GB2053496A - Fade-resistant Diazo Microfilm - Google Patents

Abstract

A diazo microfilm which is resistant to fading upon exposure to strong light for extended periods of time is provided. The fade-resistant diazo microfilm is produced by saponifying a cellulose alkanoate film to an extent defined by certain infrared absorption parameters.

Description

SPECIFICATION Fade-resistant Diazo Microfilm Background of the Invention This invention relates to microfilm having improved properties. In one of its more particular aspects this invention relates to microfilm in which images contained on the microfilm are less susceptible to fading upon exposure to light than ordinary microfilm.

Diazo microfilm is typically made by applying a coating of, for example, 0.1 mil (2.5 microns) to 0.2 mil (5 microns) of a cellulose alkanoate to a polyester film base. This coating may incorporate light sensitive diazo chemicals or they may be impregnated into the layer from solvent solutions in a separate step. Such a product is then developed by application of an alkaline developer. Although microfilm prepared in accordance with this method is generally satisfactory, if exposed to radiation such as strong light in microfilm readers for extended periods of time, fading may occur with the result that in time the microfilm images may become illegible. For instance, as much as 90% of the image may be lost in a period of 1 6 hours exposure to the light from a microfilm reader.

Surface saponification of cellulose alkanoate films has been previously disclosed for the purpose of enhancing the substantivity of such films to photosensitive solutions. Dinaburg, for example teaches that the problems caused by non-uniform distribution of the photosensitive solution on the surface of the base layer of the film can be eliminated by coating the photosensitive solution onto the surface of cellulose which has previously been made hydrophilic by hydrolysis to a depth of 3-4 microns.

(Dinaburg, M.S., Photosensitive Diazo Compounds and their uses, The Focal Press, London and New York). Other references teach superficial hydrolysis or deacylation, usually to a depth of approximately 4 microns. United States Patent Nos. 1,340,4162,238,044; 3,311,475; 3,338,713; 3,397,058; 3,397,985; 3,442,651; and 3,442,652 contain such teachings. Dutch Patent Application 72/07099 teaches surface hydrolysis to a depth of 5 microns. United States Patent No. 3,365,293 teaches hydrolyzing a cellulose alkanoate to a depth of 5-10 microns.

None of the prior art, however, discloses controlled hydrolysis of a cellulose alkanoate layer to an extent defined by certain infrared absorption parameters to produce a fade-proof microfilm.

The invention in one aspect provides a process for producing a fade-resistant diazo microfilm which comprises controlling the saponification of a cellulose ester film such that the infrared absorbance of the saponified cellulose ester film of 5.8 #u is within range of about 0.5 to 1.5 times the infrared absorbance at 6.1 # as determined by the infrared multiple internal reflectance band ratio method and applying within the saponified cellulose ester film a two component light sensitive diazo composition comprising an acid stabilized combination of a photosensitive diazonium compound and an azo coupler.

In a further aspect the invention provides a fade-resistant diazo microfilm comprising a polyester base, a partially saponified cellulose ester film having a thickness of a minimum 0.5 mil adhered thereto and a two component light sensitive diazo composition comprising an acid stabilized combination of a photosensitive diazonium compound and an azo coupler in the partially saponified cellulose ester, the saponification of said cellulose ester film having been controlled such that the infrared absorbance of the partially saponified cellulose ester film at 5.8 #F# is within range of about from 0.5 to 1.5 times the infrared absorbance at 6.1 # as determined by the infrared multiple internal reflectance band ratio method.

In the invention the controlled saponification of cellulose ester films used in the production of diazo microfilms results in microfilms which, when developed, exhibit a high degree of resistance to fading. The extent of saponification is controlled by determining certain infrared absorption parameters of the partially saponified cellulose ester film which are directly related to the extent of saponification.

Description of the Preferred Embodiments The method of controlling the saponification level of the cellulose ester layer used in producing the microfilm of this invention consists of using an infrared multiple internal reflectance band ratio method to determine the degree of surface saponification. The multiple internal reflectance band ratio method is effective in determining the chemical constitution of films at or near the surface thereof. This technique is readily adaptable for determining the depth of saponification and hence the saponification level of cellulose ester films. Other methods such as bulk analysis of the saponified films are cumbersome and difficult to use as a control method. The infrared technique of multiple internal reflectance using the ratio of two infrared absorption bands is uniquely satisfactory for this purpose.

Since the saponification level of the film is directly related to certain readily measureable infrared absorptions, this method can be used as a convenient control method in microfilm production.

