JP2001334769A - Support body for planographic printing plate and its manufacturing method, and the plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an occurrence of print dropouts after having developed, by preventing an overcoat layer from peeling from the top of a photosensitive layer without thickening the overcoat layer even in such a case it is rewound into a roll-like form, after the overcoat layer and the photosensitive layer are respectively provided on the surface in the manufacturing process. SOLUTION: An aluminum plate 12 is ground by a sanding machine 18, 20 until an undersurface-roughness (JIS center line average roughness) of the aluminum plate becomes 0.20 μm or less. After these surface treatments, a photosensitive layer and an overcoat layer are formed on the plate which is made to be a web roll 34, and further the web 34 is made to be a web roll 36, stress concentrations which arise along roller stripes and the like between front and rear faces of the web 34 are tempered, and in the case the web roll 36 is to be unrolled, peeling of the overcoat layer consisting of polyvinyl alcohol is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate support for use in a lithographic printing plate in which the surface of a photosensitive layer or a heat-sensitive layer is covered with a thin-film overcoat layer, a method for producing the same, and a method for producing the same. The present invention relates to a lithographic printing plate in which the surface of a heat-sensitive layer is covered with a thin-film overcoat layer.

[0002]

2. Description of the Related Art In recent years, with the development of digital processing technology for image processing, the use of photo-radical polymerization as a photosensitive material for a lithographic printing plate to realize a direct plate-making system has made it possible to control laser light in the visible region. In some cases, a photopolymer with high sensitivity is used. In a lithographic printing plate having a photosensitive layer formed of the photopolymer (hereinafter, referred to as a “photopolymer type lithographic printing plate”), an image forming surface of the lithographic printing plate is irradiated with a laser beam having a sufficiently small beam diameter based on image data. By scanning the (photosensitive layer) and causing a photopolymerization reaction on the photosensitive layer provided on the support to cure the exposed portion, characters, images, and the like can be directly obtained without using a film original (lith film). It can be formed on the image forming surface of a lithographic printing plate. Here, in a lithographic printing plate using a photopolymer as a photosensitive layer, a transparent resin such as polyvinyl alcohol (PVA) is usually provided on the surface layer of the image forming surface because oxygen in the air becomes a hindrance to a photopolymerization reaction. Provides an overcoat layer as an oxygen barrier film, and the overcoat layer covers the photosensitive layer.

On the other hand, the support of the photopolymer type lithographic printing plate as described above is often in the form of a long strip made of aluminum or an alloy mainly composed of aluminum (hereinafter referred to as "aluminum alloy"). After one or both surfaces of the aluminum plate are roughened, an anodized film is formed by anodizing to improve abrasion resistance. On this support, a photosensitive material (photopolymer) is applied on the anodic oxide film and dried to form a photosensitive layer, and then PVA is applied so as to cover the entire surface of the photosensitive layer.
Is applied and dried to form an overcoat layer. The web as a material of the lithographic printing plate manufactured in this way is once wound up in a roll shape, and then supplied as a web roll to a lithographic printing plate processing line, where a protective interleaf is pasted, Cutting to size is performed.

[0004]

However, in the case of a web roll on which a web serving as a material of a photopolymer type lithographic printing plate is wound, the surface (overcoat layer) of the web is increased from the roll outer peripheral side to the inner peripheral side. The contact pressure (surface pressure) with the back surface gradually increases, and the contact pressure between the front surface and the back surface of the web has a high value of 10 to 30 kgf / cm ^{2 at} the innermost periphery. In the lithographic printing plate processing line, the web is unwound from the web roll at a speed corresponding to the processing speed, but if the contact pressure between the front and back surfaces of the web is extremely high, the overcoat layer is locally pressed to the back surface of the web. Then, when the web is unwound from the web roll, the overcoat layer may be peeled off from the photosensitive layer in a spot shape. In the region where the overcoat layer of the photosensitive layer has thus been peeled off, the photopolymerization is inhibited by oxygen in the air during image exposure, so that the photopolymerization efficiency is significantly reduced. As a result, spot-shaped image defects having a diameter of 1 mm or less (hereinafter, referred to as “white spots”) that do not become image portions due to development even when exposed are generated in the developed photopolymer type lithographic printing plate.

