JPS6143596A - Offset blanket for printing - Google Patents

Abstract

PURPOSE:To enable a ultrafine pattern for a printed board with a line DIA. of 60mum or below to printed and markedly enhance working efficiency, by constituting a surface printing layer of a flexible elastic layer of an oil-resistant elastic material with a JIS hardness of 20-40, the surface thereof being substantially smooth, namely, having a 10-point average roughness of 2mum or below. CONSTITUTION:The offset blanket for printing comprises a surface printing layer provided on a single of a plurality of support layer, with or without a porous compressible layer therebetween, in which the surface printing layer consists of a lexible elastic layer of an oil-resistant elastic material with a JIS hardness of 20-40, the surface of which is substantially smooth, namely, it has a 10-point average roughness of 2mum or below. An example of formulation for the surface printing layer comprises 100pts.wt. of acrylonitrile-butadiene copolymer rubber (NBR), 5.0pts.wt. of zinc oxide, 1.0pts.wt. of stearic acid, 40.0pts.wt. of hydrous silicic acid, 40.0pts.wt. of DOA, 0.5pts.wt. of TS as a vulcanization accelerator, 1.0pts.wt. of DM as a vulcanization accelerator and 3.0pts.wt. of sulfur, and after valcanization, it shows a JIS hardness of 40 and a surface roughness (10-point average value) of 0.9mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Scope of Application of the Invention] The present invention relates to an offset blanket for printing, particularly an offset blanket suitable for printing patterns for printed wiring boards.

[Traditional technique]

BACKGROUND ART Conventionally, printing of patterns for printed wiring boards such as integrated circuits has generally been carried out by a dry film method or a screen printing method because it is necessary to draw a pattern with a line width of several tens to several hundreds of μm.

Screen printing methods have the advantage of being less labor intensive and much more efficient than dry film methods, but on the other hand, they cannot print lines with a line width of several hundred micrometers or more, and as a result, the use of screen printing methods has been increasing in recent years. The drawback is that it cannot adequately meet the demands for higher density integrated circuits. In this regard, the dry film method is capable of drawing ultra-fine line widths of 50 μm or less, but as mentioned earlier, there are problems in workability and economy.

Recently, in response to the high precision and high density printing of printed circuit boards, off-the-shelf printing has been widely used as a general printing method in place of the conventional dry film method and screen printing method, and has extremely high work efficiency. The introduction of this technology has been actively researched, and examples of its development were briefly introduced in the Nikkan Kogyo Shimbun on July 22 and 25, 1981. These developed technologies are related to improvements to the offset printing machine itself or the printing plate (elastic intaglio) used in the printing machine.In particular, the latter technology, compared to the lithographic printing method, is capable of improving printed circuit board patterns. This makes it possible to transfer a uniform and sufficient amount of ink (wire paint) even on ultra-fine line widths of <30 to 50 μm.

However, the success or failure of the introduction of the offset printing method to printed circuit board printing is determined by the improvement of the intaglio plate alone, and the improvement of the rubber or polyurethane material used to transfer the ink on the intaglio plate onto the printed circuit board. It is no exaggeration to say that it is greatly influenced by the image reproducibility of the offset blanket made of a shaped elastic material.

〔Problems to be solved〕

Under the above circumstances, the present inventor conducted an experiment by combining an offset blanket for printing, which is currently on the market for general printed matter, with an elastic intaglio plate related to the developed technology described above, and installing it in an offset printing machine. It has been found that satisfactory results cannot always be obtained in terms of the sharpness and definition of the pattern outline) or the uniformity of the ink thickness within the pattern. Incidentally, the unclearness of the outline and the local non-uniformity of the ink thickness cause local non-uniformity in the electric resistance value in the electronic circuit, which results in an adverse effect on the functions of electronic equipment.

[Purpose of the invention]

Although the present invention is much more efficient than the known dry film method or screen printing method, it has conventionally been used only for printing general printed matter, and has been used for printed circuit boards with ultra-fine line widths. The present invention provides an offset printing blanket that can adapt offset printing techniques, which have been considered unsuitable for pattern printing, to pattern printing for printed circuit boards.

[Specific configuration]

According to the present invention, in order to achieve the above object, a surface printing layer and one or more support layers with or without a porous compressible layer interposed on the lower surface of the surface printing layer are laminated. An offset blanket for printing comprising: the surface printing layer is formed of an oil-resistant elastic material having a JIS hardness of 20 to 40 so that the surface has a 10-point average roughness of 2 μm or less; An offset blanket for printing is provided which is characterized by a smooth surface and a flexible elastic layer.

