GB2124399A

GB2124399A - A light-sensitive planographic printing plate precursor

Info

Publication number: GB2124399A
Application number: GB08314367A
Authority: GB
Inventors: Akira Nagashima; Yasuhito Naruse; Akira Hasegawa
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1982-05-25
Filing date: 1983-05-24
Publication date: 1984-02-15
Also published as: GB8314367D0; DE3318950A1; JPS58205154A

Abstract

The plate is comprised of a support base (1) having one (2) or more (3, 4) light-sensitive layers positioned thereon. The light-sensitive layer or layers comprises an o- quinonediazide compound and an alkali-soluble resin. The concentration of the o-quinonediazide compound in the light-sensitive layer(s) decreases in the direction through the layer(s) towards the support base. Accordingly, the light-sensitive layer(s), prior to exposure to light have increasing solubility in the direction towards the support base. However, after exposure to light, the light-sensitive layer(s) have decreasing solubility in the direction towards the support base. The printing plate aids in preventing the formation of scum and has a high oil-attractive property in the image area. The printing plate precursor has high light- sensitivity and can be developed under a wide range of development conditions. <IMAGE>

Description

SPECIFICATION Light-sensitive planographic printing plate precursor Field of the invention The present invention relates to a light-sensitive planographic printing plate precursor and, in greater detail, to a light-sensitive planographic printing plate precursor having a positive type sensitive layer containing an o-quinonediazide compound.

Background of the invention Planographic printing is a printing process utilizing the property that water does not substantially mix with oils. In this process, the face of the printing plate has an area having hydrophilic property, thereby repelling oily inks (non-image part) and an area having a hydrophobic property thereby accepting oily inks (image part). By increasing the degree of these properties on planographic printing plate, it becomes possible to easily produce prints having good quality. Further, inking in the beginning of printing can be easily carried out, whereby good prints can be produced with a smaller amount of wasted paper at start-up of the press.Hitherto, in order to improve such properties, a process which comprises adding a substituted phenol-formaldehyde resin such as t-butyl phenol-formaldehyde resin to a sensitive layer containing an o-quinonediazide compound has been described in U.S. Patent 4,1 23,276. By addition of the substituted phenol-formaldehyde resin, the oil attractive property (property of accepting oily inks) of the image part is improved as compared with the case of no addition. However, there are problems in that the developing property of the non-image part is inferior to the extent that it causes scumming or deterioration of sensitivity.

The higher the light-sensitivity of the planographic printing plate precursor is, the shorter the time required for exposure. Thus the plate-making operation can be speedily carried out. However, if the amount of sensitizing materials in the light-sensitive layer of the planographic printing plate precursor using an o-quinoediazide compound is reduced in order to increase the sensitivity, the range of proper development conditions becomes narrow. Consequently, there are problems in that a part of the image part is damaged and dissolved during development because of excessive development. According to a process which comprises adding cyclic acid anhydride to a light-sensitive layer described in U.S. Patent 4,11 5,128, the sensitivity can be increased.However, when the anhydride is added in a certain amount or more, the range of proper development conditions becomes narrow.

Japanese Patent application (OP I) No. 1 26836/81 has disclosed a light-sensitive planographic printing plate precursor using an o-quinonediazide compound in a layer wherein the upper layer part is more alkali-insoluble than the lower layer part. However, as will be apparent from the following description, this plate is essentially different from that of the present invention, because, in the printing plate precursor disclosed in OPI No. 126386/81, the upper layer is not easily dissolvable in an aqueous alkali solution both before exposure to light and after exposure to light, as compared with the lower layer.

Summary of the invention The present invention provides a light-sensitive planographic printing plate precursor having high sensitivity and which can be developed under a wide range of development conditions. Using the printing plate precursor of this invention, it is possible to obtain a printing plate which is resistant to scumming and has a high oil-attractive property in the image part.

The present invention provides a light-sensitive planographic printing plate precursor comprising at least one light-sensitive layer containing an o-quinonediazide compound and an alkali-soluble resin provided on a support base, wherein said light-sensitive layer (single or plural) contains the oquinonediazide compound in such an amount that its content in the portion of the layer remote from the support base is higher than in the portion adjacent the support base.

