JPH0858226A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE: To provide an ink jet recording sheet suitable as a light permeable recording medium for OHP excellent in ink absorbability, ink color developability and water resistance and especially excellent in transparency. CONSTITUTION: In an ink jet recording sheet obtained by coating a support with an aq. compsn. and irradiating the coating layer with electron beam to form a recording layer, the recording layer contains polyvinyl pyrrolidone, an electron beam curable compd. and fine crosslinked resin particles with a mean particle size of 10-600nm. The obtained ink jet recording sheet is excellent in color developability, ink absorbability and the water resistance of the relording layer and further excellent in transparency. Therefore, this ink jet recording sheet has excellent aptitude as an OHP sheet.

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 medium, which is particularly excellent in ink absorbency, ink color development and water resistance and is suitable for a light transmissive recording sheet for overhead projectors (OHP). It is a thing.

[0002]

2. Description of the Related Art An ink jet recording method is one in which recording is carried out by ejecting ink into fine droplets and adhering them to a recording medium, and the flexibility of recording patterns is large and it is easy to achieve multicolor. Therefore, it has recently been rapidly spread as a hard copy device.

In this ink jet recording system, normally,
Since an ink in which a binder, a dye, a solvent, an additive and the like are dissolved in water is used, the recording medium needs to have appropriate water absorption. Therefore, a paper or film provided with a recording layer containing a water-soluble polymer or a water-absorbing pigment as a main component is used depending on the application.

The light-transmissive recording medium is widely used for conferences, academic conferences, briefing sessions, lectures, etc. for OHP, and the demand for recording medium for signboards, show windows, etc. is also increasing. . The conventional light-transmissive recording medium is mainly prepared by an electronic copying method (PPC) or the like, but recently, as the demand for colorization increases, an inkjet recording method excellent in sharpness of a recorded image has recently been adopted. It's getting a lot of attention.

Plastic films such as polyethylene terephthalate are generally used as transparent recording media used for conventional OHP, but since these films do not have sufficient water absorption, they absorb ink for ink jet recording. However, there is a drawback that the image becomes unclear due to the flow of the ink, or the recorded image becomes dirty or stuck due to rubbing or superposition due to poor drying of the ink.

Therefore, in order to provide the plastic film with an appropriate ink absorption property, for example, Japanese Patent Laid-Open No. 59-1 is used.
74381, 60-132785, 60-
145879, 60-224578, 61
No. 32788 proposes to provide a recording layer made of a water-soluble polymer such as starch, water-soluble cellulose derivative, polyvinyl alcohol and polyvinylpyrrolidone on the film. However, with these methods, although the ink absorbency is improved to some extent, the ink absorbency is still slow and the ink easily bleeds, the drying property is insufficient, and the tackiness of the recording surface remains for a long time, which makes it difficult to handle. There is a problem such as. Further, the water resistance of the recording layer is insufficient, so that problems such as stickiness under high humidity and blurring of recorded images due to adhesion of water droplets or sweat remain.

As a means for improving 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 as the water resistance is improved, there is a problem that the sharpness of the printed image is lowered.

Further, JP-A-1-229685 discloses a water-soluble polymer and polyethylene glycol di (meth).
There has been proposed a method of forming a recording layer by crosslinking a composition containing acrylate and water as essential components by irradiation with active energy rays. However, although this method improves ink absorbency and water resistance, it is difficult to balance the qualities of the two and it has not always been possible to obtain stable and satisfactory results. Moreover, in this method, if the composition contains water and irradiation with active energy rays is not performed, a sufficient improvement effect cannot be obtained. Therefore, water should be present in the composition upon irradiation with active energy rays. Is essential. However,
When active energy rays are irradiated in the presence of water, water evaporates and adheres to the irradiation device to corrode the device, or water droplets drop on the recording material in the irradiation device and stain the surface of the recording material. It is associated with serious deficiencies that must be resolved in terms of operability.

[0009]

The present invention is excellent in ink absorption and water resistance and is excellent in transparency without the above-mentioned defects, and is particularly suitable as a light transmissive recording medium for OHP or the like. The present invention provides an inkjet recording sheet.

