JP5523032B2 - Silicone blanket - Google Patents

Description

  The present invention relates to a silicone blanket used in a printing method such as an offset printing method.

The offset printing method has an advantage that an ink pattern can be formed easily and efficiently with a small number of steps and at a low cost, and since printing accuracy has been improved in recent years, Use is spreading in the electronics field.
For example, in fields where fine and high-precision patterns are required, such as electrical wiring patterns, phosphor patterns, and various patterns in plasma display panel (PDP) and liquid crystal display panel (LCD) components, etc. Instead of pattern formation by the conventional photolithographic method, the offset printing method has become widespread.

In the offset printing method, a pattern is printed on the surface of the substrate by transferring the ink patterned on the surface of the plate to the surface of the blanket and then transferring it again to the surface of the substrate as the substrate. .
As the blanket, a silicone blanket provided with at least a surface layer constituting the surface, and the surface layer formed of silicone rubber having excellent releasability with respect to ink is widely used.

Since the surface layer is repeatedly contacted with the ink, the solvent contained in the ink is impregnated and gradually swelled as printing is repeated, and the wettability of the surface with respect to the ink gradually increases accordingly. Therefore, it is difficult to keep the printing accuracy at a high level over a long period from the initial printing.
If an ink containing a solvent with low wettability that hardly swells silicone rubber is used, the wettability hardly changes even when printing is repeated, so that it seems that stable printing can be performed. However, an ink containing a solvent with low wettability has a low transferability from the surface of the plate to the surface of the surface layer.

  The disconnection is one of the most problems to be avoided, and in order to prevent this, a solvent that can swell silicone rubber to some extent must be used. However, when printing is repeated using the ink containing the solvent, the surface layer gradually swells and the wettability with respect to the ink gradually increases. Along with this, the ink tends to bleed, and in particular, the line width of the fine line pattern gradually widens, or fine stains on the plate surface are transferred, or the ink from the surface layer surface to the substrate surface The transferability of the ink gradually decreases, and the printing accuracy gradually decreases.

It is considered to remove the solvent swelling the surface layer by heating the silicone blanket. However, in order to do so, it is necessary to heat the silicone blanket to about 40 to 200 ° C. When the high-temperature surface immediately after heating is brought into contact with the plate, the plate is thermally expanded and the printing accuracy is lowered. There is.
It has been proposed to remove a swollen solvent by bringing a solvent absorber having a function of absorbing the solvent into contact with the surface of the surface layer (see Patent Document 1, etc.). If the solvent absorber is used, the solvent can be removed without heating the silicone blanket, so that the printing accuracy can be maintained at a high level.

  However, the removal of the solvent by the solvent absorber must be carried out by stopping printing every one or several times of printing in order to keep the swelling state of the surface layer constant. That is, the average time required to set a substrate on the printing press and print a ink on the surface of the substrate according to a predetermined procedure to form a pattern and then set a new substrate on the printing press becomes longer. Therefore, there is a problem of reducing the productivity of the product.

Patent Document 2 describes that a predetermined amount of silicone gel is contained in a surface layer made of silicone rubber.
Silicone gel has basically the same polysiloxane structure as silicone rubber, but has a crosslinking density after crosslinking reaction that is lower than silicone rubber and hardens into a soft gel that cannot be measured with a normal rubber hardness meter. Say. Such a silicone gel is excellent in the ability to absorb a solvent as compared with the silicone rubber forming the surface layer.

  Therefore, by absorbing the solvent in the silicone gel contained in the surface layer, the surface wettability of the surface layer is prevented from greatly increasing in a short period of time, and the solvent removal process by the solvent absorber etc. It can be omitted.

JP 2006-188015 A JP 2008-49495 A

However, as is clear from the results of Examples and Comparative Examples described later, the surface layer contains only a small amount of silicone gel of 50 parts by mass or less per 100 parts by mass of silicone rubber as defined in Patent Document 2. The expected effect cannot be obtained, and it is impossible to suppress a significant increase in the wettability of the surface layer in a short period of time.
The object of the present invention is to suppress a significant increase in the wettability of the surface layer over a long period of time and to continue good printing. The object is to provide a silicone blanket that can shorten the tact time and improve the productivity of the product.

