DE1192667B - Composition and process for making visible, strengthening and protective coating of the exposed image areas of a lithographic printing plate - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

B41n

German class: 151-7 / 05

Number: 1192 667

File number: M 30971VT b / 151

Filing date: June 30, 1956

Open date: May 13, 1965

In general, in the photomechanical production of planographic printing forms, a water-soluble, light-sensitive coating on a grained metal plate by means of a suitable master copy to the light exposed, whereby the exposed part becomes insoluble. The unexposed part of the coating will be later washed away leaving a hydrophobic image on a hydrophilic plate. With dichromate sensitized albumin provides z. B. a typical water-soluble photosensitive coating. After exposure, the plate is usually lightly coated with developing liquid that remains on the entire cover adheres. The plate is then wiped dry. Washing the plate with water removed then the soluble parts of the coating together with the developer liquid adhering to it, whereby the colored and therefore easily visible, insolubilized, exposed part of the image remains and for that Printing by the planographic printing process can be used.

Another method is to use a newly developed type of planographic printing plate, as will be described in more detail below, the plate immediately after exposure washed to remove the soluble parts of the coating, the practically not visible, insolubilized image portion remains in a state suitable for printing. When applying from Druckfabre, z. B. in a lithographic press, the image is then visible. However it will as preferred in the earlier method described at the beginning, the image initially until it becomes visible develop so that the printer can assess the value of the plate and properly insert the plate into the press can be. The present invention provides an improved developer for such uses.

Although the novel developer of the present invention is extensively effective for dichromate protein printing plates, it is particularly suitable for planographic printing plates previously treated with alkali silicate, as described in particular in German patent specification 907147. Such plates use extremely thin, photosensitive diazo resin coatings. The low thickness of these coatings makes it necessary that the unexposed parts are removed before the application of printing ink. The application of prior type of ink to the exposed plate prior to placing it in the press is unsatisfactory. If extreme care is not taken in applying the ink to the image, ink will often adhere to the non-image parts of the plate, especially in the halftone masses and methods of visualization,
Reinforcing and protective covering of the
exposed image areas of a lithographic
printing plate

Applicant:

Minnesota Mining and Manufacturing Company, St. Paul, Minn. (V. St. A.)

Representative:

Dr.-Ing. H. Ruschke, patent attorney,

Berlin 33, Auguste-Viktoria-Str. 65

Named as inventor:

Myron W. Hall, St. Paul, Minn. (V. St. A.)

surfaces. The printing ink does not protect against wear and tear when the press is in use. Other developers of the earlier type, protective asphalt solutions, etc., also tend to do so shown to adhere not only to the image areas but also to the other surfaces of the plate. These known developers are also attacked by the printing ink oils used in the press have been or have the original image against mechanical abrasion or mechanical Wear not adequately protected.

A basically poor way of working is from the Engelmann reference, »The offset printing in practice ", p. 84, second paragraph, with a large number of successive operations, among which, among other things, the definition of the original print image on the plate with a Primer paint is suggested.

In contrast, the novel image developer compositions according to the invention enable exposed ones Printing plates according to a much simplified process, bypassing a number of previously to produce the required operations. With this new, simplified and time-saving process the new type of image developer is applied directly to the hydrophilic surface and the hydrophobic image areas applied to the exposed and developed plate without previously gumming the plate with Color in the printing ink and the printing ink again

509 569/226

to have to remove. The image is developed and the subsurface is protected at the same time. The plate is then only wiped clean before it is inked and used for printing. In contrast for this, in the above-mentioned known method, which works with ordinary paint, the The picture is first colored, the plate is gummed, the excess printing ink is removed, then coated with varnish and finally paint and rubber on the surfaces are removed. According to the invention novel masses thus make it possible to produce a series of difficult and time-consuming processes To omit work steps, which is not possible with the use of conventional paint.

According to the method according to the invention, the application of the new image developer compositions Image made visible at the same time in one operation, the thickness of the image surfaces many times over reinforced and provided with a protective coating that extends the life of the developed printing plate improved blackening and printing properties significantly increased.

