JPH09218483A - Photosensitive capsule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain such a photosensitive capsule that the material in the capsule hardly flows out of the capsule and the photosensitivity does not decrease by specifying the solubility of the all materials with water in the photosensitive capsule except a material insoluble with water. SOLUTION: The capsule contains at least an image-forming material such as a dye or pigment, and a photosensitive material which reacts with light and changes its mechanical strength. The solubility of the all materials with water included in the photosensitive capsule except a material which does not dissolve in water is specified to about <=5g/l. This photosensitive capsule consists of an outer shell and an inner liquid component. The liquid component contains at least an image-forming material such as a dye and pigment, and a photosensitive material which reacts with light to change its mechanical strength. The solubility of the all liquid component with water is required to be about <=5g/l.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive capsule used in an image forming apparatus, a printer or the like.

[0002]

2. Description of the Related Art Conventionally, a photosensitive capsule, which contains an image forming material such as a dye precursor, a dye, and a pigment, and whose mechanical strength is changed in response to light, is used after exposing the capsule.
Image forming apparatuses for forming an image on an image receiving paper by a developing method that destroys only weakly encapsulated toner by applying pressure are disclosed in JP-A-4-324861 and 4-3244862.
No. 4, No. 4-324863, No. 5-68871, No. 5
No. 666559 and No. 5-297552. The photosensitive capsules used in these image forming apparatuses have various production methods, but it is considered that they are often produced by an in-situ method. This in-si
In the tu method, when the inclusion is oil-soluble, the inclusion is emulsified and dispersed in water to prepare an oil-in-water (hereinafter referred to as O / W) emulsion. After that, a material to be the source of the outer shell is added and reacted at the O / W interface to form a capsule. According to this method, it was possible to prepare a capsule by adjusting the conditions even if the encapsulated substance contained a substance having a high solubility in water.

[0003]

However, in a photosensitive capsule containing a substance having a high solubility in water as an inclusion, the inclusion passes through the outer shell of the capsule,
There was a phenomenon that the substance was released outside the capsule very quickly. It is considered that this is because a large number of pores are formed in the outer portion. When the encapsulated substance in the capsule is released in this way, there arises a problem that the photosensitivity of the capsule is lowered.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photosensitive capsule in which the inclusion does not easily flow out and the photosensitivity is not lowered.

[0005]

In order to achieve this object, the photosensitive capsule according to claim 1 of the present invention comprises at least an image forming material such as a dye or a pigment and mechanical strength in response to light. Targeting the inclusion of a photosensitive substance whose content changes, in particular, among the substances included in the photosensitive capsule, the solubility in water of all other substances excluding those not soluble in water is about 5 g. / L or less. Therefore, the release of the inclusions from the outer portion of the capsule is suppressed, and as a result, the decrease in the photosensitivity is prevented.

[0006]

Embodiments of the present invention will be described below.

The photosensitive capsule is composed of an outer shell portion and a liquid component inside the outer shell portion.

The average particle size of the photosensitive capsules is 5 μm.
˜50 μm is desirable, but is not particularly limited.

The liquid component is composed of at least an image forming material such as a dye or a pigment, and a photosensitive substance whose mechanical strength changes in response to light. All of these liquid components must have a solubility in water of about 5 g / l or less.

As the image forming material, dyes, inorganic pigments, organic pigments, and dye precursors that change color by reacting with a color developer can be used, but the pigments are basically insoluble in water. However, since there are many dyes or dye precursors that are soluble in water, it is necessary to conduct a solubility test in advance before use.

As the pigment, substances conventionally used can be used as they are, and monoazo pigments, disazo pigments, azo lake pigments, quinacridone pigments, perylene pigments, anthrapyrimidine pigments, isoindolinone pigments. Examples thereof include organic pigments such as selenium pigments and phthalocyanine pigments, and inorganic pigments such as carbon black, yellow lead, red iron oxide, titanium oxide, molybdenum red, cadmium red, cobalt blue, and chrome green.

