JP3349803B2 - Inkjet recording sheet - Google Patents

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 on which an image is formed by an ink jet printer. More specifically, the present invention relates to an ink jet recording sheet having high gloss and image density, and having excellent color reproducibility, ink absorption and blocking resistance.

[0002]

2. Description of the Related Art In an ink jet recording system, fine droplets of ink are made to fly and adhere to a recording sheet such as paper according to various operating principles, thereby recording images and characters. Inkjet printers have features such as high-speed printing, low noise, great flexibility in recording patterns, and no need for development and fixing, and can form complex images accurately and quickly. In recent years, it has been rapidly popularized in various applications as a hard copy creation device for image information such as characters and various figures created by a computer.

In the ink jet recording system, multicolor recording can be easily performed by using a plurality of ink nozzles. In the multi-color inkjet recording method,
Compared with multicolor printed matter and color photographs, it is possible to obtain an image comparable to that of multicolor printed matter, and in applications where the number of copies is small, it is becoming cheaper than printing technology and photographic technology, and is therefore being widely used.

Recently, the fields of application of ink-jet printers, which have attracted particular attention, include the production of color proofs in the printing field, which requires high image quality close to photographs, and the output of design images in the design field. Furthermore, it is also common practice to output character and image information created by a computer to a transparent recording sheet using an ink jet printer, and to use this as a document of an overhead projector for a presentation at a meeting or the like.

[0005] The characteristics required of the recording sheet used in such an ink jet recording system include high gloss of the surface of the ink receiving layer, high image density, good color reproducibility, and ink absorption. Is high, and the blocking resistance is good.

Conventionally known techniques include, for example,
No. 61-60793, Japanese Unexamined Patent Publication No. Hei 3-215081, etc., silica,
There is disclosed an ink jet recording sheet having an ink receiving layer comprising an inorganic pigment such as colloidal silica, alumina sol, and calcium carbonate, and a water-soluble binder such as oxidized starch, polyvinyl alcohol, carboxymethyl cellulose, and polyacrylic acid. However, the above-mentioned ink jet recording sheet has gloss, image density,
Color reproducibility, ink absorbency and blocking resistance were not always at satisfactory levels.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording sheet having high gloss and image density, which is impossible with the prior art, and excellent in color reproducibility, ink absorption and blocking resistance. To provide.

[0008]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a mixture of gelatin having a specific range of surface pH and a water-soluble cellulose derivative is mainly used. It has been found that the provision of an ink receiving layer provides an ink jet recording sheet having high gloss and printing density, and excellent in color reproducibility, ink absorption and blocking resistance, and has completed the present invention.

That is, in the ink jet recording sheet of the present invention, the ink receiving layer mainly comprises a mixture of gelatin and a water-soluble cellulose derivative and a pH buffer.
Wherein the agent is an inorganic salt and the surface pH of the ink receiving layer is from 4.0 to 8.0.

[0010]

In the present invention, as the support, paper, film, metal foil, synthetic paper, cloth, non-woven fabric or a composite thereof can be used, but resin-coated paper is preferred in view of image quality, gloss, smoothness and the like. And the use of films. The thickness of the support is not particularly limited, but is preferably about 50 to 300 μm from the viewpoint of handling properties and suitability for paper passing of the printer.

Before the ink receiving layer is provided on the support, an undercoat layer may be provided to improve the coating property of the ink receiving layer coating liquid. Pigments, various water-soluble polymers, latex, hardeners, surfactants and the like can be added to such an undercoat layer in an appropriate combination.

In the present invention, the ink receiving layer is preferably composed mainly of a mixture of gelatin and a water-soluble cellulose derivative in order to obtain high transparency and ink absorbability. For example, as gelatin, lime-treated gelatin, acid-treated gelatin, enzyme-treated gelatin, phthalated gelatin,
Examples of water-soluble cellulose derivatives such as maleated gelatin and fumarated gelatin include carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, viscose and the like. The weight ratio of gelatin to the water-soluble cellulose derivative in the ink receiving layer is from 10:90 to 9
A range of 0:10 is preferred. When the weight ratio of gelatin to the water-soluble cellulose derivative is smaller than 10:90,
This is not preferable because the image density decreases. Also, 90: 1
If the value is larger than 0, the ink absorbency decreases, which is not preferable.

The ink receiving layer contains, in addition to gelatin and a water-soluble cellulose derivative, transparent pigments such as silica, colloidal silica, alumina sol, silicon resin fine particles, polystyrene resin fine particles and starch particles, polyvinyl alcohol, starch, polyvinyl pyrrolidone, Polyvinylpyridinium halide, sodium polyacrylate, polyethylene glycol, polypropylene glycol, polyvinyl ether, alkyl vinyl ether / maleic acid copolymer,
Styrene / maleic acid copolymer, polyacrylamide,
Polyethylene imine, melamine resin, urea resin, water-soluble resin such as polyamide resin, anionic, cationic, nonionic, amphoteric surfactants, active halogen compounds,
Hardening agents such as vinylsulfone compounds, aziridine compounds, epoxy compounds, acryloyl compounds, and isocyanate compounds, preservatives, dyes, fluorescent agents, ultraviolet absorbers, antioxidants, antiblocking agents, antifoaming agents, etc. are appropriately combined and added. can do.

