JPH0725134A - Recording sheet - Google Patents

Abstract

PURPOSE:To obtain a recording sheet having an ink receiving layer occurring no crack or embrittlement and having excellent ink drying properties and proper ink adsorbing capacity by providing the ink receiving layer on at least one surface of a base material sheet so as to form the same in such a state that at least fine particles having a multilayered structure are mutually connected. CONSTITUTION:A recording sheet consists of a base material sheet 2 and the ink receiving layer 4 provided on at least one surface of the base material sheet 2 and the ink receiving layer 4 is formed so that at least fine particles having a multilayered structure are mutually connected. As a result, the recording sheet having the ink receiving layer 4 occurring no crack or embrittlement, having excellent ink drying properties and proper ink absorbing capacity, excellent in dot reproducibility and providing a sharp printing image can be 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, and more particularly to a recording sheet capable of excellent recording by an ink jet 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, since 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 ink jet printer, and this is used as a manuscript for OHP (overhead projector) and the like, at conferences, various academic conferences, etc. 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 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.

In particular, the ink receiving layer of a recording sheet used as an OHP sheet is required to have the following characteristics.

Good ink receptivity, absorption / drying property, and fixing property.

High transparency.

No blocking occurs when stored in a laminated state.

Excessive spreading and bleeding of ink dots.

The color of the ink should be clear and should not change.

There is no stickiness or sticking of fingerprints or the like.

From such a viewpoint, as a conventional recording sheet, a receptive layer formed on a base sheet is filled with silica or the like for absorbing water of an ink into a water-soluble polymer to facilitate drying. An ink receiving layer containing an agent has been proposed (JP-A-56-99692, JP-A-2-
276670).

For ink jet recording, an ink receiving layer containing polystyrene beads or copolymer beads thereof, or hollow beads of polystyrene or copolymer thereof as a filler is provided as an ink receiving layer having a high ink color density. A sheet has been proposed (JP-A-4-235086).

[0014]

However, although a recording sheet having an ink receiving layer containing a filler such as silica has an excellent ink drying property, if the content of the filler is high, the ink adsorbing power becomes strong. Since it is too large, an appropriate dot spread cannot be obtained, resulting in a fine line drawing, and the required image cannot be obtained. Furthermore, in the case of OHP sheets,
The drawback is that 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,
The 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, a recording sheet having polymer beads as a filler contained in the ink receiving layer has a disadvantage in that the beads themselves do not have ink absorbability and thus a sufficient drying speed cannot be obtained.

The present invention has been made in view of the above circumstances, has no cracks or embrittlement in the ink receiving layer, is excellent in ink drying property, has a proper ink adsorption force, and has a dot shape. An object of the present invention is to provide a recording sheet having excellent reproducibility and a clear printed image.

[0017]

In order to achieve such an object, the present invention comprises a substrate sheet and an ink receiving layer provided on at least one surface of the substrate sheet. The layers were configured such that at least fine particles having a multilayer structure were connected to each other.

[0018]

The ink receiving layer provided on at least one surface of the base sheet is formed of at least fine particles having a multi-layered structure, and the fine particles are connected to each other to cover the surface of the ink receiving layer. There are no cracks or embrittlement on the surface, and since the ink adhering to the ink receiving layer is adsorbed with an appropriate adsorption force, it has excellent dot reproducibility. At the same time, the above adsorption force enables a sufficient drying speed. To do.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of the recording sheet of the present invention. In FIG. 1, a recording sheet 1 is a base sheet 2
And an ink receiving layer 4 formed on one surface of the base sheet 2 with the primer layer 3 interposed therebetween. Further, the curl prevention layer 5 is provided on the other surface of the base material sheet 2.

As for the base sheet 2, the recording sheet 1 is OHP.
When used as a sheet for transparency, transparency, heat resistance,
Those formed of a thermoplastic having dimensional stability and rigidity are preferable. Specifically, polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polypropylene resin, polystyrene resin,
Thickness of polyvinyl alcohol resin, polyethylene resin, diacetate resin, triacetate resin, polyimide resin or the like is about 5 to 250 μm, preferably 50 to 180 μm.
A film-shaped or plate-shaped material may be used.

When the use of the recording sheet 1 is not limited to OHP, synthetic paper such as polystyrene, fine paper, art paper, coated paper, cast coated paper, wallpaper, backing paper, synthetic paper is used as the base sheet. It is also possible to use various colored or white papers such as resin-impregnated paper, emulsion-impregnated paper, synthetic rubber latex-impregnated paper, synthetic resin internal-addition paper, and paperboard.

