Thermo reversible recording medium, member having information memorizing part, thermo reversible recording label, method of and apparatus for image processing

Abstract: The thermo reversible recording medium comprises a substrate and a heat sensitive layer. This heat sensitive layer is made of resin and organic lower molecular weight substance and can become transparent or non-transparent or vice versa depending on temperature. The organic lower molecular weight substance is a linear hydrocarbon-containing compound having no carboxyl group (A) and a linear hydrocarbon-containing compound having no carboxyl group (B) having a melting point lower than the melting point of the linear hydrocarbon-containing compound having no carboxyl group (A) by 20 °C or more.

Description: The present invention relates to a technology for forming or deleting images repeatedly by utilizing a heat sensible layer manifesting reversible change between transparent and non-transparent condition depending on temperature. , Recently, attention has been given to a thermo reversible recording medium having a heat sensible layer of which transparency can be reversed based on temperature. When such a recording medium is used in display monitors, images can be repeatedly formed or deleted when desired. As typical examples, there are known thermo reversible recording media obtained by dispersing an organic lower molecular weight substance such as a higher fatty acid and the like in a resin mother material such as a vinyl chloride-vinyl acetate copolymer and the like, as described, for example, in Japanese Patent Application Laid-Open (JP-A) No. 55-154198. However, in case of the above-mentioned thermo reversible recording medium the temperature range in which transparency is manifested is as narrow as 2 to 4 °C. Therefore, there is a drawback that a minute temperature control, which is very difficult, is required to be performed when forming or deleting images. The temperature range may be made wider by the use of higher fatty acid, higher ketone or fatty ester and an aliphatic dicarboxylic acid in admixture as suggested in, for example, JP-ANos. 2-1363, 3-2089, 4-366682 or 6-255247. Since the temperature range becomes wider, temperature control becomes easier. The thermo reversible recording media are often used in, for example, point cards (a card given to a customer by a shopkeeper and in which points are added each time some service is used) . Such point card are used repeatedly over a long period of time . Such a card may be put in pant pocket, purse or in table drawer. In other words, the card is stored under various conditions or environments. However, if basic substances such as ammonia, amine and the like exist where the card has been stored, there is a problem that an opaque image cannot be formed even if the amount of such substances is extremely small. The reason for this is supposed that a carboxyl group on an organic lower molecular weight substance and a basic substance forms salt which increases the melting point of the organic lower molecular weight substance. JP-A No. 5-294062 suggests use of higher ketone or fatty ester and a saturated aliphatic bisamide in admixture to make the temperature range wider. Since organic lower molecular weight substance having a carboxyl group is not used, the influence by a basic substance is small, the temperature is somewhat wider, deleting property is better. However, there is a drawback that the contrast is low. Further, JP-A No. 11-58988 suggests, to decrease influence by a basic substance, use of organic lower molecular weight substance having lower melting point such as fatty ester and fatty acid metal salt such as copper stearate, or fatty amide and the like. However, if copper stearate is used, there is a drawback that the medium becomes blue colored blue due to blue color of the raw material. Moreover, if fatty amide is used, since the melting point of the fatty amide is not so higher, there is a drawback that the temperature range becomes narrower. JP-A No. 10-16409 discloses a reversible thermosensible recording medium comprising a macromolecular matrix having a urea compound dispersed therein. EP-A-891875 discloses a reversible thermosensitive recording medium and its use in the manufacture of cards, labels and information storage members. It is an object of the present invention to provide a thermo reversible recording medium which can provide sufficient opacity even if it is stored in the presence of a basic substance. It is another object of the present invention to provide a thermo reversible recording medium which has a wider temperature range showing transparency, and by which excellent image deleting ability and high contrast image are obtained even if environmental temperature changes. It is another object of the present invention to provide a thermo reversible recording label, a member having an information memorizing part and a reversible display part, and an image processing method to which a thermo reversible recording medium, solution means of the first and second objects, is applied. The thermo reversible recording medium of one aspect of this invention comprises a substrate and a heat sensible layer. This heat sensible layer is made of resin and organic lower molecular weight substance and can becoming transparent or non-transparent or vice versa depending on temperature. The organic lower molecular weight substance is a linear hydrocarbon-containing compound having no carboxyl group. The organic lower molecular weight substance may be any one or more of (1) linear hydrocarbon-containing compounds having a urethane bond, (2) linear hydrocarbon-containing compounds having a sulfonylbond, (3) linear hydrocarbon-containing compounds having an oxalic diamide bond, or (4) linear hydrocarbon-containing compounds having a diacylhydrazide Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing change in degree of transparency by a thermo reversible recording medium of the present invention. Fig. 2 is a graph illustrating the clearing upper limit temperature, opacification lower limit temperature, clearing initiation temperature and clearing temperature range of the thermo reversible recording medium of the present invention. Fig. 3 is a view showing an example in which the thermo reversible recording label is pasted on a MD disk cartridge . Fig. 4 is a view showing an example in which the thermo reversible recording label is pasted on CD-RW. Fig. 5 is a view showing an example in which the thermo reversible recording label is formed on an optical information memorizing medium (CD-RW) using an AgInSbTe-based phase change-type recording material. Fig. 6 is a view showing a display label of a video tape cassette. Fig. 7A to Fig. 7C are views for explaining an example of the layer constitution of the thermo reversible recording medium of the present invention. Fig. 8 is a view illustrating one example of the use of the thermo reversible recording medium of the present invention. Fig. 9A and Fig. 9B are views illustrating another example of the use of the thermo reversible recording medium of the present invention. Fig. 10A and Fig. 10B are views illustrating still another example of the use of the thermo reversible recording medium of the present invention. Fig. 11 is a view illustrating one example of a thermo reversible recording apparatus of the present invention. First, the mechanism of thermo reversibility of the recording medium of the present invention will be described. The thermo reversible recording medium of the present invention has a substrate carrying thereon a heat sensible layer manifesting reversible change between transparent condition and non-transparent condition (also called opaque condition) depending on temperature, and the transparent condition and non-transparent condition are supposed to be formed according to the following mechanisms. In the transparent condition, it is believed that particles of organic lower molecular weight substance dispersed in a mother material resin are closely contacted with the resin without clearance and no clearance is present also in the particle, consequently, light entered from one side is not scattered and permeates through toward the opposite side, to give transparency. On the other hand, in the non-transparent condition, it is believed that particles of organic lower molecular weight substance are constituted of polycrystal made of fine crystals aggregated and clearance is formed at the interface of the crystals or at the interface between the particle and the resin, consequently, light entering from any side is refracted or reflected and scattered at the interfaces between the clearance and the crystal and between the clearance and the resin, to give white appearance. Fig. 1 is a view illustrating one example of temperature-transparency change of a thermo reversible recording medium of the present invention. In Fig. 1, a heat sensible layer containing a resin and an organic lower molecular weight substance dispersed in this resin as main components is, for example, in non-transparent condition at room temperatures of To or less. When the material is heated, it begins to become transparent gradually from temperature T 1 , and becomes completely transparent when the temperature is between T 2 and T 3 . Even if thematerial cools to roomtemperature To or less it remains transparent. The reason for this is believed that resin begins to be soften from around temperature T 1 , and with the progress of softening, the resin, for example, shrinks to decrease the clearance at the interface with the organic lower molecular weight substance or in the particle, consequently, transparency increases gradually, and the organic lower molecular weight substance becomes semi-transparent condition at temperatures from T 2 to T 3 and the remaining clearance is buried with the organic lower molecular weight substance to give transparency, and a seed crystal remains and is cooled to reveal crystallization at relatively higher temperature, and the resin is still in softened condition in this process, therefore, the resin follows change in volume of particles by the crystallization, consequently, no clearance is formed and transparent condition is maintained. When the resin is heated to temperature T 4 or more, it becomes semi-transparent between, i.e. a condition between the maximum transparency and the maximum non-transparency. Next, when this temperature is lowered, the