IMAGE-RECEIVING MATERIAL

Abstract: An image-receiving material for use in an image-forming process using as an inking material a dye capable of forming color when adsorbed on an electron-accepting substance, which comprises a substrate having provided thereon a color-developing layer containing silica as a main agent for developing color of the dye. The use of silica as color-­ developing agent improves transparency of the color-­ forming layer and provides a clear image having a high coloration density.

Description: SPECIFICATION TITLE OF THE INVENTION IMAGE RECEPTOR TECHNICAL FIELD This invention relates to an image receptor used for image recording such as electrophotography or printer. More specifically, the invention relates to an image receptor useful for image recording using only a dye material itself as inking material. BACKGROUND ART A variety of image recording methods using only a dye material itself as inking material have been proposed hitherto. For instance, there are known a one-shot electrophotographic method using light transmitting particles containing a subliming color former as disclosed in Japanese Patent Publication No. 49307/80; a sublimation transfer method in which a color sheet prepared by coating a condenser paper or the like with a subliming dye is heated by a heating element so that the sublimed dye develops color on an image receptor; and a gas jet recording method disclosed in Japanese Patent Publication No. 2020/81 in which gas of a subliming dye is electrically injected and controlled to obtain a dye image on an image receptor. In any of the above-described methods, it is necessary to let the dye develop color in a molecular state and uniformly on an image receptor for obtaining a clear dye image. For this purpose, there is usually used an image receptor carrying a dye developer. In the prior art, bottom paper for pressure-sensitive recording using activated clay as color developer has been used for said image receptor. Such bottom pauper, however, had the problem of reduced color purity of the dye image for such reasons that (1) activated clay is tinted in light brown, and (2) the color-forming layer becomes opaque because of poor transparency of activated clay. Therefore, said bottom paper was not suitable for color recording especially. DISCLOSURE OF INVENTION The object of this invention is to provide an image receptor used for image recording employing only a dye material itself as inking material, in which the color-forming layer containing color developer is transparent. The image receptor of this invention is of a structure in which a color forming layer principally composed of silica is provided on a substrate, and said color forming layer has the function to let the dye develop color in a molecular state and uniformly. BRIEF DESCRIPTION OF DRAWING The drawing is a schematic sectional view showing an embodiment of image receptor in accordance with this invention. BEST MODE FOR CARRYING OUT THE INVENTION In an embodiment of image receptor in accordance with this invention, a color-forming layer 3 principally composed of silica 2 is carried on a substrate 1 as illustrated in the drawing. Silica 2 is used as color developer and has excellent transparency. It is colorless and suffers from no thermal yellowing because of heat resistance, making it possible to obtain a dye image with high color purity. As silica used in this invention, there can be employed silicates represented by xM2 ySiO2 such as xNa2O-ySiO2r xA12O3.ySiO2 and xMgO.ySiO2, silicic acids represented by xH2O.ySiO2, and amorphous, glassy or colloidal silicon dioxide. Among them, colloidal silica with a pH of 6 or below is especially excellent as it has the excellent ability to cause color development of dye and that the color forming layer can be easily made transparent. For substrate 1, various types of substrate material can be applied according to the purpose of use. For instance, fine-quality paper or art paper with high whiteness is suited for reflective pictures such as documents. Plastic sheet with excellent transparency and heat resistance such as vinylon, cellophane, acetyl-cellulose or the like is suited for transmitting pictures such as slides. Color forming layer 3 can be made transparent by coating silica finely dispersed in a binder on substrate 1 by a usual means such as bar coater. In this case, the particle size of silica is preferably not greater than 0.1 micron. The binder is preferably one which is strong in binding force, transparent and also excellent in silica dispersability. For instance, styrene-butadiene copolymer, ethyl cellulose, acrylic resin or the like is preferred. A combination of styrene-butadiene copolymer and colloidal silica is especially suited for the applications where the image receptor is heated since such combination is hardened and improved in heat resistance when heated. For attaining better color developing efficiency of the dye, it is preferred to make the color forming layer porous so that the dye becomes more easily absorbed by silica. For this purpose, it is desirable