Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
  • B41M5/3333—Non-macromolecular compounds
  • B41M5/3335—Compounds containing phenolic or carboxylic acid groups or metal salts thereof
  • B41M5/3336—Sulfur compounds, e.g. sulfones, sulfides, sulfonamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
  • B41M5/3333—Non-macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/337—Additives; Binders
  • B41M5/3377—Inorganic compounds, e.g. metal salts of organic acids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/04—Direct thermal recording [DTR]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/323—Organic colour formers, e.g. leuco dyes
  • B41M5/327—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
  • B41M5/3275—Fluoran compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/337—Additives; Binders
  • B41M5/3372—Macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/337—Additives; Binders
  • B41M5/3375—Non-macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/41—Base layers supports or substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/426—Intermediate, backcoat, or covering layers characterised by inorganic compounds, e.g. metals, metal salts, metal complexes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds

Definitions

• the present invention relates to a heat-sensitive recording material. Specifically, the invention relates to a heat-sensitive recording material having superior apparatus applicability that does not cause deterioration of apparatus durability such as head abrasion, and the like; having photographic applicability and stability as a recording medium; having printing applicability, stamping applicability, environment applicability, and the like; and having usefulness as a plain paper-like recording medium.
• heat-sensitive recording material Historically, dye-type heat-sensitive paper containing a colorless leuco dye and a phenolic acidic substance was developed as a heat-sensitive recording technology by NCR Inc. in the 1960s, and this system has become the mainstream of heat-sensitive recording systems. Thereafter, demand for heat-sensitive paper (hereinafter referred to as "heat-sensitive recording material") has increased rapidly since (1) miniaturization and price reduction of apparatuses became possible due to development of thermal heads based on semiconductor technologies and significant improvement in cost and performance; (2) besides (1), high quality (high sensitivity, improvement of head matching property, and the like) of heat-sensitive paper (heat-sensitive recording material) itself was realized; and (3) heat-sensitive recording systems were evaluated to be advantageous in view of user-friendliness, i.e., convenience, low costs, freedom from frequent maintenance, and the like as compared to other recording systems such as static recording, ink jet recording, PPC recording, and the like.
• heat-sensitive recording materials have been widely used since they are relatively inexpensive and recording apparatus therefor are compact and free from frequent maintenance. Under such circumstances, competition in the marketing of heat-sensitive recording materials has become tough, and demand for heat-sensitive recording materials having higher performance that can be differentiated from conventional performance, and specifically heat-sensitive recording materials having high density of developed color, whiteness of background, sharpness, storage stability, good hue and sharpness for a full-color image recorded by an ink jet recording system, or the like has increased. Therefore, intensive investigations regarding various characteristics such as color developing property, storability, and the like of heat-sensitive recording materials are now being conducted in order to satisfy such demands.
• the characteristics that heat-sensitive recording materials should have include, for example, (1) high sensitivity (capability to provide high density); (2) high whiteness of a background portion (non-printed portion) (low background fogging property); (3) superior image storability after photographic printing; (4) superior light fastness; (5) superior resistance to chemical substances; (6) sharpness and high image quality; (7) good hue and sharpness of colors for a full-color image recorded by an ink jet recording system; (8) good thermal head matching property and head resistance property by which thermal head abrasion is decreased; (9) plane paper-like feeling; (10) printing applicability that enables printing on a heat-sensitive recording layer, and stamping applicability free from bleeding; (11 applicability for high performance printers such as a high speed printer, and the like; and (12) nvironment applicability.
• the heat-sensitive recording layer or the like is formed by applying a coating solution the support, due to the drying or rolling into a roll-like shape thereafter, if the h eat-sensitive recording material is produced by cutting the obtained material into sheets (e.g. square or rectangular shape), the four comers of each sheet tend to be curved and curled up toward the heat-sensitive recording layer side after the cutting [(13) curling tendency].
• curling shape is significant, not only the product value or quality is deteriorated but also transportation failure is caused at the time of recording.
• bisphenol A 2,2-bis(4-hydroxyphenyl)propane
• such a system also has a problem in view of (14) ink jet applicability. Namely, full color information is sometimes recorded on a heat-sensitive recording material using inks for ink jet recording.
• inkjet recording is carried out on a recording surface of a conventional heat-sensitive recording material containing bisphenol A
• hues of inks cannot be reproduced faithfully, sharp hues cannot be obtained, and when an image is already formed on the recording surface by heat-sensitive recording, the image sometimes fades.
• the above-mentioned conventional heat-sensitive recording material is placed in contact with a medium having an image recorded by an ink jet printer, background fogging or fading of a recorded image sometimes occurs.
• the heat-sensitive recording material is relatively economical and the recording appliance for the material is compact and maintenance free, so that it has been used in a wide range.
• the selling competition of the thermal recording paper (heat-sensitive recording materials) has been escalating and therefore higher functions differentiated from the conventional functions are required for the heat-sensitive recording materials and investigations and studies on improvements of coloring density of the heat-sensitive recording materials, image storability, chemical resistance (especially, plasticizer resistance), high speed printing suitability and the like have enthusiastically been carried out.
• image storability and the chemical resistance especially, plasticizer resistance
• JP-A Japanese Patent Application Laid-Open
• JP-A No. 6-135159 discloses recording materials using salicylic acid derivatives having aryloxyalkyloxy group as a substituent group and/or metal salts thereof as electron-accepting compounds and describes that the chemical resistance is improved.
• head stain there still remains a margin for further improvements.
• the purpose of the invention is to solve the above-mentioned conventional problems and accomplish following objects.
• an object of the invention is to provide a heat-sensitive recording material which is scarcely curled and suitable for high quality recording and transportation; which is useful for forming images with high sensitivity and high density with suppressed fogging density (background fogging) in the background portion (non-image portions); which is excellent in the image storability and chemical resistance after printing and has ink-jet suitability without causing hue failure and blurring of the ink jet images or image color fading attributed to the ink for ink jet; and which shows good matching property to the thermal head and scarcely causes head wear or head stain even in the case of application to a high speed or a high functional printer having a partial graze structure (good head matching property in the high speed printing) and another object of the invention is to provide a heat-sensitive recording material, in addition to the above-mentioned properties, which gives sharp and high quality images, is excellent in the light fastness of the formed images, comprises a heat-sensitive recording layer or a protective layer for printing or stamping without blurring, is produced at a
• the means can be provision of a undercoat layer including a pigment which has a high oil-absorbing property to decrease the amount of a binder used in the undercoat layer as much as possible, incorporation of hollow particles in the undercoat layer, or the like.
• the heat-sensitive recording layer contains many components those do not contribute to development of color, and the heat capacities of these components are unnecessarily consumed.
• examples of such components include a releasing agent and waxs, which suppress adhesion between the thermal head and the recording layer, an oil-absorbing pigment, which absorbs melted components, binders, in which materials are dispersed and which provides film strength, and the like. Since the heat consumption by these components accounts for about 20% to 30% of the total heat consumption, it is expected to increase sensitivity by about 10% to 15% by reducing the amounts of these components by half.
• sensitivity can be increased by decreasing the amounts of a pigment and a binder in a recording layer. Since sensitivity can be increased unexpectedly by decreasing the amount of the binder, it is considered that factors other than heat capacity contribute to increased sensitivity. However, it is unclear what the factors are. It should be noted that, however, when the amount of the binder is simply decreased, a head matching property with respect to a thermal head, film strength, and the like deteriorate. Accordingly, it is important to use as effective incorporation rates as possible, i.e., to use desired components in desired layers in minimum amounts.
• a sensitizer was selected as an agent which decreases melting points of an electron-donating colorless dye and an electron-accepting compound in order to develop color at a lower temperature.
• a sensitizer there is a limitation in increasing sensitivity while keeping a temperature at which color development starts. Consistency between background fogging prevention and increased sensitivity is difficult.
• the inventors considered a sensitizer as a material for dissolving an electron-donating colorless dye and an electron-accepting compound and investigated a sensitizer that realizes high sensitivity without unnecessarily decreasing a co-melting point, in other words, with keeping background fogging at a low level, and found that, in order to increase sensitivity, it is more advantageous to more rapidly diffuse the electron-donating colorless dye and the electron-accepting compound in the melted sensitizer. Accordingly, in order to increase sensitivity, it is advantageous and preferable to select a sensitizer having not only high solubility but also a low melt viscosity, and to decrease the dispersion liquid particle size of the electron-donating colorless dye and the electron-accepting compound. It should be noted that, however, when the dispersion liquid particle size is too small, background fogging becomes worse. Therefore, it is important to select a suitable size.
• Printing is carried out on a heat-sensitive recording material by bring a thermal head, which is a heat generating element, into direct contact with the recording surface of the recording material (surface of the heat-sensitive recording layer), and rubbing the recording surface with the head. Accordingly, the melted components in the recording layer sometimes adhere to the head and deposit as smutch thereon. Furthermore, the components physically abrade or corrode the surface of the thermal head and then the lifetime of the head sometimes shortens.
• a developed image is specifically vulnerable to moisture, and easily fades out due to a reverse reaction caused by chemical agents such as oils and fats, plasticizers, and the like, since chemical reaction that is caused by heat melt and contact of a leuco dye and a developer, which chemical reaction is a principle of color development of heat-sensitive recording materials, is reversible reaction.
• problems regarding heat resistance, image storability (specifically moisture resistance) and chemical resistance such as problems in which a developed image fades out due to heat or moisture during storage, or in daily life in which users may touch their hands, onto which a hand cream, any other cosmetic, oil or fat adheres, to the recording material, or in which the image may be brought into contact with a plastic product including a plasticizer, a product including an organic solvent or a leather product (an eraser, a desk mat or food wrapping film made of vinyl chloride, a marker pen, an ink for ink jet, a wallet, a commuter-pass holder, and the like).
• a plastic product including a plasticizer, a product including an organic solvent or a leather product (an eraser, a desk mat or food wrapping film made of vinyl chloride, a marker pen, an ink for ink jet, a wallet, a commuter-pass holder, and the like).
• a heat-sensitive recording material has problems in that usage of the material is limited to short-time application such as measuring labels to be adhered to perishable foods sold in supermarkets, and the like, and that, even if a cross-linking substance is added, it takes substantially long period of time from color development to exhibit the effect thereof, ane the like. Therefore, storability, which is a basic characteristic, has not been satisfied yet.
• a specific electron-accepting compound is useful for improvement in heat resistance and image storability and for prevention of background fogging, and that background fogging can be further prevented by combining the compound with a specific sensitizer and/or a specific electron-donating colorless dye. Furthermore, the inventors have found that heat resistance, image storability and light fastness can be further improved without deteriorating background fogging by combining the compound with a specific image stabilizer. According to the above findings, it is also possible to provide not only heat resistance and image storability , which are difficult to realize in conventional techniques in which an overcoat is formed to provide storability, but also stamping applicability and handling property at a high level. Accordingly, stamping applicability and image storability or heat resistance can be achieved simultaneously.
• a heat-sensitive recording material having superior light fastness is necessary for some applications.
• a leuco dye which contributes to image formation, easily decompose due to ultraviolet light, and the like, and fades after a long-time exposure to natural light. Therefore, the material including a leuco dye has a problem in point of light fastness.
• an ultraviolet light absorbent an image stabilizer
• microcapsules encapsulating a liquid ultraviolet light absorbent in a protective layer in order to effectively shut out ultraviolet light before it arrives at the heat-sensitive recording layer.
• Offset printing is sometimes conducted on the recording surface of a heat-sensitive recording material (surface of a heat-sensitive recording layer) depending on application.
• the material is required to have enough surface strength to bear a printing vecocity of more than 100 m/min in a rotary form printing machine, and to have a dampening water-absorbing property.
• a preferable pigment for this purpose is an oil-absorbing pigment such as calcium carbonate, or the like.
• a preferable binder for this purpose is polyvinyl alcohol (PVA). Sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol are specifically preferred.
• heat-sensitive recording materials As a result of wide use of heat-sensitive recording materials as recording paper for facsimile machines in offices and at home and as recording paper for various printers, the heat-sensitive recording materials are compared with general paper (PPC paper, and woodfree paper such as a notebook, writing paper, or the like), and differences between the heat-sensitive recording materials and general paper, such as a slick surface, a bad writing property, and, when held by a hand, thinness and unsufficient strengh, have been often pointed out. These are some of reasons why facsimile machines used in offices have been recently replaced with PPC type facsimile machines using plane paper.
• a heat-sensitive recording material having plain paper-like feeling is considered to have no defects of converted paper which conventional heat-sensitive recording paper has, and to have a matted surface, and, when touched by hands, to have no slick feeling, and to have resistance to abrasion and stain, and to provide a recorded image having fading resistance, and the like. Accordingly, materials having a protective layer on a recording layer have been proposed to provide plane paper-like feeling. However, in conventional protective layers, too much importance was placed on hand feeling, appearance (matted surface), a writing property, and the like, and stamping applicability was not considered.
• stamping applicability no bleeding, rapid drying of a stamped image, or the like
• stamping applicability no bleeding, rapid drying of a stamped image, or the like
• the inventors have found that the following materials are useful as a pigment and a binder of a protective layer in order to obtain plain paper-like feeling including stamping applicability.
• a suitable oil-absorption amount are preferred as a pigment, in order to place importance on stamping applicability, appearance (matted surface) and a writing property.
• image quality sometimes becomes worse.
• particle size is too small, a writing property and appearance sometimes become worse.
• the oil-absorption amount is too large, the level of opacity of the protective layer raises, which leads to a decreased recording density.
• stamping applicability drying
• heat-sensitive recording materials have been recently applied to many fields and applications.
• a heat-sensitive recording system has advantages such as miniturization, low running cost, freedom from frequent maintenance, and that techniques regarding both printers (hardware) and recording paper (medium) have been improved.
• high performance printers which have high performance similar to that of conventional dot printers and laser printers, such as those having a recording speed of 10 inch (about 25 cm)/sec, a maximum recording width of A0 size (about 900 mm) and resolution of 600 dpi (24 dot/mm), were developped. Therefore, it is important to produce hardware having an optimal design and a controlling means by combining techniches according to application thereof.
• the high performance printer is preferably a high speed printer having a recording velocity of not less than 10 cm/sec, a printer having a thermal head which has a partially glazed structure, or the like.
• a conventional heat-sensitive recording material is combined with the high speed printer having a recording velocity of not less than 10 cm/sec, sensitivity is sometimes insufficient.
• head stain tends to occur.
• the inventors investigated the optimal design of heat-sensitive recording materials, and have found that, even when specifically combined with the high speed printer that has a recording velocity of not less than 10 cm/sec or the printer having a thermal head which has a partially glazed structure, a heat-sensitive recording material, in which a specific developer (an electron-accepting compound) is selectively used, not only satisfies, at a high level, the above-mentioned performance necessary for heat-sensitive recording materials but also can exhibit high sensitivity and a good head matching property.
• a specific developer an electron-accepting compound
• a facximile machine receives a photograph
• quality of recorded image is important for hardware (apparatuses) using a heat-sensitive recording material.
• the inventors have found that it is effective to provide a undercoat layer including an oil-absorbing pigment as a main component, and specifically to apply a undercoat layer by a curtain coating method or a blade coating method (specifically by a blade coating method).
• the recording material is wound or accordingly folded and bent to result in transportation failure in the printer during the transportation. Further, in the case where the recording material in form of a sheet is stacked after printing, the positioning is shifted while the material is stacked or accordingly, recording materials stacked in unbalanced state are slid to result in inferior stacking.
• the invention is accomplished based on the above-mentioned finding and the practical means for solving the above-mentioned problem are as follows.
• the heat-sensitive recording material comprises a heat-sensitive recording layer of a coloration system containing an electron-donating colorless dye and an electron-accepting compound in combination and as the electron-accepting compound, a compound defined as R 1 -Ph-SO 2 R 2 is contained and the maximum value of the curl height of the heat-sensitive recording material itself is 5.0 mm or less.
• the first embodiment of the heat-sensitive recording material of the invention comprises one or two or more heat-sensitive recording layers on a support and preferably a protective layer. Furthermore, if required, the material may have other layers such as an intermediate layer, etc.
• the heat-sensitive recording layer includes at least an electron-donating colorless dye and an electron-accepting compound that reacts with the electron-donating colorless dye to develop color, and preferably includes an image stabilizer (an ultraviolet light blocking agent), an inorganic pigment, an adhesive and a sensitizer. If required, the layer may include any other component.
• the heat-sensitive recording layer used in the invention includes an electron-donating colorless dye as a color-developing component.