resin returns to the original opaque non-transparent condition without forming transparent condition again. The reason for this is believed that, after the organic lower molecular weight substance is completely melted at temperatures of T 4 or more, super-cooling condition is formed, and crystallization occurs at a temperature slightly higher than To, and the resin can not follow the change in volume by crystallization, to cause generation of clearance. However, a temperature-transparency change curve shown in Fig. 1 is only a typical example, and transparency at each condition may change, by variation of materials, depending on the material. A thermo reversible recording medium forming reversibly transparent condition and non-transparent condition depending on heat temperature change according to the above-described mechanism has a basic structure in which a heat sensible layer containing a resin and an organic lower molecular weight substance as main components is provided on a substrate. One object of the present invention is solved by using, the organic lower molecular weight substance is a linear hydrocarbon-containing compound (A) having no carboxyl group and it may be any one of the following compounds (1) to (4): (1) linear hydrocarbon-containing compounds having a urethane bond, (2) linear hydrocarbon-containing compounds having a sulfonyl bond, (3) linear hydrocarbon-containing compounds having an oxalic diamide bond, (4) linear hydrocarbon-containing compounds having a diacylhydrazide bond. Namely, this linear hydrocarbon-containing compound (A) dose not have a carboxyl group as described above, and has a polar group as described below in the molecule. Urethane bond (-NHCOO-), sulfonyl bond (-SO 2 -), oxalic diamide bond (-NHCOCONH-), diacylhydrazide bond (-CONHNHCO-), urea bond (-NHCONH-) and amide bond (-CONH-). It is preferable that this linear hydrocarbon-containing compound (A) does not have a hydroxyl group. The linear hydrocarbon-containing compound (A) may be a mixture of two or more of the compounds (1) to (4) listed above. It is preferable that the total carbon number of linear hydrocarbons of the linear hydrocarbon-containing compound (A) is preferably between 6 and 60, more preferably between 8 and 50. It is preferable that, among linear hydrocarbon-containing compounds (A), (1), (2), (3) and (4) contain a cyclic structure such as a cyclic hydrocarbon (cyclohexane, cyclopentane and the like), an aromatic ring (benzene, naphthalene and the like), a heterocyclic ring (cyclic ether, furan, pyran, morpholine, pyrrolidine, piperidine, pyrrole, piridine, pirazine, piperazine, pyrimidine and the like), or a condensed hetarocyclic ring (benzopyrrolidine, indole, benzooxazine, quinoline and the like). Further, it is preferable that the end of a molecule has a methyl group. Themeltingpoint of the linear hydrocarbon-containing compound (A) is preferably above 100 °C and below 180 °C. More preferably, the melting point should be between 130 °C and 150 °C. When the melting point is too low, the clearing temperature range cannot be made wider so that the deleting ability lowers. On the other hand, when the melting temperature is too high, sensitivity in forming an opaque image decreases undesirably. Examples of the linear hydrocarbon-containing compound (A) include, but not limited to, compounds of the following general formulae (1) to (6). R 1 -X-R 2 -Y-R 3 (wherein, at least one of X and Y represents a urethane bond or sulfonyl bond or urea bond, and the remaining one represents one selected from a urethane bond, sulfonyl bond and amide bond. R 1 and R 3 represent CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, and R 2 represents -(CH 2 ) m - or a group of the following general formula (i) or (ii), and m and n are preferably from 0 to 30.). R 1 -X-R 3 (wherein, X represents an oxalic diamide bond or diacylhydrazide bond, R 1 and R 3 represent CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, and m and n are preferably from 0 to 30.). (in the formulae (3) and (4), at least one of X and Y represents a urethane bond, sulfonyl bond, oxalic diamide bond or diacylhydrazide bond. R 1 and R 2 represent -(CH 2 ) m - or -(CH 2 ) m -O- (CH 2 ) n -, and R 3 represents CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, [A] represents a phenyl group, cyclohexyl group or a group of the following general formulae (iii) to (v), and m and n are preferably from 0 to 30.). (wherein, 1 represents an integer from 1 to 3, R 1 OCO-, R 1 O-, R 1 , and R 1 represents CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, and m and n are preferably from 0 to 30.). (in the formulae (5) and (6), X' represents a urethane bond, sulfonyl bond, urea bond, amide bond, oxalic diamide bond or diacylhydrazide bond. R ' / 1 represents -(CH 2 ) m - or -(CH 2 ) m -O-(CH 2 ) n -, and R ' / 1 represents CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, and m and n are preferably from 0 to 30.). Specific examples of the linear hydrocarbon-containing compound (A) include, but not limited to, compounds of the following general formulae (7) to (11). R 1 -OOCNH-R 2 -NHCOO-R 3 R 1 -NHCOO-R 2 -OOCNH-R 3 R 1 -SO 2 -R 2 -SO 2 -R 3 R 1 -NHCOCONH-R 3 R 1 -CONHNHCO-R 3 (in the formulae (7) to (11), R 1 and R 3 represent CH 3 (CH 2 ) m - or CH 3 (CH 2 ) m -O-(CH 2 ) n -, R 2 represents -(CH 2 ) m - or a group of the above-mentioned general formula (i) or (ii), and m and n are preferably between 0 and 30.). Wherein, m and n are preferably from 1 to 30, more preferably from 3 to 26, further preferably from 5 to 22. The total carbon number of linear hydrocarbons in the molecule is preferably 8 or more, more preferably 10 or more, further preferably 14 or more. The total carbon number of linear hydrocarbons in the molecule is preferably 60 or less, more preferably 50 or less, further preferably 40 or less. When the carbon number is too small, a problem occurs that compatibility with a resin is improved, a lower molecular weight particle is not formed easily, consequently, contrast decreases, and when the carbon number is too large, a problem occurs that compatibility with a lower melting point and lower molecular weight substance lowers and the clearing temperature range can not be enlarged, undesirably. As the compound of the above-mentioned general formula (7), the following compounds are exemplified. Melting Point (MP) CH 3 (CH 2 ) 11 OOCNH(CH 2 ) 6 NHCOO(CH 2 ) 11 CH 3 113°C CH 3 (CH 2 ) 17 OOCNH(CH 2 ) 6 NHCOO(CH 2 ) 17 CH 3 119°C CH 3 (CH 2 ) 21 OOCNH(CH 2 ) 6 NHCOO(CH 2 ) 21 CH 3 121°C The compound of the above-mentioned general formula (8) may be any one of the following. MP CH 3 (CH 2 ) 17 NHCOO(CH 2 ) 2 OOCNH(CH 2 ) 17 CH 3 115°C CH 3 (CH 2 ) 17 NHCOO(CH 2 ) 4 OOCNH(CH 2 ) 17 CH 3 119°C CH 3 (CH 2 ) 17 NHCOO(CH 2 ) 6 OOCNH(CH 2 ) 17 CH 3 111°C Chemical formula 3 The compound of the above-mentioned general formula (9) may be any one of the following. MP CH 3 (CH 2 ) 11 SO 2 (CH 2 ) 4 SO 2 (CH 2 ) 11 CH 3 149°C CH 3 (CH 2 ) 17 SO 2 (CH 2 ) 2 SO 2 (CH 2 ) 17 CH 3 150°C CH 3 (CH 2 ) 17 SO 2 (CH 2 ) 4 SO 2 (CH 2 ) 17 CH 3 148°C The compound of the above-mentioned general formula (10) may be any one of the following. MP CH 3 (CH 2 ) 11 NHCOCONH(CH 2 ) 11 CH 3 124°C CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 121°C The compound of the above-mentioned general formula (11) may be any one of the following. MP CH 3 (CH 2 ) 10 CONHNHCO(CH 2 ) 10 CH 3 151°C CH 3 (CH 2 ) 16 CONHNHCO(CH 2 ) 10 CH 3 134°C CH 3 (CH 2 ) 16 CONHNHCO(CH 2 ) 16 CH 3 147°C CH 3 (CH 2 ) 20 CONHNHCO(CH 2 ) 16 CH 3 136°C CH 3 (CH 2 ) 20 CONHNHCO(CH 2 ) 20 CH 3 143°C Examples of the method of preparing the above-mentioned linear hydrocarbon-containing compound (A) include, but not limited to, the following methods. Synthesis of compound in the general formula (7): Synthesis of [CH 3 (CH 2 ) 17 OOCNH(CH 2 ) 6 NHCOO(CH 2 ) 17 CH 3 ] A solution of 20.1 g of stearyl alcohol and 5.1 g of hexamethylene diisocyanate in 125.5 g of tetrahydrofuran was stirred for 3 hours under reflux. The deposited crystal was filtrated, and re-crystallized from toluene, to obtain 17.7 g of the intended compound. Synthesis of compound in the general formula (8): Synthesis of [CH 3 (CH 2 ) 17 NHCOO(CH 2 ) 4 OOCNH(CH 2 ) 17 CH 3 ] A solution of 2.6 g of 1,4-butanediol and 18.0 g of steary isocyanate in 103.0 g of tetrahydrofuran was stirred for 5 hours under reflux. The deposited crystal was filtrated, and re-crystallized from toluene, to obtain 17.5 g of the intended compound. Synthesis of compound in the general formula (9): Synthesis of [CH 3 (CH 2 ) 17 SO 2 (CH 2 ) 2 SO 2 (CH 2 ) 17 CH 3 ] To a solution of 35.5 g of stearyl mercaptane and 8.5 g of potassium hydroxide in 177.5 g of ethanol was added 11.1 g of 1,2-dibromoethane dropwise at room temperature, and stirred for 5 hours under reflux. After completion of stirring, 275 g of a 0.8% hydrochloric acid aqueous solution was added at room temperture. . The deposited crystal was filtrated, washed with water and dried to obtain 18.4 g of 1,2-dioctadecylthioethane. Then, a mixture of 18.4 g of 1,2-dioctadecylthioethane, 184 g of acetic acid and 184 g of hydrogen peroxide (35%) was stirred at 80 to 90 °C for 5 hours. The reaction solution was added into ion exchange water under room temperature, and the deposited crystal was filtrated, and re-crystallized from toluene, to obtain 10.6 g of the intended compound. Synthesis of compound in the general formula (10): Synthesis of [CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 ] To a solution of 53.5 g of stearylamine and 15.7 g of pyridine in 599.2 g of tetrahydrofuran was added under room temperature a solution of 12.0 g of oxalyl chloride in 120.0 g of tetrahydrofuran dropwise. After stirring, the mixture was stirred at room temperature for 5 hours. The deposited crystal was filtrated, washed with water and re-crystallized from toluene, to obtain 19.6 g of the intended compound. Synthesis of compound in the general formula (11): Synthesis of [CH 3 (CH 2 ) 16 CONHNHCO(CH 2 ) 17 CH 3 ] To a solution of 20.0 g of stearic hydrazide, 21.0 g of stearic acid, 10.3 g of 1-hydroxybenzotriazole in 205.0 g of tetrahydrofuran was added 9.3 g of diisopropylcarbodiimide dwopwise at room temperature, and the mixture was stirred for 3 hours under reflux. The deposited crystal was filtrated, and re-crystallized from isopropyl alcohol, to obtain 23.9 g of the intended compound. Another object of the present invention is solved by