EP1419888B1 - Thermokopfdrucker und Verfahren zum Drucken auf thermographischen Aufzeichnungsmaterialien - Google Patents

Thermokopfdrucker und Verfahren zum Drucken auf thermographischen Aufzeichnungsmaterialien Download PDF

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Publication number
EP1419888B1
EP1419888B1 EP03103788A EP03103788A EP1419888B1 EP 1419888 B1 EP1419888 B1 EP 1419888B1 EP 03103788 A EP03103788 A EP 03103788A EP 03103788 A EP03103788 A EP 03103788A EP 1419888 B1 EP1419888 B1 EP 1419888B1
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EP
European Patent Office
Prior art keywords
thermal head
substantially light
heating elements
thermal
thermographic material
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EP03103788A
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English (en)
French (fr)
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EP1419888A2 (de
EP1419888A3 (de
Inventor
Eric Kaerts
Ivan Hoogmartens
Geert Defieuw
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Agfa HealthCare NV
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Agfa HealthCare NV
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33545—Structure of thermal heads characterised by dimensions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/3357—Surface type resistors

Definitions

  • the present invention concerns a thermal head printer and process for printing substantially light-insensitive recording materials.
  • Thermography is an image-forming process including a heating step and hence includes photothermography in which the image-forming process includes image-wise exposure and direct thermal processes in which the image-forming process includes an image-wise heating step.
  • direct thermal printing a visible image pattern is produced by image-wise heating of a recording material e.g. image signals can be converted into electric pulses and then via a driver circuit selectively transferred to a thermal head, which consists of microscopic heat resistor elements, thereby converting the electrical energy into heat via the Joule effect. This heat brings about image formation in the substantially light-insensitive thermographic material.
  • thermal heads only those regions which produce heat higher than a certain value are effective for printing, and the regions capable of generating sufficient heat for the printing spread in proportion to voltage applied to the heating resistors. If, therefore, higher voltage is applied to the heating resistors, the size of the printing dots increases in proportion.
  • US 5,825,395 discloses a printing system, comprising: a thermal head, color thermal recording paper having a surface with a plurality of different color developing layers disposed thereon, said plurality of different color developing layers corresponding to a plurality of different colors, and means for feeding said color thermal recording paper in a feed direction at a feed pitch; said thermal head producing printed dots in a desired color developing layer over said surface of said color thermal coloring paper by selectively and directly heating said color thermal recording paper; said thermal head comprising an array of a predetermined number of heating elements, each of said heating elements having a length, in said feed direction of said color thermal recording paper, and being controllable to radiate a selected level of thermal energy, said array being operationally disposed with respect to said color thermal recording paper so that said selected level of thermal energy radiated by said each heating element produces one of said dots without damaging said color thermal recording paper; and said length of each heating element having a value of from 2 to 3.5 said feed pitch.
  • the feed pitch is defined in US 5,825,395 as the distance between adjacent image density peaks in the feed direction as can be seen from Figure 4 and heating element lengths in the feed direction of m, 310 ⁇ m, 360 ⁇ 360 ⁇ m, 460 ⁇ m and 560 ⁇ m are disclosed therein, which according to the specification are longer than those in the case of conventional thermal heads. No information is provided with respect to distance between adjacent heating elements.
  • EP-A 0 500 334 discloses a thermal recording device for forming an image with a dot matrix by applying a thermal head consisting of heat emitting elements arranged in a single row at a first pitch along a primary scanning direction onto a surface of a thermal recording material and moving said thermal recording material relative to said thermal head in a secondary direction perpendicular to said primary scanning direction, and selectively heating said heat emitting elements for each successive movement of said thermal recording material at a second pitch in said scanning direction, wherein: a ratio of a length of said heating elements of said thermal head in said primary scanning direction to said first pitch is 30 to 70%, and a ratio of a length of each of said heat emitting elements of said thermal head in said secondary scanning direction to said second pitch is 60 to 95%.
  • Figure 2 also shows that the pitch in the primary direction, P a , is the distance between the centre of one heat-emitting element and the centre of the next heat-emitting element in the primary direction.
  • P b is the dot pitch of the matrix in the secondary direction.
