CA1062532A - Fixing of toner images on thermo-adhesive layers - Google Patents

Abstract

Abstract of the disclosure A process for obtaining a fixed toner image on a sheet or web material comprising the steps of image-wise depositing toner particles on a thermo-adhesive fixing layer that itself permanently adheres to a support and heating said material carrying the toner image in such a degree that softening of the thermo-adhesive fixing layer takes place without reaching a temperature at which permanent deformation of the support occurs, wherein the support is a thermoplastic resin support whose glass transition temperature (Tg) is higher than the glass transition temperature (Tg) of the thermoplastic polymer or polymer composition of the thermo-adhesive layer and the toner particles comprise at least 10 % by weight of a polymer or polymer composition whose glass transition temperature (Tg) is at least 10°C higher than that of the thermoplastic polymer or polymer composition of the thermo-adhesive fixing layer.

Description

~06Z532 ~his invention relates to a combination of materials suitable for producing fixed toner images and to a method for the production of fixed toner images.
Electrophotography and electrography are well-known imaging technigues wherein electrostatic charge patterns are made visible with finely divided electrostatically attractable material called "toner".
Historically, a one-component dry powder toner was first used for developing electrostatic images. Other development processes presently known as cascade, fur brush, powder cloud, magnetic brush and liquid electrophoretic development were introduced. A survey and description of these processes is given e.g. by R.M. ~chaffert, ~he Focal Press, London and ~ew York (1965)~ In the same book a variety of electrophoto-graphic, electrographic and magnetic printing processes using toner development is described.
Many of the powdered toners used in xerography consist primarily of fusible resins. When such toners are deposited or transferred to a receptor paper sheet, the toner images can be permanently fixed by heating or by applying a solvent vapour, which partially dissolves the toner and causes it to fuse into the paper.
Developers of the electrophoretic type initially com-prised basically a simple dispersion of a pigment and no binder was present. It was later proposed e.g. by Metcalfe and Wright, Journal of Oil and Colour Chemists'Association, GV.819 PCT - 1 -~ 6Z53Z
39 (1956) pages 851-853, to use liquid developers incorporating a resin. ~he resultant images are then made of so-called "self-fixing" toners.
Electrophoretically formed toner images using a liquid comprising dispersed toner particles are fixed by adhesion and absorption into paper supports and usually do not reguire additional fixing on said supports.
A problem of permanent adherence arises, however, when electrophoretlcally deposited toner particles have to be adhered to smooth non-porous supports e.g. resin, metal or glass supports.
Even self-fixing toners are still not sufficiently per-manently adhering to smooth surfaces and therefore the resul-tant toner images have to be fixed by a subseguent procedure.
One use~ul procedure for subsequent fixing of toner images is by the application of a lacquer overcoat. Various pro-cedures have been suggested for applying such a lacquer over-coat. In practice the lacquer is usually applied by spraying a resin solution on the toner image. Another method has been to apply the resin solution with an applicator roller.
~he applicator roller system has the disadvantage that the resin solution is exposed to the air, which causes drying of the solution.
The spraying technique requires a propellant gas or air under pressure, which makes the apparatus rather sophisticated.
In addition thereto the spray nozzle is blocked when the GV.819 E~ - 2 -~Z532 apparatus is out of run.
Further it has been suggested that a transparent sheet be laminated over the toner images. When carefully done the protection of the image is excellent but the image is often damaged during the application of the protective material.
From the United Kingdom Patent 1,149,265 a method for fixing photoelectrophoretic toner images is known in which the photo-electrophoretically formed particle image is embed-ded in a thermo-adhesive layer while the thermo-adhesive layer is in an adhesive state, and following the embedding the thermo-adhesive layer is returned to its non-adhesive state.

~he photoelectrophoretic toner particles are pigments that are free from resin and have a fairly high melting point.
When the support of the toner image is a resin sheet or fllm a strong heating in order to fix the toner image will result in the shrinking or wrinkling of the support. ~his is particularly disadvantageous in machine processing because materials that are liable to shrink or wrinkle may yield choking or jamming in the machine during their transport.

Because of their transparency thermoplastic resin supports such as polyester resin supports are particularly useful in ob-taining electrographic or electrophotographic transparencies.U~ng such supports one should take care that in the heat-fixing of the toner image the temperature be not surpassed at which permanent deformation of the support occurs.

