Title:
PROCESS FOR MAKING FLAT PHOTOGRAPHIC FILM PRODUCT
United States Patent 3861942


Abstract:
A concave curvature is imparted to the backing surface of a polyester photographic film support (prior to coating the other surface) by a process which comprises applying to said backing surface a solution of treating composition comprising a volatile phenolic compound and a surfactant in a volatile solvent and drying and heating the film above the second order transition temperature of the polymer for a time sufficient to volatilize the solvent and phenolic compound from the surface. A flat photographic film product having no anti-curl backing layer is produced from the concavely curved film upon coating the other surface of the film with one or more layers of the usual coatings used in the structure on the photosensitive side of the film, at least one of said layers being such that it shrinks when drying and imparts a compensating countercurvature force to the film, thereby flattening the film.



Inventors:
GUESTAUX CLAUDE
Application Number:
05/287131
Publication Date:
01/21/1975
Filing Date:
09/07/1972
Assignee:
EASTMAN KODAK COMPANY
Primary Class:
Other Classes:
428/480, 430/930
International Classes:
G03B21/00; C08J7/02; G03C1/795; G03C1/81; (IPC1-7): B44D1/092
Field of Search:
117/34,47A,47R,118,138
View Patent Images:
US Patent References:



Primary Examiner:
Trenor, William R.
Attorney, Agent or Firm:
Milan E. W.
Claims:
I claim

1. A method for making a substantially flat photographic film product having a polyester or polycarbonate support coated on one surface with at least one layer including photosensitive material and a hydrophilic binder for said material, said method consisting essentially of

2. A method according to claim 1, characterized in that a biaxially stretched poly(ethylene terephthalate) support is treated, and the heating temperature is in the range of about 120° to 130° C.

3. A method according to claim 1, characterized in that the solution contains an effective amount of a surfactant agent.

4. The method of claim 1 wherein the layer of coating composition comprises photographic silver halide.

5. The method according to claim 1 wherein the support is polyester.

6. The method according to claim 5 wherein the treating composition, by weight, consists essentially of from about 1 to about 50 parts of said volatile hydroxy aromatic compound and from about 99 to 50 parts of said solvent.

7. The method according to claim 6 wherein said solvent is water.

8. The method according to claim 7 wherein said treating composition contains from about 0.05 to about 2 parts of surfactant agent.

9. The method according to claim 8 wherein said treating composition contains from about 15 to 20 parts of said volatile hydroxy aromatic compound.

10. The method according to claim 9 wherein said volatile hydroxy aromatic compound is phenol, resorcinol, pyrogallol or 4-hexylresorcinol.

11. The method of claim 10 wherein said volatile hydroxy aromatic compound is resorcinol.

12. The method of claim 11 wherein said photosensitive material is photographic silver halide.

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the manufacture of film supports used in the production of flat photographic films. Particularly, it relates to a process for treatment of thermoplastic film supports which renders the latter suitable for the preparation of flat photographic film products, especially film for moving picture camera use, without it being necessary to apply to the non-sensitized surface of a support film an anticurl backing layer to compensate the undesirable incurvature of the sensitized surface produced by the coating on the latter surface of a photosensitive layer the binder of which is a hydrophilic colloid.

It is known that, without particular precautions, photographic film products having polyester film supports are strongly incurved (concavely curved viewed from the sensitized surface) as a result of the contraction of the sensitized hydrophilic colloid layer, or layers, on the sensitized surface during the drying of the layer(s) on the support film. This incurvature effect is well known and is undesirable for many reasons. At the time of the picture taking as well as at time of projection or printing, the incurvature makes it necessary that the film be flattened by a pressure-applying device to overcome the incurvature. Consequently, the wear and tear of cinematographic films is increased by the rapid deformations imposed on the films by the pressure-applying device of the photographic camera or projector. In still photography, the handling of incurved strips of film also poses a problem which must be overcome to avoid distorted pictures. Furthermore, in film-carrying cartridges, where the film is only very slightly stretched, it is difficult to obtain a sufficient flatness if the film strip is overly incurved as a result of its manufacture.

