JP2007161551A - Transparent member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent member for reading which is less liable to attachment of dust such as a toner or paper powder, etc., by static charge, and is highly durable. <P>SOLUTION: This transparent member is positioned between a light source and a script in an image reader which optically reads a delivered script, and a transparent electroconductive film is formed on the opposite side of the surface on which the script is in contact (paper passing surface), and there is a region having different surface resistance in the transparent electroconductive film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reading transparent member mounted on a PPC copying machine, a scanner, or the like.

  In general, in an image reading apparatus (scanner or the like) that optically reads a document, a transparent member such as glass is used for the purpose of correctly regulating and arranging the document at a focal position.

  As a transparent member of a document table of an automatic document conveyance type copying machine, a glass member having both high surface slipperiness and low charging property has been adopted.

  For example, when automatically feeding a document, an ITO film (a conductive film made of indium oxide doped with tin) or an oxidation film is used as an antistatic film on the surface of the reading glass in order to prevent paper feeding failure due to static electricity generated by friction. A technique for covering a transparent conductive film such as a tin film so as not to generate static electricity is disclosed.

  However, when rubbed repeatedly with paper, the transparent conductive film has a relatively weak film strength, and an antistatic film that is more resistant to wear has been demanded.

  In response to such a demand, a method of applying a lubricating layer (see, for example, Patent Document 1) by increasing the flatness (Ra = 3 nm or less) to reduce the friction coefficient, and increasing the adhesive strength of the transparent conductive film. Although a technique (for example, refer to Patent Document 2) is disclosed, a stronger film strength is required and it is still insufficient.

On the other hand, if an antistatic film is formed on the contrary to the surface to be worn, the antistatic film is certainly not directly worn and thus becomes more durable, but there is a disadvantage that the antistatic function is remarkably inferior.
JP-A-9-208264 JP 2005-29463 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent member for reading a transported original that is difficult to adhere to dust such as toner and paper dust due to static electricity and that is highly durable.

  The above problem could be solved by the following configuration.

  1. A transparent member that is positioned between a light source and an original of an image reading apparatus that optically reads a conveyed original, and has a transparent conductive film formed on a surface of the transparent member that is opposite to the surface that contacts the original (sheet passing surface). And a transparent member having a region with different surface resistance in the transparent conductive film.

  2. 2. The transparent member according to 1 above, wherein the regions having different surface resistances are divided into a region (Sa) formed in the central portion of the transparent member and a region (Sb) forming the outer periphery thereof.

  3. 3. The transparent member according to 1 or 2, wherein the transparent member is float glass, and a transparent conductive film is formed on the bottom surface of the float glass.

  4). 4. The transparent member as described in 3 above, wherein the surface of the transparent member that contacts the document (sheet passing surface) is the top surface of the float glass.

  5. 5. The transparent member as described in 3 or 4 above, wherein a low friction antifouling layer is formed on at least one of the top surface and the bottom surface of the float glass.

  According to the present invention, it is possible to provide a transparent member for reading a conveyed document that has high durability and high antistatic performance.

  Hereinafter, the present invention will be described in more detail.

  The present invention relates to an image reading transparent member for focusing between a light source and an original of an image reading apparatus that conveys and scans a paper-like original image such as a copying machine or a scanner. Since the dust adhering to the document or paper dust generated during conveyance adheres to the transparent member and causes a reduction in copy image quality, it is opposite to the surface of the transparent member in contact with the document (paper passing surface). By forming a transparent conductive film on the surface and making the shape of the formed transparent conductive film into a specific shape, the reading has high antistatic performance, prevents adhesion of dust, and maintains its performance for a long time A transparent member is provided.

  FIG. 1 is a structural sectional view showing an example of a copying machine in which the transparent member of the present invention is used.

  In FIG. 1, a copier 100 is provided with a back frame (not shown) and left and right frames 101 </ b> A and 101 </ b> B, which form a skeleton of the copier 100. The frames 101A and 101B include an automatic document conveying unit A, a reading unit B for reading an image of a document conveyed by the automatic document conveying unit A, an image control unit C for processing the read document image, and a photosensitive member. An image forming means E including an electrostatic latent image forming unit comprising a body 110, an exposure device D and a charging electrode 114, a developing device 116, a cleaning device 121 and the like, and a paper feeding means F for storing recording paper P are provided. ing.

  The automatic document conveying means A has a document placing table 126 and a document conveying processing unit 28 including a roller group including a roller R1 and a switching means for switching a document moving path (no reference symbol).

  The reading unit B is provided with the transparent member G1 and the platen glass G2 according to the present invention, and below the two mirror units 130 and 131, the imaging lens 133, which can reciprocate so as to keep the optical path length constant. It is composed of a linear CCD 135.

  When reading the original placed on the platen glass G2, the fixed original can be scanned and read by the relative movement of the exposure means L and the mirror units 30 and 31.

  On the other hand, the original placed on the document placing table 26 of the automatic document conveying means A is conveyed by the original conveying processing section 128 and is exposed between the roller R1 and the transparent member G1 while being exposed. Exposure is performed by L, and the reflected light from the original enters the fixed CCD 135 through the fixed mirror units 130 and 131 and the imaging lens 133. After the first sheet is read, the document is sequentially conveyed and read.

  Image information read by the reading unit B is processed by the image control unit C, encoded, and stored in a memory provided on the image control unit C.

  The semiconductor laser in the image writing means D is driven according to the image data, and scanning exposure is performed on the photosensitive member 110 by the rotation of the rotary polygon mirror.

  In image formation, the photoconductor 110 rotating in the direction of the arrow (counterclockwise) is given a predetermined surface potential by the corona discharge action of the charging electrode 114, is exposed by the image writing means D, and is electrostatically applied on the photoconductor 110. A latent image is formed. The electrostatic latent image on the photoconductor 110 is reversely developed by the developing device 116 to form a toner image.

  The recording paper P is conveyed by a registration roller R10 that rotates in synchronization with toner image formation on the photoconductor 110.

  In the transfer region, the toner image on the photoconductor 110 is electrostatically transferred onto the recording paper P by the transfer electrode, and then the recording paper P is discharged by the separation electrode and separated from the photoconductor 110.

  The fixing unit H includes a heating roller, a pressure roller, and a cleaning unit Z. By pressing and heating the fixing unit, the toner image is melted and fixed on the recording paper P, and the recording paper P passes through a discharge roller. The paper is discharged onto the paper discharge tray T.

  FIG. 2 is an enlarged cross-sectional view of the vicinity of the transparent member G1 according to the present invention. The roller R1 conveys the original while being pressed against the transparent member G1, is exposed by the exposure means L, and the reflected light passes through the mirror unit 130.131 and enters the CCD through an imaging lens (not shown).

  The transparent member of the present invention is required to be applied to at least the transparent member of a transported document reading unit in a copying machine or a scanner, and the sheet passing surface (the surface that contacts the document) is repeatedly subjected to contact friction with the document. Frictional charging is likely to occur, and by forming the transparent conductive film of the present invention on the light source side of the transparent member (the surface opposite to the paper passing surface), charging of the paper passing surface is effectively prevented, and paper dust and dust are adhered. It has been found that the antistatic performance can be maintained over a long period of time.

