JPH01115677A - Recording medium - Google Patents

Abstract

PURPOSE:To enhance after yellowing resistance of a recording medium under preservation while maintaining excellent color development properties of images, by jointly using synthetic silica having a specific surface area according to the BET method of not less than a specified value and a thioether antioxidant. CONSTITUTION:Silica having a specific surface area according to the BET method of at least 100m<2>/g and a thioether antioxidant are incorporated in a recording medium, whereby various useful properties, particularly, after yellowing resistance during preservation can be enhanced. By use of silica having such a specific surface area, it is possible to achieve excellent color development properties for a watersoluble dye in an ink and optimum shape and size of droplets of ink jet. The thioether antioxidant may be, for example, 4, 4'-thiobis(3-methyl-6-t-butylphenol) or 2,2'-thiobis(4-methyl-6-t-butylphenol). The amount of the thioether antioxidant added is preferably 10-50wt.% based on synthetic silica.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a recording medium, and more particularly to an improved inkjet recording medium having various properties such as excellent storage stability, non-staining property, and color development. Regarding the medium.

(Prior art) Inkjet recording methods include various recording liquid (hereinafter referred to as F ink) ejection methods (for example, electrostatic suction method, method of applying mechanical vibration or displacement to ink using a piezoelectric element, and method of applying mechanical vibration or displacement to ink using a piezoelectric element). In this method, small droplets of ink are generated using a method that uses the pressure of foaming and foaming, etc., to fly, and some or all of them adhere to a recording medium such as paper to perform recording. However, it is attracting attention as a recording method that generates little noise and can perform high-speed printing and multicolor printing.

Water-based inks are mainly used for inkjet recording in view of safety and printability.

On the other hand, conventional paper has generally been used as a recording medium. When recording on such paper using liquid ink, it is generally necessary that the ink does not bleed onto the recording medium and cause the print to become blurry, and that the ink dries as quickly as possible after recording. It is desirable not to accidentally contaminate the paper surface.

In other words, in the inkjet recording method, (1) Even if the ink is quickly absorbed into the recording medium, ink deposited later may mix with ink deposited earlier, disturb ink dots, or flow out. (2) The diameter of the ink dot should not become larger than necessary due to the ink droplets spreading on the recording medium; (3) The shape of the ink dot should be close to a perfect circle and the surrounding area should be smooth; It is necessary to satisfy various requirements such as (4) high density of ink dots and no blurring around the dots, and (5) high whiteness of the recording medium and high contrast with the ink dots.

Conventionally, in order to satisfy these conditions, recording media containing silica have been proposed as inkjet recording media, and in particular, as described in JP-A-60-204390, silica with a large BET specific surface area has been proposed. The recording medium containing the recording material has the advantage of being particularly excellent in the color development of the recording agent.

However, recording media containing silica with such a high specific surface area can be stored in files, tape, glue, etc.
If the recording medium is in contact with a printer's platen rubber roll, etc. for a long time, the silica in the recording medium will adsorb the additive components from the contact objects such as files, causing the recording medium to turn yellow and seriously impairing its appearance. There is a point.

(Problems to be Solved by the Invention) An object of the present invention is to satisfy all the problems that the prior art could not solve in the above-mentioned technical field.

In particular, the present invention meets the above-mentioned requirements before and after recording images using the inkjet recording method, especially non-staining (non-yellowing) during storage of the recording medium and when in contact with tape, glue, rubber, etc.
In particular, it aims to improve non-yellowing when using a silica-containing recording medium with a high specific surface area, which provides excellent color development but is prone to yellowing when stored in files, etc. .

(Means for Solving the Problems) The above and other objects are achieved by the present invention as described below.

That is, in the present invention, the specific surface area by the BET method is 1oo
This recording medium is characterized by containing synthetic silica of rn''7g or more and a thioether antioxidant.

(Function) By containing silica and a thioether antioxidant having a BET specific surface area of 100 m'/g or more in a recording medium, various useful properties, particularly non-yellowing during storage, can be improved.

In other words, silica-containing recording media with a high specific surface area, which conventionally produce images with excellent color development, but whose non-staining properties (yellowing) are insufficient, are being treated with 1,000-onythyl-based antiseptics. By including an oxidizing agent, the non-yellowing property of the recording medium during storage is significantly improved while maintaining the excellent color development of images formed with inks, particularly inks containing water-soluble dyes.

Incidentally, conventional recording media containing antioxidants include, for example, Japanese Patent Application Laid-open No. 57-74192 and No. 57-8798.
As described in Publication No. 9, as an anti-fading agent for dye images,
A recording medium containing an antioxidant is exemplified for the purpose of improving the light resistance of an image.

It is well known that antioxidants are used to improve the light resistance of images, but as shown in the present invention, they are used in combination with synthetic silica having a specific surface area of 100 m2/g or more to improve the yellowing resistance of recording media. Not all antioxidants are effective in improving.