The present invention is a silicone blanket for printing, comprising at least a surface layer made of silicone rubber that constitutes a surface for carrying the printing ink, and the surface layer is 60 mass per 100 parts by mass of the silicone rubber. More than 150 parts by weight of silicone gel is included.
According to the present invention, since the printing layer contains a large amount of silicone gel of 60 parts by mass or more per 100 parts by mass of the silicone rubber forming the printing layer, it is contained in the ink and impregnated in the surface layer. By selectively absorbing the solvent to be absorbed by the large amount of the silicone gel, the swelling of the silicone rubber is suppressed, and the increase in the wettability of the surface layer made of the silicone rubber is suppressed over a long period of time. It becomes possible.

  In the present invention, the blending ratio of the silicone gel is limited to 150 parts by mass or less per 100 parts by mass of the silicone rubber. When a large amount of silicone gel exceeding the above range is contained, the surface layer becomes too soft. This is because the strength is lowered, the printing pressure when contacting the plate or the substrate during printing, the nip width or the like is greatly changed, causing a problem in printability, and as a result, the printing accuracy is lowered.

In addition, considering that it is possible to reliably prevent the above problem from occurring due to the surface layer becoming too soft even if a large amount of silicone gel is contained as described above, the silicone rubber forming the surface layer is independent. The type A durometer hardness when cured is preferably A40 / S or more.
The silicone blanket of the present invention preferably comprises a film-like or sheet-like substrate and the surface layer formed on one side of the substrate. By providing the base material, it is possible to maintain the strength of the entire silicone blanket and to ensure good handleability.

  According to the present invention, since the wettability of the surface layer on the surface layer can be prevented from significantly increasing over a long period of time and good printing can be continued, the step of removing the solvent during printing can be omitted. It is possible to provide a silicone blanket that can shorten the tact time and improve the productivity of the product.

The silicone blanket of the present invention comprises at least a surface layer made of silicone rubber that constitutes a surface for carrying printing ink, and the surface layer is 60 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the silicone rubber. It is characterized by including the following silicone gel.
Examples of the silicone rubber forming the surface layer include various silicone rubbers, and dimethyl silicone rubber is particularly preferable in consideration of availability and imparting good printability to the surface layer.

The silicone rubber is preferably a liquid silicone rubber that exhibits a liquid or paste shape when uncured.
The liquid or paste-like silicone rubber can form a surface layer by applying a predetermined thickness on a substrate using, for example, a doctor knife, bar coater, roll coater, etc., and then curing it. At the same time, the surface of the coating film that becomes the basis of the surface layer, that is, the surface of the surface layer after curing can be smoothed and the thickness of the surface layer can be made uniform by the so-called self-leveling effect.

Therefore, a silicone blanket with a surface layer with excellent surface smoothness that is suitable for forming fine and high-precision patterns on the surface of the substrate as the substrate to be printed is manufactured with high productivity without passing through polishing and other processes. it can. Needless to say, the surface of the surface layer may be polished as necessary.
The silicone blanket is manufactured by injecting and curing the liquid or pasty silicone rubber having a shaping surface corresponding to the surface shape of the surface layer into a mold in which a base material is set. Also good.

  For example, as will be described later, a two-component addition reaction type liquid silicone rubber composed of a main agent and a curing agent is used, and the surface layer containing the silicone gel is first a predetermined amount in one of the main agent and the curing agent, for example, the main agent. A silicone gel is added and mixed, then a curing agent is added and further mixed to prepare a liquid composition (coating liquid, injection liquid, etc.) for the surface layer, and then any of the above methods using the composition Can be formed.

  The silicone rubber is preferably room temperature curable (RTV). Since the room temperature curable silicone rubber can be cured at room temperature (5 to 35 ° C.) without heating as the name suggests, it is possible to simplify the manufacturing process and equipment for manufacturing the silicone blanket. Moreover, since the expansion by heating and the contraction at the time of cooling are not performed, the accuracy of the thickness of the surface layer can be improved.

