JPH0310252A - Recording method - Google Patents

Abstract

PURPOSE:To improve the light resistance of color developed images by applying heat to an image forming material to execute recording and irradiating the material with light to activate an optical radical generating agent to develop colors in the parts other than impressed parts with the heat and applying the heat to the front surface of the image forming material. CONSTITUTION:The process for executing the recording by using the image forming material essentially consisting of the optical radical generating agent, microcapsules contg. the dye leuco body which develops colors by reacting with the optical radical generating agent and a reducing agent disposed on the outside of the capsules and by applying the heat to the image forming material, the process for irradiating the material with the light which can activate the optical radical generating agent to develop the colors of the parts exclusive of the parts impressed with the heat and the process for applying the heat over the entire surface of the image forming material are successively executed. The reducing agent is injected into all the capsules in the full-surface heating process in this way to trap the attack of the dyes developing the colors by the activation of the excess optical radical generating agent and, therefore, the light resistance of the color developed images is greatly improved.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a fixing type light and heat sensitive recording material comprising a photo-radical generator, a leuco dye which reacts with the photo-radical generator to form a color, and a reducing agent. More specifically, the present invention relates to a recording method that provides a colored image that is stable against light, heat, etc.

"Prior Art" Recently, thermal recording has attracted attention as a simple and maintenance-free recording method. As a heat-sensitive recording material,
A method using an electron-donating dye precursor and a phenol compound has been known for a long time, and is disclosed in Japanese Patent Publication No. 33712/1983.
It is described in detail in Japanese Patent Publication Nos. 60-43318, 58-87094, and 58-69089.

However, with heat-sensitive recording materials that use electron-donating dye precursors and phenolic compounds, the thermal activity of the unrecorded areas is not lost even after recording, so additional recording is possible or when exposed to high temperatures. It has the disadvantage of causing color development on the entire surface.

As a way to solve this drawback, research has long been carried out on heat-sensitive recording materials that utilize the dye-forming reaction between diazo compounds and couplers.After recording, the diazo compound can be decomposed and fixed by irradiating the entire surface with light. It is. (JP-A-59-190886, JP-A-61-1219688, etc.).

On the other hand, as another fixable heat-sensitive recording method, a heat-sensitive recording material containing a photo-radical generator, a leuco dye that reacts with the photo-radical generator to develop color, and a reducing agent as main components has also been proposed. (Patent Application No. 63-245819, etc.).

That is, a photoradical generator and a leuco dye are encapsulated in thermoresponsive microcapsules, while a recording layer containing a reducing agent capable of trapping the activated photoradical generator is placed on a support outside the capsule. By applying heat to the recording material, the reducing agent is injected into the capsule through the capsule wall, and then by irradiating light that can activate the photoradical generator, the heat is released. The photoradicals activated by light react with the leuco dye in areas other than the areas to which it is applied, producing color. At this time, the photoradicals activated by light in the heat-applied area selectively react with the reducing agent and do not cause the leuco dye to develop color.

The recording method using the above-mentioned recording material has characteristics such as high recording density, high photosensitivity, and the ability to obtain a "negative" image for thermal printing, which is advantageous when recording with many colored parts. have However, it was found that the light fastness of the developed color image was weak as a drawback.

``Problem to be solved by the inventionj'' Research by the present inventors has shown that the light resistance of heat-sensitive recording materials using photo-radical generators depends on the amount of photo-radical generators remaining after recording. It was confirmed that the smaller the amount of photo-radical generator used, the better the light resistance of the recorded color image.On the other hand, the more photo-radical generator is used, the lower the photosensitivity during color development. It was also confirmed that the optimum points of the two do not match, and new methods are needed to provide a fixing type heat-sensitive recording material using a photoradical generator that has high color density and good light resistance of the color image. It was found that some improvement measures were needed.

``Object of the Invention'' The object of the present invention is to produce a color image using an image forming material containing a photo-radical generator, a leuco dye that reacts with the photo-radical generator to form a color, and a reducing agent. The object of the present invention is to provide a recording method with improved performance.

