JP2010090018A - Chemical polishing fluid for glass substrate, and method for manufacturing liquid crystal display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein the flaws or the like on a glass surface are enlarged and flatness is deteriorated in a chemical polishing step for reducing the thickness of a glass substrate for a liquid crystal display. <P>SOLUTION: The enlargement of the flaws is suppressed and the liquid crystal display having an excellent display surface quality is efficiently manufactured at a low cost by polishing a glass substrate surface by a chemical polishing fluid containing a mixture liquid of hydrofluoric acid and ammonium fluoride in a molar concentration ratio of 1-2.5 and using water as the solvent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chemical polishing liquid for glass substrates capable of suppressing the occurrence of defects such as scratches on the glass surface and a method for producing a liquid crystal display device excellent in display characteristic quality produced using the same.

  In recent years, various flat panel displays such as liquid crystal displays and plasma displays have been manufactured. In this manufacturing process, a glass substrate having a substrate size of approximately 1200 (width) × 1000 (length) × 0.4 (thickness) mm is used as a mother glass substrate, and a plurality of display panel substrates are formed therein. However, liquid crystal displays used for applications such as mobile devices and portable terminals have a significant need for reduction in size and weight, and the thickness of a display panel required as a product is generally said to be 0.2 mm or less. Therefore, in the production of a liquid crystal display, it is necessary to thin the mother glass substrate to a desired thickness using means such as polishing.

  Glass substrate thinning methods are roughly classified into chemical etching (hereinafter referred to as chemical polishing) and mechanical polishing (hereinafter referred to as mechanical polishing). The former is generally a method in which a glass substrate is dissolved using an etching solution mainly containing hydrofluoric acid, and the latter is a method in which a glass substrate is polished using a cerium oxide-based polishing solution. However, particularly in the thinning of the glass substrate by chemical polishing, if scratches are present on the glass substrate surface before polishing, the etching solution acts to further enlarge the scratches, and as a result, the flatness of the glass substrate is impaired. There was a big problem.

  In view of the fact that such scratches are enlarged, Patent Document 1 proposes a method of removing minute defects by mechanical polishing after chemical polishing. Patent Document 2 proposes a method for suppressing the expansion of scratches by polishing a glass substrate surface using a 30 to 60 wt% hydrogen fluoride aqueous solution having a polishing rate of 1 μm / sec or more. Further, Patent Document 3 proposes a quartz glass surface treatment liquid in which hydrofluoric acid, ammonium fluoride, and acetic acid are mixed with water.

JP 2003-15111 A JP 2003-226552 A JP-A-7-267679

  When the method described in Patent Document 1 is applied to the manufacturing process of a liquid crystal display panel, two polishing steps, chemical polishing and mechanical polishing, are required, leading to significant equipment restrictions and an increase in panel production costs. There was a problem.

  On the other hand, although the method described in Patent Document 2 suppresses the spread of scratches, the polishing rate is large, and thus the etching amount on the glass surface is likely to be uneven, and as a result, the undulation of the glass surface is noticeable. Had the problem of becoming. Further, when there is a large scratch on the surface of the glass substrate, for example, when there is a scratch having a length of 40 μm or more, there is a defect that the scratch is not suppressed by etching and is enlarged to a diameter of 100 μm or more.

  Further, Patent Document 3 discloses a quartz glass surface treatment liquid in which hydrofluoric acid, ammonium fluoride, and acetic acid are mixed with water as a surface treatment liquid for quartz glass. However, this surface treatment liquid is intended to form fine irregularities on the surface of quartz glass, and is a polishing liquid for glass substrates for liquid crystal displays that are required to have a thin and excellent surface state. Is not appropriate.

  The objective of this invention is providing the chemical polishing liquid for glass substrates which can suppress the growth of a damage | wound, without forming fine unevenness | corrugation on the glass substrate surface, and the manufacturing method of a liquid crystal display device using the same.

  A suitable chemical polishing liquid for solving the above-described problems is as follows. In addition, the composition of the chemical polishing liquid was expressed in molar concentration or volume%.

