JP2009080414A - Laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic printing laminated sheet which is improved in terms of toner-blocking. <P>SOLUTION: The electrophotographic printing laminated sheet is constituted so that one or more layers composed of one or more thermoplastic resins are laminated on at least one side of a base material, and a coating layer containing an n-paraffine is provided on the thermoplastic resin layer. The n-paraffine of ≥12 wt.% is contained per total solid volume of the coating layer. When using for an electrophotographic printing system, the sheet is improved in prevention of toner-blocking, and also, the sheet can satisfactorily maintain toner fixation properties. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laminated sheet, particularly a laminated sheet suitable for an electrophotographic printing type recording sheet.

As the recording sheet used for the transfer type electrophotographic printing method, paper is usually used. However, when water resistance is required, so-called synthetic paper or laminated paper is used. Laminated paper is obtained by laminating a thermoplastic resin on a paper base material. For example, a laminated paper is manufactured by laminating a thermoplastic resin on one or both sides of a paper base material by an extrusion lamination method or a coextrusion lamination method (Patent Document). 1).
Japanese Patent No. 2763011

In the transfer type electrophotographic printing method, after toner is transferred to a recording sheet, it is heat-sealed and fixed under a high temperature condition of about 200 ° C. When mass printing is performed, printed recording sheets discharged from a recording apparatus such as an LBP (laser beam printer) are stacked, and a high temperature state is maintained near the center of the stacked recording sheets. In addition, the weight of the recording sheet itself is added, and the degree of adhesion between the toner and the recording sheet in contact with the toner increases to cause fusion. This is a phenomenon called toner backing (toner blocking). However, when the recording sheets are separated one by one, there is a problem that the toner peels off from the printing surface. This phenomenon is not observed when face-down paper is discharged, but is observed when face-up paper is discharged.
Some printers have a straight paper discharge mechanism to suppress curling during printing and to reduce the risk of paper jam. This mechanism is called face-up discharge because the paper is discharged with the print side up. In face-up paper discharge, the paper is discharged immediately after the high-temperature pressure bonding process using a heat roll, so that the paper overlaps before it is sufficiently cooled, and there is a high risk of backing. On the other hand, there is a mechanism that discharges paper from the top of the printer as a mechanism that is always provided in all printers. This mechanism is called face-down paper discharge because the paper is discharged with the print side down. In face-down paper discharge, there is a distance from the heat roll to paper discharge, so the paper cools down longer than in face-up paper discharge, and backing is less likely to occur.

Toner backing is a particularly significant problem for laminated paper having a thermoplastic resin that hardly releases heat, but a major improvement method has not been studied. As a method for preventing toner backing, a release agent is applied to one side of a laminated sheet. However, the release agent application surface is not suitable for double-sided printing because of poor toner fixing properties.
An object of the present invention is to provide a laminated sheet having improved toner backing.

The main configuration of the present invention is as follows.
(1) An electrophotographic printing characterized in that a layer made of one or more thermoplastic resins is laminated on at least one surface of a substrate, and a coating layer containing n-paraffin is provided on the thermoplastic resin layer. Laminated sheet.
(2) The laminated sheet according to (1), containing n-paraffin in an amount of 12% by weight or more per total solid content of the coating layer.

  When used in an electrophotographic printing method, it is excellent in preventing toner lining and can maintain good toner fixing properties.

<About the coating layer>
The coating layer serves as a toner fixing layer and is composed of n-paraffin and a binder.

(N-paraffin)
The n-paraffin (normal paraffin) is a hydrocarbon having a linear molecular structure represented by the following formula 1, and when the carbon number is 4 or less (n ≦ 2), the gas is 5 or more and 15 or less (3 ≦ n). ≦ 13) exists as a liquid, and 16 or more (n ≧ 14) exists as a solid. The n-paraffin used in the present application refers to those having 16 or more (n ≧ 14) carbon atoms present as a solid at room temperature.
(Formula 1)
_{CH 3 - (CH 2) n} -CH 3

  n-paraffin has a melting point characteristic of its carbon number. That is, the melting point can be changed by changing the number of carbon atoms. In general, the higher the carbon number, the higher the melting point. For example, the melting point of n-paraffin having 20 carbon atoms is about 20 ° C., and the melting point of n-paraffin having 80 carbon atoms is about 105 ° C. By using n-paraffin having a carbon number close to the heat roll temperature (about 160 to 190 ° C.) in the high-temperature pressure bonding step of the laser beam printer, the n-paraffin is liquefied from a solid in the high-temperature pressure bonding step of the printing, It is considered that the temperature rise on the surface of the recording sheet is suppressed by taking heat away from the recording sheet by the endothermic reaction at that time.