GV.819 PC~ - 3 -~6Z53Z
It is an object of the presen-t invention to provide a combination of materials suitable for producing by heating fixed toner images on a thermoplastic resin support without causing permanent deformation of said support.
It has been found that a particularly well fixed toner image on a sheet or web material is obtained in a process comprising the steps of image-wise depositing toner particles on a thermo-adhesive fixing layer that itself is permanently adhering to a support and heating the material carrying the toner image to such a degree that softening of the thermo-adhesive fixing layer takes place without reaching a temperature at which permanent deformation of the support occurs, characterized thereby,that the support is a thermoplastic resin support whose glass transition temperature is higher than the glass transition temperature of the thermo-plastic polymer or polymer composition of the thermo-adhesive layer, and the toner particles comprise at least 10 % by weight of a polymer or polymer composition whose glass transition temperature is at least 10C higher than that of the thermoplastic polymer or polymer composition of the thermo-adhesive fixing layer.
~ he definition of "glass transition temperature" (Tg) and practical tests for its determination are given e.g. by D.H.
Solomon in ~he Chemistry of Organic Film Formers, John Wiley &
Sons, Inc. New York (1967) p.26-27 a~d by F.W. Billmeyer, Jr.
in the ~extbook of Polymer Chemistry (1957) p.40-44. ~he specific ~g valuesm~ntioned in the present description are GV.819 PC~ _ 4 _ measured by constan-t heating stream thermal analysis (see E.
~teffens, J.Appl.Pol.Sci., 12, 2317-2324 (1968).
'~he '~g of a polymer is related to its chemical composition, molecular weight,crystallinity, and degree of cross-linking.
The glass transition temperature of a copolymer is inter-mediate between those of the two homopolymers.
An alternative method of modifying the Tg is to add a low molecular weight compound as a plasticizer for the polymer.
'~herefore, when speaking of "thermoplastic polymer or polymer composition" such wording includes according to the present in-vention a mixture of a thermoplastic polymer or of a polymer composition comprising (a) plasticizing agent(s) that modifies or modify the 'lg of the polymer or polymer compositions for the toner fixing purposes of the present invention.
According to a preferred embodiment of the present invention the '~g of the polymer or polymer composition of the thermo-adhesive fixing layer is at least 30C and preferably below 60C and the 'lg of the resin support at least 60C e.g.
between 60 and 85C.
'~he polymer(s) of the thermo-adhesive fixing layer and the polymer(s) of the toner have not to be compatible,in other words have not to form a solid solution after melting together.
'~he thickness of the thermo-adhesive layer is not critical and can be adapted according to the desired result. Preferably, however, the thickness is in the range of 2 to 20 ~m.
The thermo-adhesive fixing layer for use according to the present invention preferably comprises one of the polymers GV.819 PC'l - 5 -~062532 listed with their ~g in the following ~able 1.
~able 1 ~ ~ C
B 1. PICCOLAS~IC A 75 (trade name of Pennsylvania Ind. 33 Chem.Corp., Clairton, Penn. U.S.A. for a plasticized polystyrene)

2. PICCOVAR ~ 60 (trade name of Pennsylvania Ind.Chem. 32 Corp., Clairton, Penn. U.S.A. for an alkyl-aromatic polymer)

3. LEMAC 541-10 (trade name of Borden Comp., New York, 38 N.Y. U.S.A. for a copo]ymer of vinyl acetate and crotonic acid having the following structure :

2 ~
co L COOH J

_ x x : 96.3 % by weight y : 3.7 % by weight

4. NEOCRYL~ 707 (trade name of Polyvinyl Chemie 30 Holland, Waalwijk, Netherlands for a copolymer of vinyltoluene-isobutyl methacrylate-acrylic acid-stearate having the following structure :

~ E12-CE~ ~ E2 ~ H2-CE - ~ tearat n = 70-75 % by weight m = 21 % by weight p = 0.3 % by weight q = 5 to 10 % by weight t~le ~k GV.819 PC~ - 6 -~ ~;Z53Z

5. CVP E 041 (trade name of Cray Valley Prod/Ltd., ~5 3L3 St.Mary, Orpington, Kent, U.K. for a copolymer of styrene-vinyl acetate-ethyl acrylate-acrylic acid and having the following structure :

CH2-CH ~ FH2-cH -~ h LCH2-CH-- ~ H2 CH
L ~ ~ O-CO-CH3~ L cooc2H5~ L COOH ~

x = 30 % by weight y = 25 % by weight z = 44 % by weight m = 1 yo by weight

6. ACRONAL 500 L (trade name of BASF - Ludwigshafen, 24 W.Germany for a 55 % by weight solution of poly-acrylate containing a plasticizing agent)