Prior to developing the above-mentioned specific means, the present inventor investigated the drawbacks of the conventional offset blanket described above when it was used for pattern printing for printed circuit boards, and found that a sufficient amount of ink could be found in the aforementioned elastic intaglio. Even though the offset blanket is unable to completely transfer the ink from the ultra-fine line width recesses on the intaglio onto its surface, the pattern on the printed circuit board is The thickness of the ink becomes unrestricted (for example, a phenomenon commonly known as "white spots" in the industry), and in order to eliminate this drawback, it is impossible to imagine from the common sense of conventional offset blankets. We found that it is best to make the material softer. By the way, conventional printing offset
In blankets, the hardness of the surface printing layer is usually JI from the viewpoint of image reproducibility such as distortion of printed images and thickening of halftone dots.
The S hardness is said to be around 60, and the softest is around 50.

On the other hand, in the present invention, the hardness of the surface printing layer is 20 to 4.
0 (JIS hardness). Within this hardness range,
The offset blanket of the present invention has a blanket cylinder (
When pressed against the elastic intaglio plate by a cylinder), the second
As shown in the figure (the rubber elastic material of the surface rubber layer is sufficiently pushed into the recesses of the ultra-fine line width of the intaglio plate, and the ink in the recesses is completely transferred to the surface of the rubber layer). In the present invention, the surface printing layer is made of a synthetic rubber such as acrylonitrile-butadiene copolymer comb (NBR) or chloroprene rubber (CR), or an oil-resistant elastic material such as polyurethane. It is also possible to have a structure in which a thin plastic layer is further laminated on the surface of the elastic layer.

On the other hand, as a result of examining another drawback when applying the conventional printing offset blanking method to pattern printing for printed circuit boards, which is that the outline of the printed image becomes unclear, it was found that the surface printing layer of the plantain 1- After molding, the surface is smoothed by abrasive means such as puffing, but the degree of smoothing (depth of surface irregularities - depth of depressions) is measured using a stylus using a conventional method. When measured using a device, the roughness varies depending on the type of product, but is 1.
The zero point average value was 2 to 15 μm, and it was found that this was the cause of the blurring of the contour. It has been found that in order to eliminate this drawback, the height of the recesses should be set to 2 μm or less. In addition, in order to realize the smooth surface without affecting the flexibility of the surface printing layer mentioned above, press molding or casting molding is performed using a mirror-finished mold, or thick release molding is performed using a mirror-finished mold. The surface printing layer may be spread-formed (glued-formed) on the paper pattern.

In addition, if the thickness of the target printed circuit board is strictly controlled, there will be no problem, but if the thickness varies slightly, the printing offset blanket of the present invention can sufficiently compensate for the variation in thickness. In order to obtain good printing results, it is preferable that the material has absorption ability. To cope with this, microcapsules of foamed material or micro glass beads or thermoplastic synthetic resin (e.g. polyvinylidene chloride etc.) may be used between the surface printing layer and the support layer or between a plurality of support layers.
A porous compressible layer made of a rubber composition mixed with fine particles of plastic foam or cork may be interposed.

The support layer can be made of fiber-reinforced cloth made of cotton cloth or synthetic fibers such as polyester or rayon, as in the case of conventional blankets, as well as non-stretchable or low-stretchable, flexible materials such as plastic sheets or gold i-thin plates. The support may be made of a transparent material, and one or more layers of the support may be used as required. This support layer then prevents undesirable longitudinal and widthwise stretching of the overall blanket.

〔Example〕

FIG. 1 is a partially enlarged sectional view of an offset blanket for printing according to an embodiment of the present invention. The blanket (1) of this example includes a surface printing layer (2) made of a rubber composition with the following formulation, and a fiber support layer (3) made of one layer of plain woven fabric laminated on the bottom surface of the printing layer (2). , a compressible layer (4) made of acrylonitrile-butadiene copolymer rubber (NBR) mixed with a large number of microencapsulated polyvinylidene chloride, and two layers further laminated on the lower surface of the compressible layer (4). It consists of fiber support layers (5), (5) made of plain woven fabric.

