Radiation imagery chemistry: process – composition – or product th – Transfer procedure between image and image layer – image... – Imagewise heating – element or image receiving layers...
Reexamination Certificate
2000-05-03
2001-06-05
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Transfer procedure between image and image layer, image...
Imagewise heating, element or image receiving layers...
C430S200000, C430S271100, C430S273100, C430S275100, C430S964000
Reexamination Certificate
active
06242152
ABSTRACT:
This invention relates to methods for light induced transfer of layers from a donor element to a receptor.
BACKGROUND
Some transfer methods include thermal mass transfer of crosslinkable components from a donor element to a receptor. The transferred material may then be crosslinked on the receptor after transfer. While crosslinking after transfer has been taught to provide such desirable qualities as toughness, durability, solvent resistance, and other performance related benefits, crosslinking after transfer can be an inconvenient extra step in the production of an imaged receptor.
SUMMARY OF THE INVENTION
The present inventors have made the surprising discovery that, contrary to the teachings of the known references, good images can be formed by light induced thermal transfer even when the transferred material has been partially or fully crosslinked before transfer. Crosslinking before transfer can have the benefit that crosslinking can be performed on the donor web on a continuous process basis. As a value added step, crosslinking of transfer layer material may be performed by the manufacturer of the donor material and need not be performed by the individual using the donor material for image formation. In addition, crosslinked transfer layers may be more robust than corresponding uncrosslinked transfer layers, thereby allowing easier handling of donor sheets and/or use or storage of donor sheets, for example in stacks or rolls, without significant damage to the transfer layer. Donors having crosslinked transfer layers can also be used to transfer materials to sensitive receptors that might be damaged by, for example, the heat or radiation that might otherwise be used to crosslink the materials after transfer.
In one aspect, the present invention provides a thermal transfer donor element that includes a substrate, a transfer layer that includes a crosslinked material, and a light-to-heat converter material disposed in the thermal transfer donor element to generate heat when the donor element is exposed to imaging radiation, the heat generated being sufficient to imagewise transfer the transfer layer from the donor element to a proximately located receptor. The light-to-heat converter can be disposed in a separate light-to-heat conversion layer disposed between the substrate and the transfer layer.
In another aspect, the present invention provides a method of patterning which includes the steps of placing the transfer layer of a thermal transfer donor element proximate a receptor and imagewise transferring portions of the transfer layer to the receptor by selectively exposing the donor element to imaging radiation capable of being absorbed and converted into heat by the converter material, wherein the donor element includes a substrate, a transfer layer that includes a crosslinked material, and a light-to-heat converter material.
In yet another aspect, the present invention provides a method of making a thermal transfer donor element, including the steps of providing a donor substrate, coating a layer that includes a crosslinkable material adjacent to the substrate, crosslinking the crosslinkable material to form a crosslinked transfer layer, and disposing a light-to-heat converter material in the donor element, the light-to-heat converter material capable of generating heat upon being exposed to imaging radiation, the heat generated being sufficient to imagewise transfer portions of the crosslinked transfer layer.
DETAILED DESCRIPTION
The present invention is believed to be applicable to thermal transfer of materials from a donor element to a receptor. In particular, the present invention is directed to thermal mass transfer donor elements, and methods of thermal transfer using donor elements, where the transfer layers of the donor elements include a crosslinked material. Donor elements of the present invention are typically constructed of a substrate, a transfer layer that includes a crosslinked or partially crosslinked organic, inorganic, organometallic or polymeric material, and a light-to-heat converter material.
Crosslinked materials can be transferred from the transfer layer of a donor element to a receptor substrate by placing the transfer layer of the donor element adjacent to the receptor and irradiating the donor element with imaging radiation that can be absorbed by the light-to-heat converter material and converted into heat. The donor can be exposed to imaging radiation through the donor substrate, or through the receptor, or both. The radiation can include one or more wavelengths, including visible light, infrared radiation, or ultraviolet radiation, for example from a laser, lamp, or other such radiation source. Portions of the transfer layer can be selectively transferred to a receptor in this manner to imagewise form patterns of the crosslinked material on the receptor. In many instances, thermal transfer using light from, for example, a lamp or laser, is advantageous because of the accuracy and precision that can often be achieved. The size and shape of the transferred pattern (e.g., a line, circle, square, or other shape) can be controlled by, for example, selecting the size of the light beam, the exposure pattern of the light beam, the duration of directed beam contact with the thermal mass transfer element, and/or the materials of the thermal mass transfer element. The transferred pattern can further be controlled by irradiating the donor element through a mask.
The mode of thermal mass transfer can vary depending on the type of irradiation, the type of materials and properties of the light-to-heat converter, the type of materials in the transfer layer, etc., and generally occurs via one or more mechanisms, one or more of which may be emphasized or de-emphasized during transfer depending on imaging conditions, donor constructions, and so forth. One mechanism of thermal transfer includes thermal melt-stick transfer whereby heating the transfer layer results in an increase in the relative adhesion of the transfer layer to the receptor's surface. As a result selected portions of the transfer layer can adhere to the receptor more strongly than to the donor so that when the donor element is removed, the selected portions of the transfer layer remain on the receptor. Another mechanism of thermal transfer includes ablative transfer whereby localized heating can be used to ablate portions of the transfer layer off of the donor element, thereby directing ablated material toward the receptor. The present invention contemplates transfer modes that include one or more of these and other mechanisms whereby the heat generated in light-to-heat converter material of a donor element can be used to cause the transfer of crosslinked materials from a transfer layer to receptor surface.
A variety of radiation-emitting sources can be used to heat donor elements. For analog techniques (e.g., exposure through a mask), high-powered light sources (e.g., xenon flash lamps and lasers) are useful. For digital imaging techniques, infrared, visible, and ultraviolet lasers are particularly useful. Suitable lasers include, for example, high power (≧100 mW) single mode laser diodes, fiber-coupled laser diodes, and diode-pumped solid state lasers (e.g., Nd:YAG and Nd:YLF). Laser exposure dwell times can vary widely from, for example, a few hundredths of microseconds to tens of microseconds or more, and laser fluences can be in the range from, for example, about 0.01 to about 5 J/cm
2
or more. Other radiation sources and irradiation conditions can be suitable based on, among other things, the donor element construction, the transfer layer material, the mode of thermal transfer, and other such factors.
When high spot placement accuracy is required (e.g., for high information full color display applications) over large substrate areas, a laser is particularly useful as the radiation source. Laser sources are also compatible with both large rigid substrates (e.g., 1 m×1 m×1.1 mm glass) and continuous or sheeted film substrates (e.g., 100 &mgr;m polyimide sheets).
During
Chang Jeffrey C.
Hanzalik Kenneth L.
Staral John S.
3M Innovative Properties
Pechman Robert J.
Schilling Richard L.
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