[0005] White spots in a photopolymer type lithographic printing plate improve the strength of the overcoat layer, that is, PV
This can be prevented by making the overcoat layer made of A sufficiently thick. However, as the overcoat layer becomes thicker, light scattering in the overcoat layer also increases, and the dot diameter becomes unstable due to the flare phenomenon, thereby deteriorating the image quality. For this reason, in recent years,
From the viewpoint of improving image quality, which is strongly demanded by users, it is desirable that the overcoat layer be as thin as possible without impairing the function as an oxygen barrier film.

In recent years, it has been studied to apply the overcoat layer to a lithographic printing plate other than the photopolymer type, that is, to apply the overcoat layer to a purpose other than oxygen cutoff. It has been studied to apply an overcoat layer to a thermal lithographic printing plate or the like on which an image is formed. Therefore, even when applied to such a lithographic printing plate, spot-like peeling of the overcoat layer may cause various image defects including white spots.

One object of the present invention is to provide a lithographic printing plate, in which a photosensitive layer or a heat-sensitive layer and an overcoat layer are provided on the surface in the course of manufacturing the lithographic printing plate, and then wound into a roll. Provide a lithographic printing plate support that can prevent peeling of the overcoat layer from above the photosensitive layer even when it is performed, and can also be a material for such a lithographic printing plate support, the surface roughness of the front and back surfaces An object of the present invention is to provide a method of manufacturing a lithographic printing plate support that can easily and inexpensively manufacture an aluminum plate having a (JIS center line average roughness) of 0.20 μm or less.

Another object of the present invention is to provide a lithographic printing plate support having a photosensitive layer or a heat-sensitive layer and an overcoat layer provided on a lithographic printing plate support. It is an object of the present invention to provide a lithographic printing plate capable of preventing peeling of an overcoat layer from a photosensitive layer and effectively preventing occurrence of image defects such as white spots after development even when wound in a roll. .

[0009]

The lithographic printing plate support of the present invention is a lithographic printing plate support in which the surface of a photosensitive layer or a heat-sensitive layer is covered with an overcoat layer. It is composed of a strip-shaped aluminum plate as a material, and has a surface roughness (J
IS center line average roughness) is 0.20 μm or less.

According to the lithographic printing plate support having the above structure,
By setting the surface roughness (JIS center line average roughness) of the aluminum plate as a support of the lithographic printing plate having an overcoat layer to 0.20 μm or less,
In the process of manufacturing a lithographic printing plate, a photosensitive film and an oxygen barrier film are respectively provided on the surface of the aluminum plate, and then wound into a roll, and the front side (the surface of the overcoat layer) and the back side of the aluminum plate Even when pressure contact is performed with a high contact pressure, the stress concentration caused by the influence of the unevenness existing on the front and back surfaces of the aluminum plate can be sufficiently reduced.

That is, on the surface of a thin aluminum plate supplied from a manufacturer through hot rolling and cold rolling, irregularities called rolling streaks to which irregularities of a rolling roll are transferred are scattered. The size of the rolling streak mainly determines the surface roughness of the aluminum plate. The surface roughness (JIS center line average roughness) of the aluminum plate supplied from the manufacturer usually varies within a range of about 0.22 to 0 and 25 μm because the state of the rolling roll changes with time. The surface roughness of such an aluminum plate is
Even after mechanical or electrochemical surface roughening treatment and anodizing treatment, the microscopic shape itself changes but the size itself hardly changes.

For this reason, after a photosensitive layer or a heat-sensitive layer and an oxygen barrier film are respectively provided on an aluminum plate which has been subjected to a surface roughening treatment and an anodic oxidation treatment, it is wound up in a roll shape so that the front and back surfaces of the aluminum plate are high. Contact pressure (for example, 10k
gf / cm ² or more), the contact pressure is several times to several tens times the local average contact pressure in a region where the front surface convex portion and the rear surface convex portion of the aluminum plate overlap each other. Is generated.