7. I ~ SGA (trade name of SO~VAY-Belgium for a 47 copolymer of vinyl chloride-vinylidene chloride-maleic acid-maleic anhydride acrylonitrile)having the following structure :

~2-~C~2~8_o~ c~2c~j Cl m Cl Cl n P CO CN x OH H q 20m = 58 % by weight n = 39 % by weight ~p = 1 % by weight q = 1 % by weight x = 1 % by weight

8. ~LIO~I~ ~S5E (trade name of Goodyear - U.S.A., The 36 Goodyear ~ire and Rubber Comp. Akron, Ohio, USA
for a copolymer of butadiene-styrene) ~2-c~=c~-c~2~ff~2-~ t ~ t~ldQ ~ k GV.819 PCT _ 7 -~6Z532 x _ 15 % by weight y = 85 % by weight

9. PO~YSTYROL-B (trade name of BASF, ~udwigshafen, W.Germany for a copolymer of styrene and butyl acrylate) 56

10.E~VACIT ~2046 (trade name of E.I. du Pont de 42 Nemours & Co. (Inc.) Wilmington, Del., U.S.A. for a n-butyl methacrylate-isobutyl methacrylate having the followi~ structure :

_--CH2-C . --CX2-C-C=O \

(C 2)3 x _ H3C CH3 _ Y

x = 50 % by weight y = 50 % by weight

11.A copolymer of acrylic acid-glycidyl methacrylate having the following structure : 36 2 ~ ~ CX3 _ _ l COOH~ 2 I ~0 Y

x = 5 % by weight y = 95 % by weight The toner particles may be of the type used in "dry"
development, which includes developing techniques known as t~ r~k~
GV.819 ECT - 8 -powder cascade, powder cloud, free brush and magnetic brush development. Suitable thermo~Lastic resin constituents for the production of toner particles applied in dry development e.g. powder cloud development are e.g. a polymer or polymer mixtures including homo- and copolymer of methacrylic acid esters, e.g. poly(methyl methacrylate) ~g: 105C, and poly (ethyl methacrylate ) q~g: 65C, poly(styrene) lg: 100C and/
or poly~inyl butyral ~g: 49 C,optionally in ad~nixture with acrylic acid esters having a lower ~g value e.g. poly(methyl acrylate) q~g: 8C.
A preferred toner is described in the ~rench Patent 2,120,948 filed December 27, '1971 by the Applicant. According to said patent the toner consists essentially of finely divided particles formed of a generally uniform mixture comprising 5 to 15% by wei~ht of a coloured material and 95 to 85 % by weight of resin mixture consisting essentially of (A) 40 to 60 % by weight of a polymer having at least 50 %
of the recurring units thereof constituted by at least one styrene monomer of the formula:
R
R-CzCH
~, ~IJ R

wherein R is hydrogen or methyl, and the balance of such recurring units derived from at least one alkyl meth-acrylate monomer wherein alkyl comprises 1-4 carbon atoms, GV.819 PCl - 9 -~06Z532 (B) 20 to 40 % by weight of a homopolymer of butyl acrylate or butyl methacrylate, or copolymers thereof with up to 80 %
by weight of methyl acrylate or methyl methacrylate, and (C) 5 to 20 % by weight of a polymeric plasticizer selected from polyvinylbutyral, polyethylene and co(vinyl acetate/
ethylene).
Said electrostatic toner material consists of particles having a diameter between 1 and 30 ~m.
The Tg values of said electrostatic toner material are in the range of 40 to 60 C
The toner particles may likewise beof the "wet" electro-phoretic type incorporating a resin or resin mixture.
The preparation and composition of such toner particles suitable for use in electrophoretic development and fixing according to the present invention is described e.g. in the United Kingdom Patents 1,151,141 filed February 4, 1966 by Gevaert-Agfa N.V. and 1,312,776 filed July 25, 1969 by the Applicant and in the published German Patent Applications (DOS) P 2,334,353 filed July 6, 1973 and P 2,333,850 filed July 3, 1973 both by Agfa-Gevaert A.G. Normally the electro-phoretic toner consists essentially of finely divided resin-coated pigment particles dispersed in an insulating liquid having a dielectric constant of not more than 3.
Particularly useful toners for electrophoretic development and fixing according to the present invention contain a polymer essentially consisting of methacrylic acid esters. The pigment or colouring agent contained in the toner particles GV.819 PCT - 10 -may be any of the pigments or dyestuffs commonly employed for that purpose.

