CN115232553A

CN115232553A - Polarizer preparation method, polarizer and display device

Info

Publication number: CN115232553A
Application number: CN202210899215.6A
Authority: CN
Inventors: 任浩
Original assignee: Guangzhou China Star Optoelectronics Semiconductor Display Technology Co Ltd
Current assignee: Guangzhou China Star Optoelectronics Semiconductor Display Technology Co Ltd
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2022-10-25

Abstract

The application discloses a polaroid preparation method, a polaroid and a display device. The preparation method of the polaroid comprises the following steps: a surface-providing substrate; coating a polyimide layer on the substrate; and coating a liquid crystal polymer mixed with a dichroic dye on the polyimide layer, and curing to obtain the alignment layer. According to the preparation method, different solutions are coated and then baked and cured to obtain the corresponding polyimide layer and the corresponding alignment layer, so that the thickness of the finally obtained polarizer is thinner.

Description

Polarizer preparation method, polarizer and display device

Technical Field

The application relates to the technical field of display, in particular to a polaroid preparation method, a polaroid and a display device.

Background

The TFT-LCD is one of the mainstream display modes at present, the industry thereof is mature, and the lower price is the main advantage. The basic principle is that the TFT controls the liquid crystal deflection, so that linearly polarized light passing through the lower polarizer passes through the upper polarizer in different degrees. The conventional polarizer has a multi-layer structure, and has a multi-layer protective film in addition to the stretched PVA containing iodine molecules, which plays a role of polarizing light. At present, the traditional polaroid is relatively low in price, mature in industry and good in optical performance. However, with the current demand for flexible displays, it is also desirable to produce polarizers with thinner thicknesses.

Disclosure of Invention

The embodiment of the application provides a polarizer preparation method, a polarizer and a display device, wherein different solutions are coated and then baked and cured to obtain a corresponding polyimide layer and an alignment layer, so that the thickness of the finally obtained polarizer is thinner.

In a first aspect, an embodiment of the present application provides a method for manufacturing a polarizer, which includes providing a substrate;

coating a polyimide layer on the substrate;

and coating a liquid crystal polymer mixed with dichroic dyes on the polyimide layer, and curing to obtain the alignment layer.

In some embodiments, the coating a polyimide layer on the substrate includes:

coating polyimide on the substrate, and baking at a first temperature to obtain a first polyimide layer;

heating the first polyimide layer and a cyclizing agent at a second temperature, so that steam of the cyclizing agent is contacted with the first polyimide layer to perform cyclization reaction, and obtaining a second polyimide layer;

and aligning the second polyimide layer to obtain the polyimide layer.

In some embodiments, the coating of polyimide on the substrate and baking at the first temperature to obtain the first polyimide layer comprises:

diluting the anhydride into a pyridine solvent by 3-5 w% to obtain the cyclizing agent.

In some embodiments, the first temperature is in the range of 80-130 ℃ and the second temperature is in the range of 220-240 ℃.

In some embodiments, after the polyimide layer is coated with a liquid crystal polymer mixed with a dichroic dye and cured to obtain an alignment layer, the method includes:

and coating a protective layer on the alignment layer.

coating a functional layer on the alignment layer;

and coating a protective layer on the functional layer.

In a second aspect, the present application provides a polarizer, which is prepared by applying the polarizer preparation method described above, and includes:

a substrate;

a polyimide layer disposed on the substrate;

an alignment layer disposed on the polyimide layer, the alignment layer including a liquid crystal polymer mixed with a dichroic dye;

and the protective layer is arranged on the alignment layer.

In some embodiments, the polarizer further comprises a protective layer disposed on the alignment layer.

In some embodiments, the polarizer further comprises at least one functional layer disposed between the alignment layer and the protective layer.

In a third aspect, the present application provides a display device comprising a polarizer according to any of the above.

According to the preparation method of the polarizer, the polarizer and the display device, the corresponding polyimide layer and the corresponding alignment layer are obtained by coating different solutions and then baking and curing, and compared with the polyimide layer and the alignment layer obtained by adhering thin films, the thickness of the polarizer is thinner, so that the thickness of the finally obtained polarizer is thinner.

Drawings

The technical solution and other advantages of the present application will become apparent from the detailed description of the embodiments of the present application with reference to the accompanying drawings.

FIG. 1 is a schematic flow chart illustrating a method for manufacturing a polarizer according to an embodiment of the present disclosure;

FIG. 2 is a schematic flow chart illustrating a method for manufacturing a polarizer according to an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a polarizer according to an embodiment of the present application.

