JPH0267177A - Recording sheet - Google Patents

Abstract

PURPOSE:To improve recording properties or water resistance due to aqueous ink by forming a recording sheet by irradiating the recording layer based on polyvinyl alcohol having a specific structure provided on a support with ionizing radiation. CONSTITUTION:A coating composition is prepared by dissolving polyvinyl alco hol having 1-50mol.% of a functional group containing an ethylenic unsaturated double bond in one molecule thereof being a main component and other ionizing radiation curable monomer in a hydrophilic solvent and applied to a support and dried to form a recording layer which is, in turn, irradiated with ionizing radiation to prepare a recording sheet. As a concrete example of the support, there are a plastic film, a metal foil and plain paper. The polymerization degree of the aforementioned polyvinyl alcohol is pref. 50-5,000 and more pref. 200-3,000.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a sheet with excellent recording aptitude with aqueous ink, and particularly to a sheet with excellent writing properties and infusiera 1 with aqueous ink.
The present invention relates to a recording sheet which has excellent suitability for use in various types of printers using water-based inks, such as pen plotters and the like.

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

For example, plastic films are widely used as projection recording sheets for overhead projectors (hereinafter abbreviated as OHP) by copying characters and drawings from books, literature, etc. using electronic copying machines such as Xerox.

Characters and drawings produced by such copying machines are generally printed in a single color, so it is effective to convert them into colors to make them visually appealing. When using a regular plastic film sheet such as polyethylene terephthalate, the only way to color the sheet is to paste a colored film on top of the sheet, write on it with an oil-based pen, or color it. However, they have the disadvantage that they cannot be colored at all, and that sufficient recording cannot be obtained even with inkjet printers, water-based pen blocks, etc. that use water-based inks.

In addition, in order to improve toner fixability and image density in electronic copying machines, plastic films coated with resin such as polyester are commercially available as 01-IP films; It has the drawbacks of being inferior to water-based inks in terms of writing and drying properties, and having no absorbency or fixing properties.

Furthermore, coating various water-soluble polymers on a transparent support has been considered to create a transparent sheet that can be written on with water-based ink, but although it has some degree of writability with water-based ink, its absorbency is insufficient. However, since it has poor water resistance, it has problems such as becoming sticky at high temperatures.

"Problems to be Solved by the Invention" In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive research on methods for modifying plastic films, and as a result, they have developed an ionizing radiation-curable water-soluble high We proposed a method (Japanese Patent Laid-Open No. 187741/1983) in which the wettability of the surface was improved by applying molecules and irradiating the surface with ionizing radiation.

However, there is still room for improvement in the plastic film, such as insufficient writability and water resistance.
It was unsuitable as a recording sheet.

For this reason, as a result of further studies on improving writability and water resistance, the inventors discovered that a recording sheet with excellent properties could be obtained by using polyvinyl alcohol with a specific structure, leading to the completion of the present invention. Ta.

[Means for Solving the Problem] The present invention provides a recording layer mainly composed of polyvinyl alcohol having 1 to 50 mol% of a functional group containing an ethylenically unsaturated double bond per molecule on a support. The recording sheet is characterized in that the recording layer is provided with an ionizing radiation and the recording layer is irradiated with ionizing radiation.

"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. Examples of the plastic film include polypropylene, polyethylene, polycarbonate, etc., but when using an electronic copying machine, films with excellent heat resistance such as polyester, polysulfone, cellulose ester, polyamide, polyimide, etc. are used. is desirable.

The polyvinyl alcohol used in the present invention is characterized by containing ethylenically unsaturated double bonds, and the degree of polymerization of the polyvinyl alcohol is preferably in the range of about 50 to 5,000, more preferably 200 to 3,000. If the degree of polymerization is less than 50, the strength and water resistance of the formed recording layer will be poor, and the desired effect will not be obtained, and if it exceeds 5,000, it will be difficult to dissolve in solvents such as water, and even if dissolved. This is not preferable because it becomes extremely viscous, causing difficulty in the coating process.

