Abstract:
One object of the present invention is to provide a blade for forming ribs that is able to improve wear resistance; in order to achieve the object, the present invention provide a blade for forming ribs that forms ribs either on the surface of a substrate or via an undercoating layer on the surface of a substrate by moving a blade body in a fixed direction relative to a paste film in the state in which comb teeth formed on at least a portion of the periphery of said blade body are penetrated into said paste film formed on the surface of said substrate to plasticly deform said paste film; wherein, the surface of said comb teeth formed on said blade body that makes contact with said paste film is coated with a compound layer in which hard particles are dispersed in a metal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a blade for forming ribs and its production method for easily and accurately forming ribs (ceramic capillary ribs) in the production process of FPD (flat panel displays) such as PDP (plasma display panels) and PALC (plastic addressed liquid crystal displays).  
           [0003]    2. Description of the Related Art  
           [0004]    In the past, in a first method of forming ribs in these FDP, ribs  8  are made by positioning a rib-forming paste  2  containing glass powder on a glass substrate  1  in a prescribed pattern by a thick film printing method, coating several layers of the paste, and baking the paste after drying to form ribs  8  at prescribed intervals on substrate  1  as shown in FIG. 10. The height H of rib  8  is normally 100-300 μm, rib width W is normally about 50-100 μm, and the spread S of cell  9  between the ribs is normally about 100-300 μm.  
           [0005]    In addition, the sandblasting method is known as a second method of forming ribs. In this method, a ceramic paste containing glass powder is coated onto the entire surface of a glass substrate  1  using a thick film method, and after forming pattern forming layer  3  having a height of 150-200 μm by drying or laminating ceramic green tape containing glass powder, this pattern forming layer  3  is coated with a photosensitive film  4 , and this film  4  is further covered with a mask  5  followed by exposure and development to form resist layer  6  of a prescribed pattern as shown in FIG. 11. Next, after performing sandblasting treatment from above this resist layer  6  and removing the portion to serve as cell  9 , the above resist layer  6  is removed using a remover and so forth to obtain the desired ribs  8 .  
           [0006]    In the above first forming method of the prior art, since rib width W is comparatively narrow at about 50-100 μm and the paste runs easily after printing, the thickness of a single coating of the thick film must be held to a low value of about 10-20 μm at completion of baking. As a result, in order to make ribs having a height H of 100-300 μm with this method, it is necessary to coat the thick film by as many as 10-20 times, and since the value of H/W, representing the rib height H after coating divided by rib width W, is large at about 1.5-4, there was the disadvantage of it being difficult to accurately form the ribs even positioning is performed adequately during thick film printing.  
           [0007]    In addition, the above second forming method of the prior art requires the coating of a photosensitive film to form the resist layer as well as complicated steps such as exposure and development. In addition, there was also the disadvantage of requiring a large amount of material for the pattern forming layer since a large portion of the pattern forming layer is removed in sandblasting treatment.  
           [0008]    In order to eliminate these problems, a method was proposed in which a blade having prescribed comb teeth is penetrated into a paste film formed on a substrate surface, and the blade is moved in a fixed direction relative to the paste film to plasticly deform the paste film and form ribs on the substrate surface (Japanese Unexamined Patent Application, First Publication No. 11-283497). Ribs formed with this method become ceramic ribs as a result of subsequent drying and baking, thereby making it possible to form ceramic ribs both easily and accurately, without waste and in fewer steps as compared with the thick film printing method of the prior art.  
           [0009]    However, in the above method for forming ribs, when the blade for forming ribs is used continuously, there was the problem of the comb teeth of the blade that make contact with the paste film wearing down. Since ribs formed by a blade in which the comb teeth are worn have poor accuracy and the height of the formed ribs decreases, it was necessary to frequently replace the blade.  
         SUMMARY OF THE INVENTION  
         [0010]    The object of the present invention is to provide a blade for forming ribs that is able to improve wear resistance.  
