HK1057615B - Method for regenerating liquid crystal display device - Google Patents

Description

Method for regenerating liquid crystal display device

Technical Field

The present invention relates to a method for recycling a glass substrate, wherein one or more films are selectively removed from the glass substrate on which at least one or more films selected from a black matrix film, a color filter film, a protective film, an ITO film, a polyimide film, a metal film, an alloy film, an oxide film, a nitride film, and a sealant film are sequentially formed.

Background

The liquid crystal display device has two or more glass plates with transparent electrodes, polarizing plates, and the like disposed therebetween, and a liquid crystal substance is sandwiched between the glass plates. Accordingly, the direction of the liquid crystal material is changed by applying an electric charge to the transparent electrode, and the polarization direction of the transmitted light is also changed, so that the transmission/non-transmission of light can be controlled by the polarizing plate. By applying such control to a subdivided field, it is possible to display text or images. Further, the liquid crystal display device includes a Thin Film Transistor (TFT) for controlling electric charges, a color filter for coloring characters or images, and the like.

Fig. 12 is a cross-sectional view showing an example of the structure of the liquid crystal display device.

In this example, the glass substrate 11 on the light incident side and the glass substrate 1 on the light emitting side are arranged to face each other.

A black matrix film (hereinafter referred to as a BM film) 2 is formed in a grid or stripe shape on one surface of the glass substrate 1, and a color filter film (hereinafter referred to as a CF film) 3 having respective colors of red (R), green (G), and blue (B) is formed on the grid or stripe of the BM film 2. A protective film (hereinafter referred to as OC film) 4 made of a transparent resin is formed on the CF film 3. The BM film 2 is usually made of metal and/or metal oxide or synthetic resin, and the CF film 3 is made of, for example, acrylic copolymer-based colored resin. An ITO film (indium tin oxide) 5 as a transparent electrode and a polyimide film (hereinafter referred to as PI film) 6 as an alignment film for aligning a liquid crystal molecule group in a certain direction are sequentially formed on the surface of the OC film 4. The polarizing film 7 is formed on the other side of the glass substrate 1. In the present specification, a glass substrate on which one or more of the BM film 2, the CF film 3, the OC film 4, the ITO film 5, and the PI film 6 are sequentially formed like the glass substrate 1 is referred to as a color filter side glass substrate.

TFT (thin film transistor) elements 12 are formed on one surface of the glass substrate 11 at predetermined intervals. The ITO film 15 and the PI film 16 are sequentially formed on the surface of the TFT element 12. As the TFT element 12, an inverted staggered a-SiTFT is often used, and the inverted staggered a-SiTFT has two types, a channel protective type and a channel edge type.

The polarizing film 17 is formed on the other surface of the glass substrate 11.

In the present specification, a glass substrate on which one or more of the TFT element 12, the ITO film 15, and the PI film 16 are formed in this order, like the glass substrate 11, is hereinafter referred to as a TFT-side glass substrate.

The liquid crystal 8 is enclosed between the PI films 6 and 16, and a distance adjusting plate 9 is disposed between the PI films 6 and 16 in order to adjust and maintain the distance between the PI films 6 and 16.

In a liquid crystal display device, normally, a backlight is irradiated from the opposite side of the glass substrate 11 to the liquid crystal 8 side, and in this state, a voltage corresponding to an image is applied between the ITO films 5 and 15 to change the alignment of the liquid crystal 8, thereby controlling the transmission/non-transmission of light and displaying an image.

The color filter side glass substrate and the TFT side glass substrate can be used for a liquid crystal display device only if they satisfy a predetermined quality standard. If the quality standard is high and cannot be satisfied, the substrate cannot be used in a liquid crystal display device, and a large number of substrates are discarded. Therefore, the glass substrate is regenerated by removing all or only a part of various films and the like formed on the glass substrate from the substrate subjected to the disposal process, and the regenerated substrate is reused for manufacturing a color filter side glass substrate, a TFT side glass substrate, and the like.