Reference numerals:

1. a substrate; 2. a polyimide layer; 3. an alignment layer; 4. a functional layer; 5. a protective layer; 6. a heating device; 7. a flow disturbing device.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the present application and to simplify the description, and are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed in a particular orientation, and be operated in a particular orientation, and thus are not to be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as the case may be.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise direct contact of the first and second features, or may comprise contact of the first and second features not directly but through another feature in between. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application. Further, the present application may repeat reference numerals and/or reference letters in the various examples for simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or arrangements discussed. In addition, examples of various specific processes and materials are provided herein, but one of ordinary skill in the art may recognize the application of other processes and/or the use of other materials.

Referring to fig. 1 and fig. 2, an embodiment of the present application provides a method for manufacturing a polarizer, including the following steps:

s11, providing a substrate 1;

s12, coating a polyimide layer 2 on the substrate 1;

and S13, coating a liquid crystal polymer mixed with a dichroic dye on the polyimide layer 2, and curing to obtain an alignment layer 3.

Specifically, the substrate 1 may be a Thin Film Transistor (TFT) substrate 1 (TFT substrate 1) and/or a Color Filter (CF) substrate 1. The polyimide layer 2 is coated on the substrate 1, and the thickness of the polyimide layer 2 obtained by coating polyimide and then baking is thinner in this embodiment than the polyimide layer 2 formed by pasting a film layer.

In addition, a liquid crystal polymer mixed with dichroic dyes is coated on the polyimide layer 2, and cured to obtain an alignment layer 3, and finally, the prepared polarizer is obtained. The liquid crystal polymer mixed with the dichroic dye is obtained by doping and dissolving the dichroic dye in the liquid crystal material, so that the arrangement of the dichroic dye molecules is arranged along the axial direction of the liquid crystal material, and the ratio of the dichroic dye to the liquid crystal material is set according to different requirements, which is not specifically limited in this embodiment.

In the embodiment, the polyimide layer 2 and the alignment layer 3 are obtained by coating different solutions and then baking and curing, and compared with the polyimide layer 2 and the alignment layer 3 obtained by adhering thin films, the thickness of the obtained polarizer is thinner, so that the thickness of the finally obtained polarizer is thinner.

In one embodiment, a first polyimide layer is obtained by coating a polyimide on a substrate 1 and first baking, i.e., pre-baking, at a first temperature. The first temperature is in the range of 80-130 c and may be generated by heating, by hot plate or infrared, or by baking, in which case the pre-baking may also be referred to as pre-curing. The primary purpose of the first temperature is to partially evaporate the solvent in the polyimide to facilitate subsequent polymerization. Since the polyimide is in a solution state, the composition contains 80 to 90wt% of a solvent in addition to the polyimide oligomer or a mixture of the polyimide oligomer and the polyimide acid. The solvent soluble, often oligomeric, requires partial evaporation of the solvent before polymerization can be initiated at subsequent elevated temperatures to form the polymer. In addition, the pre-baking time can last for 100 to 180 seconds.

Placing the pre-baked substrate 1 coated with the first polyimide layer in a closed space, simultaneously placing a cyclizing agent, heating the first polyimide layer and the cyclizing agent at a second temperature, generating steam after the cyclizing agent is heated, contacting the steam with the film surface of the first polyimide layer, adsorbing the steam on the film surface to perform cyclization reaction to obtain a second polyimide layer, and performing hot solvent annealing to enhance the cyclization ratio of the surface of the post-baked second polyimide layer. The second temperature may range from 220 to 240 ℃. The second temperature is the temperature of the main cure (Maincure). The main curing mainly functions to further evaporate the solvent and cause the oligomer (first polyimide layer) to undergo a polymerization reaction (or cross-linking reaction) to produce a second polyimide layer of PI polymer (also referred to as main cured material). The longer the main curing time, the more sufficient the polymerization reaction occurs, and the larger the molecular weight of the resulting polymer (i.e., imidized polyimide). The degree of progress of the main curing can be expressed in terms of imidization rate. If the time is too long or the temperature is too high, the imidization rate can reach 100% theoretically, and at this time, brittle fracture occurs on the surface of the PI film, which is likely to generate debris, and the existence of the debris affects the light emission and the alignment function of the PI alignment film, so that the imidization rate and the molecular weight of the main cured product need to be controlled within a certain range. It should be noted that the first polyimide layer and the second polyimide layer are for convenience of distinguishing the polyimide layers 2 at different heating stages, and should not be understood as being coated with a new polyimide layer 2.

In view of the above, the main purpose of the pre-curing is to evaporate the solvent, but it is also possible that some polymerization may occur. The main purpose of the main cure is to allow polymerization to occur, but at the same time the solvent continues to evaporate due to the higher temperature. After the main cure is complete, the solvent is evaporated and a solid remains.

