JPH09183269A - Inkjet recording sheet - Google Patents

Abstract

(57) Abstract: An inkjet recording sheet excellent in a light-transmissive recording medium for OHP or the like is provided. An ink jet recording sheet having a recording layer provided by coating an aqueous coating composition containing polyvinylpyrrolidone and an aqueous acrylic resin as main components on a support and drying the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly to a light transmissive recording medium for an overhead projector (OHP) or the like.

[0002]

2. Description of the Related Art The ink jet recording method is one in which minute droplets of ink are ejected and adhered to a recording medium for recording, and since the flexibility of recording patterns is great and it is easy to make multiple colors, It is rapidly becoming popular as a hard copy device. Generally, in the inkjet recording method, an aqueous ink in which a dye, a wetting agent, an antiseptic agent, a dispersant, or the like is dissolved is used. Therefore, a recording sheet that is a recording medium may have an appropriate water absorption property. It is necessary, and in general, paper provided with a recording layer containing a water-soluble polymer or a water-absorbing pigment as a main component is used. On the other hand, the light transmissive recording medium is widely used for conferences, academic conferences, briefing sessions, lectures, etc. for OHP, and there is an increasing demand as a recording medium for signboards, show windows, etc. The conventional light-transmissive recording medium is mainly produced by the electronic copying method (PPC), but recently, as the demand for colorization increases, the ink jet recording method which is excellent in the sharpness of the recorded image is drawing attention. It's starting to happen.

By the way, a plastic film such as polyethylene terephthalate has been generally used as a transparent recording medium used for OHP and the like, and since these resin films do not have sufficient water absorption, they are used for ink jet recording. There was a defect that the ink did not absorb and the ink flowed to make the image unclear, and the ink was poorly dried, and the recorded image was stained or stuck due to rubbing or overlapping.

Therefore, in order to make the plastic film have an appropriate ink absorption property, for example, JP-A-59-17 is used.
No. 4381, JP-A-60-132785, JP-A-60-145879, JP-A-60-2245
Japanese Patent Laid-Open No. 78 or Japanese Patent Laid-Open No. 61-32788 proposes that a recording layer made of a water-soluble polymer such as starch, a water-soluble cellulose derivative, polyvinyl alcohol, or polyvinylpyrrolidone is provided on the film. However, in the case of these proposals, although the ink absorptivity is improved to some extent, the ink absorptivity is still slow, the ink easily bleeds, and the drying property is insufficient. There was a problem that it was difficult to handle. Further, since the water resistance of the recording layer is insufficient, there is a problem that the recording image becomes sticky under high humidity, and the recorded image is blurred due to the adhesion of water droplets or sweat.

In order to improve the water resistance of the recording layer, for example, JP-A-63-183873 proposes a method of providing a recording layer containing a modified polyvinyl alcohol and a water-proofing agent. According to this method, the ink absorbency is lowered with the improvement of water resistance, and as a result, the sharpness of the printed image is lowered. Also, Japanese Patent Application Laid-Open
JP-A-229685 proposes a method of forming a recording layer by crosslinking an aqueous composition containing a water-soluble polymer and polyethylene glycol di (meth) acrylate as essential components by irradiation with active energy rays. surely,
According to this method, ink absorbency and water resistance are improved, but it is difficult to balance the quality of the two, and satisfactory results have not always been obtained.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides an ink jet recording sheet excellent in recording image quality, ink absorbency, water resistance and transparency without any of the above-mentioned defects, particularly a light transmissive recording for OHP and the like. An inkjet recording sheet suitable as a medium is provided.