  Further, in the transparent member of the present invention, by forming a low friction antifouling layer on the paper passing surface, reducing frictional resistance, preventing the occurrence of dirt such as paper dust, and low adhesion, It has been found that adhesion of adhesives and the like can be prevented, dirt can be reduced, and this performance can be maintained for a long time.

  The transparent member of the present invention is also preferably applied to the platen glass G2.

  FIG. 3 is a diagram showing a main configuration of the transparent member of the present invention. Fig.3 (a) is a top view of the transparent member 1a, FIG.3 (b) is a sectional side view of the transparent member 1a. The transparent member 1a has a transparent conductive film 1c formed on one surface of a glass substrate 1b, and the transparent conductive film 1c is divided into a central region Sa having high conductivity and a peripheral region Sb having relatively low conductivity. .

  Moreover, FIG.3 (c) shows the transparent member 1a by which the transparent conductive film 1c was formed in the one surface of the glass base material 1b, and the low friction antifouling layer 1d was formed in both surfaces. The most preferable embodiment of the transparent member of the present invention is a mode in which the surface having the transparent conductive film of the transparent member 1a shown in FIG. .

<Transparent material>
Examples of the transparent member in the present invention include an inorganic transparent substrate such as a glass substrate and an organic transparent substrate such as a plastic substrate. Examples of the glass substrate include alkali-containing glass substrates such as soda lime silicate glass substrates and alkali-free glass substrates such as borosilicate glass substrates.

  In addition, as the resin substrate, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate phthalate, cellulose nitrate, etc. Cellulose esters or their derivatives, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide, polyether sulfone, polysulfones, polyether ketone imide , Polyamide, fluorine resin, nylon, polymethyl methacrylate It can be mentioned organic-inorganic hybrid resins such as acrylic or polyarylates, or these resins and silica.

  A transparent conductive film is formed as an antistatic layer on the substrate by the method described below, but it is a requirement that there be a region having a different surface resistance in the substrate surface.

  The regions having different surface resistances are preferably composed of two or more different regions, and are divided into a region that does not contact the side and a region that contacts the side on the projection plane.

  In FIG. 3A, the following forms are preferable for a region not in contact with the side (Sa: inner side) and a region in contact with the side (Sb: outer periphery).

  Sa is preferably 40% or more, more preferably 70% or more, and at most 90% or less in the total projected area.

  Sb is preferably 60% or less, more preferably 30% or less, and at least 10% or more in the total projected area.

  The resistance value of Sa is preferably 10 MΩ or less, more preferably 3 MΩ or less, and further preferably 1 MΩ or less.

  The resistance value of Sb is preferably higher than Sa, preferably 3 MΩ or more, and the ratio of Sa to Sb (Sb / Sa) is preferably 2 or more.

  Film thickness: The preferable film thickness of Sa is preferably 5 nm or more for the transparent conductive film in order for the surface resistance to be the above value, and there is no particular upper limit, but if it exceeds 30 nm, the transparency deteriorates. It is preferable to be within this range. Sb is preferably the same or thinner than Sa, and a preferred thickness is 0.3 nm or more and 5 nm or less.

  As a method for measuring the surface resistance and a method for detecting the areas of Sa and Sb, the resistance value is measured in increments of 3 mm for the area of the substrate to be measured by the two-terminal tester method. The entire region is divided into 3 mm intervals, and a region where at least three sides are 3M or more among the four sides of the 3 mm square region is defined as a region Sb.

  The inventors of the present invention have found that when regions having different resistance values are adjacent to each other, a sufficient antistatic effect can be obtained even if a transparent conductive layer is present on the surface opposite to the surface of the glass substrate that contacts the document. In particular, as a result of measuring the charge amount after repeatedly rubbing the paper surface, it was found that the charge amount is remarkably smaller when there is a region having a different resistance value in the surface than in the case where the resistance value is uniform in the surface. .

  In the transparent member of the present invention, when a glass substrate formed by a float method is used as the transparent substrate, the top surface / bottom surface is determined by a discrimination method using a UV lamp disclosed in JP-A-2004-67394. It is preferable that a transparent conductive film is formed on the bottom surface.

  In order to reduce the surface resistance of the transparent member, it is necessary to increase the film thickness of the transparent conductive film, but if it is too thick, the light transmittance decreases, so it is necessary to select the optimum range, In the present invention, the light transmittance is preferably 85% or more.

<Low friction antifouling film>
The transparent member formed with the transparent conductive film of the present invention has been found to exhibit a sufficient antistatic effect even when the surface on which the transparent conductive film is formed is used as the light source side. It is preferable that a low-friction antifouling film is formed.

  The low friction antifouling film used in the present invention is preferably a glass surface treated with a fluorine-based silicon coupling agent.

  The transparent member of the present invention has a surface on which a low friction antifouling film is formed as a surface in contact with a document (paper passing surface), and a surface on which a transparent conductive film is formed as a light source side. By using an arrangement that does not directly contact the original, when used as an image reading transparent member for reading a conveyed original, it can be stable for a long period of time and can maintain excellent dirt and dust adhesion prevention effects.

<Transparent conductive film>
In the transparent member of the present invention, a transparent conductive film is formed as an antistatic film on at least one of the surface of the substrate, and as the transparent conductive film, In ₂ O ₃ , Sn-doped indium oxide (ITO), ZnO, In ₂ O ₃ —ZnO amorphous oxide (IZO), ZnO (AZO) doped with Al, ZnO (GZO) doped with Ga, SnO ₂ , SnO ₂ (FTO) doped with elemental F and TiO ₂ It is preferable that at least one of the transparent conductive film-forming materials selected from ITO and AZO films have an amorphous structure or a crystalline structure. On the other hand, the IZO film has an amorphous structure.

  Examples of the method for producing a transparent conductive film according to the present invention include a sputtering method, a coating method, an ion assist method, a plasma CVD method, a plasma CVD method under atmospheric pressure or a pressure near atmospheric pressure, which will be described later, and the like. As a method for forming a transparent conductive film according to the present invention, it is preferable to use a plasma CVD method under atmospheric pressure or a pressure near atmospheric pressure, which will be described later.

  As the reactive gas used for forming the metal oxide layer that is the main component of the transparent conductive film by plasma CVD or the like, an organometallic compound having an oxygen atom in the molecule is preferable. For example, indium hexafluoropentanedionate, indiummethyl (trimethyl) acetylacetate, indium acetylacetonate, indium isoporopoxide, indium trifluoropentanedionate, tris (2,2,6,6-tetramethyl-3, 5-heptanedionate) indium, di-n-butylbis (2,4-pentanedionate) tin, di-n-butyldiacetoxytin, di-t-butyldiacetoxytin, tetraisopropoxytin, tetrabutoxytin And zinc acetylacetonate. Of these, indium acetylacetonate, tris (2,2,6,6-tetramethyl-3,5-heptanedionate) indium, zinc acetylacetonate, and di-n-butyldiacetoxytin are particularly preferable. is there.

