Back print recording medium

Abstract: A back print recording medium is provided which can realize an image having satisfactory quality and excellent storage stability. The recording medium comprises: a transparent substrate and a light scattering layer formed on the substrate, said recording medium permitting an ink composition to be applied to the light scattering layer side to form an ink image and, in addition, the image to be viewed through the transparent substrate, an UV-shielding layer being further provided between the transparent substrate and the light scattering layer.

Description: The present invention relates to a "back print recording medium" which permits a printed image to be viewed from the surface of the recording medium which is the other surface on which an ink composition has been applied to from the image. A recording medium called "back print medium" is known in the art. Such a recording medium basically comprises a transparent layer and a light scattering layer composed mainly of silica formed on the transparent layer. An ink composition is applied to the light scattering layer side, for example, by ink jet recording. The ink permeates the light scattering layer and reaches the interface of the transparent layer and the light scattering layer. The formed ink image is viewed through the transparent layer. By virtue of gloss and smoothness of the transparent layer, the viewed printed image has a good texture. Therefore, the back print recording medium has been utilized in printing of an image which is desired to give an impression of high quality. In the Patent Abstract of Japan corresponding to JP-A-62261476, a recording material and a recording method are described comprising an ink transporting layer fulfilling the purpose of an ink absorbent layer and a light scattering layer. The ink transporting layer comprises a UV absorber. Patent Abstracts of Japan corresponding to JP-A- 61242871 discloses a UV-absorber which is possibly incorporated in a substrate. The recorded ink image is viewed from the side to which an ink is applied. Patent Abstracts of Japan corresponding to JP-A-07108755 discloses an ink jet recording material with an ink absorbent layer and an ink transporting layer. The ink transporting layer contains and ultraviolet absorber. EP-A-0280650 discloses the use of UV absorbing material which is incorporated into a transparent substrate or provided on a surface of a transparent substrate. It is an object of the present invention to provide a back print recording medium which can realize an image having a satisfactory quality and an excellent storage stability. The present inventors have found that, in the so-called "back print recording medium", the provision of an ultraviolet (UV) shielding layer between a transparent substrate and a light scattering layer results in markedly improved storage stability of a printed image. The object can be attained by a recording medium having the features of claim 1 or claim 4 or a recording method having the features of claim 3. Fig. 1 is a schematic view, partly in section, of one embodiment of the recording medium according to the present invention, wherein on a transparent substrate 2, an UV-shielding layer 3, an ink-absorbent layer 4, and a light scattering layer 5 are provided in that order; and Fig. 2 is a schematic view , partly in section, of another embodiment of the recording medium according to the present invention, wherein on a transparent substrate 2, an UV-shielding layer 3, and a light scattering layer 7 having an ink-absorbent activity are provided in that order. The recording medium according to the present invention is utilized in recording methods using an ink composition. Recording methods using an ink composition include, for example, an ink jet recording method, a recording method where recording is performed with a writing material, such as a pen, and other various printing methods. Ink compositions usable herein are not limited to a liquid ink and include, besides the liquid ink, a wide variety of other ink compositions, such as a solid colorant and a colorant which, in use, is heat-melted. In particular, the recording medium according to the present invention is preferably used in the ink jet recording method. According to the back print recording medium of the present invention, at least a light scattering layer is provided on a transparent substrate. An ink composition is applied to the light scattering layer side, while the printed image is viewed through the transparent layer. A UV-shielding layer is further provided between the transparent substrate and the light scattering layer. When an ink-absorbent layer is further provided between the transparent substrate and the light scattering layer, it is preferred to provide the UV-shielding layer between the substrate and the ink-absorbent layer. A preferred structure of the back print recording medium according to the present invention is shown in Fig. 1. Fig. 1 is a partly sectional view of the recording medium. In the drawing, a recording medium 1 comprises: a transparent substrate 2; and an UV-shielding layer 3, an ink-absorbent layer 4, and a light scattering layer 5 provided in that order on the transparent substrate 2. In this recording medium, an image is recorded by an ink from the light scattering layer 5 side. Preferably, the recording is performed by ink jet recording. The ink deposited on the recording medium permeates through the light scattering layer 5 and reaches the ink-absorbent layer 4. This ink image is viewed from the direction indicated by an arrow in the drawing. According to a preferred embodiment of the present invention, the ink image is viewed by taking advantage of light from a light source 6. By virtue of good texture of formed images, back prints are expected to be used as advertising media. Many of the advertising media are provided in the outside of a room, not to mention of the interior of the room. Therefore, it is considered that deterioration of the image by natural light and, in some case, direct sunlight should be effectively prevented. According to the back print recording medium of the present invention, the UV light from the direction indicated by the arrow in the drawing does not reach the ink image because the UV-shielding layer 3 is interposed between the formed ink image and the transparent substrate 2. The transparent