GB2380695A

GB2380695A - Recording material

Info

Publication number: GB2380695A
Application number: GB0124268A
Authority: GB
Inventors: Roger Leslie Brentnall; Patricia Mary Dunwoody; Kathleen Durr
Original assignee: Ilford Imaging UK Ltd
Current assignee: Ilford Imaging UK Ltd
Priority date: 2001-10-10
Filing date: 2001-10-10
Publication date: 2003-04-16
Anticipated expiration: 2021-10-10
Also published as: GB2380695B; GB0124268D0

Abstract

There is provided a recording material suitable for ink jet recording comprising a sheet like substrate and on at least one side of the substrate at least one ink-receptive recording layer comprising in combination: <SL> <LI>1) gelatin; <LI>2) a vinyl alcohol polymer; and <LI>3) a styrene- acrylate polymer. </SL> There is also provided a recording material suitable for ink jet recording comprising a support, at least one lower ink-receptive layer, and at least one upper ink-receptive layer, wherein the lower ink-receptive layer comprises: <SL> <LI>1) gelatin; <LI>2) a vinyl alcohol polymer; and <LI>3) a styrene-acrylate polymer; </SL> and the upper ink-receptive layer comprises: <SL> <LI>1) gelatin; <LI>2) a vinyl alcohol polymer; <LI>3) a styrene-acrylate polymer; and <LI>4) at least one cationogenic substance. </SL> The substrate may be coated paper selected from resin coated paper, polyethylene coated paper, or barrier layer coated paper. The ink receptive layers may also comprise absorbent fillers or pigments.

Description

Recording Materials Field of the Invention The present invention relates to a recording material for recording using the ink jet printing process.

Background of the Invention Ink jet recording is a non-impact method that in response to a digital signal produces droplets of ink that are deposited on a recording medium such as paper or transparent film.

The ink droplets generally comprise a colorant which may be a dye or a pigment, and a carrier liquid, which typically is made up mainly of water, together with at least one water miscible organic cosolvent such as a monohydric alcohol or a polyhydric alcohol.

Frequently the ink also comprises one or more surfactants.

There are several classes of ink jet printer, for instance thermal drop-on-demand printers, piezo drop-on-demand printers, and continuous ink jet printers. Ink jet recording has been intensively used because of its low noise characteristic, capability of high speed printing, and facility of multi-colour printing, and has found broad application as output for personal computers in the office and the home. In recent years, ink jet printing techniques, particularly those using mainly aqueous inks, have undergone rapid development both in respect of reliability and the image quality that the printing apparatus can achieve, and in respect of the cost price of the printing apparatus. Consequently, increasingly severe requirements are being set for the recording materials. The recording produced by means of an ink jet processes is required to have, for example, good water and smear resistance, high resolution, high colour density, sufficient ink gradation, and good light fastness.

Furthermore the material must be robust and resistant to mechanical damage such as cracking.

However the cheapest recording materials, such as so-called plain paper, generally provide poor images from ink jet printers due to problems such as bleeding, feathering, and cockling. Consequently it has become common to provide recording materials comprising at least one ink-receptive recording layer arranged on a suitable substrate. The recording

layer frequently consists of one or more water-accepting polymeric binders, optionally in combination with an additive such as a cationic compound in order to bind the dyes from the inks or with an absorbent pigment. Such recording materials may provide prints and images of good quality, and are adequate for printing text. However they can still show deficiencies, particularly when printing a multi-colour image in which very dark or dense tints are to be reproduced. Due to the greater quantity of ink laid down, the ink can be slow to absorb in to the surface as this absorption depends on swelling of the polymer layer. This slow absorption is becoming more of a problem as printers develop and printing speeds increase, and can lead to certain print deficiencies such as smudging caused by subsequently printed sheets being stacked on top of incompletely dry prints.

More recently, so-called microporous and nanoporous recording materials have been developed wherein the image receiving layer comprises very fine particles of an absorbent pigment. The liquid phase of the ink absorbs very rapidly into the pores within and between the particles, and prints on such materials are quickly dry to the touch and provide excellent image quality, particularly when printed with dyed inks. Such materials are relatively less successful when printed with pigmented inks, however, as the pigment from the ink remains on the surface of the medium and the print may be susceptible to damage such as scratching and smudging when handled.

Thus there is still a requirement for an image receiving material which is rapid to dry, robust to handling, and provides good image quality. We have developed such a material.