  Examples of the reactive gas used for doping include aluminum isopropoxide, nickel acetylacetonate, manganese acetylacetonate, boron isopropoxide, n-butoxyantimony, tri-n-butylantimony, di-n-butylbis ( 2,4-pentanedionate) tin, di-n-butyldiacetoxytin, di-t-butyldiacetoxytin, tetraisopropoxytin, tetrabutoxytin, tetrabutyltin, zinc acetylacetonate, propylene hexafluoride, A cyclobutane octafluoride, methane tetrafluoride, etc. can be mentioned.

  Examples of the reactive gas used for adjusting the resistance value of the transparent conductive film include titanium triisopropoxide, tetramethoxysilane, tetraethoxysilane, and hexamethyldisiloxane.

  Below, the atmospheric pressure plasma CVD method which can be used suitably as a manufacturing method of the transparent conductive film of this invention is demonstrated in detail.

  The plasma CVD method is also called a plasma-assisted chemical vapor deposition method or PECVD method, and various inorganic substances can be applied in a three-dimensional form with good coverage and adhesion, and without increasing the substrate temperature too much. This is a technique capable of forming a film.

  In ordinary CVD (chemical vapor deposition), volatile and sublimated organometallic compounds adhere to the surface of a high-temperature substrate, causing a decomposition reaction due to heat, producing a thermally stable inorganic thin film. That's it. Such a normal CVD method (also referred to as a thermal CVD method) normally requires a substrate temperature of 500 ° C. or higher, and thus cannot be used for film formation on a plastic substrate.

  On the other hand, in the plasma CVD method, an electric field is applied to the space in the vicinity of the substrate to generate a space (plasma space) where a gas in a plasma state exists, and a volatilized / sublimated organometallic compound is introduced into the plasma space. The inorganic thin film is formed by spraying on the base material after the decomposition reaction occurs. In the plasma space, a high percentage of gas is ionized into ions and electrons, and although the temperature of the gas is kept low, the electron temperature is very high, so this high temperature electron or low temperature Is in contact with an excited state gas such as ions and radicals, so that the organometallic compound as the raw material of the inorganic film can be decomposed even at a low temperature. Therefore, it is a film forming method that can lower the temperature of a substrate on which an inorganic material is formed and can sufficiently form a film on a plastic substrate.

  However, in the plasma CVD method, it is necessary to ionize the gas by applying an electric field to the gas, and since the film is usually formed in a reduced pressure space of about 0.101 kPa to 10.1 kPa, a large area is required. When forming the film, the equipment is large and the operation is complicated, and this method has a problem of productivity.

  On the other hand, the plasma CVD method near atmospheric pressure does not need to be reduced in pressure and has higher productivity than the plasma CVD method under vacuum, and has a high film density because the plasma density is high. Faster, and even under high pressure conditions under atmospheric pressure, compared to the normal conditions of CVD, the mean free path of gas is very short, so that a very flat film is obtained. The optical properties are good. From the above, in the present invention, it is more preferable to apply the atmospheric pressure plasma CVD method than the plasma CVD method under vacuum.

  As one method for forming a transparent conductive film according to the present invention, the transparent conductive film contains a transparent conductive film-forming gas in a first discharge space in which a high-frequency electric field is generated under atmospheric pressure or a pressure in the vicinity thereof. A first step of forming a transparent conductive film (reduced body) on the base material is performed by supplying and exciting the gas 1 and exposing the base material to the excited gas 1. A second step of supplying the excited gas 2 containing an oxidizing gas to the generated discharge space and exciting it to expose the transparent conductive film (reduced body) formed in the first step to the excited gas 2 A transparent conductive film (oxidized body) is formed by performing the above.

  In the present invention, the excited gas means that at least part of the molecules in the gas move from the existing state to a higher state by obtaining energy, and the excited gas molecules and radicalized gas molecules. A gas containing ionized gas molecules corresponds to this.

  That is, the space between the counter electrodes (discharge space) is at or near atmospheric pressure, a metal oxide forming gas including a discharge gas, a reducing gas and a metal oxide gas is introduced between the counter electrodes, and the high frequency voltage is opposed. A metal oxide forming gas is applied between the electrodes to form a plasma state, and then the substrate is exposed to the metal oxide forming gas in a plasma state to form a thin film on the transparent substrate. A transparent conductive film is formed by exposing the thin film formed above to a gas in which a discharge gas and an oxidizing gas are excited to a plasma state.

  Next, the gas for forming the transparent conductive film according to the present invention will be described. The gas used is basically a gas containing a discharge gas and a transparent conductive film forming gas as constituent components.

  The discharge gas becomes a excited state or a plasma state in the discharge space and performs a role of applying energy to the transparent conductive film forming gas to bring it into an excited or plasma state, and is a rare gas or a nitrogen gas. Examples of the rare gas include Group 18 elements in the periodic table, specifically, helium, neon, argon, krypton, xenon, radon, and the like. The discharge gas is preferably contained in an amount of 90.0 to 99.9% by volume with respect to 100% by volume of the total gas.

  In the formation of the transparent conductive film according to the present invention, the transparent conductive film-forming gas is a gas that receives energy from the discharge gas in the discharge space and enters an excited state or a plasma state to form a transparent conductive thin film, or controls the reaction. It is also a gas that promotes the reaction. The transparent conductive film forming gas is preferably contained in an amount of 0.01 to 10% by volume, more preferably 0.1 to 3% by volume in the total gas.

  In the present invention, in forming the transparent conductive film, the transparent conductive thin film is more uniformly and densely formed by containing a reducing gas selected from hydrogen, hydrocarbons such as methane, and water in the transparent conductive film forming gas. It is possible to improve electrical conductivity, adhesion, and crack resistance. The reducing gas is preferably 0.0001 to 10% by volume, more preferably 0.001 to 5% by volume with respect to 100% by volume of the total gas.

  In addition, the transparent conductive film according to the present invention is formed by exposing a discharge gas and an oxidizing gas to a gas excited to a plasma state. The oxidizing gas used in the present invention is oxygen, ozone, peroxidation. Examples thereof include hydrogen and carbon dioxide. Examples of the discharge gas at this time include a gas selected from nitrogen, helium, and argon. The concentration of the oxidizing gas component in the mixed gas composed of the oxidizing gas and the discharge gas is preferably 0.0001 to 30% by volume, more preferably 0.001 to 15% by volume, particularly 0.01 to 10% by volume. It is preferable to make it. The optimum value of the concentration of each of the oxidizing gas species and the discharge gas selected from nitrogen, helium, and argon can be appropriately selected depending on the substrate temperature, the number of oxidation treatments, and the treatment time. As the oxidizing gas, oxygen and carbon dioxide are preferable, and a mixed gas of oxygen and argon is more preferable.

