CA1264594A - Sublimation transfer imaging system - Google Patents
Sublimation transfer imaging systemInfo
- Publication number
- CA1264594A CA1264594A CA000488441A CA488441A CA1264594A CA 1264594 A CA1264594 A CA 1264594A CA 000488441 A CA000488441 A CA 000488441A CA 488441 A CA488441 A CA 488441A CA 1264594 A CA1264594 A CA 1264594A
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- CA
- Canada
- Prior art keywords
- dye
- receptor
- dyes
- image
- iodonium
- Prior art date
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- Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
- Thermal Transfer Or Thermal Recording In General (AREA)
Abstract
ABSTRACT
SUBLIMATION TRANSFER IMAGING SYSTEM
A process for forming an image which comprises image-wise exposing to radiation of selected wavelength a carrier element comprising, as image forming components, in one or more imaging layers coated on a support a bleachable dye in reactive association with iodonium ion thereby bleaching the dye in exposed areas to form a positive image, and thereafter transferring the positive dye image to a receptor which is either a receptor layer present on the carrier or a separate receptor element by heating the carrier element to a sufficient temperature to allow the dye image to sublime to the receptor thereby forming an image on the receptor.
SUBLIMATION TRANSFER IMAGING SYSTEM
A process for forming an image which comprises image-wise exposing to radiation of selected wavelength a carrier element comprising, as image forming components, in one or more imaging layers coated on a support a bleachable dye in reactive association with iodonium ion thereby bleaching the dye in exposed areas to form a positive image, and thereafter transferring the positive dye image to a receptor which is either a receptor layer present on the carrier or a separate receptor element by heating the carrier element to a sufficient temperature to allow the dye image to sublime to the receptor thereby forming an image on the receptor.
Description
SUBLI~ATION TRANSFER IMAGING SYSTEM
Field of the Invention This invention relates to a method of forming an imaye in which a sheet bearing a radiation-sensitive image-forming layer is image-wise exposed to record an image in said layer and thereafter the image-forming components are transferred to a receptor layer or sheet to form a permanent image. In 10 particular, the invention relates to a sublimation transfer imaging process employing a radiation-sensltive sheet comprising one or more bleachable dyes.
Background of the Invention Positive working non-silver systems in which an originally coloured species is decolourised (bleached) in an imagewise manner upon exposure to light have received a considerable amount of attention. A large variety of dyes and activators
Field of the Invention This invention relates to a method of forming an imaye in which a sheet bearing a radiation-sensitive image-forming layer is image-wise exposed to record an image in said layer and thereafter the image-forming components are transferred to a receptor layer or sheet to form a permanent image. In 10 particular, the invention relates to a sublimation transfer imaging process employing a radiation-sensltive sheet comprising one or more bleachable dyes.
Background of the Invention Positive working non-silver systems in which an originally coloured species is decolourised (bleached) in an imagewise manner upon exposure to light have received a considerable amount of attention. A large variety of dyes and activators
2~ have been disclosed for such systems, see, for example, .J. Kosar, ~ight Sensitive Systems, page 387, Wiley, New ~ork 1965.
The reaction relies on the fact that the dye absorption is sensitising the dye's own destruction or 25 decolourisation, for example a yellow dyes absorbs blue light; the excited dye thus formed reacts with an activator which releases the species to bleach the dye. Similarly green light would destroy the magenta and red light the cyan dyes.
This dye bleach-out process is thus capable of producing colour images in a simple way. However, in spite of its apparent simplicity, the bleach-out process poses a number of problems. In particular, the purity of the whites in the final image leaves =2=
much to be desired, image stability may not be good and a fixing step may be re~uired to stabilise the image.
Our copending European Patent Application No.
5 84301156.0 (Serial No. 0 120 601) discloses a radiation-sensitive element capable of recording an image upon image-wise exposure to radiation of selected wavelength, the element comprising, as the image-forming components, an effective amount of a 10 bleachable dye in reactive association with an iodonium ion.
The element is capable of recording a positive image simply upon exposure to radiation of selected wavelength; the radiation absorbed by the dye which is 15 in reactive association with an iodonium ion causes the dye to bleach. The dyes are believed to sensitise spectrally the reduction of the iodonium ion through the radiation absorbed by the dyes associated with the iodonium ion. Thereafter the element may be 20 stabilised to fix the image by destruction of the iodonium ion or by separation of the dye relative to the iodonium ion.
The dyes used may be of any colour and any chemical class which i5 capable vf bleaching upon 25 exposure to radiation of selected wavelength in the presence of an iodonium ion.
By a suitable selection of dye an element may be prepared which is sensitive to radiation of a selected wavelength band within the general range 300 30to 1100 nm, the particular wavelength and the width of the band depending upon the absorption characteristics of the dye. In general, where a dye has more than one absorption peak it is the wavelength corresponding to S~4 =3=
the longest wavelength peak at which one would choose to irradiate the element.
Elements intended for the production of images from radiation in the visible region (400 to 700 nm) will contain dyes which will bleach from a coloured to a substantially colourless or very pale state. In practice, such bleachable dyes will undergo a change such that the transmission optical density at the ~ max will drop from 1.0 or more to less than 0.09, 10 preferably less than 0.05. The dyes will generally be coated on the support to provide an optical density of about 3.0 or more.
In the case of elements sensitive to ultraviolet radiation (300 to 400 nm) the dyes will 15 not normally b~ coloured to the eye and there may be no visible change upon exposure to ultraviolet radiation and bleaching. The image-wise exposed elements may be used as masks for further ultraviolet exposure after fixing.
Infrared sensitive elements contain dyes having an absorption peak in the wavelength range 700 to 1100 nm. These dyes may also have absorption peaks in the visible region before and/or after bleaching.
Thus, as well as providing a means for obtaining masks ?5 for subsequent infrared exposure in a similar manner to the ultraviolet masks, infrared sensitive elements may record a visible image upon image-wise exposure to infrared radiation.
Exposure may be achieved with a wide variety 30 of sources including incandescent, gas discharge and laser sources. For laser scanning applications the laser beam may need to be focussed in order to achieve sufficient exposure.
55~
=~=
The dyes used may be anionic, cationic or neutral. Anionic dyes give very good photo-sensitisation which is believed to be due to an intimate reactive association betwean the negatively charged dye and the positively charged iodonium ion.
Also anionic dyes may readily be mordanted to cationic polymer binders and it is relatively simple to remove surplus iodonium ions in an aqueous bath in a fixing step if the mordanting polymer is cationic. However, 10 neutral dyes also give good results and are preferred over cationic dyes for overall photosensitivity.
Cationic dyes are least preferred since it is more difficult to achieve intimate reactive association between the positively charged dye and iodonium ion, 15 and selective remcval of iodonium ion after imaging is more difficult.
The bleachable dyes may be generically referred to as polymethine dyes which term characterises dyes having at least one electron donor 20 and one electron acceptor group linked by methine groups or aza analoyues. The dyes have an oxidation potential between 0 and +1 volt, preferably between +0.2 and +0.8 volt. The bleachable dyes may be selected from a wide range of known classes of dyes 25 including allopolar cyanine dye bases, complex cyanine, hemicyanine, merocyanine, azine, oxonol, streptocyanine and styryl.
The dye and iodonium system has its greatest sensitivity at the lmax f the longest wavelength 30 absorbance peak. Generally, it is necessary to irradiate the system with radiation of wavelength in the vicinity of this ~max for bleaching to occur.
Thus, a combination of coloured dyes may be used, e.g.
~2~5~
=5-yellow, magenta and cyan, in the same or different layers in an element and these can be selectively bleached by appropriate visible radiation to form a full colour image. Monochromatic or polychromatic images may be produced using the photosensitive materials with relatively short exposure times in daylight or sunlight or even artificial sources of light (e.g. fluorescent lamps or laser beams). The exposure time, for adequate results, for example when 10 using an 0.5 kW tungsten lamp at a distance of 0.7 m, may be between 1 second to 10 minutes.
The iodonium salts used in the imaging system are compounds consisting of a cation wherein a positively charged iodine atom bears two covalently 15 bonded carbon atoms, and any anion. Preferably the acid from which the anion is derived has a pKa ~ 5.
The preferred compounds are diaryl, aryl/heteroaryl or diheteroaryl iodonium salts in which the carbon-to-iodine bonds are from aryl or heteroaryl groups.
20 Aliphatic iodonium salts are not normally thermally stable at temperatures above 0C. However, stabilised alkyl phenyl iodonium salts such as those disclosed in Chem. Lett. 1982, 65-6 are stable at ambient temperatures and may be used.
The ~leachable dye and iodonium salt are in reactive association on the support. Reactive association is defined as such physical proximity between the compounds as to enable a chemical reaction to take place between them upon exposure to light. In 30 practice, the dye and iodonium salt are in the same layer or in adjacent layers on the support.
In general, the weight ratio of bleachable dye to iodonium salt in the element is in the range from 1:1 to 1:50, preferably in the range from 1:2 to 1:10.
~69~
=6=
The bleachable dye and iodonium salt may be applied to the support in a binder. Suitable binders are transparent or translucent, are generally colourless and include natural polymers, synthetic resins, polymers and copolymers, and other film forming media. The binders may range from thermoplastic to highly cross-linked, and may be coated from aqueous or organic solvents or emulsions.
Suitable supports include transparent film, 10 e.g. polyester, paper e.g. baryta-coated photographic paper, and metallised film. Opaque vesicular polyester films are also useful.
The fixing of the radiation-sensitive elements may be effected by destruction of the iodonium ion by 15 disrupting at least one of the carbon-to-iodine bonds since the resulting monoaryl iodine compound will not react with the dye. The conversion of the iodonium salt to its non-radiation sensitive form can be effected in a variety of fashions. Introduction of 20 ammonia and amines in reactive association with the iodonium ion, or a reaction caused on heating, or UV
irradiation of a nucleophilic anion such as I~, Br~, Cl~, BAr4~ (tetra-arylboronide), Ar~ (e.g.
phenoxide~, or 4-NO2C6H4CO2~, with the iodonium ion, 25 will effect the conversion.
