JPH11291617A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light fastness, at the same time, enhance safety without adversely affecting the physical properties or recording characteristics of a recording medium by incorporating a faded melanin of a specific range of wt.% in at least one layer of a base material and/or coating layer. SOLUTION: Light fastness is improved by incorporating faded melanin in at least one layer of a base material, an ink receptive layer (a single layer or multilayer structure), a glossy layer, and a UV ray absorbing layer. Melanin has a high affinity with water, and melanin faded from black, brown, or the like through a treatment of an oxidant and a reducing agent is also water soluble, and retain a UV absorbing ability as well. The content of the faded melanin is set at 0.1-20 wt.% to the weight of a base material, or at 0.01-10 wt.% to the weight of a coating layer to be allowed to contain faded melanin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium having excellent light resistance, and more particularly to a recording medium for ink jet recording having excellent light resistance.

[0002]

2. Description of the Related Art Conventionally, ordinary paper has been used as a recording medium. However, with the improvement of the performance of the inkjet recording apparatus such as high-speed recording or multi-color recording, a porous ink receiving layer called an inkjet recording paper is provided on a base material, and the ink absorbing property is improved. Recording media have been developed.

Further, with the development of optical devices such as slides and OHPs, transparent substrates such as plastic films which are recorded using an ink jet recording apparatus have been used as recording media used for those optical devices. Ink jet recording media have also been proposed.

[0004] Since these recording media are deteriorated by light, particularly high-energy ultraviolet rays, it has been proposed to use an ultraviolet absorber for these recording media. (JP-A-57-74192, JP-A-57-74192)
-74193, JP-A-57-87988,
JP-A-8-143795, etc.)

[0005]

Although the use of various ultraviolet absorbers has been conventionally proposed, most of them are water-insoluble or hardly water-soluble, and there is a problem in applying them to recording media. Was. That is, the water-insoluble or poorly water-soluble ultraviolet absorber has a problem in that it has poor compatibility with the water-soluble ink and repels the water-soluble ink to lower the print quality and discolor the dye. In addition, phenolic UV absorbers are known as water-soluble ones, but all have safety problems such as carcinogenicity / donation, and can be directly touched by hands or put into the mouth by infants. However, there is a problem in that the dye is easily discolored as in the case of a water-insoluble or hardly water-soluble recording medium.

The present invention has been made in view of the above problems, and an object thereof is to provide melanin which has been discolored from black, brown or the like by treatment with an oxidizing agent or a reducing agent (in the present invention, By using melanin obtained by the fading means described in detail later, referred to as "fading melanin", that is, by using a material derived from a natural substance having high safety, recording using a conventional ultraviolet absorber is performed. An object of the present invention is to provide a recording medium that solves the problem of the medium.

[0007]

Means for Solving the Problems The present inventor has proposed that melanin, which originally has a high affinity for water, is subjected to treatment with an oxidizing agent or a reducing agent to be bleached from black, brown, or the like, and is also water-soluble. The UV absorbing ability is also maintained, and when the bleached melanin is added to at least one of the substrate, the ink receiving layer, the gloss layer, the UV absorbing layer, and the like, the recording medium is found to have light resistance. The invention has been completed.

That is, the recording medium according to the present invention is characterized in that at least one of the base material and / or the coating layer is
A recording medium comprising fading melanin. "
(Claim 1) is the gist (items specifying the invention).

Further, the recording medium according to the present invention includes: "The content of bleached melanin is 0.1 to 2 with respect to the weight of the substrate.
0% by weight or 0.01 to 10% by weight based on the weight of the coating layer containing the bleached melanin "(claim 2), whereby when the amount of the bleached melanin is less than the lower limit, the light resistance is improved. Insufficient effect, exceeding this upper limit may adversely affect physical properties such as strength and coloring of the substrate or coating layer, or adversely affect recording characteristics such as ink absorbency of the recording medium.・ “At least one of the coating layers is an ink receiving layer containing bleached melanin”.
(Claim 3) As a result, the color material such as the bleached melanin and the dye come closer to each other, and the action is further increased, the light resistance is further improved, and compared to the addition to other layers. Light resistance can be further improved because the amount of addition can be increased by that amount, that at least one of the coating layers is a glossy layer containing bleached melanin (Claim 4),
By this, it becomes possible to absorb ultraviolet rays by fading melanin before the ultraviolet rays reach the coloring materials such as dyes,
Other coating layers including a glossy layer by functional separation, because the light resistance can be improved, and "at least one of the coating layers is an ultraviolet absorbing layer containing bleached melanin" (claim 5). The ability to easily control the ultraviolet absorption capacity while minimizing the effects of the various characteristics of the base material. ・ By containing the bleached melanin in the base material, not only the recording medium without the coating layer but also the coating layer on the base material Light resistance can be improved even in a coated recording medium, and the light resistance can be improved even when used for a transparent film used for slides, OHPs, and the like. is there.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a recording medium characterized in that the substrate and / or the coating layer contains bleached melanin. That is, the recording medium of the present invention has improved light fastness by containing fading melanin in at least one of the substrate, the ink receiving layer (single-layer or multilayer structure), the gloss layer, and the ultraviolet absorbing layer. It is a recording medium. In the present invention, the “coating layer” refers to an ink receiving layer, a gloss layer,
A single layer or a layer having a plurality of layers having at least one ultraviolet absorbing layer.

