JPH09272257A - Sheet for ink-jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet for ink-jet recording in which printability such as ink acceptability, drying properties, fixation properties and reproducibility of a dot is excellent and also film strength and water resistance of an ink acceptance layer are excellent and clarity of the ink acceptance layer is remarkably improved. SOLUTION: An ink acceptance layer is formed at least on one side of a base material sheet. The ink acceptance layer contains (a) aluminum oxide fine particles having γ type crystal form of <=200nm average particle diameter and (b) noncrystalline silica fine particle which are bonded by a binder consisting of water-soluble cellulose ether etherified by a methoxyl group and a hydroxylpropyl group.

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 specifically, an ink jet recording having an ink receiving layer (image receiving layer) capable of recording with an ink jet printer formed on at least one surface of a base material sheet. For seats.

[0002]

2. Description of the Related Art In ink jet recording, ink is ejected from a nozzle to form minute droplets, which are attached to a base material such as paper as pixels in accordance with an electric input signal to form characters,
This is a recording method for forming figures, image patterns, and the like, and has features such as low noise, high resolution, and high-speed recording. An inkjet printer for inkjet recording only needs to include a printer head and an ink cartridge as components necessary for printing, and does not require a heating roller or a photosensitive drum for fixing ink.
Inkjet printers are small and inexpensive, and can easily print out color images simply by adding heads. Inkjet recording is used for printing on personal computers, word processors, etc. because of these excellent features.
Recently, application to various output devices such as a copying machine, a facsimile, and a plotter has been attempted. Further, the recording medium in inkjet recording is not limited to paper,
Cloth, glass and plastic are also being considered.

In recent years, as one of the fields of application of the ink jet recording system, an overhead projector (OH
The base paper for P) is receiving attention. That is, since inkjet recording can obtain a clear picture and can easily perform color printing (multicoloring), it is expected to be applied to a transparent synthetic resin sheet and used as an OHP base paper. There is. OHP is used for various conferences, academic conferences, lectures, briefing sessions, product advertisements, etc., but this requires recording on a transparent synthetic resin sheet. However, O
A polyester sheet or the like used for HP base paper has a problem that it is difficult to receive ink for inkjet recording.

In the ink jet printer, in order to prevent the viscosity of the ink from increasing due to the drying of the ink in the jet nozzle portion and causing ejection failure, ink that is difficult to dry is used. Inkjet inks are generally
Since a water-soluble dye, a binder, an additive, etc. are dissolved in water, the drying and fixing of the ink will be poor on the hydrophobic synthetic resin sheet. In order to perform printing with an inkjet printer, it is necessary to use a recording sheet having a function of rapidly absorbing the moisture of the ink and drying and solidifying it. Therefore, conventionally, OHP
In the field of (1), a transparent synthetic resin sheet having an ink receiving layer showing rapid water absorption formed on the surface is used as an inkjet recording sheet.

As a recording sheet for OHP suitable for ink jet ink, on a transparent synthetic resin sheet,
It is required that an ink receiving layer having the following characteristics be formed. It has excellent ink receptivity, absorption and drying properties, and fixing properties, has high transparency, does not cause blocking between sheets even when stored in a laminated state, and can express the edges of images sharply. The ink dots should have a suitable spread, should not have excessive bleeding, the color of the ink should be clear and should not be discolored, and it should not be sticky or have fingerprints on it.

Conventionally, in order to achieve these objects, for example, (1) an ink jet recording sheet having an ink receiving layer containing polyvinylpyrrolidone provided on the surface of a transparent support (JP-A-61-32788). Issue),
(2) Recording sheet in which a transparent layer made of colloidal silica and a water-soluble resin such as polyvinyl alcohol or gelatin is provided on a transparent support (JP-A-61-19389), (3) Transparent support On the body, average particle size 1-100
A recording sheet provided with a thin film of a water-soluble polymer containing ultrafine particles of mμ and fine particles having an average particle size of 1 to 20μ (JP-A-61-61)
-280983), (4) on a transparent film,
Film for overhead projector in which glass beads or micro beads made of crosslinked polystyrene, polystyrene, acrylic resin and the like having a particle size of 5 to 50 μm are applied by using a transparent adhesive or a transparent adhesive containing a super absorbent polymer. (Japanese Patent Laid-Open No. 61-24494) and the like have been proposed.

However, a swelling recording sheet having a water-soluble polymer such as polyvinylpyrrolidone or polyvinyl alcohol as an ink receiving layer has an insufficient ink fixing ability, and therefore the image is sharp due to a change with time after printing. Has the drawback that In addition, the swellable recording sheet has tackiness due to moisture absorption, and the handleability such as blocking decreases. A water-absorbent recording sheet with a porous ink-receptive layer containing a water-soluble polymer as a binder and a high proportion of an inorganic filler such as colloidal silica or alumina has poor transparency or the receiving layer is fragile. It has the drawback of being fragile. The ink receiving layer consisting of synthetic resin microbeads bonded and fixed with a binder made of a water-soluble polymer has good ink absorbability, but has poor ink fixability and has a lot of bleeding, and the receiving layer is fragile and easily cracked. There is a drawback that.

