RECORDING MEDIUM AND RECORDING METHOD UTILIZING THE SAME

Abstract: A recording medium is provided which comprises a record­ ing surface causing a directional diffuse reflection. The record­ ing medium has ink receptability, and its recording surface has a specific specular gloss and specific Y 10D65 value. A record­ ing method which employs the recording medium is also pro­ vided.

Description: This invention relates to a recording medium suitable for use in recording methods using ink, particularly a recording medium excellent in ink receptibility and distinctness of recorded image. In ink jet recording, a recording-liquid is discharged and converted to flying droplets by various discharging methods such as (a) an electrostatic attraction method, (b) a method wherein a recording liquid receives mechanical vibration or displacement by a piezoelectric element and (c) a method wherein a recording liquid is heated to foam and the resulting pressure is utilized, whereby the part or whole of the flying droplets are allowed to deposit on a recording medium such as a paper or the like. This ink jet recording is drawing public attention as a recording method which generates less noise and enables high speed and multi-color printing. As the ink for ink jet recording, there are mainly used aqueous inks from the requirements for safety and recording characteristics, and these inks contain, in many cases, a polyhydric alcohol or the like for prevention of nozzle plugging and enhancement of discharging stability. As the recording medium for ink jet recording, conventionally there have been used ordinary papers and so-called ink jet recording papers constituted of a substrate and a porous ink-receiving layer formed on the substrate. However, with the improvements of performance of ink jet recording equipment such as faster recording, multi-color recording and the like as well as with the spread of such equipment, superior and wider characteristics are being required for recording media. That is, a recording medium for ink jet recording capable of providing a recorded image of high resolution and high quality must satisfy basic requirements such as shown below. (1) The reception of an ink by the recording medium is as quick as possible. (2) When two ink dots overlap, the dot formed later does not penetrate into the dot formed previously. (3) Ink dots spread on the recording medium within the range of the maximum acceptable diameter. (4) The shape of ink dots formed on the recording medium is close to a true circle and the circumference of the circle is smooth. (5) The ink dots formed on the recording medium have a high optical density and their circumferences are not blurred. In order to obtain a recorded image quality comparable to that in color photography, by multi-color ink jet recording, the recording medium must further satisfy such requirements as mentioned below in addition to the above basic requirements. (6) The coloring components of ink can develop excellent colors on a recording medium. (7) Since the ink droplets as many as the number of ink colours may possibly be attached at the same spot, the recording medium is excellent particularly in ink fixing. (8) The recording medium has a high degree of whiteness. No recording medium is known yet which satisfies all the above requirements. Other ink recording methods are known, for example, heat-sensitive methods of the sublimating recording type in which a sublimating dye in an ink ribbon is sublimated by thermal head heating and is applied to the ink-receiving layer of a recording medium. In many conventional recording media constituted of a substrate, and a porous ink-receiving layer formed on the substrate, recording liquid is received by the pores of the ink-receiving layer and is fixed. Consequently, the recording liquid penetrates deep into the ink-receiving layer and results in poor distinction of the recorded image. Alternatively, in conventional recording media constituted of a substrate and a non-porous ink-receiving layer formed on the substrate, a non-volatile component in ink such as a polyhydric alcohol remains on the recording media for a long time. (That is, the drying and fixing of ink takes a long time.) This causes, when the recorded image is touched, staining of clothes or impairment of the recorded image. Hitherto, in the art of ink recording media, the substrate has been modified to provide a light reflective backing to enhance image brightness for episcopic projection. In United Kingdom Patent Specification No. 1312115 there is described an image support having one or more gelatine recording layers and a backing substrate having a reflective layer of metal which is preferably finished to be smooth and specularly reflecting. The latter is adopted in place of a diffusing layer. In United States Patent No. 3,222,986 there is disclosed a medium having a pigment or dye receiving coat and a backing substrate that is retro-reflectively reflecting and incorporates for this purpose an arrangement of retro-reflecting cube corners. Other media are also disclosed wherein the substrate incorporates an assembly of retro-reflecting