Examples of dyes and dye precursors include coumarin dyes, merocyanine dyes, thiazine dyes, azine dyes, methine dyes, oxazine dyes, phenylmethane dyes, cyanine dyes, anthraquinone dyes, and pyrazoline dyes. Dyes, stilbene-based dyes, quinoline-based dyes, and the like, and desirable dye precursors are diphenylmethane-based compounds, triphenylmethane-based compounds, bisphenylmethane-based compounds, xanthene-based compounds, thiazine-based compounds, and fluorane-based compounds. Examples thereof include spiropyran-based compounds and the like and mixtures thereof, but the solubility in water needs to be about 5 g / l or less. In general, a substance having a large molecular weight and having no hydroxyl group is considered to have low solubility in water, and thus such a substance is more preferable.

As the polymerizable substance, an unsaturated compound can be used, and examples thereof include a compound having an ethylenically unsaturated group and a compound having an epoxy group, but a compound having an ethylenically unsaturated group is preferable. Of course, this polymerizable substance must also have a solubility in water of about 5 g / l or less.

Examples of the compound having an ethylenically unsaturated group include acrylic acid esters, acrylamides, methacrylic acid and its salts, methacrylic acid esters, methacrylamides, maleic anhydride, maleic acid esters,
Itaconic acid esters, styrenes, vinyl ethers,
Examples thereof include vinyl esters, N-vinyl heterocycles, allyl ethers, allyl esters, and derivatives thereof. Particularly preferred are acrylic acid esters or methacrylic acid esters.

Specific examples of acrylic acid esters include:
2-hydroxy-3-phenoxypropyl acrylate, 1,3-dioxolane acrylate, hexanediol diacrylate, butanediol diacrylate,
Tripropylene glycol diacrylate, bisphenol A diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, hexaacrylate of dipentaerythritol caprolactone adduct, trimethylolpropane triacrylate, triacrylate of propylene oxide adduct of trimethylolpropane , Polyoxyethylenated bisphenol A diacrylate, polyester acrylate, polyurethane acrylate and the like.

Specific examples of methacrylic acid esters include noniphenyloxyethyl methacrylate, 1,3
-Dioxolane methacrylate, hexanediol dimethacrylate, butanediol dimethacrylate, neopentyl glycol dimethacrylate, tricyclodecane dimethylol dimethacrylate, tripropylene glycol dimethacrylate, bisphenol A dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, Hexamethacrylate, a trimethylolpropane trimethacrylate, a propylene oxide adduct of trimethylolpropane, a dimethacrylate of polyoxyethylenated bisphenol A, a polyester methacrylate, a polyurethane methacrylate and the like can be mentioned.

These polymerizable substances may be used alone or as a mixture of two or more kinds.

The photopolymerization initiator is one which is sensitive to light and initiates polymerization of the resin, and a direct cleavage type, hydrogen abstraction type, two-molecule type initiator or the like can be used. Specific examples of these initiators include aromatic carbonyl compounds, acetophenones, organic peroxides, diphenylhalonium salts, organic halides, 2,4,6-substituted-S-triazines, 2,4,5 -Triarylimidazole dimer, azo compound, dye borate complex, iron arene complex,
And titanocene compounds. Desirably, benzophenone, benzyl, xanthone, thioxanthone, anthraquinone, acetophenone, 2,2-dimethyl-2
-Morpholino-4'-methylthioacetophenone, benzoyl peroxide, 3,3 ', 4,4'-tetrakis (t-butyldioxycarbonyl) benzophenone, diphenyliodonium bromide, diphenyliodonium chloride, carbon tetrachloride, tetrabromide Carbon, 2,
4,6-tristrichloromethyl-S-triazine,
(Η ⁵ -2,4-cyclopentadien-1-yl)
[(1,2,3,4,5,6-η)-(1-methylethyl) benzene] iron (1+) hexafluorophosphate (1-) and the like. Further, these photopolymerization initiators may be used alone or as a mixture of two or more kinds.