[0008]

An object of the present invention is to provide an ink jet recording sheet having an ink receiving layer formed on at least one side of a substrate sheet, which has ink receiving property, drying property, fixing property and dot reproduction. It is an object of the present invention to provide an ink jet recording sheet which is excellent in printability such as properties, is excellent in film strength and water resistance of the ink receiving layer, and is significantly improved in transparency of the ink receiving layer. We have
In the course of research on the ink receiving layer based on the ink absorbing type inorganic fine particles, it was bound to at least one surface of the substrate sheet by a binder composed of a water-soluble cellulose ether etherified with a methoxyl group and a hydroxylpropoxyl group. It was found that an ink jet recording sheet having excellent properties can be obtained by forming an ink receiving layer containing γ type crystal form aluminum oxide fine particles having an average particle diameter of 200 nm or less.
We filed a patent application (Japanese Patent Application No. 7-219890).
After that, as a result of research for further improvement, as inorganic fine particles, in addition to γ-type crystal form aluminum oxide fine particles, by using amorphous silica fine particles in combination,
It has been found that the transparency of the ink receiving layer is further enhanced.

The amorphous silica fine particles are preferably those having an average particle diameter of 200 nm or less obtained by pulverizing secondary agglomerates of primary particles having an average particle diameter of 20 nm or less. Also,
The γ-type crystal form of aluminum oxide fine particles and amorphous silica fine particles have an average particle diameter of 2 when a mixture of these secondary aggregates is used.
It is preferable to use as mixed inorganic fine particles obtained by pulverizing to a particle size of 00 nm or less. The reason why transparency is improved by adding amorphous silica particles is not always clear, but in polar media such as water, γ-type aluminum oxide particles are positively charged and amorphous silica particles are negatively charged. Therefore, it is presumed that the two attract each other by the electrostatic charge interaction and the voids between the particles become small. The present invention has been completed based on these findings.

[0010]

According to the present invention, at least one surface of a substrate sheet is bound with a binder comprising a water-soluble cellulose ether etherified with a methoxyl group and a hydroxylpropoxyl group (a).
Provided is an ink jet recording sheet, which is characterized in that an ink receiving layer is formed which contains γ-type crystal form aluminum oxide fine particles having an average particle diameter of 200 nm or less and (b) amorphous silica fine particles.

According to the present invention, the following embodiments are provided. 1. (B) The amorphous silica fine particles have an average particle diameter of 20 nm.
The above-mentioned ink jet recording sheet having an average particle diameter of 200 nm or less obtained by pulverizing the following secondary agglomerates of primary particles. 2. The content ratio of (a) γ-type crystal form aluminum oxide fine particles and (b) amorphous silica fine particles is 80 to 99% by weight of (a) γ-type crystal form aluminum oxide fine particles.
And (b) the inkjet recording sheet, wherein the amorphous silica is 1 to 20% by weight. 3. (A) γ-type crystal form aluminum oxide fine particles and (b) amorphous silica fine particles are mixed inorganic fine particles obtained by pulverizing a mixture of these secondary aggregates until the average particle diameter becomes 200 nm or less. The above-mentioned inkjet recording sheet. 4. (A) γ-type crystal form aluminum oxide fine particles and (b) amorphous silica fine particles are dispersed in water to obtain a secondary aggregate mixture, and the mixture is averaged by a pulverizing means such as an ultrasonic homogenizer or a high-pressure homogenizer. The above-mentioned inkjet recording sheet, which is mixed inorganic fine particles obtained by pulverizing to a particle diameter of 200 nm or less. 5. Water-soluble cellulose ether has a methoxyl group 19-
The solution viscosity of a 2% aqueous solution (20 ° C.) which is etherified at a ratio of 30% and a hydroxyl propoxyl group of 4 to 12% and measured by a torsional vibration type viscometer is 2,000 mPa ·
The above inkjet recording sheet having a thickness of s or more. 6. The ink jet recording sheet as described above, wherein the ink receiving layer is cross-linked by a cross-linking agent having reactivity with a hydroxyl group of water-soluble cellulose ether.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Base Material Sheet The base material sheet used in the present invention is preferably one made of a synthetic resin having transparency, heat resistance, dimensional stability, rigidity and the like. Polyethylene terephthalate), cellulose triacetate, polycarbonate, polyvinyl chloride, polystyrene, polypropylene, polyimide and the like (including films) can be mentioned. The thickness of the base sheet is usually about 50 to 250 μm. Among these, a stretched polyethylene terephthalate film having a thickness of 75 to 180 μm is particularly preferable. The base sheet is usually
It is preferably colorless and transparent, but may be colored and transparent, and if it is not limited to OHP, a paper substrate such as synthetic paper or coated paper, or a colored or white synthetic resin sheet having poor transparency may be used. It can also be used. If desired, a glass plate can also be used as the base sheet. If necessary, a primer layer may be provided on the base sheet in order to improve the adhesiveness, or after performing corona discharge machining, an ink receiving layer may be formed thereon.
The ink receiving layer is usually formed on one side of the substrate sheet, but may be formed on both sides if desired. By providing an ink receiving layer on both sides of the base sheet, a curl preventing effect can be obtained. An ink receiving layer is formed on one side of the base sheet,
An anti-curl layer made of another material may be provided on the opposite surface.

