JPH0911612A - Ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ink absorbabillty, water resistance and transparency by applying an aq. coating compsn. containing one of casein and soy protein and polyvinyl pyrrolidone to a transparent support and specifying a ratio of casein, soy protein and polyvinyl pyrrolidone. SOLUTION: An aq. coating compsn. containing at least one of casein and soy protein and polyvinyl pyrrolidone is applied to a transparent support to provide a recording layer. In this case, the ratio of casein in the aq. coating compsn. is 10-80wt.% per the total wt. of polyvinyl pyrrolidone and casein and the ratio of soy protein is 30-70wt.% per the total wt. of polyvinyl pyrrolidone and soy protein. The aq. coating compsn. contains an electron beam curable compd. and the recording layer is irradiated with electron beam. By this constitution, excellent ink absorbability, water resistance and transparency can be obtained.

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 is particularly suitable for a light transmissive recording medium for an overhead projector (OHP) or the like.

[0002]

2. Description of the Related Art The ink jet recording system is one in which minute droplets of ink are ejected and adhered to a recording medium to perform recording, and since the flexibility of recording patterns is large and it is easy to make multiple colors, It is rapidly becoming popular as a hard copy device. In this ink jet recording method, since an ink in which a binder, a dye, a solvent, an additive, etc. are dissolved in water is usually used, the recording sheet needs to have an appropriate water absorption property, and generally a water-soluble polymer or Paper or the like provided with a recording layer containing a water-absorbent 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.
In addition, demand for recording media for billboards, show windows, etc. is also increasing. The conventional light transmissive recording medium is mainly made by the electronic copying method (PPC).
With the increasing demand for colorization, an inkjet recording method, which is excellent in clearness of recorded images, has recently been drawing attention.

However, plastic films such as polyethylene terephthalate are generally used as transparent recording media conventionally used for OHP and the like, and since these films do not have sufficient water absorption, inks for ink jet recording are used. However, since the ink does not absorb, the image becomes unclear due to the flow of ink, and the ink is poorly dried.

Therefore, in order to provide the plastic film with an appropriate ink absorbability, for example, Japanese Patent Laid-Open No. 59-1 is used.
74381, JP-A-60-132785,
JP-A-60-145879, JP-A-60-224
In Japanese Patent Laid-Open No. 578 and Japanese Patent Laid-Open No. 61-32788, it is proposed to provide a recording layer on the film with a water-soluble polymer such as starch, a water-soluble cellulose derivative, polyvinyl alcohol and polyvinylpyrrolidone. However, although this method improves the ink absorption to some extent,
Since the ink absorbency is still slow, the ink easily bleeds and the drying property is insufficient, and thus the tackiness of the recording surface remains for a long time, which makes it 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 adhesion of water drops or sweat.

In order to improve the water resistance of the recording layer, for example, JP-A-63-183873 discloses a method of providing a recording layer containing a modified polyvinyl alcohol and a water-proofing agent. Since the ink absorbency is lowered with the improvement of the property, there is a problem that the sharpness of the printed image is lowered. Further, JP-A 1-229685 proposes a method of forming a recording layer by cross-linking a composition containing a water-soluble polymer, polyethylene glycol di (meth) acrylate and water as essential components by irradiation with active energy rays. ing. Certainly, this method improves the ink absorbency and the water resistance, but it is difficult to balance the qualities of the two, and it is not always possible to obtain stable and satisfactory results.

[0007]

The present invention is excellent in ink absorption and water resistance and is excellent in transparency without the above-mentioned defects. Therefore, the present invention is a light transmissive recording medium especially for OHP. And an ink jet recording sheet suitable as the above.

[0008]

An ink jet recording sheet according to the present invention is formed by coating a support with an aqueous coating composition containing at least one selected from casein and soybean protein and polyvinylpyrrolidone. It has a recording layer. The ratio of casein in the aqueous coating composition is 1 with respect to the total weight of polyvinylpyrrolidone and casein.
It is preferably in the range of 0 to 80%.

