An ink jet receptive coating composition

Description

Field of the Invention

[0001] The invention pertains to an ink jet ink receptive coating composition, and to an ink jet recording media prepared therewith by applying said coating composition to a surface of a suitable base substrate.

Background of the Invention

[0002] Ink jet ink receptive coating layers used for ink jet recording media have to meet a number of performance requirements. These requirements include dry time, color density, resolution, tack, color fidelity and lightfastness, as well as cost. There are many materials, both organic and inorganic, that have been proposed for this application. Among them, cellulose derivatives and alumina particulates have shown promising performance, and cellulose derivatives have been used alone or in combination with an inorganic pigment other than alumina. For example, U.S. Patent 4,555,437 describes a hydroxyethyl cellulose coating, and U.S. Patent 4,575,465 describes a hydroxypropyl cellulose coating.

[0003] Alumina has been extensively used as a filler or pigment for ink jet recording media. For example, U.S. Patent 4,780,356 discloses a two-layer coating that contains silica or alumina with a particle size of 0.1 µm - 50 µm, U.S. Patent 5,104,730 discloses a coating that contains pseudo-boehmite and polyvinyl alcohol, U.S. Patent 5,264,275 discusses a two-layer coating that contains pseudo-boehmite and polyvinyl alcohol/polyvinyl pyrrolidone.

Summary of the Invention

[0004] An objective of the present invention is to provide an ink jet ink receptive coating composition that can be used in preparing ink jet recording media, which upon printing possess the improved combination of properties of (i) good black ink optical density, (ii) low pigment ink cracking, and (iii) good dry time.

[0005] In accordance with this objective, we herein provide for:

(a) an inventive ink jet ink receptive coating composition, (b) an inventive ink jet recording media prepared therewith, and (c) an ink jet printing process that utilizes the inventive ink jet recording media.

[0006] Specifically, we provide an ink jet ink receptive coating composition that is useful in preparing an ink jet recording media, wherein the coating composition - when appropriately applied to a suitable base substrate and subsequently printed upon in an ink jet printing process - provides an ink jet recording media that offers the improved properties mentioned above.

[0007] More specifically, we provide for an inventive ink jet ink receptive coating composition that is useful in preparing an inventive ink jet recording media, where the coating composition comprises a cellulose ether in combination with an alumina particulate.

[0008] The cellulose ether used in the inventive coating composition is preferably methylcellulose or a hydroxyalkyl methylcellulose. It is also preferable that the cellulose ether used in the inventive coating composition possess a hydroxyalkyl content of 0% to about 32% and a methoxy content of about 16% to about 32%, when tested according to ASTM D-3876 and ASTM D-2363. Furthermore, it is preferable for the cellulose ether to be present in the inventive coating compositions at a level of from about 50% to about 95% on a weight/weight basis, based on the amount of solids in the coating composition.

[0009] The alumina particulate used in the inventive coating compositions preferably has an average dispersed particle size of about 10 nm to about 200 nm, and more preferably about 30 nm to about 170 nm.

[0010] The good ink jet printing performance that is associated with the ink jet recording media of the present invention, results from the fact that they comprise a suitable substrate having on a surface thereof an ink jet recording layer that is made from one of the inventive ink jet ink receptive coating compositions.

Detailed Description of the Invention

[0011] The following detailed description is provided as an aid to those desiring to practice the present invention. It is not to be construed as being unduly limiting to the present inventive discovery, since those of ordinary skill in the art will readily recognize that the embodiments of the inventors' discovery disclosed herein may be modified using standard techniques and materials known in the art, without departing from the spirit or scope of the present inventive discovery.

[0012] In arriving at the present invention, we have discovered that several design parameters are important to achieving the objective of the present invention. These design parameters include:

(1) Inorganic oxides such as alumina should be used in ink jet ink receptive coating compositions in combination with polymeric binders to achieve optimal performance.

(2) Polyvinyl alcohol and polyvinyl pyrrolidone are not appropriate for use as binders for some ink jet recording media applications.

(3) The use of cellulose derivatives alone in preparing ink jet ink receptive coating compositions does not result in an ink jet recording media having the desired combination of properties.

(4) Not all cellulose derivatives are capable of providing the desired properties in an ink jet recording media, when present in the ink jet recording layer thereof.

[0013] In order to meet the objective of the present invention, our inventive ink jet ink receptive coating compositions contain at least (i) a cellulose ether and (ii) an alumina particulate.

[0014] The ink jet ink receptive coating compositions of this invention preferably contain about 50% to about 95% of the cellulose ether therein, on a weight/weight basis, based on the amount of solids in the coating compositions.

