JP2007134317A - Glass base plate for plasma display panel front plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass base plate for a plasma display panel front plate and a conductive membrane base plate for a plasma display panel front plate which have an excellent patterning accuracy, and a manufacturing method of the above. <P>SOLUTION: The glass base plate for a plasma display panel front plate has a surface roughness distribution obtained in a formula : a surface roughness distribution (%)=(Ramax-Ramin)/(Ramax+Ramin)×100, shall be ±10% or less, based on the maximum value Ramax and the minimum value Ramin out of the measured Ra's after measuring a surface roughness Ra of at least of one of the faces at points A to I in Fig., and has an average surface roughness of at least one of the faces shall be 0.3 nm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glass substrate for a plasma display panel front plate, a substrate with a conductive film for a plasma display panel front plate, and a method for producing them.

In the front plate of a plasma display panel, a transparent conductive film formed on a glass substrate patterned by a wet etching method using photolithography is used as a transparent electrode or the like. In the plasma display panel, when the distance between the transparent electrodes to be discharged changes, the discharge voltage changes and the luminance changes. Therefore, with the recent high definition of plasma display panels, improvement in patterning accuracy of the transparent conductive film is required.
As a method for improving the patterning accuracy, for example, a film such as a method mainly by changing a patterning process, such as a resist coating condition, an exposure machine condition, an etching condition, or a method by changing the material or forming conditions of the transparent conductive film itself. A method that focuses on patterning accuracy caused by itself has been implemented. However, this method has a limit in improving patterning accuracy. Recently, with higher definition of plasma display panels, further improvement in patterning accuracy is required.

By the way, as a glass substrate for a plasma display panel front plate, for example, a glass substrate is used in which an Oscar type polishing machine is used and the surface of the glass substrate is polished while supplying a polishing liquid to a polishing pad of the Oscar type polishing machine. As the abrasive contained in the polishing liquid, cerium oxide particles are usually used (see, for example, Patent Documents 1 and 2). A continuous polishing method is also disclosed (see, for example, Patent Document 3).
JP 2000-273443 A JP-A-10-255669 Japanese Patent No. 2853148

However, when the present inventors formed a conductive film on the surface of the glass substrate obtained by the above polishing method and patterned the formed conductive film by a wet etching method using photolithography, the same line width was obtained. Despite forming a resist film and performing wet etching under the same conditions, the line width of the patterned conductive film differs depending on the location of the conductive film, that is, the side etching amount (under the resist film in the horizontal direction) It has been found that the amount of the conductive film eroded by the etching progresses varies.
When the amount of side etching varies, the distance between the electrodes to be discharged changes, so that the discharge voltage between the electrodes changes, and as a result, the brightness of the screen varies. Thus, the glass substrate obtained by the conventional polishing method has a limit in the patterning accuracy of the conductive film.

  Accordingly, an object of the present invention is to provide a glass substrate for a front panel of a plasma display panel and a substrate with a conductive film for a front panel of a plasma display panel, which have excellent patterning accuracy when the conductive film formed on the surface is patterned by a wet etching method using photolithography. And providing a method for manufacturing the same.

The glass substrate for a plasma display panel front plate of the present invention is characterized in that the surface roughness distribution determined by the following method for at least one surface is within ± 10%.
(Surface roughness distribution)
(I) A region excluding a region having a width of 10 mm from the periphery of the glass substrate is defined as an effective surface of the glass substrate.
(Ii) Draw two virtual lines (vertical direction and horizontal direction) that pass through the center point A of the effective surface and are orthogonal to each other.
(Iii) Both ends of the vertical virtual line in the effective plane are point B and point C, an intermediate point between point A and point B is point D, and an intermediate point between point A and point C is point E .
(Iv) Both ends of the horizontal imaginary line in the effective plane are point F and point G, an intermediate point between point A and point F is point H, and an intermediate point between point A and point G is point I .
(V) The surface roughness Ra at points A, B, C, D, E, F, G, H, and I is measured.
(Vi) A surface roughness distribution is obtained from the maximum value Ramax and the minimum value Ramin among the Ra values measured at nine points by the following equation.
Surface roughness distribution (%) = (Ramax−Ramin) / (Ramax + Ramin) × 100

In the glass substrate for a plasma display panel front plate of the present invention, the surface having a surface roughness distribution within ± 10% is preferably a surface subjected to polishing treatment.
The substrate with a conductive film for a plasma display panel front plate of the present invention has a conductive film on the surface of the glass substrate for a plasma display panel front plate of the present invention having a surface roughness distribution within ± 10%. And
The conductive film may be a film subjected to a wet patterning process.

