AU626290B2 - Recording medium and ink jet recording method by use thereof - Google Patents

Abstract

A recording medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink absorptivity. A recording medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink absorptivity, and having a Stöckigt sizing degree according to JIS-P-8122 of 0 to 15 sec. An ink jet recording method performs recording by imparting small droplets of an aqueous ink to a recording medium, wherein said aqueous ink contains an acidic dye and/or a direct dye, and said recording medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink absorptivity. A recording medium comprising a surface layer composed mainly of aluminum oxide particles containing polyaluminum hydroxide and/or polyaluminum chloride and a lower layer having ink absorptivity. A recording medium comprises a surface layer composed mainly of aluminum oxide particles having particle sizes of 5 mu m or less provided on a liquid absorptive base paper.

Description

S F Ref: 87571 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION 626290 9;

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name and Address of Applicant: Canon Kabushiki Kaisha 30-2, 3-chome, Shimomaruko Ohta-ku Tokyo

JAPAN

Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Recording Medium and Ink Jet Recording Method by Use Thereof The following statement is a full description of this invention, including the best method of performing it known to me/us ;j 5845/3 1 On 1- 1 ABSTRACT OF THE DISCLOSURE A recording medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink absorptivity. A recording medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink absorptivity, and having a Stbckigt sizing degree according to JIS-P-8122 of 0 to 15 sec. An ink jet recording method performs recording by imparting small droplets of an aqueous ink V 10 to a recording medium, wherein said aqueous ink contains an acidic dye and/or a direct dye, and said recording 0 medium comprises a surface layer composed mainly of aluminum oxide particles and a lower layer having ink f "l absorptivity. A recording medium comprises a surface i$ layer composed mainly of aluminum oxide particles containing polyaluminum hydroxide and/or polyaluminum chloride and a lower layer having ink absorptivity.

A recording medium comprises a surface layer composed 0 0 mainly of aluminum oxide particles having particle sizes of 5 pm or less provided on a liquid absorptive base paper.

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1 TITLE OF THE INVENTION: Recording Medium and Ink Jet Recording Method by Use Thereof BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a recording medium suitably used for the ink jet recording method, particularly to a recording medium having excellent absorptivity and color forming characteristic of an aqueous ink, as well as excellent sharpness of the recorded image obtained.

Further, the present invention relates to a recording medium which can provide a recorded image with little' in-room decoloration of the image and excellent storability of the image and a recording method which can provide the above recorded image.

Further, the present invention relates to a recording medium having excellent water resistance and light resistance of the recorded image, while having various characteristics as mentioned above.

Related Background Art In the prior art, as the recording medium for ink jet recording, there have been known: one obtained by making paper in general mm- 2 1 composed mainly of pulp into a sheet with low sizing degree like filter paper or blotting paper; one having an ink absorbing layer by the use of a porous inorganic pigment provided on a base paper with low ink absorptivity such as usual paper of fine quality, etc., as disclosed in Japanese Laid-open Patent Publication No.56-148585, etc.

On the other hand, in the ink jet recording system for which formation of a color image of high quality and high resolution is particularly demanded, the recording medium to be used is required to have the following characteristics, namely: good color forming characteristic of the ink attached on the recording medium; good true sphericity of the ink dot; good ink absorption capacity such that the ink attached will not flow out even when a plurality of ink droplets may be attached on the same spot; good ink fixability such that the ink droplets attached will not be blurred even when they may be rubbed immediately after attachment; good image storability of the image formed such as water resistance, light resistance, etc.

However, no recording medium which satisfies all of the above requisite performances has been known 3 1 yet.

Particularly, recently, the problem of in-room decoloration of the recorded image inherent in coated paper has been taken a close-up.

The problem of light resistance which has been the problem in the prior art is a problem of fading of the image by irradiation of, for example, UV-ray or visible light, etc., which is raised on any image printed on any kind of paper from papers for PPC in 10 general or fine quality paper to coated papers for ink jet. However, the problem of in-room decoloration as 9 herein mentioned is a problem separate from light resistance which is raised in the image also stored in, for example, a place where no direct sunlight is irradiated, but not raised in the image printed on a non-coated paper such as paper for PPC, etc.

oo 0-& SFor example, the method as disclosed in Japanese Laid-open Patent Publication No. 60-49990 is a method for improving light resistance, and no effect can be seen for in-room decoloration. Thus, the problem of in-room decoloration is a problem inherent in coated paper, and it may be estimated to be a problem caused by the pigment forming the coated layer.

For example, the coated paper by use of highly i 4 1 active silica as dislosed in Japanese Laid-open Patent Publication No. 56-185690 can give an image with high optical density, while it involves a marked problem of in-room decoloration. On the contrary, if fillers in general for paper with low specific surface area such as calcium, kaolin, talc, silica, etc. are used, although in-room decoloration may be suppressed, there is now the problem that the image density is lowered.

Thus, particularly the problems of in-room 10 decoloration and image density are antagonistic to each other, and they have been problems not solved by o U the prior art technique.

0 SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording medium which can Sgive an image of high quality and high resolution which is high in density of the recorded image, and yet excellent in ink absorptivity and color forming

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characteristic of dye.

Another object of the present invention is to provide a recording medium which can give a recorded image with good storability, particularly a recorded image with little deterioration due to in-room decoloration and an ink jet recording method for

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forming such image.

Still another object of the present invention is to provide a recording medium which has excellent water resistance and light resistance of the recorded image, while having various characteristics as mentioned above.

I The above and other objects of the present invention can be accomplished by the inventions as specified below.

According to one aspect of the present invention, there is provided a recording medium, comprising a surface layer composed substantially of aluminum oxide particles and a base paper, wherein the aluminum oxide particles have a BET surface area within the range of from 60 to i 170 m 2 /g.

The present invention also provides, in a second aspect, a recording medium, comprising a surface layer composed substantially of 15 aluminum oxide particles and a base paper, and having a Stbckigt sizing degree according to JIS-P-8122 of 0 to 15 sec, wherein the aluminum oxide particles have a BET surface area within the range of from 60 to 170 m 2 /g.

The present invention also provides, in a third aspect, a recording medium, comprising a surface layer composed substantially of aluminum oxide particles and containing polyaluminum hydroxide and/or polyaluminum chloride, and a base paper, wherein the aluminum oxide particles have a 1 2 BET surface area within the range of from 60 to 170 m 2/g.

ij ii 7 I F/0478E ~L1IY- -I 1 IU-- 6 Further, the present invention provides, in a further aspect, a recording medium, comprising a surface layer composed substantially of aluminum oxide particles having particle sizes of 5 ptm or less provided on a liquid absorptive base paper, wherein said aluminum oxide particles 2 have a BET surface area within the range of from 60 to 170 m /g.