The photosensitive capsule having the above-mentioned structure can be manufactured by a method which is already known in the art. For example, US Pat. No. 2,800,457,
No. 2800458, Phase separation method from aqueous solution as shown in each specification, etc., Japanese Patent Publication Nos. 38-19574 and 4
No. 2-446, No. 42-771, and other interfacial polymerization methods, Japanese Patent Publication No. 36-9168, Japanese Patent Laid-Open No. 5168/1985
No. 1-9079, in-situ method by polymerization of monomer as disclosed in each publication, British Patent No. 9
Although there are melt dispersion cooling methods and the like shown in the respective specifications of No. 52807 and No. 965074, the present invention is not limited thereto. Generally, the in-situ method is known as the most desirable method.

The material for forming the outer shell may be an inorganic substance or an organic material as long as the outer shell can be produced by the capsule manufacturing method. Desirably, the material is an organic substance that can sufficiently transmit light.

Specific examples include gelatin, gum arabic, starch, sodium alginate, polyvinyl alcohol, polyethylene, polyamide, polyester, polyurethane, polyurea, polyurethane, polystyrene, nitrocellulose, ethyl cellulose, methyl cellulose, melamine-formaldehyde resin, urea-formaldehyde. Examples thereof include resins and their copolymers.

In the photosensitive capsule having the above structure, the release of the encapsulated material is suppressed, and as a result, the deterioration of the photosensitivity can be prevented. This is because the release of the inclusion is caused and the following reasoning is made.

It is considered that when a substance having a high water solubility is used for the encapsulated substance, the substance having a high water solubility is dissolved into water during the production of the capsule to form pores in the outer shell of the capsule. To be Strictly speaking, the outer shell of the capsule always has pores, but it is considered that the degree of pores (diameter or number) varies depending on the degree of solubility in water. Therefore, the degree of solubility of the inclusion in water determines the release of the inclusion. As a result of various studies, it was found that the release of the inclusions was within the allowable range if the solubility in water was about 5 g / l or less. Therefore, the solubility of all substances contained in capsules in water is approximately 5 g / l.
By the following, the release of the inclusions is suppressed, and as a result, it is possible to prevent the deterioration of the photosensitivity.

[0024]

Next, specific examples of the present invention will be described.

Example 1 550n containing a magenta pigment as an image forming material
A magenta image recording microcapsule having a photosensitivity near m is prepared.

To 100 parts by weight of a mixture of 2-hydroxy-3-phenoxypropyl acrylate and dipentaerythritol hexaacrylate in a ratio of 3: 4, 3 parts by weight of a quinacridone pigment is dispersed using a polymer polyurethane as a dispersant. Solubility in water is 1.9g
0.3 parts by weight of a cyanine dye, 0.5 parts by weight of N, N-dimethylaniline, and 2 parts by weight of 2,4,6-tristrichloromethyl-S-triazine, which is a photopolymerization initiator. In addition, a hydrophobic liquid component was obtained by heating at 100 ° C. for 10 minutes. The quinacridone pigment is obtained by using the image forming material of the present invention with a cyanine dye, N, N-
Dimethylaniline and 2,4,6-tristrichloromethyl-S-triazine are photosensitive substances.

The solubility of the cyanine dye was determined as follows. First, an excess cyanine dye is added to 1 liter of water and stirred for 1 hour. Then the solution is filtered,
The undissolved dye was separated and dried, the weight was measured, and the solubility was calculated from the difference from the amount initially added.

Next, the hydrophobic liquid component was added to 100 cc of a 1: 1 aqueous solution of a 5% polystyrene sulfonic acid partial sodium salt aqueous solution as an emulsifier and a 5% styrene-maleic anhydride copolymer aqueous solution, 6 with a homogenizer
5,000 rotations, stirring for 5 minutes, the liquid component in the aqueous solution is 5
So-called O / that exists as droplets with a size of 20 μm
A W emulsion was obtained.

Separately, commercially available melamine powder was added to a 37% aqueous formaldehyde solution, adjusted to pH 9.0 with a sodium hydroxide solution, and heated at a water temperature of 60 ° C. for 30 minutes to obtain a melamine-formaldehyde prepolymer.