  The chemical polishing liquid for a glass substrate of the present invention is characterized by containing 1 to 2.5 of hydrofluoric acid and ammonium fluoride in a molar concentration ratio. It has been found that by controlling the mixing ratio of these chemical liquid components to an appropriate value, the growth of scratches can be suppressed without forming fine irregularities on the glass surface.

  As a more preferable example, the growth of scratches can be suppressed without forming fine irregularities on the glass surface by blending with hydrofluoric acid to 2 to 18% by volume, preferably 4 to 12% by volume. And by adjusting the concentration of ammonium fluoride to 2 to 20% by volume, desirably 6 to 14% by weight, the flatness of the glass surface can be further improved and the growth of scratches can be further suppressed.

  The components of the polishing liquid important for polishing the glass substrate have been described above. However, they are used as follows in the manufacturing process of the liquid crystal display device. That is, a method for manufacturing a liquid crystal display device includes a step of forming a thin film transistor on a first glass substrate, a step of forming a color filter on a second glass substrate, and the first glass substrate and the second glass. A step of bonding through a sealing material so that the respective film formation surfaces face each other, a step of thinning and polishing the surface of at least one glass substrate of the pair of bonded glass substrates, and the pair of glasses A step of cutting the substrate into individual display panel substrates, a step of sealing liquid crystal in a region surrounded by the sealing material of the display panel substrate, and a step of sealing the sealing port; and polarization on the surface of the display panel substrate And a step of pasting a plate.

  In addition to the examples described above, the present invention can be applied to a method of dropping and enclosing liquid crystal, a method of cutting a pair of glass substrates into individual display panel substrates, and then thinning and polishing.

  The above-described thinning polishing process is performed using the polishing liquid having the composition components described above. As an example, a polishing aqueous solution containing 4 to 12% by volume of hydrofluoric acid and 6 to 14% by volume of ammonium fluoride is supplied to the surface of a target glass substrate until a predetermined thickness (for example, 0.2 mm or less) is reached. Polish the surface of the glass substrate. Note that controlling the etching rate at this time to 0.1 to 10 μm / min is effective in suppressing the flatness of the substrate surface and scratches.

  By using the chemical polishing liquid for glass substrate of the present invention containing 1 to 2.5 of hydrofluoric acid and ammonium fluoride in a molar concentration ratio, the growth of scratches can be suppressed without forming fine irregularities on the surface of the glass substrate. .

  For example, by polishing the surface of a mother glass substrate having a large size or a display panel substrate obtained by dividing the mother glass substrate using the chemical polishing liquid for glass substrate of the present invention, it is suitable for mobile phones and mobile devices, In addition, a glass substrate having excellent display characteristics can be provided at a low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the same description is omitted. The composition of the chemical polishing liquid is expressed in terms of molar concentration or volume%.

  First, a method for manufacturing a display display panel of a mobile phone or mobile device will be described. FIG. 1 is a process flowchart for explaining the manufacturing process. FIG. 2 is a view schematically showing a cross section of the display panel after chemical polishing.

  Step 101 in FIG. 1 is a step of forming a plurality of thin film transistor elements 3 (array) using a well-known thin film process on the first glass substrate 1 (mother glass), and includes exposure, development, etching, and the like. It is formed by repeating the photolithography process. Thereafter, an alignment film (not shown) is formed on the formed thin film transistor element 3, and a rubbing process for aligning the liquid crystal 6 is performed on the alignment film. On the other hand, the process 102 is a color filter forming process for forming the color filter element 4 made of RGB on the second glass substrate 2 (mother glass). The color filter element 4 is formed by a well-known dye coating method or printing method.

  Next, on at least one glass substrate of the first glass substrate 1 or the second glass substrate 2, a region corresponding to each thin film transistor element 3 or color filter element 4 and a display pixel is formed, and a liquid crystal Application of a product seal 5 in an area where 6 is sealed, and an outer peripheral seal (not shown) around a glass substrate forming a display area composed of a plurality of display pixels by a well-known dispenser Printing simultaneously using the printing method and screen printing method. Here, a coating method using a dispenser was used.

