JPWO2004087411A1 - LAMINATE, RECORDING MATERIAL AND METHOD FOR PRODUCING THEM - Google Patents

Abstract

Provided are a novel paper support laminate having high surface smoothness, a recording material having high surface uniformity and ink absorbency, and a method for producing them. Injecting the raw material solution from the orifice while applying a voltage between an electrode in contact with the raw material solution of the long fiber filled in a container having an orifice and an electrode plate disposed to face the orifice, A layer containing long fibers is formed on the surface of the paper support disposed on the electrode plate.

Description

  The present invention relates to a laminate including a paper support mainly composed of cellulose fibers, a recording material, and a method for producing them. More specifically, the present invention is intended to improve the surface smoothness of the paper support. Furthermore, the basic properties such as surface water absorption and printability, and the mechanical properties such as the rigidity of the paper itself are also conventionally known. The present invention provides a laminate and an ink jet recording paper having a layer containing fine fibers, which can be dramatically improved.

In recent years, various hard copy systems have been proposed with the improvement of computer performance and the spread of computers. As a hard copy recording system, a sublimation transfer recording system, an electrophotographic system, a melt heat transfer system, an ink jet system, and the like are known.
The ink jet method is a method in which ink droplets are ejected from a nozzle toward a recording paper at a high speed. This type of printer is fast as a terminal for personal computers in offices and homes because of its advantages such as easy colorization and miniaturization, low printing sound, simple device structure and easy maintenance. Has become popular. The performance of the apparatus has been remarkably improved, the image quality has been remarkably improved, and the momentum is approaching that of silver halide photography.
In the printing by the ink jet method, the image quality varies greatly depending not only on the performance of the printer, but also on the properties of the ink, the properties of the recording material, etc. Therefore, the selection of the recording material is an important factor in determining the quality. Furthermore, since the dependency between the ink and the recording material is high, not only the selection of the individual materials, but also the combination method becomes an element for determining the quality.
Ink components used for inkjet are roughly classified into dye-based inks and pigment-based inks, and each is classified into water-based ink and oil-based ink.
Water-based direct dyes, acid dyes, basic dyes, edible pigments, etc. are mainly used as dye-based water-based inks. In addition, reactive dyes used in the process of printing on recording paper twice and curing it. There is also. Other ink constituent materials include surfactants, dye solubilizers, viscosity adjusters, pH adjusters, fungicides, and drying speed adjusters, which are used in combination as necessary. Examples of the oil-based ink include an oil-based ink jet mainly composed of an oil-soluble dye and oil.
A pigment-based water-based ink is obtained by dispersing a pigment ultra-dispersed powder in water using a surfactant or the like. Similar to a dye-based ink, a viscosity adjuster, a pH adjuster, an antifungal agent, and a drying speed adjuster. Etc. are used in combination as necessary.
The important properties of the recording material that accepts these various inks are surface uniformity and ink absorbability, and the quality (recordability) of printing is affected by these two properties.
However, paper supports such as paper and paperboard used for inkjet recording paper are one-dimensional cellulose fibers assembled as a constituent element into a two-dimensional material, and the surface uniformity of the paper support is , It is governed by the thickness, length, and non-uniformity of the aggregated state of its constituent elements such as cellulose fibers. For this reason, paper supports usually have voids ranging from tens of microns to hundreds of microns or even millimeters.
Such voids impair the surface uniformity of the paper support and cause various problems when printing such as coating and ink jet recording. For example, when the gap is formed over the thickness direction of the paper support and the through hole is formed, when coating or inkjet recording is performed on the surface of the paper support, the ink reaches the surface opposite to the surface, It causes surface defects such as print-through and roll stains.
In addition, even if it does not become a through hole, due to the non-uniformity of the aggregated state of cellulose fibers, when a void distribution occurs on the surface of the paper support, the recording surface is not suitable for printing or surface processing such as inkjet recording. Unevenness or surface processing does not work well. One reason for this is that there are high and low liquid-absorbing parts on the paper support surface between the parts with and without voids on the surface, and there is quantitative variation when water or ink soaks. As a result, unevenness occurs when recording.
Therefore, it is not considered that cosmetic printing such as gravure printing is performed on the paper itself, and such cosmetic printing is an art in which a large amount of inorganic material is applied to a paper support to fill the gap. It is only applied to paper and coated paper.
Therefore, improving the non-uniformity and surface smoothness of the paper support surface is still a lot of money and wisdom as a basic technical problem of papermaking in the production of the paper support.
For example, for the purpose of avoiding non-uniformity of the aggregation state of cellulose fibers on the paper support surface, for example, when making paper, fine fiber elements are generated from the surface of the cellulose fibers and the bonding strength between the fibers is increased. The beating process is performed. Furthermore, in order to distribute the fibers as uniformly as possible to form a sheet, mechanical vibrations on the paper machine wire are caused and a dehydration process is devised.
However, by such a treatment, it has not been possible to obtain a paper support having a sufficient surface uniformity such that the fibers exhibit a truly random orientation. In addition, the cellulose fiber is cut and shortened by the beating process, and the rigidity of the paper support is reduced.
In addition, in order to improve the surface uniformity of the paper support, fine fibers and pigments are added at the paper making stage of the paper support to fill the voids formed by the cellulose fibers, or after paper making or wet paper size. In general, a method of applying a surface of a pigment to paper with a press or a gate roll, or impregnating or applying a coating solution containing a resin or a pigment to the finished paper to fill the gap is also performed.
For example, JP-A-58-214595, JP-A-4-194097, and JP-A-2001-28892 disclose that fine fibers such as refined pulp are applied to the surface of a paper support. . These fine fibers have a very short fiber length of about several microns to several hundreds of microns, and are considered to improve surface smoothness by filling the voids and filling the voids.
However, in either method, it is difficult to obtain a paper support having sufficient surface smoothness. For example, in JP-A-58-214595 and JP-A-4-194097, if the fine fiber is not applied in an amount sufficient to fill the gap, the gap is not sufficiently filled and the surface smoothness of the paper support is improved. Can not. Therefore, a good print surface cannot be obtained even if printing is simply performed thereon. Therefore, it is necessary to increase the amount of the coating liquid and fine fibers more than necessary, or after passing through the paper rolls and after applying the coating liquid, a large number of passes between the calender rolls to which strong pressure is applied, Not only material costs but also increased drying load and excessive equipment are required.
On the other hand, if the gap is completely filled, there arises a problem that printing characteristics such as ink absorbability and ink drying properties are deteriorated. Therefore, it is not desirable to apply a large amount of coating liquid. In addition, in the ink jet recording paper, a thin and stiff paper is required, but in order to obtain a paper support with a uniform surface, pressing with a calendar roll or the like, the paper support obtained is The rigidity decreases due to the decrease in thickness, and this requirement cannot be met. Therefore, at present, it is difficult to obtain a paper support having a sufficient surface uniformity with a limited basis weight.
In addition, it is possible to improve the surface smoothness by laminating a large amount, but since there is a significant difference between the amount of fine fibers filled in the voids and the amount of fine fibers laminated on the cellulose, the ink can be used when printing. A significant difference in absorbability can be made and a good printed surface cannot be obtained. Furthermore, when processing in large quantities, it is necessary to pass many times between the calender rolls to which a strong pressure is applied, and not only material costs but also an increase in drying load and excessive facilities are required.
Although it is usual to apply a small amount of resin or pigment with a size press or gate roll to improve smoothness and ink acceptability, cellulose fibers can be used in minute amounts in the same manner as the above-mentioned fine fibers. If the gap between the gaps cannot be filled, and if the gap is completely filled, simply to obtain surface smoothness, the barrier properties of the resin film are high, and the printing characteristics such as ink acceptability and ink drying properties are reduced. Therefore, it is not desirable to apply a large amount of coating liquid.
In addition, for newspaper paper, printing paper, and the like, thin and firm paper is required, but it can be obtained by pressing with a calender roll or the like to obtain a paper support with a smooth surface. The paper support has a reduced rigidity due to a decrease in thickness, and cannot meet this requirement. Therefore, at present, it is difficult to obtain a paper support having sufficient surface smoothness.
As described above, various methods have been developed on the basis of a long history of technology, but they have aspects that cannot be said to be innovative technological advances, and produce a paper support with high surface smoothness. It was difficult.
On the other hand, many methods for improving the recording performance by improving the ink absorbability of the ink jet recording paper have been proposed.
For example, in Japanese Patent Application Laid-Open No. 2001-205921, a water-absorbing substance and a water-soluble substance are chemically added to the papermaking pulp itself, which is a main material of the ink-jet paper, in order to obtain a high-quality ink-jet paper without dot distortion due to ink bleeding. JP-A-7-61110 discloses a method for obtaining an ink jet paper having a good dot diameter by modification, and in order to improve ink acceptability and print quality, a chlorine-free bleached pulp In JP-A-10-100533, the penetration of the colorant into the ink jet recording paper is conveniently and economically reduced, thereby increasing the color gamut that can regenerate the ink set. In order to obtain ink jet paper that can stably hold the ink on the paper surface, pits (pits) of pulp fibers The wall hole) in the cell, the metal salt to stop the dispersing action of the ink medium to or dispersing to dissolve the ink colorant conveniently method supplies have been proposed respectively.
These methods are intended to impart inkjet suitability to non-coated paper mainly composed of pulp sheets. However, both methods do not control the state of pulp aggregation at the papermaking stage, but attempt to improve the familiarity of the ink by chemically modifying the pulp surface, and the effect is limited.
Recently, among the water-based inkjet printer performance, especially with improved printing speed, resolution, saturation, etc., excellent color and image clarity, high-speed printability, and high absorbency for inkjet recording paper. High recording properties such as low ink bleeding are required. In order to cope with this, efforts have been made to develop ink jet recording paper in which an ink receiving layer is provided on the surface of a support.
For example, in JP-A-10-309863 and JP-A-10-329409, a two-layer structure in which a primer layer is provided and then a water-absorbing resin layer is provided on the surface thereof has high water-based ink absorbability, color reproducibility, and It is disclosed to produce an ink jet recording paper having a high density. Japanese Patent Application Laid-Open No. 55-5830 discloses an ink jet recording paper in which an ink-absorbing coating film is provided on the surface of a support. Japanese Laid-Open Patent Publication No. 55-11829 discloses a coated paper having a two-layer structure with different ink absorption rates.
In the case of ink jet recording paper provided with such an ink receiving layer on the surface of the support, the coating liquid for forming the ink receiving layer penetrates and is fixed to the paper support. However, the degree of penetration of the coating liquid depends on the dispersion non-uniformity of the cellulose fibers in the paper support and is uneven. For this reason, for example, in a portion where the cellulose fibers are not concentrated, the coating film thickness is too large for ink reception, so that the recording density is lowered, or in the portion where the cellulose fibers are concentrated, the received ink amount is inadequate. The film thickness is sufficient, and problems such as smearing and running out of the printer due to insufficient drying occur.
As described above, a process for applying a large amount of a coating liquid containing a pigment or a synthetic resin to the surface of an ink jet recording paper, or using a technique such as size press or impregnation to make the surface properties more uniform. In addition, a chemical modification of pulp or a process for improving ink absorbency by forming an ink receiving layer on a support is performed. However, although these methods have advanced over the long history of technology, they have aspects that are difficult to say as innovative technological advances, and still have good surface uniformity and good ink absorption. Is not obtained.
On the other hand, in recent years, research and development of nanotechnology has been actively performed in the field of solid state physics such as semiconductors. As one of them, recently, the application of the technique called electrospray method, which is used in mass spectrometry, to the manufacturing technology of non-woven fabrics made of fibers of micron order or less like nanofibers has been studied. Yes. For example, the Journal of Textile Society Vol. 59, no. 1 p3 (2003), and Polymer Journals Vol. 59, no. 11, pp. 706-709 (Nov., 2002) introduces nanofibers using an electrospray method and a thin film coating technique using the nanofibers. Japanese Patent Application Laid-Open No. 2000-508008 describes a method of coating a substrate surface by spraying a solution as oil droplets under a voltage application condition. These can be made into a non-woven fabric by themselves, or a filter can be made by forming a nanofiber layer on the surface of a woven fabric or non-woven fabric as a base material. Thus, there is no concept of the present invention.
The electrospray method is a method in which a high voltage of about 2 to 20 kV is applied between the tip of the nozzle containing the polymer solution and the base, and the charged polymer is ejected from the tip of the nozzle to deposit on the base. And the manufacturing method of the nonwoven fabric by this method is called the electrospinning method.
The electrospinning method is said to be the first in the patent documents U.S. Pat. No. 4,043,331, U.S. Pat. No. 4,044,404, U.S. Pat. In the United States in the early 1990s, it was studied as one of the military studies for manufacturing gas filters for biological weapons, and various other reports on electrospinning technology were made. For example, in US Pat. No. 6,110,590, US Pat. No. 6,308,509, and US Pat. No. 6,382,526, various kinds of nanofibers and electrospinning methods are introduced as a method for producing them. In addition, Journal of Polymer Science: Partb: Polymer Physics, Vol. 37, 3488-3493 (1999), a styrene-butadiene-styrene copolymer has been studied as a material suitable for producing nanofibers by electrospinning.
However, there is only an application example based on the concept of a functional non-woven member such as a filter, and US Patent No. US2002 / 0192468 and US Patent No. US2002 / 0100725 disclose a technique for forming fine fibers on a paper material or filter paper. However, it is an application to a filter or a filter device, and it is not considered that the electrospinning technology is applied to the pulp and paper industry.