Preferred embodiments of the present invention will be described below. However, the present invention is not limited to the following first to fourth embodiments, but falls within the scope of the matters specifying the invention. It can be changed as appropriate.

(First Embodiment) A recording medium having a substrate and at least an ink receiving layer, wherein at least one of the coating layers is an ink receiving layer containing bleached melanin. An inkjet recording medium that may have a gloss layer and an ultraviolet absorbing layer.

(Second Embodiment) A recording medium having a base material and at least an ink receiving layer, comprising a base material containing fading melanin and an ink receiving layer, further comprising a gloss layer,
An inkjet recording medium that may have an ultraviolet absorbing layer.

(Third Embodiment) A recording medium having a base material and at least an ink receiving layer, wherein both the base material and the ink receiving layer contain bleached melanin, and further comprise a gloss layer and an ultraviolet absorbing layer. An ink jet recording medium that may have.

(Fourth Embodiment) A recording medium having a substrate and at least an ink receiving layer, wherein at least one of the coating layers is a gloss layer containing fading melanin and an ultraviolet absorbing layer. Recording media for inkjet.

The bleached melanin used in the present invention is obtained as follows. Suitable melanin for bleached melanin is obtained from a wide variety of sources, such as natural and synthetic sources. For example, melanin can be isolated from a wide range of natural sources, for example, human, primate, bovine, bird, rodent, cephalopod, bacterial and fungal sources. Melanin, on the other hand, can be prepared synthetically by enzymatic oxidation of many mono-, di- and polyphenols, and by chemical and autoxidation of a wide variety of phenolic compounds. A method for the isolation and enzymatic synthesis of melanin is disclosed in U.S. Pat. No. 4,806,360. Melanin is also obtained by expression in cell culture of a melanin gene obtained from any of the above natural sources. Usually, the grown cells are recombinantly modified for overexpression of the melanin gene, and the melanin is recovered from the cells by conventional purification techniques.

The melanin used as starting material for the bleached melanin has a wide variety of natural colors, typically reddish orange, brown, dark brown and black. In the present invention, the specific color is Principles o
f Color Technology. 2nd edition (Billmeyer, FWand Sal
tzman, M.S. 1981) Represented by the CIE L ^* a ^* b ^* system described in Wiley-Interscience, New York. L ^*
The value is a measure of lightness. The completely white object of the clear solution has an L ^* value of 100. A completely black object is 0 L ^*
Has a value. The a ^* and b ^* values are chromaticities. Positive a ^*
The value is a measure of redness and a negative a ^* value is a measure of greenness. Positive b ^* values indicate yellowness and negative b ^* values indicate blueness.

The selected melanin is dissolved or suspended in an aqueous medium before treatment with the bleaching agent described below. Most melanin can be dissolved using an alkaline solution, for example, aqueous ammonia. Also, a suspension of finely dispersed melanin particles is neutral or slightly acidic (p of about 5 or less).
H). Preferred recombinant melanin is alkaline conditions (eg, 0.2 M ammonia)
Below, it can be dissolved in a weight ratio ranging typically from about 3:20 to 1: 100 melanin: solution.

The dissolved or suspended melanin is thoroughly stirred, a fading agent is added and mixed with stirring, and further thoroughly stirred. The bleaching agent combined with the dissolved or suspended melanin is selected based on the nature of the melanin starting material and the desired final color. Suitable bleaching agents are oxidizing or reducing agents, such as hydrogen peroxide,
There are potassium permanganate, potassium periodate, sodium hypochlorite and the like, and as the reducing agent, there are sodium borohydride, sodium dithionite and the like.

Melanin changes color during the process. Therefore, it is necessary to stop the reaction when the desired color is reached. Usually, the processing time required to reach a particular final color is determined experimentally by treating the melanin starting material with a particular bleaching agent. (The recording medium can be colored to a desired color by the presence of the layer containing fading melanin.)

