Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/028—Layers in which after being exposed to heat patterns electrically conductive patterns are formed in the layers, e.g. for thermoxerography
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G13/00—Electrographic processes using a charge pattern
  • G03G13/04—Exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/913—Material designed to be responsive to temperature, light, moisture
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/3188—Next to cellulosic
  • Y10T428/31884—Regenerated or modified cellulose
  • Y10T428/31891—Where addition polymer is an ester or halide

Definitions

• ABSTRACT A method is disclosed of making an image on a layer, which comprises exposing a layer of polyethylene to infrared radiation in heat-conductive relation with a master to form a latent image, charging the layer with an electrostatic charge at a substantially later time to produce a charge image corresponding to the latent image, developing the charge image with a toner, and fusing the toner to said layer.
• a method of making an offset printing plate comprises exposing a layer of cellulose acetate to infrared radiation in heat-conductive relation with a master to form a latent image corresponding to the master, charging the layer electrostatically at a substantially later time to produce a charge image, developing the charge image by applying a toner, fusing the toner to said layer and saponifying the surface of said layer to render the non-image areas hydrophilic thereby forming a layer suitable for use as an offset printing plate.
• the present invention relates to an image-recording process by image-wise heat action on a resin coating which undergoes loss of specific electrical resistance under the influence of heat, in which the resin coating is exposed image-wise to heat, then electrostatically charged and the latent electrostatic image is made visible.
• the image is fixed by methodsknown in electrophotography.
• the image-wise action of heat on the resin coating can be effected in various ways, e.g., the coating is exposed image-wise to heat radiation by means of an optical system or it is contacted with a heated object having the form of the image or it is placed under a master and exposed to radiant heat so that the heat is absorbed primarily in the image parts of the master and transferred by conduction to the resin coating.
• the heat action can thus be effected either by a contact process or by absorption of rays in the resin coating.
• heated members of the usual type can be used, e.g., commercially available radiators. Where radiant heat is used for image-wise production of-heat, the temperature of these radiators is in the range of from about 400' to about 2,500C, preferably 1,500 2,000C. Also, heated stamps can be used.
• the resin coating is reduced to a temperature lower than that of the image-wise treatment.
• This can be done in various ways, e.g., by removal of the heat source so that the resin coating cools of its own accord to a lower temperature. Also, rapid cooling by the introduction of the coating into a refrigerating device gives good results.
• the coating is advantageously cooled to the initial starting temperature, i.e., the temperature it had before the heat treatment, but temperatures both higher and lower than this can be employed. In this way, a latent electrical resistance image, in which the image parts have lower electrical resistance than the image-free parts, is produced on the resin coating.
• Suitable resins for use in the invention are those in which the specific resistance under normal conditions is within the range of about 10 ohm-cm. to about 10" ohm-cm. and in which the specific resistance in the surface area in contact with infra-red absorbing image parts of the master is reduced by at least two powers of 10 under the influence of heat.
• the value of this reduced specific resistance is preferably under 10 to 10 ohm-cm.
• the suitability of a resin coating for the process of the invention may be ascertained, for example, as follows.
• the current flow resistance of the coating is evaluated as a function of temperature, whereupon it will be apparent whether there is adequate loss of resistance with increase in temperature.
• the loss in resistance of the resin coating that is applied to the support can, in the case of some resins, be improved by the addition of plasticizers to the resin tricresyl phosphate is for example suitable in the case of polystyrene so that there are very favorable resistance characteristics.
• a resin for the process of the invention can also be very simply assessed by the following test: A solution of the resin is poured upon a supporting material, e.g., a paper foil; the solvent is driven off in a current of air of moderate temperature; a master is placed on the coating and radiant heat is briefly beamed upon the master. The coating is then charged by a corona discharge and the charged coating is contacted with an electroscopic powder. If there is adequate differentiation in the resistance at the temperature employed, an image of the master will be obtained.
• a supporting material e.g., a paper foil
• the solvent is driven off in a current of air of moderate temperature
• a master is placed on the coating and radiant heat is briefly beamed upon the master.