2. Description of the Prior Art

It is known to remedy, at least in part, the incurvature defect of the support film by coating on the back surface of the film a counter-acting anti-curl layer, such as a layer of a lacquer or varnish (see U.S. Pat. No. 2,963,366) or hydrophilic colloid, e.g. a suitably tanned gelatin layer or a substratum of polymeric material (see U.S. Pat. No. 3,492,122). The contraction of such a counteracting layer tends to produce a compensating incurvature force in the opposite direction to that produced on the opposite surface by the sensitized surface layers and it is possible to succeed in obtaining a sufficient flatness by balancing of these opposite incurvature forces. However, the presence of an anti-curl backing layer, generally a gelatin layer, complicates the preparation and subsequent handling of the photographic product. For example, the fragility of such a backing layer is a cause for local defects that can form in the course of manufacture of the photographic product, of picture taking, of chemical treatment of the exposed film during developing, or of use of the finished photographic document. This difficulty is one of the reasons why no backing layer is applied to cinematographic films, the emulsified surfaces of which are usually very concave in the absence of external pressure, as they must move at a great speed on rollers. It is thus desirable to be able to prepare a systematically incurved photographic film support, the incurvature being in the opposite direction to that of the other surface on which the photosensitive layers are to be applied, to which other surface it will then be possible to apply a layer or a number of layers of hydrophilic colloid with or without photosensitive material incorporated therein among the usual layers of coatings used in the structure on the photosensitive side of a photographic film and obtain a substantially flat photographic product.

SUMMARY OF THE INVENTION

According to the invention, one applies to the backing surface, only, of a polyester or polycarbonate film intended for use as a support for a photographic film product a solution in a volatile solvent of a volatile agent having the properties of swelling or similarly attacking the surface of the film material, said agent having a volatilization point above that of the solvent, and being easily removed by heating at a temperature above the second order transition temperature of the polymer of which the film is made. For photographic quality polyester film the heating is done at 120° to 130° C. The treated film is dried by means of heating at such temperature above the second order transition point of the polymer of the film that is treated, so as to remove the solvent first, and then to volatilize the attacking agent, substantially completely. By "backing surface" is meant the surface intended to be reverse to that surface which ordinarily would become concave by the application thereon of a layer or several layers of photosensitive materials at least one of which being such that it tends to shrink when drying. Usually, this layer contains a hydrophilic colloid, such as gelatin. The attacking agent is a volatile hydroxy aromatic compound, preferably a phenolic compound, such as resorcinol.

The treatment, according to the invention, preferably, is effected on photographic film supports intended for coating with preselected photosensitive materials, so that the final photographic products predictably will be flat. In fact, in order to compensate in advance the incurvature produced by the photographic layers that will be applied to the support, it is obviously necessary to know which layers and how many layers will be applied. The incurvature can be controlled by varying the concentration of the surface-attacking agent and the maximum temperature of volatilization. It appears that the surface attack on the film at the specified temperature range creates internal tensions in the attacked surface area of the latter and in this way produces the incurvature, the concavity being on the attacked surface.

The invention thus makes it possible to obtain substantially flat photographic film products, as well as other one-side-coated film products, having film supports free of a special anti-curl backing layer, the disadvantages of which backing layers are indicated above. The invention, therefore, is a substantial advance in the art of manufacture of thermoplastic photographic and other film supports and products.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention concerns more particularly photographic film products having film supports consisting of polyester or polycarbonate resin films of photographic quality, particularly poly(1,4-cyclohexylenedimethylene terephthalate) films, and, more particularly, poly(ethylene terephthalate) films. The surface treatments of such films with compositions producing a surface attack for the purpose of increasing adherence of one layer, or numerous sub-layers, to the polyester or polycarbonate film is known. For example, in U.S. Pat. No. 3,271,345, dihydroxy aromatic compounds are taught to be included in polymeric subbing compositions as anchoring compositions. Specific adhesion-improving dihydroxy aromatic compounds disclosed in said patent are exemplified by resorcinol, and include, in addition, orcinol, 4-chloro-resorcinol, 1,3-naphthalene diol, 1,6-naphthalene diol, catechol, and 2,4-dihydroxy toluene. Similarly, in U.S. Pat. No. 3,492,122, certain hydroxy aromatic compounds, including phenol, o-chlorophenol, p-chlorophenol, cresol and "other phenol derivatives," are disclosed as examples of organic solvents capable of swelling, softening or dissolving poly(ethylene terephthalate) and are included in the ingredients of a polyester-cellulose ester mixture applied as a substratum to the backing surface of a poly(ethylene terephthalate) photographic film support to enhance adhesion of an anti-halation layer thereto. The substratum layer is also stated to improve the mechanical properties of the film, including its flatness, after removal of the adhered anti-halation layer. Also, U.S. Pat. No. 3,271,190 teaches an anti-blocking composition for polyester sheeting which is comprised of (1) an anionic surface-active agent and (2) an adhesion promoter. The adhesion promoter is selected from a group including hydroxy, dihydroxy and trihydroxy aromatic compounds, specifically, resorcinol, orcinol, catechol, pyrogallol, 1-naphthol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, 4-chlororesorcinol, 2,4-dihydroxytoluene, 1,3-naphthalenediol, 1,6-naphthalenediol and o-cresol. An aqueous solution of the anti-blocking composition is applied to at least one surface of a polyester sheet and dried with sufficient heat to remove only the water, leaving the anti-blocking composition as a residue on the sheet. The anti-blocking composition serves to keep polyester sheets from adhering to each other.

