JPH1063030A5 - - Google Patents

Description

[0003]
Electrophotographic printing using such liquid toner is carried out by the method shown in Figure 1. Specifically, it is carried out in the following manner.
(1) Digital data of the image to be printed, which has been created in advance by a prepress system such as DTP or CEPS on a data input machine 2, is directly read online 3 into the controller 4 of the electrophotographic printing machine 1, or the jog to be printed is screened (data input) from the data transferred to the hard disk of the controller 4 by a disk, tape, etc. 5 and read into the image memory 6.
(2) Next, the data in the image memory that has been binarized for each color by the screening is written onto the surface of the photosensitive drum 8 with a laser beam using a laser scanner 7, and recorded as an electrostatic latent image.

[0004]
(3) Then, liquid toner 11 supplied from a liquid toner tank 10 is sprayed from an injector 12 into the gap between the photosensitive drum 8 and the developing roll 9, thereby carrying out liquid development.
1 shows a four-color full-color development performed by a single developing roll 9. In this case, liquid toners Y, M, C, and B are sequentially supplied one by one and mixed with liquid (oil) L, scraped off by wiper blades 13 on the developing roll 9 for each color, and collected in liquid toner tanks 20 for each color. [Development]
(4) The developed image on the photosensitive drum 8 is transferred to a blanket cylinder 14 heated to 60 to 120°C, which rotates in the opposite direction in contact with the drum. The heat of the blanket cylinder 14 volatilizes the solvent, and the toner melts, forming a sticky film.

[0005]
(5) Then, printing paper 17 is supplied from a printing paper storage tray 16 between the blanket cylinder 14 and the impression cylinder 15 which rotates in contact with the blanket cylinder 14, and the adhesive film-like material is transferred to the surface of the printing paper 17 and fixed onto the printing paper 17 by the pressure of the impression cylinder 15.
When performing full-color development using four colors, the printing paper 17 rotates four times while being fixed on the impression cylinder 15, and the liquid toners of the colors Y, M, C, and B are transferred successively onto the printing paper 17 in this order. [Transfer/Fixing]
(6) The printing paper 17 printed by the above transfer/fixing process is discharged by the rotation of the impression cylinder 15 and falls naturally (under its own weight) to be accumulated on a storage tray 18 provided diagonally below the impression cylinder 15.
The printing paper 17 on which the printing has been carried out is cooled by a cooler 19, and the print (toner) is cooled by the impression cylinder 15 and the cooler 19 and solidifies at room temperature.
In this way, liquid toner has the advantage that the particle size can be made as small as possible because there is no risk of the toner contained in the liquid (oil) L floating in the air, and therefore such toner can produce printing with higher resolution than powder toner.
Furthermore, liquid toner has higher transparency than powder toner, allowing for vivid color reproduction when used on a color OHP document. Furthermore, it also has the advantage of providing good secondary color reproduction when colors are superimposed.

[0007]
[Means for solving the problem]
The present inventors have conducted extensive research in light of the above problems and have completed the present invention.
That is, the electrophotographic printing paper of the present invention is a printing paper for use in electrophotographic printing using liquid toner, in which a photosensitive drum is charged with electric charge by corona discharge treatment, an electrostatic latent image is formed on the surface by laser irradiation, liquid toner is sprayed onto the photosensitive drum from an injector to develop the developed image, the developed image is transferred to a heated blanket cylinder which is in contact with the photosensitive drum and rotates in the opposite direction, the heat of the blanket cylinder causes the solvent in the liquid toner to fly off and the toner to thermally melt, forming a sticky film-like substance, printing paper fed by a rotating impression cylinder is then brought into contact with the blanket cylinder, the film-like substance is secondarily transferred onto the surface of the printing paper, and the secondarily transferred film-like substance is fixed, and the printing paper is characterized in that it is a laminated film having a layer of the following modified graft copolymer (A) provided on the surface of a thermoplastic resin film substrate.
Modified graft copolymer (A): A modified graft copolymer (A) in which an α,β-unsaturated dicarboxylic acid is graft polymerized onto a hydrogenated product of a styrene-conjugated diene block copolymer, and 25 mol % or more of the grafted α,β-unsaturated dicarboxylic acid is half-esterified with a monoalcohol and/or half-amidated with a mono-secondary amine.

