JP2005138324A - Offset printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an offset printing method by which printing precision can be maintained for a long time and the life of a printing blanket can be prolonged. <P>SOLUTION: In this offset printing method, a transition process for transiting printing ink by rolling the printing blanket 13 fitted to a blanket cylinder 12 over the surface of a printing plate 10; and a transfer process for transferring an ink pattern by rolling the printing blanket 13 over the surface of an object 14 to which the ink pattern is transferred are provided. The printing blanket 13 is moved in an axial direction (x) after performing the transition process and the transfer process a specified number of times. Further, when a printing process is again performed following the deviation of a position of the printing blanket 13 relative to the printing plate 10, it is possible to inhibit the generation of a change in the surface shape of the printing blanket 13, its surface roughness, the content of a low-molecular siloxane and the like. Consequently, the life of the printing blanket 13 can be prolonged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printing method based on an offset printing method, and more particularly to an offset printing method suitable for printing using a printing ink containing a solvent that penetrates a printing blanket.

In recent years, so-called flat panel displays such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display (PDP), etc. have been used for display devices such as color televisions and computer displays instead of cathode ray tubes (CRT). ing.
In this flat panel display, for example, a striped electrode pattern is mainly formed on a transparent substrate such as glass, such as a front substrate (front substrate) for PDP, a rear substrate (rear substrate), and an electrode substrate for EL display. In such an electrode substrate, an extremely fine stripe pattern having a line width of about 10 to 200 μm is formed on the order of 0.1 to 10 μm using an ink containing a conductive substance. It is required to form with the thickness of. In LCD, a member called a color filter is formed by forming three types of stripe patterns of R (red), G (green), and B (blue) on a transparent substrate such as glass or a light-shielding pattern with high blackness. This color filter is also required to form a fine and thick film pattern similar to that of the electrode substrate.

  Conventionally, photolithography is mainly adopted as a method for forming a fine and thick film pattern with high accuracy, but the process is complicated, and materials and manufacturing equipment necessary for pattern formation are expensive. There is a problem that the manufacturing cost becomes extremely high. In addition, the cost for processing harmful waste liquid generated by development processing and the like is high, and the waste liquid also has environmental problems. Moreover, in order to form a large electrode substrate by photolithography, it is necessary to increase the size of the exposure apparatus and development etching apparatus, which is extremely disadvantageous in terms of cost, so it is difficult to cope with the recent increase in size of displays. There is also.

  Therefore, research has been conducted on a method of forming a pattern at a low cost without causing harmful waste liquid, and the thickness of the ink pattern to be printed can be freely controlled by the depth of the recess, and several An intaglio offset printing method capable of forming a fine line pattern with a width of 10 to several hundred μm has attracted attention as an alternative to photolithography. In particular, according to the intaglio offset printing method using a blanket (silicone blanket) whose surface rubber is made of silicone rubber, the ink can be transferred almost 100% from the blanket to the substrate to be transferred. It is possible to accurately reproduce and reproduce a simple pattern.

However, even when a silicon blanket is used and an electrode pattern or the like is formed by intaglio offset printing, repeating the printing process may cause problems such as deterioration of the pattern shape and printing accuracy. Has been pointed out.
One of the causes of such problems is that the printing ink solvent gradually permeates to swell the silicone blanket. Therefore, the present inventors previously performed a process of transferring an ink pattern on a printing blanket onto a transfer target as a method for manufacturing an electrode substrate for PDP employing an intaglio offset printing method, and then printing. A method is proposed in which a heating / drying process such as spraying hot air is performed on the surface of a blanket for cooling and a cooling process such as spraying cold air is performed. According to such a printing method, a simple method such as jetting of warm air or cold air can be used, and without interrupting the flow of a series of printing steps for transferring and transferring ink from the intaglio to the transfer medium via a printing blanket. The problem that the printing blanket is swollen by the solvent of the ink can be solved and prevented (Patent Document 1).

