JP2003005351A - Regenerative system plate making and printing method on printing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regenerative system plate making and printing method on a printing machine. SOLUTION: (A) A photosensitive plate material comprising a positive photosensitive composition is supplied and applied from a plate material supplying mechanism (4) on a support (3) fixed on a plate cylinder (21) to form a photosensitive planographic printing plate. (B) The photosensitive planographic printing plate is imagewise exposed with an exposure mechanism (5) and (C) a processing agent for plate making is supplied from a processing agent supplying mechanism onto the imagewise exposed photosensitive planographic printing plate, a physical impetus is give if necessary and an image is formed. (D) Printing ink and dampening water are supplied from an ink supplier (6) and a dampening device (7) to the surface of the image on the photosensitive planographic printing plate, the plate cylinder (21), a blanket cylinder (22) and a platen (23) are rotated under contact and printing paper is supplied between the blanket cylinder (22) and the platen (23) to carry out printing, and (E) the image area on the support (3) is removed with plate material removing mechanisms (81)-(85) to regenerate the support.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative printing plate making / printing method.

[0002]

2. Description of the Related Art A plate-making method using a lithographic printing machine, that is, a plate-making method on a printing machine has heretofore been known. For example, Japanese Patent Application Laid-Open No. 11-2168 proposed by the present applicant.
JP-A-35-35 describes an improved on-press plate making method.

The above-mentioned on-press plate making method is carried out on a lithographic printing machine equipped with a printing section consisting of a plate cylinder, a blanket cylinder and an impression cylinder, in which (A): imagewise exposed photosensitive lithographic printing fixed on the plate cylinder. The plate-making treatment agent is supplied from a plate-making treatment agent supply roller arranged in contact with the plate, and then (B):
A method for making a plate on a printing machine of a photosensitive lithographic printing plate, which comprises rotating the plate cylinder and the blanket cylinder in contact to form an image by applying a physical stimulus on the photosensitive lithographic printing plate, wherein The method is characterized in that the operation of (B) above is performed after the cylinder is placed in a separated state and the feeding of the paper to the impression cylinder is stopped. This is a method in which printing is performed after the lithographic printing plate is fixed and the plate is made, in order to reduce the waste of paper (waste paper) and to reduce the inclusion of dust in the plate making agent (printing ink, fountain solution, etc.). It is a method.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve a conventional on-press plate making method so that the plate can be regenerated on the printing machine. To provide. Another object of the present invention is to provide a regenerative printing plate making / printing method having a white surlight property and excellent in working environment.

[0005]

That is, the gist of the present invention is to provide a lithographic printing machine equipped with a printing section consisting of a plate cylinder, a blanket cylinder and an impression cylinder, in which the cylinders are separated from each other and After stopping the paper feeding, (A):
From a positive photosensitive composition containing a photothermal conversion substance (a) which absorbs light of an image exposure light source from a plate supply mechanism and converts it into heat on a support fixed on a plate cylinder and an alkali-soluble resin (b) To form a photosensitive lithographic printing plate, and then (B): after image-exposing the photosensitive lithographic printing plate by the exposure mechanism, (C): image-exposed photosensitive lithographic printing plate A plate-making treatment agent is supplied to the above from the plate-making treatment agent supply mechanism, and if necessary, a physical stimulus is given to form an image, and then (D): on the image surface of the photosensitive lithographic printing plate. Printing ink and dampening water are supplied from the ink inking device and the dampening device, respectively, and the printing cylinder, the blanket cylinder and the impression cylinder are brought into contact rotation, and the printing paper is supplied between the blanket cylinder and the impression cylinder. After printing,
After separating the cylinders from each other and stopping the feeding of the paper to the impression cylinder, (E): the image portion on the support is removed by the plate agent removing mechanism to reproduce the support. It is characterized by a regenerative on-press plate making / printing method.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram of an example of an apparatus for performing a regenerative on-press plate making / printing method according to the present invention.