The present invention further provides in a still further aspect, a recording medium comprising, a base paper and an ink receiving layer comprising a layer constitution of two or more layers provided on the base paper, wherein said ink receiving layer comprises a surface layer composed substantially of aluminum oxide particles, wherein the aluminum oxide particles have a BET surface area within the range of 60 to 170 m 2 /g.

The present inventors investigated about the relationship between the pigment forming the coated layer which becomes the ink receiving layer and in-room decoloration on the basis of recognition that in-room decoloration is a phenomenon which does not occur on non-coated paper but is generated only on coated paper, and consequently found that the problem of in-room decoloration can occur with difficulty when a specific pigment is used as the pigment which forms the ink receiving layer, particularly the recording surface which captures the dye.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is described in more E ./0478E i 7 1 detail by referring to preferred embodiments.

The first specific feature of the recording 11 medium of the present invention resides in that the }I surface layer which is the recording surface is formed ti 5 mainly of aluminum oxide particles.

The aluminum oxide particles as herein mentioned is produced by the method generally called the Bayer method by calcining aluminum hydroxide obtained by hot caustic soda treatment of bauxite which is a natural ore. Otherwise, there can be also used those produced by the method in which metallic aluminum pellets are subjected to arc discharging in water and then the resultant aluminum hydroxide is calcined, or the method in which aluminum chloride is i 15 gasified at high temperature and oxidized in gas i phase, or the method in which inorganic aluminum salt (alum, etc.) is decomposed.

The crystal structures of the aluminum oxide particles have been known to be transitioned depending on the temperature for heat treatment from aluminum hydroxide of the giftsite type, the boehmite type to aluminum oxide of r, d, 7, 0, a type. Of course, in the present invention, any of these preparation methods and crystal structures may be available.

The purity of aluminum oxide particles may be I- 8- 1 different depending on the preparation method, the degree of purification, but those available in the present invention are not limited to one containing 99.99% of aluminum oxide (A1 2 0 3 generally called as high purity alumina, but those containing 80 to 90% or more of Al 203 may be sufficiently available.

The aluminum oxide particles to be used in the present invention should preferably have a BET specific surface area within the range of from 60 to 170 m more preferably from 90 to 170 m 2/g. If the BET specific surface area of the aluminum oxide particles exceeds 170 m the in-room decoloration of the recorded image will become undesirably marked.

According to the knowledge of the present inventors, in-room decoloration of recorded image is due to oxidation decomposition of the dye, and when the dye is captured on the surface layer of the recording medium, the dye will be correspondingly susceptible to oxidation by contact with air.

Particularly when the dye is captured with a pigment with large specific surface area, the contact area with air becomes the maximum, whereby the in-room decoloration is caused excessively.

Accordingly, in the present invention, it is preferable to use a pigment with a specific surface L s .i c, 9 1 area of 170 m 2 /g or less.

In contrast, in the prior art, when such a pigment as silica or calcium carbonate used for ink jet recording paper having a specific surface area of 170 m2/g is used for the ink receiving layer, due to poor adsorptivity of the pigment to the dye, the dye in the ink attached is perameted deep into the paper layer together with the solvent in the ink, whereby color forming characteristic of the dye and image density were insufficient, although the problem of inroom decoloration may be solved.

This is the first reason why a pigment with a 2 BET surface area of 170 m /g or lsss has not been used in the prior art for the coated paper as described above.

Whereas, according to the knowledge of the present inventors, even a pigment with a BET specific surface area of 170 m /g or less can give sufficient in-room decoloration inhibiting effect and also excellent image density, when aluminum oxide particles are used.

The reason why only aluminum oxide particles among various inorganic pigments can provide an image with excellent optical density as described above remains to be not clarified, but according to the

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10 1 imagination by the present inventors, it may be considered because aluminum oxide particles have positive charges on their surfaces and also can readily absorb electrically acidic dyes and/or direct dyes, and the paper by use of such aluminum oxide particles can capture more dyes near the surface, namely at the surface layer of the ink receiving layer, and also because the dyes and the aluminum oxide particles are electrically bonded, and therefore the dyes existing near the surface layer are stabilized to be decomposed with difficulty, etc.

On the other hand, when aluminum oxide particles not satisfying a BET specific surface area of 60 m 2/g or more are used, the density of the image formed becomes insufficient and therefore it is desirable to use those having a BET specific surface 2/g area of 60 m /g or more.

According to the knowledge of the present inventors, when silica is used as the pigment forming the recording surface (surface layer), since the relationships between the specific surface area of silica and image density and between the specific surface area and in-room decoloration is strong, prevention of in-room decoloration and improvement of image density cannot be compatible with each other, 1 i 1 11 1 whereby it has been difficult to improve the both at the same time.

Thus, the tendency of the both characteristics to be antagonistic to each other may be similar also in the case of aluminum oxide particles as silica, but when aluminum oxide particles are used, the elevating tendency of image density relative to the specific surface area of the pigment is more marked than silica, having the advantage that a desired image density can be achieved with partices having lower m2 specific surface area (170 m /g or less) as compared a with ;ilica. This is the reason why both prevention a 4 of in-room decoloration and improvement of image density can be improved by the preset invention.

l 15 The aluminum oxide particles to be used in the present invention have an average particle size preferably of 5 gm or less, more preferably 3 pm or less, further preferably 1 pm or less.

Thus, by use of the aluminum oxide particles having the specific surface area as specified above, the image density and the in-room storability can be improved to considerable extent, but yet the image density and the in-room storability have the trade-off relationship.

In other words, according to the knowledge of iI

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12 1 the present inventors, for having further excellent inroom storability, while retaining high image density, it is preferable to use the above aluminum oxide particles, having an average particle size of 5 um or less, more preferably 3 pm or less, further preferably 1 lim or less.

An average particle size exceeding 5 pm is insufficient for inhibiting in-room decoloration. The average particle size as herein mentioned is the particle size under the state where the ink receiving layer is formed. Generally speaking, since the primary particle size of aluminum oxide particle is about 1 nm to 1 pm, particles forming no secondary particle are preferred in the present invention.