The carbon number of n-paraffin is preferably 40 or more. If it is less than 40, the melting point becomes low, and the effect of suppressing the increase in paper surface temperature cannot be obtained sufficiently.
The amount used is preferably 12% by weight or more, more preferably 30% by weight or more, based on the total solid content of the coating layer. If the amount is too small, the effect of suppressing the increase in the paper surface temperature cannot be obtained sufficiently. However, if the amount is too large, the coating layer strength is lowered, so that the upper limit is about 50% by weight.

(binder)
The binder is selected in consideration of the adhesiveness to the laminated thermoplastic resin layer in addition to the toner fixing property and writing property. For example, as such a binder, styrene, butadiene, acrylonitrile, various acrylic acids, ethylene, propylene, vinyl acetate, vinyl chloride, and the like, a homopolymer, a copolymer and / or a modified product thereof, such as urethane resin or It can be used with or without mixing with an epoxy resin or the like.

  Also, two types of hydrophilic polymers having different Tg, such as a hydrophilic polymer substance (A) having a glass transition temperature of 80 ° C. or higher and a hydrophilic polymer substance (B) having a glass transition temperature of 50 ° C. or lower. Substances can also be used. 80 ° C. is close to the sheet temperature at the time of discharge after printing, and 50 ° C. is a temperature at which the film-forming property of the coating layer can be kept good. More preferably, (A) is 90 ° C. or higher, which is higher than the discharge temperature of the printed sheet, and (B) is 40 ° C. or lower, which is lower than the film forming temperature.

In this case, at the time of forming the coating layer, a so-called sea-island structure is formed in the low Tg hydrophilic polymer substance, in which the high Tg hydrophilic polymer substance exists in a state of maintaining the particle shape without melting. Since the toner is fixed with a roll near 200 ° C. during LBP printing or the like, the high Tg hydrophilic polymer substance is also in a molten state, and the adhesion between the coating layer and the toner is greatly increased, which is favorable. Toner fixability can be obtained. After toner fixing, the high Tg hydrophilic polymer substance quickly becomes a glass state, and it is considered that the toner fixing property is also improved by the anchor effect by the toner that has entered the interparticle voids. Similarly, the presence of the high-Tg hydrophilic polymer substance that has become a glass state after toner fixing has high peelability from a high-temperature conveyance roll such as a fixing roll, and improves the conveyance characteristics.

  The hydrophilic polymer substance is preferably an emulsion having a hydrophilic functional group. The hydrophilicity here means that the resin is dispersed or dissolved and stabilized in water or a medium composed of water and a small amount of an organic solvent. These resins are dispersed or dissolved as particles in the coating solution, but form a coating layer upon coating and drying.

  Examples of hydrophilic polymer substances include styrene, butadiene, various acrylic acids, acrylonitrile, ethylene, propylene, vinyl acetate, vinyl chloride, and other homopolymers, copolymers and / or modified products thereof, and polyesters. A resin, a urethane resin, an epoxy resin, or the like may be mixed or not used alone. These hydrophilic polymer substances are preferably produced by conventionally known polymerization methods such as emulsion polymerization, soap-free emulsion polymerization, and suspension polymerization, and are polymers having a weight average molecular weight of 100,000 or more.

Among these, an acrylic polymer is preferable for the reason of toner fixability. Examples of the acrylic polymer include polyacrylic acid ester, polymethacrylic acid ester, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer. Both (A) and (B) are desirably acrylic polymers, and in particular have a core-shell structure comprising a core portion having a glass transition temperature of 80 ° C. or higher and a shell portion having a glass transition temperature of 50 ° C. or lower. Acrylic polymers exhibit two performances with a single substance, so that workability is improved and they are preferably used. The acrylic polymer having such a core-shell structure is manufactured by, for example, a method described in JP 2001-323004 A or the like. In this case, it is considered that the shell portion is not formed as a film covering the core, but exists as a protective colloid around the core.

The use ratio of the hydrophilic polymer substance is preferably (A) / (B) = 80/20 to 30/70. When the amount of (A) is too large, the film formability and the toner fixing property are inferior. Therefore, the balance between the two is important, and more preferably (A) / (B) = 65/35 to 45/55.
In addition to the above, various additives can be added to the toner fixing layer as long as the object of the present invention is not impaired. For example, an antistatic agent or a lubricant can be added.

(Other ingredients)
Although it is desirable not to contain a pigment from the viewpoint of paper transportability, it can be used for improving roll adhesion during printing, and examples thereof include silica. About 5 parts by weight of the pigment is used with respect to 100 parts by weight of the binder.

  In addition, if necessary, for example, a lubricant, a crosslinking agent, an adhesion improver, an antifoaming agent, an applicability improver, a thickener, an antistatic agent, an ultraviolet absorber, and a dye may be added. Particularly when an electrophotographic printing type recording sheet is used, it is desirable to contain an antistatic agent.

