JPS6155670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a lithographic printing plate that does not require dampening water, and more specifically to a lithographic printing plate that has extremely excellent properties in terms of resolution, printing durability, etc. Concerning printing plates and their manufacturing method.

In lithographic printing, a plate is used that does not have clear heights on the plate surface like letterpress or intaglio, and has a printed area and a non-printed area on the same plane in appearance.This printing method involves the following process. It will be held in In other words, first of all, water and fat repel each other,
The non-image area is made hydrophilic by chemical or mechanical treatment, and the image area is made lipophilic by transfer of a fatty resin or photographic printing, and then water is transferred to the printing plate. After that, water is applied only to the hydrophilic non-image areas, and then ink is further transferred to this plate surface. In this way,
This ink does not adhere to the non-print areas where water is present, but only to the lipophilic print areas, so
This is then transferred to a substrate to obtain the desired printed material.

However, in this lithographic printing method, for example, the transfer of the dampening water to the ink roller causes the ink to emulsify on the ink roller, which causes stains, and also The transfer to the printing material also causes a change in the dimensions of the printing material, so there is a major drawback that the printed image becomes unclear, especially in multicolor printing. In addition, in this lithographic printing method, in order to obtain printed matter with a constant color tone, it is necessary to maintain a constant amount of dampening water and ink. It is very difficult to maintain this balance, which has the disadvantage of causing variations in the color tone of printed matter.

For this reason, attempts have been made to develop printing plates for lithographic printing that do not require dampening water in order to improve the above-mentioned disadvantages, but none of the plates known to date are sufficiently satisfactory for practical use. It has not yet reached the point where it shows the characteristics it should have.

For example, a diazo photosensitive layer made of a diazo type photosensitive composition and a dimethylpolysiloxane rubber layer are formed on a substrate such as an aluminum plate, and then a positive film is further laminated thereon and then exposed. A method of insolubilizing the diazo photosensitive layer in the exposed areas, removing the diazo photosensitive layer in the non-exposed areas by development treatment, and then peeling off the dimethylpolysiloxane rubber layer in the non-exposed areas (Tokuko Sho)
44-23042), or on a substrate such as an aluminum plate, a diazo photosensitive layer, an adhesive layer, and a silicone rubber layer are sequentially formed, and then a negative film is superimposed on this layer and exposed. A method of obtaining a printing plate for lithographic printing by developing the photosensitive layer using photodecomposition and then peeling off the silicone rubber layer in the exposed area (Japanese Patent Publication No. 1973-
16044 publication process) is known. However, in all of these methods, a non-photosensitive silicone rubber exists between the diazo photosensitive layer and the positive or negative film, so it is difficult to accurately reproduce the pattern appearing on the positive or negative film. Furthermore, since the silicone rubber layer is peeled off by utilizing changes in the solvent solubility of the photosensitive layer, the edges of the image formed by the silicone rubber layer after peeling off are poor. There is a serious drawback that it does not become sharp,
This also has the disadvantage of a complicated operation, since its manufacture involves the steps of successively depositing two or three layers on a substrate, exposing and developing.

As a method to eliminate the above-mentioned drawbacks in the development operation, there are methods of destroying the silicone layer by electron beam, laser light, electric discharge, etc. (see Japanese Patent Publication No. 42-21879), and by scanning the silicone layer with glow or corona beam. How to make it lipophilic
8207) is known. According to this, by destroying the silicone layer with an electron beam, laser beam, electric discharge, etc., or processing it with a corona beam, offset printing can be performed without any developing operation and without dampening water. However, high energy is required to destroy the ink repellent layer of dimethylpolysiloxane and generate low molecular weight dimethylpolysiloxane, and the plate making apparatus becomes large-scale. Furthermore, when patterning the silicone layer, the silicone is thermally destroyed with high energy, which causes the edges of the image to swell and the sharpness of the image to be lost, resulting in a reduction in resolution and print quality. . Also,
When using a corona beam, the printing plate takes a long time to form an image by scanning the ink repellent layer, and special equipment is required.