The apparatus shown in FIG. 1 makes it possible to separate the plate cylinder (21), the blanket cylinder (22) and the impression cylinder (23) from each other and to control the stoppage of the feeding of the paper to the impression cylinder (23). It is possible to separate the inking roller of the ink inking device (6) and the watering roller of the dampening device (7) as a plate-making processing agent supply mechanism from the plate cylinder (21), and fix the support. In addition to the means (31), the plate agent supply mechanism (4), and the exposure mechanism (5), the plate agent solution supply mechanism (81), a plate agent peeling roller (82) provided as necessary, and a cleaning water supply mechanism. (83), an auxiliary device such as a plate material removing mechanism including a waste liquid collecting mechanism (84) and an air-type drying mechanism (85) is arranged, and the entire front surface is accommodated in a slidable casing (1). It is the same as the conventionally known lithographic printing machine except that

The above-mentioned separation between the cylinders is performed by an appropriate mechanical means such as using an eccentric bush for the blanket cylinder (22) and the impression cylinder (23), and the plate cylinder (21).
The inking roller of the inking device (6) and the watering roller of the dampening device (7) are separated from each other by a suitable mechanical device such as a cam provided on the plate cylinder (21) and a link provided on each roller. It can be done by means. The support fixing means (31) can be implemented by means of a structure in which both ends of the support (3) are inserted into the grooves on the plate cylinder (21) and wedge-fastened.

The plate supply mechanism (4), the plate solution supply mechanism (81) and the wash water supply mechanism (83) are all arranged in a liquid receiving bucket and partially inserted in the liquid receiving bucket. The waste liquid recovery mechanism (84) is composed of a roller, and the waste liquid collecting mechanism (84) is substantially the same as the liquid receiving bucket and the roller partially inserted in the liquid receiving bucket and capable of sucking as needed (support (3)). The air type drying mechanism (85) is composed of a blowing fan. Plate agent supply mechanism (4), Plate agent solution supply mechanism (81)
The cleaning water supply mechanism (83) can be configured by a spray device in addition to the roller mechanism described above. Further, the plate release roller (82) can be formed by, for example, imparting appropriate friction resistance or tackiness to the roller surface.

Plate supply mechanism (4), plate solution supply mechanism (81), plate release roller (82), wash water supply mechanism (83), waste liquid recovery mechanism (84) and air type drying mechanism (85). ) Can be configured to be mounted on a rack-shaped stand arranged opposite to the plate cylinder (21) and can be raised and lowered by a gear mechanism of a rack and pinion. With such a configuration, the elements required for each process of plate making, printing, and reproducing are arranged close to the plate cylinder (21) each time.

The exposure mechanism (5) is composed of an optical device for irradiating light having a wavelength suitable for the curing reaction of the positive photosensitive composition which constitutes the photosensitive plate material, based on the digital data of the image. The light source is preferably a semiconductor laser having a wavelength of 600 to 1300 nm, particularly a laser having a wavelength of 830 nm or a laser having a wavelength of 1060 nm. If necessary, the pollution prevention tray (86) may be slidably arranged between the plate cylinder (21) and the blanket cylinder (22). Also, such a pollution control tray (86) can be arranged between the blanket cylinder (22) and the impression cylinder (23). The slide mechanism of the pollution prevention tray (86) can be constituted by, for example, a rack and pinion gear mechanism.

A casing (1) having an open front surface
Can be easily slid by a guide rail (not shown) installed on the floor, for example. In addition, a dust filter (1) installed on the ceiling of the casing (1)
As 1), an appropriate commercial product can be used.
Reference numeral (12) in FIG. 1 is an exhaust duct provided at the bottom of the casing (1) as necessary.

Those means and mechanisms for improving the lithographic printing machine as described above can be easily constructed by those skilled in the art based on well-known and commonly used means.

According to the method of the present invention, the steps of plate making, printing and recycling are repeated on a lithographic printing machine equipped with a printing section comprising a plate cylinder (21), a blanket cylinder (22) and an impression cylinder (23). . Hereinafter, each step will be described.