• the coating is then charged by a corona discharge and the charged coating is contacted with an electroscopic powder. If there is adequate differentiation in the resistance at the temperature employed, an image of the master will be obtained.
• Resins which may be used in the invention under the conditions specified above include both synthetic and natural resins, e.g., polyolefins such as polyethylene, polyisobutylene, polypropylene and polybutylene, polyvinyl compounds such as polyvinyl chloride, chlorinated polyvinyl chloride, polyvinyl acetate, polystyrene particularly modified polystyrene interpolymers and polymer mixtures of the compounds already mentioned, polyesters such as polyterephthalic acid ester, cellulose esters such as cellulose acetate and cellulose propionate, maleinate resins, coumarone resins and ketone resins.
• polyolefins such as polyethylene, polyisobutylene, polypropylene and polybutylene
• polyvinyl compounds such as polyvinyl chloride, chlorinated polyvinyl chloride, polyvinyl acetate, polystyrene particularly modified polystyrene interpolymers and polymer mixtures of
• shellac for example, has properties which make the use thereof in the present invention particularly advantageous. Also, conversion products of natural resins, e.g., polymerized resins, are very suitable.
• the resins on which the resistance images are produced may be used as such, in self-supporting form, or they may be applied to a support, e.g., in known manner in the form of a melt or from solvents or in the form of dispersions.
• the thickness of the coated resin layer may vary within wide limits. For example, coatings of between 10 and 30 u may be applied. It is also possible for coatings that are thinner or thicker than this to be used. If it is desired for the resistance images to be made visible in the manner to be described below it is often advantageous for coatings of not less than 5 y. to be selected so that disruptive discharge will not occur when the electrostatic charge is applied.
• the supporting material many different substances are suitable, e.g., paper, plastics, metals, pottery, and glass. Foils made of these materials are used with particular advantage.
• the latent electrical resistance images described above can be converted into a visible image.
• the resistance images are charged by means of a corona discharge.
• the charge is retained in the parts that have not been heated, while in the heated parts, which have a considerably lower resistance, the charge leaks away, at least partially, so that an electrostatic image corresponding to the resistance image is obtained and which is converted in known manner, by being contacted with a finely divided pigmented resin or carbon black particles, into a visible image which can be fixed by heat or treatment with a solvent vapor.
• the resins are advantageously applied to supports which possess adequate electrical conductivity, e.g., foils or plates made of metal, glass plates of which the surface has been made electrically conductive, and paper, plates or foils made of electrically conductive, non-fibrous material (plastics, resins).
• Materials which possess adequate electrical conductivity for use in the present invention are those with a specific resistance of l ohm-cm. at the most.
• paper is used as a support for the coating which becomes conductive when heated, it is recommended that the paper he treated beforehand to prevent penetration of the coating solution, e.g., with methyl cellulose in aqueous solution or polyvinyl alcohol in aqueous solution or with a solution of an interpolymer of acrylic acid methyl ester and acrylonitrile in acetone and methyl-ethyl-ketone or with solutions of polyamides in aqueous alcohols.
• aqueous dispersions of materials suitable for the pretreatment of the paper surface can be used.
• the resin cellulose acetate is used on a waterresistant supporting material, after the processes already described of image-production and fixing of the image parts by heat treatment, the cellulose acetate can be superficially saponified in the image-free parts by means e.g., of alcoholic potassium hydroxide so that it is hydrophilic. Printing plates suitable for planographic printing are thus produced.
• the resin coating absorbs heat rays adequately.
• a material such as carbon black, which'abs'orbs infra-red rays, can be incorporated in the coating or a suitably absorbent coating can be placed in contact'therewith.
• the resin coating can, for example, be placed on infra-red absorbent supporting material, e.g., black pigmented paper.
• the resistance images obtained by the heat treatment can then be made visible by electrostatic charging and development with a white or otherwise pigmented resin powder.
• Colorless material can also be used if it is closely contacted with an infra-red absorbent substance during the irradiation with infra-red rays.
• the recording material may, for example, be run over a blackened roller while irradiation is performed or it can be brought, during this process, into close contact with a blackened film, e.g., a blackened silver film.
• EXAMPLE I A base paper with a weight of grams/sq. meter is coated by extrusion with polyethylene so that the coating thickness is about 15a and a master with text on one side only is placed on the polyethylene coating.
