JPH01286886A - Production of recording sheet - Google Patents

Abstract

PURPOSE:To provide excellent writability, absorptivity, drying properties and fixing properties for water-based inks by coating a base with a solution of an inonizing radiation-curable type hydrophilic monomer or oligomer in a hydrophilic monomer or oligomer in a hydrophilic solvent, and irradiating the applied material with ionizing radiations while the solid content is in a specified concentration range, thereby providing a recording layer. CONSTITUTION:A coating composition prepared by dissolving or dispersing an ionizing radiation-curable type hydrophilic monomer and/or hydrophilic oligomer (prepolymer) in a hydrophilic solvent is applied to a base to provide a coat layer, and while the solid content of the coat layer is in the range of 10-95wt.%, the layer is irradiated with ionizing radiations to provide a recording layer. If the solid content at the time of irradiation is more than 95wt.%, writability and fixing and drying properties for water-based inks are markedly lowered. If the solids content at the time of irradiation is less than 10wt.%, a large quantity of energy is required for drying the hydrophilic solvent left after irradiation with the ionizing radiations. The coating weight of the coating composition, as solids, is 0.1-20g/m<2>. Where the ionizing radiations are electron rays, the quantity thereof is desirably 0.1-20Mrad. Where the ionizing radiations are UV rays, it is necessary to blend a sensitizer with the coating composition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sheet that has excellent aptitude for recording with aqueous ink, and in particular has excellent aptitude for writing with aqueous pens, inkjet printing, etc.
The present invention relates to a recording sheet having excellent suitability for use in various types of printers using water-based ink, such as pen plotters.

(Prior Art) Plastic films, metallized paper, metal foil, film laminated paper, etc. are currently used in various fields, but problems may occur depending on the use because they are inferior in recording suitability with water-based inks.

For example, plastic films are widely used as projection recording sheets used in overhead projectors (hereinafter abbreviated as OHP).

When a plastic film sheet is used, characters and drawings from books, literature, etc. can be easily copied using an electronic copying machine such as a Xerox, and a clear projected image can be obtained using an OHP. However, text and drawings produced by such copying machines are generally monochromatic, and in order to be visually appealing,
Coloring is effective.

However, when using ordinary plastic film sheets such as polyethylene terephthalate, it is necessary to paste a colored film on top of the sheet or write and color it with an oil-based pen, or write with a water-based pen or marker. The problem was that it couldn't be colored. Furthermore, there is a problem in that sufficient recording cannot be obtained even with inkjet printers, water-based pen plotters, etc. that use water-based inks.

Conventionally, plastic films coated with polyester or other resin have been commercially available as OHP films in order to improve toner fixability and image density in electronic copying machines, but such films cannot be used with water-based inks. It has the disadvantages of poor writing and drying properties, as well as no absorbency or fixing properties.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems, that is, the recording layer maintains water resistance and has good writability, absorbency, drying property, and fixability with a writing instrument using water-based ink. The purpose of the present invention is to provide a recording sheet that can be written on and colored with a water-based pen, a water-based marker, a fountain pen, etc., and that can also be printed with an inkjet printer, a pen blotter, etc. using water-based ink. I'm going to do it.

(Means for Solving the Problems) The present invention provides a coating composition in which an ionizing radiation-curable hydrophilic monomer and/or a hydrophilic oligomer (prepolymer) is dissolved or dispersed in a hydrophilic solvent on a support. A coating layer is provided by coating, and the solid content concentration of the coating layer is 10 to 95% by weight.
This is a method for producing a recording sheet, characterized in that a recording layer is formed by irradiating ionizing radiation in a state within the range of .

(Function) The support used in the present invention is not particularly limited, and examples thereof include plastic films, metal foils, metallized paper, film laminated paper, coated paper, and plain paper. Although improvements can be made, plastic films are mainly used from the viewpoint of transparency, especially when used for OHP purposes. Plastic films include polypropylene, polyethylene,
Examples include polycarbonate, but when using an electronic copying machine, it is particularly desirable to use films with excellent heat resistance such as polyester, polysulfone, cellulose ester, polyamide, polyimide, etc.