In addition, after the TFT-side glass substrate is stopped for maintenance of the manufacturing apparatus or the like, the manufacturing using the film formation condition setting glass substrate (hereinafter referred to as a dummy substrate) is first performed and each setting condition of the manufacturing apparatus is confirmed before resuming the continuous manufacturing. As the dummy substrate, a glass substrate having a metal film, an alloy film (Ta, Mo, W, Ti, Cr, Al, or an alloy thereof), and an oxide film (SiO) formed on the entire surface thereof is used_x、Ta₂O₅、Al₂O₃ITO), nitride film (SiN)_x) A single layer film, a multilayer film, a PI film, etc., and a sealant is applied along the lines. Usually, the dummy substrate cannot be made into a product, and is often used for one or more times for the same purposeAnd then discarded. Therefore, the glass substrate is regenerated by removing all or a part of the various films and the like formed from the discarded dummy substrate.

Conventionally, a stripping solution has been used to remove various films and the like from a glass substrate. For example, when all or a part of three films, i.e., a BM film, a CF film and an ITO film made of Cr is removed from a color filter side glass substrate, the color filter side glass substrate needs to be immersed in a tank containing a stripping liquid shown in table 1 below.

TABLE 1

Film seed	Stripping liquid
		BM film made of Cr	Mixed solution of ammonium ceric nitrate and nitric acid mixed aqueous solution of ammonium ceric nitrate and perchloric acid contains chloroazotic acid
CF film	Caustic soda aqueous solution containing perfluoroalkyl acid as alkaline aqueous solution
		ITO film	The mixed solution of hydrochloric acid and nitric acid, ferric chloride and the mixed solution of hydrochloric acid, and the dilute hydrochloric acid contain zinc powderMixed liquid of hydrogen iodide hydrochloride and phosphoric acid

However, when various films are removed by this method, for example, the following problems occur.

(1) When only the ITO film does not satisfy the quality, only the ITO film cannot be removed without damaging the CF film.

(2) When the CF film and the ITO film are removed simultaneously, the etching amounts of the BM film and the glass substrate cannot be reduced, and for example, the etching amount of the glass substrate in one treatment cannot be made 5nm (50 Å) or less.

In addition to the above 3 films, a glass substrate for a color filter side on which an OC film and a PI film are formed is also required to be regenerated by removing a part or all of the films which do not satisfy the quality standards, but a stripping solution which can regenerate the glass substrate without damaging the films and the glass substrate to be left has not been found.

In addition, in the TFT-side glass substrate and the dummy substrate, the TFT elements, the predetermined film, and the sealing agent are generally removed by immersing them in a storage tank containing a stripping liquid, but when a known stripping liquid is used, there are problems such as damage to the remaining thin film and etching of the glass substrate, as in the case of the color filter-side glass substrate.

Disclosure of Invention

In view of the above-described circumstances, an object of the present invention is to provide a method for regenerating a glass substrate such as a color filter-side glass substrate, a TFT-side glass substrate, or a dummy substrate for liquid crystal display, which can selectively remove only one or more films that do not satisfy quality standards by using a predetermined stripping solution, and which does not cause problems such as damage to the residual film or etching of the glass substrate.

More specifically, the present invention relates to a method for recycling a glass substrate, and aims to provide the following (1) to (7).

(1) A color filter side glass substrate and a method for regenerating a TFT side glass substrate, wherein when an ITO film is formed on the lower surface of a PI film located on the front side of a glass substrate, only the PI film can be removed without damaging the films under the ITO film by using a solution containing a neutral organic solvent or a neutral organic solvent and a polyhydric alcohol and/or water.

(2) A method for recycling a glass substrate on a color filter side, wherein when an OC film and/or a CF film is formed on the lower surface of an ITO film on the front side of a glass substrate, only the ITO film can be removed without damaging the films under the OC film by using an aqueous solution containing a halogen-based inorganic acid, organic acid, or a mixture thereof with a polyhydric alcohol.

(3) A method for recycling a glass substrate on a color filter side, wherein when a CF film and a BM film are formed on the lower surface of an OC film on the front side of a glass substrate, the OC film and the CF film can be removed without damaging the BM film and the glass substrate by using an aqueous solution containing an inorganic acid or an organic or inorganic alkaline aqueous solution.

(4) A method for recycling a glass substrate on a color filter side, wherein when a BM film made of a metal and/or a metal compound is formed on a glass substrate, the BM film can be removed without etching the glass substrate by using an aqueous solution containing an inorganic acid, an organic acid, or cerium ammonium nitrate.