  • US 5,559,546 discloses a method of perforating a heat sensitive stencil, the method comprising the steps of: bringing the heat sensitive stencil into contact with a thermal head having a plurality of heating resistors arranged in a row; moving the heat sensitive stencil in a sub-scanning direction which is orthogonal to a main-scanning direction in which the plurality of heating resistors are arranged; and perforating the heat sensitive stencil in a dot matrix shape with selectively heated heating resistors of said plurality of heating resistors; the method further comprising the further steps of: making the heat sensitive stencil of substantially only a thermoplastic resin film; and making a width of a space between two adjacent heat resistors of said plurality of heating resistors in the main scanning direction 30% or more of a pitch between the two adjacent heating resistors in the main scanning direction so as to regulate a width of a non-perforated portion of the heat sensitive stencil between two adjacent perforations in the main scanning direction to be 20% or more of the pitch between the two adjacent
  • JP 58-089385A discloses the obtaining of a constant print density all the time even when thermal heads are exchanged by a method in which the same resistor elements as heating elements are provided to the thermal head having plural resistor heating elements, and on the basis of the resistance values of the elements, applied voltage is controlled.
  • a resistor element 5 made of the same material as that of a heating resistor element 2 is provided to part of a thermal head in which heating resistor elements 2-1-2-7 are provided on a ceramic base plate 1, and also the resistor element 5 is connected to the terminals Ra and Rb of a constant-voltage regulation circuit through a lead pattern.
  • the base voltage of a transistor Tr2 rises because the resistance value of the resistor element 5 is also lower than standard, and therefore, collector current is increased and the voltage drop of the resistor R1 is increased.
  • the impedance between the collector bases of the transistor Tr1 is increased and output voltage Vout becomes lower than standard.
  • the resistance value of the heating element 2 is high, the output voltage also becomes higher.
  • US 4,841,120 discloses a thermal head for recording on a recording medium comprising: a substrate having a thick portion and a thin portion having a first flat surface and a second surface formed on an opposite side of said substrate from said first flat surface, said second surface being adapted to contact said recording medium, a plurality of heat resistor elements formed on said first flat surface of said thin portion of said substrate, wiring circuit means for said heat resistor elements formed on said first flat surface of said substrate and driving means for driving said heat resistor elements formed by said first flat surface of said substrate, said thin portion being made by grinding said second surface of said substrate.
  • Figures 7 and 8 illustrate split resistors.
  • JP 61-086271A discloses the elimination of the need to provide an interpolation line even at the time of high-speed recording, by a construction wherein the first and the second heating dot group are provided on the same substrate, and the two systems of the heating dot group are selectively used in accordance with recording condition, i.e., high resolution recording or high-speed recording.
  • the first and third feeder lines 3, 19 and the second and fourth feeder lines 4,20 are so provided as to clamp respectively both side parts of a heating resistor 2 therebetween, and two heating dots 17, 18 differing in length are provided on the same substrate.
  • the first heating dot 17 is selectively operated for recording by using the first and second feeder lines 3,4 whereas in high-speed recording, the second heating dot is selectively operated for recording by using the third and fourth feeder lines 19,20.
  • US 5,485,193 discloses a line-type thermal head for half-tone printing which expresses various densities by utilizing printing dots of various sizes, the thermal head having a main scanning axis and comprising: a substrate, a plurality of heating elements arranged on a substrate along the main scanning axis, each of the heating elements including at least one non-rectangular parallelogramatic resistor for generating heat; and means for supplying electric energy, an amount of which corresponds to a size of a printing dot to be recorded, to each of the heating elements to make the resistor generate heat, wherein the resistor has a region which generates sufficient heat for recording the printing dot, and a size of the region is changed in response to the amount of electric energy applied to the resistor so that printing dots having various sizes are produced by each of the resistors, the supply means including lead electrodes connected electrically to one pair of opposite sides of the resistor, each of the lead electrodes having a width not less than a length of one side of the one pair of opposite sides of the resistor
  • US 5,483,274 discloses a thermal head for a thermal recording apparatus, comprising: means for recording a continuous line of elliptic dots on a recording sheet, said means including a plurality of heat generation resistors arranged one-dimensionally along a given direction, each of the heat generation resistors formed to have a parallelogram shape including four sides and two diagonal lines and configured such that the four sides of the parallelogram shape have directions crossing the given direction and such that two diagonal lines extending between opposing corners of the parallelogram have directions crossing the given direction; and a plurality of drive electrodes respectively connected to said heat generation resistors; wherein an ink film and the recording sheet for thermal recording, which are stacked on one another, are brought into contact with said heat generation resistors and moved in a direction orthogonal to the given direction along which said heat generation resistors are arranged and, during this movement, ink coated on the ink film is melted by said heat generation resistors to allow and image to be transferred to the recording sheet.
