KR101285590B1 - Method for separating and recycling substrate of TFT-LCD - Google Patents

Abstract

The present invention relates to a method for separating and reproducing a substrate of a liquid crystal display device. Specifically, the liquid crystal display device is disassembled to remove a liquid crystal to reuse a substrate included in the liquid crystal display device, and a color filter substrate (upper substrate) and The present invention relates to a method of separating and regenerating upper and lower substrates by removing various component layers and films including color filters, transparent electrodes, polarizing films, and the like stacked on a TFT-array substrate (lower substrate).
On one side of the upper substrate, a polarizing film is attached with epoxy, and on the other side, a color filter substrate (upper substrate) formed by laminating color filters and a common electrode, a gate electrode, a silicon nitride film, an active layer, a source, a drain electrode, and a pixel electrode The TFT-array substrate (lower substrate), which is laminated on one side of the lower substrate and is formed by attaching an epoxy film on the other side, between the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate). A liquid crystal display device composed of liquid crystals filled and preserved by a sealant, the method of separating and reproducing a substrate of a liquid crystal display device according to the present invention comprises: separating the liquid crystal display device into a color filter substrate and a TFT-array substrate, respectively; Removing residual liquid crystals of the separated color filter substrate (upper substrate) and the TFT-array substrate (lower substrate); Removing the polarizing film attached to one surface of the upper substrate and the lower substrate and removing residual epoxy on the upper substrate and the lower substrate; Removing the color filter and the transparent electrode layer formed on the other side of the upper substrate; And dissolving the silicon nitride film disposed on one surface of the lower substrate to remove the active layer, the source, the drain electrode, and the pixel electrode (transparent electrode).

Description

Substrate separation and regeneration method of liquid crystal display device {Method for separating and recycling substrate of TFT-LCD}

The present invention relates to a method of separating and reproducing a substrate of a liquid crystal display (TFT-LCD). Specifically, the liquid crystal display is decomposed so as to reuse a substrate included in the liquid crystal display, thereby removing liquid crystals, and the upper and lower portions thereof. The present invention relates to a method for separating and regenerating upper and lower substrates by removing various component layers including color-filters, transparent electrodes, polarizing films, and the like, stacked on the substrate.

LCD (liquid crystal display) is a display device that displays characters, images, etc. by refracting the light generated in the liquid crystal whenever an electrical stimulus is inserted into the liquid crystal having a solid and liquid intermediate between the two substrates.

The image is realized using the orientation of the liquid crystal material to be aligned only in a specific direction. According to the formation method of the driving electrode and the liquid crystal material, TFT-LCD, STN-LCD (Super Twisted Nematic-LCD), and ferroelectric LCD (Ferroelectric-LCD) are used. Divided.

Among them, a thin film transistor-liquid crystal display (TFT-LCD) includes an upper substrate on which a color filter is formed, a lower substrate on which a thin film transistor (TFT) is formed, a liquid crystal filled between the substrate, and a backlight unit (light source). back light unit (BLU). A thin film transistor (TFT), a circuit in which a semiconductor film is formed on a very thin lower substrate, transmits an electrical signal to control liquid crystals and independently controls pixels, which are the smallest unit of a screen. The liquid crystal controls the transmission of light by varying the molecular structure according to the applied voltage, and the color filter is coated on the upper substrate with pixels of three colors such as red, blue, green, and passes the light controlled by the liquid crystal. Function to realize the desired color and image.

Since LCD displays images by transmitting voltage to liquid crystals, CRT monitors do not have electron guns, which makes them much thinner. They are only one tenth the thickness and weight of conventional CRTs. Power consumption is only 1/4 level, and the control speed is fast, which is good for moving picture processing. In addition, since the clarity and capacity are greatly improved compared to the existing LCD, it is widely used in the display of laptops, desktop computers, mobile phones, televisions, and digital cameras.

Recently, as the liquid crystal display device is widely used, the interest in recycling thereof is also increasing. Existing liquid crystal display products are mostly made of powder through crushing and then separated through a melting process to recycle each element.

However, this regeneration process has to go through shredding-selection-dissolving-separation-recycling process, and the process is complicated, and since the strong acid etching solution such as nitric acid and hydrochloric acid is used in the dissolution process, contaminants and waste water are generated to cause environmental pollution. do.