Accordingly, it is an object of the present invention to provide a laminate and a recording material having high surface smoothness and a method for producing a laminate and a recording material using an electrospinning method based on a completely new concept.
As a result of intensive studies to solve the above problems, the present inventors,
(1) A laminate (recording material) in which a layer containing fine long fibers is laminated on the surface of a paper support has high surface smoothness, and (2) the laminate (recording material). As a manufacturing method of the above, while applying a voltage between an electrode in contact with a raw material solution of long fibers filled in a container having an orifice and an electrode plate arranged to face the orifice, the raw material solution is supplied from the orifice It was found that a method of forming a layer containing long fibers on the surface of the paper support disposed on the electrode plate was suitable, and the present invention was completed.
This laminate has not only good surface smoothness but also can improve non-uniformity in printing characteristics such as improved rigidity, lower density, and ink acceptability on the surface.
This laminate (recording material) not only has good surface uniformity and ink absorbency, but also can improve non-uniformity in printing characteristics such as improved rigidity, lower density, and ink acceptability on the surface.
That is, the present invention includes the following embodiments.
(1) A laminate comprising a paper support mainly composed of cellulose fibers and a layer containing fine long fibers laminated on at least one side of the paper support.
(2) The laminate according to (1), wherein the long fibers have a fiber diameter of 1 nm to 10 μm and a length of 1 mm or more.
(3) The laminate according to (1) or (2), wherein the long fibers form a network structure.
(4) The laminate according to any one of (1) to (3), which is for printing, and the long fibers include at least one kind of ink repellent polymer.
(5) The long fiber is a linear polymer having a functional group capable of forming a hydrogen bond, and the functional group is chemically bonded to a compound having a molecular weight of 40 to 5000 (1) to (4) The laminated body in any one.
(6) A step of injecting the raw material solution from the orifice while applying a voltage between the electrode in contact with the raw material solution of the long fiber filled in the container provided with the orifice and the electrode plate arranged to face the orifice. And a step of forming a layer containing long fibers on the surface of the paper support disposed on the electrode plate by the sprayed raw material solution.
(7) A recording material comprising a paper support mainly composed of cellulose fibers and a layer containing fine long fibers laminated on at least one side of the paper support.
(8) The recording material according to (7), wherein the long fibers have a fiber diameter of 1 nm to 10 μm and a fiber length of 1 mm or more.
(9) The recording material according to (7) or (8), wherein the long fibers form a network structure.
(10) The recording material according to any one of (7) to (9), wherein the recording material is for printing, and the long fibers include at least one kind of ink repellent polymer.
(11) The recording material according to any one of (7) to (10), further including a coating layer laminated on the layer containing the long fibers.
(12) The long fiber is a linear polymer having a functional group capable of forming a hydrogen bond, and the functional group is chemically bonded to a compound having a molecular weight of 40 to 5000 (7) to (11) The recording material according to any one of the above.
(13) An ink jet recording paper comprising the recording material according to any one of (7) to (12).
(14) Injecting the raw material solution from the orifice while applying a voltage between the electrode in contact with the raw material solution of the long fiber filled in the container provided with the orifice and the electrode plate arranged to face the orifice And a method for producing a recording material, wherein a layer containing long fibers is formed on the surface of a paper support disposed on the electrode plate by the injected raw material solution.

1A to 1C are schematic diagrams illustrating an example of a network structure of long fibers.
2A and 2B are schematic views of an electrospinning apparatus preferably used in the present invention.