  • US 4,970,530 discloses a thermal head arranged in a printing device so as to be opposite to a printed object fed in a constant direction, the thermal head comprising: a base member, a plurality of heating resistors arranged in said base member; electrodes disposed in said base member corresponding to said heating resistors; and a slit formed on a surface of said heating resistors and having a shape in which the width of the slit in a feeding direction of said printed object is less than that in an arranging direction of said heating resistors perpendicular to said feeding direction and the width of the slit in the arranging direction of the heating resistors is approximately equal to a half length of a pitch of said resistors in said arranging direction thereof.
  • thermal heads such as used in the thermal head printers manufactured by AGFA-GEVAERT N.V. e.g. DRYSTAR TM 2000, DRYSTAR TM 3000 and DRYSTAR TM 4500, have a ratio of heating element length in the transport direction, L, to the pitch, P, between adjacent heating elements, the so-called aspect ratio L/P, of between 1.5 and 1.80.
  • the thermal head disclosed in EP-A 1 006 000 , EP-A 1 006 403 and EP-A 1 006 404 had heating elements with dimensions 85 ⁇ m x 85 ⁇ m i.e. an aspect ratio L/P of 1.0.
  • thermographic material developed for high throughput with a conventional thermal head for printing at lower throughputs without a significant change in image tone and other imaging properties.
  • thermo head printer for printing a substantially light-insensitive thermographic material with a particular image tone with printing configurations with different printing speeds.
  • thermographic material it is therefore a further aspect of the present invention to provide a process for printing a substantially light-insensitive thermographic material at different printing speeds with a thermal head comprising heating elements without significant variation in image tone.
  • a thermal head printer for printing a substantially light-insensitive thermographic material
  • the thermal printer comprising: a transport system having a transport direction, n thermal heads, where n is an integer, each of the thermal heads comprising an array of substantially rectangular energizable heating elements, the heating elements having a length L n in the transport direction and a pitch P n between adjacent heating elements, and a means for supplying electrical energy to each of the substantially rectangular energizable heating elements in at least one of the thermal heads, wherein the transport system being capable of transporting the light-insensitive thermographic material in contact or proximity with at least one of the thermal heads, wherein at least one of the thermal heads comprises heating elements for which L n /P n is between 0.25 and 0.88, wherein at least one of the thermal heads comprises heating elements with a width of the space between adjacent resistors along a line in the plane of said heating elements which bisects all the heating elements of 20% or less of P n ,
  • thermographic material with the above-described thermal head printer comprising the steps of: choosing a thermal head, providing the substantially light-insensitive thermographic material, transporting the substantially light-insensitive thermographic material past the thermal head, and image-wise heating of the substantially light-insensitive thermographic material by supplying electrical energy to the heating elements.
  • aspects of the present invention are also realized by a second process for printing a substantially light-insensitive thermographic material at different printing speeds with a different thermal head at each printing speed without significant variation in image tone, wherein each of the different thermal heads comprises heating elements with a different length in the transport direction of the substantially light-insensitive thermographic material and the length of the heating elements in the transport direction of the substantially light-insensitive thermographic material decreases with decreasing printing speed and the different thermal heads are each on different substrates.
  • the L*, a* and b* CIELAB-values are defined in ASTM Norm E179-90 in a R(45/0) geometry with evaluation according to ASTM Norm E308-90.
  • a heating element as used in disclosing the present invention is a resistor, which becomes hot upon being energized.
  • a split resistor is a U-shaped heating element with the arms of the U parallel to the transport direction of the substantially light-insensitive recording material, which enables contacts to be made at the same side of the thermal head.
  • thermal head resolution is the number of lines that can be distinguished in an image on a thermographic material expressed in lines or dots per unit length e.g. in lines/mm or dots/mm, or in dots per inch (dpi).
  • the thermal head pitch, P is the distance between the geometric middle of one heating element and the geometric middle of an adjacent heating element along a line in the plane of the heating elements which bisects all the heating elements (see Figures 1 and 2). This line is lateral to the transport direction of the substantially light-insensitive recording material.
  • the geometric middle may be in the gap between the two arms of the split resistor (see Figure 2).
  • the heating element aspect ratio is the length of the heating element in the transport direction, T, of the substantially light-insensitive recording material L (see Figures 1 and 2) divided by the thermal head pitch P (see Figures 1 and 2).