Therefore, in the area where the above-mentioned stress concentration phenomenon occurs on the front and back surfaces of the aluminum plate, the oxygen barrier film having a strength capable of withstanding the contact pressure obtained by multiplying the average contact pressure by the required safety factor is peeled off. Will occur. At this time, as the surface roughness of the aluminum plate increases, the contact pressure at the stress concentration portion increases, and the number of spot-shaped regions per unit area where stress concentration occurs increases. On the other hand, since the overcoat layer is generally made of a flexible material (for example, PVA), as the thickness of the overcoat layer increases, the stress concentration is reduced.

The inventor of the present application has found that peeling of the overcoat layer is due to the above-mentioned stress concentration phenomenon,
Based on this finding, we researched the critical value of the surface roughness of an aluminum plate that does not cause overcoat layer peeling due to stress concentration while maintaining the overcoat layer sufficiently thin as required from the image quality viewpoint Investigate, the value is 0.
It was found to be 20 μm.

However, in order to reliably manufacture an aluminum plate having a surface roughness of 0.20 μm or less by an aluminum maker, it is necessary to strictly control rolling rolls and the like. ) Purchase price rises significantly. For this reason, the inventor of the present application has studied various methods for manufacturing an aluminum plate satisfying the above-mentioned standards. As a result, before performing a surface roughening treatment on an aluminum plate purchased from a manufacturer, a buffing is performed. It has been found that an aluminum plate having a surface roughness of 0.20 μm or less on the back surface can be manufactured easily and at low cost.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A photopolymer type planographic printing plate according to an embodiment of the present invention and a method for manufacturing the same will be described below with reference to the drawings.

FIG. 1 shows a web production line as a material of a photopolymer type lithographic printing plate according to an embodiment of the present invention. A delivery device 16 is disposed at the most upstream side of the production line 10. The delivery device 16 has an aluminum coil 14 on which an aluminum plate 12 having a thickness of 0.1 to 0.5 mm is wound in a roll shape. Is loaded. The delivery device 16 delivers the aluminum plate 12 to the downstream side at a speed corresponding to the production speed of the entire production line 10.

Here, the aluminum plate as a material of the lithographic printing plate support is, for example, JIS1050 material, JI
S1100 material, JIS1070 material, Al-Mg based alloy,
Al-Mn alloy, Al-Mn-Mg alloy, Al-Z
An r-based alloy, an Al-Mg-Si-based alloy, or the like can be used. In the manufacturing process of an aluminum plate by a manufacturer, an ingot of aluminum conforming to the above-described standard is manufactured, and after hot-rolling this aluminum ingot, a heat treatment called annealing is performed as necessary, and a predetermined process is performed by cold rolling. Finish the aluminum strip into a thick strip. The aluminum plate is wound into a roll to form an aluminum coil.

In the production line 10, first, the delivery device 16
In order to improve the flatness, the aluminum plate 12 sent out to the downstream side is straightened by a straightening device (not shown) such as a roller leveler or a tension leveler to obtain necessary flatness. On the downstream side of the straightening device, a lower surface polishing device 18 and an upper surface polishing device 20 are sequentially arranged along the transport path of the aluminum plate 12.

The lower surface polishing device 18 includes an aluminum plate 1
A polishing roller 22 supported so as to contact the lower surface of the aluminum plate 2 is provided, and a pair of tension rollers 24 is provided so as to contact the upper surface of the aluminum plate 12. The polishing roller 22 has a roller surface formed of, for example, a nonwoven fabric, and is rotated at a high speed during polishing so that the linear velocity of the roller surface becomes sufficiently higher than the transport speed of the aluminum plate 12. At this time, the rotation direction of the polishing roller 22 is the forward rotation direction in which the direction of movement of the roller surface at the contact portion with the aluminum plate 12 is the same as the transport direction of the aluminum plate 12, and the direction of movement of the roller surface is the aluminum plate. 12 may be in the reverse rotation direction opposite to the conveyance direction. Further, the pair of polishing rollers 22 are used for the aluminum plate 12.
Is arranged so as to sandwich the polishing roller 22 along the transport direction of the roller, and urges the aluminum plate 12 downward to press the lower surface of the aluminum plate 12 against the roller surface of the polishing roller 22 with a predetermined contact pressure.