The glass substrate for a plasma display panel front plate of the present invention preferably has an average surface roughness of 0.3 nm or less determined by the following method for at least one surface.
(Average surface roughness)
Arbitrary 10 points are selected from the area (effective surface) excluding the area of 10 mm width from the peripheral edge of the glass substrate, the surface roughness Ra is measured, and the average value of each value is “average surface roughness”. And

The substrate with a conductive film for a plasma display panel front plate of the present invention has a conductive film on the surface of the glass substrate for a plasma display panel front plate of the present invention having an average surface roughness of 0.3 nm or less. Features.
The conductive film may be a film subjected to a wet patterning process.

The film thickness of the conductive film is preferably 20 to 500 nm.
The side etching amount of the conductive film is preferably 1.8 μm or less.
The method for producing a glass substrate for a plasma display panel front plate according to the present invention is a method for producing a glass substrate for a plasma display panel front plate in which the glass substrate surface is polished. A polishing liquid in which silica particles are dispersed in a dispersion medium is used.

  The method for manufacturing a substrate with a conductive film for a plasma display panel front plate of the present invention includes a step of measuring a surface roughness distribution of a glass substrate, a step of inspecting whether the surface roughness distribution is within a predetermined range, When the surface roughness distribution is outside a predetermined range, the method has a step of adjusting the surface roughness distribution of the glass substrate and a step of forming a conductive film on the glass substrate.

According to the plasma display panel (hereinafter referred to as PDP) front plate glass substrate of the present invention, the patterning accuracy is excellent when the conductive film formed on the surface is patterned by a wet etching method using photolithography.
According to the method for producing a glass substrate for a PDP front plate of the present invention, a glass substrate for a PDP front plate having excellent patterning accuracy when a conductive film formed on the surface is patterned by a wet etching method using photolithography can be obtained. .
The board | substrate with the electrically conductive film for PDP front plates of this invention is excellent in the patterning precision of an electrically conductive film.
According to the method for manufacturing a substrate with a conductive film for a PDP front plate of the present invention, the specific resistance value of the conductive film can be kept within a certain range, and the productivity of the substrate with a conductive film for the PDP front plate is remarkably improved. . In addition, the specific resistance value of the conductive film can be adjusted without changing the method for forming the conductive film.

<Glass substrate for PDP front plate>
The glass substrate for a PDP front plate of the present invention (hereinafter also referred to as a glass substrate) has a surface roughness distribution of at least one surface within ± 10%. The glass substrate whose average surface roughness of the surface whose surface roughness distribution is within ± 10% may be 0.3 nm or less may be used. In particular, it is preferable that the average surface roughness of at least one surface is 0.3 nm or less and the surface roughness distribution is within ± 10%. The surface roughness distribution is particularly preferably ± 8.5% or less.
By making the surface roughness distribution within ± 10%, when the conductive film formed on the surface is patterned by the wet etching method by photolithography, the variation in the side etching amount depending on the location is suppressed, and the patterning accuracy is improved. .
Furthermore, when the average surface roughness is 0.3 nm or less, a conductive film with a small amount of side etching and a small specific resistance value of the film can be formed.

The present inventors examined the extent to which the amount of side etching varies depending on the location of the substrate. As a result, it was found that when the surface roughness of the glass substrate is different, the crystal orientation of the conductive film formed thereon is changed, and the film characteristics are changed, that is, the ease of etching (side etching amount) is changed. Characteristically, even when the conductive film is manufactured under exactly the same conditions, the characteristics of the film (specific resistance value of the film, amount of side etching, etc.) change due to the difference in surface roughness of the glass substrate. It is. This means that a film having appropriate film characteristics can be formed by adjusting the surface roughness of the glass substrate.
Even if the transparent conductive film formation conditions, patterning process, etc. are improved, if there is a large variation in the surface roughness of the glass within a single glass substrate, the variation in the amount of side etch will inevitably increase, resulting in patterning accuracy. Decreases. In order to suppress the variation in the side etching amount depending on the location, it is necessary to make the variation (distribution) of the surface roughness as uniform as possible in one glass substrate, and to reduce the surface roughness of the glass substrate. I found out that I should do it. The basis of “the surface roughness distribution is within ± 10%”, which means the variation in surface roughness, will be described later.
The feature here is not the surface roughness value itself of the glass substrate but the distribution of the surface roughness. If the surface roughness is too high, problems may occur. However, if the variation in a specific location on the substrate is small (the deviation is not great), the side etching amount of the entire film should be a certain value. As a result, the distance between the discharged electrodes can be kept constant. However, even if the surface roughness of the glass substrate itself is very small, if there is a part with a very large surface roughness somewhere on the glass surface, the characteristics of the film formed on that part will change. . As a result, the amount of side etching differs, and the problem arises that the distance between the discharge electrodes differs only at that point.