Termination of the bleaching reaction can be achieved by various means depending on the particular bleaching. For pH-sensitive oxidation reactions, quenching can be achieved by changing the pH. For example, in reactions using hydrogen peroxide, quenching can typically be achieved by lowering the pH to 5 or lower by the addition of a strong inorganic acid, such as HCl. Other redox reactions can be stopped by the addition of supplemental reducing or oxidizing agents such as sodium metabisulfite, sodium sulfite, ascorbic acid and the like.

The bleached melanin thus obtained is
Before being used in the present invention, they are subjected to cleaning. In particular, the bleaching agent is completely extracted and the low molecular weight degradation products of melanin are separated.

The following methods are used for the method of bleaching melanin, all of which can be applied in the present invention. Method using hydrogen peroxide. Method using potassium permanganate. Method using sodium hypochlorite. Method with peracetic acid. Method using perchloric acid. Method using sodium periodate. Further, a method for fading melanin by an oxidation / reduction reaction other than the above or other methods can also be applied to the present invention.

As the base material of the recording medium, a paper or plastic sheet is used, and a light-transmitting material is used.
Both light impermeable ones are used. As such a base material, in addition to ordinary paper made of cellulose, synthetic paper, or the like as paper, a sheet made of synthetic or natural resin and a modified product thereof is used. For example, polyester resin, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, celluloid and the like can be mentioned. When the base material contains bleached melanin, the bleached melanin can be used while being supported on polymer beads.

The ink receiving layer is formed of a coating material containing or not containing fading melanin. A known inorganic filler for further improving the ink absorbing property of the ink receiving layer, and a UV absorbing material are known. It may be formed by a known ultraviolet absorber and other additives for causing the addition, for example, a surfactant, a penetrant, a water retention agent, a foam inhibitor, a coloring agent, and the like, if necessary.

As such a coating material, the following natural resins and synthetic resins are used. That is, polyvinyl alcohol, albumin, gelatin, casein, starch, kaotin starch, gum arabic, natural resins such as sodium alginate, polyamide, polyacrylamide,
Polyvinylpyrrolidone, polyvinylpyrrolidone tetrachloride,
Polyethylene imine, polyvinyl pyridium halide, melamine resin, polyurethane, carboxymethyl cellulose, polyvinyl alcohol, polyester, sodium polyacrylate, RBS latex, NBR latex, polyvinyl formal, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, polyvinyl chloride, poly Synthetic resins such as vinyl acetate, phenolic resins and alkyd resins are used.

As the inorganic filler for further improving the ink absorption of the ink receiving layer, alumina, silica,
Clay, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, synthetic zeolite, zinc oxide, lithobon, satin white and the like are used.

The ink receiving layer is formed by dissolving or dispersing the polymer for coating in a suitable solvent, and adding or not adding discoloration melanin thereto by dissolving or dispersing. And then coating the obtained ink receiving layer forming liquid on the above substrate by a known coating method such as a roll coating method, a spray coating method, a rod bar coating method, an air knife coating method, and drying. Made by

The glossy layer is a glossy layer forming solution obtained by dissolving or dispersing the above-mentioned coating polymer in a suitable material and adding the following synthetic silica, colloidal silica, and the following cationic polymer electrolyte. Is formed by coating the above-mentioned ink-receiving layer with the above-mentioned known coating method, with or without addition of bleached melanin to the above-mentioned ink-receiving layer, and while the coating layer is in a wet state, it is pressed against a heated mirror surface and dried. Is done.

Examples of the synthetic silica generally include amorphous silica, amorphous silica, silicic anhydride, hydrated silicic acid, finely divided silica, and silicic acids called white carbon.

Examples of the cationic polymer electrolyte include polyvinylbenzyltrimethylammonium halide, polydiacryldimethylammonium halide, polydimethylaminoethyl methacrylate hydrochloride, polyethyleneimine, dicyandiamide formalin condensate, epichlorohydrin-modified polyalkylamine, polyvinylpyridinium halide, and polyamine. And polyethyleneimine quaternary ammonium salts.

The UV-absorbing layer is prepared by dissolving or dispersing the above-mentioned coating polymer in a suitable material, and adding a known UV-absorbing agent and / or discolored melanin described below to the UV-absorbing layer forming solution. It is formed by coating on the ink receiving layer or the gloss layer by the known coating method and drying.

Examples of known UV absorbers include salicylic acid UV absorbers, benzotriazole UV absorbers,
Known UV absorbers such as a benzophenone UV absorber and a cyanoacrylate UV absorber are used.