The inventors of the present invention have comprehensively studied material selection and manufacturing methods, taking into account the above-mentioned drawbacks of conventional lithographic printing plates that do not require dampening water.
By selectively chemically treating with activated chemical species in a plasma state, the oil-repellent organopolysiloxane cured film changes to lipophilicity, and unlike corona discharge or flame treatment, this change makes the cured film layer more oleophilic. It extends not only to the surface but also to the inside, and by using a protective layer containing plasma resistance, it is possible to selectively prevent chemical treatment with a thin protective layer, and it can be processed in a short time with low energy. , and found that it has high resolution, and arrived at the present invention.

That is, in the present invention, a cured film layer of organopolysiloxane is provided on one surface of a substrate, and then a protective layer containing plasma resistance is provided in a pattern on the cured film layer. By chemically treating the non-protective layer portion of the cured film layer with the cured chemical species and then removing the protective layer, the non-image area consisting of the organopolysiloxane cured film layer and the chemical treatment are formed on the substrate. The gist of the present invention is a method for producing a printing plate for lithographic printing, characterized in that an image area is formed of an organopolysiloxane layer.
The method for producing a printing plate for lithographic printing of the present invention applies chemical treatment using plasma, and therefore has the following excellent characteristics.

(1) Since the organopolysiloxane itself does not require pattern forming ability, it can be freely selected from organopolysiloxanes with excellent solvent resistance, abrasion resistance, adhesion to substrates, etc.

(2) Chemical treatment using plasma utilizes a reaction between the gas phase and the solid phase, so almost no physical force is applied to the protective layer, and its adhesion to the organopolysiloxane cured film layer is comparatively low. It's good to have a small target. The resolution depends only on the resolution of the protective layer itself and is not affected by patterning, so high resolution can be obtained.

(3) The organopolysiloxane cured film layer has high gas permeability, and active chemical species can easily penetrate into the layer. For this reason, not only the surface but also the inside is chemically treated.

(4) Since activated chemical species in a plasma state can be guided from the plasma generation chamber to other chambers, activated chemical species can be supplied from one generator to multiple chambers, and at the same time Multiple printing plates can be made in an hour, and the equipment is relatively inexpensive.

(5) The printing plate for lithographic printing of the present invention has no difference in height between the image area and the non-image area, so compared to the conventional planar intaglio plate obtained by removing the silicone layer.
The transfer of ink to the plate blanket is improved, resulting in improved print quality.

(6) Negative and positive plates can be easily produced by selecting the protective layer.

The present invention will be explained in detail below.

First, the present invention will be explained based on the drawings.
The figure is a partially enlarged cross-sectional view schematically illustrating the structure of the printing plate for lithographic printing of the present invention. layer 2 (non-printing part),
It has an ink-receptive layer 2' (image area) consisting of an organopolysilosane cured film layer chemically treated by plasma.

Next, a method for producing a printing plate for lithographic printing according to the present invention will be explained. As shown in FIG.
After providing the film with a thickness of 2 to 50 μm,
As shown in FIG. 2, a protective layer 3 containing plasma resistance is provided in a pattern on the organopolysiloxane cured film layer 2. As shown in FIG. Next, when chemically treated with plasma, the organopolysiloxane cured film layer in the area where the protective layer 3 is not provided is modified and made lipophilic, as shown in FIG. ' is formed. Thereafter, the protective layer 3 is removed to obtain the printing plate of the present invention as shown in FIG.

The above-mentioned substrates are made of materials that are not affected by oxidation or etching due to chemical treatment using plasma, or photodegradation reactions caused by ultraviolet light generated by plasma. Specific examples include copper plates, aluminum plates, and stainless steel plates. Metal plates such as plates, zinc plates, iron plates, nickel-plated copper plates or iron plates, or chrome-plated iron plates, and the above-mentioned various metal foils placed on other substrate materials such as paper and plastic, as well as paper and plastic alone or Compounds etc. can be used.

Next, as the organopolysiloxane used to form the organopolysiloxane cured film layer 2 on the substrate, it is desirable that the organopolysiloxane has excellent strength and abrasion resistance, has good printing durability, and has strong ink repellency. Various thermosetting organopolysiloxanes containing as a main component are preferably used. As a thermosetting organopolysiloxane,
There are one-component type and two-component type, and the two-component type cures ≡Si-OH, ≡Si-OR, ≡Si-H, ≡Si-CH.
This is due to a catalytic crosslinking reaction between siloxanes having reactive groups such as =CH ₂ , and crosslinking reactions occur through dehydration condensation, dealcoholization condensation, dehydrogenation condensation, addition polymerization, etc. One-component curing reacts with moisture in the air to cause a condensation curing reaction, and includes deacetic acid type, deamined type, dealcoholized type, and deoxime type. These are applied to one surface of the substrate by dissolving them in a suitable solvent such as benzene or toluene, applying them by a spin coating method, dipping method, dripping method, etc., and then heating and drying.

