US3203798A

US3203798A - Diazotype transfer developing method

Info

Publication number: US3203798A
Application number: US240575A
Authority: US
Inventors: Muller Peter
Original assignee: Andrews Paper and Chemical Co Inc
Current assignee: Andrews Paper and Chemical Co Inc
Priority date: 1962-11-28
Filing date: 1962-11-28
Publication date: 1965-08-31
Anticipated expiration: 1982-08-31
Also published as: GB1103187A

Description

Aug. 31, 1965 P. MULLER 3,203,798

DIAZOTYPE TRANSFER DEVELOPING METHOD Filed NOV. 28, 1962 ,wsrf/iL Ef United States Patent O 3,203,798 DIAZTYPE TRANSFER DEVELOPING METHOD Peter Muller, Port Washington, NSY., assigner to Andrews Paper & 'Chemical Co., Inc., Great Neck, NX., a corporation of New York Filed Nov. 28, 1962, Ser. No. 240,575 2 Claims. (Cl. 96-49) This invention relates to an improved diazotype transfer developing method and to an improved developer sheet for use in such method.

The diazotype reproduction process is based on the sensitivity of the diazo compounds to the short Wave length portion of the visible spectrum and to ultraviolet light and also on the capacity of diazo compounds to react with certain compounds generally called couplers to form azo dyes under controlled pH conditions.

Diazotype light sensitive material are available in two general forms:

(l) The two component or dry system in which the backing sheet has a diazo sensitized coating or coatings is exposed to actinic radiation behind the master which is to be reproduced and thereafter the exposed diazo sensitized sheet is exposed to aqueous ammonia vapor which induce the development of the azo dye in the areas which have not been exposed to light.

(2) The single component or semi-moist system in which the backing sheet has a diazo sensitized coating is exposed to light behind a master, thereafter diazo reproduction sheet is moistened with an aqueous solution containing a dye forming coupler and other compounds thereby inducing the development of an azo dye in the areas which have not been exposed to light.

Both of these systems have certain recognized dithculties and disadvantages. Thus, in the iirst or two component system, difficulty is encountered with the arnmonia vapors which must be exhausted so as not to annoy and inconvenience the persons present in the printing room. This problem is particularly aggravated in the case of air-conditioned buildings where the ammonia is drawn into the recirculated air. The second or single component system involves the inconvenience of handling and disposing of developing liquids which are particularly troublesome and annoying in business oflices.

Attempts have been made to overcome these difficulties and disadvantages by completely dry development methods, such as the thermal development methods. The thermal development methods heretofore attempted fall into three general classification:

(1) Single sheet processes which contain in the sheet a light sensitive diazo compound at least one coupler and a stabilizing substance which prevent azo dye formation under ordinary temperatures and conditions, but which permit 'dye formation under the elevated temperatures encountered in the thermal development equipment. In methods of this type the diazo material generally has insuicient sheli:` life, or if they are adequately stabilized, require excessively high temperatures and prolonged exposures thereto with detrimental eifect on the dye and occasional charring of the paper backing. ln addition, such methods fail to provide the desired density of color. Furthermore, difficulty is encountered in providing the moisture required for development.

(2) Double sheet process using one light sensitive sheet containing the diazo compound and a second sheet containing a dye forming coupler and at least another substance of an alkaline character. The sheets are brought into close contact with each other under elevated temperature controlled conditions to cause transfer of the dye forming coupler to the light sensitive sheet. The double hjg Patented Aug. 3l, 1965 sheet process has not been generally successful because of the slow mobility and low volatility of adequate dye forming couplers under conditions which are not detrimental to the dye formed therefrom or the paper material.

(3) Developer sheet process using one light sensitive sheet containing the diazo compound, a dye forming coupier and a stabilizer and a developer sheet which contains the developing agents and transfers them to the light sensitive sheet under proper thermal conditions. The developer sheet processes heretofore available have been of low eiiiciency. Frequently very high developing temperatures were needed and the Water was driven off before the ammonia was generated and was able to enter the light sensitive layer to create the proper pH conditions. In other instances using lower developing temperatures, the ammonia was released prematurely at room temperature resulting in a short shelf life and also causing the same inconvenient smell associated with the two component ammonia system.

lt is a particular object of the present invention to overcome the difiiculties and disadvantages heretofore encountered and to provide an improved diazotype transfer developing method and developer sheet for use therein in which high rate of synchronized development and printing is maintained; in which the development takes place at moderate temperatures in a reasonable period of time so that no damage is caused to the dyes or backing sheets; and which produces prints of very satisfactory dye density and intensity.