[0034]

EXAMPLES Next, the present invention will be described in detail with reference to Examples of the present invention and Comparative Examples. The ratio is expressed on a weight basis. The bleached melanin used in all Examples and Comparative Examples was prepared as described below, but other bleached melanin can be similarly prepared and used. Further, the same can be achieved by using another substance such as peracetic acid or sodium hypochlorite as the oxidizing agent. As a melanin source for use in a white recording medium, a light-colored one such as dopa / cysteine pheomelanin was used. 100 g of this melanin was dispersed in 500 ml of 0.2 M ammonia water. During the night, 0.2 M ammonia water and 2% hydrogen peroxide solution were added.
After adding 00 ml and stirring for 30 minutes, the pH was lowered to 3 for sedimentation, followed by sedimentation by a centrifuge. An aqueous solution of potassium permanganate was added to the precipitate, and the mixture was added excessively until a specific color indicating oxidizing power appeared, and then the mixture was allowed to stand for 10 minutes.
Thereafter, the oxidizing power of excess potassium permanganate was neutralized with a reducing agent such as sodium metabisulfite, followed by centrifugation, and washing with 0.001 M hydrochloric acid and acetone several times to obtain bleached melanin. The obtained bleached melanin had L * = 95.7, a * = 0.1, and b * = 8.4.

The light resistance test was performed as follows. Printing: Seiko Epson Inkjet Printer P
M-700C Evaluation: Evaluation based on the change in optical density of magenta full solid Attach xenon wafer with a sample stuck inside a south-facing window and left for 2 weeks, 1 month or equivalent irradiation The optical density is more than 90% with respect to the unirradiated A by using the Ziometer Ci35A. A: The optical density is 80 to 90% with respect to the unirradiated B. The optical density is less than 80% with respect to the unirradiated C. did.

(Examples 1-5, Comparative Examples 1-2) Weighing 100 g / m
^{2 Based} on high quality paper or white PET synthetic resin film with a thickness of 100μm, dry coating amount 20g on this substrate
/ M ² was coated with a composition for forming an ink-receiving layer having the following composition when dried (aqueous dispersion having a solid content of 8%) to obtain a recording medium. Coating is performed by a bar coater method and drying is performed by hot air drying at 110 ° C for 5 minutes.

Example 1 Silica (X-37B manufactured by Tokuyama) 75% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 17.99% Discolored melanin 0.01% Waterproofing agent (P-104 manufactured by Senka) 7%

Example 2 Silica (Tokuyama X-37B) 75% Polyvinyl alcohol (Kuraray PVA-117) 17.9% Fading melanin 0.1% Waterproofing agent (Senka P-104) 7%

Example 3 Silica (X-37B manufactured by Tokuyama) 75% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 17% Discolored melanin 1% Waterproofing agent (P-104 manufactured by Senka) 7%

Example 4 Silica (Tokuyama X-37B) 75% Polyvinyl alcohol (Kuraray PVA-117) 15% Fading melanin 5% Waterproofing agent (Senka P-104) 5%

Example 5 Silica (X-37B manufactured by Tokuyama) 70% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 15% Discolored melanin 10% Waterproofing agent (P-104 manufactured by Senka) 5%

Comparative Example 1 Silica (X-37B manufactured by Tokuyama) 75% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 17.995% Discolored melanin 0.005% Waterproofing agent (P-104 manufactured by Senka) 7%

Comparative Example 2 Silica (X-37B manufactured by Tokuyama) 70% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 13% Fading melanin 13% Waterproofing agent (P-104 manufactured by Senka) 4%

(Examples 6 and 7, Comparative Examples 3 and 4) Weighing 100 g
/ M ² high-quality paper or 100 μm thick white PET synthetic resin film as the base material, and coated with the ink-receiving layer forming liquid having the following dry composition (coating amount at dry time 20 g / m ² )
Example 6 below on the ink-receiving layer formed by drying
-7, coating with a gloss layer forming liquid (aqueous dispersion having a solid content of 10%) for preparing a gloss of the composition as described in Comparative Examples 3 and 4 (coating amount at drying: 3 g / m ² ) Thus, a glossy recording medium was obtained.