  • the line time is the time taken to print one line lateral to the transport direction of the substantially light-insensitive recording material i.e. at an angle to the transport direction of 90° ⁇ 20°.
  • Transport speed i.e. the speed of the substantially light-insensitive thermographic material, is the distance between adjacent lines of image dots in the transport direction divided by the line time.
  • a transport system can consist of a moving belt, motor-driven drums, capstans etc.
  • Substantially rectangular means having angles which deviate from 90° by no more than 20°.
  • Substantially light-insensitive means not intentionally light sensitive.
  • aqueous in the term aqueous medium includes mixtures of water-miscible organic solvents such as alcohols e.g. methanol, ethanol, 2-propanol, butanol, iso-amyl alcohol etc.; glycols e.g. ethylene glycol; glycerine; N-methyl pyrrolidone; methoxypropanol; and ketones e.g. 2-propanone and 2-butanone etc. with water in which water constitutes more than 50% by weight of the aqueous medium with 65% by weight of the aqueous medium being preferred and 80% by weight of the aqueous being particularly preferred.
  • alcohols e.g. methanol, ethanol, 2-propanol, butanol, iso-amyl alcohol etc.
  • glycols e.g. ethylene glycol
  • glycerine N-methyl pyrrolidone
  • methoxypropanol methoxypropanol
  • ketones e
  • a leuco-dye is a colourless or weakly coloured compound derived from a dye.
  • Colourless or light coloured dye precursor leuco-dye systems include leuco triarylmethane, indolyl phthalide, diphenylmethane, 2-anilinofluoran, 7-anilinofluoran, xanthene and spiro compounds such as disclosed in EP-A 754 564 .
  • a thermal head printer for printing a substantially light-insensitive thermographic material
  • the thermal printer comprising: a transport system having a transport direction, n thermal heads, where n is an integer, each of the thermal heads comprising an array of substantially rectangular energizable heating elements, the heating elements having a length L n in the transport direction and a pitch P n between adjacent heating elements, and a means for supplying electrical energy to each of the substantially rectangular energizable heating elements in at least one of the thermal heads, wherein the transport system being capable of transporting the light-insensitive thermographic material in contact or proximity with at least one of the thermal heads, wherein at least one of the thermal heads comprises heating elements for which L n /P n is between 0.25 and 0.88 wherein at least one of the thermal heads comprises heating elements with a width of the space between adjacent resistors along a line in the plane of said heating elements which bisects all the heating elements of 20% or less of P n , wherein
  • the thermal head printer comprises a replaceable thermal head or set of thermal heads.
  • the thermal head printer comprises at least two thermal heads, configured such that a first thermal head can be replaced by an nth thermal head while being capable of maintaining a comparable image tone with said substantially light-insensitive thermographic material.
  • the substantially rectangular heating element is a split resistor.
  • the heating elements are exclusive of a slit formed on a surface of the heating elements and having a shape in which the width of the slit in a feeding direction of the printed object is less than that in an arranging direction of the heating elements perpendicular to the feeding direction and the width of the slit in the arranging direction of the heating elements is approximately equal to a half length of a pitch of the heating elements in the arranging direction thereof.
  • said heating elements of at least one thermal head have a length, L n , in the transport direction of less than 88 ⁇ m.
  • said heating elements of at least one thermal head have a pitch, P n , of less than 100 ⁇ m.
  • At least one of the thermal heads comprises heating elements for which L n /P n is between 0.40 and 0.75.
  • At least one of the thermal heads comprises heating elements with a width of a space between adjacent resistors along a line in the plane of the heating elements which bisects all the heating elements which is 15% or less of the pitch, P n , between two adjacent heating elements.
  • the line time has been defined above as the time taken to print one line lateral to the transport direction of the substantially light-insensitive recording material i.e. at an angle to the transport direction of 90° ⁇ 20°. It should be pointed out that for a particular transport speed and for heating elements with a particular dimension, the image tone attained for printed pixels with a length in the transport direction no larger than the length of the heating element in the transport direction does not depend upon the line time, since varying the line-time simply results in a variation in the length of the printed pixel in the transport direction, the length of the printed pixel being proportional to the line-time.
  • said heating elements are thin film heating elements.
  • said heating elements are connected to the means of supplying electrical energy on the same side of the heating elements.