[0010]

The present invention relates to an ink jet recording sheet having a recording layer formed by coating an aqueous composition on a support and irradiating it with an electron beam, wherein the recording layer is polyvinylpyrrolidone and electron beam. An ink jet recording sheet comprising a curable compound and fine crosslinked resin particles having an average particle diameter of 10 to 600 nm.

[0011]

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, a plastic film having excellent transparency and flexibility is used. Examples thereof include polyethylene terephthalate, polyvinyl chloride, polycarbonate, polyimide, triacetate, polyethylene and polypropylene.

Further, an opaque substrate such as paper, synthetic paper or a white film can be used. In these cases, since the recording layer according to the present invention is essentially transparent, it is excellent in glossiness for ink jet recording. You can get a sheet. Examples of the paper include high quality paper, medium quality paper, coated paper, art paper, cast coated paper and the like.

In the present invention, polyvinylpyrrolidone, an electron beam curable compound and an average particle size of 10 are provided on the above support.
A recording layer is formed by applying an aqueous coating composition containing fine cross-linked resin particles of ˜600 nm and irradiating it with an electron beam.

As the polyvinylpyrrolidone (hereinafter referred to as PVP) used in the present invention, those which are generally commercially available can be used and are not particularly limited. If the molecular weight is too large, there is no problem in terms of quality, but since it is difficult to dissolve in water and it becomes highly viscous even after dissolution, it becomes difficult to handle, so the average molecular weight is about 100,000 to 1,000,000. Is preferred.

Further, it is preferable to add an appropriate amount of polyvinyl alcohol (hereinafter referred to as PVA) to PVP because the absorbability of the ink, the stickiness of the surface, the water resistance of the recording layer and the image quality are improved. As PVA, generally commercially available fully saponified or partially saponified PVA can be used, but one having a saponification degree of 80% or more is preferable from the viewpoint of ink absorbency and image quality. The degree of polymerization is preferably about 100 to 3000,
If the degree of polymerization is too small, the water resistance tends to be poor, and if the degree of polymerization is too large, there is no particular problem in terms of quality, but it becomes difficult to dissolve in water, and the compatibility with the PVP tends to become poor.

When PVA is blended, the above-mentioned blending ratio of PVP and PVA is 90 to 5 parts by weight of PVA to 10 to 95 parts by weight of PVP, and more preferably 30 to 9 parts of PVP.
70 to 10 parts by weight of PVA with respect to 0 parts by weight. If the PVA is less than 5 parts by weight, the effect of improving the water resistance and ink absorbency of the recording layer is small, and the effect of improving the stickiness of the surface is small. On the other hand, if the amount exceeds 70 parts by weight, the water resistance of the recording layer, the ink absorbency, and the image quality may deteriorate.

Next, the electron beam curable compound has a (meth) acryloyl group, a (meth) acrylamide group, and
A monomer or oligomer containing an electron beam curable group such as a vinyl group, and (a) a hydroxyl group, a carboxyl group (and a metal salt thereof), an amide group, a sulfone group, an ammonium group, a phosphate group in the molecule. , Having a hydrophilic group such as a polyethylene glycol group and being water-soluble or water-dispersible (self-emulsifying emulsion) itself, or (b) itself is not water-soluble or water-dispersible, This is a dispersion (forced emulsification type emulsion) in which a surfactant is added and vigorously stirred to make it water dispersible. Among these,
It is preferable to use the type (a) type because a transparent recording layer can be easily obtained, the effect of waterproofing is high, and the stability of the coating liquid tends to be excellent.

Examples of (a) include polyethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylamide, polyethylene glycol diglycidyl di (meth) acrylate, glycerin poly (meth) acrylate, self-emulsifying acrylate emulsion, self-emulsion Emulsion type polyester acrylate emulsion etc. are mentioned.

Examples of (b) are electron beam-curable compounds other than (a), such as 1,6-hexanediol diacrylate, diethylene glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane triacrylate. Examples thereof include those obtained by adding a surfactant to a rate, a polyester acrylate, a urethane acrylate and the like and stirring the mixture strongly to form an aqueous dispersion. And, of course, it is possible to use two or more kinds of the above electron beam curable compounds in combination.

