Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Finishing or perfecting composition or product
Reexamination Certificate
1999-10-05
2002-04-02
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Finishing or perfecting composition or product
C430S466000, C510S176000
Reexamination Certificate
active
06365330
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developer concentrate which comprises water, at least one agent which is alkaline in water, and an amphoteric surfactant, and the developer itself which is obtainable by dilution with water and is suitable for imagewise exposed recording materials, such as printing plates, photoresists, copying materials, etc., as well as to a corresponding replenisher, and methods for making developer concentrates and replenishers.
2. Description of the Related Art
The developers known to date have a number of disadvantages. Thus, they often contained significant amounts of organic solvents which are undesired because they constitute a fire hazard and owing to their low boiling point, their unpleasant odor, the pollution of wastewater and waste air and the expensive apparatuses for the safe disposal of the spent developer. They should therefore no longer be present in modem developers.
A large amount of organic solvents is contained by, for example, the aqueous developer concentrates according to EP-A 432 450, U.S. Pat. No. 5,155,011, EP-A 432 451 and U.S. Pat. No. 5,155,012, which can be diluted with tap water to give ready-to-use developers. The concentrates furthermore contain an alkaline agent, an anionic surfactant, salts of an n-alkanoic acid, emulsifiers, alkali metal salts of an oligomeric phosphate and/or N-(2-hydroxyethyl)ethylenediaminetriacetic acid and a buffer. According to EP-A 432 450, the buffer is specified as tris(hydroxyalkyl)aminomethane.
Alkali metal salts of N-(2-hydroxyethyl)ethylenediaminetriacetic acid are known to be poorly biodegradable. German industry has therefore undertaken to reduce the polution of the environment with these substances.
To simplify the cleaning of the developing machines, the developers frequently contain surfactants. However, these often foam to such a great extent that antifoams have to be added. In addition, the foam may result in already detached components of the layer being deposited again on the recording material or in these components being carried into downstream stations (washbath, gumming station) of the developing machine. Already developed recording materials may become useless in this way. It is mainly during development in machines that components of the layer which are contained in the developer in the form of cakes, filaments or pigment residues are deposited on the printing plates.
In continuously operating developing machines, the composition of the developer is kept constant by the continuous addition of fresh developer or of a special replenisher. The required feed intervals can be controlled, for example, by determining the conductivity of the developer. The action of components of the ambient air (oxygen, carbon dioxide) influences the conductivity of the developer to a relatively small extent but has a major effect on the activity of the developer. The conductivity control is consequently not capable of sufficiently compensating a developer whose activity has been reduced by oxidation or carbonate formation after prolonged standing. The result of the development consequently deteriorates.
A process for the production of a lithographic printing plate, in which an imagewise exposed recording material whose back is covered with a layer of an organic polymer is developed with an alkali metal silicate developer, as disclosed in EP-B 490 515. The developer is replenished with an aqueous alkali metal silicate solution in which the molar [SiO
2
]: [M
2
O] ratio is in the range from 0.3 to 1.0 and the SiO
2
content is in the range from 0.5 to 4% by weight. The developer and/or the replenisher can moreover contain organic solvents, surfactants and/or antifoams. The surfactants may be anionic, cationic, amphoteric or nonionic.
A developer free of organic solvents intended for positive- and negative-working recording materials is disclosed in JP-A 62-187 855. It contains from 1 to 10% by weight of alkali metal silicate and from 0.1 to 5% by weight of an amphoteric or anionic surfactant.
EP-A 732 628 discloses a developer and a corresponding concentrate which contains nonionic, anionic or amphoteric wetting agents in addition to alkali metal silicates. The developer has a higher developing capacity, results in less foam and has less tendency to cause deposition of layer components on the plates or in the automatic developing units.
In the process for the production of the lithographic printing plate according to JP-A 8-248 643, a recording material having an imagewise exposed, photopolymerized layer is developed with an alkali metal silicate developer. For replenishment, an alkali metal silicate solution is likewise added to the developer. Developer and/or replenisher contain an amphoteric surfactant of the betaine, glycine, alanine or sulfobetaine type. The developer is intended in particular for automatic developing units. The fact that no solid or gel-like precipitates form in this developer during use is stated as a particular advantage.
The developer for positive-working, negative-working or image reversal plates according to EP-A 274 044 contains from 5 to 30% by weight of an alkaline agent, in particular sodium metasilicate, and from 0.01 to 10% by weight of an ethylene oxide/propylene oxide block copolymer. The block copolymer may also be prepared from ethylene oxide, propylene oxide and ethylenediamine. The developer can moreover contain antifoams or softeners.
To prevent precipitates from the developer being deposited on the plates—which, during subsequent printing, result in an undesired ink transfer (known as “scumming”) in nonimage areas—the developer according to EP-A 720 060 contains softeners of the alanine type having at least 3 COOA units, in which A=H, Na, K, NH
4
or NR
4
(R=alkyl).
SUMMARY OF THE INVENTION
However, it remains one object to provide a developer which is suitable for imagewise exposed, positive-working, negative-working or image reversal reproduction layers, has a high developing capacity (as far as possible higher than that of known developers), and at the same time does not tend to form undesired deposits on the already developed plates, or in the developing units. The developer should furthermore, preferably be capable of being brought onto the market in the form of a developer concentrate or replenisher concentrate in order to reduce transport and storage capacities. The ready-to-use developer or the ready-to-use replenisher can then be prepared from the concentrate by dilution with (tap) water. On the other hand, many known developers must from the outset be provided in dilute form since the corresponding concentrates separate over a shorter or longer time and/or form precipitates, particularly at low storage temperatures.
These and other objects can be achieved by a developer concentrate which comprises water, at least one agent which is alkaline in water, an amphoteric surfactant, at least one anionic surfactant, at least one complexing agent, at least one amino alcohol, and at least one N-alkoxylated mono- or polyfunctional amine.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The agent which is alkaline in water is preferably an alkali metal, an alkaline earth metal or ammonium hydroxide, in particular LiOH, KOH or NaOH, or an alkali metal, alkaline earth metal or ammonium salt of an inorganic or organic acid, in particular sodium hydrogen phosphate or potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate, sodium metasilicate or potassium metasilicate, sodium borate, an alkali metal salt of an aliphatic, aromatic or araliphatic carboxylic a
Boxhorn Mario
Elsaesser Andreas
Leichsenring Thomas
Lifka Thorsten
Zertani Rudolf
Agfa-Gevaert AG
Le Hoa Van
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