Under the same alignment condition, the anisotropy of light is improved, and the alignment capability is enhanced. The alignment direction of the liquid crystal in the second polyimide layer is more uniform, the polarization intensity of the coating type polarizer is increased after UV curing, and the thickness of the required second polyimide layer is reduced. And finally, aligning the second polyimide layer to obtain the polyimide layer 2. The alignment includes a process of irradiation with polarized ultraviolet light and a post-heating process. The main function of irradiation with polarized ultraviolet light is to cause the imidized polyimide high polymer (second polyimide layer) to be selectively photodegraded under the irradiation of ultraviolet light, and anisotropy occurs. The anisotropy of the second polyimide layer enables the liquid crystal molecules to form an anisotropic alignment capability, thereby aligning the liquid crystal molecules, i.e., achieving the alignment effect of the second polyimide layer. The main function of the post-heating process is to remove the photo-degraded products.

The temperature of the post-heating process is greater than or equal to the first temperature and is 50 ℃ to 80 ℃ less than the second temperature. Since the post-heating process is mainly to remove the photo-degraded products, it needs to be lower than the second temperature for the main curing, otherwise the main curing process will occur. The post-heating process cannot be too low, and if it is too low, it is difficult to remove the photo-degraded product, and therefore, the temperature of the post-heating process is adjusted to be greater than or equal to the first temperature.

In one embodiment, the cyclizing agent is a mixture of an anhydride and pyridine. The acid anhydride is organic acid anhydride or inorganic acid anhydride. The organic acid anhydride includes acetic anhydride, propionic anhydride, phthalic anhydride, benzoic anhydride, or the like, but is not limited thereto. The inorganic acid anhydride includes nitric anhydride, sulfuric anhydride, etc., but is not limited thereto. The cyclizing agent is obtained by diluting anhydride into a pyridine solvent by 3-5 w%.

The higher the cyclization ratio of the polyimide layer 2, the greater its uv-photo-alignment capability, which can reach or even exceed the photo-alignment capability of the current polyimide layer 2 without the need for higher curing temperatures. The ultraviolet light alignment capability of the current polyimide layer 2 has a certain positive correlation with the curing temperature, and the higher the curing temperature is, the stronger the ultraviolet light alignment capability is. In order to improve the alignment ability, a higher curing temperature is required, and the higher curing temperature may cause some damage to the structure of the polyimide layer 2 itself. The application adopts the cyclizing agent, so that the stronger ultraviolet alignment capability can be obtained without higher curing temperature, and the higher the alignment capability of the polyimide layer 2 is, the better the alignment effect on liquid crystal molecules is. Thus, the present application improves the alignment capability of the polyimide layer 2 through the combined effect of the cyclizing agent and the lower curing temperature.

The cyclizing agent is applied as a vapor, however, in other embodiments, the cyclizing agent can be applied by a vapor method, such as by atomization, spraying, or the like. The liquid drops of the cyclizing agent generated by the steam method are smaller and can be more uniformly distributed on the surface of the polyimide layer 2, the temperature of the steam generated by the steam method is more controllable and more consistent, and the local overheating phenomenon occurs with a small probability, so that the cyclization reaction is more uniformly distributed on the surface of the whole polyimide layer 2, the alignment angle of the liquid crystal molecules can be more consistent by the subsequent polyimide layer 2, and the display effect of the display device is better. If the cyclization ratio of local areas is too high and the cyclization ratios of other areas are low in the cyclization process, the cyclization ratio of the surface of the whole PI alignment film is inconsistent, and the light-emitting uniformity of the LCD display device is influenced. The steam method in the embodiment of the present application can well solve the above technical problems.

The steam generation method comprises the following steps: the mixture of anhydride and pyridine is warmed to 5-10 ℃ below the boiling point of the cyclizing agent and the cyclizing agent is vaporized by disturbing the air above the liquid surface of the cyclizing agent, producing a vapor of the cyclizing agent. The steam is generated by low-temperature heating, namely the heating degree is below the boiling point of the cyclizing agent, so that the cyclizing agent can be prevented from boiling, and the cyclizing agent cannot perform cyclization due to deterioration is avoided. During low-temperature heating, the air above the cyclizing agent is disturbed to take away the stagnant vapor above the liquid surface of the cyclizing agent, so as to reduce the saturated vapor pressure above the liquid surface of the cyclizing agent, thereby enabling the cyclizing agent in the cyclizing agent liquid to form more vapor phase in the form of vapor, and smoothly acting on the surface of the polyimide layer 2.

The thermal solvent annealing by the cyclizing agent is performed in a closed space, and the generation of the cyclizing agent vapor can be realized by the following apparatus. The polyimide layer 2 is placed over the substrate 1 and is right up. Around the polyimide layer 2 several heating means 6 are placed. The heating means 6 holds a cyclisation agent liquid and is capable of heating the cyclisation agent liquid therein to a desired temperature to allow the cyclisation agent to escape from the liquid phase to form a gas. The heating device 6 heats the cyclizing agent solution to 5-10 ℃ below the boiling point.