Brief description of the drawings Figure 1 is a schematic cross section through a light-sensitive planographic printing plate precursor according to an embodiment of the invention. Figures 2 and 3 are similar cross sections after imagewise exposure and after development respectively, wherein 1 is the support base, 2 is the lightsensitive layer (or 3 the lower end of the upper light-sensitive layer) and 5 is the transparent original.

Detailed description of the invention In the present invention, the o-quinonediazide compound used in the upper part of the lightsensitive layer or the upper such layer (hereinafter referred to as the upper layer) may be identical to or different from that used in the lower part of the light-sensitive layer or the lower such layer (hereinafter referred to as the lower layer). Further, two or more o-quinonediazide compounds may be contained in one layer. When different kinds of o-quinonediazide compound are used in the upper layer and the lower layer, the contents of the o-quinonediazide compound in the upper layer and the lower layer are calculated on the basis of densities of diazo groups contained in each layer. Further, the upper layer and the lower layer may be mixed with each other to a certain extent as long as the effect of the present invention is not missing.The present invention may include a light-sensitive planographic printing plate precursor with a layer composition wherein the concentration o-quinonediazide compound decreases in the direction toward the base and increases in the direction away from the base.

A resin which is soluble in an aqueous alkali solution but insoluble in neutral water (alkali-soluble resin) is used as a binder in the upper layer and the lower layer. Although the binder in the upper layer and that in the lower layer may be identical or may be different from each other, it is more preferred that the binder in the lower layer is more soluble in the aqueous alkali solution than the binder in the upper layer.

In the present invention, it is important that the upper layer of the sensitive layer is not easily dissolved in a developing solution (aqueous alkali solution) before exposure to light as compared with the lower layer, and the solubility of the upper layer becomes equal to or higher than that of the lower layer after exposure to light. Such a property is caused by the fact that the amount of the o-quinonediazide compound contained in the upper layer part is larger than that in the lower layer part.

In the following, the present invention is illustrated in greater detail with reference to the appended drawings. Figure 1 is a section which indicates the constitution of a light-sensitive planographic printing plate precursor of the present invention wherein a sensitive layer 2 is provided on a base 1.

The sensitive layer 2 is composed of two layers consisting of a lower layer 3 and an upper layer 4.

The lower layer contains a mixture of an o-quinonediazide compound and an alkali soluble resin, and the upper layer contains a mixture of an o-quinonediazide compound and an alkali soluble resin or only an o-quinonediazide compound. The content of the o-quinonediazide compound in the upper layer is higher than that in the lower layer. The upper layer is preferred to contain at least 20% of the oquinonediazide compound.

As shown in Figure 2, when the printing plate is exposed to light (which is shown as arrows) through a transparent original having a positive image laid thereon, the quinonediazide compound in the exposed part 2b (3b and 4b) corresponding to the image part of the original causes photolysis to form a compound having a carboxylic acid group which is alkali-soluble. On the other hand, the unexposed part (3a and 4a) corresponding to the image part does not change. When it is developed with an aqueous alkali solution, the upper part 4b in the exposed part 2b (3b and 4b) is particularly easily dissolved, because it contains a large amount of a photolysis product of o-quinonediazide compound. On the other hand, the unexposed part 2a is difficult to dissolve in the aqueous alkali solution.Accordingly, there is almost no damage to the image part due to excessive development, because the unexposed part has the upper layer part 4a which contains a larger amount of alkali insoluble quinonediazide compound. Thus it is possible to obtain a planographic printing plate precursor having a wide range of proper development conditions by carrying out development with the aqueous alkali solution, because the exposed part can be completely removed, as shown in Figure 3, and the unexposed part remains undamaged.

Since the image part of the planographic printing plate has a larger content of o-quinonediazide compound in the upper layer thereof, the image part is rich in oleophilic properties. Accordingly, the plate can produce good quality prints. It is particularly advantageous for a plate to have a good ink adhesive property when beginning a printing operation in order to obtain good prints without causing a large amount of wasted paper.

