EP0785465A1

EP0785465A1 - Molecular grafting of carboxyl reactive hardeners to energetically treated polyesters to promote adhesion of layers

Info

Publication number: EP0785465A1
Application number: EP97200037A
Authority: EP
Inventors: Jeremy M. c/o Eastman Kodak Company Grace; Louis J. c/o EASTMAN KODAK COMPANY Gerenser; Richard A. c/o Eastman Kodak Company Castle; Janglin C/O Eastman Kodak Company Chen; Edgar E. c/o Eastman Kodak Company Riecke
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1996-01-19
Filing date: 1997-01-08
Publication date: 1997-07-23
Also published as: JPH09197618A; CA2193040A1

Abstract

The present invention comprises a polyester film support in which the surface has been subjected to an energetic treatment to produce carboxyl groups on the polyester surface. The treated surface is then coated with a dilute solution of carboxyl reactive hardener and solvent (e.g., water) or a blend of carboxyl reactive hardener and gelatin and solvent (e.g., water). After drying the hardener or hardener/gelatin coated support, a photographic emulsion is coated on the surface. The resulting film element has excellent adhesion of the photographic emulsion after photoprocessing. Furthermore, the support coated with hardener/gelatin blend is safer to coat and handle than previously known methods involving grafting of hardener directly to the support.

Description

Field of the Invention

The present invention relates to the manufacture of photosensitive materials. More specifically, the present invention relates to polyester material which has been subjected to energetic treatment and a thin layer of hardener grafted thereon. In addition, the present invention relates to a gelatin grafted layer, in which a mixture of hardener and gelatin is grafted to the energetically treated polyester.

Background of the Invention

Conventional subbing chemistry has not proven totally effective on biaxially oriented polyester support, and thus, there is a problem of adhesion in the photoprocessor environment of aqueous coats of photographic emulsions to these highly inert polymer surfaces. Recent approaches to overcoming the challenges of subbing biaxially oriented polyester support have involved plasma treatments, UV treatments, and other surface modification techniques often combined with heating the support material and/or complicated subbing chemistry. Recent advances in subbing technology have shown promise for replacing a U-coat/gelatin sub system with a single subbing layer applied to a plasma treated biaxially oriented polyester support. This is described in more detail in U.S. Patent 5,425,980 issued 20 June 1995 entitled "Use of Glow Discharge Treatment to Promote Adhesion of Aqueous Coats to Substrate".
As described in U.S. Patent 5,425,980, it has been shown that photographic emulsions may adhere to plasma treated support using gelatin sub and no U-coat, a single subbing layer containing a terpolymer and gelatin (as described in US Patents 4,695,532 and 4,689,359), or no subbing at all. The plasma treatment technology has enabled the coating of photographic emulsions and gelatin based subbing layers directly onto biaxially oriented polyesters.
As described in USSN 08/415,826, filed 03 April 1995, there are some problems associated with mechanical strength and/or treatment process latitude, for subbing layers coated directly onto energetically treated polyester support. In addition, subbing layers based on gelatin may exhibit sensitivity of adhesion to keeping conditions prior to adhesion testing. In USSN 08/415,826 it is demonstrated that acceptable mechanical strength, wide treatment process latitude, and insensitivity of adhesion to keeping conditions can all be achieved by molecular grafting of amine reactive hardener to an energetically treated surface of a biaxially oriented polyester support. USSN 08/415,826 deals specifically with amine reactive hardeners and the appropriate energetic treatment chemistry. Furthermore, it relates to the use of the amine reactive hardener as the subbing layer or the major constituent, thereof. USSN 08/588,765 entitled,
MOLECULAR GRAFTING OF HARDENER/GELATIN BLENDS TO ENERGETICALLY TREATED POLYESTERS TO PROMOTE ADHESION OF LAYERS
filed concurrently herewith discloses an improvement over USSN 08/415,826 by use of hardener/gelatin blends and is also specific to amine reactive hardeners and the appropriate energetic treatment chemistry.
Although there may be a variety of energetic treatment techniques capable of producing appropriate surfaces for the amine reactive chemistry disclosed in USSN 08/588,765 and USSN 08/415,826, nitrogen glow-discharge treatment -- a vacuum process -- is the most mature and most readily implemented form of energetic treatment that is chemically appropriate. Am atmospheric process, such as corona treatment, would be comparatively simpler and less expensive to implement. Unfortunately, such treatment processes yield very different surface chemistries from the nitrogen glow-discharge treatment process. Thus, there is a need to expand the useful hardener and treatment chemistry to lower the cost and increase the ease of implementation of the technology disclosed in USSN 08/588,765 and USSN 08/415,826. It should also be noted that other hardener chemistries may be far less stable than the vinylsulfone chemistry demonstrated in USSN 08/415,826, making the need for a hardener/gelatin blend (demonstrated in USSN 08/588,765) not only an improvement from the standpoint of safety (as described in USSN 08/588,765), but also from the standpoint of performance.
Therefore alternatives to the use of amine reactive hardeners which may present health and safety issues are needed. Furthermore, process latitude in effecting the surface treatment is desirable. The present invention extends the technology previously disclosed to carboxyl reactive hardeners and energetic treatment chemistry appropriate to the carboxyl reactive chemistry. This chemistry affords safer candidates for hardener and alternatives for treatment technology.