The specific type of organopolysiloxane used to form the ink-repellent organopolysiloxane cured film layer 2 is one that crosslinks and cures at room temperature or by heating after coating to become an ink-repellent silicone rubber elastic body. Highly polymerized organopolysiloxanes (which have excellent ink repellency), in which 90 mol% or more of all organic groups bonded to elementary atoms are methyl groups, are preferred; Highly polymerized diorganopolysiloxane in which 90 mol% or more of organic groups are methyl groups, with both chain ends capped with hydroxyl groups, methylhydrodiene polysiloxane or ethyl polysilicate as a crosslinking agent, and organic acid metal salt as a condensation catalyst. (2) a vinyl group-containing highly polymerized diorganopolysiloxane (at least 90 mol% of organic groups other than vinyl groups are methyl groups), a methylhydrodiene polysiloxane as a crosslinking agent, and an addition reaction catalyst. (3) a highly polymerized diorganopolysiloxane in which 90 mol% or more of the organic groups with both ends of the molecular chain blocked with hydroxyl groups are methyl groups;
Examples of crosslinking agents include silanes or low polymerization degree siloxane compounds having three or more hydrolyzable groups such as acetoxy groups, amino groups, oxime groups, or propenoxy groups in one molecule. In the present invention, the types exemplified in (1) or (2) above are particularly suitable.

In addition, organic groups other than methyl groups in the above generally include aryl groups such as phenyl groups, alkenyl groups such as vinyl groups, alkyl groups such as ethyl groups and propyl groups, and halogen-substituted alkyl groups such as trifluoropropyl groups. is exemplified.

If necessary, the compositions exemplified in (1), (2) and (3) above may contain conventional diorganopolysiloxanes such as dimethylpolysiloxane to further improve ink repellency, which have an adverse effect on the properties of the cured coating film. There is no problem in adding a small amount of reinforcing filler such as fine powder of silica, aluminum oxide, titanium oxide, zinc oxide, etc. for the purpose of improving printing durability.

In order to form a uniform film of organopolysiloxane, it is desirable to clean the surface of the substrate in advance by an appropriate method and, if necessary, roughen the surface to improve the adhesion with the film. In addition, a primer may be applied to the surface of the substrate in advance to improve adhesion with the coating.
This primer includes vinyltris(2-methoxyethoxy)silane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, N-(3-trimethoxysilylpropyl)ethylenediamine, 3-glycidoxypropyltrimethoxysilane,
Silanes such as aminopropyltriethoxysilane alone or mixtures thereof, as well as partial hydrolysates or co-hydrolysates thereof, are used;
These are applied by conventional methods such as spin coating, rod coating, brush coating, and spray coating.

Next, the protective layer 3 formed on the organopolysiloxane cured film layer 2 is not significantly affected by various radical reactions, photodecomposition reactions, etc. that occur during chemical treatment using plasma, and is not significantly affected by the organopolysiloxane cured film layer 2. Materials that do not peel off from the surface of the film layer are used, but if the film is thicker than a few microns, many materials can be used because chemical treatment using plasma is usually carried out within tens of seconds to several minutes. Become. Examples of such materials include commercially available photoresists such as Photoresist AZ manufactured by Shippray Co., Ltd., Photoresist OMR and TPR manufactured by Tokyo Ohka Co., Ltd., and a number of photosensitive resins and coatable photosensitive materials. In the case of a commercially available product, it is patterned by a normal photoresist plate making method. In addition, to form a photoresist image, there are two methods: directly applying a photoresist solution onto the organopolysiloxane cured film layer using a conventional coating method, and applying the photoresist solution onto a film of polyethylene, polypropylene, etc., drying it, and then heat-pressing it. A method of transferring onto an organopolysiloxane cured film layer can be applied, and patterning is then performed. In the method of directly coating onto the organopolysiloxane cured film layer, the photoresist solution may be repelled by the cured organopolysiloxane film, so it is necessary to reduce the viscosity of the photoresist solution by adding an appropriate surfactant or the like.

