Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Structurally defined
Reexamination Certificate
2002-12-20
2004-09-28
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Structurally defined
C430S533000, C264S173150, C264S173160, C264S210700, C428S480000
Reexamination Certificate
active
06797458
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a photographic polyester multilayer film base having improved properties. The multilayer film base comprises PET-based polyester materials with a specified relationship between the level of monomeric units derived from 1,4-cyclohexane dimethanol (CHDM) in a first layer and the level of 1,4-cyclohexanedimethanol in the other layers of the multilayer film base such that a specified cutting-related property is obtained.
BACKGROUND OF THE INVENTION
Silver-halide photographic elements comprise one or more light-sensitive layers coated on a support. Typically the support comprises a sheet of a transparent or translucent film, commonly referred to as a film base. Other layers, such as backing or subbing layers, may be laminated onto either side of the film base. Common film-base materials for photographic elements are cellulose triacetate (CTA) and poly(ethylene terephthalate) (PET). More recently it has been proposed to use poly(ethylene naphthalate) (PEN) as a film base for photographic elements which are intended to be used in a cartridge of reduced diameter which requires rolling the film more tightly than previously.
CTA has generally a good mix of physical properties for various types of photographic films. However, its manufacturing process involves high levels of gaseous emissions, and it is relatively costly. The manufacturing process for PET, on the other hand, is environmentally benign Poly(ethylene terephthalate) (PET) films exhibit excellent properties for use as photographic film base with regard to transparency, dimensional stability, mechanical strength, resistance to thermal deformation. However, compared to CTA, PET films are extremely tough and, therefore, not well suited for finishing operations, i.e., slitting, chopping and/or perforating processes, which are required in the manufacture or preparation of photographic films. Moreover, such films are difficult to cut in various steps of the photofinishing process such as splicing, notching, and sleeving. This is one of the reasons that PET materials have been considered unusable as a film base in certain consumer photographic film applications, such as 35 mm film, especially consumer films requiring non-centralized external processing or minilab processing where finishing must be easily handled. PET materials are presently used in photographic films in which less decentralized processing is not required, for example, X-ray films, motion picture films, and graphic arts films. With respect to the latter types of films, adjustments to processing can be more easily made to handle cutting and the like. The process for making a polyester-based photographic film base typically comprises the steps of casting a molten polyester resin in a machine direction onto a casting surface to form a continuous sheet, drafting the sheet by stretching in the machine direction, tendering the sheet by stretching in the transverse direction, heat-setting the drafted and tentered sheet, and cooling the heat-set sheet to form a stretched, heat-set film, such as described in, e.g., U.S. Pat. No. 4,141,735, the disclosure of which is incorporated by reference herein. U.S. Pat. Nos. 5,385,704 and 5,607,826 disclose a method for improving the finishing characteristics of photographic materials employing a PET film base involving lowering the planar birefringence of the film base to below 0.150 by performing a detentering step which allows the tentered film to shrink in width by 2 to 20% (pref. 10-18%) after the heat-setting step during film manufacturing. Improvement in finishing characteristics of PET-based photographic film, as manifested by decrease in dirt and debris generated during finishing operations, is also disclosed in U.S. Pat. No. 6,228,569 and U.S. Ser. No. 09/223,876 hereby incorporated by reference in their entirety. These latter inventions disclose a method utilizing relatively high heat-set temperatures (>220° C.) applied during the film manufacturing process, which substantially improves the finishing and cutting characteristics of PET-based photographic supports. However, even with the demonstrated improvements in finishability, the PET-based film is still difficult to cut in various steps of the photofinishing process.
Another general problem with PET film is its tendency to take up high levels of curl during storage in cartridges at high temperatures and its inability to sufficiently lower this curl during photoprocessing as commonly exhibited by CTA-based photographic films. A solution to the latter problem was proposed in U.S. Pat. No. 5,556,739 to Nakanishi et al, U.S. Pat. No. 5,387,501 to Yajima et al., and U.S. Pat. No. 5,288,601 to Greener et al. in which multilayered supports comprise polyesters modified by sulfonate and other hydrophilic moieties that facilitate, in wet processing, recovery of curl imposed on the film during storage in a cartridge. Another general approach to lowering the tendency of a polyester film base to take up curl (core-set) during storage is through annealing at elevated temperature and/or by raising the glass transition temperature (Tg) of the polyester.
U.S. Pat. No. 3,326,689 to Murayama discloses glow discharge treatment for improved curl of a film base made from a polyester material, preferably a PEN material. In one case, the polyester material comprises a PET-type material in which 25 mol % of the glycol component repeat units are derived from CHDM. U.S. Pat. No. 5,294, 473 to Kawamoto similarly discloses a PET polyester film base in which 25 mol % of the glycol component repeat units are derived from CHDM, with improved (reduced) curl.
U.S. Pat. No. 5,925,507 to Massa et al. discloses a PET film-base material having less tendency to core set, comprising polyester containing at least 30 weight % 1,4-cyclohexane dimethanol (CHDM), which polyester is blended with a polycarbonate that contains bisphenol. U.S. Pat. No. 4,141,735 to Schrader et al. discloses a polyester film base having improved core-set curl, involving the use of heat tempering, in one example using poly(1,4-cyclohexylene dimethylene terephthalate). However, this polymer crystallizes rapidly, therefore the making of its oriented film is difficult. Also, the polymer becomes opaque or hazy and useless for photographic applications where transparency is required.
The use of high heat-set temperature during the film-base manufacturing process has also been used to improve the finishability of PET-based photographic film. However, even with the demonstrated improvements in finishability, the PET-based film is still difficult to cut in various steps of the photofinishing process. U.S. Pat. No. 5,034,263 to Maier et al. disclosed a laminated film comprising a poly(ethylene terephthalate) core and, on at least one surface thereof, an overcoat of a poly(1,4-cyclohexylene dimethylene terephthalate) polyester, in order to allow the laminated film to be readily slit and perforated using techniques commonly employed with consumer film. Maier et al. states that the CHDM component should comprise at least 70 mol % of the glycol component of the polyester. However, such laminates have been found prone to delamination.
The blending or copolymerizing of conventional polyester with other polyester constituents (polymers or comonomers), in order to improve the cutting performance of a film, has also been proposed for PEN-based polyester films, as disclosed in U.S. Pat. No. 6,232,054 B1 to Okutu et al. However, PEN is generally considerably more costly and more difficult to manufacture than PET, so a clear need exists for improving the cuttability of PET-based polyester supports.
Outside the photographic field, poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) are common commercial semicrystalline polyesters, which are widely used for packaging applications due to the combination of desirable properties that they possess. The high oxygen barrier properties of these polyesters render them particularly valuable for packaging oxygen-sensitive food and other goods and mat
Greener Jehuda
Lai Yeh-Hung
Massa Dennis J.
Rao YuanQiao
Eastman Kodak Company
Konkel Chris P.
Schilling Richard L.
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