JP2009184268A - Porous silicone rubber sheet and silicone blanket using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous silicone rubber sheet which does not go through the process of polishing, and in addition, for which the effect for suppressing the adhesion of the surface is not lost in a short period of time, or a peeled article making the picture quality of printing fall is not generated, and the adhesion is favorably suppressed, and by which a good printing can always be performed when being used as an under blanket or a cushion layer for silicone blankets, and to provide a silicone blanket for which the sheet is incorporated as the cushion layer. <P>SOLUTION: For this porous silicone rubber sheet, the surface of at least one side is coated with a coating layer consisting of a silicone resin of which the scratch hardness (the pencil method) is from B to 3H. For this silicone bracket, the sheet has been incorporated as the cushion layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a porous silicone rubber sheet used as a cushion layer or under blanket for a silicone blanket, and a silicone blanket incorporating the porous silicone rubber sheet as a cushion layer.

  An ink pattern formed by supplying ink to the surface of a plate such as an intaglio is transferred to the surface of the surface rubber layer of a blanket having a rubber layer (surface rubber layer) on the outermost surface, and then covered from the surface. The blanket used in the offset printing method, which is retransferred to the surface of the printed material, improves the retransfer of the ink from the surface of the surface rubber layer to the surface of the material to be transferred and improves the reproducibility of the ink pattern. Therefore, a so-called silicone blanket in which the surface rubber layer is formed of a silicone rubber having a small surface tension and excellent ink releasability is widely used.

  A conventional silicone bracket is formed in a two-layer structure in which a surface rubber layer made of silicone rubber is directly laminated on the surface of a synthetic resin film or a metal thin plate as a base material. Then, the silicone blanket is called an under blanket, with a porous or non-porous rubber or resin layer stacked on the lower side, for example, wrapped around the blanket cylinder of an offset printing machine and fixed, Generally used for printing. The under blanket is a subtle surface rubber layer surface that is caused by tailoring of the silicone blanket, that is, adjusting the dimension in the thickness direction from the outer peripheral surface of the blanket cylinder to the surface of the surface rubber layer of the silicone blanket, or uneven winding around the blanket cylinder. It functions to alleviate unevenness and adjust printing pressure (see, for example, Patent Document 1).

  As the under blanket to be combined with the silicone blanket, those having a porous structure in which hollow microspheres are dispersed in silicone rubber are preferably used. In some cases, a cushion layer having a porous structure similar to that of the under blanket is incorporated below the surface rubber layer of the silicone blanket, and the under blanket is omitted. A porous silicone rubber sheet in which hollow microspheres are dispersed in silicone rubber, used as a porous under blanket or a cushion layer of a silicone blanket, is formed in the layer by the thickness and hollow microspheres. High accuracy is required for the void ratio of the voids to be formed.

  Therefore, as a silicone rubber, a liquid room-temperature-curing silicone rubber that does not need to be heated during the curing reaction and does not cause a variation in voids due to expansion or collapse of hollow microspheres due to heating or a variation in thickness, etc. Preferably used. The room temperature curable silicone rubber is blended with a predetermined amount of hollow microspheres, and if necessary, a coating solution prepared by blending an organic solvent, silicone oil, or the like to adjust the viscosity on the base. The shell forming the hollow microspheres is softened so that it does not expand and collapse, and the room temperature curable silicone rubber is sufficiently cured, preferably at room temperature (15 to 15 A porous silicone rubber sheet is produced by a curing reaction at a temperature in the vicinity of 35 ° C.).

  However, since the conventional porous silicone rubber sheet is sticky on the surface and is difficult to slip, for example, when the sheet is used as an under blanket, it is wrapped around a blanket cylinder of an offset printing machine together with a silicone blanket. As a result of undulation of the sheet itself or the silicone blanket, or unevenness in thickness due to partial expansion and contraction of the sheet, the surface of the surface rubber layer of the silicone blanket may be uneven or uniform on the silicone blanket. There is a problem that it is impossible to apply a proper tension. The same applies when the porous silicone rubber sheet is incorporated as a cushion layer in the lowermost layer of the silicone blanket in contact with the blanket cylinder.