  The present invention supplies the gas 1 containing a thin film forming gas to the discharge space at or near atmospheric pressure, and excites the gas 1 by applying a high frequency electric field to the discharge space, thereby exciting the substrate. In the thin film manufacturing method in which at least step 1 of forming a thin film on a substrate by exposure to gas 1 is performed, after step 1, gas 2 containing an oxidizing gas in the discharge space under atmospheric pressure or a pressure in the vicinity thereof. Even if the production rate is increased by the two-step method in which the gas 2 is excited by supplying and applying a high frequency electric field to the discharge space, and the substrate 2 having a thin film is exposed to the excited gas 2 This is a preferable method in the present invention.

  In the two-step method preferably used in the present invention, in step 1 of the method for producing a transparent conductive film, the gas 1 supplied between the counter electrodes (discharge space) receives at least a discharge gas excited by an electric field and its energy. A thin film forming gas for forming a thin film in a plasma state or an excited state.

  In the present invention, following step 1, the gas 2 containing an oxidizing gas is supplied to the discharge space under atmospheric pressure or a pressure in the vicinity thereof, and the high-frequency electric field is applied to the discharge space to Step 2 of exciting and exposing the substrate having the thin film to the excited gas 2 is performed.

  The gas 2 preferably contains a discharge gas, and preferably contains 50% by volume or more of nitrogen as the discharge gas from the viewpoint of cost.

  It is preferable to perform the process by alternately repeating the process 1 and the process 2, and even if the substrate is reciprocated between the process 1 and the process 2, the process 1 and the process 2 are installed alternately and continuously. It is also possible that the substrate passes through them and is continuously processed.

  Hereinafter, the present invention will be described in more detail.

  First, step 1 will be described.

  The high-frequency electric field in step 1 is preferably a superposition of the first high-frequency electric field and the second high-frequency electric field, and the discharge space is constituted by the first and second electrodes facing each other, and the first high-frequency electric field is formed. A method of applying an electric field to the first electrode and applying the second high-frequency electric field to the second electrode is preferable.

The frequency ω2 of the second high-frequency electric field is higher than the frequency ω1 of the first high-frequency electric field, the strength V1 of the first high-frequency electric field, the strength V2 of the second high-frequency electric field, and the strength of the discharge start electric field. It is preferable that the relationship with IV1 satisfies V1 ≧ IV1> V2 or V1> IV1 ≧ V2, and the output density of the second high-frequency electric field is 1 W / cm ² or more.

  When the superimposed high-frequency electric field is both a sine wave, the frequency ω1 of the first high-frequency electric field and the frequency ω2 of the second high-frequency electric field higher than the frequency ω1 are superimposed, and the waveform has the frequency ω1. The sine wave has a sawtooth waveform in which a sine wave having a higher frequency ω2 is overlapped.

  In the present invention, the strength of the discharge starting electric field refers to the strength of the lowest electric field at which discharge can be started in the discharge space (electrode configuration, etc.) and reaction conditions (gas conditions, etc.) used in the actual thin film formation method. Refers to that. The strength of the discharge start electric field varies somewhat depending on the gas type supplied to the discharge space, the dielectric type of the electrode, or the distance between the electrodes, but in the same discharge space, it is governed by the strength of the discharge start electric field of the discharge gas. Is done.

  By applying a high frequency electric field to the discharge space, it is presumed that a discharge capable of forming a thin film is caused and high density plasma necessary for forming the thin film can be generated.

  Although the superposition of the continuous wave of the sine wave has been described above, the present invention is not limited to this, and both pulse waves may be used, one may be a continuous wave and the other may be a pulse wave. Further, it may have a third electric field.

  Here, the strength of the high-frequency electric field (applied electric field strength) and the strength of the discharge starting electric field referred to in the present invention are those measured by the following method.

Measuring method of strength V1 and V2 (unit: kV / mm) of high frequency electric field:
A high-frequency voltage probe (P6015A) is installed in each electrode portion, and an output signal of the high-frequency voltage probe is connected to an oscilloscope (Tektronix, TDS3012B), and the electric field strength is measured.

Measuring method of intensity IV (unit: kV / mm) of electric field for starting discharge:
A discharge gas is supplied between the electrodes to increase the strength of the electric field between the electrodes, and the strength of the electric field at which discharge starts is defined as the strength IV of the discharge start electric field. The measuring instrument is the same as the measurement of the strength of the high-frequency electric field.

  By adopting such a discharge condition, even a discharge gas having a high discharge start electric field strength, such as nitrogen gas, can start discharge, maintain a high density and stable plasma state, and form a thin film at high speed. It can be done.

  When the discharge gas is nitrogen gas according to the above measurement, the intensity IV (1/2 Vp-p) of the discharge start electric field is about 3.7 kV / mm. Therefore, in the above relationship, the first high frequency electric field is Is applied as V1 ≧ 3.7 kV / mm, whereby the nitrogen gas can be excited to be in a plasma state.

  Here, the frequency of the first power supply is preferably 200 kHz or less. The electric field waveform may be a continuous wave or a pulse wave. The lower limit is preferably about 1 kHz.

  On the other hand, the frequency of the second power source is preferably 800 kHz or more. The higher the frequency of the second power source, the higher the plasma density, and a dense and high-quality thin film can be obtained. The upper limit is preferably about 200 MHz.

  The application of a high frequency electric field from such two power sources is necessary for initiating discharge of a discharge gas having a high discharge start electric field strength by the first high frequency electric field, It is an important point of the present invention to form a dense and high-quality thin film by increasing the plasma density by high frequency and high power density.

  Also, by increasing the output density of the first high-frequency electric field, the output density of the second high-frequency electric field can be improved while maintaining the uniformity of discharge. Thereby, a further uniform high-density plasma can be generated, and a further improvement in film formation speed and an improvement in film quality can be achieved.

  As described above, a gas 1 containing a thin film forming gas introduced between the counter electrodes is discharged into a plasma state, and the substrate which is left stationary between the counter electrodes or transferred between the electrodes A thin film is first formed on the substrate by exposure to the excited gas 1.

  Next, step 2 will be described.

  In the present invention, following the step 1 of forming a thin film on a substrate, a step 2 of exciting the gas 2 containing an oxidizing gas by atmospheric pressure plasma and exposing the thin film to the excited gas 2 is performed. It is necessary to do. Thereby, a high-performance thin film can be formed even if the production rate is increased.

  The high-frequency electric field in step 2 is also preferably a superposition of the third high-frequency electric field and the fourth high-frequency electric field, and the discharge space is constituted by the third and fourth electrodes facing each other, and the third high-frequency electric field is formed. A method of applying an electric field to the third electrode and applying the fourth high-frequency electric field to the fourth electrode is preferable. Thereby, a dense and high-quality thin film can be obtained.

The frequency ω4 of the fourth high-frequency electric field is higher than the frequency ω3 of the third high-frequency electric field, the third high-frequency electric field strength V3, the fourth high-frequency electric field strength V4, and the discharge start electric field strength. The relationship with IV2 satisfies V3 ≧ IV2> V4 or V3> IV2 ≧ V4, and the output density of the second high-frequency electric field is preferably 1 W / cm ² or more from the viewpoint of obtaining a high-quality thin film.