Further, as described above, the silicone rubber is preferably a two-component addition reaction type that consists of two components of a main agent and a curing agent, and can cure both of them by an addition reaction.
The two-component addition reaction type silicone rubber does not produce a by-product during the curing reaction, so that the dimensional accuracy of the surface layer can be improved and a uniform surface layer free of bubbles or the like based on the by-product can be formed.

  Examples of the room temperature curing type two-component addition reaction type liquid dimethyl silicone rubber include, for example, product numbers KE1600, KE1603, KE1606, KE1310ST, KE1300T, KE1314, KE1241, KE106, KE103, manufactured by Shin-Etsu Chemical Co., Ltd., Momentive Performance -Product numbers TSE3402, TSE3453, TSE3455T, TSE3457, TSE3466, etc. manufactured by Materials are listed.

The silicone rubber is measured in an environment of a temperature of 23 ± 3 ° C. and a relative humidity of 55 ± 5% when cured alone without containing a silicone gel. Japanese Industrial Standard JIS K6253: 2006 It is preferable that the type A durometer hardness specified in “Sulfur rubber and thermoplastic rubber—How to obtain hardness” is A25 / S or more, particularly A40 / S or more.
Due to this, even if a large amount of silicone gel is contained, the surface layer becomes too soft and the strength decreases, or the printing pressure and nip width when contacting the plate or substrate at the time of printing change greatly, and there is a problem in printability Can be prevented, or the printing accuracy can be reduced.

  The surface layer becomes too hard, and the transferability of the ink from the surface of the plate to the surface of the surface layer is deteriorated, or the printing shape is disturbed due to the influence of subtle irregularities on the surface of the surface layer. In view of preventing this, the type A durometer hardness of the silicone rubber when it is cured alone without containing a silicone gel is preferably A90 / S or less, particularly preferably A70 / S or less.

The silicone gel contained in the surface layer is basically a soft gel that has the same polysiloxane structure as silicone rubber, but has a crosslinking density after the crosslinking reaction that is smaller than that of silicone rubber and cannot be measured with a normal rubber hardness meter. The one that hardens into a shape.
As the silicone gel, various silicone gels such as dimethyl silicone gel and methylphenyl silicone gel classified according to the type of polysiloxane constituting the main chain can be used, and in particular, compatibility and affinity with the silicone rubber. It is preferable to select and use a silicone gel excellent in heat resistance, particularly a silicone gel similar to silicone rubber. For example, when the silicone rubber forming the surface layer is dimethyl silicone rubber, it is preferable to use dimethyl silicone gel in combination.

The silicone gel is preferably a liquid silicone gel in consideration of forming a smooth surface layer by the self-leveling effect described above.
In addition, as the silicone gel, various one-pack type and two-pack type silicone gels can be used. When the two-component addition reaction type silicone rubber described above is used as the silicone rubber, the silicone gel to be combined is used. In order to prevent the curing reaction of the silicone rubber from being inhibited, a two-component addition reaction type silicone gel which is also composed of two components of a main agent and a curing agent and can cure both of them by an addition reaction. It is preferable to use it.

  Moreover, when using a silicone gel of room temperature curing type and two-component addition reaction type as the silicone gel, for example, the workability when forming the surface layer by applying the coating solution on the substrate is improved. In view of the above, it is preferable to use the one having a pot life, that is, the time from when the silicone gel main ingredient and the curing agent are blended to when the viscosity starts to rise is 30 minutes or more.

As room temperature curing type and two-component addition reaction type liquid dimethyl silicone gel satisfying the pot life time, for example, Shin-Etsu Chemical Co., Ltd. product number KE1052, KE1051J, manufactured by Momentive Performance Materials, Inc. Part numbers TSE3062, TSE3070, YE5818, TSE3080, TSE3081 etc. are mentioned.
In addition, as the silicone gel, a thermosetting type is used, and the above thermosetting type silicone gel is used in combination with a room temperature curable type silicone rubber. After the silicone rubber is cured, the silicone gel is heated to obtain proper physical properties. May be cured.