[0015] The typical examples of cellulose ethers that are useful in the present invention are methylcellulose and hydroxyalkyl methylcelluloses, such as hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and hydroxybutyl methylcellulose. Preferably, the cellulose ether should have a hydroxyalkyl content of 0% to about 32% and a methoxyl content of about 16% to about 32%.

[0016] The alumina particulates used in this invention should possess an average dispersed particle size of about 10 nm to about 200 nm, preferably about 30 nm to about 170 nm. Typical examples of alumina particulates that are useful in the present invention include alumina, boehmite, pseudo-boehmite, aluminum hydrate and aluminum oxide.

[0017] According to a preferred embodiment of the invention, the ink jet ink receptive coating compositions comprise about 0.01 to about 15% by weight of particulates therein (not including the aforementioned alumina particulates), based on the weight of the dry coating. In this way it is possible to modify the surface properties of the ink jet recording layer in the prepared ink jet recording media. Examples of such particulates include inorganic particulates, such as silica, kaolin, glass beads, calcium carbonate, titanium oxide, barium sulfate, aluminum silicate, zirconium oxide and tin oxide and organic particulate such as polyolefins, polystyrene, polyurethane, starch, poly(methyl methacrylate) and polytetrafluoroethylene.

[0018] In practice, various additives may also be employed in the ink jet ink receptive coating compositions of this invention. These additives can include surface active agents which control the wetting or spreading action of coating solutions, antistatic agents, suspending agents and acidic compounds to control pH of the coating. Other additives may also be used, if so desired.

[0019] The ink jet ink receptive coating compositions of this invention can be applied to a surface of a variety of different base substrates (e.g., transparent plastics, translucent plastics, matte plastics, opaque plastics or papers), to prepare one of the inventive ink jet recording media. Suitable polymeric materials for use as the base substrate include polyester, cellulose esters, polystyrene, polypropylene, poly(vinyl acetate), polycarbonate, and the like. Poly(ethylene terephthalate) film is a particularly preferred base substrate. Further, while almost any paper can be used as the base substrate, clay coated or polyolefin coated papers are particularly preferred as base substrate papers. The thickness of the base substrate is not particularly restricted but should generally be in the range of from about 1 to about 10 mils, preferably from about 3.0 to about 5.0 mils. The base substrate may be pretreated to enhance adhesion of the ink receptive coating thereto.

[0020] The thickness of the inventive coating is not particularly restricted, but should generally be in the range from about 2 grams per square meter to about 30 grams per square meter, on a surface of the base substrate.

[0021] A surface of the base substrate that does not bear the ink jet ink receptive coating may have a backing material placed thereon in order to reduce electrostatic charge and to reduce sheet-to-sheet friction and sticking and reduce curl, if so desired. The backing material may either be a polymeric coating, a polymer film or paper.

[0022] Any number of coating methods may be employed to coat the ink jet ink receptive coating composition onto the surface of the base substrate. For example, roller coating, blade coating, wire-bar coating, dip coating, extrusion coating, air knife coating, curtain coating, slide coating, doctor coating or gravure coating, may be used and are well known in the art.

[0023] The following Examples are given merely as illustrative of the invention and are not to be considered as limiting thereto. In the Examples "parts" refers to parts by weight, based on the total weight of solids in the coating compositions.

EXAMPLE I

[0024] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0025] 

Methylcellulose1	3.2 parts
Hydroxypropyl methylcellulose2	6.1 parts
Alumina Sol3	5.4 parts
Water	85.3 parts
Crosslinked poly(methyl methacrylate)4	0.01 parts

1. Methocel A15LV, Dow Chemical Company

2. Methocel K3LV, Dow Chemical Company

3. Dispal 23N4-20, Vista Chemical Company

4. Soken Chemical & Engineering Company, Ltd.

[0026] The coating is applied to a polyester film (ICI Films) using a No. 24 Meyer rod, and the coating is dried at about 130°C for about 2 minutes.

EXAMPLE II

[0027] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0028] 

Hydroxypropyl methylcellulose1	4.1 parts
Alumina Sol2	3.8 parts
Water	92.1 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. Methocel K35LV, Dow Chemical Company

2. Dispal 11N7-12, Vista Chemical Company

[0029] The coating is applied to a polyester film (ICI Films) using a No. 50 Meyer rod, and is dried at about 130°C for about 2 minutes.

EXAMPLE III

[0030] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0031] 

Hydroxypropyl methylcellulose1	2.6 parts
Alumina Sol2	2.4 parts
Water	95.0 parts
Crosslinked poly (methyl methacrylate)	0.01 parts

1. Methocel K100LV, Dow Chemical Company

2. Nyacol AL20, Nyacol Products, Inc.

[0032] The coating is applied to a polyester film (ICI Films) using a No. 70 Meyer rod, and is dried at about 130°C for about 2 minutes.