The above object of the present invention is to provide microcapsules containing a photoradical generator and a leuco dye that reacts with the photoradical generator to form a color on a support, and a microcapsule containing a leuco dye that reacts with the photoradical generator to form a color. (2) performing recording by applying heat to the line image forming material using an image forming material provided with at least one light and heat sensitive recording layer containing a reducing agent as a main component; (2) the photo radical generating agent; This was achieved by a recording method characterized by sequentially performing the following steps: (3) applying heat to the entire surface of the image forming material; and (3) applying heat to the entire surface of the image forming material.

That is, the conventional recording method for a heat-sensitive recording material provided with at least one heat-sensitive recording layer containing a photo-radical generator, a dye Koico which reacts with the photo-radical generator to form a color, and a reducing agent is: a step of recording by applying a voltage to the recording material;
While the two steps involved irradiating light that can activate the photo-radical generator and developing color in areas other than the areas to which heat has been applied, the process now involves the addition of a step of applying heat to the gold surface of the image-forming material. It has been found that the light resistance of the developed color image is significantly improved by this method. The reason for this is presumed to be that the reducing agent is injected into all the capsules in the entire surface heating step (2), trapping the excess photoradical generator from activating and attacking the colored dye.

The fixing type image forming material used in the present invention will be described in detail below.

The leuco dye used in the present invention is, for example, U.S. Pat.
Those described in the specification of No. 445234 can be used, and typical structures include the following.

1) Aminotriarylmethane 2) Aminoxanthine 3) Aminothioxanthine 4) Amino-9,10-dihydroacridine 5) Aminophenoxazine 6) Aminophenothiazine 7) Aminodihydrophenazine 8) Aminodiphenylmethane 9) Leucomendamine 10) Aminohydrocinnamic acid (cyanoethane, leucomethine) II) Hydrazine 12) Leucoidigoid dye 13) Amino-2,3-dihydroanthraquinone 14)
Tetrahalo p, p, -hiphenol 15) 2-(p-
Hydroxyphenyl)-4,5-diphenylimidazole 16) Phenethylaniline Among these leuco forms, 1) to 9) are modified by losing one hydrogen atom to 10) to 16)! A parent dye is produced by losing two more hydrogen atoms.

Examples of specific compounds include Leukoku I) star violet, tris-(4-diethylamino 0-tolyl)
-methane, bis-(4-diethylamino-0-tolyl)
-phenylmethane, bis(4-diethylamino-0-)
lyl)-thienyl 2-methane, bis-(2-chloro-4
-diethylaminophenyl)-phenylmethane, 2-(
2-chlorophenyl)amino-6-N,N-dibutylamino-9-(2-methoxycarbonyl)-phenylxanthine, 2-N,N-dibenzylamino-6-N,N-diethylamino-9-(2-methoxy carbonyl)-phenylxanthine, benzo(a)-6-N,N-diethylamino-9-(2-methoxycarbonyl)-phenylxanthine, 2-(2-chlorophenyl)-amino-6
-N,N-dibutylamino-9-2-methylphenylcarboxamide)-phenylxanthine, 3゜6-simethoxy9-(2-methoxycarbonyl)-phenylxanthine, 3,6-dinitoxyethyl-9-(2 -methoxycarbonyl)-phenylxanthine, benzoylleucomethylenepurine, 3,7-bis-diethylaminophenoxazine, and the like.

On the other hand, preferred photoradical generators that can be used in the imaging materials used in the present invention are normally inert, but when exposed to active radiation such as visible light, ultraviolet light, infrared radiation, and X-rays, dye leuco It produces a chemical species that oxidizes to its colored form.