In addition, in order to maintain the high resolution and high resolution of the liquid crystal display device, the cleanliness and precision of the substrate itself is required, and it must be alkali-free for the safety of the LCD panel, and have a strong durability against chemicals to withstand high-temperature manufacturing processes of 300 or more. In addition, surface qualities such as surface staining, scratching, uniformity, thickness variation, and fine bending are also very important for adhesion with various layers of thin films deposited on the substrate.

Electro-Chemical Macnining method for regenerating such a substrate is also a fine etching polishing method, but in this case, the cost of the electrolytic processing equipment is high, and the color filter or silicon nitride (SiNx) formed below after the electrolytic processing Since the same protective layer must be removed, the process becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to remove and regenerate the upper and lower substrates of the liquid crystal display by removing various layers of the substrate without breaking the liquid crystal display. Is to provide a way.

Another object of the present invention is to provide a substrate separation and regeneration method capable of reducing contaminants generated during the regeneration of upper and lower substrates of a liquid crystal display.

On one side of the upper substrate, a polarizing film is attached with epoxy, and on the other side, a color filter substrate (upper substrate) formed by laminating color filters and a common electrode, a gate electrode, a silicon nitride film, an active layer, a source, a drain electrode, and a pixel electrode The TFT-array substrate (lower substrate), which is laminated on one side of the lower substrate and is formed by attaching an epoxy film on the other side, between the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate). In the liquid crystal display device comprising a liquid crystal filled and preserved by a sealant, the substrate separation and regeneration method of the liquid crystal display device according to the present invention,

Separating the liquid crystal display into a color filter substrate (upper substrate) and a TFT-array substrate (lower substrate), respectively;

Removing residual liquid crystals of the separated color filter substrate (upper substrate) and the TFT-array substrate (lower substrate);

Removing the polarizing film attached to one surface of the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) and removing residual epoxy on the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) ;

Removing the color filter and the transparent electrode layer formed on the other side of the color filter substrate (upper substrate);

Removing a protective layer such as a silicon nitride film disposed on one surface of the TFT-array substrate (lower substrate) to remove the active layer, the source and drain electrodes, and the pixel electrode (transparent electrode). It features.

Preferably, the substrate separation and regeneration method of the liquid crystal display according to the present invention further comprises the step of reinforcing the surface of the separated and regenerated substrate.

The substrate separation and regeneration method of the liquid crystal display device according to the present invention promotes the recycling of resources by separating the upper and lower substrates of the liquid crystal display device without breaking the liquid crystal display device, and increases the securing rate of the weakly localized substrate. In addition, it is possible to provide an environmentally friendly recycling method that minimizes the amount of contaminants generated during substrate separation.

1 is a view showing a general structure of a liquid crystal display device.
2 is a flowchart showing a substrate separation and regeneration method of the liquid crystal display according to the present invention.
3 is a graph showing surface roughness of a substrate constructed by a liquid crystal display substrate separation and regeneration method according to the present invention.
4 is a graph showing the light transmittance of a substrate constructed by the liquid crystal display substrate separation and regeneration method according to the present invention.

The substrate separating and reproducing method of the liquid crystal display according to the present invention separates the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate), respectively, without breaking the liquid crystal display, and then remains on the upper substrate and the lower substrate. By removing the existing structures, a reusable substrate can be obtained.

1 is a view showing a general structure of a liquid crystal display device, and FIG. 2 is a flowchart showing a substrate separating and reproducing method of the liquid crystal display device according to the present invention.

As shown in Fig. 1, a liquid crystal display generally includes a color filter substrate (upper substrate) and a TFT-array substrate (lower) after liquid crystal is filled between a color filter substrate (upper substrate) and a TFT-array substrate (lower substrate). Between the substrates) is fixed by a sealant to preserve the liquid crystal.

On one side of the color filter substrate (upper substrate), a polarizing film is attached with epoxy, and on the opposite side, a color filter is formed which functions to realize an image by coating a pixel having three colors such as red blue green on the substrate. A common electrode made of indium tin oxide (ITO), which is a transparent electrical conductor, is formed on the color filter to apply voltage to the liquid crystal cell.