[0011]
Specifically, a polyolefin film containing 8 to 65% by weight of inorganic fine powder, for example, calcined clay, diatomaceous earth, titanium oxide, vermiculite, heavy calcium carbonate, or talc having a particle size of 0.05 to 10 μm, is uniaxially stretched, thereby generating fine cracks on the surface of the film centered on the inorganic fine powder particles, and forming a large number of fine voids (5/mm) inside the film. Examples of such synthetic paper include a laminated film having a surface layer formed from a biaxially oriented thermoplastic resin film containing ⁵ to 40% by weight of inorganic fine powder, and a base layer formed from a biaxially oriented thermoplastic resin film containing 5 to 40% by weight of inorganic fine powder laminated on the surface layer (see JP-B-40794/1971); a multilayer synthetic paper as described in JP-A-61-003748 and JP-B-1-6041, in which a polyolefin film layer having a thickness of 0.5 to 3 μm and containing substantially no inorganic fine powder is further formed on the surface of the laminated film; and a pearlescent synthetic paper made from a biaxially oriented thermoplastic resin film containing 10 to 40% by weight of inorganic fine powder.

[0016]
The radical polymerization initiator may be any of ordinary radical polymerization initiators, and examples thereof include alkyl peroxides such as ditertiary butyl peroxide and tertiary butyl hydroperoxide, allyl peroxides such as dicumyl peroxide and cumyl hydroperoxide, acyl peroxides such as dilauroyl peroxide, aroyl peroxides such as dibenzoyl peroxide, ketone peroxides such as methyl ethyl ketone peroxide, peroxycarbonates, and azonitriles such as azobisisobutyronitrile.
The unreacted α,β-unsaturated dicarboxylic acid can be easily removed by subjecting the reaction mixture to a reduced pressure treatment while heating and melting it, or by repeatedly washing the reaction mixture with a solvent such as acetone, but it is also possible to carry out half-esterification and/or half-amidation without further purification.
As the α,β-unsaturated dicarboxylic acid, maleic acid, itaconic acid, citraconic acid, chloromaleic acid, dimethylmaleic acid, and acid anhydrides thereof can be used.
The concentration of grafted α,β-unsaturated dicarboxylic acid units (graft ratio) in the modified graft copolymer (A) is preferably in the range of 0.1 to 10% by weight.
If the graft ratio is less than 0.1% by weight, the adhesion to polyolefin is good, but the toner adhesion and paper feeding/discharging properties are poor. On the other hand, even if the graft ratio exceeds 10% by weight, no further improvement in toner adhesion can be expected, and the cost increases.

[0023]
[3] Coating Agent The coating of the above-mentioned modified graft copolymer (A) itself has an antistatic function (surface resistivity value of 1× ¹⁰ to 9× ¹⁰ Ω/□) and improves paper feeding and ejection properties. However, when this is provided on only one side of the base layer, it is preferable to use a thermoplastic resin film for the base material into which an antistatic agent has been kneaded, or to use a base material film coated with a coating agent containing an antistatic agent on the back or both sides thereof.

[0024]
(A) Coating agent layer components In particular, it is preferred that an antistatic agent containing the following components <1>, <2>, <3> and <4> be blended on the side opposite to the toner printing surface in terms of paper feeding and ejection properties and multicolor offset printing and multicolor screen printing properties.
<1> Component: 100 parts by weight of an antistatic agent comprising a water-soluble quaternary nitrogen-containing polymer; <2> Component: 10 to 200 parts by weight of a polyethyleneimine-based polymer selected from the group consisting of polyethyleneimine, alkyl-modified polyethyleneimine, poly(ethyleneimine-urea), and an ethyleneimine adduct of polyamine polyamide; <3> Component: 10 to 200 parts by weight of an epichlorohydrin adduct of polyamine polyamide; Optionally,
<4> Component: 80 parts by weight or less of an alkali metal salt or an alkaline earth metal salt.