The lower surface polishing device 18 is provided with a slurry in which an abrasive containing ceramic particles and the like is dispersed in water.
A slurry supply unit (not shown) for supplying to a contact portion between the aluminum plate 12 and the aluminum plate 12 is provided. The slurry supply unit supplies a predetermined amount of slurry per unit time when the aluminum plate 12 is polished. When the abrasive in the slurry is rubbed against the lower surface of the aluminum plate 12 by the polishing roller 22, the slurry is polished so that the microscopic irregularities on the lower surface of the aluminum plate 12 are averaged, and the surface roughness becomes smaller.

Here, polishing by the lower surface polishing apparatus 18 is performed as follows.
At least the surface roughness of the lower surface of the aluminum plate 12 (JI
S center line average roughness) is 0.20 μm or less. Polishing conditions for this are initial surface roughness of the aluminum plate 12 supplied from the manufacturer, It changes depending on the transport speed. Therefore, the initial surface roughness of the aluminum plate 12,
It is necessary to set the rotation speed of the polishing roller 22, the type and size of the abrasive, and the like according to the transport speed and the like. Further, in the present embodiment, the lower surface of the aluminum plate 12 is polished by one lower surface polishing device 18.
8 may be arranged along the transport path of the aluminum plate 12, and the lower surface of the aluminum plate 12 may be polished stepwise by the respective lower surface polishing devices 18 until the surface roughness becomes 0.20 μm or less.

The aluminum plate 12 whose lower surface is polished
Upper surface polishing device 2 arranged downstream of lower surface polishing device 18
Polishing is performed such that the surface roughness (JIS center line average roughness) of the upper surface is set to 0.20 μm or less. Here, the structure of the upper surface polishing device 20 is the same as that of the lower surface polishing device 18 except that the polishing roller 22 and the pair of tension rollers 24 are arranged upside down via the aluminum plate 12, and thus the description will be made. Omitted.

The aluminum plate 12 is provided with a lower surface polishing device 18.
And the surface roughness (JIS center line average roughness) of the upper surface and the lower surface is set to 0.
It becomes 20 μm or less. The upper and lower surfaces of the aluminum plate 12 can be sufficiently polished up to about 0.10 μm in practical use by the polishing apparatuses 18 and 20.

Next, a method for measuring the surface roughness of the aluminum plate 12 will be described. In this embodiment, a center line surface roughness standardized in JIS B0601 was adopted as a method for measuring the surface roughness. As a measuring device,
Surfcom 550A manufactured by Tokyo Seimitsu Co., Ltd. was used. The measurement conditions at that time were a measurement length of 2.5 mm, a cutoff value (75%) of 0.08 mm, and a measurement speed of 0.3.
mm / sec.

The surface of the aluminum plate 12 polished by the polishing devices 18 and 20 is mechanically or electrochemically roughened downstream of the polishing devices 18 and 20. As such a roughening method, there are a mechanical graining method, an electrochemical graining method, and the like, and the roughening is performed by appropriately combining them. Examples of the mechanical graining method include a ball grain, a wire grain, a brush grain, and a liquid honing method. As an electrochemical graining method, an AC electrolytic etching method is generally adopted. As an electrolytic current, a normal sine wave AC current, a rectangular wave, a special alternating current, or the like is used. As a pretreatment for the electrochemical graining, the aluminum plate may be subjected to an etching treatment with caustic soda or the like.

