U.S. patent number 3,640,863 [Application Number 04/828,784] was granted by the patent office on 1972-02-08 for a liquid electrostatic having pigment particles coated with a cyclized rubber.
This patent grant is currently assigned to Kabushiki Kaisha Ricoh. Invention is credited to Ikuyo Kondoh, Akinori Mizuno, Zenjiro Okuno.
United States Patent |
3,640,863 |
Okuno , et al. |
February 8, 1972 |
A LIQUID ELECTROSTATIC HAVING PIGMENT PARTICLES COATED WITH A
CYCLIZED RUBBER
Abstract
A liquid developer for use in developing an electrostatic latent
image formed on an electrostatic recording material or an
electrophotographic copying material which is prepared by
dispersing, in a suitable carrier liquid, a toner consisting
substantially of pigment particles whose surfaces are coated with a
coating agent selected from the group consisting of cyclized
rubber, a resin containing cyclized rubber, and a resin combining a
resin having a high solubility for said carrier liquid and a resin
having a low solubility for said carrier liquid.
Inventors: |
Okuno; Zenjiro (Tokyo,
JA), Mizuno; Akinori (Tokyo, JA), Kondoh;
Ikuyo (Tokyo, JA) |
Assignee: |
Kabushiki Kaisha Ricoh (Tokyo,
JA)
|
Family
ID: |
26377776 |
Appl.
No.: |
04/828,784 |
Filed: |
May 28, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Jun 5, 1968 [JA] |
|
|
43/38516 |
|
Current U.S.
Class: |
430/114; 523/205;
523/206; 523/208 |
Current CPC
Class: |
G03G
9/08 (20130101); G03G 9/131 (20130101); G03G
9/132 (20130101) |
Current International
Class: |
G03G
9/12 (20060101); G03G 9/08 (20060101); G03G
9/13 (20060101); G03g 009/04 () |
Field of
Search: |
;252/62.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Brammer; J. P.
Claims
What we claim is:
1. In a liquid developer for developing electrostatic images on
electrostatic charge carriers, and liquid developer consisting
essentially of a toner dispersed in a carrier liquid, said carrier
liquid being selected from the group consisting of paraffinic
hydrocarbons, isoparaffinic hydrocarbons, naphtha hydrocarbons and
halogenated hydrocarbons having an electric resistance of not less
than 10.sup.10 .OMEGA..sup.. cm. and a dielectric constant of not
greater than 3, said toner consisting essentially of pigment
particles coated with a coating agent, said pigment particles being
selected from the group consisting of carbon black (C.I. No.
77266), aniline black (C.I. No. 50440), spirit black (C.I. No.
50415), phthalocyanine blue (C.I. No. 74160), benzidine yellow
(C.I. No. 21090), carmine 6B (C.I. No. 15850), lake red (C.I.No.
15585) and zinc oxide;
the improvement in which said coating agent consists essentially of
a member selected from the group consisting of (1) cyclized rubber,
(2) said cyclized rubber and resin A, and (3) said cyclized rubber
and resin C,
said cyclized rubber having recurring structural units of the
formula ##SPC3##
and having a molecular weight in the range of from about 50,000 to
two million;
said resin A is selected from the group consisting of
phenolaldehyde resin and phenol modified xylene resin; and
said resin C is selected from the group consisting of alkyd resin,
polymerized linseed oil, polystyrene resin and styrene-butadiene
rubber.
2. A liquid developer according to claim 1, in which the coating
agent consists of said cyclized rubber whose molecular weight
distribution extends over a wide range.
3. A liquid developer according to claim 1, in which the coating
agent consists of said cyclized rubber and said resin C and in
which said resin C forms an inner coating layer on said pigment
particles and said cyclized rubber is an outer coating layer
covering said inner coating layer.
4. A liquid developer according to claim 1, in which said coating
agent consists of a mixture of said cyclized rubber and said resin
C forming a coating layer on said pigment particles.
5. A liquid developer according to claim 1, in which said coating
agent consists of said cyclized rubber and resin A and in which
said resin A forms an inner coating layer on said pigment particles
and said cyclized rubber is an outer coating layer covering said
inner coating layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid developer for use in
developing the electrostatic latent image formed on an
electrostatic charge carrier such as an electrophotographic copying
material and an electrostatic recording material.