Although the commercially available photoresists mentioned above cannot necessarily be said to have good affinity with organopolysiloxane cured films, photosensitive silicone liquids in which photosensitive groups have been introduced into organopolysiloxanes show good affinity and are the most suitable for coating. Cheap. In this case, the film thickness is 2~
Shows sufficient plasma resistance at 5 μm.

The photosensitive silicone liquid (photocurable organopolysiloxane) needs to have good wettability to the organopolysiloxane cured film layer 2,
For this purpose, organopolysiloxane cured film layer 2
It is preferable that the surface tension is approximately the same as that of the photocurable organopolysiloxane. The surface tension is 18 to 25 dyn/cm, preferably 20 to 23 dyn/cm.

Among the above-mentioned photosensitive silicones, organopolysiloxanes having siloxane units bonded to maleimide groups or maleimide groups containing substituted atoms or groups (JP-A-51-120804, 51−
No. 125277, No. 52-13907, No. 52-105002, No.
52-116304, etc.), organopolysiloxanes having siloxane units bonded to acryloxy groups or acryloxy groups containing substituted atoms or groups (JP-A-48-16991, JP-A-48-19682, JP-A-48-19682)
No. 48-21779, No. 48-23880, No. 48-47997,
No. 48-48000, No. 48-83722, No. 51-34291
No. 51-52001, No. 52-105003, No. 52-
No. 105004, No. 52-113805, No. 52-113801, etc.), a mixture of an organopolysiloxane having a mercapto group-containing siloxane unit and an organopolysiloxane having a vinyl group-containing siloxane unit (JP-A-53-17405) ), mixtures of organopolysiloxanes and organohydrodiene polysiloxanes having vinyl group-containing siloxane units (see JP-A-53-15907, etc.), organopolysiloxanes having amide group-containing siloxane units (see JP-A-53-15907), JP-A-52-139200, JP-A-52-139504, etc.), mixtures of organopolysiloxanes having acryloxy group-containing siloxane units and organopolysiloxanes having vinyl-containing siloxane units (see JP-A-52-139505, etc.) ) etc. are exemplified.

Examples of mixtures of silicone and photosensitive substances include mixtures of organopolysiloxanes and photosensitive substances such as azide compounds, p-quinonediazide compounds, cinnamic acids, acrylic acids, and acrylates (Japanese Patent Application Laid-open No. 49-1989-1). No. 68803, 49-
Examples include various silicones such as No. 86102, No. 49-121601, No. 51-134204, etc.).

The resist layer can also be formed into a pattern by screen printing using an ink containing ethyl cellulose, ethyl hydroxy cellulose, acrylic resin, or the like. In this case as well, direct printing and transfer methods are available, but addition of a thinner reduces printing suitability, so transferability is desirable. Furthermore, the resist layer can also be formed by electrostatic printing using electrostatic photographic toner or the like as a resist material. In this case, since the organopolysiloxane cured film layer is an insulator, it is possible to form good electrostatic latent images and toner images. More simply, the film-forming resin liquid may be hand-painted or transferred by an appropriate printing means.

In the present invention, chemically treating the surface of the cured film layer of organopolysiloxane using plasma
Plasma treatment with inert gases such as Ar, He, Ne or active gases such as oxygen or air is suitable. In chemical treatment using plasma,
(1) Etching, (2) Chemical modification, (3) Crosslinking, (4) Polymerization
Although it is said that a complex combination of types of changes occur, in the plasma treatment using an inert gas or active gas in the present invention, electron microscopic observation and infrared absorption measurements show that surface etching does not occur, but mainly organopolymerization. Chemical modification of the siloxane cured film layer, ie, elimination of alkyl groups and generation of hydroxyl groups and carbonyl groups, occurs. As a result, active chemical species in the plasma state collide with the surface of the cured organopolysiloxane film, resulting in the elimination of alkyl radicals and the generation of silicon radicals.
Three-dimensionalization of organopolysiloxane by crosslinking,
It is thought that hydroxyl groups, carbonyl groups, etc. are generated due to oxidation of alkyl groups, etc. Furthermore, these reactions proceed not only on the surface of the cured organopolysiloxane film layer but also considerably deep inside the organopolysiloxane cured film layer depending on the processing time. It is presumed that this is because the cured organopolysiloxane film layer generally has high gas permeability, so that the active chemical species reach the inside of the layer.

