WO2021179386A1

WO2021179386A1 - Transparent conductive film having horizontal alignment function, liquid crystal display, and preparation method therefor

Info

Publication number: WO2021179386A1
Application number: PCT/CN2020/083620
Authority: WO
Inventors: 兰松
Original assignee: Tcl华星光电技术有限公司
Priority date: 2020-03-10
Filing date: 2020-04-08
Publication date: 2021-09-16
Also published as: CN111333346A; CN111333346B

Abstract

Disclosed is a transparent conductive film having a horizontal alignment function, the transparent conductive film comprising a conductive alignment layer. The structural general formula thereof is (I), wherein C is graphene or carbon nanotubes (CNTs); Sp₁ is a -CONH or -COO group; B is a photosensitive group; Sp₂ is -(CH₂)m-, with m being 0 to 8; R is an alkyl; and n is 100 to 10,000. By subjecting graphene or CNTs to oxidation with an strong acid and then to acyl chlorination, graphene oxide and CNTs having an alignment function are obtained, and graphene or a CNT conductive material having the alignment function is prepared.

Description

Transparent conductive film with horizontal alignment function, liquid crystal display and preparation method

Technical field

The present invention relates to the technical field of sludge treatment technology accessory devices, in particular to a stirring powder spraying device for sludge solidification.

Background technique

In a TFT-LCD liquid crystal display, it usually includes a CF substrate, a TFT substrate, and PI materials, liquid crystal materials, and sealant materials between the two. For the common VA display mode, it is necessary to coat a transparent conductive film on the CF substrate and the TFT substrate at the same time. The main function of the transparent conductive film is to form an electric field between the CF substrate and the TFT substrate to drive the deflection of liquid crystal molecules. So as to achieve bright and dark display.

At present, the traditional transparent conductive film uses an indium tin oxide (ITO) film prepared by a physical vapor sputtering (PVD) method. In the PVD device, a strong current bombards the ITO target, and a transparent conductive ITO film is deposited on the substrate. However, due to the physical properties of ITO's own oxide, the ITO film cannot exhibit bending characteristics under a certain external force, which also limits its application in flexible panels and wearable devices. On the other hand, with the guidance of national policies, the cost of indium has gradually increased. Therefore, looking for ITO substitutes with high conductivity and light transmittance, simple preparation method, and abundant resources has strong application value.

In addition, on the CF substrate and the TFT substrate, there is also a layer of thin film material, whose main function is to arrange the liquid crystal molecules in a certain direction, which we call an alignment film (commonly used polyimide (PI) material). This kind of alignment film is mainly divided into friction matching type PI material and light matching type PI material, but no matter which kind of alignment material has its own shortcomings. First of all, the friction alignment is likely to cause problems such as dust particles, static electricity residues, and brush marks to reduce the process yield. Although optical matching materials can avoid these problems, due to the limited material properties, heat resistance and aging resistance are poor. At the same time, the ability to anchor LC molecules is also weak, which affects the quality of the panel; secondly, the PI material itself has high polarity and high water absorption, storage and transportation are easy to cause deterioration and cause uneven matching, and the PI material is expensive , The process of forming a film on the TFT-LCD is also more complicated, leading to an increase in the cost of the panel.

technical problem

At present, there is a way to omit the PI film, but it is necessary to add a small organic molecule containing polar groups (PI-less liquid crystal) to the liquid crystal to achieve the purpose of making the liquid crystal molecules vertical alignment similar to PI; Small molecules have poor diffusibility on the surface of silicon nitride and non-polar substrates, which can lead to poor liquid crystal alignment.

Technical solutions

In order to solve the above technical problems, the present invention provides a transparent conductive film with horizontal alignment function, which uses graphene or CNT with alignment function to simultaneously replace the ITO transparent conductive film and the alignment film. In the prepared liquid crystal display, the graphene in the transparent conductive film plays the role of both conduction and alignment. At the same time, the graphene oxide structure chemically bonds a photo-alignment group on the surface to facilitate the alignment effect .

The present invention provides a transparent conductive film with horizontal alignment function, which includes a conductive alignment layer, and its general structural formula is:

Wherein, C is graphene or carbon nanotube (CNT); Sp ₁ is a -CONH or -COO group; B is a photosensitive group; Sp ₂ is -(CH ₂ )m-, R is an alkane; where n Is 100-10000.

