JPS6072794A - Supporter for lithographic print plate - Google Patents

Abstract

PURPOSE:To obtain a positive type lithographic print plate having sufficient point reducing effect by providing an anodized film having a branched pore cross sectional structure on the surface of an aluminium plate subjected to a sand blasting and/or chemical etching treatment as needed. CONSTITUTION:An anodized film having a branched pore cross sectional structure is provided on the surface of an aluminium plate subjected to an etching treatment. The surface reflectivity of the aluminium plate after provided with the anodized film should preferably be 50% or less at absorption wave length (350-450nm) of ultraviolet rays for the photo-sensitive substance coated on the upper layer. To attain such a reflectivity, the amount of the anodized film is controlled preferably to 1.0g/m<2> or more.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a lithographic printing plate (PS plate) in which a photosensitive layer is provided on an aluminum support for lithographic printing plates. The invention relates to a positive type lithographic printing plate.

[Prior art]

In general, aluminum supports used in lithographic printing plates are required to have excellent hydrophilicity and water retention, and for this purpose, fine irregularities are formed by mechanical, chemical, or electrochemical methods, and the surface is roughened ( It is well known that grains are grained. Furthermore, it is known to anodize the grained surface in order to increase its mechanical strength and further to increase its water retention capacity. Therefore, by adding an amount of anodic oxide film (hereinafter referred to as A I) of about 2.0 g/rr!, which currently does not meet these objectives, water retention is good and the mechanical surface is PS with relatively high strength
version is widely used.

-4. One of the characteristics of the PS plate is its faithful reproducibility from the film original, which is an advantage in the case of proof printing, but in the case of actual printing, the dots become thicker due to the pressure during printing. This results in disadvantages such as the halftone dots in the shadow area being crushed.

For this reason, the positive type I) S version currently in use is
It is said that compared to plano-intaglio printing plates, which have a large dot loss, ink cannot be applied and voluminous prints cannot be obtained. Therefore, in order to obtain better prints, PS
In the plate-making method, dots are reduced by making the exposure time longer than specified during plate-making, or
A film for scattering light is placed between the S plates or on top of the lithographic film as a spacer, and printing (by scattering and diffusely reflecting the four light rays, the dots are reduced to produce printed matter with a flat intaglio-like finish). As a result, the actual exposure time becomes much longer than specified (that is, the effective sensitivity decreases), the work efficiency decreases, and the exposure amount increases, or Due to the increased scattering or diffused reflection of light, the reproducibility of small dots deteriorates, making it difficult to produce good printed matter with high resolution.

For example, as an improved method to increase the effective sensitivity by -1,
A method of increasing the reflectance by increasing or devising the treatment (desmutting) for the grain chamber is known, as disclosed in Japanese Patent No. 92804. Furthermore, as disclosed in Japanese Unexamined Patent Publication No. 56-162693, the amount of anodic oxide film can be varied from 2.5 g/rd to 5.0 g/rd. 0g/
There is a known method of increasing the effective sensitivity by setting it to ld. However, as a result of examining these conventional methods, in order to improve the point reduction effect, (11 centerline average surface thickness Ha) must be 0.6μ or more and have a grain size of 1-1, and (2) surface reflectance. It has been found that three conditions are essential: (3) the amount of anodic oxide film is 2.5 g/rrr or more. Therefore, the actual situation is that only a limited number of positive PS plates with high effective sensitivity have been obtained.

[Purpose of the invention]

An object of the present invention is to provide a positive type lithographic printing Wl1 plate which has a sufficient dot reduction effect regardless of whether or not the three conditions listed in (-) are satisfied.

The object of the present invention is to have a center line average surface roughness of 0. It is an object of the present invention to provide a positive planographic printing plate having a sufficient dot reduction effect even when the thickness is 6μ or less.

Another object of the present invention is to provide a positive planographic printing plate that has a sufficient dot reduction effect even when the surface reflectance is 50% or less.

Another object of the present invention is to provide a positive planographic printing plate which has a sufficient dot reduction effect even when the amount of anodized film is 2.5 g/rd or less.

