CA1243876A

CA1243876A - Aqueous-alkaline developer for negative-working reproduction layers

Info

Publication number: CA1243876A
Application number: CA000457885A
Authority: CA
Inventors: Fritz Uhlig; Monika Gruber; John E. Walls
Original assignee: Hoechst Celanese Corp
Current assignee: CNA Holdings LLC
Priority date: 1983-08-25
Filing date: 1984-06-29
Publication date: 1988-11-01
Also published as: DE3463577D1; JPH0414783B2; JPS6070449A; BR8404222A; EP0134407A1; EP0134407B1; ZA845108B

Abstract

ABSTRACT

Provided is an aqueous-alkaline developer for an irra-diated radiation-sensitive negative-working reproduction layer, which developer is based on water, an anionic surfactant, at least one inorganic salt having an alka-line reaction and at least one alkanoic diacid or a salt thereof, wherein the developer has a pH of from about 8 to 12 and comprises a) 0.05 to 10 % by weight of a sodium, potassium or lithium sulfate salt of octyl, decyl or dodecyl alcohol;

b) 0.001 to 5 % by weight of a sodium, lithium or potassium metasilicate salt;

c) 0.1 to 15 % by weight of a lithium, potassium or sodium borate salt;

d) 0.01 to 5 % by weight of an alkanoic diacid, or sodium or potassium salt thereof having from 2 to 6 carbon atoms;

e) 0.5 to 12 % by weight of di- or tri-sodium or potassium phosphate;

f) 0.02 to 10 % by weight of a substituted or unsubstituted benzoic acid, or the sodium, potassium, lithium or ammonium salt thereof;
and g) 0.5 to 5 % by weight of an ethylene glycol monoether or an ethylene glycol diether, and the weight ratio of sodium ions to potassium ions in the developer ranges from 1:1 to 1.4:1; and a method of developing reproduction layers using the above aqueous alkaline developer.

Description

BACKGROUND OF THE INVEI~TIO~

The present invention relates to a composition for deve-loping reproduction layers. More specifically, the pre-sent invention relates to a method of developing printing plates and similar elements. More particularly, the invention relates to aqueous alkaline developing compo-sitions suitable for use with such elements.

The art of lithographic printing depends upon the immi-scibility of grease and water, upon the preferential re-tention of a greasy image-forming substance by an image area, and upon the similar retention of an aqueous dam-pening fluid by a non-image area. When a greasy image is imprinted upon a suitable surface and the entire surface is then moistened with an aqueous solution, the image area will repel the water and the non-image area will retain the water. Upon subsequent application of greasy ink, the image portion retains ink whereas the moistened non-image area repels it. The ink on the image area is then transferred to the surface of a material on which the image is to be reproduced, such as paper, cloth and the like, via an intermediary, a so called offset or blanket cylinder, which is necessary to prevent mirror-image printing.

The most common type of lithographic plate to which the present invention is directed has a coating of a light-sensitive substance that is adherent to an aluminum base sheetO Depending upon the nature of the photosensitive coating employed, the treated plate may be -utilized to 3~

reproduce directly the image to which it is exposed, in which case it is termed a positive-acting plate, or to produce an image complementary to the one to which it is exposed, in which case it is termed a negative-acting plate. In either case the image area of the developed plate is oleophilic and the non image is hydrophilic.

In the case of a negative plate that is exposed to light through a negative transparency, the light sensitive material, commonly a diazo compound, is caused to harden and thereby become insoluble in a desensitizing solution applied to the plates after light exposure for the pur-pose of removing that part of the light sensitive coating which, because it was protected i-rom the light by the negative, was not light hardened. The light hardened sur-face of a negative plate will be the oleophilic surface compatible with the greasy ink and is called the "image-area". The surface from which the non-hardened light sen-sitive material has been removed by a desensitizer will be, or can be, converted to a hydrophilic surface having lit~le affinity for the greasy ink and is called the "non-image" area. t The present invention provides a developer for negative-working lithographic printing plates.

Most developing compositions for negative-working printing plates disadvantageously contan strong organic solvents. These are bcth expensive and ecologically not favoured. ~n recent years certain aqueous alkaline deve-loping compositions have been developed and employed for ~ ~31~

such purposes. While they are less costly and dangerous to the environment, they do pose several technical prob-lems. Specifically, they tend to corrode aluminum, foam and precipitate when used in developing machinery and additionally have a relatively slow development speed.
The present invention provides a developing composition which substantially alleviates these problems.