  That is, since the cushion layer is sticky on the surface and is difficult to slip, the silicone blanket undulates when wrapped around the blanket cylinder of the offset printing machine. There is a problem that unevenness is generated or uniform tension cannot be applied to the silicone blanket. In addition, for example, in a laminate in which a cushion layer made of a porous silicone rubber sheet is laminated on one surface of a base material, the surface on the opposite side of the base material includes a silicone rubber that becomes a surface rubber layer. When a coating solution is applied and cured to form a surface rubber layer to produce a silicone blanket, the cushion layer undulates on the work table where the coating operation is performed, and the opposite side of the substrate If irregularities are formed on the surface, there is a problem that a surface rubber layer having a uniform thickness and a smooth surface cannot be formed thereon.

Therefore, the surface of the porous silicone rubber sheet is polished, or a coating layer made of a fluorine-based resin such as ethylene tetrafluoride (PTFE) and having a low surface energy and low adhesiveness is formed on the surface. It has been studied to improve the slip by suppressing the adhesion of the surface (for example, see Patent Document 2).
JP 2004-42503 A JP 2006-312282 A

  In recent years, it has been studied to form electrodes of a large-screen display device such as a plasma display panel (PDP) or a liquid crystal display (LCD) by an offset printing method. In order to suppress the adhesion of the surface of the large-area porous silicone rubber sheet for the large-area silicone blanket to be used, it is substantially difficult to polish the entire surface with high accuracy and uniformity. And when it cannot polish uniformly, as a result of causing unevenness in the thickness of the porous silicone rubber sheet itself, the silicone using the sheet as an under blanket or cushion layer even though the surface adhesion is suppressed by polishing. There arises a problem that the surface of the surface rubber layer of the blanket is uneven, and a uniform tension cannot be applied to the silicone bracket.

  In addition, since the coating layer made of a fluororesin has low adhesion to the surface of the porous silicone rubber sheet and is less stretchable than the sheet, a silicone blanket using the sheet as an under blanket or cushion layer is used. Not only will the sheet peel off easily due to the expansion and contraction of the sheet, such as when it is wrapped around the blanket cylinder, and the effect of suppressing the adhesion of the surface will be lost in a short period of time, but also the debris of the removed coating layer will be mixed in the ink As a result, there also arises a problem that the print formed on the surface of the printing material appears as a defect and deteriorates the image quality of the print.

  The object of the present invention is to pass the adhesive without passing through the polishing step, and without losing the effect of suppressing the adhesion of the surface in a short period of time or causing a stripped object that deteriorates the image quality of printing. An object of the present invention is to provide a porous silicone rubber sheet that is satisfactorily suppressed and can always perform good printing without causing various problems when used as an under blanket or cushion layer of a silicone blanket. . Another object of the present invention is to provide a silicone blanket incorporating the porous silicone rubber sheet as a cushion layer.

  The present invention is a porous silicone rubber sheet made of silicone rubber and having a porous structure, and a coating layer made of a silicone resin having a scratch hardness (pencil method) of B or more and 3H or less on at least one surface. It is characterized by being formed. According to the present invention, at least one surface of the porous silicone rubber sheet has a scratch hardness of B or more and is equivalent to a coating layer made of a fluororesin and has a small surface energy and low adhesiveness. By forming the coating layer made of a resin, the adhesion can be suppressed while omitting the step of polishing the surface. Therefore, it is possible to prevent unevenness on the surface of the surface rubber layer of the silicone blanket or uneven tension on the silicone blanket from being applied due to uneven polishing.

  Further, the coating layer is formed of a silicone resin having a molecular structure similar to that of the silicone rubber forming the porous silicone rubber sheet, and has superior adhesion to the sheet compared to the coating layer made of the fluororesin. In addition, the scratch hardness is B or more, it has an appropriate strength, and there is no risk of being easily worn away. For this reason, the coating layer peels off or wears away from the surface of the porous silicone rubber sheet in a short period of time, and the effect of suppressing the adhesiveness of the surface is lost in a short period of time, or peels off which deteriorates the image quality of printing. It is also possible to prevent the occurrence of problems such as things.

  In addition, the coating layer has a scratch hardness of 3H or less and good flexibility, and does not impair the printing properties of the silicone blanket by inhibiting the flexibility of the porous silicone rubber sheet. Therefore, according to the porous silicone rubber sheet of the present invention, when used as an under blanket or cushion layer of a silicone blanket, the porous silicone rubber can always perform good printing without causing the above various problems. A sheet can be provided.