(Composition of surface printing layer) (Parts by weight) Acrylonitrile/Bukgen copolymer rubber (NBR) 100 Zinc oxide 5.0 Stearic acid 1.0 Hydrous silicic acid
40. OD OA
40.0 Vulcanization accelerator TS
□、5〃DM
1. g sulfur
3.0 JIS hardness after vulcanization 4゜Surface roughness 10 point average value) 0.9 μm In addition, this example blanket (1) uses Kent paper mirror-finished with silicon coating as release paper,
Rubber paste of the above composition is spread on the paper to a required thickness using a spreading device in a conventional manner to form a surface printing layer (2), and further a fiber reinforced layer (3) and a compressible rubber layer (4). and fiber reinforced layer (5) (51) were sequentially laminated, the laminate was vulcanized, and finally the release paper was removed.

Next, the completed blanket of this example was mounted on the offset cylinder of a printing press in which the above-mentioned elastic intaglio plate was mounted on the plate cylinder.
Line width 30-50μm for each extremely thick printed circuit board
When I printed the printed wiring test bag, the second
As shown schematically in the figure, the surface printing layer (2) is an ultra-fine intaglio plate (
By sufficiently digging into the recesses (r) of ρ), there are no uneven areas of coating thickness including "white spots" over the entire surface, and the surface has a sharp outline due to its smoothness. I was able to get the image. Furthermore, the printing speed was 900 sheets per hour, which was about three times more efficient than the conventional method used for printed circuit board printing.

Disaster Prevention Plate 21 This example is the same as the previous example except that the composition of the surface printing layer (2) was changed as follows, and excellent printing results were obtained like the previous example.

(Composition of surface printing layer) (Parts by weight) Oil-extended N B R150 Zinc oxide 5.0 Stearic acid 1.5 Hydrous silicic acid
30.0 Processing aids 5.
0 factis 20.0 titanium oxide 10.0 vulcanization accelerator DM
1.0〃TS
1.5 Sulfur Yellow 1.5 JIS hardness after vulcanization 30 Surface roughness (average of 10 points) 1 μm 1 Ri Plate This example blanket (1) was surface printed with the NBR composition of the following formulation as shown in Figure 3. This example differs from the previous two examples in that layer (2) was formed and a porous compressible layer was not formed. That is, the blanket of this example (1) does not have a porous compressible layer (cushion layer) like the previous two examples, but the surface printing layer (2) is made more flexible, which makes the line It is possible to print printed circuit boards with a width of approximately 60 μm.

(Composition of surface printing layer) (Parts by weight) Oil-extended N B R150 Zinc oxide 5.0 Stearic acid 1.0 Hydrous silicic acid
30.0D OA
10.0 Processing aid 5.0 Factis 20.0 Titanium oxide
10.0 Vulcanization accelerator DM
1.0 TS 1.5 Sulfur 1.5 JIS hardness after vulcanization 20 Surface roughness 10 point average value) 0.8 μm In each of the above examples, the surface printing layer (2) is N
Although it is made of a rubber composition mainly composed of BR, it can be made of a plastic such as polyurethane instead of the rubber as described above. Further, the fiber reinforcing layer (3) may be one layer or a plurality of layers other than the exemplified three layers, and may also be composed of a plastic sheet or a thin gold plate.

〔Effect of the invention〕

As detailed above, the printing offset blanket of the present invention has a hardness and surface smoothness of the surface printing layer that is flexible (JIS hardness 20~ 40) and smooth (10-point average roughness of 2 μm or less), it is possible to print ultra-fine print substrates with a line width of 100 μm or less, more specifically 60 μm or less, which was previously considered impossible with screen printing layers. In addition to making it possible to print plate patterns,
Work efficiency can be greatly improved compared to conventional dry film methods and screen printing methods.

[Brief explanation of drawings]

FIG. 1 shows a printing offset according to an embodiment of the present invention.
FIG. 2 is a partial enlarged sectional view schematically showing the action of the surface printing layer of the blanket shown in FIG. 1; FIG. 3 is an offset plunket for printing according to another embodiment of the present invention. FIG. The meanings of the symbols in each figure are as follows. 1: Whole off-cent plumket, 2: Surface printing layer, 3: Support layer (fiber reinforced layer), 4: Compressible layer, 5: Support layer (fiber reinforced layer), p: Intaglio, ra
concavity of p.

Claims (1)

[Claims] (1) A printing offset blanket comprising a surface printing layer and one or more support layers with or without a porous compressible layer interposed on the lower surface of the surface printing layer. The above-mentioned surface printing layer is a flexible elastic layer with a substantially smooth surface formed of an oil-resistant elastic material with a JIS hardness of 20 to 40 so that the surface has a 10-point average roughness of 2 μm or less. A distinctive printing offset blanket.