In particular, BIT which is exemplified as a suitable example in the above publication
According to the inventor's study, phenolic compounds such as hydroquinone antioxidants, benzotriazole compounds, and diphenylamine compounds are used as pigments with a large specific surface area and high adsorption ability in order to improve color properties. When used together, they catch oxygen radicals in the air as antioxidants, form quinone structures, dimers, etc., and cause yellowing of the white area (pigment-coated surface) of the recording medium.

Additionally, according to the findings of the present inventors, when a recording medium is stored in a binder made of polyethylene, polypropylene, vinyl chloride resin, etc., or when the recording medium comes into contact with tape, glue, rubber, etc., the surface area is large and the adsorption capacity is large. Phenolic, quinone, and amine antioxidants in binders, tape adhesives, glues, rubbers, etc. volatilize and are adsorbed by the silica in the recording medium, which has a high It was denatured and caused yellowing of the white part.

On the other hand, if a pigment with a small surface area such as calcium carbonate or silica with a low BET specific surface area of less than 100 m2/g is used, the above problem will not occur, but sufficient color development of the image will occur. I can't get sex. Therefore, B
Such antioxidants had the opposite effect on preventing yellowing of white areas of recording media containing silica pigments with an ET specific surface area of 100 m'/g or more.

As described above, the present invention uses a silica pigment with a high specific surface area and a specific antioxidant to achieve high color development and excellent yellowing resistance during storage, which are unattainable with conventional techniques. Provide a recording medium with

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The recording medium of the present invention is characterized in that various conventionally known recording media are combined with specific compounds, that is, silica with a high specific surface area and a thioether antioxidant. objective was achieved.

The recording medium of the present invention uses various conventionally known recording media such as plain paper, processed paper, synthetic paper, and plastic film as a base material, and the base material also contains silica with a high specific surface area and a thioether antioxidant. obtained by

Particularly preferable silica for use in the recording medium of the present invention has a specific surface area of 100 g/g or more according to the BET method;
Synthetic fine particle silica with a specific surface area of 100 to 700 rn"/g is preferable. By using silica with such a specific surface area, excellent color development of the water-soluble dye in the ink and optimum shape and size of ink dots can be achieved. can be achieved.

The thioether antioxidant used in the present invention may be any conventionally known thioether antioxidant, such as 4,4'-thiobis(3-methyl-6-t-butylphenol). ), 2.2'-thiobis(4-methyl-6-t-butylphenol), 4.4'-thiobis(2-methyl-6-t-butylphenol), distearylthiodipropionate, (R =C,.-14 alkyl group) (R=C+2 alkyl group) S@CH2C1(2GO-R) 2 (C)(R=G
+3 alkyl group), for example, the above compounds (A) to (C)
Of course, compounds in which the number of carbon atoms in the alkyl group (R) is changed to a number other than those mentioned above can also be used, and in terms of shape, aqueous dispersions such as emulsions and diversions can also be used.

Any method may be used to incorporate the silica and thioether antioxidants into the base material, but for example, these two components may be added simultaneously or separately in the paper making process of such a base material to make paper. There are methods such as adding these two components to an impregnating liquid for paper and a post-treatment method in which the substrate is immersed in this impregnating liquid, but any method may be used.

In such a method, the amount of the thioether antioxidant added is preferably in the range of 10 to 50% by weight based on the synthetic silica. That is, if the content is less than 10% by weight, the effect of preventing yellowing is insufficient, while if the content exceeds 50% by weight, color development and ink absorbability will be reduced.

On the other hand, the recording medium of the present invention of the type containing the above-mentioned two components in the coating layer on the surface of the base material is produced by adding the above-mentioned two components to a coating solution for a substrate such as paper, and using this coating solution as a base material. It is manufactured by coating it on a material and drying it. Other components of the coating liquid in this case include clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, magnesium chloride, satin white, alumina, aluminum silicate, Inorganic pigments such as lithopone: starch, gelatin, casein, gum arabic, sodium alginate, carboxymethyl cellulose,
Water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and sodium polyacrylate; Synthetic resin latex such as synthetic rubber latex; Organic solvent-soluble resins such as polyvinyl butyral and polyvinyl chloride; Furthermore, dispersants, fluorescent dyes, PL + regulators, Various additives such as antifoaming agents, lubricants, preservatives, surfactants, and waterproofing agents can be mentioned. In this case as well, the amount of the thioether antioxidant to be added is preferably in the range of 10 to 50% by weight of the synthetic silica, as in the above case.

The solid content of the coating solution is preferably about 1 to 50% by weight, and the coating solution is usually coated with a coating solution of 1 to 50% by weight by a known method such as a roll coater method, a blade coater method, an air knife coater method, etc. An amount of about 50 g/m 2 (dry coating amount) is applied onto the substrate. The recording medium of the present invention can be obtained by coating preferably about 2 to 30 g/m 2 (dry coating amount).