An alternative method of achieving post-imaging stabilisation or fixing is to remove the iodonium ion from reactive association with the dye by washing with an appropriate solvent. For example, in 30 the case of elements using mordanted oxonol dyes and water soluble iodonium salts formulated in gelatinl after imaging, the iodonium salt is simply removed by an aqueous wash, which leaves the immobilised dye in i9~
the binder. The dye stability to light is then equivalent to that of the dye alone. An element in which the dye and iodonium salt is formulated in polyvinylpyridine may be treated with aliphatic ketones to remove the iodonium salt and leave the dye in the binder.
The elements may be used as transparencies for use with overhead projectors, for making enlarged or duplicate copies of colour slides and for related 10 graphics or printing applications, such as pre-press colour proofing materials.
Dye diffusion transfer systems are known and are becoming increasingly important in colour photography (see C.C. Van de Sande in Angew Chem.
15 1983, 22, 191-209). These systems allow "rapid access" colour images without a complicated processing sequence. The construction of these colour materials may be donor-receptor type (e.g. Ektaflex commercially available from Kodak) integral peel-apart type (e.g.
20 Polaroid, E.H. Land, H.G. Rogers, V.X. Walworth in J.
Sturge Nebelette's Handbook o$ Photography and Reprography, 7th Ed. 1977, Chapter 12), or integral single sheet type (e.g. Photog. Sci. and Eng., 1976, 20~ 155)o Silver halide diffusion transfer systems 25 are also known (e.g. E.H. Land. Photog. Sci. and Eng., 1977, _ , 225). Examples of diffusion transfer fixing in non-silver, dye-forming reactions employing solvent application to effect the transfer are disclosed in United States Patent Specification Nos. 3 460 313 and 30 3 598 583. The latter patent also describes a full-colour imaging element, applicable for preparation of colour proofs, fixed by transfer of dye precursors in register to a receptor. Other examples ~2i~ S~
of non-silver diffusion transfer imaging systems are disclosed in British Patent Specification Nos.
1 0S7 703, 1 355 61~ and 1 371 898. The latter two Patents also disclose the transfer of dye images under the influence of dry heat.
It has now been found that certain dyes which are bleachable upon exposure to radiation in the presence of iodonium ion are susceptible to diffusion or sublimation transfer and this property may be 10 utilised to separate such dyes from the iodonium ion and produce a clean, stable image by transfer from a radiation-sensitive layer to a receptor layer or separate receptor element.
Brief Summary__f the Invention According to the present invention there is provided a process for ~orming an image which comprises image-wise exposing to radiation of selected wavelength a carrier element comprising, as image forming cornponents, in one or more imaging layers 20 coated on a support a bleachable dye in reactive association with iodonium ion thereby bleaching the dye in exposed areas to form a positive image, and thereafter transferring the positive d~e image to a receptor which is either a receptor layer present on 25 the carrier or a separate receptor element by heating the carrier element to a sufficient temperature to allow the dye image to sublime to the receptor thereby forming an image on the receptor.
g The process of the invention provides stable dye images, optionally full colour images, of high quality with low background fog. The imaging system does not require the presence of silver halide.
Description of the Preferred Embodiments In accordance with the invention the bleachable dyes are sublimable and after image-wise exposure the carrier element is placed in intimate contact with a receptor and the resulting composite 10 heated for a sufficient time and to a sufficient temperature to allow the dye to sublime across the interface to the receptor thereby forming a laterally reversed positive image on the receptor. Thereafter the carrier element is separated from the receptor.
.
6~
=10=
The sublimation transfer allows the formation of a stable dye image having high colour purity. The process is entirely dry and takes only a few minutes to give colour prints. A single transfer from the carrier element to a receptor results in a mirror image. If a true image; right-reading, is required a double transfer process may be employed transferring the dyes from the carrier element to an intermediate receptor and thereafter transferring the dyes from the 10 intermediate receptor to the final receptor.
Alternatively, a true image may be formed by reversing the transparency used for exposure.
The process may be used to achieve a multi-colour print either by sequentially transferring 15 dyes from separate carrier elements or by utilising a carrier element having two or more coloured dyes, e.g.
magenta, cyan and yellow, and transferring the dyes simultaneously~
Suitable dyes for use in this system are those 20 which are both bleachable upon exposure to radiation in the presence of an iodonium ion and are sublimable, preferably in the temperature range 80 to 160C, more preferably 100 to 150C. In general, the dyes are electrically neutral (i.e. not charged) and have a 25 molecular weight of less than 400, preferably less than 350. The dyes also generally possess a compact or aball-like" structure; dyes having an elongate structure, e.g. those having long methine chains, do not readily sublime. The dyes are also selected such 30 that they do not fade or undergo a change in colour on - sublimation. When more than one dye is employed it is desirable to match the sublimation characteristics of the dyes to ensure an even transfer rate for all the dyes.
~26~5~
Suitable bleachable dyes may be generically referred to as polymethine dyes which term characterises dyes having at least one electron donor and one electron acceptor group linked by methine groups or a~a analogues. The dyes have an oxidation potential between 0 and +1 volt, preferably between ~0.2 and ~0.8 voltO The bleachable dyes may be selected from a wide range of known classes of dyes including allopolar cyanine dye bases, complex 10 cyanine, hemicyanine, merocyanine, azine, oxonol, streptocyanine and styryl.
In general, suitable dyes for use in the invention will have the structure:
.'~
in which:
n is 0, 1 or 2, and ~.z~
Rl to R4 are selected to provide an electron donor moiety at one end of the conjugated chain and an electron acceptor moiety at the other, and may be selected from substituents including hydrogen, halogen, cyano, carboxy, alkoxy, hydroxy, nitro, alkyl, aryl groups or heterocyclic rings any of which may be substituted. The skeletal structure of the groups Rl to R4 generally contain up to 14 atoms selected from C, N, O and S. When the skeletal lO structure of a Rl to ~4 group is in the orm of a linear chain there will usually be no more than 6 carbon atoms in the chain. When the skeletal structure is cyclic there will be no more than 7 atoms in any single ring. Cyclic structures may comprise l5 two or more fused rings containing up to 14 atoms. If the skeletal structure of a Rl to R~ group comprises two unfused cyclic groups there will be no more than 3 atoms in the linear chain between the groups.
Alternatively, R1 and R2 and/or R3 and R4 may 20 represent the necessary atoms to complete optionally substituted aryl groups or hetreocyclic rings, generally containiny up to 14 atoms selected from C, N, O and S and having a structure as defined above.
The conjugated chain is preferably composed of 25 carbon atoms but may include one or more nitrogen atoms providing the conjugation is not disrupted. The free valences on the chain may be satisfied by hydrogen or any substituent of the type used in the cyanine dye art including fused ring systems.
The particular selection of substituents Rl to R4 effects the light absorbance properties of the dye which may be varied to provide absorption peaks ranging from the ultraviolet (300 to 400 nm), near ILZ6~5'~
=13=
visible (400 to 50~ nm), far visible (500 to 700 nm) and infrared (700 to 1100 nm).
Dyes of the above formula are well known particularly in the silver halide photographic art and S are the subject of numerous patents. Exemplary dye structures are disclosed in The Theory of the Photographic Process, T.H. James, Ed. MacMillan Editions 3 and 4, and Encyclopaedia of Chemical Technology, Kirk Othmer, 3rd Edition, Vol. 18, 1983.
Within the above general structure of dyes are various classes of dye including:
1) Merocyanine dyes of the general formula:
R `B
in which:
q is an integer of 0 to 2, R5 represents hydrogen or a substituent which may be present in conventional cyanine dyes, e.g.
alkyl (preferably of 1 to 4 carbon atoms), etc., the groups A and B, which need not necessarily complete a ayclic structure with the methine chain, 2S independently represent alkyl, aryl or heterocyclic groups or the necessary atoms to complete heterocyclic rings which may be the same or different.- The skeletal structure of the groups A and B generally contain up to 14 atoms selected from C, N, O and S.
30 When the skeletal structure of A or B is in the form of a linear chain there will usually be no more than 6 carbon atoms in the chain. When the skeletal structure completed by A or B is cyclic there will be , s~
=1~=
no more than 7 atoms in any single ring. Cyclic structures may comprise two or more fused rings containing up to 14 atom~. If the skeletal structure complete by A or B comprises two unfused cyclic yroups there will be no more than 3 atoms in the linear chain between the groups. Additionally B may complete a carbocyclic ring.
These dyes are well known in the silver halide photographlc art and are described in The Theory of 10 the Photo~raphic Process, reEerred to above.
It is to be understood that these cyanine, merocyanine, anionic and oxonol dyes may bear substituents along the polymethine chain composed of C, N, O and S, and that these substituents may 15 themselves join to form ~, ~ or 7 membered rings, or may bond with rings A and B to form further rings, possibly with aromatic character. Rings A and B may also be substituted by C, N, H, O and S containiny groups such as alkyl, substituted alkyl, alkoxy, amine 20 (primary, secondary and tertiary), aryl (e.g. phenyl and substituted phenyl), halo, carboxyl, cyano, nitro, etc. Exemplary substituents are well known in the cyanine dye art.
2~ Benzylidene and cinnamylidene dyes of the 25 structure:
~ ~3 C ~1 R R
in which:
~4S~
=15=
A is as defined above, and may additionally be cyano, or carboalkoxy or other carbonyl-containing groups, e.g. ketone, or S=O containing groups, e.g.
S02Me, n is 0 or 1, R6 and R7 independently represent a hydrogen atom or an alkyl group (optionally substituted) or aryl group containing up to 12 carbon atoms, R8 is H or CN or CO2R9, in which R9 is an lOopticnally substituted alkyl group of up to 6 carbon atoms, and the Eree valences may be satisfied by hydrogen or alkyl groups, or together may form a 6-membered carbocyclic saturated or aromatic ring.