The proportion of soybean protein in the aqueous coating composition is preferably in the range of 30 to 70% based on the total weight of polyvinylpyrrolidone and soybean protein. The aqueous coating composition may further contain an electron beam curable compound, and the recording layer may be irradiated with an electron beam. It is even better if the support is transparent.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors used polyvinylpyrrolidone in combination with other substances because the property of polyvinylpyrrolidone is that the color development of the ink is excellent but the stickiness of the printed part is poor. As a result of diligent investigations on whether or not this drawback can be compensated, it was surprisingly found that use of casein or soybean protein in combination with polyvinylpyrrolidone eliminates this drawback, and completed the present invention. Due to the background of the study, casein or soybean protein alone hardly contribute to the ink drying property.
It was found that coexistence of polyvinylpyrrolidone and casein or soybean protein is very effective not only for color development but also for ink drying property. It was also confirmed that the same effect can be obtained even when casein and soybean protein are used in combination.

It was noted that casein and soybean protein were not completely dissolved in water, but were dispersed in water in a colloidal state and became cloudy, but when applied to a sheet and then dried, it became transparent. Was confirmed.

Here, polyvinylpyrrolidone (hereinafter referred to as PV
As for P), those which are commercially available can be used,
Although not particularly limited, if the molecular weight is too small,
Irradiation with an electron beam may have little effect of improving water resistance. If the molecular weight is too large, there is no particular problem in terms of quality, but it may be difficult to dissolve in water and have a high viscosity even after dissolution, which makes handling difficult. Therefore, the average molecular weight is 100,000 to 1
About 1,000,000 is preferable.

Casein is a major protein of milk, and there are three kinds of acid casein, lactic casein, and rennet casein in the production method. However, rennet casein has a large amount of ash and is difficult to dissolve in alkali, so acid casein and lactic casein. Casein is preferred.

There are three types of soybean protein: unmodified soybean protein, hydrolyzed soybean protein, and carboxyl-modified soybean protein. Carboxyl-modified soybean protein has a higher adhesive strength and pigment dispersibility than other soybean proteins. Good and low viscosity is preferable.

The mixing ratio of PVP and casein described above is
80 to 10 wt% of casein, preferably PVP30 to 20 to 90 wt% of PVP based on the total weight of both.
70 to 40% by weight of casein with respect to 60% by weight. Here, if the casein content is less than 10% by weight, the effects of improving the water resistance and ink absorbency of the recording layer are lost, and the surface becomes sticky. On the other hand, if it is more than 80% by weight, the water resistance of the recording layer is inferior and the ink absorbency is insufficient, so that the image quality is deteriorated.

The blending ratio of PVP and soybean protein is 30 to 70% by weight of PVP based on the total weight of both, and
Soy protein 70-30% by weight, preferably PVP40
Soy protein is 60 to 40% by weight with respect to 60% by weight. Here, if the soybean protein content is less than 30% by weight, the effects of improving the water resistance and ink absorbency of the recording layer are lost, and the surface becomes sticky. Also,
If the amount is more than 70% by weight, the water resistance of the recording layer is poor, and the ink absorbency is insufficient, so that the image quality is deteriorated.

As the support used in the present invention, an opaque base material such as paper, synthetic paper, white film, etc. can also be used, in which case the recording layer according to the present invention is essentially transparent. An inkjet recording sheet having excellent gloss can be obtained. Examples of the paper include high quality paper, medium quality paper, coated paper, art paper, cast coated paper and the like.

As described above, the support used in the present invention is not particularly limited, but when it is used as a light transmissive recording medium for OHP or the like, a plastic film excellent in transparency and flexibility is used. Are preferred, and examples thereof include films of polyethylene terephthalate, polyvinyl chloride, polycarbonate, polyimide, polyacetate, polyethylene, polypropylene and the like.