The present invention also provides a method for preparing a transparent conductive film with horizontal alignment function, which includes the following steps:

Step 1) Preparation of graphene oxide or CNT;

Step 2) Mix the purified graphene powder or CNT with concentrated HNO ₃ or/and H ₂ SO ₄ , heat at 70-90°C and reflux for 10-12 hours, wash and dry for use;

Step 3) Synthesize graphene or carbon nanotubes (CNT) with alignment function, add graphene oxide powder or CNT solvent in tetrahydrofuran solvent (THF), add excess SOCl ₂ , react at room temperature for 6-10 hours, and obtain after purification Acyl chlorinated graphene powder or CNT; graphene powder: THF=1:10-20; the addition ratio of _{excess SOCl 2 is 2-5 times;}

Step 4) Prepare alignment conductive film; ultrasonically dissolve the prepared alignment function graphene oxide and surfactant in water, and apply the solution on the color filter CF substrate or TFT substrate by spin coating. Above, the CF substrate or the TFT substrate is heated at 80-120°C to form an aligned conductive film on the substrate.

The present invention also provides a method for preparing a liquid crystal display with a transparent conductive film with a horizontal alignment function, which includes the following steps:

Step 1) Preparation of graphene oxide or CNT;

Step 2) Mix the purified graphene powder or CNT with concentrated HNO ₃ and H ₂ SO ₄ , heat at 70-90°C and reflux for 10-12 hours, wash and dry for later use;

Step 3) Synthesize graphene or carbon nanotubes (CNT) with alignment function, add graphene oxide powder or CNT solvent in tetrahydrofuran solvent (THF), add excess SOCl ₂ , react at room temperature for 6-10 hours, and obtain after purification Acyl chlorinated graphene powder or CNT;

Step 4) Prepare alignment conductive film; ultrasonically dissolve the prepared alignment function graphene oxide and surfactant in water, and apply the solution on the color filter CF substrate or TFT substrate by spin coating. Above, heating the CF substrate or the TFT substrate at 80-120°C to form an aligned conductive film on the substrate;

Step 5) Prepare a liquid crystal screen Cell; irradiate the prepared CF substrate and TFT substrate with linearly polarized light, and the photo-alignment groups are arranged chaotically before the irradiation;

Step 6) Drop the liquid crystal onto the TFT or CF substrate in the ODF method, coat the sealant on the surface of the CF substrate or the TFT substrate, and coat the conductive glue on the periphery and perform vacuum grouping. At this time, the graphene is photosensitive. The alignment layer has been aligned. Without the liquid crystal aligning agent PI, the liquid crystal can be automatically aligned horizontally in the liquid crystal screen cell to obtain a liquid crystal display with a horizontal alignment function.

Beneficial effect

Compared with the prior art, the present invention modifies the composition and structure of the transparent conductive film, soaks and heats graphene powder or CNT with concentrated acid, and then performs acylation treatment to add groups with alignment function on the surface of the graphene. Obtain graphene oxide with alignment function. When preparing a transparent conductive film, on the surface of the TFT or CF substrate, the graphene or CNT first needs to be oxidized to produce -OH or -COOH on the surface, and then undergo a condensation reaction to combine with -NH ₂ and -OH with a photosensitive group The small molecular material of the preparation can replace TFT and CF ITO and PI horizontal photo-alignment type liquid crystal display.

In addition, in the preparation process of the liquid crystal display, the graphene film is irradiated with linearly polarized UV. Due to the action of the photosensitive group, the alignment groups on the graphene surface are aligned; in the ODF process, the normal liquid crystal material is dropped; Cell, due to the presence of the alignment agent on the surface of the graphene, the liquid crystal can be automatically arranged horizontally. The preparation of graphene or CNT conductive materials with alignment function can save PI and ITO materials and manufacturing processes at the same time.

Description of the drawings

1 is a schematic diagram of the oxidation treatment structure of graphene or CNT in the transparent conductive film of the present invention;

2 is a schematic diagram of the structure of graphene or CNT in the transparent conductive film of the present invention combined with a photo-alignment type group;

3 is a schematic diagram of the reaction process of the graphene or CNT acylation reaction in the transparent conductive film of the present invention;

4 is a schematic diagram of the directional arrangement of the photo-alignment groups of the transparent conductive film of the present invention after being irradiated with polarized light;

Fig. 5 is a schematic diagram of the manufacturing process of the liquid crystal display of the present invention.

