JPH0367685A - Ink jet recording medium - Google Patents

Abstract

PURPOSE:To enhance ink receiving properties by using a dye adsorbent as a main component of porous pigment which constitutes an ink receiving layer adjacent to a support. CONSTITUTION:Basic porous pigments such as fine particle alumina are used as an adsorbent for coloring component of water ink when acidic, linear dye inks are used. The porous pigment which constitutes an ink receiving layer must be porous and be of fine particle form so that adequate ink receiving properties are ensured. Preferably the pigment should have 80m<2>/g or more of specific surface area by BET method(nitrogen method) and 0.1 to 12mum of average particle diameter, if it is in the form of a dispersed particle (measure ment value by the coal-tar counter; AP=50mum) in a coating liquid for ink receiv ing layer formation. Especially the porous pigment having 100 to 500m<2>/g of specific surface area and 0.5 to 7mum of average particle diameter is capable of high water ink reception and contributes to the efficient release of water ink medium after ink reception.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an inkjet recording medium suitable for recording with aqueous ink, and particularly has excellent ink receptivity during recording, recorded image quality, and recorded image storage stability. It is related to recording media.

``Prior art'' The inkjet recording method, which allows a recorded image to be obtained at the same time as the input signal, is used in a wide variety of fields, mainly in the field of printers, because it has low noise, can perform high-speed recording, and can easily print in multiple colors. There is.

As the base material of the recording medium used in these inkjet recording methods, so-called paper is generally used, and several proposals have been made in the past.

For example, attempts were made from the early stages of development to provide a coating layer (ink-receiving layer) mainly composed of a pigment with good ink absorption and a binder on the base material, and silica-based pigments are generally used as pigments. (Unexamined Japanese Patent Publication No. 52-9074, No. 55)
-51583, 56-148583, 58-7
No. 2495).

Proposals have been made to provide a water-soluble polymer coating layer on the ink-receiving layer (JP-A-55-144172 and JP-A-55-146786), and to use a basic latex polymer (JP-A-57-3).
6692) is also available. In addition, in order to improve the poor water resistance inherent in recording using water-based inks, an attempt was made to apply a water-resistant agent to a water-soluble polymer coating layer after inkjet recording (Japanese Patent Laid-Open No. 55-150396). , 56
-58869), and the use of specific pigments and resins that adsorb coloring components in water-based inks (Japanese Patent Laid-Open No. 55-14
4172) is also available. In addition, images recorded with water-based ink using the above-mentioned recording media lack gloss, and depending on the intended use, such as fine art printing, advertising media such as posters, or video photography, the aesthetic value may be reduced. By applying so-called uminate processing using a transparent film over the recorded image, or by providing an ink-receiving layer containing synthetic silica as a main component on the transparent film base material, the image recorded from the ink-receiving layer side is transferred to the transparent film base material. Ideas for viewing from the side (
However, in these proposals, the former ξ veneer process loses the primary recording characteristics of inkjet recording and is economically disadvantageous. In addition, although the latter proposal maintains the characteristics of primary recording, it uses specific pigments such as base silica, so in order to obtain sufficient ink receptivity, there are restrictions on the amount of binder used, and the surface strength is limited. Not only is it necessary to provide a recording layer with a weak coating layer or a thick coating layer, but it is also not water resistant, and if it gets wet with water, it will elute again, causing a decrease in the density of the recorded image or disappear, and it is also necessary to provide a thick coating layer. This poses a practical problem in that the recorded image becomes blurred due to the influence of this phenomenon, and improvements have been desired.

"Problems to be Solved by the Invention" The present invention provides an inkjet recording medium that not only has excellent ink receptivity, but also excellent recorded image quality and recorded image storage stability, and furthermore, provides a clear recorded image that can be seen even from the support. The purpose is to

"Means for Solving the Problems" The present invention provides an inkjet recording medium in which an ink-receiving layer containing a porous pigment is provided on a transparent support. This is an inkjet recording medium characterized in that the main component is a dye adsorbent.