<Plate-making process (AC)> As the support (3), for example, a grained aluminum plate can be used. The positive photosensitive composition constituting the photosensitive plate agent is not particularly limited as long as it contains a photothermal conversion substance (a) which absorbs light of an image exposure light source and converts it into heat and an alkali-soluble resin (b). However, such a positive photosensitive composition known in the related art can be used without limitation.

The above-mentioned positive-type photosensitive composition is a heat-decomposable substance (hereinafter referred to as a "heat-decomposable substance") which is decomposed by the action of heat generated by the light-heat converting substance described later absorbing the light of the image exposure light source. (Sometimes referred to)) is preferably not included. The above-mentioned thermally decomposable substances are onium salts, diazonium salts and quinonediazide compounds as described in JP-A-7-28527. Such a photosensitive composition containing no heat-decomposable substance has substantially no sensitivity to light in the ultraviolet region and can be handled under a white lamp.

Here, "having substantially no sensitivity to light in the ultraviolet region" means that there is a substantially significant difference in solubility in an alkali developing solution before and after irradiation with light having a wavelength of 360 to 450 nm. No, it means that it does not have an image forming ability in a practical sense. For example, a white fluorescent lamp (36W white fluorescent lamp "Neolmi Super FLR40 manufactured by Mitsubishi Electric Corporation"
(S-W / M / 36 "), showing the result that the solubility of the composition in an alkali developing solution after being left for 10 hours under irradiation with a light intensity of 400 lux does not substantially change compared to before being left. Say

As the photothermal conversion substance which absorbs the light of the image exposure light source and converts it into heat in the above-mentioned positive type photosensitive composition, for example, a near infrared ray having a wavelength range of usually 650 to 1300 nm, preferably 800 to 1300 nm. Examples thereof include organic or inorganic pigments, dyes, organic pigments, metals, metal oxides, metal carbides, metal borides and the like which have an absorption band in a part or all of the region. Of these, light absorbing dyes are particularly effective. Such a light-absorbing dye efficiently absorbs light in the above-mentioned wavelength range, but hardly absorbs light in the ultraviolet region, or does not substantially react even if it absorbs light. Is a compound which does not act to modify the photosensitive composition.

As the above-mentioned light absorbing dye, a so-called cyanine dye in a broad sense, in which a heterocycle containing a nitrogen atom, an oxygen atom, a sulfur atom or the like is bonded with polymethine (-CH =) _n , is typical. Can be mentioned. Specifically, for example, quinoline-based (so-called cyanine-based in a narrow sense), indole-based (so-called indocyanine-based), benzothiazole-based (so-called thiocyanine-based), aminobenzene-based (so-called,
Polymethine type), pyrylium type, thiapyrylium type, squarylium type, croconium type, and azurenium type. Of these, quinoline-based, indole-based, benzothiazole-based, aminobenzene-based, pyrylium-based or thiapyrylium-based are preferred. Other,
Aminium-based, immonium-based, phthalocyanine-based, and anthraquinone-based dyes are also representative. Of these, aminium-based or immonium-based dyes are preferable.

The alkali-soluble resin used in the present invention is
Basically, in the combination with the photothermal conversion substance, the exposed part and the unexposed part are mainly changed by a change other than a chemical change,
It is a polymer that causes a difference in solubility in an alkali developer, and naturally, the polymer itself includes a polymer compound whose solubility in an alkali developer changes mainly due to changes other than chemical changes. Examples of such polymers include novolac resins, resole resins, polyvinylphenol resins, alkali-soluble resins such as copolymers of acrylic acid derivatives, and the like. Among these, a resin having a phenolic hydroxyl group, particularly a polymer containing a nopolak resin and / or a phenol resin is preferable.

In particular, the following positive photosensitive compositions proposed by the Applicant are suitable examples.