The present invention is described in detail below.
In the laminate (recording material, ink jet recording paper) of the present invention, a layer containing fine long fibers (hereinafter referred to as a long fiber layer) is laminated on one side or both sides of a paper support mainly composed of cellulose fibers. Is.
By laminating a long fiber layer containing such long fibers on the paper support surface, pores formed on the paper support surface by the voids are bridged by the long fibers, and the surface of the paper support is smooth. Improved. Further, even when ink is received on the pores when printing such as inkjet recording, the ink is received by the long fibers on the pores, so that the ink absorbability is improved and the inkjet recording is performed. The printing characteristics such as are improved.
In addition, unlike the case where a conventional coating liquid is applied, a layer is formed by cross-linking so that the inside of the void is not blocked, so that the liquid absorbability (liquid absorbability) of water or ink is good. Moreover, it is lightweight and has good air permeability.
In addition, since the paper support has inherently non-uniform gaps, the surface of the paper support varies in liquid absorbency such as hygroscopicity and ink absorbability depending on the site. However, in the present invention, the liquid absorbability can be made uniform by selecting the type and physical properties of the long fiber material. For example, when printing, a hydrophobic material is used when water-based ink is used, and a hydrophilic material is used when oil-based ink is used. Thus, excessive ink absorption can be suppressed. Moreover, you may provide a coating layer on this layer.
In addition, in an ink jet recording paper in which a coating layer is further provided on such a long fiber layer, since the surface uniformity of the long fiber layer is high and the liquid absorbency is uniform, it is formed thereon. The surface and film thickness of the ink receiving layer are also uniform. Therefore, there is no blurring, dot reproducibility is good, and recording properties such as running properties are excellent.
Further, the long fiber layer improves the rigidity of the paper support. For example, by selecting a material having rigidity as the material of the long fiber layer, the rigidity of the paper support is remarkably improved regardless of the density and structure inside the paper support.
In the present invention, the cellulose fiber contained in the paper support may be any paper as long as it is paper made using various pulps. As for the types of pulp, chemical pulp fibers obtained by digesting coniferous and hardwood craft methods, sulfite methods, soda methods, polysulfide methods, etc., mechanical pulp fibers that have been pulped by mechanical force such as refiners and grinders, and after chemical pretreatment Examples thereof include semi-chemical pulp fibers pulped by mechanical force, waste paper pulp fibers, ECF pulp fibers, TCF pulp fibers and the like, which can be used in an unbleached or bleached state, respectively. Non-wood fibers produced from herbs include, for example, fibers obtained by pulping cotton, manila hemp, flax, straw, bamboo, pagas, kenaf and the like in the same manner as wood pulp.
In the present invention, the “paper support mainly composed of cellulose fibers” is a paper support basically composed of cellulose fibers. In addition to these cellulose fibers, an acrylonitrile resin is used as long as its properties are not impaired. , Inorganic fibers such as polyamide resin, glass fiber, carbon fiber, alumina fiber, silicon carbide fiber, aramid fiber, polyarylate fiber, organic fiber such as high strength polyolefin fiber (for example, high strength fiber called high polymerization degree polyethylene fiber), Synthetic resin fibers such as polyester fibers, polyamide fibers, polyacrylonitrile fibers, polyolefin fibers, and polyvinylidene fibers may be included. Cellulose fibers are preferably contained in an amount of 50% by mass or more based on the total solid content constituting the paper support. A paper support made of a two-dimensional sheet using these fibers as a one-dimensional material is paper or paperboard obtained by wet papermaking, and the basis weight thereof is not limited. Moreover, what is generally marketed can be used. Further, chemicals such as a sizing agent, a paper strength agent and a yield improver, and fillers such as calcium carbonate, talc, clay and silica can be internally and / or externally added to these pulps. If necessary, a support obtained by melting and laminating a thermoplastic resin such as polyethylene resin on a paper support can also be used.
The “fine long fiber” in the present invention has a fiber diameter smaller than the fiber diameter of the cellulose fiber constituting the paper support, and is formed on the paper support surface by voids formed in the paper support. The fiber has a fiber length longer than the diameter of the opening (pore). When the fiber diameter of the long fiber is smaller than the fiber diameter of the cellulose fiber of the paper support, a laminate, recording material, or ink jet recording paper with high surface smoothness is obtained.
Long fibers may have various cross-sectional shapes in the radial direction, such as circular, elliptical, flat, and star-shaped, but a high aspect ratio (paper support) is required to obtain smoothness with a small layer thickness. Those having a flat cross section having a horizontal diameter / vertical diameter relative to the body surface are preferred. The more complicated the shape of the long fiber, the larger the specific surface area of the long fiber. The larger the specific surface area of the long fibers, the larger the amount of ink absorbed by the long fiber layer (ink receiving amount), which is preferable depending on the application. In the present invention, the specific surface area of the long fiber layer is 10 to 1000 m. ² / G, preferably 100 to 500 m ² / G is more preferable.
Further, the fiber diameter of the long fiber, that is, the fiber diameter approximated by a circle including the entire outer periphery of the cross section of the long fiber is not particularly limited as long as it is smaller than the fiber diameter of the cellulose fiber of the paper support, but preferably 1 nm to 10 μm. More preferably, the thickness is 10 nm to 1 μm. The fiber diameter of the long fibers is 1/2 or less, preferably 1/5 or less, more preferably 1/10 or less, of the fiber system of the cellulose fiber of the paper support. When the fiber diameter of the long fibers is within this range, a laminate and a recording material having high surface smoothness, uniform liquid absorbency, and good printability can be obtained. Further, if the fiber diameter is 200 nm or less, preferably 100 nm or less, the fiber diameter is smaller than the wavelength of light, so that almost transparent long fibers can be obtained. When the fiber system of long fibers exceeds 1/2 of the fiber system of cellulose fibers, the effect of improving the surface smoothness cannot be expected. When the surface of the paper support is covered with a layer containing such transparent long fibers, a laminate (recording material) is obtained without impairing the paper's original color, depth, touch, and other sensibility characteristics of the paper. It is possible to print on a flat surface without damaging the originally required appearance and texture of fancy paper, etc., and characteristics that cannot be imagined by conventional techniques can be obtained.
Further, the fiber length of the long fiber is not particularly limited as long as it is longer than the diameter of the pores of the paper support, but if it has a length of 1 mm or more, almost all fine particles present on the paper support surface are present. This is preferable because it can be bridged to the hole. The fiber length referred to here is the length when a certain focused fiber is traced in a one-stroke manner. In the present invention, as long as it has a length of 1 mm or more, the cellulose fibers can be bridged and covered to form a uniform long fiber layer. Moreover, since the aggregate | assembly of the folded long fiber is formed, so that the length of a long fiber is long, the surface smoothness improvement effect by a long fiber layer becomes high.
In addition, the actual long fiber layer often contains a plurality of long fibers of various fiber diameters and fiber lengths, but if the conditions at the time of production are selected, the contained long fibers can be made closer to a uniform one. I can do it.
The thickness of the long fiber layer is 0.01 g / m as the basis weight. ² ~ 30g / m ² It is preferable to make it thickness. More preferably 0.1 g / m ² -10g / m ² It is. More preferably 0.5 g / m ² ~ 3g / m ² It is. By setting the thickness of the long fiber layer within this range, pores and irregularities on the surface of the paper support can be eliminated, and surface smoothness can be improved. Also, the rigidity is improved. Basis weight is 0.01g / m ² If it is below, the number of pores of the paper support by the long fibers is insufficient, and the effect of improving the surface smoothness cannot be obtained. 30g / m ² If it exceeds 1, the effect of improving the surface smoothness becomes small, which is not economical, and the pores of the long fiber layer become very dense and the ink absorbability may be extremely lowered, which is not preferable.
In addition, the long fiber layer has sufficient surface uniformity and ink absorbency with a thickness of about 0.1 to 10 μm when a new coating layer is not provided thereon. However, if it is intended to obtain sufficient ink absorbency with only the long fiber layer, a very long specific surface area is obtained when thinner fiber having a fiber diameter of 100 nm or less is used and the thickness of the long fiber layer is about 20 to 60 μm. It becomes the long fiber layer which has. By providing such a long fiber layer, surface uniformity and ink absorbability are further improved, and an ink jet recording paper having very high recording properties can be obtained.
In the long fiber layer, the long fibers may exist in a state where they do not overlap at all (single fibers), but it is preferable to form a network structure. Since the long fibers form a network structure, the surface smoothness is further improved. Further, the mechanical properties of the paper support surface such as tensile strength, tear strength, and burst strength are improved.
Examples of the network structure include structures as shown in FIGS.
The network structure shown in FIG. 1A is a lattice structure in which one or two or more linear long fibers are folded through a plurality of intersections. In this case, since it is comprised with the thin fiber diameter, it is easy to fill the unevenness | corrugation of the surface of paper, and higher smoothness is obtained.
The network structure shown in FIG. 1B is a dendritic structure as seen on the surface of a masked melon, in which spirally swirling fibers or fibers having a partially flattened or completely flat cross section are entangled. The long fibers are branched into a large number to form a complicated network structure, and are substantially constituted by one continuous long fiber. In the case of such a structure, compared with the case of a single fiber or the network structure of FIG.
The network structure shown in FIG. 1C is a structure in which a plurality of beads are formed on the long fibers of the network structure shown in FIG. 1A. In the case of such a structure, the pulling resistance is large as in FIG. 1B. Therefore, a dramatic improvement in tensile strength can be expected as compared with a single fiber alone.
Actually, the fiber layers of these structures are overlapped in the thickness direction to form a layer. For this reason, in the present invention, it is preferable that the long fiber layer includes one type of such a network structure or a combination of a plurality of network structures.
As a material constituting the long fiber (long fiber material), a polymer that can be made into a solution or an emulsion by adding water and / or an organic solvent, a polymer that melts in a heated state and shows a liquid state, The polymer is not particularly limited as long as it is a polymer that exhibits a liquid state at room temperature, and can be used from thousands of oligomers to millions of ultrapolymers as long as it has a molecular weight. However, the form and properties of the long fiber that can be formed vary depending on the molecular weight, and thus it is necessary to select them as appropriate. For example, generally known materials can be used as a water-soluble polymer for paper coating, a solvent-soluble organic resin, and a nonwoven fabric material. Since these resins become fibrous at the final stage of electrospinning, they need to be a polymer that forms a film at the temperature at which electrospinning is performed. These long fiber materials are mainly used in the form of an aqueous solution or water emulsion in the production of the laminate (recording material) of the present invention, but alcohol, toluene, methyl ethyl ketone (MEK), xylene, ethyl acetate, etc. It may be used in the form of an organic solvent solution or an organic solvent emulsion dissolved in the organic solvent.
As a polymer that can be made into a solution by adding water and / or an organic solvent, natural or synthetic water-soluble polymers having hydrophilic groups such as ether groups, epoxy groups, carboxy groups, hydroxyl groups, sulfonic acid groups, A water dispersion type emulsion resin or the like is preferably used.
Examples of water-soluble polymers include starches such as oxidized starch and dextrin; polyvinyl alcohol and derivatives thereof; carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, pulp Natural or synthetic cellulose such as cellulose itself in which fibers are dissolved; gelatin, casein, starch; polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, polyhydroxyethyl acrylate, polyacryloylmorpholine, water-soluble polyvinyl acetal, poly-N-vinylacetamide And poly-N-vinylformamide. Among these, polyvinyl alcohol and derivatives thereof, and starches are preferable because they are inexpensive and can provide long fibers having properties suitable for various purposes.
Among water-soluble polymers, linear polymers such as polyvinyl alcohol are preferable. In the case of polyvinyl alcohol, it is suitable for electrospinning alone, but in many cases it cannot be electrospun due to the electrospinning conditions or the physical properties of the solution. In particular, polyvinyl alcohol having a saponification degree of 80% or more is very often sprayed as fine droplets without being able to follow rapid centrifugation when it is drawn out from an orifice and rapidly stretched into a thin filament. This is because polyvinyl alcohol, which has a high degree of saponification, has a strong hydrogen bonding force in the molecule and is in the form of a mali in the solution. It is considered that the extensional viscosity is greatly reduced and torn into droplets. In particular, when the solution supply capacity is large (10 μL or more) and the concentration of the water-soluble polymer is 5% or more, droplets tend to be formed.
Therefore, the present inventors added polyvinyl alcohol by adding a compound that chemically bonds to a functional group capable of forming a hydrogen bond such as a hydroxyl group, a carboxylic acid, and an amino group in order to weaken the hydrogen bond due to the hydroxyl group of polyvinyl alcohol. It has been found that the electrospinning suitability of an aqueous solution is greatly improved. In particular, the electrospinning can be stably performed when the orifice has a relatively large diameter of 0.1 mm to 5 mm, a voltage of 10 kV to 100 kV, and a flow rate of 10 μL / sec to 10 mL / sec. Here, “chemically bonded” refers to a state of bonding by a factor other than the dispersion force such as a hydrogen bond, a covalent bond, or an ionic bond. It was confirmed that not only polyvinyl alcohol but also other water-soluble linear polymers such as starch, carboxymethyl cellulose and polyacrylamide showed a great effect.
As the compound that chemically bonds to a functional group capable of forming a hydrogen bond, a silane coupling agent, an alkoxide silane, an epoxy compound, a cationic resin, glyoxal, an organic compound having a carboxylic acid, and the like are preferable. The molecular weight of the compound that reacts with a hydroxyl group is preferably 30 to 10,000, more preferably 40 to 3,000, and still more preferably 50 to 1,000. When a compound having a large molecular weight exceeding 10,000 is bonded to a functional group capable of forming a hydrogen bond in a linear polymer, the linearity of the linear polymer is lost (approaching a branched spherical polymer) and an extensional viscosity. Decreases rapidly, and the electrospinning suitability is deteriorated. A molecular weight of less than 40 is not preferable because many of them easily evaporate and are unstable in a solution.
Water-dispersed emulsion resins include synthetic polymers and latexes that contain acidic components such as acrylic acid esters, methacrylic acid esters, styrene, ethylene, butadiene, carboxylic acid, and maleic acid. For example, conjugated diene polymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic copolymer, vinyl copolymer latex such as styrene-vinyl acetate copolymer, polyurethane, etc. Latex, polyester latex and the like.
In the case of an emulsion (or latex or dispersion), the dispersed particle size is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm or less, and further preferably 10 nm to 100 nm. When the dispersed particle diameter exceeds 500 nm, the resulting long fiber may have a fiber diameter of 10 μm or more, or may not be in an electrospinning state and may be sprayed in the form of droplets, which is not preferable. An emulsion of less than 1 nm is not preferable because the emulsion becomes unstable (aggregation or viscosity change) during electrospinning. In particular, a particle size of 10 nm to 100 nm is preferable because the interaction between particles becomes strong, so that electrospinning is easy and the fiber system of long fibers can be easily controlled by electrospinning production conditions.
In addition, hydrophobic resins that are soluble in organic solvents such as alcohol and toluene, for example, polymethacrylic acid esters such as ethyl cellulose, polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, and polyisopropyl methacrylate, or polymethacrylate Resins comprising acid derivatives, polystyrene resins (PS), acrylonitrile / styrene copolymer resins (AS), acrylonitrile / butadiene / styrene copolymer resins (ABS), polyurethane resins, and polyvinyl acetate resins can also be used.
Among these, the use of a highly crystalline polymer such as polystyrene or liquid crystal polymer increases the rigidity, and the use of a highly rigid material makes it possible to obtain a laminate having a high rigidity even if the long fiber layer is thin and a small amount. Therefore, it is preferable.
In addition, it is preferable that the material constituting the long fiber contains a cationic resin because the water resistance of the printed image is improved.
The following can be illustrated as a cationic resin.
1) Polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof,
2) Acrylic resin having secondary amine group, tertiary amine group, quaternary ammonium group,
3) polyvinylamine, polyvinylamidines,
4) Dicyan cationic resin represented by dicyandiamide-formalin polycondensate,
5) Polyamine cationic resin represented by dicyandiamide-diethylenetriamine polycondensate,
6) Epichlorohydrin-dimethylamine addition polymer,
7) Dimethyl diallylammonium chloride-SO ₂ Copolymer,
8) Diallylamine salt-SO ₂ Copolymer,
9) Dimethyl diallylammonium chloride polymer,
10) Polymer of allylamine salt,
11) Dialkylaminoethyl (meth) acrylate quaternary salt polymer,
12) Cationic compounds such as acrylamide-diallylamine salt copolymer.
Furthermore, in order to improve the adhesion between the paper support and the long fiber layer, an acrylate polymer, an epoxy compound, a urethane compound, or the like used for an adhesive or an adhesive may be used.
Further, the moisture (or organic solvent) of the paper support is 8% to 70%, more preferably 15% to 60%, and even more preferably 20% to 50%, by laminating long fibers on the paper support. The characteristics are greatly improved. The smaller the length of the long fiber, the greater the effect of improving the adhesion when the moisture is contained in the above range. The reason why the adhesion is improved is considered to be that the area of the paper support surface in contact with excess moisture increases because the diameter of the long fibers is very small. In addition, when the long fibers are hydrophilic, the water solubility or plasticization increases dramatically as the diameter of the long fibers decreases, so that some of the long fibers laminated on the paper support dissolve or plasticize. This is presumably because it adheres strongly to the paper support.
As a method for improving the adhesion, it is also effective to control the evaporation amount of the long fiber solution and laminate it on the paper support with the solvent remaining, but the fiber diameter and form of the long fiber or the apparatus Since the above restrictions (distance from the orifice to the counter electrode, the diameter of the orifice, etc.) and the physical properties of the solution (surface tension, viscosity, concentration, conductivity, etc.) are limited, the method of adjusting the moisture content of the paper support Is preferred.
Moreover, adhesiveness can also be improved by heat-treating or pressing the obtained laminated body. Moreover, adhesiveness and the intensity | strength of the long fiber layer itself can be improved also by apply | coating a steam process or a solvent to the obtained laminated body, and drying. In the case of applying a solvent (including water), an adhesive, a first adhering agent, a cross-linking agent, or the like may be included so as not to impair the network structure of the long fiber layer.
As the polymer that melts in a heated state and shows a liquid state, a polyolefin resin such as polyethylene or polypropylene, or a plastic material such as polystyrene, polyester, or polyamide can be used. Furthermore, as a polymer that shows a liquid state at room temperature, an electron beam curable unsaturated organic compound such as a silicone resin, an electron beam or an ultraviolet curing oligomer or a prepolymer can be used.
The electron beam curable unsaturated organic compound may be a monofunctional monomer, a polyfunctional monomer or an oligomer as long as it can form a highly crosslinked resin layer. These may be used alone or in combination of two kinds. A mixture of the above may be used. For example, oligomers include (1) epoxy acrylates such as bisphenol A type, bisphenol S type, bisphenol F type, epoxidized oil type, phenol novolac type, alicyclic type, (2) urethane acrylate (3) unsaturated polyester ( 4) Polyester acrylate (5) Polyether acrylate (6) Vinyl / acrylic oligomer (7) Polyene / thiol (8) Silicon acrylate (9) Polybutadiene acrylate (10) Polystyryl ethyl methacrylate In addition, polydimethylsiloxane is used as the silicone resin.
These long fiber materials may be used alone or in combination of two or more according to the purpose. By mixing and using two or more types of long fiber materials, the hydrophilicity and hydrophobicity of the obtained long fibers can be adjusted by adjusting the compatibility and the difference in solubility in the solvent (water or organic solvent) used during production. Property and morphology (fiber diameter, fiber length, cross-sectional shape, fiber surface shape, etc. of long fibers) can be adjusted.
When the long fiber contains cellulose as the long fiber material, it is preferable because the compatibility with the paper support is good and a transparent layer can be formed, so that the texture of the paper support is not impaired. Furthermore, there are advantages such as easy recycling.
Moreover, when the laminated body of this invention is for printing, it is preferable that a long fiber contains an ink repellent polymer. The ink repellent polymer is, for example, a hydrophilic polymer when the ink is hydrophobic, and a hydrophobic polymer when the ink is hydrophilic. When the ink-repellent polymer is contained, the long fiber layer functions as a barrier when printing such as ink jet recording, and the ink is prevented from being excessively absorbed in a specific portion, for example, a void portion. be able to. That is, the barrier property against the ink of the long fiber layer is improved, and the printing characteristics are improved. In addition, when an ink receptive coating layer is further provided on the long fiber layer, the barrier property against the coating liquid for forming the ink receptive coating layer is also increased. Can be made more uniform, and the printing characteristics are improved.
Examples of the hydrophilic polymer include the water-soluble polymers described above. Moreover, as a hydrophobic polymer, the hydrophobic resin mentioned above is mentioned, for example. These can be blended alone or as a mixture.
In addition to the fiber material as described above, the long fiber is within a range not impairing the effects of the present invention. In order to change the rate, the solid content concentration which is the ratio of the long fiber material and the solvent and the molecular weight of the long fiber are adjusted, organic salts such as NaCl, inorganic salts such as polyphosphates, sodium salts and ammonium salts of various carboxylic acids Surfactants such as salts, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, wetting agents such as polycarboxylic acids, sulfosuccinic acids, polyethylene glycols, antifoaming agents, and more In order to adjust the conductivity, an additive such as styrene sulfonate, quaternary cation or amine compound may be included.
Linear polymers such as polyethylene glycol, polyglutamic acid, and high molecular weight proteins such as DNA are preferred because the electrospinning phenomenon is stabilized. In particular, a linear polymer that binds weakly in a molecule and takes a helical structure in a solution is preferable.
Such a linear polymer is added in an amount of 1 to 30%, preferably 3 to 20%, more preferably 5 to 10% with respect to the long fiber material.
In the laminate (recording material) of the present invention, the long fiber layer as described above is formed on one or both sides of the paper support, and two or more paper supports on which these long fiber layers are formed. Further, a laminate (recording material) obtained by laminating a long fiber layer on a paper support and further laminating the paper support is also included.
Furthermore, in the laminate (recording material) of the present invention, the long fiber layer may be a multilayer. It may have a multilayer structure in which a plurality of long fiber layers having different physical properties are stacked using long fibers having different physical properties such as fiber diameter and resin contained therein. For example, after a first long fiber layer including a network structure composed of long fibers having a fiber diameter of 100 nm is formed on an inclined structure in which the fiber diameter is gradually narrowed, for example, a paper support, the length of the fiber diameter is 50 nm. A laminate (recording) in which a second long fiber layer including a network structure composed of fibers and a third long fiber layer (outermost layer) including a network structure composed of long fibers having a fiber diameter of 10 nm are stacked in this order. The material) not only has a dense surface with extremely high surface smoothness due to the outermost layer, but also the first and second long fiber layers are easy to absorb ink and the like, and are excellent in printing characteristics.
Further, for example, on a paper support, a laminate in which a first long fiber layer containing hydrophobic long fibers and a second long fiber layer containing hydrophilic long fibers are laminated in this order, When printing with oil-based ink, the barrier effect of the second long fiber layer prevents variation in the amount of ink adhering to the surface of the laminate, and the ink adhering to the second long fiber layer is used as the first long fiber layer. Since the layer absorbs quickly, it has excellent printing properties.
Furthermore, in recording materials such as inkjet recording paper and printing paper of the present invention, a coating layer generally formed on inkjet recording paper and printing paper is further formed on the long fiber layer. preferable. In the case of ink jet recording paper, the surface uniformity of the long fiber layer is high and the liquid absorbency is uniform, so that the surface and film thickness of the ink receiving layer formed thereon are also uniform. Therefore, printing characteristics such as dot reproducibility are also excellent.
The configuration of the ink receiving layer is not particularly limited, but as the component contained in the ink receiving layer, generally the same components as those contained in the ink receiving layer can be used.
<Inorganic fine particles>
Examples of the inorganic fine particle material to be contained in the ink receiving layer include zeolite, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, and zinc carbonate. , Satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, silica, aluminum hydroxide, alumina, alumina hydrate, aluminosilicate, boehmite, pseudoboehmite, etc. In particular, silica, alumina, alumina hydrate and aluminosilicate are preferable, and silica is particularly preferable.
In addition, the inorganic fine particles have a specific surface area of 100 m by the BET method. ² / G or more is preferable. There is no upper limit to the specific surface area by the BET method, but 1000m ² / G or less is preferable. More preferably 200-400m ² / G.
The BET method referred to in the present invention is one of powder surface measurement methods by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm.
When the inorganic fine particles are aggregated particles (secondary particles) in which primary particles are aggregated, the average secondary particle diameter is not particularly limited, but is preferably 0.05 to 1.0 μm, more preferably 0.05 to 0.5 μm.
The amount of inorganic fine particles used in the ink receiving layer is preferably about 20 to 90% by mass, more preferably about 30 to 80% by mass, based on the solid content of the ink receiving layer. In this range, there is no possibility that the coating strength of the ink receiving layer is lowered, the ink absorbability and the ink drying property are excellent, and a higher image quality is obtained.
In the present invention, as described above, silica is preferably used as the inorganic fine particles. Silica is roughly classified into natural silica obtained by pulverizing natural silica such as quartz and synthetic silica produced by synthesis. Synthetic silica is broadly classified into vapor-phase silica and wet silica. In the present invention, the wet method fine silica described later is preferably used among the vapor phase method silica and the wet method silica because high ink absorbability, transparency, and gloss can be obtained.
Vapor phase silica is also called a dry method as opposed to a wet method, and is made by a flame hydrolysis method. Specifically, it is made by burning silicon tetrachloride with hydrogen and oxygen. In place of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or mixed with silicon tetrachloride. Vapor phase method silica is commercially available as a powder having a very low bulk density.
When the aqueous dispersion of vapor phase silica is dried, it becomes porous silica gel, and the pore volume of the gel by the BET method is generally 1.2 to 1.6 ml / g. This pore volume is convenient for absorbing ink. However, cracks tend to occur during drying, and it is not easy to produce an ink receiving layer free of cracks.
As the wet method silica, silica by a precipitation method and silica by a gel method are known.
For example, as disclosed in JP-A-55-116613, the precipitated silica is produced by adding a mineral acid stepwise to an alkali silicate aqueous solution and filtering the precipitated silica.
The gel method silica is obtained by mixing a mineral acid with an alkali silicate solution, gelling, washing, and pulverizing.
Precipitated silica and gel silica are formed by combining primary particles of silica to form secondary particles, and there are many voids between the primary particles and between the secondary particles. In addition to being large, the property of scattering light is small, so a high printing density can be obtained.
Further, as a wet process silica by a slightly special production method, for example, active silicic acid is condensed as described in US Pat. No. 2,574,902, JP-A No. 2001-354408, JP-A No. 2002-145609. There is fine silica (hereinafter, referred to as wet method fine silica) produced. Here, the active silicic acid refers to an aqueous silicic acid solution having a pH of 4 or less obtained by ion-exchange treatment of an aqueous alkali metal silicate solution with a hydrogen cation exchange resin, for example.
