Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-08-31
2002-05-07
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031650, C106S031890, C106S031900
Reexamination Certificate
active
06383278
ABSTRACT:
The present invention relates to a recording liquid employing an aqueous medium. Particularly, it relates to a recording liquid for writing or ink jet printing, especially a recording liquid suitable for ink jet printing.
Heretofore, a water-color ink containing an acid dye or a direct dye dissolved in an aqueous medium, or a solvent-type ink containing an oil-soluble dye dissolved in an organic solvent, has been used as a recording liquid for ink jet printing. The solvent type ink contains a solvent and thus has a problem from the viewpoint of environmental safety, and it is not suitable for use in offices. On the other hand, the water-color ink containing a water-soluble dye, has a problem that the record will be poor in water resistance, when recording is made on a pulp paper. The record with the ink also has a poor light resistance. The same problems are also found in the recording liquid for writing.
To solve such problems, it has been proposed to use an aqueous dispersion ink employing a water-insoluble pigment with excellent water resistance and light resistance as a coloring material. However, with the conventional aqueous dispersion ink of a water-insoluble pigment, its storage stability and the recording density of the record were inadequate, and it was difficult to satisfy the properties of the record such as improvement of the printing density, prevention of printing irregularities, etc. and the properties of the recording liquid such as the storage stability, the jetting stability, etc., at the same time. Accordingly, further improvements have been desired.
It is an object of the present invention to provide an aqueous dispersion ink which, even when recorded on pulp paper or regenerated paper by writing or ink jet recording, gives a record with a high density and good printing quality and which is excellent in the storage stability and the jetting durability, whereby a record excellent also in fastness such as light resistance or water resistance, can be obtained.
As a result of various studies for improving the printing density of an aqueous dispersion black ink employing a water-insoluble pigment, the present inventors have found that the S.A.D. (Surface Area Difference) of a printed portion when a recording liquid is solid-printed on a pulp paper, interrelates to and gives a substantial influence to both the storage stability of the recording liquid and the printing irregularities, and recording density of the printed product. The present invention has been accomplished on the basis of this discovery. By the present invention, it will be possible to obtain a recording liquid which is capable of satisfying the high printing density of the record and the storage stability and jetting stability of the recording liquid, at the same time.
That is, the present invention provides a recording liquid characterized in that when it is printed with 100% duty and with a resolution of 600×300 dpi on an electrophotographic paper having a S.A.D (Surface Area Difference) of from 6.0 to 9.0 and a pH of from 6 to 8, the S.A.D. of the printed portion is at least 59.5.
In short, the present invention defined the recording liquid in terms of the S.A.D. of the printed portion which is in the specific range. Whereas, with conventional ink jet recording liquids, the S.A.D. values as defined by the present invention are at a level of about 59.2 at best.
Now, the present invention will be described in detail with reference to the preferred embodiments.
The S.A.D. (Surface Area Difference) as defined by the present invention, represents the specific surface area of a record and is a parameter defined by the following formula. In the present invention, the following conditions are to be employed for its measurement.
S.A.D (Surface Area Difference)={(&Sgr;Si/&Sgr;Pi)−1}×100 (%)
where Si is the area of every triangle formed by adjacent three data points, Pi is the area when Si is projected to a xy plane, &Sgr;Si is the sum of all Si, and &Sgr;Pi is the sum of all Pi.
Measuring Method
Apparatus: Scanning Probe Microscope
Type of Machine: NanoScope III, manufactured by Digital Instruments Company
Scanner: J-Head
Measured Region: 1 &mgr;m×1 &mgr;m
Number of Pixels: 512×512
Scan Rate: 1.5 Hz
Measuring Mode: Tapping AFM
Probe: Si-DF 20, manufactured by Seiko Instruments Company
Image Treatment: Planefit Auto Tertiary
In the present invention, printing is carried out with 100% duty and with a resolution of 600×300 dpi on an electrophotographic paper, such as 4024 paper (manufactured by Xerox Corporation) having a S.A.D. within a range of from 6.0 to 9.0 and a pH within a range of from 6 to 8 as measured by a cool water extraction method as described in JIS P8133, and the surface of the printed portion is measured under the above described measuring conditions to determine the S.A.D. The measured regions are portions other than fiber portions of the paper, and an average of four points (four regions) is taken as the data. The above-mentioned 4024 paper is an electrophotographic paper containing a rosin-type abietic acid as a sizing agent and from 1.8 to 2.2 wt % of Ti atoms in the paper.
As described above, with the recording liquid of the present invention, the S.A.D. of the printed portion is at least 59.5. However, with a view to improvement of the recording density, it is preferably at least 60.0, more preferably at least 62.0, most preferably at least 65.0. But, in consideration of smear, the S.A.D. is preferably at most 90.0, more preferably at most 85.0, further preferably at most 80.0, most preferably at most 70.0. Namely, in consideration of the overall performance of the recording liquid, it can not be said that the higher the S.A.D. value, the better, and it is advisable that the S.A.D. value is within the above-mentioned specific range. The present invention is based on the discovery of the optimum range for the S.A.D.
Further, it has been found that when the recording liquid of the present invention is used, it is possible to accomplish high density printing of such a level that the density OD of the printed portion is at least 1.5 as measured by means of a Macbeth reflection densitometer (RD914).
The recording liquid of the present invention has good storage stability as compared with conventional recording liquids and has a characteristic such that the change in the particle size distribution of the recording liquid is small even when stored at a high temperature for a long period of time. Specifically, it is possible to present a recording liquid whereby, when the particle size distribution measured immediately after the preparation of the recording liquid is compared with the particle size distribution measured after storing the recording liquid for one week at 70° C., to take differences for the respective fractions of the measured particle sizes, the total of such differences is at most 20%, preferably within a range of from 1 to 18%, more preferably from 2 to 15%. If this total value is too small, flocculation on a recording sheet when recorded, tends to be poor, whereby the printing density tends to be low, or printing irregularities tends to result, such being undesirable.
In the present invention, the method for calculating the total of differences between the particle size distribution immediately after the preparation of the recording liquid and the particle size distribution after storage of the recording liquid for one week at 70° C., is as follows.
{circle around (1)} Measurement of the particle size distribution immediately after the preparation of the recording liquid
Firstly, the recording liquid immediately after the preparation, is used at the concentration as it is, and measurements are carried out by a particle size distribution meter (MicrotracUPA, sold by Nikkiso) under the following conditions.
Measuring Conditions (Input Parameters)
Transparent Particles: No, Spherical Particles: No,
Particle Refractive Index: 1.81
Particle Density: 1.86
Fluid Refractive Index: 1.33
High Temp: 30.0° C., Viscosity: 0.797 cP
Hirasa Takashi
Murayama Tetsuo
Sasaki Ken-ichiro
Klemanski Helene
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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