As a representative photo-radical generator,
728, 2. described in Japanese Patent Publication No. 63-2099. 4.
5-) Lofine dimer compounds such as aryl imidazole dimers, azide compounds such as 2-azidobenzoxazole, benzoyl azide, and 2-azidobenzimidazole described in U.S. Pat. No. 3,282,693, U.S. Pat.
3'-ethyl-1-methoxy-2 described in No. 615568
-Pyridothiacyanine verchlorate, 1-methoxy-
Pyridinium compounds such as 2-methylpyridinium-p-)luenesulfonate, N-promosuccinimide, tribromomethylphenylsulfone, diphenyliodine, 2
-Trichloromethyl-5-(p-butoxystyryl)-
Organic halogen compounds such as 1,3,4-oxacyazole, 2,6-dydrichloromethyl-4-(p-methoxyphenyl)-triazine, azide polymers described in the abstract of the 1968 Spring Research Presentation of the Photographic Society of Japan, page 55 etc. can be mentioned. Among these, lophine dimer compounds and organic halogen compounds are preferred, and the combination of both is optimal because high sensitivity can be achieved.

In producing the image forming material used in the present invention, the molar ratio of the leuco dye and the photoradical generator is 10:1 to 1.
The mixing ratio is preferably 1:10, and the more preferable mixing ratio is 2:1 to 1:2.

In order to promote the oxidative color development of the leuco dye, an acid is additionally required, and the required amount is 0.2 to 3 mol per 1 mol of the leuco dye.

The required amount of acid varies depending on the type of leuco dye, and adding too much will actually reduce the coloring ability.

As the wall material of the capsule used in the present invention, gelatin, polyurea, polyimide, polyester, polycarbonate, melamine, etc. can be used. In addition, in order to impart thermal responsiveness to the capsule wall, the Tg of the capsule wall may be set to be above room temperature and below 200°C, especially 7
A range of 0°C to 150°C is preferred.

The glass transition moisture content of the capsule wall can be controlled by selecting a type of polymer for the capsule wall. Preferred wall materials include polyurethane, polyurea, polyamide, polyester, polycarbonate, etc. Polyurethanes and polyureas are preferred.

The microcapsules used in the present invention are produced by emulsifying a core material (a solution of a hydrophobic solvent for boat fishing) containing an image-forming substance such as a leuco dye and a photoradical generator, and then emulsifying the core material around the emulsified oil droplets. It is made by forming a wall of polymeric material. In this case, the wall-forming reactant is added to the interior of the oil droplet and/or to the exterior of the oil droplet.

When the microcapsule wall of the present invention is made using a microcapsule method by polymerizing a glue actant from inside an oil droplet, it has a uniform particle size within a short period of time, and has excellent storage stability. A capsule can be obtained which is preferable as a material.

For specific examples of microencapsulation techniques, materials and compounds used, see U.S. Pat.
No. 796696.

For example, when polyurethane or polyurea is used as a turnip or cell wall material, a polyvalent isocyanate and a second substance (e.g. polyol or polyamine) that reacts with it to form the capsule wall are added to the aqueous phase or the oily liquid to be encapsulated. The microcapsule wall is formed by emulsifying and dispersing it in water, and then raising the temperature to cause a polymer formation reaction at the oil droplet interface.

By appropriately selecting the polyvalent isocyanate as the first wall-forming substance and the polyol or polyamine as the second wall-forming substance, the glass transition point of the capsule wall can be significantly changed.

High boiling point oils are used as the organic solvents forming the core of the capsules, specifically phosphoric acid esters, phthalic acid esters, acrylic acid esters, methacrylic acid esters, other carboxylic acid esters, fatty acid amides, Examples include alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, diarylethanes, and chlorinated paraffins.

Low boiling point co-solvents can also be added to aid in dissolving the wall material. Specific examples of the auxiliary solvent include ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride, cyclohexanone, and the like.

Furthermore, in order to make the emulsified oil droplets stable, protective colloids and surfactants can be added to the aqueous phase. As the protective colloid, water-soluble polymers can be used for boat fishing.

In the present invention, the size of the microcapsules is set at a volume average of 2
The thickness is preferably 0 μm or less and 0.3 μm or more, more preferably 4 μm or less and 0.8 μm or more.