The wet method fine silica described in US Pat. No. 2,574,902 prepares an aqueous solution of active silicate by treating a diluted aqueous solution of sodium silicate with a cation exchange resin to remove sodium ions. Part of the solution is stabilized by adding alkali to polymerize to form a liquid in which silica seed particles are dispersed (seed liquid), and the remaining portion of the active silicic acid aqueous solution (feed liquid) is maintained while maintaining alkaline conditions. It is produced by gradually adding silica to polymerize silicic acid and growing colloidal silica particles.
This fine silica has a feature that it has a diameter of 3 nm to several hundreds nm, does not undergo secondary aggregation, and has a very narrow particle size distribution. Usually, a product of 7 nm to 100 nm, which is called colloidal silica, is commercially available as an aqueous dispersion, and when used for an ink receiving layer, a receiving layer having extremely high gloss and high transparency can be obtained.
On the other hand, the wet method fine silica described in JP-A No. 2001-354408 is “the specific surface area by the BET method is 300 m. ² / G-1000m ² / G with a colloidal dispersion of silica fine particles having a pore volume of 0.4 ml / g to 2.0 ml / g as a seed solution, and after adding alkali to the seed solution, A specific surface area according to the BET method is 100 m, characterized in that a silica fine particle is grown by adding a small amount of at least one feed liquid selected from an aqueous solution of active silicic acid and alkoxysilane. ² / G-400m ² / G, a method for producing a silica fine particle dispersion in which silica fine particles having an average secondary particle diameter of 20 nm to 300 nm and a pore volume of 0.5 ml / g to 2.0 ml / g are colloidally dispersed. ", Or" specific surface area by BET method is 300m ² / G-1000m ² / G and a liquid in which fine silica particles having a pore volume of 0.4 ml / g to 2.0 ml / g are colloidally dispersed is used as a seed liquid, and the seed liquid is selected from an active silicic acid aqueous solution and an alkoxysilane. A specific surface area according to the BET method is 100 m, characterized in that a mixture of at least one kind of feed liquid and alkali is added little by little or silica fine particles are grown by simultaneously adding the feed liquid and alkali little by little. ² / G-400m ² / G, a silica fine particle dispersion obtained by colloidal dispersion of silica fine particles having an average secondary particle diameter of 20 nm to 300 nm and a pore volume of 0.5 ml / g to 2.0 ml / g " Fine particles.
Further, the wet method fine silica described in JP-A No. 2002-145609 is “a suspension containing an aggregate composed of silica fine particles by heating an aqueous solution containing at least one selected from activated silicic acid and alkoxysilane. Next, at least one selected from an aqueous solution containing active silicic acid in the presence of alkali and alkoxysilane was added little by little to the suspension to grow silica fine particles in the suspension. Then, the silica fine particles obtained by the “method for producing a silica fine particle dispersion characterized by wet pulverizing the suspension”.
The wet method fine silica disclosed in Japanese Patent Application Laid-Open Nos. 2001-354408 and 2002-145609 is a silica having both the advantages of precipitation method silica and gel method silica and the advantages of colloidal silica. This silica is a secondary particle in which primary particles of silica (for example, the colloidal silica described above) are bonded, and it is easy to adjust the secondary particle diameter to be equal to or less than the wavelength of light. It is most preferably used in the present invention because an ink-receiving layer having excellent resistance can be easily produced. Hereinafter, these wet process fine silicas are referred to as secondary fine silicas.
Among these, in particular, the secondary fine silica obtained by the condensation method disclosed in JP-A-2001-354408 is directly related to the average secondary particle diameter (20 nm to 300 nm) and fineness, without depending on mechanical means. Secondary fine silica having a pore volume (0.5 ml / g to 2.0 ml / g) can be produced, and the particle size distribution is narrow, so that the obtained ink receiving layer has good transparency and gloss, which is preferable in the present invention. Can be used.
In the condensation method disclosed in Japanese Patent Application Laid-Open No. 2001-354408, as the active silicic acid, for example, an aqueous silicic acid solution having a pH of 4 or less obtained by ion exchange treatment of an alkali metal silicate aqueous solution with a hydrogen cation exchange resin. (Activated silicic acid aqueous solution) is preferably used.
The active silicic acid aqueous solution is SiO ₂ The concentration is preferably 1 to 6% by mass, more preferably 2 to 5% by mass, and preferably pH 2 to 4.
The alkali metal silicate may be a commercially available industrial product, more preferably SiO. ₂ / M ₂ It is preferable to use sodium water glass having a molar ratio of O (where M represents an alkali metal atom) of about 2 to 4.
As a method for condensing active silicic acid, the above active silicic acid aqueous solution is dropped into hot water, or the active silicic acid aqueous solution is heated to produce seed particles, before the dispersion is precipitated or gelled. The alkali is added to stabilize the seed particles, and then the active silicic acid aqueous solution is added to the SiO particles contained in the seed particles while maintaining the stable state. ₂ SiO per mole ₂ Preferably, the seed particles are added at a rate of 0.001 to 0.2 mol / min to grow primary particles of the seed particles.
Moreover, the wet method fine silica has a specific surface area of 100 to 400 m by the BET method. ² It is preferable that the pore volume is 0.5 to 2.0 ml / g. Fine silica in this range has a very good balance of cracks in the ink receiving layer, ink absorbency, and gloss.
<Cationic compound>
As the cationic compound used in the present invention, various publicly known cationic compounds in the field of inkjet recording sheets such as a cationic polymer, a water-soluble aluminum compound, a water-soluble zirconium compound, and a water-soluble titanium compound are appropriately used. . In particular, from the viewpoint of water resistance, a cationic polymer, a water-soluble aluminum compound and a water-soluble zirconium compound are preferably used, and among these, a cationic polymer is preferably used.
These cationic compounds may be used alone or in combination of two or more.
As the cationic polymer, for example, a primary amine type cation having a primary amine salt such as monoallylamine salt, vinylamine salt, N-vinylacrylamidine salt, dicyandiamide / formalin polycondensate, dicyandiamide / polyethyleneamine polycondensate as a structural unit. Polymer, secondary amine type cationic polymer having a secondary amine salt such as diallylamine salt, ethyleneimine salt as a structural unit, tertiary amine type cationic polymer having a tertiary amine salt such as diallylmethylamine salt as a structural unit, diallyldimethyl Quaternary ammonia such as ammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride, dimethylamine / epichlorohydrin polycondensate Quaternary ammonium type cationic polymers having a ium salt as a constituent unit thereof.
Examples of the water-soluble aluminum compound include basic aluminum chloride, basic aluminum sulfate, and basic fatty acid aluminum.
Examples of the water-soluble zirconium compound include zirconyl chloride, basic zirconyl chloride, zirconyl nitrate, and fatty acid zirconyl.
Specific examples of fatty acids in basic fatty acid aluminum, fatty acid zirconyl and the like include, for example, formic acid, acetic acid, propionic acid, butanoic acid, glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutanoic acid, glycine, β-alanine 4-aminobutanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and the like, among which acetic acid is particularly preferable.
<Silica-cationic compound>
Further, the ink-receiving layer has a silica-cationic compound obtained by pulverizing silica-cationic compound aggregate particles obtained by mixing and aggregating amorphous silica and a cationic compound to an average particle size of 0.7 μm or less. Aggregate fine particles are preferably used.
By using the silica-cationic compound aggregate fine particles, the ink receiving layer can be made into a porous layer having good transparency, ink absorbability, ink color development, weather resistance and the like.
The silica-cationic compound aggregate fine particles are a silica colloid particle solution composed of secondary particles substantially formed by aggregation of primary particles. In the case of silica sol in which primary particles are monodispersed (for example: general commercially available colloidal silica), the porous layer obtained by applying to the base material becomes relatively dense, and it is easy to lose transparency. In order to provide ink absorbency, a high coating amount is inevitable. However, when the coating amount is high, the coating film tends to crack, and the coating process tends to be complicated. Of course, primary particles may be partially contained in the silica colloid particle solution.
In the present invention, when silica-cationic compound aggregate particles are blended in the ink receiving layer together with a binder (particularly polyvinyl alcohol is preferred), the transparency of the printed part can be obtained, and a gloss equivalent to that of a photograph can be obtained. is there. Further, since the entire ink receiving layer is transparent, it can be used as an OHP sheet or the like.
Silica-cationic compound aggregate fine particles are obtained by pulverizing silica-cationic compound aggregate particles obtained by mixing and aggregating amorphous silica and a cationic compound to an average particle size of 0.7 μm or less. Is.
Silica-cationic compound aggregated fine particles refer to a state in which fine particles having an average particle size of 0.7 μm or less and a maximum particle size of about 1000 nm or less are uniformly dispersed.
Silica-cationic compound aggregated fine particles can be obtained by applying a strong force by mechanical means to a mixture of amorphous silica such as general commercially available synthetic amorphous silica (several microns) and a cationic compound. . That is, it can be obtained by a breaking down method (a method of subdividing a bulk material). The silica-cationic compound aggregate fine particles may be a slurry. Examples of the mechanical means include ultrasonic, high-speed rotary mill, roller mill, container drive medium mill, medium agitation mill, jet mill, cracker, sand grinder and the like.
The average particle diameter referred to in the present invention is a particle diameter observed with an electron microscope (SEM and TEM) (taken an electron micrograph of 10,000 to 400,000 times, and measured and averaged the diameter of the particles in a 5 cm square. (It is described in "Particle Handbook", Asakura Shoten, p52, 1991, etc.).
The average particle diameter of the silica-cationic compound aggregate fine particles (substantially secondary particles) is 0.7 μm or less, preferably 10 to 300 nm, more preferably 20 to 200 nm. When silica-cationic compound aggregate fine particles having an average particle diameter exceeding 0.7 μm are used, the transparency is remarkably lost, the print density is remarkably lowered, and an ink jet recording sheet having high gloss after printing cannot be obtained. There is a fear. On the other hand, if silica colloidal particles having an extremely small average particle diameter are used, there is a possibility that a sufficient ink absorption rate cannot be obtained.
The amorphous silica constituting the silica-cationic compound aggregate fine particles preferably has an average primary particle diameter of 3 nm to 40 nm. If it is less than 3 nm, the gap between the primary particles becomes extremely small, and the ability to absorb the solvent and ink in the ink is remarkably lowered. On the other hand, if it exceeds 40 nm, the aggregated secondary particles become large, and the transparency of the ink receiving layer may be lowered.
As the cationic compound used in the silica-cationic compound aggregate fine particles, various known cationic compounds generally used in ink jet paper can be used, for example, monoallylamine salt, vinylamine salt, N-vinylacrylamidine salt. A primary amine type cationic polymer having a primary amine salt such as dicyandiamide / formalin polycondensate or dicyandiamide / polyethyleneamine polycondensate as a structural unit, or a secondary amine salt such as diallylamine salt or ethyleneimine salt as a structural unit Secondary amine type cationic polymer, tertiary amine type cationic polymer having a tertiary amine salt such as diallylmethylamine salt as a structural unit, diallyldimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride Aluminum such as quaternary ammonium type cationic polymer, basic polyaluminum chloride, basic polyfatty acid aluminum, etc. having quaternary ammonium salts such as lide, (meth) acrylamidopropyltrimethylammonium chloride, dimethylamine / epichlorohydrin polycondensate Examples thereof include zirconyl compounds such as compounds, zirconyl chloride, basic zirconyl chloride and fatty acid zirconyl. In addition, as addition amount of a cationic compound, it is adjusted in the range of 1-30 mass parts with respect to 100 mass parts of amorphous silica, More preferably, it is 5-20 mass parts.
In the present invention, when silica-cationic compound aggregate fine particles are used as the inorganic fine particles, PVA is most effective as a binder from the viewpoint of dispersion suitability and paint stability. In particular, in order to obtain dispersibility and ink absorbability, PVA having a polymerization degree of 2000 or more is preferably used. The degree of polymerization of PVA is more preferably 2000 to 5000. In order to obtain water resistance, PVA having a saponification degree of 95% or more is effective.
The solid mass ratio of the silica-cationic compound aggregate fine particles and the binder is not particularly limited, but is adjusted to a range of 10/1 to 10/10, preferably 10/2 to 10/6. If the amount of the binder added is large, the pores between the particles may be small, and a sufficient ink absorption rate may not be obtained, while if the binder is small, the coating layer will crack and become unusable. Sometimes it becomes.
<Binder>
Examples of binders incorporated in the ink receiving layer include starch derivatives such as oxidized starch and etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, proteins such as casein, gelatin and soybean protein, and complete (partial) saponification. Polyvinyl alcohol, silicon-modified polyvinyl alcohol, polyvinyl alcohols such as acetoacetyl group-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, salts of styrene-maleic anhydride copolymer, styrene-butadiene latex, acrylic latex, polyester polyurethane latex , Water-based adhesives such as vinyl acetate latex, or polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer Polyvinyl butyral, and an organic solvent-soluble resins such as alkyd resin. These binders may be used alone or in combination.
Among these binders, polyvinyl alcohols are preferable because they have high transparency, high water resistance, are nonionic, can be mixed with various materials, and have a relatively low swelling property near room temperature. In addition, there is an advantage that the ink does not swell at the initial permeation of the ink and does not block the gap.
Among the polyvinyl alcohols, completely (partially) saponified polyvinyl alcohol, cation-modified polyvinyl alcohol or silicon-modified polyvinyl alcohol is particularly preferably used.
As the complete (partially) saponified polyvinyl alcohol, a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol having a saponification degree of 80% or more, particularly 95% or more is preferable. 000 is preferable, and 500 to 5,000 is more preferable.
The reason why a portion having a saponification degree of 80% or more or completely saponified polyvinyl alcohol is preferable is that it has excellent water resistance. The reason why the average degree of polymerization is preferably from 200 to 5,000 is that when a polymer having a degree of polymerization within this range is used, the viscosity is excellent in water resistance and easy to handle.
The cation-modified polyvinyl alcohol is preferably polyvinyl alcohol having a primary, secondary, or tertiary amino group or a quaternary ammonium base in the main chain or side chain of the polyvinyl alcohol.
The binder is used in an amount of preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the inorganic fine particles.
<Others>
It is more preferable to use a crosslinking agent in the aqueous solution contained in the above from the viewpoint of suppressing cracks.
Specific examples of the crosslinking agent include, for example, boron compounds such as boric acid, borax, and borate, glyoxal, melamine / formaldehyde, glutaraldehyde, methylol urea, polyisocyanate compound, epoxy compound, aziridine compound, carbodiimide compound, dihydrazide A compound, an aluminum compound, a zirconium compound, etc. are mentioned. Of these, boron compounds are preferable, and borax is particularly preferable.
By applying a mixed liquid of borax and polymer (A), the heat and humidity resistance of the image is particularly high and the cracking suppressing effect is high.
In addition, the ink receiving layer can contain known additives such as an antifoaming agent, a surfactant, and a crosslinking agent, if necessary.
The laminate of the present invention and recording materials such as inkjet recording paper and printing paper can be produced by the production method of the present invention described below.
≪Method for manufacturing laminate (recording material) ≫
The method for producing a laminate (recording material) according to the present invention is a method using electrospinning as described above, and an electrode that contacts a raw material solution of a long fiber filled in a container having an orifice, and is disposed opposite to the orifice. The raw material solution is sprayed from the orifice while applying a voltage between the electrode plate and the electrode plate, and a layer containing long fibers is formed on the surface of the paper support disposed on the electrode plate. To do.
In electrospinning, a droplet that has oozed out at the tip of an orifice is charged by an electric field generated by a voltage applied between the opposing electrode plates. When the surface tension of the liquid droplet is larger than the repulsive force due to the electric charge on the surface of the liquid droplet, liquid discharge does not occur, but discharge starts when the voltage is increased to a charge density that overcomes the liquid surface tension. As a result of the evaporation of the solvent from the ejected droplets and the surface area of the liquid being reduced, the charge density on the liquid surface is further increased, the ejection force is accelerated, and stable continuous ejection is obtained. The liquid to be discharged becomes a single continuous state in a state thinner than the diameter of the orifice. When the continuous state continues to a certain length, the state of the thin liquid becomes unstable and spreads in a flash manner, while the solvent evaporates and the thin long fibers land on the electrode in a mesh shape.
A first embodiment of the manufacturing method of the present invention will be described using the electrospinning apparatus shown in FIG.
As shown in FIG. 2A, the electrospinning apparatus 1 includes a container 3 having an orifice 2 and an electrode plate 4 that is disposed opposite to the orifice 2 at a predetermined distance, and the orifice 2 and the electrode plate. 4 are connected to grounds 5 and 6, respectively. In the present invention, the container 3 having the orifice 2 is not particularly limited as long as it can be applied to the raw material solution filled in the container and can push out the raw material solution from the orifice 2. For example, a syringe made of metal or glass, a pipette or the like can be used.
In addition, the container 3 and the electrode plate 4 can be arranged in any direction up and down and left and right as long as the orifice 2 and the electrode plate face each other.
The size and number of the orifices 2 are not particularly limited, and may be appropriately determined according to the fiber diameter of the long fibers to be obtained, the size of the paper support on which the long fibers are laminated, and the like.
The inner diameter of the orifice 2 is 10 μm to 10 mm, more preferably 100 μm to 1 mm. Small diameter orifices handle solutions with low viscosity and wide orifices are suitable for solutions with high viscosity. In addition, since electrospinning produces long fibers having a diameter smaller than these orifice diameters, troubles such as clogging of the orifices are hardly caused.
The distance between the orifice 2 and the electrode plate 4 is preferably set to several millimeters to several tens of centimeters. By changing this distance, the fiber diameter and fiber length of the long fibers, the form of the network structure, and the like can be changed.
For example, the longer the distance between the orifice 2 and the electrode plate 4, the smaller the fiber diameter of the obtained long fibers and the longer the fiber length. On the other hand, the shorter the distance, the larger the fiber diameter of the obtained long fiber and the smaller the fiber length. Of course, since there is a certain relationship between the surface tension, viscosity or conductivity of the raw material solution and the applied voltage, the fiber diameter and fiber length are not determined only by the distance between the electrodes. For example, when the distance between the orifice and the electrode is constant, generally, a long fiber length with a thin fiber diameter can be obtained by reducing the surface tension or decreasing the viscosity. Moreover, if the surface tension is constant, the higher the applied voltage, the smaller the fiber diameter and the longer the fiber length.
When the long fiber has a network structure, the longer the distance between the orifice 2 and the electrode plate 4, the closer the form of the obtained long fiber is to the above-described FIG. 1A, and the shorter the distance between the orifice 3 and the electrode plate 4. The shape of the obtained long fiber is closer to the above-described FIG. 1B. FIG. 1C is supposed to include an object that has landed on the electrode plate 4 before the distance between the orifice 2 and the electrode plate 4 is further shortened and the droplets are completely in a fiber state.
First, a raw material solution 7 is obtained by adding a solvent or heating to the above-described long fiber material and optional additives. The viscosity of the raw material solution 7 is preferably 1 cps to 10000 cps, and more preferably 10 cps to 1000 cps.
As the solvent, water is preferably used, but an organic solvent such as alcohol or toluene may be used. When cellulose is used as the long fiber material, it is preferably used as a copper-ammonia solution or a copper-ethylenediaminetetraacetic acid (EDTA) solution. It is also effective to heat the liquid as necessary.
The raw material solution 7 may be in the form of a solution in which the long fiber material and optional additives are completely dissolved and mixed thoroughly with the solvent, and the dissolved liquid particles are colloidal particles or coarser particles in the solvent. The emulsion may be in the form of an emulsion.
Next, the raw material solution 7 is filled in the container 3, the paper support 8 is disposed on the electrode plate 4 between the container 3 and the electrode plate 4, and a voltage is applied between the orifice 2 and the electrode plate 4. Then, the raw material solution 7 is pushed out from the orifice 2 and discharged.
The discharge amount of the raw material solution may be such that a droplet of the raw material solution 7 appears at the tip of the orifice 2. When the liquid droplets are charged and discharge starts, the liquid in the container 3 is automatically continuously supplied. Depending on the purpose, the discharge amount can be controlled by applying pressure to the container 3 to increase or decrease pressure. I can do it.
The voltage applied between the orifice 2 and the electrode plate 4 is preferably 1 kV to 500 kV, more preferably 2 kV to 200 kV, and even more preferably 5 kV to 100 kV. If the voltage is less than 1 kV, the charging of the droplets due to the electric field is insufficient, the ejection of long fibers does not occur, and if the voltage exceeds 500 kV, not only there is a risk of short circuit between the electrodes, Leakage or discharge phenomenon is likely to occur, and it becomes a large-scale device for insulation of the device.
The earth 5 may be connected to the orifice 2 when the orifice 2 is made of metal, for example, and connected to the earth 5 via a copper wire or the like in the raw material solution 7 filled in the container 3. May be.
When a voltage is applied between the orifice 2 and the electrode plate 4, as shown in FIG. 2B, an electrostatic field is formed between the orifice 2 and the electrode plate 4, the raw material solution 7 is charged, and the electrode plate 4 is charged. Move in the direction. As the polarity of charging, either positive or negative is selected according to the properties of the long fiber material. Further, not only direct current but also alternating current or pulsed electric energy may be used.
The current per orifice that flows during electrospinning is preferably 0.1 μA to 500 μA, more preferably 1 μA to 200 μA, and still more preferably 5 μA to 100 μA. This current value is the difference between the current value when no solution is supplied (leakage current) and the current value during electrospinning. If it is smaller than 0.1 μA, electrospinning becomes unstable, and the shape of the fiber is deformed, a lump called a bed is formed, or in a severe case, it is not preferable because it is formed into particles. In addition, when the current value exceeds 500 μA, the change in the electric field is small even if the voltage is changed, so that not only stable production becomes difficult, but also the possibility of discharge increases. In particular, when discharge occurs at a voltage of 5 kV or more at a current of 500 μA or more, it is not preferable because a hole is formed in the paper support or it burns when it is severe.
The charged raw material solution 7 has a higher surface charge density as the solvent evaporates when moving in the direction of the electrode plate 4. When the viscosity or surface tension of the raw material solution 7 competes with an electrostatic force and the electrostatic force wins, a bend 7a appears as if the raw material solution 7 is lashed. When the electrostatic force further increases, the state of the bending 7a further changes to a state 7b in which droplets are sprayed. In the raw material solution 7, the solvent is completely evaporated between the state 7 b in which the droplets are sprayed and the surface of the paper support 8 to form long fibers 7 c. The formed long fibers 7c are laminated on the surface of the paper support 8 to form a long fiber layer.
Although there is no restriction | limiting in particular about the surface tension of a raw material solution, Preferably it is 10-70 dynes, 20-60 dynes, 30-50 dynes.
The conductivity of the raw material solution is preferably 1 μS / m to 10 mS / m, more preferably 10 μS / m to 5 mS / m, and still more preferably 50 μS / m to 2 mS / m. When the electrical conductivity is less than 1 μS / m, electrospinning does not occur and the droplets are easily sprayed. Moreover, when it becomes larger than 10 mS / m, it is sprayed with one thick liquid, without appearing whipping bend 7a.
Generally, when the conductivity of the raw material solution is 100 μS / m, particularly 500 μS / m or more, the electrospinning phenomenon tends to become unstable. This is because if the conductivity of the liquid is large, the charge is not concentrated on the surface of the raw material solution that has exited from the orifice, but the charge is dispersed inside the raw material solution, so that the viscosity and surface tension are overcome and the electrospinning phenomenon does not occur. It is done. However, when the applied voltage is 5 kV or more, the current value is 5 μA, the surface tension of the solution is 20 to 60 dyne / m, the supply amount of the solution is 10 μl / sec or more, and the inner diameter of the orifice is 0.1 mm or more. Rather, it was found that the electrospinning phenomenon is more stable when the conductivity is higher.
Although FIG. 2A shows an example in which one container 3 is provided, the present invention is not limited to this. For example, a plurality of containers each having an electrode connected thereto are prepared, and each is filled with a raw material solution containing different long fiber materials. And a long fiber layer can be easily made into a multilayer by applying to each container in order.
When a continuous wide paper is used as a support and a long fiber layer is to be formed thereon, a long fiber layer is formed so as to cover the entire surface of the paper support by arranging a plurality of containers in the width direction. You can also
In FIG. 2A, the container 3 and the electrode plate 4 are disposed horizontally, but the electrode plate 4 may be disposed below the container 3. In this case, the raw material solution 7 is naturally discharged from the orifice 2 by gravity without being pushed out.
Further, in the present invention, as is usually done in paper production, these long fiber layers are formed on a paper support and then smoothed through the nips of the rolls or laminated on a heated smooth mirror surface. It is also possible to obtain a smooth surface by applying the long fiber layer side of (recording material) and drying it.
In addition, long fibers can be formed only at a specific desired location on the paper support to give specific physical properties only to specific portions.
In addition, in US Pat. No. 6,110,590, US Pat. No. 6,308,509, and US Pat. No. 6,382,526, various nanofibers and electrospinning methods as methods for producing the same are introduced. The methods described may be used.
Furthermore, in this invention, you may form a coating layer by apply | coating the coating liquid containing a pigment and resin further on the formed long fiber layer. In the case of ink jet recording paper, since the surface of the long fiber layer is uniform and the liquid absorbency is uniform, the thickness of the formed ink receiving layer can be easily made uniform. Therefore, an ink receiving layer having high surface uniformity and uniform ink absorbability can be obtained. Similarly, in the case of printing paper, printing with high dot reproducibility can be obtained.
For example, as a method for forming an ink receiving layer such as a coating method of a coating liquid, a method generally used for forming an ink receiving layer can be used. For example, an air knife coater, a bar coater, a die coater can be used. And a gravure coater, a micro gravure coater, a lip coater, a cap coater, a blade coater, and a cast coater. Moreover, it is good to carry out multilayer coating combining these.
In addition to the electrospinning method, there are a flash spinning method and a melt blown method known as a method for producing a bulky nonwoven fabric as a method for forming a long fiber layer by dry method.
The flash spinning method is a method in which a long fiber is obtained instantaneously by ejecting a resin whose solubility in a solvent changes depending on the pressure applied to the solution from a nozzle. However, only those having a specific resin composition can be applied, and only long fibers having a fiber diameter equal to or larger than that of cellulose fibers can be obtained. Therefore, the effect of fine long fibers as in the present invention cannot be expected.
In the melt blown method, molten olefin-based resin is injected from a nozzle at a high pressure, and a turbulent flow is created around the periphery of the resin to cause the injected fibers to land on a target substrate. However, it is not preferable because the distribution of the obtained fibers is controlled by an air flow and a uniform thin layer cannot be formed.
Example:
EXAMPLES The present invention will be specifically described below with reference to examples. However, the following examples do not limit the present invention. Moreover, unless otherwise indicated, the part in an Example shows a mass part and shows by solid content.