When the aqueous coating composition used in the present invention contains an electron beam-curable compound having two or more radically polymerizable groups and is irradiated with an electron beam, the recording surface of the ink jet recording sheet is further water resistant. Is improved. Here, the electron beam curable compound having two or more radically polymerizable groups means
It is a monomer or oligomer having two or more radically polymerizable groups such as (meth) acryloyl group, (meth) acrylamide group, and vinyl group in the molecule. The electron beam curable compound is mixed with the above-mentioned PVP or casein to prepare an aqueous coating composition. Therefore, as an electron beam-curable compound, (a) a hydrophilic group such as a hydroxyl group, a carboxyl group (and a metal salt thereof), an amide group, an imide group, a sulfone group, an ammonium group, a phosphate group, and a polyethylene glycol group in the molecule. When using a group having a group, which itself is water-soluble or water-dispersible (self-emulsifying emulsion),
(B) There is a case where it is not water-soluble or water-dispersible by itself, but a case where a surfactant is added and vigorously stirred to make an aqueous dispersion (forced emulsion emulsion) is used.
It is preferable to use the type (1) because a transparent recording layer can be easily obtained, the effect of waterproofing is high, and the stability of the coating solution is excellent.

Examples of (a) are water-soluble electron beam curable compounds having two or more radically polymerizable groups, such as polyethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylamide, polyethylene glycol diglycidyl di ( Examples thereof include meth) acrylate and glycerin poly (meth) acrylate. Further, a water-dispersible electron beam curable compound having two or more radically polymerizable groups, such as a self-emulsifying urethane acrylate emulsion and a self-emulsifying polyester acrylate emulsion, may be mentioned.

As (b), an electron beam curable compound having two or more radically polymerizable groups other than those described in (a), for example, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, polypropylene glycol diacrylate. Examples thereof include polyfunctional monomers such as trimethylolpropane triacrylate and polyfunctional oligomers such as polyester acrylate and urethane acrylate to which a surfactant is added and the mixture is vigorously stirred to prepare an aqueous dispersion.

Of course, it is possible to use two or more kinds of the above electron beam-curable compounds having two or more radically polymerizable groups. In addition, the radical polymerizable group is 1
Electron beam curable compounds having individual compounds such as (meth) acrylic acid, (meth) acrylic acid dimer, (meth) acrylamide, (meth) acrylamide derivative, polyethylene glycol mono (meth) acrylate, and glycerin mono (meth) acrylate. It can also be used together.

The compounding amount of the electron beam curable compound having two or more radically polymerizable groups varies depending on the kind thereof, but is 0.1 per 100 parts by weight of PVP and casein or PVP and soybean protein in total. The amount is preferably about 100 to 100 parts by weight, more preferably about 0.5 to 50 parts by weight. If it is less than 0.1 parts by weight, the water resistance effect may not be exhibited, and if it is more than 100 parts by weight, the ink absorbency may decrease.

In the coating composition for forming the recording layer in the present invention, in addition to the above-mentioned PVP, casein, soybean protein, water-soluble polymer such as polyvinyl alcohol, starch, starch derivative, water-soluble cellulose derivative, poly Acrylic acid, sodium polyacrylate, polyacrylamide, 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, calcium carbonate and silica are used for the purpose of preventing stickiness and blocking of the surface of the recording sheet and controlling ink bleeding. Acid aluminum,
It is also possible to add synthetic zeolite, alumina, zinc oxide and the like, and further fine powders such as cellulose powder and starch powder. Further, various additives such as a dispersant, a defoaming agent, a lubricant, a dye, a fluorescent dye, a preservative, and an ultraviolet absorber can be added.

The above aqueous composition is applied onto a substrate by a known coating means such as bar coating method, blade coating method, air knife coating method and gravure coating method. The coating amount is preferably about 1 to 50 g / m ² after drying, and more preferably about 3 to ²⁰ g / m ² . If it is less than 1 g / m ² , the ink absorption tends to be insufficient and 50 g / m ²
If there is more, the effect will be saturated, and it will be a cost disadvantage,
Curl is likely to occur.

In order to suppress the occurrence of curl, a curl prevention layer may be provided on the surface of the substrate opposite to the surface provided with the recording surface. The curl prevention layer is not particularly limited, but it is effective to use a composition similar to that of the recording layer.

