JPH07228039A - Recording sheet - Google Patents

Abstract

PURPOSE:To improve ink drying properties and dot reproducibility by arranging an ink receiving layer constituted of multilayered fine particles and a binder resin on the surface of a base material sheet and partially welding the multilayered fine particles so as to provide gaps therebetween. CONSTITUTION:A recording sheet is constituted by arranging an ink receiving layer on at least one surface of a base material sheet and the ink receiving layer is constituted of partially crosslinked multilayered fine particles and a binder resin. At that time, the multilayered fine particles are formed into a layered state and the particle size thereof is specified to 10-500nm. The binder resin is composed of a polyvlnyl alcohol resin with a saponification value of 70-80 and a polymerization degree of 300-1000 and may be composed of a polyvinyl acetal resin. By this constitution, the recording sheet generating no crack in its ink receiving layer, excellent in ink drying properties and capable of obtaining a sharp printing image is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet,
In particular, the present invention relates to a recording sheet that enables good recording by an inkjet printer.

[0002]

2. Description of the Related Art Conventionally, as an output print of a computer or a word processor, a wire dot recording system,
Various systems such as a thermal color recording system, a thermal melt transfer recording system, a thermal sublimation transfer recording system, an electrophotographic recording system and an inkjet recording system have been developed. Among them, the ink jet recording method is characterized in that plain paper can be used as a recording sheet, the printing cost is low, the apparatus is compact and there is no noise, and high speed recording is possible. Therefore, its use as a printer that outputs image information such as characters and figures created by a computer or the like quickly and accurately is drawing attention. Also, because it is easy to colorize and the picture is clear, the image information created by the computer is recorded on a transparent recording sheet by an inkjet printer, and this is used as a document such as an OHP (overhead projector) for meetings and various academic conferences. The demand for use in announcements is also increasing.

In general, an ink jet printer ejects recording ink from a nozzle by the pressure of a fine piezoelectric element (piezo element) or the pressure of air (bubble jet) generated by heating a thermal head, and adheres to the recording sheet. By doing so, recording is performed. For this reason, as a recording ink used in inkjet recording, an ink that is difficult to dry is used in order to prevent ejection failure of the ink due to an increase in viscosity of the ink at the nozzle due to the drying of the ink. Usually, this ink component is generally a dye, resin, additive, etc. dissolved in water and alcohol.

Therefore, a recording sheet for recording with an ink jet printer is required to absorb the moisture of the adhered ink and dry and solidify the ink. For this reason, a recording sheet is used in which an ink receiving layer is formed on a resin film to enhance the ink absorbency. As a conventional recording sheet, the receptive layer formed on the base sheet is an ink receptive layer containing a filler such as silica for absorbing water in the water-soluble polymer and facilitating drying. Things have been proposed. (JP-A-56-99692
No. 2-276670). Further, the ink receiving layer has a porous structure (JP-A-60-214989).
No.) etc. have been proposed.

[0005]

However, although a recording sheet having an ink receiving layer containing a filler such as silica has excellent ink drying property, if the content of the filler is high, the ink adsorbing power becomes strong. Since it is too large, a proper spread of dots cannot be obtained, resulting in a fine line drawing,
I can't get the requested image. Further, in the case of the OHP sheet, there is a drawback that the transparency is impaired. On the other hand, when the content of the filler is low, there is a problem that sufficient drying property cannot be obtained and blocking and image disorder occur. Furthermore, addition of a filler or the like causes fine cracks on the surface of the recording sheet, resulting in a lack of image clarity and a loss of flexibility of the ink receiving layer. On the other hand, when the organic fine particles are used when forming the ink receiving layer having a porous structure, there is a disadvantage that a sufficient porous structure cannot be obtained because a film is formed by heating.

The present invention has been made in view of the above circumstances, and in a recording sheet provided with an ink receiving layer having a porous structure, the ink receiving layer is free from cracks and the ink drying property is low. It is an object of the present invention to provide a recording sheet which is excellent in printing quality and can obtain a clear printed image.