Further, in aspect of ink absorptivity, the average primary particle size of aluminum oxide particles 1 should be preferably 0.5 pm or less. Those exceeding pm have insufficient ink absorptivity.

Also, according to the knowledge of the present inventors, although the correlation between the particle size of the aluminum oxide particles and the image density is low, in-room storability becomes better as the particle size is smaller.

This may be considered to be due to the fact that the apparent surface area on the recording 1.3 1 surface is larger when a pigment with larger particle sizes is used during formation of the recording surface as compared when particles with smaller particles are laminated, whereby the dye adsorbed is susceptible to oxidation.

In the recording medium of the prior art, for improving ink absorptivity, secondary particles are formed, and a pigment with such large particle size has been employed. In the present invention, there is no problem in ink absorptivity even by formation of a surface layer with particles of submicron order without formation of secondary particles, because of the special constitution of the ink receiving layer as described below.

The second specific feature of the present invention resides in that the recording medium of the present invention is constituted of a surface layer containing the above aluminum oxide particles and a lower layer having ink absorptivity.

The surface layer as herein mentioned is a layer constituting the recording surface, and cannot itself absorb and retain all the ink amount attached, but has the function of adsorbing primarily the dye in the ink and permeates most of the ink solvent to migrate it to the ink absorptive lower layer.

r::i 14 1 For this reason, the recording medium of the present invention includes the embodiment of having a recording surface in which the pigment forming the surface layer and the fibrous material of base paper exist in mixture and/or the embodiment of having a recording surface covered with a surface layer with the maximum thickness of 20 im, more preferably 15 pm or less.

A preferable amount of the surface layer coated as herein mentioned may be within the range of from 0.3 to 7 g/m 2 as the total amount of the pigment.

When the coated amount is less than 0.3 g/m there is no effect as compared with the case when no surface layer is provided, while if it is provided in excess of 7 g/m 2 or the maximum thickness of the surface layer exceeds 20 gm, similarly as in the case of the above recording medium there ensue such problems as remarkable lowering in ink absorptivity, lowering in in-room decoloration prevention or generation of paper powder even when the above aluminum oxide particles may be used.

In the present invention, a more preferable amount of the pigment coated on the surface layer is 2 within the range of from 1 to 7 g/m further 2

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preferably from 2 to 7 g/m 2 i 15 1 The maximum thickness of the surface layer as herein mentioned refers to the maximum value in the depth direction of the surface layer in the crosssection of the recording medium, and the amount of the pigment coated is the amount of the pigment coated as the surface layer. The amount of the pigment coated in the surface layer is determined according to the method of JIS-P-8128, and can be obtained as the value of the amount of the ash in the whole recording medium from which the amount of ash in the base paper is removed.

In the present invention, the surface layer is formed mainly of the above aluminum oxide particles, but may also use inorganic pigments known in the art, such as silica, aluminum silicate, magnesium silicate, calcium silicate, calcium carbonate, clay, kaolin, talc, diatomaceous earth, etc., or organic pigments such as urea resin, etc. mixed in the pigment in an i amount within the range which does not exceed 20% by weight.

The pigment for forming the surface layer as described above should desirably contain 80% by weight or more of aluminum oxide particles, and when aluminum oxide particles are contained in an amount less than 80% by weight, the image density will be lowered, and A 16 1 also the problem of in-room storability may not be cancelled depending on the kind of the pigment used in combination.

As described above, in the recording medium of the present invention, a recording medium which can satisfy the respective requisite performances can be obtained by providing a relatively minute amount of the surface layer, because it is used in combination 01 with an ink absorptive lower layer as described below.

The present invexntion, as shown above, is distinct in its constitutional aspect from, for example, a prior art example comprising an ink receiving layer in an amount as much as 15 g/m 2 with the use of aluminum particles having a particle size of 30 im on a polyethyleneterephthalate film as shown in Example 2 in Japanese Laid-open Patent Publication No. 58-110287 or an example comprising aluminum particles filled internally in pulp fibers during sheet making as disclosed in Japanese Laid-open Patent Publication No. 58-110288.

Specific examples of preferable recording medium having ink absorptive lower layer in the present invention may include: the embodiment in which a surface layer is provided on an liquid absorptive base paper, and the f 17 00 0 '3 ,~00 0 3~0 '33 3' 3,0 00 0 0000 c>000 (c,0 00 o 0 00 >0 '3 0 3 00 '3" 0 '3 0 0 3,0 00 0 0 0 1 base paper also functions as the ink absorptive lower layer; and the embodiment in which a pigment layer with excellent ink absorptivity is provided on a base paper, on which a sur'face layer is provided, etc.

In the following, the respective embodiments are to be described in detail.

The embodiment is the most preferred embodiment in the present invention in aspect of the 10 problems of in-room decoloration, paper powder, etc., stability in production or cost.

The surface layer of this embodiment is constituted of a pigment containing the above aluminum oxide particles and a binder. Examples of the binder 15 to be used in the present invention may include watersoluble polymers such as polyvinyl alcohol, starch, oxidized starch, cationized starch, casein, carboxymethyl cellulose, gelatin, hydroxyethyl cellulose, acrylic resin, etc. and aqueous dispersion type polymers such as SBR latex, polyvinyl acetate emulsion, etc. known in the art, which can be used either singly or as a mixture of two or more kinds.

In this embodiment, a preferable use ratio (weight ratio) of all the pigments to the binder may be 1/4 to 20/1, more preferably 1/2 to 4/1. If the L I possessed by the coated layer is lowered, while if it is lower than 20/1, powder drop-off of the above pigment from the coated layer becomes undesirably excessive.

The base paper on which the above surface layer is provided is required to be ink absorptive, having a preferable Stockigt sizing degree of within the range of from 0 to 15 sec., more preferably from 0 to 10 sec., further preferably from 0 to 8 sec. When a base paper having a Stockigt sizing degree in excess of 15 is used, the ink absorptivity of the recording medium as a whole is undesirably deficient.

The recording medium having the above coated layer provided on the base paper should desirably have a Stockigt sizing degree within the range of from 0 to sec., more preferably from 0 to 10 sec., further preferably from 0 to 5 sec. If it exceeds 15 sec., most of ink absorptivity depend on the coated layer within the above range, whereby ink absorptivity will be deficient.

In the present invention, the pulp constituting the base paper is not particularly limited, but it may be composed mainly of wood pulp as represented by LBKP or NPKP known in the art, but j 19 1 synthetic fibers or glass fibers may be also mixed therein, if desired.