Further, it is possible to obtain a light-sensitive planographic printing plate precursor having higher sensitivity by using a resin which is more alkali-soluble as a binder contained in the lower layer 3 in Figure 1.

The entire thickness of the light-sensitive layer in the sensitive planographic printing plate precursor of the present invention is 0.5 yam~8 ym and, preferably, 1 #m-4 #m, wherein the thickness of the upper layer is 0.002 #m or more and, preferably, 0.1 #m or more and that of the lower layer is 0.1 ym or more and, preferably, 0.3 ym or more.

The planographic printing plate precursor of the present invention can be produced by applying a solution containing the lower layer components of the light-sensitive layer (sensitizing solution) by means of a known coating apparatus such as a squeeze coater, a reverse roll coater, a gravure coater, an extrusion coater or a blade coater, etc. and drying and subsequently applying a sensitizing solution containing the upper layer components by means of the above described known coating apparatus and drying.

Another process is carried out by applying a sensitizing solution containing the upper layer components and the lower layer components wherein two or more solvents are used one of which easily dissolves the upper layer component but hardly dissolves the lower layer components and the other of which easily dissolves the alkali-soluble resin but hardly dissolves the upper layer components.

The boiling point of the former solvent is at least 1 OOC higher than that of the latter. This makes it possible to carry out separation (or incomplete phase separation) of the upper layer and the lower layer during application and drying.

However, other processes can be used for producing the planographic printing plate precursor of the present invention.

Useful bases include those used for known planographic printing plates precursor. Examples of them include aluminium plates subjected to hydrophilic treatment such as an aluminium subjected to silicate treatment or an anodic oxidation aluminium plate, zinc plates, stainless steel plates, chromium treated copper plates, plastic films subjected to hydrophilic treatment and papers.

Examples of useful o-quinonediazide compounds include esters of 1 ,2-diazobenzoquinonesulfonic acid chloride and polyhydroxyphenyl, and esters of 1 ,2-diazonapththoquinone sulfonic acid chloride and pyrogallol-acetone resin, described in U.S. Patent 3,635,709. Examples of other suitable o-quinonediazide compounds include esters of 1 ,2-diazobenzoquinonesulfonic acid chloride or 1,2diazonaphthoquinonesulfonic acid chloride and phenol formaldehyde resin, described in U.S. Patents 3,046,120 and 3,188,210. Examples of other useful o-quinonediazide compounds are described in Japanese Patent Application (OP I) Nos. 63802/73, 63803/73, 96575/73 and 38701/74, Japanese Patent Publication Nos. 11222/66, 9610/70 and 17481/74, U.S.Patents 3,644,118, 3,785,825, 3,711,285,2,797,213, 3,454,400,3,544,323, 3,573,917,3,674,495 and 3,785,825, British Patents 1,227,602, 1,251,345, 1,267,005, 1,329,888 and 1,330,932 and German Patent 854,890. etc.

Useful alkali soluble resins include novolak resins, examples of which include phenolformaldehyde resin, cresol-formaldehyde resin, p-tert-butylphenol-formaldehyde resin, phenol modified xylene resin and phenol modified xylene-mesitylene resin, etc. Examples of other useful alkali soluble resin include polyhydroxystyrene, polyhalogenohydroxystyrene and copolymers of acrylic acid (or methacrylic acid) and other vinyl compounds (for example, methyl methacrylate), etc.

In the light-sensitive layer comprising the o-quinonediazide compound and the alkali soluble resin of the light-sensitive planographic printing plate precursor of the present invention, the amount of the o-quinonediazide compound is 10~100% by weight and, preferably,20~90% by weight in the upper layer and O~40% by weight and, preferably,5~30% by weight in the lower layer. More preferably, the ratio of the concentration of o-quinonediazide compound contained in the upper layer to that in the lower layer is more than 1.3, the concentration of o-quinonediazide in each layer being based on the total amount of the composition of each layer.

