Ink jet recording sheet

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Reexamination Certificate

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C428S195100, C428S211100, C428S331000

Reexamination Certificate

active

06312794

ABSTRACT:

The present invention relates to an ink jet recording sheet, particularly to a high-quality ink jet recording sheet improved against yellowing under a blank state and excellent in ink absorptivity.
The ink jet recording system is a system which jets and deposits fine droplets of ink on a recording sheet such as a paper sheet on various operational principles representatively by the deflection method, the cavity method, the thermo-jet method, the bubble jet method, the thermal ink jet method, the slit jet method or the spark jet method to record images or letters. By virtue of its merits such as high speed, low noise, easiness of multicolor recording, flexibility in recording patterns and exemption from development-fixation, it has been rapidly finding versatile applications in recording apparatus for various patterns including Chinese characters and for color images.
Further, images recorded by the ink jet recording system with color inks containing coloring materials of yellow, magenta, cyan and black in solvents such as water and hydrophilic solvents can be comparable to those obtained by multicolor printing involving platemaking. Further, for the purpose of making a small number of copies, the ink jet recording system has been applied widely even in the field of full color image recording, because the ink jet recording system costs less than development of silver salt photographs.
The recent technological developments has broadened the applications of the ink jet recording system, and its applications, even only in output of hard copies, are roughly classified into three: (1) for common use (for home use and for hobby use), (2) for OA (for office use) and (3) for industrial use (for EA and for FA). Especially for industrial use, the ink jet recording system has been spreading due to demand for highly fine hard copies of at least 400 dpi (16 dots/mm).
In particular, highly fine hard copies obtainable by ink jet recording are a potent substitute for silver salt photographs, and storage stability is an important characteristic requisite for ink jet recording sheets not to speak of color reproducibility and gradation of images. The storage stability of ink jet recording sheets generally refers to fading, discoloration and blurring of printed images (storage stability of printed images) and to discoloration and foxing of blank sheets (storage stability under a blank state).
With respect to storage stability of images, it is known that change from conventional water-soluble dyes to such fast pigments as proposed in JP-A-57-10660, JP-A-57-106601, JP-A-4-234467, JP-A-5-156189, JP-A-5-179183, JP -A-5-202324, JP-A-5-263029, JP-A-5-331397, JP-A-6-122846 and JP-A-6-136311 improves light resistance, water resistance and ozone resistance drastically.
Besides, change to oil-soluble dyes such as naphtol dyes, azo dyes, metal complex salt dyes, anthraquinone dyes, quinoimine dyes, indigo dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, carbonium dyes, naphthoquinone dyes, naphthalimide dyes, phthalocyanine dyes and perinine dyes proposed, for example, in JP-B-7-78187, JP-B-7-78188, JP-B-8-6057, JP -B-8-26259, JP-B-6-247034 and JP-B-6-306319 enables production of ink jet recording sheets with high image density excellent in color development as well as in water resistance and cockling resistance.
As discussed above, the recognition of the importance of comprehensive research for improvement of not only ink jet recording sheets but also ink to storage stability of printed images has actually brought great improvement.
On the other hand, with respect to storage stability under a blank state, improvement against yellowing is the main subject to investigate. Yellowing under a blank state is not only attributable to light, ozone, NO
x,