  The third power supply for supplying the third high-frequency electric field and the fourth high-frequency electric field, the fourth power supply and the third electrode, the fourth electrode, and other application methods are the same as the first high-frequency electric field and the second high-frequency electric field in step 1 above. A method similar to that used in the electric field can be applied.

<Gap between electrodes>
The distance between the first electrode, the second electrode, and the third electrode and the fourth electrode facing each other is such that when a dielectric is provided on one of the electrodes, the conductive metal matrix of the dielectric surface and the other electrode is provided. It means the shortest distance from the surface of the material, and when a dielectric is provided for both electrodes, it means the shortest distance between the dielectric surfaces. The distance between the electrodes is determined in consideration of the thickness of the dielectric provided on the conductive metallic base material, the strength of the applied electric field, the purpose of using the plasma, etc. From the viewpoint of performing, 0.1 to 5 mm is preferable, and 0.5 to 2 mm is particularly preferable.

<container>
In order to avoid the influence of outside air, it is preferable that the whole atmospheric pressure plasma processing apparatus used in the present invention is stored in one container, or the process 1 and the process 2 are stored in separate containers. As the container, a processing container made of Pyrex (registered trademark) glass or the like is preferably used, but it is also possible to use a metal as long as insulation from the electrode can be obtained. For example, polyimide resin or the like may be attached to the inner surface of an aluminum or stainless steel frame, and the metal frame may be thermally sprayed to obtain insulation.

<Power supply>
As the first power source (high frequency power source) and the third power source (high frequency power source) installed in the atmospheric pressure plasma processing apparatus used in the present invention,
Manufacturer Frequency Product name Shinko Electric 3kHz SPG3-4500
Shinko Electric 5kHz SPG5-4500
Kasuga Electric 15kHz AGI-023
Shinko Electric 50kHz SPG50-4500
HEIDEN Laboratory 100kHz * PHF-6k
Pearl industry 200kHz CF-2000-200k
Pearl Industry 400kHz CF-2000-400k
And the like, and any of them can be used.

As the second power source (high frequency power source) and the fourth power source (high frequency power source),
Manufacturer Frequency Product name Pearl Industry 800kHz CF-2000-800k
Pearl industry 2MHz CF-2000-2M
Pearl Industry 13.56MHz CF-5000-13M
Pearl industry 27MHz CF-2000-27M
Noda Rf Technology 27MHz NR7N27M-01
Pearl Industry 150MHz CF-2000-150M
And the like, and any of them can be preferably used.

  Of the above power supplies, * indicates a HEIDEN Laboratory impulse high-frequency power supply (100 kHz in continuous mode). Other than that, it is a high-frequency power source that can apply only a continuous sine wave.

<Power>
In the present invention, the electric field applied between opposing electrodes, the power density of the second electrode (the second high-frequency electric field) and a fourth electrode (fourth high frequency electric field) is applied to 1W / cm ² or more, the plasma And energy is given to gas 1 or gas 2. The upper limit value of the power supplied to the second electrode is preferably 20 W / cm ² , more preferably 10 W / cm ² . The lower limit is preferably 1.2 W / cm ² . The discharge area (cm ² ) refers to an area in a range where discharge occurs in the electrode.

Further, by applying an electric field having an output density of 1 W / cm ² or more to the first electrode (first high-frequency electric field) and the third electrode (third high-frequency electric field), the uniformity of the second high-frequency electric field is achieved. The output density can be improved while maintaining the above. Thereby, a further uniform high-density plasma can be generated, and a further improvement in film forming speed and an improvement in film quality can be achieved. Preferably it is 5 W / cm ² or more. The upper limit value of the power density applied to the first electrode and the third electrode is preferably 50 W / cm ² .

<Current value>
At this time, the relationship between the current I1 of the first high-frequency electric field and the current I2 of the second high-frequency electric field is preferably I1 <I2. I1 is preferably ^{0.3mA / cm 2 ~20mA / cm 2} , more preferably at ^{1.0mA / cm 2 ~20mA / cm 2} , I2 is preferably ^{10mA / cm 2 ~1000mA / cm 2} , more preferably is ^{20mA / cm 2 ~500mA / cm 2} .

The relationship between the current I3 of the third high-frequency electric field and the current I4 of the fourth high-frequency electric field is preferably I3 <I4. I3 is preferably ^{0.3mA / cm 2 ~20mA / cm 2} , further preferably a ^{1.0mA / cm 2 ~20mA / cm 2} . The current I4 of the fourth high frequency electric field is preferably ^{10mA / cm 2 ~1000mA / cm 2} , more preferably ^{20mA / cm 2 ~500mA / cm 2} .

<Waveform>
Here, the waveform of the high-frequency electric field is not particularly limited. There are a continuous sine wave continuous oscillation mode called a continuous mode, an intermittent oscillation mode called ON / OFF intermittently called a pulse mode, and either of them may be adopted, but at least the second electrode side (second The high-frequency electric field is preferably a continuous sine wave because a denser and better quality film can be obtained.

<electrode>
An electrode used in such a method for forming a thin film by atmospheric pressure plasma must be able to withstand severe conditions in terms of structure and performance. Such an electrode is preferably a metal base material coated with a dielectric.

In the dielectric-coated electrode used in the present invention, it is preferable that the characteristics match between various metallic base materials and dielectrics. One of the characteristics is linear thermal expansion between the metallic base material and the dielectric. The combination is such that the difference in coefficient is 10 × 10 ⁻⁶ / ° C. or less. It is preferably 8 × 10 ⁻⁶ / ° C. or less, more preferably 5 × 10 ⁻⁶ / ° C. or less, and further preferably 2 × 10 ⁻⁶ / ° C. or less. The linear thermal expansion coefficient is a well-known physical property value of a material.

As a combination of a conductive metallic base material and a dielectric whose difference in linear thermal expansion coefficient is within this range,
1: Metal base material is pure titanium or titanium alloy, dielectric is ceramic spray coating 2: Metal base material is pure titanium or titanium alloy, dielectric is glass lining 3: Metal base material is stainless steel, Dielectric is ceramic spray coating 4: Metal base material is stainless steel, Dielectric is glass lining 5: Metal base material is a composite material of ceramics and iron, Dielectric is ceramic spray coating 6: Metal base material Ceramic and iron composite material, dielectric is glass lining 7: Metal base material is ceramic and aluminum composite material, dielectric is ceramic sprayed coating 8: Metal base material is ceramic and aluminum composite material, dielectric The body has glass lining. From the viewpoint of the difference in linear thermal expansion coefficient, the above 1 or 2 and 5 to 8 are preferable, and 1 is particularly preferable.

  In the present invention, titanium or a titanium alloy is particularly useful as the metallic base material from the above characteristics. By using titanium or titanium alloy as the metal base material and using the dielectric as above, there is no deterioration of the electrode in use, especially cracking, peeling, dropping off, etc., and long-term use under harsh conditions Can withstand.