           [0011]    Another object of the present invention is to provide a production method of a blade that lowers the frequency of blade replacement and improves the accuracy of the ribs that are formed.  
           [0012]    In order to achieve the object, the present invention provide, as shown in FIG. 2, a blade for forming ribs  13  either on the surface of a substrate  10  or via an undercoating layer on the surface of a substrate by moving a blade body  12  in a fixed direction relative to a paste film  11  in the state in which comb teeth  12   b  formed on at least a portion of the periphery of blade body  12  are penetrated into a ceramic paste film  11  formed on the surface of substrate  10  to plasticly deform paste film  11 , the surface of comb teeth  12   b  formed on blade body  12  that makes contact with paste film  11  is coated with a compound layer  12   c  in which hard particles are dispersed in a metal.  
           [0013]    According to the blade for forming ribs, since compound layer  12   c  in which hard particles are dispersed in a metal is coated onto the surface of comb teeth  12   b  that make contact with paste film  11  when ribs  13  are formed on the surface of substrate  10 , this compound layer  12   c  inhibits wear of comb teeth  12   b  caused by contact with paste film  11  and the surface of substrate  10 . Thus, the wear resistance of blade  12  can be improved.  
           [0014]    In the blade, it is preferable for the material of the comb teeth to be stainless steel.  
           [0015]    In the blade, it is also preferable for the compound layer to contain 1-50% by volume of hard particles with respect to 100% by volume of the compound layer.  
           [0016]    In the blade, it is also preferable for the thickness of the compound layer to be 0.1-20 μm.  
           [0017]    In the blade, it is also preferable for the metal of the compound layer to be selected from the group consisting of Ni, Ni—P, Ni—B, Ni—W, Ni—Co and Co.  
           [0018]    In the blade, it is also preferable for the Vickers hardness H of the hard particles of compound layer to be 1,000 or more.  
           [0019]    In the blade, it is also preferable for the hard particles of the compound layer are one type or two or more types of inorganic particles selected from diamond, amorphous diamond, silicon carbide, c-boron nitride, silicon nitride, alumina, tungsten carbide, titanium carbide, titanium nitride, tetraboron carbide, mullite, aluminum nitride and zirconia.  
           [0020]    In the blade, it is also preferable for the average particle diameter of the hard particles to be 0.1-10 μm.  
           [0021]    In the blade, it is also preferable for the compound layer to further contain an additive.  
           [0022]    In the blade, it is also preferable for the additive to be a microcrystallizing agent, stress relief agent, brightening agent, dispersion stabilizer, surface potential controller or hardness enhancer.  
           [0023]    In addition, in order to achieve the object, the present invention provides a method of producing a blade for forming ribs  13  and  23  either on the surface of a substrate  10  or via an undercoating layer  22  on the surface of substrate  10  by moving a blade body  12  in a fixed direction relative to a paste film  11  in the state in which comb teeth  12   b  formed on at least a portion of the periphery of blade body  12  are penetrated into ceramic paste film  11  formed on the surface of substrate  10  to plasticly deform paste film  11 ; comprising the step of: a step in which in which comb teeth  12   b  are formed on one edge of a plate-shaped blade body  12  made of ceramic or metal; and a step in which the surface of comb teeth  12   b  is coated with a compound layer  12   c  in which hard particles are dispersed in a metal.  
           [0024]    According to the method of producing, since the blade is coated with a compound layer on its surface, the replacement frequency of the blade can be lowered and the accuracy of the ribs that are formed can be improved.  
           [0025]    In the blade production method, it is preferable for the material of the comb teeth to be stainless steel.  
           [0026]    In the blade production method, it is also preferable for the compound layer to contain 1-50% by volume of hard particles with respect to 100% by volume of the compound layer.  
           [0027]    In the blade production method, it is also preferable for the thickness of the compound layer to be 0.1-20 μm.  