The resin support of the thermo-adhesive fixing layer when being transparent may be made e.g. of cellulose nitrate, cellulose ester e.g. cellulose triacetate, cellulose acetate butyrate, polyvinylacetal, polystyrene,polymethacrylic acid esters or highly polymeric linear polyesters e.g. polyethylene terephthalate having in amorphous and crystalline state a glasstransition temperature of 67 and 81C respectively (see V.V. Korshak and S.V. Vinogradova in "Polyesters"

Pergamon Press N.Y. (1945) p.339.
~ hese supports being highly transparent for visible light allow the inspection of the toner image with light projected through the image-containing material e.g. on a light-table or in a transparency projector (slide projector).
Preferred are the polyethylene terephthalate supports because of their moisture resistance and high mechanical strength obtained e.g. by stretching.

Particularly strong adherence of the thermo-adhesive layer to the resin support is obtained when the hydrophobic resin support,preferably a polyethylene terephthalate support, is subbed with a layer, which is directly adherent to the said hydrophobic film support and substantially consists of a copolymer formed from 45 to 99.5 % by weight of at least one of the chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0~5 to 10 % by weight of at least an ethylenically unsaturated hydrophilic monomer, and from 0 to GV.819 PCT - 11 -54.5 % by weight of at least one other copolymerisable ethylenically unsaturated monomer.

~ he vinylidene chloride copolymer may be formed from vinylidene chloride and/or vinyl chloride and hydrophilic monomeric units alone in the ratio indicated above. Preférably up to 54.5 % by weight of other recurring units, for instance acrylamides, methacrylamides, acrylic acid esters, methacrylic acid esters, maleic esters and/or N-alkylmaleimides, may also be present.
10Suitable vinylidene chloride copolymers are e.g.:

the copolymer of vinylidene chloride, N-t-butylacrylamide, n-butyl acrylate, and N-vinylpyrrolidone (70:23:3:4), the copolymer of vin~lidene chloride, N-t-butylacrylamide, n-butyl acrylate, and itaconic acid (70:21:5:2), the copolymer of vinylidene chloride, N-t-butylacrylamide, and itaconic acid (88:10:2), the copolymer of vinylidene chloride, n-butylmaleimide, and itaconic acid (90:8:2), the copolymer of vinyl chloride, vinylidene chloride, and 20methacrylic acid (65:30:5), the copolymer of vinylidene chloride, vinyl chloride, and itaconic acid (70:26:4), the copolymer of vinyl chloride, n-butyl acrylate, and itaconic acid (66:30:4), the copolymer of vlnylidene chloride, n-butyl acrylate, and itaconic acid (80:18:2), -the copolymer of vinylidene chloride, meth;yl acrvlate, and GV.819 PCT - 12 itaconic acid (90:8:2), the copolymer of vinyl chloride, vinylidene chloride, N-t-butylacrylamide, and itaconic acid (50:30:18:2).
All the ratios given between brackets in the above-mentioned copolymers are ratios by weight.
~ he above copolymers are only examples of the combinations, which can be made with the different monomers.
~ he different monomers indicated above may be copolymerised according to varioùs methods. ~or example, the copolymeri-sation may be conducted in aqueous dispersion containing a catalyst and an act;vator. Alternativelyj polymerisation of the monomeric components may occur in bulk without added diluent, or the monomers are allowed to react in appropriate organic solvent reaction media.
~he vi ~ lidene chloride copolymers may be coated on the hydrophobic film base according to any suitable technique, e~g., by dip-coating or immersion of the surfaces of the film into a solution of the coating material. Theymay also be applied by spray, brush, roller, doctor blade, air brush, or wiping techniques. ~he thickness of the dried layer may vary between 0.3 and 3 lum preferably.
D ~
D Various wetting or dispersing agents e.g. UL~RAVO~ (trade name) and/or HOS~APO ~(trade name) may be used when the vinylidene chloride copolymer layer is applied from an agueous dispersion. These dispersions are obtained directly when the copolymer has been made by an emulsion polymerisation process.
When coating aqueous dispersions of vnylidene chloride copolymer k . 81 9-ePC~ - 13 on a polyethylene terephthalate film support a very strong adherence to the support is obtained when said dispersions are applied before or during stretching of the polyethylene tere-phthalate film. The aqueous dispersion may be applied to at least one side of the non-stretched film, but may also be applied to polyethylene terephthalate film, ~ich has been oriented biaxially. ~he vinylidene chloride copolymer layer may also be coated on at least one side of a polyester film, which has been stretched in only one direction, e.g. longi-tudinally, whereafter the subbed polyester film is stretchedin a direction perpendicular thereto, in this case transvers-all~.
~ he thickness of the subbing layer is already sufficient from about 0.3 ~m.
~ he preparation of said vinylidene chloride copolymers suited for said subbing layer is described e.g. in the United Kingdom Patent 1,234,755 filed September 28, 1967 by the Applicant.