• the electron-donating colorless dye can be selected from conventionally known dyes. Examples thereof include, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluorane, 2-anilino-3-methyl-6-di-n-amylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluorane, 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluorane, 3-di-(
• these electron-donating colorless dyes can be used alone or in combination in a single heat-sensitive recording layer.
• color development density can be increased while keeping background fogging at low level.
• image storability of a formed image portion can be simultaneously improved.
• the particle size (volume mean diameter) of the electron-donating colorless dye is preferably not more than 1.0 ⁇ m, and more preferably 0.4 to 0.7 ⁇ m.
• the volume mean diameter exceeds 1.0 ⁇ m, heat sensitivity sometimes decreases, and, when the volume mean diameter is less than 0.4 ⁇ m, background fogging sometimes deteriorates.
• the volume mean diameter can be easily measured by a laser diffraction type size distribution measuring instrument (e.g., trade name: LA500, manufactured by Horiba, Inc.), or the like.
• a laser diffraction type size distribution measuring instrument e.g., trade name: LA500, manufactured by Horiba, Inc.
• the coating amount of the electron-donating colorless dye is preferably 0.1 to 1.0 g/m 2 , and, in view of color development density and background fogging, more preferably 0.2 to 0.5 g/m 2 .
• the heat-sensitive recording layer used in the first embodiment of the invention includes at least one kind of the compound represented by general formula (1) as an electron-accepting compound that reacts with the electron-donating colorless dye during heating to develop color.
• this compound in the heat-sensitive recording layer.
• R 1 represents a hydroxyl group or an alkyl group
• R 2 represents -Ph, -NH-Ph, -Ph-OH or -NH-CO-NH-Ph
• Ph represents a phenyl group, which is optionally substituted with a substituent having -SO 2 R 2 .
• the alkyl group represented by R 1 is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group, an ethyl group, an isopropyl group, or the like. Among these, R 1 is specifically preferably a hydroxyl group.
• Ph may be a substituted phenyl group wherein the phenyl group is substituted with a "substituent including -SO 2 R 2 ", and R 2 of the substituent may be substituted with a methyl group, a halogen atom, or the like.
• R 2 of the substituent may be substituted with a methyl group, a halogen atom, or the like.
• the substituent include -CH 2 -C 6 H 5 -NHCONH-SO 2 -C 6 H 5 , -SO 2 -C 6 H 4 -CH 3 , -SO 2 -C 6 H 4 -Cl, and the like.
• the substituent can be -SO 2 -C 6 H 5 .
• R 2 is preferably -NH-Ph, and specifically preferably -NH-C 6 H 5 .
• 4-hydroxybenzenesulfoneanilide is the most preferable in view of balance between image storability and background fogging.
• the amount of the electron-accepting compound in a single heat-sensitive recording layer is preferably 50 to 400% by mass, and more preferably 100 to 300% by mass relative to the mass of the electron-donating colorless dye.
• Any other known electron-accepting compound may be used in combination with the electron-accepting compound represented by general formula (1), so long as the effects of the invention (specifically decrease in background fogging level, improvement in sensitivity, and improvements in image storability, chemical resistance and a head matching property) are not deteriorated.
• the known electron-accepting compound is properly selected and used. It is spedicfically preferably a phenolic compound or a salicylic acid derivative or a polyvalent metal salt thereof from the viewpoint of suppression of background fogging.
• 2,2'-bis(4-hydroxyphenol)propane bisphenol A
• 4-t-butylphenol 4-phenylphenol, 4-hydroxydiphenoxide
• 1,1'-bis(4-hydroxyphenyl)cyclohexane 1,1'-bis(3-chloro-4-hydroxyphenyl)cyclohexane, 1,1'-bis(3-chloro-4-hydroxyphenyl)-2-ethylbutane
• 4,4'-sec-isoctylidenediphenol 4,4'-sec-butylidenediphenol
• 4-tert-octylphenol 4-p-methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4'-isopentylidenephenol, 4-hydroxy-4-isopropyloxy
• 4-pentadecylsalicylic acid 3,5-di-( ⁇ -methylbenzyl)salicylic acid, 3,5-di-(tert-octyl)salicylic acid, 5-octadecylsalicylic acid, 5- ⁇ -(p- ⁇ -methylbenzylphenyl)ethylsalicylic acid, 3- ⁇ -methylbenzyl-5-tert-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid, and the like, and zinc salts, aluminum salts, calcium salts, copper salts and lead salts thereof, and the like.
• the amount of the electron-accepting compound represented by general formula (1) is preferably not less than 50% by mass, and specifically preferably not less than 70% by mass relative to the total mass of the electron-accepting compounds.
• the particle size (volume mean diameter) of the electron-accepting compound is preferably not more than 1.0 ⁇ m, and more preferably 0.4 to 0.7 ⁇ m.
• volume mean diameter exceeds 1.0 ⁇ m, heat sensitivity sometimes decreases.
• volume mean diameter is less than 0.4 ⁇ m, background fogging sometimes deteriorates.
• the volume mean diameter can also be readily measured by using a laser diffraction type size distribution measuring instrument (e.g., LA500 manufactured by Horiba, Inc.), or the like.
• a laser diffraction type size distribution measuring instrument e.g., LA500 manufactured by Horiba, Inc.
• the layer used in the invention preferably includes a sensitizer.
• the layer preferably includes at least one kind selected from the group consisting of 2-benzyloxynaphthalene, dimethylbenzyl oxalate, m-terphenyl, ethylene glycol tolyl ether, p-benzylbiphenyl, 1,2-diphenoxymethylbenzene, 1,2-diphenoxyethane and diphenylsulfone (hereinafter sometimes referred to as "sensitizer according to the invention").
• the total amount of the sensitizer selected in the heat-sensitive recording layer is preferably 75 to 200 parts by mass, and more preferably 100 to 150 parts by mass relative to 100 parts by mass of the electron-accepting compound.
• the sensitizer When the sensitizer is contained in the layer such that the amount of the sensitizer is suitable for the amount of the electron-accepting compound, sensitivity can be effectively improved without deterioration of other characteristics.
• Any other sensitizer selected from conventionally known ones can be used in combination with the sensitizer selected from the above-mentioned group, so long as the effects of the invention are not deteriorated.
• the amount of the sensitizer selected from the above-mentioned group is preferably not less than 50% by mass, and more preferably not less than 70% by mass relative to the total amount of the sensitizers included in the layer.
• sensitizer examples include, for example, aliphatic monoamide, aliphatic bisamide, stearylurea, di(2-methylphenoxy)ethane, di(2-methoxyphenoxy)ethane, ⁇ -naphthol(p-methylbenzyl)ether, ⁇ -naphthylbenzylether, 1,4-butanediol-p-methylphenylether, 1,4-butanediol-p-isopropylphenylether, 1,4-butanediol-p-tert-octylphenylether, 1-phenoxy-2-(4-ethylphenoxy)ethane, 1-phenoxy-2-(chlorophenoxy)ethane, 1,4-butanediolphenylether, diethyleneglycolbis(4-methoxyphenyl)ether, 1,4-bis(phenoxymethyl)benzene, and the like.
• the heat-sensitive recording layer used in the invention preferably includes an image stabilizer (including an ultraviolet light absorbent).
• the ultraviolet light absorbent may be microcapsuled.
• storability of a developed image image storability
• the image stabilizer for example, a phenol compound, specifically a hindered phenol compound is effective.
• Examples thereof include, for example, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-ethyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris(3,5-di-tert-butyl-4-hydroxyphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)propane, 2,2'-methylene-bis(6-tert-butyl-4-methylphenol), 2,2'-methylene-bis(6-tert-butyl-4-ethylphenol), 4,4'-butylidene-bis(6-tert-butyl-3-methylphenol), 4,4'-thio-bis(3-methyl-6-tert-butylphenol), and the like.
• 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane and 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane are specifically preferred.
• the total amount of the image stabilizer in a single heat-sensitive recording layer is preferably 10 to 100 parts by mass, and more preferably 20 to 60 parts by mass relative to 100 parts by mass of the electron-donating colorless dye in view of suppression of background fogging and effective improvement in image storability.
• the amount of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane and/or 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane in a single heat-sensitive recording layer is preferably at least 50% by mass, and more preferably at least 70% by mass relative to the total mass of the image stabilizers.
• ultraviolet light absorbent examples include the ultraviolet light absorbents shown below.
• the amount of the ultraviolet light absorbent in a single heat-sensitive recording layer is preferably 10 to 300 parts by mass, and more preferably 30 to 200 parts by mass relative to 100 parts by mass of the electron-donating colorless dye from the viewpoint of effective improvement in image storability.
• the heat-sensitive recording layer of in the first embodiment of the invention preferably includes an inorganic pigment, specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• an inorganic pigment specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• Light calcium carbonate generally has crystalline forms of calcite, aragonite, baterite, and the like.
• calcite (light) calcium carbonate is preferred in view of color development density and prevention of head stain when recording is conducted with a thermal head and in view of an absorbing property, hardness, or the like.
• those having a spindle-like or scalenohedron-like particle shape are specifically preferred.
• the calcite (light) calcium carbonate can be prepared by a conventional preparation method.
• the average particle size (volume mean diameter) of the calcite (light) calcium carbonate is preferably 1 to 3 ⁇ m.
• the volume mean diameter can be measured in the same manner as the method for measuring the volume mean diameter of the electron-donating colorless dye, or the like.
• the amount of the "inorganic pigment according to the invention" in a single heat-sensitive recording layer is preferably 50 to 500 parts by mass, more preferably 70 to 350 parts by mass, and specifically preferably 90 to 250 parts by mass relative to 100 parts by mass of the electron-accepting compound in view of improvement in color development density and prevention of adhesion of foregin matter to a thermal head.
• any other inorganic pigment can be used in combination with the above-mentioned inorganic pigment according to the invention to such an extent that the effects of the invention (specifically improvement in a head matching property, printing applicability and plain paper-like property) are not deteriorated.
• any other inorganic pigment examples include calcium carbonate other than calcite (light) calcium carbonate, barium sulfate, lithpone, agalmatolite, kaolin, calcined kaolin, magnesium carbonate, magnesium oxide, and the like.
• the volume mean diameter of any other inorganic pigment measured by a laser diffraction type size distribution measuring instrument is preferably 0.3 to 1.5 ⁇ m, and more preferably 0.5 to 0.9 ⁇ m.
• the ratio of the total mass (V) of the "inorganic pigment according to the invention” and the total mass (W) of any other inorganic pigment (V/W) is preferably 100/0 to 60/40, and more preferably 100/0 to 80/20.
• an inorganic pigment having Mohs hardness of not more than 3 is preferred in view of suppression of abrasion of a thermal head.
• the "Mohs hardness” means Mohs hardness described in "English-Japanese Plastic Industrial Dictionary, 5 th eddition, p. 616" (Shin Ogawa, Kogyo Chosakai Publishing Co., Ltd.).
• Examples of the inorganic pigment having Mohs hardness of not more than 3 include calcium carbonate, aluminum hydroxide, and the like.
• a mixture of the inorganic pigment according to the invention and magnesium carbonate and/or magnesium oxide is preferable since it is effective in suppression of background fogging.
• the content of magnesium carbonate and/or magnesium oxide is preferably 3 to 50% by mass, and specifically preferably 5 to 30% by mass relative to the total mass of the inorganic pigments.
• the heat-sensitive recording layer used in the first embodiment of the invention preferably includes, as an adhesive (or a protective colloid at the time of dispersion), at least one kind selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol (i.e., modified polyvinyl alcohols (hereinafter sometimes referred to as "specific modified PVA").
• modified polyvinyl alcohols hereinafter sometimes referred to as "specific modified PVA”
• the specific modified PVA in the heat-sensitive recording layer as an adhesive, plain paper-like feeling can be provided, and adhesive force between the heat-sensitive recording layer and the substrate can be increased to prevent troubles such as peeling of paper that may occur during offset printing, or the like, which can lead to improvement in printing applicability.
• color development density when the recording material is recorded with a thermal head can be increased while background fogging is more suppressed during recording, which can lead compatibility between improvement in sensitivity and further decrease in
• the specific modified PVAs can be used alone or in combination, or in combination with any other modified PVA or polyvinyl alcohol (PVA).
• the rate of the specific modified PVA is preferably not less than 10% by mass, and more preferably not less than 20% by mass relative to the total mass of the adhesive components.
• the specific modified PVA is preferably one having a saponification degree of 85 to 99% by mole.
• the saponification degree of any other modified PVA and/or PVA is preferably in the above-mentioned range.
• the polymerization degree of the specific modified PVA is preferably 200 to 2000.
• the polymerization degree is less than 200, peeling of paper easily occurs during offset printing. Furthermore, when the addition amount thereof is increased in order to avoid such peeling of paper, color development density sometimes decreases. Furthermore, when the polymerization degree exceeds 2000, the modified PVA becomes hardly-soluble in a solvent (water), and the viscosity of liquid during preparation increases, which makes preparation of a coating solution for forming a heat-sensitive recording layer and the application thereof difficult.
• the polymerization degree of any other modified PVA and/or PVA is preferably in the above-mentioned range.
• the polymerization degree used herein refers to an average polymerization degree obtained by the method described in JIS-K6726 ( 1994).
• the content of the specific modified PVA in the heat-sensitive recording layer is preferably 30 to 300 parts by mass, more preferably 70 to 200 parts by mass, and specifically preferably 100 to 170 parts by mass relative to 100 parts by mass of the electron-donating colorless dye in view of improvement in color development density and provision of offset printing applicability (prevention of peeling of paper, or the like).
• the specific modified PVA functions not only as an adhesive for increasing adhesive force between layers but also as a dispersing agent, a binder, and the like.
• the sulfo-modified polyvinyl alcohol can be prepared by a method including: copolymerizing an olefinsulfonic acid or a salt thereof such as ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, or the like with a vinylester such as vinyl acetate, or the like in an alcohol or a mixed solvent of an alcohol and water to form a polymer and saponifying the obtained polymer; a method including: copolymerizing an amide sodium salt and a vinyl ester such as vinyl acetate, or the like and saponifying the obtained polymer; a method including: treating PVA with bromine, iodine, or the like and heating the treated PVA in an acidic aqueous sodium sulfite solution; a method including: heating PVA in a concentrated aqueous sulfuric acid solution; a method including: acetalating PVA with an aldehyde compound including a sulfonic acid group; or the
• the diacetone-modified polyvinyl alcohol is a partially or completely saponified product of a copolymer of a monomer having a diacetone group and a vinyl ester, and can be prepared by a method including: copolymerizing the monomer having a diacetone group and the vinyl ester to form a resin and saponifying the obtained resin.
• the proportion of the monomer having a diacetone group (repeating unit structure) in the diacetone-modified polyvinyl alcohol is not specifically limited.
• the acetoacetyl-modified polyvinyl alcohol can be generally prepared by adding liquid or gaseous diketene to a solution, a dispersion liquid or powder of a polyvinyl alcohol resin to cause the diketene to react with the resin.
• the acetylation degree of the acetoacetyl-modified polyvinyl alcohol can be suitably selected according to the desired quality of an objective heat-sensitive recording material.
• the heat-sensitive recording layer used in the first embodiment of the invention may include, according to the purpose or need, other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• the heat-sensitive recording layer may include a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like. By incorporating such a cross-linking agent, water resistance of the heat-sensitive recording material can be improved.
• the cross-linking agent can be suitably selected from cross-linking agents which can cross-link the specific modified PVA (and preferably the above-mentioned other modified PVA, and the like).
• cross-linking agents which can cross-link the specific modified PVA (and preferably the above-mentioned other modified PVA, and the like).
• an aldehyde compound such as glyoxal, or the like
• a dihydrazide compound such as adipic acid dihydrazide, or the like is specifically preferred.
• the content of the cross-linking agent in the heat-sensitive recording layer is preferably 1 to 50 parts by mass, and more preferably 3 to 20 parts by mass relative to 100 parts by mass of the specific modified PVA, other modified PVA and the like to be cross-linked.
• the content of the cross-linking agent is in the above-mentioned range, water resistance can be effectively improved.
• the heat-sensitive recording layer may include a mordant for the purpose of preventing bleeding at the time of ink jet recording.
• mordant examples include compounds having at least one cationic group selected from an amide group, an imide group, a primary amino group, a secondary amino group, a tertiary amino group, a primary ammonium salt group, a secondary ammonium salt group, a tertiary ammonium salt group and a quatenary ammonium salt group.
• polyamide epichlorohydrin polyvinylbenzyltrimethylammonium chloride, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl- ⁇ -hydroxyethyldimethylammonium chloride, polydimethylaminoethylmethacrylate hydrochloride, polyethyleneimine, polyallylamine, polyallylamine hydrochloride, polyamide-polyamine resins, cationated starch, dicyanodiamide-formalin condensates, dimethyl-2-hydroxypropylammonium salt polymers, and the like.
