JP3388550B2 - Method for forming translucent image - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording method capable of forming a clear recorded image, and more particularly to a light transmitting method suitable for observing a projected image, such as an overhead projector. The present invention relates to an ink jet recording method capable of forming a recording image having a characteristic. 2. Description of the Related Art In recent years, ink-jet recording methods have attracted attention because of their low cost and easy formation of color images. In the case of color ink jet recording, plain paper or special coated paper is used as a recording medium. On the other hand, with the development of color recording technology, there is an increasing demand for colorization of images used for projection image observation such as an overhead projector. For example, the overhead projector image is often used mainly for presentation, but if a color image can be used at this time, it is more preferable because the content can be deeply impressed. Furthermore, the inkjet recording method is compared with the conventional silver halide photography, electrophotography, or the method of attaching a color film,
A color translucent image can be easily formed at low cost. As a translucent recording medium for ink jet recording, conventionally, a transparent film such as a polyethylene terephthalate film provided with an ink receiving layer formed by applying a hydrophilic resin or ultrafine particles has been proposed. . Such a recording medium is disclosed in, for example,
Recording media described in JP-A-9-174381, JP-A-60-199689 and JP-A-2-276670 are exemplified. [0003] One of the presentation methods using an overhead projector is a method of expressing a design to be expressed in a high brightness color in a low brightness background (such as a so-called blue slide). , Which will be hereinafter referred to as a white blank type). In particular, when it is desired to squeeze and emphasize a design to be expressed in a single document, for example, rather than placing color characters in a plain background, a colorless (or lightness) It is more effective to arrange the Nuki characters of (high color). However, in order to obtain an image of a white printing type using an ink jet recording method, it is necessary to print a solid background color over the entire recording medium. In particular, to enhance the contrast, the background color
It is preferable to use a mixture of two or more colors obtained by combining Y, M, C, and Bk inks. However, in this case, there arises a problem that the consumption amount of the ink increases more than necessary or the printing speed decreases. In addition, beading that causes curling after image formation caused by applying a large amount of ink to the entire surface and unfixed ink droplets collect on the recording surface and become uneven like beads. The problem is that the background becomes non-uniform, such as occurrence of streaks occurring at the joint of each scanning line, unevenness of density in the head nozzle, or the problem of lacking sharpness due to the collapse of the blank portion. . SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an ink jet recording method particularly suitable for providing a high-quality white printing type image. [0005] The above-mentioned problems are achieved by the present invention described below. That is, the present invention comprises a light-transmissive substrate and an ink-receiving layer mainly composed of a hydrophilic resin or inorganic fine particles provided on the substrate, and the above-mentioned ink-receiving layer is discolored by a change in pH. hints, in advance at a predetermined position on the recording surface of the colored by light-transmitting recording medium that is kept, by attaching the ink was adjusted to pH vanishing Iroryo area of the dye in the ink jet recording method,
The dye attachment moiety consists in decoloring a method of forming a translucent image with a high color characters or symbols colorless or brightness in a background color. The present inventors have conducted intensive studies to solve the problems of the prior art. As a result, according to the ink jet recording method using the translucent recording medium having the above structure, the conventional ink jet recording method It has been found that the ink consumption can be reduced without the above-mentioned problems described above, and that a transparent white-type image can be efficiently provided. Furthermore, the inventors have found that the obtained transparent white light-transmitting image has an excellent image quality equivalent to that of a white transparent image formed by using a conventional silver halide photograph, and have reached the present invention. still,
According to the method of the present invention, it goes without saying that the above-mentioned excellent translucent image can be formed at a much lower cost and in a shorter time than the conventional method. Preferred embodiments of the present invention will be described below in more detail. A first feature of the present invention is to use a light-transmissive recording medium having a specific configuration. The recording medium comprises a light-transmitting substrate and an ink-receiving layer mainly composed of a hydrophilic resin or inorganic fine particles provided on the substrate, and the ink-receiving layer is p-type.