  The thickness of the coating layer is preferably 0.1 μm or more and 10 μm or less. If the thickness is less than the above range, even if the scratch hardness is B or more and has an appropriate strength, the absolute thickness of the coating layer is too small, so that the coating layer is worn out in a short period of time. Then, the effect of suppressing the adhesiveness of the surface may be lost in a short period of time. In addition, when the above range is exceeded, for example, a coating solution containing a silicone resin is applied, and the coating layer formed by a curing reaction has a large variation in the thickness of the coating layer. As a result of unevenness in the thickness, there is a possibility that the surface of the surface rubber layer of the silicone blanket using the sheet as an under blanket or cushion layer may be uneven or the silicone bracket may not be uniformly tensioned. .

  The porous silicone rubber sheet of the present invention can be used as an under blanket of a silicone blanket or used by being incorporated in a silicone blanket as a cushion layer, as in the prior art. That is, the silicone blanket of the present invention is characterized by including a cushion layer made of the porous silicone rubber sheet and a surface rubber layer made of silicone rubber.

  According to the present invention, the adhesive does not go through a polishing step, and the effect of suppressing the adhesion of the surface is lost in a short period of time, or the exfoliation that reduces the image quality of printing is generated. A porous silicone rubber sheet that is satisfactorily suppressed and capable of always performing good printing without causing the above-mentioned various problems when used as an under blanket or cushion layer of a silicone blanket can be provided. . Moreover, according to this invention, the silicone blanket which incorporated the said porous silicone rubber sheet as a cushion layer can be provided.

  The porous silicone rubber sheet of the present invention is made of silicone rubber, has a porous structure, and has a silicone resin having a scratch hardness (pencil method) of B or more and 3H or less on at least one surface thereof. A coating layer is formed. Various conventionally known silicone resins can be used as the silicone resin for forming the coating layer. However, it is not necessary to heat at the time of the curing reaction, and a room temperature curable silicone resin that does not cause a variation in the void of the porous silicone rubber sheet or a variation in thickness due to expansion or collapse of the hollow microspheres by heating is preferable. .

  The coating liquid containing the silicone resin is applied to the surface of at least one side of the porous silicone rubber sheet by a coating method such as a bar coating method (wire coating method), a gravure coating method, a spray coating method, and the like, and dried. The coating layer is formed by a curing reaction at room temperature. In the present invention, the reason why the scratch hardness of the coating layer made of silicone resin is limited to the above range is as described above. In view of further improving the strength while maintaining good flexibility of the coating layer, the scratch hardness of the coating layer is preferably H or more and 2H or less even within the above range.

  In order to adjust the scratch hardness of the coating layer within the above range, various methods such as changing the type and amount of the curing agent added to cure the silicone resin, adjusting the degree of crosslinking of the silicone resin, etc. Can be adopted. In the present invention, the scratch hardness of the coating layer is measured according to the Japanese Industrial Standard JIS K5600-5-4: 1999 “Paint General Test Method” for the coating layer of the same thickness formed on a metal substrate as a measurement sample. Based on the measurement method defined in “Part 5: Mechanical Properties of Coating Film—Section 4: Scratch Hardness (Pencil Method)”, the measurement is performed at room temperature (15 to 35 ° C.).

  The thickness of the coating layer is preferably 0.1 μm or more and 10 μm or less. The reason for this is as described above. In order to set the thickness of the coating layer within the above range, the conditions of the coating method described above may be adjusted. In particular, as the coating solution used in the coating method, it is preferable to use a silicone resin diluted with an organic solvent that is removed from the coating film by drying, for example, so that the solid content concentration is 10% by mass or less. . Thereby, after apply | coating a coating liquid and drying, the thickness of the coating layer formed by carrying out hardening reaction can be adjusted to the thinnest possible range also in the said range.

  The porous silicone rubber sheet can be formed in the same manner as before. That is, a coating solution containing a room temperature curable silicone rubber, hollow microspheres, and, if necessary, an organic solvent or silicone oil for adjusting the viscosity of the coating solution, etc. The room temperature curable silicone rubber is applied at a temperature at which the shell forming the hollow microspheres does not soften and expand or collapse, and the curing reaction of the room temperature curable silicone rubber proceeds sufficiently. A porous silicone rubber sheet is formed by a curing reaction at a temperature within the range, preferably around room temperature. The room temperature curable silicone rubber is liquid at a temperature range in which the coating liquid is handled, preferably at room temperature, or is liquid by blending an organic solvent, silicone oil or the like, and is cured at a temperature near room temperature. Any of various silicone rubbers can be used.