The functional group containing an ethylenically unsaturated double bond contained in polyvinyl alcohol must be present in the range of 1 to 50 mol%, preferably 2 to 20 mol%. If it is less than 1 mol%, the effect of water resistance due to crosslinking is poor, and if it exceeds 50 mol%, the crosslinking density becomes too high, resulting in poor writing properties of the aqueous ink. The term "mol%" used herein refers to the number of functional groups containing ethylenically unsaturated double bonds per 100 repeating units of vinyl alcohol and substituted vinyl groups.

Examples of the functional group containing the ethylenically unsaturated double bond include a (meth)acryloyloxy group and a functional group having the following structure: (a) -0-CH, -NH-Co-CH=CH.

(R represents a hydrogen atom or a methyl group) etc.

The coating composition for a recording layer of the present invention is mainly composed of polyvinyl alcohol having a functional group containing an ethylenically unsaturated double bond as described above, but in order to control the crosslinking density and hydrophilicity, other ionizing radiation curing compositions are used. Type monomers and oligomers (prepolymers) can be mixed as appropriate. Such monomers and oligomers (prepolymers) have good compatibility with the above-mentioned polyvinyl alcohol, and for the purpose of improving the writing properties of water-based inks, it is desirable that they are water-based.Specifically, they are as follows: Examples are given.

(a) (meth)acrylic acid, CIIz□CR-COO・(CHz・CHR-COO)
Ethylenically unsaturated monocarboxylic acid, such as (meth)acrylic acid dimer trimer, or ethylenically unsaturated monocarboxylic acid, represented by I, ・H (1≦n≦20, R represents a hydrogen atom or a methyl group) Monofunctional monomers containing a carboxyl group represented by the following, and monofunctional monomers containing a carboxylic acid group such as alkali metal salts, ammonorum salts, and amine salts thereof (b) Ethylenically unsaturated (meth)acrylamide or alkyl Amide group-containing monomers represented by substituted (meth)acrylamides, N-vinylpyrrolidone, etc. (c) Sulfonic acid group-containing monofunctional monomers represented by aliphatic or aromatic vinyl sulfonic acids, and their alkali metal salts, ammonorum Monofunctional monomers containing sulfonic acid groups such as salts and amine salts. Monofunctional monomers containing OH groups such as (di)2-hydroxyethyl (meth)acrylate and glycerin acrylate. Epoxy group-containing monofunctional monomers such as (v)glycidyl (meth)acrylate. Monofunctional monomer (f) Quaternary ammonium base-containing monofunctional monomer (g)
Hydrophilic macromonomers with a (meth)acryloyl group at one end, such as hydrophilic segments, such as polyN-methylolacrylamide, poly2-hydroxyethyl methacrylate, and polyethylene glycol (a) Polyethylene glycol di(meth)acrylate, polyethylene glycol di (Meth)acryloyl groups are introduced at both ends of a polyether skeleton such as (meth)acrylate. Furthermore, polyether urethane (meth)acrylate is a polyether urethane (meth)acrylate in which a (meth)acrylate containing a hydroxyl group is bonded to a polyether skeleton with diisocyanate interposed at both ends. The above polyether is (
It is a polymer having a repeating unit of M-0)-, and M
is a methylene group, an ethylene group, a polymethylene group, or a derivative thereof, and may be a single type or may contain two or more types.

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

Furthermore, if necessary, antistatic agents, lubricants, dispersants, etc.
Various additives such as dyes, pigments, anti-blocking agents, wetting agents, leveling agents, and antifoaming agents, as well as ionizing radiation-curable monomers and/or oligomers (prepolymers) and non-ionizing radiation-curable resins other than those mentioned above. It can also be added within a range that does not impede the effects of the invention.