           [0028]    In the blade production method, it is also preferable for the metal of compound layer to be selected from the group consisting of Ni, Ni—P, Ni—B, Ni—W, Ni—Co and Co.  
           [0029]    In the blade production method, it is also preferable for the Vickers hardness H of the hard particles of compound layer is 1,000 or more.  
           [0030]    In the blade production method, it is also preferable for the hard particles of compound layer to be one type or two or more types of inorganic particles selected from diamond, amorphous diamond, silicon carbide, c-boron nitride, silicon nitride, alumina, tungsten carbide, titanium carbide, titanium nitride, tetraboron carbide, mullite, aluminum nitride and zirconia.  
           [0031]    In the blade production method, it is also preferable for the average particle diameter of the hard particles to be 0.1-10 μm.  
           [0032]    In the blade production method, it is also preferable for the compound layer to further contain an additive. I In the blade production method, it is also preferable for the additive to be a microcrystallizing agent, stress relief agent, brightening agent, dispersion stabilizer, surface potential controller or hardness enhancer.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]    [0033]FIG. 1 is a perspective view of the blade for forming ribs of the present invention.  
         [0034]    [0034]FIG. 2 is a perspective view showing the state in which ribs are formed using the blade of the present invention.  
         [0035]    [0035]FIG. 3 is a cross-sectional view showing ceramic ribs obtained by drying, heating and baking the ribs in the cross-section taken along line A-A of FIG. 2.  
         [0036]    [0036]FIG. 4 is a front view of that blade.  
         [0037]    [0037]FIG. 5 is a cross-sectional view taken along line B-B of FIG. 4.  
         [0038]    [0038]FIG. 6 is a perspective view corresponding to FIG. 2 showing the state in which ribs having an undercoating layer are formed.  
         [0039]    [0039]FIG. 7 is a cross-sectional view corresponding to FIG. 3 showing ceramic ribs having an insulating layer obtained by drying, heating and baking ribs having an undercoating layer in cross-section taken along line C-C of FIG. 6.  
         [0040]    [0040]FIG. 8 is a cross-sectional view of a substrate suited for use of the blade of the present invention.  
         [0041]    [0041]FIG. 9 is a drawing showing the relationship between the height h of the gaps between comb teeth and the number of treated substrates of Example 1 and Comparative Example 1.  
         [0042]    [0042]FIG. 10 is a cross-sectional view showing the sequence of steps for forming ceramic ribs of the prior art.  
         [0043]    [0043]FIG. 11 is a cross-sectional view showing the sequence of steps for forming other ceramic ribs of the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0044]    The following provides an explanation of a first embodiment for carrying out the present invention based on the drawings.  
         [0045]    In the rib forming blade for forming ribs  13  on the surface of substrate  10 , a plurality of comb teeth  12   b  are formed at equal intervals and in the same direction on one edge of plate-shaped blade body  12  made of ceramic or metal as shown in FIGS. 4 and 5.  
         [0046]    As shown in FIG. 1, the characteristic constitution of the blade for forming ribs of the present invention lies in the coating of the surface of comb teeth  12   b  formed on blade body  12  that make contact with paste film  11  with a compound layer  12   c  in which hard particles are dispersed in a metal. Stainless steel having superior corrosion resistance that is not react with the paste and is not dissolved in the paste is used for the material of comb teeth  12   b.    
         [0047]    The compound layer  12   c  that coats the surface of comb teeth  12   b  contains hard particles at a ratio of 1-50% by volume to 100% by volume of the compound layer. If the blending ratio of hard particles is less than the 1% by volume, the effect of improving wear resistance is small, and if the blending ratio exceeds 50% by volume, the fixing of hard particles to the film is inadequate, causing them to fall off during the course of wear. The blending ratio of hard particles is preferably 3-20% by volume.  