further using a linear hydrocarbon-containing compounds (B) having a melting point lower than the melting point of the linear hydrocarbon-containing compound (A) by 20 °C or more and having no carboxyl group, in addition to the linear hydrocarbon-containing compound (A), as the organic lower molecular weight substance. This linear hydrocarbon-containing compound (B) may be one compound or a combination of two or more compounds. The melting temperature of the linear hydrocarbon-containing compound (B) is preferably 50 °C or more and less than 100 °C. This melting point is more preferably 60 °C or more, further preferably 70 °C or more, and more preferably 90 °C or less. If the melting point is too low, the heat resistance of an image lowers, and when too high, the clearing temperature range cannot be enlarged, and deleting property decreased, undesirably. The mixing ratio by weight of the linear hydrocarbon-containing compound (A) to the linear hydrocarbon-containing compound (B) is preferably from 80:20 to 1:99. Regarding this mixing ratio, the proportion of the linear hydrocarbon-containing compound (B) is more preferably 97 or less, further preferably 95 or less, more particularly preferably 90 or less. Further, it is preferably 30 or more, more preferably 40 or more, further preferably 50 or more. The linear hydrocarbon-containing compounds (A) and (B) may be used each alone or in admixture of two or more. When the proportion of the linear hydrocarbon-containing compound (B) is too high, even in the clearing temperature range, such difference in transparency occurs that transparency is higher at lower temperature side and transparency is lower at higher temperature side, consequently, uniform clearing can not be accomplished, undesirably. When the proportion of the linear hydrocarbon-containing compound (B) is too low, sufficient transparency cannot be obtained, undesirably. The linear hydrocarbon-containing compound (B) preferably has no hydroxyl group, and preferably has a methyl group at the end of the molecule. The linear hydrocarbon-containing compound (B) may be, but are not limited to, fatty esters, ketones having a higher alkyl group, dibasic acid esters, polyhydric alcohol difatty esters, aliphatic monoamide compounds, aliphatic monourea compounds. Specific examples of the linear hydrocarbon-containing compound (B) are listed below. The fatty ester may be octadecyl laurate, dococyl laurte, dococyl myristate, dodecyl palmitate, tetradecyl palmitate, pentadecyl palmitate, hexadecyl palmitate, octadecyl palmitate, triacontyl palmitate, octadecyl palmitate, docodyl palmitate, vinyl stearate, propyl stearate, isopropyl stearate, butyl stearate, amyl stearte, heptyl stearate, octyl stearate, tetradecyl stearate, hexadecyl stearate, heptadecyl stearate, octadecyl stearate, dococyl stearate, hexaconyl stearate, triacontyl stearate, dodecyl behenate, octadecyl behenate, dococyl behenate, tracocyl lignocerate, myricyl melissate. The ketone having a higher alkyl group may be 8-pentadecanone, 9-heptadecanone, 10-nonadecanone, 11-heneicosanone, 12-tricosanone, 14-heptadosanone, 16-hentriacontanone, 18-pentatriacontanone, 22-tritetracontanone, 2-pentadecanone, 2-hexadecanone, 2-heptadecanone, 2-octadecanone, 2-nonadecanone. The dibasic acid ester is preferably diesters, and it is represented by the following general formula (I). ROOC-(CH 2 ) n -COOR' (wherein, R and R' represent an alkyl group, and the carbon number of this alkyl group is preferably from 1 to 30, more preferably from 1 to 22. RandR' maybe the same or different. n is preferably from 1 to 30, more preferably from 2 to 20.). Specifically, succinic acid diester, adipic acid diester, sebacic acid diester, 1,18-octadecamethylenedicarboxylic acid ester and the like are listed. As the polyhydric alcohol difatty ester, those of the following general formula (II) are listed. CH 3 (CH 2 ) m-2 COO(CH 2 ) n OOC(CH 2 ) m-2 CH 3 (wherein, n is from 2 to 40, preferably from 3 to 30, more preferably from 4 to 22. m is from 2 to 40, preferably from 3 to 30, more preferably from 4 to 22.). Specifically, 1,3-propanediol dialkanoic acid ester, 1,6-hexanediol dialkanoic acid ester, 1,10-dicanediol dialkanoic acid ester, 1, 18-octadecanediol dialkanoic acid ester and the like are listed. As the fatty monoamide, those of the following general formula (III) are listed. R 1 -CONH-R 2 (wherein, R 1 represents a linear hydrocarbon chain having 1 to 25 carbon atoms, R 2 represents a linear hydrocarbon chain having 1 to 26 carbon atoms, a methylol group or hydrogen, and at least any one of R 1 and R 2 is a linear hydrocarbon chain having 10 or more carbon atoms.). Specifically, N-lauryllauric amide, N-palmitylpalmitic amide, N-stearylpalmitic amide, N-behenylpalmitic amide, N-palmitylstearic amide, N-stearylstearic amide, N-behenylstearic amide, N-palmitylbehenic acid, N-stearylbehenic amide, N-behenylbehenic amide and the like. As the aliphatic urea compound, those of the following general formula (IV) are listed. R' 3 -NHCONH-R' 4 (wherein, R' 3 and R' 4 represent an alkyl group, alicyclic group or aromatic group, and at least any one of them is a linear hydrocarbon chain having 1 to 26 carbon atoms.). Specifically, N-butyl-N-stearylurea, N-phenyl-N-stearylurea, N-stearyl-N-stearylurea, N-behenyl-N-stearylurea, N-stearyl-N-behenylurea, N-behenyl-N-behenylurea and the like are listed. It is preferable that the thermo reversible recording medium of the present invention has the following (i) to (iii) together as the condition manifesting reversible change between transparent condition and non-transparent condition depending on temperature: (i) the clearing upper limit temperature is 110 °C or more, (ii) the temperature difference between the clearing upper limit temperature and the opacifying lower limit temperature is 20 °C or less, (iii) the clearing temperature range is 30 °C or more. The clearing upper limit temperature (T WX ), opacifying lower limit temperature (T VO ), temperature difference (Δ T WV ) between the clearing upper limit temperature and the opacifying lower limit temperature, clearing initiation temperature (T WD ), clearing temperature range (ΔT z ) are determined as described below. First, an opacified thermo reversible recording medium is prepared. For of a cleared medium or a medium which is not sufficiently opacified, the medium is opacified previously by pushing the medium to a hot plate sufficiently heated to heat the medium. The heating time may be from 10 to 30 seconds. To confirm that the heating temperature is sufficiently high for the opacification, it may be advantageous to heat the medium again at temperature somewhat higher than that temperature (for example, temperature higher by 10 °C). If degree of opacification is the same in the both cases, it is known that the initial heating temperature is temperature sufficient to cause opacification. If the degree of opacification is higher when the medium is heated at somewhat higher temperature, it is known that the initial temperature is still lower, therefore, it may be recommendable to raise heating temperature and repeat the same procedure again. Then, this opacified recording medium is heated at varied temperatures, and temperature at which clearing occurs is checked. For heating of a recording medium, heat gradient tester (manufactured by Toyo Seiki K.K., HG-100) is used. This heat gradient tester has 5 heating blocks, and each block can set at individual temperature, and the heating time and pressure can also be controlled, and a medium can be heated at 5 different temperatures simultaneously under set conditions. Specifically, the heating time is 1 second, the pressure in heating is about 2.5 kg/cm, and the heating temperature is changed at a constant temperature interval of 1 to 5 °C from lower temperature at which whiteness does not change by heating to temperature at which sufficient opacification occurs. To prevent sticky adhesion of a medium to a heating block, a thin film (10 µm or less) of polyimide and polyamide may also be place on the block. After thus heated, a medium is cooled to room temperature, and the concentration of heated part at each temperature is measured using Machbeth RD-914 reflection densitometer, and a graph is made in which the set temperature of a heat gradient tester is recorded along the abscissa and the reflection density is recorded along the vertical axis as shown in Fig. 2. Fig. 2 is a graph showing the relation between the set temperature and the reflection concentration of this heat gradient tester. When the thermo reversible recording medium uses a transparent substrate, a sheet absorbing light or a sheet manifesting regular reflection of light obtained by vapor-depositing a metal such as Al and the like is placed on the rear surface of this medium. This graph is completed, by plotting concentration values against respective temperatures, then, connecting the plotted respective adjacent points by straight lines. The graph drawn usually show a trapezoid form as shown in Fig. 2. These data is influenced by the thickness and raw material of a heat sensible layer and the medium including a substrate. The thickness of the medium is not influenced by the thickness providing it is 300 µm or less, and approximately the same data are obtained, and in the case of thickness of not less than 300 µ m, it may be recommendable that the substrate side is shaved or peeled to make the thickness to 300 µ m or less, or the value exceeding 300 µ m is converted. The raw material is not restricted providing it is composed mainly of a polymer, however, in the case of a metal and the like, conversion is necessary. From this graph, the above-mentioned clearing upper limit temperature and opacifying lower limit temperature and the like are read and calculated. First, the maximum concentration value (D PD ) is read in this graph. Then, a line of y = 0.7 × D PD is drawn, and plotting points of higher concentration than this line are selected. The number of the plotting points is preferably from 5 to 20. When the number of plotting points is small, the later calculation result becomes incorrect. When the number of plotting points is small, it is necessary that the temperature interval of heating by the above-mentioned heat gradient tester is narrow and the number is increased. Of the selected plotting points, the same number of points of larger concentration values and points of smaller concentration values are removed