A further object of my invention is to provide a developing method for developing a diazo print using a standard type of machine as for instance a conventional and widely existing ammonia diazotype processing machine, without the objectionable use of aqueous ammonia vapors therein.

My improved method presents the further advantages that it may utilize standard diazo reproduction sheets used in the two component ammonia system. It presents a further advantage that it utilizes the developer sheet which is dry, which is not light sensitive, which has an indefinite shelf life, which does not generate adverse odors when subjected to heat, and which may be used one or more times for developing a sensitized diazo reproduction sheet.

In my copending application Serial No. 230,850, tiled Gctober 16, 1962 briefly stated, l provide a developer sheet for the thermal development of diazo sensitized prints. The diazo sensitized sheet is superimposed on a developer sheet constaining an organic amine, that is non-volatiie at normal ambient temperatures and atmospheric conditions and a source of water that may take the form of crystals having water of crystallization combined therewith. Subjecting the superimposed sheets to elevated temperatures, the organic amine volatilizes and the water is released mixing with the sensitized layer of the reproduction sheet and raising the pH level to permit the coupler to combine with the diazo compound to form an azo dye.

My invention contemplates in addition to the use of a eveloper sheet containing an organic amine which is non-volatile at normal ambient temperatures and atmospheric conditions, an improved developing method for developing a print on a diazo reproduction sheet which comprises subjecting the diazo reproduction sheet to actinic radiation behind a master, superimposing the developer sheet and the exposed diazo reproduction sheet and exposing both to an atmosphere containing water vapor at elevated temperatures so that the organic amine and water vapors penetrate the diazo sensitized coating to cause the coupling compound contained in the diazo reproduction sheet to couple with the diazo compound therein and thereby develop the image in the unexposed portion of the diazo reproduction sheet.

In a preferred form, my invention contemplates arranging in superimposed relationship an exposed diazo reproduction sheet and a developer sheet containing an organic amine which has a low vapor pressure and is substantially non-volatile at ambient temperatures and subjecting the superimposed sheets to an atmosphere containing steam which volatilizes the organic amine so that both the organic amine and steam induce the development of the diazo compound with the coupler in the sensitized layer of the reproduction sheet to form an azo dye.

In the accompanying drawing:

FIG. 1 is a perspective View of a developer sheet embodying my invention;

FIG. 2 is a diagrammatic view showing a master superimposed upon a diazo reproduction sheet and exposed to light; and

FIG. 3 is a diagrammatic view showing the exposed diazo reproduction sheet superimposed on the developer sheet exposed to a water vapor generator.

For a more detailed description of my improved diazo developing method reference is made to the accompanying drawings.

In FIG. 1 I show my developer sheet comprising a suitable backing sheet as shown, made of suitable material that is permeable to water vapors, such as paper, ber board or plastic, which is inert to the coating materials applied thereto and also to the materials in the diazo sensitized layer of the reproduction sheet. The backing sheet should either be sufciently absorbent to be partially impregnated with the coating materials, or if it is not absorbent, it should have surface characteristics of a type that the coating materials will adhere thereto. For the backing sheet I have found that various types of paper, such as kraft paper, serve very satisfactorily.