When the adhesion of the base sheet 2 to the ink receiving layer formed on the surface thereof is insufficient, it is preferable to subject the surface to a primer treatment or a corona discharge treatment. In the illustrated example, the primer layer 3 is formed on the surface of the base material sheet 2. The primer layer 3 can be usually formed by applying the material used as the primer layer by a conventional method, although it depends on the type of the base sheet 2.
For example, a solution composed of 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 may be used. As a method for applying these solutions, gravure coating, reverse roll coating, or the like can be adopted, and the thickness of the primer layer is preferably about 0.2 to 0.3 μm. The ink receiving layer 4 is for absorbing and drying the ink of the inkjet printer and maintaining the formed image.
The recording sheet of the present invention is characterized in that the ink receiving layer 4 is formed by connecting at least fine particles having a multi-layer structure (hereinafter referred to as multi-layer fine particles). That is,
From the viewpoint of improving the drying property of an ink for an inkjet printer, the sharpness of an image, and the durability, the ink receiving layer mainly contains multilayer fine particles. The multilayer fine particles may be inorganic fine particles or organic fine particles, and the average particle diameter thereof is about 0.01 to 20 μm, preferably about 0.03 to 5 μm. When the average particle diameter of the multi-layered fine particles is less than 0.01 μm, sufficient ink drying property cannot be obtained, which causes image disturbance, and is 20 μm.
If it exceeds, the dots of the image become large and the sharpness is lost, 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, a method of synthesizing by grafting a polymer on the surface of the inorganic fine particles, and the like. For example, as a known method, Polymer Journal, Vol.21, No.6, p475 (1989)
, Journal of Polymer Science, A, Vol.29, p697 (19
92), surface Vol.28, No.4, p286 (1990), surface, Vol.3
0, No. 1, p74 (1992) and the like.

Examples of the inorganic filler used in the inorganic multilayer fine particles include calcium carbonate, barium sulfate, titanium dioxide, mica, silica, talc, alumina, aluminum oxide, magnesium oxide and the like.

Examples of the coupling agent used for producing the inorganic multi-layer fine particles include titanate-based, aluminate-based, and silane-based coupling agents.

On the other hand, the organic multi-layered fine particles can be produced by a method of synthesizing by performing emulsion polymerization of a pre-crosslinked polymer latex (microgel) having a three-dimensional network structure inside the polymer latex particles. it can. For example, as a known method, Makromolekulare Ch
emie, Vol.181, p2517 (1980), Polymer Journal, Vo
l.17, No.1, p179 (1985) and Journal of coatings Tec
hnology, Vol.60, No.767, p69 (1988) and surface, Vol.2
5, No. 2, p86 (1987) and the method described in Japanese Examined Patent Publication No. 3-42312. The microgel used in the production of 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.

The outermost layer of the multilayer fine particles as described above is preferably made of a thermoplastic resin. As the thermoplastic resin used for the outermost layer, polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polypropylene resin, polystyrene resin,
Examples thereof include polyvinyl alcohol resin, polyethylene resin, diacetate resin, triacetate resin, and polyimide resin. Further, it is preferable that the multilayer fine particles have a distribution of the softening point temperature and the softening point temperature of the outermost layer is the lowest.
The distribution of the softening point temperature in this case may gradually decrease from the center of the multilayer fine particles to the outside, and there is a portion having a high softening point temperature between the center of the multilayer fine particles and the outermost layer. In any case, it is preferable that the outermost layer of the multilayer fine particles has the lowest softening point temperature.

Further, the ink receiving layer 4 has a single layer structure fine particles (hereinafter referred to as single layer fine particles) in addition to the above-mentioned multilayer fine particles for the purpose of improving the drying property of the ink and the sharpness of the image. May be included. Examples of the single-layer fine particles include fine particles made of an inorganic compound such as silica, alumina, and titanium dioxide, styrene, and an acrylic-based microgel. The average particle diameter of the monolayer fine particles is 0.01 to 20 μm, preferably 0.03 to 5 μm.
It is about m. The average particle diameter of single-layer fine particles is 0.01μ
If it is less than m, the ink absorbency and dryness deteriorates,
If it exceeds μm, the sharpness of the image is lost, which is not preferable.

