JP2003335044A - Ink jet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording sheet which is excellent in strength, color development or the like, has an appropriate opacity and is especially suitable of illumination service. <P>SOLUTION: The ink jet recording sheet has a substrate, an intermediate layer provided on at least one side surface of the substrate and a top layer. The intermediate layer contains a plastic pigment of a hollow state. An opacity of the substrate and the intermediate layer is 30-80% when being integrally measured. The top layer has an opacity of 5-50%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ink jet recording sheet. More specifically, the present invention relates to an inkjet recording sheet which is excellent in strength and color developability of a coating layer and which is particularly suitable for electrical decoration applications.

[0002]

2. Description of the Related Art In recent years, due to the widespread use of computers, it has become common to print out materials produced by computers using a printer or the like. As a printer used at that time,
Examples include dot impact printers, laser printers, thermal printers, inkjet printers, and the like, but inkjet printers are widely used because they have almost no mechanical noise during printout and the running cost associated with printout is low.

In this ink jet printer, minute droplets of ink are ejected from a nozzle toward a recording sheet at high speed and adhered to a recording surface to record an image or characters. In the ink jet recording sheet used for such an ink jet printer, the electric decoration use is known as one of the uses. In the case of this lighting application, since the light source is behind the printed sheet (the other side of the sheet when viewed from the observer) and the image is viewed with transmitted light, a sheet that transmits light is used. A sheet having a coating layer formed on a highly transparent plastic film is used. The plastic film is more advantageous than paper in terms of processability, water resistance, anti-curl property, etc., but is inferior in printability. Therefore, a coating layer is provided as described above for the purpose of imparting this printability. It is provided and used.

By the way, when a plastic film having high transparency is used, opacity generally tends to be insufficient. Although it is necessary to transmit light in the illumination use, a certain degree of opacity is necessary in order to obtain the image density and make the light source inconspicuous. Therefore,
Inorganic fillers such as titanium oxide have been included in the ink receiving layer, but it is not easy to obtain the required opacity by the ink receiving layer, not by the base material. Is it necessary to add a large amount of inorganic filler? , The layers need to be thick.
As a result, there have been problems that the strength of the ink receiving layer is lowered, the coloring material is hidden by the inorganic filler, and the coloring property is lowered.

[0005]

Under the circumstances, the present invention provides an ink jet recording which is excellent in the strength and color developability of the coating layer and has a suitable opacity, and is particularly suitable for lighting applications. The purpose is to provide a sheet for use.

[0006]

As a result of intensive studies to develop an ink jet recording sheet having the above-mentioned preferable properties, the present inventor has provided an intermediate layer and an upper layer on a substrate, and has an intermediate layer. It was found that the object can be achieved by containing hollow plastic pigment in the above and controlling the opacity of the base material and the intermediate layer integrally measured and the opacity of the upper layer within specific ranges. .
The present invention has been completed based on such findings.

That is, the present invention provides (1) an ink jet recording sheet having a substrate, an intermediate layer provided on at least one surface of the substrate, and an upper layer, wherein the intermediate layer is hollow. An opacity of 30 to 80% including a plastic pigment and the substrate and the intermediate layer integrally measured.
And an upper layer having an opacity of 5 to 50%, (2) a base material is a polyester film, and the intermediate layer contains a polyester resin as a binder ( The inkjet recording sheet of 1) and (3) the inkjet recording sheet of (1) above, wherein the substrate is a polypropylene film and the intermediate layer contains a styrene-acrylic copolymer resin as a binder. It is a thing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The ink jet recording sheet of the present invention comprises a substrate, an intermediate layer and an upper layer provided on at least one surface of the substrate. The base material is not particularly limited as long as it is in a sheet form, but the recording sheet of the present invention is preferably a plastic film, since it is mainly used for electrical decoration applications, and is particularly highly transparent. Is preferred. This plastic film can be appropriately selected and used from general thermoplastic resin films such as polyesters such as polyethylene terephthalate, polypropylene, vinyl chloride, polystyrene and polycarbonate.
Further, although it is poor in transparency, it is possible to use, if necessary, an inorganic powder such as calcium carbonate internally added, an organic pigment internally added, or a foamed plastic film.