It is to be noted that in each of the above discussed patents the hydroxy-containing aromatic compound remains as a component of the polymeric subbing composition, adhesive substratum or anti-blocking composition, respectively.

In contrast to the above prior art uses of hydroxy aromatic compounds to treat polyester photographic film, the process of the invention uses substantially the same hydroxy aromatic compounds in a different manner to achieve a different result. According to the present invention, one of the same hydroxy aromatic compounds as described above, for example, resorcinol, is applied in a treating composition to only one surface of the polyester or polycarbonate photographic film support and then the film is heated to a temperature above the second order transition point of the polymer to volatilize the resorcinol substantially completely away from the film. The result obtained is that the treated film surface is made concave. Such a result and the manner in which it is obtained are not taught or suggested in the above patents. Therefore, prior to the present invention it was not known to treat a film with a composition formed of a volatile solvent and a volatile attacking agent, then to heat the film so as to expel the composition substantially completely, and to obtain an incurvated film practically unchanged in its physical properties except for the incurvature and containing substantially no residue of the treating composition.

In practicing the present invention, the selection of the volatile attacking agent to be used depends on the chemical nature of the photographic film to be used as a support film. For use with photographic film made of a polyester resin, a solution of a hydroxy aromatic compound is used advantageously, which compound can be any of the hydroxy, dihydroxy or trihydroxy aromatic compounds listed in the patents discussed above, provided only that the compound is volatile at a temperature above about the second order transition point of the polymer forming the film. Preferably, the compound is, for example, phenol itself, resorcinol, pyrogallol, or 4-hexylresorcinol. These preferred phenols are volatile; and the first three listed are water-soluble, and are used advantageously in the form of aqueous solutions. It is also possible to use these phenolic compounds in solution in an organic solvent, such as dichloromethane or methylisobutylketone.

In order to obtain a treating composition layer of uniform composition and consequently, a treated film surface of a uniform incurvature, it is often advantageous to add to the treating composition an auxiliary product facilitating its coating, i.e., a product having a surface active action. Such products are well known, and surface active agents of the anionic type disclosed in U.S. Pat. No. 3,271,190, for example, the sodium salts of fatty alcohol sulfates or of alkyl aryl sulfonates, may be used. U.S. Pat. No. 3,271,190 is incorporated herein by reference. Nonionic surface active agents may also be used to practice the invention. Especially preferred is the use of the "Antarox CO 436" agent, sold by the General Aniline and Film Corporation.

The means for coating the treating composition on the surface of the film are well known in the art and any of such coating or applicator means may be used. It is preferred, however, to apply the composition by means of a wick and then to smooth the coated layer with an air knife in a known way.

The treating composition whether containing an aqueous or an organic solvent is used in concentrations which can be readily determined by one skilled in the art. The amount of solvent should be sufficient to form a solution which easily can be applied by a particular applicator means to the surface to be treated. Advantageously, the treating composition will contain by weight from about 1 to about 50 parts of hydroxy aromatic compound dissolved in from 99 to 50 parts of solvent per 100 parts of composition. Preferably the amount of hydroxy aromatic compound present in the composition will be from about 15 to about 20 parts. The composition also may, and preferably will, contain by weight from about 0.05 to about 2 parts, preferably about 0.1 part, of a surface active agent, in place of an equivalent amount of solvent. Thus, preferred treating compositions according to the invention will consist essentially of from about 15 to 20 parts of hydroxy aromatic compound, about 0.1 part of surface active agent and about 79.9 to 84.9 parts of solvent, all parts being by weight.

The drying temperature used to remove the treating composition from the treated surface is higher than that of the second order transition temperature point of the polymer forming the film. For photographic quality poly(ethylene terephthalate) films, a temperature above approximately 120° C., e.g. between 120° and 130° C. is very suitable. The period of heating is generally between about 10 and 20 seconds, these limits not being absolutely required.

