching process on a glass plate or a metal plate to form a concave portion (5). Of course, in place of the intaglio plate (1), another plate commonly used in offset printing, for example, a lithographic plate or a relief plate may be used.

As the ink (2a), any kind of ink can be used as long as it is an ink used in a usual offset printing method. Generally, the ink contains an inorganic powder and / or an organic powder as a pigment, stabilizes the dispersion of the powder, contains a resin for holding the powder when dried, and a solvent for dispersing the pigment and the like. It also contains additives such as thickeners, plasticizers, surfactants, defoamers or antioxidants.

For example, when a conductive pattern such as an electrode pattern of a plasma display is formed by offset printing, silver fine particles are used as a main component, ethyl cellulose or acrylic resin is used as a resin, and butyl carbitol acetate is used as a solvent. What is called “silver paste” is used as ink. Generally, this silver paste is dried and sintered after printing. However, depending on the type of additive, some silver paste does not require sintering. When an insulating pattern is formed, a paste containing an insulating material is used as ink.

When a colored pattern of a liquid crystal color filter is formed, an ink containing a pigment or dye as a coloring material, an epoxy resin or an acrylic resin as a resin, and butyl carbitol acetate as a solvent is used as an ink. In general, after printing red, green, and blue inks respectively, drying and curing are performed to obtain a colored pattern.

In the conventional offset printing method, a solvent having a high boiling point and a low vapor pressure, such as butyl carbitol or butyl carbitol acetate, is used as a solvent for the ink in order to prevent drying of the ink. Was common. However, according to the method of the present invention, drying of the ink can be effectively prevented irrespective of the type of the solvent. And methyl ethyl ketone and the like can be used as a solvent for the ink.

The supply of the ink (2a) to the intaglio (1) can be carried out in a conventional manner. In FIG. 1, after the ink is supplied to the entire surface of the intaglio (1) to fill the recess (5) with the ink, the doctor blade (6) removes the ink except for the recess (5). (2
a) is being scraped. It is desirable to adopt an appropriate ink supply method according to the type of plate.

In the offset printing method, the specific mode of the step of holding the plate in the atmosphere of the solvent contained in the ink has been described. In the step of holding the plate in the atmosphere of the solvent contained in the ink, A step other than the step of supplying the plate surface to the ink may be included. In addition, the step of holding the plate in the atmosphere of the solvent contained in the ink preferably occupies as long a time as possible in all the steps of the offset printing, and all steps or operations except for the step of transferring the ink from the plate to the blanket are performed. Is most preferably carried out in a step of holding the plate in an atmosphere of a solvent.

The offset printing method of the present invention preferably includes, in addition to or instead of the above steps, a step of maintaining at least a part of the blanket in an atmosphere containing no solvent contained in the ink. By keeping at least part of the blanket in an atmosphere that does not contain the solvent contained in the ink, the solvent adhering to the blanket evaporates into the atmosphere and the solvent absorbed in the blanket oozes out to the surface. This step is effective as a method for removing the solvent from the blanket because it is easily evaporated. Therefore, according to this step, the "repelling" of the ink on the blanket surface due to the solvent present in the blanket is reduced, and transfer failure from the plate to the blanket can be suppressed.

In the step of maintaining at least a part of the blanket in an atmosphere containing no solvent contained in the ink, it is particularly desirable to blow an airflow containing no solvent contained in the ink onto the blanket surface on which the ink has not been transferred. . An example of the embodiment is shown in FIG.

In FIG. 3, an air stream (8) containing no solvent contained in the ink is blown from a nozzle (9) onto a rotating blanket (3). By blowing the airflow (8) onto the surface of the blanket (3), the evaporation and leaching of the solvent present in the blanket (3) is promoted, and the evaporated solvent is exhausted together with the airflow (8), and in some cases condensed by cooling or the like. And collect.

The air current (8) is sprayed while the ink is not transferred to the blanket (3) surface.
Is carried out so that Therefore, it is preferable that the blowing of the air current (8) is performed after the transfer of the ink from the blanket (3) to the support is completed and before the ink is next transferred to the blanket (3). The solvent can be efficiently removed from the blanket (3) by appropriately adjusting the flow rate and the temperature of the airflow (8).