• a cationic polymer is also preferred.
• a cationic polymer include, for example, polyethyleneimine, polydiallylamine, polyallylamine, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl- ⁇ -hydroxyethyldimethylammonium chloride, polyallylamine hydrochloride, polyamide-polyamine resins, cationated starch, dicyanodiamide formalin condensates, dimethyl-2-hydroxypropylammonium salt polymers, polyamidine, polyvinylamine, and the like.
• the molecular weight of the mordant is preferably about 1000 to 200000.
• the molecular weight is less than 1000, water resistance tends to become insufficient, and, when the molecular weight exceeds 200000, viscosity increases, which sometimes leads to bad handling applicability.
• the cationic polymer may be contained in either the heat-sensitive recording layer or the protective layer described later.
• the metal soap can be a higher fatty acid metal salt, and specifically zinc stearate, calcium stearate, aluminum stearate or the like.
• wax examples include, for example, paraffin wax, microcrystalline wax, carnauba wax, methylolstearoamide, polyethylene wax, polystyrene wax, fatty acid amide wax, and the like. These can be used alone or in combination.
• the surfactant can be, for example, an alkali metal salt of a sulfosuccinic acid, a fluorine-containing surfactant, or the like.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer, and other components can be suitably dispersed in a water-soluble binder.
• the binder used herein is preferably a compound that can be dissolved by not less than 5% by mass in water at 25°C.
• Specific examples of the binder include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, starchs (including modified starchs), gelatin, gum arabic, casein, a saponified product of a styrene-maleic anhydride copolymer, and the like.
• the binder not only functions as a material in which substances are dispersed but also functions to improve film strength of the heat-sensitive recording layer.
• a synthetic polymer latex binder such as a styrene-butadiene copolymer, a vinyl acetate copolymer, an acrylonitrile-butadiene copolymer, a methyl acrylate-butadiene copolymer, polyvinylidene chloride, or the like can be used in combination with the above-mentioned binder.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer can be simultaneously or separately dispersed with a stirrer or a crusher such as a ball mill, an attritor, a sand mill, or the like and then a coating solution is prepared.
• the coating solution may include the above-mentioned other components, i.e., a cross-linking agent, a mordant, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye and the like.
• the coating solution is prepared and applied onto the surface of a support, whereby a heat-sensitive recording layer is formed.
• the coating method for applying the coating solution is not specifically limited, and may be suitably selected from coating methods using an air knife coater, a roll coater, a blade coater, a curtain coater, or the like. After the application, the resultant coating is dried, and the dried coating is subjected to smoothing treatment, preferably calendar treatment, and the resultant material is used.
• the dried coating amount of the coating solution for forming a heat-sensitive recording layer is preferably less than 6 g/m 2 , more preferably not more than 5 g/m 2 a curtain coating method using a curtain coater is specifically preferred.
• the reasons for this are as follows.
• the components can be concentrated on a recording surface.
• high density (high sensitivity) can be obtained even when smaller amounts of materials are used.
• image quality can be simultaneously improved.
• a layer or layers other than a heat-sensitive recording layer, such a protecitve layer are laminated as mentioned later, the amount of energy consumed during preparation can be further decreased by simultaneously applying multiple layers by a curtain coating method.
• a specific example of such a method is as follows.
• the heat-sensitive recording material is preferably prepared by applying at least one coating solution onto the surface of a substrate by a curtain coating method to form a part or whole of one or more layers to be provided on the substrate and drying the formed layer(s).
• the layers formed by a curtain coating method are not specifically limited, and specific examples thereof include a undercoat layer, a heat-sensitive recording layer, a protective layer, and the like.
• a series of layers which adjoin each other are simultaneously applied by a curtain coating method.
• combinations of layers to be simultaneously applied include, but are not limited to, a combination of a undercoat layer and a heat-sensitive recording layer, a combination of a heat-sensitive recording layer and a protective layer, a combination of a undercoat layer, a heat-sensitive recording layer and a protective layer, a combination of two or more of different kinds of undercoat layers, a combination of two or more of different kinds of heat-sensitive recording layers, a combination of two or more of different kinds of protective layers, and the like.
• Examples of a curtain coating apparatus used in a curtain coating method include, but are not limited to, an extrusion hopper type curtain coating apparatus, a slide hopper type curtain coating apparatus, and the like.
• a slide hopper type curtain coating apparatus described in Japanese Patent Application Publication (JP-B) No. 49-24133, which is used in preparation of photographic photosensitive materials is specifically preferred.
• JP-B Japanese Patent Application Publication
• the maximum value of the curl height of the heat-sensitive recording material curved and coming up from the plane where the heat-sensitive recording material is placed is adjusted to be 5.0 mm or less.
• the curl height means the distance between the flat plane where one surface of the heat-sensitive recording material is placed still appressedly (e.g. the surface where no heat-sensitive recording layer is formed) and the surface of the portions of the heat-sensitive recording material curved and coming up from the flat plane (e.g. four corners of the heat-sensitive recording material), that is, the side of the surface at which no heat-sensitive recording layer in the portion.
• the distance is approximately same as the distance from the heat-sensitive recording material surface which is not curved on the flat plane to the portions of the heat-sensitive recording material curled up from the flat plane.
• the maximum value of the curl height By adjusting the maximum value of the curl height to be 5.0 mm or less, the transportation property in a printer and the accumulation of sheets (of the heat-sensitive recording material) after printing can be kept good and according the heat-sensitive recording material with excellent handling easiness can be obtained. It is more preferable to adjust the height of the curl height to be 4.0 mm or less.
• an aqueous solution containing a binder, a surfactant, an antistatic agent and the like in water is preferable.
• the binder may include polyvinyl alcohol, carboxy-modified polyvinyl alcohol, vinyl acetate-acrylamide copolymer, silicon-modified polyvinyl alcohol, starch, modified starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatins, gum arabi, casein, hydrolyzed product of styrene-maleic acid copolymer, polyacrylamide derivatives, polyvinylpyrrolidone, latexes such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion.
• the surfactant examples include alkylbenzenesulfonic acid salts such as sodium dodecylbenzenesulfonate; sulfosuccinic acid alkyl ester salt such as dioctyl sulfosuccinate sodium salt; polyoxyethylene alkyl ether phosphoric acid ester; sodium hexametaphosphate; and perfluoroalkylcarboxylic acid.
• the antistatic agent are inorganic salts such as sodium chloride; anionic electrolytic polymers such as sodium polystyrenesulfonate; and conductive metal compounds such as conductive zinc oxide and tin oxide.
• the absolute value of the application amount of the above-mentioned back liquid is not particularly limited and can be selected in a proper range so as to adjust the maximum value of the curl height (especially four corners) of the heat-sensitive recording material to be 5.0 mm or less.
• known methods can be employed for coating the back liquid.
• At least one protective layer is preferably disposed on the heat-sensitive recording layer.
• the protective layer may include organic or inorganic micropowder, a binder, a surfactant, a heat-melting substance, and the like.
• micropowder examples include, for example, inorganic micropowder such as calcium carbonate, silicas, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, kaolin, clay, talc, surface-treated calcium and silica, and the like, and organic micropowder such as a urea-formalin resin, a styrene/methacrylic acid copolymer, polystyrene, and the like.
• inorganic micropowder such as calcium carbonate, silicas, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, kaolin, clay, talc, surface-treated calcium and silica, and the like
• organic micropowder such as a urea-formalin resin, a styrene/methacrylic acid copolymer, polystyrene, and the like.
• binder to be included in the protective layer examples include, for example, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, a vinyl acetate-acrylamide copolymer, silicon-modified polyvinylalcohol, starch, modified starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatins, gum arabic, casein, a styrene-maleic acid copolymer hydrolysate, polyacrylamide derivatives and polyvinylpyrrolidone, and latexes such as a styrene-butadiene rubber latex, an acrylonitrile-butadiene rubber latex, a methyl acrylate-butadiene rubber latex, a vinyl acetate emulsion, and the like.
• the protective layer may contain a waterproofing agent for cross-linking a binder component in the protective layer to further improve storage stability of the heat-sensitive recording material.
• a waterproofing agent for cross-linking a binder component in the protective layer to further improve storage stability of the heat-sensitive recording material.
• the waterproofing agent include, for example, N-methylolurea, N-methylolmelamine, water-soluble initial condensates such as urea-formalin, and the like, dialdehyde compounds such as glyoxal, glutalaldehyde, and the like, inorganic cross-linking agents such as boric acid, borax, colloidal silica, and the like, polyamide epichlorohydrin, and the like.
• the protective layer includes at least one inorganic pigment selected from aluminum hydroxide, kaolin and amorphous silica, and a water-soluble polymer.
• the protective layer may also include a surfactant, a heat-melting substance, and the like.
• the volume mean diameter of the inorganic pigment to be included in the protective layer is preferably 0.5 to 3 ⁇ m, and more preferably 0.7 to 2.5 ⁇ m.
• aluminum hydroxide having a volume mean diameter of 0.5 to 1.2 ⁇ m is preferred in view of improvement in stamping applicability, and amorphous silica is preferred in view of improvement in inkjet applicability.
• the volume mean diameter can be measured in the same manner as the method for measuring the volume mean diameter of the electron-donating colorless dye, or the like.
• aluminum hydroxide, kaolin and amorphous silica is preferably 10 to 90% by mass, and more preferably 30 to 70% by mass relative to the total solid content (mass) of the coating solution for forming a protective layer.
• any other pigment such as barium sulfate, zinc sulfate, talc, clay, colloidal silica, or the like can be used in combination with aluminum hydroxide, kaolin, or amorphous silica, so long as the effects of the invention (specifically improvement in storability, and provision of a handling property and stamping applicability) are not deteriorated.
• water-soluble polymer examples include, among the above-mentioned binders, polyvinyl alcohol and modified polyvinyl alcohols (hereinafter generally referred to as "polyvinyl alcohol”), starch, modified starch such as oxidized starch, urea phosphate esterified starch, and the like, carboxyl group-containing polymers such as a styrene-maleic anhydride copolymer, an alkyl esterified product of a styrene-maleic anhydride copolymer, a styrene-acrylic acid copolymer, and the like.
• polyvinyl alcohol modified polyvinyl alcohols
• starch modified starch such as oxidized starch, urea phosphate esterified starch, and the like
• carboxyl group-containing polymers such as a styrene-maleic anhydride copolymer, an alkyl esterified product of a styrene-maleic
• polyvinyl alcohol, oxidized starch, urea phosphate esterified starch are preferred in view of stamping applicability, and a mixture of polyvinyl alcohol (x) and oxidized starch and/or urea phosphate esterified starch (y) at a mass ratio (x/y) of 90/10 to 10/90 is specifically preferred.
• the mass ratio (y 1 /y 2 ) of oxidized starch (y 1 ) and urea phosphate esterified starch (y 2 ) is preferably 10/90 to 90/10.
• the modified polyvinyl alcohol is preferably acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol and amide-modified polyvinyl alcohol.
• sulfo-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and the like are also used.
• cross-linking agent that reacts with polyvinyl alcohol can further improve storability, a handling property and stamping applicability.
• the rate of the water-soluble polymer is preferably 10 to 90% by mass, and more preferably 30 to 70% by mass relative to the total solid content (mass) of a coating solution for forming a protective layer.
• cross-linking agent for cross-linking the water-soluble polymer include polyvalent amine compounds such as ethylenediamine, and the like, polyvalent aldehyde compounds such as glyoxal, glutalaldehyde, dialdehyde, and the like, dihydrazide compounds such as adipic acid dihydrazide, phthalic acid dihydrazide, and the like, water-soluble methylol compounds (urea, melamine and phenol), multifunctional epoxy compounds, polyvalent metal salts (Al, Ti, Zr, Mg, and the like), and the like.
• polyvalent aldehyde compounds, and dihydrazide compounds are preferred.
• the content of the cross-linking agent is preferably about 2 to 30% by mass, and more preferably 5 to 20% by mass relative to the mass of the water-soluble polymer.
• the mixing ratio of the inorganic pigment selected from aluminum hydroxide, kaolin and amorphous silica and the water-soluble polymer in the protective layer depends on the kind and the particle size of the inorganic pigment, the kind of the water-soluble polymer, and the like, and the amount of the water-soluble polymer is preferably 50 to 400% by mass, and more preferably 100 to 250% by mass relative to the mass of the inorganic pigment.
• the total mass of the inorganic pigment and the water-soluble polymer in the protective layer is preferably not less than 50% by mass of the total solid mass of the protective layer.
• the protective layer i.e., a coating solution for forming a protective layer (hereinafter sometimes referred to as "coating solution for a protective layer”) may contain a surfactant in view of improvement in ink jet ink applicability.
• the surfactant include alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and the like, alkyl sulfosuccinates such as sodium dioctylsulfosuccinate, and the like, polyoxyethylene alkyl ether phosphates, sodium hexametaphosphate, perfluoroalkylcarboxylates, and the like. Among these, alkyl sulfosuccinates are more preferred.
• the content of the surfactant is preferably 0.1 to 5% by mass, and more preferably 0.5 to 3% by mass relative to the total solid mass of the coating solution for forming a protective layer.
• the coating solution for a protective layer can be prepared by dissolving or dispersing the inorganic pigment selected from aluminum hydroxide, kaolin and amorphous silica, and water-soluble polymer, and if required, a cross-linking agent, a surfactant, and the like in a desired water-based solvent.
• the coating solution may include a lubricant, a defoaming agent, a fluorescent brightening agent, a colored organic pigment, and the like, so long as the effects of the invention (specifically improvement in storability and provision of a handling property and stamping applicability) are not deteriorated.
• lubricant examples include, for example, metal soaps such as zinc stearate, calcium stearate, and the like, wax such as paraffin wax, microcrystalline wax, carnauba wax, and synthetic polymer wax, and the like.
• supports can be applied to the support.
• Specific examples tehreof includesupportsupport paper supports such as woodfree paper, and the like, coated paper in which paper is coated with a resin or a pigment, paper on which a resin layer is laminated, woodfree paper having a undercoat layer, synthetic paper, plastic films, and the like.
• a support including recycled pulp as a main component i.e. a support in which the mass of recycled pulp is 50% by mass of the components of the support can be also used.
• the support is preferably a smooth support having smoothness defined by JIS-P8119 in the range of 300 seconds to 500 seconds in view of dot reproducibility. Furthermore, for the same reason, the smoothness of the support defined by JIS-P8119 is more preferably not less than 100 seconds, and still more preferably not less than 150 seconds.
• the recycled pulp is made by the combination of the following three steps 1) to 3).
• bleaching can be carried out simultaneously with deinking or in another step.
• a support for a heat-sensitive recording material is made of the thus-obtained recycled pulp (100% by mass) or a mixture of recycled pulp and virgin pulp (the content of the virgin pulp is less than 50% by mass) by a conventional methodsupport.
• a undercoat layer may be disposed on the support.
• the undercoat layer is preferably provided on a surface of a support having a Stockigt size of not less than 5 seconds, and the undercoat layer is preferably mainly made of a pigment and a binder.
• the pigment in the undercoat layer all of general inorganic and organic pigments can be used, and an oil-absorbing pigment having an oil absorbency defined by JIS-K5101 of not less than 40 ml/100 g (cc/100 g) is specifically preferred.
• the oil-absorbing pigment include calcined kaolin, aluminum oxide, magnesium carbonate, calcined diatomaceous earth, aluminum silicate, magnesium aluminosilicate, calcium carbonate, barium sulfate, aluminum hydroxide, kaolin, calcined kaolin, amorphous silica, urea-formalin resin powder, and the like.
• calcined kaolin having an oil absorbency of 70 ml/100 g to 80 ml/100 g is specifically preferred.
• the coating amount of the pigment during application and formation of a undercoat layer on a support is preferably not less than 2 g/m 2 , more preferably not less than 4 g/m 2 , and specifically preferably 7 to 12 g/m 2 .
• binder of the undercoat layer examples include water-soluble polymers and aqueous binders. These may be used alone or in combination.
• the water-soluble polymer examples include, for example, starch, polyvinyl alcohol, polyacrylamide, carboxymethylcellulose, methylcellulose, casein, and the like.
• the aqueous binder is generally a synthetic rubber latex or a synthetic resine emulsion, and examples thereof include, for example, a styrene-butadiene rubber latex, an acrylonitrile-butadiene rubber latex, a methyl acrylate-butadiene rubber latex, a vinyl acetate emulsion, and the like.