The method of obtaining the “surface roughness distribution” in the present invention will be described below with reference to FIG.
(I) A region excluding a region having a width of 10 mm from the periphery of the glass substrate 10 (inside the broken line 11 in FIG. 1) is defined as an effective surface 12 of the glass substrate 10.
(Ii) Draw a vertical virtual line 13 and a horizontal virtual line 14 that pass through the center point A of the effective surface 12 and are orthogonal to each other.
(Iii) Both ends of the vertical imaginary line 13 in the effective plane 12 are point B and point C, an intermediate point between point A and point B is point D, and an intermediate point between point A and point C is point E And
(Iv) Both ends of the horizontal imaginary line 14 in the effective plane 12 are point F and point G, an intermediate point between point A and point F is point H, and an intermediate point between point A and point G is point I And
(V) The surface roughness Ra at points A, B, C, D, E, F, G, H, and I is measured.
(Vi) The surface roughness distribution is obtained by the following equation (1) from the maximum value Ramax and the minimum value Ramin among the Ra values measured at nine points.
Surface roughness distribution (%) = (Ramax−Ramin) / (Ramax + Ramin) × 100 (1)

The region excluded from the effective surface is a region where the conductive film is not used as an electrode when the member becomes a product, and the characteristics of the film (the specific resistance value of the film, the amount of side etching, etc.) are not a problem. .
The surface roughness Ra is an arithmetic average height Ra specified in JIS B0601 (2001), and is an atomic force microscope (Digital Instruments, Nano Scope IIIa; Scan Rate 1.0 Hz, Sample Lines 256, Off-Line Modify Flat). (order-2, Planfit order-2) by measuring a measurement area of 1 μm × 1 μm at each point.

A surface having a surface roughness distribution within ± 10% preferably has a Ramax of 0.1 to 1 nm. By setting Ramax to 1 nm or less, the unevenness of the conductive film formed on the surface having a surface roughness distribution within ± 10% can be reduced. Similarly, Ramin is preferably 0.1 to 1 nm. Both Ramax and Ramin are particularly preferably 0.3 nm or less.
Moreover, it is preferable that the surface whose surface roughness distribution is within ± 10% is a surface which has been subjected to a polishing treatment described later. Note that the normal polishing process is performed by rotating a polishing plate having a polishing pad using a polishing liquid containing an abrasive, as will be described later. Therefore, it is considered that the surface roughness distribution is likely to be generated due to uneven rotation of the polishing plate. Nine points selected for measuring the surface roughness distribution in the present invention are points that are considered preferable in consideration of the position of the rotating polishing plate.
Note that the selection method itself for the nine points cannot be easily determined. It can be selected only after understanding the polishing method and characteristics of the glass substrate. The details will be described below.
In general, polishing of a glass substrate for a PDP front plate is performed to improve the surface cleanliness of the glass substrate, to reduce the relatively macro roughness of a pitch of several hundred μm to several hundred mm, generally called flatness, or glass This is done for the purpose of making the thickness of the substrate constant. However, the micro surface roughness itself with a pitch of 1 μm or less as in the present invention has hardly been discussed so far, and naturally, the surface roughness distribution was not a problem (Patent Documents 1 to 3). reference).
In addition, even if the surface roughness of the glass substrate is measured and used as some parameter, it is considered that it was almost always used on the premise that the roughness of the entire glass substrate is almost uniform. It is done. That is, the measurement value of the surface roughness of the glass substrate is obtained by measuring a plurality of surface roughness values at arbitrary positions on the surface of the glass substrate and calculating an average value thereof, or at one point on the glass substrate. It is considered that most cases were obtained by representing the surface roughness value.
However, in the present invention, as described above, the surface roughness distribution has an influence on the conductive film, and the roughness distribution at the measurement points is measured and within the above range, the patterning property is excellent. It has been found that a conductive film can be formed. Here, what is important is that it has been found that the roughness of the entire surface of the glass substrate itself is not constant, and that the fact that it is not constant affects the patterning property of the conductive film. Obviously, in the measurement of the average value as described above and the measurement at one point, attention is not paid to the distribution of the surface roughness.
The selection of these nine points is determined due to the characteristics of the polishing machine. Polishing of the glass substrate for the PDP front plate is performed by pouring a plurality of polishing pads such as an Oscar type polishing machine, a Hoffman type polishing machine, or the upper surface plate 23 shown in FIG. Usually, it is carried out using a polishing machine that performs continuous polishing.
The nine points selected for measuring the surface roughness distribution in the present invention are considered to be preferable in consideration of the shape, position, rotational speed, pressure distribution, etc. of the polishing pad rotating by the polishing machine as described above. Selected.
For example, when using a polishing machine in which a plurality of polishing pads are arranged in a straight line and a glass substrate is flowed in a direction perpendicular thereto and used for continuous polishing, depending on the position in the direction perpendicular to the traveling direction of the glass substrate, the glass The difference in the relative speed, polishing pressure, and processing time between the substrate and the polishing pad increases the surface roughness of the glass in a direction perpendicular to the traveling direction rather than the traveling direction (a plurality of polishing pads are arranged in a row. It is found that the deviation of the surface roughness is large in the direction in which they are arranged and the deviation occurs in a certain direction. “Generating in a certain direction” means, for example, that the surface roughness value increases from left to right in the direction perpendicular to the glass traveling direction, from left to right or from right to left. This means that the roughness value increases in a certain direction.
Then, the deviation of the roughness of the surface of the glass substrate is measured by measuring the three points of the center of the surface of the glass substrate and the portion close to the end thereof, and by evaluating these distributions, It has been found that the entire surface of the glass substrate can be evaluated without measuring the roughness.
Further, the traveling direction of the glass substrate during polishing is either a direction parallel to the short side of the glass substrate or a direction parallel to the long side of the glass substrate. Therefore, by measuring the surface roughness distribution in the vertical and horizontal directions of the glass substrate, it becomes possible to measure the surface roughness distribution that is not influenced by the direction in which the glass advances.