(Effects) According to the present invention as described above, a silica-containing recording medium with a high specific surface area (BET method specific surface area of 100 g or more) can be used as a conventional recording medium, especially as a recording medium in an inkjet recording method. Although it is known to exhibit excellent color development, when recording with ink made of water-soluble dyes on such silica-containing recording media, the yellowing resistance of white areas during storage is extremely low. There was, but
According to the present invention, by including a thioether antioxidant as described above in the silica-containing recording medium,
It was possible to significantly improve the yellowing resistance during storage, which had been a drawback of silica-containing recording media, without losing any of the excellent color development properties inherent in them.

Furthermore, according to the present invention, the ink is quickly absorbed into the recording medium, and even if ink of different colors is repeatedly deposited on the same cylinder within a short period of time, there is no ink flow or oozing phenomenon, resulting in a high Clear images with high resolution can be obtained. Therefore, the recording medium of the present invention is suitable not only for general recording but also particularly for inkjet recording.

Hereinafter, the present invention will be explained in more detail according to Examples and Comparative Examples. However, parts or percentages in the text are based on weight unless otherwise specified.

Example 1 and Comparative Example 1 The base material had a size degree of 30 based on JISP8122.
Using general high-quality paper (basis weight 65 g/rn"), coat the coating solution with the following composition on this base material with a blade coater at a dry coating weight of Bg/d, and then apply it by a conventional method. By drying, recording media of the present invention and comparative examples were obtained.

Synthetic silica (Fuji Davison Chemical, Cyroid 404
, specific surface area 340rn2/g) 100 parts polyvinyl alcohol (manufactured by Kuraray, PVA117)
40 parts antioxidant
X part water
400 copies of the above recording medium was placed between a polypropylene holder and a neoprene rubber roller, and after 30 days, the decrease in whiteness on the coated side of the recording medium was evaluated, and the results shown in Table 1 below were obtained. The measurement was carried out using a high-speed spectrophotometer model CA-35 (manufactured by Murakami Color Technology Research Co., Ltd.) to determine the color difference (△E"), which was used as a measure of the degree of yellowing during storage. The smaller the value, the better the yellowing resistance. In good condition.

b)-1-J〈--711 (ratio N(a) 8 stones 15.0 1
0 18 (specific gravity (a) + 1 + quinone 15
．． 0Is25 (l soil m4.4'-thiobis(3-methyl-6-tert-methyl 15.0
2 3 (IU.I,.

], /-ru (Sumirai Zashi WX-R1 (Makiihise t1 Yo) Compound A (MARK An-21J: Storage 1 of 15
．． 01 2 (MARK A)
()-503 Iriseiyu → Kari's 15.01 3 (Miboro (i) Dilaurylthiodifuropionate 15.023
(l.41 (a) As shown in Table 1 above, the non-staining property of the recording medium of the present invention is significantly improved compared to that of the comparative example, and the non-staining property of the recording medium of the present invention is significantly improved compared to that of the comparative example. Even when the ink was used, there was no ink bleeding, and the ink was clear with high resolution.The color development was equally excellent in the examples and comparative examples.

Example 2 and Comparative Example 2 Recording media of the present invention and comparative examples were obtained in the same manner as in Example 1, except that the pigments and antioxidants in Example 1 were used in combinations shown in Table 2 below.

These recording media were evaluated in the same manner as in Example 1, and the results shown in Table 2 below were obtained.

As is clear from Table 2, when pigments with a small surface area are used, there is little yellowing during storage, but the image density is insufficient; if silica with a small surface area is used, the image density is good, but , yellowing occurs in dogs, and the above silica contains B as an antioxidant.
If conventional products such as HT are used, the yellowing will be even worse. On the other hand, it is clear that when the above-mentioned silica and thioether antioxidant are used in combination as in the present invention, excellent image density and excellent yellowing resistance during storage can be achieved at the same time.

(Left below) Calcium carbonate 5--0.62 (Sealed phase a Silica 1" 40--0.7
2 (Comparative example) Silica 1 40
8+17 15.00.7 3 (Comparative example) Silica 2" 280 - -1
．． 2 9 (specific gravity (a) silica 2 2
60 B117 15.0 1.2 +2
(Comparative example) Silica 2260 #” 15
．． 0” 1.2 2 (Example) Silica 226
0 Compound A” 5.0”1.2 6 (
Reference example) Silica 2260 Compound A” 100.0
I'50.9 1 (Reference example) *l: Print solidly with black ink using an inkjet device, measure that part with Macbeth RD-918, and check the color density of Tsurak (0, D,
) was displayed.

*2: Mizukashi JL4'-527 (manufactured by Mizusawa Chemical) *3:
Fine Seal X-37CB) (manufactured by Tokuyama Soda) *4
: Emulsion of emulsion (manufactured by Adeka Argus, MAI)
IK 1. X-45) *5: Values are solid content equivalent values.

Claims (2)

[Claims] (1) A recording medium characterized by containing synthetic silica having a specific surface area of 100 m^2/g or more by the BET method and a thioether antioxidant. (2) The recording medium according to claim (1), wherein the content of the thioether antioxidant is 10 to 50% by weight of the content of the synthetic silica.