(Ink-receiving layer dry composition) Silica (X-37B manufactured by Tokuyama) 75% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 17.995% Discolored melanin 0.005% Waterproofing agent (P-104 manufactured by Senka) 7%

Example 6 Colloidal silica (Catalyst Chemical Industry, Cataloid-S150) 50% Polyvinyl alcohol (Kuraray PVA-117) 49.99% Fading melanin 0.01%

Example 7 Colloidal silica (Catalyst Chemical Industries, Cataloid-S150) 49% Polyvinyl alcohol (Kuraray PVA-117) 49% Fading melanin 2%

Comparative Example 3 Colloidal silica (Catalyst Chemical Industries, Cataloid-S150) 50% Polyvinyl alcohol (Kuraray PVA-117) 49.995% Fading melanin 0.005%

Comparative Example 4 Colloidal silica (Catalyst Chemical Industry, Cataloid-S150) 44% Polyvinyl alcohol (Kuraray PVA-117) 44% Fading melanin 12%

(Examples 8-9, Comparative Examples 5-6) 100 g weighing
/ M ² high-quality paper or a 100 μm thick white PET synthetic resin film as a base material, and coated with an ink receiving layer forming liquid having the following dry composition (coating amount at dry time 20 g / m ² )
On the ink receiving layer formed by drying, the following Examples 8 to
9. Coating (coating amount: 0.5 g / m ² ) with the ultraviolet absorbing layer forming solution (water dispersion having a solid content of 10%) having the composition as described in Comparative Examples 5 to 6 upon drying I got

(Composition at the time of drying the ink receiving layer) Silica (X-37B manufactured by Tokuyama) 75% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 17.995% Discolored melanin 0.005% Waterproofing agent (P-104 manufactured by Senka) 7%

・ Example 8 of real clay Silica (X-37B manufactured by Tokuyama) 74% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 25.99% Fading melanin 0.01%

Example 9 Silica (X-37B manufactured by Tokuyama) 70% Polyvinyl alcohol (PVA-117 manufactured by Kuraray) 25% Fading melanin 5%

Comparative Example 5 Silica (Tokuyama X-37B) 74% Polyvinyl alcohol (Kuraray PVA-117) 25.995% Fading melanin 0.005%

Comparative Example 6 Silica (Tokuyama X-37B) 65% Polyvinyl alcohol (Kuraray PVA-117) 20% Fading melanin 15%

Table 1 shows the evaluation results of the above Examples and Comparative Examples. "Insufficient ink absorbency" in the remarks column in the table is "bleeding" due to insufficient ink absorbency in the initial image.
Indicates that the outline is “blurred”.

[0057]

[Table 1]

The following Examples 10 and 11 are examples in which bleached melanin was added to a substrate. Example 10 When weighing 100 g / m ² of high quality paper, the dry weight was 0.1%.
The bleached melanin was mixed so as to be ~ 20%. to this,
A recording medium was obtained by mounting the ink receiving layer having the following composition at the time of drying. Silica (Tokuyama X-37B) 75% Polyvinyl alcohol (Kuraray PVA-117) 18% Waterproofing agent (Senka P-104) 7% All of these recording media have a light resistance of B or higher after one month exposure Showed sex. If the amount of addition is less than this, it will be ranked C in one month exposure. In addition, 20% of fading melanin
It was confirmed that when added in excess of, the paper strength was significantly reduced, and the practicality of the recording medium was impaired.

Example 11 Instead of the paper of Example 10, a bleached melanin was incorporated during the production of a PET film whitened with barium sulfate.
The same ink receiving layer was coated. Example 1
As with 0, the effect of improving light resistance is low at 0.1% or less.
If it is added in excess of 0%, the strength (particularly the surface strength) of the PET film decreases, and the practicability decreases.

From the description of the above Examples and Comparative Examples, it is clear that the light fastness of the recording medium was improved by using a melanin subjected to a fading treatment (faded melanin).

[0061]

According to the present invention, as described in detail above, a substrate,
By adding fading melanin to at least one of the ink receiving layer, gloss layer, and ultraviolet absorbing layer, it is possible to improve the light resistance, not adversely affect the physical properties and recording characteristics of the recording medium, and record with high safety. A medium is obtained.

Claims (5)

[Claims] 1. A recording medium characterized in that at least one of the substrate and / or the coating layer contains bleached melanin. 2. The method according to claim 1, wherein the content of the bleached melanin is 0.1 to 20% by weight based on the weight of the substrate or 0.01 to 10% by weight based on the weight of the coating layer containing the bleached melanin. Item 2. The recording medium according to Item 1. 3. The recording medium according to claim 1, wherein at least one of the coating layers is an ink receiving layer containing bleached melanin. 4. The recording medium according to claim 1, wherein at least one of the coating layers is a glossy layer containing bleached melanin. 5. The recording medium according to claim 1, wherein at least one of the coating layers is an ultraviolet absorbing layer containing bleached melanin.