(1) In order to increase the surface hardness of the photosensitive layer in the novolac resin (a), the cyanine-based, aminium-based or imonium-based photothermal conversion substance (b) having a structure in which a heterocycle is bonded via a polymethylene chain, As the component (c), a vinyloxy compound (JP-A-11-231515) or an acyloxyalkoxy compound (JP-A-11-231).
No. 513), a positive photosensitive composition containing the same.

(2) In order to enhance the image reproducibility of the novolac resin (a), a cyanine-based, aminium-based or imonium-based photothermal conversion substance (b) having a structure in which a heterocycle is bonded via a polymethylene chain, component (c) is used. A positive photosensitive composition containing an acid-coloring dye (JP-A-11-190903) or a base-coloring dye (JP-A-11-143076) as a component.

(3) To improve the printing resistance of the novolac resin (a) and the cyanine-based, aminium-based or imonium-based photothermal conversion substance (b) having a structure in which a heterocycle is bonded via a polymethylene chain, (c) A positive photosensitive composition containing an ester compound as a component (JP-A-11-2880).
No. 89).

Among the above, the positive photosensitive composition (2)
And (3) are preferable because they are excellent in printing durability and image formation.
Further, the positive photosensitive composition may contain a heat-crosslinkable compound. Examples of such thermally crosslinkable compounds include nitrogen compounds having crosslinkability, preferably compounds having an amino group, and more specifically, for example, as a functional group, a methylol group, or an alcohol condensation-modified thereof. Examples thereof include amino compounds having two or more alkoxymethyl groups, acetoxymethyl groups and the like. Among the compounds having an amino group, a compound having a heterocyclic structure, particularly a nitrogen-containing heterocyclic structure is preferable, and a compound having a melamine skeleton is particularly preferable. Examples of such a heat-crosslinkable compound include the heat-crosslinkable compounds described in JP-A No. 11-202481.

First, the plate cylinder (21) and the blanket cylinder (2
2) and the impression cylinder (23) are separated from each other and the paper feeding to the impression cylinder (23) is stopped,
(A): A photosensitive lithographic printing plate prepared by supplying and coating a photosensitive plate agent composed of a positive photosensitive composition from a plate agent supply mechanism (4) onto a support (3) fixed on a plate cylinder (21). Eggplant

Next, (B): the photosensitive lithographic printing plate is image-exposed by the exposure mechanism (5), and (C): the plate-making treatment agent is supplied from the plate-making treatment agent supply mechanism onto the image-exposed photosensitive lithographic printing plate. Supply, and if necessary, physical stimulation,
Then, an image is formed.

Further, depending on the type of the photosensitive layer of the photosensitive lithographic printing plate, it is not necessary to give a physical stimulus such that the plate cylinder (21) and the blanket cylinder (22) are rotated in contact with each other. In some cases, it is sufficient to simply rotate the plate cylinder (21) while keeping the blanket cylinder (22) in a separated state.

As the plate-making treatment agent, a hydrophilic agent (penetrating agent) capable of penetrating into the exposed area to reduce the adhesive strength between the support and the photosensitive layer in the exposed area, for example, a surfactant or an organic agent. A solvent, an alkaline agent, etc. can be used (Japanese Patent Application No. 9-170117). Usually, these plate-making treatment agents are removed by washing with water after image formation.

<Printing process (D)> After the plate making process is completed,
(D): Printing ink and dampening water are supplied from the ink inking device (6) and the dampening device (7) to the image surface on the photosensitive lithographic printing plate, respectively, and the plate cylinder (21) and the blanket cylinder (22) and the impression cylinder (23) are contact-rotated, and printing paper is supplied between the blanket cylinder (22) and the impression cylinder (23) for printing. Such an operation can be performed according to a conventionally known method.

<Recycling Step (E)> After the printing step, the cylinders are separated from each other and the feeding of the paper to the impression cylinder (23) is stopped, and then (E): the plate agent. The image part on the support (3) is removed by the removing mechanism to regenerate the support. In the apparatus shown in FIG. 1, the plate material removing mechanism includes a plate material dissolving liquid supply mechanism (81), a plate material peeling roller (82) provided as necessary, a wash water supply mechanism (83), and a waste liquid collecting mechanism (84). ) And an air type drying mechanism (85).