The method of obtaining the “average surface roughness” in the present invention is as follows.
Arbitrary 10 points are selected from the area (effective surface) excluding the area of 10 mm width from the peripheral edge of the glass substrate, the surface roughness Ra is measured, and the average value of each value is “average surface roughness”. And
The area excluded from the effective surface is an area where the conductive film is not used as an electrode when the member becomes a product, and the characteristics of the film (the specific resistance value of the film, the amount of side etching, etc.) are not a problem. .
The surface roughness Ra is an arithmetic average height Ra specified in JIS B0601 (2001), and is an atomic force microscope (Digital Instruments, Nano Scope IIIa; Scan Rate 1.0 Hz, Sample Lines 256, Off-Line Modify Flat). (order-2, Planfit order-2) by measuring a measurement area of 1 μm × 1 μm at each point.

Examples of the glass substrate include alkali-containing glass substrates such as soda lime silicate glass substrates; non-alkali glass substrates such as borosilicate glass substrates.
The magnitude | size of a glass substrate is not specifically limited, It is preferable that it is 100-3000 mm in both length and width. Moreover, it is preferable that the thickness of a glass substrate is 0.3-3 mm.

<Glass substrate manufacturing method>
The glass substrate of the present invention can be produced by polishing at least one surface of a glass substrate using a polishing liquid in which silica particles having an average particle diameter of 0.02 to 0.2 μm are dispersed in a dispersion medium.
For the polishing treatment of the glass substrate, a known polishing machine such as an Oscar type polishing machine or a Hoffman type polishing machine can be used.
Hereinafter, the glass substrate polishing process using an Oscar type polishing machine will be described.

FIG. 2 is a side view showing an example of an Oscar-type polishing machine, and FIG. 3 is a top view. The Oscar-type polishing machine 20 is a disk-shaped lower surface plate 21, a rotating shaft 22 extending downward from the center of the lower surface plate 21, connected to a motor (not shown), and a disk shape smaller than the lower surface plate 21, and is made of glass. An upper surface plate 23 facing the lower surface plate 21 across the substrate 10, a rotating shaft 24 extending upward from the center of the upper surface plate 23, a polishing pad 25 provided on the upper surface of the lower surface plate 21, and the upper surface plate 23 And a template frame 26 for preventing the glass substrate 10 being polished from being detached.
In the Oscar type polishing machine 20, the lower surface plate 21 rotates in the a direction by driving a motor. Further, the upper surface plate 23 swings in an arc shape on the upper surface of the lower surface plate 21 as indicated by an arrow c while rotating in the b direction following the rotation of the lower surface plate 21 by friction. A set polishing pressure P can be applied from the upper part of the upper surface plate 23.

Polishing of the glass substrate 10 using the Oscar-type polishing machine 20 is performed as follows.
First, the glass substrate 10 is affixed so that the surface polished in the template frame 26 on the lower surface of the upper surface plate 23 faces downward.
Next, the polishing liquid is dropped from above the polishing pad 25, the upper surface plate 23 is lowered, the set polishing pressure P is applied, the motor is driven, and the lower surface plate 21 is rotated in the a direction.
The upper surface plate 23 is rotated in the b direction following the rotation of the lower surface plate 21 and is oscillated in an arc shape indicated by an arrow c.
In this way, the lower surface of the glass substrate 10 is polished.

Examples of the polishing pad 25 include a foamed resin material, a non-woven fiber material, a suede material, and a two-layer composite obtained by bonding them together.
As the polishing liquid, a solution in which silica particles are dispersed in a dispersion medium is used. Examples of the dispersion medium include water and organic solvents. Examples of the silica particles include colloidal silica (Colloidal SiO ₂ ), fumed silica (Fumed SiO ₂ ), precipitated silica (Precipitated SiO ₂ ), and the like. Of these, colloidal silica is preferred. When cerium oxide particles are used as an abrasive as in the conventional polishing liquid (for example, Patent Document 1), it is difficult to make the surface roughness distribution of the surface of the glass substrate subjected to the polishing treatment within ± 10%. It becomes.

