US3564597A - Thermographic recording process for reproducing continuous tone transparencies - Google Patents

Thermographic recording process for reproducing continuous tone transparencies Download PDF

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Publication number
US3564597A
US3564597A US608572A US3564597DA US3564597A US 3564597 A US3564597 A US 3564597A US 608572 A US608572 A US 608572A US 3564597D A US3564597D A US 3564597DA US 3564597 A US3564597 A US 3564597A
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heat
light
transparency
sensitive
screen
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US608572A
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English (en)
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Marcel Nicolas Vrancken
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Agfa Gevaert NV
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Agfa Gevaert NV
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/36—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties
    • B41M5/366—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties using materials comprising a polymeric matrix containing a polymeric particulate material, e.g. hydrophobic heat coalescing particles

Definitions

  • the present invention relates to a method of making screened reproductions from a continuous-tone transparency on heat-sensitive materials.
  • thermographic copying materials were only considered to be useful for the reproduction of documents and line work.
  • Continuous-tone work applies to originals, which besides black and white may also comprise the whole range of intermediate gray tones, as e.g. in silver image negatives of soft gradation.
  • Continuous-tone work can be reproduced on very contrasty silver halide emulsion layers known in the graphic art by use of a screening technique, which consists in printing the continuous-tone original together with a screen.
  • a screening technique two types of screens are commonly used viz. glass-screens and contact screens.
  • glass-screens glass-screens
  • contact screens contact screens
  • the contact screen On exposure the contact screen is placed in contact with the light-sensitive material. Due to the modulation of the continuous-tone transparency and the characteristics of the contact screen dots, the original is reproduced on a very contrasty copying material as a large number of very small dots the size of which is determined depending on the luminosity of the corresponding parts of the continuous-tone transparency.
  • a latent or visible screen image of a continuous tone transparency is produced by exposing to electromagnetic radiation, through such transparency and a screen, a heat-sensitive recording layer containing substance(s) which become(s) heated by the irradiation and consequently bring(s) about a physical and/or chemical change in the said layer, the exposure being for such brief time that heating sufficient to effect such change does not occur in any areas of such layers as a result of heat conduction from the material of the screen.
  • the radiation used may be infrared and/ or visible light radiation provided that the composition of the heat-sensitive layer is appropriately chosen.
  • heatsensitive layers which respond to such different types of irradiation we refer to the specifications filed in the published Dutch patent application 64/ 14226 filed Dec. 7, 1964 by Gevaert Photo-Producten N.V., the published Dutch patent application 66/06719 filed May 17, 1966 and in the published Dutch patent application 66/ 08711 filed June 23, 1966 both by Gevaert-Agfa N.V. which should be read in conjunction herewith.
  • the invention is particularly but not exclusively concerned with using heat-sensitive layers the composition of which undergoes a decrease in solubility in water when irradiated so that after image-wise irradiation the non irradiated areas can be washed away so that a relief image results.
  • the radiation source Provided that a high intensity radiation is emitted by the radiation source, it is easily possible to avoid heating of the heat-sensitive layer by heat conduction from the screen since the exposure time can be of such short duration that there is insuflicient time for such heat conduction to take place.
  • thermo-sensitive layer containing sufficiently light-absorbing substance(s) that convert that light into heat is subjected to a very short contact-exposure to light of very high intensity through a continuous-tone transparency in contact with a contact screen, a very sharp screened print of the continuous-tone transparency can be obtained due to the very locally internally produced heat in the said substance(s).
  • a too high absorption of light and corresponding too high production of heat in the screen dots of the contact screen and image areas of the original can be avoided by a high intensity very short exposure, particularly when forming a screen image of a continuous-tone transparency of rather low density and using a corresponding contact screen.
  • very sharp high density screened prints possessing the complete tone scale of the continuous-tone transparency can be obtained.
  • a normal density silver transparency can be reduced in density prior to being used by a conventional reducer solution. It is also recommendable to use a contact screen of which the silver dots are of less density than normal.