Optionally, in some embodiments, the top of the polyimide layer 2 is provided with turbulators 7. The turbulence device 7 can disturb the airflow above the polyimide layer 2, so that the upper surface of the polyimide layer 2 can be uniformly contacted with cyclizing agent vapor. In addition, the air flow induced by the turbulent device 7 can also reduce the vapor pressure above the cyclizing agent liquid contained in the heating device 6, so that the vapor pressure is always in an unsaturated state, thereby facilitating the cyclizing agent gas to be evaporated from the cyclizing agent liquid, and thus, exposing the polyimide layer 2 to the cyclizing agent vapor.

Alternatively, in some embodiments, the flow perturbation device 7 may be a fan. However, if the rotation speed of the fan is controlled to be too high, the turbulent flow is too large, and it is difficult to achieve uniform contact of the cyclizing agent vapor with the upper surface of the polyimide layer 2. In order to keep the atmosphere of the processing chamber stable, the rotation speed of the fan is set to be 30-60 rpm.

In one embodiment, the polarizer application requires a protective layer 5 outside the cell and not on the inside, and therefore, the protective layer 5 is coated on the alignment layer 3 when the protective layer 5 is required. The protective layer 5 is PVA (polyvinyl alcohol).

In one embodiment, the polarizer may have different functional requirements under different application scenarios, and therefore the functional layer 4 may be coated between the alignment layer 3 and the protective layer 5. The functional layer 4 includes, but is not limited to, a low blue layer, an anti-reflection layer, etc., and the polarizer as shown in fig. 3 is finally obtained.

In this embodiment, different solutions are coated and then baked and cured to obtain the corresponding polyimide layer 2 and the corresponding alignment layer 3, and compared with the polyimide layer 2 and the alignment layer 3 obtained by pasting a film, the thickness of the obtained polarizer is thinner, so that the thickness of the finally obtained polarizer is thinner. In addition, the cyclization rate of the polyimide layer 2 is increased by carrying out thermal solvent annealing through a cyclizing agent, and the polarization performance of the prepared polarizer is better under the same alignment mode.

Referring to fig. 3, an embodiment of the present disclosure provides a polarizer, which is manufactured by the method for manufacturing a polarizer according to the above embodiment, and includes:

a substrate 1;

a polyimide layer 2 provided on the substrate 1;

an alignment layer 3 disposed on the polyimide layer 2, the alignment layer 3 including a liquid crystal polymer mixed with a dichroic dye;

and the protective layer 5 is arranged on the alignment layer 3.

In one embodiment, the polarizer further comprises a protective layer 5 disposed on the alignment layer 3.

In one embodiment, the polarizer further comprises at least one functional layer 4 disposed between the alignment layer 3 and the protective layer 5.

The embodiment of the application provides a display device, which comprises the polarizer in the embodiment.

In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above detailed descriptions of the polarizer preparation method, the polarizer and the display device provided in the embodiments of the present application, and the specific examples are applied herein to explain the principles and embodiments of the present invention, and the descriptions of the above embodiments are only used to help understand the method and the core ideas of the present invention; meanwhile, for those skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a polarizer, comprising:

providing a substrate;

coating a polyimide layer on the substrate;

and coating a liquid crystal polymer mixed with a dichroic dye on the polyimide layer, and curing to obtain the alignment layer.

2. The polarizer manufacturing method of claim 1, wherein the coating of the polyimide layer on the substrate comprises:

and aligning the second polyimide layer to obtain the polyimide layer.

3. The polarizer manufacturing method according to claim 2, wherein the step of coating polyimide on the substrate and baking at the first temperature to obtain the first polyimide layer comprises:

4. The polarizer manufacturing method of claim 2, wherein the first temperature is in a range of 80 to 130 ℃ and the second temperature is in a range of 220 to 240 ℃.

5. The polarizer manufacturing method according to claim 1, wherein after the polyimide layer is coated with a liquid crystal polymer mixed with a dichroic dye and cured to obtain an alignment layer, the method comprises:

and coating a protective layer on the alignment layer.

6. The method for preparing a polarizer according to claim 5, wherein after the polyimide layer is coated with a liquid crystal polymer mixed with a dichroic dye and cured to obtain an alignment layer, the method comprises:

coating a functional layer on the alignment layer;

and coating a protective layer on the functional layer.

7. A polarizer prepared by the method of preparing a polarizer according to any one of claims 1 to 6, comprising:

a substrate;

a polyimide layer disposed on the substrate;

and the protective layer is arranged on the alignment layer.

8. The polarizer of claim 7, further comprising a protective layer disposed on the alignment layer.

9. The polarizer of claim 8, further comprising at least one functional layer disposed between the alignment layer and the protective layer.

10. A display device comprising the polarizer according to any one of claims 7 to 9.