In particular, the invention proposes a method of visualization, reinforcement and protection Coating the exposed image areas of a lithographic printing plate, which is known per se Way through an exposure process with a thin, essentially invisible, hydrophobic Diazo resin image was obtained; this method is characterized in that one with Water-covered plate in the presence of an aqueous rubber solution a colored, two-phase, liquid fixing emulsion easily removes, which (1) an aqueous phase consisting of water and a soluble Thickener and optionally a wetting agent, and (2) a non-aqueous, no threads pulling, liquid resin phase, which consists of a water-insoluble, color-insoluble resin and a volatile, water-immiscible solvent, contains until the entire image with an adherent Layer of this resin is covered, and that the plate is then washed. The invention also proposes a Composition which is suitable for the above process and which consists of a colored two-phase emulsion consists, which contains an aqueous and a non-aqueous phase, wherein the non-aqueous phase consists of a color-insoluble and water-insoluble resinous solution.

In the examples below, parts are parts by weight, unless otherwise noted.

example 1

Aqueous phase parts

Water 90

25 ⁰ / oig ^e gum arabic in water 18 wetting agent (sodium lauryl sulfate; may optionally be omitted) 1.8

Non-aqueous phase

Ethylene dichloride 60

Cyclohexanone 40

Soft epoxy resin 30

Pigment (toluidine clay) 9

The epoxy resin used was an epichlorohydrin-bisphenol resin having a melting point of 4O ⁰ C, an epoxy equivalent 300 to 375, a hydroxyl equivalent of 105; it was very viscous at normal room temperatures, but still flowable.

The "toluidine toners" used in this and the following examples are Precipitates of organic dyes in the form of dyestuff salts, without any is based on the colorless substrate to be colored. The toluidine clay is one of the strong red permanent tones. The manufacturing process corresponds to that of the red p-nitroaniline dyes, with m-nitrootoluidine is used as a nitro compound.

The pigment, the resin and about 8 parts of the cyclohexanone were combined in a paint mill, whereupon the resulting mixture in a container in the mixed remaining solvents was dispersed. Combining the aqueous and non-aqueous phases in a mixer then provided one Water-in-oil emulsion of high viscosity, which did not separate even when standing for a long time. On a exposed and treated lithographic plate, this developer provided a clearly visible image, without running at the semitones.

Example 2

Aqueous phase
The same composition as in example 1.

Non-aqueous phase

The same composition as in Example 1, except that a normally hard, brittle, violin-like epoxy resin was used in place of the soft resin of Example 1. This hard resin had a melting point of 100 ⁰ C, an epoxy equivalent from 905 to 985 and a hydroxyl equivalent of 175th

Mixing the two solutions resulted in a stable water-in-oil emulsion. Used as a developer the emulsion provided clear images without bleeding of the halftones. The developed image was in the Press extremely abrasion-resistant and in this regard even better than that, especially at elevated temperatures prepared with the emulsion of Example 1.

Example 3

Aqueous phase
The same composition as in Example 1.

Non-aqueous phase parts

Ethylene dichloride 50

Cyclohexanone 50

Epoxy resin of Example 2 30

Toluidine clay 9

A non-separating water-in-oil emulsion was obtained when the resin, pigment and 10 parts Cyclohexanone were ground together and the mixture then in the remaining solvents dissolved and finally the liquid homogeneous mixture with the aqueous phase in a high-speed mixer was mixed.

Example 4

Aqueous phase
The same composition as in example 1.

Non-aqueous phase

The same composition as in Example 3, except that carbon black is used instead of toluidine clay became.

Mixing the two phases produced an oil-in-water emulsion in this example, the low one

5 6

Tended to separate into two layers. the plate still with the gum arabic solution Separation could, however, be bypassed and the emulsion is moist, a certain amount of the Entdurch will be just shaking in a bottle back-curler, e.g. B. the one described in Example 1, on the be formed; or the speed of the separation plate brought and across the image surface with a 5 soft rags or cotton balls could be smeared by increasing the amount of gum arabic,

are reduced in composition. until the image is evenly coated. The re-

". -ic getting this treatment loosens and removes all parts

Example of _the developer resin, which temporarily affects the non-image

Aqueous phase parts surfaces of the plate, for. B. on the surfaces between the

Water 112 ¹⁰ halftone digits, adhered. Once the picture

25 ° / ₀ gum arabic solution is coated in completely, and before a further waste

Water 23 resin can occur, the over-

Sodium lauryl sulfate 2.3 liquid developer by washing with water

Non-aqueous phase rinsed off ^{the plate.} The record is then ready

R + u ι α · μ -A cc \ ^{15 for} printing. You can also use the developed plate

Atnyiendicftlond ■ ······ 60 J _n well known way with a protective layer of rubber