are removed respectively, and the remaining concentration values are averaged to obtain average transparent concentration (D WDY ). The proportion of removal of larger concentration values and smaller concentration values is from 10 to 30%, preferably from 15 to 25%, respectively, based on the selected plotting points. By thus removing large concentration values and smaller concentration values, the correct value of transparent concentration of a medium can be calculated. Then, the clearing lower limit concentration (D WP ) is calculated according to the following numerical formula (1) D WP = D WDY - 0.2 × (D WDY - D PLQ ) Here, D PLQ means the maximum opacification concentration, and calculated from the average value of concentrations of adjacent 3 points which have reached within 0.3 during raising temperature. D WP represents, when at this concentration or more, concentration which looks almost transparent visually. Further, a line of y=D WP is drawn on the graph, and the crossing pointsthereof with a concentration-emperature curve are obtained. Of these crossing points, one of lower temperature side is called clearing lower limit temprature (T WO ) and one of higher temperature side is called clearing upper limit temprature (T WX ). The clearing temperature range (ΔT Z ) is calculated according to the following numerical formula (2). ΔT W = T WX - T WO The opafication upper limit temperature (Ds) is calculated according to the following numerical formula (3). Ds = D PLQ + 0.1 × (D WDY - D PLQ ) A line of y=Ds is drawn on the graph, and the temperature at a crossling point thereof with part of a concentration-temperature curve over which transparency changes to opacification is called opacification lower limit temperature (T vo ). The difference (ΔT WV ) between the clearing upper limit temperature and the opacification lower limit temperature is calculated according the following numerical formula (4). ΔT WV = T VO -T WX The clearing initiation concentration (D WD ) is calculated according to the following numerical formula (5). D WD = D PLQ + 0.25 × (D WDY -D PLQ ) The clearing initiation temperature (T WD ) is obtained from crossing points of y=D WV with the graph as shown in Fig. 2. The clearing upper limit temperature (T tu) is preferably 110 °C or more, and further preferably 115 °C or more. When T WX rises, expansion of the clearing temperature range becomes possible without lowering image durability. The clearing upper limit temperature (T WX ) is preferably 120 °C or more, more preferably 125 °C or more, further preferably 130 °C or more. When this temperature is higher, printing sensitivity increases. T WX is preferably 170 °C or less, more preferably 160 °C or less, further preferably 150 °C or less. When this temperature is lower, the printing sensitivity increases. The difference ( Δ T WV ) between the clearing upper limit temperature and the opacification lower limit temperature is preferably 20 °C or less. When T WV is larger than this, temperature to cause opacification increases than necessary, consequently, in forming an opacified image, extremely high energy is necessary, and if formation of an image and deletion of the image are repeated, the surface of a medium is injured and the degree of opacification of the image lowers, undesirably. ΔT WV is preferably 15 °C or less, more preferably 10 °C or less. The clearing initiation temperature (T WD ) is preferably less than 95 °C, more preferably 90 °C or less, further preferably 85 °C or less. T WD is preferably 70 °C or more, more preferably 75 °C or more. When this temperature is lower, image deleting property increases, and when higher, image durability is improved. The clearing temperature range (ΔT Z ) is preferably 30 °C or more. When ΔT z is smaller than this, image deleting property decreases. The clearing temperature range (ΔT z ) is more preferably 40 °C or more, further preferably 45 °C or more, particularly preferably 50 °C or more. When this temperature range is larger, image deleting property increases. ΔT z is preferably 100 °C or less, more preferably 90°C or less, further preferably 80 °C or less. Particularly, when the clearing temperature range ( Δ T Z ) is larger, a merit is generated that uniform deletion is possible even if the treating speed in deletion increases . In this case, ΔT Z is preferably 60 °C or more, more preferably 70 °C or more. Particularly, when the clearing temperature range (ΔT Z ) is larger, a merit is generated that uniform deletion is possible even if the treating speed in deletion increases. In this case, ΔT z is preferably 60 °C or more, more preferably 70 °C or more. The maximum average particle size of an organic lower molecular weight substance in a heat sensible layer is preferably 2.5 µ m or less, further preferably 2.0 µ m or less. This maximum average particle size represents dispersed condition of particles of an organic lower molecular weight substance dispersed in a polymer matrix resin of a heat sensible layer, and smaller numerical value thereof indicates more excellent dispersed condition, meaning uniform dispersion of particles of an organic lower molecular weight substance. When the maximum average particle size is smaller, the initial image opacified degree and image deleting property increase, and contrast is improved. The maximum average particle size is measured by the following method. First, a recording material is embedded in an epoxy resin, and a ultra thin sliced sample is made using a diamond cutter. Then, any 5 positions on the section of a heat sensible layer of this sample were observed using a transmission electron microscope (hereinafter, called TEM, H-9000 manufactured by Hitachi, Ltd.) at an acceleration voltage of 300 kV, and this sample is photographed at a magnification of 10000. The number of larger particles in a 10% range based on the total number of an organic lower molecular weight substance in the area of this photograph image (10 cm × 10 cm) is determined, and the average particle size is calculated from particle sizes of particles in this 10% range. This measurement is conducted on the above-mentioned 5 positions, and the average particle size is calculated on each position, and the average value of 5 average particle sizes is used as the maximum average particle size. In this measuring method, an organic lower molecular weight substance in the area of the photograph image is not in uniform circular form, the maximum particle size of particles is used. Further, when particles in the area of the photograph image are remarkably large and the number of them is less than 10, the particle size of the maximum particle of them is measured, and used as the maximum average particle size. The substrate is not particularly restricted, and films or plates made of synthetic resins such as polyester, polyvinyl chloride, polyimide, further, metal deposited films obtained by vapor-depositing metals such as aluminum and the like on these materials, are exemplified. The resin as a mother material used in a heat sensible layer is a material which forms a layer in which an organic lower molecular weight substance is uniformly dispersed an kept and exerts an influence on transparency at the maximum transparency. Therefore, a resin mother material is preferable compose of a resin having excellent transparency, mechanical stability and excellent film forming property. This resin preferably has a glass transition temperature preferably of 50 °C or more, more preferably of 60 °C or more, further preferably of 70 °C or more. Further, the glass transition temperature is preferably less than 100 °C, more preferably less than 90 °C. When the glass transition temperature is too low, the image durabilitydecreases, andwhentoohigher, the image deleting property decreases, undesirably. This resin has a gel proportion preferably of 30% or more, more preferably of 50% or more, further preferably of 50% or more, more particularly preferably of 80% or more. The gel proportion means a rate of production of gel when resin solutes lose independent mobility due to mutual action in a solvent and aggregate to form solidified condition (gel). When the gel proportion is small, repeating durability decreases, therefore, for improving gel proportion, it may be advantageous that a hardenable resin which is hardened by heat, UV, EB and the like is mized in a resin, or a resin itself is cross-linked. For measuring gel proportion, a film is peeled from a substrate and the initial weight of the film is measure, then, the film is clamped by 400 mesh wire gauzes and immersed in a solvent in which a resin before cross-linking is soluble for 24 hours, then, dried in vacuo, and the weight after drying is measured. The gel proportion is calculated according to the following formula. Gel proportion (%) = [weight after drying (g)/initial weight (g)] × 100 When the gel proportion is calculated according to this calculation, calculation is conducted excepting weights of particles of an organic lower molecular weight substance, and the like other than a resin components in a heat sensible layer. In this calculation, when the weight of an organic lower molecular weight substance is not previously known, it may be advantageous that area ratio occupying unit area is measured by observation of section by TEM, SEM and the like and weight ratio is calculated from specific gravities of a resin and organic lower molecular weight substance, and the weight of an organic lower molecular weight substance is calculated from them, and the value of gel proportion is calculated. Further, in the above-mentioned measurement, when a reversible heat sensible layer is mounted on a substrate and other layers such as a protective layer and the like are laminated on this, or when other layer is present between a substrate and a heat sensible layer, it may be advantageous, as described above, that film thickness of a reversible heat sensible layer and other layers are first checked by observation of section by TEM, SEM and the like, the surface is cut to a depth corresponding to thickness of other layers to expose the surface of a reversible heat sensible layer, and further, the reversible heat sensible layer is peeled, and the gel proportion is measured in the same manner as in the above-mentioned measuring method. Further, when a protective layer and the like made of a ultraviolet ray-hardening resin and the like are placed on the top of a heat sensible layer, it is