JPH08156397A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE: To provide an ink jet recording sheet excellent in ink receptivity, water resistance, high sharpness and transparency and in particular having no blur in a thin black printing part. CONSTITUTION: An ink jet recording sheet is formed by providing an ink receiving layer containing a polyvinyl acetal resin (A) and a polyvinyl methyl ether/ maleic anhydride copolymer (B) on at least the single surface of a plastic film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly to an ink jet recording sheet excellent in ink receiving property, water resistance, sharpness of recorded image and durability of ink receiving layer.

[0002]

2. Description of the Related Art Ink jet recording has rapidly become widespread in recent years as a recording method capable of high-speed printing and multi-color printing with less noise. As this inkjet recording material, a paper provided with a porous ink absorbing layer called ordinary paper or inkjet recording paper on a substrate is used. However, with the improvement of the performance of the ink jet type recording apparatus to enable higher-speed printing or high-resolution multicolor printing, a recording material (hereinafter sometimes referred to as “recording sheet”) ) Has come to require more advanced characteristics.

That is, an ink jet recording sheet for obtaining an image of high resolution and high quality is (1) that fixing of ink to the recording sheet is as quick as possible, and (2) even when ink dots overlap. The ink deposited later does not flow into the dots deposited before, and (3) the ink droplets diffuse to some extent on the recording material, but the diameter of the ink dot does not become larger than necessary and the desired size is obtained. To be
(4) To meet basic requirements such that the shape of the ink dot is close to a perfect circle and the circumference is smooth, (5) the OD (optical density) of the ink dot is high, and the periphery of the dot is not blurred. It is necessary to have performance.

Further, in order to obtain a high-resolution recording image quality comparable to that of a color photograph by recording with a multi-color ink jet system, the recording sheet has (6) coloring of ink coloring components in addition to the performance required for the above basic requirements. (7) The ink fixability is particularly excellent because (7) the same number of ink droplets as the number of ink colors may be adhered to the same place, and (8) on the surface. Being shiny, (9)
It is necessary to have the performance to meet the requirements such as high whiteness and (10) smooth transportation when applied to a printer.

Further, the image recorded by the ink jet recording method has been conventionally used exclusively for observing the surface image, but as the performance of the ink jet recording apparatus is improved, it can be used for purposes other than observing the surface image. become,
A recording sheet suitable for the use has been required.

[0006] Applications other than surface image observation include those used for observing recorded images on a screen or the like by an optical device such as a slide or an OHP (overhead projector) and observing those images; Examples thereof include a color separation plate when creating a plate and a CMF (color mosaic filter) used for a color display such as liquid crystal.

Since the transmitted light of the recorded image is mainly observed in the recording sheet for these uses, it is required that it has excellent translucency (light transmittance). Therefore, in addition to the general required characteristics of a conventional recording sheet for inkjet recording used for diffused light observation for surface image observation, translucency has also been required.

Various proposals have hitherto been made as an ink jet recording sheet. For example, two ink layers, a hydrophilic polymer layer and an inferior hydrophilic polymer layer, are used as the ink receiving layer.
Layer structure (Japanese Patent Laid-Open No. 62-134286)
Is proposed. As the hydrophilic polymer, polyamide, polyvinyl alcohol, polyvinylpyrrolidone,
It has been proposed to use a water-soluble resin such as carboxymethyl cellulose, but in such an ink receiving layer, it is difficult to obtain high resolution image quality due to bleeding or running of ink dots. There is also a drawback that the recording sheet has no water resistance and the image easily flows out when it is exposed to water.

As a recording sheet with the above drawbacks improved, for example, a recording sheet using a polyvinyl acetal resin in the ink receiving layer (JP-A-5-262028) is proposed. However, such a recording sheet has a drawback that the printing density is lower than that of an ink receiving layer using a hydrophilic resin. In particular, when the print density of the black print portion is low, characters or the like may be blurred and necessary information may not be transmitted.

[0010]

The object of the present invention is to solve the drawbacks of the prior art using a polyvinyl acetal resin, and to achieve excellent ink receptivity, water resistance, high clarity and transparency, especially thin black printing. An object of the present invention is to provide a recording sheet capable of multicolor printing without blurring of a portion.

[0011]

The object of the present invention is to:
According to the present invention, it can be achieved by an ink jet recording sheet in which an ink receiving layer containing (A) a polyvinyl acetal resin and (B) a polyvinyl methyl ether-maleic anhydride copolymer is provided on at least one surface of a plastic film.