that the amount of the binder used is not greater than 30% by weight based on silica. The coating weight of the color forming layer for effecting sufficient color development of the dye is preferably 1 - 10 glm2 although it is variable depending on the type of the dye used. It is of course possible, where necessary, to add a dispersant when dispersing silica in binder or to add an anti-oxidant or a quencher to the color forming layer for the purpose of preventing color fading oY eV 9 dye. Further, an electron acceptant material such as a known organic or inorganic acid may be used jointly with silica as a color developing assistant. Example 1 The following materials were well stirred and mixed by a mixer to form a color forming layer solution. Color developer: Silica (colloidal silica "Snowtex O" produced by Nissan Kagaku KK (pH: 2-4, solids: 20 wt%)) .. - 100 parts by weight Binder: Styrene-butadiene copolymer ("Danbond" produced by Nippon Zeon KK (solids: 40 wt%)) ..... 5 parts by weight This color forming layer solution was coated on a sheet of art paper to a coating weight (after drying) of 6 g/mê to obtain an image receptor A for reflective picture. Example 2 The color forming layer solution of Example 1 was coated on a vinylon sheet to a coating weight of 6 g/mê to obtain an image receptor B for transmitting picture. Transmittance of the image receptor was 90%. Example 3 A mixture of the following formulation was sufficiently dispersed by an attritor to prepare a color forming layer solution. Color developer: Silica ("Finesil T-32" (pH 6) produced by Tokuyama Soda KK) .. 100 parts by weight Binder: Ethyl cellulose ........... 10 parts by weight Solvent: Nethylene chloride ......... 100 parts by weight This color forming layer solution was coated on a fine-quality paper to a coating weight (after drying) of 8 g/m2 to obtain an image receptor C for reflective picture. Experiment 1 A yellow disperse dye ("PT-52Y" produced by Mitsubishi Kasei Kogyo KK), a magenta basic dye (C.I. Basic Red 9) and a magenta subliming color former (7'diethylamino-1,3,3,5-tetramethyl-indolinobenzospiropyran) were coated on a 15 micron thick condenser paper by using ethyl cellulose as binder to prepare three types of color sheets D, E and F. The image receptor obtained in the Examples and said color sheets were placed one upon the other and heated under the conditions of 1800 C, 5 seconds and 1 kg/cm21 whereby the distinct yellow and magenta color images such as shown in Table 1 were obtained on the image receptor. The numerical figures in the table indicate color density. Table 1 Color sheet EMI7.1 <tb> <SEP> D(Db) <SEP> D(Db) <SEP> E(Dg) <SEP> F(Dg) <tb> Image <SEP> A <SEP> 1.3 <SEP> 1.3 <SEP> 1.6 <tb> receptor <SEP> B <SEP> 1.3* <SEP> 1.4* <SEP> T <SEP> <SEP> 1.7* <tb> <SEP> C <SEP> 1.1 <SEP> 1.2 <SEP> 1.5 <tb> *: transmission density Experiment 2 Color sheet F was superposed on the yellow color images obtained by using color sheet D in Experiment 1, and heated under the same conditions as Experiment 1, whereby the distinct red color images such as shown in Table 2 were obtained. Table 2 Color sheet D + F EMI8.1 <tb> <SEP> Db <SEP> Dg <SEP> j <SEP> <SEP> DR <tb> <SEP> A <SEP> 1.6 <SEP> 1.7 <SEP> 0.2 <tb> Image <SEP> B <SEP> 1.6* <SEP> 1.8* <SEP> O.2t <SEP> <tb> pto <SEP> <tb> <SEP> C <SEP> 1.3 <SEP> 1.4 <SEP> 0.2 <tb> *: transmission density INDUSTRIAL APPLICABILITY The image receptor of this invention can make the color forming layer transparent as silica with excellent transparency is used as color developer. Therefore, there is no possibility that the dye which developed color below the color forming layer be concealed by the color developer thereabove to reduce the developed color density, and the whole color forming layer becomes a colored transparent body, so that a dye image with high developed color density can be obtained, enabling realization of high-quality pictures by electrophotography or printers.

Claims: WHAT IS CLAIMED IS: 1. An image receptor having a structure in which a color forming layer causing color development of a dye which develops color when adsorbed by an electronacceptant material is provided on a substrate, characterized in that said color forming layer contains silica as main color developer of said dye. 2. An image receptor according to Claim 1, wherein the color forming layer contains silica and a transparent resin binder. 3. An image receptor according to Claim 2, wherein the amount of the resin binder is 30% by weight or less based on silica. 4. An image receptor according to Claim 2, wherein the resin binder is a styrene-butadiene copolymer. 5. An image receptor according to Claim 1, wherein silica is a solidfied material of colloidal silica having a pH of 6 or below. 6. An image receptor according to Claim 1, wherein the substrate is paper. 7. An image receptor according to Claim 1, wherein the substrate is a transparent plastic film.

Inventors: SHIMIZU, TOKIHIKO, TAKASHIMA, YUJI, YUBAKAMI, KEIICHI
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1984
Main classification: B41M5
IPC codes: B41M5