• the amount of the binder used in the undercoat layer is determined in accordance with the film strength, the heat sensitivity of a heat-sensitive-color developing layer, or the like, and is preferably 3 to 100% by mass, more preferably 5 to 50% by mass, and specifically preferably 8 to 15% by mass relative to the mass of the pigment in the undercoat layer.
• the undercoat layer may include wax, a color fading preventing agent, a surfactant, and the like.
• a coating solution for forming a undercoat layer can be applied according to a known coating method.
• a coating method using an air knife coater, a roll coater, a blade coater, a gravure coater, a curtain coater, or the like are preferable, and a coating method using a blade coater is more preferable.
• the undercoat layer may be subjected to smoothing treatment such as calendaring, and the like, if necessaryundercoat layer.
• the method using the blade coater is not limited to coating methods using a bevel type blade or a bent type blade, and examples of the method include a coating method using a rod blade, a coating method using a bill blade, and the like. Furthermore, the coating method is not limited to methods using an off-machine coater, and coating can be carried out using an on-machine coater provided on a paper machine.
• the coating solution for forming a undercoat layer may include carboxymethylcellulose having an etherification degree of 0.6 to 0.8 and an weight average molecular weight of 20000 to 200000 in an amount of 1 to 5% by mass, and preferably 1 to 3% by mass relative to the amount of the pigment.
• the coating amount of the undercoat layer is not specifically limited, and is preferably not less than 2 g/m 2 , more preferably not less than 4 g/m 2 , and specifically preferably not less than 7 to 12 g/m 2 in accordance with characteristics of the heat-sensitive recording material.
• primer base paper having a undercoat layer (specifically preferably a undercoat layer having a high oil-absorbing property, a high adiabatic effect and high flatness) is preferred, and primer base paper having a undercoat layer which includes an oil-absorbing pigment and which has been made using a blade coater is specifically preferred in view of improvement in a head matching property with respect to a thermal head and improvements in sensitivity and image quality.
• the total ion concentration of Na + ions and K + ions included in the heat-sensitive recording material is preferably not more than 1500 ppm, more preferably not more than 1000 ppm, and specifically preferably not more than 800 ppm in view of prevention of head corrosion of a thermal head to be brought into contact with the heat-sensitive recording material.
• the total ion concentration in the whole of the heat-sensitive recording material including the support, layers, and the like can be suppressed and the amount of ions adhered to a head can be suppressed, which can lead to improvement in an anticorrosion property (durability) of the thermal head.
• the ion concentration of Na + ions and K + ions can be measured by extracting these ions in a heat-sensitive recording material with hot water and measuring the mass of Na + ions and K + ions in the hot water by an ion quantitative analysis method using an atomic absorption method.
• the total ion concentration is represented by ppm relative to the total mass of the heat-sensitive recording material.
• wettablity of the surface of the heat-sensitive recording layer i.e., the contact angle of a droplet of distilled water when 0.1 seconds have lapsed since dripping of the droplet on the surface of the heat-sensitive recording layer is preferably not less than 20°, and more preferably not less than 50°.
• the contact angle in the above-mentioned range can be obtained by incorporating an electron-accepting compound represented by general formula (1) (preferably 4-hydroxybenzenesulfonanilide) into the heat-sensitive recording material.
• an electron-accepting compound represented by general formula (1) preferably 4-hydroxybenzenesulfonanilide
• a method including: adding at least one of materials capable of keeping the contact angle of distilled water on the recording surface high, such as a sensitizer and paraffin wax according to the invention, to the heat-sensitive recording layer is also preferable.
• the contact angle can be measured by dripping distilled water on the surface (recording surface) of the heat-sensitive recording layer of a heat-sensitive recording material and measuring the contact angle when 0.1 seconds have lapsed since the dripping by a conventional method.
• the contact angle can be measured with a dynamic contact angle absorption tester such as FIBRO system (trade name: DAT1100, manufactured by FIBRO system, ab), or the like.
• the first embodiment of the heat-sensitive recording material in the invention is useful in view of superior image storability, and a level of density of a formed image, which has been left under environmental conditions of a temperature of 60°C and a relative humidity of 20% for 24 hours, is retained at a rate of not less than 65% relative to that of the formed image before leaving (The density retention rate after the leaving is not less than 65%).
• the electron-accepting compound represented by general formula (1) specifically preferably 4-hydroxybenzenesulfoneanilide
• the density retention rate can be adjusted in the above-mentioned range.
• the formed image can be maintained at a high density for a long period of time, and the heat-sensitive recording material can be applied to fields in which image reliability is required for a long period of time such as fields of storage of important documents, advance tickets, receipts, cash vouchers, and the like.
• the density retention rate of an image is represented, as shown in the following equation, by the ratio (%) of the density of an image which has been printed and has been left under the atmosphere of a temperature of 60°C and a relative humidity of 20% for 24 hours after the printing, to the density of an image immedeately after the image has been printed in the same manner as the printing method of the image that has been left.
• the densities are measured with a Macbeth reflection densitometer (e.g., RD-918).
• Density retention rate [(Image density after leaving) /(Image density immediately after printing)] ⁇ 100
• the heat-sensitive recording material comprises a heat-sensitive recording layer of a coloration system containing an electron-donating colorless dye and an electron-accepting compound in combination and as the electron-accepting compound, a compound defined as R 1 -Ph-SO 2 R 2 is contained and the image density formed by printing with a thermal head by energy application at 15.2 mJ/mm 2 by a thermal head is 1.20 or more.
• the second embodiment of the heat-sensitive recording material of the invention comprises one or two or more heat-sensitive recording layers on a support and preferably a protective layer. Furthermore, if required, the material may have any other layer such as an intermediate layer, or the like.
• the heat-sensitive recording layer includes at least an electron-donating colorless dye and an electron-accepting compound that reacts with the electron-donating colorless dye to develop color, and preferably includes an image stabilizer (an ultraviolet light blocking agent), an inorganic pigment, an adhesive and a sensitizer. If required, the layer may include any other component.
• the heat-sensitive recording layer used in the second embodiment of the invention includes an electron-donating colorless dye as a color-developing component.
• the description of the electron-donating colorless dye is same as that for the electron-donating colorless dye included in the heat-sensitive recording layer described in the first embodiment of the invention.
• the heat-sensitive recording layer used in the invention includes at least one kind of the compound represented by general formula (1) as an electron-accepting compound that reacts with the electron-donating colorless dye during heating to develop color.
• this compound in the heat-sensitive recording layer.
• R 1 represents a hydroxyl group or an alkyl group
• R 2 represents -Ph, -NH-Ph, -Ph-OR 3 or -NH-CO-NH-Ph
• R 3 represents an alkyl group
• Ph represents a phenyl group, which is optionally substituted with a substituent having -SO 2 R 2 .
• the alkyl group represented by R 1 is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group, an ethyl group, an isopropyl group, or the like. Among these, R 1 is specifically preferably a hydroxyl group.
• R 3 represents an alkyl group, and the alkyl group preferably has 1 to 4 carbon atoms, and is specifically preferably an isopropyl group, or the like.
• Ph may be a substituted phenyl group wherein the phenyl group is substituted with a "substituent including -SO 2 R 2 ", and R 2 of the substituent may be substituted with a methyl group, a halogen atom, or the like.
• the substituent include -CH 2 -C 6 H 5 -NHCONH-SO 2 -C 6 H 5 , -SO 2 -C 6 H 4 -CH 3 , -SO 2 -C 6 H 4 -Cl, and the like.
• the substituent can be -SO 2 -C 6 H 5 .
• R 2 is preferably -NH-Ph, and specifically preferably -NH-C 6 H 5 .
• 4-hydroxybenzenesulfoneanilide is the most preferable in view of balance between image retention property and background fogging.
• the amount of the electron-accepting compound in a single heat-sensitive recording layer is preferably 50 to 400% by mass, and more preferably 100 to 300% by mass relative to the mass of the electron-donating colorless dye.
• Any other known electron-accepting compound may be used in combination with the electron-accepting compound represented by general formula (1), so long as the effects of the invention (specifically decrease in background fogging level, improvement in sensitivity, and improvements in image storability, chemical resistance and a head matching property) are not deteriorated.
• the known electron-accepting compound is properly selected and used. It is spedicfically preferably a phenolic compound or a salicylic acid derivative or a polyvalent metal salt thereof from the viewpoint of suppression of background fogging.
• the amount of the electron-accepting compound represented by general formula (1) is preferably not less than 50% by mass, and specifically preferably not less than 70% by mass relative to the total mass of the electron-accepting compounds.
• the particle size (volume mean diameter) of the electron-accepting compound is preferably not more than 1.0 ⁇ m, and more preferably 0.4 to 0.7 ⁇ m.
• volume mean diameter exceeds 1.0 ⁇ m, heat sensitivity sometimes decreases.
• volume mean diameter is less than 0.4 ⁇ m, background fogging sometimes deteriorates.
• the volume mean diameter can also be readily measured by using a laser diffraction type size distribution measuring instrument (e.g., LA500 manufactured by Horiba, Inc.), or the like.
• a laser diffraction type size distribution measuring instrument e.g., LA500 manufactured by Horiba, Inc.
• the heat-sensitive recording layer used in the second embodiment of the invention preferably includes a sensitizer.
• the description of the sensitizer is same as that for the sensitizer described in the first embodiment of the invention.
• the heat-sensitive recording layer used in the second embodiment of the invention preferably includes an image stabilizer ((including an ultraviolet light absorbent).
• an image stabilizer (including an ultraviolet light absorbent)
• the description of the image stabilizer is same as that for the image stabilizer duscribed in the first embodiment of the invention.
• the heat-sensitive recording layer of the second embodiment of the invention preferably includes an inorganic pigment, specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• an inorganic pigment specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• the description of the inorganic pigment is same as that for the inorganic pigment described in the first embodiment of the invention.
• the heat-sensitive recording of the second embodiment of the invention preferably includes, as an adhesive (or a protective colloid at the time of dispersion), at least one kind selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol (i.e., modified polyvinyl alcohols (hereinafter sometimes referred to as "specific modified PVA").
• an adhesive or a protective colloid at the time of dispersion
• at least one kind selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol i.e., modified polyvinyl alcohols (hereinafter sometimes referred to as "specific modified PVA").
• specific modified PVA modified polyvinyl alcohols
• the heat-sensitive recording layer of the seconnd embodiment of the invention may include, according to the purpose or need, other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• the heat-sensitive recording layer may include a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• water resistance of the heat-sensitive recording material can be improved.
• the description of the cross-linking agent is same as that for the cross-linking agent described in the first embodiment of the invention.
• the heat-sensitive recording layer may include a mordant for the purpose of preventing bleeding at the time of ink jet recording.
• the description of the mordant is same as that for the mordant described in the first embodiment of the invention.
• metal soap, wax and surfactant are same as that for the metal soap, wax and surfactant described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer, and other components can be suitably dispersed in a water-soluble binder.
• the description of the binder is same as that for the binder described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer can be simultaneously or separately dispersed with a stirrer or a crusher such as a ball mill, an attritor, a sand mill, or the like and then a coating solution is prepared.
• the coating solution may include the above-mentioned other components, i.e., a cross-linking agent, a mordant, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye and the like.
• the coating solution is prepared and applied onto the surface of a support, whereby a heat-sensitive recording layer is formed.
• the coating method for applying a coating solution, the dried coating amount of the coating solution for applying and forming the heat-sensitive recording layer, the simultaneously multiple layers coating by a curtain coating method which is a preferable coating method of the invention, and the curtain coating method apparatus to be used for curtain coating method are same as that for those described in the first embodiment of the invention.
• adjustment of the image density to be 1.20 or more in the case of thermal printing by energy application at 15.2 mJ/mm 2 can be achieved by properly selecting above-mentioned respective components and layer structure and application method, particularly the types and the amounts of the electron-donating colorless dye, electron-accepting compound, adhesive, and sensitizer, application method, and existence or absence of the protective layer, in desirable manner.
• the image density of the images by the above-mentioned energy application is particularly preferable to be 1.25 to 1.35.
• At least one protective layer is preferably disposed on the heat-sensitive recording layer.
• the protective layer may include organic or inorganic micropowder, a binder, a surfactant, a heat-melting substance, and the like.
• the description of the protective layer is same as that for the protective layer described in the first embodiment of the inveniton.
• supports can be applied to the supports.
• Specific examples tehreof includesupports paper supports such as woodfree paper, and the like, coated paper in which paper is coated with a resin or a pigment, paper on which a resin layer is laminated, woodfree paper having a undercoat layer, synthetic paper, plastic films, and the like.
• a support including recycled pulp as a main component i.e. a support in which the mass of recycled pulp is 50% by mass of the components of the support can be also used.
• the description of the total ion concentration of Na + ions and K + ions included in the heat-sensitive recording material is same as that described in the first embodiment.
• the surface wettability of the heat-sensitive recording layer that is the contact angle after 0.1 seconds after of dropwise dropping distilled water on the surface of the heat-sensitive recording layer is preferably 20° or more and more preferably 50° or more.
• the above-mentioned contact angle can be obtained by adding the electron-accepting compound (preferably 4-hydroxybenzenesulfoneanilide) represented by the above-mentioned general formula (1) and besides, as a material for keeping the contact angle of the recording face to the distilled water high, a method of adding a sensitizer, paraffin wax and the like to the heat-sensitive recording layer according to the invention is also preferably employed.
• the electron-accepting compound preferably 4-hydroxybenzenesulfoneanilide
• the second embodiment of the heat-sensitive recording material of the invention is advantageous in terms of excellent image storability and it is preferable to keep the density retention rate of the formed image 65% or more in the case where the formed image is left still under environmental conditions of 60°C temperature and 20% relative humidity for 24 hours after the printing.
• the density retention rate can be kept in the above-mentioned range by adding the electron-accepting compound (particularly preferably 4-hydroxybenzenesulfoneanilide) represented by the general formula (1) and preferably an image stabilizer as well. Accordingly, the formed image can be kept with a high density for a long duration and thus the heat-sensitive recording material can be employed in fields such as important document storage, prepaid tickets, receipts, money certificates, and the like for which long term image reliability is required.
• the description of the density retention rate of the image is same as that described in the first embodiment of the invention.
• the heat-sensitive recording material includes a heat-sensitive recording layer of a coloration system containing an electron-donating colorless dye and an electron-accepting compound in combination and the image density formed by printing with a thermal head by energy application at 15.2 mJ/mm 2 by a thermal head is 1.20 or more and the static friction coefficient and the dynamic friction coefficient are in the range of 0.2 to 0.5 in the case where the outermost surface of the front side having at least one heat-sensitive recording layer and the outermost surface of the rear side are rubbed against each other.
• the outermost surface in the front face side means the surface of the heat-sensitive recording layer or the surface of the layer formed in the most outside (the remotest side from the support) among the layers in the case where other layers such as a protective layer or the like are formed on the heat-sensitive recording layer.
• the outermost surface of the rear side means the surface in the side of the support where the heat-sensitive recording layer is not formed or the surface of the layer formed in the most outside among the layers in the case where other layers are formed on the rear side of the heat-sensitive recording layer.
• the static friction coefficient and the dynamic friction coefficient are lower than 0.2, the friction force to the transportation means such as a rubber roller is insufficient and therefore the transportation means slips on the material to result in increase of sending failure at the time of transporting the heat-sensitive recording material and deterioration of the transportation property.
• the static friction coefficient and the dynamic friction coefficient exceed 0.5, the slippage among the respective sheets is worsened in the case where the sheets of the heat-sensitive recording material are used while being stacked and when the heat-sensitive recording material is transported in form of sheets, the probability that a plurality of sheets are stacked and transported together is increased and therefore, similarly the transportation property is deteriorated.
• the static friction coefficient is preferably in the range of 0.25 to 0.45, more preferably 0.30 to 0.45 and similarly, the dynamic friction coefficient is preferably in the range of 0.25 to 0.45, more preferably 0.30 to 0.45.
• the above-mentioned static friction coefficient and dynamic friction coefficient can be measured according to ASTM D 1897-73. Practically, they can be measured by the following method.
• the heat-sensitive recording material having the heat-sensitive recording layer only in one face is cut into a size of 100 mm width and 200 mm length at a thermostat chamber at 23°C (a heat-sensitive recording material piece A) and stuck to a smooth plate while the recording face being set upside.
• the sleigh is connected to the load cell by a monofilament string and the sleigh wrapped with the heat-sensitive recording material piece B is lightly put on the heat-sensitive recording face (the outermost surface in the front face) of the heat-sensitive recording material piece A stuck to the smooth plate and the smooth plate is moved at a testing speed 600 mm/min to measure the static friction coefficient and the dynamic friction coefficient.
