Patent EP0355876A1 successfully refreshed from Google Patents.
EP0355876A1
Expired / Lapsed
EP
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Process for controlling the curl of photographic film
Assignee: Agfa Gevaert NV
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Filing: 1989-06-15
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Granted: —
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Expires: 2009-06-15
Abstract
Abstract A process of making biaxially oriented polyethylene terephthalate photographic film having a controlled amount of curl in the longitudinal direction, where the longitudinal stretching of the film is done while the film is asymmetrically heated across its thickness, and the stock roll of produced film is heat-tempered. The stock roll of film thus produced may further be longitudinally slit, cut and rewound on small cores in a direction in which the core-set curl opposes the longitudinal curl induced in the film during the longitudinal stretching.
Inventors
- 👤 Marc Petrus Stevens
- 👤 Gery Vancoppenolle
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 12:57
CPC Classifications
G; G03; G03C; G03C1/00; G03C1/76; G03C1/795; G03C1/7954; B; B29; B29C; B29C48/00; B29C48/03; B29C48/07; B29C48/08; B29C55/00; B29C55/02; B29C55/04; B29C55/06; B29C55/10; B29C55/12; B29C55/14; B29C61/00; B29C61/06; B29C71/00; B29C71/02; B29C35/00; B29C35/02; B29C35/08; B29C35/0805; B29C2035/0822; B29K; B29K2067/00; B29K2105/00; B29K2105/25; B29K2105/253; B29K2105/256
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
147 words
A process for making biaxially oriented photographic polyethylene terephthalate film having a controlled amount of longitudinal curl, comprising extruding molten polyethylene terephthalate polymer through a flat die onto a cooling drum, subjecting the film to molecular orientation by stretching the cooled film longitudinally and transversely while heating the film to a temperature above the Tg (glass transition temperature), the heating of the film during the longitudinal stretching occurring asymmetrically thereby to establish a temperature gradient across the thickness of the film and to introduce into the film a given amount of curl, then heat-setting the film, winding the film to a stock roll of film, and subjecting the film to a heat-tempering treatment by heating it for a period of about 0.1 to about 1500 hours at a temperature ranging from about 30°C up to the Tg and at an ambient relative humidity less than 100 %.
Claim 2
Dependent Claim
147 words
A process for making biaxially oriented photographic polyethylene terephthalate film having a controlled amount of longitudinal curl, comprising extruding molten polyethylene terephthalate polymer through a flat die onto a cooling drum, subjecting the film to molecular orientation by stretching the cooled film longitudinally and transversely while heating the film to a temperature above the Tg (glass transition temperature), the heating of the film during the longitudinal stretching occurring asymmetrically thereby to establish a temperature gradient across the thickness of the film and to introduce into the film a given amount of curl, then heat-setting the film, winding the film to a stock roll of film, and subjecting the film to a heat-tempering treatment by heating it for a period of about 0.1 to about 1500 hours at a temperature ranging from about 30°C up to the Tg and at an ambient relative humidity less than 100 %.
Claim 3
Dependent Claim
28 words
A process according to claim 1, wherein the film is heat-tempered during a period between 24 and 240 hours at a temperature ranging between 50° and 80 °C.
Claim 4
Dependent Claim
41 words
A process according to claim 1 or 2, wherein the temperature gradient across the film thickness during the longitudinal stretching is larger than 10°C, and that the longitudinal tension of the film during the longitudinal stretching is less than 10 N/sq.mm.
Claim 5
Dependent Claim
17 words
A process according to claim 1, 2 or 3, wherein the temperature gradient is larger than 15°C.
Claim 6
Dependent Claim
21 words
A process according to claim 3, wherein the longitudinal tension of the film during said stretching is less than 7 N/sq.mm.
Claim 7
Dependent Claim
38 words
A process according to any of claims 1 to 5, wherein the longitudinal stretch-heating of the film occurs by exposing one film side to medium wave IR-radiation and the opposite side of the film to short wave IR-radiation.
Claim 8
Dependent Claim
20 words
A process according to claim 6, wherein the medium wave IR-radiation produces the highest of the two film surface temperatures.
Claim 9
Dependent Claim
29 words
A process according to any of claims 1 to 7, wherein the longitudinally stretched film is cooled by the conveying of the film through a body of cooling liquid.
Claim 10
Dependent Claim
64 words
A process according to any of claims 1 to 8, wherein the heat-set film is heat-relaxed prior to the winding to a stock roll of film. 10. A process according to any of claims 1 to 9, wherein the heat-set film is wound to a roll with the film side that was subjected to the highest longitudinal stretching temperature, facing inwardly of the roll.
Claim 11
Dependent Claim
57 words
A process according to any of claims 1 to 10, comprising rewinding the stock roll of film on rolls of a diameter that is smaller than that of the stock roll of film and in a direction that causes a core-prone curl that is opposite to the curl which the film has obtained during the longitudinal stretching.
Claim 12
Dependent Claim
55 words
A process according to any of claims 1 to 11, comprising unwinding and coating the stock roll of film, slitting and cutting the film, and winding the different film strips thus obtained each separately onto small rolls, the film surface that was subjected to the highest longitudinal stretching temperature facing outwardly of the small rolls.
References Cited (Backward Citations)
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