(Coating amount)
Although not particularly limited, it is 0.5 to 7.5 g / m ² (dry weight), preferably 1 to 5 g / m ² (dry weight).

(Coating method)
Known methods such as a bar coater, a blade coater, an air knife coater, a curtain coater, a slide die coater, a roll coater, and a gravure coater can be appropriately used.

<About the thermoplastic resin layer / substrate laminate>
(Base material)
In the present invention, the base material typically refers to a paper produced by intertwining vegetable fibers or plant fibers and other fibers and glued together, such as fine paper, recycled paper, coated paper (coated paper), etc. Can be mentioned. In addition, processed paper, synthetic paper, film, or the like may be used.

(Thermoplastic resin)
The laminated sheet of the present invention is obtained by, for example, laminating a thermoplastic resin on at least one side of this paper base material, and usable thermoplastic resins are polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, polymethyl. Any resin that can be laminated, such as pentene, may be used. These thermoplastic resins may use a single resin in a single layer, or may use a plurality of resins in multiple layers.

  In the outermost layer, inorganic fillers such as titanium oxide and calcium carbonate can be blended for the purpose of providing opacity. However, since the blending of the inorganic filler also causes the surface properties of the laminated sheet to deteriorate, the blending amount is preferably 25% by weight or less, preferably 15% by weight or less, based on the outermost layer in which the blending is performed.

  In addition to the above, various additives can be added as long as the object of the present invention is not impaired. For example, commonly used additives such as anti-blocking agents (acrylic beads, glass beads, silica, etc.) and adhesion improvers can be used.

(Method for forming thermoplastic resin layer)
As a method of laminating a thermoplastic resin layer on a paper substrate, there is a method of laminating a film and a paper substrate, such as a wet lamination method and a dry lamination method, in addition to the extrusion lamination method and the coextrusion lamination method. However, one-side processing is possible with the wet laminating method, but when films are bonded to both sides, the back surface of the paper substrate is covered with the film when the solvent is dried. These expand and push up the film, and voids (non-adhered portions) called blisters are likely to occur. In addition, the dry laminating method has poor adhesion between the paper substrate and the film, and when printing or recording by electrophotography, moisture in the paper substrate evaporates by heating with a heat roll to fix the toner. It tends to expand and blisters, making it difficult to process. Therefore, when the laminated sheet of the present invention is used for printing or recording in an electrophotographic system, an extrusion lamination method or a coextrusion lamination method is preferable as a processing method.

As described above, the thermoplastic resin layer of the present invention is a known method such as an extrusion lamination method or a coextrusion lamination method, or a combination of these methods as appropriate. The layers are formed so as to have a degree. As described above, when an inorganic filler such as titanium oxide is blended with the resin forming the outermost layer for the purpose of opacity and the like, the lamination processability deteriorates, but in such a case, the resin blended with this inorganic filler is inorganic. If coextrusion laminating with a resin not containing a filler, even if the thickness of the resin layer is reduced, it is possible to stably perform lamination while suppressing the occurrence of trouble such as so-called film breakage. In addition, when the adhesion to the paper substrate is poor due to the paper substrate or operating conditions, it is possible to apply or laminate an adhesive layer on the paper substrate in advance, and to the outermost layer or other layers It is also possible to co-extrusion and laminate the thermoplastic resin and adhesive resin used. An acrylic resin, an epoxy resin, or the like is used as the adhesive resin. When the thermoplastic resin layers are present on both sides of the paper substrate, the type of thermoplastic resin, the order of lamination, and the like may be the same or different on one side and the other side.

[Example]
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, parts and% indicate parts by weight and% by weight. Moreover, the result of having performed the following evaluation about the obtained laminated sheet is shown in Table 1.

<Evaluation method>
Samples were continuously printed under the following conditions, and the following items were evaluated.
Printer used: Casio SPEEDIA N5300
Paper setting: Very thick paper Feeding: Bypass tray Paper ejection: Face-up paper ejection and toner backing prevention We confirmed how many sheets can be continuously printed without backing.
-Toner fixability: After scratching the nail, the degree of toner peeling was visually evaluated according to the following criteria.
○ There is no toner peeling △ There is a minute peeling of toner.
× Toner is peeled off.

Resin with 100 parts by weight of molten polymethylpentene (melting point 220 ° C., trade name “TPX DX820” manufactured by Mitsui Chemicals, Inc.) on both sides of fine paper with a basis weight of 157 g / m ² at an extrusion temperature of 300 ° C. using a T-die Extrusion lamination was performed so that the layer thickness was 20 μm, and these molten resin and fine paper were immediately pressed and pressure-bonded at a linear pressure of 15 kgf / cm using a cooling roll and a nip roll having a hardness of 95 degrees. A material sheet was obtained. Based on 100 parts by weight of a cationic core-shell type acrylic resin (concentration 34.5% by weight, core part Tg: 50 ° C., shell part Tg: 40 ° C., core part / shell part = 50/50), the number of carbon atoms A coating solution having a solid content of 10% was prepared by containing 80 n-paraffins in the solid content of 18.8% by weight. A toner fixing layer is prepared by applying 8 g / m ^{2 of} this coating liquid on both sides of the base sheet using a gravure coating machine so that 0.15 g of n-paraffin having 80 carbon atoms per square meter is applied. And a laminated sheet was obtained.