"Function" In the inkjet recording medium of the present invention, the porous pigment as a dye adsorbent constituting the ink-receiving layer provided adjacent to the transparent support efficiently absorbs water-based ink during recording and quickly absorbs water-based ink. In order to adsorb the colored components in the water-based ink and efficiently release the water-based ink medium (7) from the surface of the ink-receiving layer 1 into the air after recording, it has a dye-adsorbing property and is porous and has a fine particle shape. There needs to be.

The method for selecting these porous pigments as dye adsorbents is to dilute the water-based ink used for recording with an appropriate amount of water and adjust the concentration to make the following distinctions easy. This can be determined by whether or not there is a decrease in color density when a predetermined amount of porous pigment corresponding to a unit area of adhering to a recording medium is introduced. At this time, in order to make the effects of the present invention more effective, it is necessary to have a porosity that has excellent adsorption properties for the colored components in the aqueous ink, so that the diluted aqueous ink becomes a colorless and transparent liquid. It is desirable to use pigments selectively. By using such pigments, the colored components in the water-based ink that adhere to the recording medium are effectively adsorbed and fixed on the surface of the ink-receiving layer in contact with the transparent support, resulting in clear and aesthetically pleasing recorded images. An inkjet recording medium with excellent properties and excellent storage stability can be obtained.

Porous pigments that act as adsorbents for coloring components in water-based inks include, for example, for acidic and direct dye-based inks, which are the mainstream in this technical field, finely divided alkaline powder, basal hydrotalcite, and phyllosilicic acid. Basic porous pigments such as salts are exemplified, and synthetic silica, calcium carbonate, etc. commonly used in the technical field do not exhibit dye adsorption properties. If necessary, porous pigments that do not inherently have dye adsorption ability or have weak adsorption ability may be surface treated with metal compounds such as aluminium, zinc, magnesium, etc., and organic compounds such as cations and other resins. It can also be used by imparting dye adsorption properties.

In the present invention, the porous pigments constituting the ink-receiving layer need to be porous and in the form of fine particles in order to provide even more sufficient ink-receptivity, and preferably have a specific surface area ( Nitrogen method) is 80nf/g
The above, and in the coating liquid for forming an ink receiving layer, dispersed particles (Coulter counter; measured value at AP = 50 μm)
So 0. Those having an average particle diameter of 1 to 12 μm are used. In particular, porous pigments with a specific surface area of 100 to 500 rrf/g and an average particle diameter of 0.5 to 7 μm have excellent receptivity for aqueous ink and are also effective in efficiently releasing the aqueous ink medium after receiving the ink. In order to contribute
A more preferred embodiment can be given.

If the specific surface area is less than 80rrr/g, the ink receptivity will be insufficient, and if the average particle diameter is less than 0.1 μm, not only will the ink receptivity decrease, but the recorded image will lose its sharpness and become dull. It gives a recorded image. If the average particle diameter exceeds 12 μm, the ink dots not only spread unevenly in the lateral direction but also lose sharpness.

It goes without saying that porous pigments having these physical properties can be appropriately selected and used from various pigments known in the technical field, but they can also be processed to have desired physical properties if necessary. I can do it.

In the present invention, these porous pigments with excellent dye adsorption properties are preferably used alone or in combination if necessary to constitute an ink receiving layer adjacent to the transparent support. Since the coloring components of each color in the water-based ink used are chemically different, if there is a significant difference in adsorption to the pigment, select a pigment with particularly good adsorption for each color and add a specified amount as necessary. It is also possible to use them by mixing them in different ratios, and it is also possible to use other pigments in combination in order to impart various aptitudes such as imparting writability, imparting suitability to equipment, and controlling ink absorption.

