JPH0250466B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a conductive support used in electrostatic recording media, electrophotographic recording media, electrostatic transfer media, electrically conductive heat-sensitive recording media, and the like. ``Conventional technology'' In electrostatic recording and electrophotographic recording, characters and figures are converted into electrostatic latent images via electrical signals and optical signals, and are visualized and recorded using toner. The supports used are generally subjected to some kind of low resistance treatment. Ionic conductive substances such as inorganic salts and polymer electrolytes are a type of conductive substance used for low-resistance processing, but their resistance value changes greatly depending on changes in the humidity of the external environment. The scope of use is limited. Therefore, metal oxide semiconductors such as tin oxide, zinc oxide, and indium oxide, which contain impurities in their crystals and exhibit electronic conductivity, are preferably used as conductive substances that are not easily affected by humidity changes. However, these metal oxide semiconductors usually
Since a large amount of processing is required to obtain a desired resistance value, there is a cost problem. For example, a conductive support for an electrostatic recording medium requires a resistance value of approximately 10 ⁷ Ω, and to obtain this value it is necessary to coat approximately 10 g or more of zinc oxide. Further, in the case of an electrically conductive heat-sensitive recording medium, the resistance values obtained with these metal oxide semiconductors are insufficient, so a conductive substance such as copper iodide is used.
However, since copper iodide liberates iodine, it has disadvantages such as corrosion of the metal and unnecessary coloring of the recording medium. "Problems to be Solved by the Invention" In view of the current situation, the present inventors have aimed to improve the conductivity of metal oxide semiconductors to reduce the amount of expensive metal oxide semiconductors coated, resulting in lower costs. As a result of intensive research on technology that can reduce energy consumption and save energy in the manufacturing process, as well as avoid the use of conductive substances such as copper iodide, which are associated with problems such as corrosion and coloring, we have developed a sulfoxylate derivative that exhibits reducing properties. The present inventors have discovered that the conductivity of a metal oxide semiconductor is significantly improved when the metal oxide semiconductor is used in combination with the metal oxide semiconductor, and the present invention has been achieved. "Means for Solving the Problems" The present invention is a conductive support comprising a conductive layer containing a metal oxide semiconductor and a sulfoxylate derivative. "Function" Metal oxide semiconductors used in the present invention include zinc oxide, tin dioxide, cadmium oxide, titanium dioxide, indium oxide, etc., and metals such as titanium oxide with conductive tin oxide formed on the surface. Examples include composites containing oxide semiconductors as the main conductive component (Japanese Unexamined Patent Publication No. 11825/1983), but among these, zinc oxide is relatively inexpensive, easy to handle, and has little impact on the environment. It is particularly preferably used because of its saturation. The conductivity of all these metal oxide semiconductors is controlled by valence control, but conductive zinc oxide, for example, is manufactured by adding a small amount of impurities such as aluminum, indium, tin, etc. to zinc oxide and firing it. (Japanese Patent Application Laid-Open No. 162477/1983).
Conductivity can be controlled to some extent by controlling the manufacturing conditions, such as the firing temperature and reducing atmosphere, but the resistance value of the resulting conductive zinc oxide depends on the coloring and particle size of the resulting zinc oxide powder. Of course there are limits. In the conductive support of the present invention, a sulfoxylate derivative is used in combination with the metal oxide semiconductor, and specific examples of the sulfoxylate derivative include derivatives represented by the following general formula. MSO _{2 .X.nH 2} O or MHSO ₂ . ] Furthermore, specifically NaHSO ₂ , ZnSO ₂ ,
_CoSO2 , _NaHSO2・_CH2O・_2H2O , _ZnSO2・
Examples include CH ₂ O and H ₂ O. Among these,
Sodium formaldehyde sulfoxylate (NaHSO ₂ CH ₂ O 2H ₂ O) obtained by the reaction of sodium hyposulfite and formalin, and zinc formaldehyde sulfoxylate obtained by adding formalin to zinc hydrosulfite and reacting it with zinc powder. Sulfoxylate (ZnSO ₂ .CH ₂ O.H ₂ O) is more preferably used because it provides a particularly excellent effect of improving conductivity. Although it is not necessarily clear why these sulfoxylate derivatives have an excellent conductivity-improving effect on metal oxide semiconductors,
Since sulfoxylate derivatives exhibit strong reducing properties, they efficiently remove gas molecules, especially oxygen molecules, adsorbed on the surface of metal oxide semiconductors, and as a result,
It is speculated that this is because the conductive performance of the metal oxide semiconductor, which had been inhibited by the influence of adsorbed molecules, is significantly improved. In addition, the reason why sulfoxylate derivatives exhibit strong reducing properties is that This is because the SO ₂ group absorbs oxygen and strongly reduces the other party. In the present invention, the proportion of the sulfoxylate derivative in combination with the metal oxide semiconductor is desirably adjusted within a range of 20 parts by weight or less, more preferably, based on 100 parts by weight of the metal oxide semiconductor.
It is adjusted within a range of about 0.001 to 5 parts by weight. In addition,
If it is less than 0.001 part by weight, a sufficient improvement effect will not be obtained, and if it exceeds 20 parts by weight, contact between metal oxide semiconductors will be hindered, so that a satisfactory improvement effect will not be obtained. When using a metal oxide semiconductor and a sulfoxylate derivative in combination, it is preferable to use them together so that the sulfoxylate derivative is directly contacted and adsorbed onto the surface of the metal oxide semiconductor. Methods such as spraying a solution of a salt derivative in the form of a mist and adsorbing it, or mixing and adding a sulfoxylate derivative into a metal oxide semiconductor slurry are employed. As the binder for fixing the metal oxide semiconductor to the support, water-soluble polymer binders such as polyvinyl alcohol, hydroxymethylcellulose, starch, styrene-maleic acid copolymer, polyvinylbenzylammonium chloride, etc. Emulsion-based binders such as polymer electrolytes, acrylic emulsions, and styrene-butadiene latex are preferably used, but organic solvent-based binders such as butyl methacrylate, polyvinyl butyral, and polyester, and electron beam-curable and photo-curable binders are used. resins etc. can also be used. The blending ratio of the binder to the metal oxide semiconductor is 5 to 100 parts by weight of the metal oxide semiconductor.
It is desirable to adjust within a range of about 60 parts by weight. 5
If it is less than 60 parts by weight, there is a risk that the metal oxide semiconductor will fall off due to insufficient adhesion, whereas if it is added in an amount exceeding 60 parts by weight, the contact between the metal oxide semiconductors will be inhibited and the conductivity will decrease. Resulting in. The conductive support of the present invention is generally produced by applying a conductive coating liquid containing a metal oxide semiconductor and a binder to a suitable support. Various auxiliary agents such as a dispersant, an antifoaming agent, and a dye can be added as appropriate. The prepared conductive coating liquid can be applied to, for example, synthetic paper, paper,
The coating is applied to one or both sides of a suitable support such as a film or a plastic plate, but the coating method is not particularly limited. Appropriately applied. In the thus obtained conductive support of the present invention, the conductivity of the metal oxide semiconductor is significantly improved by the combined use of the sulfoxylate derivative, so that the desired conductivity can be obtained even with a relatively small coating amount. . Therefore, the amount of expensive metal oxide semiconductor used can be significantly reduced, and as the amount of coating is reduced, the amount of drying energy consumed can also be significantly reduced. Additionally, since the use of conductive materials such as copper iodide is avoided, problems such as corrosion and staining are also eliminated. [Example] The present invention will be described in more detail below with reference to Examples, but the present invention is of course not limited to these. Note that all parts in the examples indicate parts by weight. Examples 1 to 2, Comparative Example 1 100 parts of conductive zinc oxide produced by adding aluminum as an impurity and firing were mixed with 100 parts of water, and then 1 part of sodium formaldehyde sulfoxylate was added as a sulfoxylate derivative. [Example 1] and 3 parts of zinc/formaldehyde/sulfoxylate [Example 2] were added and dispersed using a ball mill. Note that Comparative Example 1 was an example in which no sulfoxylate derivative was added. Polyvinyl alcohol (manufactured by Kuraray Co., Ltd.,
100 parts of each 10% aqueous solution of PVA105) was mixed to prepare a conductive coating liquid. The above conductive coating liquid was applied to one side of 58 g/m ² of high-quality paper while changing the dry weight from 5 g/m ² to 15 g/m ² , and the surface resistance value when the applied amount was 12 g/m ² was calculated. It was measured. Further, the amount of coating required to achieve a surface resistance value of 1×10 ⁷ Ω was determined and is listed in Table 1. As is clear from the results in Table 1, the electrical conductivity of the metal oxide semiconductor obtained in each example of the present invention was significantly improved by the addition of the sulfoxylate derivative, so that a small amount of the sulfoxylate derivative was added. It had sufficient desired conductivity with a coating amount of .