Summary of the Invention According to this invention there is provided a recording material suitable for ink jet recording comprising a sheet like substrate and on at least one side of the substrate at least one ink-receptive recording layer comprising in combination: 1) gelatin ; 2) a vinyl alcohol polymer; and 3) a styrene-acrylate polymer.

Detailed Description of the Invention Suitable substrates for the recording materials of the invention include any of those commonly used for printing and imaging media, for example paper, high wet-strength paper, tracing paper, heavyweight paper, card, board, coated paper such as resin coated, polyethylene coated, and barrier layer coated paper, transparency materials, synthetic papers, canvas, cloth, fabric, metals such as aluminium, and polymeric substrates such as cellulose acetates, poly (ethylene), poly (propylene), poly (vinyl chloride), and polyesters including poly (ethylene terephthalate) and poly (ethylene naphthalate). Preferably the substrate is a coated paper.

Any gelatin may be used for the ink-receptive layer of the recording materials of the invention, for example skin or bone gelatin, treated gelatin such as deionised gelatin, modified gelatin such as phthalated gelatin or phenylcarbamoylated gelatin, or a cationically modified gelatin. It is necessary that the gelatin is compatible with the other components, and a particularly suitable gelatin is a deionised ossein gelatin of high isoelectric point.

By a vinyl alcohol polymer is meant a polymer comprising vinyl alcohol repeat units, optionally together with at least one other ethylenically unsaturated monomer. Suitable binders include poly (vinyl alcohol) and copolymers and derivatives thereof. It is to be understood that commercial samples of poly (vinyl alcohol) are normally prepared from poly (vinyl acetate) and may contain a proportion of unhydrolysed ester groups. A preferred binder for this invention is poly (vinyl alcohol) which has a degree of hydrolysis of at least 85%.

Suitable vinyl alcohol copolymers include particularly copolymers with cationic or basic monomers, and a particularly suitable example is a copolymer of vinyl alcohol with vinyl amine, as disclosed in European Patent Application 0 869 010 A. Suitable derivatives of poly (vinyl alcohol) include cationically modified poly (vinyl alcohols).

By styrene-acrylate polymer is meant a copolymer of styrene with acrylic, methacrylic, or maleic acids, together with optionally additional ethylenically unsaturated comonomers

such as acrylate esters. Many suitable styrene-acrylate polymers are commercially available having various monomer ratios and molecular weights. Such styrene-acrylate polymers may be supplied commercially in the form of concentrated solutions in aqueous base, or may be supplied as solids which are to be dissolved in water in the presence of a base.

Suitable bases for neutralising such polymers include sodium or potassium hydroxide, ammonia, or an organic amine base Optionally the ink receiving layer of the invention may also comprise one or more absorbent filler or pigment, such as for example clay, kaolin, talc, silica, calcium carbonate, diatomaceous earth, barium sulphate, titanium dioxide, aluminium oxide, zinc oxide, boehmite, starch, synthetic organic pigments, and mixtures of two or more of the above fillers. Preferred fillers include porous synthetic amorphous silica, porous boehmite, or porous synthetic alumina, and a preferred combination of fillers comprises a combination of precipitated calcium carbonate and synthetic amorphous silica.

Furthermore the ink receiving layer of the invention may also comprise one or more cationogenic substance as a dye fixative. By cationogenic substance is meant a substance which carries a positive charge when present in the material and which may complex or mordant anionic components in an ink. Suitable cationogenic substances include polyvalent metallic cations, simple organic cations and cationogenic organic polymers. Suitable organic polymers include quaternary ammonium and phosphonium polymers such as poly (dimethyl diallyl ammonium chloride); basic polymers such as polyethyleneimine and polymers and copolymers comprising monomers such as vinyl pyridine, vinyl imidazole, and amine containing acrylates or methacrylates ; quatemised reaction products from such basic polymers; or a reaction product of a low molecular weight polyfunctional amine with a compound polyfunctional to amino groups such as epichlorohydrin. A preferred cationogenic polymer is a methylated copolymer of vinyl imidazole with vinyl pyrrolidone.

In addition to the components already mentioned, it is to be understood that the ink-receptive layer or layers may advantageously also contain further auxiliary agents as are known in the art, for example surfactants, plasticisers, lubricants, latexes, cross linking agents, fungicides, dispersants, antifoams, ultraviolet absorbers, and optical brighteners.

There may also be present in the ink-receptive layer or layers additional water soluble polymeric binders, for example carbohydrates such as tragacanth gum or sodium alginate; water-soluble starch derivatives ; water-soluble cellulose derivatives such as hydroxyethyl cellulose, methyl hydroxypropyl cellulose, or carboxymethyl cellulose; and polyalkylene oxides such as polyethylene oxide.