Aluminum Oxide Fine Particles In the present invention, γ type crystal form aluminum oxide fine particles having an average particle diameter of 200 nm or less are used as a main component of the ink receiving layer. Aluminum oxide has various crystal forms, and can be roughly classified into two crystal forms, which are thermodynamically stable α-form and unstable γ-form. What is used in the present invention are fine particles having a γ-type crystal form. The γ type can be further divided into a γ group and a δ group when crystallographically classified, but fine particles having a crystal form of the δ group are preferable. The γ-type crystal form of aluminum oxide can be reduced to an average particle size of primary particles of about 10 nm, but in general, the primary particles form a secondary agglomerated form to form a few thousands to tens of thousands nm. The particle size becomes large. When aluminum oxide particles having such a large particle size are used, the printability of the ink receiving layer is good,
It lacks transparency.

In order to obtain aluminum oxide fine particles having an average particle diameter of 200 nm or less, γ in the secondary aggregation form is usually used.
The average particle size of the aluminum oxide particles in the form of crystal is 200 nm or less, preferably 1 by a pulverizing means such as a bead mill, an ultrasonic homogenizer, or a high-pressure homogenizer.
The particles are pulverized to ultrafine particles of 50 nm or less, more preferably 80 to 120 nm. Average particle size is 200 nm
If it exceeds, the transparency of the ink receiving layer is lowered. As the pulverizing means, a pulverizing method using an ultrasonic homogenizer or a high-pressure homogenizer is preferable, and in other pulverizing methods such as a bead mill, since the aluminum oxide in the γ-type crystal form is a hard crystal, a contaminant from the pulverizing container is used. Easily enters, which causes a decrease in transparency. The γ-type crystal form aluminum oxide fine particles are excellent in printability such as ink absorbency, drying property and fixing property, and by making them ultrafine particles, even if they are contained in a high ratio in the ink receiving layer, they are transparent. It is possible to obtain a recording sheet having excellent properties.

Amorphous Silica Fine Particles In the present invention, amorphous silica fine particles are used in combination with γ-type crystal form aluminum oxide fine particles. The particles of amorphous silica have a primary particle diameter of 20 nm or less, and further 5 to 15 n.
It is possible to make it as small as m, but normally,
The primary particles do not exist alone, but form secondary particles (secondary aggregates) having a fluffy network structure and having a particle size of several μm. This secondary agglomerate has a large specific surface area of 100 to 400 m ² / g according to the BET method. In the present invention, amorphous silica fine particles are used from the viewpoint of transparency. In order to obtain amorphous silica fine particles, the average particle size of the secondary aggregate particles is 200 nm or less, preferably 150 nm or less, more preferably 80 to 120.
Grind until it becomes ultrafine particles of about nm. As the crushing means, a crushing method using an ultrasonic homogenizer, a high-pressure homogenizer, or the like is preferable.

Milling of the secondary agglomerates of amorphous silica particles
It may be carried out alone, but if the amorphous silica particles are made into fine particles by themselves and then the pulverized liquid is mixed with γ-type aluminum oxide pulverized liquid, the mixing of both is poor and stable and good results are obtained. Is difficult. Therefore, the secondary agglomerates of γ-type aluminum oxide particles and the secondary agglomerates of amorphous silica particles are dispersed in ion-exchanged water, and the mixture of these secondary agglomerates is pulverized by an ultrasonic homogenizer or a high-pressure homogenizer. The average particle size of both is 200 nm or less, preferably 150 nm or less, more preferably 80 to
It is preferable to pulverize to 120 nm.

The finer the average particle size of these inorganic fine particles, the more the transparency tends to be improved, and in order to obtain high transparency, it is preferable to grind the average particle size to 80 to 120 nm. The transparency is improved in proportion to the amount of the amorphous silica fine particles, but the solution viscosity of the dispersion liquid sharply increases, and thus the coatability is deteriorated. Therefore, in consideration of the transparency improving effect and the coating property, the mixing ratio of the γ-type crystal form aluminum oxide fine particles and the amorphous silica fine particles is preferably 80-99. weight%,
It is more preferable that the content is 85 to 95% by weight, and the ratio of the amorphous silica fine particles is preferably 1 to 20% by weight, and more preferably 5 to 15% by weight.