A subbing layer polymer prepared according to the following preparation receipt yields particularly good adherence to the polyethylene terephthalate support and to the thermo-adhesive layer applied for fixing a toner image according to the present invention.
- Preparation of a copolymer of vinylidene chloride, vinyl chloride, n-butyl acrylate and itaconic acid (30:50:18:2 by weight).

GV.819 PC~ - 14 --In an autoclave were placed 1650 ml of water and 9.6 g of itaconic acid. After dissolution a solution of 6 g of sodium hydrogen carbonate in 120 ml of water was added. Subsequently 98 ml of a 10 % aqueous solution of the disodium salt of disulphonated dodecyl diphenyl ether and 49 ml of a 10 %
agueous solution of the sodium salt of sulphonated dodecylben-zene were added as emulsifying agents. ~hen 96 g of n-butyl acrylate, 144 g of vinylidene chloride, 9.8 g of ammonium persulphate, and 4.9 g of potassium metabisulphite were added. The autoclave was sealed and stirring started.
Under nitrogen pressure 240 g of vinyl chloride were pressed into the autoclave, which was then heated to50C, while stirring. When this temperature had been reached, stirring was continlled for 15 to 30 min. The temperature of the latex rose to about 65C. The reaction was contimled for about 3 h whereupon the latex was cooled to room temperature. The pH
thereof amounted to 2.6 and was brought to 6 by means of 100 ml of 1~ agueous sodium hydroxide. The latex was readily filtrable and consisted of the copolymer of vinylidene chloride, vinyl chloride, n-butyl acrylate, and itaconic acid (30:50:18:2) in a concentration of 20 %.
In "indirect" electrophotography the toner image is formed on a photoconductive recording member e.g. selenium_coated drum and transferred to a receiving material e.g. plain paper or transparent resin sheet. The transparent resin sheet for use in "indirect" electrophotography is according to the GV.819 PCT - 15 -~06Z532 present invention coated with the described thermo-adhesive fixing layer.
In electrographic systems, an electrostatic charge pattern is produced by in~ormation-wise applying electric charge carriers e.g. electro~sand/or ions to an electrically insulating surface. For example in electrography an electro-static charge pattern is built up by image-wise modulated corona-charging, information-wise modulated charge deposition with a conductor e.g. a conductive stylus or pin-matrix or with an information-wise modulated electron beam.
A survey of electrographic recording techniques is given by R.M. Schaffert in the already above mentioned book.
A special type of producing electrostatic charge patterns is based on photo-emission of charged particles.
Processes in which the electrostatic image formation is based on photo~electron emission are described e.g. in the United States Patents 2,221,776 of Chester F.Carlson issued November 19, 1940, 2,692,948 of Kurt S.~ion issued October 26, 1954, 2,900,515 of Eduard ~.Criscuolo and Donald ~.O'Conner issued August 18, 1959, 3,057,997 of Edward E.Eaprelian issued October 9, 1962 and 3,526,767 of Walter Roth and Alex F.Jvirblis issued September 1, 1970 and the United Kingdom Patent 778,330 filed April 15, 1955 by Compagnie Fran~aise Ihomson-Houston, the German Patent 1,497,093 filed ~ovember 11, 1962 by Siemens A.G., and the published German Patent Applications 2,231,954 filed June 29, 1972 and 2,233,538 filed July 7, 1972 both by Diagnostic Instruments. Except GV.819 PC~ - 16 -for the processes described in the latter three patents the photoelectron emission proceeds with a solid photocathode.
A particularly interesting recording technique is known as ionography in which the formation of the electrostatic charge pattern proceeds through the information-wise ionization of photo-ionizable gas e.g. as described in the Belgian Patent 792,334 filed December 6, 1972 by Xonics Inc.
According to the radiographic process described in said Belgian Patent an electrostatic charge pattern is formed on a dielectric sheet in an imaging chamber, which comprises between electrodes an interspace filled with a gas having an atomic number of at least 36, e.g. xenon, that is kept at a pressure above atmospheric pressure. During the image-wise X-ra~
