Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
2001-12-21
2003-04-29
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S533000
Reexamination Certificate
active
06555303
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polyester photographic film base having improved properties and to a method of preparing the same. More particularly, the invention relates to a poly(ethylene terephthalate)-based photographic film base having improved properties with regard to slitting, perforating and other finishing or cutting operations. The film base comprises a material in which a specified amount of monomeric units derived from 1,4-cyclohexane dimethanol (CHDM), such that the film base has a specified cutting-related property.
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 mini-lab 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.
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. 5,326,689 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 valuable commercial semicrystalline polyesters, which are widely used for packaging materials 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 materials. PEN has advantages over PET due to its higher Tg and higher oxygen barrier properties, although PEN, as mentioned above, is considerably more costly and is somewhat harder to process than PET.
The toughness and cutting difficulty of PET and similar polyesters is generally attributed to the crystal structure and molecular orientation of the film. It is known that changes in these factors, driven either by formulary changes or by modified process conditions, can be used to lower the toughness and improve the cutting performance of PET. Generally, the crystallinity of PET can be lowered or altogether eliminated by adding suitable crystallization modifiers. Crystallization modifiers like isophthalic acid (IPA) and 1,4-cyclohexane dimethanol (CHDM) are often copolymerized into PET and PEN polyesters to form copolyesters that have better processing properties. Modest levels of IPA slow down crystallization and raise the oxygen barrier properties. Higher levels of IPA break up crystallinity and lead to amorphous copolyesters with good barrier properties, but these copolyesters, are known to those skilled in the art, to possess poor impact and other mechanical properties. Modest levels of CHDM also slow down crystallization, but decrease oxygen barrier properties. Higher levels of CHDM are well known to form families of amorphous copolyesters, which are widely used in commerce in a multitude of applications including heavy gauge sheet, signage, medical packages, etc. These copolyesters have excellent impact resistance and other mech
Greener Jehuda
Lai Yeh-Hung
Rao Yuanqiao
Eastman Kodak Company
Konkol Chris P.
Schilling Richard L.
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