Examples of the thermosetting and two-component addition reaction type liquid dimethyl silicone gel include product numbers KE104 and KE1056 manufactured by Shin-Etsu Chemical Co., Ltd., and product number TSJ3175 manufactured by Momentive Performance Materials.
As described above, the blending ratio of the silicone gel is limited to the range of 60 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the silicone rubber.

If the blending ratio is less than the above range, good printing can be achieved by suppressing the increase in wettability of the surface layer over a long period of time by absorbing the solvent by the silicone gel by containing the silicone gel. The effect of continuing is not obtained.
On the other hand, when the blending ratio exceeds the above range, the surface layer becomes too soft and the strength is lowered, or the surface layer becomes sticky.

Therefore, for example, it becomes difficult to separate after the surface layer is brought into contact with the surface of the substrate as a plate or a printing object, the surface layer is partially peeled at the time of separation after the contact, or the peeled surface layer is a plate or It tends to adhere to the surface of the substrate.
Further, the partially peeled surface layer adheres to the surface of the plate or the substrate, thereby causing a problem that the state of the pattern printed on the surface of the substrate is deteriorated.

The blending ratio of the silicone gel is 7 even within the above range, considering that the amount of solvent that can be absorbed is further increased to suppress the increase in the wettability of the surface layer over a longer period of time. It is preferably 0 parts by mass or more. Further, considering the reduction in strength and stickiness of the surface layer, it is preferably 130 parts by mass or less, particularly 90 parts by mass or less even within the above range.

The thickness of the surface layer is preferably about 0.1 mm or more and 1 mm or less in the case of a precision printing silicone blanket that requires high printing accuracy, such as the PDP and LCD patterns described above.
The hardness of the surface layer is not less than A5 / S in terms of type A durometer hardness measured in an environment of a temperature of 23 ± 3 ° C. and a relative humidity of 55 ± 5% as defined in the above-mentioned JIS K6253: 2006. A70 / S or less, particularly A10 / S or more and A50 / S or less.

Further, the surface state of the silicone blanket is preferably as flat as possible because the finer the ink pattern, the more influence is exerted on the accuracy. For example, the surface roughness of the above-mentioned silicone blanket for precision printing can be found in Japanese Industrial Standard JIS B0601: 2001 “Product Geometrical Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definitions, and Surface Property Parameters” Annex 1 It is preferably about 0.01 μm or more and 1 μm or less in terms of ten-point average roughness Rz _JIS94 defined by

The silicone blanket of the present invention preferably comprises a film-like or sheet-like substrate and the surface layer formed on one side of the substrate. By providing the base material, it is possible to maintain the strength of the entire silicone blanket and to ensure good handleability.
Examples of the base material include various resin films or sheets, metal thin plates, and the like. Among these, as a resin film or sheet, polyethylene terephthalate (PET), polyvinyl chloride, polyethylene, polypropylene, polystyrene and copolymers thereof, polyvinylidene chloride, polyvinyl alcohol, fluororesin, polycarbonate, cellulose acetate, polyamide, polyimide, Examples thereof include films or sheets made of resins such as modified polyphenylene ether, polysulfone, polyarylate, polyethersulfone, polyetheretherketone, polyetherimide, polyphenylene sulfide, TPX polymer, and polyparaxylene.

The metal thin plate is preferably a thin plate made of a metal such as copper or an alloy thereof, aluminum or an alloy thereof, stainless steel, or nickel.
In particular, it is preferable to use as a substrate a PET film or sheet that is easily processed into a film or sheet having an arbitrary thickness and surface roughness and that is excellent in dimensional stability.
In the case of the precision printing silicone blanket, the thickness of the substrate is preferably about 0.01 mm or more and 0.4 mm or less.

The surface of the base material before forming the surface layer may be subjected to, for example, a pretreatment such as plasma treatment or flame treatment or an arbitrary underlayer in order to improve the adhesion of the surface layer. Good.
The silicone blanket of the present invention is, for example,
(1) An offset printing method in which an ink patterned on the surface of a plate such as an intaglio plate or a lithographic plate is transferred to the surface of a silicone blanket and then re-transferred to the surface of a substrate as a substrate.
(2) The ink is applied to the entire surface of the silicone blanket and then brought into contact with the intaglio, thereby selectively removing the ink in contact with the area other than the concave portion of the intaglio from the surface of the silicone blanket. After pattern formation, the reverse printing method of transferring to the surface of the substrate,
(3) a printing method in which an ink pattern is drawn directly on the surface of the silicone blanket and then transferred to the surface of the substrate;
It can be used for various printing methods.