[0007]

The above object can be achieved by the present invention described below. That is, the present invention comprises a substrate sheet and an ink receiving layer provided on at least one surface of the substrate sheet, the ink receiving layer comprising partially crosslinked multilayer fine particles and a binder resin. Is formed by partially fusing so as to have voids.

[0008]

In the ink receiving layer, the multi-layered fine particles are partially fused so as to have voids between the particles, so that the ink absorbency is excellent. It is possible to prevent the phenomenon that minute cracks occur. In addition, the binder resin acts as an emulsifier that stabilizes the dispersion of the multilayer fine particles. Further, since the multilayer fine particles have a layered structure, the inside of the fine particles has a high cross-linking density and the minimum film forming temperature is also high.
Although the particle structure is not easily deformed, the crosslinking density becomes lower toward the outside and the minimum film forming temperature also becomes lower, so that fusion occurs at the outside of each particle and a good porous structure can be obtained. That is, in layered fine particles such as core / shell and core / hair type, particles designed such that the core part is crosslinked, the shell part is non-crosslinked, the core part is non-thermoplastic, and the shell part is thermoplastic In the low to middle temperature range, fusion is performed only in the shell portion, and deformation and fusion due to heating are not performed in the core portion, so that voids between particles can be maintained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The recording sheet of the present invention is
It is possible to have an ink receiving layer on the base sheet and, if necessary, provide a curl prevention layer on the back surface of the primer layer or the base sheet between the base sheet and the ink receiving layer.

When used as an OHP sheet, the base sheet used in the recording sheet of the present invention is formed of a thermoplastic resin having transparency, heat resistance, dimensional stability and rigidity. Those are preferable. Specific examples of preferable base film include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride and the like having a thickness of 5 to 2
A film or plate having a thickness of about 50 μm, preferably about 50 to 180 μm can be used. In addition, when the recording sheet is not limited to OHP applications, the base sheet may be synthetic paper such as polystyrene, fine paper, art paper,
It is also possible to use various colored or white papers such as coated paper, cast coated paper, wallpaper, backing paper, synthetic resin-impregnated paper, emulsion-impregnated paper, synthetic rubber latex-impregnated paper, synthetic resin-internally added paper, and paperboard.

Further, the back surface of the base sheet is formed for the purpose of improving the feedability on the printing machine, that is, slipping, and preventing curling due to adhesion of foreign matters and expansion and contraction of the ink receiving layer due to dehumidification and absorption of the ink receiving layer. It is a layer. This anti-curl layer is made of the same resin as the material of the fine particles constituting the ink receiving layer,
Alternatively, it can be formed of a resin that does not expand or contract depending on the environment when OHP is used. For example, it can be formed by applying a solution of a polyacrylic acid ester-based resin, a polyester-based resin or the like by a known means. The thickness of such a curl prevention layer is preferably about 1 to 5 μm.
An antistatic agent may be added to the anti-curl layer. The antistatic agent to be used is a known antistatic agent, for example, a cationic antistatic agent such as a quaternary ammonium salt or a polyamine derivative, an anionic antistatic agent such as an alkyl phosphate, or a nonionic antistatic agent such as a fatty acid ester. Is mentioned.