More particularly, the absorbance ratio R is determined where R is given by the equation A5#8-b R= A6, - b where As 8and Aó, are the absorbance values at infrared absorption maxima near 5.8 y and 6.1 , the bands due to carbonyl absorption and molecular water, respectively, and b is a base-line correction taken by drawing a line tangent to the absorption minimum near 5.5 , and parallel to the abscissa on a plot of infrared absorption against wavelength of infrared radiation.

Specifically, ratios of between 0.5 and 1.5 for saponified cellulose acetate films and cellulose acetate propionate coatings on polyester films were found to produce desirable results with respect to fade resistance.

The diazo microfilm of this invention can be produced by applying a clear coating of a cellulose ester such as cellulose acetate, cellulose propionate, cellulose acetate propionate or cellulose butyrate to a polyester film and then saponifying the cellulose ester layer by treatment with a methanolic aqueous solution of potassium hydroxide, to provide the desired controlled level of saponification. The treatment of the film results in the hydrolysis of some of the ester groups to free hydroxyl groups which imparts a highly hydrophilic character to the resulting saponified film. Such saponified film will readily absorb aqueous solutions of diazo formulations. Similar treatment of unsupported cellulose acetate films can also be employed.

This invention will be better understood by reference to the following examples which are included for purposes of illustration and are not to be construed as limiting the scope of the instant invention which is defined in the claims appended hereto.

Example 1 Cellulose diacetate film 5 mils thick was saponified with an aqueous methanolic solution of potassium hydroxide (80 cc. H2O, KOH-7 gm., CH3OH- 20 cc.) by immersion for a period of 22 seconds at 900F followed by neutralization in a solution containing 100 cc. water, 1.0 gm. sulfuric acid and thoroughly washing in water.

The saponified film was found to have an absorbance ratio of 1.5.

The saponified film was coated with a diazo stabilized solution of: Water 85 cc.

Butyl Cellosolve 10 cc.

Citric Acid 1.5 cc.

Zinc Chloride 1.5 gms.

beta-oxynaphthoic monoethanolamide 1.5 gms.

2,5-diethoxy-4-morpholino-benzene diazonium chlorozincate 1.5 gms.

Saponin 0.2 gm.

Coating to the saponified film was applied by the conventional air knife doctorinq method.

Another coating containing the same coupler and diazo combination was applied to unsaponified cellulose diacetate to match the dye density of the coating applied to the saponified film. Coating formulation was: Methyl Cellosolve 60 cc.

Methanol 30 cc.

Formic Acid 4 cc Water 6 cc.

Zinc Chloride 0.5 gm.

Citric Acid 1.0 gm.

Thiourea 0.3 gm.

Beta-oxynaphthoic monoethanolamide 2,5-diethoxy-4-morpholino-benzene diazonium 1.0 gm.

chlorozincate 1.5 gm.

Coating was applied to the unsaponified cellulose diacetate by the dip bead coating method.

Imaging of the films was made in a carbon arc and prints were ammonia developed in a Bruning 880 diazo printing machine having an anhydrous ammonia developing chamber.

Exposure of the resulting prints in a commercially available microfilm viewer (IBM-IIB viewer) for a period of about 16 hrs. resulted in a 3% fade compared to an 85% fade in the case of the unsaponified film.

Example 2 The procedure of Example 1 was followed except that N-(3-morpholino-1 -propyl)-3-hydroxy-2naphthylamide was used as the coupler instead of beta-oxynaphthoic monoethanolamide. The percent fade of the unsaponified film was found to be 52% compared to 0.5% for the saponified film.

Example 3 The procedure of Example 1 was repeated except that resorcinol was used as the coupler. The percent fade of the unsaponified film was found to be 1 8% compared to 0.5% for the saponified film.

Example 4 The procedure of Example 1 was repeated except that acetoacetanilide was used as the coupler.

The percent fade of the unsaponified film was found to be 57% compared to 12% for the saponified film.

Example 5 The procedure of Example 1 was followed except that p-diazodiethyl aniline zinc chloride was used as the diazonium salt instead of 2,5-diethoxy-4-morpholinobenzene diazonium chlorozincate. The percent fade of the unsaponified film was found to be 95% after exposure over a weekend compared to 3% for the saponified film.

Example 6 The procedure of Example 1 was followed except that p-diazodiethylaniline zinc chloride was used as the diazonium salt and N-(3-morpholino-1 -propyl)-3-hydroxy-2-napthylamide was used as the coupler. The percent fade of the unsaponified film was found to be 75% compared to 11% for the saponified film.

Example 7 The procedure of Example 1 was followed except that p-diazodiethylaniline zinc chloride was used as the diazonium salt and resorcinol was used as the coupler. The percent fade of the unsaponified film was found to be 24% compared to 0.4% for the saponified film.