I apply a developer coating embodying my invention to one or both of the surfaces and the backing sheet, and, as previously indicated, it may be at least partially absorbed therein. The developer coating includes an organic amine which has low vapor pressure at ordinary ambient temperatures, such as room temperature or temperatures lower than 100 C., but which is sufficiently volatile and will volatilize at temperatures between 100 and 180 C., and which will volatilize in the presence of water vapor at temperatures between 70 to 180 C. The amine selected should also be of a type which has no undesired effect on the diazo and coupling compounds in the sensitized layer of the reproduction sheet during the development period. Representative amines which may be used for this purpose are piperazine, t-butylamineethanol, t-butyl-diethanolamine, diethanolamine, aminoethylethanolamine, methane diamine, aminoethyl-piperazine, 1,2,ll-trimethylpiperazine, 2,6-dimethyl-morpholine, and triethanolamine. The organic amine used may be ether in solid crystalline form, such as piperazine or tbutylamine-ethanol, or may be a liquid such as 2,6-dimethyl-morpholine. However, the organic amine used should be one in which it is substantially non-volatile at ambient temperatures and which is volatile at between 100-180 C., and which will volatilize in the presence of water vapor at temperatures between 70-180 C. I prefer to use piperazine which gives very satisfactory results.

I have found that the developer sheet suitable for the thermal development method as disclosed in my copending application Serial No. 230,850, tiled October 16, 1962, serves very satisfactorily for use in developing diazo prints in my present invention. However, I have found that very satisfactory prints are also obtained when the crystalline salts are not employed in the developer coating.

As indicated above, I may include in the developer sheet as a component in the developer or coating a reservoir of water which under normal ambient temperatures is retained in combined dry form but which is released when subjected to temperatures in excess of C. For this purpose I have found that crystalline salts having water of crystallization combined therewith serve very satisfactorily. Examples of such salts are sodium acetate, sodium thiosulfate, sodium carbonate, sodium sulfate, magnesium sulfate, magnesium chloride and piperazine. Piperazine, when mixed with water becomes hydrated with the addition of six molecules of water to the piperazine molecule and when subjected to development temperature, the water is released; thus serves the double function of an amine and as a crystalline salt as a reservoir for water. The crystalline salts should preferably be selected and mixed together so as to provide a pH, close to neutral. I have found that undesirable results are obtained if the coating contains strongr non-volatile alkalies or acids. Thus, if the coating is highly alkaline, the amine is prematurely released. If the coating is excessively acid, the release or volatilization of the amine is delayed or retarded. I also prefer to include an acetate salt as I have found that this serves to neutralize any trace of odor from the amine.

Under certain circumstances the crystalline salts may be omitted from the developer coating and the water supplied from other sources, such as water absorbed in the backing sheet or from a water vapor generator in the developing apparatus.

The developer coating also may include suitable binders and adhesives, such as polyvinyl acetate, casein, or the like. Additionally, it preferably includes dispersing agents, such as finely milled silica, titanium oxide, clay, starch grains or absorptive materials like activated carbon or diatomaceous earth or plasticizers such as urea.

The developer coating may be applied to the backing sheet in aqueous solution or dispersion by conventional diazotype coating equipment.

The proportions and quantities of materials applied t0 the backing sheet may be varied. I have found that satisfactory results are obtained if between 0.4 and 5.0 grams of organic amine and between 0.5 and 7.0 grams of crystalline salt having combined water of crystallization per square meter are applied to the backing sheet. Dispersing pigments in such concentrations as to yield coating weights of 0.5 to 5 grams per square meter and binders or adhesives in the amount of from 10 to 100% in proportion to the organic amine have proved advantageous.

After the developer coating has been applied to the backing sheet, the coating may be suitably dried as in a high velocity air dryer at elevated temperatures but below 100 C.

Optionally, the opposite surface of the backing sheet may have applied thereto a coating containing some of the water reservoir material or a coating identical to the one on the front side. This coating may comprise one or more of the `indicated crystalline salts applied in aqueous solution by means of simple diazotype coating equipment. If an optional coating of this type is applied, satisfactory results are obtained if between 0.5 and 6.0 grams per square meter are applied to the opposite surface of the backing sheet. After the second coating is applied, it may be simply dried as in a high velocity air dryer at a temperature below 100 C.

Developer sheet material thus prepared may be cut into individual sheets of a size to register with diazotype reproduction sheets with which it is to be used. If preferred, the developer sheet material may be supplied in roll form for use in a developing machine in which case the web of developer material is brought into contact with the exposed diazotype reproduction sheets of the developing machine.