(5) A method for regenerating a TFT-side glass substrate, wherein, when an ITO film and a TFT element are formed, all the formed films can be removed by using an aqueous solution containing an inorganic acid, an organic acid or ammonium ceric nitrate.

(6) A method for regenerating a dummy substrate capable of removing all films without etching a glass substrate, comprising: when one or more of a PI film, an ITO film, a metal film, an alloy film, an oxide film, and a nitride film is formed on a glass substrate, the glass substrate is immersed in a solution containing a neutral organic solvent, or a neutral organic solvent and a polyhydric alcohol and/or water to remove the PI film, the glass substrate is immersed in an aqueous solution containing a halogen-based inorganic acid or organic acid, or a mixture thereof with a polyhydric alcohol to remove the ITO film, the glass substrate is immersed in an aqueous solution containing an inorganic acid, an organic acid, or ammonium ceric nitrate to remove the PI film and the film other than the ITO film.

(7) A method for regenerating a dummy substrate, wherein when a sealant film is formed on a glass substrate, only a sealant can be removed without etching the glass substrate by using an aqueous solution containing an inorganic acid or an organic acid.

A first aspect of the present invention is to provide a method for recycling a glass substrate, comprising: one or more of the BM film, the CF film, the OC film, the ITO film, and the PI film are selectively removed from the outer layer side of the glass substrate on the film formation side by using a predetermined stripping liquid. Here, since the BM film is used for blocking light between the color filters of the respective colors, the BM film is usually formed in a grid shape or a stripe shape, but is not limited thereto. The CF film is formed of R, B, G color filters, is formed on a glass substrate to display a predetermined color, and is preferably formed on the BM film in a frame manner as shown in fig. 12 in order to ensure light shielding between the color filters. An OC film is designed to cover the surface of the CF film, an ITO film is designed as a transparent electrode, and a PI film is designed as an alignment film for aligning liquid crystals. The glass substrate according to the first aspect of the present invention is generally used as a color filter-side glass substrate for a liquid crystal display device. As the glass substrate according to the first aspect of the present invention, only one film selected from the BM film, the CF film, the OC film, the ITO film, and the PI film may be formed, or a plurality of films may be formed in sequence. Further, all of the BM film, the CF film, the OC film, the ITO film, and the PI film may be formed in this order.

In the first aspect of the present invention, one or more films are selectively removed from the film on the outer layer side of the film formed as described above. As a result, only one or a plurality of films that do not satisfy the quality standard can be removed, and the glass substrate can be regenerated in a state where the film that satisfies the quality standard remains.

A second aspect of the present invention relates to a method for recycling a glass substrate, comprising: immersing a glass substrate having a PI film and an ITO film formed thereon (wherein the PI film is on the outer layer side) in an organic solvent containing at least one selected from cyclic esters having 4 to 10 carbon atoms and hydroxyl-substituted aliphatic ethers having 3 to 10 carbon atoms, or a solvent containing the organic solvent and polyhydric alcohols and/or water, and selectively removing the PI film. According to the regeneration method of the second aspect of the present invention, only the PI film can be selectively removed without causing damage or contamination to the ITO film, which may cause a change in the resistance value. Examples of the glass substrate to which the second aspect of the present invention is applied include a glass substrate on the color filter side and a glass substrate on the TFT side for a liquid crystal display device, and if the PI film is formed on the outer layer side, a film or an element other than the PI film or the ITO film may be provided.

The cyclic ester having 4 to 10 carbon atoms and the hydroxy-substituted aliphatic ether having 3 to 1O carbon atoms are neutral organic solvents, and specific examples thereof include gamma-butyrolactone, methyl cellosolve and the like. The solvent for impregnating the glass substrate is preferably γ -butyrolactone, methyl cellosolve, or a mixed solvent thereof, and particularly preferably a solvent containing 50% by weight or more of γ -butyrolactone.