Second order transition temperature or glass transition temperature (Tg) is defined as the temperature at which a discontinuity occurs in the curve of a first derivative thermodynamic quantity with temperature. It is correlated with yield temperature and polymer fluidity and can be observed from a plot of density, specific volume, specific heat, sonic modulus or index of refraction against temperature. The glass transition temperature of polyester resin is characterized by a change from a relatively hard, brittle, glassy material to a soft, more flexible, rubbery substance as the temperature is raised through the glass transition temperature Tg. The glass, or second order, transition temperature varies somewhat with the nature of the glycol and the dibasic acid reacted together to form the polyester. For poly(ethylene terephthalate) of a photographic quality, which is biaxially oriented and highly crystalline, the second order transition temperature (Tg) is about 120° C. Because of its high crystalline melting point (about 265° C.) and second order transition temperature, such poly(ethylene terephthalate) retains good mechanical properties at temperatures up to about 150°-175° C. Accordingly, in heating the treated photographic film support to remove the composition the heating should not be carried above said temperature range (150°-175° C.) and preferably should be kept in the range of about 120° to 130° C. Overheating of the film will be detrimental to its physical properties.

The invention is further illustrated in the following examples wherein Examples 1 and 3 show the effects of varying the concentration of the phenolic compound and Example 2 shows the effects of different temperatures of heating of the film to remove the treating composition.

In the following examples, the incurvature depth of the concavity is expressed by the sagitta in 1/32's of an inch for an arc of 35mm, on a 35mm-wide film strip, that is, on a usual cinematographic film. The relative humidity is expressed in percent at the indicated drying temperature.

EXAMPLE 1

To a poly(ethylene terephthalate) film, stretched biaxially and 100μ thick, an aqueous solution of treating composition was applied containing, by weight, 15% of resorcinol and 0.1% of "Antarox CO 436" surface active agent. A cotton wick was used to spread the composition, then the layer was smoothened by means of an air knife, under a pressure of 0.014 psi. The layer was dried at 130° C., in one set of samples, and at 85° C. in a second set of samples. The results are shown in Table I. Measurements were carried out in a more or less dry atmosphere, on the recently treated support (Column A, Table I), or else the samples were kept for 17 hours at 50° C., with no application of stress (Column B, Table I). The relative humidities are expressed in percent.

TABLE I __________________________________________________________________________ A B Incurvature of the recently Incurvature of the dried treated product for relative product for a relative Drying humidity of: humidity of: Temperature 20% 50% 75% 20% 50% 75% __________________________________________________________________________ 85°C. 0 0 0 0 0 0 130°C. 2.0 2.4 2.5 4 4 3.5 __________________________________________________________________________

These results show that incurvatures of from 2.0 to 2.5 1/32's inch were obtained on recently treated film and of from 3.5 to 4.0 on treated product dried further at 50° C. for 17 hours before testing are obtained at a drying and treating temperature of 130° C., but none is obtained at a drying and treating temperature of 85° C. If to the untreated surface of the thusly treated photographic support, a high-contrast photographic emulsion, of the type used in the photochemical processes, is applied, a substantially flat photographic product is obtained by compensation of the incurvature itself of the support and of the incurvature in the opposite direction produced by the drying of the photographic emulsion.

EXAMPLE 2

One operates in a manner similar to Example 1, by using as processing solution a solution containing 15% of resorcinol in methylisobutylketone. The results obtained are indicated in Table II.

TABLE II __________________________________________________________________________ Incurvature of the recently Incurvature of the treated product for a dried product for a Drying relative humidity of: relative humidity of: Temperature 20% 50% 75% 20% 50% 75% __________________________________________________________________________ 85°C. 0 0 0 0 0 0 130°C. 2 2 2 2 2 1 __________________________________________________________________________

After coating the untreated surface with a usual type of silver halide photographic emulsion layer, a practically flat photographic product is obtained.

EXAMPLE 3

Examples 1 and 2 are repeated by using as processing solution a solution containing 50% of phenol in dichloromethane. The following results are obtained, the drying temperature being 130° C.

TABLE III ______________________________________ Measurements of recently Percent treated products Relative Humidity Incurvature ______________________________________ 20 6.0 50 6.0 75 5.5 Measurements of products having rested 17 hours in oven at 50°C. 20 8.9 50 7.2 75 6.7 ______________________________________

example 3 shows that upon increasing the concentration of the processing solution and using a different phenolic compound, phenol, in place of the resorcinol used in Examples 1 and 2 the amount of incurvature of the film was substantially increased to a high degree. The incurvature forces on the other surface accordingly can be made correspondingly great and a flat film product will be obtained by applying sufficient layers and thicknesses of coating materials, including a hydrophilic binder material.

For example, an incurvature in the order of 2 yields a more or less flat final product with a poly(ethylene terephthalate) support, 100μ thick, coated with a negative photographic emulsion layer, of the usual type and of average thickness.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention to obtain the advantages thereof. For example, while the invention has been illustrated in its application to photographic film it will be clear to those skilled in the film coating art that other types of coatings can also be applied to the untreated surface of the treated film along with a hydrophilic material in one or more layers thereon to obtain a flat film in accordance with the teachings of the invention.