The production line 10 is provided with an anodizing apparatus (not shown) for performing a known anodizing process on the aluminum plate 12 which has been subjected to the surface roughening process. The anodizing apparatus forms an anodized film having high hardness on the surface of the aluminum plate 12 by anodizing the surface of the aluminum plate 12 by a known submerged power supply method. At this time, 0.1 to 10 g /
m ² anodized film, more preferably 0.3 to 5 g / m ²
Is formed. The conditions of the anodic oxidation treatment are not determined unequivocally because the setting needs to be changed depending on the electrolytic solution to be used. However, in general, the concentration of the electrolytic solution is 1 to 80 wt%, and the temperature of the electrolytic solution is 5 to 70%. ° C., a current density of 0.5 to 60 a / dm ^2, voltage is 1 to 100 V, electrolysis time is set respectively within a range of 1Sec～5min.

As shown in FIG. 1, in the production line 10, a coating device 26 and a drying device 28 for applying a photosensitive material (photopolymer) to the aluminum plate 12 are provided downstream of the anodic oxidation device.

The coating device 26 is provided with a pair of support rollers 40 that are in contact with the back surface of the aluminum plate 12, and between the pair of support rollers 40 along the transport direction so as to approach or contact the surface of the aluminum plate 12. Is provided with an application roller 42. Above the coating roller 42, a polymer supply unit 44 is provided so as to form a gap S at a predetermined interval between the coating roller 42 and the roller surface of the coating roller 42. The polymer supply unit 44 has one end into the gap S. A supply path 45 for the photopolymer whose part is opened is formed. The other end of the supply channel 45 is connected to a photopolymer supply device (not shown). The supply device supplies the photopolymer liquefied through the supply channel 45 with a gap S.
Pressurized supply. On the other hand, the application roller 42 rotates while adhering the photopolymer supplied into the gap S on the roller surface, and makes the layer thickness of the photopolymer constant by a narrow portion formed at the end of the gap S. This application roller 42
Transfers the photopolymer on the roller surface onto the surface of the aluminum plate 12.

The drying device 28 disposed downstream of the coating device 26 is provided with a drying tank 46 having an explosion-proof and heat-insulating structure, and a plurality of support rollers 48 are disposed in the drying tank 46. I have. The aluminum plate 12 to which the photopolymer has been transferred moves in the drying tank 46 while being supported from the back side by the support rollers 48. At this time, by supplying hot air into the drying tank 46, the photopolymer on the aluminum plate 12 is dried to form a photosensitive layer.

In the production line 10, polyvinyl alcohol (PVA) is provided downstream of the photopolymer drying device 28.
Are respectively provided with a coating device 30 and a drying device 32.

The coating device 30 is provided with support rollers 50 that are respectively in contact with the back surface of the aluminum plate 12, and a wedge-shaped coater 52 is disposed between the coating roller 30 and the roller surface of the support roller 50 so as to sandwich the aluminum plate 12. I have.
In the coater 52, a PVA supply path 54 is formed so that one end thereof opens to the tapered surface 53 on the downstream side of the coater 52. The other end of the supply path 54 is connected to a PVA supply device (not shown).
The liquefied PVA flows out onto the tapered surface 53 of the coater 52 through the supply path 54. The PVA flowing out onto the tapered surface 53 is separated from the tip of the coater 52 and the aluminum plate 12.
A puddle is formed in the vicinity of the vicinity. The PVA in the liquid pool adheres to the surface of the aluminum plate 12 so as to have a predetermined layer thickness as the aluminum plate 12 moves downstream.

The drying device 32 disposed downstream of the coating device 30 has basically the same structure as the drying device 28 for the photopolymer. The PVA on the aluminum plate 12 is dried with hot air while being supported by the support rollers 58.
Thus, an overcoat layer as an oxygen blocking layer is formed on the aluminum plate 12 so as to cover the photosensitive layer. However, since appropriate drying conditions are different between the photosensitive layer and the overcoat layer, the temperature of the hot air supplied to the drying tanks 46 and 56 and the temperature of the drying tank 4 depend on the respective drying conditions.
Lengths and the like along the transport direction of 6, 56 are set.