  The average particle diameter of the silica particles is 0.02 to 0.2 μm, preferably 0.05 to 0.12 μm. By setting the average particle diameter of the silica particles in this range, the surface roughness distribution of the surface subjected to the polishing treatment of the glass substrate can be made within ± 10%. The “average particle diameter of silica particles” is an average particle diameter measured by a dynamic light scattering method.

  1-20 mass% is preferable and, as for content of the silica particle in polishing liquid (100 mass%), 8-12 mass% is more preferable. If the content of silica particles is less than 1% by mass, a sufficient polishing rate cannot be obtained. On the other hand, even if it exceeds 20% by mass, it is uneconomical because it is difficult to further increase the polishing rate.

The supply amount of the polishing liquid is preferably 10 to 200 ml / min.
The polishing pressure is preferably 5000 to 30000 Pa, the rotation speed of the lower surface plate 21 is preferably 10 to 120 rpm, and the polishing time is preferably 120 to 1800 seconds.

<Manufacturing method of substrate with conductive film for PDP front plate>
The method for producing a substrate with a conductive film for a PDP front plate of the present invention (hereinafter referred to as a substrate with a conductive film) measures the surface roughness distribution of a glass substrate and inspects whether the value is within a predetermined range. And it is the method of adjusting the specific resistance value of the electrically conductive film formed on a glass substrate by adjusting so that the surface roughness distribution of a glass substrate may enter into a predetermined range as needed.
By adjusting the surface roughness distribution of the glass substrate, it has been found that the specific resistance value of the conductive film can be adjusted, so that the above adjustment method can be performed. In addition to measuring the surface roughness distribution of the glass substrate, it is also possible to measure the average surface roughness of the glass substrate in the same manner.

Specifically, the specific resistance value of the conductive film is adjusted as follows.
The surface roughness distribution of the glass substrate is measured. Then, it is inspected whether the surface roughness distribution is within a predetermined range. The method for measuring the surface roughness distribution is as described above. The predetermined range is specifically within ± 10% in the case of surface roughness distribution.

If the result of the inspection is outside the predetermined range, the surface roughness distribution of the glass substrate is adjusted. Specifically, the polishing conditions are adjusted, polishing is performed, and the surface roughness distribution of the glass substrate is measured again. This operation is continued until the surface roughness distribution falls within a predetermined range.
When the surface roughness distribution falls within a predetermined range, a conductive film is formed on the glass substrate. The formed conductive film has a specific resistance value within a certain range. By using the method for adjusting the specific resistance value of the conductive film of the present invention, it is possible to suppress variations in the average surface roughness and surface roughness distribution of the initial glass substrate without changing the method of forming the conductive film, As a result, the specific resistance value of the conductive film can be kept within a certain range, and the productivity is remarkably improved.
In addition, when forming a conductive film on a glass substrate, it is also possible to form a conductive film after preparing a glass substrate different from the glass substrate whose surface roughness is measured and polishing under the same conditions. .

Moreover, it is also possible to measure the specific resistance value of a conductive film for confirmation after forming the conductive film.
Moreover, although the said method is an adjustment method of the specific resistance value of an electrically conductive film, it can also be set as the adjustment method of the side etching amount of an electrically conductive film.

<Substrate with conductive film>
The substrate with a conductive film of the present invention has a conductive film on the surface where the surface roughness distribution of the glass substrate of the present invention is within ± 10%, or on the surface where the average surface roughness is 0.3 nm or less. is there. The thickness of the conductive film is preferably 20 to 500 nm from the viewpoint of resistance value, transmittance, and the like. The specific resistance value of the conductive film is preferably 4 × 10 ⁻⁴ Ω · cm or less.

  Examples of the conductive material for forming the conductive film include indium oxide, tin oxide, zinc oxide, indium oxide doped with tin oxide (ITO), zinc oxide doped with aluminum oxide (AZO), silver alloy, and chromium alloy. . The conductive film may be a single layer film made of one kind of conductive material, or may be a laminated film having two or more layers made of different kinds of transparent conductive materials. Among these, the conductive film is preferably a film containing the conductive material as a main component, that is, a film containing 90% by mass or more of the conductive material. In particular, the conductive film is preferably a film containing indium oxide as a main component, and a film made of ITO (hereinafter referred to as an ITO film) is particularly preferable.

The ITO film preferably contains 1 to 20% by mass of tin oxide in a total of 100% by mass of indium oxide and tin oxide.
The thickness of the ITO film is preferably 20 to 500 nm from the viewpoint of resistance value, transmittance, and the like.
The specific resistance value of the ITO film is preferably 4 × 10 ⁻⁴ Ω · cm or less.