• the static friction coefficient and dynamic friction coefficient between the outermost surface in the front face and the outermost surface of the rear side can be adjusted in the above-mentioned ranges by controlling the addition amounts of a lubricant as well as a metal soap, a wax, a surfactant and the like in the respective outermost layers.
• a lubricant examples include metal soap such as zinc stearate, calcium stearate and waxes such as paraffin wax, microcrystalline wax, carnauba wax, synthesized polymer wax and the like.
• the third embodiment of the heat-sensitive recording material of the invention comprises one or two or more heat-sensitive recording layers on a support and preferably a protective layer. If necessary, other layers such as an intermediate layer may be formed.
• the heat-sensitive recording layer includes at least an electron-donating colorless dye and an electron-accepting compound that reacts with the electron-donating colorless dye to develop color, and preferably includes an image stabilizer (an ultraviolet light blocking agent), an inorganic pigment, an adhesive and a sensitizer. If required, the layer may include any other component.
• the heat-sensitive recording layer used in the third embodiment of the invention includes an electron-donating colorless dye as a color-developing component.
• the description of the electron-donating colorless dye is same as that for the electron-donating colorless dye described in the first embodiment of the invention.
• the heat-sensitive recording layer used in the invention includes at least one kind of the compound represented by general formula (1) as an electron-accepting compound that reacts with the electron-donating colorless dye during heating to develop color.
• this compound in the heat-sensitive recording layer.
• R 1 represents a hydroxyl group or an alkyl group
• R 2 represents -Ph, -NH-Ph, -Ph-OR 3 or -NH-CO-NH-Ph
• R 3 represents an alkyl group
• Ph represents a phenyl group, which is optionally substituted with a substituent having -SO 2 R 2 .
• the alkyl group represented by R 1 is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group, an ethyl group, an isopropyl group, or the like. Among these, R 1 is specifically preferably a hydroxyl group.
• R 3 represents an alkyl group, and the alkyl group preferably has 1 to 4 carbon atoms, and is specifically preferably an isopropyl group, or the like.
• Ph may be a substituted phenyl group wherein the phenyl group is substituted with a "substituent including -SO 2 R 2 ", and R 2 of the substituent may be substituted with a methyl group, a halogen atom, or the like.
• the substituent include -CH 2 -C 6 H 5 -NHCONH-SO 2 -C 6 H 5 , -SO 2 -C 6 H 4 -CH 3 , -SO 2 -C 6 H 4 -Cl, and the like.
• the substituent can be -SO 2 -C 6 H 5 .
• R 2 is preferably -NH-Ph, and specifically preferably -NH-C 6 H 5 .
• 4-hydroxybenzenesulfoneanilide is the most preferable in view of balance between image retention property and background fogging.
• the amount of the electron-accepting compound in a single heat-sensitive recording layer is preferably 50 to 400% by mass, and more preferably 100 to 300% by mass relative to the mass of the electron-donating colorless dye.
• Any other known electron-accepting compound may be used in combination with the electron-accepting compound represented by general formula (1), so long as the effects of the invention (specifically decrease in background fogging level, improvement in sensitivity, and improvements in image storability, chemical resistance and a head matching property) are not deteriorated..
• the known electron-accepting compound is properly selected and used. It is spedicfically preferably a phenolic compound or a salicylic acid derivative or a polyvalent metal salt thereof from the viewpoint of suppression of background fogging.
• the amount of the electron-accepting compound represented by general formula (1) is preferably not less than 50% by mass, and specifically preferably not less than 70% by mass relative to the total mass of the electron-accepting compounds.
• the particle size (volume mean diameter) of the electron-accepting compound is preferably not more than 1.0 ⁇ m, and more preferably 0.4 to 0.7 ⁇ m.
• volume mean diameter exceeds 1.0 ⁇ m, heat sensitivity sometimes decreases.
• volume mean diameter is less than 0.4 ⁇ m, background fogging sometimes deteriorates.
• the volume mean diameter can also be readily measured by using a laser diffraction type size distribution measuring instrument (e.g., LA500 manufactured by Horiba, Inc.), or the like.
• a laser diffraction type size distribution measuring instrument e.g., LA500 manufactured by Horiba, Inc.
• the heat-sensitive recording layer used in the third embodiment of the invention preferably includes a sensitizer.
• the description of the sensitizer is same as that for the sensitizer described in the first embodiment of the invention.
• the heat-sensitive recording layer used in the theird embodiment of the invention preferably includes an image stabilizer ((including an ultraviolet light absorbent).
• an image stabilizer (including an ultraviolet light absorbent)
• the description of the image stabilizer (including an ultraviolet light absorbent) is same as that for the image stabilizer duscribed in the first embodiment of the invention.
• the heat-sensitive recording layer of the third embodiment of the invention preferably includes an inorganic pigment, specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• an inorganic pigment specifically at least one kind selected from calcite calcium carbonate, amorphous silica and aluminum hydroxide (inorganic pigments according to the invention).
• the description of the inorganic pigment is same as that for the inorganic pigment described in the first embodiment of the invention.
• the heat-sensitive recording of the third embodiment of the invention preferably preferably includes, as an adhesive (or a protective colloid at the time of dispersion), at least one kind selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol (i.e., modified polyvinyl alcohols (hereinafter sometimes referred to as "specific modified PVA").
• an adhesive or a protective colloid at the time of dispersion
• specific modified PVA modified polyvinyl alcohols
• the heat-sensitive recording layer of the third embodiment of the invention may include, according to the purpose or need, other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• the heat-sensitive recording layer may include a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• water resistance of the heat-sensitive recording material can be improved.
• the description of the cross-linking agent is same as that for the cross-linking agent described in the first embodiment of the invention.
• the heat-sensitive recording layer may include a mordant for the purpose of preventing bleeding at the time of ink jet recording.
• the description of the mordant is same as that for the mordant described in the first embodiment of the invention.
• metal soap, wax and surfactant are the same as that for those described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer, and other components can be suitably dispersed in a water-soluble binder.
• the description of the binder is same as that for the binder described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer can be simultaneously or separately dispersed with a stirrer or a crusher such as a ball mill, an attritor, a sand mill, or the like and then a coating solution is prepared.
• the coating solution may include the above-mentioned other components, i.e., a cross-linking agent, a mordant, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye and the like.
• the coating solution is prepared and applied onto the surface of a support, whereby a heat-sensitive recording layer is formed.
• he coating method for applying the coating solution is not specifically limited, and may be suitably selected from coating methods using an air knife coater, a roll coater, a blade coater, a curtain coater, or the like.
• the resultant coating is dried, and the dried coating is subjected to smoothing treatment, preferably calendar treatment, and the resultant material is used.
• the dried coating amount of the coating solution for forming a heat-sensitive recording layer is, although it is not particularly limited, preferably about 2 to 7g/m 2 based on the dried coarting amount.
• a curtain coating method using a curtain coater is specifically preferred.
• the reasons for this are as follows.
• the components can be concentrated on a recording surface.
• high density high sensitivity
• image quality can be simultaneously improved.
• adjustment of the image density to be 1.20 or more in the case of thermal printing by energy application at 15.2 mJ/mm 2 can be achieved by properly selecting above-mentioned respective components and layer structure and application method, particularly the types and the amounts of the electron-donating colorless dye, electron-accepting compound, adhesive, and sensitizer, application method, and existence or absence of the protective layer, in desirable manner.
• the image density of the images by the above-mentioned energy application is particularly preferable to be 1.25 to 1.35.
• At least one protective layer is preferably disposed on the heat-sensitive recording layer.
• the protective layer may include organic or inorganic micropowder, a binder, a surfactant, a heat-melting substance, and the like.
• the description of the protective layer is same as that for that described in the first embodiment of the inveniton.
• supports can be applied to the supports.
• Specific examples tehreof includesupports paper supports such as woodfree paper, and the like, coated paper in which paper is coated with a resin or a pigment, paper on which a resin layer is laminated, woodfree paper having a undercoat layer, synthetic paper, plastic films, and the like.
• a support including recycled pulp as a main component i.e. a support in which the mass of recycled pulp is 50% by mass of the components of the support can be also used.
• the description of the total ion concentration of Na + ions and K + ions included in the heat-sensitive recording material is same as that described in the first embodiment.
• the surface wettability of the heat-sensitive recording layer that is the contact angle after 0.1 seconds after of dropwise dropping distilled water on the surface of the heat-sensitive recording layer is preferably 20° or more and more preferably 50° or more.
• the above-mentioned contact angle can be obtained by adding the electron-accepting compound (preferably 4-hydroxybenzenesulfoneanilide) represented by the above-mentioned general formula (1) and besides, as a material for keeping the contact angle of the recording face to the distilled water high, a method of adding a sensitizer, paraffin wax and the like to the heat-sensitive recording layer according to the invention is also preferably employed.
• the electron-accepting compound preferably 4-hydroxybenzenesulfoneanilide
• the description of the measurement of the contact angle is same as that for the description in the first embodiment.
• the third embodiment of the heat-sensitive recording material of the invention is advantageous in terms of excellent image storability and it is preferable to keep the density retention rate of the formed image 65% or more in the case where the formed image is left still under environmental conditions of 60°C temperature and 20% relative humidity for 24 hours after the printing.
• the density retention rate can be kept in the above-mentioned range by adding the electron-accepting compound (particularly preferably 4-hydroxybenzenesulfoneanilide) represented by the general formula (1) and preferably an image stabilizer as well. Accordingly, the formed image can be kept with a high density for a long duration and thus the heat-sensitive recording material can be employed in fields such as important document storage, prepaid tickets, receipts, money certificates, and the like for which long term image reliability is required.
• the description of the density retention rate of the image is same as that for the description of the density retention rate described in the first embodiment of the invention.
• the heat-sensitive recording material comprises a heat-sensitive recording layer containing an electron-donating colorless dye, an electron-accepting compound for coloring by reacting with the electron-donating colorless dye, and a pigment on a support and is characterized in that the pigment has the boiled linseed oil absorption amount of 30 to 200 ml/ 100g and a volume average particle diameter of 0.5 to 3 ⁇ m and the heat-sensitive recording material is used for a recording apparatus capable of thermal printing at speed of 10 cm/sec or more.
• the fourth embodiment of the heat-sensitive recording material of the invention comprises one or two or more heat-sensitive recording layers on a support and preferably a protective layer. If necessary, other layers such as an intermediate layer may be formed.
• the heat-sensitive recording layer includes at least an electron-donating colorless dye and an electron-accepting compound that reacts with the electron-donating colorless dye to develop color, and preferably includes an image stabilizer (an ultraviolet light blocking agent), an inorganic pigment, an adhesive and a sensitizer. If required, the layer may include any other component.
• the heat-sensitive recording layer of the forth embodiment of the invention includes an electron-donating colorless dye as a color-developing component.
• the description of the electron-donating colorless dye is same as that for the electron-donating colorless dye described in the first embodiment of the invention.
• the heat-sensitive recording layer used in the invention includes at least one kind of the compound represented by general formula (1) as an electron-accepting compound that reacts with the electron-donating colorless dye during heating to develop color.
• this compound in the heat-sensitive recording layer.
• R 1 represents a hydroxyl group or an alkyl group
• R 2 represents -Ph, -NH-Ph, -Ph-OR 3 or -NH-CO-NH-Ph
• R 3 represents an alkyl group
• Ph represents a phenyl group, which is optionally substituted with a substituent having -SO 2 R 2 .
• the alkyl group represented by R 1 is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group, an ethyl group, an isopropyl group, or the like. Among these, R 1 is specifically preferably a hydroxyl group.
• R 3 represents an alkyl group, and the alkyl group preferably has 1 to 4 carbon atoms, and is specifically preferably an isopropyl group, or the like.
• Ph may be a substituted phenyl group wherein the phenyl group is substituted with a "substituent including -SO 2 R 2 ", and R 2 of the substituent may be substituted with a methyl group, a halogen atom, or the like.
• the substituent include -CH 2 -C 6 H 5 -NHCONH-SO 2 -C 6 H 5 , -SO 2 -C 6 H 4 -CH 3 , -SO 2 -C 6 H 4 -Cl, and the like.
• the substituent can be -SO 2 -C 6 H 5 .
• R 2 is preferably -NH-Ph, and specifically preferably - NH-C 6 H 5 .
• 4-hydroxybenzenesulfoneanilide is the most preferable in view of the balance between image retention property and background fogging.
• the amount of the electron-accepting compound in a single heat-sensitive recording layer is preferably 50 to 400% by mass, and more preferably 100 to 300% by mass relative to the mass of the electron-donating colorless dye.
• Any other known electron-accepting compound may be used in combination with the electron-accepting compound represented by general formula (1), so long as the effects of the invention (specifically decrease in background fogging level, improvement in sensitivity, and improvements in image storability, chemical resistance and a head matching property) are not deteriorated..
• the known electron-accepting compound is properly selected and used. It is spedicfically preferably a phenolic compound or a salicylic acid derivative or a polyvalent metal salt thereof from the viewpoint of suppression of background fogging.
• the amount of the electron-accepting compound represented by general formula (1) is preferably not less than 50% by mass, and specifically preferably not less than 70% by mass relative to the total mass of the electron-accepting compounds.
• the particle size (volume mean diameter) of the electron-accepting compound is preferably not more than 1.0 ⁇ m, and more preferably 0.4 to 0.7 ⁇ m.
• volume mean diameter exceeds 1.0 ⁇ m, heat sensitivity sometimes decreases.
• volume mean diameter is less than 0.4 ⁇ m, background fogging sometimes deteriorates.
• the volume mean diameter can also be readily measured by using a laser diffraction type size distribution measuring instrument (e.g., LA500 manufactured by Horiba, Inc.), or the like.
• a laser diffraction type size distribution measuring instrument e.g., LA500 manufactured by Horiba, Inc.
• the boiled linseed oil absorption amount of the pigment is set in the range of 30 to 200 ml/ 100g, and by adjusting the boiled linseed oil absorption amount in the above-mentioned range, excellent high speed printing suitability can be provided, that is, the head staining hardly occurs even in the case of high speed printing.
• the boiled linseed oil absorption amount is less than 30 ml/100 g, the head staining easily occurs and if it is 200 ml/100 g or more, the sensitivity is hardly exhibited.
• the boiled linseed oil absorption amount of the pigment is more preferably 40 to 150 ml/100 g and furthermore preferably 50 to 100 ml/100 g.
• the volume mean diameter of the pigment is set in the range of 0.5 to 3 ⁇ m and if it is smaller than 0.5 ⁇ m, the head staining easily occurs and if it is 3 ⁇ m or more, the sensitivity is hardly exhibited.
• the volume mean diameter of the pigment is more preferably 0.7 to 2.5 ⁇ m and furthermore preferably 1.0 to 2.0 ⁇ m.
• pigment more specifically, at least one of calcite type calcium carbonate, amorphous silica, and aluminum hydroxide (pigments according to the invention) is preferably added. Addition of such pigments improves the head matching property with a thermal head with which the heat-sensitive recording material is brought into contact and simultaneously provides printing suitability and plain paper-like touch.
• Light calcium carbonate generally includes those having crystal forms of calcite, aragonite, vaterite and like and from a viewpoint of coloring density at the time of recording by a thermal head, prevention of head staining as well as absorption property and hardness, calcite type (light) calcium carbonate is preferable and above all, those having a spindle-like shape or scalenohedron shape are preferable.
• the calcite type (light) calcium carbonate can be produced by a known production method.
• the average particle size of the above-mentioned calcite type (light) calcium carbonate is preferably 1 to 3 ⁇ m on the basis of the volume mean diameter.
• the volume mean diameter can be measured in the same manner as that for the above-mentioned electron-donating colorless dye.
• the content of "the pigments according to the invention” in a single heat-sensitive recording layer is preferably 50 to 500 parts by mass, more preferably 70 to 350 parts by mass, and furthermore preferably 90 to 250 parts by mass to 100 parts by mass of the electron-accepting compound from a viewpoint of improvement of the coloring density and prevention of scam adhesion to the thermal head.
• calcium carbonate except the calcite type (light) calcium carbonate, barium sulfate, lithopone, agalmatolite, kaolin, calcined kaolin, amorphous silica, kaolin, magnesium carbonate, magnesium oxide, and the like can be exemplified.
• the volume mean diameters of other pigments are preferably 0.3 to 1.5 ⁇ m and more preferably 0.5 to 0.9 ⁇ m [by measurement using laser diffraction particle size distribution measurement method (e.g. LA 500 manufactured by Horiba Co., Ltd.)].
• the ratio (v/w) of the total amount (v) of the pigment according to the invention and the total amount (w) of other pigment is preferably (100/0) to (60/40) and more preferably (100/0) to (80/20).