spheres. The present invention is intended to provide a recording medium for ink jet recording that whilst being altogether satisfactory in ink receptibility is also capable of recording a distinct image that has sharp contrast, and gives both a perspective feeling and a high quality sensation. In common with the media just mentioned the ink recording medium of the present invention comprises a substrate; an ink receiving layer thereon; and light reflecting means. In accordance with this invention, this ink recording medium is characterised in that: it has a property of directional diffuse reflection so that light incident thereupon is both diffused and reflected to be concentrated in directions in and about the direction of specular reflection for the incident light. The ink recording medium may be characterised as aforesaid by including: a filler material dispersed in said ink-receiving layer, which filler material thus dispersed is both light diffusing and compatible with the ink receptibility of said ink-receiving layer; and light reflecting means; wherein said light reflecting means and the light diffusing dispersed filler material together impart to the medium said property of directional diffuse reflection. When an image is recorded by ink on the ink recording medium aforesaid, and then observed, it can be perceived to have an improved quality. Larger amounts of reflected light than would occur for ordinary diffuse reflection are observed at certain angles and at these angles any whiteness of the image is intensified. Accordingly the recorded image has a sharp contrast. It also has a mellowness and a perspective feeling neither obtainable by ordinary diffuse reflection nor by non-diffuse reflection. By way of reference it is acknowledged that other image recording media (but not ink recording media including ink receiving layers), having a character of directional diffuse reflection have been disclosed previously. Thus in French Patent Specification No. 1,268,800 there is disclosed a colour photographic medium having photographic colour film layers supported upon a substrate that has a property of directional diffuse reflection. This result, so it is said, is obtained, for example, using a layer incorporating small elements that are microscopic and reflecting - e.g. partially aligned reflector strips. In another example there is provided a supportive substrate having one surface that is roughened, and another that is polished and rendered reflecting e.g. by the evaporation of a reflecting material. Examples of retro-reflective media are also disclosed. Although it is said that the principles disclosed are not limited to colour photographic application, no details of other recording media are given. Mention is also made of French Patent Specification No. 1,349,217. This concerns not a medium for recording as such but a finished recording formed in a recording medium. In one example described, photographic colour film layers are supported on a paper substrate having a matt metallic reflecting coating of e.g. aluminium foil, located between the substrate and the film layers. A finishing lacquer is applied to the top film layer and treated to have a light-scattering matt finish. In other examples described the final photographic colour film layer itself ultimately is given a light scattering matt finish. In these latter examples the film layers are either mounted on a matt metallic reflecting coating or upon a light diffusing lacquer layer and specular reflecting foil. The lacquer layer contains microdispersed mica or other transparent pigment. In all these examples light is diffused at incidence upon the matt finished layer surface reflected from the substrate and again diffused at the surface so to impart a character of directional diffuse reflection. By way of comparison it will be noted that in the preferred embodiments of this invention, to be discussed below, the ink recording layer is produced to a gloss finish. Improved results have been obtained, as tabled below, for ink-receiving layers with a recording surface having a 60° specular gloss of 30% or more and a spectral reflectance Y₁₀D65 value of 60 or more. Filler materials which are not only compatible with the ink receptibility of the ink receiver layer but which also contribute to enhance the same may be chosen from the following: silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulphate, barium sulphate, aluminum silicate, synthetic zeolite, alumina, zinc oxide, lithopone and satin white. It is preferable that the ink receiver layer is a combination of the filler and a resin in which combination the ratio thereof is 2:1 or less so as not to degrade surface smoothness, resolution, gloss and contrast. In the drawings accompanying this specification: Fig. 1 shows the directional diffuse reflection of a recording medium, an embodiment of the present invention, wherein a reflection light flux is distributed in an ellipsoidal form in the direction of specular reflection; Fig. 2 shows an ordinary diffuse reflection wherein a reflection light flux is distributed in an almost spherical form. In order that this invention might