necessary, for preventing mixing of this layer to the utmost, to shave the surface to a depth corresponding to the thickness of a protective layer and to slightly shave also the surface of a heat sensible layer to prevent influence on the value of gel proportion. It is preferable that this resin is cross-linked, and when cross-linked, the thermo recording medium does not easily manifest change of the structure in a heat sensible layer even if printing and deleting are repeated, and does not cause reductions in the degree of opacity, transparency and the like, meaning improvement in repeating durability. When cross-linked, it is preferable that the resin contains a functional group such as a hydroxyl group, carboxyl group, epoxy group, acryloyl group, methacryloyl group and the like. As the cross-linking method, there are methods by thermal cross-linking, irradiation with UV and EB, and it is preferable to add a cross-linking agent such as an isocyanate compound, functional acryl or methacryl monomer and the like, to cause cross-linking. As this resin, there are exemplified vinyl chloride-based copolymers such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer and the like; vinylidene chloride-based copolymers such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer and the like; polyesters; polyamides; polyacrylate or polymethacrylate or acrylate-methacrylate copolymer; silicone resins and the like. These resins may be used alone or in admixture of two or more. In the case a combination of a thermoplastic resin having a hydroxyl group with an isocyanate compound, it is preferable that a linear isocyanate compound and a cyclic isocyanate cmpound are mixed and used. When a linear isocyanate compound is solely used, a resin cross-linked becomes usually flexible and deleting property increases, however, when a heat sensible layer is too soft, such a demerit as reduction in repeating durability and image heat resistance occurs. However, when only a cyclic isocyanate compound is used, there are defect that the cross-linked resin becomes rigid, repeating durability and image heat resistance are improved, however, deleting property lowers. By use of a linear isocyanate compound and a cyclic isocyanate compound in admixture, deleting property, durability and heat resistance can be satisfied simultaneously. The mixing ratio of a linear isocyanate compound to a cyclic isocyanate compound is preferably from 90:10 to 10:90, more preferably from 90:10 to 30:70, further preferably from 80:20 to 30:70, by weight. When the proportion of a linear isocyanate compound is larger, deletion rate and maximum deletion tendency are improved, resulting in possibility of improvement in contrast. As the linear isocyanate compound, for example, those obtained by reacting a linear compound having a hydroxyl group such as triol and the like with an aliphatic isocyanate such as hexamethylene diisocyanate and the like directly or via a single or a plurality of ethylene oxides or propylene oxides are listed. A linear isocyanate compound has a molecular weight preferably of 500 or more, more preferably of 700 or more, further preferably of 1000 or more. Further, is it preferably 5000 or less, more preferably 4000 or less, further preferably 3000 or less. When the molecular weight is too small, a cross-linked film does not easily get a flexible structure, consequently, deleting property decreases, and when the molecular weight is too large, molecules cannot move easily, consequently, the degree of cross-linking decreases to lower durability. The molecular weight per one isocyanate group is preferably 250 or more, more preferably 300 or more, further preferably 400 or more. Further, it is preferably 2000 or less, more preferably 1500 or less, further preferably 1000 or less. When the molecular weight per one isocyanate group is too small, a cross-linked film does not easily get a flexible structure, consequently, deleting property decreases, and when the molecular weight is too large, molecules cannot move easily, consequently, the degree of cross-linking decreases to lower durability. The cyclic isocyante compund is an isocyanate compound having a benzene ring or isocyanurate ring. Among them, a type having an isocyanurate ring is suitably used since it shows no yellowing. It is preferable that also a cyclic isocyanate compound have a linear structure such as an alkylene chain and the like other than a cyclic structure. The molecular weight of a cyclic isocyanate compound is preferably 100 or more, more preferably 200 or more, further preferably 300 or more. Further, it is preferably less than 1000, more preferably less than 700. When this molecular weight is too small, the compound evaporates by heat in forming a film, and cross-linking of the film becomes impossible and durability decreases, and when too large, a rigid structure cannot be formed and durability decreases . As the mixture of a linear isocyanate compound and a cyclic isocyanate compound, the above-mentioned materials may be mixed and used, or a commercially available mixture may be used. Examples of the commercially available mixture include, but not limited to, "Coronate 2298-90T" manufactured by Nippon Polyurethane K.K., and the like. The heat sensible layer of the thermo reversible recording medium of the present invention has a thickness of preferably from 1 to 30 µ m, more preferably from 2 to 20 µ m, further preferably from 4 to 15 µ m. When the recording layer is too thick, distribution of heat is generated in the layer and uniform clearing becomes difficult. When the heat-sensible layer is too thin, the degree of opacification lowers, to decrease contrast. The degree of opacification can be increased by increasing the amount of fatty acids in the recording layer and cross-linking the resin in the heat-sensible layer. The ratio by weight of an organic lower molecular weight substance to a resin in a heat-sensible layer is preferably from about 2:1 to 1:16, more preferably from 1:2 to 1:8, particularly preferably from 1:2 to 1:5, more particularly preferably from 1:2 to 1:4. Most preferable is from 1:2.5 to 1:4. When the proportion of a resin is not more than the above-mentioned value, it is difficult to form a film in which an organic lower molecular weight substance is held in a resin, and when the proportion is not less than the above-mentioned value, opacification becomes difficult since the amount of an organic lower molecular weight substance is small. In the present invention, a protective layer can be provided on a heat-sensible layer for protecting the heat-sensible layer. The thickness of this protective layer is appropriately from 0.1 to 5 µm, and as the raw material thereof, there are exemplified silicone-based rubber or silicone resins as described in JP-A No. 63-221087, polysiloxane graft polymers as described in JP-A No. 63-317385, ultraviolet ray-curing resins or electron beam-curing resins as described in JP-A No. 02-566, and the like. Further, the protective layer can contain an organic or inorganic filler. Further, an intermediate layer can be provided between a protective layer and a heat-sensible layer as described in JP-A No. 1-133781, for protecting the heat-sensible layer from a solvent and monomer components and the like in a protective layer forming solution. As the raw material of the intermediate layer, resins used in a heat-sensible layer can be exemplified, and in addition, thermosetting resins, thermoplastic resins, UV-curing resins and EB-curing resins can be used. As such resins, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like are listed. The thickness of the intermediate layer is preferably from about 0.1 to 2 µ m, and when it is 0.1 µ m or more, the effect of a protective layer can be maintained, and when 2 µ m or more, heat sensitivity does not lower. Further, a lay showing regular reflection of light can be provided between a substrate and a heat-sensible layer and the like to improved contrast. This light reflection layer can be usually formed by a method such as vapor-deposition of metal, and the like, and thickness thereof is preferably from about 100 to 1000 Armstrong. The thermo reversible recording label of the present invention has an adhesive layer or a sticker layer provided on the opposites surface to a surface on which a heat sensible layer is formed of a substrate constituting the above-mentioned thermo reversible recording medium. The thermo reversible recording labels are classified into those having an adhesive layer of sticker layer formed (no-releasing paper type) and those having releasing paper attached under the adhesive layer of sticker layer (releasing paper type), and as the material constituting the adhesive layer, those of hot melt type are usually used. As the materials of the adhesive layer or sticker layer, those generally used can be used. Examples thereof include, but not limited to, urea resins, melamine resins, phenol resins, epoxy resin, vinyl acetate-based resins, vinyl acetate-acryl-based copolymers, ethylene-vinyl acetate copolymers, acrylic resins, polyvinyl ether-based resins, vinyl chloride-vinyl acetate-based copolymers, polystyrene-based resins, polyester-based resins, polyurethane-based resins, polyamide-based resins, chlorinated polyolefin-based resins, polyvinyl butyral-based resins, acrylate-based copolymers, methacrylate-based copolymers, natural cubber, cyanoacrylate-based resins, silicon-based resins and the like. Then, a member having an information memorizing part and a reversible display part in which at least the above-mentioned heat-sensible layer constituting a thermo reversible recording medium is used as this reversible display part will be described. As specific examples of this member having an information memorizing part and a reversible display part, following examples are listed. (1) Members in which part of a member having an information memorizing part is used as a substrate of a thermo reversible recording medium, and a heat-sensible layer is directly formed. (2) Members in which the surface of a substrate of a thermo reversible recording medium having a heat-sensible layer on the substrate, separately formed, is adhered to a member having an information memorizing member. (3) Members in which the above-mentioned thermo reversible recording label is adhered, via an adhesive layer or sticker layer, to a member having an information memorizing member. (4) Members in which an information memorizing part