A developer which comprises components a) to e) of the present invention is described in Canadian Patent appli-cation No. 432 42~-5, filed July 14th, 1983, having an earlier priority date and being not pre-published (com-pared with the present invention).

_._._.

3~6 SUMMA~Y OF THE INVENTION

The invention provides an aqueous-alkaline developer for an irradiated radiation-sensitive negative-working repro-duction layer, which developer is based on water, an anionic surfactant, at least one inorganic salt having an alkaline reaction and at least one alkanoic diacid or a salt thereof, wherein the developer has a pH of from about 8 to 12 and comprises a) 0.05 to 10 % by weight of a sodium, potassium or lithium sulfate salt of octyl, decyl or dodecyl alcohol;

b) 0.001 to 5 % by weight of a sodium, lithium or potassium metasilicate salt;

c) 0.1 to 15 % by weight of a lithium, potassium or sodium borate salt;

d) 0O01 to 5 % by weight of an alkanoic diacid, or sodium or potassium salt thereof having from 2 to 6 carbon atoms;

e) 0.5 to 12 U/o by weight of di- or tri-sodium or potassium phosphate;

f) 0.02 to 10 % by weight of a substituted or unsubstituted benzoic acid, or the sodium, potassium, lithium or ammonium salt thereof;
and g) 0~5 to 5 % by weight of an ethylene glycol monoether or an ethylene glycol diether, and the weight ratio of sodium ions to potassium ions in the developer ranges from 1:1 to 1.4:1.

It is, therefore, an object of the present invention to provide a negative-working lithographic printing plate developer which is an aqueous alkaline solution.

It is a further object of the present invention to pro-vide a negative-working lithographic printing plate which alleviates the hereinbefore mentioned problems.

These and other objects of the instant invention will be in part discussed and in part apparent upon consideration of the detailed description of the preferred embodiment.

7~

DETAILED ~ESCRIPTION OF TH~ PREFERR~D ~MBODIMENT

In the production of a photographic element, a sheet substrate, preferably aluminum and the alloys thereof especially those aluminum compositions sui-table for the manufacture of lithographic printing plates such as Alcoa 3003 and Alcoa 1100 which may or may not have been pre-treated by standard graining and/or etching and/or ano-dizing techniques as are well known in the art, may be coated by spraying, brushing, dipping or other means with a composition suitable for use as an interlayer for lithographic plates. Standard metal substrate pretreat-ments include electrolytically anodizing in sulfuric and/or phosphoric acids, electrolytically etching in hydrochloric acid, and chemical or mechanical graining by well known methods, which are all known to the skilled worker. Interlayer compositions employable in the prac-tice of this invention include aqueous solutions of alkali silicate and polyvinyl phosphonic acid~

Said substrate is then coated by means well known in the art with a radiation-sensitive (photosensitive) coating which comprises a negative working diazo photosensitizer arld may contain suitable colorants, resins, acid stabili-zers and other art recognized ingredients. AEter drying, the coated substrate is exposed to ultraviolet radiation through a photographic mask in a known manner.

The exposed photographic element is then developed to remove the non-image areas by cleaning with the deve]oper solution provided in this invention.

-- 1 o --The developer employed is an aqueous based solution which has an alkaline pH in the range of from about 8 to about 12, more preferably from about 9 to about 11 and most preferably from about 9.5 to about 10.5 The composition contains a surfactant which is a sodium, potassium or lithium sulfate salt of octyl, decyl or dodecyl alcohol and most preferably octyl. These surfac-tants provide a stable solution at low temperatures. The surfactant concentration ranges from about 0.05 % to about 10 % by weight, preferably 0.5 % to 6 % and most preferably 1.0 % to ~ %. The solution also contains, as a corrosion inhibiting silicate compound, a metasilicate.
Useful silicates include sodium, potassium or lithium metasilicate in an amount of from about 0.001 % to about 5.0 % by weight, preferably 0.005 % to 0.5 % and most preferably 0.01 % to 0.1 %. The composition further con-tains a borate, preferably a tetraborate or pentaborate in the form of its lithium, potassium or sodium salt~ The borate, which aids corrosion resistance and desensitizes aluminum background areas, is present in an amount ranging from about 0.1 % to about 15 % by weight, pre-ferably 0.5 % to 8 % and most preferably 1.0 % to ~ %.
The composition also contains an alkanoic acid having from 2 to 6 carbon atoms or the salts thereof. These include oxalic, malonic, succinic, glutaric and adipic acids or the salts thereof such as the lithium, potassium or sodium salts thereof. A preferred salt is potassium oxalate. This ingredient is present in an amount of from about 0.01 % to about 5 % by weight, preferably from 0.1 %
to ~ % and most preferably from 0.5 % to 3 %. The compo-~2~