be better understood embodiments thereof will now be described and reference will be made to the drawings aforesaid. The description that follows is given by way of example only. The recording medium of the present invention generally comprises a substrate and an ink-receiving layer formed on the substrate. Particularly preferred embodiments of the recording medium include the following: (1) Embodiments wherein the substrate is opaque and causes diffuse reflection, the ink-receiving layer causes directional diffuse reflection, and the recording medium as a whole causes directional diffuse reflection; and (2) Embodiments wherein the substrate is transparent, the ink-receiving layer causes directional diffuse reflection and the recording medium as a whole causes directional diffuse reflection. As the substrate causing directional diffuse reflection used in the present invention, there are films causing multiple reflection, films containing a pigment causing directional diffuse reflection, and substrates obtained by dispersing in a resin a pigment causing directional diffuse reflection and coating the resulting resin on an ordinary substrate. Specific examples of pigments causing directional diffuse reflection include mica, pearl pigments, powders of metals such as aluminum, etc. As the resin, there can be used any conventionally known resins. They include, for example, PVA, starch, acrylic resins and SBR latexes. Besides, all the transparent or opaque substrates which have hitherto been known can be used in the present invention. Preferable as the transparent substrates are, for example, films or sheets of polyester resins, diacetate resins, triacetate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, Cellophane (brand name) and Celluloid (brand name), as well as glass plates. Preferable as the opaque substrates are, for example, ordinary papers, cloths, wood, metal plates, opaque films and synthetic papers, as well as substrates obtained by converting one of the above mentioned transparent substrates into an opaque substrate in accordance with a known method. As the ink-receiving layer used in the present invention, there are mentioned materials having affinities with water and polyhydric alcohols used as liquid components of ink, such as, for example, natural resins (e.g. a polyvinyl alcohol, albumin, gelatin, casein, starch, cationic starch, gum arabic, sodium alginate) and synthetic resins e.g. a polyamide, a polyvinylpyrrolidone, a quaternized polyvinylpyrrolidone, a polyethyleneimine, a polyvinylpyridium halide, a melamine resin, a polyurethane, a carboxymethyl cellulose, a polyester, a SBR latex, an NBR latex, a polyvinyl formal, a polyvinyl methacrylate, a polyvinyl butyral, a polyacrylonitrile, a polyvinyl chloride, a polyvinyl acetate, a phenolic resin, and an alkyd resin. At least one of these materials is used so as to meet the application purpose. The ink-receiving layer can be given a character of diffuse reflection by dispersing in the layer any of the above mentioned pigments. In order for the ink-receiving layer to possess a controlled directionality in diffuse reflection and an enhanced ink receptibility, there can be dispersed in the ink-receiving layer fillers such as silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulphate, barium sulphate, aluminum silicate, synthetic zeolite, alumina, zinc oxide, lithopone and satin white. The mixing ratio of filler to resin is preferably 2:1 or less. A ratio of more than 2:1 is not preferable because the recording medium becomes inferior in surface smoothness, resolution, gloss and contrast. The ink-receiving layer can be formed according to the following methods. In a preferred method, the above mentioned resin and, as necessary, fillers are dissolved or dispersed in an appropriate solvent to prepare a coating fluid, and the coating fluid is coated on a light-transmissive substrate in accordance with a known method such as roll coating, rod bar coating, spray coating or air knife coating and then is dried rapidly. Besides, there can be used a method wherein the above mixture of resin and fillers is subjected to hot melt coating, or a method wherein a sheet for use as an ink-receiving layer is prepared from the above mentioned materials and the resulting sheet is laminated onto a substrate. Cast coating may be employed in place of the above mentioned coating processes. The thickness of the ink-receiving layer formed on the substrate is usually about 0.1 to 200 µm, preferably about 1 to 50 µm. The present invention has been described above by explaining typical embodiments of the recording medium of the present invention. However, the recording medium of the present invention is not restricted to these embodiments. In any embodiment, the ink-receiving layer itself and/or a protective layer can contain various known additives such as a dispersing agent, a fluorescent dye, a pH-adjusting agent, an antifoaming agent, a lubricant, an antiseptic agent, a surfactant or the like. In an ordinary diffuse reflection, as shown in Fig. 2, when an incident light flux reflects on the surface of an object, the distribution of the diffuse