[0025]
(a) Antistatic Agent <1> An antistatic agent comprising a water-soluble quaternary nitrogen-containing polymer (component <1>)
Specific examples of antistatic agents used as the above component <1> include those that can be produced by polymerizing the corresponding nitrogen-containing monomer and, if necessary, quaternizing the resulting tertiary nitrogen-containing polymer, as described in JP-A-59-43065.
Specific examples of the quaternary nitrogen-containing monomer suitable for use in the present invention include those represented by the following chemical formulas (a) to (d).
Chemical formula (A)

[0030]
[In each of the above chemical formulas (A) to (D), ^R1 represents a hydrogen atom or a methyl group, ^R2 and ^R3 each represent a lower alkyl group (particularly having 1 to 4 carbon atoms, more preferably having 1 to 2 carbon atoms), ^R4 represents a saturated or unsaturated alkyl group or cycloalkyl group having 1 to 22 carbon atoms, ^X- represents a counter anion of quaternized N ⁺ (e.g., a halide (particularly chloride)), M represents an alkali metal ion (particularly sodium, potassium, or lithium), and A represents an alkylene group having 2 to 6 carbon atoms.]
It goes without saying that the polymers of the quaternary nitrogen-containing monomers represented by the above chemical formulas (A), (B), (C), and (D) can be made to exist in the polymer by polymerizing the precursor quaternary nitrogen-containing monomer and then quaternizing it with a cationizing agent such as alkyl halide, dimethyl sulfate, or monochloroacetic acid ester.
In the present invention, the antistatic agent must be water-soluble, but excessive water solubility is not desirable. Therefore, the quaternary nitrogen-containing polymer of component <1> is preferably a copolymer with a hydrophobic monomer. Examples of hydrophobic monomers include styrene or its nucleus or side chain substitutions, acrylic or methacrylic acid esters, vinyl halides, and others.

[0031]
Suitable antistatic polymers In the present invention, a particularly preferred antistatic polymer as component <1> is a copolymer of the following components (i) to (iii):
Component (i): 20 to 40% by weight of a quaternary nitrogen-containing monomer represented by the chemical formulas (a) to (d)

[0034]
Most Preferred Antistatic Polymer In the present invention, the most preferred antistatic polymer for component <1> is one in which the quaternary nitrogen-containing monomer for component (a) is the above-described monomer (a) in which X- is ^{Cl- .}
Furthermore, as described in JP-A-6-25447, the component <1> is
(i') General formula

[0042]
That which is represented by
^R7 and ^R8 may be the same or different and are each represented by an alkyl group having 1 to 3 carbon atoms.
General formula [VI]

[0045]
The polymerization method for obtaining the copolymer, which is the water-soluble antistatic agent of component <1>, can be any known polymerization method using a radical polymerization initiator, such as bulk polymerization, solution polymerization, or emulsion polymerization. Among these, solution polymerization is preferred, in which each monomer is dissolved in a solvent, a radical polymerization initiator is added, and the mixture is heated and stirred under a nitrogen stream. Preferred solvents include water and alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and these solvents may be mixed and used. Suitable polymerization initiators include peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile and azobisvaleronitrile. The monomer concentration is typically 10 to 60% by weight, and the polymerization initiator concentration is typically 0.1 to 10% by weight relative to the monomers.
The molecular weight of the quaternary ammonium salt copolymer can be adjusted to any level by adjusting polymerization conditions such as polymerization temperature, type and amount of polymerization initiator, amount of solvent used, chain transfer agent, etc. The molecular weight of the resulting polymer is generally 1,000 to 1,000,000, with a range of 1,000 to 500,000 being preferred.

[0046]
<2> Polyethyleneimine polymer (component <2>)
In addition to the quaternary nitrogen-containing polymer, a polyethyleneimine polymer is added to the coating layer as a component that contributes to the adhesion of ink, particularly the adhesion of ultraviolet-curable offset printing ink.
Examples of such polyethyleneimine-based polymers include polyethyleneimine, poly(ethyleneimine-urea), polyethyleneimine adducts of polyamine polyamides, and alkylated polyethyleneimine (preferably alkyl groups having 1 to 8 carbon atoms) (see JP-A-1-141736).
Among these, it is preferable to use modified polyethyleneimine obtained by modifying polyethyleneimine or a polyethyleneimine adduct of polyamine polyamide with an alkyl halide, alkenyl halide, cycloalkyl halide, or benzyl halide having 1 to 24 carbon atoms, from the viewpoint of improving adhesion and transferability with offset ink.
Here, polyethyleneimine having any degree of polymerization may be used, but preferably has a degree of polymerization of 20 to 300.