Summary of the Invention

The present invention comprises a method of coating a polyester support which includes passing a surface of the polyester support through an energetic treatment to produce carboxyl groups on the surface. The surface of the polyester support is then coated with a carboxyl reactive hardener solution. The coated support is then dried. The surface of the support is then coated with a photographic emulsion. The photographic emulsion can contain silver halide, or other photosensitive materials. Typically carboxyl reactive hardeners are hydrolytically unstable. Hence, it is not obvious that this approach would produce good adhesion.
An alternative method of coating comprises passing a surface of the polyester support through an energetic treatment which produces carboxyl groups on the surface. The surface of the polyester support is then coated with a combination of carboxyl reactive hardener and gelatin in solution. The coated support is then dried. The surface of the support is then coated with a photographic emulsion. The difficulty with blending hardener and gelatin is well demonstrated by Work, III et al (U.S. Patent 4,241,169 issued 23 December 1980). Work, III et al find that hardener/gelatin blends do not produce good adhesion unless a water soluble polyester is added to the coating solution. The difficulty encountered by Work, III et al may arise from an inappropriate match of the surface chemistry of the treated support with the hardener employed.
In a preferred embodiment of the present invention the hardener is selected from the group consisting of bis(pyridylium)ethers as described in US 4,877,724, imidazolopyridinium compounds and pyrazolopyridmium compounds as described in US 5,236,822, carbamoylpyridinium compounds as described in US 4,063,952, carbamoyloxypyrdinium compounds as described in US 4,055,427, chlorotriazines as described in US 4,216,108, succinimidyloxyformamidiniums as described in US 4,612,280, chloroformamidiniums as described in US 4,673,632, alkylsulfonyloxysuccinimides as described in U.S. 4,111,926.
The present invention also includes a film element comprising a polyester support having a surface which has been exposed to an energetic treatment. A coating of carboxyl reactive hardener which is selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, alkylsulfonyloxysuccinimides is grafted to the surface of the polyester support. Finally, a photographic emulsion is applied to the treated and coated surface of the polyester support.
A further embodiment of the present invention includes a film element which comprises a polyester support having a surface which has been exposed to an energetic treatment. A blend of hardener and gelatin, with the hardener selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccinimides is coated onto the treated support. Finally, a photographic emulsion is applied to the treated and coated surface of the polyester support.

Brief Description of the Drawing

Figure 1 shows a film element of the present invention.
For a better understanding of the present invention together with other objects, advantages and capabilities thereof, reference is made to the following description and appended claims in connection with the above described drawing.