Examples of such dyes include:
CN
Me 2 ~ Me 2N~
The reaction relies on the fact that the dye absorption is sensitising the dye's own destruction or 25 decolourisation, for example a yellow dyes absorbs blue light; the excited dye thus formed reacts with an activator which releases the species to bleach the dye. Similarly green light would destroy the magenta and red light the cyan dyes.
This dye bleach-out process is thus capable of producing colour images in a simple way. However, in spite of its apparent simplicity, the bleach-out process poses a number of problems. In particular, the purity of the whites in the final image leaves =2=
much to be desired, image stability may not be good and a fixing step may be re~uired to stabilise the image.
Our copending European Patent Application No.
5 84301156.0 (Serial No. 0 120 601) discloses a radiation-sensitive element capable of recording an image upon image-wise exposure to radiation of selected wavelength, the element comprising, as the image-forming components, an effective amount of a 10 bleachable dye in reactive association with an iodonium ion.
The element is capable of recording a positive image simply upon exposure to radiation of selected wavelength; the radiation absorbed by the dye which is 15 in reactive association with an iodonium ion causes the dye to bleach. The dyes are believed to sensitise spectrally the reduction of the iodonium ion through the radiation absorbed by the dyes associated with the iodonium ion. Thereafter the element may be 20 stabilised to fix the image by destruction of the iodonium ion or by separation of the dye relative to the iodonium ion.
The dyes used may be of any colour and any chemical class which i5 capable vf bleaching upon 25 exposure to radiation of selected wavelength in the presence of an iodonium ion.
By a suitable selection of dye an element may be prepared which is sensitive to radiation of a selected wavelength band within the general range 300 30to 1100 nm, the particular wavelength and the width of the band depending upon the absorption characteristics of the dye. In general, where a dye has more than one absorption peak it is the wavelength corresponding to S~4 =3=
the longest wavelength peak at which one would choose to irradiate the element.
Elements intended for the production of images from radiation in the visible region (400 to 700 nm) will contain dyes which will bleach from a coloured to a substantially colourless or very pale state. In practice, such bleachable dyes will undergo a change such that the transmission optical density at the ~ max will drop from 1.0 or more to less than 0.09, 10 preferably less than 0.05. The dyes will generally be coated on the support to provide an optical density of about 3.0 or more.
In the case of elements sensitive to ultraviolet radiation (300 to 400 nm) the dyes will 15 not normally b~ coloured to the eye and there may be no visible change upon exposure to ultraviolet radiation and bleaching. The image-wise exposed elements may be used as masks for further ultraviolet exposure after fixing.
Infrared sensitive elements contain dyes having an absorption peak in the wavelength range 700 to 1100 nm. These dyes may also have absorption peaks in the visible region before and/or after bleaching.
Thus, as well as providing a means for obtaining masks ?5 for subsequent infrared exposure in a similar manner to the ultraviolet masks, infrared sensitive elements may record a visible image upon image-wise exposure to infrared radiation.
Exposure may be achieved with a wide variety 30 of sources including incandescent, gas discharge and laser sources. For laser scanning applications the laser beam may need to be focussed in order to achieve sufficient exposure.
55~
=~=
The dyes used may be anionic, cationic or neutral. Anionic dyes give very good photo-sensitisation which is believed to be due to an intimate reactive association betwean the negatively charged dye and the positively charged iodonium ion.
Also anionic dyes may readily be mordanted to cationic polymer binders and it is relatively simple to remove surplus iodonium ions in an aqueous bath in a fixing step if the mordanting polymer is cationic. However, 10 neutral dyes also give good results and are preferred over cationic dyes for overall photosensitivity.
Cationic dyes are least preferred since it is more difficult to achieve intimate reactive association between the positively charged dye and iodonium ion, 15 and selective remcval of iodonium ion after imaging is more difficult.
The bleachable dyes may be generically referred to as polymethine dyes which term characterises dyes having at least one electron donor 20 and one electron acceptor group linked by methine groups or aza analoyues. The dyes have an oxidation potential between 0 and +1 volt, preferably between +0.2 and +0.8 volt. The bleachable dyes may be selected from a wide range of known classes of dyes 25 including allopolar cyanine dye bases, complex cyanine, hemicyanine, merocyanine, azine, oxonol, streptocyanine and styryl.
The dye and iodonium system has its greatest sensitivity at the lmax f the longest wavelength 30 absorbance peak. Generally, it is necessary to irradiate the system with radiation of wavelength in the vicinity of this ~max for bleaching to occur.
Thus, a combination of coloured dyes may be used, e.g.
~2~5~
=5-yellow, magenta and cyan, in the same or different layers in an element and these can be selectively bleached by appropriate visible radiation to form a full colour image. Monochromatic or polychromatic images may be produced using the photosensitive materials with relatively short exposure times in daylight or sunlight or even artificial sources of light (e.g. fluorescent lamps or laser beams). The exposure time, for adequate results, for example when 10 using an 0.5 kW tungsten lamp at a distance of 0.7 m, may be between 1 second to 10 minutes.
The iodonium salts used in the imaging system are compounds consisting of a cation wherein a positively charged iodine atom bears two covalently 15 bonded carbon atoms, and any anion. Preferably the acid from which the anion is derived has a pKa ~ 5.
The preferred compounds are diaryl, aryl/heteroaryl or diheteroaryl iodonium salts in which the carbon-to-iodine bonds are from aryl or heteroaryl groups.
20 Aliphatic iodonium salts are not normally thermally stable at temperatures above 0C. However, stabilised alkyl phenyl iodonium salts such as those disclosed in Chem. Lett. 1982, 65-6 are stable at ambient temperatures and may be used.
The ~leachable dye and iodonium salt are in reactive association on the support. Reactive association is defined as such physical proximity between the compounds as to enable a chemical reaction to take place between them upon exposure to light. In 30 practice, the dye and iodonium salt are in the same layer or in adjacent layers on the support.
In general, the weight ratio of bleachable dye to iodonium salt in the element is in the range from 1:1 to 1:50, preferably in the range from 1:2 to 1:10.
~69~
=6=
The bleachable dye and iodonium salt may be applied to the support in a binder. Suitable binders are transparent or translucent, are generally colourless and include natural polymers, synthetic resins, polymers and copolymers, and other film forming media. The binders may range from thermoplastic to highly cross-linked, and may be coated from aqueous or organic solvents or emulsions.
Suitable supports include transparent film, 10 e.g. polyester, paper e.g. baryta-coated photographic paper, and metallised film. Opaque vesicular polyester films are also useful.
The fixing of the radiation-sensitive elements may be effected by destruction of the iodonium ion by 15 disrupting at least one of the carbon-to-iodine bonds since the resulting monoaryl iodine compound will not react with the dye. The conversion of the iodonium salt to its non-radiation sensitive form can be effected in a variety of fashions. Introduction of 20 ammonia and amines in reactive association with the iodonium ion, or a reaction caused on heating, or UV
irradiation of a nucleophilic anion such as I~, Br~, Cl~, BAr4~ (tetra-arylboronide), Ar~ (e.g.
phenoxide~, or 4-NO2C6H4CO2~, with the iodonium ion, 25 will effect the conversion.
An alternative method of achieving post-imaging stabilisation or fixing is to remove the iodonium ion from reactive association with the dye by washing with an appropriate solvent. For example, in 30 the case of elements using mordanted oxonol dyes and water soluble iodonium salts formulated in gelatinl after imaging, the iodonium salt is simply removed by an aqueous wash, which leaves the immobilised dye in i9~
the binder. The dye stability to light is then equivalent to that of the dye alone. An element in which the dye and iodonium salt is formulated in polyvinylpyridine may be treated with aliphatic ketones to remove the iodonium salt and leave the dye in the binder.
The elements may be used as transparencies for use with overhead projectors, for making enlarged or duplicate copies of colour slides and for related 10 graphics or printing applications, such as pre-press colour proofing materials.
Dye diffusion transfer systems are known and are becoming increasingly important in colour photography (see C.C. Van de Sande in Angew Chem.
15 1983, 22, 191-209). These systems allow "rapid access" colour images without a complicated processing sequence. The construction of these colour materials may be donor-receptor type (e.g. Ektaflex commercially available from Kodak) integral peel-apart type (e.g.
20 Polaroid, E.H. Land, H.G. Rogers, V.X. Walworth in J.
Sturge Nebelette's Handbook o$ Photography and Reprography, 7th Ed. 1977, Chapter 12), or integral single sheet type (e.g. Photog. Sci. and Eng., 1976, 20~ 155)o Silver halide diffusion transfer systems 25 are also known (e.g. E.H. Land. Photog. Sci. and Eng., 1977, _ , 225). Examples of diffusion transfer fixing in non-silver, dye-forming reactions employing solvent application to effect the transfer are disclosed in United States Patent Specification Nos. 3 460 313 and 30 3 598 583. The latter patent also describes a full-colour imaging element, applicable for preparation of colour proofs, fixed by transfer of dye precursors in register to a receptor. Other examples ~2i~ S~
of non-silver diffusion transfer imaging systems are disclosed in British Patent Specification Nos.
1 0S7 703, 1 355 61~ and 1 371 898. The latter two Patents also disclose the transfer of dye images under the influence of dry heat.
It has now been found that certain dyes which are bleachable upon exposure to radiation in the presence of iodonium ion are susceptible to diffusion or sublimation transfer and this property may be 10 utilised to separate such dyes from the iodonium ion and produce a clean, stable image by transfer from a radiation-sensitive layer to a receptor layer or separate receptor element.
Brief Summary__f the Invention According to the present invention there is provided a process for ~orming an image which comprises image-wise exposing to radiation of selected wavelength a carrier element comprising, as image forming cornponents, in one or more imaging layers 20 coated on a support a bleachable dye in reactive association with iodonium ion thereby bleaching the dye in exposed areas to form a positive image, and thereafter transferring the positive d~e image to a receptor which is either a receptor layer present on 25 the carrier or a separate receptor element by heating the carrier element to a sufficient temperature to allow the dye image to sublime to the receptor thereby forming an image on the receptor.
g The process of the invention provides stable dye images, optionally full colour images, of high quality with low background fog. The imaging system does not require the presence of silver halide.