It is presumed that the reason why the transparency is improved by the addition of the amorphous silica fine particles is that the electrostatic charge interaction between the two attracts each other to reduce the voids in the ink receiving layer. Ultrafine particles obtained by mixing and pulverizing amorphous silica fine particles with aluminum oxide fine particles are fixed with a water-soluble cellulose ether binder, and the ink receiving layer has ink absorbability, ink drying property, fixability, and other printability. Is excellent, and the addition of hydrophilic amorphous silica fine particles tends to further improve transparency. The smaller the average particle size of the primary particles of the hydrophilic amorphous silica fine particles, the more the transparency tends to improve, and the average particle size is preferably 20 nm or less, more preferably 5 to 15 nm. Therefore, from the viewpoint of transparency, the average particle diameter 2 obtained by pulverizing the secondary aggregate of the amorphous silica particles having the average primary particle diameter of 20 nm or less is 2
Amorphous silica fine particles of 00 nm or less are particularly preferable.

In order to use a mixture of finely pulverized γ-type crystal form aluminum oxide fine particles and amorphous silica fine particles of the water-soluble cellulose ether as an ink receiving layer, it is important to select a binder having a good film-forming property. is there. When polysodium acrylate, polyvinylpyrrolidone, starch, or a derivative thereof, which has been generally used as a binder, is used, the film-forming property is poor, cracking occurs, or the transparency is significantly reduced, It is not possible to obtain the desired transparent ink receiving layer. In the present invention, by using a specific grade of water-soluble cellulose ether, an ink receiving layer having good film-forming property, transparency and printability is formed.

That is, in the present invention, a water-soluble cellulose ether etherified with a methoxyl group and a hydroxylpropoxyl group is used as a binder. There are many types of water-soluble cellulose ethers, such as viscosity grades that correlate with the type and substitution ratio of ether substituents, and molecular weight, but the average particle size is 200 nm.
As a binder for a mixture of the following γ-type crystal form aluminum oxide fine particles and amorphous silica fine particles, a water-soluble cellulose ether etherified with a methoxyl group and a hydroxylpropoxyl group exhibits excellent properties.

The proportion of methoxyl groups is usually 15-35.
%, Preferably 19-30%, the proportion of hydroxylpropoxyl groups is usually 2-20%, preferably 4-1.
2%. The water-soluble cellulose ether used in the present invention has a solution viscosity (20 ° C.) of a 2% by weight aqueous solution of 2,000.
A relatively high molecular weight of 0 mPa · s or more is particularly preferable from the viewpoint of film forming property. Even water-soluble cellulose ethers etherified with other substituents have poor film-forming properties and cannot form a good ink-receiving layer.

Ink-Receptive Layer The ink-receptive layer of the present invention is a water-soluble material obtained by etherifying mixed inorganic fine particles containing γ-type crystal form aluminum oxide fine particles and amorphous silica fine particles with a methoxyl group and a hydroxylpropoxyl group. It is fixed to a base sheet with a binder composed of a soluble cellulose ether.
The mixing ratio of the water-soluble cellulose ether to the mixed inorganic fine particles of γ-type crystal form aluminum oxide and amorphous silica is preferably 85 to 97% by weight of the mixed inorganic fine particles and 3 to 15% by weight of the water-soluble cellulose ether. . If the proportion of the water-soluble cellulose ether is too large, the printability will be deteriorated, and if it is too small, the coating strength will be weak, and thus both are not preferable. In the range not impairing the object of the present invention, together with the specific water-soluble cellulose ether,
A general-purpose binder may be used together in a small amount.

The ink receiving layer using the mixed inorganic fine particles of γ-type crystal form aluminum oxide and hydrophilic amorphous silica of the present invention and the water-soluble cellulose ether is a water-soluble polymer such as polyvinyl alcohol or polyvinylpyrrolidone. Although it has excellent water resistance as compared with the ink receiving layer containing as a main component, the water resistance can be further improved by adding a crosslinking agent capable of reacting with the residual hydroxyl group of the water-soluble cellulose ether. Examples of the crosslinking agent include melamine / formaldehyde resin, polyamide resin, epoxy resin, dialdehyde starch and the like.
The use ratio of the cross-linking agent can be appropriately determined depending on the kind of the cross-linking agent, the desired degree of cross-linking, etc., but is usually 1 to 20 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the water-soluble cellulose ether. Parts by weight. In addition, this cross-linked system has a high saponification degree (95% or more) at a ratio of 5% by weight or less.
When polyvinyl alcohol is used in combination, the water resistance improving effect becomes more remarkable. However, as the amount of polyvinyl alcohol added increases, the transparency tends to slightly decrease. Therefore, in applications where high transparency is required, it is preferable to keep the addition amount to the minimum necessary.