Specific examples of -the fillers in the base paper to be used in the present invention may include clay, talc, kaolinite, titanium oxide, calcium carbonate, etc. generally employed, and particularly in the present invention, these fillers are contained 2 in an amount of 1 to 20 g/m more preferably 2 to 2 1 g/m as calculated on the ash content.

10 According to the knowledge of the present inventors, particularly blurring and dot shapes of ink droplets attached on the recording medium are greatly affected by the ash content in the base paper of this type of paper, and when the ash content is less than 1 15 g/m 2 the ink droplets attached will be blurred greatly along the fiber direction on the base paper I i surface, whereby the dot shapes are bad and also blurring of the ink droplets will become larger than i is necessary. On the contrary, if it exceeds 20 g/m, the recording medium itself will lose firmness, and in addition thereto, powder drop-off from the base paper will occur undesirably.

Further, of the above fillers, calcium carbonate is particularly preferable, because the dot shape and the color forming characteristic become 1

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.i j 20 1 good.

The ash content in the base paper in the above embodiment can be determined by, for example, eliminating the ink receiving layer from the recording medium by use of a good solvent for the binder and determining only the ash content in the base paper according to the method of JIS-P-8128, as the mass of the ash content per unit area of the paper at that O time. For example, in conventional paper for ink jet, o: 1 10 polyvinyl alcohol is used as the binder, and in this case, the coated layer is eliminated by dipping the 'recording medium in stationary hot water, and then the ash content as the base paper can be determined.

The base paper to be used in the above embodiment can be made with the use of the above materials optionally together with sheet making aids, sizing agents, yield enhancers, paper force strengthening agents, etc. known in the art, if desired.

Also, a preferable basis weight of the base paper to be used in the embodiment may be within 2 the range of from 60 to 120 g/m 2 Thus, since the recording medium of the embodiment absorbs ink through the base paper, if the basis weight of the 2 I base paper is less than 60 g/m 2 there may ensue L- i(-i i. i 1 21 1 problems such as generation of strike-through or cockling, etc. when high density printing is performed. On the contrary, if it exceeds 120 g/m, the paper becomes too firm, whereby a problem is involved in conveyability within the recording device.

The recording medium of the embodiment (2) absorbs ink only with the pigment layer, and therefore is excellent in ink absorptivity and dot shape, thus being suitable for providing images of high resolution op 10 and high quality.

e, I The specific feature of the recording medium of the embodiment resides in that the ink receiving layer comprises a layer constitution of two or more layers and contains an ink holding layer formed primarily of a pigment with larger particle size than the above aluminum oxide particles.

The ink holding layer is preferably formed mainly of a pigment having an (average) particle size of 5 to 30 pm, more preferably a silicon containing type pigment, further preferably a synthetic silica, and is arranged lower than the layer containing the aluminum oxide particles constituting the recording surface as described above.

In the above embodiment by use of a pigment with larger particle sizes as the ink holding 22 1 layer and embedding the small unevennesses on the surface with a pigment with smaller particle sizes of the layer constituting the recording surface, images with further better dot shape and without feeling of coarseness can be obtained without occurrence of powder drop-off, while utilizing also the advantage when using a pigment with large particle sizes.

The specific surface area of the pigment

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6 ,1 forming the ink holding layer should be preferably i 10 larger than the pigment forming primarily the surface a 2 Slayer, more preferably 200 m /g or higher, also in aspect of ink absorptivity. Also, in aspect of color 0 rforming characteristic and ink absorptivity, a constitution with the ink absorption speed of the surface layer which is slow to the extent that ink droplets iay be blurred in appropriate sizes and with Io a a the ink absorptivity of the ink holding layer being large is preferable. For this purpose, the use ratio I of the pigment to the binder in the surface layer constituting the recording surface may be preferably 1/3 to 5/1, more preferably 1/2 to 3/1, preferably 1/1 to 10/1 as the total of the ink receiving layer.

Also, any of the binders known in the art can be used for formation of the ink holding layer. The amount of the total ink receiving layer coated may be preferably

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iw i 1 4 t -23 2 1 within the range of from 2 to 50 g/m more preferably 2 from 8 to 30 g/m with the coated amount of the ink holding layer being preferably larger than that of the surface layer.

Further, for making the ink absorptivity of the recording medium of the embodiment better, preferably as the pigment forming the ink holding layer, porous silica particles having spherical particle shapes as disclosed in Japanese Laid-open Patent Publication No. 62-183382 can be used.

Particularly, when the above spherical silica having an average part'icle size of 5 to 30 im is used for the 0 .0 ink holding layer, an ink receiving layer with higher void volume as compared with that by use of amorphous pigment of the prior art can be formed, whereby a recording medium having excellent ink absorptivity can be provided.

In preparing the recording medium of the present invention according to the respective embodiments as described above, a coating solution containing the components as described above is coated on the substrate surface according to the method known in the art, such as the roll coater method, the blade coater method, the air knife coater method, the gate roll coater method, the size press method, etc. Also, i i. 24 1 after an aqueous coating solution comprising a pigment and a binder is coated on the substrate, the coating can be dried according to the method known in the art by using, for example, hot air drying furnace, hot drum, etc. to give the recording medium of the present invention.

Also, for making the ink receiving layer surface smooth, or enhancing the surface strength of the ink receiving layer, a super calender may be used in the steps.

The recording medium of the present invention ij formed as described above has high image density, excellent ink absorptivity and yet excellent characteristics without occurrence of in-room decoloration.

For improving further water resistance and light resistance of the recorded image, while retaining the above various recording characteristics, it is necessary to incorporate a polyaluminum hydroxide and/or a polyaluminum chloride in the pigment layer containing the aluminum oxide particles.

The polyaluminum hydroxide as herein mentioned is a compound having two or more compounds represented by [Al(OH) 3 a in the molecule, including, for example, compounds represented by: 25 1 [Al(OH) 3 ]nAICl 3 (n 2), and the above compounds are commercially availabe under the trade name of paho#2S from Asada Kagaku Kogyo.

The polyaluminum chloride is a compound having two or more compounds represented by (A1C13_ b in the molecule, including, for example, compounds represented by the formula: [Al 2 (OH) C1 6- 1 1 m (m 1), and the compounds are commercially available under the trade name of PAC from Taki Kagaku Kogyo.

The recording medium of the present invention should preferably contain these compounds in an amount within the range of from 0.01 g/m 2 to 5 g/m 2 If it 2 is less than 0.01 g/m water resistance is insufficient, while if it is contained in excess of g/m 2 there are problems such as lowering in ink absorptivity and image density.