Here, the foamed plastic film is
It refers to a plastic film that has cracks or defects that form on the surface or inside of the film, or fine bubbles and cavities.These bubbles and cavities are drawn by stretching a film containing inorganic powder such as calcium carbonate. Such as those generated around the inorganic powder (micro void film) or formed by foaming the foaming agent in the film containing the foaming agent, regardless of its name, formation method, or formation form of bubbles or cavities .

The plastic film referred to here includes those called synthetic paper and biodegradable plastic. The base material may have a single-layer structure or a multi-layer structure. Examples of the multi-layer structure include a method in which layers are bonded together via an adhesive, a so-called co-forming method in which a plurality of raw materials are extruded from a plurality of extruders and joined together. Any of known methods such as an extrusion method and a so-called extrusion laminating method in which a film is directly laminated on an extruding machine while being extruded from the extruder and is laminated can be used.
The thickness of these base materials is usually 10 to 400 μm,
It is preferably selected in the range of 50 to 150 μm.

When a plastic material is used as the base material, one or both surfaces of the base material may be used, if desired, for the purpose of improving the adhesion and wettability with the layer provided thereon. The surface treatment can be performed by an oxidation method, a textured method, or the like. As the oxidation method,
For example, corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, etc. may be mentioned. Further, examples of the unevenness method include a sandblast method and a solvent treatment method. The surface treatment method is appropriately selected according to the type of the base material, but in general, the corona discharge treatment method is preferably used from the viewpoint of effect and operability. Also, an easy adhesion treatment can be applied.

In the recording sheet of the present invention, an intermediate layer and an upper layer are provided on at least one surface of the base material. The intermediate layer is a layer containing a hollow plastic pigment, and the hollow plastic pigment has a porosity in the particles of 20% or more and a true spherical shape having an average particle diameter of 0.3 to 3.0 μm. The organic polymer fine particles can be preferably mentioned. Such a hollow plastic pigment has a greater effect of improving the opacity than the inorganic filler, and therefore, a smaller amount than the case of using the inorganic filler, and as a result, the proportion of the binder contained in the intermediate layer is large. Therefore, the strength of the intermediate layer itself and the adhesion strength with the base material can be improved. Further, the intermediate layer becomes softer than in the case of using the inorganic filler, which also has the effect of improving the adhesion strength with the base material. Further, when the inorganic filler is used, voids are formed to easily absorb moisture, which causes peeling of the sheet end portion due to invasion of rainwater or the like, but this can also be prevented by using the hollow plastic pigment.

If the porosity of the hollow plastic pigment is less than 20%, the above effect is not sufficiently exhibited.
A more preferable porosity is in the range of 30 to 80%. Further, if the average particle size is less than 0.3 μm, it is difficult to obtain the desired opacity, and if it exceeds 3.0 μm, unevenness may cause roughness in the coating layer. A more preferable average particle size is in the range of 0.5 to 1.5 μm. The average particle size can be measured by a laser diffraction method. Also,
The hollow plastic pigment may have a through hole that leads from the surface to the internal space.

Examples of the hollow plastic pigment include polystyrene, styrene-acrylic copolymer, polymethylmethacrylate, polyethylene, urea-
Examples thereof include organic polymer fine particles such as formalin resin, melamine-formalin resin, benzoguanamine-formalin resin, and melamine-benzoguanamine-formalin resin. Of these, styrene-acrylic copolymer fine particles are preferable from the viewpoint of performance and economy. As such a hollow plastic pigment, for example, "Rhopaque" manufactured by Rohm and Haas Co. is commercially available.

In the present invention, the hollow plastic pigments may be used alone or in combination of two or more. Further, the content of the hollow plastic pigment in the intermediate layer is 20 to 8
A range of 0% by weight is preferred. If this content is less than 20% by weight, it is difficult to obtain sufficient concealing properties, while if it exceeds 80% by weight, the interlayer strength decreases. The more preferable content of the hollow plastic pigment is 40-6.
It is in the range of 0% by weight.