Example 8 The procedure of Example 1 was followed except that p-diazodiethylaniline zinc chloride was used as the diazonium salt and acetoacetanilide was used as the coupler. The percent fade of the unsaponified film was found to be 67% compared to 0.5% for the saponified film.

Example 9 A coating to polyester (5 mil ICI-505 grade) for the purpose of saponification was prepared as follows: Sub Coat Formula: Methyl Ethyl Ketone 80 cc.

Methyl Cellosolve 20 cc.

Alcohol Soluble Cellulose Acetate Propionate 275 gm (Eastman Kodak) The acetate solution was applied to the polyester film by a wire bar (#65) coating method, to a dry thickness of a minimum 0.5. The lacquered film was saponified with KOH solution as described in Example 1 but varying immersion times to obtain absorbance ratios of 1.8, 1.3, 1.05 and 0.85. The lacquered film unsaponified had a ratio of 2.10. The various films were diazo sensitized, exposed and ammonia developed as described in Example 1.

All of the diazo sensitized films were exposed to 16 hours in a lighted IBM-IIB reader and percent fade recorded.

Absorbancy Ratio Percent Reader Fade 2.10 95 1.80 68 1.30 24 1.05 15 0.85 5 This invention has been described with reference to certain specific embodiments and to various suggested conditions of operation. However, other embodiments can be utilized in the practice of this invention. It is therefore intended that this invention is not to be limited except as defined in the following claims.

Claims (18)

Claims

1. A process for producing a fade-resistant diazo microfilm which comprises controlling the saponification of a cellulose ester film such that the infrared absorbance of the saponified cellulose ester film at 5.8 u is within range of about 0.5 to 1.5 times the infrared absorbance at 6.1 y as determined by the infrared multiple internal reflectance band ratio method and applying within the saponified cellulose ester film a two component light sensitive diazo composition comprising an acid stabilized combination of a photosensitive diazonium compound and an azo coupler.

2. A process according to claim 1 wherein said cellulose ester is a cellulose alkanoate.

3. A process according to claim 1 wherein the cellulose ester is cellulose diacetate.

4. A process according to claim 1 wherein the cellulose ester is cellulose acetate-propionate.

5. A fade-resistant diazo microfilm comprising a polyester base, a partially saponified cellulose ester film having a thickness of a minimum 0.5 mil adhered thereto and a two component light sensitive diazo composition comprising an acid stabilized combination of a photosensitive diazonium compound and an azo coupler in the partially saponified cellulose ester, the saponification of said cellulose ester film having been controlled such that the infrared absorbance of the partially saponified cellulose ester film at 5.8 iu is within range of about from 0.5 to 1.5 times the infrared absorbance at 6.1 y as determined by the infrared multiple internal reflectance band ratio method.

6. A microfilm according to claim 5 wherein the thickness of the cellulose ester film is about 5 microns.

7. A microfilm according to claim 5 wherein the cellulose ester is a cellulose alkanoate.

8. A microfilm according to claim 5 wherein the cellulose ester is cellulose diacetate.

9. A microfilm according to claim 5 wherein the cellulose ester is cellulose acetate-propionate.

10. A microfilm according to claim 5 wherein the image produced upon development of said microfilm fades less than about 30% upon exposure to strong light for a period of about 16 hours.

11. A process according to claim 1 wherein the cellulose ester film is an unsupported cellulose ester film.

12. A process according to claim 1 wherein the cellulose ester film has a thickness of a minimum 0.5 mil and is adhered to a polyester base.

13. A fade-resistant diazo microfilm comprising a partially saponified unsupported cellulose ester film and a two component light sensitive diazo composition comprising an acid stabilized combination of a photosensitive diazonium compound and an azo coupler in the partially saponified cellulose ester, the saponification of said cellulose ester film having been controlled such that the infrared absorbance of the partially saponified cellulose ester film at 5.8 ju is within the range at about from 0.5 to 1.5 times the infrared absorbance at 6.1 1l as determined by the infrared multiple internal reflectance band ratio method.

14. A microfilm according to claim 13 wherein the cellulose ester is a cellulose alkanoate.

15. A microfilm according to claim 13 wherein the cellulose ester is cellulose diacetate.

16. A microfilm according to claim 13 wherein the cellulose ester is cellulose acetate-propionate.

1 7. A microfilm according to claim 13 wherein the image produced upon development of said microfilm fades less than about 30% upon exposure to strong light for a period of about 16 hours.

18. A process for producing a fade-resistant diazo microfilm substantially as herein described.

1 9. A fade-resistant microfilm substantially as herein described.