|Publication number||US3871065 A|
|Publication date||Mar 18, 1975|
|Filing date||Aug 2, 1972|
|Priority date||Aug 2, 1972|
|Publication number||US 3871065 A, US 3871065A, US-A-3871065, US3871065 A, US3871065A|
|Inventors||Yoshimichi Iomiyama, Takashi Yamahata, Tomoya Yasuda|
|Original Assignee||Gen Co Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (5), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Sttes Pate 1 1 1111 3,871,065 Iomiyama et a]. 1 Mar. 118, 1975 1 THERMAL PRINTING PROCESS 3,679,410 7/1972 Vrancken et 51. 250/316 3,689,302 9/1972 Kubo et al ll7/36.8
 Inventors: Yoshimichi Iomiyama, Osaka;
Takashi Yamahata, Yamatokohriyama; Tomoya Yasuda, Kyoto, all of Japan Primary Examiner-Michael Sofocleous Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto  Assignee: General Company Limited,
Osaka-shi, Japan  ABSTRACT  Filed; Aug 2 972 A thermal printing process is disclosed in which an image is formed on a heat-sensitive recording sheet composed of a support having superposed thereon a heatsensitive layer which is composed of a heat-  Appl. No.: 277,476
 US. C1. 117/368, 250/316 Sensitive Composition dispersed in a binder therefor,
51 1111, c1. B41111 5/18 the Process Comprising Contacting a thermally-heated 5s F1611! 61 Search 117/368; 250/316 Print head with the Surface of the heat-sensitive layer to thereby form the printed image thereon, wherein 56 References Cited the improvement comprises eliminating exfoliation of UNITED STATES PATENTS the heat-sensitive layer by employing as the binder ei- 3 442 682 5/1969 Fukawa 117/36 8 ther methyl cellulose or acetyl cellulose having a melt- 31592 44 7/1971 Vrancken et a1. 250/316 mg pomt of not lower than 3,615,423 10/1971 Vrancken 250/316 3 Claims, 4 Drawing Figures 1 THERMAL PRINTING PROCESS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printing.
2. Description of the Prior Art Thermal recording processes include direct recording and indirect recording. It is well known that the direct method has the advantage that a visible image can be directly produced while the indirect method disadvantageously requires a chemical treatment to produce a visible image. Thermal printing is among the direct recording processes, wherein a thermal printer is provided with a print head having an electric heating element. Recording is effected by bringing the electric heating element into contact with a heat sensitive sheet. In comparison with conventional mechanical processes the direct heat sensitive recording process is high in printing speed, and less noisy so that it is suitable for an output of electronic computer operated at high speed. The utilization of these processes will increase as the stations are popularized.
Letters provided at the print head are usually composed of a matrix of dots, or several bars.
Conventional heat sensitive recording paper cannot be used as is for thermal printing. In conventional heat sensitive recording processes the heat is applied to the heat sensitive paper by an optical means by the projection of light a pattern thereon. On the contrary, in thermal printing processes a solid print head directly contacts the surface of the heat sensitive paper. This direct contact of the print head causes softening of the heat sensitive coating and exfoliation of the heat sensitive coating from the support which may be paper.
The coating thus exfoliated is attached to and deposited on the print head. This deposit disturbs the heat transfer from the print head to the heat sensitive recording paper and thereby results in unsatisfactory printing. Further the deposit is often formed irregularly and thereby a uniform print pattern cannot be obtained. Even if conventional heat sensitive recording paper can be used for the thermal printing, it cannot be regarded as practical unless more than ten million letters can be printed.
Heat-sensitive recording sheets proposed heretofore are those usable only for thermal duplicating with infrared radiation, that is, so called "thermofax.
In thermal printing where the image is formed by chemical reaction, the reaction may be between two components, or one component may be converted into a third component which is reactable with the other component, or one comconent may be converted into a colored substance to form a coloring image, etc.
