Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-11-02
2004-03-30
Berman, Susan (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S029000, C522S026000, C522S182000, C522S183000, C430S281100
Reexamination Certificate
active
06713523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photopolymerizable composition and a photosensitive thermal recording material which are sensitive to a broad wavelength range including UV rays and visible to IR rays thus enabling high-sensitivity recording and which are favorable for use in various fields including those of ink, color filters, holograms, proofs, sealants, adhesives, lithography, resin relieves, photoresists and the like. More precisely, the invention relates to such a photopolymerizable composition and a photosensitive thermal recording material which are particularly sensitive to rays whose wavelength are not longer than 450 nm to enable high-sensitivity recording.
2. Description of the Related Art
Various dry-type image-recording methods in which liquid developers are not used and waste is not generated have heretofore been investigated. Much attention is being paid to a method in which a photocurable composition is used. The method is characterized in that a photocurable composition in a recording material is cured through exposure to light to form a latent image on the material, and a component of the non-exposed area which has the effect forming or erasing color when heat is applied, is caused to migrate to thereby form a color image. More specifically, a recording material is exposed to light through an original image so that the exposed area of the material is cured to forma latent image thereon, and thereafter the material is heated so that a component of the non-cured area (non-exposed area) which is used in the color formation or color erasing reaction is caused to migrate in the material to thereby form a visible image.
The method realizes a complete dry-type image-recording system in which waste is not generated. This is usable in black-and-white image recording, but is especially favorable for color image recording.
Some recording materials employable in the method have been proposed. For example, known is a two-component type, photosensitive thermal color image-recording material described in JP-A No. 52-89915. This contains two components which are an electron-receiving compound and an electron-donating leuco-dye, and contains a photocurable composition inside and/or outside the microcapsules therein. In this method, however, even though the photocurable composition in the microcapsules is fully cured, it is still impossible to sufficiently control color formation in the cured area of the material. Therefore, the material is defective in that the non-image area thereof is colored and the image contrast is low.
JP-A 61-123838 discloses a recording material free from the problem of coloration in the non-image area. This comprises a layer of a photopolymerizable composition that contains an acidic group-having vinyl monomer and a photopolymerization initiator, a spacer layer, and a layer that contains an electron-donating leuco-dye. Color formation does not occur in the non-image area, that is, the area cured through photopolymerization, but there is the disadvantage that its color density is somewhat low.
Given that situation, the present applicant has previously proposed recording materials that enable high image density with no coloration in the non-image area, as in JP-A Nos. 3-87827 and 4-211252. The former is a two-component type, photosensitive thermal color-image forming material, in which one of the two components is encapsulated in microcapsules, and the other is a curable compound in a photocurable composition or the other is outside the microcapsules along with a photocurable composition. The latter is a photosensitive thermal recording material which comprises a layer that contains an electron-donating leuco-dye in the microcapsules and outside the microcapsule contains a photocurable composition that comprises an electron-receiving compound, a polymerizing vinyl monomer and a photopolymerization initiator.
For recording color images on photosensitive thermal recording materials of those types, used are multi-color forming recording materials each having, on a support, plural recording layers, the respective layers being sensitive to particular wavelength ranges of light thus forming different colors.
One example of such multi-color forming recording materials is the above-mentioned photosensitive thermal recording material which the present applicant has proposed. Specifically, it comprises plural recording layers sensitive to the respective wavelength ranges of light and forms different colors, and more specifically, it comprises a first recording layer sensitive to light having a center wavelength of &lgr;
1
and forms a color, an interlayer that absorbs the light having a center wavelength of &lgr;
1
, a second recording layer sensitive to light having a center wavelength of &lgr;
2
and forms a color that differs from the color formed by the first recording layer, . . . an interlayer that absorbs light having a center wavelength of &lgr;
(i−1)
an i'th recording layer sensitive to light having a center wavelength of &lgr;
1
and forms a color that differs from the colors formed by the first, second, . . . (i−1)th recording layers, laminated in that order on a support with i≧2, wherein the first layer is the furthest from the support and is the nearest to the light source to which is it exposed. The center wavelength, &lgr;, of the light to which it is exposed is in the order of &lgr;
1
<&lgr;
2
< . . . <&lgr;
1
.
However, small-sized inexpensive IR lasers and blue to red light emitters are useless as a light source for recording images on such recording materials. If small-sized inexpensive IR lasers or blue to red light emitters are used for recording fine images thereon at high speed, the recording layer must contain a dye capable of absorbing visible rays that fall within the wavelength range of the light source. However, when such a dye, especially that capable of absorbing light that falls within a visible-ray range is introduced into the recording layer, the background of the recording material is colored, thereby lowering the contrast and the quality of the images formed. For increasing the image contrast, the dye in the recording layer will have to be decolored. This, however, requires an extremely long exposure time, and interferes with high-speed image output.
On the other hand, if a dye capable of absorbing near-IR light is used in such recording materials, the background coloration can be prevented. However, this has another drawback in that the lasers usable for the recording materials are expensive.
A high-power violet laser having a laser wavelength of around 405 nm has been developed recently as the light source that emits blue to red rays having wavelengths not exceeding 450 nm, but its power is at most 5 mW or so. Therefore, if the laser falling within the wavelength range is to be used, the sensitivity of the recording materials in that wavelength range must be increased. However, in order to increase the sensitivity, it is necessary to introduce a dye component into the recording layer of the materials for the same reasons described hereinabove. If a dye component capable of absorbing light that falls within the wavelength range is introduced thereinto, the recording materials are yellowed; and if the dye component therein is not completely decolored, the background area of the images formed (that is, the non-image area) in the materials is yellowish, and the images are fogged and their commercial value decrease. Introducing such a dye component into the recording layer is therefore problematic with respect to these points.
As mentioned above, no one has as yet succeeded in providing a photopolymerizable composition for a photosensitive thermal recording material which is highly sensitive to rays having a wavelength of less than 450 nm and which is capable of forming thereon detailed and high-contrast images of high quality with no yellowish fog in the background area around the images even when exposed with a relatively low-power light sour
Nagata Kozo
Washizu Shintaro
LandOfFree
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