Detailed Description of the Preferred Embodiments

Traditional subbing technology represents an adhesive layer approach to solving an interfacial adhesion problem. In short some layer or pair of layers is coated onto a polyester support, typically polyethylene naphthalate (PEN) or polyethylene terephthalate (PET), in order to create a surface to which the desired functional layers,(e.g., photographic emulsions) will adhere. Generally, the interaction of the subbing layers with the polyester or functional layers can be rather complex, and success hinges on the ability of the aqueous subbing layer to penetrate the polyester surface. In contrast, by appropriately bonding hardener molecules directly to an energetically treated surface, it is possible to create a very thin layer that can interact readily with the coated photographic emulsion layer to produce excellent adhesion. Typical energetic treatment include electrical discharge treatment, UV treatment, plasma treatment, electron-beam treatment, laser treatment, corona treatment and glow discharge treatment. USSN 08/415,826 discloses an invention that includes exposing a polyester support to an energetic treatment that produces amine groups on the surface of the polyester support, coating the treated support with a dilute solution of hardener and appropriate solvent (e.g. water, or organic solvent), and drying the coated support. The hardener coated polyester support is then ready for photographic emulsion coating.
USSN 08/588,765 filed concurrently herewith discloses an invention that includes exposing a polyester support to an energetic treatment that produces amine groups on the surface of the polyester support, coating the treated support with a dilute solution of hardener/gelatin blend and appropriate solvent (e.g. water, or organic solvent), and drying the coated support. The gelatin grafted polyester support is then ready for photographic emulsion coating.
The present invention includes exposing a polyester support to an energetic treatment that produces carboxyl groups on the surface of the polyester support, coating the treated support with a dilute solution of hardener and appropriate solvent (e.g. water, or organic solvent), and drying the coated support. The hardener coated polyester support is then ready for photographic emulsion coating. The preferred hardeners include carboxyl reactive hardeners bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccinimides.
The present invention also includes exposing a polyester support to an energetic treatment that produces carboxyl groups on the surface of the polyester support, coating the treated support with a blend of carboxyl reactive hardener and gelatin in solvent (e.g. water, or organic solvent), and drying the coated support. The gelatin grafted support is then ready for emulsion coating. The preferred hardeners include carboxyl reactive hardeners bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccinimides.
The examples disclosed below are for plasma treated PEN (polyethylene naphthalate) coated with a dilute solution of bis(N-methyl-2-pyridylium tetrafluoroborate) ether (PD9) in water and then coated with a representative photographic emulsion. Additional examples discussed below are for plasma treated PEN coated with a dilute blend of PD9 and gelatin and then coated with a representative photographic emulsion.
The plasma treatments were carried out in a vacuum chamber equipped with a web drive. A controlled gas pressure was established in the electrode region of the chamber, and an AC high voltage was applied to the electrode. The polyester support was conveyed through the resulting plasma and was then wound onto a take-up spindle. The treated support was then removed from the chamber and was coated with a water/hardener solution or a water/hardener/gelatin solution. The aqueous coated polyester support was then conveyed through a drying region and wound onto a take-up spindle. A representative photographic emulsion was then coated onto the plasma treated, hardener coated polyester support.
Figure 1 shows the film element 10 produced by the process of the present invention. The film element 10 includes a polyester support 12. The polyester support is typically PEN or PET. A backing layer 14 for a variety of functions such as magnetic recording, antistatic protection, lubricity, antiabrasion, antihalation and the like can be included on the backside of the support 12. On the topside of the support 12 is grafted a monolayer 15 of hardener molecules subsequent to oxygen plasma treatment of the support or a gelatin grafted layer (hardener/gelatin blend) 15 subsequent to oxygen plasma treatment. A photographic emulsion layer 17 adheres to the hardener-containing layer 15. The present invention also includes the polyester support having either a monolayer of hardener molecules grafted to the support or a gelatin grafted layer formed from the reaction of hardener molecules with both the treated support and the gelatin.
While the examples are for oxygen plasma treatment to produce carboxyl groups on the support surface, a variety of methods can produce carboxyl groups on the surface of a polymer. For example electrical discharges and/or UV irradiation can be carried out in gases containing molecular oxygen or molecules having oxygen attached such as carbon dioxide, carbon monoxide, ozone, and the like.
For typical plasma conditions, pressures may be in the range of 0.02 to 2 Torr and plasma powers and web speeds may be set to deliver treatment doses from about 0.1 to 4.0 J/cm². In the examples presented below, the gas pressures ranged from 0.05 to 0.15 Torr; powers ranged from 150 to 600 watts, and the web speeds ranged from approximately 5.1 to 25.4 cm/s, yielding treatment doses in the range of 0.18 to 3.6 J/cm². For the hardener/water mixtures, hardener (PD9) concentrations ranged from 0.005 to 0.18% by weight. The hardener solution was delivered at a wet coverage of approximately 0.22 cc/dm², resulting in hardener levels of 0.011 to 0.39 mg/dm². The hardener/gelatin solution was delivered at wet coverages ranging from 0.054 cc/dm² to 0.43 cc/dm², to obtain respective hardener and gelatin dry coverages in the range 0.032 to 0.32 mg/dm² and 0.538 to 5.38 mg/dm². Saponin was added at a level of 0.01% by weight of solution in all cases. Other surfactants such as sodium alkylarylpolyether sulfonate or p-isononylphenoxypoly(glycidol) and the like could be used as well. The polyester support was dried at 93°C for 5 minutes as it passed through the coating apparatus.
The plasma treated PD9 coated polyester support was then coated with a representative photographic emulsion. The emulsion was coated 4 days after the PD9 or PD9/gelatin blend was coated. Samples were taken from this roll and incubated for 24 hours at 32°C and 50% relative humidity (32/50). Am additional set of samples was kept at 21 °C and 50% relative humidity for 10 days (21/50).
Both sets of samples were tested for wet adhesion in the presence of photoprocessing chemicals, using a wet abrasion test in Process C-41 (Kodak Flexicolor®) developer. In this wet abrasion test, a rubber pad 3 cm in diameter is weighted with 900 grams and rubbed back and forth across a scribe line in the emulsion. The rubbing is done for 100 cycles in the presence of the developer solution.
As can be seen from Table I, the hardener (PD9) coverage can be adjusted to give excellent adhesion for the samples kept in 32/50 conditions. The adhesion for samples kept at 21/50 conditions is not excellent, but it clearly improves with PD9 coverage. The plasma condition B referred to in Table I is as follows: oxygen plasma at a pressure of 0. 1 Torr, a power of 150 W, and a web speed of 8.5 cm/s. TABLE I