The coating composition of the present invention is generally applied after being dissolved in a hydrophilic solvent, and examples of the hydrophilic solvent include water, methyl alcohol, ethyl alcohol, propyl alcohol, methyl cellosolve, ethyl cellosolve, etc. From the standpoint of safety and ease of management, it is preferable to use water. At this time, it is possible to dry before irradiating with ionizing radiation, but if irradiated while still containing a certain amount of solvent,
Better writability with water-based ink can be obtained. If the coating layer contains a hydrophilic solvent and is irradiated with ionizing radiation, some or all of the hydrophilic solvent will evaporate, but if the coating layer remains sticky after irradiation with ionizing radiation, For example, it is preferable to further perform a drying step.

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

That is, polyvinyl alcohol, which has an ionizing radiation-curable functional group, has hydrophilicity due to the OH group, and further undergoes polymerization and crosslinking reactions when irradiated with ionizing radiation, resulting in a hydrophilic alcohol with an appropriate crosslinking density. It is presumed that a coating layer with a network structure is formed and has water absorption ability. Since the aqueous ink is quickly absorbed and retained within the hydrophilic network structure thus formed, it is considered that the aqueous ink has excellent recording properties (writing properties, fixing properties, drying properties). At this time, the presence of a hydrophilic solvent prevents hydrogen bonding between the OH groups of polyvinyl alcohol and a decrease in hydrophilicity, and moderately suppresses the increase in crosslink density.
Furthermore, it is thought that part or all of the hydrophilic solvent evaporates instantaneously upon irradiation with ionizing radiation, and at this time, uniform micropores are formed in the coating layer, thereby further improving water absorption. In addition, since this coating film has a crosslinked structure, it also has excellent water resistance and solvent resistance.

The coating composition of the present invention is coated on one or both sides of the support, and the coating means in this case may be a generally known coating method such as a bar coater, a roll coater/air knife coater,
Coating machines such as gravure coaters and offset gravure coaters are used.

The coating amount of the coating composition is 0.1 to 20 g/r in terms of solid amount.
rf, more preferably in the range of 0.2 to 10 g/rlf. Incidentally, if it is less than 0.1 g/rr+, it is difficult to obtain the desired effect of the present invention, and if it exceeds 20 g/rrf, 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.
The adhesion of the recording layer can be improved.

In the recording sheet of the present invention, the recording layer formed as described above is cured by irradiation with ionizing radiation. Examples of ionizing radiation include electron beams, ultraviolet rays, alpha rays, beta rays,
Examples include T-rays and X-rays, but α-rays, β-rays, T-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 widely used industrially.

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 plastic film.

Examples of electron beam irradiation methods include scanning method,
Curtain beam method, broad beam method, etc. are adopted, and the acceleration voltage when irradiating the electron beam is 100 to 300 kV.
The degree is appropriate. The electron beam irradiation method has the advantage of higher productivity than ultraviolet irradiation, no problems with odor or coloring caused by addition of a sensitizer, and the ability to easily form a uniform crosslinked structure.

When using ultraviolet light, it is necessary to incorporate a sensitizer into the coating composition, such as thioxanthone, hengeine, benzoin alkyl ether xanthone, dimethylxanthone, benzophenone, anthracene, 2,2-jethoxyacetophenone, benzyldimethyl. ketal,
Hensyl diphenyl disulfide, anthraquinone, l
- Kuro.

Anthraquinone, 2-ethylanthraquinone, 2-t
One or more sensitizers such as er-butylanthraquinone, N,N'-tetraethyl-4,4'-diaminobenzophenone, and 1,1-dichloroacetophenone are appropriately blended.

The amount of the sensitizer used is 0.2 to 10% by weight, preferably 0.2% to 10% by weight, based on the ionizing radiation-curable compound in the coating composition.
It is desirable to adjust the amount within a range of about 5 to 5% by weight. Furthermore, in addition to such sensitizers, to accelerate curing, for example triethanolamine, 2-dimethylaminoethanol, dimethylaminobenzoic acid, isoamyl dimethylaminobenzoate, dioctylaminebenzoic acid, lauryl dimethylaminobenzoate, etc. It is also possible to blend tertiary amines such as 0.05 to 3% by weight based on the ionizing radiation-curable compound in the coating composition.

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 μW/cn are preferably irradiated.