  The metallic base material of the electrode useful in the present invention is a titanium alloy or titanium metal containing 70% by mass or more of titanium. In the present invention, if the titanium content in the titanium alloy or titanium metal is 70% by mass or more, it can be used without any problem, but preferably contains 80% by mass or more of titanium. As the titanium alloy or titanium metal useful in the present invention, those generally used as industrial pure titanium, corrosion resistant titanium, high strength titanium and the like can be used. Examples of pure titanium for industrial use include TIA, TIB, TIC, TID, etc., all of which contain very little iron atom, carbon atom, nitrogen atom, oxygen atom, hydrogen atom, etc. As content, it has 99 mass% or more. As the corrosion-resistant titanium alloy, T15PB can be preferably used, and it contains lead in addition to the above-mentioned atoms, and the titanium content is 98% by mass or more. Further, as the titanium alloy, T64, T325, T525, TA3, etc. containing aluminum and vanadium or tin in addition to the above atoms except lead can be preferably used. As a quantity, it contains 85 mass% or more. These titanium alloys or titanium metals have a thermal expansion coefficient that is about 1/2 smaller than that of stainless steel, such as AISI 316, and are combined with a dielectric described later applied on the titanium alloy or titanium metal as a metallic base material. It can withstand the use at high temperature for a long time.

  On the other hand, as a required characteristic of the dielectric, specifically, an inorganic compound having a relative dielectric constant of 6 to 45 is preferable, and examples of such a dielectric include ceramics such as alumina and silicon nitride, Alternatively, there are glass lining materials such as silicate glass and borate glass. In this, what sprayed the ceramics mentioned later and the thing provided by glass lining are preferable. In particular, a dielectric provided by spraying alumina is preferable.

  Alternatively, as one of the specifications that can withstand high power as described above, the porosity of the dielectric is 10% by volume or less, preferably 8% by volume or less, preferably more than 0% by volume and 5% by volume or less. It is. The porosity of the dielectric can be measured by a BET adsorption method or a mercury porosimeter. In the examples described later, the porosity is measured using a dielectric fragment covered with a metallic base material by a mercury porosimeter manufactured by Shimadzu Corporation. High durability is achieved because the dielectric has a low porosity. Examples of the dielectric having such a void and a low void ratio include a high-density, high-adhesion ceramic spray coating by an atmospheric plasma spraying method described later. In order to further reduce the porosity, it is preferable to perform sealing treatment.

  The above-mentioned atmospheric plasma spraying method is a technique in which fine powder such as ceramics, wire, or the like is put into a plasma heat source and sprayed onto a metallic base material to be coated as fine particles in a molten or semi-molten state to form a film. A plasma heat source is a high-temperature plasma gas in which a molecular gas is heated to a high temperature, dissociated into atoms, and further given energy to release electrons. The plasma gas injection speed is high, and since the sprayed material collides with the metallic base material at a higher speed than conventional arc spraying or flame spraying, high adhesion strength and high density coating can be obtained. Specifically, reference can be made to a thermal spraying method for forming a heat shielding film on a high-temperature exposed member described in JP-A No. 2000-301655. By this method, the porosity of the dielectric (ceramic sprayed film) to be coated can be obtained.

  Another preferable specification that can withstand high power is that the dielectric thickness is 0.5 to 2 mm. The film thickness variation is desirably 5% or less, preferably 3% or less, and more preferably 1% or less.

In order to further reduce the porosity of the dielectric, it is preferable to further perform a sealing treatment with an inorganic compound on the sprayed film such as ceramics as described above. As the inorganic compound, a metal oxide is preferable, and among these, a compound containing silicon oxide (SiO _x ) as a main component is particularly preferable.

  The inorganic compound for sealing treatment is preferably formed by curing by a sol-gel reaction. In the case where the inorganic compound for sealing treatment contains a metal oxide as a main component, a metal alkoxide or the like is applied as a sealing liquid on the ceramic sprayed film and cured by a sol-gel reaction. When the inorganic compound is mainly composed of silica, it is preferable to use alkoxysilane as the sealing liquid.

  Here, it is preferable to use energy treatment for promoting the sol-gel reaction. Examples of the energy treatment include thermal curing (preferably 200 ° C. or less) and ultraviolet irradiation. Furthermore, as a method of sealing treatment, when the sealing liquid is diluted and coating and curing are sequentially repeated several times, mineralization is further improved and a dense electrode without deterioration can be obtained.

In the case of performing a sealing treatment that cures by a sol-gel reaction after coating a ceramic sprayed film using the metal alkoxide or the like of the dielectric-coated electrode according to the present invention as a sealing liquid, the content of the metal oxide after curing is 60 It is preferably at least mol%. When alkoxysilane is used as the metal alkoxide of the sealing liquid, the content of SiO _x (x is 2 or less) after curing is preferably 60 mol% or more. The cured SiO _x content is measured by analyzing a tomographic layer of the dielectric layer by XPS (X-ray photoelectron spectroscopy).

  In the electrode used for forming the transparent conductive film of the present invention, the maximum height (Rmax) of the surface roughness defined by JIS B 0601 on the side in contact with at least the base material of the electrode is adjusted to be 10 μm or less. However, from the viewpoint of obtaining the effects described in the present invention, the maximum value of the surface roughness is more preferably 8 μm or less, and particularly preferably adjusted to 7 μm or less. In this way, the dielectric surface of the dielectric-coated electrode can be polished and the dielectric thickness and the gap between the electrodes can be kept constant, the discharge state can be stabilized, the heat shrinkage difference and Distortion and cracking due to residual stress can be eliminated, and durability can be greatly improved with high accuracy. The polishing finish of the dielectric surface is preferably performed at least on the dielectric in contact with the substrate. Furthermore, the centerline average surface roughness (Ra) defined by JIS B 0601 is preferably 0.5 μm or less, more preferably 0.1 μm or less.

  In the dielectric-coated electrode used in the present invention, another preferred specification that can withstand high power is that the heat-resistant temperature is 100 ° C. or higher. More preferably, it is 120 degreeC or more, Most preferably, it is 150 degreeC or more. The upper limit is 500 ° C. The heat-resistant temperature refers to the highest temperature that can withstand normal discharge without causing dielectric breakdown at the voltage used in the atmospheric pressure plasma treatment. Such heat-resistant temperature can be applied within the range of the difference between the linear thermal expansion coefficient of the metallic base material and the dielectric material by applying the dielectric material provided by the above-mentioned ceramic spraying or layered glass lining with different bubble mixing amounts. This can be achieved by appropriately combining means for appropriately selecting the materials.

  Hereinafter, an apparatus for forming a transparent conductive film using a plasma CVD method at or near atmospheric pressure will be described in detail.

  In the present invention, it is preferable that the plasma discharge treatment is performed at atmospheric pressure or a pressure in the vicinity thereof. Here, the atmospheric pressure vicinity represents a pressure of 20 kPa to 110 kPa, in order to obtain a good effect described in the present invention. Is preferably 93 kPa to 104 kPa.

