KR101130937B1 - Method for fabricating flexible display - Google Patents

Abstract

In the manufacturing method of the flexible display of the present invention, the same heat treatment process is performed on the upper and lower plastic substrates before the bonding process, so that the substrate warpage due to the stress difference in the substrate due to the process of each of the upper and lower substrates is processed. In order to minimize, performing a color filter process to form a color filter and a black matrix on the first substrate; Forming a gate line, a data line, and a switching device on the second substrate by performing an array process; Forming an alignment layer on surfaces of the first substrate subjected to the color filter process and the second substrate subjected to the array process; The first substrate and the second substrate on which the alignment layer is formed are simultaneously heat-treated at the same temperature to the first substrate and the second substrate in order to minimize the stress difference generated during the respective color filter process and the array process. step; And bonding the first and second substrates subjected to the heat treatment, wherein the heat treatment is equal to the temperature of the unit process proceeding at the highest temperature among the unit processes constituting the color filter process and the array process. It is characterized by proceeding at a temperature.

Flexible Display, Plastic Substrate, Heat Treatment Process

Description

Manufacturing method of flexible display {METHOD FOR FABRICATING FLEXIBLE DISPLAY}

1A and 1B are exemplary diagrams illustrating a general flexible display.

2 is an exemplary view schematically showing a cross section of a flexible display according to an embodiment of the present invention.

3 is a flow chart schematically showing a manufacturing process of a flexible display according to an embodiment of the present invention.

Figure 4 is a flow chart showing in detail the progress of the heat treatment process and the cell gap process shown in FIG.

DESCRIPTION OF REFERENCE NUMERALS

105,110: plastic substrate 120: liquid crystal layer

130: thread pattern

The present invention relates to a method of manufacturing a flexible display, and more particularly, a flexible display capable of manufacturing a thinner panel by arranging a thin film transistor (TFT) device layer using a plastic substrate or forming a color filter layer. It relates to a manufacturing method of.

In today's information society, display is more important as a visual information transmission medium, and in order to gain a major position in the future, it is necessary to satisfy requirements such as low power consumption, thinness, light weight, and high definition.

The display itself has a cathode ray tube (CRT), an electroluminescent element (EL), a light emitting diode (LED), a vacuum fluorescence display (VFD), an electric field It can be divided into emission type such as Field Emission Display (FED), Plasma Display Panel (PDP), and non-emission type such as Liquid Crystal Display (LCD). .

Meanwhile, a flexible display, which is not damaged even when the display device is folded or rolled up, is expected to emerge as a new technology in the display field. At present, there are various obstacles to the implementation of flexible displays, but with the development of technology, liquid crystal display (LCD), organic light emitting diodes (OLED), and electrophoretic technologies have become mainstream. Will be achieved.

Hereinafter, the flexible display will be described in detail with reference to the accompanying drawings.

1A and 1B are exemplary diagrams illustrating a general flexible display.

The flexible display is called a display, which is implemented in a thin substrate such as plastic and is not damaged even when folded or rolled like paper, and is one of the next-generation displays, and is now an organic EL that can be made thinner than 1 mm. (Organic Light Emitting Diodes; OLED) and liquid crystal display devices are promising.

The organic EL has excellent visibility even in dark places or outside light because the device itself emits light, and the response speed, which is an important criterion for determining the performance of a mobile display, is the fastest among existing displays. You can make the perfect video.

In addition, the organic EL has an ultra-thin design and can slim down various mobile devices such as mobile phones.

On the other hand, the liquid crystal display device is an apparatus for expressing an image using optical anisotropy of liquid crystal. It is attracting attention as a display device.

In the liquid crystal display device, in order to implement a flexible display, it is necessary to secure flexibility of the liquid crystal display panel, and in order to secure such substrate flexibility, a plastic substrate is used instead of a conventional glass substrate.

However, the plastic substrate is well bent, thermal stability is relatively weak compared to the glass substrate.

Therefore, when the process of bonding the upper and lower substrates, the difference between the bending of the substrate occurs due to the difference in stress in the substrate, and this causes a failure in adhesion or detachment or misalignment after the upper and lower substrates are bonded. And cause related defects such as light leakage.

An object of the present invention is to provide a method of manufacturing a flexible display that can proceed the bonding process of the upper and lower substrates without bending the substrate by performing the same heat treatment process on the upper and lower plastic substrates. do.

Other features and objects of the present invention will be described in detail in the configuration and claims of the invention below.

In order to achieve the above object, the manufacturing method of the flexible display of the present invention comprises the steps of forming a color filter and a black matrix on the first substrate by a color filter process; Forming a gate line, a data line, and a switching device on the second substrate by performing an array process; Forming an alignment layer on surfaces of the first substrate subjected to the color filter process and the second substrate subjected to the array process; The first substrate and the second substrate on which the alignment layer is formed are simultaneously heat-treated at the same temperature to the first substrate and the second substrate in order to minimize the stress difference generated during the respective color filter process and the array process. step; And bonding the first and second substrates subjected to the heat treatment, wherein the heat treatment is equal to the temperature of the unit process proceeding at the highest temperature among the unit processes constituting the color filter process and the array process. It is characterized by proceeding at a temperature.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the manufacturing method of the flexible display of the present invention.

FIG. 2 is an exemplary view schematically illustrating a cross section of a flexible display according to an exemplary embodiment of the present invention, and illustrates a flexible liquid crystal display panel manufactured using a plastic substrate.