is provided in a thermo reversible recording medium (as the substrate constituting a thermo reversible recording medium, those having large thickness are preferable). In any case, it is necessary that an information memorizing part and reversible display part are so set that functions thereof can be manifested, respectively, and in this case, the information memorizing part can be provided on the opposite surface to a surface on which a heat-sensible layer is provided of a substrate in a thermo reversible recording medium, between a substrate and a heat-sensible layer, or on part of a heat sensible layer. The member having this information memorizing part is not particular restricted, and cards, disks, disk cartridges and tape cassettes are generally exemplified. The following examples are listed. Thick cards such as IC cards (contact type and non-contact type), optical cards and the like, disk cartridges containing a disk which can re-write recorded information such as a floppy disk, optical magnetic recording disk (MD), DVD-RAM and the like, re-writable disks using no disk cartridge such as CR-RW, DVD-RW and the like, write one type disks such as CD-R and the like, video tape cassettes, and the like. This member having both of a reversible display part and an information memorizing part is illustrated below using a card having such a structure. By displaying part of information recorded in the information memorizing part on a heat sensible layer, the owner of the card can recognize the information only by looking at the card without a specific apparatus, namely, the availability thereof increases extremely as compared with cards using no thermo reversible recording medium. The information memorizing part is not particularly restricted only providing it can record necessary information, and for example, magnetic recording layers, contact type IC, non-contact type IC or optical memories are useful. The magnetic recording layer is formed by applying metal compounds such as iron oxide, barium ferrite and the like usually used or resins such as vinyl-chloride-based resins, urethane-based resins and nylon-based resins on a substrate, or according to methods such as vapor deposition, sputtering and the like using the above-mentioned metal compound without using a resin. Further, in thermo reversible recording meda used for display, a heat-sensible layer can also be used as a recording part utilizing bar cord, two dimensional cord and the like. Regarding the example using the above-mentioned thermo reversible recording label (3), in the case of a thick substrate on which application of a heat-sensible layer is difficult. An adhesive layer or sticker layer can be provided on the whole surface of part of it. By this, availabilities of this medium can be improved, such as display of part of information recorded on a magnetic medium, and the like. This thermo reversible recording label having an adhesive layer or sticker layer provided can be applied not only to the above-mentioned magnetic vinyl chloride cards, but also to thick cards such as IC cards, optical cards and the like. Further, this thermo reversible recording label can be used instead of a display label on a disk cartridge containing a disk which can re-write recorded information, such as a floppy disk, MD, DVD-RAM and the like. Fig. 3 shows an example in which the thermo reversible recording label is pasted on MD disk cartridge. Further, in the case of a disk using no disk cartridge, such as CR-RW and the like, it is also possible to paste a thermo reversible recording label directly on a disk, and to provide a heat-sensible layer directly on a disk. Thus, applications to uses such as automatic alteration of display contents corresponding to alteration of recorded contents, and the like, are possible. Fig. 4 shows an example in which the thermo reversible recording label is directly pasted on CD-RW. In the thermo reversible recording label of the present invention, it is also possible that a thermo reversible recording medium is pasted on a once write type disk such as CD-R and the like and part of recorded information once-written in CD-R can also be re-written and displayer. Fig. 5 is an example having a constitution in which a thermo reversible recording label is formed on an optical information memorizing medium (CD-RW) using AgInSbTe-based phase-variation type recording material. In a basic constitution, a first dielectric layer, oprical information memorizing layer, second dielectric layer, reflection heat radiation layer and intermediate layer on a substrate having guide grooves, and a hard coat layer is provided on the rear surface of the substrate. Further, a thermo reversible recording label is pasted on the intermediate layer. Though a dielectric layer is not necessarily required to be provided on both side of a recording layer, when a substrate is made of a material having low heat resistance such as a polycarbonate resin, it is desirable to provide a first dielectric layer. Further, as shown in Fig. 6, it can also be used as a display label for a video tape cassette. As the method of providing a thermo reversible recording function on a thick card, disk cartridge and disk, there are a method of directly applying a heat-sensible layer on them, method in which a heat-sensible layer is previously formed on a separate substrate and the heat-sensible layer is transferred onto a thick card, disk cartridge and disk, and other methods, in addition to the above-mentioned method of pasting a thermo reversible recording label. In the case of transfer, an adhesive layer and sticker layer of hot melt type and the like may also be provided on a heat-sensible layer. When a thermo reversible recording label is pasted or a heat-sensible layer is provided on a rigid substrate such as a thick card, disk, disk cartridge, tape cassette and the like, it is preferable to provide a layer or sheet having elasticity and acting as cushion between the rigid substrate and a label or a heat-sensible layer, to improved contact property with a thermal head, and to form an image uniformly. For example, the reversible heat-sensible recording medium of the present invention can be processed into a film in which a reversible heat-sensible recording layer (13) and a protective layer (14) are provided on a substrate (11) as shown in Fig. 7A, a film in which an aluminum reflection layer (12), a reversible heat-sensible recording layer (13) and a protective layer (14) are provided on a substrate (11) as shown in Fig. 7B, a film in which an aluminum reflection layer (12), a reversible heat-sensible recording layer (13) and a protective layer (14) are provided on a substrate (11) and a magnetic recording layer (16) is provided on the rear surface of the substrate (11) as shown in Fig. 7C, and a card (21) having a printed display part (23) as shown in Fig.8. Further, as shown in Fig 9A for example, it is possible that a film having an aluminum reflection layer (12), a reversible heat-sensible recording layer (13) and a protective layer (14) provided on a substrate (11) is processed into a card, a concave part (23) is formed to accommodate an IC tip, and processing into a card is effected. In this example, a re-writing recording part (24) is label-processed on a reversible heat-sensible recording medium in the form of a card, and a concave part for burying IC tip (23) is formed on a given position on the rear surface of the reversible heat-sensible recording medium, and in this concave part (23), a wafer (231) as shown in Fig. 9B is integrated and fixed. In the wafer (231), an integrated circuit (233) is provided on a wafer substrate (232) and a plurality of contact terminals (234) connected electrically to this integrated circuit (233) is provided on the wafer substrate (232). This contact terminal (234) is exposed to the rear side of the wafer substrate (232), and a dedicated printer (readerwriter) is in electrical contact with this contact terminal (234), to form a constitution so that reading and re-writing of given information are possible. Examples of use of the reversible heat-sensible recording card are illustrated in Fig. 10A and Fig. 10B. Fig. 10A is a schematic constitution block view showing the integrated circuit (233), and Fig. 10B is a constitution block view showing one example of recording data of RAM. The integrated circuit (233) is constituted, for example, of LSI, and it contains CPU (235) which can execute control motion in a given order, ROM (236) accommodating motion program data of the CPU (235), and RAM (237) which can write and read necessary data. Further, the integrated circuit (233) contains an input out put interface (238) which receives an input signal and impart the input data to the CPU (235) and receives an output signal from the CPU (235) and outputs the signal, and though not shown, a power on reset circuit, a clock generating circuit, pulse dividing circuit (interrupt pulse generation circuit), and address decoder circuit. The CPU (235) can execute motion of an interrupt control routine, corresponding to an interrupt pulse imparted periodically from the pulse division circuit. Further, the address decoder circuit decodes address data from the CPU (235), and imparts signals to the ROM (236), RAM (237) and input output interface (238), respectively. To the input output interface (238) is connected a plurality (8 in the figure) of contact terminals (234), and given data from the above-mentioned dedicated printer (readerwriter) is input from this contact terminal (234) via the input output interface (238) into the CPU (235). The CPU (235) responds to an input signal and conducts each motion according to program data accommodated in the ROM (236), and outputs given data and signals to the card readerwriter via the input output interface (238). As shown in Fig. 10B, the RAM (237) contains a plurality of memory regions (239a) to (239f). For example, card numbers are memorized in the region (239a), and ID data such as the name, address, telephone number and the like of the card owner is, for example, memorized in the region (239b), and information corresponding to remaining valuable value or valuable paper which can be used by the owner is, for example, memorized in the region (239c), and information corresponding to remaining valuable value or valuable paper used by the owner is memorized in the regions (239d), (239e), (239f) and (239g). The present invention further provides an image processing