In the present invention, the surface pH of the ink receiving layer
Is preferably 4.0 to 8.0. The surface pH of the ink receiving layer can be determined by dropping pure water onto the ink receiving layer and measuring the pH of the dropped pure water using a surface pH meter or a pH indicator after a certain period of time. When the surface pH of the ink receiving layer is lower than 4.0, the hue of the ink changes, which is not preferable. Further, the surface pH is 8.0.
If it is higher, it becomes difficult to make the gelatin water resistant,
It is not preferable because the water resistance of the ink receiving layer decreases.

The surface pH of the ink receiving layer can be adjusted by adjusting the amount of an acidic material and a basic material contained in the ink receiving layer, by using an acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, sodium hydroxide, or potassium hydroxide. , Ammonia, triethanolamine and the like can be adjusted.

Further, by adding a material having a pH buffering action to the ink receiving layer, a change in pH over time or a change in pH when printing with a high pH ink can be suppressed. Can be enhanced.

Sodium bicarbonate as a pH buffer;
Sodium carbonate, potassium phosphate, potassium dihydrogen phosphate,
Examples thereof include inorganic salts such as dipotassium hydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium borate, and ammonium chloride.

The dry coating amount of the ink receiving layer is 1
It is preferably 50 g / m ² . When the coating amount of the ink receiving layer is less than 1 g / m ² , the ink absorbency is poor, so that the ink overflows from the ink receiving layer after printing, and the image is likely to be contaminated by color mixing or rubbing. Also, 5
If it exceeds 0 g / m ² , problems such as coloring of the ink receiving layer and curling of the recording sheet occur.

In the present invention, the ink receiving layer is coated on the support by a general coating device such as a rod, a wire bar, a slide hopper, a curtain, an extrusion die, an air knife, a roll, and a blade.
Use of a slide hopper is preferred because a very smooth coating surface like a mirror can be obtained.

The ink receiving layer may be a single layer or a multilayer of two or more layers. In the case of a multilayer, each layer can have a different composition or the same composition. When a multilayer is formed, two or more layers may be applied at a time or one layer at a time.

The ink receiving layer is provided on at least one side of the support, but may be provided on both sides of the support for the purpose of performing double-sided printing or preventing curling.

In the present invention, a backing layer can be provided on the side of the support opposite to the ink receiving layer in order to impart antistatic properties, transport properties, curl preventing properties, and the like. To such a backing layer, an inorganic or organic antistatic agent, a water-soluble binder, a synthetic resin latex, a hardener, a pigment, a surfactant and the like can be appropriately combined and added.

Such a backing layer is applied on a support by a general coating apparatus such as a rod, a wire bar, a slide hopper, a curtain, an extrusion die, an air knife, a roll, and a blade.

[0025]

According to the present invention, by providing an ink receiving layer mainly composed of a mixture of gelatin and a water-soluble cellulose derivative having a surface pH of 4.0 to 8.0, high gloss can be obtained and the ink receiving layer Since the transparency is high, the print density is high, and there is no change in the hue of the ink, so that an ink jet recording sheet having good color reproducibility, good ink absorbency and good water resistance can be obtained.

[0026]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the contents of the present invention are not limited to these examples.

Example 1 A resin composition comprising 85 parts by weight of low-density polyethylene and 15 parts by weight of titanium dioxide after subjecting a surface of a high-quality paper made of LBKP having a basis weight of 100 g / m ² to a corona discharge treatment, by a melt extrusion method. was 16g / m ² coating was subjected to corona discharge treatment on the reverse side, high-density polyethylene 60 parts by weight and the low-density polyethylene 40 parts by weight of resin composition 16
g / m ^{2 was} applied to prepare a resin-coated paper support.

[0028]

[0029]

[0030]

[0031]

[0032]

A corona discharge treatment is applied to the surface of the resin-coated paper.
After the application, a coating amount of the ink receiving layer having a solid content concentration of 10% having the following composition and a dry coating amount of 7 g / m 2 was applied using a slide hopper.
^The resultant was coated and dried to obtain an ink jet recording sheet. Make this ink receiving sheet 8 × 15mm
Cut, Horiba Seisakusho C-1 CARDYCOMPAC
T pH METER to adjust the surface pH of the ink receiving layer
It was 4.2 when measured . <Ink receiving layer coating liquid formulation 1 > Gelatin 50 parts by weight Hydroxyethyl cellulose 50 parts by weight Colloidal silica 10 parts by weight Octyl sulfosuccinate 0.1 parts by weight Ammonium chloride 0.2 parts by weight

[0034]

[0035]