[Structure of the invention]

As a result of extensive studies, the inventors of the present invention have developed an anodized skin having a branched bore structure on the surface of an aluminum plate that has been subjected to grain and/or chemical etching treatment as necessary. ! It has been found that the object of the present invention can be achieved by providing l&. Although the anodic oxide film itself, in which the cross-sectional structure of the bore has a branched structure, was known in the field of aluminum surface treatment, the above-mentioned effects of such an aluminum plate were completely unknown. . For this reason, the use of such aluminum plates as lithographic printing plates had not hitherto been thought of.

Hereinafter, the method for producing a lithographic printing support according to the present invention will be explained in detail step by step.

The aluminum plate used in the present invention includes pure aluminum and aluminum alloy plate. Various aluminum alloys can be used, such as aluminum alloys with metals such as silicon, iron, copper, manganese, magnesium, chromium, zinc, bismuth, and nickel. The aluminum plate may be in the form of a sheet or a band, and may also be made of aluminum on the surface and laminated with paper, plastic, or other metal. The aluminum plate must be such that when it is installed as a printing plate in a printing machine, the dimensions do not change; for example, in the case of an aluminum plate alone, it is generally 0.1
A thickness of ~0.5 m/m is used.

Prior to the roughening treatment, the surface of the aluminum plate may be subjected to a degreasing treatment to remove rolling oil from the surface, if necessary.

The positive PS plate of the present invention with high effective sensitivity can be obtained without roughening the surface of the aluminum plate in advance. However, it is desirable to roughen the surface of the aluminum plate in advance in order to improve water retention and adhesion with the layer of photosensitive material coated thereon. As a method for roughening, a commonly used mechanical roughening method, chemical roughening method, electrochemical roughening method, or a combination thereof can be used.

As the mechanical surface roughening method, a wire brush graining method, a brush clay lining method, a sandplast method, and a ball graining method are used. Also electrochemical '111
As the surface roughening method, a method of roughening with direct current or alternating current in a dilute aqueous solution of nitric acid, hydrochloric acid, or a salt thereof is used. As a particularly preferred surface roughening method, a mechanical surface roughening method is advantageous from the viewpoint of mass production stability. Additionally, a combination of the two disclosed in Japanese Patent Laid-Open No. 54-63902 can also be used. As for desirable graining, the center line surface thickness Dla) is preferably in the range of 0.25 to 0.65 μm in consideration of printability. If Ha is 0.65μ or more, the developability may be impaired by In or printing may be easily smudged.

The roughened aluminum surface is chemically etched as necessary to uniformly perform the anodizing treatment described later. Particularly in the case of mechanical roughening, if an anodic oxide film is immediately applied without chemical etching, the abrasives remaining on the aluminum surface will cause blackening and defects in the anodic oxide film.

The etching solution used in the present invention is usually selected from aqueous base or acid solutions that dissolve aluminum. In this case, the etched surface must be such that no film different from aluminum or aluminum derived from the etching solution components is formed. Examples of preferred etching agents include basic substances such as sodium hydroxide, potassium hydroxide, trisodium phosphate,
Trisodium phosphate, tripotassium phosphate, dipotassium phosphate, etc.; @-based substances include sulfuric acid, persulfuric acid, phosphoric acid, sediment @
metals with a lower ionization tendency than aluminum, such as zinc, chromium, cobalt, disokel, etc.
Salts such as copper are not preferred because they form an unnecessary film on the etched surface. These etching agents have a dissolution rate of 0.3 grams per minute of immersion time to 40 grams per minute of immersion time, depending on the concentration and temperature used.
It is most preferable to carry out the test so that the
There is no problem even if it is more than or less than this.

Etching is performed by immersing the aluminum plate in the above-mentioned etching solution or applying the etching solution to the aluminum plate, and the etching amount is in the range of 0.5 to 10 g/I. is preferred.

For the above-mentioned etching, it is desirable to use an aqueous base solution because of its high etching speed. In this case, since smut is generated, desmut processing is usually performed. The acids used in the desmutting treatment include nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrobutic acid, and hydrofluoric acid.