The ionizing radiation-curable hydrophilic hexamer and hydrophilic oligomer (prepolymer) used in the present invention are not particularly limited, but specifically include the following.

(a) Monofunctional monomer or oligomer (prepolymer); (i) (meth)acrylic acid, CH, +=CR-Co
o・(C1lz -CIIR-Coo) , l-11(
1≦n≦20. R represents a hydrogen atom or a methyl group) represented by ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid dimers and (meth)acrylic acid trimers, or ethylenically unsaturated polycarboxylic acids, etc. Monofunctional monomers containing carboxyl groups and monofunctional monomers containing carboxylic acid groups such as alkali metal salts, ammonium salts, and amine salts thereof (b) Ethylenically unsaturated (meth)acrylamides or alkyl-substituted monomers An amide group-containing monofunctional monomer represented by meth)acrylamide, N-vinylpyrrolidone, etc.

(c) Sulfonic acid group-containing monofunctional esters represented by aliphatic or aromatic vinyl sulfonic acids 1 and sulfonic acid group-containing monofunctional esters such as alkali metal salts, ammonium salts, and amine salts thereof ( d) OH group-containing monofunctional monomers such as 2-hydroxyethyl (meth)acrylate.

(e) Epoxy group-containing monofunctional monomers such as glycidyl (meth)acrylate.

(f) Monofunctional hexamer containing a quaternary ammonium base; (g) Hydrophilic segment, such as polyN-methylolacrylamide, poly2-hydroxyethyl methacrylate, polyethylene glycol, etc., with a (meth)acryloyl group at one end. macromonomer.

(b) Multifunctional monomer or oligomer (prepolymer); (a) Ethyl alcohol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propyl alcohol di(meth)acrylate, polypropyl Esters of polyhydric alcohols and multiple (meth)acrylic acids, such as alcohol di(meth)acrylate and glycerin tri(meth)acrylate. Furthermore, polyether urethane (meth)acrylate is made of a polyether skeleton, with diisocyanate interposed at both ends, and (meth)acrylate containing a hydroxyl group bonded thereto. The above-mentioned polyether is a polymer having a repeating unit of -(M-0)-, where M is a methylene group, a polymethylene group, or a derivative thereof, and may be a single one or Although two or more types may be included, methylene groups and ethylene groups are preferred because hydrophilicity generally decreases as the number of carbon atoms increases.

(b) N,N'-methylenebis(meth)acrylamide.

(c) At least the following (1) 2 (R is a hydrogen atom or A natural or synthetic water-soluble polymer compound into which multiple methyl groups have been introduced.

Incidentally, natural polymer compounds include casein, gelatin, starch polysaccharides (dextrin, soluble starch, pregelatinized starch, Prilan, etc.) and their derivatives, and cellulose derivatives [
Nitrocellulose, carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose,
ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.).

Examples of the synthetic polymer compound include completely saponified or partially saponified polyvinyl alcohol.

(d) (meth)acryloyl group, haloalkyl (meth)
Polyvinyl alcohol and the like having a plurality of at least one functional group selected from acryloyl group and N-methylolacrylamide.

These monomers or oligomers (prepolymers) can be used alone or mixed as appropriate, but
If the cured density is too high, the writability with water-based ink will decrease, and if the cured density is too low, the coating strength and water resistance will decrease, so choose by considering the number of functional groups, molecular weight, etc. It is necessary to.

These monomers and/or oligomers (prepolymers) are dissolved or dispersed in a hydrophilic solvent to prepare a coating composition.

Examples of the hydrophilic solvent include water, methyl alcohol, ethyl alcohol, propyl alcohol, methyl cellosolve, and ethyl cellosolve.

However, from the viewpoint of safety and ease of management, it is preferable to use water. Further, these monomers and/or oligomers (prepolymers) may be dissolved or dispersed in a hydrophilic solvent, but it is generally preferable to dissolve them because it is easier to obtain a transparent and strong coating film.