In order to form the ink receiving layer, an aqueous dispersion in which each component is dispersed or dissolved is prepared, and this is applied to at least one side of the base sheet. As a preferred method for preparing the aqueous dispersion (coating solution), first, an aqueous dispersion of mixed particles (secondary aggregates) of aluminum oxide in the γ-type crystal form and hydrophilic amorphous silica is prepared, and this solution is prepared. Is pulverized and stirred by an ultrasonic homogenizer or a high-pressure homogenizer to obtain inorganic fine particles having an average particle size of 200 nm or less, and then the dispersion is mixed with water-soluble cellulose ether and, if necessary, other components. If necessary, water is added to adjust the solid content concentration.

As a means for applying the ink receiving layer on the surface of the base material sheet, a coating solution is applied using a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, etc. The method of drying can be adopted. The thickness of the ink receiving layer after drying is usually 5 to 50 μm, preferably 10 to 30 μm.
m. If the thickness of the ink receiving layer is too thin, the ink absorption capacity becomes insufficient and the printability deteriorates. On the other hand, if it is too thick, the film may crack and the transparency may decrease, which also causes a cost increase. Therefore, neither is preferable.

[0026]

The present invention will now be described more specifically with reference to examples and comparative examples.

[Example 1] 540 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.], which is an aluminum oxide powder having a γ-type crystal form, and Aerosil 380 [Japan Aerosil Co., Ltd.], which is an amorphous silica powder. Manufactured] 60 g, ion-exchanged water 24 in which 12 g of acetic acid as a dispersion stabilizer is dissolved
On the other hand, it was dispersed in 100 g by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. This liquid was applied to a high-pressure homogenizer, Gorin homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.), at a pressure of 700 kg / cm ² for 3 times.
The mixture was pulverized once to obtain a milky-white slurry-like viscous dispersion liquid.
The average particle size of the inorganic fine particles dispersed in this dispersion was 90 nm. The average particle diameter was measured by a laser diffraction / scattering type particle size distribution measuring device LA-910 (manufactured by Horiba Ltd.).

The composition of the coating liquid for the ink receiving layer is as follows. <Coating formulation A of coating liquid> Crushed inorganic fine particles (average particle size: 90 nm) ... 92 g (solid content) Aerosil AL ₂ O ₃ C (γ type aluminum oxide fine particles) 90% by weight Aerosil 380 ( Amorphous silica fine particles, primary particle size: about 7 nm) 10% by weight Water-soluble cellulose ether: 8 g (solid content) Metroze 60SH-10000 [Shin-Etsu Chemical Co., Ltd.] Made]: methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa · s (2% aqueous solution, 20 ° C.) melamine-formaldehyde resin (crosslinking agent) 0.5 g ( Solid content) Sumirez Resin 613 (manufactured by Sumitomo Chemical Co., Ltd.) Ion-exchanged water: adjusted to a solid content concentration of 10% by weight, solution viscosity: 3.4 Pa · s (3 ° C.) 100 [mu] m transparent polyester film having a thickness of one side of the [Toyobo Ester Film A-4100, Toyobo Co., Ltd.], a coating solution of Formulation A coating thickness after drying 25μ
It is applied with a comma coater so that it becomes m, and is 110 ° C.
Was dried for 3 minutes to obtain an ink jet recording sheet having an ink receiving layer formed thereon. This recording sheet had good transparency and strong film strength. As a result of a printing test using an inkjet printer MJ700V2C (manufactured by Seiko Epson Corp.), the ink receptivity, the drying property and the fixing property were good, the dot reproducibility was excellent, and there was no bleeding. Further, this recording sheet had good water resistance, and the sharpness of the image did not change with time.

[Example 2] 510 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.], which is an aluminum oxide powder having a γ-type crystal form, and Aerosil 380 [Japan Aerosil Co., Ltd.], which is an amorphous silica powder. Manufactured] 90 g, ion-exchanged water 24 in which 12 g of acetic acid as a dispersion stabilizer is dissolved
On the other hand, it was dispersed in 100 g by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. This liquid was pulverized three times with a high-pressure homogenizer, Gorin homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.) at 700 kg / cm ² pressure to obtain a milky white slurry-like viscous dispersion liquid. . The average particle size of the inorganic fine particles dispersed in this dispersion is
It was 92 nm. The average particle size is measured by a laser diffraction / scattering particle size distribution measuring device LA-910 [Horiba Ltd.
Manufactured).