The ink receiving layer formed on the other surface of the base sheet is composed of multi-layered fine particles obtained by partially cross-linking a resin and a binder resin, and is formed by partially fusing the fine particles so as to have voids. It is characterized by being The size of the voids between the fine particles is preferably 300 nm or less. Since the fine particles have such voids, it is possible to absorb the ink, and it is possible to prevent a phenomenon that fine cracks occur on the surface due to the presence of the binder resin in the partial fusion of the fine particles. Furthermore, since the multi-layered fine particles have a multi-layer structure, the cross-linking density is high inside the fine particles and the minimum film formation temperature is high, so the particle structure is less likely to deform, but the cross-linking density is lower toward the outer side and the minimum film formation Since the temperature also becomes low, fusion occurs at the outer portion of each particle, and a good porous structure is obtained. That is, in layered fine particles such as core / shell and core / hair type, the core part is crosslinked, the shell part is non-crosslinked, and the core part is non-thermoplastic,
When particles designed so that the shell portion is thermoplastic are used, fusion is performed only in the shell portion in the low to medium temperature range, and deformation and fusion due to heating are not performed in the core portion, so voids between particles are formed. It is possible to maintain. This multilayer particle is
It may be inorganic fine particles or organic fine particles, and the average particle diameter thereof is 0.01 to 1 μm, preferably 10 to 50.
It is about 0 nm. If the average particle size is 0.01 μm or less, sufficient ink drying property cannot be obtained and the image is disturbed, and if it is 1 μm or more, the sharpness of the image is impaired, which is not preferable.

The inorganic multi-layered fine particles can be produced by a method of synthesizing an inorganic filler with a coupling agent, or a method of synthesizing by grafting a polymer on the surface of the inorganic fine particles. . For example, as a known method, PolymerJou
rnal, Vol. 21, No. 6, and Journal
of PolymerScience, A, Vol. 29
And surface Vol. 28, No. 4 and surface Vol. 30, N
o. 1 and the like. Examples of the inorganic filler used in the inorganic multilayer fine particles, for example, calcium carbonate, barium sulfate, titanium dioxide, mica, silica,
Examples thereof include talc, alumina, aluminum oxide and magnesium oxide. Examples of the coupling agent used for producing the inorganic multi-layer fine particles include titanate-based, aluminate-based, and silane-based coupling agents.

The organic multi-layered fine particles can be produced by a method of synthesizing a plurality of cross-linked polymer latexes (microgels) having a three-dimensional network structure in the polymer latex particles by emulsion polymerization. For example, as a known method, Makromolek
ulareChemie, Vol. 181 and Poly
merJournal, Vol. 17, No. 1 or J
ouralofcoatingTechnology
y, Vol. 60, No. 767 and the surface Vol. 25,
No. 2 and the like. The microgel used for producing the organic multilayer fine particles can be synthesized mainly with a vinyl polymer. Examples thereof include polymers and copolymers of styrene, acrylic monomers, methacrylic monomers, vinyl acetate and the like.

In the above-mentioned multi-layered fine particles, the cross-linking density is high inside the fine particles and the softening point is high, so that the particle structure is not easily deformed, but the cross-linking density is lower toward the outer side and the softening point is lower. A good porous structure can be obtained because fusion occurs at the outer portion of each particle. That is, the multi-layer fine particles are
It is preferable that the outermost layer has the lowest softening point temperature and has the softening point temperature distribution. Examples of the thermoplastic resin used for the outermost layer include polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polypropylene resin, polystyrene resin, polyvinyl alcohol resin, polyethylene resin, diacetate resin, triacetate resin, and polyimide resin. To be Furthermore, it is preferable that the outermost layer of the multilayer fine particles has a functional group.

As the functional group which the multilayer fine particles have in the outermost layer, for example, --COOH, --COOH salt, sulfonate, --OH, tertiary amine, malate, acrylic triple bond, amide, etc. are provided on the surface or inside thereof. It was introduced. Among the above functional groups, especially --COOH,
Over SO ₃ Na, chromatography PEO, over NH ₂ are preferred. When the multi-layered fine particles have such a hydrophilic functional group, the fine particles are made hydrophilic and the dispersion is improved, and the fine particles are fused to each other.

The multilayer fine particles are obtained by partially cross-linking the constituent resin. It is preferable that the inside of the fine particles has a high crosslink density, and the crosslink density becomes lower toward the outside. The degree of crosslinking is 0 to 5 mmol / g
If the crosslinking degree is too high, the fusion between the particles becomes insufficient, the film formability is lowered, and an ink receiving layer having high durability cannot be obtained. Further, if the degree of crosslinking is too low, the particles cannot be partially fused while maintaining the shape of the particles.