reflection light flux takes an almost spherical form except for the region of specular reflection. Accordingly, the amount of reflected light is largest in the direction normal to the object surface. On the other hand, in the directional diffuse reflection referred to in the present invention, the distribution of the diffuse reflection light flux takes a form of an ellipsoid extending to the direction of specular reflection except for the region of the specular reflection. Accordingly, there are regions whose amounts of reflected light are larger than that in the direction normal to an object on which incident light reflects. Hence, in directional diffuse reflection, larger amounts of reflected light than in ordinary diffuse reflection are observed at certain angles, and at these angles the whiteness of the object is observed very high visually. Because of this reason, when ink jet recording is conducted, even if the directional diffuse reflection gives the same optical density as that of an ordinary diffuse reflection, the recorded cage results in very sharp contrast, mellowness and perspective feeling which cannot be obtained in ordinary diffuse reflection, within a certain range of solid angles of illumination and observation of the recorded image. Further, in the recording medium of the present invention, when it has a 60° specular gloss of 30 % or more as measured in accordance with JIS Z 8741, its surface is smooth and the recorded image has an improved resolution. This gloss in combination with high whiteness provides a distinct recorded image of high quality. However, when the directionality of diffuse reflection light is extremely high, it occurs in some cases that the recorded image is observed dark at other visual angles. Hence, the recording medium of the present invention preferably has a Y 10D65 value of 60 or more as measured in accordance with JIS Z 8722 (D-O). The Y 10D65 value of 60 or more as measured under the condition of (D-O) means that 60% of the total amount of reflected light including specular reflection light is perceived visually and accordingly a certain amount of reflected light is secured at regions other than those of directional diffuse reflection so that the recorded image is not observed dark even when viewed from these regions. The present invention will be explained in more detail below referring to Examples. In the following, parts refer to parts by weight. Example 1 As a substrate, there was used a white film causing a directional diffuse reflection [Melinex (brand name) # 329 manufactured by ICI]. On this substrate was coated the following composition using the bar coater method so that the film thickness as dried became 3 µm. The coated substrate was dried for 10 min at 80°C to obtain a recording medium a of the present invention. Example 2 As a substrate, there was used a cast coated paper [Mirror Coat (brand name) manufactured by Kanzaki Paper Mfg. Co. ]. This substrate was coated by the following composition using the bar coater method so that the film thickness as dried became 5 µm. The coated substrate was dried for 5 min at 100°C to obtain a recording medium b of the present invention Comparative Example 1 As a substrate, there was used an art paper [OK Art Post (brand name) manufactured by Oji Paper Mfg. Co.]. This substrate was coated by the following composition A using the bar coater method so that the film thickness as dried became 1 µm. The coated substrate was dried for 3 min at 100°C. Thereon was further coated the following composition B using the bar coater method so that the film thickness as dried became 3 µm. It was subjected to drying for 10 min at 80°C to obtain a recording medium c. Comparative Example 2 The art paper used in Comparative Example 1 was used as a recording medium d. Comparative Example 3 A commercially available ink jet paper having no gloss [Ink Jet Mat Coat M (brand name) manufactured by Mitsubishi Paper Mills] was used as a recording medium e. Ink jet recording was carried out with the recording media of the above Examples and Comparative Examples, using the following four kinds of inks and a recording equipment having an ink jet recording head of on-demand type wherein an ink is discharged using a piezoelectric vibrator (diameter of discharging orifice: 60 µm, voltage for driving a piezoelectric vibrator: 70 v, frequency : 2 KHz). The evaluation results for the recording media of the above Examples and Comparative Examples are shown in Table 1. The evaluation items in Table 1 where measured in accordance with the following methods: (1) Time of ink fixing: There was measured a time from recording to a moment at which no ink sticks to a finger when the finger touches a recorded image on a recording meidum. (2) Dot optical density: The O.D. of black dot was measured by applying JIS K 7505 to printed microdots and using a Sakura Microdensitometer PDM-5 (manufactured by Konishiroku Photo Industry). (3) Gloss: 60° specular gloss was measured in accordance with JIS Z 8471 using a Digital Variable Angle Gloss Meter UGV-5D (manufactured by Suga Shikenki Co.). (4) Y 10D65 value: This value was obtained in accordance