Coat epoxy resin from Example 2 30 arabic solution, wipe dry and up

1 olmdmtoner y _ZUJ . Cancel use. The one by the developer

The emulsion obtained was an oil-in-water imparted color allowing the location and grade Emulsion. With this 20 exposed printing plates became the perfection of the hydrophobic image parts

Emulsion developed satisfactory, especially when determining.

Temperatures slightly below normal room- When the printing process is after the plate

temperatures. has been placed in a lithographic press,

Example 6 ^the gum arabic coating - if present -

25 first by wiping with a sponge and

Aqueous phase water or with the help of a weak shower removed. The same composition as in Example 1. First, the dampening rollers should run and after a few revolutions of the press after the non-aqueous phase then the inking should be done. _t . , ".._, .. ,, rolling. The image is to _be quickly _provided with the ink The same composition as Example 5 nn. _{There are no} special printing inks, only that trichloroethane _or special moist solutions are required instead of ethylene chloride; it has been used. ^ found that most of the materials ordinarily used for this purpose were as in Example 1 a water-in-oil-used material. Get a typical emulsion. When this emulsion for lithographic printing ink contains suitable pigments, wound lithographic halftone plates which were applied in a quick-drying liquid vehicle, slight bleeding of the halftone spots dispersed in the drying oil base was observed. Curve drawings and the like are. Developed satisfactorily for the largest possible number of. After developing satisfactory prints, the press of the plates should preferably be 1 hour or carefully set to the minimum pressure, left to stand longer or briefly heated to all 40 of the time necessary to achieve good printing. by retention of solvent in the The picture can periodically eliminate the stickiness caused by scuffs on the resin coating. the press by repeatedly applying the agent

. . to be protected.

Example 7 pj _e epoxy resins described in the examples

Aqueous phase 45 are insoluble in water. You are in

The same as in Example 1. Suitable volatile organic solvents soluble,

■ \ v ~ u + ", ~ η · ο t> u from which they are formed in the form of solid tough films

JNonwassnge phase parts j 1 ·· ο · ι. ^ 1 *. t λ t> -ij

.. can be delighted. They adhere firmly to the picture

Ethylene dichloride, 60 parts, of the plate and provide a surface that

Epoxy resin as in Example 1 30 _{50 is} receptive to printing inks without being in the

Tolmdmtoner 6 printing ink to be soluble or harmful by it

An oil-in-water emulsion was obtained to be affected. The epoxy resin surface has

which as a lithographic plate developer also has excellent abrasion resistance, which is particularly important for

was as effective as the emulsion of Example 5. lithographic, with extremely thin image layers

When these developers are applied to plates coated with diazo, such as those coated with diazo resin

sensitized printing plates, as is important in the above-referenced plates of the above-mentioned patent.

mentioned patent, the following was The epoxy resins are prepared by reacting

Procedure found to be effective. agreed polyhydric phenols, one of which is that

The previously sensitized plate first becomes bisphenol (ρ, ρ'-dioxydiphenyldimethylmethane) exposed through a master copy, a typical example being 60, with polyfunctional, alcohol exposure from 2 to 4 minutes in duration with a group-bearing reactant such as epichloro 25 ampere carbon arc lamp at a distance of hydrin, the extent of conversion 60 cm being found suitable. After exposure and thus the molecular weight of the product through is made by washing with water that has a low the ratio of the main ingredients and / or by Amount of gum arabic containing the unexposed 65 introducing measured small amounts of soluble part of the diazo sensitizer is dissolved and unsuitable monofunctional »chain termination is removed. At this point, the one left behind is "punch", e.g. B. phenol or ethylene chlorohydrin exposed Part of the image is practically invisible. While is true. The resin obtained can be polymeric

7 8

polyhydric alcohol, and as an addition of another volatile solvent, such as

such he is capable of further sales, e.g. B. with cyclohexanone, an even further improvement in

drying oil fatty acids, resin acids, acid anhy- Image development properties of the means of the pre-

drides, aldehydes, etc .; causes such reaction products lying invention. Cyclohexanone is in

are in many cases soluble as constituents of Bildent 5 water and cause, if it is the only one.