         [0048]    The thickness of the coated compound layer is 0.1-20 μm. If the thickness is less than 0.1 μm, the effect of improving wear resistance is small, and if the thickness exceeds 20 μm, cracks form in the compound layer or the compound layer comes off of the blade base material during rib formation. The thickness of the coated compound layer is preferably 1-10 μm.  
         [0049]    The metal material of compound layer  12   c  is selected from the group consisting of Ni, Ni—P, Ni—B, Ni—W, Ni—Co and Co. Among these, Ni, Ni—P and Ni—B are preferable from the viewpoint of material cost and characteristics.  
         [0050]    The hard particles of compound layer  12   c  have a Vickers hardness of 1,000 or more. Vickers hardness HV is one kind of indentation hardness, and is typically used as one of the values for expressing the hardness of an object. The measurement method consists of using a diamond quadrangular pyramid having an angle between opposing sides of 136° as an indenter, and determining the length of the diagonal line of the square indentation that results when that indenter is pressed into the sample at a fixed load. The surface area of the indentation is then determined from the length of this diagonal line, and value obtained by dividing the load by the surface area is obtained as the Vickers hardness. This Vickers hardness is expressed as a value only without units.  
         [0051]    In addition, the material of the hard particles is one type or two or more types of inorganic particles selected from diamond, amorphous diamond (DLC), silicon carbide (SiC), c-boron nitride (c-BN), silicon nitride (Si 3 N 4 ), alumina (Al 2 O 3 ), tungsten carbide (WC), titanium carbide (TiC), titanium nitride (TiN), tetraboron carbide (B 4 C), mullite, aluminum nitride (AlN) and zirconia (ZrO 2 ). Among these, silicon carbide is preferable from the viewpoint of material cost and characteristics.  
         [0052]    The average particle diameter of the hard particles is 0.1-10 μm. If the average particle diameter is less than 0.1 μm, the effect of improving wear resistance is small, and if the average particle diameter exceeds 10 μm, variations in the shape of the blade openings become large. The average particle diameter of the hard particles is preferably 1-5 μm.  
         [0053]    Blade durability and accuracy of the intervals between the ribs formed using this blade are improved by additionally containing an additive in the compound layer.  
         [0054]    Examples of additives include a microcrystallizing agent, stress relief agent, brightening agent, dispersion stabilizer, surface potential controller and hardness enhancer. More specifically, examples of microcrystallizing agents and stress relief agents include sulfur compounds such as saccharin, examples of brightening agents include butenediol, examples of hard particle dispersion stabilizers and surface potential controllers include amino compounds such as aminosilane coupling agents, and examples of hardness enhancers include phosphoric acid compounds such as hypophosphorous acid.  
         [0055]    Examples of methods for coating the surface of comb teeth  12   b  with the compound layer include electrolytic plating and non-electrolytic plating. Annealing treatment may also be performed after the compound layer is formed on the blade. The hardness of the compound layer can be increased by this annealing treatment.  
         [0056]    The following provides an explanation of an example of a method for coating the surface of the comb teeth of the blade with the compound layer using electrolytic plating.  
         [0057]    To begin with, the surface of a stainless steel blade is degreased with base, and then cleaned with hydrochloric acid. Next, nickel strike plating is performed on the surface of the blade. Next, a compound plating bath is prepared in the ratio of 450 g/l of nickel sulfaminate, 5 g/l of nickel chloride, 30 g/l of boric acid and 50 g/l of silicon carbide powder having an average particle diameter of 3.0 μm. The blade is immersed in the prepared compound plating bath as the cathode, while a plate made of nickel metal is immersed in the compound plating bath as the anode. Moreover, a compound plated film is formed on the stainless steel blade serving as the cathode under conditions of a cathode current density of 5 A/dm 2 , plating time of 10 min., pH of 4.0 and bath temperature of 45° C. As a result of electrolytic plating under these conditions, a compound plated film having a film thickness of 5 μm can be formed on the stainless steel blade. The amount of silicon carbide powder contained in this compound plated film is 10% by volume.  