[0007]

The present invention is characterized in that an aqueous coating composition containing polyvinylpyrrolidone and an aqueous acrylic resin as a main component is applied on a support and dried to form a recording layer. It is a recording sheet.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that when polyvinylpyrrolidone (hereinafter referred to as PVP) is blended in a recording layer,
The image quality (color development) of the water-based ink when recorded on the recording layer with an inkjet printer is excellent, but the drying property of the ink is slow, the printed part is sticky, and the white paper part (unrecorded part of the recording layer) Since it has a problem that the stickiness is poor, the inventors of the present invention have earnestly studied whether these defects can be improved by using PVP together with other substances. As a result, they have found that these drawbacks can be eliminated by using an aqueous acrylic resin together. Incidentally, in the case of the recording layer formed only of the water-based acrylic resin, it hardly absorbs the water-based ink and the image quality is remarkably inferior.
In the case of a recording layer formed of a coating liquid in which P and an aqueous acrylic resin are mixed, not only excellent image quality (coloring property) is maintained, but also ink drying property is excellent and stickiness of a printing portion or a blank portion is obtained. You can get excellent quality that won't happen.
It was found that the water resistance was also excellent, and the present invention was completed.

That is, the ink jet recording sheet of the present invention is characterized in that an aqueous coating composition containing PVP and an aqueous acrylic resin is coated on a support and dried to form a recording layer. . The mixing ratio of PVP and the aqueous acrylic resin is not particularly limited,
As a preferable range, a more excellent effect can be obtained when the mixing ratio of both is in the range of 80:20 to 20:80 in terms of solid content. Incidentally, if the PVP exceeds 80% by weight, the ink drying property is deteriorated, and further, the stickiness in the printed portion and the white paper portion is likely to occur. There is a risk of deterioration in image quality and ink drying property.

Here, as PVP, commercially available ones can be used and are not particularly limited. However, if the molecular weight is too small, it is easily dissolved in water, which is advantageous from the viewpoint of preparing a coating composition. When the recording sheet is finished, the water resistance of the recording layer tends to be poor. On the other hand, if the molecular weight is too large, there is no particular problem in terms of quality, but it becomes difficult to dissolve in water, the viscosity of the solution after dissolution becomes high, and handling may become difficult. Therefore, in the present invention, P
The average molecular weight of VP is preferably about 100,000 to 1,000,000.

On the other hand, the aqueous acrylic resin is not particularly limited as long as it is soluble or dispersible in water, and it is used as an aqueous solution or an aqueous dispersion (emulsion), respectively. An acidic functional group such as a carboxyl group is introduced into the water-based acrylic resin in order to impart hydrophilicity, and an acid value of 50 to 150 is particularly preferable. By the way, if the acid value is less than 50, there is a concern that the ink absorbency may decrease, while if it exceeds 150, the printed part may easily become sticky and the water resistance may also decrease. The acid value is defined as the number of mg of potassium hydroxide required to neutralize the acid component contained in 1 g of the resin. The main components of the monomers used in the synthesis of the aqueous acrylic resin include, for example, acrylic acid, methacrylic acid, acrylic acid ester,
Methacrylic acid ester can be mentioned, and further, styrene,
Vinyl chloride, vinyl acetate, acrylonitrile, ethylene, acrylamide, N-methylol acrylamide,
Itaconic acid, maleic acid and the like are also used if necessary.
Here, as the acrylic acid ester and the methacrylic acid ester, methyl (meth) acrylate, ethyl (meth) acrylate, -n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylic acid- 2-
Examples thereof include ethylhexyl, tert-butyl methacrylate, lauryl methacrylate, octadecyl methacrylate and the like.

As the support in the present invention, a transparent base material or an opaque base material such as paper, synthetic paper or white film can be used. In particular, when an opaque substrate is used, the recording layer according to the present invention is essentially transparent, so that an inkjet recording sheet having excellent gloss can be obtained. In addition, as paper, high-quality paper, medium-quality paper, coated paper,
Art paper, cast coated paper, etc. can be appropriately used. As described above, the support used in the present invention is not particularly limited, but when used as a light transmissive recording medium for OHP or the like, it is preferable to use a plastic film having excellent transparency and flexibility. Preferable examples are films of polyethylene terephthalate, polyvinyl chloride, polycarbonate, polyimide, polyacetate, polyethylene, polypropylene and the like.