  • a first process for printing a substantially light-insensitive thermographic material with the above-described thermal head printer comprising the steps of: choosing a thermal head, providing the substantially light-insensitive thermographic material, transporting the substantially light-insensitive thermographic material past the thermal head, and image-wise heating of the substantially light-insensitive thermographic material by supplying electrical energy to the heating elements.
  • aspects of the present invention are also realized by a second process for printing a substantially light-insensitive thermographic material at different printing speeds with a different thermal head at each printing speed without significant variation in image tone, wherein in that each of said different thermal heads comprises heating elements with a different length in the transport direction of the substantially light-insensitive thermographic material and said length of the heating elements in the transport direction of the substantially light-insensitive thermographic material decreases with decreasing printing speed and the different thermal heads are each on different substrates.
  • the operating temperature of common thermal heads is in the range of 300 to 400°C and the pressure contact of the thermal printhead with the recording material to ensure a good transfer of heat being e.g. 200-1000g/linear cm i.e. with a contact zone (nip) of 200 to 300 ⁇ m a pressure of 5000 to 50,000 g/cm 2 .
  • Activation of the heating elements can be power-modulated or pulse-length modulated at constant power.
  • At least one thermal head has a line-time of less than 20 ms.
  • thermographic material substantially light-insensitive thermographic material
  • substantially light-insensitive thermographic material includes all materials which produce a change in optical density upon the application of heat.
  • the substantially light-insensitive thermographic material is a black and white material.
  • the substantially light-insensitive thermographic material is a two sheet material in which an ingredient necessary for the image-forming process is transferred upon image-wise application of heat from one sheet to the other where it reacts with one or more further ingredients to produce an image.
  • the substantially light-insensitive thermographic material is a monosheet material.
  • the substantially light-insensitive thermographic material contains a thermosensitive element comprising one or more layer, the one or more layers containing an image-forming system.
  • Suitable image-forming systems include monosheet substantially light-insensitive thermographic materials such as colourless or light coloured dye precursor leuco-dye systems, as disclosed in US-P 4,370,370 , EP-A 479 578 and EP-A 754 564 , diazo systems, as disclosed in JP 60-01077A , or two-sheet thermal dye transfer systems, such as disclosed in EP-A 656 264 and US-P 4,943,555 .
  • monosheet substantially light-insensitive thermographic materials such as colourless or light coloured dye precursor leuco-dye systems, as disclosed in US-P 4,370,370 , EP-A 479 578 and EP-A 754 564 , diazo systems, as disclosed in JP 60-01077A , or two-sheet thermal dye transfer systems, such as disclosed in EP-A 656 264 and US-P 4,943,555 .
  • the image-forming systems may comprise at least one substantially light-insensitive organic silver salt and at least one organic reducing agent therefor either in a two-sheet material in which upon image-wise application of heat at least one organic reducing agent is image-wise transferred to a sheet containing the at least one substantially light-insensitive organic silver salt whereupon the image-forming reaction takes place or in a monosheet material in which the at least one substantially light-insensitive organic silver salt is in thermal working relationship with the at least one organic reducing agent therefor.
  • the substantially light-insensitive thermographic material is a monosheet material comprising a thermosensitive element and a support, the thermosensitive element comprising at least one substantially light-insensitive organic silver salt, at least one organic reducing agent therefor in thermal working relationship therewith, i.e. during the thermal development process the organic reducing agent must be present in such a way that it is able to diffuse to the substantially light-insensitive organic silver salt particles so that reduction of the substantially light-insensitive organic silver salt can take place, and a binder.
  • Such materials include the possibility of one or more substantially light-insensitive organic silver salts and/or one of more organic reducing agents therefor being encapsulated in heat-responsive microcapsules, such as disclosed in EP-A 0 736 799 herein incorporated by reference.
  • Preferred substantially light-insensitive organic silver salts for use in the thermosensitive element of the substantially light-insensitive elongated imaging material used in the present invention are silver salts of aliphatic carboxylic acids known as fatty acids, wherein the aliphatic carbon chain has preferably at least 12 C-atoms, which silver salts are also called silver soaps.
  • Suitable organic reducing agents for the reduction of the substantially light-insensitive organic silver salts are organic compounds containing at least one active hydrogen atom linked to O, N or C.
  • the choice of reducing agent influences the thermal sensitivity of the imaging material and the gradation of the image. Imaging materials using gallates, for example, have a high gradation.