[Example 1 Examples are shown below to explain the present invention more specifically,
Of course, it is not limited to these.

In addition, unless otherwise specified, "1 part" and "1-%" in the examples indicate "part by weight" and "% by weight," respectively.

Example 1 One side of a 100 μm thick polyethylene terephthalate film was treated with an anchor coat to facilitate adhesion, and then a recording layer coating liquid containing about 8 ionizing radiation-curable functional groups having the following structure [1] A 10% aqueous solution of polyvinyl alcohol containing mol% and a degree of polymerization of about 660 was applied so that the dry weight was 41 S/bo, and then using an electron beam irradiation device (Electro Curtain CB 150, manufactured by ESI). After irradiating with 5 Mrad electron beam, 70°C
The sheet was dried for 5 minutes to obtain a recording sheet.

0-CH, -NH-Co-CR=CH2N) (R represents a hydrogen atom or a methyl group) Example 2 An ionizing radiation-curable functional group having the structure of the following formula (II) was used as a recording layer coating liquid. A recording sheet was obtained in the same manner as in Example 1, except that a 1O% aqueous solution of polyvinyl alcohol containing about 20 mol % and having a degree of polymerization of about 700 was used.

0-CH-CH-NH-Co-CR=CH.

0HOH [■] (R represents a hydrogen atom or a methyl group) Comparative Example 1 In Example 1, a recording sheet was obtained by drying at 70° C. for 5 minutes without irradiating with an electron beam.

Comparative Example 2 A 10% aqueous solution of polyvinyl alcohol containing about 70 mol% of an ionizing radiation-curable functional group having the structure of formula (II) and having a degree of polymerization of about 700 was used as the recording layer coating liquid. A recording sheet was obtained in the same manner as in Example 1.

Comparative Example 3 Polyvinyl alcohol (PVA-
A recording sheet was obtained in the same manner as in Comparative Example 1 using a 10% water solution of 117 (manufactured by Kuraray ■).

Comparative Example 4 Polyester resin (Vylon 10
3. A recording sheet] was obtained in the same manner as in Comparative Example 1 using a 15% toluene solution (manufactured by Toyobo ■).

The five types of recording sheets obtained in the above manner were evaluated in terms of writing performance of water-based ink, fixing/drying performance of water-based ink, water resistance, and solvent resistance as follows, and the results were evaluated in the following manner. Shown in the table.

(1) Writing on the recording layer was performed using a water-based fluorescent marker (manufactured by KOKUYO ■), and the presence or absence of repellency was visually determined.

◎: No repelling occurred at all.

○: Although there was 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 poor repellency.

(2) Fixation and drying of water-based ink After writing on the film using a water-based fluorescent marker (manufactured by KOKUYO ■), the ink was lightly rubbed with a finger to evaluate the time until it was fixed.

◎: Fixed within 5 seconds.

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

Δ: Fixing and drying took from 60 seconds to 1 hour, which was at a level that was problematic in practice.

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

(3) Three drops of water were dropped onto the coating layer using a water-resistant dropper, and the damage to the coating layer was evaluated after wiping it off with gauze.

O: There was no damage to the coating layer.

x: The entire coating layer was wiped off.

(4) Three drops of toluene were dropped onto the coating layer using a solvent-resistant dropper, and the damage to the coating layer was evaluated after wiping it off with gauze.

○: There was no damage to the coating layer.

Δ: Some damage was observed in the coating layer.

x: The entire coating layer was wiped off.

When shadowed, a clear and high-contrast projected image was obtained.

As described above, the recording sheet according to the present invention has excellent recording properties with respect to water-based ink, and is particularly suitable for writing with a water-based pen or marker, and recording with an inkjet printer, pen plotter, etc. It has extremely high commercial value as an OHP film.

Claims (1)

[Claims] (1) A recording layer mainly composed of polyvinyl alcohol having 1 to 50 mol% of functional groups containing ethylenically unsaturated double bonds in one molecule is provided on the support, and the recording layer is irradiated with ionizing radiation. A record sheet featuring what you have done.