The composition of the coating liquid for the ink receiving layer is as follows. <Compound formulation B of coating liquid> Crushed inorganic fine particles (average particle diameter: 92 nm) ... 92 g (solid content) Aerosil AL ₂ O ₃ C (γ-type aluminum oxide fine particles) 85 wt% Aerosil 380 ( Amorphous silica fine particles, primary particle size: about 7 nm) 15% by weight Water-soluble cellulose ether: 8 g (solid content) Metroze 60SH-10000 [Shin-Etsu Chemical Co., Ltd.] Made]: methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa · s (2% aqueous solution, 20 ° C.) melamine-formaldehyde resin (crosslinking agent) 0.5 g ( Solid content) Sumirez Resin 613 (manufactured by Sumitomo Chemical Co., Ltd.) Ion-exchanged water: Adjusted to a solid content concentration of 8% by weight, solution viscosity: 5.2 Pa · s (3 C.) The same as Example 1 except that the amount of Aerosil 380 (amorphous silica fine particles) was increased to 15% by weight, and the amount of ion-exchanged water was increased to reduce the solid content concentration to 8% by weight for adjusting the solution viscosity. A coating solution of formulation B was prepared. Although this coating solution is slightly inferior in the drying property at the time of coating, the ink jet recording sheet obtained in the same manner as in Example 1 has good transparency, and the coating strength, printability, etc. are those of Example 1. As good as.

Example 3 540 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.], which is an aluminum oxide powder having a γ-type crystal form, and Aerosil 200 [Nihon Aerosil Co., Ltd.], which is an amorphous silica powder. Manufactured] 60 g, ion-exchanged water 24 in which 12 g of acetic acid as a dispersion stabilizer is dissolved
On the other hand, it was dispersed in 100 g by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. This liquid was pulverized three times with a high pressure homogenizer, Gorin Homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.) at a pressure of 700 kg / cm ² to obtain a milky white slurry-like viscous dispersion. The average particle size of the inorganic fine particles dispersed in this dispersion is 1
It was 02 nm. The average particle size is measured by a laser diffraction / scattering particle size distribution measuring device LA-910 [Horiba Ltd.
Manufactured).

The composition of the coating liquid for the ink receiving layer is as follows. <Coating formulation C of coating liquid> Crushed inorganic fine particles (average particle diameter: 102 nm) ... 92 g (solid content) Aerosil AL ₂ O ₃ C (γ-type aluminum oxide fine particles) 90% by weight Aerosil 200 ( Amorphous silica fine particles, primary particle size: about 12 nm) 10% by weight Water-soluble cellulose ether: 8 g (solid content) Metroses 60SH-10000 [Shin-Etsu Chemical Co., Ltd.] Made]: methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa · s (2% aqueous solution, 20 ° C.) melamine-formaldehyde resin (crosslinking agent) 0.5 g ( Solid content) Sumirez Resin 613 (manufactured by Sumitomo Chemical Co., Ltd.) Ion-exchanged water: Adjusted to a solid content concentration of 10% by weight, solution viscosity: 5.8 Pa · s Except for using Aerosil 200 is a 30 ° C.) amorphous silica particles having different primary particle size, the coating solution formulation C in the same manner as in Example 1 was prepared to prepare an ink jet recording sheet. This recording sheet was slightly inferior in transparency to that of Example 1, but showed transparency enough to be used as an OHP sheet. The printability and the like were as good as those of Example 1.

[Comparative Example 1] 540 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.] which is an aluminum oxide powder having a γ-type crystal form and Aerosil OX50 [Nihon Aerosil Co., Ltd.] which is an amorphous silica powder. Made] 60 g,
Ion-exchanged water 2 in which 12 g of acetic acid is dissolved as a dispersion stabilizer
On the other hand, 400 g was dispersed by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. This liquid was pulverized three times with a high-pressure homogenizer, Gorin homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.) at 700 kg / cm ² pressure to obtain a milky white slurry-like viscous dispersion liquid. . The average particle size of the inorganic fine particles dispersed in this dispersion was 110 nm. The average particle diameter was measured with a laser diffraction / scattering type particle size distribution analyzer LA-910 [manufactured by Horiba, Ltd.].

The composition of the coating liquid for the ink receiving layer is as follows. <Coating formulation D of coating liquid> Crushed inorganic fine particles (average particle diameter: 110 nm) ... 92 g (solid content) Aerosil AL ₂ O ₃ C (γ type aluminum oxide fine particles) 90% by weight Aerosil OX50 ( Amorphous silica fine particles, primary particle size: about 40 nm) 10% by weight Water-soluble cellulose ether ... 8 g (solid content) Metroze 60SH-10000 [Shin-Etsu Chemical Co., Ltd.] Made]: methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa · s (2% aqueous solution, 20 ° C.) melamine-formaldehyde resin (crosslinking agent) 0.5 g ( Solid content) Sumirez Resin 613 (manufactured by Sumitomo Chemical Co., Ltd.) Ion-exchanged water: adjusted to a solid content concentration of 10% by weight, solution viscosity: 5.4 Pa. (30 ° C.) large Aerosil O of the amorphous silica particles primary particle size
An ink jet recording sheet was prepared by preparing a coating solution of formulation D in the same manner as in Example 1 except that X50 was used instead. This recording sheet had not only poor transparency but also ink bleeding and poor printability.