exposure a potential difference is applied between the electrodes and electrons and positive ions formed in said interspace are attracted and moved towards the anode and cathode respectively whereby a charge pattern is formed with one of the types of charged particles on said dielectric sheet.
~he recording materials applied in X-ray recording are preferably transparent for visible light so that smooth resin films or sheets, which give rise to the above explained problem with regard to toner adherence, are normally used. ~he combin-ation of thermo-adhesive fixing la~er and toner having the characteristics specified in the present description is of particular interesting advantage in the use of said trans-parent filn~or sheets.
GV.819 PC~ - 17 -~he recording of a charge pattern by photo-emission or ionographic techniques asks for an insulating charge-reeeiving thermo-adhesive layer that retains the applied eharge for a sufficiently long time to enable the toner development of the charge pattern to take place.
In order to prevent -that the deposited charge pattern after its deposition fades, the rear side of the charge-receiving material is provided with a transparent electrically eonductive layer that makes contact with an electrode of opposite eharge sign with respect to the deposited charge pattern.
In order to offer a good adherenee of the eonduetive layer to the transparent hydrophobic resin support a subbing layer of the above deseribed type is used. Suitable eonduetive layers B are on the basis of polyionic resins, for example CALGON ~
aONDUC~IVE PO~YMER 261 (trade name) containing 39.1 % by weight of active conductive solids, whieh contain a conductive poly-mer having reeurring units of the following type :
H3C~+,CH3 H2C CH2 .Cl and the polyionic resins deseribed in the United Kingdom Patent 1,301,661 filed January 29, 1969 ~y the Applieant or in the published German Patent Applieations (DOS~ P 23 01 266 filed January 11, 1973 and P 23 26 413 filed May 24, 1973 both by Agfa-Gevaert A.G.
~ trade r~k GV.819 PC~ - 18 -Other conductive coatings are e.g. vapour-deposited films of chromium or nickel-chromium about 3.5 llm thick and being transparent for about 65 to 70 % in the visible range.
Copper(I) iodide conducting films or sheets can be made by vacuum depositing copper on a relatively thick resin base and subsequently treating with iodine vapour under controlled conditions (see J.Electrochem.Soc., 110-119, Feb. 1963). Such films are over 90 % transparent and have surface resistivities as low as 1500 ohms per square.
~he heating of the thermo-adhesive layer for fixing the toner image may proceed by infrared irradiation as described e.g. in the United ~tates Patent ~,772,497 of Donald R.Gray and Richard W.Germuska issued ~ovember 1~, 197~ or by contact of the support of the thermo-adhesive layer with a hot body.
~he present invention is illustrated by the following examples without, however, limiting it thereto.
Exam~le To one side of a longitudinally stretched polyethylene terephthalate film of 0.8 mm thickness a subbing layer was applied at 25C at a coverage of 50 mg/sq.m from a latex con-taining 5% by weight of the copolymer of vinylidene chloride, vinyl chloride, n-butyl acrylate and itaconic acid (30:50:18:2 by weight), the preparation of which has been described hereinbefore.
lhis subbed film was simultaneously stretched longitu-dinally and transversally to about 3.5 times its original size and heat-setted. lhe lg of the polyethylene terephtha-GV.819 PC~ - 19 -la-te was 75C.
~ o the subbed film a thermo-adhesive fixing layer was applied by coating it at 25C at a coverage of 70 g per sq.m with a 10% (weight/volume) NEOCRY~ B 707 (trade name3 polymer (lg=30C) solution in a 3/1 by volume mixture of dichloro-ethane and methylene chloride.
~ he dried film was electrostatically charged at the side of the thermo-adhesive layer with a negative corona whose ion stream was directed through image-wise distributed aper-tures in a copper plate while the rear side of the filmduring the charging was held in contact with a copper plate as counter electrode.
~ he corona charge was of such an intensity that the average voltage of the charge applied to the subbed layer was -1000 V.