  The room temperature curable silicone rubber is classified according to the form of the curing reaction and the state before the curing reaction, a condensation type one or two liquid type room temperature curable silicone rubber, an addition type one liquid, and two liquids. Alternatively, a three-component room temperature curable silicone rubber, an ultraviolet curable one-component room temperature curable silicone rubber, and the like can be given. Among them, a gas or liquid is not generated during the curing reaction, and a porous silicone rubber sheet having a uniform thickness and excellent dimensional accuracy can be formed. Before the curing reaction is started by mixing two liquids with two liquids In addition, since the hollow microspheres can be mixed in any one liquid and the mixing workability is excellent, the addition type two-liquid type room temperature curable silicone rubber is preferable.

  Further, as the hollow microsphere, for example, the shell disclosed in US Pat. No. 4,770,928, JP-A-3-244595, JP-A-7-505341, etc. is made of a thermoplastic resin. Any of various conventionally known hollow microspheres formed can be used. In particular, when a porous silicone rubber sheet is used as an under blanket or a cushion layer for a silicone blanket, a single polymerizable monomer such as vinylidene chloride or (meth) acrylonitrile is considered in consideration of oil resistance to ink. Hollow microspheres in which a shell is formed by a polymer, a copolymer of two types of monomers including these monomers, a multi-component copolymer of three or more types of monomers, and the like are preferable.

  The particle size of the hollow microspheres is not particularly limited, but an under blanket or cushion layer having a uniform independent pore structure is formed to alleviate subtle irregularities on the surface of the rubber blank surface of the silicone blanket or to reduce the printing pressure. In order to satisfactorily exert the effect of adjusting, the average particle diameter of the hollow microspheres is preferably 20 μm or more and 200 μm or less, particularly 40 μm or more and 150 μm or less. In the case of unfoamed hollow microspheres described below, the particle size is the particle size after heating and foaming.

  Specific examples of the hollow microspheres include, for example, the Expandance series hollow microspheres manufactured by Nobel, or the hollow microspheres manufactured by Matsumoto Yushi Seiyaku Co., Ltd. Both of these hollow microspheres are a non-foamed material in which an organic solvent that becomes a void is enclosed in a thermoplastic resin shell, and the organic solvent is vaporized by heating. In the present invention, any of these can be used. When using the former, non-foamed hollow microspheres, it is not easy to control the particle size by foaming in the coating solution. Therefore, before forming the coating solution in addition to the liquid silicone rubber, the shell should be heated by heating. It is preferable that the organic solvent in the body is vaporized, the hollow microspheres are foamed to a predetermined particle size, and further classified as necessary.

  The mixing ratio of the hollow microspheres varies depending on the particle size of the hollow microspheres used, the presence or absence of surface treatment, etc., but 100 parts by mass of the room temperature curable silicone rubber (total amount of components that form the porous silicone rubber sheet by the curing reaction, For example, in the case of a two-component type, it is preferably 1 part by mass or more and 30 parts by mass or less, particularly 5 parts by mass or more and 15 parts by mass or less with respect to the total amount of the main agent and the curing reaction agent. If the blending ratio is less than the above range, the porosity of the formed porous silicone rubber sheet is lowered, and there is a possibility that good compression characteristics as an under blanket or a cushion layer of the silicone blanket cannot be obtained. In addition, when the blending ratio exceeds the above range, the viscosity of the coating solution increases even if diluted with an organic solvent or silicone oil, and the hollow microspheres are uniformly dispersed in the coating solution. It becomes difficult and the thickness and porosity of the porous silicone rubber sheet may vary.

  Examples of the base for forming the porous silicone rubber sheet by applying the coating liquid include a base material that forms an under blanket or a silicone blanket together with the porous silicone rubber sheet after the curing reaction. By covering the surface of the porous silicone rubber sheet with a coating layer made of a silicone resin, a laminate having a three-layer structure including the coating layer, the porous silicone rubber sheet, and a substrate is obtained. As the substrate, films of various resins such as polyethylene terephthalate (PET) and polycarbonate (PC), metal sheets, cloths, and the like can be used.

  In particular, when used as an under blanket, the formed porous silicone rubber sheet is porous silicone such as the base material, or a glass plate or a metal plate at any time before or after the formation of the coating layer. The rubber sheet may be peeled off from the surface of a work table or the like to produce a two-layer structure of the covering layer and the porous silicone rubber sheet. Alternatively, a coating layer can also be formed on the opposite surface of the porous silicone rubber sheet exposed by peeling off from the substrate or the like, and used as a three-layer structure. The thickness of the porous silicone rubber sheet used as a cushion layer for the under blanket or silicone blanket is preferably 0.05 mm or more and 2 mm or less, particularly 0.3 mm or more and 1 mm or less.