Curlers according to this invention can be used. This solvent is used for the resin that

various epoxy resins including the deposition of a thin foam all over

The derivatives just described are used as constituents of the plate surface. However, if cyclohexanone or

of the novel developing substances preferred, whether- another equivalent volatile and with water

probably other equivalent resins or resinous solvents which are miscible with ethylene dichloride, such as

Substances are not excluded here from being given in Examples 1 to 4 above

are striving. Surprisingly, even a lower tendency to

Another example is a developer foam formation, as it occurs when ethylenedi-

mass which gives excellent results when chloride is used alone.

it is properly applied and treated; In addition, the concentration of the resin in the solution view of the speed of application is medium or the solvent mixture can be changed greatly, but less advantageously than the previous ones. In case of excessive dilution, medium. longer treatment is of course required to remove _R. -ίο to develop a reasonably visible and abrasion-resistant coating ^{e 1 s} P ' ^e 20, which is why it is preferred at least

Aqueous phase about 30 parts of resin per 100 to 150 parts of solvent

Use the same composition as in example 1. Too high concentrations can

Non-aqueous phases, however, cause the emulsion to "curdle";

Solution of melamine-formaldehyde parts such viscous solutions also have a stronger tendency to

Butanol resin 45 ²⁵ to form "stripes" and thus a "running" of the halftone

Xvlol 45 pose and smear the non-image surface

Toluidine tone 9 ^to cause. The reduction of the ethylene

chloride content in Example 1 to much less than about

The resin solution consisted of 65 parts of the resin divided into 20 parts e.g. B. causes the emulsion to clot

35 parts of xylene dissolved. 30 and bleeding of the shark tones. It is therefore preferred

Mixing the two solutions in an amount of at least equal to the amount of resin High speed mixers provided a water-in-oil emulsion, using water immiscible solvents. which on an exposed and washed lithographic It was found that the presence of both Plate was applied as a developer. The resin of an aqueous as well as a non-aqueous or adhered well to the image, but remained in the developer for a longer period of time in the oily phase, as it did on the effective Print too soft until it is lighted and washed overnight at the above room temperature or is applied for 10 minutes at 127 ° C, for good has been hardened. After curing, the plate had a very desirable image development. The excellent one Lifespan. application of the resin solution in the absence of the aqueous

The properties of the resins used in each case 4 ° phase z. B. causes deposition of resin are for the successful work of lithographic on practically the entire picture surface. Such Very important to the plate developers of this invention. Resin solution can be effective on a dichromate, however is the applicability and usability of the egg white plate to be applied where the not this novel developer does not depend solely on the exposed parts of the sensitized coating depends on the resin used. 45 homely only after application of the developer The solvent or solvent mixture that will be removed; In this process of applying pigment or other dyes that are water-soluble, the concentration of the resin can be greatly increased Ingredients, the proportions of these different are changed. However, it has been found that Substances and other factors are the ones previously used for success - also for such uses Carrying out this invention, as further 50 formed emulsion has a number of advantages, is explained in more detail below, just as important. Surprisingly, it was observed that both