In order to more clearly exhibit the effects of the present invention, the ink-receiving layer, which is provided in contact with the transparent support and whose main component is a dye adsorbent, should be coated with the aqueous ink applied during recording with as little coating amount as possible. It is desirable to select and use the ink so that the coloring components therein can be sufficiently adsorbed, and it is necessary to carefully select the materials and the formulation of the coating liquid for constituting the ink-receiving layer so that the thickness is preferably set to 10 μm or less. In this case, the resulting inkjet recording medium has a recorded image adsorbed and held at high density adjacent to the transparent support, so the recorded image viewed from the support side has particularly excellent clarity and storage stability. It is possible to obtain a recording medium which is not only excellent in performance but also suitable for, for example, OHP suitability.

In the present invention, only an ink receiving layer mainly composed of a dye-adsorbing porous pigment provided adjacent to a transparent support can
If ink absorption or opacity is insufficient depending on the application,
By further providing a pigment coating layer containing a non-dye adsorption pigment as a main component on the ink-receiving layer, ink absorption and opacity can be improved. The use of pigments has a greater effect of imparting opacity than the refractive index effect that pigments inherently have.
A more preferred embodiment can be given.

Incidentally, the non-dye adsorption pigment constituting the outer layer is appropriately selected from pigments known in the technical field; In addition to contributing to absorption, since the pigment does not adsorb dye, it also contributes to release of the aqueous ink medium into the air without inhibiting dye adsorption to the dye adsorbent provided near the transparent support. I can do it. Furthermore, since the pigment coat layer dried after being released from the aqueous ink medium has appropriate opacity, it is possible to provide a recording medium with excellent aesthetics, especially when the recorded image is viewed from the transparent support side. In order to provide a pigment coat layer with better opacity than the refractive index inherently possessed by the pigment, those having a specific surface area of 100 m/g or more and an average particle diameter of 1 to 15 μm are preferably selected and used. .

Furthermore, when the ink-receiving layer has a multilayer structure, the outermost layer and/or the intermediate layer can be a white, black, or colored colored layer, if necessary, and can contain colored dyes, colored pigments, titanium oxide, Carbon powder, metal powder, etc. can be used.

In the present invention, the ink-receiving layer requires, in addition to the dye-adsorbing porous pigment described above, other pigments to impart suitability such as imparting writability within a range that does not inhibit the function of the ink-receiving layer. It is also possible to use it together with various viadders depending on the situation. Other pigments used in combination as auxiliaries include, for example, calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide,
Inorganic pigments such as zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, amorphous silica, aluminum hydroxide, alumina, lithopone, styrene plastic pigments, acrylic plastic pigments, microcapsules Examples include pigments known in the general pigment coating field, such as organic pigments or organic/inorganic composite pigments such as pigments based on pigments, urea resin pigments, and melamine resin pigments.

Examples of binders include oxidized starch, etherified starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, natural or semi-synthetic polymers such as soybean protein, polyvinyl alcohol and its derivatives, polystyrene-based resins, Polyvinylpyrrolidone resin, poly(meth)acrylic acid or its copolymer, maleic anhydride copolymer, acrylamide resin, (meth)acrylic acid ester resin, polyamide resin, polyurethane resin, (unsaturated) polyester Synthetic water-soluble or solvent-soluble resins such as polyvinyl butyral resins, alkyd resins, epoxy resins, epichlorohydrin resins, urea resins, melamine resins, styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers Conjugated diene polymer latexes such as polymers, acrylic polymer latexes such as polymers or copolymers of acrylic acid esters and methacrylic acid esters, vinyl polymer latexes such as ethylene-vinyl acetate copolymers, Alternatively, functional group-containing modified polymer latexes obtained by adding anionic groups and/or cationic groups to these various polymers, and polyvinylbenzyltrimethylammonium chloride, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl-β-hydroxyethyl Examples of resins known in the technical field include so-called conductive resins typified by dimethylammonium chloride, polydimethylaminoethyl methacrylate hydrochloride, and the like, which may be used alone or in combination. The amount of these binders to be used can be arbitrarily selected by taking into account the required recording suitability of the recording medium, suitability for use, smearability of the coating liquid for forming the ink-receiving layer, etc.; 1 to 200% by weight,
It is preferably added and used in a range of 5 to 50% by weight.