  The silicone blanket of the present invention includes the cushion layer made of the porous silicone rubber sheet and the surface rubber layer made of silicone rubber. The surface rubber layer includes, for example, a coating solution for a surface rubber layer containing room temperature curable silicone rubber, and a three-layer structure of a coating layer, a porous silicone rubber sheet, and a substrate described above. The base material is coated on the exposed surface, and the room temperature curable silicone rubber is not expanded or collapsed by softening the shell forming the hollow microspheres contained in the sheet, In addition, the room temperature curable silicone rubber can be formed by a curing reaction within a temperature range where the curing reaction sufficiently proceeds, preferably at a temperature around room temperature.

  As a result, a silicone blanket having a four-layer structure of a surface rubber layer, a base material, a cushion layer made of a porous silicone rubber sheet, and a coating layer made of a silicone resin is manufactured. The surface rubber layer may contain hollow microspheres to have a porous structure. However, in consideration of improving the smoothness of the surface and further improving the printing accuracy, the surface rubber layer includes hollow microspheres. It is preferable to form in a non-porous structure without containing. The thickness of the surface rubber layer is preferably 0.01 mm or more and 1.2 mm or less, particularly 0.1 mm or more and 1 mm or less.

Example 1
Additive type two-component room temperature curable silicone rubber main component [liquid, KE-1600 manufactured by Shin-Etsu Chemical Co., Ltd.] 100 parts by mass, hollow microsphere [MFL80CA manufactured by Matsumoto Yushi Seiyaku Co., Ltd., average 10 parts by mass of particle diameter 100 μm, heat distortion temperature 140 to 150 ° C.], mixed and dispersed, and then added 10 parts by mass of the room temperature curable silicone rubber curing reagent and further mixed to prepare a coating solution. did. Next, the coating solution is applied to a rectangular area of 120 cm in length and 150 cm in width on one side of a PET film having a thickness of 0.30 mm as a base material by a bar coating method, and allowed to stand at room temperature for 24 hours. Then, the room temperature curable silicone rubber was subjected to a curing reaction to form a porous silicone rubber sheet having a thickness of 0.70 mm.

  Next, a room temperature curable silicone resin in which the scratch hardness of the coating layer after the curing reaction, which is measured based on the measurement method defined in JIS K5600-5-4, is H, is dissolved in toluene. A coating solution having a solid content concentration of 5% by mass was prepared, and the coating solution was applied to the exposed surface of the porous silicone rubber sheet by a bar coating method, and allowed to stand at room temperature for 24 hours to evaporate toluene. At the same time, the silicone resin is cured to form a coating layer having a thickness of 1 μm, and a three-layer laminate of the coating layer, the porous silicone rubber sheet, and the PET film as the substrate is obtained. It was.

  Next, 100 parts by mass of the main component of a two-component room temperature curable silicone rubber of the same addition type as described above and 10 parts by mass of a curing reaction agent are mixed to prepare a coating solution. By applying this method, the PET film of the laminate is coated on the opposite surface of the PET film and allowed to stand at room temperature for 24 hours to cure the silicone rubber to form a surface rubber layer having a thickness of 0.50 mm. Thus, a silicone blanket having a four-layer structure of the surface rubber layer, a PET film as a substrate, a cushion layer made of a porous silicone rubber sheet, and a coating layer was produced.

Example 2
A silicone blanket having a four-layer structure was produced in the same manner as in Example 1 except that the coating layer was formed using a room temperature curable silicone resin having a scratch hardness of 2H after the curing reaction.
<< Comparative Example 1 >>
A silicone blanket having a three-layer structure consisting of a surface rubber layer, a PET film as a base material, and a cushion layer made of a porous silicone rubber sheet was prepared in the same manner as in Example 1 except that the coating layer was not formed. Manufactured.

<< Comparative Example 2 >>
A toluene dispersion of PTFE was prepared, and the toluene dispersion was applied to the exposed surface of the porous silicone rubber sheet by a spray coating method, and allowed to stand at room temperature for 24 hours to evaporate the toluene. A 4-layer silicone blanket was produced in the same manner as in Example 1 except that a coating layer made of 1 μm PTFE was formed.