In the present invention, a binder may be used for forming the layer in the intermediate layer. The binder is not particularly limited, and any known binder that has been conventionally used as a binder in the ink receiving layer can be appropriately selected and used. Examples of such a binder include polyvinyl alcohol, polyvinyl butyral, gelatin, polyvinyl acetal, carboxymethyl cellulose, polyvinylpyrrolidone, polyester resin, acrylic resin, polyurethane resin, copolymers thereof, and styrene-acrylic copolymer. Examples thereof include polymers, ethylene-vinyl acetate copolymers and styrene-butadiene rubbers. These may be used alone or in combination of two or more.

In the present invention, in particular, when a polyester film is selected as the substrate, a polyester resin is selected as the binder, and when a polypropylene film is selected as the substrate, a styrene-acrylic type binder is selected. It is preferable to use a copolymer from the viewpoint of improving the adhesion strength between the base material and the intermediate layer. In the present invention, the content of the binder in the intermediate layer is preferably 20 to 80% by weight. If the content is less than 20% by weight, the interlaminar strength may decrease, while if it exceeds 80% by weight, the content of the hollow plastic pigment becomes small and it is difficult to obtain sufficient hiding property. The more preferable content of the binder is in the range of 40 to 60% by weight.

If necessary, the intermediate layer may contain a filler other than the hollow plastic pigment for the purpose of preventing blocking. In this case, the usable filler may be either organic or inorganic particles such as calcium carbonate, talc, clay,
Particles of diatomaceous earth, aluminum hydroxide, polystyrene, polymethacrylate, titanium oxide, calcined kaolin, and the like can be used, and these may be used alone or in combination of two or more. It is important to use fillers other than these hollow plastic pigments in an amount that does not impair the effects of the present invention.

If necessary, various additives, such as an antifoaming agent, may be added to the intermediate layer as long as the effects of the present invention are not impaired.
An antistatic agent, an ultraviolet absorber, a fluorescent whitening agent, a preservative, a pigment dispersant, a thickener and the like can be contained. The thickness of the intermediate layer is preferably in the range of 5 to 40 μm. If the thickness is less than 5 μm, it is difficult to obtain the concealing property.
If it exceeds m, the strength may decrease. The more preferable thickness of the intermediate layer is in the range of 10 to 30 μm.

In the present invention, it is necessary to control the opacity of the substrate and the intermediate layer, which are measured integrally, within the range of 30 to 80%. When the opacity is less than 30%, the image density is insufficient and the light source is too conspicuous, and when it exceeds 80%, the transmitted light is insufficient, and the effect of the appearance of the electric decoration is impaired. The opacity can be adjusted by adjusting the ratio of the components and the layer thickness. The opacity in the present invention is a value measured according to JIS P8138.

In the ink jet recording sheet of the present invention, the upper layer provided on the intermediate layer generally contains a filler and a binder. The filler contained in the upper layer is not particularly limited and may be organic or inorganic particles, for example, silica, calcium carbonate, talc, clay, diatomaceous earth, aluminum hydroxide, polystyrene, polymethacrylate, Examples thereof include particles of titanium oxide and calcined kaolin, and these may be used alone or in combination of two or more.

On the other hand, the binder is not particularly limited, and any one can be appropriately selected and used from the known binders conventionally used as the binder in the ink receiving layer. Examples of such a binder include polyvinyl alcohol, polyvinyl butyral, gelatin,
Polyvinyl acetal, carboxymethyl cellulose,
Examples thereof include polyvinylpyrrolidone, polyester resin, acrylic resin, polyurethane resin, copolymers thereof, styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene rubber and the like. These may be used alone or in combination of two or more.

The upper layer in the present invention has an opacity of 5
~ 50%. When the opacity exceeds 50%, the effect of the present invention that the color is sharp when used as the front type is not sufficiently exhibited. On the other hand, it is difficult to achieve less than 5% while satisfying various characteristics. Also,
When used as a front type, in order to improve color development, it is preferable that the opacity of the base material and the intermediate layer measured integrally is higher than the opacity of the upper layer. Further, in order to improve overall color development, hiding power, image density, etc., and obtain a suitable image, the opacity is 40 to 60 when the substrate and the intermediate layer are integrally measured.
%, And the opacity of the upper layer is 30 to 50%. The opacity of the upper layer can be adjusted by adjusting the ratio of components, selecting the filler, adjusting the layer thickness, and the like. In particular, in order to reduce the opacity, it is effective to use synthetic silica having a low refractive index as a filler.