[Comparative Example 2] 540 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.], which is an aluminum oxide powder having a γ-type crystal form, and Snowtex O [manufactured by Nissan Chemical Co., Ltd.], which is fine particles of colloidal silica. ] 60 g of ion-exchanged water 24 in which 12 g of acetic acid as a dispersion stabilizer is dissolved
On the other hand, it was dispersed in 100 g by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. This liquid was pulverized three times with a high-pressure homogenizer, Gorin homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.) at 700 kg / cm ² pressure to obtain a milky white slurry-like viscous dispersion liquid. . The average particle size of the inorganic fine particles dispersed in this dispersion is
It was 90 nm. The average particle size is measured by a laser diffraction / scattering particle size distribution measuring device LA-910 [Horiba Ltd.
Manufactured).

The composition of the coating liquid for the ink receiving layer is as follows. <Coating formulation E of coating liquid> Crushed inorganic fine particles (average particle diameter: 90 nm) ... 92 g (solid content) Aerosil AL ₂ O ₃ C (γ type aluminum oxide fine particles) 90% by weight Snowtex O (Colloidal silica, primary particle size: 10 to 20 nm) 10% by weight Water-soluble cellulose ether ... 8 g (solid content) Metroses 60SH-10000 [Shin-Etsu Chemical Co., Ltd.] ]: Methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa · s (2% aqueous solution, 20 ° C.) melamine / formaldehyde resin (crosslinking agent) ... 0.5 g (solid) Min) Sumirez Resin 613 [manufactured by Sumitomo Chemical Co., Ltd.] ion-exchanged water: adjusted to a solid content concentration of 10% by weight, solution viscosity: 11.3 Pa. Instead of (30 ° C.) amorphous silica particles, Snowtex O is colloidal silica particles that do not form secondary aggregate
A coating liquid of formulation E was prepared in the same manner as in Example 1 except that was used to prepare an inkjet recording sheet. Although this recording sheet had good transparency, it had a large amount of bleeding and had poor printability such as ink absorption and drying.

Comparative Example 3 600 g of Aerosil Al ₂ O ₃ .C [manufactured by Nippon Aerosil Co., Ltd.], which is an aluminum oxide powder having a γ-type crystal form, was mixed with 12 g of acetic acid as a dispersion stabilizer.
Was dissolved in 2400 g of ion-exchanged water in which was dissolved by stirring with a stirrer to prepare a dispersion liquid having a concentration of 20% by weight. Using a Gorin homogenizer 15MR-8TA type (manufactured by Doei Shoji Co., Ltd.), which is a high-pressure homogenizer,
The mixture was pulverized three times at a pressure of 00 kg / cm ² to obtain a milky white slurry-like viscous dispersion liquid. The average particle size of the inorganic fine particles dispersed in this dispersion was 89 nm. Average particle size is measured by laser diffraction / scattering particle size distribution analyzer L
It was measured by A-910 [manufactured by Horiba, Ltd.].

The composition of the coating liquid for the ink receiving layer is as follows. <Coating Formulation F of Coating Liquid> Crushed inorganic fine particles (average particle diameter: 89 nm) ... 100 g (solid content) Aerosil AL ₂ O ₃ C (γ-type aluminum oxide fine particles) Water-soluble cellulose ether ... ..... 8 g (solid content) METOLOSE 60SH-10000 [manufactured by Shin-Etsu Chemical Co., Ltd.]: methoxyl group 28 to 30%, hydroxypropoxyl group 7 to 12%, viscosity 8 to 12 Pa.s (2% aqueous solution, 20 ° C) Melamine formaldehyde resin (crosslinking agent) ... 0.5 g (solid content) Sumirez Resin 613 [Sumitomo Chemical Co., Ltd.] ion-exchanged water ... ... Adjusted to a solid content concentration of 10% by weight, solution viscosity: 11.3 Pa · s (30 ° C.), without adding amorphous silica fine particles, Aerosil AL ₂ O ₃ ·
An ink jet recording sheet was prepared by preparing a coating solution of compounding formulation F in the same manner as in Example 1 except that only C was used as the inorganic fine particles. This recording sheet was good in printability, coating strength and water resistance, but was slightly inferior in transparency to the system to which the amorphous silica fine particles were added. Table 1 shows the measurement results of the properties.