In the prior art, as the dye fixing agent availabe in recording medium for ink jet, there may be included those disclosed in Japanese Laid-open Patent Publications Nos. 56-8t992, 59-20696, 59-33176, 60-11389, 61-58788, 61-252189, etc., and all of them are of the amine type, but cannot sufficiently satisfy both of water 26

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4 Soo 4 00 so o o o o 0 00 00 0 0 0 SQ 0 00 a 00 8 0 ft 0 it a 1 resistance and light resistance, although improved.

The recording medium of the present invention, which uses an aluminum type compound as different from the amine type as in the prior art as the dye fixing agent, has the effect of improving water resistance of the dye, and also has no deleterious effect on light resistance.

Further, although the polyaluminum compound can be used with an amine type dye fixing agent as described above mixed therein, the amine type water resistant agent in this case should be preferably within the range of 70% by weight or less, more preferably 25% by weight or less, of the polyaluminum compound. If it is contained in excess of 70%, the bad influence by use of the amine type water resistance-affording agent will appear to lower undesirably light resistance.

In the present invention, the ink receiving layer may also contain fluorescent brighteners, surfactants, defoaming agents, pH controllers, antifungal agents, UV-absorbers, antioxidants, etc., if necessary.

By use of the ink jet recording system for the recording medium of the present invention with a constitution as described above, for example, OIL- I :i;l 27 j 4 44 0 6 a o Q a< 0 0 4> 0 4 0 00 4440 o o 0 0 4 0 4I 44 00 I according to the recording method of the present invention which performs recording with a multi-colr aqueous ink such as yellow magenta cyan black etc., no in-room decoloration occurs on the image obtained to give a recorded image with excellent storability.

The method of the present invention is a recording method by use of the recording medium of the present invention as described above, and the ink itself which is imparted by the ink jet recording method to the specific recording medium as described above in the recording method may be also known. For example, its recording agent may be water soluble dyes as represented by direct dyes, acidic dyes, basic dyes, reactive dyes, dyes for foods, etc. Preferable examples of the dyes particularly suitable for the ink in the ink jet recording system, which can give images satisfying requisite performances in combination with the above recording medium such as color forming characteristic, sharpness, stability, light resistance and others may include: j I i

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i r :ii 28 1 Direct Acidic i0 dyes such as C.I. Direct Black 17, 19, 32, 51, 71, 108, 146, C.I. Direct Blue 6, 22, 25, 71, 86, 90, 106, 199, C.I. Direct Red 1, 4, 17, 28, 83, C.I. Direct Yellow 12, 24, 26, 86, 98, 142, C.I. Direct Orange 34, 39, 44, 46, C.I. Direct Violet 47, 48, C.I. Direct Brown 109, C.I. Direct Green 59, etc.; dyes such as C.I. Acid Black 2, 7, 24, 26, 31, 52, 63, 112, 118, C.I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113, 117, 120, 167, 229, 234, C.I. Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 180, 256, 317, 315, C.I. Acid Yellow 11, 17, 23, 25, 29, 42, 61, 71, C.I. Acid Orange 7, 19, C.I. Acid Violet 49, etc.;

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a

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1 r s j e and, otherwise, C.I. Basic Black 2, 20 C.I. Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, 29, C.I. Basic Red 1, 2, 9, 12, 13, 14, 37, C.I. Basic Violet 7, 14, 27, C.I. Food Black 1, 2, etc.

can be also used.

OIL-.ii 29 1 The above examples of dyes set forth above are particularly preferred for the ink applicable to the recording method of the present invention, and the dyes for the ink to be used in the present invention are not limited to these dyes.

Such water soluble dyes are used generally in the ink of the prior art at a ratio about 0.1 to by weight of the ink, and the same ratio may be used also in the present invention.

The solvent to be used for the aqueous ink to be used in the present invention is water or a solvent mixture of water with a water soluble organic solvent, particularly preferably a solvent mixture of water and a water soluble organic solvent. As the water soluble organic solvent, one containing a polyhydric alcohol having drying prevention effect on ink is preferred.

As the water, it is preferable to use deionized water i instead of water in general containing various ions.

The content of the water soluble organic solvent in the ink may be generally within the range of from 0 to 95% by weight, preferably from 2 to by weight, more preferably from 5 to 50% by weight.

A preferable water content may be 20 to 98%, more preferably 50 to 90%, based on the total weight of the ink.

1 i I_ i 30 5555 OrO 5555 a Iu: 1 The ink to be used in the present invention can also include surfactants, viscosity controllers, surface tension controllers, etc., if desired, in addition to the above components.

The method for performing recording by imparting the above ink to the above recording medium in the method of the present invention may be any recording method, but preferably the ink jet recording method, and said method may be any system, provided that it is a system capable of eliminating effectively the ink from the nozzle and imparting the ink to the recording medium which is the target of injection.

Particularly, the ink jet system which discharges ink through nozzle by the acting force due 15 to the state change by the abrupt volume change of ink having received the action of heat energy according to the method disclosed in Japanese Laid-open Patent Publication No. 54-59936 can be effectively used.

The recording medium of the present invention as described above is suitable as the recording medium for ink jet recording, particularly by use of aqueous ink, and exhibits the following effects.

Since it is highly absorptive of aqueous ink, it becomes substantially the same state as dried immediately after imparting of ink, and a part of the 1J 1": 1 -31 1 recording device, hands or fingers when contacted with the medium will not be contaminated, or the recorded image will not be contaminated.

When used for ink jet recording, in addition to the above effect the dot has high density with a shape approximate to true sphere, without excessive blurring of dot or occurrence of feathering from dot, whereby a sharp image with high resolution can be formed.

Since it has excellent color characteristics, it is suitable for color printer.

There is little problem of image storability inherent in coated paper and, in the ink jet recording method by use of the recording medium of the present invention and a multi-color ink, there occurs no problem of in-room decoloration which has occurred when the image obtained is stored on the wall or in the drawer in an office where no direct sunlight is irradiated for one to several months.

The recording medium of the present invention, while possessing the above characteristics to is also excellent in water resistance and light resistance of the recorded image.

The present invention is described in more detail below by referring to Examples and Comparative I 32- I examples, in which parts and are based on weight unless otherwise noted.