  Next, in step 103, the first glass substrate 1 and the second glass substrate 2 are bonded together so that the element formation surfaces face each other. In order to use the display panel 7 composed of a pair of glass substrates as a display for a mobile phone or a portable terminal, the thickness of at least one glass substrate (1 or 2) is reduced to about 0.2 mm. It is necessary. Step 104 is a step of reducing the thickness of the glass substrate using a chemical polishing liquid. In this step, since a chemical polishing liquid is used, if a minute scratch is present on the surface of the glass substrate, the scratch is enlarged and the function as a display panel is impaired. Therefore, it is desired that the polishing liquid to be used not only can suppress the expansion of scratches but also has a characteristic capable of maintaining the flatness of the entire glass substrate surface. Needless to say, the sealing performance of the sealing material is not adversely affected. Here, when either the first glass substrate 1 or the glass substrate 2 of 2 does not require thinning polishing, a method of attaching a protective film or the like is generally performed.

  Thereafter, step 105 is an individual cutting step for cutting the pair of bonded mother glass substrates into the liquid crystal display panel 7 having a predetermined display area. The glass substrate was cut by combining a scribe cutting method using a cutter wheel and a break cutting method for dividing the glass substrate. In step 106, liquid crystal is sealed in the region surrounded by the product seal 5 described above, and then the sealing port is sealed.

  Finally, step 107 is a step of attaching a polarizing plate to the surface of the display panel substrate described above, whereby the liquid crystal display panel 7 is completed.

  By the way, in the manufacturing process of the above-mentioned liquid crystal display panel, the pair of glass substrates (1 or 2) bonded together in the state of mother glass was thinned and polished in the state of mother glass. However, the liquid crystal is sealed in a region surrounded by the product seal 5 in advance by a dropping method, the order of the 105 process and the 104 process is changed, and after cutting into a display panel of a predetermined size, at least one of the glass substrates Thinning polishing may be performed on the surface. That is, after the 101 step and the 102 step, the liquid crystal in which liquid crystal is dropped on the surface of the first glass substrate 1 on which the thin film transistor element 3 is formed or on the surface of the second glass substrate 2 on which the color filter element 4 is formed. A dripping process is performed, 103 processes are performed after that, 105 processes are performed after that, 104 processes are performed after that, 107 processes may be performed after that.

  Next, optimization of the chemical polishing liquid used in the 104 process was examined.

  FIG. 3 is a diagram showing the relationship between the molar concentration ratio and the depth of scratches generated on the glass surface, using a mixed solution of hydrofluoric acid and ammonium fluoride as the chemical polishing liquid. In addition, the mixed solution of hydrofluoric acid and ammonium fluoride was adjusted and mixed so that it might become a predetermined molar concentration ratio using water as a solvent using the solution adjusted to the density | concentration of stock solution 50% and 40%, respectively. In each molar concentration ratio, the total amount of hydrofluoric acid and ammonium fluoride was adjusted to 20% by volume. Further, the temperature of the chemical polishing liquid was adjusted to 35 ° C. for use. Although 35 degreeC was used in this Embodiment, the temperature of a chemical polishing liquid may be 25 to 50 degreeC.

  The glass substrate used for the study is immersed in a chemical polishing solution filled in a plastic etching tank (not shown), and one side of the glass substrate has a predetermined thickness (for example, 0.2 mm or less). Etching is performed for a predetermined time. Here, the etching was performed for a predetermined time so that the average etching amount was 30 μm. After the etching, the chemical polishing liquid was completely removed by a conventional cleaning method.

  Next, evaluation of scratches generated on the surface of the glass substrate due to chemical polishing was performed according to the following procedure. First, a scratch having a depth of about 2 to 3 μm was formed on the glass surface with a constant pressure using a sharp tool such as a diamond pen. Then, the depth of the scratches grown after chemical polishing was measured using a laser displacement meter.