Run Plasma Condition PD9 Coverage (mg/dm²) Wet Adhesion 32/50 Keeping (% Fail) Wet Adhesion 21/50 Keeping (% Fail)

AI B 0.01 23 100

A2 B 0.07 0 77

A3 B 0.39 0 47
The data in Table II provides examples of sensitivity to keeping conditions (and treatment power) for runs made by coating the emulsion directly to the glow discharge treated support. In these comparative runs, the treatment gas was oxygen, the pressure was 0. 1 Torr, and the web speed was 8.5 cm/s. In addition to the examples provided in Table II, there were runs made using other treatment powers, pressures, and web speeds that showed even higher sensitivity to keeping conditions. In particular, coating under some treatment conditions exhibited 0 - 1 % removal in the wet adhesion tests when tested after 10 day keeping at 21°C and 50% relative humidity, but when the samples from the same coating events were incubated for 24 hours at 32°C and 50% relative humidity prior to testing, they exhibited 99% removal in the wet adhesion test.
Comparing Tables I and II, it is seen that the use of the PD9 layer (Table I) significantly improves the wet adhesion for samples kept in 32/50 conditions and reverses the effect seen with no hardener layer (Table II), where the 32/50 adhesion is poor. It is expected that more energetic oxygen glow-discharge conditions, coupled with shorter times between coating the PD9 and emulsion layers may improve the 21/50 adhesion performance. TABLE II

Run Plasma Power (Watts) Wet Adhesion 32/50 Keeping (% Fail) Wet Adhesion 21/50 Keeping (% Fail)

B1 50 99 100

B2 330 41 0

B3 600 15 0
In order to improve the performance (relative to Table I) and make the adhesion less sensitive to delay between coating hardener and emulsion, hardener/gelatin blends were explored. Hardener and gelatin were dissolved in water and were then coated onto treated support and dried. After four days, a representative photographic emulsion was coated on the gelatin grafted layer. Wet adhesion tests were then performed. This procedure was followed using PD9 as a hardener and oxygen as the treatment gas. Blends of PD9 and gelatin, coated on oxygen-treated PEN support gave results shown in Table III.

The plasma conditions listed in Table III are as follows. A: oxygen plasma at a pressure of 0.150 Torr, a power of 150 Watts, and a web speed of 25.4 cm/s; B: oxygen plasma at a pressure of 0.1 Torr, a power of 150 W, and a web speed of 8.5 cm/s; C: oxygen plasma at a pressure of 0.05 Torr, a power of 600 W, and a web speed of 5 cm/s.