Furthermore there may also be present additional layers in the recording materials of this aspect of the invention. In particular the recording material of the invention may comprise two or more ink-receptive layers, any of which may comprise the inventive combination of gelatin, a polyvinyl alcohol, and a styrene-acrylate polymer as hereinbefore described. It is preferred that the layer of the invention is used as the upper ink receptive layer of a recording material comprising two or more layers. The other layer or layers may be any image receiving layers as known in the art. According to a preferred embodiment of this aspect of the invention there is provided an ink recording material comprising at least one lower ink receptive layer comprising a water soluble binder together with optionally a pigment; and an upper layer comprising the inventive combination of gelatin, a polyvinyl alcohol, and a styrene-acrylate polymer together with optionally a cationogenic polymer.

The binder and pigment in the lower layer or layers of such an assembly may be any of the binders and pigments as hereinbefore defined.

An especially preferred ink-receptive system comprising two layers according to this aspect of the invention comprises a lower layer comprising the inventive combination of gelatin, a polyvinyl alcohol, and a styrene-acrylate polymer, together with optionally a pigment ; and an upper layer comprising the inventive combination of gelatin, a polyvinyl alcohol, and a styrene-acrylate polymer together with optionally a cationogenic polymer.

Therefore according to this preferred embodiment of the invention there is provided a recording material suitable for ink jet recording comprising in the following order, a sheet like substrate, at least one lower ink-receptive layer, and at least one upper ink-receptive layer, wherein the lower ink-receptive layer comprises:

1) gelatin ; 2) a vinyl alcohol polymer ; and 3) a styrene-acrylate polymer ; and the upper ink-receptive layer comprises: 1) gelatin; 2) a vinyl alcohol polymer; 3) a styrene-acrylate polymer; and 4) at least one cationogenic substance; wherein the gelatin, vinyl alcohol polymer, styrene-acrylate polymer and cationogenic substance are as hereinbefore defined. Any of the ink receiving layers of this aspect of the invention may optionally also comprise one or more absorbent filler or pigment, as hereinbefore defined. Preferably the pigment is located in the lower layer or layers.

Preferred pigments include porous synthetic amorphous silica, porous boehmite, or porous synthetic alumina, and a preferred combination of pigments comprises a combination of precipitated calcium carbonate and synthetic amorphous silica.

The coated amount of the ink-receptive layer or layers may be determined by the printing apparatus, the quantity of ink to be printed, the substrate, and the components used. A suitable total dry coating weight is from about 5 gm-2 to about 50 gm-2 and a preferred dry coating weight for a single ink-receptive layer on a non-absorbent substrate such as resin coated paper is from about 20 gm-2 to about 40 gar'. A suitable dry coating weight for each layer of an ink-receptive system consisting of two or more layers is from about 5 gm-2 to about 25 gm-2 and a preferred total dry coating weight for an ink-receptive system comprising two or more layers on a non-absorbent substrate is from about 20 gm' to about 40 gm-2. Lower coating weights may be used on absorptive substrates such as plain paper.

The ratio of the dry coating weight of the gelatin, vinyl alcohol polymer, and styrene-acrylate polymer is not particularly limited and may vary between about 1: 0. 1 : 0-1 and about 1: 5: 5.

One of the advantages of the recording materials of the present invention is that the ink-receptive layer or layers may conveniently be produced as aqueous formulations and coated on to the substrate by any suitable coating means, such as a slide bead coater, a

curtain coater, a rod coater, a gravure coater, a blade coater, an air knife coater, or a bar coater. Some of these methods allow for simultaneous coatings of two or more layers, which is preferred from a manufacturing economic perspective.

If desired, the surface of the support may be treated in order to improve the adhesion of the bottom layer to the support prior to applying the coating layer to the support. Suitable treatments include buffing, corona discharge, or the application of an undercoating or subbing layer to the surface of the support. Such subbing layers are known in the art.

The back surface of the material may be left uncoated or may have a coating for lay-flat or for write on properties. Additionally, lubricants to promote paper transport in the printing apparatus may be added to the back layer. Alternatively, the ink-receptive layer or layers may be formed on both sides of the substrate.