2. Description of the Prior Art
An electrostatic latent image is generally formed by the
electrostatic recording method wherein said image is directly
formed through impression of an electrostatic charge on an
electrostatic recording paper such as a synthetic resin film and
the electrophotographic method wherein said image is indirectly
formed through the step of imparting an electrostatic charge with
corona discharge on the surface of a photoconductive layer of an
electrophotographic copying paper and exposure subsequent
thereto.
As for the method of developing the electrostatic latent images
formed as above, they are classified into two categories, namely,
the dry-developing method which employs a powder developer and the
wet-developing method which employs a liquid developer. According
to the dry-developing method, the development is effected by
thermal fixing of a powder developer on an electrostatic charge
carrier provided with an electrostatic latent image, while,
according to the wet-developing method, the development is effected
by merely dipping said electrostatic charge carrier in a liquid
developer.
As for the liquid developer for use in developing an electrostatic
latent image, the one which has hitherto been popular is a
developer prepared by the steps of coating a single resin combining
a property of providing pigment particles with polarity
controlability, to wit, a distinct electric charge and a property
of providing a carrier liquid with stability, to wit, a property of
satisfactorily dispersing pigment particles in a carrier liquid on
said pigment and then dispersing thus treated pigment in a carrier
liquid comprising petroleum hydrocarbon having a comparatively high
electric resistance (more than 10.sup.10 .OMEGA. -cm.) and a low
dielectric constant (less than 3). Other well-known developers
include a developer prepared by dispersing, in a carrier liquid,
pigment particles coated with two kinds of resins simultaneously,
both of which are easily soluble in a carrier liquid providing that
one is capable of controlling the polarity of the pigment and the
other is superior in dispersibility though somewhat inferior in
polarity controlability, and a developer which is a modification of
the preceding one, wherein a field activator is further added to
said resin of superior dispersibility to thereby control its
polarity. However, with these conventional developers, it has been
extremely difficult to maintain the initial efficiency thereof as
displayed in the early period subsequent to their manufacture since
the resin coated on the pigment particles, to wit, a toner
contained in any of said developers, has such a drawback that it
breaks away gradually from the pigment of the toner while the
developer is used or stored, to thereby cause a deterioration of
developing efficiency thereof. This phenomenon has hitherto been
considered inevitable inasmuch as it is mainly attributable to the
fact that a resin for use in coating on the pigment is easily
soluble in the carrier liquid. In addition to the foregoing
developers, a liquid developer on the market, whose composition is
characterized by the fact that the pigment particles are coated
with microlith resin (maleic resin of denatured rosin) and
dispersed in a carrier liquid together with an oil having a
dispersing effect such as tung oil, has also been popular. However,
this liquid developer, when put to practical use, has also been
deficient from the viewpoint of control or prevention of said
polarity deterioration phenomenon of the toner as well as the
fixability thereof on the surface of an electrostatic charge
carrier. In other words, the wet-developing method has a remarkable
advantage that the fixing operation is quite simple as compared
with the thermal fixing in case of the dry-developing method in so
far as the fixing under the former method is effected through the
steps of dipping an electrostatic charge carrier having the
electrostatic latent image in a liquid developer wherein a toner
charged with a positive or negative charge has been dispersed and
pulling it out subsequent thereto, and then evaporating the carrier
liquid contained in said developer to thereby fix the toner on the
surface of said electrostatic charge carrier, but, on the other
hand, it has the drawback that the fixability of the toner which
functions to form an image is comparatively poor. For instance, an
image fixed on a copy is so easily erased by mere rubbing with a
finger that in case of protracted preservation of such a copy or
frequent taking in and out thereof during the preservation may
cause the image not only to get blurred but also to be entirely
eliminated. For this reason, such a copy could hardly be put to
practical use for important papers such as official documents. The
foregoing drawback is considered attributable to the small amount
of resin adsorbed onto the pigment particles in the toner. (Said
amount has been usually in the range of less than 1 part by weight
of resin against 1 part by weight of pigment particles.) With a
view of preventing said drawback, there has been an attempt to
employ a toner prepared by coating pigment particles with such a
resin which is comparatively insoluble in a carrier liquid, but it
has also proved unsatisfactory because said toner is apt to cause
aggregation and have an inferior dispersibility in a carrier
liquid.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a liquid
developer for use in developing electrostatic latent images, which
contains a toner dispersed in a carrier liquid, said toner having
such a polarity that is will never become indistinct during
protracted preservation or repeated use thereof and also having a
superb fixability with respect to the latent image area of an
electrostatic charge carrier.