However, when the number of printing processes increases, the surface shape or surface roughness of the silicone blanket changes, or the content of low molecular siloxane in the silicone blanket changes. However, it cannot be solved. If there is a problem such as a decrease in printing accuracy due to changes in the surface shape or surface roughness of the silicone blanket or changes in the content of low molecular siloxane, the silicone blanket is discarded. Although it is necessary to replace the blanket, it is extremely important to extend the life of one blanket as much as possible in consideration of the time and effort required for replacing the blanket and the cost of the blanket itself.
JP 2002-245931 (paragraph [0011], FIG. 2)

  An object of the present invention is to provide an offset printing method capable of maintaining printing accuracy over a long period of time and extending the life of a printing blanket.

In order to achieve the above object, an offset printing method according to the present invention comprises:
A printing blanket mounted on the blanket cylinder rolls on the surface of the printing plate to transfer printing ink from the printing plate to the surface of the printing blanket, and the printing blanket is placed on the surface of the transfer object. A transfer step of rolling and transferring the ink pattern on the printing blanket to the surface of the transfer object, and an offset printing method comprising:
The printing blanket is moved in the axial direction after the transfer step and the transfer step are performed a predetermined number of times.

  As described above, a transfer step of transferring printing ink from a printing plate such as an intaglio to the surface of a printing blanket such as a silicone blanket, and a transfer blanket such as a glass substrate from a printing blanket that carries an ink pattern on the surface. After a series of printing steps including a transfer step for transferring the ink pattern to the surface is repeated a predetermined number of times, the printing blanket is moved in the axial direction by a predetermined amount to position the printing blanket relative to the printing plate. When shifted, it is possible to suppress changes in the surface shape, surface roughness, low molecular siloxane content, etc. of the printing blanket when the printing process is performed again. The lifetime of the blanket can be extended.

  The phenomenon that the printing blanket is swollen by the solvent of the ink mainly occurs around the ink pattern transferred to the surface of the printing blanket. If the print pattern is a stripe pattern, from the viewpoint of pattern printing accuracy (the shape of the transferred pattern, the accuracy of the printing position, etc.), the direction along the line of the pattern as much as possible is the rotational direction of the printing blanket. In such a case, the stripe pattern is repeatedly transferred to the same position on the surface of the printing blanket, so that the surface of the printing blanket swells in a streak shape. become. As a result, there arises a problem that the printing blanket is deteriorated at an early stage due to the swollen streaks.

  On the other hand, when printing is performed according to the method of the present invention, when the printing process is repeated a predetermined number of times, a process for shifting the position of the printing plate and the printing blanket in the axial direction of the blanket is performed. Each time this treatment is performed, the transfer position of the ink pattern on the printing blanket surface is different. Therefore, although the surface shape, surface roughness, low molecular siloxane content, etc. of the printing blanket change as the ink solvent penetrates and swells, such a phenomenon may occur in a part of the printing blanket. Rather, it will be distributed throughout the printing blanket. Therefore, the lifetime of the printing blanket as a whole can be extended by employing the offset printing method according to the present invention.

(Print pattern shape)
The offset printing method of the present invention is particularly preferably used for printing and forming a stripe pattern in which patterns are regularly arranged. However, the shape of the print pattern to which the method of the present invention can be applied is not limited to the above-described stripe pattern. For example, the stripe pattern has several line widths, and the line width and the pattern pitch are irregular. A stripe pattern, a lattice pattern (matrix pattern), or the like may be used. Even when these patterns are printed and formed, the surface shape and surface roughness of the printing blanket can be adjusted as the ink solvent penetrates and swells by appropriately adjusting the amount of displacement between the printing plate and the printing blanket. Further, it is possible to appropriately disperse a portion where the low molecular siloxane content and the like are changed, and to obtain the operation and effect of the present invention that extends the life of the entire printing blanket.

  As described above, the offset printing method of the present invention is particularly suitable for the formation of a stripe pattern in which the patterns are regularly aligned. It is preferable that the distance between one end of adjacent patterns including the pattern itself is twice or more larger than the maximum line width of the pattern. In this case, by moving the printing blanket in the axial direction, it is possible to set the ink pattern transfer position so as not to cause an overlapping portion, so that the functions and effects of the present invention can be exhibited more reliably. If the stripe pattern pitch is twice or more larger than the maximum line width of the pattern, the printing blanket is set by setting the movement amount of the printing blanket at least equal to or greater than the maximum line width of the pattern. It is possible to set so that the transfer pattern of the ink pattern on the surface of the ink does not overlap.