Further, the softening point temperature of the multi-layered fine particles may be in the range of 20 to 150 ° C, preferably 40 to 90 ° C. When the softening point temperature of the multi-layered fine particles is less than 20 ° C., the stability of the multi-layered fine particles over time becomes insufficient, and deformation easily occurs due to the environment, so that the strength of the ink receiving layer is lowered, which is not preferable. Further, if the softening point temperature exceeds 150 ° C., high temperature treatment is required for forming the ink receiving layer, the damage to the base sheet becomes large, and the film surface of the formed ink receiving layer may be cracked. There is.

As the binder resin which is another component in the ink receiving layer of the present invention, polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polypropylene resin, polystyrene resin,
Examples thereof include polyvinyl alcohol resins or modified products thereof, polyvinyl acetal resins, polyethylene resins, diacetate resins, triacetate resins, and polyimide resins. Of these, the preferable degree is a saponification degree of 70 to 80,
When a polyvinyl alcohol resin having a degree of polymerization of 300 to 1000 is used, a polyvinyl alcohol resin having a degree of saponification of 70 to 80 is preferable in that it has both hydrophilicity and hydrophobicity,
If the saponification degree is 70 or less, the hydrophilicity is lowered, and if the saponification degree is 80 or more, the hydrophobicity is lowered. Further, the lower the degree of polymerization is, the more preferable in terms of dispersion stability of fine particles, and the degree of polymerization of 1000 or more causes a problem in that fine particles aggregate. By using such a polyvinyl alcohol resin, it is possible to stably emulsify and disperse the particles while maintaining the primary particle size without agglomerating the particles. Further, the polyvinyl acetal resin is preferable in that it can be stably dispersed while maintaining the primary particle diameter without causing the particles to aggregate and gel like the polyvinyl alcohol resin. By using these binder resins in the ink receiving layer of the present invention, it is possible to prevent a phenomenon in which fine cracks are generated on the surface of the recording sheet and to stabilize the dispersion of the multilayer fine particles. The ratio of the multilayer fine particles to the binder resin is 100% of the binder resin.
The amount of the multi-layered fine particles is preferably 200 to 1000 parts by weight with respect to parts by weight. If the content of the multi-layered fine particles is higher than this, problems such as fine cracks on the surface may occur. On the other hand, if the content of the binder resin is higher than this, sufficient voids cannot be provided between the particles, which is not preferable.

Further, as other additives, film forming aids such as ethylene glycol, ethylene glycol n-butyl ether, diethylene glycol n-butyl ether, propylene glycol n-butyl ether and dipropylene glycol n-butyl ether can be added.
In addition, the addition of surfactants such as alkylammonium acetate and trialkylammonium halides, and sizing agents such as rosin and starch improve the wettability of the ink adhering to the ink-receiving layer and dry it. It is possible to improve the sex.

In order to form the ink receiving layer, the coating liquid containing the ink receiving layer composition as described above is dried by a known method such as gravure coating, roll coating (direct or reverse), wire bar coating or air knife coating. The subsequent coating amount is 1.0 to 60 g / m ² , preferably 10
It is applied so as to be about 40 g / m ² . The drying temperature after coating is such that the multilayer fine particles are partially fused while maintaining the particle shape to form voids between the particles. The drying temperature varies depending on the softening point temperature and the degree of crosslinking of the multilayer fine particles used, but is usually 30 to 160 ° C., preferably 30.
The drying temperature can be set in the temperature range of 120 ° C.

