Image recording medium

Details Image recording medium Image recording medium

2000-09-21

2003-08-19

Hamilton, Cynthia (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Dye image from radiation sensitive dye or dye former by dry...

Composition or product

C430S340000, C430S344000, C430S944000, C430S342000, C430S341000, C430S343000, C503S201000, C503S218000, C503S208000, C503S209000

Reexamination Certificate

active

06607871

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a high-sensitivity image recording medium comprising a compound which amplifies heat generation by the action of heat.
BACKGROUND OF THE INVENTION
A heat-sensitive recording material shows an image area and a non-image area as a temperature difference distribution. For this recording material, many systems have been devised such as those utilizing melt transfer or sublimation transfer of a colorant, color development reaction of two components by heat fusion or destruction of capsules and change of optical properties by phase inversion. This kind of a heat-sensitive recording medium is advantageous in that it can provide a recorded image in a simple dry system and requires no maintenance. Thus, the heat-sensitive recording medium has been widely used as an output material for various printers, word processors and facsimile machines. With the recent development of laser recording apparatus, the application of the heat-sensitive recording medium to optical disc and plate-making material has been studied. By incorporating a light and heat change material in such an image recording medium, heat mode recording is made possible.
Examples of image recording system utilizing heat generation by irradiation with laser beam include many processes involving the formation of an image by the removal or transfer of a dye such as laser ablation system disclosed in JP-A-7-164755 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-7-149063, and JP-A-7-149065, ablation transfer system disclosed in U.S. Pat. No. 5,171,650. However, these image forming systems are disadvantageous in that dust and waste materials must be disposed off.
On the other hand, besides these physical processes, there has been known a process utilizing the heat generation by laser beam for the color development or decolorization of a compound. A process utilizing the heat development by laser beam for the color development reaction of a leuco dye is disclosed in JP-A-10-337954, JP-A-11-91247, JP-A-11-91248, JP-A-11-91249, JP-A-11-180048, JP-A-11-181031, EP-A-909656, etc. A process utilizing the heat development by laser beam for the color decolorization reaction of a dye is disclosed in JP-A-10-16410, JP-A-8-292517, etc. These systems have no problems of dust and waste materials.
It is said that the temperature developed by the heat generation during irradiation with laser beam in the foregoing laser heat mode system is 1,000° C. or higher. Since the heat generation time is extremely short, a high power laser is required to give a sufficient sensitivity. It is also disadvantageous in that writing speed must be sacrificed to enhance the radiation energy density.
A system utilizing the color development/decolorization reaction of a compound by chemical reaction is disadvantageous in that the enhancement of radiation energy density causes the occurrence of ablation that leads to the occurrence of haze. The industry also has been in a dilemma that when the activation energy of chemical reaction is lowered to enhance sensitivity, it impairs the storage stability of the recording medium. Under these circumstances, it has been desired to develop a technique for maintaining the heat generation during the irradiation with laser beam while controlling the heat generation to a level such that no ablation takes place.
For the foregoing laser ablation system, the heat transfer ink ribbon described in JP-A-58-212625, JP-A-60-178082, and JP-A-60-145892, and the heat-sensitive recording material described in JP-A-7-164739, JP-A-7-323663, and JP-A-8-187948, a sensitivity enhancement technique utilizing a heat-generating compound capable of amplifying the heat generation has been developed. However, there is no reference to the development of such a technique to laser heat mode non-ablation or non-transfer type recording medium (image formation by color development/decolorization utilizing the absorption change of a compound).
SUMMARY OF THE INVENTION
An object of the present invention is to provide a technique for an image recording medium adapted for heat-sensitive recording system, in particular, laser heat mode system utilizing the absorption change of a compound which can attain enhancement of sensitivity of the recording medium without impairing the storage stability thereof and minimize the occurrence of haze due to ablation, thereby forming a sharp image, and provide an effective heat generator.
The objects of the invention are accomplished by the following aspects (1) to (12) of the invention.
(1) An image recording medium capable of recording an image with laser beam comprising a light and heat change material, characterized in that therein are incorporated a heat generator having no absorption at a wavelength of 500 nm or more which undergoes exothermic decomposition to amplify heat generation when acted upon by heat and a compound which undergoes thermochemical reaction to show an absorption change at a wavelength of from 360 nm to 900 nm.
(2) The image recording medium according to Clause (1), wherein the light and heat change material is a dye having absorption in the near infrared region.
(3) The image recording medium according to Clause (1) or (2), wherein the heat generator is a compound which decomposes at a temperature of from 80° C. to 400° C. to generate a heat of 100 J/g or more.
(4) The image recording medium according to any one of Clauses (1) to (3), wherein the heat generator is an ammonium salt of perchloric acid represented by the following general formula (1):
R
1
R
2
R
3
R
4
N
+
ClO
4
−
  (1)
wherein R
1
, R
2
, R
3
and R
4
may be the same or different, each represents a hydrogen atom, alkyl group, aryl group, alkenyl group, alkynyl group, aralkyl group or heterocyclic residue and may be connected to each other to form a ring.
(5) An image recording medium comprising the ammonium salt of perchloric acid represented by the general formula (1) defined in Clause (4) and a compound which undergoes thermochemical reaction to show an absorption change at a wavelength of from 360 nm to 900 nm.
(6) The image recording medium according to any one of Clauses (1) to (5), wherein the compound which shows an absorption change at a wavelength of from 360 nm to 900 nm is a colorless or light-colored leuco dye which undergoes thermochemical reaction induced by heat to develop color.
(7) An image recording medium comprising the heat generator definedin Clause (1), (3) or (4) anda compound which shows an absorption change at a wavelength of from 360 nm to 900 nm with the separation of a substituent caused by the action of heat or an acid.
(8) The image recording medium according to any one of Clauses (1) to (6), wherein the compound which shows an absorption change at a wavelength of from 360 nm to 900 nm is a compound which shows a change in the foregoing absorption range with the separation of a substituent caused by the action of heat or an acid.
(9) An image recording medium comprising the heat generator defined in Clause (1), (3) or (4) and a compound which generates an acid by the action of heat or an acid.
(10) The image recording medium according to Clause (9), wherein the compound which generates an acid by the action of heat or an acid is represented by the following general formula (2):
W
1
OP
1
  (2)
wherein W
1
represents a moiety to constitute the acid of formula W
1
OH, and P
1
represents a substituent separable by the action of heat or an acid.
(11) The image recording medium according to Clause (10), wherein the compound represented by the general formula (2) is a polymer formed by connecting plural monomers having a partial structure represented by W
1
OP
1
.
(12) The image recording medium according to any one of Clauses (1) to (8), further comprising the compound which generates an acid by the action of heat or an acid defined in any one of Clauses (9) to (11).
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be further described hereinafter.
The heat gener

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