[Table] Example 3, Comparative Example 2 Conductive tin oxide was used instead of conductive zinc oxide, and 0.1% of sodium formaldehyde sulfoxylate was used as the sulfoxylate derivative.
A conductive coating liquid was prepared in the same manner as in Example 1, except for partially mixing. Note that Comparative Example 2 was an example in which no sulfoxylate derivative was added. The obtained conductive coating liquid was applied to a polyester sheet at varying film thicknesses, the surface resistance value was measured when the film thickness was 5μ, and the film required to achieve a surface resistance value of 1×10 ⁷ Ω The thickness was determined and listed in Table 2.

[Application to electrostatic recording medium]

The five types of conductive supports obtained in Example 1 and Comparative Example 1 were each treated with a supercalender so that the Beck smoothness was 300 seconds. Polyester resin (manufactured by Toyobo Co., Ltd., Byron)
200) 50 parts, calcium carbonate powder (manufactured by Bihoku Funka Co., Ltd.,
Softon 1800) 50 parts and methyl ethyl ketone 200
A dielectric layer coating solution prepared by dispersing in a ball mill for about 1 hour was applied to the conductive support at a dry coating amount of 5 g/m ² to form five types of electrostatic recording materials. I got it. This was recorded with an electrostatic recording facsimile device (UF-520, manufactured by Matsushita Densen Co., Ltd.), and the image density was measured with a Macbeth densitometer, and the results are shown in Table 3. As is clear from the results in Table 3, the image density
To obtain a value of 1.0 or more, it is usually necessary to apply a conductive coating liquid of around 12 g/m ² , but with the conductive support of the embodiment of the present invention, a coating amount of 8 g/m ² or less is sufficient. The desired image density was obtained.

【table】

Claims (1)

[Scope of Claims] 1. A conductive support comprising a conductive layer containing a metal oxide semiconductor and a sulfoxylate derivative. 2. The conductive support according to claim 1, wherein the sulfoxylate derivative is at least one selected from sodium formaldehyde sulfoxylate and zinc formaldehyde sulfoxylate. 3. The conductive support according to claim 1, wherein the metal oxide semiconductor is zinc oxide.