  In FIG. 3, the flaw depth on the glass surface shows a tendency that an appropriate range exists with respect to the molar concentration ratio of the hydrofluoric acid and ammonium fluoride mixed solution. Here, it was found that the molar concentration ratio of hydrofluoric acid and ammonium fluoride may be adjusted to 1 to 2.5 in order to control the depth of the scratch to a target value of 10 μm or less. Further, the etching rate at this time was approximately 5 μm / min.

  Further, when the concentration of hydrofluoric acid is 14% or more, the depth of the scratch is 10 μm or more. Further, the etching rate at this time was approximately 7 μm / min.

  Controlling the etching rate to 0.1 to 10 μm / min is effective in suppressing the flatness of the substrate surface and scratches.

  The reason why the depth of the scratch must be controlled to 10 μm or less will be described with reference to the schematic diagram shown in FIG. As described above, the polarizing plate 9 is attached to the surface of the glass substrate 1 or 2 after the thinning polishing. Here, when a relatively large scratch 8 exists on the surface of the glass substrate 1 or 2, a space is generated between the polarizing plate 9 and the scratch 8. Therefore, light is scattered in the space between the scratch 8 and the polarizing plate 9 in the inspection process, and it is determined as an optical defect. On the other hand, when a relatively small scratch 8 'exists on the surface of the glass substrate 1 or 2, the adhesive (not shown) of the polarizing plate 9 is deformed and embedded in the scratch 8', so that the apparent scratch 8 'is repaired. Expected to be effective. In order to confirm this repair effect experimentally, a liquid crystal panel was produced using a glass substrate having various scratch depths. Next, it was confirmed that the maximum value of the depth of the scratch that satisfies the standard value of the predetermined optical display performance in the inspection process is 10 μm.

  FIG. 5 shows the relationship with the depth of scratches on the glass substrate when the molar concentration ratio of hydrofluoric acid and ammonium fluoride is constant at 2.0 and the concentration of hydrofluoric acid is changed. Here, the concentration of the mixed solution was adjusted using water as a solvent. The temperature of the mixed solution was 35 ° C.

  As is apparent from this figure, the depth of scratches on the surface of the glass substrate can be kept small by adjusting the concentration of hydrofluoric acid contained in the mixing liquid to 2 to 18% by volume. In order to control the depth of the scratch to 10 μm or less, it has been found that the concentration of hydrofluoric acid should be 4 to 12% by volume. Further, although not shown, the glass substrate surface irregularity was not abnormal in the above concentration range.

  FIG. 6 shows the relationship with the depth of scratches on the glass substrate surface when the molar concentration ratio of hydrofluoric acid and ammonium fluoride is constant at 2.0 and the concentration of ammonium fluoride is changed as in FIG. . Water was used for dilution of the mixed solution, and the temperature of the mixed solution was set to 35 ° C.

  As is apparent from this figure, the depth of scratches on the surface of the glass substrate can be kept small by adjusting the concentration of ammonium fluoride contained in the mixing liquid to 2 to 20% by volume. If the concentration of ammonium fluoride is in the range of 6% to 14%, the depth of the scratch can be suppressed to 10 μm or less which does not affect the display characteristics of the display panel. There was no problem with the surface roughness of the glass substrate.

  As described above, by appropriately managing the concentration of hydrofluoric acid and ammonium fluoride mixed solution in the thinning process of the glass substrate, the depth of scratches generated on the glass substrate surface can be suppressed, and It was also confirmed that the surface was suppressed to a level that would not hinder the product.

  However, a requirement for a display panel substrate completed through the process flow of FIG. 1 is display characteristics and reliability over time. Therefore, a pair of display panel substrates subjected to thinning processing using the above-described chemical polishing liquid was applied to a mobile device, and display / operation characteristic tests and environmental tests were performed. As a result, it was confirmed that there were no problems with the optical characteristics such as brightness by lighting test, electrical characteristics such as drive voltage and current, and display characteristics required for liquid crystal display devices in the items of mechanical strength test and environmental test. .