~ he charge pattern was developed according to the powder cloud technique (see United States Patent 2,725,304 of Richard B.Landrigan, Ray ~.Tom and Donald L.Fauser issued November 29, 1955) with toner particles prepared by mixing 5.2 parts by weight of polystyrene having a molecular weight of approxi-mately 30,000 and 1 part by weight of polyvinylbutyral having a molecular weight of approximately 30,000, which in addition to the vinylbutyral groups contains also approxi-mately 20% by weight of vinyl alcohol groups and 2.5 %
by weight of vinyl acetate groups, 2.8 parts by weight of copoly(methyl methacrylate/n-butyl methacrylate)(50:50 mole % with an intrinsic viscosity of 0.2 measured in chloroform GV.819 PC~ - 20 -~06Z532 ~ at 20C) and ~ part by weight of Spezialschwarz IV~ trade - name for carbon black sold by Deutsche Gold- und Silberscheide-anstalt, Frankfurt a/M, W.Germany).
~ he components were mixed in dry condition and then melted at 150-160C. ~he melt was then kneaded for approximately 30 min at the same temperature. After cooling and breaking to a particle size of approximately 1 mm the powder was ground in aqueous medium in a vibration ball mill for 30 h.
After drying and sievi~g a toner having a particle size of 4 ~m was obtained. Ihe lg value of this toner was 42C.
lhe transparent recording material carrying the non-fixed toner image on the thermo-adhesive fixing layer was introduced into a drying oven whose temperature was kept at 1~0C.
At that temperature the fixing of a toner image on a poly-ethylene teréphthalate film sheet having no thermo-adhesive fixing layer did not proceed within a period of 30 s.
On the film sheet provided with the thermo-adhesive fixing layer the toner image was fixed already at 120C within 15 s. ~he resistance to abrasion of the fixed toner image was very good.
Ihe thermoadhesive layer did not show fingerprints when manipulated below 40C.
Example 2 200 g of S~AYBELI~E ES~ER 10 (registered trade name of ~he Hercules Powder Company Inc., Wilmington, Del., U.S.A.
for a glycerin ester of hydrogenated wood rosin with acid number 8) and 100 g of HELIOECH~ BLAU H ~(trade name of Bayer G ~ 8~ PC~ ~ - 21 -AG, Leverkusen, W.Germany) were mixed at 60-65C in a mixing and kneading apparàtus of Meili, Switserland, type ~iliput 030 ~.N. ~he kneaded mass was cooled and ground in a grinding apparatus I.K.A., model A10 (of Janke & Kunkel, W.Germany) to obtain a fine powder of resin-coated pigment.
In a ball-mill 2 g of the above resin-coated pigment powder were ground for 10 h together with:
- 11.5 g of a 25 % by weight solution of ~EOCRYL B 702 (trade name of Polyvinylchemie, ~he Netherlands for a copolymer of butyl methacrylate and stearyl methacrylate comprising about 1 % by weight of methacrylic acid in ISOPAR G (trade name of Esso Standard Oil Company for an aliphatic hydro-carbon solvent having a boiling range of 160-175C and a Kauri-Butanol value of 27, - 0.5 g of a 25 % by weight solution of ANlARON~$216 (trade name of General Aniline & ~ilm Corporation, ~ew York, ~.Y., USA) in ISOPAR G (trade name) - 2 ml of a 0.2 % (g/100 ml solution in ISOPAR G (trade name) of the zinc salt of mono-2-butyloctyl phosphate, - 25 ml of ISOPAR G (trade name) When 10 ml of the above concentrated liquid developing composition were diluted with 1 litre of ISOPAR G (trade name) a stable positive-working electrostatographic liquid developer was formed suited for the development of a latent electrostatic image formed on a conventional electrophotographic recording element comprising paper coated with photoconductive zinc oxide in a resinous binder by negative charging and image-a ~
GV.819 P~ - 22 -wise exposure to light.
The Tg value of the resin coating of the toner particles was above 200C.
~ he obtained developer was used for the development of a charge pattern formed according to the technique of Example 1 on a transparent material, which was different from the material of Example 1 in the composition of the thermo-adhesive fixing layer.
The fixing layer was prepared by dissolving 2.5 g of the vinyl acetate-crotonic acid copolymer (Tg=38C) (compound 3 of Table 1) ir. a solvent mixture of 27 ml of sym.dichloroethane and 8 ml of methylene chloride.
The solution was coated on the subbed polyethylene terephthalate film of Example 1 at such a coverage that the weight of the dried coating obtained was 4 g per sq.m~
On the film sheet provided with the thermo-a&esive fixing layer the toner image was fixed already at 120C
within 15 s.
The resistance to abrasion of the fixed toner image was very good.