  • the copying light absorbed in the said light-absorbing substance (s) present internally in the thermo-sensitive layer produce therein the desired image differentiation based on a heat-induced and/ or promoted chemical and/ or physical change.
  • the maximum density in the dots of the contact-screen should not be substantially different from the maximum density of the transparency and is preferably equal thereto.
  • the maximum optical density of the continuous-tone transparency is comprised between 0.2 and 1.0.
  • composition of the heat-sensitive layer and the kind of physical and/ or chemical change obtained therein on heating determines whether a direct visible image or latent image developable by an after-treatment will be obtained.
  • heat-sensitive gelatin layers such as the heat-sensitive gelatin layers described in the published Dutch patent application 66/08711 filed June 23, 1966 by Gevaert-Agfa N.V., the exposed gelatin parts of which possess an increased water-permeability, water-solubility and swellability in water.
  • heat-sensitive recording layers of the gelatin type preferably contain at least 80% by weight of gelatin.
  • heat-sensitive layers are mainly cOmposed of polyvinyl alcohol and the heat-exposed parts of such layers show a decrease in water-solubility and waterpermeability in respect of the unexposed areas.
  • vinyl polymers containing at least 95% of vinyl alcohol units are suited.
  • hydrophilic colloid layers containing in a weight ratio of at least 1:1 in respect of the colloid dispersed particles of a hydrophobic thermoplastic polymer and showing in heated areas a decrease in water-permeability, hydrophility and watersolubility, as is disclosed in published Dutch patent application 64/14226 filed Dec. 7, 1964 by Gevaert Photo- Producten N.V. and published Dutch patent application 66/06719 filed May 17, 1966 by Gevaert-Agfa N.V.
  • the recording layer is preferably for at least 50% by Weight composed of the dispersion consisting of the said hydrophobic thermoplastic polymer particles in said colloid or hydrophilic binder.
  • the heat-sensitive recording layers for use in the recording process according to the present invention preferably adsorb at least 80% of the light passing through the sandwich of continuous-tone transparency and contact screen.
  • heat-sensitive materials of the type described in the latter published Dutch patent application 66/06719 filed May 17, 1966 by Gevaert-Agfa N.V. are used, such material preferably having a heat-sensitive layer wherein copying light-absorbing substances are dispersed in such an amount that an optical density of at least 1 is obtained.
  • Heat-sensitive materials on the basis of gelatin as de scribed in the published Dutch patent application 66/ 08711 filed June 23, 1966 by Gevaert-Agfa N.V. are suited for positive-positive printing, in other words for produc ing by a selective washing away of water-soluble portions a positive screen transparency of a positive continuoustone transparency, whereas heat-sensitive materials on the basis of a dispersion of latex particles, which are solid at room temperature in a hydrophilic colloid binder as described in the published Dutch patent application 66/ 06719 filed May 17, 1966 by Gevaert-Agfa N.V. are suited for negative-positive printing.
  • thermo-sensitive layer Substances absorbing infra-red light and visible light and which are suited for being incorporated into the thermo-sensitive layer as substances converting that light into heat are described, e.g., in published Dutch patent application 66/06719 filed May 17, 1966 and published Dutch patent application 66/08711 filed June 23, 1966 both by Gevaert-Agfa N.V.
  • visible light and infra-red absorbing substances we would particularly mention finely divided carbon black, graphite, prussian blue, oxides, sulphides or carbonates of heavy metals having an atomic weight between 45 and 210, such as manganese or lead sulphide or these heavy metals themselves in finely divided state e.g. silver, bismuth, lead, iron, cobalt and nickel.
  • the particle size of these substances preferably should not exceed 0.1,u.
  • the reproduction process of the present invention is not limited to the reproduction of black-and-white transparencies.
  • Monochromatic transparencies can be reproduced by using in the heatsensitive material substance(s) absorbing light corresponding to the colour of the original or light of a colour complementary to the colour of the original.
  • the heatsensitive material can be made sensitive to light of a limited range of wavelengths. This can be done by incorporating into the heat-sensitive layer coloured substances, which absorb light of a particular part of the visible spectrum and convert that light into heat. Examples of such layers and ingredients therefor are given in the published Dutch patent application 66/06719 filed May 17, 1966 by Gevaert-Agfa N.V. wherein spectrally sensitized heat-sensitive layers are described for recording coloured originals in terms of differences in water-solubility and swelling tendency.
  • mixtures of said coloured substances can be used too, so that light of the whole visible spectrum is absorbed.
  • the said substances have not necessarily to absorb in the range of the visible spectrum alone, they may also absorb infrared light to a more or less extent.