In the present invention, in the combination of the substrate, the intermediate layer and the upper layer, the substrate is a polyester film and the intermediate layer is a hollow plastic pigment made of a styrene-acrylic copolymer and a polyester resin. A layer containing a binder and an upper layer containing silica particles as a filler and a polyurethane resin as a binder has a large peel strength particularly when wet, and is preferable.

If necessary, various additives such as defoaming agents, antistatic agents, ultraviolet absorbers, optical brighteners, preservatives, and pigment dispersions are added to the upper layer as long as the effects of the present invention are not impaired. Agents, thickeners and the like can be included. The thickness of the upper layer is preferably in the range of 10 to 45 μm. If this thickness is less than 10 μm, the ink absorbency tends to be insufficient,
On the other hand, if it exceeds 45 μm, the strength tends to decrease. The more preferable thickness of the upper layer is in the range of 15 to 40 μm.

In the present invention, the intermediate layer and the upper layer can be formed, for example, by the following method. First,
A binder, a filler containing a hollow plastic pigment as an essential component, and various additives as necessary are dissolved or dispersed in a predetermined medium at predetermined ratios, respectively, to obtain a solid content concentration suitable for coating. A layer coating solution is prepared. On the other hand, a binder, a filler and, if necessary, various additives are dissolved or dispersed in a suitable medium at a predetermined ratio to prepare an upper layer coating liquid having a solid content concentration suitable for coating. .

Next, one or both surfaces of the base material are first coated with the coating solution for an intermediate layer so that the thickness after drying becomes a predetermined value, and dried to form an intermediate layer. Then, the upper layer coating liquid is applied onto the intermediate layer so that the thickness after drying becomes a predetermined value, and dried to form an upper layer. At this time, as a coating method, a known coating method such as reverse roll coating, air knife coating, gravure coating, blade coating, or the like can be used.

In the present invention, in addition to the intermediate layer and the upper layer thus provided on one side or both sides of the substrate, one or more layers may be provided within a range not impairing the effects of the present invention. For example, the intermediate layer in the present invention usually has excellent adhesion to the base material and the upper layer, and plays a role of an anchor coat layer. However, when further adhesion strength is required, the intermediate layer and the base material are separated from each other. An anchor coat layer can be provided.
In this case, the “opacity measured as a whole of the base material and the intermediate layer” in the present invention means the opacity measured integrally from the base material to the intermediate layer including the anchor coat layer.

An ultraviolet protection layer or a surface protection layer may be provided on the upper layer. In this case, the "upper layer opacity" in the present invention means the opacity obtained by integrally measuring all the layers provided at a position farther from the substrate than the intermediate layer. The anchor coat layer, an ultraviolet protection layer,
The surface protective layer or the like is prepared by dissolving or dispersing necessary components in a suitable medium to prepare a coating solution, reverse roll coating,
It can be formed by coating by a known coating method such as air knife coating, gravure coating, blade coating and drying treatment.

The ink jet recording sheet of the present invention having the above structure has the following effects. (1) For lighting purposes, you should watch the coating layer side (printed screen),
There is a method called front type, surface printing, etc., and a method called back printing in which a reverse image is printed and viewed from the opposite side (base material side). Can also be used, but more particularly when used as the front type. That is, since the opacity of the intermediate layer is high and the opacity of the upper layer is low, the coloring material in the ink that has penetrated into the upper layer is less likely to be hidden by the upper layer itself, and when used as a front type, excellent coloring properties are obtained. To be demonstrated.

(2) As a method for ensuring the opacity, it is also possible to consider a structure in which the ink receiving layer is provided on one surface of the base material and the back surface layer is provided on the opposite side, and the back surface layer has high opacity. To be On the other hand, the recording sheet of the present invention is suitable for providing the intermediate layer and the upper layer on one surface of the base material and providing the adhesive layer on the opposite surface. In particular, when a removable adhesive layer is provided, for example, when a printed sheet is used by pasting it on a board and then peeled off after the period of use, the coating layer and the adhesive remain on the board. Can be avoided.

