Ink jet ink receptive coating compositions for use in preparing ink jet recording media are provided. The coatings contain a cellulose ether and an alumina particulate. Preferably, the coating compositions contain about 50% to about 95% of the cellulose ether on a weight/weight basis, based on the amount of solids in the coating composition. Exemplary cellulose ethers that may be used in the coating compositions include methylcellulose and hydroxyalkyl methylcellulose. Preferably, the cellulose ether has a hydroxyalkyl content of 0% to about 32% and a methoxy content of about 16% to about 32%. With the ink jet ink receptive coating compositions, one can provide ink jet recording media that possess the combined properties of (i) a low level of ink cracking, (ii) good optical density, and (iii) a good dry time, when printed in an ink jet printing process.
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.
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.
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.
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.
In accordance with this objective, we herein provide for:
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.
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.
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.
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.
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.
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.
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:
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.
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.
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%.
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.
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.
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.
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.
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.
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.
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.
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
A coating composition is prepared according to the following formulation:
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.
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.
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.
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.
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.
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 (tdry).
The black ink optical density, ink cracking and dry time (measured in minutes) for each Example and Comparative Example is provided in Table I.
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.
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.
The improved dry time of the examples allows a higher throughput of the media in ink jet printing devices.
Each of the patents and publications referred to herein are incorporated by reference in their entirety into the present application.