Examples 1 to 4 By use of a substrate having a Stockigt sizing degree of 5 sec., a basis weight of 66 g/m and containig calcium carbonate in an amount of 9.0% (5.9 g/m 2 as calculated on ash content according to JIS-P- 8128, a coating solution having the composition shown below was coated according to the bar coater method to a coated amount on drying of 5 g/m 2 and dried at 110 °C for 3 minutes to obtain a recording medium of the present invention.

Coating solution composition Pigment 24 parts Polyvinyl alcohol (PVA-117, produced by Kuraray) 8 parts Polyvinyl alcohol (PVA-117, produced by Kuraray) 8 parts Water 200 parts The pigments used are shown below in Table 1.

Comparative example 1 A recording medium was prepared in the same manner as in Example 1 except for using a paper for PPC having a St6ckigt sizing degree of 24 sec. and a basis weight of 66 g/m 2 (paper for Canon NP dry) as

I-

*i 33 1 the base paper.

Examples 5 to 8 and Comparative examples 2 and 3 By use of a paper having a Stockigt sizing 2 degree of 0 sec., a basis weight of 65 g/m and calcium carbonate in an amount of 2.4% (1.6 g/m 2 as calculated on ash content as the base paper, a coating solution with the same composition as in Example 1 was coated by the bar coating method to a coated amount on 2 o drying of 7 g/m and dried at 110 C to obtain the recording media of the present invention and Comparative example.

As the pigments, the mixtures of alumina with other pigments as shown in Table 2 were used.

UI

34 Example Example 1 Example 2 Example 3 Example 4 Comparative example 1 Table 1 I II III IV V VI Alumina

AKP-G

(Sumitomo Kagaku) Aerosil aluminum oxide-C (Degussa) Alumina UA-5605 (Showa Denko) Alumina

CAH-G

(Sumitomo Kagaku) Alumina

AKP-G

0.05 0.05 136 3.6 0.02 0.02 100 3.4 1.8 0.05 64 3.5 4.1 0.1 115 3.5 0.05 0.05 136 3.4 24 i iII S- 35 1 Remarks I Kind of particles (manufacturer) II Average particle size (pm) III Average primary particle size (pm) IV BET specific surface area (m2/g) 2 V Amount of pigment coated (g/m 2 VI Sizing degree of recording medium (sec) r, rI -36 1 Table 2 I II III IV Example 5 24 parts 0 parts 4.8 (g/m 1 (sec) Example 6 20 4 4.8 1 Comparative 0 24 4.5 1 example 2 Remarks I Alumina (AKP-G, Sumitomo Kagaku) II Zinc oxide (active zinc white AZO, produced by Seido Kagaku, Particle size 0.8 pm, specific surface area 64 m 2 /g) III Amount of pigment coated (g/m) IV Sizing degree of recording medium (sec) I II III IV Example 7 24 parts 0 parts 4.6 (g/m 2 (sec) Example 8 20 4 4.6 2 Comparative 0 24 4.8 1 example 3 1 i -e 37 SRemarks I Aerosil aluminum oxide-C (Degussa) II Finesil X-37 (Tokuyama soda, Particle size 2 2.7 pm, Specific surface area 260 m /g) III Amount of pigment coated (g/m 2 IV Sizing degree of recording medium (sec) 1 I S'i t -ta.

i i I I i i I I

I

'I

1 Si 38 1 The ink jet recording adaptability of the above recording medium was evaluated by performing the ink jet recording with an ink having the composition shown below by means of an ink jet printer having ink 5 jet heads equipped with 128 nozzles with nozzle interval of 1 mm/16 nozzles corresponding to the four colors of Y, M, C and Bk.

Ink Composition Dye 5 parts Diethylene glycol 20 parts Water 78 parts Dye Y: C.I. Direct Yellow 86 M: C.I. Acid Red C: C.I. Direct Blue 199 Bk: C.I, Food Black 2 Evaluation was conducted for the items shown below. The results are shown below in Table 3.

Ink absorptivity was evaluated by means of the ink jet printer as described above. Sharp printed image without color mixing at the printing boundary between the printed letters printed with the respective colors of Y, M, C and Bk was evaluated as O, and one which is not so as x.

For image density, the image density of a

F'I

39 1 printed matter (BK) of solid printing by means of the same ink jet printer was evaluated by use of a Macbeth reflection densitometer RD-918.

Storability in room was measured by leaving the printed matter used in the above (Bk) plastered on the wall in an office to stand for 6 months. The difference AE ab oetween the chromaticity of the image immediately after printing (before standing) and the chromaticity of the image after standing was determined for evaluation of storability in room.

For paper powder, when the ink receiving layer surface is scratched with a pencil with a hardness of H, one with much generation of paper powder by peel-off or cutting of the coated layer is evaluated as x, and good one as O.

i.

OIL- 9 L I 40 Table 3 Ink Image In-room Paper Absorptivity Density storability Powder (aE*ab) 3 Example 1 0 1.65 4.5 O Example 2 O 1.48 2.5 O Example 3 0 1.36 9.4 O Example 4 O 1.56 11.9 O Comparative 1.30 5.6 O Example 1 Example 5 O 1.58 5.2 O Example 6 O 1.48 4.6 O Comparative X 1.16 2.1 0 Example 2 Example 7 O 1.42 3.2 O Example 8 O 1.47 6.8 O Comparative 25.4 O O 1.57 25.4 0 Example 3

L/

41 1 Examples 9 to 11 and Comparative examples 4 and By use of a usual paper of fine quality (Ginkan, trade name, manufactured by Sanyo Kokusaku Pulp) as the substrate, it was coated with a coating solution I shown below to a coated amount on drying of g/m 2 by the bar coater method and dried at 110 0C for 5 minutes to form an ink holding layer, and on the ink holding layer was coated a coating solution II shown below to a coated amount on drying of 7 g/m 2 by the bar coater method, followed by drying at 110 C for 3 minutes, to form a surface layer to prepare recording media, of the present invention and Comparative example.

k 15 1 r 42 1 Composition of coating solution I Synthetic silica (spherical silica, BET specific surface area 700m 2 average particle size 20um, produced by Asahi Glass) 18 parts Polyvinyl alcohol (PVA-117/R-1130, produced Kuraray) 6 parts Water 76 parts 4 44 5444 4I 4 4 iS 4 44 Composition of coating solution II Example 9 Porous alumina (RG-40, produced by Iwatani Kagaku Kogyo specific surface area 48m 2 /g) 13 parts Polyvinyl alcohol (PVA-110, produced by Kuraray) 10 parts Water 77 parts Example Fine particulate alumina (Aerosil, aluminum oxide-C, 2 produced by Nihon Aerosil, BET specific surface area 2 /g) 13 parts Polyvinyl alcohol (PVA-110, produced by Kuraray) parts 2 Water 77 parts Example 11 High purity alumina (AKP-G, produced by Sumitomo Kagaku, BET specific surface area 130m 2 13 parts