  The present invention provides a chemical polishing liquid for glass substrate that can suppress the growth of scratches without forming fine irregularities on the surface of the glass substrate, and the production of a liquid crystal display device having excellent surface quality with few defects such as scratches on the glass substrate. In particular, it contributes to improving the quality and yield of liquid crystal panels and reducing costs.

It is a flowchart which shows the manufacturing process of the liquid crystal display device explaining embodiment of this invention. It is a schematic diagram which shows the cross-sectional structure of the liquid crystal panel explaining embodiment of this invention. It is a graph which shows the relationship between the molar concentration ratio of the liquid mixture of hydrofluoric acid and ammonium fluoride, and the depth of a flaw explaining embodiment of this invention. It is a schematic diagram which shows the state which affixed the polarizing plate on the cross section of the crack | wound which generate | occur | produced on the glass substrate explaining embodiment of this invention, and a glass substrate. It is a graph which shows the relationship between the density | concentration of hydrofluoric acid and the depth of a flaw explaining embodiment of this invention. It is a graph which shows the relationship between the density | concentration of ammonium fluoride and the depth of a flaw explaining embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st glass substrate 2 2nd glass substrate 3 Thin-film transistor element 4 Color filter element 5 Product seal 6 Liquid crystal 7 Liquid crystal display panel 8 The damage | wound which generate | occur | produced on the glass substrate 9 Polarizing plate

Claims (8)

  A chemical polishing liquid for glass substrates, comprising a mixed solution of hydrofluoric acid and ammonium fluoride in a molar concentration ratio of 1 to 2.5.   2. The chemical polishing liquid for glass substrate according to claim 1, wherein the concentration of hydrofluoric acid is 2 to 18% by volume.   The chemical polishing liquid for glass substrates according to claim 1, wherein the concentration of ammonium fluoride is 2 to 20% by volume. A thin film transistor forming step for forming a thin film transistor element on a first glass substrate, a color filter forming step for forming a color filter element on a second glass substrate, and a surface on which the elements are formed are arranged facing each other and sealed. A bonding step of bonding the first glass substrate and the second glass substrate through a material, and a thinning polishing step of thinning and polishing at least one glass substrate of the pair of bonded glass substrates; A method of manufacturing a liquid crystal display device, comprising: a polarizing plate forming step of forming a polarizing plate on the surface of the display panel substrate,
In the thinning polishing step, at least a surface of the first glass substrate or the second glass substrate containing a polishing liquid containing a mixed solution of hydrofluoric acid and ammonium fluoride in a molar concentration ratio of 1 to 2.5. A method for manufacturing a liquid crystal display device, characterized in that the method is a step of supplying to the substrate and polishing.   After the thinning polishing step, an individual cutting step for cutting the pair of glass substrates into a display panel substrate, and a liquid crystal encapsulation / sealing step for encapsulating / sealing liquid crystal in the display panel substrate, 5. The method for manufacturing a liquid crystal display device according to claim 4, wherein the polarizing plate forming step is performed thereafter.   After the thin film transistor forming step and the color filter forming step, liquid crystal is dropped on the surface of the first glass substrate on which the thin film transistor element is formed or on the surface of the second glass substrate on which the color filter element is formed. A liquid crystal dropping step is performed, then the laminating step is performed, and then a paired glass substrate is cut into a display panel substrate, and then the thinning polishing step is performed. Item 5. A method for producing a liquid crystal display device according to Item 4.   In the thinning polishing step, at least the surface of the first glass substrate or the second glass substrate is polished with the chemical polishing liquid, so that the depth of scratches on the polished glass substrate surface is 10 μm or less. The method of manufacturing a liquid crystal display device according to claim 4.   5. The method of manufacturing a liquid crystal display device according to claim 4, wherein an etching rate in the thinning polishing step is 0.1 to 10 [mu] m / min.

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