After washing the etched aluminum plate with water if necessary, an anodic oxide film having a bore having a branched cross-sectional structure is provided. The surface reflectance after this anodic oxide film is applied is the absorption wavelength of the photosensitive material coated on the upper layer.
Normally, the self-recording spectrophotometer needle (Hitachi 340Record lngSpectr
It is preferable that it be 50% or less as measured by a photometer. The amount of anodized film required to achieve such reflectance is preferably 1.0 g/
rrf or more, preferably 2.0 g/rrr or more.

Treatment baths used to form such an anodized film include, for example, treatment baths used to improve the corrosion resistance and aesthetic appearance of building materials, such as ematal baths, chromic acid baths, and low concentration (1 to 10 commercially available) baths. %) phosphoric acid bath, low concentration (1 to 0 to 10% by weight) oxalic acid bath, low concentration (1 to 10% by weight)
degree) sodium borate bath, etc. Generally, the bath temperature is 5°C to 50°C, the bath voltage is 20V to 200V, the current density is 0.5 A/d- to I, although it varies depending on the treatment bath composition.
The processing may be performed at OA/d% for about 10 seconds to IO minutes. The present invention is characterized in that the cross-sectional structure of the bore of the anodic oxide film has a branched structure,
Any method that can form a film with such a structure can be used.

In an anodic oxide film where the cross-sectional structure of the bore has a "branched structure", there is a lot of scattering and diffused reflection within the oxide film, so the surface reflectance decreases, but the reflected light becomes scattered light. Therefore, the point reduction effect becomes large. However, in a normal anodic oxide film, such as sulfuric acid bath alumite, in which the bore does not have a branched structure, scattering and diffused reflection are extremely low. Therefore, in the conventional method, diffuse reflection was caused by increasing the surface roughness (Ha) of the aluminum surface to 0.6 μ or more. Furthermore, if the weight resistance decreases, the diffusely reflected light becomes insufficient, so it was necessary to make the reflectance 50% or higher. On the other hand, in an anodized film where the bores have a branched structure, light is diffusely reflected by the branched structure of the bores, so even if the surface roughness of the aluminum surface is small, a sufficient point reduction effect can be obtained. be able to. Moreover, a larger point reduction effect can be obtained by setting the surface reflectance to 50% or less.

The anodized aluminum plate can be washed with water if necessary.
After drying, it is further treated by methods such as immersion in an aqueous solution of an alkali metal silicate, such as sodium silicate, as described in U.S. Pat. Nos. 2,714,066 and 3,181,461. or U.S. Patent No. 3,86
As described in No. 0,4.26, a subbing layer of hydrophilic cellulose (such as carboxymethyl cellulose) containing a water-soluble metal salt (such as zinc acetate) may also be provided.

2. On the lithographic printing support according to the present invention, a conventionally known photosensitive layer can be provided as a 28th plate photosensitive layer to obtain a photosensitive lithographic printing plate, which can be subjected to plate-making processing. The obtained lithographic printing plate has excellent printing performance.

The composition of the photosensitive layer includes a diazo resin, an 0-quinonediazide compound, a photosensitive azide compound, a photopolymerizable composition, and a photosensitive resin having an unsaturated double bond in the molecule. These are described in detail in JP-A-55-32+186, but positive-working photosensitive layers made of 0-quinonediazide compounds are particularly useful.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on Examples.

Note that % indicates weight % unless otherwise specified.

Example] After degreasing an aluminum plate (material 1050) with a thickness of 0.3 mm with Triclean, the surface was grained using a nylon brush and 400 mesh of Bamisu water suspension, and thoroughly rinsed with water. Washed (center line average surface roughness Ha) 0.65μ), B: Similar graining with surface roughness Ha) 0.5μ,
C: No graining (surface roughness Ha) 0
．． 23μ) were prepared respectively. Then A was heated to 2 at 60°C.
Etching was performed by immersing it in a 5% aqueous sodium hydroxide solution for 25 seconds, washing with water, and then immersing it in 20% nitric acid for 20 seconds and washing with water. The amount of etching on the grained surface at this time was about 8 g/rd (A-1). In addition, B and C were etched at 45° C. for 10 seconds and the etching amount was about 2 g/rd (B-2, C-2). Next, these aluminum INA-1, B-2, and C-2 were subjected to DC anodic oxidation treatment using 15% sulfuric acid as an electrolyte at a current density of 1.6^/dnf, and the bores had a branched structure. After forming a free oxide film (3.0 g/rrf), the aluminum plates were washed with water and dried to obtain aluminum plates A-1-α, B-1-4 α, and C-2-α, respectively. Separately, using an ematal bath having the composition shown in Table 1 below, a current density of 2 A/drr! From I
Aluminum 1A-1, B-2, and C-2 were treated at A/d n(dropped at 120 cm and bath temperature at 60°C) to form a film in which the bores had a branched structure (film 13. 0g/r
After washing with water and drying, aluminum plates A-1-β, B-2-β, and C-2-β were obtained, respectively.