[Plastic Film] In the present invention, a plastic film is used as a film substrate, but for applications requiring transparency, it is preferable to use a plastic film having good translucency, and a biaxially stretched polyester film. Is particularly preferable. For applications requiring light-shielding properties, it is preferable to use a plastic film containing an inorganic pigment, such as TiO ₂ or SiO ₂
A biaxially stretched polyester film containing a pigment such as the above is particularly preferable.

The polyester constituting the polyester film is preferably a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component, and examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate,
Examples thereof include polyethylene-2,6-naphthalate.

The above polyester may contain a film property improving agent. For example, by blending inorganic particles such as calcium carbonate, kaolin, silicon oxide, barium sulfate, etc. or crosslinked resin particles such as crosslinked polystyrene particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, etc., or used for polyester synthesis reaction. By depositing fine particles from the catalyst residue, it is possible to form fine irregularities on the film surface and improve the slipperiness and the like. Further, a compound having a sulfonate group such as sodium dodecylbenzene sulfonate can be contained as an antistatic agent. Polyesters without these modifiers can also be used.

Such a film can be manufactured by a conventionally known method. For example, in biaxially stretched polyester film, after drying polyester, it is melted by an extruder, extruded from a die (for example, T-die, I-die, etc.) onto a rotary cooling drum, and rapidly cooled to produce an unstretched film. Then, the unstretched film can be biaxially stretched and heat-set to produce the film. The thickness of the film is not particularly limited, but is preferably 5 to 250 μm.

[Ink Receiving Layer] In the present invention, (A) polyvinyl acetal resin and (B) polyvinyl methyl ether are provided on at least one surface of the plastic film.
It is necessary to provide an ink receiving layer containing a maleic anhydride copolymer.

The weight% ratio of (A) polyvinyl acetal resin and (B) polyvinyl methyl ether-maleic anhydride copolymer constituting the ink receiving layer is as follows (1).
The range shown by the formula is preferable.

[0018]

## EQU00001 ## 99.8 / 0.2.ltoreq.A / B.ltoreq.50 / 50 (1) (where A is the weight% of polyvinyl acetal resin, B
Is the weight% of the polyvinyl methyl ether-maleic anhydride copolymer. If the proportion of the polyvinyl methyl ether-maleic anhydride copolymer is less than 0.2% by weight at this ratio, the black printing density becomes insufficient, and clear character printing cannot be obtained, which is not preferable. On the other hand, when the proportion of the polyvinyl methyl ether-maleic anhydride copolymer is more than 50% by weight, the adhesiveness of the sheet is developed and the practical properties such as printer running property are remarkably deteriorated, which is not preferable.

In order to improve the above characteristics, it is more preferable that this ratio is within the range represented by the following formula (2).

[0020]

## EQU00002 ## 99 / 1.ltoreq.A / B.ltoreq.80 / 20 (2) Further, the thickness of the ink receiving layer is about 1 to 50 .mu.m,
It is preferably about 5 to 20 μm. If this thickness is too thin, the fixability (dryability) of the ink may be insufficient,
If it is too thick, handling problems such as blocking may occur, which is not preferable.

[Polyvinyl acetal resin] The polyvinyl acetal resin (A) used in the ink receiving layer in the present invention is a polymer obtained by reacting polyvinyl alcohol with an aldehyde to form an acetal. Further, it may be a polymer obtained by performing saponification and acetalization in parallel using, as a starting material, a compound in which a part or all of polyvinyl alcohol such as vinyl acetate is esterified. As an acetalization method, a conventionally known method such as a dissolution method, a precipitation method, a homogeneous method can be adopted.

The polyvinyl alcohol used as the raw material of the polyvinyl acetal resin is not particularly limited, but those having a polymerization degree of 300 to 4500, preferably 500 to 4500 are generally used, and the higher the degree of polymerization is, the ink fixing is performed. It is preferable because it has good properties and water resistance.
Further, the saponification degree of the polyvinyl alcohol component is not particularly limited, but usually 80.0 to 99.5 mol% is used, and the lower the saponification degree, the better the ink fixability. preferable.

Examples of the aldehyde used as a raw material for the polyvinyl acetal resin include aliphatic aldehydes such as formaldehyde, acetaldehyde, butyraldehyde, hexylaldehyde, octylaldehyde, decylaldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4 -Methylbenzaldehyde, other alkyl-substituted benzaldehydes, chlorbenzaldehyde, other halogen-substituted benzaldehydes, phenylacetaldehyde, β
-Aromatic aldehydes such as phenylpropionaldehyde and other phenyl-substituted alkyl aldehydes, and aromatic aldehydes having a substituent such as a hydroxy group, an alkoxy group, an amino group and a cyano group on the aromatic ring can be exemplified. . Further, it may be an aldehyde having a condensed aromatic ring such as naphthaldehyde or anthraldehyde. Among these, aromatic aldehydes are particularly preferably used because a resin having good fixability, water resistance and transparency of ink can be obtained.