One of the liquid developers according to the present invention is
a liquid developer obtained by dispersing, in a carrier liquid
comprising petroleum hydrocarbon having an electric resistance of
more than 10.sup.10 .OMEGA. -cm. and a dielectric constant of less
than 3, a toner prepared by coating pigment particles with such a
resin, which has a low solubility for said carrier liquid, so that
it is insoluble or hard to dissolve in a carrier liquid and also
having a polarity controlling effect on said pigment together with
a second resin, which has a high solubility for said carrier
liquid, so that it is soluble or easily soluble in a carrier liquid
and also contributes to the dispersibility of said pigment in a
carrier liquid.
Another liquid developer according to the present invention is such
a developer obtained by dispersing, in a carrier liquid having a
high resistance and a low dielectric constant as stated in the
foregoing, a toner prepared by coating pigment particles with a
cyclized rubber or a resin containing a cyclized rubber.
The resin which is insoluble or hard to dissolve in a carrier
liquid according to the present invention, means a resin which is
soluble in an organic solvent having an aniline point below
50.degree. C. but which is insoluble in an organic solvent having
an aniline point above 70.degree. C. Accordingly, the carrier
liquid employed for the present invention is a hydrocarbon having
an aniline point above 70.degree. C. coupled with a resistance
value and a dielectric constant as stated above. Further, it goes
without saying that the second resin which is soluble or easily
soluble in a carrier liquid refers the property of the resin
relative to the foregoing carrier liquid comprising a
hydrocarbon.
As for the carrier liquid having a high resistance and a low
dielectric constant to be employed for the present invention, any
of those known carrier liquids which have hitherto been employed
for electrophotographic liquid developers-- for instance,
paraffinic hydrocarbon, isoparaffinic hydrocarbon, naphtha
hydrocarbon, halogentated hydrocarbon, etc.-- is applicable. And,
as for commercially available carrier liquids, such petroleum
hydrocarbons as are manufactured by ESSO Standard Sekiyu Ltd. and
sold under the name of "ISOPAR-H" and "ISOPAR-G," a product of
Shell Oil Co., Ltd. sold under the name "SHELLSOL" and a product of
Mobil SEKIYU Co., Ltd. sold under the name "PEGASOL" are most
suitable.
In connection with said carrier liquid, the coating agent for the
pigment particles which constitute the toner to be dispersed in the
carrier liquid is elucidated in the following.
A. re: resins hard to dissolve or insoluble in a carrier liquid
For the coating agent in the present invention, a phenol resin
obtained from the group of phenols (such as phenol, cresol, xylenol
and resorcinol) and the group of aldehydes (such as formaldehyde,
acetaldehyde and furfural) and modified resins thereof are
employed. Concrete and typical examples are as follows:
phenol resin, having 100 percent or less oil dissolving
property
phenol modified xylene resin
And, as for commercially available coating agents, those resins
whose principal component is phenol modified xylene resin, such as
products of Japan Gas-Chemical Co., Inc. sold under the name
"NIKANOL HP-100" and "NIKANOL HP-120," are most suitable for the
present invention.
B. re: resins easily soluble in a carrier liquid
Vinyl polymer resins
The suitable resins in this category include
laurylmethacrylate-diemthylaminoethylmethacrylate copolymer,
laurylmethacrylate-n-butylmethacrylate copolymer (containing more
than 20 percent laurylmethacrylate in terms of mol ratio) and the
like.
Further, such copolymers as laurylmethacrylate-isobutylmethacrylate
and the like are also applicable.
And, as for commercially available resins, those resins whose
principal component is acryl copolymer, the products of ROHM &
HASS Co., U.S.A. sold under the name "Plexol No. 966" and "Plexol
No. 917," are most suitable.
Cyclized rubbers
The cyclized rubbers suitable for the present invention can be
obtained through the following processes by employing a natural
resin having a molecular weight in the range of
50,000-2,000,000.
1. Said rubber and any one of sulfuric acids or sulfonic acids are
caused to interact.
2. A halogenide rubber is reduced to a dehalogenated hydrogen.
3. A solid rubber or a rubber solution is heated up to more than
250.degree. C. in the presence of a catalyzer.
4. The rubber and a nonmetal halogenide or a hydroxy-halogenide are
caused to interact.
5. The rubber and an amphoteric metal chloride are caused to
interact, and the metal chloride is subjected to decomposition by
alcohol.
6. The rubber is exposed to ultraviolet rays.
7. A cyclizing agent such as sulfuric acid is caused to act on an
acid latex.
And, as for cyclized rubbers as stated above, products of SEIKO
CHEMICAL Co., Ltd. sold under the names "Thermolite P." "Thermolite
S," "Thermolite O" and "Thermolite N" are available. Further, a
manufacture of Goodyear Co., U.S.A. sold under the name "Pliolite
NR" is also suitable.
C. re: resins to be employed in combination with cyclized
rubbers
This kind of resin includes:
1. alkyd resins
2. varieties of synthetic resin varnishes, to wit, varnishes
obtained from synthetic resins and drying oils (e.g., polymerized
linseed oil)
3. styrene-containing resin, such as styrene-butadiene rubber, and
polystyrene.
According to the present invention, the various coating agents as
stated above are combined as follows for use in coating pigment
particles therewith.
I. resins (A) hard to dissolve + at least one member of easily
soluble resins (B) + pigment particles
Ii. cyclized rubbers + pigment particles
Iii. cyclized rubbers + resins (C) + pigment particles
In this context, it is noted that the cyclized rubber proves
effective in coating pigment particles whichever combination among
(I) through (III) above it may be employed in, as will be
elucidated later on.
To begin with, when a toner of said combination (I) is prepared by
coating pigment particles with a coating agent combining the
foregoing resins (A) and (B) and employing such materials as set
forth above, the intended liquid developer is obtained through the
steps of dissolving a resin insoluble in a carrier liquid (i.e.,
resin (A) ) by means of a small amount of an organic solvent such
as toluene having an aniline point below 50.degree. C., kneading
the resultant mixture together with the granular or powdery
pigment, adding thereafter an easily soluble resin (i.e., resin (B)
) dissolved in a small amount of the same organic solvent as above
for further kneading, and dispersing the thus kneaded compound
(i.e., a concentrated toner) in a carrier liquid. A toner contained
in a liquid developer thus prepared according to the present
invention is capable of increasing the amount of insoluble resin
coated on pigment particles several times as large as that of
conventional toners, which could provide a coating of about 1 part
by weight of the resin employed per 1 part by weight of pigment at
the utmost, but is used to provide a coating of only 0.3 part by
weight thereof. As a result, when an image is actually formed by
way of the use of an ample quantity of said coating, there is
effected quite a stable fixing of the toner onto an electrostatic
charge carrier. Moreover, since the toner under the present
invention is composed of pigment particles coated with the resin
which comprises an easily soluble resin (B) and an insoluble resin
(A) adsorbed with each other or combined chemically in a body, it
has such advantages, as compared with conventional toners composed
by way of merely adsorbing a resin onto the active center for
adsorption of the pigment employed therefore, that not only the
stability of the toner dispersion in a carrier liquid is
remarkable, but also there occurs no such phenomenon as desorption
of the resin, i.e., coating agent from pigment particles, resulting
in the durability of its superb developing efficiency. In other
words, such a toner contained in a liquid developer according to
the present invention is of such a composition that the pigment
particles within the developing liquid are covered with a resin
insoluble or hard to dissolve in the carrier liquid all over their
surfaces and the exterior of the thus-covered surfaces is further
coated with a resin easily soluble in a carrier liquid which has
been firmly combined with or adsorbed to the foregoing insoluble or
hard-to-dissolve type resin. And, as for the mode of combination of
said pigment with a resin hard to dissolve and a resin easily
soluble, it is considered that the hydroxyl radical, for instance,
of molecules consisting a resin hard to dissolve is firmly combined
with, for instance,
laurylmethacrylate-dimethylaminoethylmethacrylate copolymer in such
a mode of combination as is expressed by the following summary
formula.
Formula expressing the mode of combination of resins (A) and
(B)
hard-to-dissolve type resin coated on the surface of pigment
(Note: DA in the above formula denotes
dimethylaminoethylmethacrylate, and LMA denotes
laurylmethacrylate.)
According to the present invention, therefore, the employment of
resin (A) and resin (B) for coating pigment particles in the order
as stated above will be most effective.
Meanwhile, a cyclized rubber is considered to have the following
structural formula: ##SPC1##
Since it is considered to be a compound composed of molecules of
such structure as having a molecular weight with a relatively large
numerical value of n in said formula and molecules of such
structure as having a molecular weight with a relatively small
numerical value of n in the formula arising out of the cutting of
the principal chain of rubber, the molecular weight distribution of
cyclized rubber extends over a wide range.
A cyclized rubber of said composition can be coated on the surfaces
of pigment particles as much as desired regardless of the varieties
of the carrier liquids, to wit, with no such restriction of the
amount of coating according to the kind of carrier liquid employed.
Moreover, when it is combined with resin (A), it displays
properties and actions equivalent to those of resin (B).
In this context, it is considered that molecules with a structure
of low molecular weight within a cyclized rubber coated on the
surfaces of pigment particles accelerate the dispersibility of
pigment particles or the dispersibility of pigment particles
containing an adsorbed resin in a carrier liquid and act as a
dispersion stabilizer, while molecules with a high molecular weight
structure are adsorbed on said pigment particles and are in a
swollen state in the carrier liquid so that in case of development
they are absorbed in an electrostatic latent image area in that
condition and are fixed firmly on said latent image area by
evaporation of said carrier liquid. With respect to said
properties, it is presumed that a molecule with a high molecular
weight contained in a cyclized rubber has a property corresponding
to that of resin (A) as stated above while a molecule with a low
molecular weight has a property corresponding to that of resin (B)
as stated above. And, a cyclized rubber having such a property is
equally adaptable even to a carrier liquid prepared by blending
different kinds of carrier liquids and it retains said property
without being influenced by changes of temperature of the carrier
liquid. Such property or action as stated above cannot be expected
of any ordinary rubber such as natural rubber or isoprene rubber or
any synthetic rubber such as butadiene rubber and the like.
Further, a cyclized rubber has a peculiar field-activating effect
in addition to the extensive molecular weight distribution as
stated above.
Moreover, a cyclized rubber is capable of controlling the polarity
of pigment particles per se to thereby provide a distinct polarity.
For instance, in case of a substrate obtained by dispersing carbon
black alone in an appropriate carrier liquid, there is not
displayed any distinct polarity as required for development.
However, in case of a liquid developer according to the present
invention which is prepared by dispersing a kneaded mixture of
carbon black and a cyclized rubber in a carrier liquid, that is, a
developer prepared by employing a toner according to the aforesaid
combination (II), the polarity becomes quite distinct. Further,
even in case of a developer containing such a toner as has hitherto
been of no practical use for the reason that is apt to cause
aggregation within a carrier liquid, it is possible to improve said
developer so as to make it suitable for practical use by employing
a cyclized rubber, combination.
To take an illustration, when a vinyl polymer such as
styrene-butadiene copolymer, polymer acrylate or styrene-acrylic
copolymer is employed as a polarity-controlling resin for pigment
particles, a satisfactory dispersion may be expected if said vinyl
polymer has a superior affinity towards the carrier liquid
employed, but the amount of such a resin adsorbed onto pigment
particles is so small--in this case it is 30 percent or thereabout
at the utmost--that the fixability of the toner on an electrostatic
charge carrier is unsatisfactory. However, if a resin which is apt
to somewhat swell in a carrier liquid is jointly used, the
dispersibility will be deteriorated and aggregation will easily
take place. On such an occasion, employment of a cyclized rubber
together with such a defective resin as above is effective in
preventing the occurrence of said phenomenon. Therefore, even in
case of applying the aforesaid combination (III) in coating the
surfaces of pigment particles, not only a distinct polarity in a
carrier liquid can be expected, but also a toner of superior
dispersibility can be obtained.
When preparing a toner of the foregoing combination mode (II)
according to the present invention, a cyclized rubber and a small
amount of a carrier liquid are kneaded together with pigment
particles. A toner of the combination mode (III) may be prepared
either by employing the same components as the combination mode
(II) plus the resin (C) and kneading them together, or by employing
the resin (C) and a small amount of an organic solvent added
thereto, kneading them together with pigment particles, and then
adding a cyclized rubber and an organic solvent for further
kneading subsequent thereto. And, the most suitable toner for the
present invention is the latter one of the foregoing toners
provided with a coating of the combination mode (III).
As for pigment particles to be employed for the present invention,
any of those known heretofore is applicable. They include, for
instance, inorganic or organic pigments such as carbon black (C.I.
No. 77266 ), Aniline Black (C.I. No. 50440), spirit black (C.I. No.
50415), phthalocyanine blue (C.I. No. 74160), benzidene yellow
(C.I. No. 21090), Carmine 6B (C.I. No. 15850), zinc oxide powder
and Lake Red (C.I. No. 15585).
A liquid developer according to the present invention contains a
toner which contributes to displaying a much more distinct polarity
than any conventional developer and maintains a uniform
dispersibility by virtue of the polarity-controlling action as well
as dispersion-stabilizing action of the coating agent as stated
above, and said toner has a large fixability with respect to an
electrostatic latent image consisting of a delicate electric charge
and an image once fixed onto an electrostatic charge carrier cannot
be erased so readily with an india rubber eraser or the like, so
that it serves to form an image of superb preservability and
durability. The thus-formed image, when once fixed, does not become
swollen even if it is dipped in a carrier liquid and retains a
solvent resistance. And, especially when a toner employing a
cyclized rubber is used, the rubber itself possesses superb
electric properties, so that it is possible to adsorb an additional
toner onto the image formed as above. Such being the case, said
liquid developer according to the present invention is quite
suitable for use in such repeated development as in case of
developing color films of electrophotography.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Among the following Examples, 1 through 8 show the embodiments
wherein the coating agents cyclized rubber and (C) are employed
respectively, Examples 9 through 12 show the embodiments wherein
the coating agents (A) and (B) are employed respectively and
Example 13 is an embodiment of the use of cyclized rubber and
coating agents (A).
EXAMPLE 1
A mixture, comprising: Carbon black (manufactured by Asahi Carbon
Mfg. Co., Ltd. and sold under the name "XC- 550" ) 4.5g. spirit
black (manufactured by Orient Chemicals Co., Ltd. and sold under
the name "Spirit Black-SB") 0.5 g. 5%-toluene solution of
styrene-butadiene copolymer (manufactured by Good Year Co., Ltd.
and sold under the name "CPR" ) 62.5 g.
toluene 400.0 g.
was put in a ball mill for 16 hours kneading, and then taken out
and subjected to spray drying. Subsequently, a mixture comprising 5
g. of a dry powder thus obtained, 36 g. of 25-percent toluene
solution of a cyclized rubber (i.e., Thermolite-P) and 59 percent
of naphtha hydrocarbon (i.e., a manufacture of ESSO Standard Oil
Co., Ltd. sold under the name "Naphtha-No. 6" ) was also kneaded
with a ball mill for 16 hours to thereby prepare a concentrated
toner. Then, 10 g. of said toner was dispersed in 500 cc. of
isoparaffin hydrocarbon (i.e., a manufacture of Standard Oil Co.,
Ltd. sold under the name "ISOPAR-H" ), whereby there was obtained a
liquid developer for use in developing an electrostatic image.
In this connection, it is noted that said spirit black was employed
for the purpose of modifying the shade of the toner into pure
black.
EXAMPLE 2
A mixture, comprising: carbon black (manufactured by Mitsubishi
Kasei Kogyo Co., Ltd. and sold under the name "Mitsubishi No. 44" )
4.5 g.
spirit black 0.5 g. 5 %-toluene solution of styrene-butadiene
copolymer (manufactured by Good Year Co., Ltd. and sold under the
name "Pliolite S- 5 5D" ) 12.5 g.
toluene 400 g.
was treated in the same way as Example 1 for preparing a dry
powder. Subsequently, a mixture comprising 5 g. of the dry powder
thus prepared, 36 g. of 25-percent toluene solution of a cyclized
rubber (i.e., Thermolite-S) and 59 g. of naphtha hydrocarbon was
treated in the same way as Example 1 for preparing a concentrated
toner. Then, 10 g. of said toner was dispersed in 500 c.c. of
isoparaffin hydrocarbon, whereby there was obtained a liquid
developer for use in developing electrostatic images.
Example 3
by applying the same mixture and same treatment as Example 1,
except that said cyclized rubber was replaced by Pliolite-NR, a
liquid developer for use in developing electrostatic images was
prepared.
Example 4
by applying the same mixture and same treatment as Example 1,
except that said cyclized rubber was replaced by Thermolite-O, a
liquid developer for use in developing electrostatic images was
prepared.
Example 5
by applying the same mixture and same treatment as Example 1,
except that said cyclized rubber was replaced by Thermolite-N, a
liquid developer for use in developing electrostatic images was
prepared.
EXAMPLE 6
A mixture, comprising: Carbon black (XC-550) 4.5 g. spirit black
0.5 g. styrene-butadiene copolymer (aforesaid CPR) 6 g. toluene 40
g. cyclized rubber (Thermolite-P) 72 g. naphtha hydrocarbon 77
g.
was subjected to 16 hours kneading within a ball mill to thereby
prepare a concentrated toner. Then, 10 g. of said toner was
dispersed in isoparaffin hydrocarbon, whereby there was obtained a
liquid developer (of positive-to-positive type) for use in
developing electrostatic images.
EXAMPLE 7
A mixture, comprising: carbon black (MOGAL-A, manufactured by
Cabbot Co., Ltd.) 5.0 g. cyclized rubber 36 g. Naphtha hydrocarbon
51 g.
was subjected to 16 hours kneading within a ball mill to thereby
prepare a concentrated toner. Then, 5 g. of said toner was
dispersed in 500 cc. of isoparaffin hydrocarbon, whereby was
obtained a liquid developer (of negative- to -positive type) for
use in developing electrostatic images.
Those developers which were prepared as in Example 1 through 6
above, when employed for dipping and developing an
electrophotographic copying paper having positive electrostatic
latent images impressed by a commercially available copying machine
(i.e., a manufacture Kabushiki Kaisha Ricoh sold under the name
"BS-1" ), proved capable of forming copied images of superb
distinction and stability. Besides, when an acetate film employed
as an electrostatic recording paper was impressed with a latent
image by applying a voltage of -10 kv. for 0.5 second and subjected
to developing by those developers of Example 1 through 6, the
fixing of copied images, was quite satisfactory, and further when
the foregoing film was impressed with images by applying a voltage
of +10 kv. for 0.5 second and subjected to developing with a
developer of Example 7, the resultant images also displayed superb
fixability.
Example 8
by applying the mixture and same treatment as Example 1, except
that said carbon black was replaced by copper phthalocyanine,
carmine 6B and benzine yellow, respectively, an indigo-blue liquid
developer, a red liquid developer and a yellow liquid developer for
use in developing electrostatic images were respectively prepared.
All of those developers proved superb in dispersibility as well as
fixability, and also displayed a superb efficiency in the
multilayer development (color development) by way of the
three-color separation chart employing a conventional
electrophotographic copying paper.
EXAMPLE 9
A mixture, comprising: carbon black (manufactured by Mitsubishi
Kasei Kogyo Co., Ltd., and sold under the name "Carbon Black No.
100") 5 g. 40%-toluene solution of NIKANOL HP- 100) 30 g.
was subjected to 1 hour's kneading within a ball-mill, and then
Plexol No. 966 10 g. toluene 55 g. were added to the thus kneaded
mixture and was followed by further kneading for 16 hours.
Subsequently, 5 g. of the resultant mixture thus kneaded was
dispersed in 1 liter of ISOPAR-H (a carrier liquid), whereby there
was obtained a liquid developer for use in developing electrostatic
latent images.