with JIS Z 8722 from the spectral reflectance measured using a CA-35 Color Analyser (manufactured by Murakami Color Research Laboratory). (5) Gloss by directional diffuse reflection (reflectivity at 15° direction): This was obtained by applying a light onto a recording medium at an incident angle of -30° using Variable Angle Spectrophotometer of CA-35 Color Analyzer manufactured by Murakami Color Research Laboratory), measuring reflectivities at the directions of 0° and 15°, and calculating the reflectivity % at 15° direction as compared with the reflectivity at 0° direction being taken as 100%. (6) Panel test: This was conducted for overall evaluation of recorded image. An illustration of 15 cm x 20 cm was printed on a recording medium; the resulting recording medium was shown to 20 panelists consisting of 12 males and 8 females; and there was counted the number of panelists who answer "yes" to the question whether they perceive especially high degree of whiteness and contrast, and high quality with distinctness and mellowness in the image-printed paper. Effect As described above, when ink jet recording is conducted on a recording medium causing directional diffuse reflection, the resulting recorded image has a very high degree of whiteness at a certain visual angle. Hence, a recorded image of sharp contrast and distinctness can be obtained. Further, when the recording medium has a gloss, there can be obtained a recorded image excellent in resolution, gloss, perspective feeling due to pearl gloss and high quality feeling. In the above, the recording medium of the present invention has been described in connection with ink jet recording. However, the recording medium is not restricted thereto and can of course be used for other methods of ink recording such as, for example, heat-sensitive recording, where ink is recorded on a medium having an ink receiving layer.

Claims: A recording medium for recording an image produced by ink-jet printing, which medium has a recording surface and comprises: a substrate; and an ink-receiving layer for receiving ink-jet printing ink; which medium is characterised in that it has a property of directional diffuse reflection so that light incident thereupon is both diffused and reflected to be concentrated in directions in and about the direction of specular reflection for the incident light. A medium as claimed in claim 1 wherein said recording surface has a gloss finish. A medium as claimed in claim 2, wherein said recording surface has a 60° specular gloss of 30% or more as measured in accordance with JIS Z 8741. A medium as claimed in either one of claims 2 or 3, wherein said recording surface has a spectral reflectance Y10 D 65 of 60 or more as measured in accordance with JIS Z 8722 (D-O). A medium as claimed in any one of the preceding claims wherein said ink-receiving layer comprises a resin having affinity with at least one of water or a polyhydric alcohol. A medium as claimed in any one of the preceding claims, wherein said ink-receiving layer has a thickness in the range 0.1 to 200 um, preferably 1 to 50 um. A medium as claimed in any one of the preceding claims further characterised by: a filler material dispersed in said ink-receiving layer, which filler material thus dispersed is both light diffusing and compatible with the ink receptability of said ink-receiving layer; and light reflecting means; wherein said light reflecting means and the light diffusing dispersed filler material together impart to the medium said property of directional diffuse reflection. A medium as claimed in claim 7, wherein said substrate includes a dispersed pigment selected from mica, pearl pigment and metal powder and provides thus light reflecting means. A medium as claimed in either one of claims 7 and 8, wherein said ink-receiving layer comprises a resin having affinity with at least one of water or a polyhydric alcohol, in which the ratio of filler and resin is 2:1 or less. A medium as claimed in claim 9, wherein said ratio is substantially 1:10. A medium as claimed in any one of the preceding claims 7 to 10, wherein said filler material comprises material selected from: silica; clay; talc; diatomaceous earth; calcium sulphate; barium sulphate; lithopone; and satin white. A medium as claimed in any one of the preceding claims 1 to 6, wherein said substrate has said property of directional diffuse reflection and said ink-receiving layer comprises a transparent resin. A medium as claimed in claim 12, wherein said substrate includes a dispersed pigment selected from mica, pearl pigment and metal powder. Use of a recording medium, as claimed in any one of the preceding claims, in ink-jet printing to produce a distinct recorded image. A recording medium as claimed in any one of the preceding claims 1 to 13, when bearing a recorded image produced by ink jet printing. A recording medium as claimed in any one of the preceding claims 1 to 13, when bearing a recorded image produced by heat sensitive recording.

Inventors: ARAI, RYUICHI, MATSUI, SHINYA, SAKAKI, MAMORU
Applicants: CANON KABUSHIKI KAISHA
Application year: 1985
Main classification: B41M1
IPC codes: B41M5