According to another aspect of the present invention, there is provided an ink jet recording method comprising the steps of ejecting droplets of an ink composition comprising at least a colorant and a carrier liquid onto the recording medium of the present invention to deposit the ink droplets onto the recording medium. The materials of the invention are suitable for use with inks comprising dyes or pigments as colorants, but the use of pigments is preferable. Preferably the ink is an aqueous ink, that is to say an ink in which the carrier liquid is predominantly water, but may also comprise one or more water soluble organic cosolvents. Such inks are well known in the art.

Although the recording materials disclosed herein have been referred to primarily as being useful for ink jet printers, they may also be used as recording media for pen plotter assemblies and as conventional writing and recording materials.

The following examples will serve to illustrate the invention.

Example 1 A recording material according to the invention was prepared by coating three layers comprising the components shown in table 1 using a curtain coater on to a conventional poly (ethylene) coated imaging paper base of total substance 190 gem-2. All three individual layers in this assembly comprise the inventive combination of gelatin, polyvinyl alcohol, and a styrene-acrylate polymer. The first two layers (layers 1 and 2) are coated as separate layers for ease of manufacture but are made up of the same components and are functionally identical, comprising silica and calcium carbonate fillers in addition to the inventive combination of polymers. The top layer comprises a cationic polymer in addition to the inventive combination. The figures in table I give the dry coating weight of the active species.

Table 1

Coating Weight gm-2 Layer 1 Layer 2 Layer 3 Gelatin 2. 99 3, 067 1-467 Phenol 0, 0055 0, 0048 0. 0024 Surfactant B 0-4 0-415 0-235 Glycerol 1 869 0. 891 Silica0-61 0-626 Calcium Carbonate 0-691 0-709 Surfactant A 0, 307 Cationic polymer 0-407 Polyvinyl Alcohol 1-578 1-619 0-405 Styrene-Acrylate polymer 2. 106 2. 16 2. 613 TOTAL 9-2535 9-4918 5-4364 In the formulation, phenol is present as a biocide and glycerol as a plasticiser. Surfactant A is a nonionic wetting agent based on octylphenol ethoxylate (average 9 to 10 moles ethylene oxide) available under the trade name Triton XI 00 from Union Carbide Chemicals and Plastics Company Inc. , Danbury, CT, USA. Surfactant B is Olin 10G commercially available from Olin Chemicals. The silica was used as a 13-33% aqueous dispersion of Gasil 23D silica available from Crosfield Chemicals. The calcium carbonate was a precipitated calcium carbonate manufactured by Speciality Minerals available under the trade name Jet Coat 30, and is supplied in a 30% dispersion in water. The gelatin was a

high isoelectric point imaging gelatin from Stoess. The cationic polymer was a vinyl pyrrolidone/3-methyl-l-vinyl imidazolium methyl sulphate copolymer manufactured by BASF under the trade name MS370 supplied as a viscous 50% aqueous solution. The polyvinyl alcohol was a commercial sample from Harco available under the trade name Mowiol 26-88 used as a 10% aqueous solution. The styrene-acrylate polymer was JonCryl 8082 supplied as a solution polymer by Johnson Polymers.

A test chart was printed on the material prepared according to the invention with an Encad 600i printer using ILFORD Archiva Extreme pigmented inks. For comparison, the same test chart was printed on a sheet of ILFORD IDPI SP9 nanoporous semi-glossy ink jet paper. Both materials dried sufficiently rapidly to be stacked or rolled within 10 minutes after printing with no residual tackiness on printed or unprinted areas.

The optical density of yellow, magenta, cyan, and black test patches was measured, and the results are given in table 2. It is seen that the measured density of the prints on the inventive material is generally greater than that of those on the comparison commercial material. It was also found that the prints on the inventive material were less susceptible to smudging on handling.

Table 2

Measured Density Sample Yellow Print Magenta Print Cyan Print Black Print Invention 1. 1-7'1-66 1-98 Comparison"1-47 145 1-49'1-85 In addition, cross sections through the inventive material after printing using a light microscope clearly showed the pigment of the ink trapped in the uppermost layer of the coating. This is the desired finding since it will maximise colour density and gamut.

Example 2 Two recording materials according to the invention were prepared. The first comprised the formulations in table 1 coated using a cascade coater. In the second coating the pigments in the lower layers were replaced by an equal weight of binder and comprised the components shown in table 3 coated using the same coater on to the same poly (ethylene) coated imaging paper base. All three individual layers in this assembly comprise the inventive combination of gelatin, polyvinyl alcohol, and a styrene-acrylate polymer; the top layer comprises in addition a cationic polymer. The figures in table 3 give the dry coating weight of the active species.