Syringe (plastic) with a capacity of 50 cc after removing 2% aqueous solution (conductivity 10 μS / m, surface tension 48 dyne / cm) of polyvinyl alcohol (Kuraray Co., Ltd. PVA117) by centrifugation (2000 rpm, 5 minutes) And a metal needle (inner diameter: 0.5 mm) with a flat cross-section at the tip was attached. A stainless steel plate was placed at a position 32 cm away from the tip of the needle, and a high-quality paper for electrophotography (64 g / m2 water content 12%) with water slightly sprayed thereon was placed thereon. . When the voltage is gradually increased while changing the voltage between 0 and 100 kV between the syringe needle and the stainless steel plate so that the syringe needle becomes positive, liquid discharge starts from the tip of the needle at 10 kV, and 12 kV. As a result, a fine fibrous lump (long fiber layer) was formed on the surface of the fine paper. The current value at this time was 5 to 10 μA, and the flow rate was 5 μL / sec.
When the formed long fiber layer was observed with an electron microscope (magnification: 100,000 times), a fiber layer as shown in FIG. 1A could be confirmed. The fiber diameter of each long fiber was about 400 nm, and the length following the continuous fiber was mostly at least 2 mm or more.
However, when the voltage was set to 20 kV and the flow rate was set to 50 μL / sec, droplets were formed, and a fine long fiber layer could not be formed.