Next, in order to fix the image forming material in the present invention, it is sufficient to prevent the photoradical generator from being activated.
For that purpose, active reducing agents are used. By placing a reducing agent in the vicinity of the photoradical generator, the activated photoradicals are immediately reduced and lose their ability to oxidize the leuco dye.

That is, such a reducing agent acts as a so-called free radical scavenger that traps free radicals.

Specific examples of the reducing agent include hydroquinone compounds and aminophenol compounds that have a hydroxyl group on a benzene ring and at least another hydroxyl group or an amino group at another position on the benzene ring, as described in US Pat. No. 3,042,515;
Examples thereof include the cyclic phenylhydrazide compound described in '39728, and further compounds selected from guanidine derivatives, alkylene diamine derivatives, and hydroxyamine derivatives. They can be used alone or in combination of two or more, but are not limited to these as long as they are reducing substances that have the function of acting on so-called oxidizing agents.

In the image forming material, the reducing agent is preferably used in an amount of 1 to 100 times, more preferably 5 to 20 times, the amount of the photooxidizing agent component.

In the present invention, known photosensitizers, ultraviolet absorbers, and antioxidants may be added as additional components of the photoradical generator.

Further, in the present invention, it is possible to use an auxiliary agent for the purpose of freely controlling thermal recording or thermal fixing. This auxiliary agent has the effect of lowering the melting point of each component constituting the system and lowering the glass transition point of the capsule wall.

Such auxiliary agents include phenolic compounds, alcohol compounds, amide compounds, sulfonamide compounds, etc., and these may be contained in the core material or added as a dispersion outside the microcapsule. .

Next, a method for producing the image forming material used in the present invention will be described, and since microcapsules are useful, this will be taken as an example.

The leuco dye, the photoradical generator, and the photoreductor are all dissolved in a high boiling point solvent. In addition, organic acids to promote the color reaction, antioxidants to suppress the reaction before use, and ultraviolet absorbers to control the photosensitive wavelength are added to the high boiling point solvent, and the capsule wall A forming material, such as an isocyanate, is added.
At this time, a low boiling point solvent may also be used as a solubilizing agent. This oil is poured into a water-soluble polymer solution and emulsified by vigorously stirring with a homogenizer or the like. A polyol, etc., which is a capsule wall forming material, is further added to the emulsion and heated to form a wall at the interface between the oil and water layers.

The reducing agent is generally used after being pulverized to several μm in a water-soluble polymer solution using a wet dispersion machine such as a ball mill or a sand mill.

The capsule liquid and the reducing agent dispersion are mixed to form a coating liquid. In order to realize multicolor recording, it is necessary to prepare at least two or more types of coating liquids with different color hues.

This coating liquid is applied onto the support. At this time, a binder is added to the above 6- coating solution for the purpose of strengthening the strength of the coating film, and an organic or inorganic pigment is added for the purpose of improving the whiteness of the coated surface to improve handling and to add heat during heating. Waxes, metal soaps or surfactants may be added to prevent adhesion to heat sources such as drums and thermal heads.

The coating amount of the image forming layer in the present invention is 0.1 to 2 g/mm2, especially 0.1 to 2 g/mm2 in terms of solid content as dye leuco body.
2 to 1 g/mm2 is preferred.

Suitable materials for the support include papers and regenerated cellulose,
Examples include plastics such as cellulose acetate, cellulose nitrate, polyethylene terephthalate, polyethylene, polyvinyl acetate, polymethyl methacrylate, and polyvinyl chloride, synthetic paper, and the like.

Methods for coating the support include air knife coating, curtain coating, slide coating, roller coating, dip coating, wire barcoding, blade coating, gravure coating, spin coating, or extrusion coating. etc., but are not limited to these.

In the present invention, when an image is formed by heating, it is exactly the same as ordinary thermal recording, and can be performed using a thermal pen or a thermal head.

For color development and fixation using light, fluorescent lamps, mercury lamps,
Metal halide lamps, xenon lamps, tungsten lamps, etc. can be used as light sources.

Furthermore, as methods for heating the entire surface, there are methods such as heating with a heat drum, a heat head, an infrared lamp, etc. Examples are shown below, but the present invention is not limited thereto. Note that "parts" indicating the amount added indicate "parts by weight."

"Example" Example 1 Preparation of dye leuco into capsule liquid (blue coloring): Leuco crystal violet 1. 0 parts photoradical generator 2.2'-bis-(0-chlorophenyl)-4,4',
5.5'-tetetraphenylimidazole 2.
0 parts Additives Nidodecylbenzenesulfonic acid 0. 4 parts 2.5-Getashary-octylhydroquinone 0. 6 parts Capsule wall agent: 15 parts xylylene diisocyanate/trimethylolpropane adduct Auxiliary solvent: 20 parts ethyl acetate 18 parts high-boiling solvent nitricresyl phosphate were uniformly dissolved. This solution was added to 54 parts of a 6% by weight aqueous solution of polyvinyl alcohol (degree of polymerization 1700, degree of saponification 88%) and emulsified and dispersed using a homogenizer at 20°C to obtain an emulsion with an average particle size of 1 μm. . 68 parts of water was added to the resulting emulsion, and stirring was continued at 40°C for 3 hours. Thereafter, the temperature was returned to room temperature to obtain capsule liquid A.

9 Preparation of reducing agent dispersion 1-phenylpyrazolidin-3-one (phenidone A)
30 parts of the above polyvinyl alcohol 4% by weight aqueous solution 15
0 parts and dispersed in a horizontal sand mill to obtain an average particle size of 1 part.
A phenidone A dispersion of μm was obtained.

Next, a coating solution having the following composition was prepared.

6.8 parts of the above capsule liquid 2.0 parts of the above reducing agent dispersion This coating liquid was applied to high-quality paper (basis weight 76 g/m2) with a coating rod so that the dye leuco body coating amount was 0.4 g/m2. ,
The image forming material used in the present invention was obtained by drying at 50°C.

The obtained recording sheet was subjected to a printing test machine using a Kyocera KLT type thermal head at a printing power of 0. 35
W/ data, printing density 8x7.7dot/m
Images were recorded under conditions of m2 and printing time of 1.0 ms.
After that, a 40W ultraviolet fluorescent lamp (emission wavelength 420
When exposed to light for 15 seconds at a distance of about 10 cm using a 200 nm), a bright blue color was developed except for the area recorded with a thermal head. When this sample was passed through a hot roll heated to 120° C. at a speed of 2 cm/s, no change in appearance was observed.

Example 2 In Example 1, the leuco dye was changed to Henzo[a]-6-N
, N-diethylamino-9-(2-methoxycarbonyl)phenylxanthine was used, but the same procedure was followed.

The coloring hue is a bright magenta color.

Example 3 The same procedure as in Example 1 was carried out except that the reducing agent in Example 1 was changed to tert-butylhydroquinone. In appearance, an image completely similar to that of Example 1 was obtained.

Comparative Example 1-3 In Example 1-3, only the final entire surface heat treatment step was omitted.

Table 1 shows the values measured using the Hitachi Model 307 spectrophotometer for the color density of the thermal printing area and the non-thermal printing area (both are 380
(indicates the maximum absorption density at nm-780 nm) and the results of measuring the density by the same means after the coloring part was left under illumination such as fluorescence of 10001 ux for 100 hours.

It can be seen from Table 1 that the printing method of the present invention significantly improves the light resistance of the developed color image.

Table 1 23

Claims (1)

[Claims] On a support, at least a light- and heat-sensitive recording layer containing a photo-radical generator, a microcapsule containing a leuco dye that reacts with the photo-radical generator to form a color, and a reducing agent disposed outside the capsule is provided as a main component. Using an image forming material provided with one layer, (1) recording by applying heat to the image forming material, (2) irradiating light that can activate the photoradical generator, and applying heat to the area other than the area to which the heat was applied. a step of developing color, (3)
A recording method characterized by sequentially performing the step of applying heat to the entire surface of the image forming material.