Description of the Preferred Embodiments In accordance with the invention the bleachable dyes are sublimable and after image-wise exposure the carrier element is placed in intimate contact with a receptor and the resulting composite 10 heated for a sufficient time and to a sufficient temperature to allow the dye to sublime across the interface to the receptor thereby forming a laterally reversed positive image on the receptor. Thereafter the carrier element is separated from the receptor.
.
6~
=10=
The sublimation transfer allows the formation of a stable dye image having high colour purity. The process is entirely dry and takes only a few minutes to give colour prints. A single transfer from the carrier element to a receptor results in a mirror image. If a true image; right-reading, is required a double transfer process may be employed transferring the dyes from the carrier element to an intermediate receptor and thereafter transferring the dyes from the 10 intermediate receptor to the final receptor.
Alternatively, a true image may be formed by reversing the transparency used for exposure.
The process may be used to achieve a multi-colour print either by sequentially transferring 15 dyes from separate carrier elements or by utilising a carrier element having two or more coloured dyes, e.g.
magenta, cyan and yellow, and transferring the dyes simultaneously~
Suitable dyes for use in this system are those 20 which are both bleachable upon exposure to radiation in the presence of an iodonium ion and are sublimable, preferably in the temperature range 80 to 160C, more preferably 100 to 150C. In general, the dyes are electrically neutral (i.e. not charged) and have a 25 molecular weight of less than 400, preferably less than 350. The dyes also generally possess a compact or aball-like" structure; dyes having an elongate structure, e.g. those having long methine chains, do not readily sublime. The dyes are also selected such 30 that they do not fade or undergo a change in colour on - sublimation. When more than one dye is employed it is desirable to match the sublimation characteristics of the dyes to ensure an even transfer rate for all the dyes.
~26~5~
Suitable bleachable dyes may be generically referred to as polymethine dyes which term characterises dyes having at least one electron donor and one electron acceptor group linked by methine groups or a~a analogues. The dyes have an oxidation potential between 0 and +1 volt, preferably between ~0.2 and ~0.8 voltO The bleachable dyes may be selected from a wide range of known classes of dyes including allopolar cyanine dye bases, complex 10 cyanine, hemicyanine, merocyanine, azine, oxonol, streptocyanine and styryl.
In general, suitable dyes for use in the invention will have the structure:
.'~
in which:
n is 0, 1 or 2, and ~.z~
Rl to R4 are selected to provide an electron donor moiety at one end of the conjugated chain and an electron acceptor moiety at the other, and may be selected from substituents including hydrogen, halogen, cyano, carboxy, alkoxy, hydroxy, nitro, alkyl, aryl groups or heterocyclic rings any of which may be substituted. The skeletal structure of the groups Rl to R4 generally contain up to 14 atoms selected from C, N, O and S. When the skeletal lO structure of a Rl to ~4 group is in the orm of a linear chain there will usually be no more than 6 carbon atoms in the chain. When the skeletal structure is cyclic there will be no more than 7 atoms in any single ring. Cyclic structures may comprise l5 two or more fused rings containing up to 14 atoms. If the skeletal structure of a Rl to R~ group comprises two unfused cyclic groups there will be no more than 3 atoms in the linear chain between the groups.
Alternatively, R1 and R2 and/or R3 and R4 may 20 represent the necessary atoms to complete optionally substituted aryl groups or hetreocyclic rings, generally containiny up to 14 atoms selected from C, N, O and S and having a structure as defined above.
The conjugated chain is preferably composed of 25 carbon atoms but may include one or more nitrogen atoms providing the conjugation is not disrupted. The free valences on the chain may be satisfied by hydrogen or any substituent of the type used in the cyanine dye art including fused ring systems.
The particular selection of substituents Rl to R4 effects the light absorbance properties of the dye which may be varied to provide absorption peaks ranging from the ultraviolet (300 to 400 nm), near ILZ6~5'~
=13=
visible (400 to 50~ nm), far visible (500 to 700 nm) and infrared (700 to 1100 nm).
Dyes of the above formula are well known particularly in the silver halide photographic art and S are the subject of numerous patents. Exemplary dye structures are disclosed in The Theory of the Photographic Process, T.H. James, Ed. MacMillan Editions 3 and 4, and Encyclopaedia of Chemical Technology, Kirk Othmer, 3rd Edition, Vol. 18, 1983.
Within the above general structure of dyes are various classes of dye including:
1) Merocyanine dyes of the general formula:
R `B
in which:
q is an integer of 0 to 2, R5 represents hydrogen or a substituent which may be present in conventional cyanine dyes, e.g.
alkyl (preferably of 1 to 4 carbon atoms), etc., the groups A and B, which need not necessarily complete a ayclic structure with the methine chain, 2S independently represent alkyl, aryl or heterocyclic groups or the necessary atoms to complete heterocyclic rings which may be the same or different.- The skeletal structure of the groups A and B generally contain up to 14 atoms selected from C, N, O and S.
30 When the skeletal structure of A or B is in the form of a linear chain there will usually be no more than 6 carbon atoms in the chain. When the skeletal structure completed by A or B is cyclic there will be , s~
=1~=
no more than 7 atoms in any single ring. Cyclic structures may comprise two or more fused rings containing up to 14 atom~. If the skeletal structure complete by A or B comprises two unfused cyclic yroups there will be no more than 3 atoms in the linear chain between the groups. Additionally B may complete a carbocyclic ring.
These dyes are well known in the silver halide photographlc art and are described in The Theory of 10 the Photo~raphic Process, reEerred to above.
It is to be understood that these cyanine, merocyanine, anionic and oxonol dyes may bear substituents along the polymethine chain composed of C, N, O and S, and that these substituents may 15 themselves join to form ~, ~ or 7 membered rings, or may bond with rings A and B to form further rings, possibly with aromatic character. Rings A and B may also be substituted by C, N, H, O and S containiny groups such as alkyl, substituted alkyl, alkoxy, amine 20 (primary, secondary and tertiary), aryl (e.g. phenyl and substituted phenyl), halo, carboxyl, cyano, nitro, etc. Exemplary substituents are well known in the cyanine dye art.
2~ Benzylidene and cinnamylidene dyes of the 25 structure:
~ ~3 C ~1 R R
in which:
~4S~
=15=
A is as defined above, and may additionally be cyano, or carboalkoxy or other carbonyl-containing groups, e.g. ketone, or S=O containing groups, e.g.
S02Me, n is 0 or 1, R6 and R7 independently represent a hydrogen atom or an alkyl group (optionally substituted) or aryl group containing up to 12 carbon atoms, R8 is H or CN or CO2R9, in which R9 is an lOopticnally substituted alkyl group of up to 6 carbon atoms, and the Eree valences may be satisfied by hydrogen or alkyl groups, or together may form a 6-membered carbocyclic saturated or aromatic ring.
Examples of such dyes include:
CN
Me 2 ~ Me 2N~
3) Quinoline merocyanine dyes of the general structures:
X
~3 CH) p=C~ ~ (CH-CH) p C~
~26~5~
=16 =
in which:
R6 is as defined above, p is 0 or 1, and at least one of X and Y is an electron withdrawing group, e.g. cyano, nitro, carbonyl (in aldehyde, ketone, carboxylic acid, ester or amide), sulphonyl containing up to 6 atoms selected from C, N, 0 and S, or X and Y together form a 5 or 6 membered ring with additional atoms selected from C, N, 0 and S, and containing an electron withdrawing group ~e.g.
keto).
Examples of such dyes include:
~ and Et ~e
X
~3 CH) p=C~ ~ (CH-CH) p C~
~26~5~
=16 =
in which:
R6 is as defined above, p is 0 or 1, and at least one of X and Y is an electron withdrawing group, e.g. cyano, nitro, carbonyl (in aldehyde, ketone, carboxylic acid, ester or amide), sulphonyl containing up to 6 atoms selected from C, N, 0 and S, or X and Y together form a 5 or 6 membered ring with additional atoms selected from C, N, 0 and S, and containing an electron withdrawing group ~e.g.
keto).
Examples of such dyes include:
~ and Et ~e
4) Phenoazine dyes of the general structure:
Z ~ Q ~ O
in which:
2 is an electron donor, e.g. NR6R7, in which R6 and R7 are as defined above, and Q represents 0, S, NH, NCH3, NC2H5, CH2, e.g.
Me2N 5 ~64~
-17=
Z ~ Q ~ O
in which:
2 is an electron donor, e.g. NR6R7, in which R6 and R7 are as defined above, and Q represents 0, S, NH, NCH3, NC2H5, CH2, e.g.
Me2N 5 ~64~
-17=
5) A2amethine or indoaniline dyes of the general structure:
, ~ NR6R
ll~N --O `-B
in which:
r is 0 or 1, and A, B, R6 and R7 are as deEined above.
The group NR6R7 may also be positioned in a para-disposition to the chain, in addition to the ortho-disposition shown. Simiariy the carbonyl group may be in other dispositions on the ring.
These dyes have been used in chromogenic photographic processes. Specific examples of such dyes include:
~ M ~ ~ ~ 3 N and ~ ,, NMe2 ~Z64~
= l&
The iodonium ions used in the invention are compounds consisting of a cation wherein a positively charged iodine atom bears two covalently bonded carbon atoms, and any anion. The preferred compounds are diaryl, aryl/heteroaryl or diheteroaryl iodonium salts in which the carbon-iodine bonds are from aryl or heteroaryl groups and one of the aryl or heteroaryl groups is substituted with an alkyloxy group.