Similar to Example 1 using an aqueous solution (conductivity 12 μS / m, surface tension 42 dyne / cm) obtained by adding 0.1 part by mass of polyethylene glycol (molecular weight 100,000) to 100 parts by mass of the aqueous polyvinyl alcohol solution described in Example 1. A fine long fiber layer was formed. The voltage at this time was 20 kV, the flow rate was 50 μ / sec, and the current value was 10 to 20 μA. When the formed long fiber layer was observed with an electron microscope, the fibers were about 600 nm, and most of the lengths following the continuous fibers were at least 2 mm.
When the concentration of the polyvinyl alcohol aqueous solution was 5%, the flow rate was 100 μ / sec, and the voltage was 50 kV, the fine long fiber layer could not be formed under the conditions of Example 2 resulting in droplets.

One part by mass of an epoxy-modified silane coupling agent (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) is added to 100 parts by mass of a 10% aqueous solution of polyvinyl alcohol (PVA117 manufactured by Kuraray Co., Ltd.), and further styrene butadiene latex (manufactured by Nippon Zeon, S1X2, Tg12 ° C., Syringe (plastic) with a capacity of 50 cc after removing foreign matter by centrifugation (2000 rpm, 5 minutes) with an aqueous liquid (conductivity 20 μS / m, surface tension 45 dyne / cm) to which 5 parts by mass of solid content (50%) has been added And a metal needle (inner diameter: 0.5 mm) with a flat cross-section at the tip was attached. Place a stainless steel plate at a position 32 cm away from the tip of the needle, and place a high quality paper for electrophotography (64 g / m ² water content 12%) with water slightly sprayed on it. It was. A high voltage power source was connected to the syringe needle so as to be positive, and a long fiber layer was formed between the syringe needle and the stainless steel plate under the conditions of a voltage of 70 kV and a flow rate of 200 μ / sec.
When the formed long fiber layer is observed with an electron microscope (magnification: 100,000 times), the fiber diameter of each long fiber is about 50 to 200 nm, and the length following the continuous fiber is at least 2 mm or more. Most of them.
By repeating these procedures, the following properties were evaluated by the following procedure for the laminate in which the coating amount was 0.5 g / m ² so as to cover the entire surface of the fine paper and the long fiber layer was laminated. did. The results are shown below.
(Surface smoothness)
Surface smoothness was measured with a Oken smoothness meter. The portion where the long fiber layer was formed was 200 seconds to 300 seconds, but the portion where the long fiber layer was not formed was 30 seconds, and the smoothness of the paper on which the long fiber layer was formed as in the present invention. Sex was much improved.
(Halftone dot reproducibility)
In order to examine the printability of the laminate, J. Org. TAPPI Paper Pulp Test Method No. When the printing quality was evaluated in accordance with 24 m “Testing method for paper gravure printing aptitude (printing bureau type)”, the laminate of the present invention was excellent in quality because it did not show blurring and thickening of dots. Those that were not formed had a problem in practical use because the dots were blurred and thickened.
(Ink drying)
Using an RI printing suitability evaluation machine (Meiji Seisakusho), 0.5cc of black ink for offset sheet printing is developed and printed on the long fiber layer surface of the laminate, and on the printed surface of the laminate 20 seconds after printing. On the other hand, the high quality paper was pressed at a pressing pressure of 5 MPa, and the transfer property of the ink to the surface of the high quality paper was evaluated. Almost no transfer of printing ink was observed in the laminate of the present invention, but the transfer of ink was remarkably observed in the fine paper having no long fiber layer formed thereon.
(rigidity)
The Clark stiffness defined in the paper pulp test method of JIS P 8143 was measured. The value of the fine paper obtained by laminating a long fiber of the present invention, but was 22~26cm ^3/100 in CD, fine paper that does not form a long fiber layer was 18cm ^3/100. Generally, the stiffness of high-quality paper for electrophotography is said to affect the paper-passability of the electrophotographic copying machine, and it can be seen that the electrophotographic paper laminated with the long fiber layer of the present invention has remarkably improved rigidity. .
(Whiteness, opacity)
When the whiteness was measured, the value of the fine paper on which the long fibers of the present invention were laminated was 85 to 90%, but the quality paper without the long fiber layer was 79%. The long fiber layer of the present invention has an effect of greatly improving whiteness. As for the opacity, the value of the fine paper on which the long fibers were laminated was 80 to 85%, and the value of the fine paper without the long fiber layer was 75%.
From these results, the laminate of the present invention in which the long fiber layer is formed has not only surface smoothness but also basic performance such as printing characteristics such as ink drying property and ink acceptability, and mechanical properties such as rigidity of the paper itself. It is clear that the physical properties are also dramatically improved compared to the conventional one.