• the copying material arranged in this way is passed in close contact, at a speed of several meters a minute, past a focussed 1,350 watt infra-red radiator.
• a heat image is formed which is transferred to the polyethylene coating as a result of the close contact.
• the specific electrical resistance of the polyethylene coating drops and a resistance differentiation is obtained which corresponds to the image parts of the master.
• the polyethylene coating is positively charged, by means of a corona discharge, to a surface potential of about 300 volts above ground.
• the latent resistance image then changes into a latent charge image, which is negative with respect to the master, because the charge immediately leaks away in the low resistance parts produced by the transfer of the heat image. Only the unheated areas corresponding the image-free parts of the original retain the electrostatic charge.
• the electrostatic charge image, which is a negative of the original is made visible by means of a developer which may consist, for example, of parts by weight of glass balls ofa grain size of 300 400 p. and 2.5 parts by weight of a resin powder of a grain size of 20 50 M.
• the resin powder is obtained by melting together 30 parts by weight of polystyrene, 30 parts by weight of resin-modified maleic acid resin (Beckacite K and 3 parts by weight of carbon black (Peerless Black Russ 552), after which the melt is ground and screened.
• EXAMPLE ll A wax paper of a weight of 40 grams/sq. meter is mechanically coated on both sides with a solution of 10 parts by weight of polyvinyl chloride in 75 parts by volume of ethyl acetate. After the coating has dried, the reproduction material is placed upon a master, with text on one or both sides, and infra-red rays are beamed upon the side remote from the master. A resistance differentiation is obtained on the surface of the polyvinyl chloride coating which corresponds to the image parts of the master and which is adequately maintained for up to an hour, so that even after that period has elapsed, conversion into an electrostatic image, as described in detail in Example 1, is still possible. The charge image is made visible in known manner by dusting over with a pigmented resin powder.
• a cellulose acetate foil of a thickness of 30 [L is laminated to a paper of I40 grams/sq. meter that has been made water-resistant by treatment with melamine resin.
• the cellulose acetate coating is exposed under a film master to a brief intensive infra-red radiation.
• the latent image formed on the acetate coating is made visible if the acetate coating is positively charged, by means of a corona discharge, and the resultant charge image is developed with the developer made up of glass balls and resin powder described in Example 1. After the powder image has been fixed by brief heating, the
• the image-bearing acetate coating is wiped over with a methanol solution of potassium hydroxide obtained by dissolving 12 parts by weight of potassium hydroxide in 90 parts by volume of methanol, the solution then being made up with water to 150 parts by volume.
• the acetate film is saponified in the image-free parts by the methanolic potassium hydroxide while the image parts, consisting of the fixed resin powder, are unaffected.
• the imagefree parts are water receptive, in contradistinction to the image parts which can be linked up with greasy ink.
• This paper printing foil can be used for printing in a planographic apparatus.
• EXAMPLE IV A solution of 22 parts by weight of a maleinate resin, the resin having a softening temperature of 95 105C, in 200 parts by volume of ethyl alcohol is applied mechanically to a paper of a weight of 110 grams/sq. meter that has been precoated to prevent the penetration of organic solvents. After the coating has dried, the reproduction material is exposed behind a positive film master to brief irradiation with infrared. To make the latent image visible, the maleinate resin coating is positively charged by means of a corona discharge. The electrostatic charge is retained only in those parts of the reproduction coating that have not received heat from the original. A negative charge image of the original is obtained which is made visible by treatment with the developer made up of glass balls and a pigmented resin powder described in Example 1. Fixing of the powder image is effected by a brief treatment with trichloroethylene vapor.
• a method of making an image on a layer which comprises the steps of:
• a method of making an offset printing plate which comprises the steps of:

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Printing Methods (AREA)

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Citations (4)

• 0
  • BE BE611542D patent/BE611542A/xx unknown
  • NL NL272099D patent/NL272099A/xx unknown
• 1960
  • 1960-12-17 DE DEK42434A patent/DE1137449B/de active Pending
• 1961
  • 1961-11-06 US US3732418D patent/US3732418A/en not_active Expired - Lifetime
  • 1961-11-22 CH CH1357161A patent/CH408072A/de unknown
  • 1961-11-27 LU LU40875A patent/LU40875A1/xx unknown
  • 1961-12-11 GB GB4417161A patent/GB976100A/en not_active Expired
  • 1961-12-16 DK DK505561A patent/DK106497C/da active

Patent Citations (4)

Non-Patent Citations (1)

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