The light-sensitive layer of the present invention may contain cyclic acid anhydrides for increasing sensitivity, printout agents for obtaining visible images immediately after exposure to light, dyes as image coloring agents, and fillers, etc. Examples of cyclic acid anhydrides include phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride, 3,6-endooxy-A4-tetra- hydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, maleic acid anhydride, chloromaleic acid anhydride, acphenylmaleic acid anhydride, succinic acid anhydride and pyromellitic acid, etc.

described in U.S. Patent 4,115,128. These cyclic acid anhydrides are added in an amount of 1 to 15% by weight based on the composition composing the sensitive layer, by which the maximum sensitivity can be increased three times or so.

Useful printout agents for obtaining visible images immediately after exposure to light include a combination of a light-sensitive compound which releases an acid by exposure to light and an organic dye capable of forming a salt. Examples of such agents include combinations of o-naphthoquinonediazide-4-sulfonic acid haiogenide and a salt forming organic dye described in Japanese Patent Application (OPI) No. 8128/78 and U.S. Patent 3,969,118, and combinations of a trihalomethyl compound and a salt forming organic dye described in Japanese Patent Application (OPI) No.

36223/78 and U.S. Patent 4,232,106. Useful coloring agents for images include the above described salt forming organic dyes and other dyes. As suitable dyes including salt-forming organic dyes, there are oil-soluble dyes and basic dyes. Examples of them include Oil Yellow #1 01, Oil Yellow &num;130, Oil Pink &num;312, Oil Green BG, Oil Blue BOS, Oil Blue &num;603, Oil Black BY, Oil Black BS, Oil Black T-505 (which are produced by Orient Chemical Industry Co.), Crystal Violet, Methyl Violet, Rhodamine B, Malachite Green and Methylene Blue, etc.

The upper layer and the lower layer in the sensitive layer of the sensitive planographic printing plate of the present invention are formed by applying solutions prepared by dissolving the above described components in a solvent to a base. Examples of the solvent used include ethylenedichloride, cyclohexanone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethylacetate, toluene, ethyl acetate, ethyl alcohol and methyl alcohol, which are used alone or as a mixture of two or more 6f them. The concentration of the above described components (solid content) is 2~60% by weight.

The developing solution for the light-sensitive planographic printing plate precursor of the present invention may be an aqueous solution of inorganic alkali agents such as sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium tertiary phosphate, sodium secondary phosphate, ammonium tertiary phosphate, ammonium secondary phosphate, sodium metasilicate, sodium bicarbonate or aqueous ammonia, etc. These alkali agents are added so as to have a concentration of 0.1-10% by weight and, preferably, O.5~5% by weight.

Further, it is possible to add, if necessary, surface active agents and organic solvents such as alcohol, etc. to the above described aqueous alkaline solution.

In the following, the present invention is illustrated in greater detail with reference to examples.

However, the scope of the invention is not limited to these examples. All percentages in the following examples are by weight unless otherwise stated.

Example 1 A 2S aluminium plate having a thickness of 0.1 5 mm was degreased by dipping in a 10% aqueous solution of sodium tertiary phosphate kept at 800C for 3 minutes. After being grained with a nylon brush, desmutting treatment was carried out with a 3% aqueous solution of sodium hydrogen sulfate. The resulting aluminium plate was treated with a 1.5% aqueous solution of sodium silicate at 700C for 1 minute to produce an aluminium plate (I).

To this aluminium plate, a sensitizing solution (A) was applied by an extrusion coater and dried at 1 000C for 1 minute. Further, to the resulting layer, a sensitizing solution (B) was applied by an extrusion coater and dried at 1000C for 1 minute to produce a light-sensitive planographic printing plate (1).

As a comparative example, a sensitizing solution (C) was applied to the aluminium plate (I) by an extrusion coater and dried at 1 000C for 2 minutes to produce a sensitive planographic printing plate (2). The light-sensitive planographic printing plate precursors were produced so that the content of each component in the light-sensitive layer per unit area was equal to the same unit area in the other plates.