Furthermore, if necessary, pigment dispersants, thickeners, fluidity improvers,
Antifoaming agents, foaming inhibitors, foaming agents, mold release agents, penetrating agents, wetting agents, thermal gelling agents, lubricants, dyes for color adjustment such as blue tinting, pigments, fluorescent dyes, ultraviolet absorbers, oxidation inhibitor, quencher
A coating liquid for forming an ink-receiving layer is prepared by adding various auxiliary agents known in the technical field, such as additives, preservatives, anti-mold agents, antistatic agents, water-resistant agents for binders, and cross-linking agents. If the pigment coating liquid containing the various components described above does not become a uniformly dispersed liquid due to aggregation, etc., make two or more separate coating liquids and apply the coating two or more times to form the desired recording layer. You can also get it. These ink-receiving layer forming coating liquids are
Agitators, Coles disperser, KDξru, ball mill, attritor, sand mill, colloid [
It is made into a coating liquid using various dispersion machines such as a bar coater,
Air knife coater, blade coater, rondo blade coater, roll coater, flash coater,
This is also smeared in a conventional manner using various known smearing methods such as a curtain coater, a gravure coater, a flexo coater, a cast coater, and a spray device. For drying after smearing, any of the usual drying methods such as hot air heating, gas heater, electric heater, infrared heater, steam heating drum heater, etc. can be applied.

In the present invention, as a support, synthetic resin films such as cellophane, glass, polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyethylene, and polypropylene can be used as long as they are transparent and non-water soluble, but ink In order to improve the smearability and/or adhesion of the coating liquid for forming the receptive layer, common surface treatments such as corona discharge treatment, plasma treatment, chemical cleaning treatment, etc., and resin layers such as gelatin, nitrocellulose, and polyester are used. And/or it is also possible to use a known anchor coat layer, such as a layer treated with an auxiliary agent such as colloidal silica, a metal coupling agent, or isocyanates.

The thus obtained inkjet recording medium can be used as it is, but if necessary, it may be surface-treated by a conventional method by passing it between roll nips under pressure and/or heat using a super calender, cross calender, matte calender, etc. You can also do that.

According to the present invention, a recorded image formed at high density on the surface of an ink-receiving layer mainly composed of a dye-adsorbing porous pigment formed adjacent to a transparent support can be viewed from the transparent support side ( At this time, a recorded material is provided which is characterized in that a mirror image is generally recorded and viewed as a normal image, but if necessary, it can also be used as an OHP film for projection images, After inkjet recording, the surface of the ink-receiving layer may be brought into close contact with another support, and the ink-receiving layer may be used for, for example, fine art printing, advertising media such as posters, displays, etc. The support to be brought into close contact with the ink-receiving layer can be transparent or opaque, such as paper, synthetic paper, cloth, polymer film, metal foil, plastic products, metal products, glass plates, wood boards, plywood, etc. Any material can be selected depending on the purpose of the wall surface, etc. Methods for bringing the inkjet recording medium into close contact with the support surface after recording include methods using various adhesives such as adhesives, pressure-sensitive adhesives, and heat-sensitive adhesives, and various known adhesive methods such as the dry lamination method. However, in the present invention, especially by using a dye adsorbent as the water-based ink receiving layer, records with particularly excellent water resistance can be obtained, and it is also possible to use a water-based adhesive. It has the advantage that it can be easily and inexpensively adhered to various supports without being restricted by the selection of adhesives and adhesion methods.

The present invention will be described below with reference to Examples, but of course the present invention is not limited thereto. In the examples, parts and % mean parts by weight and % by weight, respectively.