  Examples of the ITO film forming method include a thermal decomposition method (a method of forming a film by applying a raw material solution and then heating), a chemical vapor deposition method (CVD) method, a sputtering method, a vapor deposition method, an ion plating method, and the like. It is done. Among these, a method of forming by RF (high frequency) or DC (direct current) sputtering using an ITO target is preferable. As the sputtering gas, it is preferable to use an argon-oxygen mixed gas and determine the gas ratio of argon and oxygen so that the specific resistance value of the ITO film is minimized. The film forming temperature during sputtering is preferably 100 to 500 ° C. By setting the film forming temperature to 100 ° C. or higher, the ITO film is less likely to be amorphous, and the chemical resistance of the ITO film is improved. By setting the film forming temperature to 500 ° C. or lower, the crystallinity is suppressed and the unevenness of the film surface is difficult to increase.

When an alkali-containing glass substrate is used, alkali ions contained in the glass substrate may diffuse into the ITO film and affect the resistance value of the ITO film. Therefore, it is preferable to form a silicon dioxide film or the like as an alkali barrier layer between the glass substrate and the ITO film.
Examples of the method for forming the alkali barrier layer include a thermal decomposition method, a CVD method, a sputtering method, a vapor deposition method, and an ion plating method. The thickness of the alkali barrier film is preferably 10 nm or more from the viewpoint of alkali barrier performance, and preferably 500 nm or less from the viewpoint of cost.

A transparent electrode or the like is formed by patterning the conductive film. This patterning process is generally performed by a wet process. Specifically, a resist film is formed on the entire surface of the conductive film, mask exposure and development are performed, and then wet etching of the conductive film is performed to form a predetermined electrode shape. It implements by the method of forming a transparent conductive film.
The glass substrate on which the transparent electrode is formed is used as the glass substrate of the PDP front plate.

Hereinafter, examples will be described. First, in Example 1, the relationship between the surface roughness Ra of the glass substrate and the side etching amount of the conductive film was verified.

[Example 1-1]
Four types of high strain point glass substrates for PDP with different surface roughness (PD200, length 100 mm × width 100 mm × thickness 2.8 mm, manufactured by Asahi Glass Co., Ltd.) were prepared, and glass substrate (I) and glass substrate (II ), Glass substrate (III), glass substrate (IV) (glass substrate (IV) is a reference example). About each glass substrate, surface roughness Ra of arbitrary 10 points | pieces was measured in the area | region (effective surface) except the area | region of width 10mm from the periphery of a glass substrate, and the average value was calculated | required.
(1) Surface roughness Ra is an arithmetic average height Ra defined in JIS B0601 (2001), and is an atomic force microscope (Digital Instruments, Nano Scope IIIa; Scan Rate 1.0 Hz, Sample Lines 256, Off- It was determined by measuring a measurement area of 1 μm × 1 μm at each point by lineModify Flatten order-2, Planfit order-2). The results are shown in Table 1.

An ITO film having a thickness of 180 nm was formed on the surface of each glass substrate by an magnetron sputtering method using an ITO target made of indium oxide containing 10% by mass of tin oxide in a total of 100% by mass of indium oxide and tin oxide. . As a sputtering gas, a mixed gas of 72.9 sccm of argon and 2.3 sccm (3%) of oxygen was used, and the film formation temperature was 250 ° C. The composition of the formed film was equivalent to the target.
(2) The sheet resistance R of the ITO film of each glass substrate is measured with a surface resistance meter (Lorestar IP MCP-250), and the film thickness of the ITO film is measured with a shape measuring instrument (DEKTAK3-ST). ) To determine the specific resistance value of the ITO film. The results are shown in Table 1.
Specific resistance value of ITO film = sheet resistance of ITO film R × film thickness of ITO film (2)

  (3) The X-ray diffraction pattern of the ITO film of each glass substrate was measured using an X-ray diffractometer (Uriga III, manufactured by Rigaku Corporation), and the integrated intensity of 222 peaks around 30 ° was determined. The results are shown in Table 1.

(4) The side etching amount Z was determined as follows.
Each glass substrate with an ITO film was washed with pure water and dried, and then a positive resist (manufactured by Fujifilm Arch) was spin-coated on the ITO film at 500 rpm for 5 seconds, then at 1000 rpm for 10 seconds, and at 105 ° C. for 30 seconds. A resist film was formed by partial heating. Cover the resist film with a positive mask on which a transparent electrode pattern is formed, expose for 2 seconds, develop by immersing in a 0.5% by weight aqueous sodium hydroxide solution for 1 minute, and heat at 110 ° C. for 5 minutes. A resist pattern was formed. About each glass substrate, the line width X of the resist pattern of the same position (10 places) as the position which measured surface roughness Ra was measured, and the average value was calculated | required.