Furthermore, the coating composition may contain additives such as antistatic agents, lubricants, dispersants, dyes, pigments, anti-blocking agents, wetting agents, leveling agents, antifoaming agents, and other ionizing agents other than those mentioned above. It is also possible to add radiation-curable monomers and/or oligomers (prepolymers) and non-ionizing radiation-curable resins to the extent that they do not impede the effects of the present invention.

The concentration of the coating composition is 10 when irradiating with ionizing radiation.
The content is adjusted to 95% by weight, more preferably 20 to 70% by weight. Incidentally, if the concentration when irradiating ionizing radiation is higher than 95% by weight, the writability, fixation, and
Drying performance is significantly reduced. On the other hand, if it is less than 10% by weight, a large amount of energy is required to dry the hydrophilic solvent remaining after irradiation with ionizing radiation, which is not only economically disadvantageous, but also reduces the strength and water resistance of the coating film. The fixing properties of the ink also become insufficient.

The coating composition for a recording layer of the present invention is coated on at least one side of the support, and in this case, the coating means is generally known, such as a bar coater, roll coater, air knife coater, gravure coater, etc. is used.

The coating amount of the above coating composition is 0.1 to 20g7 in terms of solid amount.
, f, more preferably in the range of 0.2 to Log/%. Incidentally, if it is less than 0.1 g/m, it is difficult to obtain the desired effect of the present invention, and if it exceeds 20 g/rd, the effect becomes saturated and is meaningless.

The coated surface of the support may be pretreated as necessary by anchor coating treatment, corona discharge treatment, radiation treatment, plasma treatment, etc. to improve the wettability of the coated surface and the adhesion of the recording layer. can do.

In the method of the present invention, the coating composition layer formed as described above is cured by irradiation with ionizing radiation. Examples of ionizing radiation include electron beams, ultraviolet rays, α rays, β rays, β rays, X rays, etc. can be mentioned. Since alpha rays, beta rays, gamma rays, and X-rays are associated with the problem of danger to the human body, electron beams and ultraviolet rays are preferably used because they are easy to handle and are not suitable for industrial use.

When using an electron beam, the amount of electron beam irradiated is 0.1~
It is desirable to adjust within a range of about 20 Mrad. 0.
If it is less than 1 Mrad, sufficient irradiation effect cannot be obtained;
Irradiation in excess of Mrad is undesirable because it may deteriorate the support, especially paper and some types of plastics. As the electron beam irradiation method, for example, a scanning method, a curtain beam method, a broad beam method, etc. are adopted, and the acceleration voltage when irradiating the electron beam is 100 to 30 O.
Approximately Kv is appropriate. The electron beam irradiation method has the advantages of higher productivity than ultraviolet irradiation, no problems with odor or coloring caused by the addition of a sensitizer (and also easier to form a uniform crosslinked structure).

When using ultraviolet light, it is necessary to incorporate a sensitizer into the coating composition, such as thioxanthone, benzoin, benzoin alkyl ether xanthone, dimethylxanthone, benzophenone, anthracene, 2,2-jethoxyacetophenone, benzyldimethyl. ketal,
Benzyl diphenyl disulfide, anthraquinone, 1
-chloroanthraquinone, 2-ethylanthraquinone,
2-ter-butylanthraquinone, N,N'-tetraethyl-4,4'-diaminobenzophenone, 1,
One or more sensitizers such as 1-dichloroacetophenone are appropriately blended.

The amount of aggravating agent used is 0.2 to ionizing radiation-curable monomer/oligomer (prepolymer) in the coating composition.
It is desirable to adjust the amount within a range of about 10 to 10% by weight, preferably about 0.5 to 5% by weight. Furthermore, in addition to such sensitizers, to accelerate curing, e.g. triethanolamine, 2-dimethylaminoethanol, dimethylaminobenzoic acid, isoamyl dimethylaminobenzoate, dioctylaminobenzoic acid, lauryl dimethylaminobenzoate, tertiary amines such as 0.05 to 3% by weight based on the ionizing radiation curable monomer/oligomer in the coating composition.
It is also possible to mix them to some extent.