Sensitizing solution (A): Esterified product of naphthoquinone-1 ,2-diazide-5-sulfonyl chloride and pyrogallol-acetone resin (that described in Example 1 in U.S. Patent 3,635,709) 0.2 g Cresol-formaldehyde resin 2.6 g Tetrahydrophthalic acid anhydride 0.1 g Naphthoquinone-1 ,2-diazide-4-sulfonyl chloride 0.02 g Oil Blue &num;603 (produced by Orient chemical Industry Co.) 0.03 g Methyl ethyl ketone 8g 2-Methoxyethyl acetate 15g Sensitizing solution (B):: Esterified product of naphthoqui none- 1 ,2-diazide-5-su Ifonyl chloride and pyrogallol-acetone resin 1.6 g Cresol4ormaldehyde resin 1.2 g Tetrahydrophthalic acid anhydride 0.1 g Naphthoquinone- 1 ,2-diazide-4-su Ifonyl chloride 0.02 g Oil Blue &num;603 (produced by Orient chemical Industry Co.) 0.03 g Methyl ethyl ketone 18g 2-Methoxyethyl acetate 59 Sensitizing solution (C):: Esterified product of naphthoquinone-1 ,2-diazide-5-sulfonylchloride and pyrogallol-acetone resin 1.8 g Cresol-formaldehyde resin 3.8 g Tetrahydrophthalic acid anhydride 0.2 g Naphthoquinone- 1 ,2-diazide-4-sulfonyl chloride 0.04g Oil Blue &num;603 (produced by Orient Chemical Industry Co.) 0.06 g Methyl ethyl ketone 8g 2-Methoxyethyl acetate 15g In the light-sensitive planographic printing plate precursor (1), the coating amount (weight after drying; same as above) of the lower layer (layer formed by the sensitizing solution (A)) was about 1.2 g/m2 and the coating amount of the upper layer (layer formed by the sensitizing solution (B)) was about 1.2 g/m2, and a total of the coating amounts was about 2.4 g/m2.The coating amount in the lightsensitive planographic printing plate precursor (2) was about 2.4 g/m2 These light-sensitive planographic printing plate precursors were imagewise exposed to light at a distance of 70 cm from a 30 ampere carbon arc lamp, respectively. They are developed with a 5.25% aqueous solution of sodium silicate having a molar ratio: SiOdNa,O of 1.74 (pH: 12.7) at 250C for 60 seconds, and their sensitivity was measured. The proper exposure time in this case was a point at which 5 steps in the gray scale having density differences of 0.15 were completely whitened (the point at which the light-sensitive layer was completely removed by dissolution).Further, the range of proper development conditions was shown as the development time for which the whitened part in the gray scale having a density difference of 0.1 5 changes one step by the same developing solution at 250C.

Further, the degree of oil-attractive property of the image part was shown as the number of paper sheets supplied from the beginning of printing till the printing ink adhered completely to the image part (number of sheets before good inking).

It is understood from the results shown in Table 1 that the light-sensitive planographic printing plate precursor of the present invention has a wide range of proper development conditions and has an excellent oil-attractive property.

Table 1 Sensitive Range of planographic Proper proper Oil printing plate development development attractive precursor time conditions property (sensftivity) (number of sheets before good inking) (1) 100 seconds 30 seconds to 6 sheets 5 minutes (2) 100 seconds 30 seconds to 10 sheets 3 minutes Example 2 A 1 S aluminium plate having a thickness of 0.24 mm was degreased by dipping in a 10% aqueous solution of sodium tertiary phosphate kept at 800C for 3 minutes. After being grained with a nylon brush, etching was carried out with sodium alminate for about 10 seconds and desmutting treatment was carried out with a 3% aqueous solution of sodium hydrogen sulfate. The resulting aluminium plate was subjected to anodic oxidation in 20% sulfuric acid at a current density of 2 A/dm2 for 2 minutes to produce an aluminium plate (II).

To this aluminium plate (II), a sensitizing solution (D) (the same sensitizing solution as the sensitizing solution (A) except that the same amount of phenol-formaldehyde resin was used instead of the cresol-formaldehyde resin) was applied and dried by the same manner as in Example 1. Then, to the resulting layer, a sensitizing solution (B) was applied and dried by the same manner as in Example 1 to produce a light-sensitive planographic printing plate precursor (3).As a comparative example, a sensitizing solution (E) (the same sensitizing solution as the sensitizing solution (C) except that 2.6 g of the cresol-formaldehyde resin was replaced with 2.6 g of phenol-formaldehyde resin) was applied to an aluminium plate (II) by the same manner as when producing the light-sensitive planographic printing plate precursor (2) in Example 1 to produce a light-sensitive planographic printing plate precursor (4).

