JP2508694B2 - Method for producing photoconductive powder - Google Patents

Description

The present invention relates to a photoconductive material that can be used as a raw material for a photoconductive toner for forming a color image in a single step by electrophotography without using a photoconductor. The present invention relates to a method for producing a powdery powder.

[Conventional technology]

In conventional color copiers that use electrophotography,
In forming a color image, a system is employed in which toner particles colored in three primary colors (subtractive color mixture) are used to sequentially repeat the process of exposure → development → fixing three times. Since this method is complicated and requires a long time, a method of forming a color development by a single step, that is, a single exposure → development → fixing has been proposed and is attracting attention. Regarding the method performed in this single step, see JP-A-59-113448 and JP-A-60-
It is disclosed in Japanese Patent No. 31149 and uses a photoconductive toner. Photoconductive toner is photoconductive powder,
These powders consist of colored substances that exhibit the three subtractive primary colors, a charge control agent, and a binder. In this case, as the photoconductive powder, a mixture of a photoconductive substance such as ZnO and three kinds of spectral sensitizers such as dyes is used. However, since they are easily separated by simple mixing and the spectral sensitizing effect cannot be expected for a long period of time, a method is used in which the two are bound together using a resin binder to form a photoconductive powder.

[Problems to be solved by the invention]

In such a conventional photoconductive powder, the spectral sensitivity (photocurrent characteristic with respect to wavelength) for each light of the three primary colors (additive color mixture) is very low, and their sensitivity curves are much larger than the peak value. Since they overlap each other, it is unavoidable that the color image formed by the photoconductive toner using the same has poor color, and the colors are light, and that uneven colors and bleeding occur.

The present invention has been made in order to solve the above-mentioned problems, and has high spectral sensitivity to the three primary color lights of additive color mixture, and photoconductive powder that can reduce the overlap of sensitivity curves compared to the peak value. Therefore, the present invention aims to solve a good color image by using a photoconductive toner made of this photoconductive powder.

[Means for solving problems]

The method for producing a photoconductive powder according to the present invention comprises a first method comprising at least one compound selected from metal alkoxides and metal acetylacetonates and combined with the same metal.
A main raw material A ₁ , a first pigment body D ₁ having a spectral characteristic of absorbing one of the three primary colors of additive colors, a second main raw material A ₂ containing one or more of the above compounds, and one of the above three primary colors A second pigment body D ₂ having a spectral characteristic of absorbing blue, a third main raw material A ₃ containing one or more of the above compounds, and one of the above _three primary colors.
A third dye D ₃ having a spectral characteristic of absorbing two greens is mixed in a solution to prepare mixed solutions B ₁ , B ₂ and B ₃ , respectively.
Fine particles of metal oxides or metal hydroxides of the above-mentioned metals having a large number of void micropores by hydrolyzing the main raw materials A ₁ , A ₂ and A ₃ in B ₁ , B ₂ and B ₃ respectively and a pigment body C _The composite powders C ₁ , C ₂ and C ₃ containing ₁ , ₁ , D ₂ and D ₃ as main components were obtained.

[Operation] In the method for producing a photoconductive powder according to the present invention, a metal alkoxide or acetylacetonate is hydrolyzed in a solution by a so-called sol-gel method to form a homogeneous metal oxide or metal hydroxide. Fine particles having a uniform particle size can be obtained. The fine particles have many very fine pores. During the hydrolysis, if the pigment body (pigment) is present in the solution, the pigment body (pigment) is incorporated into the structure during the formation process of the metal oxide or metal hydroxide, that is, in the fine pores of the fine particles. And, by being adsorbed on the surface and adsorbed and stably retained, finally, a composite powder composed of composite particles in which the above-mentioned metal oxide or metal hydroxide and the pigment body (pigment) are firmly bound is produced. Since the composite powder is composed of composite particles in which the metal oxide and the pigment body (pigment) are completely integrated as described above, the spectral sensitivity characteristics are improved.

Further, the first dye body D ₁ having a spectral characteristic of absorbing one of the three primary colors of additive colors, red, sensitizes the spectral sensitivity characteristic originally possessed by the metal oxide to red. The same applies to the second dye body D ₂ and the third dye body D ₃ .

〔Example〕

Hereinafter, for the method for producing a photoconductive powder of the present invention,
Specific examples will be described.