As a light source for ultraviolet irradiation, 1 to 50 ultraviolet lamps (for example, low-pressure, medium-pressure, high-pressure mercury lamps with operating pressures from several mmHg to about 10 atmospheres), xenon lamps, tungsten lamps, etc. are used. ~800
Ultraviolet rays having an intensity of about 0 p W/cm'' are preferably irradiated.

In the present invention, the coating layer is irradiated with ionizing radiation while containing a hydrophilic solvent. At this time, the hydrophilic solvent partially or completely evaporates; If the coating film is sticky, it is preferable to perform an additional drying step.

The reason why the recording sheet obtained by the manufacturing method of the present invention has excellent recording properties with water-based inks and water resistance is not necessarily clear, but it is assumed as follows.

That is, hydrophilic monomers and/or oligomers (prepolymers) undergo polymerization and crosslinking reactions when irradiated with ionizing radiation, but at this time, due to the presence of a hydrophilic solvent, the crosslinking density increases due to the crosslinking reaction. moderately suppresses
It is presumed that a hydrophilic network structure having an appropriate crosslinking density is formed in the recording layer. Furthermore, part or all of the hydrophilic solvent evaporates instantaneously upon irradiation with ionizing radiation, and it is thought that uniform micropores are formed in the recording layer at this time. Through the micropores formed in this way,
Since water-based ink is rapidly absorbed and retained and fixed within a hydrophilic network structure, it is considered that water-based ink has excellent writing properties, fixing and drying properties. In addition, since this coating film has a crosslinked structure, it also has excellent water resistance.

(Example) The present invention will be explained in more detail with reference to Examples below.
Of course, it is not limited to these.

Note that unless otherwise specified, "parts" and "%" in the examples indicate "parts by weight" and "% by weight," respectively.

Examples 1 to 5, Comparative Examples 1 to 4 The following mixed coating composition was applied onto a polyethylene terephthalate film (thickness 100 μm) that had been subjected to anchor coating treatment with a thermosetting resin so that the dry weight was 4 g/m2. This was coated and then irradiated with an electron beam of 5 Mrad using an electron beam irradiation device (Electro Curtain CB150, manufactured by [!Sr) to obtain nine types of recording sheets.

[Coating composition]

Solid content 70 parts consisting of 40 parts of acrylamide, 10 parts of polyethylene glycol diacrylate (KAYARAD PEG400DA; manufactured by Nippon Kakami Co., Ltd.) and 21 parts of water.
% (30% water content) coating composition (Example 1).

Solid content concentration 50 consisting of 40 parts of acrylamide, 10 parts of polyethylene glycol diacrylate (KAYARAD PEG400DA; manufactured by Nippon Kakami Co., Ltd.) and 50 parts of water.
% (water content 50%) coating composition (Example 2).

Solid concentration 3 consisting of 40 parts of acrylamide, 10 parts of polyethylene glycol diacrylate (KAYARAD PEG400D^; manufactured by Nippon Kayaku 01) and 117 parts of water.
0% (water content 70%) coating composition (Example 3).

Using the same coating composition as in Example 1, it was applied in the same manner as in Example 1, dried at 100°C for 2 minutes to completely evaporate water, and then exposed to an electron beam in the same manner as in Example 1. irradiated (Comparative Example 1).

Solid content concentration 7 consisting of 40 parts of acrylamide, 10 parts of polyethylene glycol diacrylate (KAYARAD PEG400DA i manufactured by Nippon Kakami Co., Ltd.) and 664 parts of water.
% (moisture content 93%) coating composition. Note that since stickiness remained even after electron beam irradiation, drying was performed at 100° C. for 2 minutes (Comparative Example 2).

A hydrophilic prepolymer (E
NT2000; made by Kansai Paint ■) 30 parts, acrylamide 10 parts, polyethylene glycol diacrylate (KAYARAD PEG400DA, made by Nippon Kakami Co., Ltd.) 10 (Yi 4k) parts, and water 50 parts, solid content concentration 50% (water content 50
%) coating composition (Example 4).