EXAMPLE IV

[0033] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0034] 

Methylcellulose1	8 parts
Alumina Sol2	6 parts
Water	86 parts

1. Methocel A15LV, Dow Chemical Company

2. Dispal 23N4-20, Vista Chemical Company

[0035] The coating is applied to a polyester film (ICI Films) using a No. 50 Meyer rod, and the coating is dried at about 130°C for about 2 minutes.

COMPARATIVE EXAMPLE C-I

[0036] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0037] 

Methylcellulose sodium salt1	4.1 parts
Alumina Sol2	3.7 parts
Water	92.2 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. Hercules, Inc.

2. Dispal 23N4-20, Vista Chemical Company

[0038] The coating is applied to a polyester film (ICI Films) using a No. 50 Meyer rod, and is dried at about 130°C for about 2 minutes.

COMPARATIVE EXAMPLE C-II

[0039] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0040] 

Polyvinyl alcohol1	5.8 parts
Alumina Sol2	5.3 parts
Water	88.9 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. Airvol 823, Air Products and Chemicals, Inc.

2. Dispal 23N4-20, Vista Chemical Company

[0041] The coating is applied to a polyester film (ICI Films) using a No. 50 Meyer rod, and is dried at about 130°C for about 2 minutes.

COMPARATIVE EXAMPLE C-III

[0042] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0043] 

Polyvinyl pyrrolidone1	5.7 parts
Alumina Sol2	5.2 parts
Water	89.1 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. PVP K-90, ISP Technologies, Inc.

2. Dispal 11N7-12, Vista Chemical Company

[0044] The coating is applied to a polyester film (ICI Films) using a No. 50 Meyer rod, and is dried at about 130°C for about 2 minutes.

COMPARATIVE EXAMPLE C-IV

[0045] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0046] 

Hydroxypropyl methylcellulose1	15 parts
Water	85 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. Methocel K3LV, Dow Chemical Company

[0047] The coating is applied to a polyester film (ICI Films) using a No. 24 Meyer rod, and is dried at about 130°C for about 2 minutes.

COMPARATIVE EXAMPLE C-V

[0048] A coating composition is prepared according to the following formulation:

Ink Receptive Coating Composition:

[0049] 

Hydroxypropyl methylcellulose1	9.7 parts
Colloidal Silica Sol2	8.8 parts
Water	81.5 parts
Crosslinked poly(methyl methacrylate)	0.01 parts

1. Methocel K3LV, Dow Chemical Company

2. Ludox SK, Dupont Company

[0050] The coating is applied to a polyester film (ICI Films) using a No. 24 Meyer rod, and is dried at about 130°C for about 2 minutes.

[0051] Each of the prepared ink jet recording media of Examples I-III and Comparative Examples C-I to C-V, are evaluated to determine whether they offer the following improved combination of properties of (i) a good level of black ink optical density, (ii) a low level of pigment ink cracking, and (iii) a good dry time, when printed in an ink jet printing process.

[0052] The prepared ink jet recording media are evaluated by printing on the ink jet recording surface thereof a test plot, with a Hewlett Packard DESKJET 660C printer using HP 51629A and HP 51649A ink cartridges. The black ink is pigment based in the evaluation.

[0053] The black ink optical density of each test sample is measured with a MACBETH TD 904 densitometer (Macbeth Process Measurements) using the beige filter setting. A measurement is taken at three different locations along a solid black image stripe. The average of the three measurements is the black ink optical density.

[0054] The amount of pigmented ink cracking that is associated with each sample is quantitatively rated with a numerical scale of 0 to 5 (0=worst and 5=best). Each Example and Comparative Example is imaged with a test print. The Examples are given a numerical rating by comparing the Examples to standard prints that exhibit each level of ink cracking.

[0055] The dry time of each Example is measured by first printing each example with the test plot. The Example is then placed on top of a 20 lb. ream of XEROX 4200 paper. This is time zero (t₀). Thereafter, at thirty second intervals, a sheet of white bond paper is placed onto the surface of the Example, and then another 20 lb. ream of XEROX 4200 paper is placed on top of the white bond paper. After five seconds, the top ream of paper and white bond paper is removed from on top of the Example. The Example is dry when no transfer of ink between the print and the white bond paper occurs, which is termed the dry time (t_dry).

[0056] The black ink optical density, ink cracking and dry time (measured in minutes) for each Example and Comparative Example is provided in Table I.