"Example" Example 1 Commercially available polyester film with anchor coating (
A coating liquid for forming an ink-receiving layer containing a dye adsorbent as a main component with the following composition was further applied to the film (thickness: 75 μm) with a sand grinder to reduce the average particle size to 6.5 μm, and then the dry weight was reduced using a bar coater. After applying 6 g/rrf at
An inkjet recording medium having an ink receiving layer of μm was obtained.

Synthetic hydrotalcite (manufactured by Kyowa Chemical Industries) (specific surface area: 7 g of 109, average particle size: 7.8 μm) 65 parts ultrafine powder silicic acid (manufactured by Mizusawa Chemical) (specific surface area: 365 nf/g, average particle size: 8 .0μm) 35 parts 10% of silyl-modified polyvinyl alcohol (manufactured by Kuraray)
Aqueous solution 300 parts Cationic conductive agent (manufactured by Sanyo Kayi) 10 parts Water
390 parts Example 2 An ink-receiving layer forming coating liquid (liquid A) containing a dye adsorbent having the composition shown below on a commercially available polypropylene film (thickness: 50 μm) coated with an anchor coating was further treated with a sand grinder. The coarse particles were pulverized to an average particle size of 4.5 μm, and then coated with a gravure coater at a dry weight of 1.5 g/bo, followed by a smoothing process and dried. At this time, the thickness of the ink receiving layer was 3 μm.

Next, a coating liquid (liquid B) whose main component is a non-dye adsorbing pigment having the composition shown below is coated with an air knife coater at a dry weight of 5 g/rrr, dried, and then supercalendered in a conventional manner to produce inkjet recording. Got the medium.

(Liquid A) Aluminum oxide porous pigment (manufactured by Mizusawa Chemical) (specific surface area: 3
94nf/g, average particle size: 4.75μm) 100 parts 10% aqueous solution of silyl-modified polyvinyl alcohol (manufactured by Kuraray)
200 parts cationic conductive agent (manufactured by Sanyo Kakai)
5 parts water 49
5 parts (Liquid B) Ultrafine powder amorphous silica (manufactured by Tokuyama Soda) (specific surface area: 270 po/g, average particle size: 2.6 μm) 100 parts 10% aqueous solution of polyvinyl alcohol (manufactured by Kuraray) 300 parts water
400 copies Comparative Example 1.2 The same procedure as in Example 2 was carried out except that the smearing of liquid A was stopped and only liquid B was smeared at 6.5 g/% and 15 g/nf, respectively, corresponding to each example. An inkjet recording medium was obtained.

Using the four types of inkjet recording media thus obtained, cyan, magenta, yellow, and black acidic/direct dye-based inks were ejected from four inkjet heads each having a nozzle diameter of 60 am to record a mirror image. The following evaluations were made.

1) The quality of ink receptivity was determined by visually observing the occurrence of ink bleeding in the recorded matter.

2) Recorded image quality was determined by placing each recorded matter with the transparent support facing up on plain paper of the same brightness, and visually judging the image density and color sharpness as seen through the transparent support.

3) The water resistance of the recorded image was determined by visually observing the change in density of the recorded image after the recorded matter was immersed in water for 5 minutes.

(Evaluation criteria) A・・・・・・・・・・・・・・・C・・・・・・・・・
・・・・・・・・・E Practically excellent No practical "effect" As described above, all the examples of the present invention were excellent in ink receptivity during recording, recorded image quality, and recorded image storage stability. It was a recording medium.

Claims (1)

[Claims] 1) At least one porous pigment on a transparent support
1. An inkjet recording medium provided with an ink-receiving layer, characterized in that a main component of a porous pigment constituting the ink-receiving layer adjacent to a support is a dye adsorbent. 2) A pigment coating layer containing a non-dye adsorbing porous pigment as a main component is further provided on an ink receiving layer containing a dye adsorbent as a main component and provided adjacent to the transparent support. The inkjet recording medium according to claim 1).