On one side of the TFT-array substrate (lower substrate), a polarizing film is attached with epoxy, and on the opposite side, an aluminum (Al) film or aluminum-tantalum (Al-Ta) film as a gate electrode, and poly-silicon (poly-) as an insulating film Si) film or silicon nitride film (SiNx), ia-SiH and na-SiH films as active layers, chromium (Cr) films as source and drain electrodes, and indium tin oxide (ITO) Pixel electrodes (transparent electrodes) are stacked in sequence.

A method of separating and regenerating a substrate of a liquid crystal display device having such a structure,

I) separating the liquid crystal display into a color filter substrate (upper substrate) and a TFT-array substrate (lower substrate), respectively;

Ii) removing residual liquid crystals of the separated color filter substrate (upper substrate) and the TFT-array substrate (lower substrate);

I) The polarizing film attached to one surface of the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) is peeled off, and the remaining epoxy on the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) is removed. Steps to remove

Iii) removing the color filter and the electrode layer formed on the other side of the color filter substrate (upper substrate);

Iv) removing a protective layer such as a silicon nitride film disposed on one surface of the TFT-array substrate (lower substrate) to remove the active layer, the source, the drain electrode, and the pixel electrode. do.

A method of separating and regenerating the substrate of the liquid crystal display device as described above is as follows.

First, the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) of the liquid crystal display device have the color filter substrate (upper substrate) and the TFT-array inside the portion where the sealant of the liquid crystal display device is formed. Each can be separated by scribing and cutting the substrate (lower substrate), by maximizing the area of the regenerated substrate by minimizing the lost substrate by bringing the scribing position as close as possible to the sealant portion. have.

The liquid crystal residue may remain on the separated color filter substrate and the TFT-array substrate (lower substrate), respectively. The liquid crystal residue is immersed in the organic solvent, and then ultrasonic waves are applied to the separated color filter substrate and the TFT-array substrate. The organic solvent used may be removed by adding methanol, ethanol, I-propanol, isopropyl alcohol (IPA), acetone, ether, and the like.

In addition, the polarizing film attached to the side opposite to the surface of the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) on which the liquid crystal touches also remains on the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate). The epoxy used to remove the liquid crystal and to attach the polarizing film to the upper and lower substrates can also be dissolved while removing one liquid crystal.

Next, a color filter removal liquid or hydroxide based solution is added to remove the color filter and electrode layer formed on the other side of the color filter substrate (upper substrate). Dissolving the coated color filter allows the transparent electrode (ITO electrode) layer thereon to be automatically removed (Lift-off) from the upper substrate. The hydroxide based solution used at this time may be sodium hydroxide, potassium hydroxide and mixtures thereof.

As the color filter removing liquid, for example, at least one solvent selected from alkylene glycol monoalkyl ether carboxylic acid esters, alkoxycarboxylic acid esters and alicyclic ketones, chain amides and cyclic amino acids A photosensitive composition containing at least one solvent selected from Drew, sulfur-containing compounds and cyclic esters and aromatic hydrocarbons having 9 or more carbon atoms may be used, but is not necessarily limited thereto.

Through the above process, it is possible to obtain an upper substrate from which the color filter, the transparent electrode layer, and the polarizing film are all removed from the color filter substrate (upper substrate).

On the other hand, when a weakly acidic solution is added to the other surface of the TFT-array substrate (lower substrate) from which the polarizing film is removed to dissolve the silicon nitride film (SiNx), the active layer, the source and drain electrodes, and the pixel electrode (transparent electrode) formed thereon are dissolved. ) Layer can be removed automatically (Lift-off) from the lower substrate.

In this case, as the weakly acidic solution for dissolving the silicon nitride film, phosphoric acid or hydrofluoric acid (HF) may be used. For example, when using hydrofluoric acid (HF), 0.01 to 0.5 wt% of hydrofluoric acid and water (H 2 O) may be used. ) 99.5 to 99.99% by weight of the mixed, and can be removed by etching for 2 to 3 minutes while maintaining the 35 to 50, but is not necessarily limited to this.

Through the above process, the lower substrate from which the polarizing film, the silicon nitride film, the active layer, the source and drain electrodes, and the pixel electrode (transparent electrode) are removed from the TFT-array substrate (lower substrate) can be obtained.

The upper and lower substrates obtained in the method of separating and regenerating the substrate of the liquid crystal display according to the present invention are cut into sizes suitable for the purpose to increase bending strength, impact resistance and heat resistance, and then ion implantation, chemical treatment, heating, and quenching. Etc., the surface can be strengthened.