         [0058]    The respective gaps between comb teeth  12   b  are formed corresponding to the cross-sectional shape of the ribs formed by this blade  12 . In addition, the shape of the gaps of comb teeth  12   b  is not only the case of forming a rectangular shape as shown in FIG. 4, but rather the shape of the gaps of comb teeth  12   b  may form a trapezoidal shape or inverted trapezoidal shape according to the application of the FPD ultimately produced. If the shape of the gaps of comb teeth  12   b  is made to be trapezoidal, ribs  13  can be formed that are suited for applications having wide openings, while if the shape of the gaps of comb teeth  12   b  is made to be inverted trapezoidal, ribs  13  can be formed in which the apices of the ribs have a wide area and are flat.  
         [0059]    As shown in FIG. 2, in the method for forming ribs  13  on the surface of a substrate by blade  12 , a paste is first coated onto substrate  10  to form ceramic paste  11  on its surface. Examples of suitable substrates in the present invention include glass substrate  10  only shown in FIG. 8A, glass substrate  10  on which electrodes  16  are formed on its surface shown in FIG. 8B, and glass substrate  10  on which an undercoating layer  17  made of ceramic and so forth is formed on the surface shown in FIG. 8C. Among these, glass substrate  10  on which undercoating layer  17  is formed on its surface is suitable for using the blade of the present invention. Coating of paste onto the surface of substrate  10  is carried out by a known means such as screen printing, dipping or doctor blade coating. Next, comb teeth  12   b  formed on at least a portion of the periphery of blade body  12  are penetrated into paste film  11  formed by coating a paste onto the surface of substrate  10 , and edge  12   a  of blade  12  is brought into contact with the surface of substrate  10  on which paste film  11  has been formed. Next, in the state in which edge  12   a  is in contact with the surface of substrate  10 , either blade  12  is moved in a fixed direction as indicated with the solid line arrow of FIG. 2 while fixing substrate  10 , or substrate  10  is moved in a fixed direction as shown with the broken line arrow of FIG. 2 while fixing blade  12 , to plasticly deform paste film  11 . Namely, due to the above movement, the locations corresponding to comb teeth  12   b  of blade  12  in the paste coated onto the surface of substrate  10  are those locations that move to the gaps between comb teeth  12   b  or are scratched off, and only the paste located in the gaps between comb teeth  12   b  remains on substrate  10  to form ribs  13  on the surface of substrate  10 . In the case the depth of the grooves of the comb teeth is greater than the thickness of paste film  11 , paste that is scratched off when blade  12  or glass substrate  10  is moved enters the grooves, allowing the formation of ribs  13  having a height equal to or greater than the thickness of paste film  11 .  
         [0060]    Ribs  13  formed in this manner become ceramic ribs (not shown) by being subsequently dried, and by additionally heating to remove binder followed by baking, the ceramic ribs  14  shown in FIG. 3 are formed.  
         [0061]    Next, the following provides an explanation of a second embodiment for carrying out the present invention based on FIGS. 6 and 7. The same reference symbols used in FIGS. 2 and 3 indicate the same constituent members in FIGS. 6 and 7. In this embodiment for carrying out the invention, the following points are different from the previously described embodiment for carrying out the invention. Namely, by penetrating comb teeth  12   b  formed on blade  12  into paste film  11  formed by coating a paste onto the surface of substrate  10 , and moving blade  12  or substrate  10  in a fixed direction in the state in which edge  12   a  of blade  12  is lifted from the surface of substrate  10  at a prescribed height, undercoating layer  22  and ribs  23  on this undercoating layer  22  can be formed on the surface of substrate  10 . The constitution other than that described above is similar to the first embodiment for carrying out the invention.  