[0039]

[Table 1]

<Measurement Method> (1) Transparency The transparency was judged by the light transmittance and the haze (cloudiness value). Light transmittance : Color analyzer TOPSCAN TC
-1800 [manufactured by Tokyo Denshoku Co., Ltd.], 380 nm
The transmittance (%) of light having a wavelength was measured by a transmission method (2 ° field of view). The higher the light transmittance (%), the higher the transparency. Haze (haze value ): Measured by the haze (haze value) described in JIS K-7105 "Method for testing optical properties of plastics". For good transparency, haze is 10
The following is preferred. (2) Evaluation for printing The evaluation for printing was performed by printing a printability evaluation pattern with an inkjet printer MJ-700V2C manufactured by Seiko Epson Corporation. Receptivity / Drying property : When the solid printed area is touched with a finger immediately after printing, the case where the ink does not adhere to the finger is good (○), the case where the ink adheres to the finger is a little good (△), and the case where the ink adheres is poor (△). X) was evaluated. Fixability : Good after printing, when the paper is pressed against the ink receiving layer and left to stand, ink does not adhere to the surface of the paper and the image does not become blurred over time (○) The case where the ink adhered to the paper surface or the change such that the image became unclear with the passage of time was evaluated as poor (x). Dot reproducibility : The shape and size of the dots are constant when magnified and observed with a microscope.
The case where there is no feathering or the like was evaluated as good (◯), the shape and size of the dots were indefinite, and the case where there was feathering or the like was evaluated as poor (x). Bleeding : Bleeding of solid color boundaries and bleeding of overlapping print areas were observed. When there was no bleeding or the degree of bleeding was small, it was evaluated as good (◯), and when bleeding was recognized, it was evaluated as poor (x). Change with time : Stability of the image when left in the room for 6 months after printing, or 80 at 40 ° C as an accelerated daily test.
The stability of the image after standing for one day in an atmosphere of% RH was evaluated, and when the image did not change, it was evaluated as good (◯), and when there was a change, it was evaluated as poor (x). (3) Water resistance After printing, soaking it in water for 3 hours, taking it out and air-drying, good when there is no dissolution of the image-receiving layer and dissolution of the ink (○), good when there is some dissolution or dissolution (Δ), the case where the image receiving layer was dissolved and the ink was melted out was defined as (x).

[0041]

According to the present invention, there is provided an ink jet recording sheet having an ink receiving layer formed on at least one side of a substrate sheet, which is excellent in transparency and strength of the ink receiving layer and has ink receiving property. Provided is an inkjet recording sheet which has good drying properties, fixing properties, dot reproducibility, water resistance, and the like, and is free from ink bleeding and aging after printing. The inkjet recording sheet of the present invention is particularly suitable as a recording sheet for an overhead projector (OHP) when a transparent synthetic resin sheet is used as the base material sheet.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuyuki Nakamura 2-3-3 Sekiguchi, Bunkyo-ku, Tokyo Nichiban Co., Ltd. (72) Inventor Koji Mizuno 2-3-3 Sekiguchi, Bunkyo-ku, Tokyo Nichiban Incorporated (72) Inventor Hideo Tateno 2-3-3 Sekiguchi, Bunkyo-ku, Tokyo Nichiban Incorporated

Claims (5)

[Claims] 1. A γ-type crystal form having an average particle diameter of 200 nm or less, which is bound to at least one surface of a base sheet with a binder composed of a water-soluble cellulose ether etherified with a methoxyl group and a hydroxylpropoxyl group. An ink jet recording sheet, wherein an ink receiving layer containing the aluminum oxide fine particles and the amorphous silica fine particles (b) is formed. 2. The inkjet according to claim 1, wherein the amorphous silica fine particles (b) have an average particle diameter of 200 nm or less obtained by pulverizing a secondary aggregate of primary particles having an average particle diameter of 20 nm or less. Recording sheet. 3. The content ratio of (a) aluminum oxide fine particles of γ-type crystal form and (b) amorphous silica fine particles is
(A) γ-type crystal form aluminum oxide fine particles are 80 to
The ink jet recording sheet according to claim 1 or 2, wherein the amorphous silica (b) is 1 to 20% by weight at 99% by weight. 4. The water-soluble cellulose ether comprises a methoxyl group 19 to 30% and a hydroxyl propoxyl group 4 to 30%.
The solution viscosity of a 2% aqueous solution (20 ° C.), which was etherified at a rate of 12% and measured by a torsional viscometer, was 2,000.
The inkjet recording sheet according to any one of claims 1 to 3, which has a viscosity of 0 mPa · s or more. 5. The ink jet recording sheet according to claim 1, wherein the ink receiving layer is cross-linked with a cross-linking agent having reactivity with a hydroxyl group of water-soluble cellulose ether.