(3) The hollow plastic pigment contained in the intermediate layer has a greater effect of improving the opacity than the inorganic filler, and therefore, the amount used can be smaller than when the inorganic filler is used. As a result, the ratio of the binder contained in the intermediate layer can be increased, so that the strength of the intermediate layer itself and the adhesion strength with the base material can be improved. Further, the softening of the intermediate layer also improves the adhesive strength as compared with the case of using the inorganic filler. These can prevent troubles such as peeling of the coating layer due to damage during handling during construction. In particular, when used as an illuminated signboard outdoors, it is possible to prevent problems such as rainwater entering and peeling off at the edge of the sheet. (4) Since the opacity is ensured by the intermediate layer, the upper layer does not need to contain a large amount of inorganic filler or be thick, and as a result, excellent print quality and strength are provided.

[0033]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The performance of the inkjet recording sheet was evaluated according to the following procedure. Also,
The print is a pigment type inkjet printer "MC
9000 ”(manufactured by Seiko Epson Corporation) and its genuine pigment type ink.

(1) Opacity of base material + intermediate layer, opacity of upper layer, opacity of entire coating layer Measured in accordance with JIS P8138. (2) Laminate film [PET laminate film "G03EV50 manufactured by Sakurai Co., Ltd.] on a test adherend having a peel strength of 25 mm when wet
C ”] with a laminator and immersed in distilled water for 24 hours, then 180 with a universal testing machine manufactured by Toyo Seiki Co., Ltd.
The peel strength when peeled in the ° direction was measured. (3) Color development Using the printer described above, a solid blue print (200%) was made with the MC drawing material paper / recommended setting as the printing mode. Place the light source on the base material side, visually observe the printing part from the coating layer side,
The vividness of the color was evaluated. (4) Adhesive strength of coating layers (upper layer and intermediate layer) Cellophane tape [CT405A manufactured by Nichiban] on the intermediate layer.
-18 ", and a length of 10 cm] were adhered by 3 reciprocations of a pressure roll of 2 kg, and the degree of peeling when peeled in the direction opposite to the angle of 45 ° was evaluated according to the following criteria. ◯: The area of the coating layer adhered to the cellophane tape is 30% or less. Δ: The area of the coating layer adhered to the cellophane tape is larger than 30% and 60% or less ×: The area of the coating layer adhered to the cellophane tape is Greater than 60% (5) Water resistance of coating layer (scratch resistance in a wet state) The surface of an inkjet recording sheet is coated with a coating layer so that the load is 0.98 N with a sufficiently wet cotton swab. It was rubbed until it was detached, and the number of times required for it was examined. It should be noted that one round trip (one way about 50 mm) was counted as one time.

Example 1 (1) Preparation of Coating Liquid for Intermediate Layer The following components were uniformly mixed to prepare a coating liquid for intermediate layer. a) Styrene-acrylic copolymer particles as a hollow plastic pigment [Rohm and Haas, trade name "Ropaque HP-91", solid content concentration 27.5% by weight, average particle size 1 μm, porosity 50% 53.6 parts by weight b) Polyester resin as a binder [TOYOBO CO., LTD.
Made by trade name "Bironard MD-1200", solid content concentration 34.0% by weight 43.4 parts by weight c) Synthetic silica particles as a filler [Mizusawa Chemical Industry Co., Ltd.]
Product name, "Mizukasil P-526", solid content concentration 10
0.0%, average particle size 3.0 μm] 3.0 parts by weight