heat and moisture but also can be caused by certain kinds of anti-oxidants. Especially, the latter case is known to happen when highly fine hard copies are kept in a file or adhesive tape is attached to the surface of the ink receiving layer. This problem is of great importance to the ink jet recording system as a substitute for silver salt photography, and no satisfactory ink jet recording sheets are available yet in spite of various studies for improvement.
Ink jet recording sheets have to meet various requirements such as high printed dot density, a bright and vivid color tone, ink absorption swift enough to prevent the ink from running or blurring even from overlapping printed dots, avoidance of unnecessarily wide spread printed dots, ink dots with smooth peripheries which are almost completely circular in shape and are not blurred, and high brightness. Application or incorporation of synthetic amorphous silica and/or its salt to a paper surface optionally together with a binder resin as disclosed in JP-A-57-157786, incorporation of hydrated porous cationic aluminum oxide as disclosed in JP-A-60-232990, and incorporation of synthetic amorphous silica having a large BET specific surface area or hydrated cationic aluminum oxide which is cationic colloidal particles as disclosed in JP-A-60-204390 and JP-A-2-198889 work to this end.
However, these ink jet recording sheets are liable to yellowing under a blank state, and simple use of synthetic amorphous silica having a large specific surface area in pursuit of image density or color development intensified yellowing very noticeably.
Accordingly, the object of the present invention is to provide a high-quality ink jet recording sheet improved against yellowing under a blank state which can happen when highly fine hard copies obtained by ink jet recording are kept in a file or adhesive tape is attached to the surface of the ink receiving layer, and having an excellent ink absorptivity.
As a result of extensive research on the problem, the present inventors speculated that yellowing under a blank state which can happen when highly fine hard copies obtained by ink jet recording are kept in a file or when adhesive tape is attached to the surface of the ink receiving layer was attributable to phenolic anti-oxidants in the file or the adhesive tape represented by 2,6-di-tert-butyl-4-methylphenol (hereinafter referred to as BHT).
Typical examples of these phenolic anti-oxidants are BHT (Sumilizer BHT: Sumitomo Chemical Company, Ltd., Yoshinox BHT: Yoshitomi Fine Chemicals, Ltd., Antage BHT: Kawaguchi Chemical Industry Co., Ltd.), n-octadecyl 3-(3′, 5′-di-tert-butyl-4′-hydroxyphenyl)propionate (Irganox 1076: Ciba- Geigy, ADEKASTABU AO-50: ASAHI DENKA KOGYO K.K., Sumilizer BP-76: Sumitomo Chemical Company, Ltd., Tominox SS: Yoshitomi Fine Chemicals, Ltd.), 4,4′-butylidenebis-(3-methyl-6-t-butylphenol) (ADEKASTABU AO -40: ASAHI DENKA KOGYO K.K., Sumilizer BBM-S: Sumitomo Chemical Company, Ltd., Yoshinox BB: Yoshitomi Fine Chemicals, Ltd., Antage W300: Kawaguchi Chemical Industry Co., Ltd., Noclizer NS30: Ouchi Shinko Chemical Industrial Co., Ltd., Nonflex BB: Seiko Chemical Co., Ltd.), tetrakis [methylene-3-(3′,5′-di-tert-butyl-4-hydroxyphenyl)propionate]methane (Irganox 1010: Ciba-Geigy, ADEKASTABU AO-60: ASAHI DENKA KOGYO K.K., Sumilizer BP101: Sumitomo Chemical Company, Ltd., Tominox TT: Yoshitomi Fine Chemicals, Ltd., TTHP: Toray Industries, Inc.), 2,2′-methylenebis(4-methyl-6-t-butylphenol) (Sumilizer MDP-S: Sumitomo Chemical Company, Ltd., Yoshinox 2246R: Yoshitomi Fine Chemicals, Ltd., Antage W400: Kawaguchi Chemical Industry Co., Ltd., Nocrac NS-6: Ouchi Shinko Chemical Industrial Co., Ltd., Nonflex MBP: Seiko Chemical Co., Ltd.), 4,4′-thiobis(3-methyl-6-t-butylphenol) (Sumilizer WX-R: Sumitomo Chemical Company, Ltd., Yoshinox SR: Yoshitomi Fine Chemicals, Ltd., Antage crystal: Kawaguchi Chemical Industry Co., Ltd., Noclizer 300: Ouchi Shinko Chemical Industrial Co., Ltd., Nonflex BPS-R: Seiko Chemical Co., Ltd.), tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (Irganox 3114: Ciba-Geigy, ADEKASTABU AO-20: ASAHI DENKA KOGYO K.K.), and triethylene glycol bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)pronionate] (Irgano

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