On the other hand, corona treatment and flame treatment only work on the surface, and this effect is usually lost by simply rubbing it with your hands or cloth. In contrast, in the plasma treatment according to the present invention, the effect is not lost even if the treated film is rubbed to the point of wear.

The low-pressure atmosphere for forming plasma active chemical species may generally be air, but it may also contain inert gases such as Ar, Ne, He, etc., active gases such as O ₂ , N ₂ , NH ₃ , CO ₂ , fluorinated hydrocarbon gases, etc. Gas can be used.

The plasma lipophilization treatment time varies depending on the conditions, but for example, under the conditions of 3 × 10 ^-2 Torr and 300 W, the organopolysiloxane cured film layer is effectively modified in 30 seconds or more, but under the same conditions If the time is longer than 20 minutes, the protective layer will deteriorate due to the etching effect, which is not preferable.

When the plasma protective layer is made thinner to provide higher resolution, plasma resistance generally decreases. This is because the general organic protective layer, like the silicone layer, is attacked by plasma and vaporized and scattered for a while, becoming thinner. Therefore, according to the present invention, if a substance having plasma resistance is mixed in the organic protective layer, even a thin protective layer can function sufficiently and high resolution can be obtained. Organic or inorganic fillers are generally used, with inorganic fillers being particularly preferred. The reason for this is that even if the inorganic filler is attacked by oxygen plasma and undergoes a chemical change, it tends to remain as an oxide. Therefore, if metal oxides such as ZnO, TiO ₂ , Cu ₂ O, etc., no chemical change occurs and they will not be attacked.

Since the characteristic of plasma attack is that it attacks perpendicular objects at right angles, even a material simply placed on the organopolysiloxane cured film layer has a protective effect.
For this reason, the filler in the protective layer can therefore be regulated to a suitable amount.

These inorganic substances include SiO ₂ , TiO ₂ , ZnO,
_PbO2 , _Al2O3 , Al(OH) _{3 ,} Fe, Zn, Sn, Ni,
It is desirable that metal powders such as Cu, Ge, Al, or metal sulfides, double salts, complex salt powders, etc. (inorganic pigments are preferred) be mixed alone or in a mixture of about 10 to 70% by weight in the protective layer. .

When the organopolysiloxane cured film layer is sufficiently plasma-treated, it becomes slightly matte and has a whiter surface than the untreated portion. However, visibility is not very good. Therefore, if the organopolysiloxane cured film layer contains a substance that causes color development, decolorization, or other color changes by utilizing the chemical reactivity of plasma gas, the plasma treatment effect becomes very obvious. For example, in oxygen or air plasma treatment, if a solvent-soluble basic dye or other oxidative decolorizing dye is present, the plasma-treated area is decolored, allowing the treated area and the degree of treatment to be recognized.

As the dye, ordinary disperse dyes and cationic dyes can be used. For example, Kayaset Blue FR (manufactured by Nippon Kayaku), TS
- Violet 501 (manufactured by Sumitomo Chemical); cationic dyes include crystal violet and methylene blue; it is desirable to contain the dye in an amount of about 0.01 to 5% by weight based on the organopolysiloxane;

On the other hand, if it contains an oxidative color-forming dye or pigment, the plasma treated area will be colored. For example, when a leuco dye is included, the color of the dye is formed only in the treated area. As examples of this type, lactone-cyclized leuco dyes (such as methylene blue) and dyes that have been reduced and made colorless (vat dyes) are generally easy to use.

Since the organopolysiloxane cured film layer has good gas permeability, active gas can penetrate into the layer during plasma treatment, and the entire layer can be treated. Therefore, in order to determine the end point of the treatment, if the subbing layer (anchor layer or silane coupling agent layer) of the organopolysiloxane cured film layer contains the above-mentioned color-changing substance, the subbing layer (anchor layer or silane coupling agent layer) of the cured organopolysiloxane film layer can be used to determine the end point of the treatment. It can act on the discoloration substance in the coating layer to cause color development, decolorization, and other discoloration. This method is extremely effective in determining the end point of plasma processing.