  When performing continuous printing using the various printing methods, according to the silicone blanket of the present invention, the silicone gel containing the solvent contained in the ink and impregnated in the surface layer is contained in the surface layer. By selectively absorbing, the swelling of the silicone rubber can be suppressed, and the increase in the wettability of the surface layer made of the silicone rubber can be suppressed over a long period of time. Therefore, it is possible to improve the productivity of products such as PDP by omitting the solvent removing step during printing and shortening the tact time of printing.

The following examples and comparative silicone blankets were manufactured, measured for properties, and tested in an environment of 23 ± 3 ° C. and 55 ± 5% relative humidity unless otherwise specified.
< Comparative Example 1 >
Room temperature curing type and two-component addition reaction type liquid dimethyl silicone rubber (type A durometer hardness after single curing (according to JIS K6253: 2006) of A30 / S, KE1606 manufactured by Shin-Etsu Chemical Co., Ltd.) And 50 parts by mass of the main agent A and the curing agent B of a liquid dimethyl silicone gel (part number KE1051J manufactured by Shin-Etsu Chemical Co., Ltd.) that is also a room temperature curable and two-component addition reaction type The mass ratio of the main agent and the curing agent was 1: 1).

  Next, 9 parts by mass of the liquid dimethyl silicone rubber curing agent was added to the mixture and mixed, followed by defoaming to prepare a coating solution for the surface layer, and the coating solution having a thickness of 0.30 mm as a substrate After coating with a bar coater on one side of the PET film, it was allowed to stand at room temperature for 24 hours to be cured to form a surface layer having a thickness of 0.70 mm and a PET film having a dimension of 50 cm in length and 50 cm in width. A silicone blanket was produced.

In the surface layer of the silicone blanket, the blending ratio of dimethylsilicone gel per 100 parts by mass of the main component of dimethylsilicone rubber and the total amount of the curing agent was 50 parts by mass as apparent from the blending amount.
<Comparative Example 2 >
A silicone blanket was produced in the same manner as in Comparative Example 1 except that the liquid dimethyl silicone gel was not blended.

<Examples 1 and 2 and Comparative Examples 3 and 4 >
30 parts by mass (Comparative Example 3 ) of 100 parts by mass of the main component of dimethyl silicone rubber and the total amount of the curing agent in a liquid dimethyl silicone gel [Product No. KE1051J manufactured by Shin-Etsu Chemical Co., Ltd.] A silicone blanket was produced in the same manner as in Comparative Example 1 except that 80 parts by mass (Example 1 ), 140 parts by mass (Example 2 ), and 200 parts by mass (Comparative Example 4 ) were used.

<Hardness measurement>
The type A durometer hardness of the surface layer of the silicone blanket produced in Examples and Comparative Examples was measured in accordance with the above-mentioned JIS K6253: 2006.
<Printing characteristic test>
The silicone blanket produced in Examples and Comparative Examples was wound around the outer periphery of the blanket cylinder of an intaglio offset printing machine (manufactured by Nakan Co., Ltd., 300 mm x 400 mm compatible flat plate precision printing machine) with the surface layer facing outward. Fixed. As the intaglio, a glass plate was used in which concave portions having a line width of 100 μm, a pitch of 300 μm, and a depth of 8 μm were formed in a lattice pattern on the surface of the glass plate.

As the ink, an ink prepared by kneading polyester resin, butyl carbitol acetate as a solvent, and pigment powder using three rolls was used.
The printing conditions were 100 mm / s for the ink transfer speed from the concave part of the intaglio plate to the surface of the surface layer of the silicone blanket, and the ink transfer speed from the surface of the surface layer to the surface of the glass substrate as the printing medium. 50 mm continuous printing was performed while changing the glass substrate with the setting being 100 mm / s.