On the other hand, for the purpose of comparing the efficiencies of
developers, a toner comprising carbon black coated with alkyd resin
was prepared by almost the same treatment as a toner of the present
invention. Then, about 2 g. of the thus prepared comparative toner
was dispersed in 1 liter of ISOPAR-H to thereby obtain a liquid
developer for use in comparison.
Subsequently, by way of a conventional electrophotographic method,
electrostatic latent images were imparted onto commercially
available electrophotographic copying papers, and then said copying
papers were dipped in each of the above-stated developers in order
to compare their fixability with respect to said images as well as
to observe the degrees of deterioration of the developing
efficiency due to prolonged preservation of respective developers.
The results of said observations are summarized in the following
Table 1. ##SPC2##
EXAMPLE 10
a. solution, comprising carbon black (the same as Example 1 ) 5 g.
50%-toluene solution of NIKANOL HP-120 30 g. HP-120 b. solution,
comprising Plexol 966 10 g. toluene 55 g.
The above solutions (a) and (b) were respectively treated in the
same way as Example 9, whereby there were obtained liquid
developers for use in developing electrostatic latent images.
The thus-prepared developers, when put to practical use for copy
development and observed as regards their efficiency, proved to
have a fixability as well as a preservability equivalent to the
developer of Example 9 according to the present invention.
EXAMPLE 11
a. solution, comprising carbon black (manufactured by Cabbot Co.,
Ltd., U.S.A. and sold under the name "MOGAL-A" ) 5 g. 50%-toluene
solution of NIKANOL HP-100 30 g. b. solution, comprising Plexol No.
966 10 g. toluene 55 g.
The above solutions (a) and (b) were respectively treated in the
same way as Example 9, whereby there were obtained liquid
developers for use in developing electrostatic latent images. And,
the thus prepared developers proved to have efficiency equivalent
to the foregoing developers according to the present invention.
Example 12
By applying a toner preparing solution having the same composition
as Examples 9, 10 and 11 above respectively, except that only the
resin easily soluble in a carrier liquid, to wit, Plexol No, 966
alone was replaced by either Plexol No. 917 or
laurylmethacrylate-dimethyl-aminoethylmethacrylate copolymer,
liquid developers for use in developing electrostatic latent images
were prepared respectively. These developers also proved to have
efficiency equivalent to those developers of Example 9 through 11
according to the present invention.
EXAMPLE 13
A mixture, comprising: Carbon black (the same as Example 1) 5 g.
50%-toluene solution of NIKANOL HP- 100 30 g.
was subjected to 1 hours kneading within a ball-mill, and then:
25%-toluene solution of a cyclized rubber 30 g. toluene 35 g.
were added to the thus kneaded mixture and were followed by 16
hours kneading thereafter. The resultant kneaded mixture was then
treated in the same way as in case of the developer of Example 9
according to the present invention, whereby there was obtained a
liquid developer for use in developing electrostatic latent images.
The thus-prepared developer, when examined as regards its
developing efficiency, proved to have an efficiency equivalent to
the developer of Example 9 according to the present invention.
Plexol 917 is a methacrylate copolymer in solvent refined (150
SUS/100.degree. F.) neutral oil. It has a specific gravity
(60.degree. F./60.degree. F.) of 0.904, a density (pounds/gallon at
60.degree. F.) of 7.53, color (ASTM D-1500) of 3 and a
neutralization number (ASTM D-974) of 0.2.
Plexol 966 is a methacrylate copolymer in solvent refined (100
SUS/100.degree. F.) neutral oil. It has a specific gravity
(60.degree. F./60.degree. F.) of 0.899, a density (pounds/gallon at
60.degree. F.) of 7.49, color (ASTM D-1500) of 3 and a
neutralization number (ASTM D-974) of 0.2.
Nikanol HP 100 is an alkyl phenol modified xylene resin which is a
light yellow solid, having a color value of less than 8 and a
viscosity (cp.) of 200-400.
Nikanol HP 120 is an alkyl phenol modified xylene resin which is a
light yellow solid, having a color value of less than 10 and a
viscosity (cp.) of 200-400.
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