[0047]
<3> Epichlorohydrin adduct of polyamine polyamide (component <3>)
The epichlorohydrin adduct of polyamine polyamide of component <3> is a water-soluble thermosetting resin obtained by reacting a polyamide consisting of a saturated dibasic carboxylic acid having 3 to 10 carbon atoms and a polyalkylene polyamine with epichlorohydrin.
Details of such resins are described in detail in Japanese Patent Publication No. 35-3547.
Specific examples of saturated dibasic carboxylic acids having 3 to 10 carbon atoms include dicarboxylic acids having 4 to 8 carbon atoms, particularly adipic acid, and specific examples of polyalkylene polyamines include polyethylene polyamines, particularly ethylene diamine, diethylene triamine and triethylene tetramine, especially diethylene triamine.
The molar ratio of polyalkylenepolyamine to dibasic acid in the polyamide-forming reaction is typically about 0.9:1 to 1.2. In the reaction of the polyaminepolyamide with epichlorohydrin, about 0.5 to about 1.8 moles of epichlorohydrin are typically used for each secondary amine group in the polyamide.
This can contribute to improving the water-resistant adhesion to ink.

[0048]
<4> Alkali metal salt or alkaline earth metal salt (component <4>)
Examples of the water-soluble inorganic salt consisting of an alkali metal salt or alkaline earth metal salt of the optional component <4> include alkali metal salts such as sodium carbonate, sodium hydrogencarbonate, potassium carbonate, sodium sulfite, and other alkaline salts, sodium chloride, sodium sulfate, sodium nitrate, sodium tripolyphosphate, sodium pyrophosphate, and other neutral salts, and alkaline earth metal salts such as beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, and barium nitrate.
When the coating layer contains inorganic salts, the antistatic properties are improved and the drying speed of the toner increases. However, the presence of water-soluble inorganic salts reduces the water-resistant adhesion of the ink, so the presence of excessive amounts is not desirable.

[0049]
(b) Other optional ingredients (ingredients <5>)
The coating layer may further contain surfactants, water-soluble or water-dispersible polymers, finely divided powder materials, and other auxiliary materials.

[0050]
(B) Composition of Coating Layer Components The composition of the coating layer consisting of the above-mentioned constituent components is such that the ratios of the amounts of component <2>, component <3>, component <4> and component <5> used per 100 parts by weight of component <1> are as follows:
<1> Component: 100 parts by weight <2> Component: 10 to 100 parts by weight, preferably 50 to 100 parts by weight
<3> Component: 10 to 100 parts by weight, preferably 50 to 80 parts by weight,
<4> Component: 0 to 80 parts by weight, preferably 10 to 30 parts by weight,
<5> Component: 0 to 100 parts by weight, preferably 5 to 70 parts by weight,

[0053]
[II] Manufacture of electrophotographic printing paper
[1] Thickness The thickness of electrophotographic printing paper is generally 100 to 1,000 μm, preferably 200 to 400 μm, and its Clark stiffness (based on JIS-P8143) is preferably 60 to 500, preferably 80 to 300, from the viewpoint of paper feeding and ejection.
[2] Smoothness The coating layer containing the modified graft copolymer (A) preferably has a Beck smoothness (JIS-P8119) of 100 to 1,000 seconds, and more preferably 200 to 800 seconds, from the viewpoint of toner adhesion.

[0060]
Production Example 2
A 40% solution of a graft copolymer having 2.4% maleic anhydride grafted thereto was obtained by synthesis in the same manner as in Production Example 1, except that the hydrogenated styrene-butadiene-styrene block copolymer was replaced with 100 parts by weight of a hydrogenated styrene-isoprene-styrene block copolymer (hereinafter simply abbreviated as "SEPS") ("Septon 2002", manufactured by Kuraray Co., Ltd.) and the amount of maleic anhydride was changed to 5 parts by weight.
To 100 parts by weight of this graft copolymer, 3 parts by weight of N-methylcyclohexylamine was added and mixed thoroughly, and then the mixture was left at room temperature for 3 days to obtain a coating resin solution (A-2-I) having a graft rate of maleic anhydride of 2.4% and containing 40% of modified graft copolymer (A-2) in which approximately 95% of the maleic anhydride was half-amidated.

[0067]
[Evaluation method]
Transferability ⊚: Four colors are printed on the entire surface of the printing paper, the print is highly glossy, and the image is highly precise.
Good: Four-color printing is done on the entire surface of the printing paper, but the print has low gloss and there are some thick and thin lines, but this does not pose a problem in practical use.
△: Although it is printed in four colors, there are some white areas here and there, which is problematic for practical use.
×: Only the first yellow toner was transferred, which is problematic in practical use.
Adhesion : The print does not come off even when the printed surface is rubbed with a finger.
×: When the printed surface is rubbed with a finger, the toner surface is stretched and the print becomes blurred.
Water-resistant adhesion <br/>When a drop of water is dropped on the toner print surface and the surface is rubbed with a finger,
○: The print does not peel off.
×: The toner surface is stretched and the print is blurred.
Paper feeding and ejection performance : Good: Printed paper was fed and ejected smoothly during one hour of continuous printing.
x: During one hour of continuous printing, the printing paper was not fed sufficiently or the paper was not discharged sufficiently after printing, causing the operation to be interrupted (3 to 12 interruptions per hour).