• pigments with Mohs hardness 3 or less are preferable.
• Mohs hardness is described in English Japanese Plastic Industry Dictionary, 5th edition, p. 616 (Shin OGAWA, published by Kogyo Chosakai Publishing Co., Ltd.).
• Pigments with Mohs hardness 3 or less include calcium carbonate and aluminum hydroxide.
• the pigment according to the invention is used with magnesium carbonate and magnesium oxide, it is advantageously effective to lower the background fogging and the content of magnesium carbonate and/or magnesium oxide in such a case is preferably 3 to 50% by mass, more preferably 5 to 30% by mass in the total of the pigments.
• the heat-sensitive recording layer of the forth embodiment of the invention preferably includes a sensitizer.
• the description of the sensitizer is same as that for the description in the first embodiment of the invention.
• the heat-sensitive recording layer of the forth embodiment of the invention preferably includes an image stabilizer ((including an ultraviolet light absorbent).
• an image stabilizer (including an ultraviolet light absorbent)
• the description of the image stabilizer is same as that for the image stabilizer duscribed in the first embodiment of the invention.
• the heat-sensitive recording of the forth embodiment of the invention preferably preferably includes, as an adhesive (or a protective colloid at the time of dispersion), at least one kind selected from sulfo-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol (i.e., modified polyvinyl alcohols (hereinafter sometimes referred to as "specific modified PVA").
• an adhesive or a protective colloid at the time of dispersion
• specific modified PVA modified polyvinyl alcohols
• the heat-sensitive recording layer of the forth embodiment of the invention may include, according to the purpose or need, other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• other components such as a cross-linking agent, any other pigment, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye, and the like as well as the above-mentioned components.
• the heat-sensitive recording layer may include a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• a cross-linking agent that reacts with the specific modified PVA, and/or any other modified PVA used as an adhesive (or a protective colloid) and the like.
• water resistance of the heat-sensitive recording material can be improved.
• the description of the cross-linking agent is same as that for the cross-linking agent described in the first embodiment of the invention.
• the heat-sensitive recording layer may include a mordant for the purpose of preventing bleeding at the time of ink jet recording.
• the description of the mordant is same as that for the mordant described in the first embodiment of the invention.
• metal soap, wax and surfactant are the same as that for those described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer, and other components can be suitably dispersed in a water-soluble binder.
• the description of the binder is same as that for the binder described in the first embodiment of the invention.
• the electron-donating colorless dye, the electron-accepting compound, the inorganic pigment, the adhesive and the sensitizer can be simultaneously or separately dispersed with a stirrer or a crusher such as a ball mill, an attritor, a sand mill, or the like and then a coating solution is prepared.
• the coating solution may include the above-mentioned other components, i.e., a cross-linking agent, a mordant, a metal soap, wax, a surfactant, a binder, an antistatic agent, a defoaming agent, a fluorescence dye and the like.
• the coating solution is prepared and applied onto the surface of a support, whereby a heat-sensitive recording layer is formed.
• he coating method for applying the coating solution is not specifically limited, and may be suitably selected from coating methods using an air knife coater, a roll coater, a blade coater, a curtain coater, or the like.
• the resultant coating is dried, and the dried coating is subjected to smoothing treatment, preferably calendar treatment, and the resultant material is used.
• the dried coating amount of the coating solution for forming a heat-sensitive recording layer is, although it is not particularly limited, preferably about 2 to 7g/m 2 based on the dried coarting amount.
• a curtain coating method using a curtain coater is specifically preferred.
• the reasons for this are as follows.
• the components can be concentrated on a recording surface.
• high density high sensitivity
• image quality can be simultaneously improved.
• At least one protective layer is preferably disposed on the heat-sensitive recording layer.
• the protective layer may include organic or inorganic micropowder, a binder, a surfactant, a heat-melting substance, and the like.
• the description of the protective layer is same as that for that described in the first embodiment of the inveniton.
• supports can be applied to the supports.
• Specific examples tehreof includesupports paper supports such as woodfree paper, and the like, coated paper in which paper is coated with a resin or a pigment, paper on which a resin layer is laminated, woodfree paper having a undercoat layer, synthetic paper, plastic films, and the like.
• a support including recycled pulp as a main component i.e. a support in which the mass of recycled pulp is 50% by mass of the components of the support can be also used.
• the description of the total ion concentration of Na + ions and K + ions included in the heat-sensitive recording material is same as that described in the first embodiment.
• the surface wettability of the heat-sensitive recording layer that is the contact angle after 0.1 seconds after of dropwise dropping distilled water on the surface of the heat-sensitive recording layer is preferably 20° or more and more preferably 50° or more.
• the above-mentioned contact angle can be obtained by adding the electron-accepting compound (preferably 4-hydroxybenzenesulfoneanilide) represented by the above-mentioned general formula (1) and besides, as a material for keeping the contact angle of the recording face to the distilled water high, a method of adding a sensitizer, paraffin wax and the like to the heat-sensitive recording layer according to the invention is also preferably employed.
• the electron-accepting compound preferably 4-hydroxybenzenesulfoneanilide
• the description of the measurement of the contact angle is same as that for the description in the first embodiment.
• the forth embodiment of the heat-sensitive recording material of the invention is advantageous in terms of excellent image storability and it is preferable to keep the density retention rate of the formed image 65% or more in the case where the formed image is left still under environmental conditions of 60°C temperature and 20% relative humidity for 24 hours after the printing.
• the density retention rate can be kept in the above-mentioned range by adding the electron-accepting compound (particularly preferably 4-hydroxybenzenesulfoneanilide) represented by the general formula (1) and preferably an image stabilizer as well. Accordingly, the formed image can be kept with a high density for a long duration and thus the heat-sensitive recording material can be employed in fields such as important document storage, prepaid tickets, receipts, money certificates, and the like for which long term image reliability is required.
• the description of the density retention rate of the image is same as that for the description of the density retention rate described in the first embodiment of the invention.
• the fourth embodiment of the heat-sensitive recording material of the invention is used for a recording apparatus capable of carrying out thermal printing (image formation) at a speed of 10 cm/sec or more and printing (image formation) can be carried out on the heat-sensitive recording layer with the above-mentioned constitution by imagewise thermal printing directly on the surface of the heat-sensitive recording layer or on the surface via the protective layer if the protective layer is formed.
• the speed of the thermal printing (image formation) is preferably 12 cm/sec or more.
• dispersion liquid A-1 having a volume mean diameter of 0.7 ⁇ m.
• the volume mean diameter was measured with a laser diffraction type size distribution measuring instrument (trade name: LA500, manufactured by Horiba, Inc.).
• dispersion liquid B-1 having a volume mean diameter of 0.7 ⁇ m.
• the volume mean diameter was measured in the same manner as the method for measuring the volume mean diameter of dispersion liquid A.
• dispersion liquid C having a volume mean diameter of 0.7 ⁇ m.
• the volume mean diameter was measured in the same manner as the method for measuring the volume mean diameter of dispersion liquid A.
• dispersion liquid D having a volume mean diameter of 2.0 ⁇ m.
• the volume mean diameter was measured in the same manner as the method for measuring the volume mean diameter of dispersion liquid A.
• the following components were mixed to prepare a coating solution for a heat-sensitive recording layer.
• SBR styrene-butadiene rubber latex
• oxidized starch 25 parts
• Woodfree paper having smoothness measured by JIS-P8119 of 150 seconds was prepared as a support.
• the coating solution for ansupport primer layerprimer layer of a support obtained above was applied to the surface of the woodfree paper by a blade coater so that the coating amount after drying became 8 g/m 2 .
• an primer layer was formed.
• the smoothness measured by JIS-P8119 of the support became 350 seconds.
• the coating solution for a heat-sensitive recording layer obtained above was then applied to the undercoat layer with a curtain coater so that the coating amount after drying became 4 g/m 2
• the obtained heat-sensitive recording material (1) was subjected to the measurement (evaluation) in conditions by the methods as described below.
• the coloring density was 1.28 (measured by Macbeth reflection densitometer RD-918) in the case of energy application at 15.2 mJ/mm 2 by the thermal head.
• dispersion liquid E having a volume mean diameter of 0.7 ⁇ m.
• the volume mean diameter was measured in the same manner as in Example 1.
• Dispersion liquids A, B, C and D were prepared in the same manner as in Example 1 and mixed with dispersion liquid E obtained above in accordance with the following composition to prepare a coating solution for a heat-sensitive recording layer. Furthermore, the heat-sensitive recording material of the invention (2) was obtained in the same manner as in Example 1.
• Dispersion liquid E was prepared in the same manner as in Example 2 except that 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (an image stabilizer) used in the preparation of dispersion liquid E-1. Furthermore, the heat-sensitive recording material of the invention (3) was obtained in the same manner as in Example 2.
• the heat-sensitive recording materials of the invention (4) and (5) were obtained in the same manner as in Example 1 except that 20 parts of amorphous silica (trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.) and 40 parts of aluminum hydroxide (trade name: HYGILITE H42, manufactured by Showa Denko K.K.) were used, respectively, instead of 40 parts of calcite light calcium carbonate (UNIVER 70; inorganic pigment) used in the preparation of dispersion liquid D.
• amorphous silica trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.
• 40 parts of aluminum hydroxide trade name: HYGILITE H42, manufactured by Showa Denko K.K.
• the heat-sensitive recording material of the invention (6) was obtained in the same manner as in Example 1 except that a 2.5% sulfo-modified polyvinyl alcohol (trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution was used instead of a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C.
• a 2.5% sulfo-modified polyvinyl alcohol trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
• the heat-sensitive recording material of the invention (7) was obtained in the same manner as in Example 1 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% adipic acid dihydrazide aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and
• the heat-sensitive recording material of the invention (8) was obtained in the same manner as in Example 1 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% glyoxal aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210, manufactured
• Example 9 was obtained in the same manner as in Example 1 except that recycled paper (50 g/m 2 ) made of recycled pulp (70%) and LBKP (30%) and having smoothness measured by JIS-P8119 of 170 seconds was used instead of woodfree paper used as the substrate in Example 1.
• the heat-sensitive recording material of the invention (10) was obtained in the same manner as in Example 1 except that, after formation of an undercoat layer on a substrate, the coating solution for a heat-sensitive recording layer obtained in Example 1 and the following coating solution for a protective layer were applied simultaneously with a curtain coater and the resultant coatings were dried to form multiple layers and the surface of the laminated protective layer was subjected to calendaring treatment instead of applying the coating solution for a heat-sensitive recording layer, drying and calendaring the resultant coating after formation of an undercoat layer on a substrate in the ⁇ Preparation of heat-sensitive recording material> of Example 1.
• the dried coating amount of the protective layer was 2.0 g/m 2 .
• the following components were stirred with a sand mill to prepare a pigment dispersion having a volume mean diameter of 2 ⁇ m.
• the volume mean diameter was measured in the same manner as in Example 1.
• a mixture of 200 parts of a 15% urea phosphate esterified starch aqueous solution (trade name: MS4600, manufactured by Nihon Shokuhin Kako Co., Ltd.), 200 parts of a 15% polyvinyl alcohol aqueous solution (trade name: PVA-105, manufactured by Kuraray Co., Ltd.) and 60 parts of water was separately prepared.
• the pigment dispersion obtained above and 25 parts of a zinc stearate emulsified dispersion having a volume mean diameter of 0.15 ⁇ m (trade name: HYDRIN F115, manufactured by Chukyo Yushi Co., Ltd.) and 125 parts of a 2% 2-ethylhexyl sodium sulfosuccinate aqueous solution were added to the mixture to form a coating solution for a protective layer.
• HYDRIN F115 trade name: HYDRIN F115, manufactured by Chukyo Yushi Co., Ltd.
• the heat-sensitive recording materials of the invention (11) to (13) were obtained in the same manner as in Example 10 except that 40 parts of aluminum hydroxide (trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.), 40 parts of kaolin (trade name: KAOBRITE; volume mean diameter: 2.5 ⁇ m; manufactured by Shiraishi Kogyo K.K.) and 20 parts of amorphous silica (trade name: MIZUKASIL P707; volume mean diameter: 2.2 ⁇ m; manufactured by Mizusawa Industrial Chemicals, Ltd.) were used, respectively, instead of 40 parts of aluminum hydroxide (HYGILITE H42; an inorganic pigment) used in the preparation of the coating solution for a protective layer in Example 10.
• aluminum hydroxide trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.
• KAOBRITE volume mean diameter: 2.5 ⁇ m
• the heat-sensitive recording materials of the invention (14) to (20) were obtained in the same manner as in Example 1 except that dimethylbenzyl oxalate (trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.), m-terphenyl, ethylene glycol tolyl ether, p-benzylbiphenyl, 1,2-diphenoxymethylbenzene, diphenylsulfone and 1,2-diphenoxyethane were used, respectively, instead of 2-benzyloxynaphthalene (a sensitizer) used in the preparation of dispersion liquid C in Example 1.
• dimethylbenzyl oxalate trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.
• m-terphenyl ethylene glycol tolyl ether
• p-benzylbiphenyl 1,2-diphenoxymethylbenzene
• diphenylsulfone 1,2-diphenoxyethane
• the heat-sensitive recording materials of the invention (21) to (25) were obtained in the same manner as in Example 1 except that 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluorane, 2-anilino-3-methyl-6-di-n-amylaminofluorane and 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluorine were used, respectively, instead of 2-anilino-3-methyl-6-diethylaminofluorane (an electron-donating colorless dye) used in the preparation of dispersion liquid A in Example 1.
• 2-anilino-3-methyl-6-diethylaminofluorane an electron-donating colorless dye
• the heat-sensitive recording material of the invention (26) was obtained in the same manner as in Example 1 except that an air knife coater was used instead of the curtain coater used in the application of the coating solution for a heat-sensitive recording layer in Example 1.
• the comparative heat-sensitive recording materials (30) and (31) were obtained in the same manner as in Example 1 except that 2,2'-bis(4-hydroxyphenol)propane (bisphenol A) and 4,4'-di-hydroxydiphenylsulfone were used, respectively, instead of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in Example 1.
• the comparative heat-sensitive recording material (32) was obtained in the same manner as in Example 1 except that the amount of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in Example 1 was changed from 20 parts to 4 parts.
• the comparative heat-sensitive recording material (33) was obtained in the same manner as in Example 1, except that no back liquid was applied in Example 1.
• the comparative heat-sensitive recording material (34) was obtained in the same manner as in Example 1, except that the back liquid was applied excessively (12 g/m 2 ) in Example 1.
• the heat-sensitive recording materials (1) to (29) of the invention and the conparative heat-sensitive recording materials (30) to (34) obtained in the above described manner were subjected to the following measurements and evaluations. The results of the measurements and evaluations are shown in the following Table 1.
• Printing was carried out with a heat-sensitive printing apparatus including a thermal head which has a partially glazed structure (trade name: KF2003-GD31A, manufactured by Rohm Co., Ltd.).
• the printing was carried out under conditions of a head voltage of 24V and a printing cycle of 0.98 ms/line (printing velocity: 12.8 cm/seconds) and a pulse width of 0.375 ms (applied energy: 15.2 mJ/mm 2 ), and printing densities were measured with Macbeth reflection densitometer (trade name: RD-918, manufactured by Macbeth Corporation).
• Each of the heat-sensitive recording materials (1) to (99) was left under environmental conditions of a temperature of 60°C and a relative humidity of 20% for 24 hours, and each of the heat-sensitive recording materials (100) to (132) was left under environmental conditions of a temperature of 40°C and a relative humidity of 80% for 24 hours. Thereafter, the density of the background portion (non-image portion) of each material was measured with Macbeth reflection densitometer (trade name: RD-918, manufactured by Macbeth Corporation). The lower the value is, the better the background fogging is.
• Each of the heat-sensitive recording materials was cut into 1000 sheets having A4 size.
• a test chart having a printing rate of 20% was printed on 1,000 sheets of each material with a word processor (trade name: RUPO 95JV, manufactured by Toshiba Corporation).
• the number of missing dots was used as an index for evaluation of printing troubles caused by friction between a head and a recording material.
• the image density (D 1 ) immediately after the printing was measured with Macbeth reflection densitometer (trade name: RD918, manufactured by Macbeth Corporation).
• the surface of the printed heat-sensitive recording layer (printing portions on which printing had been conducted) was brought into contact with a high quality image that was formed with an ink jet printer (trade name: EPSON MJ930C, manufactured by Epson Inc.), and these were left under at 25°C for 48 hours in this state.
• the image density (D 2 ) of the heat-sensitive recording layer after the leaving was measured with Macbeth reflection densitometer RD918.