(Print blanket moving process)
In the offset printing method of the present invention, after executing a series of printing steps including the transfer step and the transfer step a predetermined number of times, the printing blanket is moved in the axial direction, and the series of printing steps is performed again. Execute. Here, the frequency of moving the printing blanket is set according to the degree to which the printing blanket swells with the solvent of the printing ink. Specifically, the frequency with which the printing blanket is moved is appropriately set according to the type of surface rubber of the printing blanket, the type of solvent of the printing ink to be used, and the like.

Therefore, in the present invention, the frequency of movement of the printing blanket is not particularly limited, but generally, a silicone blanket is used as a printing blanket, and an alcohol that is relatively difficult to swell the silicone blanket as a solvent for printing ink. [A higher alcohol represented by the formula C _n H _{2n + 1} OH (n is 6 or more, liquid at room temperature); for example, hexanol, stearyl alcohol, terpineol, etc.], alkyl ethers [for example, ethylene glycol monobutyl ether ( Butyl cellosolve), ethylene glycol monophenyl ether, diethylene glycol monobutyl ether (butyl carbitol), and the like], and mixtures thereof are preferably printed each time the printing process is repeated about 50 to 5000 times. The extent to time a repeat of about 100 to 2000 times, may be carried out the movement of the printing blanket.

  In the present invention, the amount of movement of the printing blanket is set according to the shape of the pattern to be printed. When the pattern to be printed is a stripe pattern that is regularly arranged, as described above, the movement amount of the printing blanket is set to at least the maximum line width of the pattern (more specifically, the maximum line of the pattern). It may be set in the range from the width to the minimum pitch. When printing other patterns, the amount of movement of the blanket may be appropriately set so that the transfer position of the ink pattern on the printing blanket surface is not biased at the same position.

(Method of printing method)
The offset printing method of the present invention is preferably applied to a printing method in which the film thickness of the ink pattern transferred and formed in one printing step is large (the ink amount is large). If the amount of ink transferred to the printing blanket at one time is large, the amount of ink solvent that penetrates the blanket is also large, so changes in the surface shape etc. tend to increase as the blanket swells. This is because, by applying the offset printing method of the present invention, the effect unique to the present invention of suppressing the deterioration phenomenon of the printing blanket caused by the change in the surface shape or the like can be exhibited more remarkably. .

Therefore, the offset printing method of the present invention is applied to a printing method (intaglio offset printing method) using an intaglio as a printing plate that can transfer and form an ink pattern having a large film thickness in a single printing process. Is particularly preferred.
(Printed version)
When the present invention is applied to the intaglio offset printing method, the type of printing plate to be used is not particularly limited, and various conventionally known intaglio plates can be employed. In addition, in order to produce an intaglio at low cost, it is preferable to use a metal or glass as the intaglio substrate and form a concave pattern by etching.

Soda lime glass, alkali glass, and non-alkali glass can be used as the glass as the intaglio substrate. Of these glasses, non-alkali glass is very expensive, although it can achieve very high dimensional accuracy. Therefore, soda lime glass or alkali glass is sufficient depending on the degree of printing accuracy required.
From the viewpoint of the cost of the intaglio and the durability of the plate surface (hardness to scratch, abrasion resistance, etc.), it is preferable to use a metal intaglio. Specific materials include 42 alloy and stainless steel. A metal intaglio with hard chrome plating on the surface is extremely excellent in terms of durability.

(Print blanket)
In the offset printing method of the present invention, the printing blanket to be used is not particularly limited. However, in order to improve the pattern printing accuracy (pattern shape and printing position accuracy), the ink pattern separation is not necessary. In order to improve moldability, it is preferable to use a blanket using a rubber having a low surface energy. From this point of view, it is preferable to employ a printing blanket that uses silicone rubber as the surface rubber (silicone blanket).