Using the same coating composition as in Example 4, it was applied in the same manner as in Example 4, dried at 100°C for 2 minutes to completely evaporate water, and then irradiated with an electron beam in the same manner as in Example 1. did(
Comparative Example 3).

40 parts of acrylic acid, polyethylene glycol diac IJ
L/-) (KAYARAD PEG400DA
Coating composition (Example 5) with a solid content concentration of 50% (water content 50%) consisting of 10 parts (manufactured by Nippon Kayaku e@) and 50 parts of water
.

Using the same coating composition as in Example 5, it was applied in the same manner as in Example 5, dried at 100°C for 2 minutes to completely evaporate water, and then irradiated with an electron beam in the same manner as in Example 1. did(
Comparative example 4).

Regarding the nine types of recording sheets obtained as above,
The writing properties, fixing/drying properties, water resistance, solvent resistance, and coating strength of the water-based inks were evaluated using the following evaluation methods, and the results are shown in Table 1.

[Writability of water-based ink]

It was written on a recording sheet using a water-based fluorescent marker (manufactured by KOKUYO), and the presence or absence of flickering was visually determined.

◎: No repelling occurred at all.

○: Although there was a slight reluctance, it was at a level that caused no practical problems.

Δ: There was repellency and the level was problematic for practical use.

×: It was difficult to write due to the difficulty of writing.

[Fixing and drying properties of water-based ink]

After writing on a recording sheet using a water-based fluorescent marker (manufactured by KOKUYO Co., Ltd.), the writing was lightly rubbed with a finger to evaluate the time until it was fixed.

◎: Fixed within 5 seconds.

O: It was fixed within 60 seconds and was at a level that caused no practical problems.

Δ: Fixing took 60 seconds to 1 hour, leaving a practical problem.

×: It was not fixed even after one hour, and a record could be taken by rubbing it with a finger.

〔water resistance〕

Three drops of water were dropped onto the recording layer using a dropper, and the damage to the recording layer was evaluated after wiping it off with gauze.

○: There was no damage to the recording layer at all.

×: The entire recording layer was wiped off.

[Solvent Resistance] Three drops of ethanol and toluene were dropped onto the recording layer using a dropper, and damage to the recording layer was evaluated after wiping with gauze.

○: There was no damage to the recording layer at all.

×: The entire recording layer was wiped off.

[Coating film strength] The coating film of the recording sheet was rubbed with a finger to evaluate damage to the coating film surface.

○: There was no damage at all even when rubbed strongly with fingers.

Δ: The coating surface was slightly damaged when rubbed strongly with fingers.

(Remarks) ■ to ■ in Table 1 are as follows.

■Writing properties of water-based ink■;Fixing and drying properties of water-based ink■;Water resistance■;Solvent resistance [(a)=ethanol, (b)=toluene] ■;Coating film strength (effect) Recording according to the present invention As is clear from Table 1, the sheet for
It is a recording sheet that has a recording layer that has excellent writing properties, fixing and drying properties for water-based inks, and also has excellent water resistance, solvent resistance, and coating strength, and also has excellent writing properties when writing with oil-based pens. It had fixability.

Furthermore, when the recording sheets of the present invention were written with a water-based pen, a water-based marker, and an oil-based pen and were projected onto a screen using an OHP, a clear and high-contrast projected image was obtained.

Claims (2)

[Claims] (1) A coating composition prepared by dissolving or dispersing an ionizing radiation-curable hydrophilic monomer or/and hydrophilic oligomer (prepolymer) in a hydrophilic solvent is applied onto a support to form a coating layer, and the coating A method for producing a recording sheet, comprising forming a recording layer by irradiating the recording layer with ionizing radiation in a state where the solid content concentration of the layer is in the range of 10 to 95% by weight. (2) The manufacturing method according to claim (1), wherein the ionizing radiation is irradiated while the solid content concentration of the coating layer is in the range of 20 to 70% by weight.