A

:1 i 43 S Polyvinyl alcohol (PVA-110, produced by Kuraray) Water Comparative example 4 Fine powder silica (Syloid 74, produced by BET specific surface area 300m 2 /g) Polyvinyl alcohol (PVA-110, produced by Kuraray) Water 0 Comparative example Zinc oxide (active zinc white AZO, produced Kagaku BET specific surface area 64m 2 /g) Polyvinyl alcohol (PVA-110, produced by Kuraray) Water parts 77 parts Fujidevison, 13 parts 10 parts 77 parts by Seido 13 parts 10 parts 77 parts iI

II

4$ I 1 I I iI i 44 1 Example 12 On the same base paper as in Example 9, by use of a coating solution III shown below, it was coated by the bar coater method to a coated amount on drying 2 o of 20 g/m followed by drying at 110 C for minutes, to form an ink holding layer, and on the ink holding layer was coated a coating solution IV shown below to a coated amount on drying of 7 g/m followed by drying at 110 C for 3 minutes to form a surface layer, thus providing a recording medium of the present invention.

Ir I ad/ Composition of coating solution III Synthetic silicaCSyloid 620, BET specific surface area 3 0M 2 /g average particle size 12pm, produced by Fujidevison) 20 parts 3 Polyvinyl alcohol (PVA-117, produced by Kuraray) parts Water 75 parts Composition of coating solution IV I y-alumina (UA-5605, produced by Showa Denko, BET specific surface area 64 m 2 12 parts Polyvinyl alcohol (PVA-110, produced by Kuraray) 11 parts Water 77 parts 46 1 Comparative example 6 On the same base paper as used in Example was coated a coating solution shown below by the bar coater method to a coated amount of 15 g/m followed by drying at 140 C for 5 minutes to form a lower layer with low ink absorptivity. On the lower layer was applied coating by use of the coating solution used in Example 10 in the same manner as in Example followed by drying, to obtain a recording medium 6 for comparison.

3/ 1 b I ;r iu;1~Y~ (cri i -I 47 1 Composition of coating solution Polyvinyl pyrrolidone (PVP K-90, produced by GAF) 9 parts Isobutylene/Maleic anhydride copolymer (Isovan produced by Kuraray Isoprene Chemical) 3 parts Dimethyl formamide 88 parts L 3 ,-IU 3 -48 1 The evaluation for the respective recording media of the above Examples 9 to 12 and Comparative examples 4 to 6 was conducted for the following items. The results are shown below in Table 4.

Ink absorptivity was evaluated by means of the above ink jet printer. The recorded image with excessive line boldness at the mixed color portion of two colors than at the single color portion and generation of ink flow-out is evaluated as x, one without line boldness as 0, one with slight generation as A. Further, one without line boldness even at the overlapped portion of three colors as Storability in room is measured by printing a solid pattern of Bk by use of the above printer, and leaving the printed product to stand for six months as plastered on the wall in an office. The difference between the chromaticity of the image and t' the chromaticity of the image immediately after printing (AE ab) is determined for evaluation of decoloration in room.

For the color characteristic, the chromaticity of the printed products by solid printing by use of the above printer was measured by use of a high speed color analy7er (produced by Murakami Shikisai Kagaku).

-49 1 For the image density, 0.D. of the printed product by solid printing (Bk) by use of the above printer w~as measured by use of Macbeth densitometer RD- 914.

200 1 Table 4 1 11 Y M

C

Example 9 Example 10 Example 11 Example 12 Comparative Example 4 Comparative Example 5 Comparative Example 6 Note: I: Ii II: Ii III: C IV: Ir 7.3 77.8 67.9 50.0 1.26 13.3 83.3 71.9 53.2 1.55 14.5 82.4 72.2 54.1 1.66 0 8.6 78.1 69.2 50.8 1.37 34.8 82.3 72.0 52.1 1.63 5.4 61.9 53.7 46.3 1.18 X 9.4 83.4 72.1 53.5 1.42 nk absorptivity n-room storability olor characteristic mage density (Bk) (AE*ab) C a r~x-i 51 1 Examples 13 16 and Comparative examples 7 9 Except for using the coating compositions shown below (Table recording media were prepared in the same manner as in Example 1.

Composition of coating solution Pigment Polyvinyl alcohol (PVA-110, produced by Kuraray) Water-resistant agent Water 20 parts 10 parts 3.6 parts 266 parts Table Pigment Example 13 Alumina

(AKPOG)

14 Alumina (Aerosil aluminum oxide-C) Alumina

(AKP-G)

Dye fixing agent Polyaluminum hydroxide (paho#2S, manufactured by Asada Kagaku Kogyo) Polyaluminum chloride (PAC 250A, manufactured by Taki Kagaku Kogyo) Polyaluminum hydroxide (paho#2S) 2.7 parts Polyamide epichlorohydrin (Polyfix 601, produced by Showa Kobunshi) 0.9 part Polyaluminum chloride (PAC 250A) 2.7 parts Polyallylamine manufactured by Nittobo) 0.9 parts 16 Alumina (Aerosil aluminum oxide-C) I .i b2 Table 5 (continued) P igmen t Dye fixinq aqent Re fer'ence example 1 Alumina

(AKP-G)

Comparative example 7 Ultra-fric silica p a rt icle s (Finesi 1 X-37) 8 Alumina

(AKP-G)

9 Alumina

(AKP-G)

None, amount of water is made 270 parts Polyaluininum hydroxide (paho#2S) Polyamide epichlorohydriri resin (Polytix 601) Polyallylamine (PAA-I OS) 53 1 By use of the above recording media, recording was performed evaluated in the same manner as in Example 1. The results are shown in Table 6.

Water resistance and light resistance were evaluated as described below.

Water resistance was evaluated by dipping the 0 printed product of in running water (20 C) for minutes, and determining the ratio of the image density at the M printed portion after dipping relative to the image density before dipping (residual O.D. ratio).