  An iron chloride etching solution was prepared by mixing 1000 ml of water, 500 ml of 40 mass% iron chloride (III) aqueous solution and 1000 ml of 35 mass% hydrochloric acid. The ITO film on each glass substrate was etched at 47 ± 1 ° C. for 225 seconds using the iron chloride etching solution. After exposing the entire surface of each glass substrate, the resist pattern was removed by immersion in a 0.5% by mass aqueous sodium hydroxide solution for 1 minute to form a transparent electrode. About each glass substrate, the line width Y of the transparent electrode of the same position (10 places) as the position which measured surface roughness Ra was measured, and the average value was calculated | required. As shown in FIG. 4, the line width Y of the transparent electrode is a distance between the center of the taper on one side of the transparent electrode 31 and the center of the taper on the other side.

From the line width X of the resist pattern 30 and the line width Y of the transparent electrode 31, the side etching amount Z (FIG. 4) of the ITO film was determined by the following equation (3). The results are shown in Table 1.
Side etching amount Z = (resist pattern line width X−transparent electrode line width Y) / 2 (3)

From the results of Table 1, it was found that when the average surface roughness changes, the film characteristics (specific resistance value and crystal orientation) of the ITO film change even though the manufacturing method of the ITO film is the same. And it turned out that the amount of side etching becomes large, so that a glass substrate with a large average surface roughness is. In addition, it is practically preferable that the specific resistance value is 2.6 × 10 ⁻⁴ Ω · cm or less. Further, the side etching amount is preferably practically 1.8 μm or less.

[Example 1-2]
Next, when it is assumed that two glass substrates out of the three glass substrates of glass substrate (I) to glass substrate (III) have become one glass substrate, the side etching amount distribution and the average surface roughness distribution. The relationship between and was investigated as follows.
(1) Assuming that the average surface roughness of the glass substrate (I) in Table 1 is Ramin and the average surface roughness of the glass substrate (II) is Ramax, the surface roughness distribution (%) Obtained from 1).
Further, the side etching amount distribution (%) was obtained by setting the side etching amount in the glass substrate having a small side etching amount as Zmin and the side etching amount in the glass substrate having a large side etching amount as Zmax. Specifically, the side etching amount distribution (%) when the side etching amount of the ITO film of the glass substrate (I) is Zmin and the side etching amount of the ITO film of the glass substrate (II) is Zmax is expressed by the following formula (%): It was obtained from 4).
Side etching amount distribution = (Zmax−Zmin) / (Zmax + Zmin) × 100 (4)

(2) Similarly, the surface roughness distribution (%) when the average surface roughness of the glass substrate (II) in Table 1 is assumed to be Ramin and the average surface roughness of the glass substrate (III) is assumed to be Ramax. Was obtained from the above equation (1).
Further, the side etching amount distribution (%) when the side etching amount of the ITO film of the glass substrate (II) is Zmin and the side etching amount of the ITO film of the glass substrate (III) is Zmax is obtained from the above equation (4). Asked. Zmin and Zmax are preferably 0.5 to 2 μm for practical use. Further, the side etching amount distribution is preferably 20% or less for practical use. When the side etching amount distribution is within this range, a PDP having a good in-plane luminance distribution can be formed.

(3) Further, assuming that the average surface roughness of the glass substrate (I) in Table 1 is Ramin and the average surface roughness of the glass substrate (III) is Ramax, the surface roughness distribution (%) is increased. It calculated | required from Formula (1).
Further, the side etching amount distribution (%) when the side etching amount of the ITO film of the glass substrate (I) is Zmin and the side etching amount of the ITO film of the glass substrate (III) is Zmax is obtained from the above equation (4). Asked.
The results are shown in Table 2. In Table 2, it is an order of an Example, an Example, and a comparative example from the top.

  From the results in Table 2, when the allowable range of patterning accuracy, that is, the practically preferable range of the side etching amount distribution is set within ± 20%, it is estimated that the surface roughness distribution needs to be within ± 10%. .

[Example 2]
A high strain point glass substrate for PDP (manufactured by Asahi Glass Co., Ltd., PD200, length 420 mm × width 300 mm × thickness 0.7 mm) was polished using an Oscar-type polishing machine 20 shown in FIGS. As the polishing liquid, a colloidal silica polishing solution having an average particle diameter of silica particles of 0.08 μm and a silica particle content of 10% by mass was used. As the polishing pad 25, a suede material was used. The polishing conditions were a polishing liquid supply amount of 30 ml / min, a polishing pressure of 20000 Pa, a rotation speed of the lower surface plate 21 of 80 rpm, and a polishing time of 600 seconds.

With respect to the polished surface of the obtained glass substrate, the surface roughness Ra at nine points A to I was measured using an atomic force microscope (Nano, manufactured by Digital Instruments) according to the above-described method for determining the “surface roughness distribution”. Scope IIIa) was used, and the surface roughness distribution was determined from Ramax and Ramin according to the above equation (1). The results are shown in Table 3.
In the same manner as in Example 1, a transparent electrode was formed on the polished surface of the glass substrate. Further, the side etching amount distribution was obtained in the same manner as in Example 1. The results are shown in Table 3.