When the solvent contained in the ink is a solvent having a low boiling point and a high vapor pressure, or a mixed solvent containing such a solvent, the solvent can be efficiently removed from the blanket (3). . As described above, the use of a solvent having a low boiling point and a high vapor pressure can be achieved by adopting a step of holding the plate in an atmosphere of a solvent contained in the ink.

The offset printing method including the step of maintaining at least a part of the blanket in an atmosphere containing no solvent contained in the ink is particularly suitable for the offset printing method using a silicone rubber blanket which easily absorbs the solvent.

[0033]

As described above, according to the offset printing method and the offset printing apparatus of the present invention, drying of the ink on the plate is prevented, and the ink is repelled by the influence of the solvent absorbed in the blanket. Is reduced, the ink can be transferred from the plate to the blanket with high accuracy. Therefore, according to the method and apparatus of the present invention, it is possible to continuously perform printing even on a substrate that is difficult to print, such as a glass substrate, while keeping the line width and film thickness of the printed ink constant. It becomes possible.

Therefore, the offset printing method of the present invention can be used in fields requiring precise and stable printing, such as forming a color pattern of a liquid crystal color filter, forming an electrode pattern of a plasma display, a printed circuit board, a thin film hybrid IC, and the like. It can be applied to the formation of ultra-high-definition resists for ICs and IC packages, etc., and the formation of conductors in modules, and can also be applied to ultra-compact device materials and electrode materials. Of course, the method of the present invention can be applied to general offset printing performed on paper, plastic, or the like, and in this case, there is an effect that stable printing can be performed for a long time.

[Brief description of the drawings]

FIG. 1A is a view schematically showing a state in which ink is transferred to a blanket in offset printing, and FIG. 1B is a view schematically showing a state in which ink is transferred from a blanket to a support. FIG.

FIGS. 2A and 2B are diagrams schematically showing a process of supplying ink to a plate in an atmosphere of a solvent contained in the ink.

FIG. 3 is a view schematically showing a step of blowing an airflow containing no solvent contained in the ink onto a blanket.

[Explanation of symbols]

1 ... intaglio, 2a ... ink, 3 ... blanket, 4 ...
Support (glass substrate), 5 recess, 6 doctor blade, 7 housing, 8 airflow, 9 nozzle.

Claims (14)

[Claims] 1. An offset printing method comprising the step of holding a plate in an atmosphere of a solvent contained in ink. 2. An offset printing method comprising the steps of: holding a plate in an atmosphere of a solvent contained in ink; and holding at least a part of a blanket in an atmosphere containing no solvent contained in the ink. Method. 3. The method according to claim 2, wherein in the step of holding at least a part of the blanket in an atmosphere containing no solvent contained in the ink, an air stream containing no solvent contained in the ink is blown onto the blanket surface on which the ink has not been transferred. Offset printing method. 4. The offset printing method according to claim 1, wherein in the step of holding the plate in an atmosphere of a solvent contained in the ink, the ink is supplied to the plate surface. 5. The offset printing method according to claim 2, wherein the blanket is a silicone rubber blanket. 6. The offset printing method according to claim 1, which is performed for printing an electrode pattern on a glass substrate. 7. An offset printing apparatus comprising means for holding a plate in an atmosphere of a solvent contained in ink. 8. An offset printing method comprising: means for holding a plate in an atmosphere of a solvent contained in ink; and means for holding at least a part of a blanket in an atmosphere not containing a solvent contained in ink. apparatus. 9. A means for holding at least a part of a blanket in an atmosphere containing no solvent contained in the ink, wherein the means for blowing a stream containing no solvent contained in the ink to be used onto the blanket surface on which the ink has not been transferred. The offset printing apparatus according to claim 8, wherein 10. A means for holding the plate in an atmosphere of a solvent contained in the ink, comprising: a) a housing having means for supplying the ink to the plate and the plate surface; and b) a gas containing the solvent contained in the ink. The offset printing apparatus according to any one of claims 7 to 9, further comprising a unit for introducing the inside of the housing. 11. The offset printing apparatus according to claim 8, wherein the blanket is a silicone rubber blanket. 12. The offset printing apparatus according to claim 7, which prints an electrode pattern on a glass substrate. 13. A method for manufacturing a liquid crystal color filter, comprising a step of forming a colored pattern on a substrate by the offset printing method according to claim 1. Description: 14. A method for manufacturing a plasma display, comprising the step of forming an electrode pattern on a substrate by the offset printing method according to claim 1. Description: