Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
1997-11-20
2002-10-15
Reddick, Judy M. (Department: 1713)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S031000, C430S058050, C430S058350, C430S058750, C430S059400, C430S059500, C525S060000, C525S061000
Reexamination Certificate
active
06465142
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to polymeric binders used in photoconductors. More particularly, this invention relates to low temperature cure polyvinylbutyral and a process for its synthesis.
BACKGROUND OF THE INVENTION
Electrophotography is a process in which image information in the form of electronic signals is converted to optical signals which are then converted to a latent electrostatic field and stored until developed into a visible image and transferred to paper. Commercial applications of electrophotography include photocopiers and non-impact (i.e., electronic) printers. See, generally, J. Mort,
The Anatomy of Xerography
(McFarland & Co., 1989); J. L. Johnson,
Principles of Non Impact Printing
(Palatino Press, 1986).
The conversion of an optical image pattern to a latent electrostatic charge pattern is the function of the photoreceptor. The photoreceptor is a photoconductive insulator having charge generating and charge transport properties. In the process of electrophotography, the surface of the photoreceptor is charged with ions in the dark, then selectively discharged by exposure to an optical image. The degree of discharge is proportional to the light intensity in the optical image provided that the photogenerated charge carriers are efficiently transported away from the exposed surface (i.e., the required carrier mobility must be at least 10
−6
cm
2
/V second). The latent image thus produced is subsequently developed and fixed into a permanent image.
Many photoreceptors can be used both in photocopiers and in non impact printing. Although speed, spectral sensitivity and durability requirements differ for the two applications, the main requirements of a photoreceptor are: high photosensitivity to visible light, good carrier transport properties, and high dark resistivity. Uniform and low-cost manufacturing and the ability to tailor a photoreceptor's spectral responses to particular applications are also advantageous.
For these reasons, photoconductors comprised of dye molecules dispersed in an electrically inert cross-linked polymer are widely used commercially. Photoexcitation induces electronic transitions in dye molecules and initiates a cascade of intermolecular charge transport. The efficiency of this process, which involves the hopping of holes or electrons from one dye molecule to another, requires the presence of high concentrations of dye (circa 10
20
molecules per cc) randomly dispersed in the polymer.
Various polymers have been used as pigment dispersing binders in charge generation layers, e.g., polyester, phenoxy resins, poly(vinyl acetate), and, most recently, poly(vinyl butyral) (see Proceedings, Sixth International Congress on Advances in Non-Impact Printing Technologies, Orlando, Fla., 1990, pp. 312-346). Poly(vinyl butyral) (PVB) is particularly preferred for its solubility in a wide range of solvents, its ability to coat many kinds of organic pigments thus providing stable dispersion throughout the charge generation layer, and its excellent film-forming properties. Conventional PVB has the structure,
where x=60 to 95 mol %, y=3 to 40 mol %, and z=0 to 20 mol %, and x+y+z=100%.
The only reactive functional group for cross-linking the polymer is the hydroxy group of the polyvinyl alcohol component. Because of the relatively low reactivity of this group, elevated temperatures and long reaction times or strong acid or base catalysts are required. These conditions may adversely affect the performance of the photoreceptor by altering the stability of pigment and charge transport molecules contained therein. Accordingly, there is a need for poly(vinyl butyral) that can be cross-linked readily without resorting to harsh conditions of temperature and pH and, correspondingly, for a convenient and efficient method of synthesizing such a compound.
SUMMARY OF THE INVENTION
The invention provides new polymeric compounds which are useful as binders in photoconductors as well as in surface coating materials, structural adhesives, and other applications where low temperature cure may be advantageous or required.