• the density retention rate (%; D 2 /D 1 ⁇ 100) was calculated from the obtained densities of each heat-sensitive recording material, and was used as an index for evaluating inke jet ink resistance. The higher the value is, the better the ink resistance is.
• Each heat-sensitive recording material was cut along the width direction into 10 cm square and after conditioning humidity to 45% RH at 23°C placed horizontally while the heat-sensitive recording layer of each material was set upward or downward and the height of the four corners most coming up from the horizontal plane was measured as the maximum value (mm).
• Distilled water was dripped on the surface of the heat-sensitive recording layer of each heat-sensitive recording material (a recording surface), and the contact angle when 0.1 seconds had lapsed since the dripping was measured with FIBRO system (trade name: DAT1100, manufactured by FIBRO system, ab). The greater the value is, the more useful the material is, in view of its effects.
• Na + and K + ions of each heat-sensitive recording material were extracted with hot water, and the masses of Na + and K + ions contained in the extract were measured by ion quantitative analysis using an atomic absorption method.
• the ion concentrations in Tables 1 represent the total ion concentration of Na + and K + ions of each material, and shows the total ppm value relative to the total mass of the heat-sensitive recording material.
• the heat-sensitive recording materials (2) and (3) containing the image stabilizers were provided with improved image storability and ink resistance and the heat-sensitive recording material (6) containing a preferable adhesive (protection colloid) was provided with further improved sensitivity and lowered background fogging. Addition of the image stabilizers was found effective to give particularly excellent stamping suitability and handling easiness.
• the heat-sensitive recording materials (10) to (13) having protective layers containing specified inorganic pigments suitable for the second embodiment of the invention the image storability and the ink resistance (chemical resistance) could further be improved.
• the properties and abilities which the heat-sensitive recording materials are required to have were not satisfied all together and these heat-sensitive recording materials were found inferior in the image storability, chemical resistance, and ink jet suitability even if the curl degree, handling easiness, and the sensitivity were kept good and if the image storability was considered with a high priority, the curl degree and handling easiness were deteriorated. Further, it was found effective to properly adjust the application of the back liquid to be optimum.
• the heat-sensitive recording materials of the second embodiment of the invention were produced by the following procedure by employing the following component constitutions and application methods and at the time of production, the coloring density was adjusted to be 1.20 or higher in the case of energy application at 15.2 mJ/mm 2 by the thermal head.
• the dispersion liquid A with the same composition as that of the dispersion liquid A in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion B with the same composition as that of the dispersion liquid B in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid C with the same composition as that of the dispersion liquid C in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid D with the same composition as that of the dispersion liquid D in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• compositions were mixed to produce the coating solution for the heat-sensitive recording layer.
• the coating solution for the undercoat layer of the support with the same composition as that of the solution in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• Woodfree paper having smoothness measured by JIS-P8119 of 150 seconds was prepared as a substrate.
• the coating solution for an undercoat layer of a substrate obtained above was applied to the surface of the woodfree paper by a blade coater so that the coating amount after drying became 8 g/m 2 and an undercoat layer was thus formed.
• the smoothness measured by JIS-P8119 of the substrate became 350 seconds.
• the coating solution for a heat-sensitive recording layer obtained above was then applied to the undercoat layer with a curtain coater so that the coating amount after drying became 4 g/m 2 .
• the resultant coating was dried and a heat-sensitive recording layer was thus obtained.
• the surface of the thus-formed heat-sensitive recording layer was then subjected to calendaring treatment and a heat-sensitive recording material of the invention (33) was obtained.
• the color development density of the obtained heat-sensitive recording material (33) (measured by Macbeth reflection densitometer RD-918) at an energy, applied to a thermal head, of 15.2 mJ/mm 2 , which was measured according to the same conditions and method as those in evaluations described later, was 1.28.
• Dispersion liquid E with the same composition as that in Example 2 of the first embodiment was prepared by the same manner.
• the dispersion liquids A, B, C and D-2 were prepared in the same manner as in Example 30 and together with the dispersion liquid E obtained as described above, these dispersion liquids were mixed to produce the coating solution for the heat-sensitive recording layer and further in the same manner as in Example 30, the heat-sensitive recording material (36) of the invention was obtained.
• Dispersion liquid E was prepared in the same manner as in Example 31 except that 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (an image stabilizer) used in the preparation of dispersion liquid E. Furthermore, the heat-sensitive recording material of the invention (37) was obtained in the same manner as in Example 31.
• the heat-sensitive recording materials of the invention (38) and (39) were obtained in the same manner as in Example 30 except that 20 parts of amorphous silica (trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.) and 40 parts of aluminum hydroxide (trade name: HYGILITE H42, manufactured by Showa Denko K.K.) were used, respectively, instead of 40 parts of calcite light calcium carbonate (UNIVER 70; inorganic pigment) used in the preparation of dispersion liquid D-2.
• amorphous silica trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.
• 40 parts of aluminum hydroxide trade name: HYGILITE H42, manufactured by Showa Denko K.K.
• the heat-sensitive recording material of the invention (40) was obtained in the same manner as in Example 30 except that a 2.5% sulfo-modified polyvinyl alcohol (trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution was used instead of a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C.
• a 2.5% sulfo-modified polyvinyl alcohol trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
• the heat-sensitive recording material of the invention (41) was obtained in the same manner as in Example 30 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% adipic acid dihydrazide aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and
• the heat-sensitive recording material of the invention (42) was obtained in the same manner as in Example 30 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% glyoxal aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• the heat-sensitive recording material of the invention (43) was obtained in the same manner as in Example 30 except that recycled paper (50 g/m 2 ) made of recycled pulp (70%) and LBKP (30%) and having smoothness measured by JIS-P8119 of 170 seconds was used instead of woodfree paper used as the substrate in Example 30.
• the heat-sensitive recording material of the invention (44) was obtained in the same manner as in Example 30 except that, after formation of an undercoat layer on a substrate, the coating solution for a heat-sensitive recording layer obtained in Example 30 and the following coating solution for a protective layer were applied simultaneously with a curtain coater and the resultant coatings were dried to form multiple layers and the surface of the laminated protective layer was subjected to calendaring treatment instead of applying the coating solution for a heat-sensitive recording layer, drying and calendaring the resultant coating after formation of an undercoat layer on a substrate in the ⁇ Preparation of heat-sensitive recording material> of Example 30.
• the dried coating amount of the protective layer was 2.0 g/m 2 .
• a coating solution for the protective layer with the same composition as that of the coating solution for the protective layer in Example 10 of the first embodiment was prepared by the same manner.
• the heat-sensitive recording materials of the invention (45) to (47) were obtained in the same manner as in Example 39 except that 40 parts of aluminum hydroxide (trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.), 40 parts of kaolin (trade name: KAOBRITE; volume mean diameter: 2.5 ⁇ m; manufactured by Shiraishi Kogyo K.K.) and 20 parts of amorphous silica (trade name: MIZUKASIL P707; volume mean diameter: 2.2 ⁇ m; manufactured by Mizusawa Industrial Chemicals, Ltd.) were used, respectively, instead of 40 parts of aluminum hydroxide (HYGILITE H42; an inorganic pigment) used in the preparation of the coating solution for a protective layer in Example 39.
• aluminum hydroxide trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.
• KAOBRITE volume mean diameter: 2.5 ⁇ m
• the heat-sensitive recording materials of the invention (48) to (54) were obtained in the same manner as in Example 30 except that dimethylbenzyl oxalate (trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.), m-terphenyl, ethylene glycol tolyl ether, p-benzylbiphenyl, 1,2-diphenoxymethylbenzene, diphenylsulfone and 1,2-diphenoxyethane were used, respectively, instead of 2-benzyloxynaphthalene (a sensitizer) used in the preparation of dispersion liquid C in Example 30.
• dimethylbenzyl oxalate trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.
• m-terphenyl ethylene glycol tolyl ether
• p-benzylbiphenyl 1,2-diphenoxymethylbenzene
• diphenylsulfone 1,2-diphenoxyethane
• the heat-sensitive recording materials of the invention (55) to (59) were obtained in the same manner as in Example 30 except that 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluorane, 2-anilino-3-methyl-6-di-n-amylaminofluorane and 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluorine were used, respectively, instead of 2-anilino-3-methyl-6-diethylaminofluorane (an electron-donating colorless dye) used in the preparation of dispersion liquid A in Example 30.
• 2-anilino-3-methyl-6-diethylaminofluorane an electron-donating colorless dye
• the heat-sensitive recording material of the invention (60) was obtained in the same manner as in Example 30 except that an air knife coater was used instead of the curtain coater used in the application of the coating solution for a heat-sensitive recording layer in Example 30.
• the comparative heat-sensitive recording materials (65) and (66) were obtained in the same manner as in Example 30 except that 2,2'-bis(4-hydroxyphenol)propane (bisphenol A) and 4,4'-di-hydroxydiphenylsulfone were used, respectively, instead of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in Example 30.
• the comparative heat-sensitive recording material (67) was obtained in the same manner as in Example 30 except that the amount of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in Example 30 was changed from 20 parts to 4 parts.
• the comparative heat-sensitive recording material (68) was obtained in the same manner as in Example 30, except that the application amount of the coating solution for the heat-sensitive recording layer was changed to be 10 g/m 2 in Example 30.
• the heat-sensitive recording materials (35) to (64) of the invention and the heat-sensitive recording materials (65) to (68) for comparison obtained in the above described manner were subjected to the following measurements and evaluations. The results of the measurements and evaluations are shown in the following Table 2.
• the sensitivity was measured by the same evaluation and method in Examples of the first embodiment.
• the background portions of the respective heat-sensitive recording material surfaces were measured by Macbeth reflection densitometer (trade name: RD-918, manufactured by Macbeth Co.).
• the background fogging was evaluated by the same evaluation and method in Examples of the first embodiment.
• the image storability was evaluated by the same evaluation and method in Examples of the first embodiment.
• the chemical resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the printing troubles caused by friction between a head and a recording material was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink jet recording suitability was evaluated by the same evaluation and method in Examples of the first embodiment.
• the contact angle was measured by the same evaluation and method in Examples of the first embodiment.
• the ion concentration was measured by the same evaluation and method in Examples of the first embodiment.
• the heat-sensitive recording materials (36) and (37) containing the image stabilizers were provided with improved image storability and ink resistance and the heat-sensitive recording material (40) containing a preferable adhesive (protection colloid) was provided with further improved sensitivity and lowered background fogging. Addition of the image stabilizers was found effective to give particularly excellent stamping suitability and handling easiness.
• the heat-sensitive recording materials (44) to (47) having protective layers containing specified inorganic pigments suitable for the first embodiment of the invention the image storability and the ink resistance (chemical resistance) could further be improved.
• the comparative heat-sensitive recording materials (65) to (68) containing no compound represented by the general formula (1) as the electron-accepting compound not only the high sensitivity was achieved but also the heat-sensitive recording materials were inferior in the image storability, chemical resistance, and ink jet suitability and thus the properties and abilities which the heat-sensitive recording material was required to have were not satisfied together.
• the heat-sensitive recording material (68) for which the coating amount was increased the material consumption amount was increased and effects on the environments were significant and further the energy was consumed so much at the time of drying and in addition, the drying temperature was required to be at a high temperature and accordingly, the background whiteness was deteriorated and the image storability tended to be deteriorated.
• the heat-sensitive recording materials of the third embodiment of the invention were produced by the following procedure by employing the following component constitutions and application methods and at the time of production, the coloring density was adjusted to be 1.20 or higher in the case of energy application at 15.2 mJ/mm 2 by the thermal head. ⁇ Preparation of coating solution for heat-sensitive recording layer)
• the dispersion liquid A with the same composition as that of the dispersion liquid A in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid B with the same composition as that of the dispersion liquid B in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid C with the same composition as that of the dispersion liquid C in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid D with the same composition as that of the dispersion liquid D in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the following components were mixed to give a coating solution for a heat-sensitive recording layer.
• the coating solution for the undercoat layer of the support with the same composition as that of the solution in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• Woodfree paper having smoothness measured by JIS-P8119 of 150 seconds was prepared as a substrate.
• the coating solution for an undercoat layer of a substrate obtained above was applied to the surface of the woodfree paper by a blade coater so that the coating amount after drying became 8 g/m 2 and an undercoat layer was thus formed.
• the smoothness measured by JIS-P8119 of the substrate became 350 seconds.
• the coating solution for a heat-sensitive recording layer obtained above was then applied to the undercoat layer with a curtain coater so that the coating amount after drying became 4 g/m 2 .
• the resultant coating was dried and a heat-sensitive recording layer was thus obtained.
• the surface of the thus-formed heat-sensitive recording layer was then subjected to calendaring treatment and a heat-sensitive recording material of the invention (69) was obtained.
• the color development density of the obtained heat-sensitive recording material (69) (measured by Macbeth reflection densitometer RD-918) at an energy, applied to a thermal head, of 15.2 mJ/mm 2 , which was measured according to the same conditions and method as those in evaluations described later, was 1.28.
• Dispersion liquid E with the same composition as that in Example 2 of the second embodiment was prepared by the same manner.
• the dispersion liquids A, B, C and D were prepared in the same manner as in Example 60 and together with the dispersion liquid E obtained as described above, these dispersion liquids were mixed to produce the coating solution for the heat-sensitive recording layer and further in the same manner as in Example 60, the heat-sensitive recording material (70) of the invention was obtained.
• Example 61 except that 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (an image stabilizer) used in the preparation of dispersion liquid E. Furthermore, the heat-sensitive recording material of the invention (71) was obtained in the same manner as in Example 61.
• the heat-sensitive recording materials of the invention (72) and (73) were obtained in the same manner as in Example 60 except that 20 parts of amorphous silica (trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.) and 40 parts of aluminum hydroxide (trade name: HYGILITE H42, manufactured by Showa Denko K.K.) were used, respectively, instead of 40 parts of calcite light calcium carbonate (UNIVER 70; inorganic pigment) used in the preparation of dispersion liquid D.
• amorphous silica trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd.
• 40 parts of aluminum hydroxide trade name: HYGILITE H42, manufactured by Showa Denko K.K.
• the heat-sensitive recording material of the invention (74) was obtained in the same manner as in Example 60 except that a 2.5% sulfo-modified polyvinyl alcohol (trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution was used instead of a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A B and C.
• a 2.5% sulfo-modified polyvinyl alcohol trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
• the heat-sensitive recording material of the invention (75) was obtained in the same manner as in Example 60 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% adipic acid dihydrazide aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B
• the heat-sensitive recording material of the invention (76) was obtained in the same manner as in Example 60 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% glyoxal aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210,
• the heat-sensitive recording material of the invention (77) was obtained in the same manner as in Example 60 except that recycled paper (50 g/m 2 ) made of recycled pulp (70%) and LBKP (30%) and having smoothness measured by JIS-P8119 of 170 seconds was used instead of woodfree paper used as the substrate in Example 60.
• the heat-sensitive recording material of the invention (78) was obtained in the same manner as in Example 60 except that, after formation of an undercoat layer on a substrate, the coating solution for a heat-sensitive recording layer obtained in Example 60 and the following coating solution for a protective layer were applied simultaneously with a curtain coater and the resultant coatings were dried to form multiple layers and the surface of the laminated protective layer was subjected to calendaring treatment instead of applying the coating solution for a heat-sensitive recording layer, drying and calendaring the resultant coating after formation of an undercoat layer on a substrate in the ⁇ Preparation of heat-sensitive recording material> of Example 60.
• the dried coating amount of the protective layer was 2.0 g/m 2 .
• a coating solution for the protective layer with the same composition as that of the coating solution for the protective layer in Example 10 of the first embodiment was prepared by the same manner.
• the heat-sensitive recording materials of the invention (79) to (81) were obtained in the same manner as in Example 69 except that 40 parts of aluminum hydroxide (trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.), 40 parts of kaolin (trade name: KAOBRITE; volume mean diameter: 2.5 ⁇ m; manufactured by Shiraishi Kogyo K.K.) and 20 parts of amorphous silica (trade name: MIZUKASIL P707; volume mean diameter: 2.2 ⁇ m; manufactured by Mizusawa Industrial Chemicals, Ltd.) were used, respectively, instead of 40 parts of aluminum hydroxide (HYGILITE H42; an inorganic pigment) used in the preparation of the coating solution for a protective layer in Example 69.
• aluminum hydroxide trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.
• KAOBRITE volume mean diameter: 2.5 ⁇ m
• the heat-sensitive recording materials of the invention (82) to (88) were obtained in the same manner as in Example 60 except that dimethylbenzyl oxalate (trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.), m-terphenyl, ethylene glycol tolyl ether, p-benzylbiphenyl, 1,2-diphenoxymethylbenzene, diphenylsulfone and 1,2-diphenoxyethane were used, respectively, instead of 2-benzyloxynaphthalene (a sensitizer) used in the preparation of dispersion liquid C.