sition further contains a phosphate salt. Such includesodium and potassium phosphate, preferably di- and tri-potassium and sodium phosphate salts. Such may be present in an amount of from about 0.5 % to 12 %, preferably 0.75 % to ~ % and most preferably 1.0 % to 4 %. The com-position also contains a benzoic acid or -the above indi-cated salts thereof in an amount of from about 0.02 % to about 10.0 %, more preEerably from 0.2 % to 5.0 %; if the benzoic acid is substituted its substituents include pre-ferably alkyl from C1 to Cs, halogeno, amino, hydroxy or alkoxy from C1 to Cs. The composition further contains an ethylene glycol mono or diether, preferably having as ether substituents alkyl from C1 to Cs or unsubstituted or substituted phenyl, its substituents including espe-cially the substituents mentioned before; particularly

2-phenoxy-ethanol in an amount of from about 0.5 % to 5.0 %, more preferably from 1.0 % to 3.0 %, which increases the speed of development, especially of older plates. The benzoic acid or the salt thereof lowers the amount of 2-phenoxy-ethanol required for good development and helps prevent precipitation of the composition at relatively low tempera~ures. All parts herein are by weight.

In the preferred embodiment, it is most advantageo~ls that a ratio exist between the elemental sodium and potassium within the composition. A most advantageous balance bet-ween developability and storage stability exists when the ratio of sodium to potassium ranges Erom about 1.0~ 1, more preferably 1.1-1 .3:1, and most preferably 1.15-1.25-1. This aids storage at temperatures below 7~

lO C by substantially reducing or preventing solution precipitation.

The following examples illustrate the invention.

Example l A developer is prepared having the following ingredients.
All parts are anhydrous.

% (WIW) H2O (deionized) ~7.23 sodium octyl sulfate 2.50 sodium metasilicate0.07 disodium phosphate1.50 trisodium phosphate1.50 potassium oxalate 1.70 potassium tetraborate 1.00 sodium benzoate 2.50 2-phenoxy-ethanol 2.00 The developer is found to have a solid content of 12.77 %
and a pH of 9.8. When corrosion tests are conducted for 300 hours using aluminum a 0.002 % gain in weight is noted. At -3 C no precipitation or crystal formation is observed. The solution is then frozen and allowed to re-turn to room temperature. At room temperature, a clear solution is observed in which there is no insoluble material.

- - -An electrochemically grained and anodized plate is coated with a light sensitive diazo compound disclosed in US
Patent 3,849,392 and is exposed ~2~0 mJ/cm2) using a negative test mask. The plate is developed using the com-position of this example by immersion and light agitation for 60 seconds. A 21-step Stouffer Step Wedge, which is part of the test mask is inked and found to give a solid 5 and two ghost steps. Such a result is preferred and would be expected from a proper developer.

Another plate is likewise developed and after rinsing has a finishing film applied using the subject developer. A
printing press roll-up test is conducted after 1 week of storage and was compared to a plate developed with the same developer but finished with a standard solution COIl-sisting essentially of tapioca dextrin as the Eilm former. Both plates had similar roll-up characteristics with no hint of blinding or toning on the test plate.

Comparison Example Cl A commercially available developer having a total solids content of 23 %, of which 12 % is sodium benzoate, is tested in a similar manner as detailed in Example 1.
After 300 hours, a weight loss of 5.1 % is measured. At 10 C the solution begins to form a precipitate that only returns into solution at room temperature with agitation.

A plate is processed and only after extensive development time appears to be desensitized. A solid 7 and seven ghost steps are realized after inking.

~ ~ L~

Comparision Example C2 Another commercially available developer having a solid con~ent of 16 % (> 11 % organics) is tested in similar manner as described in Example 1. The results of the corrosion test after 300 hours indicated that 17.2 % of the aluminum is dissolved. The plate developed with this developer is seen to be insufficiently desensitized in the background. A solid 9 and eight ghost steps are measured.