And after the 50th printing, the pattern printed on the surface of the surface layer of the silicone blanket and the surface of the glass substrate was observed, and the printing characteristics were evaluated according to the following criteria.
(Double-circle): The ink of the surface layer did not remain by transfer defect, and the line width was hardly increased in the pattern printed on the surface of the glass substrate.
X : Residual ink due to transfer failure was not observed, but a slight increase in the line width of the pattern was observed. Alternatively, ink residue due to transfer failure was observed, and the line width increased greatly.

By observing the printed pattern or printed 50th glass surface of the substrate was evaluated the quality of printed shapes to the following criteria.
A: No disturbance was observed in the pattern.
A: A slight disturbance was observed in the pattern, but it was within an acceptable range.

X: The pattern was so disturbed that the product could not be used.
The results are shown in Table 1.

From Table 1, Comparative Examples did not contain a silicone gel on the surface layer 2, and the mixing ratio of the silicone gel, silicone blanket silicone rubber weight per 100 parts by weight 60 parts by mass than the the ratio Comparative Examples 1 and 3, any It has also been found that by repeating printing, the wettability of the surface layer is greatly increased, resulting in an increase in line width, poor transfer, and the like.
Further, it was found that the silicone blanket of Comparative Example 4 containing a large amount of silicone gel exceeding 150 parts by mass per 100 parts by mass of the silicone rubber had a surface layer that was too soft and the printing accuracy was lowered.

On the other hand, according to the silicone blankets of Examples 1 and 2 , it is possible to suppress an increase in the wettability of the surface layer when printing is repeated, and to increase the line width or cause transfer defects. In addition, it was found that good printing accuracy can be maintained by imparting appropriate hardness to the surface layer.
<Examples 3 and 4 and Comparative Examples 5 to 7 >
As liquid dimethyl silicone rubber, 91 parts by mass of main agent and 9 parts by mass of curing agent having type A durometer hardness (based on JIS K6253: 2006) of A50 / S after single curing (KE1600 manufactured by Shin-Etsu Chemical Co., Ltd.) A silicone blanket was produced in the same manner as in Examples 1 and 2 and Comparative Examples 1 , 3, and 4 except that the part was used.

  Each of the previous tests was carried out on the silicone blankets produced in the examples and comparative examples. The results are shown in Table 2.

From Table 2, it was found that the same result was obtained even in a system in which the type A durometer hardness of the silicone rubber was set to A40 / S or more.
That is, in the silicone blankets of Comparative Examples 5 and 6 in which the blending ratio of the silicone gel was less than 60 parts by mass per 100 parts by mass of the silicone rubber, the surface layer surface wettability greatly increased by repeating printing, and the line width It has been found that an increase in image quality and transfer defects occur.

In addition, it was found that the silicone blanket of Comparative Example 7 containing a large amount of silicone gel exceeding 150 parts by mass per 100 parts by mass of the silicone rubber had a surface layer that was too soft and the printing accuracy was reduced.
On the other hand, according to the silicone blankets of Examples 3 and 4 , it is possible to suppress the significant increase in the wettability of the surface layer when printing is repeated, and to increase the line width or cause transfer defects. In addition, it was found that good printing accuracy can be maintained by imparting appropriate hardness to the surface layer.

  Further, from the results of Examples and Comparative Examples in which the blending ratio of the silicone gel is the same, the type A durometer hardness of the silicone rubber is set to A40 / S or more, thereby containing a large amount of silicone gel. It has also been found that even if it is applied, it is possible to suppress the surface layer from becoming too soft and reducing the printing accuracy.

Claims (3)

A silicone blanket for printing, comprising at least a surface layer made of silicone rubber constituting a surface for carrying the printing ink, wherein the surface layer is 60 parts by mass or more per 100 parts by mass of the silicone rubber, 150 A silicone blanket comprising a silicone gel having a mass part or less.   The silicone blanket according to claim 1, wherein the silicone rubber has a type A durometer hardness of A40 / S or more when cured alone.   The silicone blanket of Claim 1 or 2 provided with the film-form or sheet-like base material, and the said surface layer formed in the single side | surface of the said base material.