Table 3

Coating Weight gm-2 Layer 1 Layer 2 Layer 3 Gelatin 3-573"3-665 1-467 Phenol 0, 0055 0, 0048 0. 0024 Surfactant B 04150-235 Glycerol0-869 0-891 Surfactant A0-307 Cationic polymer 0-407 Polyvinyl Alcohol 1-886 1-935 0, 405 Styrene-Acrylate polymer 2#517 2#581 2#613 TOTAL 9. 2535 9. 4918 5, 4364 Both coatings were printed using a Mimaki printer. In terms of image quality and drying time there was no significant difference between the coatings. The gloss of the coatings was measured on a Dr Lange gloss meter. The results are given in table 4.

Table 4

Formulation 60 gloss Table 1 19-6 Table 346-3 It is seen that the gloss obtained from the formulation in table 3 was considerably higher than that from the formulation in table 1. It is believed that the pigments in the lower layers of the assembly from formulation 1 give this reduction in gloss.

Example 3 A recording material according to the invention was prepared by coating three layers comprising the components shown in table 5 as in example 2. In this assembly only the top layer comprises the inventive combination of gelatin, polyvinyl alcohol, and a styrene-acrylate polymer; in comparison with formulation 3 the styrene-acrylate polymer was omitted from the first two layers and replaced by binder. The figures in table 5 give the dry coating weight of the active species.

Table 5

Coating Weight gm Layer 1 Layer 2 Layer 3 Gelatin 5. 220 5, 354 1. 467 Phenol 0-0055 0-0048 0-0024 Surfactant B04 0415 0-235 Glycerol0-869 0-891 Surfactant A0-307 Cationic polymer 0-407 Polyvinyl Alcohol 2. 756 2. 827 0, 405 Styrene-Acrylate polymer 2-613 TOTAL 9-2535 9-4918 5-4364 This coating was printed and the gloss was measured as in example 2. The gloss was 30-5.

However it was found that the assembly from table 5, which is not a preferred embodiment of a two layer assembly according to the invention, was slower to dry than the assembly of the preferred embodiment formulation 3.

Example 4 A recording material according to the invention was prepared as in example 2 by coating three layers comprising the same quantity of the components shown in table 3 except that the polyvinyl alcohol used was K210 PVOH from Nippon Gohsei, Japan (The Nippon Synthetic Chemical Industry Co. , Ltd). This combination of gel and PVOH resulted in a less turbid mixture, and a smoother coated surface. The gloss value was 63-4 when measured as in example 2. However, the drying time was increased slightly.

Claims

Claims 1. A recording material suitable for ink jet recording comprising a sheet like substrate and on at least one side of the substrate at least one ink-receptive recording layer comprising in combination:

1) gelatin;

2) a vinyl alcohol polymer; and

3) a styrene-acrylate polymer.

2. A recording material according to claim 1 wherein the ink receptive recording layer also comprises at least one absorbent filler or pigment.

3. A recording material according to claim 2 wherein the absorbent filler or pigment is selected from porous synthetic amorphous silica, porous boehmite, porous synthetic alumina, and precipitated calcium carbonate.

4. A recording material according to any of claims 1-3 wherein the ink receptive recording layer also comprises one or more cationogenic substance.

5. A recording material suitable for ink jet recording comprising in the following order, a support, at least one lower ink-receptive layer, and at least one upper ink-receptive layer, wherein the lower ink-receptive layer comprises:

1) gelatin;

2) a vinyl alcohol polymer; and

3) a styrene-acrylate polymer; and the upper ink-receptive layer comprises:

1) gelatin;

2) a vinyl alcohol polymer;

3) a styrene-acrylate polymer; and

4) at least one cationogenic substance.

6. A recording material according to either of claims 4 or 5 wherein the cationogenic substance is a copolymer of vinyl imidazole with vinyl pyrrolidone.

7. A recording material according to claim 5 wherein at least one of the ink receptive recording layers also comprises at least one absorbent filler or pigment.

8. A recording material according to claim 7 wherein the absorbent filler or pigment is selected from porous synthetic amorphous silica, porous boehmite, porous synthetic alumina, and precipitated calcium carbonate.

9. A recording material according to any of claims 1-8 wherein the gelatin is a deionised ossein gelatin of high isoelectric point.

10. A recording material according to any of claims 1-9 wherein the substrate is a coated paper selected from resin coated paper, polyethylene coated paper, or barrier layer coated paper.

11. An ink jet recording method comprising the steps of ejecting droplets of an ink composition comprising at least a colorant and water onto a recording material according to any of claims 1-10 to provide an image.