Embodiments of the present invention

The specific implementation of the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but not to limit the scope of the present invention.

Among them, C is graphene or carbon nanotube (CNT); Sp ₁ is a -CONH or -COO group; B is a photosensitive group; Sp ₂ is -(CH2)m-, R is an alkane; where n is 100-10000.

In the present invention, graphene or CNT with alignment function is used to simultaneously replace the ITO transparent conductive film and the alignment film. This graphene or CNT first needs to be oxidized to produce -OH or -COOH on the surface, and then undergo condensation reaction to combine Containing -NH ₂ , -OH and small molecular materials with photosensitive groups, the horizontal photo-alignment type liquid crystal display that can replace TFT and CF ITO and PI is prepared.

In the transparent conductive film structure shown in FIGS. 1 and 2, carbon atoms are periodically arranged _{in the benzene ring SP 2 hybrid structure in 2 to 5 layers.} Referring to Figure 1, it shows that graphene or CNT undergoes oxidation treatment to generate -COOH groups on the surface. A is -NH ₂ , -OH, and then undergoes condensation reaction with -NH ₂ , -OH with photosensitive groups. The molecular materials are combined to obtain graphene oxide or CNT with alignment function. In Figure 2, the photo-alignment group is transferred from the -NH ₂ , -OH group to the Sp ₁ group. The structure of the transparent conductive film is the periodic arrangement of carbon atoms hybridized with a _{benzene ring structure SP 2 inside, and the outside contains} The branch of the photo-alignment group; the photo-alignment group and the photosensitive group are the same group.

In the present invention, the photosensitive group can have the effect of aligning the liquid crystal, and it can be any one of the following molecular structures:

Preferably, in Sp ₂ , -(CH ₂ )m-, the value of m is 0-8. Any alkyl group CH ₂ can be -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH ₂ -, -CH ₂ Replaced by O-, -CH=CH-, -CF=CF-, -CH=CH-COO-, -OCO-CH=CH-.

In the general structural formula of the conductive alignment layer, the R is a linear or branched alkane having 0-20 C atoms. The R in the general structural formula of the conductive alignment layer, wherein a certain CH ₂ group can be phenyl, cycloalkyl, -CONH-, -COO-, -O-CO-, -S-, -CO -Or -CH=CH- group substituted, one of the H atoms can also be replaced by F, Cl groups.

The following are examples of different structural formulas where R is R1, R2, R3, and R4. The specific structure is as follows:

Step 1) Preparation of graphene oxide or CNT;

Step 2) Mix the purified graphene powder or CNT with concentrated HNO ₃ and/or H ₂ SO ₄ , heat at 70-90°C and reflux for 10-12 hours, wash and dry for later use;

Step 4) Prepare alignment conductive film; ultrasonically dissolve the prepared alignment function graphene oxide and surfactant in water, and apply the solution on the color filter CF substrate or TFT substrate by spin coating. Above, the CF substrate or TFT substrate is heated at 80-120°C to form an aligned conductive film on the substrate; the mixing ratio of graphene, surfactant and water is: 1:50～500:2000～100,000; heated The time is 5 to 60 minutes.

Preferably, in step 2), the purified graphene powder or CNT is mixed with concentrated HNO ₃ and H ₂ SO ₄ in a volume ratio of 1:3. Among them, the concentration of concentrated HNO ₃ and H ₂ SO ₄ ranges from 90% to 98%; HNO ₃ and H ₂ SO ₄ can be mixed with each other or selected. The purpose of step 2) is to oxidize the graphene surface to generate -COOH groups and the like.

Preferably, in step 2), the purified graphene powder or CNT is mixed with concentrated HNO ₃ and H ₂ SO =, heated at 80° C. and refluxed for 12 hours, washed and dried for later use.

In step 3), the graphene oxide powder or CNT solvent is added to THF in excess of SOCl ₂ and reacted at room temperature for 8 hours. After purification, the acylated graphene powder or CNT is obtained; where the graphene powder: THF (press Weight ratio) = 1:10-20; the addition ratio of _{excess SOCl 2 is 2-5 times;}

Preferably, step 3) includes step 31) dissolving the chlorinated graphene powder or CNT in tetrahydrofuran solvent (THF), then adding pyridine, adding excess vertical alignment agent containing -OH groups, and reacting at room temperature for 20-30 hours , Preferably react at room temperature for 24 hours, and obtain graphene oxide or CNT with alignment function after purification; or

Step 32): Dissolve the acylated graphene powder or CNT in THF, add an excessive amount of a _{vertical alignment agent containing -NH 2} groups, and react at room temperature for 20-30 hours, preferably at room temperature for 24 hours, to obtain an alignment function after purification Graphene oxide or CNT.