  • the thermosensitive element contains a 3,4-dihydroxyphenyl compound with ethyl 3,4-dihydroxybenzoate, n-butyl 3,4-dihydroxybenzoate, 3,4-dihydroxy-benzophenone and 3,4-dihydroxy-benzonitrile being particularly preferred.
  • thermosensitive element of the substantially light-insensitive elongated imaging material used in the present invention may be coated onto a support in sheet- or web-form from an organic solvent containing the binder dissolved therein or may be applied from an aqueous medium using water-soluble or water-dispersible binders.
  • Suitable binders for coating from an organic solvent are all kinds of natural, modified natural or synthetic resins or mixtures of such resins, wherein the organic heavy metal salt can be dispersed homogeneously or mixtures thereof.
  • Suitable water-soluble film-forming binders include: polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin and modified gelatins, such as phthaloyl gelatin, polysaccharides, such as starch, gum arabic and dextrin, and water-soluble cellulose derivatives.
  • Suitable water-dispersible binders are any water-insoluble polymers. Poly(vinylbutyral) is the preferred binder.
  • the binder to organic silver salt weight ratio decreases the gradation of the image increasing. Binder to organic silver salt weight ratios of 0.2 to 6 are preferred with weight ratios between 0.5 and 3 being particularly preferred.
  • binders or mixtures thereof may be used in conjunction with waxes or "heat solvents" to improve the reaction speed of the image-forming reaction at elevated temperatures.
  • the substantially light-insensitive thermographic material used in the present invention may contain one or more toning agents.
  • the toning agents should be in thermal working relationship with the substantially light-insensitive organic silver salt and reducing agents during thermal processing.
  • Suitable toning agents are described in US 3,074,809 , US 3,446,648 and US 3,844,797 and US 4,082,901 .
  • Other particularly useful toning agents are the heterocyclic toning compounds of the benzoxazine dione or naphthoxazine dione type as disclosed in GB 1,439,478 , US 3,951,660 and US 5,599,647 .
  • the substantially light-insensitive thermographic material contains a thermosensitive element, the thermosensitive element containing one or more toning agents selected from the group consisting of phthalazinone, benzo[e][1,3]oxazine-2,4-dione, 7-methyl-benzo[e][1,3]oxazine-2,4-dione, 7-methoxy-benzo[e][1,3]oxazine-2,4-dione and 7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione.
  • phthalazinone benzo[e][1,3]oxazine-2,4-dione
  • 7-methyl-benzo[e][1,3]oxazine-2,4-dione 7-methoxy-benzo[e][1,3]oxazine-2,4-dione
  • stabilizers and antifoggants may be incorporated into the substantially light-insensitive thermographic material used in the present invention.
  • Suitable stabilizers compounds for use in the substantially light-insensitive thermographic material used in the present invention include benzotriazole, tetrachlorophthalic acid anhydride and those compounds represented by general formula I: where Q are the necessary atoms to form a 5- or 6-membered aromatic heterocyclic ring, A is selected from hydrogen, a counterion to compensate the negative charge of the thiolate group or a group forming a symmetrical or an asymmetrical disulfide.
  • the substantially light-insensitive thermographic material used in the present invention may contain one or more surfactants, which may be anionic, non-ionic or cationic surfactants and/or one or more dispersants.
  • Suitable dispersants are natural polymeric substances, synthetic polymeric substances and finely divided powders, e.g. finely divided non-metallic inorganic powders such as silica.
  • the substantially light-insensitive thermographic material has a transparent or translucent support and is preferably a thin flexible carrier made transparent resin film, e.g. made of a cellulose ester, e.g. cellulose triacetate, polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
  • the support may be in sheet, ribbon or web form and subbed if needs be to improve the adherence to the thereon coated thermosensitive element.
  • the support may be dyed or pigmented to provide a transparent coloured background for the image.
  • thermosensitive element In a preferred embodiment of the present invention a protective layer is provided for the thermosensitive element. In general this protects the thermosensitive element from atmospheric humidity and from surface damage by scratching etc. and prevents direct contact of printheads or other heat sources with the recording layers.
  • Protective layers for thermosensitive elements which come into contact with and have to be transported past a heat source under pressure, have to exhibit resistance to local deformation and good slipping characteristics during transport past the heat source during heating.
  • a slipping layer being the outermost layer, may comprise a dissolved lubricating material and/or particulate material, e.g. talc particles, optionally protruding from the outermost layer. Examples of suitable lubricating materials are a surface active agent, a liquid lubricant, a solid lubricant or mixtures thereof, with or without a polymeric binder.