The mixing ratio of the multilayer fine particles and the single layer fine particles in the ink receiving layer 4 is multilayer / single layer = 27/75 to 99.
/ 1, preferably about 50/50 to 90/10.
If the ratio of the single-layer fine particles is less than the above range, the effect of adding the single-layer fine particles is not exhibited, and if it exceeds the above range, the strength of the ink receiving layer becomes weak, which causes cracks. Not preferable.

In order to form the ink receiving layer 4 with the above-mentioned multi-layered fine particles or with multi-layered fine particles and single-layer fine particles, a coating solution containing fine particles is gravure coated, roll coated (direct or reverse), wire bar coated, By a known method such as air knife coating, the coating amount after drying is 1 to 50 g / m ² , preferably 5 to 30 g.
/ M ² so that it is applied. Drying after coating, a coating film is formed by adopting a normal drying method, but the drying temperature is higher than the softening point temperature of the outermost layer of the multilayer fine particles and lower than the softening point temperature of the central nucleus. preferable. When the drying temperature is higher than the softening point temperature of the central core of the multi-layered fine particles, fusion and film formation of the multi-layered fine particles proceed unnecessarily and the ink absorbability, which is an important factor of the ink receiving layer 4, is lowered. It will be. As described above, the outermost layer of the multilayer fine particles plays a role of a film-forming agent, so that it is not particularly necessary to add a binder to the coating liquid.

The ink receiving layer 4 may be formed in a required amount by one-time application, or may be provided with necessary aptitude by applying two or more times.

The anti-curl layer 5 provided on the back surface of the base sheet 2 improves the feedability on the printing machine, that is, the slippage, and prevents the curling due to the adhesion of foreign matter and the expansion and contraction of the ink receiving layer 4 due to dehumidification and absorption. It is a layer formed for the purpose. The curl prevention layer 5 can be formed of the same resin as the material of the fine particles forming the ink receiving layer, or a resin that does not expand or contract due to 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 5 is 1
It is preferably about 5 μm.

An antistatic agent may be added to the ink receiving layer 4 or the curl preventing layer 5. The antistatic agent used is a known antistatic agent, for example, a quaternary ammonium salt,
Examples thereof include cationic antistatic agents such as polyamine derivatives, anionic antistatic agents such as alkyl phosphates, and nonionic antistatic agents such as fatty acid esters.

Next, the present invention will be described in more detail with reference to experimental examples. (Experimental example) Preparation of sample 1 First, Makromolekulare Chemie, Vol.181, p2517 (1980)
, Polymer Journal, Vol.17, No.1, p179 (1985), J
ournal of coatings Technology, Vol.60, No.767, p69
(1988), Surface, Vol.25, No.2, p86 (1987), Japanese Patent Publication No. 3-42312, and the like.
A multilayer fine particle dispersion 1 (solid content: 30%) containing the following organic multilayer fine particles (average particle diameter: 0.1 μm) having a two-layer structure of an inner layer and an outer layer was prepared.

-Inner layer: styrene, butyl acrylate, 2-hydroxyethyl acrylate, methacrylic acid-Outer layer: methyl methacrylate, acrylic acid Next, as a base sheet, a polyethylene terephthalate sheet (Q80D manufactured by Toray Industries, Inc., thickness) 100 μm)
Was prepared, and the above-mentioned multi-layered fine particle dispersion liquid 1 was applied to one surface of this substrate sheet by a wire bar (application amount after drying = 10 g / m ² ), and dried at 80 ° C. for 2 minutes. An ink receiving layer was formed by using the above to obtain a recording sheet (Sample 1). Preparation of Sample 2 First, Polymer Journal, Vol.21, No.6, p475 (1989)
, Journal of Polymer Science, A, Vol.29, p697 (19
92), surface Vol.28, No.4, p286 (1990), surface, Vol.3
0, No. 1, p74 (1992) and the like, and a multi-layered fine particle dispersion 2 (solid content) containing inorganic multi-layered fine particles (average particle diameter: 0.15 μm) grafted with acrylate using silica as a nucleus (solid content). 30%).

Next, using the same base sheet as that used in the preparation of Sample 1, the above-mentioned multilayer fine particle dispersion 2 is applied under the same conditions as in the preparation of Sample 1 and dried to form an ink receiving layer. A recording sheet (Sample 2) was obtained. Preparation of Sample 3 First, a coating liquid containing the organic multilayer fine particles and single-layer fine particles and having the following composition was prepared.