Light resistance was evaluated by irradiating the printed product of by use of Xenon Fade-Ometer (manufactured by Ci-35 Atlas Co.) under the conditions of a black panel temperature of 63 C and a humidity of 70% RH for 100 hours, and determining the ratio of the image density at the M printed portion after irradiation relative to the image density before irradiation.

|i k 54 Table 6 Image Water Light In-room Ink absorptivity density resistance resistance storability (,6E*ab) Example 13 0 1.60 14 0 1.48 o 1.59 16 0 1.48

II

V 4 '4 Vt Reference Example 1 Comparative Example 7 8 9 95% 94% 98% 99% 72% 80% 102% 99% 83% 78% 80% 74% 88% 7 6%P 43% 38% 3.4 2.3 3.2 2.1 4 .4 26.3 3.1 1.9 1.62 1.63 1.59 1.48 I4 t

D

Claims (22)

1. A recording medium, comprising a surface layer composed substantially of aluminum oxide particles and a base paper, wherein the aluminum oxide particles have a BET surface area within the range of from to 170 m 2 /g.

2. A recording medium, comprising a surface layer composed substantially of aluminum oxide particles and a base paper, and having a Stockigt sizing degree according to JIS-P-8122 of 0 to 15 sec, wherein the aluminum oxide particles have a BET surface area within the range of from 60 to 170 m 2 /g.

3. A recording medium, comprising a surface layer composed substantially of aluminum oxide particles and containing polyaluminum hydroxide and/or polyaluminum chloride, and a base paper, wherein the aluminum oxide particles have a BET surface area within the range of from to 170 m 2 Ig.

4. A recording medium, comprising a surface layer composed substantially of aluminum oxide particles having particle sizes of 5 pm or less provided on a liquid absorptive base paper, wherein said aluminum oxide particles have a BET surface area within the range of from 60 to 170 m2/g.

5. A recording medium comprising, a base paper and an ink receiving layer comprising a layer constitution of two or more layers provided on the base paper, wherein said ink receiving layer comprises a surface layer composed substantially of aluminum oxide particles, wherein the aluminum oxide particles have a BET surface area within the range of 60 to 170 m 2 /g.

6. A recording medium comprising, a base paper and an ink receiving layer comprising two or more layers provided on the base paper, wherein said ink receiving layer comprises a surface layer that contains aluminum oxide particles in an amount of 83% by weight or more of the total amount of pigments contained in the surface layer, said particles having a BET surface area within the range of 60 to 170 m /g.

7. A recording medium according to any one of claims 1, 2, 3, or 6, wherein the aluminum oxide particles have an average particle size of 5 im or less.

8. A recording medium according to any one of claims 1 to 6, wherein the aluminum oxide particles have an average particle size of 1[Lm or less. dp I O 1 ~O O 1) IO~J I CI El 10 ~B D D j ii 1 i i i1 i 1 Iuoa i D O B Ill 01 lIb II 44444 i RLF/0478E I j- ii i I I-r r r \Li AF41? -56-

9. A recording medium according to any one of claims 1 to wherein the aluminum oxide particles comprise 80% by weight of all the pigments in the surface layer. A recording medium according to any one of claims 1 to 4, wherein the amount of the surface layer coated is within the range of from 0.3 to 7 g/m 2

11. A recording medium according to any one of claims 1 to 6, 1 wherein the base paper has a Stbckigt sizing degree according to jI JIS-P-8122 of 0 to 15 sec. I 12. A recording medium according to either claim 5 or claim 6, ?i wherein the surface layer contains polyaluminum hydroxide and/or polyaluminum chloride.

13. A recording medium according to either claim 3 or claim 12, wherein said polyaluminum hydroxide and/or polyaluminum chloride is j 2 contained in an amount within the range of from 0.01 to 5 g/m.

14. A recording medium according to either claim 5 or claim 6, wherein the ink receiving layer contains an ink holding layer formed substantially of a pigment with larger particle size than said aluminum oxide particles. A recording medium according to either claim 5 or claim 6, wherein the ink receiving layer contains an ink holding layer formed substantially of pigment having an average particle size of 5 to 30 u.m.

16. A recording medium according to either claim 5 or claim 6, S wherein the ink receiving layer contains an ink holding layer formed substantially of silicon containing pigment. wh 17. A recording medium according to either claim 5 or claim 6, wherein the ink receiving layer contains an ink holding layer formed i substantially of a pigment with larger BET surface area than said aluminum oxide particles. :18. A recording medium according to either claim 5 or claim 6, wherein the ink receiving layer contains an ink holding layer formed !2 substantially of a pigment having a BET surface area of 200 m 2/g or higher..

19. A recording medium according to either claim 5 or claim 6, wherein the amount of the ink receiving layer coated is within the range of from 2 to 50 g/m 2 A recording medium, comprising: a surface layer composed substantially of aluminum oxide SRLF/0478E ii -57- particles, said particles having a BET surface area within the range of to 170 m 2 and a lower layer having ink absorptivity, said lower layer being 1 formed of paper that includes fibrous material, wherein the aluminum oxide particles of the surface layer are in a mixture with the paper fibrous material of the lower layer.

21. A recording medium according to claim 20, wherein said recording medium has a Stbckigt sizing degree according to JIS-P-8122 of 0 to 15 sec.

22. A recording medium according to claim 20, wherein said surface layer further contains at least one of polyaluminum hydroxide and polyaluminum chloride.

23. A recording medium, comprising a surface layer composed substantially of aluminum oxide particles having a particle size of Rm or less provided on a liquid absorptive base paper, and a BET 2 surface area within the range of 60 to 170 m and wherein the aluminum oxide particles of the surface layer are mixed with paper fibrous material of a lower layer of said recording medium.

24. A recording medium substantially as hereinbefore described with reference to any one of the Examples. An ink jet recording method that performs recording by imparting small droplets of an aqueous ink to a recording medium according to any preceding claim.

26. An ink jet recording method acording to claim 25, wherein said aqueous ink contains at least one of an acidic dye and a direct dye.

27. An ink jet recording method according to either claim 25 or claim 26, wherein said small droplets of the ink are formed by permitting heat energy to act on the ink.

28. A recording medium substantially as hereinbefore described with reference to any one of the Examples.

29. An ink jet recording method which performs recording by imparting small droplets of an aqueous ink to a recording medium, substantially as hereinbefore described with reference to any onc of the Examples. DATED this TWELFTH day of MAY 1992 Canon Kabushiki Kaisha Patent Attorneys for the Applicant ,A -SPRUSON FERGUSON I R r"j RLF/0478E