Melamine-formaldehyde prepolymer was added to the O / W emulsion prepared above, and the mixture was stirred for 5 hours at 100 to 300 rpm with an Ajihomomixer or the like and kept at a water temperature of 80 ° C. for 5 hours. Then, it was adjusted to PH7 and cooled to room temperature. As a result, O
A wall material of melamine-formaldehyde resin was deposited around the droplets of the / W emulsion, and a magenta photosensitive microcapsule emulsion was obtained.

Each of the above substances other than the cyanine dye has a solubility in water of 5 g because there is a portion that does not completely dissolve when 5 g of each substance is added to 1 liter of water and stirred. It has been confirmed that it is less than / l.

Example 2 Cyanine dye having a solubility in water of 3.8 g / l
A magenta photosensitive microcapsule emulsion was obtained in the same manner as in Example 1 except that 3 parts by weight was used.

Example 3 Cyanine dye having a solubility in water of 4.7 g / l
A magenta photosensitive microcapsule emulsion was obtained in the same manner as in Example 1 except that 3 parts by weight was used.

Comparative Example 1 Cyanine dye having a solubility in water of 6.3 g / l.
A magenta photosensitive microcapsule emulsion was obtained in the same manner as in Example 1 except that 3 parts by weight was used.

Comparative Example 2 Cyanine dye having a solubility in water of 9.1 g / l.
A magenta photosensitive microcapsule emulsion was obtained in the same manner as in Example 1 except that 3 parts by weight was used.

The magenta photosensitive microcapsules of Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to an elution test, and the results are shown in FIG. As is clear from FIG. 1, when the solubility in water is approximately 5 g / l or less, the elution amount is suppressed. Especially when left for one day or more, the difference is large. When used for image formation, a capsule is usually coated on a sheet and dried before use. In this case, if the capsule manufacturing apparatus and the coating apparatus are located in different places, it is required to be stable for at least 1 to 2 days in consideration of transportation time and the like. Even if the capsule manufacturing apparatus and the coating apparatus are located at the same place, stability of about one day is required if the capsules are washed. Therefore, from FIG. 1, the solubility in water is approximately 5 g /
It can be seen that it must be 1 or less. Here, it seems that if the amount of elution is large, it may be better to add extra inclusions accordingly, but if the amount of elution is large, the number of pores in the capsule wall is large, and the diameter is also large. It is considered that curing inhibition occurs due to oxygen. Therefore, even if the amount of elution is large, it is not possible to add the inclusions excessively, and from this it can be said that a substance of approximately 5 g / l or less must be used.

Next, regarding the test method of the dissolution test,
Briefly describe.

20 g of capsule emulsion of known concentration
Take and add this to 100 g of water. 40 ° C, 50rp
Stir at m and measure the dye concentration in the aqueous solution with a spectrophotometer at regular intervals. The ratio of the dye added in the capsule and the dye dissolved in water is defined as the elution amount.

The above-described present invention is not limited to the above-mentioned embodiments, and can be carried out without changing the scope of the invention by changing the materials used, the amount ratio thereof, and the manufacturing conditions.

[0040]

As is apparent from the above description, the photosensitive capsule according to claim 1 of the present invention changes mechanical strength in response to light with at least an image forming material such as a dye or a pigment. For those containing a photosensitive substance to be included, in particular, among the substances included in the photosensitive capsule,
The solubility in water of all other substances except the substance which is not soluble in water was set to about 5 g / l or less. Therefore, the release of the inclusions from the outer portion of the capsule is suppressed, and as a result, the decrease in the photosensitivity is prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a result of a dissolution test of an example of the present invention.

Claims (1)

[Claims] 1. A photosensitive capsule containing at least an image forming material such as a dye or a pigment, and a photosensitive substance that changes in mechanical strength in response to light, wherein among the substances included in the photosensitive capsule, A photosensitive capsule characterized in that the solubility of all substances except water-insoluble substances is approximately 5 g / l or less.