The third aspect of the present invention relates to a method for recycling a glass substrate, comprising: a glass substrate on which an ITO film and an OC film and/or a CF film are formed (wherein the ITO film is the outer layer side) is immersed in (1) an aqueous solution containing one or more halogen-based inorganic acids selected from hydrochloric acid, hydrobromic acid, hydroiodic acid and chlorosulfonic acid, (2) an aqueous solution containing one or more organic acids selected from oxalic acid, acetic acid and formic acid, or (3) an aqueous solution containing the halogen-based inorganic acids or the organic acids and polyhydric alcohols, and the ITO film is selectively removed.

According to the reproduction method of the third aspect of the present invention, only the ITO film can be selectively removed without damaging the CF film such as changes in light transmittance and chromaticity. As a glass substrate to which the third aspect of the present invention is applied, a color filter side glass substrate for a liquid crystal display device is a specific example, and if the outer layer side is an ITO film, it may have a film other than a CF film, an ITO film, and an OC film.

A fourth aspect of the present invention relates to a method for recycling a glass substrate, comprising: a glass substrate on which an OC film, a CF film and a BM film are formed (wherein the BM film contains a metal and/or a metal oxide and the OC film is the outer layer side) is immersed in (1) an aqueous solution of an inorganic acid containing one or more selected from hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid or (2) an aqueous alkaline solution containing one or more selected from N-methyl-2-pyrrolidone, tetramethylammonium hydroxide, potassium hydroxide, sodium hydroxide and hydrazine, and the films other than the BM film, such as the OC film and the CF film, are removed.

According to the regeneration method of the fourth aspect of the present invention, other films such as the OC film and the CF film can be removed without damaging the BM film and the glass substrate. As a glass substrate to which the fourth aspect of the present invention is applied, a glass substrate on a color filter side for a liquid crystal display device is exemplified.

A fifth aspect of the present invention relates to a method for recycling a glass substrate, comprising: a glass substrate on which only a BM film is formed (wherein the BM film contains a metal and/or a metal oxide) is immersed in (1) an aqueous solution containing at least one selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, chlorosulfonic acid, oxalic acid, acetic acid, and formic acid, or (2) an aqueous solution containing a cerium ammonium nitrate solution, and the BM film is removed.

According to the recycling method of the fifth aspect of the present invention, only the BM film can be removed without etching the glass substrate. The glass substrate to which the fifth aspect of the present invention is applied is, for example, a color filter side glass substrate for a liquid crystal display device.

The sixth aspect of the present invention provides a method for recycling a glass substrate, comprising: one or more of a TFT element, an ITO film and a PI film are selectively removed from the outer layer side of the film and element formation side of a glass substrate on which the film or the element is formed in this order with a predetermined stripping liquid. Here, the TFT element may be a thin film transistor which is generally used in a liquid crystal display device or the like, and the ITO film and the PI film are the same as those in the first aspect of the present invention.

The glass substrate according to the sixth aspect of the present invention is generally used as a TFT-side glass substrate for a liquid crystal display device.

In the sixth aspect of the present invention, one or more films are selectively removed from the outer layer side of the film formed as described above. As a result, only one or a plurality of films that do not satisfy the quality standard can be removed, and the glass substrate can be regenerated in a state where the films or elements that satisfy the quality standard remain.

The seventh aspect of the present invention relates to a method for recycling a glass substrate, comprising: a glass substrate on which an ITO film and a TFT element are formed (wherein the ITO film is on the outer layer side), or a glass substrate on which an ITO film, a TFT element and one or more selected from a metal film, an alloy film, an oxide film and a nitride film are formed (wherein the ITO film is on the outer layer side) is immersed in (1) an aqueous solution containing at least one selected from hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, sulfuric acid, phosphoric acid, chlorosulfonic acid, oxalic acid, acetic acid and formic acid, or (2) an aqueous solution containing ammonium ceric nitrate.

According to the recycling method of the seventh aspect of the present invention, all the films can be removed without etching the glass substrate. The glass substrate to which the seventh aspect of the present invention is applied is, for example, a TFT-side glass substrate for a liquid crystal display device.

An eighth aspect of the present invention provides a method for recycling a glass substrate, comprising: one or more of the PI film, the ITO film, the metal film, the alloy film, the oxide film, the nitride film, and the sealant film are selectively removed from the outer layer side of the glass substrate on the film-forming side thereof by a predetermined stripping liquid. Here, the ITO film and the PI film are the same as those in the first aspect of the present invention.