Ethylene dichloride is an effective, volatile solvent for epoxy resins, which is immiscible with water, water-in-oil and oil-in-water emulsion, in the development of lithographic plate resins. Solutions of resins in this solvent and in particular of panels which, according to the above, are easy to emulsify with an aqueous phase. The resin solution is a good solvent for to be. In any case, the resin solution is applied to the image basic resin, as it is e.g. B. accidentally selectively absorbed on non-image areas and prevented from absorbing image parts of the plate during development from the non-image areas; or, if parts may have divorced. The ethylene dichloride of the resin happens to be on such non-image areas and evaporates quickly, so that the developed plate immediately, e.g. B. is ready for printing by excessive drying of the material bar. As shown in Examples 5 and 7 in localized areas that have been deposited, ethylene dichloride can be used as the sole resin, it is quickly redissolved and used by other solvents. Trichloroethane is an effective, water-immiscible, wiping away when developing, parts of the solution during rubbing off or falling off,
volatile solvent for epoxy resins; however, it has 65 It has also been observed that the oil-in-water is somewhat less volatile than ethylene dichloride. Emulsions are easier to apply to the plate

Although ethylene dichloride or the like can be used alone, since - as stated above - the latter benefit Provides results, it has been shown that the next coated with an aqueous rubber solution

! 192

ίο

will; and the oil-in-water emulsion is immediately and uniformly miscible with it. The presence a wetting agent is both for the consistency of the oil-in-water emulsion and for its preservation an improved wetting effect on the plate is usually desirable, but not necessary. In some In some cases, the oil-in-water emulsions separated into two layers on standing, a phenomenon that was not observed in the water-in-oil emulsions used here. However, this separation can delayed by increasing the proportion of water-soluble gum or by other means will; In any case, this is not a serious disadvantage, since the two phases are easily shortened Stirring or shaking can be reunited and emulsified.

Examples were given of two specific pigments; but many others can also be used. Appropriate dyes can also be used, although the developed image will usually be has a lower depth of color than can be achieved with pigments. The pigment or dye need not necessarily associated with the resin ingredients in the developer, although one Compound is usually preferred. When the pigment of Example 1 is from the non-aqueous phase was omitted and instead introduced into the aqueous phase, became an oil-in-water emulsion obtain. When applied as a lithographic plate developer, the pigment was oozed through the resin coating recorded on the image areas to produce a colored image.

Gum arabic is often used in lithographic printing and is therefore also suggested here. But there are also other water-soluble gums known which are completely or practically the gum arabic are equivalent for such purposes; and the replacement by such substances can be considered complete are to be regarded as falling within the scope of this invention. Is sodium carboxymethyl cellulose one such water-soluble thickener. This can be done in the same way in the previous examples used sodium lauryl sulfate can be replaced by soap or various other wetting agents; however, completely satisfactory masses have also been produced without the use of wetting agents, or in which additional water soluble rubber replaced part or all of the wetting agent. In this In connection with this, it has been observed that amine type wetting agents, e.g. B. triethanolamine oleate, the slope have the ability to cause the deposition of adherent foam or residue over the entire panel; these substances are therefore not to be used.

Claims (5)

Patent claims: 1. Process for visualizing, strengthening and protective coating of the exposed image surfaces a lithographic printing plate, which in a known manner by an exposure process obtained with a thin, essentially invisible, hydrophobic diazo resin image was, characterized in that one over the plate covered with water in In the presence of an aqueous gum solution, a colored, two-phase, liquid Emulsion easily strokes that (1) an aqueous phase made up of water and a soluble thickener and optionally a wetting agent, and (2) a non-aqueous, non-stringing, liquid resin pTiase consisting of a water-insoluble, color-insoluble resin and a volatile, water-immiscible solvent until the entire image is covered with an adherent layer of this resin is and that you then wash the plate. 2. mass, which is suitable for the method according to claim 1, for visualization, reinforcement, protective coating of the exposed image areas of a lithographic printing plate, in particular of panels pretreated with a layer of alkali silicate, characterized in that that this mass consists of a colored, two-phase emulsion, an aqueous and a non-aqueous emulsion Contains phase, the non-aqueous phase from a color-insoluble and water-insoluble resinous solution. 3. Composition according to claim 2, characterized in that the resin solution is an unmodified one hydroxyl-containing, resinous glycidyl polyether of a dihydric phenol in one with water Contains immiscible volatile solvents. 4. Composition according to claim 2 or 3, characterized in that the emulsion is a water-in-oil or an oil-in-water emulsion. 5. Composition according to claim 2 to 4, characterized in that the aqueous phase is a wetting agent contains. 509 569/226 5.65 © Bundesdruckerei Berlin