The degree of acetalization of the polyvinyl acetal resin is generally in the range of 2 to 40 mol%, preferably 3 to 30 mol%, more preferably 5 to 20 mol%. If the degree of acetalization is too low, the fixability of the ink is good, but the water resistance may be poor. Conversely, if the degree of acetalization is too high, the water resistance is good, but the fixability of the ink is good. May get worse.

[Polyvinyl methyl ether-maleic anhydride copolymer] The polyvinyl methyl ether-maleic anhydride copolymer (B) used in the ink receiving layer in the present invention is a linear chain synthesized from methyl vinyl ether and maleic anhydride. It is preferable that the copolymer has a specific viscosity η _sp in the range of 1.0 to 4.0 in a 1% MEK solution (25 ° C.).

When the intrinsic viscosity η _sp is less than 1.0, the tackiness of the sheet becomes remarkably low due to the low molecular weight, which is practically inferior. On the other hand, when the intrinsic viscosity η _sp is larger than 4.0, the compatibility with the polyvinyl acetal resin is poor due to the high molecular weight, which adversely affects the preparation and coating of the coating liquid.

In order for the above characteristics to be better, it is more preferable that the intrinsic viscosity η _sp is 1.5 to 3.6.

[Other Additives] The ink receiving layer in the present invention may contain various known additives within a range not hindering the achievement of the object of the present invention. As such an additive, glycerin, ethylene glycol, polyethylene glycol for improving the adsorption performance of the ink,
Examples thereof include ultraviolet absorbers, pigment dispersants, defoamers, preservatives, pH adjusters, fillers such as silica, talc, clay and alumina.

[Ink-Receptive Layer Coating Method] In the present invention, any known coating method can be applied as a method for coating the above-mentioned ink-receptive layer, and a resin solution is used as a roll coater method, a blade coater method, or the like. After applying by the method of
Examples of the drying method include, but are not limited to, these methods.

[Adhesive Layer] In the present invention, an adhesive layer may be provided on at least one surface of the plastic film in order to enhance the adhesion between the film and the ink receiving layer. It is preferable to use, for example, a polyester resin and / or a polyurethane resin for this adhesive layer. The preferable thickness of this adhesive layer is about 0.01 to 5 μm, more preferably about 0.1 to 2 μm. When the thickness of the adhesive layer is within the above range, the adhesiveness between the plastic film and the ink receiving layer is good, and handling problems such as blocking hardly occur.

The polyester resin used for the adhesive layer is preferably a polyester resin containing a polybasic acid component and a polyol component.

Examples of the polybasic acid component include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,
Examples thereof include adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid and the like. These are 2
It can be more than one species. Examples of the polyol component include ethylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropion. Acid, glycerin,
Examples thereof include trimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol and the like. These can be two or more.

It is preferable that the polyester resin is a copolyester because the adhesion between the ink receiving layer and the plastic film is good.

The polyurethane resin used for the adhesive layer is a polyurethane resin synthesized from a hydroxy compound component and an isocyanate compound component.

Examples of the hydroxy compound component include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol and the like. As the isocyanate compound component, for example, hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate,
Examples thereof include an addition product of tolylene diisocyanate and trimethylolpropane, an addition product of hexamethylene diisocyanate and trimethylolethane, and the like.

The adhesive layer may be made of a mixture of a polyester resin and a polyurethane resin, but the use of the polyester resin or the polyurethane resin alone gives a recording sheet having good light transmission (transparency). It is preferable because it can

Lamination of the adhesive layer to the plastic film can be carried out by, for example, a method of applying a coating liquid containing a polyester resin and / or a polyurethane resin. As a coating method, any known coating method can be applied. For example, a spin coating method, a spray coating method, a bar coating method, a gravure coating method, a reverse coating method, a comma coating method or the like can be used.

[0038]

The present invention will be further described with reference to the following examples.
Each characteristic of the film was measured by the following method.

1. Print density measurement Using an inkjet printer (DeskWriter 550C, manufactured by Hewlett-Packard Co.),
Solid printing of cyan (C), magenta (M), yellow (Y), and black (BK) was performed on the receiving layer coated surface of the recording sheet, and the portion was passed through a circular aperture having a diameter of 5 mm and a Macbeth transmission densitometer ( Measured with TR-924, manufactured by Macbeth and sold by Sakata Inx Co., Ltd.

