Thermally sensitive recording medium

Details Thermally sensitive recording medium Thermally sensitive recording medium

1999-06-30

2001-09-04

Hess, Bruce H. (Department: 1774)

Record receiver having plural interactive leaves or a colorless

Having a colorless color-former, developer therefor, or...

Identified color-former

C503S204000, C503S221000, C503S217000

Reexamination Certificate

active

06284707

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a thermally sensitive recording medium which develops navy blue or grayish blue color.
DESCRIPTION OF THE PRIOR ART
Generally, the thermally sensitive recording medium possessing a thermally sensitive recording layer mainly comprising a colorless or a pale colored electron donating dye precursor (hereinafter shortened to dye precursor) and a color developer which develops color when heated together with said (lye precursor was disclosed in Japanese Patent publication 45-14035 and had been widely utilized practically. As a recording apparatus for this thermally sensitive recording medium, a thermal printer to which a thermal head is installed can be used. The recording method mentioned above has strong points in comparison with other conventional recording methods, namely, noiseless during recording, a developing and a printing procedure are not needle, maintenance free, apparatus is relatively low price and compact and a recorded pattern is very vivid. Therefore, along with the growth of information industry, the application of this method is widely expanded, for instance, applications for a facsimile or a computer, for many kinds of measuring equipment and for a label. The developed color image of these thermally sensitive recording media is mainly black color, however, a red color developing type, a blue color developing type, a green color developing type, a full color developing type and a dual color developing type are also well known.
The developed color of thermally sensitive recording media is comparatively sharp and close to photograph quality, and recently has been used as an output means of image which is taken by a camera attached to a game machine. Accompanied with the extension of uses, a thermally sensitive recording media which develops neutral color such as navy blue color or grayish blue color is coming to be desired. In the conventional field of thermally sensitive recording media, it is commonly observed that the developed color changes to navy blue color or grayish blue color by the effect of environment such as sun light and temperature, or by the effect of chemicals, however, this color change is a phenomenon which is recognized as a problem caused by poor color preserving. And the thermally sensitive recording medium whose original developed color is navy blue color or grayish blue color is not developed yet.
The object of this invention is to provide a thermally sensitive recording medium which has a sufficient color density and develops navy blue or grayish blue color.
To accomplish the above mentioned object, the present invention provides a thermally sensitive recording media having a thermally sensitive color developing layer containing a colorless or a pale colored dye precursor and a color developer as main components on a substrate, wherein the color difference L* value, a* value and b* value regulated by JIS-Z-8729 of developed image of said thermally sensitive recording media are within the regions of,
A. L* value is 30-50, a* value is −15-0 and b* value is −30-10,
B. L* value is 30-50, a* value is 0-10 and b* value is −30-0, or
C. L* value is 30-50, a* value is 10-20 and b* value is −30-15.
The color difference L* value is a parameter which indicates brightness, and when the plus of L* is big, the brightness becomes strong. The color difference a* value is a parameter which indicates green color, and when the minus value of a* is big, the greenish tone is strong. And when the value approaches to 0, the greenish tone becomes weak. Further, plus a* value indicates the reddish tone. Meanwhile, the color difference b* value is a parameter which indicate blue tone and when the minus value of b* is big, the bluish tone of b* strong. When the value is approaches 0, the bluish tone becomes weak, and plus b* value indicates yellowish tone. When the color differences L* value, a* value and b* value, of the developed image of the thermally sensitive recording media of this invention are within the aforementioned regions, the required navy blue or grayish blue color can be obtained. Further, when the color difference L* value is 30-45, a* value color is −15-0 and b* value is −25-10 or a* value color is 0-10 and b* value is −25-0, more vivid color tone can be obtained and desirable. On the contrary, when these color difference values are out of the regions regulated in this invention, the color of developed image becomes blue or black and the aimed color tone can not be obtained.
In this invention, the term of navy blue or grayish blue means dim and dark neutral color tone developing, which is disclosed, e.g., from pages 108 to 111, in items “46 SOFT & DULL BLUE” and “47 GRAYISH BLUE” of “Color one point 10, color naming and it's episode” (Japan Standard Society, issued on Nov. 19, 1993). These colors are expressed as dim blue or dark navy blue by JIS common name, or are expressed as indigo or gray blue by idiomatic color naming. Further, the expression of color becomes different by a subjectivity of inspector or by an illumination, and in this invention, the expression of navy blue or grayish blue color are typically used containing commonly expressed navy blue, cyan color or ultramarine color, however, it is not limited to them.
The invention particularly provides thermally sensitive recording medium as described above, wherein dye precursor includes at least one component selected from 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide and 3-(4-(diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide and at least one black color developing leuco dye whose maximum absorption wave length is from 420~480 nm and 550~640 nm. In this invention, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide and 3-(4-dimethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide are the leuco dye which develops bluish color, and the maximum absorption wave length of this invention is measured in 99% acetic acid solution. Thus, by the combination use of leuco dyes whose maximum absorption wave lengths are different, the thermally sensitive recording media which develops neutral color such as navy blue color or grayish blue color can be easily obtained while maintaining sufficient color developing density.
The invention further provides thermally sensitive recording media containing 0.05-1 parts of black color developing leuco dye whose maximum absorption wave length is 420-480 nm and 550-640 nm to 1 part of 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide or 3-(4-diethylamino-2-ethoxy phenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide. When the content of black color developing leuco dye is smaller than 0.05 parts to 1 part of bluish color developing leuco dye, the aimed color tone can be obtained, however, the bluish color becomes slightly strong. On the contrary, when the content is bigger than 1 part, the black color becomes slightly strong. Therefore, it is desirable to contain the black color developing leuco dye in the above mentioned ratio to the blue color developing leuco dye to obtain the thermally sensitive recording media whose developed image is vivid navy blue or grayish blue color and the contrast of image is good.
Further, the present invention provides the thermally sensitive recording media which develops navy blue or grayish blue color, and as mentioned above, the aimed color tone of this invention is not limited to the expression of navy blue or grayish blue color.
DETAILED DESCRIPTION OF THE INVENTION
As a leuco dye which develops blue color used in this invention, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide or 3-(4-diethylamino-2-ethoxy phenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide are desirably used, however, it is not intended to be limited to them, and other bluish developing leuco dye can be used. These mentioned leuco dyes can be used alone or used together.
As a leuco dye which develops black color which is used in this invention, the leuco dye whose maximum absorptio

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