TABLE I

PERFORMANCE EVALUATION OF THE COATINGS
Example	Black Ink Optical Density	Ink Cracking	Dry Time
I	2.09	4	2.5
II	2.07	4	2
III	2.11	4	2
IV	2.08	5	2.5
C-I	1.19	1	>5
C-II	1.37	1	3.5
C-III	1.21	1	4.5
C-IV	1.08	1	3.5
C-V	.93	0	3.5

[0057] As shown in Table I, Examples I to III all exhibited improved black ink optical density, a low level of pigment ink cracking, and a good dry time as compared to the Comparative Examples C-I to C-V.

[0058] The pigmented black ink optical density is inversely proportional to ink cracking, with pigment ink cracking decreasing the black ink optical density. When ink cracking is rated below 3, ink cracking is clearly visible to the eye, and the ink jet recording media are not suitable for many commercial applications.

[0059] The improved dry time of the examples allows a higher throughput of the media in ink jet printing devices.

[0060] Each of the patents and publications referred to herein are incorporated by reference in their entirety into the present application.

Claims

1. An ink jet ink receptive coating composition for preparing an ink jet recording media, which coating composition comprises:

a cellulose ether and an alumina particulate.

2. The ink receptive coating composition according to claim 1, wherein said cellulose ether is methylcellulose or a hydroxyalkyl methylcellulose.

3. The ink receptive coating composition according to claim 2, wherein said cellulose ether has a hydroxyalkyl content of 0% to about 32% and a methoxy content of about 16% to about 32%.

4. The ink receptive coating composition according to claim 3, wherein said coating composition contains about 50% to about 95% of said cellulose ether on a weight/weight basis, based on the amount of solids in said coating composition.

5. The ink receptive coating composition according to claim 4, wherein said alumina particulate has an average dispersed particle size of about 10 nm to about 200 nm.

6. The ink receptive coating composition according to claim 3, wherein said cellulose ether is selected from the group consisting of:

methylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and hydroxybutyl methylcellulose.

7. The ink receptive coating composition according to claim 4, wherein said alumina particulate is selected from the group consisting of:

alumina, boehmite, pseudo-boehmite, aluminum hydrate and aluminum oxide.

8. The ink receptive coating composition according to claim 1, wherein said coating composition additionally comprises an inorganic particulate selected from the group consisting of:

silica, kaolin, glass beads, calcium carbonate, titanium oxide, barium sulfate, aluminum silicate, zirconium oxide and tin oxide.

9. The ink receptive coating composition according to claim 1, wherein said coating composition additionally comprises an organic particulate selected from the group consisting of:

a polyolefin, polystyrene, polyurethane, starch, poly(methyl methacrylate) and polytetrafluoroethylene.

10. An ink jet recording medium that comprises:

a base substrate having coated on a surface thereof an ink jet ink receptive layer that contains a cellulose ether and an alumina particulate.

11. The ink jet recording medium according to claim 10, wherein said cellulose ether is methylcellulose or a hydroxyalkyl methylcellulose.

12. The ink jet recording medium according to claim 11, wherein said cellulose ether has a hydroxyalkyl content of 0% to about 32% and a methoxy content of about 16% to about 32%.

13. The ink jet recording medium according to claim 12, wherein said ink jet recording layer contains about 50% to about 95% of said cellulose ether on a weight/weight basis, based on the amount of solids in said coating layer.

14. The ink jet recording medium according to claim 13, wherein said alumina particulate has an average dispersed particle size of about 10 nm to about 200 nm.

15. The ink jet recording medium according to claim 12, wherein said cellulose ether is selected from the group consisting of:

methylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and hydroxybutyl methylcellulose.

16. The ink jet recording medium according to claim 13, wherein said alumina particulate is selected from the group consisting of:

alumina, boehmite, pseudo-boehmite, aluminum hydrate and aluminum oxide.

17. The ink jet recording medium according to claim 10, wherein said ink jet recording layer additionally comprises an inorganic particulate that is selected from the group consisting of:

silica, kaolin, glass beads, calcium carbonate, titanium oxide, barium sulfate, aluminum silicate, zirconium oxide and tin oxide.

18. The ink jet recording medium according to claim 10, wherein said ink jet recording layer additionally comprises an organic particulate that is selected from the group consisting of:

a polyolefin, polystyrene, polyurethane, starch, poly(methyl methacrylate), and polytetrafluoroethylene.

19. The ink jet recording medium according to claim 10, wherein the base substrate is selected from the group consisting of:

a transparent plastic substrate, an opaque plastic substrate, a matte plastic substrate, a translucent substrate and a paper.

20. An ink jet printing process for forming an ink jet print, the process comprising:

applying an ink jet ink to the ink jet recording layer of the ink jet recording medium of claim 1, and

allowing said ink to dry.