In the MVA type display, the vertical alignment type, graphene only plays a conductive role, mainly by adding polydioxyethylthiophene: polyp-styrene sulfonic acid (PEDOT: PSS) to the graphene powder, among which, PEDOT: PSS The main function is to help graphene dissolve in water and facilitate the preparation of graphene membranes. In the present invention, the graphene powder is optimized and modified, the graphene oxide powder is used, and the photo-alignment type group is chemically bonded on the surface to facilitate the alignment effect. In a horizontally-aligned display, the oxidation-modified graphene plays a role in both conductivity and alignment.

Referring to Figures 4-5, the present invention also provides a method for preparing a liquid crystal display with a transparent conductive film with horizontal alignment function, which includes the following steps:

Step 1) Preparation of graphene oxide or CNT;

Step 3) Synthesize graphene or carbon nanotubes (CNT) with alignment function, add graphene oxide powder or CNT solvent in tetrahydrofuran solvent (THF), add excess SOCl ₂ , react at room temperature for 6-10 hours, and obtain after purification Acyl chlorinated graphene powder or CNT; refer to Figure 3, which shows the reaction formula of graphene powder or CNT acyl chlorination;

Preferably, in step 4), the surfactant is sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate or tetradecyl sulfate Sodium sulfate.

Preferably, in step 5), the CF substrate and TFT substrate prepared above are irradiated with linearly polarized light, the photo-alignment groups are arranged chaotically before the irradiation, the wavelength of UV light used is 320-400nm, the illuminance is 1-100mW/cm2, and the irradiation Time 5～30min. As shown in Figure 4; two transparent conductive films with different structures, after polarized light irradiated, the photo-alignment groups undergo photoreaction and are aligned to produce the effect shown in the figure.

In the preparation process of the conductive film, the present invention also has many differences from the preparation process of the prior art. In the prior art, the graphene powder, surfactant and deionized water are ultrasonically dissolved in a certain proportion to prepare a graphene aqueous solution. , Spin coating to prepare a graphene film, and heat curing to prepare a conductive graphene film.

The present invention adopts different modification methods for graphene. Graphene powder is acidified and modified by concentrated sulfuric acid or concentrated nitric acid. Graphene oxide is _{modified by SOCl 2} and reacted with a photosensitive vertical alignment agent to increase the surface of graphene. For the group with alignment function, graphene solution is prepared, coated, and heated to form a film to prepare graphene with alignment function. By modifying the structure of graphene, a transparent conductive film with horizontal alignment function is obtained.

In the manufacturing process of liquid crystal displays, in the prior art, polar materials are mixed into liquid crystals to obtain a liquid crystal mixture. In the ODF process, graphene is dropped on the surface of the substrate to form a cell, because the polar materials can be adsorbed on the graphene The surface of the substrate, and the topography is different, can automatically form a vertical alignment display, the whole process does not have a UV light manufacturing process.

In the present invention, the graphene film is irradiated with linearly polarized UV. Due to the action of the photosensitive group, the alignment groups on the surface of the graphene are aligned; in the ODF process, normal liquid crystal materials are dropped; combined into a cell, due to graphene With the presence of the surface alignment agent, the liquid crystal can be automatically arranged horizontally. The preparation of graphene or CNT conductive materials with alignment function can save PI and ITO materials and manufacturing processes at the same time.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements and modifications can be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims

A transparent conductive film with horizontal alignment function, which includes a conductive alignment layer, and its general structural formula is:

Wherein, C is graphene or carbon nanotube (CNT); Sp 1 is a -CONH or -COO group; B is a photosensitive group; Sp 2 is -(CH 2 )m-, R is an alkane; where n Is 100-10000.
The transparent conductive film with horizontal alignment function according to claim 1, wherein: the photosensitive group is any one of the following molecular structures:
The transparent conductive film with horizontal alignment function according to claim 1, wherein: Sp 2 is -(CH 2 )m-, and the value of m is 0-8.
The transparent conductive film with horizontal alignment function according to claim 1, wherein: in the general structural formula of the conductive alignment layer, the R is a linear or branched alkane having 0-20 C atoms.
The transparent conductive film with horizontal alignment function according to claim 3, wherein: in the alkyl group -(CH 2 )m- of the general structural formula of the conductive alignment layer, any CH 2 can be -O-,- S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH 2 -, -CH 2 O-, -CH=CH-, -CF=CF-, -CH=CH-COO-, -OCO-CH=CH-.
The transparent conductive film with a horizontal alignment function according to claim 3, wherein: R in the general structural formula of the conductive alignment layer, wherein a certain CH 2 group can be phenyl, cycloalkyl, -CONH- , -COO-, -O-CO-, -S-, -CO- or -CH=CH- groups, one of the H atoms can also be replaced by F, Cl groups.
A method for preparing a transparent conductive film with horizontal alignment function, which includes the following steps:

Step 1) Preparation of graphene oxide or CNT;

Step 2) Mix the purified graphene powder or CNT with concentrated HNO 3 and/or H 2 SO 4 , heat at 70-90°C and reflux for 10-12 hours, wash and dry for later use;

Step 3) Synthesize graphene or carbon nanotubes (CNT) with alignment function, add graphene oxide powder or CNT solvent in tetrahydrofuran solvent (THF), add excess SOCl 2 , react at room temperature for 6-10 hours, and obtain after purification Acyl chlorinated graphene powder or CNT; graphene powder: THF=1:10-20; the addition ratio of excess SOCl 2 is 2-5 times;

Step 4) Prepare alignment conductive film; ultrasonically dissolve the prepared alignment function graphene oxide and surfactant in water, and apply the solution on the color filter CF substrate or TFT substrate by spin coating. Above, the CF substrate or the TFT substrate is heated at 80-120°C to form an aligned conductive film on the substrate.
The method for preparing a transparent conductive film with horizontal alignment function according to claim 7, wherein: in step 2), the purified graphene powder or CNT is mixed with concentrated HNO 3 or/and H 2 SO 4 in a volume ratio of 1 ：3, the concentration range of concentrated HNO 3 and H 2 SO 4 is 90～98%.
The method for preparing a transparent conductive film with a horizontal alignment function according to claim 7, wherein: step 3) includes step 31) dissolving acylated graphene powder or CNT in tetrahydrofuran solvent (THF), then adding pyridine, adding Excessive vertical alignment agent containing -OH groups, react at room temperature for 20-30 hours, and obtain graphene oxide or CNT with alignment function after purification; or

Step 32): Dissolve the acylated graphene powder or CNT in THF, add an excess of a vertical alignment agent containing -NH 2 groups, react at room temperature for 20-30 hours, and obtain graphene oxide or CNT with alignment function after purification .
A method for preparing a liquid crystal display with a transparent conductive film with horizontal alignment function, which includes the following steps:

Step 1) Preparation of graphene oxide or CNT;

Step 2) Mix the purified graphene powder or CNT with concentrated HNO 3 or/and H 2 SO 4 , heat at 70-90°C and reflux for 10-12 hours, wash and dry for use;

Step 3) Synthesize graphene or carbon nanotubes (CNT) with alignment function, add graphene oxide powder or CNT solvent in tetrahydrofuran solvent (THF), add excess SOCl 2 , react at room temperature for 6-10 hours, and obtain after purification Acyl chlorinated graphene powder or CNT;

Step 4) Prepare alignment conductive film; ultrasonically dissolve the prepared alignment function graphene oxide and surfactant in water, and apply the solution on the color filter CF substrate or TFT substrate by spin coating. Above, heating the CF substrate or the TFT substrate at 80-120°C to form an aligned conductive film on the substrate;

Step 5) Prepare a liquid crystal screen Cell; irradiate the prepared CF substrate and TFT substrate with linearly polarized light, and the photo-alignment groups are arranged chaotically before the irradiation;

Step 6) Drop the liquid crystal onto the TFT or CF substrate in the ODF method, coat the sealant on the surface of the CF substrate or the TFT substrate, and coat the conductive glue on the periphery and perform vacuum grouping. At this time, the graphene is photosensitive. The alignment layer has been aligned. Without the liquid crystal aligning agent PI, the liquid crystal can be automatically aligned horizontally in the liquid crystal screen cell to obtain a liquid crystal display with a horizontal alignment function.