Example 1 20 parts by weight of a metal alkoxide of titanium propoxide was used as the first main material A ₁ , the second main material A ₂ , and the third main material A ₃ , and the spectral characteristics of absorbing one red of the three additive primary colors were determined. Tetrapromophenol blue is used as the first pigment body D ₁ having 0.1
Parts by weight, 0.1 parts by weight of cyanine as the second pigment body D ₂ having a spectral characteristic of absorbing one of the three primary colors of additive color mixture,
0.1 parts by weight of eosin is prepared as a third pigment body D ₃ having a spectral characteristic of absorbing one of the three primary colors of additive color mixture, green. Plastid D ₁ in the main raw material A _1, the plastid D ₃ was added to the main raw material A ₂ plastid D _2, the main raw material A _3, isopropyl alcohol 50 respectively
By adding parts by weight, mixed solutions B ₁ , B ₂ and B ₃ were prepared. After adjusting these solutions B ₁ , B ₂ and B ₃ to 60 ° C, the excess water was added to hydrolyze the titanium isopropoxide of the main raw materials A ₁ , A ₂ and A ₃ to form colored precipitates. did. As a result of analyzing these precipitates, amorphous TiO ₂ or metal oxide particles
It was found to be composite powders C ₁ , C ₂ and C ₃ composed of composite particles with D ₁ , D ₂ and D ₃ .

Next, prepare a substrate on which a pair of transparent electrodes are formed on a slide glass at intervals of 100 μm, and apply composite powder (in other words, photoconductive powder) C ₁ , C ₂ and C ₃ on each substrate and dry. Then, a sample was prepared and the spectral sensitivity characteristics were measured. For comparison, three kinds of photoconductive powders C ₁ prepared by the conventional method, in which the pigment bodies D ₁ , D ₂ , D ₃ and the TiO ₂ powder are bound with a resin binder (acrylic resin), The characteristics of ′, C ₂ ′ and C ₃ ′ were measured under the same conditions. The results are shown in the characteristic diagram of FIG. 1 showing the spectral sensitivity characteristics of the photoconductive powder. In the figure, the vertical axis represents photocurrent, the horizontal axis represents wavelength (nm), and the solid line characteristic curve (A) is the composite powder C ₂ obtained in Example 1 of the present invention.
The same (B) is for composite powder C ₃ and the same (C) is for composite powder C
₁ , the broken line characteristic curve (D) is the photoconductive powder C ₂ ′ according to the conventional example, (E) is the photoconductive powder C ₃ ′, and (F) is the photoconductive powder C. _It shows the spectral sensitivity characteristic of ₁ '. Characteristic curves (A) and (D) are cyanine of the second plastid D ₂ , characteristic curves (B) and (E) are eosin of the third plastid D ₃ , and characteristic curves (C) and (F) are the first. Dye sensitization is performed by the tetrabromophenol blue of the dye body D ₁ . The peak around 405 nm in each characteristic curve is the peak of the photocurrent originally possessed by TiO ₂ . Characteristic curves (D) to (F)
As is clear from the above, photoconductive powders C ₁ and C produced by the conventional method
_{In 2} and C ₃ , the sensitivities to the light of the three primary colors of the additive color mixture are considerably low, and their sensitivity curves overlap with each other at a considerably large ratio compared with the peak value. Such characteristics could not be improved even by changing the compounding ratio of the binder or dye or the kind of TiO ₂ powder. On the other hand, as is clear from the characteristic curves (A) to (C), in the photoconductive composite powders C ₁ , C ₂ and C ₃ produced by the production method of the present invention, the additive color mixture of 3
The respective sensitivities to the primary color light are very good, and the degree of overlap of the respective sensitivity curves is relatively small compared to the peak value.

Next, the three kinds of photoconductive composite powders C ₁ , C ₂ and C ₃ produced in Example 1 were mixed with a suitable leuco dye, a binder and the like to prepare a photoconductive toner, According to the photographic method, the color image forming property on the clay paper was examined by one exposure → phenomenon → fixing. As a result, when the photoconductive powders C ₁ ′, C ₂ ′ and C ₃ ′ according to the conventional method are used, the color becomes very thin, while the photoconductive powder C of Example 1 is used. It was found that a beautiful color image was formed when ₁ , C ₂ and C ₃ were used. Further, in this case, in order to remove the adverse effect due to the overlap of the spectral sensitivity curves shown in FIG. 1, using lionol yellow and lionol red as filters, the photoconductive powder C ₁ ′ by the conventional method, The toner using C ₂ ′ and C ₃ ′ had a slightly darker color, but the toner using the photoconductive powders C ₁ , C ₂ and C _{3 according} to Example 1 exhibited a filter effect. Therefore, it was found that the color became clearer.