Suitable iodonium salts may be represented by the 10 formula:
Ar ~ A~
Ar 15 in which~
Arl and Ar2 independently represent carbocyclic or heterocyclic aromatic-type groups generally having from 4 to 20 carbon atoms, or together with the iodine atom complete a heterocyclic 20 aromatic ring.
These groups include substituted and unsubstituted aromatic hydrocarbon rings, e.g. phenyl or naphthyl, which may be substituted with alkyl groups, e.g.
methyl, alkoxy groups, e.g. methoxy, chlorine, 25 bromine, iodine, fluorine, carboxy, cyano or nitro groups or any combination thereof~ Examples of hetero-aromatic groups include thienyl, furanyl and pyrazolyl which may be substituted with similar substituents as described above. Condensed 3~ aromatic/hetero-aromatic groups, e.g. 3-indolinyl, may also be present, ~ represents an anion which may be incorporated into Arl or Ar2.
=19=
Preferably Arl and Ar2 do not have more than two substituents at the alpha-positions of the aryl groups. Most preferably Arl and Ar2 are both phenyl groups.
The alpha-positions of the Arl and Ar2 groups may be linked together to include the iodine atom within a ring structure, e.g.
~ I ~ A~
in which z is an oxygen or sulphur atom. An example of such an iodonium salt is:
=2~=
N02 I ~ No2 PF6~3 Other suitable iodonium salts include polymers containing the unit:
~J ~
\ A~ I~ -Ph /
in which Ph represents phenyl.
Examples of such polymers are disclosed in Yamada and Okowara, Makromol. _hemie, 1972, 152, 61-6.
Any anion may be used as the counter-ion A~
20 provided that the anion does not react with the iodonium cation under ambient temperatures. Suitable inorganic anions include halide anions, HS04~, and halogen-containing complex anions, e.g.
tetrafluoroborate, hexafluorophosphate, 25 hexafluoroarsenate and hexafluoroantimonate. Sultable organic anions include those of the formulae:
Rl 7co~ or R17So3~
30 in which R17 is an alkyl or aryl group of up to 20 carbon atoms, e.g. a phenyl group, either of which may be substituted. Bxamples of such anlons include CH3CO ~ and CF3Cod3.
~Z6~L5~4f =21=
A~ may be present in Ar1 or Ar2, e.g.
A
in which A~ represents cod~, etc.
Furthermore, A~ may be present in a molecule containing two or more anions, e.g. dicarboxylates 10 containing more than 4 carbon atoms.
The most significant contribution of the anion is its effect upon the solubility of the iodonium salt in different solvents or binders.
Most of the iodonium salts are known, they ~ay 15 be readily prepared and some are commercially available. The synthesis of suitable iodonium salts is disclosed in F.M. Beringer et al, Journal of the American Chemical Society, 80, 4279 (1958).
Suitable substrates for the donor (or carrier) 20 for use in sublimation transfer are plastics film, paper (cellulosic or synthetic fibre), metallised plastics film and plastic film to film or plastic film to paper laminates.
The substrate should be unaffected by the 25 processing conditions. For example, the substrate must be heat-stable and not possess undesirable dimensional variation, nor degradation, nor tackiness when subjected to the sublimation conditions. A
preferred substrate is a plastics film such as 3~ polycarbonate film, cellulose acetate film or most pre~erably polyester, e.g. poly(ethylene terephthalate~, which may be biaxially orientated.
~269~5~9~
=22=
The substrates may possess surface modifying or other coatings to enhance adhesion of imaging layers, to improve smoothness, etc. Resin coated photographic grade paper is a suitable substrate. The plastics film may specifically possess a subbing layer which acts as a priming layer for gelatin and other hydrophilic coating.
Binders suitable for use in preparing the carrier element for use in sublimation transfer are 10 organic binders which dissolve readily in solvent and afford on coating clear dispersions of the dyes and iodonium salts described herein. Suitable binders include poly(vinyl butyral)l polytvinyl acetate) polymers and phenolic resins~ The preferred weight 15 range of iodonium ion to binder is from 3 to 15~. The preferred weight range of dye to iodonium salt is 1:1 to 1:15, more preferably 1:1 to 1:5.
~69LS~
=~3=
The binder must allow the dyes to migrate on heating to the processing temperature, thus allowing transfer to the receptor layer. If more than one dye is present, a general equivalence of sublimation transfer rates is desirable.
A layer containing the above components is coated preferably at 30 to 60 g/m2, wet deposition onto the substrate. It is undesirable to have overlayers as this hinders sublimation of the dyes, 10 unless the overlayer is very thin. It is also preferred for all the bleachable dyes and iodonium salts present in an element to be in a single layer.
Generally the element should be constructed so as not to inhibit the ready sublimation transfer of the dye 15 from the carrier sheet. The topmost surface of the element should allow good contact with the receptor layer and not become tacky on heating to the transfer temperature.
The carrier element is firstly exposed so as 20 to cause bleaching of the dyes by reaction with the iodonium ion. Most frequently visible light will be used, the actinic wavelengths corresponding to the absorption charact~ristics of the dyes. A variety of light sources may be used including continuous white 25 light and laser. Sufficient exposure must be given to ensure full bleaching or decomposition of the dyesr as residual, unreacted dye may transfer. Thereafter the exposed precursor element is used to effect transfer of the unreacted dyes. Exposure is normally 30 undertaken at ambient conditions of temperature although mild heating is allowable generally up to about 80Ct provided that this does not cause sublimation.
L~
=24 =
on liyht exposure the dyes react with the iodonium ions to give non-sublimable, charged species. The dyes reported in Table l are believed to react on exposure with iodonium salts to give charged photo-products of the general structure as follows:
NMe2 ~NMe2 X
~ + I0 ~
The reaction products do not significantly transfer on heating. After imaging at room temperature, the unbleached dye is readily separated by thermal transfer. Thus, the unbleached dye is transferred by sublimation to the receptor, and the 20iodonium salt and the dye photoproduct remain substantially in the imaging layer.
While the main purpose of this invention is to achieve visible dye transfer, organic ultraviolet and infrared absorbing molecules may also be transferred, 25 e.g. to make ultraviolet vr infrared masks.
The receptor material may be selected from a wide range of materials as described above including paper, particularly coated paper, e.g. poly(vinyl chloride) coated paper, plastics film materials, e.g.
30pvlyester, such as poly(ethylene terephthalate) films, including metallised films, woven and non-woven materials such as textile fabric and cloth and plastics paper.
~6~S~
=25=
The precursor and receptor should be capable of conforming together to allow transfer. The receptor material should absorb the transferred dyes for permanence and may be coated with absorbing pigments, mordants and organic polymers to improve dye absorption and stability. The receptor should withstand the transfer conditions and not exhibit adverse loss of dimensional stability or tackiness.
Typical processing times are from 30 to 120 10 seconds, with heating from 100 to 150C. Thereafter the receptor is separated giving a single or multiple te.g. full) colour reproduction. Heat may be applied through conduction or convection, contact with a heated roller, drum, platen or other surface, or in an 15 oven or by an electrically heated layer or underlayer.
The short processing time and dry conditions are particularly useful aspects of this invention.
The choice of receptor substrates is large and the transfer leaves behind various species which 20 contribute to background fog levels. The backgrounds on the receptors are much cleaner (e.g. low Dmin) and there is a reduced tendency or the dye to degrade, being removed from the proximity of iodonium ions.
Dyes transferred to a receptor substrate may 25 be further transferred from the receptor to yet another receptor. Here if the transfer is to be effected again, the first receptor should readily release the dyes again on heating. Multiple transfers of this kind will generally be accompanied by some 3~ loss in resolution and optical density. Single transfer results in a reversed-reading image. Double transfer results in a right-reading image.
Dyes may be transferred sequentially from ~2~i4~9~
=26=
separate substrates in order to achieve a multi~colour print, but generally it is desirable to transfer magenta, cyan and yellow dyes simultaneously from a single substrate if a full-colour print is required.
Once transferred the dyes may be viewed by reflection, as on paper, or by transmission. In general, only the unreacted dyes are transferred, however it is permissable for sublimable colourless stabilising additives to be transferred. Preferably 1~ such additives are incorporated in the surface of the receptor. Additives allowing maintenance of colour density are particularly useful.
The invention will now be illustrated by the following Examples.
In the following Examples the sensitivity of the element was measured by the following technique.
A 2.5 cm s~uare piece of each sample was exposed over an area of 2.5 mm2 with focussed light filtered, using a Kodak narrow band filter (551.4 nm:power output =
2~ 2.36 x 10-3 W/cm2) and the change in the transmission optical density with time was monitored usiny a Joyce Loebl Ltd. microdensitometer. A plot of transmission optical density versus time was made and the exposure time tt) for the optical density to fall from DmaX to 25 (DmaX-l) was determined. The energy required (E) was calculated as the exposure time (t) x power output (- 2.36 x 10-3 wJcm2): this gives an indication of the sensitivity of the elements.
In all cases a significant reduction of 3~ background density was achieved after transfer which gave a much cleaner image. Typically the minimum density before transfer and after exposure was approximately 0.15, this reducing to approximately 0.05 or below after transfer.
~2~45~4~
=27=
Example 1 Single dye su~limation transfer Dye No. 1 (0.06 g) in 3 ml ethanol was added fr~ to Butvar B76 (1 g) in 7 ml butan-2-one.
~- Diphenyliodonium hexafluorophosphate (0.3 g) was added to the resulting lacquer in red light. The mixture was coated at 75 micron thickness on unsubbed polyester base and dried at room temperature for 15 minutes in the dark. The following Table reports the initial and transferred maxiJnum optical densities, 10 Dmax, achieved.
A strip of the sample was imaged through a step wedge having an optical density differential between adjacent steps of 0.15, with a tungsten halide source ~1 kW, 0.5 m) for 120 seconds. The resulting 15 step image was contacted with a photographic, baryta paper receptor coated with poly(vinyl chloride) Bakelite Ltd. r type VYNS, in the dark. The construction was covered with muslin and the composite heated with an iron set at "cotton" ~temperature 20 l~O~C) for 2 minutes. Separation oE the construction gives a Nmirror image" copy of the carrier filrn transferred onto the PVC coated paper. The following Table reports the reflected density after transfer.