In the present invention, when the coating layer is irradiated with an electron beam, the desired improving effect can be obtained whether the drying step for evaporating water is before or after the electron beam irradiation.

It is also possible to coat the coating layer, dry it, wind it once, and then irradiate it with an electron beam offline. The irradiation dose of electron beam is 5 to 500k in absorbed dose
Gy, and more preferably in the range of about 10 to 200 kGy. If it is less than 5 kGy, it is difficult to obtain a sufficient cross-linking effect, and water resistance and ink absorbency are likely to be insufficient. 500
Excessive electron beam irradiation exceeding kGy not only saturates the effect, but also causes a decrease in strength depending on the type of support. Further, an accelerating voltage when irradiating with an electron beam is preferably about 100 to 300 kV.

[0030]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. In addition, unless otherwise specified, parts are parts by weight, and% is% by weight.

Examples 1 to 15 and Comparative Examples 1 to 13 As a support, a polyethylene terephthalate film (trade name: A730) having a thickness of 100 μm and treated for easy adhesion.
No. 0, manufactured by Toyobo Co., Ltd.) on which an aqueous coating composition having the composition shown in Tables 1 and 2 (coating concentration was 10%)
Was applied by bar coating so that the dry weight was 8 g / m ^2, and dried at 80 ° C. for 3 minutes to obtain an inkjet recording sheet. Although not shown in the table, in each of Examples and Comparative Examples, an antifoaming agent (trade name;
Nopco 1407K, manufactured by San Nopco Ltd. 0.01 part, surfactant (trade name; Safinol 440, manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 part, fluorine-based surfactant (trade name; FC-1)
70C, manufactured by 3M) is added to the above aqueous coating composition. Examples 4-7, Comparative Examples 1-4 and 7, 8
For 3 minutes, after drying for 3 minutes, the electron beam irradiation device (CB
-150, manufactured by ESI), 165 kV, 50 k
Irradiation was performed under Gy conditions to obtain an inkjet recording sheet.

Examples 8 and 14 White polyethylene terephthalate film having a heat of 100 μm as a support (trade name: Crisper, manufactured by Toyobo)
An ink jet recording sheet was obtained under the same conditions as in Example 4 except that the corona treated sheet was used.

Examples 9 and 15 Example 8 except that a commercially available art paper (trade name; SA Kinto, manufactured by Shin Oji Paper Co., 128 g / m ² ) was used as the support.
An inkjet recording sheet was obtained in the same manner as in.

Comparative Examples 7 and 12 In this example, the electron beam-curable compound was applied without adding water to adjust the coating concentration, and the drying step was omitted at 80 ° C. for 3 minutes, and fluorine was used as an auxiliary agent. An inkjet recording sheet was obtained in the same manner as in Comparative Example 1 except that only 0.1 part of a surfactant (trade name; FC-170C, manufactured by 3M) was added.

Comparative Examples 8 and 13 The electron beam curing type compound (concentration: 50%) in the table was used as a fluorinated surfactant (trade name; FC-170C, 3M).
An inkjet recording sheet was obtained in the same manner as in Comparative Example 1 except that only 0.1 part (manufactured by the company) was added.

Comparative Example 9 Commercially available OHP film for PPC (trade name; CAT. No. 1
35-0015, manufactured by Uchida Yoko Co., Ltd.) is used as it is.

The following items were evaluated for the ink jet recording sheet obtained as described above. still,
Printed by Canon inkjet printer (BJC8
20) was used to form a recorded image with four color inks of black, yellow, cyan and magenta. The evaluation results are also summarized in Tables 1 and 2.