Example 2. Zinc acetylacetonate of metal acetylacetonate was used as the first main raw material A ₁ , the second main raw material A ₂ , and the third main raw material A _3.
20 parts by weight are used, and the other mixed solution B ₁ and B is the same as in Example 1.
I got ₂ , B ₃ . Excess water containing a small amount of ammonia was mixed into these solutions B ₁ , B ₂ and B ₃ and sufficiently hydrolyzed to produce the same three kinds of colored precipitates as in Example 1. It was found that these precipitates were composite powders C ₁ , C ₂ and C ₃ composed of composite particles of ZnO metal oxide and pigment bodies D ₁ , D ₂ and D ₃ .

Next, the spectral sensitivity characteristics of the above composite powders C ₁ , C ₂ and C ₃ were measured in exactly the same manner as in Example 1. For comparison, three types of photoconductive powders prepared by the conventional method in which the dye bodies D ₁ , D ₂ , and D ₃ and commercially available ZnO powders are bound with a resin binder (styrene resin) The characteristics of (C ₁ ′, C ₂ ′, C ₃ ′) were measured. The results are shown in the characteristic diagram of FIG. 2 showing the spectral sensitivity characteristic of the photoconductive powder. In the figure, the vertical axis represents photocurrent, the horizontal axis represents wavelength (nm), and the solid line characteristic curve (G) is the composite powder C ₂ obtained in Example 2 of the present invention.
, (H) is for composite powder C ₃ , and (I) is for composite powder C
₁ , the broken line characteristic curve (J) is the photoconductive powder C ₂ ′ according to the conventional example, (K) is the photoconductive powder C ₃ ′, and (L) is the photoconductive powder C. _It shows the spectral sensitivity characteristic of ₁ '. The peak near 380 nm in each characteristic curve is the peak of the photocurrent that ZnO originally has. As is clear from FIG. 2, as in the case of FIG. 1, the powders prepared by the conventional method have a considerably low sensitivity to the light of the three primary colors of additive color mixture, and their sensitivity curves are considerably larger than the peak value. Overlap with each other. On the other hand, in the powder according to Example 2 of the present invention, it is clear that the above-mentioned sensitivity is very good and the degree of overlap of the sensitivity curves is relatively small compared to the peak value.

In addition, in the same manner as in the first embodiment,
C _1, C _2, C ₃ Comparative Example _{C 1 ', C 2',} ' was tried to form a color image by using both powder as a toner, conventional powder C _1' C _3, C ₂ ', C _3' whereas the color is very thin in the case of using the powder C ₁ of example 2, C _2, C ₃
The same result as in Example 1 that a clear color image can be formed was obtained when the above method was used.

As shown in FIGS. 1 and 2, the reason why the photoconductive powder produced by the method of the present invention has good spectral sensitivity characteristics is that this method is an application of the so-called sol-gel method. It is thought to be due to that. That is, first of all, in the sol-gel method, a metal having a structure having a large number of very fine pores, which is very pure and uniform as known, by hydrolyzing a metal alkoxide or a metal acetylacetonate. It is possible to obtain fine particles of oxide or metal hydroxide. In the production process of fine particles by the above-mentioned hydrolysis, the inventors have found that the metal oxide or metal hydroxide has a property that the dye molecule constituting the dye body in the solution is incorporated and stably retained in its fine structure. It is the basis of the present invention that it is first discovered that it has. That is, in the conventional photoconductive powder obtained by simply mixing the metal oxide particles and the dye or binding them with the resin binder, the energy band is not connected at the interface because direct contact between the two is weak, and It is assumed that spectral sensitization is difficult to perform smoothly. On the other hand, since the photoconductive powder produced by the method of the present invention is composed of composite particles in which the metal oxide and the dye are completely integrated as described above, the spectral sensitivity characteristics are very high. It is thought to be good.

As the pigment body according to the present invention, in the above-mentioned embodiment, the pigment bodies D ₁ , D ₂ , and D ₃ each consisting of one kind of different pigment are shown, but they may be composed of two or more kinds of pigments. However, the same dye should not be contained in the plastids D ₁ , D ₂ , and D ₃ in duplicate. Further, many dyes other than the dyes mentioned in the examples can be applied. As the dye, it is necessary to adopt a dye that has a function of sensitizing the spectral sensitivity characteristic originally possessed by the metal oxide to the three primary color lights of additive color mixture, and as described above, absorb at least the above three primary color lights. It should be selected from dyes having a spectral characteristic of If the dye has such characteristics, it is easy to transfer the energy of light obtained when absorbing one of the three primary colors of light to the metal oxide particles, and at the same time, the transfer of electrons is accompanied by the photocurrent. It is considered possible to increase (i.e., sensitize).