  • any layer of the substantially light-insensitive thermographic material used in the present invention may proceed by any coating technique e.g. such as described in Modern Coating and Drying Technology, edited by Edward D. Cohen and Edgar B. Gutoff, (1992) VCH Publishers Inc., 220 East 23rd Street, Suite 909 New York, NY 10010, USA . Coating may proceed from aqueous or solvent media with overcoating of dried, partially dried or undried layers.
  • Ad-L01 and Ad-L02 Ingredients in the adhesion layers, Ad-L01 and Ad-L02:
  • thermosensitive element Ingredients in the thermosensitive element, Th-El:
  • S-LEC BL5HP a polyvinyl butyral from SEKISUI;
  • BAYSILON a silicone oil from BAYER;
  • DESMODUR VL a 4,4'-diisocyanatodiphenylmethane from BAYER;
  • R01 3,4-dihydroxybenzonitrile
  • R02 3,4-dihydroxybenzophenone
  • T01 7-methyl-benzo[e][1,3]oxazine-2,4-dione
  • S01 glutaric acid
  • S02 tetrachlorophthalic acid anhydride
  • S03 benzotriazole
  • thermographic material substantially light-insensitive thermographic material
  • the substantially light-insensitive thermographic material used in evaluating the thermal head printer and process for printing a substantially light-insensitive recording materials consisted of a blue-pigmented PET support coated on one side with adhesion layer Ad-L01 and on the other side with adhesion layer Ad-L02.
  • the adhesion layer Ad-L01 was further coated with the thermosensitive element TH-EL which itself was further coated with a protective layer PRO-L.
  • the adhesion layer Ad-L02 was further coated with backing layer Ba-L.
  • Coating support with adhesion layers Ad-L01 and Ad-L02 Coating support with adhesion layers Ad-L01 and Ad-L02:
  • This coating solution was applied to a wet thickness of 40 ⁇ m to antistatic adhesion layer Ad-L02 on one side of the 168 ⁇ m thick blue-pigmented polyethylene terephthalate film.
  • thermosensitive element Th-El
  • thermosensitive element Th-El
  • an aqueous composition with the following ingredients, which was adjusted to a pH of 3.8 with 1N nitric acid, to a wet layer thickness of 85 ⁇ m and then dried at 40°C for 15 minutes to produce a protective layer PRO-L with the composition:
  • the protective layer was hardened by heating the substantially light-insensitive thermographic material at 50°C for 7 days.
  • thermographic material was then printed with the printing conditions given in Table 1 for COMPARATIVE EXAMPLES 1 to 3 and INVENTION EXAMPLE 1 respectively.
  • a negative CIELAB a*-value indicates a greenish image-tone becoming greener as a* becomes more negative, a positive a*-value indicating a reddish image-tone becoming redder as a* becomes more positive.
  • a negative CIELAB b*-value indicates a bluish tone which becomes increasingly bluer as b* becomes more negative and a positive b*-value indicates a yellowish image-tone becoming more yellow as b* becomes more positive.
  • the image tone of elements of the image with a density of 1.0 have a stronger effect than the image tone of elements with lower or higher optical density.
  • Table 2 gives the CIELAB a*- and b*-values for optical densities, D vis , between 0.2 and 2.8 for an AGFA-GEVAERT SCOPIX TM LT2B silver halide emulsion laser medical hardcopy film (reference hardcopy film) and for the substantially light-insensitive thermographic material printed according to COMPARATIVE EXPERIMENTS 1 and 2 and INVENTION EXPERIMENT 1.
  • the image tone of the print obtained in INVENTION EXAMPLE 1 is considerably more acceptable to image analysts than the image tone of the print obtained in COMPARATIVE EXAMPLE 1.
  • the only substantial difference between the printing conditions of COMPARATIVE EXAMPLE 1 and INVENTION EXAMPLE 1 is the length of the heating elements in the transport direction or in other words the aspect ratios of the heating elements changing from 1.76 to 0.63. This again demonstrates the benefit of the use of heating elements with aspect ratios in the range of 0.25 to 0.88.