TABLE III

Run	Plasma Condition	PD9/Gelatin ratio	Coated Solids (mg/dm²)	Wet Adhesion 32/50 Keeping (% Fail)	Wet Adhesion 21/50 Keeping (% Fail)
C1	A	0.06	0.57	100	94
C2	A	0.6	0.86	100	100
C3	B	0.06	3.1	0.3	37.7
C4	C	0.06	0.57	0	0
C5	C	0.6	0.86	0	0
C6	C	0.006	5.4	4	0
C7	C	0.06	5.7	0	1
C8	C	0.06*	0.57	0	0
C9	C	0.6*	0.86	0	0
C10	C	0.006*	5.4	24	81
C11	C	0.06*	5.7	10	100

*Examples C8 - C11 were made using acid processed pig skin gelatin (Type V). The other examples were made using alkali processed ossein gelatin (Type IV).

As can be seen from Table III, excellent wet adhesion is obtained for plasma condition C, with low coverage of PD9 and gelatin, for a wide range of PD9/gelatin ratio. Increased coverage or insufficient plasma treatment result in poor wet adhesion performance. The effect of increased coverage is particularly severe for Type V gelatin (examples C10 and C11).
As seen from Table III, preferred conditions are obtained from combinations of hardener to gelatin ratio, coated solids, and plasma treatment conditions within the limits disclosed herein. It is preferred to use combinations including plasma conditions from 0.18 to 3.6 J/cm², hardener/gelatin ratios from 0.006 to 0.6 and coated solids from 0.57 to 5.7 mg/dm². For example note that run C7 exhibited excellent adhesion performance, despite the high gelatin coverage. Apparently, the treatment conditions, hardener to gelatin ratio, and coverage are highly interactive to produce the desired adhesion. Although the above-described ranges are specifically shown in the Examples, the data suggests one skilled in the art can optimize these parameters over a larger range.
Although the present invention has been described in sufficient detail, it does not necessarily represent an optimized scenario. In particular, it may be possible to achieve the desired adhesion using carboxyl reactive hardeners (e.g. PD9) and appropriate plasma treatments (e.g., oxygen, carbon dioxide, etc.) and short delay times between coating the carboxyl reactive hardener and the emulsion. Furthermore, for the hardener/gelatin blends (to produce a gelatin grafted layer) appropriate adjustment of surfactant level and treatment process may result in the desired adhesion for different hardener/gelatin ratios and coverages, although a substantially wide range has been demonstrated above.
While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various alterations and modifications may be made therein without departing from the scope of the invention as defined by the appended claims. All such modifications are intended to be included in the present application.

Claims

A method of coating a polyester support comprising: passing a surface of the polyester support through an energetic treatment to produce carboxyl groups on the surface;
coating the surface of the polyester support with a carboxyl reactive hardener solution;

drying the hardener coated support; and

coating a photographic emulsion onto the hardener coated support.
A film element comprising:
a polyester substrate having a surface exposed to an energetic treatment producing carboxyl groups on the surface;

a coating of carboxyl reactive hardener selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccininides; and

a photographic emulsion applied to the coating of hardener.
A film base comprising:
a polyester substrate having a surface exposed to an energetic treatment producing carboxyl groups on the surface;

a coating of carboxyl reactive hardener selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiums, and alkylsulfonyloxysuccinimides grafted to the surface.
A method of coating a polyester support comprising:
passing a surface of the polyester support through an energetic treatment to produce carboxyl groups on the surface;

coating the surface of the polyester support with a solution containing a carboxyl reactive hardener and gelatin;

drying the hardener/gelatin coated support; and

coating a photographic emulsion onto the hardener/gelatin coated support.
A film element comprising:
a polyester substrate leaving a surface exposed to an energetic treatment producing carboxyl groups on the surface;

a coating of gelatin and carboxyl reactive hardener wherein the carboxyl reactive hardener selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccinimides; and

a photographic emulsion applied to the coating of gelatin and hardener.
A film base comprising:
a polyester substrate having a surface exposed to an energetic treatment producing carboxyl groups on the surface;

a coating of carboxyl reactive hardener and gelatin wherein the hardener is selected from the group consisting of bis(pyridylium)ethers, imidazolopyridinium compounds, pyrazolopyridinium compounds, carbamoylpyridinium compounds, carbamoyloxypyridinium compounds, chlorotriazines, succinimidyloxyformamidiniums, chloroformamidiniums, and alkylsulfonyloxysuccinimides.