GV.819 PCT - 23 -

Claims (21)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for obtaining a fixed toner image on a sheet or web material comprising the steps of image-wise depositing toner particles on a thermo-adhesive fixing layer that itself permanently adheres to a support and heating said material carrying the toner image to such a degree that softening of the thermo-adhesive fixing layer takes place without reaching a temperature at which permanent deformation of the support occurs, wherein the support is a thermoplastic resin support whose glass transition temperature (Tg) is higher than the glass transition temperature (Tg) of the thermoplastic polymer or polymer composition of the thermo-adhesive layer and the toner particles comprises at least 10% by weight of a polymer or polymer composition whose glass transition temperature (Tg) is at least 10°C higher than that of the thermoplastic polymer or polymer composition of the thermo-adhesive fixing layer.

2. A process according to claim 1, wherein the Tg of the resin support is at least 60°C.

3. A process according to claim 1 or 2, wherein the Tg of the polymer or polymer composition of the thermo-adhesive fixing layer is at least 30°C.

4. A process according to claim 1, wherein the support is a polyethylene terephthalate film support.

5. A process according to claim 4, wherein the support is subbed with a layer, which is directly adherent to the said film support and said thermo-adhesive layer and substantially con-sists of a copolymer formed from 45 to 99.5% by weight of at least one of the chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0.5 to 10% by weight of at least one ethyl-enically unsaturated hydrophilic monomer, and from 0 to 54.5% by weight of at least one other copolymerisable ethylenically un-saturated monomer.

6. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of vinyl acetate and crotanic acid having the structure:

wherein x is approximately 96.3% by weight and y is approximately 3.7% by weight.

7. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of vinyltoluene/isobutyl methacrylate/acrylic acid/stearate having the structure:

wherein n is approximately 70-75% by weight; m is approximately 21% by weight; p is approximately 0.3% by weight; and q is approx-imately 5 to 10% by weight.

8. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of styrene/vinyl acetate/
ethyl acrylate/acrylic acid having the structure:
wherein x is approximately 30% by weight; y is approximately 25% by weight; z is approximately 44% by weight; and m is approximately 1% by weight.

9. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of vinyl chloride/ vinyl-idene chloride/maleic acid/maleic anhydride/acrylonitrile having the structure:

wherein m is approximately 58% by weight; n is approximately 39% by weight; p is approximately 1% by weight; q is approximately 1% by weight; and x is approximately 1% by weight.

10. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of butadiene and styrene having the structure:

wherein x is approximately 15% by weight and y is approximately 85%
by weight.

11. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of n-butyl methacrylate and isobutyl methacrylate having the structure:

wherein x is approximately 50% by weight and y is approximately 50% by weight.

12. A process according to claim 1, wherein the thermo-adhesive layer is composed of a copolymer of acrylic acid and glycidyl methacrylate having the structure:
wherein x is approximately 5% by weight and y is approximately 95%
by weight.

13. A process according to claim 1, wherein the thermo-adhesive layer is composed of a plasticized polystyrene.

14. A process according to claim 1, wherein the thermo-adhesive layer is an alkyl-aromatic copolymer.

15. A process according to claim 1, wherein the thermo-adhesive layer is a 55% by weight solution of polyacrylate containing a plasticizing agent.

16. A process according to claim 1, wherein the thermo-adhesive layer is a copolymer of styrene and butyl acrylate.

17. A process according to claim 1, wherein the toner is a toner suited for dry development.

18. A process according to claim 1, wherein the toner is a toner suited for electrophoretic development.

19. A process according to claim 17, wherein the toner comprises a polymer or polymer mixture including homo-and co-polymers of methacrylic acid esters, polystyrene, polyvinylbutyral.

20. A process according to claim 17, wherein the toner is suited for powder cloud development and consists essentially of finely divided particles formed of a generally uniform mixture consisting of 5 to 15% by weight of a coloured material and 95 to 85% by weight of resin mixture consisting essentially of:
(A) 40 to 60% by weight of a polymer having at least 50% of the recurring units thereof constituted by at least one styrene monomer of the formula:
wherein R is hydrogen or methyl, and the balance of such recurring units derived from at least one alkyl methacrylate monomer wherein alkyl comprises 1-4 carbon atoms, (B) 20 to 40% by weight of a homopolymer of butyl acrylate or butyl methacrylate, or copolymers thereof with up to 80% by weight of methyl acrylate or methyl methacrylate, and (C) 5 to 20% by weight of a polymeric plasticizer selected from polyvinyl butyral, polyethylene and co(vinyl) acetate/ethylene).

21. A process according to claim 19, wherein said polymer or polymer mixture is in admixture with acrylic acid esters.