In the light-sensistive planographic printing plate precursor (3), the coating amount of the lower layer was about 1.2 g/m2 and the coating amount of the upper layer was about 1.2 g/m2, and a total of the coating amounts was about 2.4 g/m2. The coating amount in the light sensitive planographic printing plate precursor (4) was about 2.4 g/m2.

The light-sensitive planographic printing plate precursors (3) and (4) were evaluated by the same methods as in Example 1. Results were shown in Table 2. It is understood from Table 2 that the light sensitive planographic printing plate precursor of the present invention has a high sensitivity and a wide range of proper development conditions and an excellent oil-attractive property.

Table 2 Range of Proper proper Oil development development attractive Sample time conditions property (sensitivity) (number of sheets before good inking Planographic Printing 70 seconds 30 seconds to 6 sheets Plate Precursor (3) 3 minutes (Comparative Sample) 100 seconds 30 seconds to 10 sheets Planographic Printing 3 minutes Plate Precursor (4) While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

1. A light-sensitive planographic printing plate precursor comprising a support base and on the base a light-sensitive layer which comprises an o-quinonediazide compound and an alkali-soluble resin, wherein the concentration of the o-quinonediazide compound in the light-sensitive layer decreases in the direction through the layer towards the support base.

2. A light-sensitive planographic printing plate precursor as claimed in claim 1, wherein the lightsensitive layer comprises at least two light-sensitive layers being an upper light-sensitive layer remote from the support base and a lower light-sensitive layer nearer the support base, and the concentration of the o-quinonediazide compound in the upper light-sensitive layer is greater than that in the lower lightsensitive layer.

3. A light-sensitive planographic printing plate precursor as claimed in claim 1, wherein the lightsensitive layer is such that its solubility in an aqueous alkali solution before exposure to active rays increases in the direction through the layer towards the support base, and further wherein its solubility in an aqueous alkali solution after exposure to active rays remains unchanged or decreases in the direction through the layer towards the support base.

4. A light-sensitive planographic printing plate precursor as claimed in Claim 1, wherein the lightsensitive layer has a thickness within the range of 0.5 ym to 8 ym.

5. A light-sensitive planographic printing plate precursor as claimed in Claim 4, wherein the lightsensitive layer has a thickness within the range of 1 um to 4item.

6. A light-sensitive planographic printing plate precursor as claimed in Claim 2, wherein the upper light-sensitive layer has a thickness of 0.002 ym or more and the lower light-sensitive layer has a thickness of 0.1 ym or more.

7. A light-sensitive planographic printing plate precursor as claimed in Claim 6, wherein the upper light-sensitive layer has a thickness of 0.1 ym or more and the lower light-sensitive layer has a thickness of 0.3 ,um or more.

8. A light-sensitive planographic printing plate precursor as claimed in Claim 2, wherein the upper light-sensitive layer contains the o-quinonediazide in an amount within the range of 10 to 100% by weight and the lower light-sensitive layer contains the o-quinonediazide in an amount within the range of O to 40% by weight.

9. A light-sensitive planographic printing plate precursor as claimed in Claim 8, wherein the upper light-sensitive layer contains the o-quinonediazide compound in an amount within the range of 20 to 90% by weight and the lower light-sensitive layer contains the o-quinonediazide compound in an amount within the range of 5 to 30% by weight.

10. A light-sensitive planographpc printing plate precursor as claimed in any one of claims 1 to 9, wherein the light-sensitive layer is further comprised of cyclic acid anhydrides in an amount of 1 to 1 5% by weight based on the weight of the sensitive layer.

11. A light-sensitive planographic printing plate precursor as claimed in claim 1 substantially as described in either of the Examples.

12. A planographic printing plate obtained by imagewise exposure and development of a lightsensitive planographic printing plate precursor as claimed in any one of claims 1 to 11.