  • the coloured substance or mixtures of said substances converting light into heat and optically sensitizing the heat-sensitive materials are preferably light-absorbing corresponding to at least one of the primary colours (red, green, blue) or subtractive colours (cyan, magenta, yellow).
  • Substances that absorb visible light of a part of the visible spectrum and wherein absorbed light energy is converted into heat are e.g. dyes belonging to the classes of the azo dyes, the triarylmethane dyes, the xanthene dyes, the acridine dyes, the methine dyes, the azine dyes, the phthalocyanine dyes, the anthraquinone dyes and allied dyes. Said dyes can be used in dispersed as well as in dissolved form.
  • a preferred recording material in that respect comprises a heat-sensitive recording layer that incorporates thermoplastic hydrophobic polymer particles which are solid at room temperature and are dispersed in a weight ratio of at least 1:1 in a water-soluble binder.
  • the recording layer is coated on an interlayer or self-supporting sheet which is composed of or comprises hydrophobic substance(s) having a melting or softening point lower than, equal to, or not substantially higher than that of the hydrophobic thermoplastic particles present in the recording layer.
  • a heat-sensitive recording material as just described and comprising an interlayer which contains such hydrophobic substances dispersed in a hydrophilic binder which is less soluble in water than the hydrophilic binder of the recording layer.
  • poly-N-vinylpyrrolidone may be used as binder for the recording layer and gelatin as binder for the interlayer or self-supporting. sheet.
  • Continuous-tone transparencies which are specially suited for being reproduced according to the present invention by means of recording materials described in published Dutch patent application 66/06719 filed May 17, 1966 and published Dutch patent application 66/ 08711 filed June 23, 1966 both by Gevaert-Agfa N.V. have a maximum optical density not exceeding 0.5.
  • the exposure time preferably does not exceed 10- sec.
  • Suitable radiation sources producing copying light of high intensity in a very small lapse of time and which are very suited for use in processes according to the present invention are the so-called flash lamps.
  • Good results are obtained with xenon gas discharge lamps, Which can supply a light energy of 100 to 1000 watts sec. in a time interval of l to seconds.
  • These flash lamps emit a greater part of energy as visible light together with infra-red light. Details about a copying apparatus containing such a discharge lamp can be found in Belgian patent specification 664,868 filed June 3, 1965 by Agfa-Gevaert AG.
  • gas discharge lamps with a much lower energy output can be used if the emitted energy is focused onto a relatively small heat-sensitive area.
  • a gas discharge lamp with an energy output of 40 watt sec. is suited for copying 6 cm. x 6 cm. and 6 cm. x 9 cm. originals onto heat-sensitive materials as described in published Dutch patent application 66/06719 filed May 17, 1966 by Gevaert-Agfa N.V.
  • a light energy of 0.3 watt sec. per sq. cm. will suffice for the desired image-differentiation. It is further self-explanatory that exposure may be performed progressively and/or intermittently.
  • the recording material may be scanning-wise exposed, e.g. by a high-intensity light spot rapidly line-wise scanning the recording material, or may be progressively exposed through a slot wherein, e.g., light of a tube-like radiation source is focused.
  • the heat-sensitive material before or during the creation of the image-wise heat difierentiation, can if desired be subjected to overall heating to a certain temperature below the temperature of image differentiation in the heat-sensitive material.
  • EXAMPLE 1 A poly(ethylene terephthalate) support of 0.1 mm. thickness provided with a subbing layer is coated with the following composition pro rata of 30 g./sq. m.:
  • the material After drying, the material possesses an optical density of 3.5 measured by transmittance.
  • the material is exposed as schematically represented in FIG. 1, to a xenon gas discharge lamp having a capacity of 1000 watt sec.
  • element No. 1 represents the transparent support of a continuous-tone transparency of which the element 2 is the image-bearing layer.
  • Element No. 3 represents the transparent support of a contact screen and element No. 4 represents the layer containing the contact screen dots.
  • Element No. 5 represents the heat-sensitive layer containing the substances absorbing copying light and thermoplastic polymer particles and element No. 6 represents a transparent support for that layer.
  • the material After exposure, whereby the exposed areas are rendered relatively water-insoluble, the material is dipped into water and gently rubbed with a cotton pad. The heatsensitive layer is removed in the non-exposed areas.
  • a positive very true image of the continuous-tone transparency is obtained consisting of tiny dots with an equal optical density varying in diameter.
  • EXAMPLE 2 A paper support weighing g./ sq. m. provided with a baryta coating is covered pro rata of 50 g./sq. m. with the following composition:
  • Example 1 10% aqueous dispersion of gelatin 200 10% aqueous dispersion of colloidal silver 600 40% dispersion of polyethylene as described in Example 1 240 3% aqueous solution of the sodium salt of the condensation product of oleic acid and methyltaurine 40 10% aqueous solution of saponin 40 When dried, the material is exposed as described in Example 1.
  • the material is dipped in a conventional silver-bleaching bath.
  • a positive high density screen image of the negative continuous-tone transparency is obtained.
  • EXAMPLE 3 A cellulose triacetate support of 0.14 mm. thickness provided with a gelatin subbing layer is coated with the following composition:
  • the material When dried, the material is exposed as schematically represented in FIG. 2.
  • the same continuous-tone transparency is used as described in Example 1, but the material is non-differentially preheated to 70 C.
  • the element No. 1 represents the transparent support of a continuous-tone silver image transparency and element No. 2 the layer containing the silver image.
  • Element No. 3 represents the transparent support of a magenta contact screen and element No. 4 the layer containing the screen dots.
  • Element No. 5 represents the heatsensitive layer and element No. 6 the transparent support therefor.
  • Element No. 7 is a heating jacket and element No. 8 the flash exposure lamp, which is a xenon gas discharge lamp producing light with an intensity of 1000 Watt. sec. in V3000 sec.
  • the elements No. 9 are the electrodes of that lamp.
  • the elements 1 to 7 are concentrically arranged around the flash exposure lamp, the axis of which is situated at a distance of 4 cm. from the continuous-tone transparency.
  • the recording material After exposure, the recording material is dipped in water of 20 C. and gently rubbed with a wadding of cotton. The portions of the heat-sensitive layer corresponding with the non-exposed areas are removed.
  • a positive magenta screen image of the negative continuous-tone transparency is obtained.
  • EXAMPLE 4 A cellulose triacetate support of 0.12 mm. thickness provided with a subbing layer for gelatin is coated with the following composition pro rata of 50 g./sq. m.:
  • Example 1 % aqueous solution of sodium-tetradecylsulphate The layer is dried at 20 C.
  • the copying material thus obtained is exposed as described in Example 1 but through a positive transparency having a maximum density of 0.3 and a silver-contact screen having a maximum density of 0.3. After exposure, the material is dipped into water of 20 C. and gently rubbed. The heat-sensitive layer is removed in the exposed areas.
  • a process of reproducing information which comprises the steps of contact exposing to visible light through a continuous tone transparency to be reproduced having a maximum optical density between about 0.2 and 1.0 and a contact screen having a maximum optical density not greater than that of said transparency, a normally waterremovble heat-sensitive recording layer adapted to undergo a loss in water-removability upon heating, said layer comprising particles of at least on hydrophobic thermoplastic polymer dispersed in a film of a hydrophilic binder in a ratio of at least 1:1 by weight and containing uniformly distributed therethrough finely-divided material absorbing such radiation and converting the same into heat in sufficient amount that the layer absorbs at least 80% of the copying light impinged thereon, said exposure being of a time not exceeding one-tenth of a second and of such intensity as to produce in a screen dot pattern of exposed regions of said recording layer sufficient heat through the absorption thereby by said finely-divided material to render said dot pattern water-insoluble but not such as to significantly reduce the water-re
  • hydrophilic binder is a water-soluble polymer.
  • water-soluble polymer is poly(N-vinylpyrrolidone) or gelatin.
  • the recording layer mainly contains a polyvinyl polymer containing at least by weight of vinyl alcohol units.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
US608572A 1966-01-11 1967-01-11 Thermographic recording process for reproducing continuous tone transparencies Expired - Lifetime US3564597A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0351/66A GB1177482A (en) 1966-01-11 1966-01-11 Improvements relating to Thermographic Recording.

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US3564597A true US3564597A (en) 1971-02-16

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US (1) US3564597A (fr)
BE (1) BE692423A (fr)
CH (1) CH469571A (fr)
DE (1) DE1671515A1 (fr)
FR (1) FR1507875A (fr)
GB (1) GB1177482A (fr)
NL (1) NL6700358A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3737662A (en) * 1970-07-08 1973-06-05 Fuji Photo Film Co Ltd Heat-sensitive copying device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4264986A (en) * 1979-03-12 1981-04-28 Willis Craig I Information-recording process & apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3737662A (en) * 1970-07-08 1973-06-05 Fuji Photo Film Co Ltd Heat-sensitive copying device

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Publication number Publication date
CH469571A (de) 1969-03-15
BE692423A (fr) 1967-07-11
FR1507875A (fr) 1967-12-29
NL6700358A (fr) 1967-06-26
DE1671515A1 (de) 1970-11-05
GB1177482A (en) 1970-01-14

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