First, the blanket cylinder (22) and the impression cylinder (2
After the contamination prevention tray (86) is placed between the plate and the plate, the plate cylinder solution (21) is rotated while the plate agent solution supply mechanism is provided on the image surface of the photosensitive lithographic printing plate on the plate cylinder (21). (81)
To supply a plate solution (for example, an aqueous alkaline solution or an organic solvent). By this operation, the image is dissolved and the support (3) is regenerated. When the image does not dissolve but swells, the image is given a physical stimulus by the plate release roller (82), or the image is attached and removed.

Next, washing water is supplied from the washing water supply mechanism (83) to the surface of the regenerated support (3). By this operation, the plate agent solution on the surface of the support (3) is removed.

Next, after the liquid remaining on the surface of the support (3) is wiped off or sucked off by the waste liquid recovery mechanism (84), the surface of the support (3) is dried by the air type drying mechanism (85). .

In the present invention, after the above-mentioned regeneration step,
The same operation is repeated by returning to the plate making steps (A to C). Therefore, in the present invention, the steps of plate making, printing, and reproduction are performed on the printing machine, and the work efficiency is greatly improved. Moreover, in the present invention, the plate cylinder (2
Since plate making is carried out on the support body (3) fixed on 1), it is not necessary to make a particularly large modification to the plate cylinder (21), and the support body (3) can be replaced inexpensively and easily. Since it can be performed, the method of the present invention is economically advantageous.

In a preferred embodiment of the present invention,
Each of the above steps is performed by sliding the casing (1) and accommodating the entire plate making apparatus in the casing (1).
In such a mode, the casing (1) operates as follows. That is, the apparatus (lithographic printing machine) shown in FIG. 1 is arranged in the printing chamber. On the other hand, in the present invention, various positive photosensitive compositions can be used as the photosensitive plate material as described above. The casing (1) has a function of blocking illumination light which is inappropriate for the positive photosensitive composition used.

The dust filter (11) installed on the ceiling of the casing (1) operates as follows. That is, in the printing chamber, the air supply port is usually arranged near the ceiling and the exhaust port is provided near the floor so that the air can be ventilated. In this case, a ventilation air flow is formed which passes through the dust filter (11) toward the open front surface of the casing (1). As a result, the mist generated in each process of plate making, printing and reproduction is efficiently removed. The mist is removed more efficiently by connecting the exhaust duct (12) to the exhaust port.

[0038]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 <Production of support> Aluminum plate (thickness: 0.24 mm)
1 at 60 ° C. in a 5% by weight aqueous sodium hydroxide solution.
After performing degreasing treatment for 15 minutes, in a hydrochloric acid aqueous solution having a concentration of 0.5 mol / liter, temperature 25 ° C., current density 60 A / dm
^{2. The} electrolytic etching treatment was performed under the condition that the treatment time was 30 seconds. Then, in a 5% by weight aqueous solution of sodium hydroxide, 6
After performing desmutting treatment at 0 ° C. for 10 seconds, anodizing treatment was performed in a 20 wt% sulfuric acid solution at a temperature of 20 ° C., a current density of 3 A / dm ² , and a treatment time of 1 minute. Furthermore, 80
A hot water sealing treatment was performed for 20 seconds with hot water at 0 ° C. to prepare a support.

<Preparation of Photosensitive Plate Agent Composed of Positive Photosensitive Composition> 3 parts by weight of an indole dye represented by the following chemical formula (I) as the component (a) and phenol: m-cresol: as the component (b). It is composed of a polycondensate of mixed phenols having a molar ratio of p-cresol of 50:30:20 and formaldehyde, and has a weight average molecular weight of 9,4.
Novolac resin of 00 (Sumitomo Durezu "SK-18
8 ") 100 parts by weight, crystal violet lactone 3 parts by weight, and 10 parts by weight of an ester compound (weight average molecular weight 3000) represented by the following chemical formula (II) are dissolved in 1000 parts by weight of propylene glycol monomethyl ether to obtain a positive photosensitive composition. A photosensitive printing plate material was prepared.