(Composition of coating liquid) Multilayer fine particle dispersion 1 (solid content 30%) 70 parts by weight Single layer fine particle dispersion (solid content 30%) (Nippon Paint Co., Ltd. Microgel E-5001) ) 30 parts by weight Next, using the same base sheet as that used in the preparation of Sample 1, the above coating liquid was applied under the same conditions as in the preparation of Sample 1 and dried to form an ink receiving layer. A recording sheet (Sample 3) was obtained. Preparation of Comparative Sample 1 A polyethylene terephthalate sheet (Q80D, manufactured by Toray Industries, Inc., thickness: 100 μm) was prepared as a base material sheet, and one side of the base material sheet was coated with a coating liquid having the following composition with a wire bar. (Coating amount after drying = 10 g / m
² ) and dried at 70 ° C. for 2 minutes to form an ink receiving layer to obtain a recording sheet (Comparative Sample 1).

(Composition of coating liquid) -Polyvinyl alcohol (solid content 10%) (Nippon Gosei Kagaku Kogyo Co., Ltd. Gocefimer K210) ... 17 parts by weight Alumina sol (solid content 10%) (Nissan Chemical Industry ( Alumina sol 100) manufactured by K.K. Co., Ltd. 83 parts by weight Preparation of Comparative Sample 2 A recording sheet (Comparative Sample 2) was obtained in the same manner as Comparative Sample 1 except that the coating solution having the following composition was used.

(Composition of coating liquid) -Polyvinyl alcohol (solid content 10%) (Nippon Gosei Kagaku Kogyo Co., Ltd. Gocefimer K210) ... 25 parts by weight-Alumina sol (solid content 10%) (Nissan Chemical Industry ( Alumina sol 100 manufactured by K.K. Co., Ltd. 75 parts by weight Recording sheets prepared as described above (Samples 1 to 3,
The comparative samples 1 and 2) were evaluated for dryness, image quality and adhesion under the following conditions and are shown in Table 1 below. (Drying property) A test pattern was printed by a desk writer C (manufactured by Hured Packer Co., Ltd.), and immediately after that, a sensory test was conducted by touching the printed surface.

Criteria for evaluation: ○: completely dry △: dry to some extent ×: it takes 3 minutes or more to completely dry (image quality) A test pattern was printed by a desk writer C (manufactured by Hured Packer) and visually observed. evaluated.

Evaluation criteria: ◯: No ink bleeding, no flow, moderate dot spread Δ: No ink bleeding, small dot spread x: Ink bleeding (adhesion) Desk writer A test pattern was printed with C (manufactured by Hured Packer), and a scratch test was performed on the printed surface with a nail.

Evaluation Criteria: ◯ ... Difficult to peel ×: Peeling immediately

[0044]

[Table 1] As shown in Table 1, in Samples 1 to 3, the ink receiving layer had high adhesiveness, excellent image quality, and a sufficient drying rate. However, in Comparative Samples 1 and 2, the adhesion of the ink receiving layer is low, a proper spread of dots cannot be obtained, and a fine line image is formed, resulting in poor image quality and insufficient drying property. there were.

[0045]

As described in detail above, according to the present invention, the ink receiving layer provided on at least one surface of the substrate sheet is formed of at least fine particles having a multilayer structure, and the fine particles are connected to each other. The surface of the ink receiving layer is covered with this to prevent cracks or embrittlement on the surface of the ink receiving layer, and the ink adhering to the ink receiving layer is adsorbed with an appropriate adsorption force, resulting in dot reproducibility. Excellent, at the same time, sufficient drying speed is obtained, and clear printed images are possible.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a recording sheet of the present invention.

[Explanation of symbols]

 1 ... Recording sheet 2 ... Substrate sheet 3 ... Primer layer 4 ... Ink receiving layer 5 ... Curling prevention layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Yoshihara 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd. No. 1 within Dai Nippon Printing Co., Ltd. (72) Inventor Kiyoshi Oguchi 1-1-1 Ichigayaka-cho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd.

Claims (4)

[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 is formed by connecting at least fine particles having a multilayer structure to each other. Is a recording sheet. 2. The recording sheet according to claim 1, wherein the ink receiving layer contains fine particles having a single layer structure. 3. The recording sheet according to claim 1, wherein the outermost layer of the multi-layered fine particles is a thermoplastic resin. 4. The recording sheet according to claim 1, wherein the multi-layered fine particles have a distribution of softening point temperatures, and the outermost layer has the lowest softening point temperature.