  If the rubber hardness of the surface rubber of the printing blanket is too high, the surface of the blanket may not be sufficiently deformed during the transfer of ink from the printing plate and the transfer of the ink pattern to the transferred material. Cause deterioration of sex. On the contrary, if the rubber hardness of the surface is too low, the blanket surface may be greatly deformed during transfer and transfer, which causes a decrease in printing accuracy. The rubber hardness of the printing blanket is preferably 20 to 70 in terms of JIS A hardness, and more preferably 30 to 60.

  The surface shape of the printing blanket has a great influence on the printing accuracy (particularly the shape of the pattern) as the printing pattern becomes finer. Generally, the surface roughness of the printing blanket is preferably as small as possible. For example, when a fine pattern having a line width of about 20 μm is formed, the surface roughness (10-point average roughness) is preferably 1.0 μm or less, More preferably, it is 0.5 μm or less.

The thickness of the surface rubber of the printing blanket is not particularly limited, but generally, when the surface rubber is thicker than 1.5 mm, the deformation of the rubber becomes large and the printing accuracy may be lowered.
(Printing ink)
In the offset printing method of the present invention, the printing ink to be used is not particularly limited, and may be appropriately selected from conventionally known various printing inks in consideration of characteristics such as printability. The printing ink is prepared by blending an appropriate amount of conductive powder, pigment, etc., if necessary, in addition to a resin and a solvent, and mixing and stirring them with a three roll or the like.

  In addition, since the solvent of printing ink is an important factor governing the printability of offset printing, it is necessary to select it in consideration of the degree of swelling with respect to the printing blanket and the effect on the wettability of the blanket surface. . In general, by using a solvent with less swelling with respect to the printing blanket, the change in the wetting property of the surface of the blanket can be reduced, and stable printing can be realized. On the other hand, considering the ink acceptability of the printing blanket, it is preferable to select a solvent that slightly swells the blanket. In the case of performing continuous printing, it is particularly preferable to use a solvent with less swelling. This is because in continuous printing, the change in surface wettability tends to increase as the printing blanket swells. If the change in the surface wettability becomes large, the line width of the printing pattern widens, the fine stains on the printing plate surface are transferred to the blanket surface, and the transferability to the transfer medium is reduced. As a result, stable printing becomes difficult.

  Various resins such as a thermosetting resin, an ultraviolet curable resin, and a thermoplastic resin can be used as the resin forming the printing ink. Examples of the thermosetting resin include polyester-melamine resin, melamine resin, epoxy-melamine resin, phenol resin, polyimide resin, and acrylic resin. Examples of the ultraviolet curable resin include acrylic resins. Examples of the thermoplastic resin include polyester resin, polyvinyl butyral resin, cellulose resin, acrylic resin, and the like. These resins may be used alone or in combination of two or more according to the desired printability.

  When a silicone blanket is used as a printing blanket, it is preferable to add silicone oil to the printing ink. The low molecular weight silicone oil component contained in the silicone rubber blanket is extracted by contact with the printing ink, and its content decreases with time. By including silicone oil in the printing ink, the blanket This is because it is possible to suppress or prevent the silicone oil component from being extracted from the inside, or to supply the silicone oil component to the inside of the blanket. When the content of the silicone oil component in the silicone blanket decreases, problems such as variations in the line width of the printed pattern occur. By using printing ink that contains the silicone oil component, this problem can be prevented. Can be prevented.

In this case, the amount of silicone oil added to the printing ink is 3 to 50 parts by weight, preferably 5 to 30 parts by weight with respect to 100 parts by weight of the resin content of the ink. When the blending amount of the silicone oil is below the above range, a sufficient effect cannot be obtained. On the contrary, even if silicone oil is blended exceeding the above range, the effect is not changed, which is disadvantageous in terms of cost.
The silicone oil added to the printing ink is not particularly limited, and various modified silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, and the like can be employed.

