35mm format transparencies

Details 35mm format transparencies 35mm format transparencies

1995-05-16

1997-09-23

Hess, Bruce H.

Record receiver having plural interactive leaves or a colorless

Having plural interactive leaves

401592, 428 13, 428195, 428210, 428913, 428914, B41M 5035, B41M 538

Patent

active

056704470

DESCRIPTION:

BRIEF SUMMARY
This invention relates to 35 mm format "transparencies" which can, in well known manner, be used in a projector to provide a magnified version of an image stored on the transparency.
Conventionally such transparencies are produced photographically and hence consist of a transparent substrate having thereon a gelatin coating containing light sensitive chemicals in which the image is formed by exposure to light in a camera and then treatment by suitable developing techniques.
Such transparencies are relatively delicate physically and are easily scratched. It is common practice, therefore, to place the actual transparency between two sheets of glass for protection.
However, under certain conditions, this can produce a disadvantageous side effect.
Both gelatin and cellulose triacetate (the base film most commonly used for photographic film) are hygroscopic and, therefore, have an equilibrium water content which depends on the relative humidity and the temperature at which they are stored. (Gelatin/silver halide emulsion combinations are about ten times more hygroscopic than cellulose triacetate). What is more, the level of moisture in a photographic film needs to be controlled to give optimum film properties. Levels that are too low lead to problems with film brittleness, curl, static and dimensional changes and levels that are too high lead to tackiness of the film and can lead to ferrotyping problems.
When the transparency is placed in a projector a portion of the light transmitted through the transparency to form the magnified image is absorbed by the transparency image. The transparency, therefore is heated more rapidly than the glass and a temperature gradient is produced at the interface between the transparency and the glass. The moisture present in the gelatin can condense out and cause fogging or distortion of the projected image until temperature equilibrium between the transparency and the glass is reached. Clearly, the greater the initial temperature gradient, the more pronounced the effect is likely to be.
It is an object of this invention to obviate this effect.
According to one aspect of the invention, there is provided a 35 mm format transparency comprising a transparent substrate having an image on one surface thereof and positioned between two transparent protective layers, characterised in that the transparent substrate and the image layer consist of materials having, in combination, a moisture absorption of less than 1.5%
Preferably, the moisture absorption is less than 1%.
According to a preferred aspect of the invention, the transparent substrate and image layer together comprise a dye diffusion thermal transfer receiver sheet, in which the image is formed by dye diffusion thermal transfer techniques.
Dye diffusion thermal transfer is a generic term for processes in which one or more thermally transferable dyes are caused to transfer from a dye sheet to a receiver sheet in response to thermal stimuli. Using a dye sheet comprising a thin substrate supporting a dye coat containing one or more such dyes uniformly spread over an entire printing area of the dye sheet, image production can be effected by heating selected discrete areas of the dye sheet while the dye sheet is in contact with a receiver sheet, thereby causing dye to transfer to corresponding areas of that receiver sheet. Full colour, high resolution photographic quality images can be produced by using different coloured dye coats sequentially in like manner and appropriate equipment, such as a progammable thermal print head or laser controlled by electronic signals derived from, for example a video camera or similar signal generating apparatus. The resolution is particularly high if a laser is used and in practice such a heat source is preferred for 35 mm transparency preparation.
A typical receiver sheet consists of a substrate, supporting a receiver coat of a dye receptive composition containing a material highly receptive to the dyes being transferred and containing additives to promote the release of the dye sheet from the re

REFERENCES:
patent: 4910188 (1990-03-01), Akada et al.
patent: 5322832 (1994-06-01), Takeyama et al.
Derwent Publication JP-A-2049239 Feb. 1990.

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