[0069]
Comparative Example 3
The coating solution (II) was applied to both surfaces of the synthetic paper (P-1) with a roll so that the solid content was 0.2 g/ ^m² , and then dried at a temperature of 65°C to form a film, which was then rolled up to prepare printing paper (Beck smoothness: 230 seconds, Clark stiffness: 190 in the longitudinal direction, 260 in the transverse direction).
Using this printing paper [(II)/(P-1)/(II)] and an electrophotographic digital offset color printing machine "E-Print 100" (trade name) manufactured by Indigo, and using "Electro Ink, yellow (Y), magenta (M), cyan (C), black (B)" manufactured by Toyo Ink Mfg. Co., Ltd. as liquid toner, full color printing (1,000 sheets/hour) was carried out using a file in which a landscape photograph was scanned as an image and text was entered using a personal computer and input into memory.
The results of the transferability of the print, the adhesion of the toner, and the paper feeding and ejection properties are shown in Table 2.

[0072]
[Table 2]

[0073]
[Effects of the Invention]
The electrophotographic printing paper of the present invention has excellent toner transferability and adhesion, is free from paper feed and ejection problems, and allows the toner particles to be made fine, even when printed on a printer utilizing an electrophotographic system using liquid toner, resulting in delicate images and high gloss printing.

Claims (5)

1. A printing paper for electrophotographic printing using a liquid toner, which is produced by charging a photosensitive drum with electric charge by corona discharge treatment, forming an electrostatic latent image on the surface by laser irradiation, spraying liquid toner from an injector onto the photosensitive drum to develop the developed image, transferring the developed image onto a heated blanket cylinder which is in contact with the photosensitive drum and rotates in the opposite direction, causing the heat of the blanket cylinder to evaporate the solvent in the liquid toner and heat-melt the toner to form a sticky film-like substance, and then bringing a printing paper fed by a rotating impression cylinder into contact with the blanket cylinder to perform a second transfer of the film-like substance onto the surface of the printing paper, and fixing the secondarily transferred film-like substance, characterized in that the printing paper is a laminated film having a layer of the following modified graft copolymer (A) provided on the surface of a thermoplastic resin film substrate.
Modified graft copolymer (A): A graft copolymer obtained by graft polymerizing an α,β-unsaturated dicarboxylic acid onto a hydrogenated product of styrene-conjugated diene block copolymer, in which 25 mol% or more of the grafted α,β-unsaturated dicarboxylic acid has been half-esterified with a monoalcohol and/or half-amidated with a mono-secondary amine. 2. The electrophotographic printing paper according to claim 1, wherein the hydrogenated styrene-conjugated diene block copolymer used as the raw material for the modified graft copolymer (A) is a hydrogenated block copolymer having a block portion of a styrene polymer and a block portion of a butadiene and/or isoprene polymer, the α,β-unsaturated dicarboxylic acid is maleic anhydride, the monoalcohol is an aliphatic or alicyclic alcohol having 1 to 8 carbon atoms, and the mono-secondary amine is N-methylcyclohexylamine. 2. The electrophotographic printing paper according to claim 1, wherein the modified graft copolymer (A) is a hydrogenated styrene-conjugated diene block copolymer to which an α,β-unsaturated dicarboxylic acid is graft polymerized, and the concentration of α,β-unsaturated dicarboxylic acid units (graft ratio) in the graft copolymer is 0.1 to 10% by weight. 2. The electrophotographic printing paper according to claim 1, wherein an antistatic resin layer is provided on the back surface of the thermoplastic resin film substrate or on the surface on which the modified graft copolymer (A) layer is laminated. 5. The electrophotographic printing paper according to claim 1, wherein the printing paper has a thickness of 100 to 1,000 [mu]m, a Clark stiffness (S value) (JIS-P8143) of 60 to 500, and a Beck smoothness of 100 to 1,000 seconds.