In such conventional heat sensitive recording sheets, the color forming materials have been markedly improved, but the prior art has not paid any particular attention to the binder material.
The present inventors have now found that the melting point and the adhesion property of the binder are very important in thermal printing.
SUMMARY OF THE INVENTION According to the present invention there is provided a process for forming an image by thermal printing on a heat-sensitive recording sheet composed of a support and heat-sensitive layer overlying the support, the heatsensitive layer being composed of a binder selected from the group consisting of methyl cellulose and acetyl cellulose having a melting point of not lower than 180C and a heat sensitive composition.
An object of the present invention is to provide a thermal printing process which is free from exfoliation of the heat sensitive coating from the support.
Another object of the present invention is to provide thermal printing process in which neither smudging of the print head nor irregular heat transfer of the print head occurs.
A further object of the present invention is to provide a process for preparing a heat-sensitive recording sheet for thermal printing as mentioned above.
BRIEF DESCRIPTION OF THE DRAWING The FIGURES show diagrammatically enlarged views of printing heads after they have been used with a conventional heat sensitive sheet and a heat sensitive sheet of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The binder used in the present invention is methylcellulose or acetylcellulose having a melting point of not lower than 180C.
The preferred binders are (l) acetylcellulose having a weight average molecular weight ranging from 28,000 to 58,000, a degree of polymerization ranging from 175 to 360, and a viscosity (ASTM, E method, 20% concentration) ranging from 10 to 40 seconds, and added in an amount ranging from 40 to by weight based on the total solids weight, and (2) methyl cellulose having a weight average molecular weight ranging from 26,000 to 63,000, a degree of polymerization ranging from 140 to 340, viscosity a (2% aqueous solution) ranging from 8 to cps. and added in an amount ranging from 40 to 70% by weight based on the total solids weight.
A preferable formula of a heat sensitive coating composition is as shown below:
7! by weight Heat sensitive color forming ingredients (for example, compound A and compound B in prior art, infra) Inhibitor Melting material Binder (acetylcellulose or methyl cellulose) Solvent The solvent used in the present invention may be water or an organic solvent. Representative organic solvents are alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, ketones such as acetone and methylethyl ketone, esters such as ethyl acetate, aliphatic hydrocarbons such as hexane, heptane and petroleum benzine, halogen compounds such as methylene chloride and benzylchloride and aromatic hydrocarbons such as benzene, toluene and xylene.
As heat sensitive compositions, conventional heat sensitive compositions may be used, for example, the heat sensitive compositions disclosed in U.S. Pat. No. 3,442,682 and in U.S. Ser. No. 191,773 filed Oct. 22, 1971.
Further there may be used a two component heat sensitive composition in which one component (component A) contains an iron salt of an aliphatic acid and the other'component (component B) contains a compound selected from the class of gallic acid and its derivatives. The component A is reacted with the component B in the presence of an inhibitor of unusual colordevelopment to produce a black color which can then be utilized as a recording image. The preferred iron salts of the aliphatic acid are the ferrous and ferric salts of aliphatic acids containing from about 8 to 24 carbon atoms. These aliphatic carboxylic acid include lauric acid, caprylic acid, pelargonic acid, capric acid and the like. The inhibitor of unusual color-development includes ethylenediamine tetracetic acid and alkali metal salts thereof. The aforementioned solvents can be used as a solvent for both of the components A and B.
FIGS. 1 and 2 are side and top views of the printing head after printing about 20 million letters by using a conventional heat-sensitive recording sheet, indicating that a coating composition (hatched portion) 1 flaked and scratched from the support adheres on the surfaces of mesa 2 and moat 3 of a printing head 4.
FIGS. 3 and 4 are top and side views of a printing head 4 after printing about twenty million letters by using the heat-sensitive sheet of this invention, indicat- The above-mentioned two compositions were treated in the same manner as in Example 1 to produce a recording sheet. Following the procedure of Example 1, the similar good results were obtained.