[0041]

[Chemical 1]

[0042]

[Chemical 2]

<On-press plate making / printing> An apparatus similar to that shown in FIG. 1 placed in a printing chamber was used. The casing (1) was slid to accommodate the entire plate making apparatus in the casing (1). The printing room was ventilated as follows. By connecting the exhaust duct (12) to the exhaust port provided near the floor, the dust is supplied from the air supply port disposed near the ceiling and the dust filter (11) and the casing (1) are provided.
The air introduced into the casing (1) through the open front surface of the above was discharged through the exhaust duct (12) from the above exhaust port. Then, according to the following procedure, each process of plate making, printing and reproduction was performed.

First, the plate cylinder (21) and the blanket cylinder (2
2) and the impression cylinder (23) are separated from each other and the paper feeding to the impression cylinder (23) is stopped, and then the support (3) fixed on the plate cylinder (21). A photosensitive plate material composed of a positive photosensitive composition was supplied and applied from the plate material supply mechanism (4) and dried at 100 ° C. for 2 minutes to give a coating film amount of 2.4 g /
A positive photosensitive lithographic printing plate having a positive photosensitive composition layer of m ² was prepared (step A).

Then, using an exposure mechanism (5) having a semiconductor laser (wavelength: 830 nm, manufactured by Applied Techno: 40 mW) as a light source, various exposure energies of 200 are used.
A line, 1 to 99% halftone dot image was imagewise exposed (step B).
Then, an alkaline developing solution (8 times diluted solution of "DP-4" manufactured by Fuji Photo Film Co., Ltd.) was supplied as a plate-making processing agent from the plate-making processing agent supply mechanism onto the image-exposed photosensitive lithographic printing plate at 28 ° C. After contacting for 30 seconds, it was washed with water to form an image (step C). For supplying the alkaline developer and the washing water, the inking roller of the ink inking device (6) and the watering roller of the dampening device (7) are temporarily separated from each other to dissolve the plate agent of the plate agent removing mechanism described later. Liquid supply mechanism (8
1) and the wash water supply mechanism (83) were used temporarily. That is, the plate-dissolved solution supply mechanism (81) described below was temporarily used as an alkaline developer supply mechanism. By such an operation, a printing plate which reproduced a dot image of 1 to 99% was obtained. The sensitivity at that time was 150 mJcm ^-2 as a result of obtaining the amount of exposure energy for reproducing 3% halftone dots.
Met.

After the plate making steps (steps A to C), printing ink and dampening water are supplied to the image surface on the photosensitive lithographic printing plate from the ink inking device (6) and the dampening device (7), respectively. Then, the plate cylinder (21), the blanket cylinder (22), and the impression cylinder (23) are rotated in contact with each other, and printing paper is supplied between the blanket cylinder (22) and the impression cylinder (23).
0000 sheets were printed (step D). As the printing ink, the process ink "Hycho Magenta" manufactured by Toyo Ink Co., Ltd. was used, and as the fountain solution, "Astron No. 1 Mark II" manufactured by Nikken Chemical Co. was used.

After the printing step (step D), the cylinders are separated from each other and the feeding of the paper to the impression cylinder (23) is stopped, and then the plate material removing mechanism is operated according to the following procedure. The image portion on the support (3) was removed to regenerate the support (step E).

First, the blanket cylinder (22) and the impression cylinder (2
After the contamination prevention tray (86) is placed between the plate and the plate, the plate cylinder solution (21) is rotated while the plate agent solution supply mechanism is provided on the image surface of the photosensitive lithographic printing plate on the plate cylinder (21). (81)
Was supplied as a plate solution. By this operation, the image was dissolved and the support (3) was reproduced.