The minimum background density was found to be 25 significantly less after the transfer process.
Resolution test A strip of the sample was contacted with an UGRA mask (the UGRA mask was an 1976 UGRA-Gretag-Plate Control Wedge PCW) and this construction imaged as above using a tungsten halide source. In the carrier, the best resolution was 4 micron which is equivalent to 25~ lines per millimetre. The imaye was 'r~ Q ~ rl~, lZ6~S~
=28=
transferred to the PVC coated receptor by heating as above described~ The best resolution was 17 micron which is equivalent to 59 lines per millimetre.
Examples 2 to 6 Example 1 was repeated using the dyes reported in the following Table, individually in the proportions indicated. The Table reports the maximum 10 optical density by transmission achieved in the original and by reflectance in the receptor and the eneryy required at the max of the dye which gives a measure of the photosensitivity of the composition. A
significant reduction in the minimum background 15 density was observed after sublimation transfer.
~Z~ ?4 =~gC
Table Example Dye No. Structure Weight ~max in Density E
No. 9 ethanol Ini Tr (x106 mJ~m2) nm __ _ _ __ _ .
1 1 NMe2 0.06 475 1.5 1.0 1.9 ~' CN
2 2IMe2 0.06 450 1.3 0.9 8 2Me CN
3 3~ ez 0.06 550 1.3 1.3 6.2 ll ~
~0 ~y ,~
-Ini ~= Initial density (transmission) Tr = Transferred density (reflected) after heating 2 mins/150~.
1~6~5~
=30=
Table (Contd.) _ _ Example Dye No. Structure Weight ~max in Density E
No. g ethanol Ini TX (x106 mJ/m2) nm 4 4 ~ 2 0.06 570 1.0 0.8 5.1 ~3 o NMe2 0.06 560 1.3 1.2 7.6 ~ O
0~ '
, ~ NR6R
ll~N --O `-B
in which:
r is 0 or 1, and A, B, R6 and R7 are as deEined above.
The group NR6R7 may also be positioned in a para-disposition to the chain, in addition to the ortho-disposition shown. Simiariy the carbonyl group may be in other dispositions on the ring.
These dyes have been used in chromogenic photographic processes. Specific examples of such dyes include:
~ M ~ ~ ~ 3 N and ~ ,, NMe2 ~Z64~
= l&
The iodonium ions used in the invention are compounds consisting of a cation wherein a positively charged iodine atom bears two covalently bonded carbon atoms, and any anion. The preferred compounds are diaryl, aryl/heteroaryl or diheteroaryl iodonium salts in which the carbon-iodine bonds are from aryl or heteroaryl groups and one of the aryl or heteroaryl groups is substituted with an alkyloxy group.
Suitable iodonium salts may be represented by the 10 formula:
Ar ~ A~
Ar 15 in which~
Arl and Ar2 independently represent carbocyclic or heterocyclic aromatic-type groups generally having from 4 to 20 carbon atoms, or together with the iodine atom complete a heterocyclic 20 aromatic ring.
These groups include substituted and unsubstituted aromatic hydrocarbon rings, e.g. phenyl or naphthyl, which may be substituted with alkyl groups, e.g.
methyl, alkoxy groups, e.g. methoxy, chlorine, 25 bromine, iodine, fluorine, carboxy, cyano or nitro groups or any combination thereof~ Examples of hetero-aromatic groups include thienyl, furanyl and pyrazolyl which may be substituted with similar substituents as described above. Condensed 3~ aromatic/hetero-aromatic groups, e.g. 3-indolinyl, may also be present, ~ represents an anion which may be incorporated into Arl or Ar2.
=19=
Preferably Arl and Ar2 do not have more than two substituents at the alpha-positions of the aryl groups. Most preferably Arl and Ar2 are both phenyl groups.
The alpha-positions of the Arl and Ar2 groups may be linked together to include the iodine atom within a ring structure, e.g.
~ I ~ A~
in which z is an oxygen or sulphur atom. An example of such an iodonium salt is:
=2~=
N02 I ~ No2 PF6~3 Other suitable iodonium salts include polymers containing the unit:
~J ~
\ A~ I~ -Ph /
in which Ph represents phenyl.
Examples of such polymers are disclosed in Yamada and Okowara, Makromol. _hemie, 1972, 152, 61-6.
Any anion may be used as the counter-ion A~
20 provided that the anion does not react with the iodonium cation under ambient temperatures. Suitable inorganic anions include halide anions, HS04~, and halogen-containing complex anions, e.g.
tetrafluoroborate, hexafluorophosphate, 25 hexafluoroarsenate and hexafluoroantimonate. Sultable organic anions include those of the formulae:
Rl 7co~ or R17So3~
30 in which R17 is an alkyl or aryl group of up to 20 carbon atoms, e.g. a phenyl group, either of which may be substituted. Bxamples of such anlons include CH3CO ~ and CF3Cod3.
~Z6~L5~4f =21=
A~ may be present in Ar1 or Ar2, e.g.
A
in which A~ represents cod~, etc.
Furthermore, A~ may be present in a molecule containing two or more anions, e.g. dicarboxylates 10 containing more than 4 carbon atoms.
The most significant contribution of the anion is its effect upon the solubility of the iodonium salt in different solvents or binders.
Most of the iodonium salts are known, they ~ay 15 be readily prepared and some are commercially available. The synthesis of suitable iodonium salts is disclosed in F.M. Beringer et al, Journal of the American Chemical Society, 80, 4279 (1958).
Suitable substrates for the donor (or carrier) 20 for use in sublimation transfer are plastics film, paper (cellulosic or synthetic fibre), metallised plastics film and plastic film to film or plastic film to paper laminates.
The substrate should be unaffected by the 25 processing conditions. For example, the substrate must be heat-stable and not possess undesirable dimensional variation, nor degradation, nor tackiness when subjected to the sublimation conditions. A
preferred substrate is a plastics film such as 3~ polycarbonate film, cellulose acetate film or most pre~erably polyester, e.g. poly(ethylene terephthalate~, which may be biaxially orientated.
~269~5~9~
=22=
The substrates may possess surface modifying or other coatings to enhance adhesion of imaging layers, to improve smoothness, etc. Resin coated photographic grade paper is a suitable substrate. The plastics film may specifically possess a subbing layer which acts as a priming layer for gelatin and other hydrophilic coating.
Binders suitable for use in preparing the carrier element for use in sublimation transfer are 10 organic binders which dissolve readily in solvent and afford on coating clear dispersions of the dyes and iodonium salts described herein. Suitable binders include poly(vinyl butyral)l polytvinyl acetate) polymers and phenolic resins~ The preferred weight 15 range of iodonium ion to binder is from 3 to 15~. The preferred weight range of dye to iodonium salt is 1:1 to 1:15, more preferably 1:1 to 1:5.
~69LS~
=~3=
The binder must allow the dyes to migrate on heating to the processing temperature, thus allowing transfer to the receptor layer. If more than one dye is present, a general equivalence of sublimation transfer rates is desirable.
A layer containing the above components is coated preferably at 30 to 60 g/m2, wet deposition onto the substrate. It is undesirable to have overlayers as this hinders sublimation of the dyes, 10 unless the overlayer is very thin. It is also preferred for all the bleachable dyes and iodonium salts present in an element to be in a single layer.
Generally the element should be constructed so as not to inhibit the ready sublimation transfer of the dye 15 from the carrier sheet. The topmost surface of the element should allow good contact with the receptor layer and not become tacky on heating to the transfer temperature.
The carrier element is firstly exposed so as 20 to cause bleaching of the dyes by reaction with the iodonium ion. Most frequently visible light will be used, the actinic wavelengths corresponding to the absorption charact~ristics of the dyes. A variety of light sources may be used including continuous white 25 light and laser. Sufficient exposure must be given to ensure full bleaching or decomposition of the dyesr as residual, unreacted dye may transfer. Thereafter the exposed precursor element is used to effect transfer of the unreacted dyes. Exposure is normally 30 undertaken at ambient conditions of temperature although mild heating is allowable generally up to about 80Ct provided that this does not cause sublimation.
L~
=24 =
on liyht exposure the dyes react with the iodonium ions to give non-sublimable, charged species. The dyes reported in Table l are believed to react on exposure with iodonium salts to give charged photo-products of the general structure as follows:
NMe2 ~NMe2 X
~ + I0 ~
The reaction products do not significantly transfer on heating. After imaging at room temperature, the unbleached dye is readily separated by thermal transfer. Thus, the unbleached dye is transferred by sublimation to the receptor, and the 20iodonium salt and the dye photoproduct remain substantially in the imaging layer.
While the main purpose of this invention is to achieve visible dye transfer, organic ultraviolet and infrared absorbing molecules may also be transferred, 25 e.g. to make ultraviolet vr infrared masks.
The receptor material may be selected from a wide range of materials as described above including paper, particularly coated paper, e.g. poly(vinyl chloride) coated paper, plastics film materials, e.g.
30pvlyester, such as poly(ethylene terephthalate) films, including metallised films, woven and non-woven materials such as textile fabric and cloth and plastics paper.
~6~S~
=25=
The precursor and receptor should be capable of conforming together to allow transfer. The receptor material should absorb the transferred dyes for permanence and may be coated with absorbing pigments, mordants and organic polymers to improve dye absorption and stability. The receptor should withstand the transfer conditions and not exhibit adverse loss of dimensional stability or tackiness.
Typical processing times are from 30 to 120 10 seconds, with heating from 100 to 150C. Thereafter the receptor is separated giving a single or multiple te.g. full) colour reproduction. Heat may be applied through conduction or convection, contact with a heated roller, drum, platen or other surface, or in an 15 oven or by an electrically heated layer or underlayer.
The short processing time and dry conditions are particularly useful aspects of this invention.