(Transfer material)
The transfer object used in the present invention is not particularly limited, and may be appropriately selected from the base materials used in the product depending on the product to be manufactured. When an electrode substrate for a plasma display panel (PDP) is formed using the offset printing method of the present invention, soda lime glass, low alkali glass, non-alkali glass, quartz glass, or the like is used as a transfer target. Use it. In the case of forming a pattern for other uses, in addition to the glass exemplified above, a resin film such as a polyethylene terephthalate (PET) film, an imide film, and a polycarbonate film; a metal film; a ceramic, and the like are also applicable.

(Specific Embodiment of the Present Invention)
Next, an offset printing method according to the present invention will be described with reference to FIGS.
In the offset printing method according to the present invention, first, the printing blanket 13 mounted on the blanket cylinder 12 is rotated and rolled on the surface of the printing plate (for example, intaglio) 10 to thereby carry the ink on the printing plate. The ink filled in the part (in the case of an intaglio plate, the concave part) 11 is transferred to the surface of the printing blanket 13 (transfer process). Next, the printing blanket 13 carrying an ink pattern (not shown) on the surface is moved onto the transfer body 14 and rotated on the surface of the transfer body 14 while rotating, thereby printing. The ink pattern is transferred from the blanket 13 to the transfer target 14 (transfer process). When the transfer process and the transfer process are repeated a predetermined number of times, the printing blanket 13 is moved by a predetermined amount in the axial direction (direction x indicated by a white arrow in the figure) and then the process proceeds to a new transfer process and transfer process. To do. In FIG. 1, the blanket cylinder 12 ′ and the printing blanket 13 ′ indicated by dotted lines both indicate a state after moving in the axial direction x.

  By performing printing as shown in FIG. 1, the phenomenon that the surface shape, surface roughness, low molecular siloxane content, etc. of the printing blanket 13 change as the ink solvent penetrates and swells is the printing blanket. It is possible to suppress or prevent the occurrence of bias in a partial region of 13. Therefore, deterioration of the printing blanket 13 can be suppressed and its life can be extended.

In the offset printing method of the present invention, it is preferable to perform a process of drying the surface of the printing blanket after the transfer step and the transfer step.
The printing blanket is preferably dried by heating. For example, various methods such as injection of warm air, irradiation with infrared rays, and heating by a heater disposed inside or on the back surface of the printing blanket can be employed. Among these, it is preferable to perform the jetting of warm air and the irradiation of infrared rays from the viewpoint of heating / drying efficiency and handling property of the heating equipment. Heating is preferably performed every time a printing process is completed.

After the printing blanket is heated and dried, it is preferable to perform a treatment for cooling the surface of the printing blanket. Various methods can be employed for cooling the printing blanket, such as spraying cold air or contacting a low temperature roller or a roller made of a material having excellent thermal conductivity such as metal.
The drying and cooling treatment of the blanket is preferably performed when the printing blanket is moved between the printing plate and the transfer medium from the viewpoint of the work efficiency of the printing process.

Next, the present invention will be described with reference to examples and comparative examples in which a back electrode pattern of a plasma display panel (PDP) is formed by employing the offset printing method of the present invention.
[Back electrode pattern printing]
The back electrode pattern was printed by intaglio offset printing.
The printing ink used was a mixture of 2000 parts by weight of silver powder, 10 parts by weight of glass frit, and 100 parts by weight of butyl carbitol as a solvent with respect to 100 parts by weight of acrylic resin.

As the printing plate, an intaglio plate having stripe pattern-like recesses (total 1000) formed by etching was used. The recesses (pattern) were set to have an opening width of 180 μm, a depth of 30 μm, a pitch of 540 μm, and a total length of 400 mm.
As the printing blanket, a surface rubber layer having a thickness of 0.6 mm of silicone (JIS A hardness 40) was used. The surface rubber layer of this silicone blanket was prepared by applying a two-component RTV silicone rubber on a PET film (support) having a thickness of 0.35 mm and then curing it while smoothing by self-leveling.

A soda-lime glass plate having a thickness of 1.5 mm and a length and a width of 500 mm was used as the transfer object.
Printing was performed in an environment of a room temperature of 23 ° C. and a humidity of 55% RH. During the transfer process of the silicone blanket from the printing plate, the ink transfer speed was set to 15 mm / s, and the nip width of the silicone blanket was adjusted to 12 mm. During the transfer process from the silicone blanket to the transfer medium, the ink pattern transfer speed was set to 200 mm / s, and the nip width of the silicone blanket was adjusted to 12 mm.