This is a light-transmissive recording medium that contains a dye that changes color due to a change in H and is kept in a state of being colored in advance. The translucency referred to in the present invention refers to a material having a linear transmittance of 2% or more, more preferably 10% or more. When the ink receiving layer also has a property as a substrate, the substrate may not be provided. As the base material, a translucent film or plate such as plastic or glass such as polyethylene, polyester, and polypropylene can be used. As the material for forming the ink receiving layer, any known materials can be used, but hydrophilic resins such as polyvinyl alcohol, polyvinylpyrrolidone and cellulose derivatives, colloidal silica and alumina sol, and a small amount of binder for inorganic fine particles. Those to which a resin is added are exemplified. As the dye contained in the recording medium of the present invention, a compound which imparts a tint to the recording medium itself and discolors or decolors due to a change in pH within a range not impairing the light transmittance of the entire recording medium is used. Is done. Common examples of such dyes include, for example, pentamethoxy red, quinaldine red, 2,4-dinitrophenol, hexamethoxy red, heptamethoxy red, quinoline blue, 0-
Cresol, thymolphthalein, phenolphthalein, methyl orange, Congo red, salicylic, alpha-naphthylamine, 3,6-dihydroxy phthalic acid, m- cresol purple, thymol blue, dimethyl yellow, bromophenol blue, blanking Romo cresol Acid and alkali indicators such as green, methyl red, chlorophenol red, bromocresol purple, bromothymol blue, neutral red, phenol red, cresol red, thymol blue and the like. The coloring mechanism of these compounds is such that the addition or elimination of protons occurs in the chromogenic structure in the molecule due to a change in pH, and the color is reversibly changed or erased . For example, in a hydroxyazo dye,
-The proton is eliminated from the OH group and the electron donating property is high-
O ^- When changes in the electronic state of the electron resonance structure portion of the azo group changes, showed significant spectral changes, have in discoloration
It is known that discoloration occurs. In the present invention
Uses a compound that loses color due to fluctuations in pH . pH
Compounds other than those described above can be used as long as the compound loses color due to the fluctuation of the above. The ink used in the method of the present invention is a conventionally known ink containing water as a main component, an organic solvent such as a polyhydric alcohol, a dye as a recording agent, and, if necessary, other additives. It is. In the method of the present invention, the dye does not necessarily have to be contained in the ink. The pH of the ink to be used can be adjusted to a desired region by adding an acid or a base to the above ink. The method of the present invention comprises the use of the above-described translucent recording medium and the aqueous ink. The pH of the ink receiving layer of the recording medium is adjusted to the color-developing region of the dye, so that the recording surface is uniformly presented. maintaining the color state, its predetermined position on the recording surface by adhering ink adjusted to a pH of consumption Iroryo range of the dye, the dye attachment moiety is accomplished by decoloration. or,
In the method of the present invention, the four color inks of Y, M, C, and Bk may be used as they are, and may be used in common with other normal recording cases, and a white ink type ink containing no dye is newly discharged. An image may be formed by separately providing a recording head. In the former case, an image in which characters and patterns of each color ink are recorded with respect to the background color is obtained, and in the latter case, an image in which colorless (white blank) characters and patterns are recorded with respect to the background color Is obtained. As an ink jet recording method to which the method of the present invention can be applied, any one of conventionally known ink jet recording methods in which small droplets of ink are ejected from nozzles using various driving principles and recording is performed. Is also applicable. The present invention will be described in more detail with reference to the following examples. [Examples 1 to 4] Translucent recorded images as shown in FIG. 1 were created using the image forming method as shown below. 1m as recording device
By using a recording apparatus equipped with an inkjet recording head having nozzles at a density of about 16 nozzles per m, the following recording medium and ink were prepared respectively, and inkjet recording was performed on the portion corresponding to FIG. A translucent recording image of a nuqui type was obtained. Preparation of Recording Medium A coating solution having the following composition was applied to a 75 μm-thick polyethylene terephthalate film having a dry film thickness of 5 μm.
μm, and dried to form an ink receiving layer.