The compounding amount of the electron beam-curable compound in the present invention varies depending on the kind thereof, but is 0.1 to 100 parts by weight of PVP or PVP and PVA in total.
About 100 parts by weight is preferable, and 0.5 is more preferable.
It is about 50 parts by weight. If the amount is less than 0.1 parts by weight, the water resistance effect is difficult to be exhibited. On the other hand, if the amount exceeds 100 parts by weight, the ink absorbency tends to decrease.

In the present invention, as the material for forming the recording layer, in addition to the above PVP and electron beam curable compound, finely crosslinked resin particles having an average particle diameter of 10 to 600 nm are blended as an essential component. That is, according to the results of earnest studies by the present inventors, when finely crosslinked resin particles are blended as a material for forming the recording layer, the ink absorbency and the water resistance of the recording layer are improved,
It has been clarified that it is effective for obtaining uniform printing without unevenness.

The ink jet recording sheet of the present invention comprises
The reason why excellent ink absorbability and water resistance of the recording layer and uniform printing without unevenness are not necessarily clear, but due to the presence of an appropriate amount of the fine crosslinked resin particles, an appropriate crosslinked structure is formed. It is considered to be one.
That is, PVP and an electron beam curable compound form a crosslinked structure by electron beam irradiation, but it is considered that the presence of the fine crosslinked resin particles facilitates the diffusion of the aqueous ink and improves the ink absorbability and the image quality. Further, it is presumed that the water resistance is improved because the water is not excessively absorbed and the swelling is suppressed.

The micro-crosslinked resin particles are similar in chemical composition and optical composition to PVP and electron beam-curable compounds or other subcomponents, so that the recording layer is optically transparent. . According to observation with an electron microscope, it is effective that the average particle diameter of the finely crosslinked resin particles is in the range of 10 to 600 nm, and if it exceeds 600 nm, the transparency of the recording layer decreases, and if it is less than 10 nm. The viscosity of the aqueous coating composition may increase or the stability over time may decrease.

The method for producing the finely crosslinked resin particles used in the present invention is not particularly limited, but for example, the finely crosslinked resin particle dispersion liquid is obtained by emulsion-polymerizing an ethylenically unsaturated monomer with a crosslinkable copolymerization monomer in an aqueous medium. There is a method of making.

Examples of the ethylenically unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate,
Alkyl esters of acrylic acid or methacrylic acid such as n-butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and others having an ethylenically unsaturated bond copolymerizable therewith , Such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, ethylene, propylene, vinyl acetate, vinyl propionate, (meth) acrylonitrile and dimethylaminoethyl (meth) acrylate. Two or more kinds of these monomers may be used.

The crosslinkable copolymerizable monomer includes a monomer having two or more radically polymerizable ethylenically unsaturated bonds in the molecule and two kinds of ethylenically unsaturated groups each carrying a group capable of reacting with each other. Examples include monomers. Examples of the monomer having two or more radically polymerizable ethylenically unsaturated bonds in the molecule include a polymerizable unsaturated monocarboxylic acid ester of polyhydric alcohol, a polymerizable unsaturated alcohol ester of polybasic acid, and two or more. And aromatic compounds substituted with the vinyl group of Examples of the two kinds of ethylenically unsaturated group-containing monomers each carrying a group capable of reacting with each other include epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth) acrylate, (meth) acrylic acid and crotonic acid. The carboxyl group-containing ethylenically unsaturated monomer is the most typical one.

The average particle size in the present invention is 10 to 600 n.
The amount of the micro-crosslinked resin particles of m is PVP or PV.
The total amount of P and PVA is about 0.5 to 70 parts by weight, more preferably 5 to 50 parts by weight, based on 100 parts by weight.
If the amount is less than 0.5 parts by weight, the above-mentioned effects are not sufficiently exhibited, and if the amount exceeds 70 parts by weight, the coating film of the recording layer may be whitened or the ink drying property may be deteriorated.

In the coating composition for forming the recording layer of the present invention, water-soluble polymers other than the above-mentioned PVP and PVA, such as starch, starch derivatives, water-soluble cellulose derivatives, polyacrylic acid, sodium polyacrylate, poly Acrylamide, polyethylene oxide, polyethylene glycol, polyvinyl methyl ether, casein,
Gelatin etc. can be added. In addition, a cationic polymer or the like may be blended to further improve the fixability of the ink.