• dimethylbenzyl oxalate trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.
• m-terphenyl ethylene glycol tolyl ether
• p-benzylbiphenyl 1,2-diphenoxymethylbenzene
• diphenylsulfone 1,2-diphenoxyethane
• the heat-sensitive recording materials of the invention (89 to (93) were obtained in the same manner as in Example 60 except that 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluorane, 2-anilino-3-methyl-6-di-n-amylaminofluorane and 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluorine were used, respectively, instead of 2-anilino-3-methyl-6-diethylaminofluorane (an electron-donating colorless dye) used in the preparation of dispersion liquid A in Example 60.
• 2-anilino-3-methyl-6-diethylaminofluorane an electron-donating colorless dye
• the heat-sensitive recording material of the invention (94) was obtained in the same manner as in Example 60 except that an air knife coater was used instead of the curtain coater used in the application of the coating solution for a heat-sensitive recording layer in Example 60.
• BTUM 4-hydroxy-4'-isopropoxydiphenylsulfone
• 2,4-bis(phenylsulfonyl)phenol were used, respectively, instead of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B
• the comparative heat-sensitive recording material (99) was obtained in the same manner as in Example 60 except that 4,4'-di-hydroxydiphenylsulfone was used instead of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in Example 60.
• the comparative heat-sensitive recording material (100) was obtained in the same manner as in Example 60, except that the amount of 4-hydroxybenzenesulfonealinide (the electron-accepting compound) used for the preparation of the dispersion liquid B of Example 60 was changed to be 4 parts form 20 parts.
• the comparative heat-sensitive recording material (101) was obtained in the same manner as in Example 60, except that the woodfree paper with smoothness of 150 seconds measured according to JIS-P8119 used for the support for Example 60 was changed to the wood-free paper with smoothness of 30 seconds and neither dispersion liquid of 30% zinc stearate nor paraffin wax was used for the coating solution for the heat-sensitive recording layer.
• the comparative heat-sensitive recording material (102) was obtained in the same manner as in Example 60, except that the wood-free paper with smoothness of 150 seconds measured according to JIS-P8119 used for the support for Example 60 was changed to the coated paper with smoothness of 1,000 seconds and the amount of the dispersion liquid of 30% zinc stearate used for the coating solution for the heat-sensitive recording layer was changed to be 45 parts from 15 parts and the amount of the paraffin wax was changed to be 45 parts from 15 parts.
• the heat-sensitive recording materials (69) to (98) of the invention and the heat-sensitive recording materials (99) to (102) for comparison obtained in the above described manner were subjected to the following measurements and evaluations. The results of the measurements and evaluations are shown in the following Table 3.
• the sensitivity was measured by the same evaluation and method in Examples of the first embodiment.
• the static friction coefficient and dynamic friction coefficient were measured. That is, the heat-sensitive recording material having the heat-sensitive recording layer only in one face was cut into a size of 100 mm width and 200 mm length at a thermostat chamber at 23°C (a heat-sensitive recording material piece A) and stuck to a smooth plate while the recording face being set upside.
• a heat-sensitive recording material piece B cut in a size of 60 mm width ad 120 mm length in the same manner was wound around a load weight [W 0 1.96 N (200 gf): hereinafter, referred to as sleigh] while the recording face being set in the inside and fixed by a cellophane tape.
• the sleigh was connected to the load cell by a monofilament string and the sleigh wrapped with the heat-sensitive recording material piece B was lightly put on the heat-sensitive recording face of the heat-sensitive recording material piece A stuck to the smooth plate and the smooth plate was moved at a testing speed 600 mm/min to measure the static friction coefficient and the dynamic friction coefficient.
• the image storability was measured by the same evaluation and method in Examples of the first embodiment.
• the background fogging was evaluated by the same evaluation and method in Examples of the first embodiment.
• the chemical resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the printing troubles caused by friction between a head and a recording material was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink jet recording suitability was evaluated by the same evaluation and method in Examples of the first embodiment.
• the contact angle was measured by the same evaluation and method in Examples of the first embodiment.
• the ion concentration was measured by the same evaluation and method in Examples of the first embodiment.
• the heat-sensitive recording materials (70) and (71) containing the image stabilizers were provided with improved image storability and ink resistance and the heat-sensitive recording material (74) containing a preferable adhesive (protection colloid) was provided with further improved sensitivity and lowered background fogging. Addition of the image stabilizers was found effective to give particularly excellent stamping suitability and handling easiness.
• the heat-sensitive recording materials (78) to (81) having protective layers containing specified inorganic pigments suitable for the third embodiment of the invention the image storability and the ink resistance (chemical resistance) could further be improved.
• the dispersion liquid A with the same composition as that of the dispersion liquid A in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid B with the same composition as that of the dispersion liquid B in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid C with the same composition as that of the dispersion liquid C in Example 1 of the first embodiment was prepared by the same manner as in Example 1.
• the dispersion liquid D-4 with a volume mean diameter of 2.0 ⁇ m was obtained by mixing the following respective components and then dispersing them.
• the volume mean diameter was measured in the same manner as the case of the dispersion liquid A.
• the coating solution for the undercoat layer of the support with the same composition as that of the solution in Example 1 of the first embodiment was prepared by the same manner as in Example 1, except that distilled water was used for water.
• Woodfree paper having smoothness measured by JIS-P8119 of 150 seconds was prepared as a substrate.
• the coating solution for an undercoat layer of a substrate obtained above was applied to the surface of the woodfree paper by a blade coater so that the coating amount after drying became 8 g/m 2 and an undercoat layer was thus formed.
• the smoothness measured by JIS-P8119 of the substrate became 350 seconds.
• the coating solution for a heat-sensitive recording layer obtained above was then applied to the undercoat layer with a curtain coater so that the coating amount after drying became 4 g/m 2 .
• the resultant coating was dried and a heat-sensitive recording layer was thus obtained.
• the surface of the thus-formed heat-sensitive recording layer was then subjected to calendaring treatment and a heat-sensitive recording material of the invention (103) was obtained
• Dispersion liquid E with the same composition as that in Example 2 of the second embodiment was prepared by the same manner.
• the dispersion liquids A, B, C and D-4 were prepared in the same manner as in Example 90 and together with the dispersion liquid E obtained as described above, these dispersion liquids were mixed to produce the coating solution for the heat-sensitive recording layer and further in the same manner as in Example 90, the heat-sensitive recording material (104) of the invention was obtained.
• Dispersion liquid E was prepared in the same manner as in Example 91 except that 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (an image stabilizer) used in the preparation of dispersion liquid E. Furthermore, the heat-sensitive recording material of the invention (105) was obtained in the same manner as in Example 91.
• the heat-sensitive recording materials of the invention (106) was obtained in the same manner as in Example 90 except that 20 parts of amorphous silica (trade name: MIZUKASIL P832, manufactured by Mizusawa Industrial Chemicals, Ltd., boiled linseed oil absorption amount: 145 ml/100 g), instead of 40 parts of calcite light calcium carbonate (UNIVER 70; inorganic pigment) used in the preparation of dispersion liquid D-4.
• the volume mean diameter of the pigment dispersion liquid D for the present example was 2.5 ⁇ m.
• the heat-sensitive recording materials of the invention (106) was obtained in the same manner as in Example 90 except that 20 parts of aluminum hydroxide (trade name: HYGILITE H42, manufactured by Showa Denko K.K., boiled linseed oil absorption amount: 43 ml/100 g), instead of 40 parts of calcite light calcium carbonate (UNIVER 70; inorganic pigment) used in the preparation of dispersion liquid D-4.
• the volume mean diameter of the pigment dispersion liquid D for the present example was 0.8 ⁇ m.
• the heat-sensitive recording material of the invention (108) was obtained in the same manner as in Example 90 except that a 2.5% sulfo-modified polyvinyl alcohol (trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution was used instead of a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C.
• a 2.5% sulfo-modified polyvinyl alcohol trade name: GOHSERAN L3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
• the heat-sensitive recording material of the invention (109) was obtained in the same manner as in Example 90 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% adipic acid dihydrazide aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive used in the preparations of dispersion liquids A, B and C was changed to a 2.5% diacetone-modified polyvinyl alcohol (trade name: D500, manufactured by Unitika Ltd.) aqueous solution to prepare dispersion liquids A, B and
• the heat-sensitive recording material of the invention (110) was obtained in the same manner as in Example 90 except that a 2.5% polyvinyl alcohol aqueous solution (an adhesive) used in the preparations of dispersion liquids A, B and C was changed to a 2.5% acetoacetyl-modified polyvinyl alcohol (trade name: GOHSEFIMER Z210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) aqueous solution to prepare dispersion liquids A, B and C, and that 13 parts of a 5% glyoxal aqueous solution (a crosslinking agent) was added to the coating solution for a heat-sensitive recording layer obtained by mixing the thus-obtained dispersion liquids A, B and C.
• a 2.5% polyvinyl alcohol aqueous solution an adhesive
• acetoacetyl-modified polyvinyl alcohol trade name: GOHSEFIMER Z210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
• the heat-sensitive recording material of the invention (111) was obtained in the same manner as in Example 90 except that recycled paper (50 g/m 2 ) made of recycled pulp (70%) and LBKP (30%) and having smoothness measured by JIS-P8119 of 170 seconds was used instead of woodfree paper used as the substrate in Example 90.
• the heat-sensitive recording material of the invention (112) was obtained in the same manner as in Example 90 except that, after formation of an undercoat layer on a substrate, the coating solution for a heat-sensitive recording layer obtained in Example 90 and the following coating solution for a protective layer were applied simultaneously with a curtain coater and the resultant coatings were dried to form multiple layers and the surface of the laminated protective layer was subjected to calendaring treatment instead of applying the coating solution for a heat-sensitive recording layer, drying and calendaring the resultant coating after formation of an undercoat layer on a substrate in the ⁇ Preparation of heat-sensitive recording material> of Example 90.
• the dried coating amount of the protective layer was 2.0 g/m 2 .
• a coating solution for the the protective layer was prepared in the same manner and same composition of the coating solution as in Example 10 of the first embodiment.
• the heat-sensitive recording materials of the invention (113) to (115) were obtained in the same manner as in Example 99 except that 40 parts of aluminum hydroxide (trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.), 40 parts of kaolin (trade name: KAOBRITE; volume mean diameter: 2.5 ⁇ m; manufactured by Shiraishi Kogyo K.K.) and 20 parts of amorphous silica (trade name: MIZUKASIL P707; volume mean diameter: 2.2 ⁇ m; manufactured by Mizusawa Industrial Chemicals, Ltd.) were used, respectively, instead of 40 parts of aluminum hydroxide (HYGILITE H42; an inorganic pigment) used in the preparation of the coating solution for a protective layer in Example 99.
• aluminum hydroxide trade name: HYGILITE H43; volume mean diameter: 0.7 ⁇ m; manufactured by Showa Denko K.K.
• KAOBRITE volume mean diameter: 2.5 ⁇ m
• the heat-sensitive recording materials of the invention (116) to (122) were obtained in the same manner as in Example 90 except that dimethylbenzyl oxalate (trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.), m-terphenyl, ethylene glycol tolyl ether, p-benzylbiphenyl, 1,2-diphenoxymethylbenzene, diphenylsulfone and 1,2-diphenoxyethane were used, respectively, instead of 2-benzyloxynaphthalene (a sensitizer) used in the preparation of dispersion liquid C.
• dimethylbenzyl oxalate trade name: HS3520R-N, manufactured by Dainippon Ink and Chemicals, Inc.
• m-terphenyl ethylene glycol tolyl ether
• p-benzylbiphenyl 1,2-diphenoxymethylbenzene
• diphenylsulfone 1,2-diphenoxyethane
• the heat-sensitive recording materials of the invention (123) to (127) were obtained in the same manner as in Example 90 except that 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluorane, 2-anilino-3-methyl-6-di-n-amylaminofluorane and 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluorine were used, respectively, instead of 2-anilino-3-methyl-6-diethylaminofluorane (an electron-donating colorless dye) used in the preparation of dispersion liquid A in Example 90.
• 2-anilino-3-methyl-6-diethylaminofluorane an electron-donating colorless dye
• the heat-sensitive recording material of the invention (128) was obtained in the same manner as in Example 60 except that an air knife coater was used instead of the curtain coater used in the application of the coating solution for a heat-sensitive recording layer in Example 90.
• BTUM 4-hydroxy-4'-isopropoxydiphenylsulfone
• 2,4-bis(phenylsulfonyl)phenol were used, respectively, instead of 4-hydroxybenzenesulfoneanilide (an electron-accepting compound) used in the preparation of dispersion liquid B in
• the comparative heat-sensitive recording material (133) was obtained in the same manner as in Example 90, except that the amount of calcite type light calcium carbonate 40 parts used for the pigment dispersion liquid D-4 was changed to aluminum hydroxide (boiled linseed oil absorption amount: 22 ml/100 g) 40 parts.
• the volume mean diameter of the pigment dispersion liquid D-4 for the Comparative Example was 4.0 ⁇ m.
• the conparative heat-sensitive recording material (134) was obtained in the same manner as in Example 90, except that the amount of calcite type light calcium carbonate 40 parts used for the pigment dispersion liquid D-4 was changed to amorphous silica (boiled linseed oil absorption amount: 210 ml/100 g) 40 parts.
• the volume mean diameter of the pigment dispersion liquid D-4 for the Comparative Example was 2.4 ⁇ m.
• the heat-sensitive recording materials (103) to (132) of the invention and the heat-sensitive recording materials (133) and (134) for comparison obtained in the above described manner were subjected to the following measurements and evaluations. The results of the measurements and evaluations are shown in the following Table 4.
• the sensitivity was measured by the same evaluation and method in Examples of the first embodiment.
• the surface of the thermal head used for the above-mentioned sensitivity measurement and the recording quality of the heat-sensitive recording materials were observed and evaluated according to the following standards.
• the image density (density after kept still) was measured by Macbeth reflection densitometer (RD-918) after each heat-sensitive recording material printed in the above-mentioned condition (1) was closely wrapped with a sheet of a polyvinyl chloride wrapping film (trade name: Polymawrap 300, manufactured by Shin-Etsu Chemical Co., Ltd.) and left in environments at 25°C and 50% RH for 24 hours.
• the rate (the plasticizer retention rate) to the image density immediately after the printing carried out in the same condition (1) was calculated. The numeric value was higher, the image storability could be said better.
• Plasticizer retention rate [(image density after the storage under the above-mentioned condition) / (image density immediately after printing)] ⁇ 100
• the background fogging was evaluated by the same evaluation and method in Examples of the first embodiment.
• the image storability was evaluated by the same evaluation and method in Examples of the first embodiment.
• the chemical resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the printing troubles caused by friction between a head and a recording material was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink resistance was evaluated by the same evaluation and method in Examples of the first embodiment.
• the ink jet recording suitability was evaluated by the same evaluation and method in Examples of the first embodiment.
• the contact angle was measured by the same evaluation and method in Examples of the first embodiment.
• the ion concentration was measured by the same evaluation and method in Examples of the first embodiment.
• the heat-sensitive recording materials (104) and (105) containing the image stabilizers were provided with improved image storability and ink resistance and the heat-sensitive recording material (108) containing a preferable adhesive (protection colloid) was provided with further improved sensitivity and lowered background fogging. Addition of the image stabilizers was found effective to give particularly excellent stamping suitability and handling easiness.
• the heat-sensitive recording materials (112) to (115) having protective layers containing specified inorganic pigments suitable for the fourth embodiment of the invention the image storability and the ink resistance (chemical resistance) could further be improved.
• the invention can provide a heat-sensitive recording material which is scarcely curled and suitable for high quality recording and transportation; which is useful for forming images with high sensitivity and high density (good printing suitability) with suppressed fogging density in the background portion (background fogging); which is excellent in the image storability and chemical resistance after printing and has ink-jet suitability without causing hue failure and blurring of the ink jet images or image color fading attributed the ink for ink jet; and which shows good matching property to the thermal head and scarcely causes head wear or head stain even in the case of application to a high speed or a high functional printer having a partial graze structure (good head matching property in the high speed printing).
• the invention also provides a heat-sensitive recording material, in addition to the above-mentioned properties, which gives sharp and high quality images, is excellent in the light fastness of the formed images, comprises a heat-sensitive recording layer or a protective layer for printing or stamping without blurring, is produced at a low cost with a saved amount of coating (environmental friendly property), and is provided with an plain paper-like touch.

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