As the main raw material according to the present invention, the main raw material in the above embodiment
A ₁ , A ₂ , and A ₃ are all shown to be the same compound, but the main raw materials A ₁ , A ₂ , and A ₃ may be different compounds selected from metal alkoxides and metal acetylacetonates. It may be composed of two or more kinds of the same or different compounds described above. However, the compounds of the main raw materials A ₁ , A ₂ and A ₃ must be bound to the same metal.

Further, as the metal alkoxide or metal acetylacetonate according to the present invention, a metal oxide produced through hydrolysis having a characteristic as a semiconductor is used, for example, in addition to Ti and Zn used in Examples, Sn, Cu, Ni, Cd,
In, Fe, Sb, etc. are many. However, since the purpose of the present invention is to obtain a photoconductive powder having sensitivity peaks for the three primary color lights in the visible region by dye sensitization, among the above, it has good sensitivity in the ultraviolet region. From the viewpoint of easy spectral sensitization by dyes, Ti and Zn
Most preferably, the alkoxide or acetylacetonate of is used.

[Effects of the Invention] As described above, according to the present invention, a first main raw material A ₁ containing at least one compound selected from metal alkoxides and metal acetylacetonates and combined with the same metal, A first pigment body D ₁ having a spectral characteristic of absorbing one red of three additive primary colors, a second main raw material A ₂ containing one or more of the above compounds, and a spectral characteristic of absorbing one blue of the above three primary colors. second plastid D ₂ having, and third main raw material a ₃ and third plastid D ₃ each solution having a spectral property of absorbing one green the three primary colors comprising one or more of the above compounds To prepare mixed solutions B ₁ , B ₂ and B ₃ by mixing them with solutions B ₁ and B
₂ , B ₃ main raw materials in A ₁ , A ₂ , A ₃ are respectively hydrolyzed to have a large number of void micropores Metal oxide or metal hydroxide fine particles of the above metal and pigment bodies D ₁ , D ₂ By obtaining composite powders C ₁ , C ₂ , and C ₃ whose main components are D, and D ₃ , the sensitivity of photocurrent to the light of the _three primary colors of additive color mixing is high, and the overlap of sensitivity curves is small. There is an effect that conductive powder can be obtained.
Further, by using the photoconductive toner made of this photoconductive powder, there is an effect that a good color image can be obtained.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the spectral sensitivity characteristics of the photoconductive powder obtained by Example 1 of the present invention and that obtained by the conventional method, and FIG. 2 is obtained by Example 2 of the present invention. FIG. 3 is a characteristic diagram showing the spectral sensitivity characteristics of the photoconductive powder and the characteristics of those obtained by a conventional method. Characteristic curves A, G: Spectral sensitivity characteristics of photoconductive powder using the second pigment body D ₂ Characteristic curves B, H: Spectral sensitivity characteristics of photoconductive powder using the third pigment body D ₃ C, I: Spectral sensitivity characteristics of photoconductive powder using the first dye D ₁

Front page continuation (56) References JP 62-6266 (JP, A) JP 60-31149 (JP, A) JP 60-153054 (JP, A) JP 60-153053 (JP , A) JP 60-153055 (JP, A) JP 55-83053 (JP, A)

Claims (4)

(57) [Claims] 1. A _first main raw material A ₁ containing at least one compound selected from a metal alkoxide and a metal acetylacetonate and bound to the same metal, and absorbing one red of three additive primary colors. First plastid having spectral characteristics
D ₁ , a second main raw material A ₂ containing one or more of the above compounds, and a second having a spectral characteristic of absorbing one of the three primary colors blue
A dye body D ₂ , a third main raw material A ₃ containing one or more of the above compounds, and a third dye body D ₃ having a spectral characteristic of absorbing one of the three primary colors green are mixed in a solution. mixed solution B _1, B _2, B ₃ was prepared, the solution B _1, B _2, the main raw material a ₁ in B _3, a _2,
Particles and pigments of metal oxides or metal hydroxides of the above metals having a large number of void micropores by hydrolyzing A ₃ respectively
A method for producing a photoconductive powder, wherein composite powders C ₁ , C ₂ , C ₃ containing D ₁ , D ₂ , D ₃ as main components are obtained. 2. The method for producing a photoconductive powder according to claim ₁ , wherein the main raw materials A ₁ , A ₂ and A ₃ are the same. 3. The method for producing a photoconductive powder according to claim 1, wherein each of the dye bodies D ₁ , D ₂ and D ₃ is composed of one or more different dyes. 4. The method for producing a photoconductive powder according to claim 1, wherein the constituent metal of the metal alkoxide and the metal acetylacetonate is Zn or Ti.