For the purpose of preventing stickiness and blocking of the surface of the ink jet recording sheet, and adjusting ink bleeding, various inorganic or organic pigments such as silica, clay, talc, 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 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-mentioned aqueous composition is applied onto a substrate by a known application 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 the amount is less than 1 g / m ² , the ink absorption tends to be insufficient, resulting in 50 g / m ^2.
When it is more than m ² , the color becomes lighter and curling is likely to occur.

In the present invention, the desired effect can be obtained only by irradiation with an electron beam, and a sufficient crosslinked structure is not formed by irradiation with ultraviolet rays, and an ink jet recording sheet with satisfactory performance cannot be obtained.

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. However, it is preferable in operation that the coating layer is once dried and then irradiated with an electron beam. The irradiation dose of electron beam is 5 to 500 kG in absorbed dose
y, more preferably in the range of about 10 to 200 kGy. If it is less than 5 kGy, a sufficient cross-linking effect cannot be obtained, and water resistance and ink absorbency tend to be insufficient.
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.

[0033]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 9 and Comparative Examples 1 to 4 As a support, a polyethylene terephthalate film (trade name: A7) having a surface of 100 μm and having a surface subjected to easy adhesion treatment
300, manufactured by Toyobo Co., Ltd., on which an aqueous coating composition having the composition shown in Table 1 and Table 2 (coating concentration was 10% by weight) was dried by bar coating to give a dry weight of 8
It was applied so as to be g / m ² and dried at 80 ° C. for 3 minutes. Then, using an electron beam irradiation device (CB-150, manufactured by ESI), irradiation was performed under the conditions of 165 kV and 50 kGy to obtain an inkjet recording sheet. However, in Comparative Example 2, electron beam irradiation was not performed in Example 1.

Comparative Example 5 Commercially available OHP film for PPC (trade name: CAT. No. 1)
35-0015, manufactured by Uchida Yoko) was used as it was.

[0036]

[Table 1]

[0037]

[Table 2]

The following items were evaluated for the ink jet recording sheet obtained as described above. In addition, the printing is made by Sharp inkjet printer (IO
-735X), black, yellow, cyan,
A recorded image was formed with four magenta inks.
The evaluation results are summarized in Table 3.

[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 Absorption (Drying Property)] After printing, the recorded matter 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 2 minutes after printing. ◯ ': dried 5 to 10 minutes after printing. Δ: It was dried 20 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 dropper, and immediately wiped off with gauze. ◯: 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.

[0042]

[Table 3]

[0043]

As is clear from the results of Tables 1 to 3, the ink jet recording sheets obtained in Examples 1 to 9 of the present invention are excellent in color developing property and ink absorbing property, and moreover, are recording layers. It was also excellent in water resistance. Furthermore, since it is excellent in transparency, it has excellent suitability as an OHP sheet.

Claims (5)

[Claims] 1. An inkjet recording sheet having a recording layer formed by coating an aqueous composition on a support and irradiating it with an electron beam, wherein the recording layer comprises polyvinylpyrrolidone, an electron beam curable compound, and an average particle diameter of 10. An ink jet recording sheet comprising: micro-crosslinked resin particles having a particle size of up to 600 nm. 2. A polyvinylpyrrolidone 1 having a recording layer.
90 to 95 parts by weight of polyvinyl alcohol 90 to
The ink jet recording sheet according to claim 1, comprising 5 parts by weight. 3. A recording layer comprising polyvinylpyrrolidone or polyvinylpyrrolidone and polyvinylalcohol in total of 1
The ink jet recording sheet according to claim 1 or 2, which contains 0.5 to 70 parts by weight of the fine crosslinked resin particles with respect to 00 parts by weight. 4. The recording layer comprises polyvinylpyrrolidone or polyvinylpyrrolidone and polyvinylalcohol in total of 1
The electron beam curable compound is added in an amount of 0.1 to 1 to 100 parts by weight.
The ink jet recording sheet according to any one of claims 1 to 3, containing 100 parts by weight. 5. The ink jet recording sheet according to claim 1, wherein the support is transparent.