Examples 2 and 3 and Comparison Examples C3 to C9 The following examples demonstrate the results stemming from variations made in the inventive product.

3~3~7~;
o o r~ o o o ~ a o o~
. ~
,_ _ ____ _ _ _ _ _ _ _ o o r~ o o a ~o~ U~ ~ o ~ I ~ o . o ~ ~ ~
o~
. .. . . ... . _. _ .. _ ... _. _. _. _.. _ _ .... _ _ _ __ _ . ... _ . __ _ _........... .
it O O 1-- 0 0 ." ." o ~ '~ ' . o ~ ,_ . ..... .... .. _ . ._ ___ _ . ._._ _ _ . . .. _ ... _ ___ _ __ _ ___._ o o ~ o a o c~ ~ O a a~ . . o CO
. .. _ _ . ., . ....... _ _. .... _ _.. .... ... _ _.. _.. _. _ . ._,,._ _ _, __ I
I~ o ~ ~ o ~ r~
~ o =) . ~ .r~ ~ ~ o u~
C~ . . . . . . . . .
~ o ,~
o~
__. __ . __ _.~
o o ~
oo a~ o o 1~ r~ o o ~D
C~ .,,. .-- o .
o~
_ _.. _. _.. . . ..... ..... . . .. _ ... _ _. _ ., . ,,.. ,_,,. _ __ __ ~n o O ~, O '` U~ ~
I~ U~ -- . .. ..
~ ~ CS~ ~ ~ ~ C`l ~ ~
~ ~
~ .___ ...... ________.... __ _ __~_ .
. ~ o o 1~ =~ o o ,~
. . . . o C~ o~ o .
o~
__ ___ __ ..... _ _ _ ._ __ .____ . .. _ ___ __ _ o o l-- o ~
o o r~ o o C~ ~ ~ ~ o o~
__ ..... __ .. _. _ ...... _.
r~
a~
~:
a~ .
JJ
J~ ~ N
t~
~ X
O ~
~ O
E3 ~ n o ~
1~1 C O r~
J- U~ o ~ ) o n ~ ~ 00 ~ Z X
.,~ ~ t ~ o '~ o o o o ~t ~ o o ~ o ~ ~ ~t ~to o ~:
~- ~ ~ ~ -' ~ O ~ o ~ o :c ~t c~
~ ~ ' ~ ~ o c~l ~t o D~ ~ C~l ~ ~ ~ C`J ~ a:~ X ~ c~
~ ~ ~ o ~ ~ æ æ ~ ~ æ z ~ ~ z z ~; æ ~ ~ ~

~3~76 Comparison Example C3 This Example repeats Example 1 except that the potassium oxalate is omitted. The pH is 10.44 and there is no pre-cipitation at low temperatures. A plate is exposed (240 mJ/cm2) and developed. Upon inking, the background appeared to be desensitized but the Step Wedge giv~ a solid 7 and four ghost steps. Such a result is unaccep-table and demonstrates the utility of the oxalate.

Comparison Example C4 This Example repeats Example 1 except the potassium tetraborate is omitted. The pH is 11.25. An exposed plate is developed and upon inkin~ gives a solid 5 and three ghost steps. An aging test for corrosion shows after 300 hours that 3.47 ~O is lost due to the inability of the silicate alone to prevent corrosion. It can be seen that the tetraborate aids in desensitization and corrosion inhibition.

Comparison Example C5 This Example repeats Rxample 1 except that the sodium silicate is omitted. The pH is 10.37. An exposed plate is developed and upon inking gives results identical to those obtained when the silicate is present. After 300 hours, the corrosion study indicates that a 3.7 % growth had occurred due to the continued deposition of salts~
This example clearly demonstrates that the silicate and 8~6 tetraborate should be present together so as to result in an essentially zero net change in weight gain or loss, C parison Example C6 This Example uses the mole ratio equivalent amount of di and tripotassium phosphate as is used for the sodium salts in Example 1. The results are all the same except that at ~ C, the developer is crystallized into a solid mass. Here the sodium to potassium ratio is ~,16 to 1.~.

Example 2 This Example uses the acids and hydroxides in lieu of the salts to demonstrate an alternative embodiment. The de-veloper, when tested, is substantially identical with the developer of Example 1.

Comparison Example C7 A developer similar to that of Example 1 is made except that 2-phenoxy ethanol is omitted. The developer is ob-served to be slow in removing the non-image areas of the plate after exposure with an indication of only partial development. When the developer is stored at low tempe-ratures , severe non-reversible precipitation occurs.