One of the advantages of my improved developer sheet is that it may be used for developing images on conventional diazo developing equipment of the two component type, in which water replaces the aqueous ammonia that was heretofore necessary to develop a diazo print in such machines. Typical diazo reproduction sheets of this type are formed of a backing sheet having a sensitized layer applied therto, as shown in FIG. 2.

The sensitized layer includes a diazo compound, a coupling compound and an acidic stabilizing material. Representative diazo compounds used in such reproduction sheets are as follows: diazo of p-amino-diphenylamine, diazo of p-amino-dimethylaniline, diazo of pamino-diethylaniline, diazo of p-amino-N-ethyl-N-hydroxy-ethyl-aniline, diazo of p-niorpholino-aniline and diazo of 4-morpholino-2,5diethoxylaniline. Representative couplers used are as follows: resorcinol, 2,3-dihydroxynaphtalene, 2,3-dihydroxynaphtalene--sulfonic acid sodium salt, acetoacetanilide, 6,7-dihydroxy-2,3disulfonic acid sodium salt. Representative acidic stabilizers are as follows: citric acid, tartaric acid, maleic acid, boric acid, sulfamic acid, and zinc chloride. Other normal additions to sensitized layers may also be used, like thiourea, hydroxylethyl-allyl-thiorea, magnesium chloride and 1,3, G-naphthalene-trisulfonic acid, sodium salt. `For the purposes of my improved process, it is preferable that the diazo sensitized layer also includes a hygroscopic agent, such as glycerine, gylcol or a polyglycol as this favors and accelerates the development process. It has been observed that when such agents are incorporated in the coating layer of the developer sheet, the rate of development is adversely effected. However, when incorporated in the sensitized layer of the diazo reproduction sheet beneficial results are obtained.

In carrying out my improved developing method for developing a print on a diazo sensitized sheet as shown in FIGS. 2 and 3, the master which is to be reproduced is superimposed on the diazo reproduction sheet in the usual manner and is exposed to actinic radiation of the type to which the diazo material is sensitive (usually ultra-violet light or low wave length visible light) in the manner indicated in FIG. 2. The diazo material in the exposed portions of the sensitized layer is decomposed by the actinic radiation while the diazo m-aterial protected by the opaque portions of the master remains unaffected. The diazo reproduction sheet is then arranged in superimposed relationship with the developer sheet with the sensitive layer of a reproduction sheet in contact with the developer sheet. The superimposed sheets are then subjected to water va-por from a water vapor generator below the superimposed sheets in the manner indicated in FIG. 3. The water vapor elevates the temperature of the superimposed sheets Within the indicated temperature range of between 70 and 180 C. preferably approximately 100 C. The water vapor volatilizes the organic amine by a transfer of the heat energy contained in the water vapor. Subsequently, a portion of the water vapor passes through the developer sheet in suticient quantity which is transferred together with the organic amine to the sensitized coating of the reproduction sheet causing the undecomposed diazo material to combine with the coupling compound forming an azo dye i1 the unexposed portions of the reproduction sheet and thereby develop the image.

For the purpose of my invention herein the term steam is defined as water vapor or water in its vgaseous state. I have found that the development rate obtained varies depending upon several factors and is therefore a function of the following factors: the vapor pressure of the organic amine, the temperature of the water vapor, the permeability of the backing sheet, and whether a crystalline salt is employed. All of these factors affect the development rate and must be taken into consideration in setting the time 4for development. I have obtained rates varying from approximately 21/2 seconds to 30 seconds when the water vapor temperature is in excess of 70 C. and preferably between 70 to 180 C.

Example 1 On a conventional diazotype coating machine, a black kraft paper of 20 pound basis weight is coated on a kiss 6 roller airknife coating station, at a coating speed of 2,000 yards per hour with the following preparation:

The coated sheet is dried in a high velocity air dryer at .a temperature of 70 C. and then the backside of the lsheet is coated in the same machine in one and the same pass and on an identical coating station with the following solution of:

Water cc 650 Sodium thiosulfate (anhydrous) g 350 The sheet is iinally dried under the same conditions as after the first coating. The sheet thus prepared is ready for use as developer sheet. The developer sheet thus prepared may be :cut into individual sheets corresponding in size to the diazo reproduction sheets with which they are to 'oe used or may be supplied in roll form.