The recording media used in Examples 1 to 4 were adjusted. (Composition of coating liquid used in Example 1) A 10% aqueous solution of polyvinyl alcohol (PVA-
217, containing Kuraray) and 100 parts with hydrochloric acid
= 4 and a red aqueous solution containing heptamethoxy red at a concentration of 0.4% was mixed to obtain a coating liquid. (Composition of coating solution used in Example 2) A hepta used in Example 1 was a blue water / ethanol solution containing quinoline blue at a concentration of 0.4% and adjusted to pH = 10 with an aqueous sodium hydroxide solution. A coating liquid was used in the same manner as in Example 1 except that the aqueous solution of methoxy red was used. (Composition of Coating Liquid Used in Example 3) A blue water / ethanol solution containing bromothymol blue at a concentration of 0.4% and adjusted to pH = 9 with an aqueous sodium hydroxide solution was prepared in Example 3. A coating liquid was prepared in the same manner as in Example 1 except that the aqueous solution of heptamethoxy red was used instead of the aqueous solution of heptamethoxy red. (Composition of coating liquid used in Example 4) A blue aqueous solution containing m-cresol purple at a concentration of 0.1% and adjusted to pH = 9 with an aqueous sodium hydroxide solution was used as the heptamethoxy red aqueous solution in Example 1. And a coating solution was prepared in the same manner as in Example 1. Preparation of Ink (Ink Used in Example 1) A pH standard solution (aqueous sodium borate solution) having a pH of 9 was used as it was in Example 1. (Ink used in Example 2) pH standard solution of pH = 4 (aqueous potassium hydrogen phthalate solution)
Was used as it was in Example 2. (Ink used in Example 3) An aqueous solution of hydrochloric acid was added to an ink having the following composition, and the pH was adjusted to 4 to obtain an ink used in Example 3. -30 parts of diethylene glycol-67 parts of water-3 parts of dye The above ink can be used for recording on a conventionally known recording medium. An image was formed using a yellow ink (CI Direct Yellow 86 was used as a dye) among the above inks. (Ink used in Example 4) An ink was prepared in the same manner as the ink in Example 3 except that the pH was adjusted to 5 using an aqueous acetic acid solution. As a result, a projection image having a clear white pattern was obtained on a red background in Example 1 and on a blue background in Example 2. In Example 3 and Example 4, projection images having a clear yellow pattern on a blue background were obtained. [Comparative Example 1] Conventionally, using the following recording medium, the same recording method as in the embodiment was used so that the part was blue (printed with cyan ink and magenta ink) and the part was plain (no printing). The same inkjet recording as in the example was performed to form a translucent recorded image. Preparation of Recording Medium A 10% aqueous solution of polyvinyl alcohol (PVA-2) was placed on a polyethylene terephthalate film having a thickness of 75 μm.
17 Kuraray Co., Ltd.) was applied and dried to a dry film thickness of 5 μm to form an ink receiving layer, and a recording medium for comparison was prepared. [Evaluation] Comparing the ink consumption during printing, Comparative Example 1
In this example, the ink consumption was 10 times or more that of the example.
In addition, a projection image was formed by an overhead projector using the formed translucent images of the example and the comparative example, and evaluated. As a result, all of the images of the examples of the present invention formed a clear and sharp projection image, whereas the image of Comparative Example 1 curled toward the recording surface side, and a clear projection image was formed. Not formed. Further, when the recorded image is directly observed, the image of the example of the present invention has a uniform background, whereas the image of the comparative example generates beading and generates a white drop at the connection of scanning lines. And a clear image with a non-uniform background was not obtained. As described above, according to the ink jet recording method using the translucent recording medium of the present invention, unlike the conventional ink jet recording method, the ink consumption can be reduced. A translucent image of a white-tone type can be obtained efficiently. Further, the transparent white type image obtained by the present invention has a high quality image quality equivalent to that of a conventional white image formed using silver halide photography. Further, according to the present invention, it is possible to form the above-mentioned excellent translucent image at a much lower cost and in a shorter time than the conventional method.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram exemplarily showing a recorded image obtained by the present invention.

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-63-66386 (JP, A)                 JP-A-49-115337 (JP, A)                 JP-A-63-286481 (JP, A)

Claims (1)

(57) [Claim 1] The above-mentioned ink-receiving layer, which comprises a light-transmitting substrate and an ink-receiving layer mainly composed of a hydrophilic resin or inorganic fine particles provided on the substrate. There comprises a dye which changes color with a change in pH, at a predetermined position on the recording surface of the translucent recording medium is maintained in a state of pre colored, the ink was adjusted to pH vanishing Iroryo area of the dye the ink jet recording method is applied in the dye attachment moiety consists in decoloring method of forming a translucent image with a colorless or high color characters or symbols brightness in the background color.