The glass substrate according to the eighth aspect of the present invention is generally used as a dummy substrate for manufacturing a liquid crystal display device.

In the eighth aspect of the present invention, one or more films are selectively removed from the outer layer side of the film formed as described above. As a result, only one or more films that do not satisfy the quality standard can be removed, and the dummy substrate can be regenerated in a state where the films that satisfy the quality standard remain, so that the dummy substrate can be effectively reused.

A ninth aspect of the present invention relates to a method for regenerating a glass substrate on which one or more of a PI film, an ITO film, a metal film, an alloy film, an oxide film, and a nitride film is formed, the method comprising: comprising at least one of the steps (1), (2) and (3): (1) removing the PI film by immersing the glass substrate in an organic solvent containing at least one selected from cyclic esters having 4 to 10 carbon atoms and hydroxyl-substituted aliphatic ethers having 3 to 10 carbon atoms, or a solvent containing the organic solvent and polyhydric alcohol and/or water; (2) removing the ITO film by immersing the glass substrate in an aqueous solution containing one or more halogen-based inorganic acids selected from hydrochloric acid, hydrobromic acid, hydroiodic acid and chlorosulfonic acid, an aqueous solution containing one or more organic acids selected from oxalic acid, acetic acid and formic acid, or an aqueous solution containing the halogen-based inorganic acids or the organic acids, and polyhydric alcohols; and (3) immersing the glass substrate in an aqueous solution containing at least one selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, chlorosulfonic acid, oxalic acid, acetic acid, and formic acid, or an aqueous solution containing ammonium cerium nitrate solution, to remove the PI film and the film other than the ITO film.

The glass substrate according to the ninth aspect of the present invention is generally used as a dummy substrate for manufacturing a liquid crystal display device.

In the ninth aspect of the present invention, all films that do not satisfy the quality standards can be removed without etching the glass substrate.

The tenth aspect of the present invention relates to a method for recycling a glass substrate, comprising: the glass substrate on which only the sealant is formed is immersed in an aqueous solution containing at least one selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, chlorosulfonic acid, oxalic acid, acetic acid, and formic acid, and the sealant is removed.

The glass substrate according to the tenth aspect of the present invention is generally used as a dummy substrate for manufacturing a liquid crystal display device.

In the tenth aspect of the present invention, only the sealant may be removed without etching the glass substrate.

Drawings

FIG. 1 is a sectional view showing a glass substrate on the color filter side before the recycling process in example 1 of the present invention.

Fig. 2 is a cross-sectional view showing the glass substrate on the color filter side after the recycling treatment in example 1 of the present invention.

FIG. 3 is a sectional view showing a glass substrate on the color filter side before the recycling process in example 2 of the present invention.

FIG. 4 is a cross-sectional view showing a glass substrate on the color filter side after a recycling process in example 2 of the present invention.

FIG. 5 is a sectional view showing a glass substrate on the color filter side before the recycling process in example 3 of the present invention.

FIG. 6 is a cross-sectional view showing a glass substrate on the color filter side after a recycling process in example 3 of the present invention.

Fig. 7 is a graph showing the relationship between the thickness of the BM film and the number of treatments.

Fig. 8 is a graph showing the relationship between the OD value of the BM film and the number of treatments.

FIG. 9 is a sectional view showing a TFT side glass substrate before the regeneration treatment in example 4 of the present invention.

Fig. 1O is a cross-sectional view showing a dummy substrate in example 5 of the present invention.

Fig. 11 is a cross-sectional view showing a dummy substrate in example 6 of the present invention.

Fig. 12 is a cross-sectional view showing an example of the structure of the liquid crystal display device.

Description of the symbols

1, 11, 21 glass substrate

2BM film

3CF film

4OC membrane

5, 15ITO film

6, 16PI film

7 polarizing film

8 liquid crystal

9 distance adjusting plate

10 light

12TFT element

18 metal film

19 sealant

Detailed Description

The present invention will be described in detail below with reference to examples and the accompanying drawings. The examples do not limit the scope of the invention.