Table 1 Bath composition Titanium oxalate potash 40g Quen r! IIIg Shu r! 1 1.2g Boric acid 8g Add water to bring the total volume to 11.

Next, these aluminum plates were given British Patent No. 1.113,
The mixture of diazooxide resin and phenolic resin described in Example 1 of the No. 759 specification (5 parts (by weight) of the 2-diazo-1-naphthol-5-sulfonic acid ester of the condensation product of pyrrro-role) was mixed with 80 parts of cyclohexane. A diluted photosensitive lithographic printing plate was obtained by coating and drying the coating. The coating weight after drying is 2.4 to 2.5 g/r.
It was rr.

After imagewise exposing each of these photosensitive lithographic printing plates from a distance of 1 m using a 2 kW metal halide lamp, the molar specific power of 5 in2/NaZO was 5i
01 months, 25℃ with 5% sodium silicate aqueous solution
Developed for 60 seconds. The exposure time is the practical exposure time (
In other words, the exposure time was set such that the halftone dot area of halftones was reduced by 8%.

Table 2 shows the processing conditions and exposure times for the lithographic printing plate.

6 A-1-α has a sufficient point reduction effect (high practical sensitivity). Conventional anodic oxide film α
However, when the surface roughness became small or the surface reflectance decreased (B-2-α, C-2-α), the point reduction effect could not be obtained.

On the other hand, in the printing plate according to the present invention in which the bores have a branched structure, the flashing time is short in all of A-1-β, B-2-β, and C-2-β, and is sufficient. It can be seen that a point reduction effect (with high practical sensitivity) was obtained.

In addition, in printing, the method of the present invention also produced good results without staining, similar to the conventional method.

Example 2 In Example 1, the amount of anodic oxidation film of A-1-α and A-1-β was 1.5 g/n (binding, otherwise the same as Example 1), the conventional method A-1- α had a practical exposure time of 90 seconds, while the invention product A-1-β had a practical exposure time of 6 seconds.
It was 0 seconds.

8 Example 3 In Example 1, a chromic acid bath anodized film (3% chrono-acid solution, bath solution 4
The film weight was set to 3 g/rd at 0°C)
When tested, the same good results as in Example 1 were obtained.

■9 Showa year, month, day 1, case description 1981 Patent Application No. 1.81665 2, title of the invention Support for lithographic printing plate 3, person making the amendment Relationship to the case Applicant name Title (520) Fuji Photo Phil J, Co., Ltd. 4, Agent 5, Date of amendment order Voluntary 1, The scope of claims is amended as shown in the attached sheet.

2. The entries in the memorandum will be corrected as shown in the table below.

3. From the 4th line from the bottom of page 15 to the 1st line of page 16, "diazo oxide... combed)" is corrected as follows.

"A photosensitive solution prepared by dissolving 0.75 g of diazo oxide resin and 2.00 g of Talesol Novolanc resin in 16 g of ethylene dichloride and 12 g of 2-methoxyethyl acetate" Claims: Graining and/or chemical etching as necessary 1. A support for a lithographic printing plate, characterized in that an anodic oxidation test in which the cross-sectional structure of bores has a branched structure is provided on the surface of a treated aluminum plate.

(2) The support for a lithographic printing plate according to claim 1, wherein the reflectance of the surface of the support is 50% or less.

Claims (1)

[Claims] +11 A feature of the invention is that an anodic oxide film having a cross-sectional structure of the bore having a branched structure is provided on the surface of the aluminum plate, which has been subjected to graining and/or etching treatment if necessary. Support for lithographic printing. (2) The reflectance of the support surface is 50% or less.