When the adhesion between the base sheet and the ink receiving layer is insufficient, it is preferable to subject the surface to a primer treatment or a corona discharge treatment. The formation of the primer layer is
For example, a solution containing, as a main component, an acrylic resin such as a one-component curing type or a two-component curing type polyacrylic acid derivative, a polyurethane resin, a polyester resin, a vinyl chloride-vinyl acetate copolymer, or nitrocellulose is formed on a substrate sheet. Thickness 0.2
It is carried out by applying a gravure coat, a reverse coat or the like so as to have a thickness of 0.3 μm.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. Example As a base material sheet, a polyethylene terephthalate sheet (Q80D, manufactured by Toray Industries, Inc., thickness: 100 μm) was coated with coating liquids 1 to 4 for the ink receiving layer made of the following composition with a wire bar, and then at 100 ° C. After drying for 5 minutes, an ink receiving layer having a thickness of 10 μm was formed to obtain recording sheets 1 to 4 of the invention. Ink Receptor Layer Coating Liquid 1 (Example 1) Acrylic multilayer fine particles (30% solution) 5 parts (particle size 140 nm, softening point 90 ° C.) Polyvinyl alcohol (10% solution) 3 parts (saponification degree 71 to 75, Polymerization degree 600) Coating liquid 2 for ink receiving layer (Example 2) Acrylic multilayer fine particles (30% solution) 5 parts (particle size 80 nm, softening point 80 ° C) Polyvinyl acetal (10% solution) 3 parts (Acetalization 9 mol%) Coating liquid 3 for ink receiving layer (Example 3) Acrylic multilayer fine particles having -COOH introduced as a functional group 5 parts (30% solution) (particle size 140 nm, softening point 90 ° C) Modified polyvinyl alcohol ( 10% solution) 3 parts (saponification degree 71 to 75, polymerization degree 600) an ink receiving layer coating solution 4 (example 4) acrylic multi particulates obtained by introducing a functional group Toshite NH ₂ (30% Liquid) 5 parts (particle size 110 nm, softening point 90 ° C.) modified polyvinyl alcohol (10% solution) 3 parts (saponification degree 71 to 75, polymerization degree 600)

Comparative Example A recording sheet was obtained in the same manner as in Example except that the ink receiving layer coating liquid 5 was used in place of the ink receiving layer coating liquid 1. Ink-Receptive Layer Coating Liquid 5 (Comparative Example 1) Acrylic Multilayer Fine Particles (30% Solution) 5 Parts (Particle Size 140 nm, Softening Point 90 ° C.) Ink-Receptive Layer Coating Liquid 1 (Comparative Example 2) Polyvinyl alcohol ( 10% solution) 3 parts (saponification degree 71-75, polymerization degree 600)

With respect to these recording sheets, the drying property,
Table 1 shows the results of evaluation of image quality under the following conditions. Evaluation method Dryability: A test pattern was printed with a desk writer C (manufactured by Hured Packer), and immediately after that, a palpation test of the printed surface was performed. Image quality: A test pattern was printed with a desk writer C (manufactured by Hured Packer) and visually observed.

[0026]

[Table 1]

[0027]

[Effect] According to the present invention as described above, in the ink receiving layer, since the multi-layered fine particles are partially fused so as to have voids between the particles, the ink absorbency is excellent,
The presence of the binder resin can prevent a phenomenon that fine cracks are generated on the surface of the recording sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunichi Ebihara 1-1-1, Ichigayaka, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd.

Claims (5)

[Claims] 1. A substrate sheet, and an ink receiving layer provided on at least one surface of the substrate sheet, wherein the ink receiving layer comprises partially crosslinked multilayer fine particles and a binder resin. A recording sheet, which is formed by partially fusing so as to have voids. 2. The recording sheet according to claim 1, wherein the multilayer fine particles are layered. 3. The multi-layered fine particles have a particle size of 10 to 500.
The recording sheet according to claim 1 or 2, wherein the recording sheet has a thickness of nm. 4. The saponification degree of the binder resin is 70-8.
The recording sheet according to any one of claims 1 to 3, which is a polyvinyl alcohol resin having a degree of polymerization of 0 to 300 and a polymerization degree of 1000 to 1000. 5. The recording sheet according to claim 1, wherein the binder resin is a polyvinyl acetal resin.