[Comparative Example 1]
As a polishing liquid, a glass substrate was prepared in the same manner as in Example 2 except that a cerium oxide polishing liquid having an average particle diameter of cerium oxide particles of 1.0 μm and a content of cerium oxide particles of 10% by mass was used. Obtained. The surface roughness distribution was determined in the same manner as in Example 2. The results are shown in Table 3.
In the same manner as in Example 1, a transparent electrode was formed on the polished surface of the glass substrate. In the same manner as in Example 1, the side etching amount distribution was obtained. The results are shown in Table 3.

In Example 2, a glass substrate having a surface roughness distribution within ± 10% was obtained by using colloidal silica in which silica particles having an average particle diameter of 0.05 to 0.12 μm were dispersed in a dispersion medium. . In addition, by using a glass substrate having a surface roughness distribution within ± 10%, the transparent electrode could be patterned with high accuracy without causing variations in the amount of side etching.
In Comparative Example 1, since a conventional polishing liquid was used, a glass substrate having a surface roughness distribution within ± 10% could not be obtained. Moreover, since the glass substrate was used, the variation in the amount of side etching occurred, and the transparent electrode could not be patterned accurately.

  The glass substrate of the present invention is useful as a glass substrate for a PDP front plate because the transparent electrode can be patterned with high accuracy.

It is a figure which shows the measuring point of surface roughness Ra at the time of calculating | requiring the surface roughness distribution of a glass substrate. It is a side view which shows an example of an Oscar type polisher. FIG. 3 is a top view of FIG. 2. It is a schematic sectional drawing which shows the ITO film | membrane and resist film on the glass substrate immediately after an etching.

Explanation of symbols

10 Glass substrate (Glass substrate for front panel of plasma display panel)
12 Effective surface 13 Vertical virtual line 14 Horizontal virtual line

Claims (10)

A glass substrate for a front panel of a plasma display panel, wherein the surface roughness distribution determined by the following method for at least one surface is within ± 10%.
(Surface roughness distribution)
(I) A region excluding a region having a width of 10 mm from the periphery of the glass substrate is defined as an effective surface of the glass substrate.
(Ii) Draw two virtual lines (vertical direction and horizontal direction) that pass through the center point A of the effective surface and are orthogonal to each other.
(Iii) Both ends of the vertical virtual line in the effective plane are point B and point C, an intermediate point between point A and point B is point D, and an intermediate point between point A and point C is point E .
(Iv) Both ends of the horizontal imaginary line in the effective plane are point F and point G, an intermediate point between point A and point F is point H, and an intermediate point between point A and point G is point I .
(V) The surface roughness Ra at points A, B, C, D, E, F, G, H, and I is measured.
(Vi) A surface roughness distribution is obtained from the maximum value Ramax and the minimum value Ramin among the Ra values measured at nine points by the following equation.
Surface roughness distribution (%) = (Ramax−Ramin) / (Ramax + Ramin) × 100   The glass substrate for a plasma display panel front plate according to claim 1, wherein the surface having a surface roughness distribution within ± 10% is a surface subjected to polishing treatment.   A substrate with a conductive film for a plasma display panel front plate having a conductive film on a surface of the glass substrate for a plasma display panel front plate according to claim 1 or 2 having a surface roughness distribution within ± 10%. The glass substrate for a plasma display panel front plate according to claim 1 or 2, wherein an average surface roughness obtained by the following method for at least one surface is 0.3 nm or less.
(Average surface roughness)
Arbitrary 10 points are selected from the area (effective surface) excluding the area of 10 mm width from the peripheral edge of the glass substrate, the surface roughness Ra is measured, and the average value of each value is “average surface roughness”. And   A substrate with a conductive film for a plasma display panel front plate, having a conductive film on a surface having an average surface roughness of 0.3 nm or less of the glass substrate for a plasma display panel front plate according to claim 4.   The substrate with a conductive film for a plasma display panel front plate according to claim 3 or 5, wherein the conductive film is a film subjected to wet patterning.   The board | substrate with a electrically conductive film for plasma display panel front plates of Claim 3, 5 or 6 whose film thickness of the said electrically conductive film is 20-500 nm.   The board | substrate with the electrically conductive film for plasma display panel front plates in any one of Claims 3-5 whose side etching amount of the said electrically conductive film is 1.8 micrometers or less.   In the method for producing a glass substrate for a plasma display panel front plate for polishing a glass substrate surface, a polishing liquid in which silica particles having an average particle diameter of 0.02 to 0.2 μm are dispersed in a dispersion medium is used as a polishing liquid. A method for producing a glass substrate for a plasma display panel front plate. Measuring the surface roughness distribution of the glass substrate;
Inspecting whether the surface roughness distribution is within a predetermined range; and
If the surface roughness distribution is outside the predetermined range, adjusting the surface roughness distribution of the glass substrate;
Forming a conductive film on the glass substrate. A method for manufacturing a substrate with a conductive film for a plasma display panel front plate.

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