         [0062]    Namely, as shown in FIG. 6, formation of ribs  23  by blade  12  is carried out by either moving blade  12  in a fixed direction as shown with the solid line arrow while fixing substrate  10 , or moving substrate  10  in a fixed direction, in the state in which edge  12   a  of blade  12  is lifted from the surface of substrate  10  at a prescribed height. As a result of this movement, undercoating layer  22  is formed while leaving paste on the surface of the substrate to a prescribed height from the surface of substrate  10 , and the locations corresponding to comb teeth  12   b  of blade  12  in the paste above this undercoating layer  22  either move to the gaps of comb teeth  12   b  or are scratched off, and only the paste located in the gaps of comb teeth  12   b  remains on undercoating layer  22 , while ribs  23  are formed on undercoating layer  22 .  
         [0063]    The undercoating layer  22  and ribs  23  formed in this manner are subsequently dried to form a ceramic green layer and ceramic green ribs (not shown), and as a result of heating to remove binder followed by baking, dielectric layer  24  is formed on the substrate as shown in FIG. 7, and ceramic ribs  25  are formed on this dielectric layer  24 .  
       EXAMPLES  
       [0064]    The following provides a detailed explanation of Examples of the present invention along with the Examples and the Comparative Examples.  
       Example 1  
       [0065]    A soda lime-based glass substrate  10  was prepared having a diagonal dimension of 42 inches and thickness of 3 mm. A ceramic paste was coated onto this glass substrate  10  followed by baking to form a ceramic undercoating layer having a thickness of 10 μm on the glass substrate. As shown in FIG. 2, a paste was coated onto glass substrate  10  having an undercoating layer on its surface at a thickness of 350 μm by screen printing to form paste film  11 .  
         [0066]    On the other hand, a blade  12  formed from stainless steel was prepared in which the pitch of comb teeth  12   b  was 360 μm, the gap w between comb teeth  12   b  was 180 μm, the depth was 350 μm, the thickness was 0.1 mm and the edge angle was 75 degrees (FIGS. 4 and 5). The surface of comb teeth  12   b  of this blade  12  was coated with a compound layer in which hard particles in the form of silicon carbide particles were dispersed in nickel metal (FIG. 1). The composition of this compound layer consisted of 10% by volume of silicon carbide to 100% by volume of the compound layer. Comb teeth  12   b  of this blade  12  were then penetrated into paste film  11  at a printing pressure of 18 MPa, and blade  12  was moved at the rate of 10 mm/sec in the direction indicated with the solid line arrow of FIG. 2 in the state in which its edge  12   a  was in contact with glass substrate  10  to plasticly deform paste film  11  and form ribs  13  on substrate  10 .  
       Comparative Example 1  
       [0067]    With the exception of not coating the surface of comb teeth  12  of blade  12  with compound layer  12   c,  ribs  13  were formed on substrate  10  in the same manner as Example 1.  
         [0068]    Tests and Evaluation  
         [0069]    The steps of forming ribs  13  on substrate  10  of Example 1 and Comparative Example 1 were respectively repeated a plurality of times, and the depth of the gap between comb teeth  12   b  of blade  12  after forming ribs  13  was measured.  
         [0070]    The relationship between the depth h of the gaps between comb teeth  12   b  of blade  12  and the number substrates treated on which ribs  13  were formed is shown in FIG. 9 for the results of Example 1 in comparison with the results of Comparative Example 1.  
         [0071]    As is clear from FIG. 9, when ribs  13  were formed on substrate  10  using blade  12  in which the surface of comb teeth  12   b  was not coated with compound layer  12   c  in Comparative Example 1, the depth h of the gaps between comb teeth  12   b  of blade  12  decreased rapidly before the number of treated substrates reached 50 plates, thus indicating that comb teeth  12   b  had become worn down by paste film  11 . In contrast, when ribs  13  were formed on substrate  10  using blade  12  in which the surface of comb teeth  12   b  was coated with the compound layer  12   c  in Example 1, the depth h of the gaps between comb teeth  12   b  did not decrease rapidly even after forming ribs on more than 250 plates, thus indicating that the wear resistance of the blade improves significantly.