method of conducting formation and/or deletion of an image by heating using the above-mentioned thermo reversible recording medium, the above-mentioned member having an information memorizing part, or the above-mentioned label, and an image processing apparatus for conducting formation and/or deletion of an image by heating, having the above-mentioned thermo reversible recording medium, the above-mentioned member having an information memorizing part, or the above-mentioned label. For formation of images, image recording means are used which can heat the medium partially on images such as a thermal head, laser and the like. For deletion of image, a hot stamp, ceramic heater, heat roller, hot air and the like and image deletion means such as a thermal head, laser and the like are used. Among them, a ceramic heater is preferably used. By use of a ceramic heater, the size of an apparatus can be decreases, and stable deletion condition can be obtained, leading to an image having excellent contrast. The setting temperature of a ceramic heated is preferably 100 °C or more, more preferably 110 °C or more, further preferably 115 °C or more. Further, by use of a thermal heat as the image deletion means, the size of the whole apparatus can be further decreased. Furthermore, consumption electric powder can be reduced, and a handy type apparatus of battery drive can also be used. If one thermal head is used for formation and deletion simultaneously, further decrease in size is possible. When formation and deletion are conducted by one thermal head, it may be permissible that all of the previous images are deleted once, and new images are formed renewedly, and an over write mode is also possible in which previous images are once deleted and new images are formed while changing energy for each image. In the over write mode, the total time including formation and deletion is shortened, leading to speed up of recording. When a card having a heat-sensible layer and an information memorizing part is used, the above-mentioned apparatus also contains means for reading and means for re-writing information in the information memorizing part. Fig. 11 shows an example of the image processing apparatus of the present invention. In this apparatus, image deletion is conducted by a ceramic heat and image formation is conducted by a thermal head. First, information memorized in a magnetic recording layer of a recording medium is read by a magnetic head, then, images recording in a reversible heat-sensible layer are deleted by heating by a ceramic heater, further, a new information treated based on the information read by the magnetic head is recorded by a thermal head in a reverse heat-sensible layer. Then, the information in the magnetic recording layer is also re-written by new information. Namely, in the image processing apparatus of Fig. 11, a thermo reversible recording medium (1) having a magnetic recording layer provided on the opposite side of a heat-sensible layer is transported along a transporting path shown by arrows, or transported to the reverse direction in an apparatus along the transporting path. In the thermo reversible recording medium (1), magnetic recording or record deletion is effected on a magnetic recording layer between a magnetic head (34) and a transportation roller (31), and heated for deleting images between a ceramic heater (38) and a transportation roller (40), and images are formed between the thermal head (53) and the transportation roller (47), then, transported out of the apparatus. Re-writing of magnetic recording may be before or after deletion of images by a ceramic heater. Further, if desired, after passing between the ceramic heater (38) and the transportation roller (40), or after passing between the thermal head (53) and the transportation roller (47), the medium is transported to reverse direction along the transportation path, and thermal treatment can be effected again by the ceramic heater (38) and printing treatment can be performed again by the thermal head (53). Example 1 Al layer of thickness about 40 nm (400 Armstrong) was vacuum vapor-deposited on the PET film side of an original drapery manufactured by Dainippon Ink & Chemicals, Ink. (Memory Dick, DS-1711-1040: a magnetic recording layer and a self cleaning layer have been applied on a transparent PET film having a thickness of 188 µ m), to form an optical reflection layer. On this was applied a solution composed of Vinyl chloride-vinyl acetate-phosphate copolymer (manufactured by Denki Kagaku Kogyo K. K. , Denka Vinyl #1000P) 10 parts Methyl ethyl ketone 45 parts Toluene 45 parts , and the solution was dried by heating to provide an adhesion layer having a thickness of about 0.5 µ m. Then, into a resin dissolved solution prepared by dissolving 26 parts of a vinyl chloride-based copolymer (manufactured by Nippon Xeon Co., Ltd., MR110) into 230 parts of methyl ethyl ketone was added Behenyl behenate (test sample manufactured by Miyshi Yushi Kabushiki Kaisha) 6 parts CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 (test sample manufactured by Miyshi Yushi Kabushiki Kaisha) 4 parts , ceramic beads having a diameter of 2mm were placed in a glass bottle, and using a paint shaker (manufactured by Asada Tekko K.K.), and the mixture was dispersed for 48 hours to prepare a uniform dispersion. Into this dispersion, 4 parts of an isocyanate compound (manufactured by Nippon Polyurethane K.K., Coronate 2298-90T) was added to prepare a heat-sensible layer solution, and applied on an adhesive layer of a PET film having the above-mentioned magnetic recording layer, and dried by heating, then, the applied solution was further kept at 60 °C for 72 hours to cross-link the resin to provide a heat-sensible layer having a thickness of about 10 µm. On this heat-sensible layer was applied a solution composed of 75% solution of urethane acrylate-based ultraviolet ray-curing resin in butyl acetate (manufactured by Dainippon Ink & Chemicals, Ink, Unidick C7-157) 10 parts Isopropyl alcohol 10 parts , the solution was dried by heating, then, irradiated with ultraviolet ray using a high pressure mercury lamp of 80 w/cm to cure the solution to form a protective layer having a thickness of about 3 µm, giving a thermo reversible recording medium. Example 2 A thermo reversible recording medium was produced in the same manner as in Example 1 except that the amount of behenyl behenate was changed to 8 parts and the amount of CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was changed to 2 parts. Example 3 A thermo reversible recording medium was produced in the same manner as in Example 1 except that the amount of behenyl behenate was changed to 9 parts and the amount of CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was changed to 1 part. Example 4 A thermo reversible recording medium was produced in the same manner as in Example 1 except that the amount of behenyl behenate was changed to 9.5 parts and the amount of CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was changed to 0.5 parts. Example 5 A thermo reversible recording medium was produced in the same manner as in Example 2 except that behenyl behenate was replaced by diheptadecylketone (manufactured by Nippon Kasei Chemical Co., Ltd., Wax KS). Example 6 A thermo reversible recording medium was produced in the same manner as in Example 2 except that behenyl behenate was replaced by ethanolamine distearate (manufactured by Nippon Kasei Chemical Co., Ltd., Suliaid S). Example 7 A thermo reversible recording medium was produced in the same manner as in Example 4 except that CH 3 (CH 2 ) 17 NHCOCONH (CH 2 ) 17 CH 3 was replaced by CH 3 (CH 2 ) 16 CONHNHCO(CH 2 ) 16 CH 3 (test sample manufactured by Miyshi Yushi Kabushiki Kaisha). Example 8 A thermo reversible recording medium was produced in the same manner as in Example 7 except that behenyl behenate was replaced by diheptadecylketone (manufactured by Nippon Kasei Chemical Co., Ltd., Wax KS). Example 9 A thermo reversible recording medium was produced in the same manner as in Example 7 except that behenyl behenate was replaced by ethanolamine distearate (manufactured by Nippon Kasei Chemical Co., Ltd., Suliaid S). Example 10 A thermo reversible recording medium was produced in the same manner as in Example 4 except that CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was replaced by CH 3 (CH 2 ) 17 OOCNH (CH 2 ) 6 NHCOO(CH 2 ) 17 CH 3 . (test sample manufactured by Miyshi Yushi Kabushiki Kaisha). Example 11 A thermo reversible recording medium was produced in the same manner as in Example 2 except that CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was replaced by CH 3 (CH 2 ) 17 NHCOO (CH 2 ) 4 OOCNH(CH 2 ) 17 CH 3 (test sample manufactured by Miyshi Yushi Kabushiki Kaisha). Example 12 A thermo reversible recording medium was produced in the same manner as in Example 4 except that CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was replaced by CH 3 (CH 2 ) 17 SO 2 (CH 2 ) 2 SO 2 (CH 2 ) 17 CH 3 (test sample manufactured by Miyshi Yushi Kabushiki Kaisha). Example 13 A thermo reversible recording medium was produced in the same manner as in Example 2 except that CH 3 (CH 2 ) 17 NHCOCONH(CH 2 ) 17 CH 3 was replaced by the following material (test sample manufactured by Miyshi Yushi Kabushiki Kaisha). Example 14 An adhesive layer, heat-sensible layer and protective layer were formed on the Al vapor-deposited surface of an Al deposited polyester film (manufactured by Toray Industries, Inc., #50 Mtalmy) having a thickness of about 50 µ m in the same manner as in Example 1. Further, an acrylic sticker layer having a thickness of about 5 µ m was provided on the rear surface of the heat-sensible layer of the substrate, to produce a thermo reversible recording label. This label was made into a donut as shown in Fig. 4, and pasted on CD-RW as shown in Fig. 5, to produce an optical information memorizing medium equipped with a reversible display function. Using the optical information memorizing medium as produced above, part of information (date, time and the like) memorized by a CD-RW drive (manufactured by Ricoh Co., Ltd., MP6200S) was displayed and recorded on the heat-sensible layer using a recording apparatus having a recording means (thermal head) and a deleting means (ceramic heater) while controlling recording energy of the thermal head corresponding to change in recording temperature of each medium. Further, information of the memorizing layer of the optical