Next, cleaning water is supplied from the cleaning water supply mechanism (83) to the surface of the regenerated support (3). By this operation, the plate agent solution on the surface of the support (3) was removed.

Then, after the liquid remaining on the surface of the support (3) was removed by the waste liquid recovery mechanism (84), the surface of the support (3) was dried by the air type drying mechanism (85).

After the above regenerating step (step E), the same operation was repeated by returning to the plate making / printing steps (A to D). As a result, the sensitivity is the same as above, 150mJc
m ⁻² , and a high-quality printed matter similar to the printing plate before reproduction was obtained.

The positive type photosensitive lithographic printing plate obtained above had a light intensity of 400 lux of a white fluorescent lamp (36W white fluorescent lamp "Neolmi Super FLR40S-W / M / 36" manufactured by Mitsubishi Electric Corporation). When it was left under irradiation for 10 hours and then subjected to the same development treatment as described above, there was no substantial film reduction, and the handling under a white fluorescent lamp was good.

[0053]

According to the present invention described above, the conventional on-press plate making method is further improved so that the plate can be regenerated on the printing machine. Will be provided. Such a regenerative on-press plate making / printing method largely contributes to the improvement of work efficiency.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an example of an apparatus for performing a regenerative printing plate making / printing method according to the present invention.

[Explanation of symbols]

1: Casing 11: Dust filter 12: Exhaust duct 21: Plate cylinder 22: Blanket body 23: impression cylinder 3: Support 31: Support fixing means 4: Plate supply mechanism 5: Exposure mechanism 6: Ink inking device 7: Damper 81: Plate solution dissolving mechanism 82: Plate release roller 83: Wash water supply mechanism 84: Waste liquid collection mechanism 85: Air type drying mechanism 86: Contamination prevention tray

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuya Uematsu             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Mitsubishi Chemical Corporation Yokohama Research Institute (72) Inventor Mizuho Ruji             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Mitsubishi Chemical Corporation Yokohama Research Institute (72) Inventor Mitsuru Tabuchi             Hiroshima Prefecture Mihara City Itozakicho 5007 Mitsubishi Heavy Industries             Paper and printing machinery division F-term (reference) 2C034 AA12 AE36 BA02 BA18                 2H096 AA06 BA09 BA20 EA04 EA23

Claims (3)

[Claims] 1. On a lithographic printing machine having a printing section comprising a plate cylinder, a blanket cylinder and an impression cylinder, after separating the cylinders from each other and stopping feeding of paper to the impression cylinder, (A): Positive photosensitive material containing a photothermal conversion substance (a) which absorbs light from an image exposure light source from a plate supply mechanism and converts it into heat on a support fixed on a plate cylinder and an alkali-soluble resin (b). Of a photosensitive composition to form a photosensitive lithographic printing plate, and then (B): after imagewise exposing the photosensitive lithographic printing plate by an exposure mechanism, (C): image-exposed photosensitive A lithographic printing plate is supplied with a stencil processing agent from a stencil processing agent supply mechanism, and further, a physical stimulus is given if necessary,
Then, an image is formed, and then (D): printing ink and dampening water are supplied to the image surface on the photosensitive lithographic printing plate from an ink inking device and a dampening device, respectively, and a plate cylinder and a blanket cylinder. After the contact cylinder is rotated and the printing paper is supplied between the blanket cylinder and the impression cylinder to perform printing, the cylinders are again separated from each other and the feeding of the paper to the impression cylinder is stopped. After that, (E): a reproducible on-press plate making / printing method characterized in that the image portion on the support is removed by the plate agent removing mechanism to regenerate the support. 2. The positive photosensitive composition contains 800 to 1300 n.
A reproducible on-press plate making / printing method according to claim 1, wherein the positive photosensitive composition is sensitive to a near infrared laser. 3. The reproduction type on-press plate making / printing method according to claim 2, wherein the positive photosensitive composition is a positive photosensitive composition which is insensitive to light in the ultraviolet region.