Accordingly, one aspect of the invention is directed to compounds of Formula I:
wherein:
R
1
is alkyl, dialkyl ether, alkyl carbonyl, cycloalkyl, cycloalkyl alkyl, aryl, aryl carbonyl, alkaryl carbonyl, aralkyl, or alkyl aralkyl;
Z is —OH or —NHR
2
, where R
2
is independently alkyl, dialkyl ether, alkyl carbonyl, cycloalkyl, cycloalkyl alkyl, aryl, aryl carbonyl, alkaryl carbonyl, aralkyl, alkyl aralkyl, or R
2
is H.
x is 60 to 95 mol %, y is 3 to 40 mol %, z is 0 to 20 mol %; and
x+y+z is 100 mol %.
Another aspect of the invention provides a process for preparing a compound of Formula I, where Z is —OH, by hydrolysing a compound of Formula (3) having the structure:
with an acid, where R
1
, x, y, z are as defined above.
Yet another aspect of the invention is directed to an intermediate in the synthesis of a compound of Formula I, wherein the intermediate is a compound of Formula (3).
Another aspect of the invention is to provide a photoconductor for electrophotography, wherein the photoconductor comprises a charge generation layer and a charge transport layer, the charge generation layer is formed from a photoconductive pigment dispersed in a binder, and the binder is comprised of a poly(vinyl butyral) compound of Formula I.
DETAILED DESCRIPTION OF THE INVENTION
1. Definitions
The following definitions are set forth to illustrate and define the meaning and scope of the various terms used to describe the invention herein.
“t-BOC” means t-butoxycarbonyl.
“CGL” means charge generation layer.
“PVB” means poly(vinyl butyral).
As used herein, the term “alkyl” means a linear or branched chain mono- or di-valent radical consisting solely of carbon and hydrogen, containing no unsaturation and having from one to 10 carbon atoms, e.g., methyl, methylene, propyl, trimethylene, heptyl and the like, which can be optionally substituted with halogen or aryl groups.
As used herein, the term “dialkyl ether” refers to a mono- or di-valent radical of the formula —R
a
—O—R
b
, where R
a
and R
b
can be the same or different alkyl groups, and R
b
in a divalent radical forms a bond with Z of Formula I, e.g. diethyl ether,oxydiethylene, methoxyethylene, and the like.
As used herein, the term “alkyl carbonyl” refers to a mono- or di-valent radical of the formula —C(O)R
a
where R
a
is alkyl as defined above, and R
a
in a divalent radical forms a bond with Z of Formula I, e.g., methyl carbonyl, carbonyl ethylene, and the like.
As used herein, the term “cycloalkyl” refers to a mono- or di-valent ring radical consisting solely of carbon and hydrogen atoms, containing no unsaturation and having from five to seven carbon atoms, e.g,. cyclopentyl, cyclohexylene, and the like.
As used herein, the term “cycloalkyl alkyl” refers to a mono- or di-valent radical of the formula —R
a
—R
b
where R
a
is alkyl and R
b
is cycloalkyl, and R
b
in a divalent radical forms a bond with Z of Formula I, e.g., cyclopentyl methylene, cyclohexylene ethylene, and the like.
As used herein, the term “aryl” refers to a mono- or di-valent unsaturated aromatic carbocyclic radical having one or more rings, e.g., phenyl, naphthyl, phenylene, and the like, which can be optionally substituted with halogen or aryl groups.
As used herein, the term “aryl carbonyl” refers to a mono- or di-valent radical of the formula —C(O)R
c
where R
c
is aryl, and R
c
in a divalent radical forms a bond with Z of Formula I, e.g., phenylcarbonyl, carbonyl phenylene, and the like.
As used herein, the term “alkaryl carbonyl” refers to a mono- or di-valent radical of the formula —R
c
—R
a
where R
c
is aryl and R
a
is alkyl, and R
a
in a divalent radical forms a bond with Z of Formula I, e.g., methylphenyl carbonyl, methylene phenylcarbonyl, and the like.
As used herein, the term “aralkyl” refers to a mono- or di-valent radical of the formula —R
a
—R
c
where R
a
is alkyl and R
c
is aryl, and R
c
in a divalent radical form
Ganapathiappan Sivapackia
Nguyen Khe C.
Hewlett--Packard Company
Reddick Judy M.
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