In Example 1, after finishing the printing process for 250 sheets to be transferred (soda lime glass) under the above conditions, the position of the silicone blanket (printing blanket) was shifted by 180 μm in the axial direction, and again, A printing process for 250 sheets to be transferred was performed.
On the other hand, in Comparative Example 1, 500 sheets to be transferred (soda lime glass) were continuously printed under the above conditions. That is, the process of shifting the positions of the silicone blanket (printing blanket) and the intaglio (printing plate) was not performed.

Under the above printing conditions, a back electrode pattern is printed on a total of 500 transferred bodies (soda lime glass), and the printed back electrode pattern is heated at 100 ° C. for 30 minutes to be dried. It was.
[Performance evaluation]
(1) Allowable number of line width changes For each of Example 1 and Comparative Example 1, the transfer target on which the back electrode was formed was sampled every time the number of printing processes was 10 times.

About the collected sample, the printed pattern was observed with a laser microscope, and the line width of the pattern was measured at a total of 15 measurement locations in the printed surface. The average value of the obtained raw data was used as line width data, and the number of printed sheets when the line width change amount exceeded 20 μm was obtained.
(2) Evaluation of print shape The print pattern of the 500th sample was observed with a microscope to comprehensively judge the linearity of the print pattern.

(3) Evaluation of printing position accuracy With respect to the 500th sample, the printing pattern is observed with a precision two-dimensional coordinate measuring machine, and the quality of printing accuracy is judged based on the deviation between the position of the printing pattern and the alignment position. did. When forming the back electrode pattern for PDP, the printing accuracy is required to be within ± 20 μm.

  The above evaluation results are shown in Table 1.

  As shown in Table 1, a series of printing processes including an ink transfer process from an intaglio (printing plate) to a silicone blanket (printing blanket) and an ink pattern transfer process from the silicone blanket to a transfer medium. In Example 1 in which the silicone blanket was moved in its axial direction and again subjected to the printing process after repeated execution, the line width change amount was larger than that in Comparative Example 1 in which the silicone blanket was not moved in the axial direction. Significant differences occurred.

  From the measurement result of the performance evaluation (1), in Comparative Example 1, by repeating the printing process 270 times (when 270 sheets have been printed), the line is not suitable for practical use as a back electrode pattern for PDP. It was found that a width change occurred (that is, the line width change amount exceeded 20 μm). It was also found that when the ink pattern was transferred repeatedly about 300 times in the same part of the silicone blanket, the degree of swelling of the silicone blanket and the accompanying deterioration became significant.

  On the other hand, in Example 1, when the printing process was repeated 250 times (when 250 sheets were printed), the position of the silicone blanket was shifted in the axial direction, so that the printing accuracy due to the swelling of the blanket No problems such as lowering were observed. Moreover, the lifetime of the blanket was able to be extended about 1.5 to 2 times by giving the process which shifts the position of a silicone blanket to the axial direction.

  In addition, since the pattern printed and formed in Example 1 has a line width of 180 μm and a pitch of 540 μm, if setting is made so that there is no duplication in the transfer position of the ink pattern on the silicone blanket, The process of shifting the position in the axial direction can be performed twice. Therefore, it is estimated that the lifetime of the blanket can be extended to about 2 to 3.5 times finally.

  The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.

It is explanatory drawing which shows one Embodiment of the offset printing method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printing plate 12 Blanket cylinder 13 Blanket for printing 14 Transfer object

Claims (1)

A printing blanket mounted on the blanket cylinder rolls on the surface of the printing plate to transfer printing ink from the printing plate to the surface of the printing blanket, and the printing blanket is transferred to the surface of the transfer target. A transfer step of rolling and transferring the ink pattern on the printing blanket to the surface of the transfer object, and an offset printing method comprising:
An offset printing method, wherein the printing blanket is moved in the axial direction after the transfer step and the transfer step are executed a predetermined number of times.

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