  FIG. 4 is a schematic configuration diagram showing an example of a two-step type atmospheric pressure plasma apparatus preferably used in the present invention. In step 1 (in the figure, a region surrounded by a one-dot chain line, the same applies hereinafter), a counter electrode (discharge space) is formed by the movable gantry electrode (first electrode) 8 and the square electrode (second electrode) 7, A high frequency electric field is applied between the electrodes, a gas 1 containing a discharge gas 11 and a thin film forming gas 12 is supplied through a gas supply pipe 15, flows out into a discharge space through a slit 5 formed in the rectangular electrode 7, and gas 1 is excited by the discharge plasma, and the surface of the substrate 4 placed on the movable gantry electrode 8 is exposed to the excited gas 1 (37 in the figure), whereby a thin film is formed on the substrate surface.

  Next, the base material 4 gradually moves together with the movable gantry electrode 8 to the step 2 (in the figure, a region surrounded by a two-dot chain line, the same applies hereinafter). In FIG. 4, the first electrode in step 1 and the third electrode in step 2 are common electrodes, and the first power source in step 1 and the third power source in step 2 are common power sources.

  In step 2, a counter electrode (discharge space) is formed by the movable gantry electrode (third electrode) 8 and the square electrode (fourth electrode) 3, and a high frequency electric field is applied between the counter electrodes, and the discharge gas 13 and the oxidation gas are oxidized. A gas 2 containing a reactive gas 14 is supplied through a gas supply pipe 16, passes through a slit 6 formed in the rectangular electrode 3, flows into a discharge space, is excited by discharge plasma, and is placed on a movable gantry electrode 8. By exposing the surface of the material 4 to the excited gas 2 (38 in the figure), the thin film on the substrate surface is oxidized. The moving gantry electrode 8 has moving means (not shown) capable of moving and stopping on the support table 9 at a constant speed.

  In order to adjust the temperature of the gas 2, it is preferable to have a temperature adjusting means 17 in the middle of the supply pipe 16.

  A thin film having a desired film thickness can be formed by reciprocating between the thin film formation in step 1 and the oxidation treatment step in step 2 a plurality of times using a movable frame.

  A first power source 31 is connected to the first electrode (moving gantry electrode) 8, a second power source 33 is connected to the second electrode 7, and a first filter 32 and a second filter are connected between these electrodes and the power source, respectively. A filter 34 is connected. The first filter 32 makes it difficult to pass a current having a frequency from the first power supply 31 and makes it easy to pass a current having a frequency from the second power supply 33, and the second filter 34 is vice versa. Filters having respective functions of making it difficult to pass a current having a frequency from the first power source 31 and making it easy to pass a current having a frequency from the first power source 31 are used.

  In step 1 of the atmospheric pressure plasma processing apparatus of FIG. 4, the first electrode 8 and the second electrode 7 are arranged between the counter electrodes, and the first electrode 8 has a frequency ω1 from the first power source 31 and an electric field strength V1. The first high-frequency electric field of current I1 is applied, and the second high-frequency electric field of frequency ω2, electric field strength V2, and current I2 from the second power source 33 is applied to the second electrode 7. ing. The first power supply 31 can apply a higher frequency electric field strength (V1> V2) than the second power supply 33, and the first frequency ω1 of the first power supply 8 is lower than the second frequency ω2 of the second power supply 33. Can be applied.

  Similarly, in step 2, the frequency ω1 from the first power source 31 and the strength of the electric field are increased from the first electrode 8 between the counter electrode composed of the third electrode 8 (common to the first electrode) and the fourth electrode 3. The first high-frequency electric field having the current V1 and the current I1 is applied, and the fourth electrode 3 is applied with the frequency ω4 from the fourth power source 35, the electric field strength V4, and the fourth high-frequency electric field having the current I4. It has become.

  The first power supply 31 can apply a higher frequency electric field strength (V1> V4) than the fourth power supply 35, and the first frequency ω1 of the first power supply 8 is lower than the second frequency ω4 of the fourth power supply 35. Can be applied.

  FIG. 4 shows a measuring instrument used to measure the strength of the high-frequency electric field (applied electric field strength) and the strength of the discharge starting electric field. Reference numerals 25 and 26 are high-frequency voltage probes, and reference numerals 27 and 28 are oscilloscopes.

  As described above, by applying two types of high-frequency voltages having different frequencies to the rectangular electrode 7 and the movable gantry electrode 8 forming the counter electrode, a good plasma discharge can be achieved even if an inexpensive gas such as nitrogen gas is used. It is possible to form a thin film having excellent performance by performing treatment in an oxidizing atmosphere immediately thereafter. This apparatus is suitable for forming a thin film of a single wafer using a flat substrate such as glass, and is particularly suitable for forming a transparent conductive film having high conductivity and easy etching.

  In the present invention, it is more preferable to use a thin film forming apparatus having shielding blades as shown in FIG. 5 when forming a transparent conductive film. FIG. 5A is a plan view of the thin film forming apparatus, and FIG. 5B is a front view. In step 1, a counter electrode is composed of a square electrode (second electrode) 41 and a movable gantry electrode (first electrode) 42 in which a slit 55 through which gas passes through the center by two electrode plates and two space members 44 is formed. Is configured. The gas 1 supplied from the supply pipe is blown into the discharge space from the outlet of the slit 55, and plasma is generated in the discharge space formed by the gap between the bottom surface of the square electrode (second electrode) 41 and the movable frame electrode (first electrode) 42. Excited by. The substrate 4 on the movable gantry electrode 42 is exposed to the excited gas 1 (37 'in the figure) to form a thin film. The movable gantry electrode 42 gradually moves while the base material 4 is placed, and moves the thin film formed on the base material 4 to the step 2. The gas 2 supplied from the oxidizing gas supply pipe is similarly excited in the discharge space, exposing the thin film formed in step 1 to the excited gas 2 (38 'in the figure). In the above apparatus, the shielding blades 48 and 49 are provided on both sides of the square electrodes 41 and 43, and in the formation of the transparent conductive film, the oxidizing atmosphere in step 2 requires a very small amount of oxygen. Oxygen in the atmosphere contains an excessive amount and is suitable for suppressing the influence of the atmosphere and supplying a controlled oxygen concentration to the substrate surface.

Example 1
A transparent member sample 1 in which a transparent conductive film was formed as an antistatic layer was formed under the following film forming conditions.

Ten sheets of chemically strengthened soda glass having a thickness of 320 mm × 40 mm × 3 mm are used as the glass substrate, and the top surface and the bottom surface are identified by the method described in JP-A-2004-67394, and the bottom surface is a strip shape. A transparent conductive film was formed in an area of 320 mm × 400 mm side by side, and the atmospheric pressure plasma apparatus shown in FIG. 4 was used to produce a transparent conductive film having a thickness of 10 nm by the following method.