information memorizing medium was re-written using this drive, the previous record was deleted using the deleting means, and the re-written information was re-written newly by a thermal head on the heat-sensible layer, to effect display recording. Further, re-writing of this display recording was repeated 100 times, however, recording and deletion were possible. Example 15 The thermo reversible recording label in Example 14 was pasted on MD disk cartridge as shown in Fig. 3. Part of information (date, song title and the like) memorized by MD was displayed and recorded on the heat-sensible layer using a recording apparatus having a recording means (thermal head) and a deleting means (ceramic heater) while controlling recording energy of the thermal head corresponding to change in recording temperature of each medium. Further, re-writing of this display recording was repeated 100 times, however, recording and deletion were possible. Comparative Example 1 A thermo reversible recording medium was produced in the same manner as in Example 1 except that the application solution of the heat-sensible layer was changed as follows. Behenic acid (reagent manufactured by SIGMA, purity 99%) 5 parts Eicosandioic acid (manufactured by Okamura Seiyu K.K., SL-20-90) 5 parts Vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbide, VYHH) 38 parts Tetrahydrofuran 210 parts Toluene 20 parts Comparative Example 2 A thermo reversible recording medium was produced in the same manner as in Example 1 except that the application solution of the heat-sensible layer was changed as follows. The heat-sensible layer herein formed had poor uniformity showing remarkable white particles. Behenyl behenate (reagent manufactured by SIGMA) 9.5 parts Ethylenebisbehenic amide (manufactured by Nippon Kasei Chemical Co., Ltd., Sulipax B) 0.5 parts Vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbide, VYHH) 30 parts Tetrahydrofuran 160 parts [Evaluation] The following evaluations were conducted using thus produced thermo reversible recording media (Examples 1 to 13, Comparative Examples 1 and 2). (1) Contrast The medium obtained as described above was cleared previously, and heat was applied on this using a magnetic card readerwriter having print deleting function (KU-R-3001FA) manufacture by Kyushu Matsushita Electric Co. , Ltd., while setting the printing energy value of a thermal heat to 0.47 mJ/dot, the medium was cooled to room temperature, and the reflection concentration was measured by a Macbeth reflection densitometer to obtain the initial image concentration. Then, opaque images were formed on the medium using the same apparatus at the above-mentioned energy value, thermal printing was conducted while wetting the deletion temperature value of a ceramic heater to 90 °C, the medium was cooled to room temperature, and the reflection concentration was measured by a Macbeth reflection densitometer to obtain the initial deletion concentration. Next, the initial contrast was calculated from the above-obtained initial image concentration and the initial deletion concentration (initial deletion concentration initial image concentration). (2) Ammonia resistance A previously cleared medium was immersed in a 8% ammonia aqueous solution for 48 hours, then, the image concentration and deletion concentration were measured by the same apparatus according to the same method as used in the above-mentioned contrast measurement, and these were called the image concentration after test, and the deletion concentration after test. Then, the contrast after test was calculated from the above-obtained image concentration after test and deletion concentration after test (deletion concentration after test - image concentration after test). (3) Deleting property A medium was previously cleared, and partially opacified using a readerwriter (KU-R-3001FA) manufacture by Kyushu Matsushita Electric Co., Ltd., under 5 °C by a thermal inclination tester, then, deletion was effected at the optimum deletion temperature around the center of the deletion temperature. This procedure was conducted on 50 pieces of paper, and deleted condition of images was visually confirmed and evaluated. Evaluation level: ○: all can be deleted ○ to Δ: pale deletion residue occurs slightly Δ: pale deletion residue occurs sometimes ×: pale deletion residue often occurs The results of (1) to (3) are summarized in Table 1. (4) Clearing upper limit temperature (Ttu), opacification lower limit temperature (Tsl), temperature difference (Δ Tts) between clearing upper limit temperature and opacification lower limit temperature, clearing lower limit temperature (Ttl), clearing temperature range (ΔTw) Ttu, Tsl, ΔTts, Ttl and ΔTw were measured using the above-mentioned measuring methods. The results are summarized in Table 2. According to the present invention, a thermo reversible recording medium which can give sufficient degree of opacification even if preserved in the presence of a basic substance, expands clearing temperature range, can provide an image having sufficient image deleting property and high contrast even if the environment temperature changes, and can provide sufficient degree of opacification, a member having an information memorizing part, an image processing method, and image processing apparatus are provided, contribution to the thermo reversible recording field is extremely large. The present document incorporates by reference the entire contents of Japanese priority documents, 2000-176727 filed in Japan on June 13, 2000.

Claims: A thermo reversible recording medium comprising: a substrate; and a heat sensitive layer on said substrate, made mainly from resin and organic lower molecular weight substance, said heat sensitive layer reversibly achieving transparent-state and opaque-state depending on temperature, wherein the organic lower molecular weight substance is a linear hydrocarbon-containing compound (A) having no carboxyl group and selected from one or more of (1) linear hydrocarbon-containing compounds having a urethane bond, (2) linear hydrocarbon-containing compounds having a sulfonyl bond, (3) linear hydrocarbon-containing compounds having an oxalic diamide bond, or (4) linear hydrocarbon-containing compounds having a diacylhydrazide bond, The thermo reversible recording medium of claim 1 wherein (1), (2), (3) and (4) among linear hydrocarbon-containing compounds (A) have at least one of a phenylene group, cyclohexylene group, cyclohexyl group, phenyl group and heterocyclic ring. The thermo reversible recording medium of claim 1 or 2 wherein at least one end of the molecule of the linear hydrocarbon-containing compound (A) is a methyl group. The thermo reversible recording medium of any one of claims 1-3 wherein the linear hydrocarbon-containing compound (A) has a melting point above 100°Cand below 180°C. The thermo reversible recording medium of any one of claims 1-4 wherein at least one of linear hydrocarbon-containing compounds (B) having a melting point lower than the melting point of said linear hydrocarbon-containing compound (A) by 20°C or more and having no carboxyl group is further used as the organic lower molecular weight substance. The thermo reversible recording medium of claim 5 wherein the total carbon number of linear hydrocarbons of the linear hydrocarbon-containing compound (A) and the linear hydrocarbon-containing compound (B) is from 6 to 60. The thermo reversible recording medium of 5 or 6 wherein the linear hydrocarbon-containing compound (B) has a melting point of 50°C or more and less than 100°C. The thermo reversible recording medium of any one of claims 5-7 wherein the mixing ratio by weight of the linear hydrocarbon-containing compound (A) to the linear hydrocarbon-containing compound (B) is 80:20 to 1:99. The thermo reversible recording medium of any one of claims 5-8 wherein the linear hydrocarbon-containing compound (B) is at least one selected from fatty esters, ketones having a higher alkyl group, dibasic acid esters, polyhydric alcohol difatty esters, aliphatic monoamide compounds and aliphatic monourea compounds. The thermo reversible recording medium of any one of claims 1-9 wherein the clearing upper limit temperature is 110°C or more, the temperature difference between the clearing upper limit temperature and the opacifying lower limit temperature is 20°C or less, and the clearing temperature range is 30°C or more. The thermo reversible recording medium of any one of claims 1-10 wherein the resin has a gel proportion [weight after drying (g) / initial weight (g) x 100] of 30% or more. The thermo reversible recording medium of any one of claims 1-11 wherein at least part of the resin is cross-linked. A thermo reversible recording label having two surfaces, one surface provided with an adhesive layer and the other surface provided with a thermo reversible recording medium according to any one of claims 1-12. A member comprising: an information memorizing part which stores information; and a reversible display part which includes a heat sensitive layer as defined in any one of claims 1-12. The member of claim 14 wherein said information memorizing part is supported in or held by a holding member, and said reversible display part is provided on said holding member. The member of claim 15 wherein said holding member is a card, disk, disk cartridge or tape cassette. The member of any one of claims 14-16 wherein said reversible display part is a thermo reversible recording label having two surfaces, one surface provided with an adhesive layer and the other surface provided with a thermo reversible recording medium according to any one of claims 1-12. A method of processing an image in which an image is formed on or erased from a heat sensitive layer as defined in any one of claims 1-12. The method of claim 18 wherein the image is formed on said heat sensitive layer by using a thermal head. The method of claim 18 or 19 wherein the image on said heat sensitive layer is deleted by using a thermal head or a ceramic heater.

Inventors: HOSODA KAZUO, HOTTA YOSHIHIKO, KAWAI KOJI, KAWAMURA FUMIO, KOKUBO KATSUAKI, MORIYA MASAFUMI, MOROBOSHI KUNICHIKA, SUGIYAMA KATSUSHI, HOSODA, KAZUO, HOTTA, YOSHIHIKO, KAWAI, KOJI, KAWAMURA, FUMIO, KOKUBO, KATSUAKI, MORIYA, MASAFUMI, MOROBOSHI, KUNICHIKA, SUGIYAMA, KATSUSHI
Applicants: MIYOSHI YUSHI KK, RICOH KK, MIYOSHI YUSHI KABUSHIKI KAISHA, RICOH COMPANY LTD.
Application year: 2001
Main classification: B41M5
IPC codes: B41J2, B41M5, G09F3, G11B23