In using the developer sheets a diazo reproduction sheet of the two component type suitable for ammonia development as indicated on pages 10 and 11 such as those commercially available under the names SOLAR 4101: or Ozalid 200 SS, is exposed to actinic radiation with the master superimposed thereon in a conventional ammonia diazotype processing machine, for example, Ozamatic machine. The exposed reproduction sheet is then arranged in superimposed relationship with the developer sheet with the sensitized coating in contact with the developer coating. Both sheets while in superimposed relationship are passed through the developer section of a conventional type ammonia diazo developing machine, for example,

Ozarnatic machine, and subjected to steam instead of the usual aqueous ammonia vapors. The temperature of the developer section is adjusted to approximately 100 C. The stream volatilizes the organic amine, and is transferred together with steam passing through the developer sheet to the diazo sensitized reproduction sheet. The coupling compound combines with the diazo compound in the unexposed portions of the sensitized layer of the reproduction sheet forming an azo dye, producing an image in a clear vigorous blueline. The prints that are obtained are of highly satisfactory commercial quality as compared with prints obtained from the same diazo reproduction sheet developed in a conventional ammonia` development process.

Example 2 On a conventional diazotype coating machine, a white sull-ite, rosin sized, paper of 20 pound basis weight is coated on a kiss roller airknife coating station, at a coating speed of 2,400 yards per hour with the following preparation:

Water cc 650 Sodium acetate (anhydrous) g-- 130 Sodium thiosulfate (anhydrous) g 45 Piperazine (anhydrous) g-- 45 Non-colloidal silica powder (Davison) .g 45 Non-ionic polyvinyl-acetate dispersion g 65 The coated sheet is dried in a convection air dryer at` a temperature of C. and then the backside of the sheet is coated on the same machine and on an identical coating station with the following solution of:

Water cc 900 Sodium sulfate (anhydrous) -g-- The sheet is finally dried under the same conditions as after the rst coating. The sheet thus prepared is ready for use as developer sheet.

In using the developer sheet for transfer development for diazotype reproductions the same procedure is followed as described in Example 1.

'Z Example 3 On a conventional diazotype coating machine, a white sulte, rosin sized, paper of 20 pounds basis weight is coated on a kiss roller airknife coating station, at a coating speed of 2,400 yards per hour with the following preparation:

Water cc 650 Piperazine (anhydrous) g 45 Urea g 60 Non-colloidal silica powder (Davison) g 45 Non-ionic polyvinyl-acetate dispersion g 65 The coated sheet is dried in a convection air dryer at a temperature at 85 C. and then the backside of the sheet is `coated on the same machine and on an identical coating station with the following solution of:

Water cc 900 Sodium sulfate (anhydrous) g 100 Example 4 On a conventional diazotype coating machine, a kraft paper of 40 pound basis weight is coated on a kiss roller airknife coating station at a coating speed of 2,000 yards per hour with the following preparation:

Water cc 67 0 Sodium acetate (anhydrous) g 80 Sodium thiosulfate (anhydrous) g 50 t-Butyl-amino-ethanol g 50 Non-colloidal silica powder (Davison) g 50 Non-ionic polyvinyl-acetate dispersion g 100 The coated sheet is dried in a convection air dryer as a temperature of 70 C. and then the backside of the sheet is coated on the same machine land on an identical coating station with the following solution of Water cc 900 Sodium acetate (anhydrous) g-- 100 Example 5 On a conventional diazotype coating machine, a kraft paper of 40 pound basis weight is coated on a kiss roller airknife coating station at a coating speed of 2,000 yards per hour with the following preparation:

Water cc-- 670 t-Butyl-amino-ethanol g 50 Non-colloidal silica powder (Davison) g-- 50 Non-ionic polyvinyl-acetate dispersion g 100 The coated sheet is dried in a convection air dryer at a temperature of 70 C., and then the backside of the sheet is coated on the same machine and on an identical coating station with the following solution of Water cc 900 Sodium acetate (anhydrous) g 100 The sheet is finally dried under the same conditions as after the first coating. The sheet thus prepared is ready for use as developer sheet.