2. Ink fixability Perform solid printing on a recording sheet by the method of measuring print density, apply plain paper to the printing surface, and measure the time required until ink does not transfer to plain paper.

3. Dot reproducibility Solid printing was performed in cyan on a recording sheet by the method of measuring print density, the printed portion was magnified 200 times with a stereoscopic microscope, and the dot shape was visually determined as follows.

O: A circular dot shape is observed. △: Circular shape is maintained, but the periphery is blurred. ×… The shape is not kept circular.

4. Adhesiveness With a cutter knife on the surface of the receiving layer coating surface of the recording sheet,
Make a thin scratch and make 5 × 5 squares of 1/10 inch square, stick cellophane tape (made by Nichiban) on it so that air bubbles do not enter, and peel off vigorously. At that time, the adhesiveness is evaluated by the number of squares left on the sheet portion.

Example 1 Polyethylene terephthalate (containing a lubricant) having an intrinsic viscosity of 0.65 measured in 25 ° C. o-chlorophenol was melt extruded onto a rotary cooling drum maintained at 20 ° C. A stretched film was obtained, and then the unstretched film was stretched 3.5 times in the machine axis direction (longitudinal direction), followed by terephthalic acid (50 mol%), isophthalic acid (48 mol%), 5-Nasulfoisophthalic acid. An aqueous coating solution containing a modified polyester composed of (2 mol%) and 1,4-butanediol (100 mol%) was applied to one side of a uniaxially stretched film by a kiss coat method. The average coating amount at this time was 100 mg / solid basis.
m ² . Subsequently, the film was stretched at 105 ° C. in the transverse direction by 3.9 times and heat-treated at 220 ° C. to obtain a biaxially stretched polyester film having a thickness of 75 μm and having a primer coating layer coated on one side.

Then, a polyurethane resin paint (Nipporan 2304, manufactured by Nippon Polyurethane Co., Ltd., methyl ethyl ketone /
Toluene was diluted with 50/50 wt%) and dried by a reverse roll method to form an adhesive layer having a thickness of 1 μm.

Finally, a polyvinyl acetal resin solution (Sekisui Chemical Co., Ltd., S-REC KX-1) was applied on the adhesive layer.
Polyvinyl methyl ether-maleic anhydride copolymer (GANTREZ AN-1 manufactured by GAF Chemical Co.
69) is mixed in a ratio of 95/5 by weight of solid content, and
The coating was dried with a comma coater to form an ink receiving layer having a thickness of 5 μm.

The results obtained by printing the sheet obtained by the above method with an ink jet printer and evaluating it are shown in Table 1. As is clear from Table 1, this sheet exhibited excellent black ink print density and fixability, and also had excellent durability of the ink receiving layer.

[Example 2] A polyvinyl acetal resin solution and a polyvinyl methyl ether-maleic anhydride copolymer were mixed at a solid content ratio (weight% ratio) of 60/40 and coated and dried with a comma coater. The same procedure as in Example 1 was performed except that an ink receiving layer having a thickness of 5 μm was provided. The evaluation results of this sheet are shown in Table 1. This sheet had excellent print quality and high adhesiveness.

Comparative Example 1 A sheet was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin was applied by a comma coater alone. Table 1 shows the evaluation results of this sheet.
Shown in It was found that the print density of this sheet was low and the fixing property of the ink was also low.

[Comparative Example 2] The same procedure as in Example 1 except that the polyvinyl acetal resin solution and the polyvinyl methyl ether-maleic anhydride copolymer were mixed and coated at a solid content weight ratio of 40/60. Got a sheet at. The evaluation results of this sheet are shown in Table 1. This sheet was jammed during printing and could not be put to practical use.

[0051]

[Table 1]

[Effect of the Invention] The ink jet recording sheet of the present invention has ink receptivity, water resistance, sharpness of recorded image,
In the case of a recording sheet which is required to have transparency, the ink receiving layer has excellent durability and is particularly free from blurring in a thin black printed portion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C08J 7/04 CEX H C08L 29/14 LHA

Claims (3)

[Claims] 1. An ink jet recording sheet comprising a plastic film and an ink receiving layer containing (A) a polyvinyl acetal resin and (B) a polyvinyl methyl ether-maleic anhydride copolymer on at least one surface of the plastic film. 2. The ink jet recording according to claim 1, wherein the weight% ratio of (A) polyvinyl acetal resin to (B) polyvinyl methyl ether-maleic anhydride copolymer is 99.8: 0.2 to 50:50. Sheet. 3. The ink jet recording sheet according to claim 1, wherein the plastic film is a polyester film.