Figure 3 is a graph showing the surface roughness of the substrate formed by the substrate separation and regeneration method of the liquid crystal display device according to the present invention, Figure 4 is a light transmittance of the substrate formed through the substrate separation and regeneration method of the liquid crystal display device according to the present invention A graph representing.

The physical properties and characteristics of the substrate obtained through the method of separating and regenerating the substrate of the liquid crystal display according to the present invention are comparable with the new substrate which is not reused. As shown in FIGS. The root mean square (Rq) of the surface roughness is 0.895 nm, and the light transmittance (% T) is 91.55%, which is not significantly different from the effective value 0.279 nm of the surface roughness of the new substrate and 91.95% of the light transmittance. Can be.

Therefore, the substrate separation and regeneration method of the liquid crystal display device according to the present invention improves the recycling of resources by separating the upper and lower substrates of the liquid crystal display device without breaking the liquid crystal display device, and improves the securing rate of the weakly localized substrate. In addition, it is possible to provide an environmentally friendly regeneration method that minimizes the amount of contaminants generated during substrate separation.

The above description is merely illustrative of the technical details of the present invention, and those skilled in the art to which the present invention pertains may various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (7)

On one side of the upper substrate, a polarizing film is attached with epoxy, and on the other side, a color filter substrate (upper substrate) formed by laminating a color filter and a transparent electrode (common electrode), a gate electrode, a silicon nitride film, an active layer, a source, and a drain An electrode and a pixel electrode (transparent electrode) laminated on one surface of the lower substrate and a polarizing film attached on the other side with an epoxy; an TFT-array substrate (lower substrate), the color filter substrate (upper substrate) and the TFT- A liquid crystal display device comprising liquid crystals filled between an array substrate (lower substrate) and preserved by a sealant, wherein
Separating the liquid crystal display device into a color filter substrate (upper substrate) and a TFT-array substrate (lower substrate), respectively (S1);
Removing residual liquid crystal of the separated color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) (S2);
Removing the polarizing film attached to one surface of the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) and removing residual epoxy on the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) (S3);
Removing a color filter and a transparent electrode layer formed on the other surface of the color filter substrate (upper substrate) (S4);
Dissolving a silicon nitride film disposed on one surface of the TFT-array substrate (lower substrate) to remove an active layer, a source, a drain electrode, and a pixel electrode (transparent electrode) (S5); and
Reinforcing the surfaces of the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) separated and regenerated by the steps S1 to S5 (S6),
In the step (S1) of separating the liquid crystal display device into a color filter substrate (upper substrate) and a TFT-array substrate (lower substrate), the color filter substrate (upper substrate) and the inside of the portion where the sealant of the liquid crystal display device is formed; By scribing and cutting the TFT-array substrate (lower substrate), the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) are respectively separated,
Removing the residual liquid crystal (S2),
Dipping the color filter substrate (upper substrate) and the TFT-array substrate (lower substrate) in an organic solvent, respectively; And
Applying ultrasonic waves to the organic solvent,
The organic solvent is one of isopropyl alcohol, methanol, ethanol, acetone, ether,
In the removing of the color filter and the transparent electrode layer formed on the other surface of the color filter substrate (upper substrate) (S4), the transparent electrode layer is automatically removed by dissolving the color filter by adding a color filter removal solution or a hydroxide ion-based solution. The color filter removal liquid is separated and at least one solvent selected from alkylene glycol monoalkyl ether carboxylic acid esters, alkoxycarboxylic acid esters and alicyclic ketones, chain amides and cyclic amides. And a photosensitive composition containing at least one solvent selected from sulfur-containing compounds and cyclic esters and aromatic hydrocarbons having 9 or more carbon atoms.
Substrate separation and regeneration method of liquid crystal display device.
delete delete The method of claim 1,
Removing the polarizing film attached to one surface of the upper substrate and the lower substrate,
Characterized in that the removal using an organic solvent
Substrate separation and regeneration method of liquid crystal display device.
delete The method of claim 1,
By dissolving and removing the silicon nitride film, automatically separating the active layer, the source and drain electrodes, and the pixel electrode (transparent electrode),
It is characterized by using a weakly acidic solution containing phosphoric acid or hydrofluoric acid
Substrate separation and regeneration method of liquid crystal display device.
delete

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