In the examples given above any of the other indicated organic amines may be used and any of the other crystalline salts may be substituted for those listed in the examples or may be eliminated therefrom. Also, it will be appreciated that the proportions may be varied within the indicated limits.

It will be seen that I have provided an improved diazotype transfer developing method printing process and an improved developer sheet for use therein in which the shelf life of the print sheet is not affected; in which the development takes place at moderate temperatures within a reasonable period of time without damage to the dyes or backing sheet; and which produces prints of very satisfactory dye contrast, intensity and density.

Modifications may be made in the illustrated drawing and examples without departing from the spirit and scope of my invention as defined in the appended claims.

I claim:

1. A developing method for developing a print on a diazo sensitized sheet of the type having a sensitized coating containing a diazo compound and a coupling compound and which has been previously exposed to actinic radiation behind a master, said developing method comprising placing in superimposed relationship the said exposed diazo sensitized sheet and a developer sheet containing piperazine which is non-volatile at normal ambient temperatures and atmospheric conditions and which volatilizes when subjected to an atmosphere containing steam at temperatures in excess of 70 C. and then generating steam exteriorly of said superimposed sheets and passing the steam through said developer sheet to the diazo sensitized sheet at a temperature in excess of 70 C. to volatilize said piperazine and so that said volatilized piperazine and steam penetrate the diazo sensitized coating to cause said coupling compound to couple with the diazo compound in the unexposed portion of the diazo reproduction sheet and thereby develop the image.

2. A developing method for developing a print on a diazo sensitized sheet as set forth in claim 1 wherein a hygroscopic agent is incorporated in the diazo sensitized coating of the diazo sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,906,240 5/ 33 Schmidt et al. 96-49 2,172,783 9/39 Alink et al 96-91 XR 2,308,058 1/43 Crowley et al. 96-49 2,583,678 1/52 Wilde. 2,691,587 10/54 Grieg 96-49 2,732,294 1/ 56 Morrison 96--49 2,774,669 12/56 Marron et al. 96--49 3,046,128 7/62 Klimkowski et al. 96-49 3,076,707 2/ 63 Lawton et al 96--49 XR FOREIGN PATENTS 816,601 7/ 59 Great Britain. 1,249,913 11/60 France.

OTHER REFERENCES Kosar: Photographic Science and Engineering, vol. 5, No. 4, July-August, 1961, pp. 239-243.

NORMAN G. TORCHIN, Primary Examiner.

Claims

1. A DEVELOPING METHOD FOR DEVELOPING A PRINT ON A DIAZO SENSITIZED SHEET OF THE TYPE HAVING A SENSITIZED COATING CONTAINING A DIAZO COMPOUND AND A COUPLING COMPOUND AND WHICH AHS BEEN PREVIOUSLY EXPOSED TO ACTINIC RADIATION BEHIND A MASTER, SAID DEVELOPING METHOD COMPRISING PLACING IN SUPERIMPOSED RELATIONSHIP THE SAID EXPOSED DIAZO SENSITIZED SHEET AND A DEVELOPER SHEET CONTAINING PIPERAZINE WHICH IS NON-VOLATILE AT NORMAL AMBIENT TEMPERATURES AND ATMOSPHERIC CONDITIONS AND WHICH VOLATILIZES WHEN SUBJECTED TO AN ATMOSPHERE CONTAINING STEAM AT TEMPERATURES IN EXCESS OF 70*C. AND THEN GENERATING STEAM EXTERIORLY OF SAID SUPERIMPOSED SHEETS AND PASSING THE STEAM THROUGH SAID DEVELOPER SHEET TO THE DIAZO SENSITIZED SHEET AT A TEMPERATURE IN EXCESS OF 70*C. TO VOLATILIZE SAID PIPERAZINE AND SO THAT SAID VOLATILIZED PIPERAZINE AND STEAM PENETRATE THE DIAZO SENSITIZED COATING TO CAUSE SAID COUPLING COMPOUND TO COUPLE WITH THE DIAZO COMPOUND IN THE UNEXPOSED PORTION OF THE DIAZO REPRODUCTION SHEET AND THEREBY DEVELOP THE IMAGE.