After removing foreign matter from a 3% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd. PVA117) by centrifugation (2000 rpm, 5 minutes), it is placed in a syringe (made of plastic) with a capacity of 50 ml, and the cross section of the tip is processed flat. A metal needle having a hole diameter of 0.5 mm was attached. A stainless steel plate was placed at a position 30 cm away from the tip of the needle, and a fine paper for electrophotography on which water was slightly sprayed was placed thereon. When the voltage is gradually increased between 0 and 20 kV between the syringe needle and the stainless steel plate, liquid discharge starts from the tip of the needle at 18 kV and becomes a sprayed state. A lump (long fiber layer) was formed. This was repeated to form a uniform long fiber layer. The thickness of the long fiber layer was 5 μm. When the formed long fiber layer was observed with an electron microscope (magnification: 100,000 times), a network structure as shown in FIG. 1A could be confirmed. The fiber diameter of each long fiber was about 400 nm, and the length following the continuous fiber was mostly at least 2 mm or more.
The following characteristics of the inkjet recording paper on which the long fiber layer was laminated were evaluated by the following procedure. The results are shown below.
(Surface smoothness)
Surface smoothness was measured with a Oken smoothness meter. The portion where the long fiber layer was formed was 200 seconds, but the portion where the long fiber layer was not formed was 30 seconds, and the smoothness of the paper on which the long fiber layer was formed as in the present invention was remarkably improved. Was.
(Ink absorption)
As a printer for evaluation, a commercially available ink jet printer (manufactured by Epson, trade name: PM-770C) was used. The square ink-jet recording paper having a size of 10 × 10 cm is pasted on the center portion of A4 size fine paper, and black ink is solid-printed so that the ink discharge amount is 15 g / m ^2. Observed the overflow. The product of the present invention having a long fiber layer did not bleed or stain the hand even when the ink was rubbed by hand due to overflow of the ink solvent on the surface. On the other hand, the paper on which the long fiber layer was not formed slipped out like spots, and smeared or soiled when touched by hand immediately after recording.
(Dot reproducibility)
In order to investigate the printability of the ink jet recording paper, when the print quality of the recorded paper whose ink absorbability was examined was evaluated, the ink jet recording paper of the present invention was excellent in quality because the dots were not blurred and thickened. In the case where the long fiber layer was not formed, the dots bleed and thickened, and there was a problem in practical use.
[Rigidity] Clark stiffness defined in the paper pulp test method of JIS P 8143 was measured. The value of the fine paper obtained by laminating a long fiber of the present invention, but was 22 cm ^3/100 in CD quality paper which does not form a long fiber layer was 15cm ^3/100. In general, it is said that the rigidity of the ink jet printer paper affects the paper passing property of the printer, and it can be seen that the ink jet paper having the long fiber layer of the present invention has a remarkably improved rigidity.
From these results, the ink jet recording paper of the present invention in which the long fiber layer is formed has not only surface uniformity and ink absorbability, but also basic performance such as recording characteristics such as ink drying property, and mechanical properties such as rigidity of the paper itself. It is clear that the physical properties are also dramatically improved compared to the conventional one.