[Step 1: Film-forming step]
Power supply (NR7N27M-01 made by Noda Rf Technology)
ω: 27 MHz, V: 0.28 kV, I: 8 mA, output density: 4.7 W / cm ²
Gap between electrodes: 1.0mm
(Gas 1 condition)
Tetramethyltin vaporizing Ar gas: 0.2 L / min, 15 ° C
Discharge gas: Ar, 90 L / min
Reducing gas: H ₂ , 0.8 L / min
[Process 2: Oxidation process]
Power supply (common with process 1)
ω: 27 MHz, V: 0.17 kV, I: 15 mA, output density: 13 W / cm ²
Discharge gap: 1.5mm
(Gas 2 condition)
Discharge gas: Ar, 70 L / min
Oxidizing gas: O ₂ , 0.3 L / min
[Evaluation of Sa and Sb]
The obtained glass was subjected to resistance measurement by a two-terminal method at a pitch of 3 mm, and the region Sa and the region Sb were distinguished. As shown in FIG. Was formed. Sa accounted for 50% of the total projected area, and Sb accounted for 50% of the total projected area.

  Further, Samples 2 to 8 having Sa and Sb shown in Table 1 were prepared by appropriately changing the electrode width, glass substrate holding method, discharge gas conditions, gap, raw material supply amount, and the like.

(Sample 9: Production of comparative example)
An antistatic layer was formed in an area of 320 mm × 400 mm × 3 mm thick chemically strengthened soda glass, and after the formation, it was cut into a size of 320 mm × 40 mm × 3 mm in the central region.

(Measurement of charge amount)
Method for measuring charge amount;
Using a bizhub 350 manufactured by Konica Minolta as an automatic document conveyance type copier, the surface opposite to the surface on which the transparent conductive film is formed is passed through the transparent member (see G1 in FIG. 2) of the conveyance document reading unit. Each transparent member sample 1 to 9 is mounted, and after passing 100 sheets of A4 size plain paper with a basis weight of 80 g / m ^{2 at} a paper passing speed of 200 mm / s, in an environment where the temperature is 25 ° C. and the humidity is 50%. The amount of charge on the surface of each transparent member was measured by a non-contact method using a high-precision electrostatic sensor SK manufactured by Keyence Corporation.

  Table 1 shows the measurement results for each sample.

  In addition, when the glass which does not form a transparent conductive film was used as an antistatic layer, the charge amount was 5000V.

  As can be seen from the results in Table 1, it was found that excellent antistatic performance can be obtained by setting the area of the low surface resistance region (Sa) and high region (Sb) within the scope of the present invention.

Example 2
Using the transparent members for reading prepared in Example 1, the following fluorine atom-containing films were applied to both surfaces of each glass substrate as a low friction antifouling film by a dip coating method.

  As a silane coupling agent for forming a fluorine atom-containing film, Daikin Optool DSX is diluted to 0.1% with HFE-7100 manufactured by Sumitomo 3M Co., and a glass substrate is immersed in the solution. And then dried.

<Evaluation>
The following evaluation was performed using each obtained transparent member for reading.

<Forced wear test>
Using an abrasion tester HEIDON-14DR (manufactured by HEIDON), the sheet passing surface of each reading transparent member (the surface opposite to the surface on which the transparent conductive film is formed) and the copy sheet surface with a continuous weight of 55 kg are 1 kg / cm. ^2. Repeated wear test was repeated 5000 times at 20 mm / sec.

<Measurement of contact angle>
The contact angle of the surface of each transparent reading member before and after the forced wear test was measured using a G-1 contact angle measuring instrument manufactured by ERMA.

《Real machine test》
<Dust adhesion, black streaks>
Using a bizhub 350 manufactured by Konica Minolta Co., Ltd., each transparent member sample was applied to the G1 portion of the image reading section shown in FIG.

  Commercially available A4 paper having a continuous weight of 55 kg was used as a manuscript, and 200,000 sheets were automatically continuously fed. After passing the paper, a JIS standard cellophane tape (manufactured by Nichiban Co., Ltd.) cut to a length of 20 mm with a commercial tape cutter on a commercially available A4 paper with a continuous weight of 55 kg was stretched across 14 rows and 7 rows A manuscript was prepared and passed through the evaluation device four times. The number of black streaks appearing in the image printed on the fourth sheet was evaluated as a failure. Further, after passing the paper, the top plate was opened, and the number of foreign matters deposited on the reading glass was evaluated as the number of adhered dust.

<Magic wiping test>
A magic wiping test was performed using a commercially available oily black magic ink (M500-T1) on the portion of the transparent member for reading that was pushed by the roller and passed through.

  The evaluation criteria for magic wiping are as follows.

◎: Cannot write, repels well ○: Cannot write, repels △: Can write but wipe off ×: Cannot wipe off <Image quality>
Using the above samples, the image quality was visually evaluated at the following ranks.

：: Muscle noise, no point failure ○: Muscle noise, almost no point failure △: Muscle noise, point failure or slightly present ×: Muscle noise, many point failures Table 2 shows the results of each evaluation.

  The transparent member of the present invention showed good results with very few dust deposits and black streaks compared to the comparative sample. Further, it was found that the reading transparent member in which the low friction antifouling film was formed on the paper passing surface showed a good result even in the magic wiping test and showed a further excellent effect.

1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus using a reading transparent member. It is an expanded sectional view near transparent member G1 concerning the present invention. It is a figure which shows the main structures of the transparent member of this invention. It is a schematic block diagram which shows an example of a 2 step type atmospheric pressure plasma apparatus. The thin film formation apparatus which has a shielding blade | wing is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Transparent member 1b Glass base material 1c Transparent conductive film 1d Low-friction antifouling film 3,7 Square electrode 4 Base material 8 Moving mount electrode (first electrode)
DESCRIPTION OF SYMBOLS 9 Support stand 10 Discharge gas 11 Thin film forming gas 12 Auxiliary gas 13 Discharge gas 14 Oxidizing gas 31, 33, 35 High frequency power supply 101 Image forming apparatus 122, 124 Paper feed tray 130, 131 Mirror unit 135 CCD
AA Main unit A Automatic document conveying means B Document image reading means C Image processing means D Image writing means E Image forming means F Paper feeding means G1, G2 Reading glass member H Fixing means J Conveying means

Claims (5)

A transparent member that is positioned between a light source and an original of an image reading apparatus that optically reads a conveyed original, and has a transparent conductive film formed on a surface of the transparent member that is opposite to the surface that contacts the original (sheet passing surface). And a transparent member having a region with different surface resistance in the transparent conductive film. 2. The transparent member according to claim 1, wherein the regions having different surface resistances are divided into a region (Sa) formed in a central portion of the transparent member and a region (Sb) forming the outer periphery thereof. The transparent member according to claim 1 or 2, wherein the transparent member is float glass, and a transparent conductive film is formed on a bottom surface of the float glass. The transparent member according to claim 3, wherein a surface (sheet passing surface) of the transparent member that contacts the document is a top surface of the float glass. The transparent member according to claim 3 or 4, wherein a low friction antifouling layer is formed on at least one of the top surface and the bottom surface of the float glass.