At this time, the coating device 30 supplies PVA such that the weight of the overcoat layer on the aluminum plate 12 is 2.5 g / m ² . Thereby, the thickness of the overcoat layer in the photopolymer type lithographic printing plate is 2.
The overcoat layer having a thickness of about 0 to 3.0 μm does not cause a flare phenomenon that leads to a deterioration in image quality.

In the production line 10, the production of the web 34 as a material of the photopolymer type lithographic printing plate is completed by forming the overcoat layer on the photosensitive layer. The web roll 36 is wound into a roll. The web roll 36 is supplied to a web supply device of a photopolymer type lithographic printing plate processing line (not shown), is unwound by the web supply device, and is downstream of the line at a speed corresponding to the processing speed of the processing line. Supplied to

[0036]

Next, examples and comparative examples of the photopolymer type planographic printing plate according to the present invention will be described.

Here, the surface roughness (JIS center line average roughness) is 0.24, 0.22, 0.20, 0.1 in advance.
An aluminum plate whose front and back surfaces are respectively polished to have a thickness of 8, 0.15 and 0.10 μm is manufactured on a production line 10.
And these aluminum plates were used as web rolls 36, respectively. At this time, the operation of each of the polishing devices 18 and 20 of the production line 10 was stopped, and the web roll 36 was manufactured using the aluminum plate as a support. Further, the winding torque of the winding device 38 was adjusted so that the contact pressure between the front and back surfaces of the aluminum plate was approximately 30 kgf / cm ^{2 in the} vicinity of the web roll 36 where the web roll 36 was most purchased.

The web rolls manufactured using the above aluminum plates having different surface roughness as a support are supplied to a production line of a photopolymer type lithographic printing plate, and each photopolymer type lithographic printing plate is manufactured under the same processing conditions. , These lithographic printing plates were prepared as Comparative Examples 1-2 and Examples 1-2, respectively.
And 4.

Table 1 shows the evaluation of white spots on the lithographic printing plates of Comparative Examples 1 and 2 and Examples 1 to 4 described above. Here, the blank area is evaluated by exposing and developing the entire surface of the lithographic printing plate so that the tail sensitivity of the grace scale becomes 8 steps (all 15 steps), and printing is performed using the developed lithographic printing plate. The number of white spots in a printed image (solid image) was counted. Here, the definitions of the symbols “x”, “〇” and ““ ”described as the blank evaluation in Table 1 are as follows.

×: Number of white spots per unit area (= N) determined by quality standards due to peeling of overcoat layer
More white spots occur than that of 1- (N−) due to peeling of the overcoat layer.
1) White spots are generated. ◎: No white spots are generated due to peeling of the overcoat layer.

[0041]

[Table 1]

As is clear from the evaluation of white spots shown in Table 1, the number of white spots was determined by quality standards by setting the surface roughness of the front and back surfaces of the aluminum plate to 0.20 μm or less, respectively. It can be smaller than the number (N). Further, when the surface roughness of the front and back surfaces of the aluminum plate is set to 0.15 μm or less, the number of white spots can be reduced to half or less of the number (N) determined by the quality standard, and the effect of greatly suppressing white spots can be reduced. Is obtained.