substrate of the recording medium is often exposed to natural light. Therefore, that UV light passed through the transparent substrate does not reach the ink image means that the storage stability of the ink image can be improved. On the other hand, the printed surface, the light scattering layer, also is often exposed to UV light. Since, however, the light scattering layer 5 cuts off most of the UV light, it appears that consideration required of this side may be much less than that required of the transparent substrate. Further, the presence of the UV-shielding layer 3 between the transparent substrate 2 and the light scattering layer 5 can offer the following advantage. Printing an image onto a recording medium is usually carried out with a printer device. Therefore, the recording medium is carried through within the printer device, for example, by means of a roller, a star wheel or the like. In this case, when the UV-shielding layer is provided on the transparent substrate in its surface through which a print is viewed, that is, when the UV-shielding layer is provided on the arrow side of the transparent substrate 2 in Fig. 1, there is a fear of the UV-shielding layer being scratched or, in some cases, being separated. By contrast, according to the recording medium of the present inventions, the UV-shielding layer does not come into direct contact with the carrier means. This offers an advantage that UV-shielding properties are not influenced by carrying through within the printer. Further, the UV-shielding layer is not directly affected by a change in humidity of the air, wetting with water and the like, thus offering an additional advantage that the influence of external environment on the UV-shielding properties can be reduced. According to another preferred embodiment of the present invention, the light scattering layer may have an ink-absorbent activity instead of providing the ink-absorbent layer as described above. The recording medium of this embodiment is shown in Fig. 2. In the drawing, a recording medium 1 comprises: a transparent substrate 2; UV-shielding layer 3 and a light scattering layer 7 having an ink-absorbent activity. According to this embodiment, a thin recording medium can be advantageously formed. The UV-shielding layer in the recording medium according to the present invention may be formed with, for example, agents containing benzophenone derivatives such as Uvinul™ available from BASF AG, Cyasorb™ available from Shiroishi-Carushiumu Corporation, Tomisorb™ available from Yoshitomi-Pharmaceutical Corporation, and ASL available from Shonann-Kagaku-Kogyo Corporation; agents containing benzotriazole derivatives such as Tinuvin™ available from Ciba-Geigy AG, Viosorb™ available from Kyodo-Yakuhin Corporation, JF available from Jyohoku-Kagaku Corporation; and agents containing salicylic acid derivatives such as Sumisorb™ available from Sumitomo-Chemical Corporation, Seesrob™ available from Shipro-Kasei Corporation, DPS available from Eastman-Chemical Corporation. It may be formed by coating or alternatively may be formed by laminating an UV-shielding layer, which has been previously formed in a film form, onto a transparent substrate. The thickness of the UV-shielding layer may be determined by taking into consideration UV-shielding properties, the thickness of the whole recording medium and the like. In general, however, it is preferably in the range of from about 1 to 100 µm. The transparent substrate used in the back print recording medium according to the present invention may be made of a polyester resin, a polyolefin resin, a polystyrene resin, a polyvinyl chloride resin or the like. In general, the thickness thereof is preferably in the range of from about 70 to 200 µm from the viewpoint of the carriability of the recording medium through within the printer. The light scattering layer may be formed of, for example, silica, calcium carbonate, calcium silicate or the like, and a binder and a fluorescent dye. In general, the thickness thereof is preferably in the range of from about 5 to 30 µm from the viewpoint of the carriability of the recording medium through within the printer, light scattering properties of the light scattering layer and the like. A further layer such as a protective layer may be formed on the light scattering layer. The ink-absorbent layer may be formed of, for example, a material having high affinity for an ink. For example, when an water-soluble ink is used, the ink-absorbent layer is formed of preferably a water-soluble resin. Preferred water-soluble resins include polyvinyl alcohol, polyvinyl pyrrolidone, gelatin, casein, gum arabic, polyvinyl acetal, sodium polyacrylate, and carboxymethyl cellulose. Preferably, the thickness of the ink-absorbent layer is, for example, in the range of from about 5 to 10 µm. The ink-absorbent layer may be formed by two or more layers. The light scattering layer having an ink-absorbent activity may be formed with a mixture of components for forming the light scattering layer and components for forming the ink-absorbent layer.

Claims: A recording medium comprising: a transparent substrate (2), a light scattering layer (5) formed on the substrate (2), an UV-shielding layer (3) being further provided between the transparent substrate and the light scattering layer (5), and an ink-absorbent layer (4) provided between the UV-shielding layer (3) and the light scattering layer (5), said recording medium permitting an ink composition to be applied to the light scattering layer side to form an ink image and the image to be viewed through the transparent substrate (2). The recording medium according to claim 1, wherein the UV-shielding layer (3) comprises a compound having a UV-shielding activity selected from the group consisting of benzophenone derivatives, benzotriazole derivatives and salicylic acid derivatives. An ink jet recording method comprising the steps of: ejecting droplets of an ink composition; and depositing the ink droplets on the light scattering layer side of a recording medium according to claim 1 or 2. A recorded medium comprising an image recorded by an ink jet recording method according to claim 3.

Inventors: IIDA JUNICHI, ONISHI HIROYUKI, OWATARI AKIO, IIDA, JUNICHI, ONISHI, HIROYUKI, OWATARI, AKIO
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1996
Main classification: B41M5
IPC codes: B41M1, B41M5