Example 1

Fig. 1 and 2 are cross-sectional views showing an example of a color filter side glass substrate of a liquid crystal display device. Fig. 1 is a cross-sectional view showing a glass substrate on the color filter side before the recycling process of this example is performed. Fig. 1 and 2 are schematic diagrams illustrating the drawings based on the findings of the photomicrographs. In this respect, the same applies to fig. 3 to 6 and 9 to 11.

As shown in fig. 1, a BM film 2, a CF film 3, an OC film 4, an ITO film 5, and a PI film 6 having a thickness of 2 μ are formed on a glass substrate 1 before processing in this order.

The glass substrate 1 was immersed in a holding tank containing a stripping liquid composed of γ -butyrolactone (100%), immersed at 60 ℃ for 2 hours, taken out, and washed with water. Thereafter, the sheet was put into a leaf (fan) type washing machine, and pure water washing and air knife drying were performed.

Fig. 2 is a cross-sectional view showing the color filter side glass substrate subjected to the above-described treatment. In fig. 1, the PI film 6 is present, and in fig. 2, the PI film 6 is not present, indicating that only the PI film 6 is selectively removed. Further, it was confirmed that no damage such as resistance change and contamination occurred on the ITO film 5. Further, it was confirmed that the glass substrate 1 was not etched.

Example 2

Fig. 3 and 4 are cross-sectional views showing an example of a color filter side glass substrate of a liquid crystal display device. Fig. 3 is a cross-sectional view showing the glass substrate on the color filter side before the recycling process of this example is performed.

As shown in fig. 3, a BM film 2, a CF film 3, an OC film 4, and an ITO film 5 having a thickness of 1000 Å are formed on a glass substrate 1 before processing in this order.

The glass substrate 1 was immersed in a bath containing a stripping liquid composed of a mixed solvent of hydroiodic acid, ethylene glycol and water in a weight ratio of 30/30/40, immersed at 40 ℃ for 2 hours, taken out and washed with water. Thereafter, the resultant was put into a fan-blade type washing machine, and pure water washing and air knife drying were performed.

Fig. 4 is a cross-sectional view of the color filter side glass substrate after the above treatment and a photograph showing the surface state thereof. The presence of the ITO film 5 in fig. 3 and the absence of the ITO film 5 in fig. 4 indicate that only the ITO film 5 is selectively removed. Further, it was confirmed that no damage such as a change in transmittance and chromaticity was caused to the CF film 3. Further, it was also confirmed that the glass substrate 1 was not etched.

As the stripping liquid of the present example, an aqueous solution containing one or more of oxalic acid, acetic acid, and formic acid and a polyhydric alcohol may be used instead of the stripping liquid.

Example 3

Fig. 5 and 6 are cross-sectional views showing an example of a color filter side glass substrate of a liquid crystal display device. Fig. 5 is a cross-sectional view showing the glass substrate on the color filter side before the recycling process of this example is performed.

As shown in FIG. 5, a Cr BM film 2 having a thickness of 2000 Å, a CF film 3 having a thickness of 1.5 μ, and an OC film 4 having a thickness of 1 μ were formed on a glass substrate 1 before processing in this order.

The glass substrate 1 was immersed in a bath containing a stripping solution composed of a mixed solvent of N-methyl-2-pyrrolidone (NMP), tetramethylammonium hydroxide (TMAH) and water in a weight ratio of 30/30/40, immersed at 60 ℃ for 2 hours, taken out and washed with water. Thereafter, the resultant was put into a fan-blade type washing machine, and pure water washing and air knife drying were performed.

Fig. 6 is a cross-sectional view showing the color filter side glass substrate subjected to the above-described treatment. In fig. 5, the BM film 2, the CF film 3, and the OC film 4 are confirmed. In fig. 6, only the BM film 2 indicates that the CF film 3 and the OC film 4 are selectively removed. Further, it was confirmed that the glass substrate 1 was not etched.

Fig. 7 shows the relationship between the thickness of the BM film 2 and the number of treatments when the regeneration treatment (treatment using the stripping liquid in example 3) of example 3 is repeated a plurality of times based on BM films 2 having three thicknesses. The thickness is a thickness of the BM film 2 at a predetermined position measured by a stylus surface roughness meter, and represents a thickness from the glass substrate 1.