To 100 parts of kaolin (trade name: Astraplus, manufactured by Imeris), 0.2 part of sodium polyacrylate (trade name: Aron A-9, manufactured by Toa Gosei Co., Ltd.) is added as a dispersant, and dispersed in water using a Coreless disperser. Thus, a pigment slurry was prepared. To this pigment slurry, 2.0 parts of oxidized starch (trademark: Petrocoat C-8, manufactured by Nissho Chemical Co., Ltd.) and 10 parts of styrene-butadiene latex (trademark: T-2550K, manufactured by Nippon Synthetic Rubber Co., Ltd.) are added. The mixture was stirred and water was added to prepare a coating solution having a solid content of 50%.
This coating solution was applied onto the fine long fiber layer of Example 2 using a blade coater so that the coating amount as a solid content was 10 g / m ² and dried at 160 ° C. To give a coated paper.
Comparative Example 1
The same paint as in Example 5 was applied to high-quality paper for electrophotography, and a calendar process was performed to prepare a coated paper.
Comparative Example 2
To an aqueous pulp slurry containing 100 parts of LBKP (freeness (CSF) = 550 ml), 5 parts of light calcium carbonate (trademark: PC, calcium shiroishi) is added, and 1.0 part of starch and 100% alkenyl anhydrous succinate per 100 parts of pulp. 0.1 parts of acid and 0.6 parts of sulfuric acid band are added, and the resulting pulp slurry is subjected to a papermaking machine to make paper, and the obtained wet paper is dried with a starch sizing agent. A base paper having a basis weight of 60 g / m ² and a density of 0.60 g / cm ³ was prepared by applying with a size press so as to be 1.0 g / m ² .
The base paper obtained as described above was coated with the same paint as in Example 5 and calendered to prepare a coated paper.
(Macro blister and micro blister)
When the coated paper is used in an offset printer, an electrophotographic copying machine, and a printer, there is a problem that blisters are generated when the ink is dried and the toner image is heated and fixed. There are two types of blisters that occur on coated paper: macro blisters and micro blisters. The former is the one that causes the moisture contained in the base paper layer to expand and deforms the base paper layer and the coating layer. To do. In the latter case, the water vapor generated between the ink or toner and the coating layer expands, causing a fine expansion and a decrease in gloss in the image area.
The coated paper obtained in Example 5, Comparative Example 1 and Comparative Example 2 was printed using an offset ink T13 with an RI tester, and the occurrence of blisters was confirmed.
The occurrence of macro blisters was visually confirmed and evaluated according to the following evaluation criteria.
○: Macro blister is not recognized. There are no practical problems and the quality is excellent.
X: Macro blisters were observed on the entire surface of the paper. There is a problem in practical use and the quality is remarkably inferior.
The state of occurrence of microblisters was observed with an magnifying loupe (30 times) and evaluated and displayed according to the following evaluation criteria.
(Double-circle): A micro blister is not recognized. There are no practical problems and the quality is excellent.
○: Some microblisters are recognized. There is no problem in practical use.
X: Micro blister was remarkably recognized. There is a problem in practical use and the quality is remarkably inferior.

  As described above, according to the present invention, it is possible to provide a laminate having high surface smoothness, an inkjet recording paper having high surface uniformity and ink absorbency, and a method for producing them.

Claims (14)

A laminate,
A paper support mainly composed of cellulose fibers;
A laminate comprising a layer containing fine long fibers laminated on at least one side of the paper support. The laminate according to claim 1, wherein the long fibers are fibers having a fiber diameter of 1 nm to 10 µm and a length of 1 mm or more. The laminate according to claim 1 or 2, wherein the long fibers form a network structure. The laminate according to any one of claims 1 to 3, wherein the long fibers include at least one kind of ink repellent polymer. 5. The long fiber is a linear polymer having a functional group capable of forming a hydrogen bond, and the functional group is chemically bonded to a compound having a molecular weight of 40 to 5000. 6. Laminated body. A method for producing a laminate,
Injecting the raw material solution from the orifice while applying a voltage between the electrode in contact with the raw material solution of the long fiber filled in the container having the orifice and the electrode plate arranged to face the orifice; ,
Forming a layer containing long fibers on the surface of the paper support placed on the electrode plate by the sprayed raw material solution. Recording material,
A paper support mainly composed of cellulose fibers;
A recording material comprising a layer containing fine long fibers laminated on at least one side of the paper support. The recording material according to claim 7, wherein the long fibers are fibers having a fiber diameter of 1 nm to 10 μm and a fiber length of 1 mm or more. The recording material according to claim 7 or 8, wherein the long fibers form a network structure. The recording material according to claim 7, wherein the long fibers include at least one ink-repellent polymer. The recording material according to claim 7, further comprising a coating layer laminated on the layer containing the long fibers. The long fiber is a linear polymer having a functional group capable of forming a hydrogen bond, and the functional group is chemically bonded to a compound having a molecular weight of 40 to 5000. The recording material described. An ink jet recording paper comprising the recording material according to any one of claims 7 to 12. Injecting the raw material solution from the orifice while applying a voltage between the electrode in contact with the raw material solution of the long fiber filled in the container having the orifice and the electrode plate arranged to face the orifice; ,
Forming a layer containing long fibers on the surface of the paper support disposed on the electrode plate by the sprayed raw material solution.

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