(2) Preparation of upper layer coating liquid The following components were uniformly mixed to prepare an upper layer coating liquid. 1) Synthetic silica particles as filler [Mizusawa Chemical Industry Co., Ltd.
Product name "Mizukasil P-78F", solid content concentration 10
0.06%, average particle size 12.5 μm] 3.76 parts by weight 2) Synthetic silica particles as a filler [Fuji Silysia Chemical Ltd., trade name “Sylysia 440”, solid content concentration 1
00.0% by weight, average particle size 6.2 μm] 12.15 parts by weight 3) Polyurethane resin as a binder [Asahi Denka Kogyo Co., Ltd.]
Product name "Adekabon Titer UX-159", solid content concentration 32.0 wt% 45.52 parts by weight 4) Surfactant "Surfynol DF-110D" [Brand name, Nissin Chemical Industry Co., Ltd.] Made, solid content concentration 100.0%]
0.15 parts by weight 5) Cationizing agent "Neofix E-117" [trade name, manufactured by Nichika Chemical Co., Ltd., solid content concentration 50.0% by weight] 1
0.16 parts by weight 6) 28.26 parts by weight of water The particle sizes in the description of the coating liquids for the intermediate layer and the upper layer in Example 1 are based on the laser diffraction method (however, "Mizukasil P-526"). And "Mizukasil P-78F" by the Coulter Counter method).

(3) Preparation of Inkjet Recording Sheet Transparent polyethylene terephthalate film having a thickness of 100 μm [“Cosmoshine A-830” manufactured by Toyobo Co., Ltd.
[0]] on one surface thereof, the intermediate layer coating solution is applied and dried to form an intermediate layer so that the dried thickness is 20 μm. An inkjet recording sheet was produced by applying the above-mentioned upper layer coating solution so as to have a thickness of 25 μm and drying it to form an upper layer. The performance of this inkjet recording sheet is shown in Table 1.

Example 2 In Example 1 (1), instead of "ROPAK HP-91" as the hollow plastic pigment, "ROPAK OP-84J" [trade name, manufactured by Rohm and Haas Co., solid content concentration 42. 5% by weight, average particle size 0.5 μm,
Styrene-acrylic copolymer particles] was used in the same manner as in Example 1 except that 34.68 parts by weight was used to prepare an inkjet recording sheet. The performance of this inkjet recording sheet is shown in Table 1. Example 3 In Example 1 (1), “Acronal YJ-6” was used instead of “Vylonal MD-1200” as a binder.
221D "[trade name, manufactured by BASF Dispersion,
Solid content concentration 49.0% by weight, styrene-acrylic copolymer resin] was used in an amount of 30.08 parts by weight. Also, instead of "Cosmo Shine A-8300" as a base material, "Sun Orient PB-260" [trade name, manufactured by Nimura Chemical Co., Ltd.,
Polypropylene film] was used. Other than that, the same operation as in Example 1 was performed to produce an inkjet recording sheet. The performance of this inkjet recording sheet is shown in Table 1.

Comparative Example 1 In Example 1 (1), titanium dioxide particles [made by Ishihara Sangyo Co., Ltd., trade name “Taipaque R-780-] were used instead of the hollow plastic pigment“ Lowpaque HP-91 ”.
2 ", solid content concentration 100.0%, average particle size 0.24 μm
(Electron microscopy)] except that 16.20 parts by weight was used.
The same operation as in Example 1 was performed to produce an inkjet recording sheet. The performance of this inkjet recording sheet is shown in Table 1.

[0040]

[Table 1] In Comparative Example 1, titanium dioxide was used as a filler for the intermediate layer, but the opacity was adjusted to be the same as that of the example by increasing the content rate. As a result, the peel strength when wet,
The adhesion strength of the ink receiving layer and the water resistance of the coating layer were reduced.

[0041]

According to the present invention, by containing a hollow plastic pigment in the intermediate layer, an ink jet recording sheet excellent in strength and color developability of the coating layer and particularly suitable for electrical decoration is provided. be able to.

Claims (3)

[Claims] 1. An inkjet recording sheet having a base material and an intermediate layer and an upper layer provided on at least one surface of the base material, wherein the intermediate layer contains a hollow plastic pigment. An inkjet recording sheet, characterized in that the opacity of the intermediate layer and the intermediate layer measured together is 30 to 80%, and the opacity of the upper layer is 5 to 50%. 2. The ink jet recording sheet according to claim 1, wherein the base material is a polyester film, and the intermediate layer contains a polyester resin as a binder. 3. The substrate is a polypropylene film,
The ink jet recording sheet according to claim 1, wherein the intermediate layer contains a styrene-acrylic copolymer resin as a binder.