Fig. 8 shows the relationship between the OD value (optical density) of the BM film 2 and the number of times of the regeneration treatment in example 3. The OD value was measured using a light transmission concentration meter.

As can be seen from fig. 7 and 8, the thickness and OD of the BM film 2 are kept substantially constant even if the number of times of treatment is increased. Since the OD value is kept constant, it can be judged that the BM film 2 is not etched, and since the thickness of the BM film 2 from the glass substrate 1 is kept constant, it can be judged that the glass substrate 1 is not etched.

As the stripping liquid of the present embodiment, instead of the above-described stripping liquid, an aqueous solution containing one or more selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and chlorosulfonic acid, or an aqueous solution containing one or more selected from potassium hydroxide, sodium hydroxide, and hydrazine may be used.

In the case where the BM film 2 is not made of Cr but made of resin, the BM film 2, the CF film 3, and the OC film 4 are all removed by the treatment of the present embodiment. In this case, the glass substrate 1 can be reused as pure glass.

The Cr-made BM film formed on the glass substrate 1 is removed by immersing the glass substrate 1 in an aqueous solution containing one or more selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, oxalic acid, acetic acid, and formic acid, or an aqueous solution containing cerium ammonium nitrate.

As described above, by performing all the treatments of examples 1 to 3, all the films of the glass substrate on the color filter side shown in FIG. 1 can be completely removed. In addition, since the BM film 2 and the glass substrate 1 are hardly etched, the glass substrate 1 can be effectively reused.

Example 4

Fig. 9 is a cross-sectional view of an example of a TFT-side glass substrate of a liquid crystal display device before performing the regeneration process of the embodiment.

As shown in fig. 9, a TFT element 12, an ITO film 15 having a thickness of 1000A, and a PI film 16 having a thickness of 2 μ are formed in this order on a glass substrate 11 before processing.

The PI film 16 was selectively removed (no damage of the ITO film was observed in this case) in the same manner as in example 1, and after the ITO film 15 was selectively removed in the same manner as in example 2, the TFT element 12 was peeled off by immersing in sulfuric acid at 80 ℃ for 2 hours and then in phosphoric acid at 80 ℃ for 2 hours. By this process, the TFT elements 12, the ITO film 15, and the PI film 16 are completely removed from the glass substrate 11. It was also confirmed that the glass substrate 11 was not etched.

That is, as seen from this example, all of the TFT elements 12, the ITO film 15, and the PI film 16 can be removed from the TFT-side glass substrate, and the glass substrate 11 is hardly etched, so that the glass substrate 11 can be effectively reused.

Example 5

Fig. 10 shows an example of a dummy substrate, in which a metal film 18 is formed on a glass substrate 21.

The dummy substrate was immersed in sulfuric acid at 80 ℃ for 2 hours and then immersed in phosphoric acid at 80 ℃ for 2 hours, thereby completely removing the metal film 18. It was also confirmed that the glass substrate 21 was not etched.

As the stripping liquid of this example, instead of the above-described stripping liquid, an aqueous solution containing one or more kinds selected from oxalic acid, acetic acid, and formic acid, or cerium ammonium nitrate may be used.

Example 6

Fig. 11 shows an example of a dummy substrate, and a patterned sealant 19 is applied on a top surface of a glass substrate 21.

The dummy substrate was immersed in sulfuric acid at 80 ℃ for 2 hours and then immersed in phosphoric acid at 80 ℃ for 2 hours, thereby completely removing the sealant 19. It was confirmed that the glass substrate 21 was not etched.

As the stripping liquid of the present embodiment, an aqueous solution containing one or more selected from oxalic acid, acetic acid, and formic acid may be used instead of the stripping liquid.

As can be seen from the above description of the ninth aspect of the present invention, when one or more of the PI film, the ITO film, the metal film, the alloy film, the oxide film and the nitride film is formed on the dummy substrate, for example, the PI film is removed by immersing the glass substrate in a neutral organic solvent containing γ -butyrolactone and/or methylcellosolve, or a mixed solvent of the organic solvent and water, the ITO film is removed by immersing the glass substrate in an aqueous solution containing one or more halogen-based inorganic acids selected from hydrochloric acid, hydrobromic acid, hydroiodic acid and chlorosulfonic acid, or an aqueous solution containing one or more organic acids selected from oxalic acid, acetic acid and formic acid, and the glass substrate is immersed in an aqueous solution containing at least one selected from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, chlorosulfonic acid, oxalic acid, acetic acid and formic acid, or an aqueous solution containing a cerium ammonium nitrate solution, the films other than the PI film and the ITO film may be entirely removed from the glass substrate.