The choice of receptor substrates is large and the transfer leaves behind various species which 20 contribute to background fog levels. The backgrounds on the receptors are much cleaner (e.g. low Dmin) and there is a reduced tendency or the dye to degrade, being removed from the proximity of iodonium ions.
Dyes transferred to a receptor substrate may 25 be further transferred from the receptor to yet another receptor. Here if the transfer is to be effected again, the first receptor should readily release the dyes again on heating. Multiple transfers of this kind will generally be accompanied by some 3~ loss in resolution and optical density. Single transfer results in a reversed-reading image. Double transfer results in a right-reading image.
Dyes may be transferred sequentially from ~2~i4~9~
=26=
separate substrates in order to achieve a multi~colour print, but generally it is desirable to transfer magenta, cyan and yellow dyes simultaneously from a single substrate if a full-colour print is required.
Once transferred the dyes may be viewed by reflection, as on paper, or by transmission. In general, only the unreacted dyes are transferred, however it is permissable for sublimable colourless stabilising additives to be transferred. Preferably 1~ such additives are incorporated in the surface of the receptor. Additives allowing maintenance of colour density are particularly useful.
The invention will now be illustrated by the following Examples.
In the following Examples the sensitivity of the element was measured by the following technique.
A 2.5 cm s~uare piece of each sample was exposed over an area of 2.5 mm2 with focussed light filtered, using a Kodak narrow band filter (551.4 nm:power output =
2~ 2.36 x 10-3 W/cm2) and the change in the transmission optical density with time was monitored usiny a Joyce Loebl Ltd. microdensitometer. A plot of transmission optical density versus time was made and the exposure time tt) for the optical density to fall from DmaX to 25 (DmaX-l) was determined. The energy required (E) was calculated as the exposure time (t) x power output (- 2.36 x 10-3 wJcm2): this gives an indication of the sensitivity of the elements.
In all cases a significant reduction of 3~ background density was achieved after transfer which gave a much cleaner image. Typically the minimum density before transfer and after exposure was approximately 0.15, this reducing to approximately 0.05 or below after transfer.
~2~45~4~
=27=
Example 1 Single dye su~limation transfer Dye No. 1 (0.06 g) in 3 ml ethanol was added fr~ to Butvar B76 (1 g) in 7 ml butan-2-one.
~- Diphenyliodonium hexafluorophosphate (0.3 g) was added to the resulting lacquer in red light. The mixture was coated at 75 micron thickness on unsubbed polyester base and dried at room temperature for 15 minutes in the dark. The following Table reports the initial and transferred maxiJnum optical densities, 10 Dmax, achieved.
A strip of the sample was imaged through a step wedge having an optical density differential between adjacent steps of 0.15, with a tungsten halide source ~1 kW, 0.5 m) for 120 seconds. The resulting 15 step image was contacted with a photographic, baryta paper receptor coated with poly(vinyl chloride) Bakelite Ltd. r type VYNS, in the dark. The construction was covered with muslin and the composite heated with an iron set at "cotton" ~temperature 20 l~O~C) for 2 minutes. Separation oE the construction gives a Nmirror image" copy of the carrier filrn transferred onto the PVC coated paper. The following Table reports the reflected density after transfer.
The minimum background density was found to be 25 significantly less after the transfer process.
Resolution test A strip of the sample was contacted with an UGRA mask (the UGRA mask was an 1976 UGRA-Gretag-Plate Control Wedge PCW) and this construction imaged as above using a tungsten halide source. In the carrier, the best resolution was 4 micron which is equivalent to 25~ lines per millimetre. The imaye was 'r~ Q ~ rl~, lZ6~S~
=28=
transferred to the PVC coated receptor by heating as above described~ The best resolution was 17 micron which is equivalent to 59 lines per millimetre.
Examples 2 to 6 Example 1 was repeated using the dyes reported in the following Table, individually in the proportions indicated. The Table reports the maximum 10 optical density by transmission achieved in the original and by reflectance in the receptor and the eneryy required at the max of the dye which gives a measure of the photosensitivity of the composition. A
significant reduction in the minimum background 15 density was observed after sublimation transfer.
~Z~ ?4 =~gC
Table Example Dye No. Structure Weight ~max in Density E
No. 9 ethanol Ini Tr (x106 mJ~m2) nm __ _ _ __ _ .
1 1 NMe2 0.06 475 1.5 1.0 1.9 ~' CN
2 2IMe2 0.06 450 1.3 0.9 8 2Me CN
3 3~ ez 0.06 550 1.3 1.3 6.2 ll ~
~0 ~y ,~
-Ini ~= Initial density (transmission) Tr = Transferred density (reflected) after heating 2 mins/150~.
1~6~5~
=30=
Table (Contd.) _ _ Example Dye No. Structure Weight ~max in Density E
No. g ethanol Ini TX (x106 mJ/m2) nm 4 4 ~ 2 0.06 570 1.0 0.8 5.1 ~3 o NMe2 0.06 560 1.3 1.2 7.6 ~ O
0~ '
6 6 ~ 2 0.06 503 0.9 0.5 6 ,~
CN
CN
.
~'~64~
a31=
E~ o 14 Photothermographic imaging with sublimation fixin~
These Examples are for dyes which need light and heat simultaneously to react with iodonium salts.
The samples were coated in Butvar as in Example 1, but containing the dyes in the following Table, in the reported amounts. These dyes do not 10 react with iodonium salts at room temperature, e.g.
the change in the dye absorbance is zero after 5 minutes exposure to filtered light (2 mm2 spot/1.7 mW/cm2). On heating to above the Tg of the binder, e.g. 70C for Butvar B76~ the 15 light-induced reaction occurs. In some cases, there is an intermediate colour prior to bleaching.
In all cases a significant reduction in the mioimum background optical density was observed.
~;~645~
=32=
Table Example ~e No. Structure Weight ~max in Density E
r~o. g a) ethanol Ini Tr (x106 mJ/m2) b) Butvar nm _
CN
CN
.
~'~64~
a31=
E~ o 14 Photothermographic imaging with sublimation fixin~
These Examples are for dyes which need light and heat simultaneously to react with iodonium salts.
The samples were coated in Butvar as in Example 1, but containing the dyes in the following Table, in the reported amounts. These dyes do not 10 react with iodonium salts at room temperature, e.g.
the change in the dye absorbance is zero after 5 minutes exposure to filtered light (2 mm2 spot/1.7 mW/cm2). On heating to above the Tg of the binder, e.g. 70C for Butvar B76~ the 15 light-induced reaction occurs. In some cases, there is an intermediate colour prior to bleaching.
In all cases a significant reduction in the mioimum background optical density was observed.
~;~645~
=32=
Table Example ~e No. Structure Weight ~max in Density E
r~o. g a) ethanol Ini Tr (x106 mJ/m2) b) Butvar nm _
7 7 IMe2 0,04 430 a 3.0 1.8400 9 CN
8 8 CN CN 0.02 430 b 1.2 0,890 0.7 ~3 ' I
9 9 ¢~SN2 0.02 470 b 0.9 0.4 100 9 "
.
~z~
=33=
Table ~Contd.) Example Dye No. Structure W~ight ~max in Den~ity E
No. g a) ethanol Ini Tr ~x106 mJ/m2) b) ~utvar nm ~Me2 0 04 550 a 0.5 0.6 100 80 CN
_ _ _ _ . _ _ _ 11 11 0.02 S60 a 0.6 0.7 50 603 b " ~ N~ ~
~S~O
NMe2 __ _ _ . _ ~26~S~
=3~=
Table (Contd.) Example Dye No. Structure Weight ~max in Density E
No. g a) ethanol Ini Ir (x106 mJ/m2) b~ Butvar rlm 25C ~0C
__ _ . _ _ 12 12 ~ 2 0.02 660 a O.S 0.6 100 1.3 ~ Cl o 13 13 0.02 540 a 0.9 0.2 100 9 Ph O ~ N ~ NMe2 14 14 0.10 530 a 1.8 1.2 1001.8 Me O ~ N ~ NMe2 Ini = Initial density (transmitted) Tr = Transferred density (reflected) after heating 2 mins/15QC.
~;~69LS~
=35=
Example 15 Light and heat imaging fixed b~ _transfer The blue coating oE Example 12 was contacted with a black on white photocopy and the composite put through the 3M Thermofax ~odel 45CB processor at the ~medium" setting. The result was a negative copy of the photocopy, bleaching had occurred in the regions
.
~z~
=33=
Table ~Contd.) Example Dye No. Structure W~ight ~max in Den~ity E
No. g a) ethanol Ini Tr ~x106 mJ/m2) b) ~utvar nm ~Me2 0 04 550 a 0.5 0.6 100 80 CN
_ _ _ _ . _ _ _ 11 11 0.02 S60 a 0.6 0.7 50 603 b " ~ N~ ~
~S~O
NMe2 __ _ _ . _ ~26~S~
=3~=
Table (Contd.) Example Dye No. Structure Weight ~max in Density E
No. g a) ethanol Ini Ir (x106 mJ/m2) b~ Butvar rlm 25C ~0C
__ _ . _ _ 12 12 ~ 2 0.02 660 a O.S 0.6 100 1.3 ~ Cl o 13 13 0.02 540 a 0.9 0.2 100 9 Ph O ~ N ~ NMe2 14 14 0.10 530 a 1.8 1.2 1001.8 Me O ~ N ~ NMe2 Ini = Initial density (transmitted) Tr = Transferred density (reflected) after heating 2 mins/15QC.
~;~69LS~
=35=
Example 15 Light and heat imaging fixed b~ _transfer The blue coating oE Example 12 was contacted with a black on white photocopy and the composite put through the 3M Thermofax ~odel 45CB processor at the ~medium" setting. The result was a negative copy of the photocopy, bleaching had occurred in the regions
10 in contact with the black characters. This copy was then stabilised by dye sublimation to a poly(vinyl chloride) coated paper receptor by heating for 30 seconds at 100C. The result was a blue-coloured negative print of the original. A significant 15 reduction in background density was observed on transfer.