  In the coating liquid of Example 1, the solid content concentration is 10%, in which n-paraffin having 60 carbon atoms is contained in 18.8% by weight of the total solid content instead of n-paraffin having 80 carbon atoms. A liquid was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.15 g of n-paraffin per square meter.

  In the coating liquid of Example 1, the n-paraffin having 80 carbon atoms is changed to n-paraffin having 40 carbon atoms and 18.8% by weight of the total solid content is contained. A liquid was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.15 g of n-paraffin per square meter.

  In the coating solution of Example 1, a coating solution having a solid content concentration of 10% was prepared by adding 30% by weight of n-paraffin having 80 carbon atoms instead of 18.8% by weight of the total solid content, and carrying out. Coating was performed in the same manner as in Example 1 to obtain a laminated sheet coated with 0.24 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a coating liquid with a solid content concentration of 10% was prepared by adding 50% by weight of n-paraffin having 80 carbon atoms instead of 18.8% by weight of the total solid content. Coating was performed in the same manner as in Example 1 to obtain a laminated sheet coated with 0.40 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a coating liquid having a solid content concentration of 10% was prepared by adding 12% by weight of n-paraffin having 80 carbon atoms instead of 18.8% by weight of the total solid content, and carrying out. Coating was performed in the same manner as in Example 1 to obtain a laminated sheet coated with 0.10 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a cationic core-shell type acrylic resin (concentration 34.5% by weight, core part Tg: 50 ° C., shell part Tg: 40 ° C., core part / shell part = 50/50) Instead, based on 100 parts by weight of a styrene acrylic copolymer resin (concentration 43.8% by weight, Tg: 40 ° C.), the carbon number of n-paraffin is changed to 18.8% by weight of the total solid content and 50% by weight. A coating solution having a solid content concentration of 10% was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.40 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a cationic core-shell type acrylic resin (concentration 34.5% by weight, core part Tg: 50 ° C., shell part Tg: 40 ° C., core part / shell part = 50/50) Instead, except that 30 parts by weight of styrene acrylate copolymer resin (concentration 37% by weight, Tg: 102 ° C) and 70 parts by weight of styrene acrylic copolymer resin (concentration 43% by weight, Tg: 10 ° C) were used as a base. The coating liquid was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.15 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a cationic core-shell type acrylic resin (concentration 34.5% by weight, core part Tg: 50 ° C., shell part Tg: 40 ° C., core part / shell part = 50/50) Instead, except that 30 parts by weight of styrene methacrylate copolymer resin (concentration 30% by weight, Tg: 106 ° C.) and 70 parts by weight of styrene acrylic copolymer resin (concentration 25% by weight, Tg: 45 ° C.) were used as a base. The coating liquid was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.15 g of n-paraffin having 80 carbon atoms per square meter.

  In the coating liquid of Example 1, a cationic core-shell type acrylic resin (concentration 34.5% by weight, core part Tg: 50 ° C., shell part Tg: 40 ° C., core part / shell part = 50/50) Instead, a core / shell type acrylic resin (concentration: 33.5% by weight, core part Tg: 130 ° C., shell part Tg: 30 ° C., core part / shell part = 40/60) was used except 100 parts by weight as a base. The coating liquid was prepared and applied in the same manner as in Example 1 to obtain a laminated sheet coated with 0.15 g of n-paraffin having 80 carbon atoms per square meter.

[Comparative Example 1]
A laminated sheet was obtained in the same manner as in Example 1 except that the coating liquid of Example 1 did not contain n-paraffin having 80 carbon atoms.

  From the results shown in Table 1, it can be confirmed that the effect of preventing the toner from backing is improved by including n-paraffin in the coating layer. It was confirmed by touch that the paper temperature decreased when touching the paper after printing. Then, it can be confirmed that as the amount of n-paraffin applied increases, the effect of preventing toner backing improves, and as a result, a sheet suitable for continuous printing of electrophotographic printing with heating can be provided.

Claims (2)

  A laminate sheet for electrophotographic printing, wherein a layer made of one or more thermoplastic resins is laminated on at least one surface of a base material, and a coating layer containing n-paraffin is provided on the thermoplastic resin layer. .   The laminated sheet according to claim 1, which contains 12% by weight or more of n-paraffin per total solid content of the coating layer.