Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-10-29
2002-06-25
Hess, Bruce H. (Department: 1774)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C428S195100, C428S913000
Reexamination Certificate
active
06410199
ABSTRACT:
This application claims the benefit of Japanese Application No. 10-308537, filed in Japan on Oct. 29, 1998, which is hereby incorporated by reference.
This application also incorporates by reference Japanese Patent No. 2633023 and Japanese Unexamined Laid-Open Publication Nos. 08-194394, 08-334916, 08-305066, 05-27479, and 05-80586.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image receiving sheet for electrophotographic recording of images. More particularly, the present invention relates to a transparent image receiving sheet that can be used in an overhead projector.
2. Discussion of the Related Art
Full color image forming processes using electrophotography have come into practice. In these processes, images are electrophotographically formed on an image receiving sheet through mixture of toners of three colors: yellow, magenta and cyan, or mixture of toners of four colors: black in addition to these three colors.
To record and hold information, such as lines, letters, pictures, etc., with sufficient reliability, the image receiving sheet is generally composed of a substrate and a receptor layer formed on the substrate. Such an image receiving sheet is used in an overhead projector, for example, as an information transmission device for use in lecture meetings and other various presentations and exhibitions in schools, industries, etc.
However, when a full color image formed by electrophotography is projected through an overhead projector, the projected image exhibits a gray tone (graying), resulting in an undesirably narrow color-tone reproduction range. Toner particles attached to a smooth image receiving surface of the conventional image receiving sheet are often not sufficiently embedded into the receptor layer of the image receiving sheet by heat applied in fixation of the toners. As a result, portions of the toner particles protrude from the surface of the sheet and the surface of the image receiving sheet becomes uneven. Such protruded portions scatters incident light when an image is projected by an overhead projector, resulting in creation of a shadow over a screen onto which the image is projected.
One attempt to solve this graying problem is disclosed in Japanese Patent No. 2633023. The Japanese Patent proposes use of a receptor layer resin having a storage elasticity modulus, which ranges from 100 to 10000 dyne/cm
2
at 160° C., and which is higher than that of toner resin at a toner fixing temperature. The fixing temperatures in current electrophotography techniques, however, widely vary from 140° C. to 195 ° C. depending on the type of apparatus. Thus, this requirement on the storage elasticity modulus at 160° C. is not sufficient to produce clear projected images. Further, when the receptor resin having a larger storage elasticity modulus than that of the toner resin at the tone fixation temperature is used, the toners cannot be sufficiently embedded in such a receptor layer.
For similar reasons, requirements on the relationship between the storage elasticity modulus of the receptor resin and that of the toner at 150° C., as disclosed in Japanese Unexamined Laid-Open Publication No. 8-194394, are inadequate to provide for a sufficient image quality under practical conditions.
Japanese Unexamined Laid-Open Publication No. 8-334916 states that the storage elasticity modulus (E
p
) of a transparent receptor layer of a polyester resin desirably has the following relationship to the storage elasticity modulus (E
t
) of a toner resin to be fixed:
−50≦(
E
p
−E
t
)≦2500(unit: Pa).
However, the present inventors discovered through various experiments that a receptor layer having a storage elasticity modulus lower than that of the toner resin is more desirable. This is because such a receptor resin is applicable to a variety of electrophotographic copying machines and printers, and accordingly has a wider applicability.
Japanese Unexamined Laid-Open Publication No. 8-305066 specifies the storage elasticity modulus of a receptor layer containing a styrene-butadiene block copolymer in the range of 140° C. to 200° C. However, because polyester resins are predominantly used as toner resins, this type of receptor layer has a poor compatibility with toners and therefore is not suitable for producing clear projected images.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an image receiving sheet and a recording process that substantially obviate the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an image receiving sheet that possesses a satisfactory color tone reproducibility and accordingly can generate a clear projected image substantially free from graying.
Another object of the present invention is to provide an image receiving sheet that has a superior image reproducibility and is usable in a variety of electrophotographic copying machines and printers of different manufactures with various fixation temperatures, thereby providing a high quality image receiving sheet having a wide variety of usages.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides, in a first aspect, an image receiving sheet including a substrate and a receptor layer formed on at least one side of the substrate, wherein the storage elasticity modulus of a resin binder in the receptor layer is equal to or greater than about 10
6
Pa in a temperature range below about 40° C., and substantially satisfies the following relationships:
G′
130
/G′
200
≦9.0
and
G′
130
≦10
3
Pa,
where G′
130
is the storage elasticity modulus at 130° C. and G′
200
is the storage elasticity modulus at 200° C.
According to this aspect of the present invention, toners attached to a smooth image receiving surface of the image receiving sheet can sufficiently be embedded in the receptor layer by heat applied during fixation of the toner, and the toners are compatible with the receptor layer at their boundary surfaces. As a result, the surface of the resultant image receiving sheet can be made sufficiently smooth.
A preferable range of the thickness of the receptor layer is about 0.1 &mgr;m to about 10.0 &mgr;m.
More preferably, in electrophotographic recording, the storage elasticity modulus G′
A
of a toner resin of a toner to be attached to the image receiving sheet substantially satisfies the following relationship with the storage elasticity modulus G′
B
of the resin binder in the receptor layer at temperatures ranging from about 130° C. to about 200° C.:
0.1
≦G′
A
/G′
B
≦2500.
In this case, even better embedment of the toner into the receptor layer can be achieved.
It is also preferable that the resin binder of the receptor layer include at least one of epoxy resins and polyester resins having a bisphenol A skeleton.
The image receiving sheet preferably has a parallel ray transmittance equal to or greater than about 70%.
In another aspect, the invention provides an electrophotographical recording method including the step of fixing a toner on the aforementioned image receiving sheet at a surface temperature of a fixing roller ranging from about 130° C. to about 200° C.
According to these aspects, an image receiving sheet of the present invention possesses a satisfactory color tone reproducibility and accordingly can generate a clear projected image substantially free from graying. Moreover, it can be used in a variety of electrophotographic copying machines and printers of different manufactures wit
Hayashi Masafumi
Ikeuchi Nobuho
Dai Nippon Printing Co. Ltd.
Hess Bruce H.
Morgan & Lewis & Bockius, LLP
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