Example 16 This Example shows the single sheet panchromatic capability of the invention.
A mixture of Dye No. 1 (0.06 g) and Dye No. 13 (0.06 g) in 3 ml EtOH was added to a lacquer of Butvar B76 (1 g) in 7 ml butan-2-one. To the red mixture in 25 red light, was added diphenyliodonium hexafluoro-phosphate (0.3 g). The resulting lacquer was knife-edge coated at 75 micron, wet thickness onto unsubbed polyester base (100 micron). The film was dried for 15 minutes at room temperature in air.
A strip of this red film was subjected to a spot of light filtered through a narrow cut filter at 551.4 nm for 100 seconds; in the area of light, a yellow spot (5 mm diameter) formed. The imaged strip :~z~s~
=36=
was then contacted with PVC coated paper and the composite heated for 2 minutes at 150C to transfer the dyes out of Butvar layer into the receptor. Good resolution was obtained; there was no spread of mayenta into the imaged yellow spot.
Example 16 This Example shows the single sheet panchromatic capability of the invention.
A mixture of Dye No. 1 (0.06 g) and Dye No. 13 (0.06 g) in 3 ml EtOH was added to a lacquer of Butvar B76 (1 g) in 7 ml butan-2-one. To the red mixture in 25 red light, was added diphenyliodonium hexafluoro-phosphate (0.3 g). The resulting lacquer was knife-edge coated at 75 micron, wet thickness onto unsubbed polyester base (100 micron). The film was dried for 15 minutes at room temperature in air.
A strip of this red film was subjected to a spot of light filtered through a narrow cut filter at 551.4 nm for 100 seconds; in the area of light, a yellow spot (5 mm diameter) formed. The imaged strip :~z~s~
=36=
was then contacted with PVC coated paper and the composite heated for 2 minutes at 150C to transfer the dyes out of Butvar layer into the receptor. Good resolution was obtained; there was no spread of mayenta into the imaged yellow spot.
Claims (8)
CLAIMS:
1. A process for forming an image which comprises image-wise exposing to radiation of selected wavelength a carrier element comprising, as image forming components, in one or more imaging layers coated on a support a bleachable dye in reactive association with iodonium ion thereby bleaching the dye in exposed areas to form a positive image, and thereafter transferring the positive dye image to a receptor which is either a receptor layer present on the carrier or a separate receptor element by heating the carrier element to a sufficient temperature to allow the dye image to sublime to the receptor thereby forming an image on the receptor.
2. A process as claimed in Claim 1, in which the iodonium compound has the general formula:
in which:
Ar1 and Ar2 independently represent carbocyclic or heterocyclic aromatic-type groups having 4 to 20 carbon atoms, or together with the iodine atom complete a heterocyclic aromatic ring, and A? represents an anion which may be incorporated into Ar1 or Ar2.
=38=
in which:
Ar1 and Ar2 independently represent carbocyclic or heterocyclic aromatic-type groups having 4 to 20 carbon atoms, or together with the iodine atom complete a heterocyclic aromatic ring, and A? represents an anion which may be incorporated into Ar1 or Ar2.
=38=
3. A process as claimed in Claim 2, in which the carrier element comprises cyan, magenta and yellow bleachable dyes, the element being constructed and arranged to allow even transfer of each dye.
4. A process as claimed in Claim 2, in which the dye and iodonium salt are present in one or more layers in a polymeric binder, the weight ratio of dye to iodonium salt being in the range of from 1:1 to 1:50 and the binder is present in an amount from 50 to 98% by weight of the total weight of binder, dye and iodonium salt.
5. A process as claimed in Claim 2, in which the bleachable dyes are sublimable within the temperature range from 100 to 150°C and the process comprises placing the carrier element in contact with a receptor and heating to a temperature of 100 to 150°C for a period of about 30 to 120 seconds to transfer the dye image from the carrier element to the receptor.
6. A process as claimed in Claim 5, in which the bleachable dye is selected from a) merocyanine dyes of the general formula:
=39=
in which:
q is an integer of 0, 1 or 2, R5 represents a hydrogen atom or substituents which may be present in conventional cyanine dyes, A represents an alkyl, aryl or heterocyclic group or the necessary atoms to complete a heterocyclic ring, and B is selected from the same groups as A or additionally may complete a carbocyclic ring, b) benzylidene and cinnamylidene dyes of the structure:
in which:
A is as defined above, and may additionally be cyano, or carboalkoxy or other carbonyl-containing groups, or S=O containing groups, n is 0 or 1, R6 and R7 independently represent a hydrogen atom or an alkyl group (optionally substituted) or aryl group containing up to 12 carbon atoms, R8 is H or CN or CO2R9, in which R9 is an optionally substituted alkyl group of up to 6 carbon atoms, and the free valences may be satisfied by hydrogen or alkyl groups, or together may form a 6-membered carbocyclic saturated or aromatic ring, =40=
c) quinoline merocyanine dyes of the general structures:
in which:
R6 is as defined above, p is 0 or 1, and at least one of X and Y is an electron withdrawing group, sulphonyl containing up to 6 atoms selected from C, N, O and S, or X and Y together form a 5 or 6 membered ring with additional atoms selected from C, N, O and S, and containing an electron withdrawing group, d) phenoazine dyes of the general structure:
in which:
Z is an electron donor, Q represents O, S, NH, NCH3, NC2H5, CH2, and =41=
e) azamethine or indoaniline dyes of the general structure:
in which:
r is 0 or 1, and A, B, R6 and R7 are as defined above, the NR6R7 and carbonyl group optionally being in other dispositions on the rings A and B.
=39=
in which:
q is an integer of 0, 1 or 2, R5 represents a hydrogen atom or substituents which may be present in conventional cyanine dyes, A represents an alkyl, aryl or heterocyclic group or the necessary atoms to complete a heterocyclic ring, and B is selected from the same groups as A or additionally may complete a carbocyclic ring, b) benzylidene and cinnamylidene dyes of the structure:
in which:
A is as defined above, and may additionally be cyano, or carboalkoxy or other carbonyl-containing groups, or S=O containing groups, n is 0 or 1, R6 and R7 independently represent a hydrogen atom or an alkyl group (optionally substituted) or aryl group containing up to 12 carbon atoms, R8 is H or CN or CO2R9, in which R9 is an optionally substituted alkyl group of up to 6 carbon atoms, and the free valences may be satisfied by hydrogen or alkyl groups, or together may form a 6-membered carbocyclic saturated or aromatic ring, =40=
c) quinoline merocyanine dyes of the general structures:
in which:
R6 is as defined above, p is 0 or 1, and at least one of X and Y is an electron withdrawing group, sulphonyl containing up to 6 atoms selected from C, N, O and S, or X and Y together form a 5 or 6 membered ring with additional atoms selected from C, N, O and S, and containing an electron withdrawing group, d) phenoazine dyes of the general structure:
in which:
Z is an electron donor, Q represents O, S, NH, NCH3, NC2H5, CH2, and =41=
e) azamethine or indoaniline dyes of the general structure:
in which:
r is 0 or 1, and A, B, R6 and R7 are as defined above, the NR6R7 and carbonyl group optionally being in other dispositions on the rings A and B.
7. A process as claimed in Claim 6, in which the process comprises the additional step of placing the receptor in intimate contact with a final receptor and heating the composite for a sufficient time and to a sufficient temperature to allow the dye to sublime across the interface to the final receptor thereby forming a true image.
8. The combination of a radiation-sensitive carrier element comprising, as image-forming components, one or more imaging layers coated on a support, a bleachable sublimable dye in reactive association with iodonium ion and a separate receptor element comprising a substrate having coated thereon a receptor layer comprising a polymeric binder.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB84.21398 | 1984-08-23 | ||
| GB848421398A GB8421398D0 (en) | 1984-08-23 | 1984-08-23 | Sublimation transfer imaging system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1264594A true CA1264594A (en) | 1990-01-23 |
Family
ID=10565711
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000488441A Expired - Fee Related CA1264594A (en) | 1984-08-23 | 1985-08-09 | Sublimation transfer imaging system |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6169064A (en) |
| CA (1) | CA1264594A (en) |
| GB (1) | GB8421398D0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005012234A1 (en) * | 2003-07-30 | 2005-02-10 | The Hospital For Sick Children | Compounds for modulating cell proliferation |
| US7563820B2 (en) | 2002-01-18 | 2009-07-21 | The Hospital For Sick Children | Compounds for modulating cell proliferation |
| US7598419B2 (en) | 2004-03-26 | 2009-10-06 | Hsc Research And Development Limited Partnership | Compounds for modulating cell proliferation |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4041611B2 (en) * | 1998-09-24 | 2008-01-30 | 富士フイルム株式会社 | Anionic infrared absorber, photosensitive composition, and lithographic printing plate precursor using the same |
| WO2003068183A1 (en) * | 2002-02-12 | 2003-08-21 | Dsm Ip Assets B.V. | Sunscreen compositions as well as dihydropyridines and dihydropyranes |
-
1984
- 1984-08-23 GB GB848421398A patent/GB8421398D0/en active Pending
-
1985
- 1985-08-09 CA CA000488441A patent/CA1264594A/en not_active Expired - Fee Related
- 1985-08-22 JP JP18500285A patent/JPS6169064A/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7563820B2 (en) | 2002-01-18 | 2009-07-21 | The Hospital For Sick Children | Compounds for modulating cell proliferation |
| WO2005012234A1 (en) * | 2003-07-30 | 2005-02-10 | The Hospital For Sick Children | Compounds for modulating cell proliferation |
| US7598419B2 (en) | 2004-03-26 | 2009-10-06 | Hsc Research And Development Limited Partnership | Compounds for modulating cell proliferation |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8421398D0 (en) | 1984-09-26 |
| JPS6169064A (en) | 1986-04-09 |
| JPH0533779B2 (en) | 1993-05-20 |
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