<< Comparative Example 3 >>
A four-layer silicone blanket was produced in the same manner as in Example 1 except that the coating layer was formed using a room temperature curable silicone resin having a scratch hardness of 2B after the curing reaction.
<< Comparative Example 4 >>
A four-layer silicone blanket was produced in the same manner as in Example 1 except that the coating layer was formed using a room temperature curable silicone resin having a scratch hardness of 4H after the curing reaction.

<Evaluation of adhesiveness>
The silicone blanket manufactured in the example and comparative example was placed on the stone surface plate with the exposed surface of the cushion layer (only comparative example 1) or the surface on which the coating layer was formed facing down, When pulled, it was confirmed whether or not the whole moved smoothly, and the tackiness was evaluated according to the following criteria.

○: Moved smoothly without problems. The tackiness was sufficiently suppressed.
(Triangle | delta): Some catch was felt. The tackiness was not sufficiently suppressed.
X: It was caught and the movement was bad. The tackiness was not suppressed at all.
<Presence or absence of peeling of coating layer>
The silicone blanket manufactured in the examples and comparative examples was wound around the blanket cylinder of the offset printing machine, fixed and then removed, and the removed silicone blanket and the periphery of the blanket cylinder were observed. The presence or absence of peeling was evaluated.

○: No debris of the peeled coating layer was observed. No peeling off of the coating layer.
X: Debris of the peeled coating layer was observed. There is peeling of the coating layer.
《Flexibility evaluation》
When the silicone blankets produced in the examples and comparative examples were wound around and fixed around the blanket cylinder of an offset printing machine, the flexibility was evaluated according to the following criteria.

○: It was flexible and could be fixed without problems. Good flexibility.
X: The flexibility was low and there was a sense of resistance when winding or fixing. Poor flexibility.
The results are shown in Table 1.

表１より、多孔質シリコーンゴムシートからなるクッション層の表面が、被覆層によって被覆されずに露出された比較例１のシリコーンブランケットは、粘着性があって滑りにくいため、オフセット印刷機のブランケット胴の周囲に巻き付ける際に波打ったりしやすいことが判った。また、被覆層をＰＴＦＥによって形成した比較例２のシリコーンブランケットは、前記被覆層が、多孔質シリコーンゴムシートからなるクッション層の表面から剥落しやすく、剥落した被覆層が破片となってインキ中に混入して、印刷の画質を低下させる原因となることが判った。

From Table 1, the silicone blanket of Comparative Example 1 in which the surface of the cushion layer made of the porous silicone rubber sheet was exposed without being covered with the coating layer was sticky and difficult to slip. It turns out that it is easy to wave when winding around. Moreover, the silicone blanket of Comparative Example 2 in which the coating layer was formed of PTFE was easily peeled off from the surface of the cushion layer made of a porous silicone rubber sheet, and the peeled coating layer was broken into ink. It has been found that this can cause a reduction in printing image quality.

  Moreover, although the coating layer was formed with the silicone resin, it turned out that the silicone blanket of the comparative example 3 whose scratch hardness was less than B was not sufficient in the adhesive suppression effect by the said coating layer. Furthermore, although the coating layer was formed of a silicone resin, the silicone blanket of Comparative Example 4 in which the scratch hardness exceeded 3H had low flexibility, and thus it was found that the printing characteristics of the silicone blanket might be deteriorated. .

  On the other hand, the silicone blankets of Examples 1 and 2 are both evaluated as ○, and the adhesiveness of the cushion layer made of the porous silicone rubber sheet is sufficiently suppressed by the coating layer. In addition, it is difficult to wave when wrapped around the blanket cylinder of an offset printing machine, and the covering layer is not peeled off from the surface of the cushion layer, and there is no possibility of generating debris that causes deterioration in printing image quality. It has been found that because of the high flexibility, there is no risk of degrading the printing properties of the silicone blanket.

Claims (3)

  A porous silicone rubber sheet made of silicone rubber and having a porous structure, and a coating layer made of a silicone resin having a scratch hardness (pencil method) of B or more and 3H or less formed on at least one surface. Porous silicone rubber sheet characterized by   The porous silicone rubber sheet according to claim 1, wherein the coating layer has a thickness of 0.1 μm or more and 10 μm or less.   A silicone blanket comprising a cushion layer made of the porous silicone rubber sheet according to claim 1 and a surface rubber layer made of silicone rubber.