[0038]

[Table 1]

[0039]

[Table 2]

[Coloring property] The sharpness of the recorded image was visually evaluated. ⊚: A clear image without bleeding or unevenness. ◯: Bleeding and unevenness are slightly observed, but there is no problem in practical use. ○ ': Bleeding and unevenness are slightly conspicuous, which is a problematic level for practical use. Δ: Bleeding is noticeable. 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 even when the recording portion was touched with a finger was measured. ◯: It was dried within 1 minute after printing. ◯ ': dried within 2 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] Water was dropped on the recording layer with a spoid and immediately wiped lightly with gauze. ⊚: The coating film is not damaged at all. ◯: The coating film has almost no damage. ∘ ': The coating film is slightly damaged, but there is no practical problem. Δ: The coating film was partially dissolved. X: The coating film was dissolved and almost removed.

[Stickiness of Recording Part] After recording, the recording sheet was left at room temperature for 2 hours, and then the stickiness of the recording part was evaluated by touching the recording part with a finger. ○: Almost no stickiness. ○ ': There is some stickiness, but there is no problem in practical use. Δ: Sticky, which is a practically problematic level. X: Remarkably sticky.

[Symbols in Table] K-90; Polyvinylpyrrolidone (trade name; Rubiscol K-
90, manufactured by BASF) Arashid; Casein (trade name; Arashid, supplied by Nissei mutual benefit) Soy protein; Carboxyl-modified soy protein (trade name: SP2500, supplied by Nissei mutual benefit) A; PE600 Polyethylene glycol diacrylate (trade name: New Frontier) PE600, manufactured by Dai-ichi Kogyo Seiyaku) a; UE7250 Self-emulsifying urethane acrylate emulsion (trade name: UE-7250, manufactured by Toagosei Kagaku Kogyo) c; 400EA Polyethylene glycol diglycidyl diacrylate (trade name: epoxy ester 400EA, Kyoeisha Chemical) BR170 acrylamide ether type monomer (trade name: BR170, manufactured by Material Science Co.) The numbers in the table are parts.

(Evaluation) As is clear from the results shown in Tables 1 and 2, the ink jet recording sheets obtained in Examples 1 to 9 of the present invention are excellent in color forming property and ink drying property, and recording is performed. The water resistance of the layer was excellent. Further, 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. Example 8,
The ink jet recording sheet obtained in No. 9 had excellent gloss and a clear color development as compared with a normal paper-based ink jet recording sheet.
In addition, since the coating composition containing the auxiliary agent as described above is used for the sheets of the respective examples, it is possible to obtain sheets having excellent transport characteristics when passing through a printer during recording. Separately, by comparison with an inkjet recording sheet obtained without using this auxiliary agent, it was confirmed that the amount of the auxiliary agent added in each Example had almost no effect on the evaluation of the above images and the like. Further, as plastic fine particles, for example, 0.5 parts of an aqueous dispersion of polyolefin fine particles (trade name; Chemipearl W-800, manufactured by Mitsui Petrochemical Industry Co., Ltd.) is added to the auxiliary agent to evaluate the above-mentioned images and the like. It has been confirmed that, with almost no influence, the sheet conveyance characteristics when the sheet is passed through the printer at the time of recording are further excellent.

[0046]

INDUSTRIAL APPLICABILITY The ink jet recording sheet is excellent in ink absorbency and water resistance, and also excellent in transparency, and is particularly suitable as a light transmissive recording medium for OHP and the like.

Claims (5)

[Claims] 1. An inkjet recording sheet having a recording layer formed by coating an aqueous coating composition containing polyvinylpyrrolidone and at least one selected from casein and soybean protein on a support. 2. The ratio of casein in the aqueous coating composition is 1 with respect to the total weight of polyvinylpyrrolidone and casein.
The ink jet recording sheet according to claim 1, which is in the range of 0 to 80%. 3. The ink jet recording sheet according to claim 1, wherein the proportion of soybean protein in the aqueous coating composition is in the range of 30 to 70% based on the total weight of polyvinylpyrrolidone and soybean protein. 4. The ink jet recording sheet according to claim 1, 2 or 3, wherein the aqueous coating composition further contains an electron beam curable compound, and the recording layer is irradiated with an electron beam. 5. The ink jet recording sheet according to claim 1, wherein the support is transparent.