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Claims (6)

  1. Ein Thermokopfdrucker zum Bedrucken eines wesentlich lichtunempfindlichen thermografischen Materials, wobei der Thermodrucker folgende Komponenten umfasst :
    - ein Fördersystem mit einer Förderrichtung,
    - n Thermoköpfe, wobei n eine ganze Zahl ist,
    wobei jeder Thermokopf eine Matrix wesentlich rechteckiger erregbarer Heizelemente aufweist, wobei die Heizelemente eine Länge Ln in die Förderrichtung und eine Teilung Pn zwischen benachbarten Heizelementen aufweisen, und
    - ein Mittel zum Bestromen jedes der wesentlich rechteckigen erregbaren Heizelemente in zumindest einem der Thermoköpfe, dadurch gekennzeichnet, dass das Fördersystem in der Lage ist, das wesentlich lichtunempfindliche thermografische Material in Berührung mit oder nahe an zumindest einem der Thermoköpfe vorbeizufördern,
    wobei zumindest einer der Thermoköpfe Heizelemente aufweist, deren Ln/Pn-Verhältnis zwischen 0,25 und 0,88 liegt, zumindest einer der Thermoköpfe Heizelemente aufweist, bei denen die Breite des Abstands zwischen benachbarten Widerständen entlang einer Linie in der Ebene der Heizelemente, die alle Heizelemente halbiert, höchstens 20% des Pn-Wertes beträgt, der Thermokopfdrucker in der Lage ist, das wesentlich lichtunempfindliche thermografische Material bildmäßig zu bedrucken und das wesentlich lichtunempfindliche thermografische Material nicht vom Drucker perforiert wird.
  2. Thermokopfdrucker nach Anspruch 1, dadurch gekennzeichnet, dass der Thermokopfdrucker einen ersetzbaren Thermokopf oder Satz von Thermoköpfen enthält.
  3. Thermokopfdrucker nach Anspruch 1, dadurch gekennzeichnet, dass der Thermokopfdrucker zumindest zwei Thermoköpfe enthält, die so konfiguriert sind, dass ein erster Thermokopf durch einen n. Thermokopf ersetzt werden kann, der in der Lage ist, einen vergleichbaren Bildton auf dem wesentlich lichtunempfindlichen thermografischen Material aufrechtzuerhalten.
  4. Thermokopfdrucker nach Anspruch 1, dadurch gekennzeichnet, dass das wesentlich rechteckige Heizelement ein verteilter Widerstand ist.
  5. Ein Verfahren zum Bedrucken eines wesentlich lichtunempfindlichen thermografischen Materials mit einem Thermokopfdrucker nach einem der vorstehenden Ansprüche, wobei das Verfahren durch folgende Schritte gekennzeichnet ist : Auswahl eines Thermokopfes, Bereitstellen des wesentlich lichtunempfindlichen thermografischen Materials, am Thermokopf Vorbeifördern des wesentlich lichtunempfindlichen thermografischen Materials und bildmäßige Erhitzung des wesentlich lichtunempfindlichen thermografischen Materials durch Bestromung der Heizelemente.
  6. Ein zweites Verfahren, in dem ein wesentlich lichtunempfindliches thermografisches Material bei unterschiedlichen Druckgeschwindigkeiten mit jeweils für jede Druckgeschwindigkeit einem anderen Thermokopf ohne wesentliche Schwankung des Bildtons bedruckt wird, wobei in diesem zweiten Verfahren jeder der unterschiedlichen Thermoköpfe Heizelemente mit einer in die Förderrichtung des wesentlich lichtunempfindlichen thermografischen Materials unterschiedlichen Länge aufweist, die Heizelemente in die Förderrichtung des wesentlich lichtunempfindlichen thermografischen Materials umso kleiner sind, je niedriger die Druckgeschwindigkeit ist, und die unterschiedlichen Thermoköpfe jeweils auf einem anderen Substrat angebracht sind.
EP03103788A 2002-11-13 2003-10-14 Thermokopfdrucker und Verfahren zum Drucken auf thermographischen Aufzeichnungsmaterialien Expired - Fee Related EP1419888B1 (de)

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EP03103788A EP1419888B1 (de) 2002-11-13 2003-10-14 Thermokopfdrucker und Verfahren zum Drucken auf thermographischen Aufzeichnungsmaterialien

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JPS5889385A (ja) * 1981-11-24 1983-05-27 Canon Inc 感熱記録装置
JPS60143981A (ja) * 1983-12-29 1985-07-30 Konishiroku Photo Ind Co Ltd サ−マルプリンタ
JPS60984A (ja) * 1984-05-21 1985-01-07 Canon Inc 印字装置
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EP1419888A3 (de) 2004-07-28

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