In the above description of the present embodiment,
Although the present invention has been described only for the case where the present invention is applied to a photopolymer type lithographic printing plate particularly using a photopolymer as a photosensitive material, the present invention relates to a lithographic printing plate in which a photosensitive layer is covered with an oxygen barrier film. The present invention can be applied to other lithographic printing plates other than the polymer type lithographic printing plate. Specific examples of such a lithographic printing plate include, for example, the following (1)
To (11). (1) An embodiment in which the photosensitive layer contains an infrared absorber, a compound that generates an acid by heat, and a compound that crosslinks with the acid. (2) An embodiment in which the photosensitive layer contains an infrared absorbing agent and a compound which becomes alkali-soluble by heat. (3) An embodiment in which the photosensitive layer includes two layers: a layer containing a compound that generates radicals by laser beam irradiation, a binder soluble in alkali, and a polyfunctional monomer or prepolymer, and an oxygen barrier layer. (4) An embodiment in which the photosensitive layer comprises two layers: a physical development nucleus layer and a silver halide emulsion layer. (5) An embodiment in which the photosensitive layer includes three layers: a polymerized layer containing a polyfunctional monomer and a polyfunctional binder, a layer containing silver halide and a reducing agent, and an oxygen barrier layer. (6) An embodiment in which the photosensitive layer includes two layers: a layer containing a novolak resin and naphthoquinonediazide; and a layer containing silver halide. (7) An embodiment in which the photosensitive layer contains an organic photoconductor. (8) An embodiment in which the photosensitive layer includes two or three layers composed of a laser light absorbing layer removed by laser light irradiation, and a lipophilic layer and / or a hydrophilic layer. (9) a compound in which a photosensitive layer absorbs energy to generate an acid, a polymer compound having a functional group capable of generating a sulfonic acid or a carboxylic acid in a side chain by an acid, and an acid generator by absorbing visible light The embodiment which contains the compound which gives energy to. (10) An embodiment in which the photosensitive layer contains a quinonediazide compound and a novolak resin. (11) An embodiment in which the photosensitive layer contains a compound which is decomposed by light or ultraviolet rays to form a crosslinked structure with itself or another molecule in the layer, and a binder which is soluble in alkali.

When the overcoat layer is applied to a lithographic printing plate having a photosensitive layer as described in (1) to (11) above, the composition of the overcoat layer, such as the material and layer thickness, depends on the properties of the photosensitive layer. As a matter of course, even if the configuration of the overcoat layer changes, the peeling of the overcoat layer can be effectively prevented by using the aluminum plate according to the present invention as the lithographic printing plate support.

[0045]

As described above, according to the lithographic printing plate support of the present invention, after the photosensitive layer or the heat-sensitive layer and the overcoat layer are provided on the surface in the process of manufacturing the lithographic printing plate, respectively. Even when the film is wound into a roll, the overcoat layer can be prevented from peeling from the surface of the photosensitive layer or the heat-sensitive layer without increasing the thickness of the overcoat layer.

Further, according to the method for producing a lithographic printing plate support according to the present invention, an aluminum plate having a surface roughness of the front and back surfaces (JIS center line average roughness) of 0.20 μm or less can be easily and at low cost. Can be manufactured at cost.

According to the lithographic printing plate of the present invention, the photosensitive layer or the heat-sensitive layer and the overcoat layer are provided on the surface during the manufacturing process, and then the overcoat layer is formed even when the overcoat layer is wound up in a roll shape. Without increasing the thickness of the overcoat layer from the surface of the photosensitive layer or the heat-sensitive layer, the occurrence of white spots after development can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a production line for a photopolymer type lithographic printing plate according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Production line 12 Aluminum plate (lithographic printing plate support) 18 Lower surface polishing device 20 Upper surface polishing device 34 Web (lithographic printing plate)

Claims (3)

[Claims] 1. A support for a lithographic printing plate wherein a photosensitive layer or a heat-sensitive layer is provided in a process of manufacturing the lithographic printing plate, and the surface of the photosensitive layer or the heat-sensitive layer is covered with a thin-film overcoat layer. The surface roughness (JIS center line average roughness) on each of the front and back surfaces is 0.20, respectively.
A support for a lithographic printing plate characterized by having a thickness of not more than μm. 2. The method for producing a lithographic printing plate support according to claim 1, wherein a belt-like aluminum plate made of aluminum or an aluminum alloy is provided with a surface roughness (JI).
S center line average roughness) is buffed so as to be 0.20 μm or less, respectively, and then, the front and back surfaces of this aluminum plate are subjected to a surface roughening treatment, thereby producing a lithographic printing plate support. Method. 3. A lithographic printing plate support made of aluminum or an aluminum alloy and having surface roughness (JIS center line average roughness) of 0.20 μm or less on each of the front and back surfaces, and the lithographic printing plate support. A lithographic printing plate comprising: a photosensitive layer or a heat-sensitive layer provided on a body; and an overcoat layer covering the surface of the photosensitive layer or the heat-sensitive layer.