Next, in order to remove the protective layer after chemical treatment with plasma, in the case of photoresist, it is not preferable to use strong acids or strong alkalis that can damage the organopolysiloxane cured film layer, such as acetone, ethyl cellosolve, toluene, etc. It is desirable to remove it with a solvent such as for example,
Photoresist AZ manufactured by Shippray is acetone,
It can be removed by dissolving with methyl ethyl ketone (MEK), etc., and with Tokyo Ohka TPR, it can be removed with ethyl cellosolve. A resist layer formed by screen printing can be removed using a solvent such as toluene, and a resist layer formed by electrostatic printing can be removed using a polar solvent such as MEK. Furthermore, since the organopolysiloxane cured film layer generally has weak adhesion to other substances, the residual resist film can be easily removed using a suitable adhesive tape, adhesive sheet, or the like.

The lithographic printing plate of the present invention manufactured as described above has a structure as shown in FIG. When ink is supplied to a lithographic printing plate from an ink roller, the adhesion between the ink and the non-printing area, that is, the organopolysiloxane cured film layer, is reduced between the ink and the roller or the ink particles. Because the ink is lower than the cohesive force between the two, the ink is not transferred to the non-image area 2, and the ink adheres only to the image area 2' whose surface has been plasma-treated. Therefore, this provides the advantage that dampening water, which is conventionally required, is completely unnecessary.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 After forming a cured film of polydimethylsiloxane (KS774, manufactured by Shin-Etsu Chemical Co., Ltd.) to a thickness of 5 μm on an aluminum substrate, the film was coated at the interface with 100 parts by weight of a polycinnamic acid-based photosensitive resin (TPR, manufactured by Tokyo Ohka Chemical Co., Ltd.). In a mixed solution of 0.4 parts by weight of an activator (manufactured by 3M, FC431),
A liquid in which fine powders of SiO ₂ , TiO ₂ , and Al ₂ O ₃ were separately mixed and dispersed was applied. The amount of these fine powders added was 2% by weight (for the photosensitive liquid).

The coating film thickness was adjusted to 1 μm, 2 μm, and 3 μm.
Each plate was exposed and developed according to the TPR processing method, and then placed in a plasma reaction chamber and subjected to plasma treatment for 2 minutes under the conditions of 300 W and 0.3 Torr in the atmosphere.

As a result, the film thickness of each fine powder-containing photosensitive resin was 1 μm as a protective film necessary to sufficiently plasma-treat a 5 μm thick polydimethylsiloxane layer.
At 2 μm or more, it was slightly insufficient, and at 2 μm or more, it was quite good. In the case of no fine powder (filler), the protective film thickness needs to be 3 to 4 μm or more, but the objective can be achieved with about half the film thickness, and the resolution can be achieved with a film thickness of 2 μm.
The resolution limit was 5% dot for the 250 lines/inch mesh plate.

Example 2 In Example 1 (when the protective layer has a thickness of 2 μm), fine powders of SiO ₂ , TiO ₂ , and Al ₂ O ₃ were separately added to the polyorganosiloxane layer having a thickness of 5 μm at a solid content ratio of 2 μm. It was mixed and dispersed in weight%. A comparison of printing durability after plasma platemaking showed the following results.

Printing durability No filler 50,000 sheets SiO ₂ 100,000 sheets TiO ₂ 80,000 sheets Al ₂ O ₃ 70,000 sheets This shows that having some filler in the polyorganosiloxane layer is effective in improving printing durability. It turns out that there is something.

[Brief explanation of the drawing]

FIGS. 1 to 4 are partially enlarged cross-sectional views of successive steps showing the manufacturing process of a printing plate for lithographic printing according to the present invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Non-image area consisting of an organopolysiloxane cured film layer, 2'...An image area consisting of an organopolysiloxane cured film layer whose surface has been chemically treated with plasma, 3...Protective layer .

Claims (1)

[Claims] 1. A cured film layer of organopolysiloxane is provided on one side of the substrate, and then a protective layer containing a plasma-resistant substance is provided in a pattern on the cured film layer, and then an activated chemical in a plasma state is applied. By chemically treating the non-protective layer portion of the cured film layer with a seed and then removing the protective layer, the non-image area consisting of the cured film layer of organopolysiloxane and the chemically treated organopolysiloxane film layer are formed on the substrate. 1. A method for producing a printing plate for lithographic printing, comprising forming an image area made of a siloxane layer.