The thickness of the support is not particularly limited, but is 25 to 50 from the viewpoint of easy handling and cost.
The thickness is about 0 μm, more preferably about 50 to 300 μm. It should be noted that the water-based coating composition containing PVP and the water-based acrylic resin as the main components used in the present invention does not impair the recording quality by incorporating various water-proofing agents or by means such as electron beam irradiation. The water resistance can be further improved within the range.

In the present invention, in the aqueous coating composition for forming the recording layer, water-soluble polymers other than those mentioned above, for example, completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, various modified polyvinyl alcohols, casein, starch are used. , Starch derivative, water-soluble cellulose derivative, polyethylene oxide, polyethylene glycol, polyvinyl methyl ether, gelatin and the like can be added. In addition, a cationic polymer or the like may be blended to further improve the fixability of the ink.

Further, various inorganic or organic pigments such as silica, clay, talc, etc. are contained in the recording layer for the purpose of preventing stickiness or blocking on the surface of the recording sheet and controlling ink bleeding. Calcium carbonate, aluminum silicate, synthetic zeolite, alumina, zinc oxide and the like, and fine powder such as cellulose powder and starch powder can also be added. Further, various auxiliary agents such as a dispersant, a defoaming agent, a lubricant, a dye, a fluorescent dye, an antiseptic and an ultraviolet absorber can be added.

The aqueous coating composition having the above composition is coated on the substrate by a known coating means such as bar coating, blade coating, air knife coating and gravure coating. The coating amount in this case depends on the ink amount of the inkjet printer used, but the dry weight is 1 to 50 g.
/ M ² , more preferably in the range of about 3 to 30 g / m ² . Incidentally, if it is less than 1 g / m ² , the ink absorption tends to be insufficient, while if it is more than 50 g / m ² , the effect is saturated, which is disadvantageous in terms of cost and easily causes curling. Of course, it is also possible to apply several times in order to give a desired application amount. In this case, it is possible to change the compounding ratio of PVP and the aqueous acrylic resin and various additives in each coating layer.

A curl prevention layer may be provided on the surface opposite to the surface on which the recording layer is provided in order to suppress the occurrence of curl. The anti-curl layer in this case is not particularly limited, but it is presumed that the cause of the curl is caused by a change in moisture absorption / release of the recording layer due to a change in humidity, particularly due to a difference in water content between the front and back sides. Therefore, it is effective to provide a curl prevention layer having a composition similar to that of the recording layer.

Further, in the present invention, an undercoat layer may be provided under the recording layer for the purpose of promoting ink absorption. In this case, as the undercoat layer, since the image quality and quality measures such as prevention of stickiness of the surface are added with the function in the recording layer, it is necessary to provide a transparent layer having hydrophilicity to some extent. It can be achieved, for example, completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, various modified polyvinyl alcohol, PVP, casein, starch, starch derivative, water-soluble cellulose derivative,
Examples of the layer include hydrophilic polymers such as polyacrylic acid, sodium polyacrylate, polyacrylamide, polyethylene oxide, polyethylene glycol, polyvinyl methyl ether, gelatin, and cationic polymers. By providing such an undercoat layer,
It is expected that the coating amount of the recording layer can be reduced, resulting in reduction of product cost and curling suppression effect.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In addition, part and% in an example show a weight part and weight%, respectively.

Example 1 As a support, a 100 μm-thick polyethylene terephthalate film (trade name: A7300, which was subjected to an easy-adhesion treatment).
/ Toyobo), and an aqueous coating composition having the following composition (solid content concentration was 10%) was applied thereon by bar coating so that the dry weight was 10 g / m ^2, and after application It was dried at 100 ° C. for 2 minutes to obtain an inkjet recording sheet.