That is, as can be seen from the above-described examples and the like, since the metal film 18, the alloy film, the oxide film, the nitride film, the ITO film, the polyimide film, and the sealant 19 in the dummy substrate can all be removed and the glass substrate 21 is hardly etched, the glass substrate 21 can be effectively reused.

As described above, according to the present invention, all films or elements formed on the color filter side glass substrate, the TFT side glass substrate, and the dummy substrate for the liquid crystal display device can be removed. In addition, since only the film not satisfying the quality standard and the formed film can be selectively removed in the manufacturing process and the film satisfying the quality can be left, the color filter side glass substrate, the TFT side glass substrate, and the dummy substrate for the liquid crystal display device can be efficiently regenerated.

That is, by using the regeneration method of the present invention, only films or elements that do not satisfy the quality standard can be removed from the color filter side glass substrate, TFT side glass substrate, and dummy substrate that are defective in production, and can be reused. Further, all the films can be removed from the glass substrate which is a waste, thereby making it reusable.

As described by way of more specific example, according to the first aspect of the present invention, the sixth aspect of the present invention, and the eighth aspect of the present invention, only one or a plurality of films that do not satisfy the quality standards can be selectively removed, and the glass substrate can be effectively reused in a state where a film that satisfies the quality standards remains.

According to the second aspect of the present invention, only the PI film can be selectively removed without causing damage or contamination such as a change in resistance value to the ITO film, and the glass substrate can be etched.

According to the third aspect of the present invention, only the ITO film can be selectively removed without causing damage such as a change in transmittance and chromaticity to the CF film in the glass substrate on the color filter side or the like, and the glass substrate is hardly etched.

According to the fourth aspect of the present invention, it is possible to remove a film other than the BM film which does not satisfy the quality standard, with the glass substrate hardly etched.

According to the fifth aspect of the present invention, only the BM film can be removed without etching the glass substrate.

According to the seventh aspect of the present invention, in the TFT-side glass substrate, all films that do not satisfy the quality standards can be removed from the TFT-side glass substrate with the glass substrate hardly etched.

According to the ninth aspect of the present invention, all films that do not satisfy the quality standards can be removed from the dummy substrate with the glass substrate hardly etched.

According to the tenth aspect of the present invention, only the sealing material can be removed without substantially etching the glass substrate.

Claims (4)

1. A method for recycling a glass substrate, characterized in that a glass substrate having a polyimide film (6) and an ITO film (5) is immersed in gamma-butyrolactone, methylcellosolve, or a mixed solvent thereof, whereby only the polyimide film (6) in the outermost layer is selectively removed without changing the resistance value of the ITO film (5) formed on the glass substrate.

2. A method for regenerating a glass substrate, characterized in that only the ITO film (5) on the outermost layer is selectively removed by immersing a glass substrate having an ITO film (5) and a protective film (4) in an aqueous solution containing at least one halogen-based inorganic acid selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid and chlorosulfonic acid, or at least one organic acid selected from the group consisting of oxalic acid, acetic acid and formic acid, a polyhydric alcohol and water.

3. A method for recycling a glass substrate, characterized in that only the protective film (4) and the color filter film (3) located on the outer layer of the black matrix film are selectively removed by immersing a glass substrate having the protective film (4), the color filter film (3), and the black matrix film (2) in an aqueous alkaline solution containing one or more members selected from the group consisting of N-methyl-2-pyrrolidone, tetramethylammonium hydroxide, potassium hydroxide, sodium hydroxide, and hydrazine.

4. A method for recycling a glass substrate, characterized in that only a sealing agent (19) or only a metal film (18) is removed without etching the glass substrate by performing a treatment in a step 1 of immersing the glass substrate coated with only the sealing agent (19) or the glass substrate formed with only the metal film (18) in sulfuric acid and a step 2 of immersing the glass substrate in phosphoric acid after the step 1.