COMPARATIVE EXAMPLE 1 In the same manner as in Example 1, an ink receiving layer coating liquid having a solid content of 10% was applied onto the support of Example 1 so that the dry coating amount was 7 g / m ² . It dried and the inkjet recording sheet was produced. The surface pH of this ink receiving layer was measured in the same manner as in Example 1, and it was 3.7. <Ink receiving layer coating liquid formulation 2 > Gelatin 50 parts by weight Carboxymethyl cellulose 50 parts by weight Octyl sulfosuccinate 0.1 part by weight Hydrochloric acid 0.1 part by weight

COMPARATIVE EXAMPLE 2 On the support of Example 1, a coating liquid of an ink receiving layer having a solid content of 10% having the following composition was applied in the same manner as in Example 1 so that the dry coating amount was 7 g / m ² . It dried and the inkjet recording sheet was produced. When the surface pH of this ink receiving layer was measured in the same manner as in Example 1, it was 8.3. <Ink receiving layer coating liquid formulation 3 > Gelatin 50 parts by weight Carboxymethyl cellulose 50 parts by weight Octyl sulfosuccinate 0.1 part by weight Sodium hydroxide 0.1 part by weight

Comparative Example 3 An ink receiving layer coating liquid having a solid content of 10% and having the following composition was applied to the support of Example 1 in the same manner as in Example 1 so that the dry coating amount was 7 g / m ² . It dried and the inkjet recording sheet was produced. The surface pH of this ink receiving layer was measured in the same manner as in Example 1, and was 6.8. <Ink receiving layer coating solution formulation 4 > Carboxymethyl cellulose 100 parts by weight Sulfosuccinic acid octyl ester 0.1 part by weight

Comparative Example 4 On the support of Example 1, a coating solution of the ink receiving layer having the following composition and having a solid content of 10% was applied in the same manner as in Example 1 so that the dry coating amount was 7 g / m ² . It dried and the inkjet recording sheet was produced. The surface pH of this ink receiving layer was measured in the same manner as in Example 1, and it was 4.7. <Ink receiving layer coating liquid formulation 5 > Gelatin 100 parts by weight Sulfosuccinic acid octyl ester 0.1 parts by weight

The following items were evaluated for these ink jet recording sheets, and the results are shown in Table 1.

[Gloss] The gloss of the surface of the ink jet recording sheet was measured according to the method specified in JIS-P8142.

[Image Density] HEWLETT PACKA
Printing was performed using a Desk Writer 550C printer manufactured by RD Co., Ltd., and the optical density of a 100% printed portion of magenta was measured by a Macbeth RD-914 reflection densitometer.

[Color Reproducibility] HEWLETT PACKKA
An image of a person is printed using a Desk Writer 550C printer manufactured by RD Co., Ltd., and the reproducibility of skin color is visually observed. ○: Good color reproducibility, Δ: Slightly poor color reproducibility, but practical limit. X: The color reproducibility was poor and it was not practically used.

[Ink Absorption] HEWLETT PAC
Printing was performed using a Desk Writer 550C printer manufactured by KARD, and the state of ink overflow in the magenta 100% printed area was visually observed. ○: no ink overflow was observed, Δ: slight ink overflow was observed, but practical The limit is ×, ink overflow is so bad that it is not practical.
Was evaluated in three steps.

[Blocking resistance] 30 ° C., 85% RH
Under the above conditions, the surface of the ink-jet image-receiving paper was touched with a finger to measure the anti-blocking property (anti-sticking property). ：: No blocking was observed, Δ: Some blocking was observed, but it was a practical limit. The evaluation was made in three steps: blocking was remarkable, and it was not practical.

[0046]

[Table 1]

As is clear from the results in Table 1, the ink jet recording sheet of Example 1 according to the present invention had high gloss, high image density, and excellent color reproducibility, ink absorption and blocking resistance. However, in the ink jet recording sheet of Comparative Example 1, since the surface pH of the ink receiving layer was lower than 4.0, the color reproducibility was poor. In the inkjet recording sheet of Comparative Example 2, since the surface pH was higher than 8.0, the water resistance of the ink receiving layer was reduced, and the blocking resistance was reduced. In the ink jet recording sheet of Comparative Example 3, since the composition of the ink receiving layer was carboxymethyl cellulose alone, the image density was reduced. In the ink jet recording sheet of Comparative Example 4, since the composition of the ink receiving layer was solely gelatin, the ink absorbency was reduced.

[0048]

According to the present invention, an ink jet recording sheet having high gloss and image density, and excellent in color reproducibility, ink absorption and blocking resistance can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-89391 (JP, A) JP-A-1-146784 (JP, A) JP-A 2-1359 (JP, A) Table 8- 503903 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/00

Claims (1)

(57) [Claims] 1. An ink jet recording sheet having an ink receiving layer provided on a support, wherein the ink receiving layer is mainly composed of a mixture of gelatin and a water-soluble cellulose derivative and a pH value.
An ink jet recording sheet comprising a buffer , wherein the pH buffer is an inorganic salt, and the surface pH of the ink receiving layer is 4.0 to 8.0.