[Aqueous Coating Composition] 1. 500 parts of 10% aqueous solution of PVP (trade name: Rubiscol K-90 (average molecular weight of about 360,000) / manufactured by BASF) (solid content 50 parts) 2. Acrylic emulsion [Brand name: John Cryl 7001 (concentration 42%) / Johnson Polymer] 119 parts (solid content 50 parts) 3. Antiblocking agent [Product name: Ace A / Oji Cornstarch] 2 parts 4. Water 399 copies

Examples 2 to 8, Comparative Examples 1 and 2 Ink jet recording sheets were obtained in the same manner as in Example 1 except that the aqueous coating composition having the composition shown in Table 1 was used. Note that the compounding parts in the table are solid content ratios, and the aqueous coating compositions of each Example and Comparative Example were compounded so that the solid content ratio of each material was the compounding part ratio in the table, and as a whole. Was adjusted to 10% by adding water.

Comparative Example 3 Commercially available OHP film for PPC (trade name; CAT.N.
No. 135-0015 / Yoshida Uchida) was used as it was.

Example 9 As a support, a 100 μm thick white polyethylene terephthalate film (trade name; Crisper / Toyobo)
Was subjected to corona discharge treatment, and an aqueous coating composition (solid content concentration 10% by weight) similar to that used in Example 1 was applied thereon to give a dry weight of 10 g / m ² by bar coating. And then dried at 100 ° C. for 2 minutes to obtain an inkjet recording sheet.

The twelve kinds of ink jet recording sheets obtained as described above were evaluated for the following items. For the printing, an inkjet printer (Desk Jet560J) manufactured by Hewlett Packard was used, and a recorded image was formed using four color inks of black, yellow, cyan, and magenta. The recorded images were evaluated as follows, and the obtained results are summarized in Table 1.

[Coloring property] The sharpness of the recorded image was visually evaluated. ○: A clear image without blurring or unevenness. B: Bleeding and unevenness are slightly conspicuous, but there is no problem in practical use. X: Marked bleeding.

[Ink Dryability] After recording, the recording sheet was left at room temperature, and the time (drying time) until the ink did not adhere to the recording portion with a finger was measured. ◯: It was dried within 5 minutes after printing. (Triangle | delta): It dried within 5 to 30 minutes after printing. X: Does not dry even one hour after printing.

[Water resistance] A fixed amount of water was dropped on the recording layer with a spoid and immediately wiped gently with gauze. ○: There is almost no damage to the coating film. Δ: The coating film was partially dissolved. X: The coating film was dissolved and almost removed.

[Stickiness] A recording sheet is kept at 30 ° C. and 80 ° C.
After being left in an environment of% RH for 2 hours, the recording layer was touched with a finger to evaluate the stickiness. ○: Almost no stickiness. Δ: A little sticky, but at a level with no practical problems. X: Sticky and practically problematic.

[0030]

[Table 1]

[0031]

As is clear from Table 1, all of the ink jet recording sheets obtained in Examples 1 to 8 of the present invention are excellent in color forming property and ink drying property, and further excellent in water resistance of the recording layer. Was there. Furthermore, since it is excellent in transparency, it has excellent suitability as an OHP sheet.
In addition, the recording surface was less sticky and did not stick even when the sheets were stacked on top of each other. Further, the inkjet recording sheet obtained in Example 9 had excellent gloss and a clear color development as compared with a normal paper-based inkjet recording sheet.

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Claims (3)

[Claims] 1. An ink jet recording sheet comprising a support and a recording layer provided by coating an aqueous coating composition containing polyvinylpyrrolidone and an aqueous acrylic resin as main components and drying. 2. The ink jet recording sheet according to claim 1, wherein the blending ratio of polyvinylpyrrolidone and the aqueous acrylic resin is 80:20 to 20:80 in terms of solid content. 3. An aqueous acrylic resin having an acid value of 50 to 1
The ink jet recording sheet according to claim 1 or 2, wherein the water-based acrylic resin of 50 is used.