Example 3 This Example uses the stoichiometric equivalent amount of potassium succinate ~or comparison. The results are :~2L~31~76 - - -essentially identical in all respects as those obtained from the developer containing potassium oxalate.

Comparison Example C8 A developer similar to that of Example 1 is made except that sodium benzoate is omitted. The developer is observed to have good development speed but inadequate background desensitizing capability. Additionally, the solution at room temperature is not stable since the 2-phenoxy ethanol phases out of solution.

Comparison Example C9 This Example repeats Example 1 except that the sodium benzoate, sodium salt and 2-phenoxy ethanol are oMitted.
Plates can only be slowly developed, and older plates cannot be satisfactorily developed.

_ . _ . _, _ .

Claims

What is claimed is:

1. An aqueous-alkaline developer for an irradiated radiation-sensitive negative-working reproduction layer, which developer is based on water, an anionic surfactant, at least one inorganic salt having an alkaline reaction and at least one alkanoic diacid or a salt thereof, wherein the developer has a pH of from about 8 to 12 and comprises a) 0.05 to 10 % by weight of a sodium, potassium or lithium sulfate salt of octyl, decyl or dodecyl alcohol;

b) 0.001 to 5 % by weight of a sodium, lithium or potassium metasilicate salt;

c) 0.1 to 15 % by weight of a lithium, potassium or sodium borate salt;

d) 0.01 to 5 % by weight of an alkanoic diacid, or sodium or potassium salt thereof having from 2 to 6 carbon atoms;

e) 0.5 to 12 % by weight of di- or tri-sodium or potassium phosphate;

f) 0.02 to 10 % by weight of a substituted or unsubstituted benzoic acid, or the sodium, potassium, lithium or ammonium salt thereof;
and g) 0.5 to 5 % by weight of an ethylene glycol monoether or an ethylene glycol diether, and the weight ratio of sodium ions to potassium ions in the developer ranges from 1:1 to 1.4:1.

2. The developer of claim 1 wherein said ingredient (a) is sodium octyl sulfate and/or sodium decyl sulfate.

3. The developer of claim 1 wherein said ingredient (b) is sodium metasilicate.

4. The developer of claim 1 wherein said ingredient (c) is potassium tetraborate.

5. The developer of claim 1 wherein said ingredient (d) is potassium oxalate.

6. The developer of claim 1 wherein said ingredient (e) is disodium phosphate and/or trisodium phosphate.

7. The developer of claim 1 wherein said ingredient (c) is a tetraborate or pentaborate.

8. The developer of claim 1 comprising sodium octyl sulfate, sodium meta-silicate, disodium phosphate, triso-dium phosphate, potassium oxalate, potassium tetraborate, sodium benzoate and 2-phenoxy-ethanol.

9. The developer of claim 1 wherein said ingredient (f) is sodium benzoate and said ingredient (g) is 2-phenoxy ethanol.

10. The developer of claim 1 wherein said ingredient (f) is sodium benzoate.

11. The developer of claim 1 wherein said ingredient (g) is 2-phenoxy ethanol.

12. A method of developing a negative-working reproduc-tion layer, comprising treating the irradiated reproduc-tion layer with an aqueous-alkaline developer which is based on water, an anionic surfactant, at least one in-organic salt having an alkaline reaction and at least one alkanoic diacid or a salt thereof, wherein the developer has a pH of from 8 to 12 and comprises a) 0.05 to 10 % by weight of a sodium, potassium or lithium sulfate salt of octyl, decyl or dodecyl alcohol;

b) 0.001 to 5 % by weight of a sodium, lithium or potassium metasilicate salt;

c) 0.1 to 15 % by weight of a lithium, potassium or sodium borate salt;

d) 0.01 to 5 % by weight of an alkanoic diacid, or sodium or potassium salt thereof having from 2 to 6 carbon atoms;

e) 0.5 to 12 % by weight of di- or tri-sodium or potassium phosphate;

f) 0.02 to 10 % by weight of a substituted or unsubstituted benzoic acid, or the sodium, potassium, lithium or ammonium salt thereof;
and g) 0.5 to 5 % by weight of an ethylene glycol monoether or an ethylene glycol diether, and the weight ratio of sodium ions to potassium ions in the developer ranges from 1:1 to 1.4:1.