Other than acetylcellulose, methylcellulose can be used in this Example. In this case, a mixture of water and methylalcohol may be used as a solvent.
ing that the head is clear in both of the surfaces of mesa 2 and moat 3. EXAMPLE lll With the use of a conventional heat-sensitive sheet, f Suspension Component/*1 Ferric stearatc 5 parts the coating substance adheres to the surfaces of the 1pm mesa and the moat. The coating substance thus ad- Acetylceuulose 8 P" Acetone 60 parts hered produces incomplete printing and a blurred 1m- Methylalcohol 10 parts age lsopropylalcohol 10 parts I Formula for suspension component B: The following examples WlII serve to illustrate but not Lauryl ggllate 1 5 parts to limit the invention. In the following examples, all .51) 1 Acetylcellulosc 8 parts parts are by weight. Acetone 60 parts Methylalcohol l0 parts lsopropylalcohol l0 parts EXAMPLE I Th d Formula for Suspension component e above-mentionedtwo compositions were treate Ferric palmitate 3 parts in the same manner as in Example 1 to produce a re- Behenic acid 8 parts cording sh et; i fg i i g i pans Following a similar test printing as in Example 1, sim- Acetone 60 parts ilarly good results were obtained. lsopropylalcohol 10 parts We claim; Methylalcohm 1. In a thermal printing process for forming an image Formula for suspension component B:
5-Chloro-7-iodo-8-hydroxyquinoline 3 parts EDTA 4 parts Acetylccllulose (mp. 230C) 10 parts Acetone 60 parts lsopropylalcohol 10 parts Methylalcohol 10 parts Each of the above-mentioned two compositions was prepared in a ball-mill. The resulting suspension liquids A and B were mixed by an agitator to form a homogeneous liquid coating agent, applied to a white paper to form a coating of 5 ,u. in thickness, and dried at room temperature to form a heat sensitive recording sheet.
Thermal printing was carried out on the resulting recording sheet up to 20 million letters using a thermal printer having a dot matrix type heat element (contact time of i5 milli-seconds) at a surface temperature of 150 180C.
Neither flaking of the coating agent from the paper, nor adhesion on the heat element were observed.
Clear and uniform printing was obtained during the entire printing process.
on a heat-sensitive recording sheet composed of a support having superposed thereon a heat-sensitive layer which is composed of a heat-sensitive composition dis persed in a binder therefor, said process comprising contacting a thermally-heated print head with the surface of the heat-sensitive layer to form a printed image thereon, the improvement comprising eliminating exfoliation of the heat-sensitive layer from the support by employing, as the binder, a member selected from the group consisting of methyl cellulose and acetylcellulose having a melting point of not lower than 180C.
2. The process of claim 1 wherein the binder is acetyl cellulose having a weight average molecular weight from 28,000 to 58,000, a degree of polymerization from 175 to 360 and a viscosity from 10 to 40 seconds based on ASTM E standard at 20% concentration.
3. The process ofclaim 1 wherein the binder is methyl cellulose having a weight average molecular weight from 26,000 to 63,000, a degree of polymerization from 140 to 340 and a viscosity from 8 to cps at 2% aqueous solution.
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|US3442682 *||Jul 7, 1965||May 6, 1969||Gen Co Ltd||Heat-sensitive copy-sheet|
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|US4510206 *||Aug 22, 1983||Apr 9, 1985||Dennison Manufacturing Company||Thermal ink transfer recording|
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|US5371058 *||Jun 10, 1992||Dec 6, 1994||Alfred Doi||Ultraviolet protective coatings for application to heat sensitive record materials and other photodegradable printed matter|
|US20070177033 *||Jan 30, 2006||Aug 2, 2007||Microsoft Corporation||Bayesian demosaicing using a two-color image|
|U.S. Classification||101/487, 427/148, 250/316.1, 347/221, 428/913|
|Cooperative Classification||Y10S428/913, B41M5/3372|