As shown in the figure, the liquid crystal display panel has a uniform cell gap between the array substrate 110 on which a thin film transistor array is formed and the color filter substrate 105 on which a color filter is formed. The liquid crystal layer 120 is formed in the cell gap between the array substrate 110 and the color filter substrate 105.

In this case, the alignment layers 109 and 119 are formed on the surfaces of the array substrate 110 and the color filter substrate 105 facing each other, and rubbing is performed so that the liquid crystal molecules (not shown) of the liquid crystal layer 120 are fixed. To be arranged.

In addition, the array substrate 110 and the color filter substrate 105 are bonded by a seal pattern 130 formed along the outer edge of the pixel portion, and the outer surfaces of the array substrate 110 and the color filter substrate 105 bonded together. The polarizing plates 104 and 114 and retardation plates (not shown) are provided, and by selectively configuring a plurality of such components, the liquid crystals having high luminance and contrast characteristics by changing the light traveling state or the refractive index are changed. The display panel is constructed.

Although not shown in the drawing, a plurality of pixels defined by gate lines and data lines are formed on the array substrate 110, and a driving device such as a thin film transistor is formed in each pixel.

The color filter substrate 105 includes a black matrix 106 for preventing light leakage from occurring on the gate line, data line, and thin film transistor regions formed on the array substrate 110. The color filter layer 107 of red (R), green (G), and blue (B) color is formed to realize actual colors.

In addition, a pixel electrode 118 and a common electrode 108 are formed on the array substrate 110 and the color filter substrate 105, respectively, and are described above on the pixel electrode 118 and the common electrode 108. Similarly, alignment layers 109 and 119 for orienting liquid crystal molecules of the liquid crystal layer 120 are coated.

Meanwhile, the liquid crystal display panel configured as described above uses a plastic substrate instead of a glass substrate as the array substrate 110 and the color filter substrate 105 in order to implement a flexible display.

Here, the base film of the plastic substrate is preferably formed of any one selected from polyethylene terephthalate (PET), polyethylenapthanate (PEN), polycarbonate (PC), polyimide (PI) and polynorborneen (PNB).

A heat resistance improving polymer film and a protective film may be formed on one or both surfaces of the base film, and the protective film may include a solvent barrier that protects the base film and the heat resistance improving polymer film from moisture, and a gas barrier that protects the gas film from oxygen or air. And so on.

The manufacturing method of the liquid crystal display panel according to the present embodiment configured as described above is largely an array process for forming an array substrate, a color filter process for forming a color filter substrate, and a unit liquid crystal display panel by combining the array substrate and the color filter substrate. It is made of a cell process to form a, looking at this in more detail as follows.

3 is a flowchart schematically illustrating a manufacturing process of a flexible display according to an exemplary embodiment of the present invention, and illustrates an example of a manufacturing process of a liquid crystal display panel.

First, a thin film transistor, which is a switching element connected to the gate line and the data line, is formed on the transparent flexible plastic substrate to form a plurality of gate lines and data lines arranged vertically and horizontally to define a plurality of pixel regions. Form. In addition, the pixel electrode is connected to the thin film transistor through the array process and drives the liquid crystal layer as a signal is applied through the thin film transistor. Meanwhile, in the transverse electric field mode, the pixel electrode and the common electrode forming the horizontal electric field are formed together in the liquid crystal layer through the array process (S110).

In this case, the material to be used as the wiring layer such as the gate line and the data line may be a metal such as aluminum, tungsten, chromium, as well as polyaniline (polyanilne) or PEDOT: PSS (polygon doped with polyethylenediothiophene (PSS) Conductive polymer materials such as ethyledioxythiophene (PEDOT) can also be used.

In addition, when the flexible plastic substrate is applied as described above, an organic insulating layer may be used as a gate insulating layer, and the organic insulating layer may be PVP (poly-4-vinylphenol), PMMA (poly- (methyl methacrylate)), or ammonium bichromate. It is preferable to use any one selected from polyvinylalchol (PVA), polyimide, and parylene to which ammonuym dichromate is added.

A color matrix is formed on the color filter substrate to distinguish between a color filter composed of red, green, and blue subcolor filters that implement color by a color filter process, and the subcolor filter, and to block light passing through the liquid crystal layer. In operation S120, a common electrode facing the pixel electrode of the array substrate is formed on the substrate on which the black matrix and the color filter are formed.

Subsequently, an alignment layer is applied to the array substrate and the color filter substrate, respectively, and then the alignment layer is provided to provide alignment control force or surface fixation force (ie, pretilt angle and alignment direction) to the liquid crystal molecules of the liquid crystal layer formed between the two substrates. Orientation treatment. In this case, a method of rubbing or photoalignment may be applied as the alignment treatment method (S130).

In this case, as described above, the array substrate and the color filter substrate are manufactured through different array processes and color filter processes, respectively, and thus have a stress difference in the substrate. Thus, the substrates are detached again during the cell gap process, which will be described later. There is a problem that is fixed or misaligned.

Accordingly, in the present invention, in order to improve the warpage problem as described above, the substrates are subjected to heat treatment at the same temperature in the pre-stage of silver coating and seal printing processes for bonding the array substrate and the color filter substrate together. The heat treatment process is performed, which will be described in detail with reference to FIG. 4.

FIG. 4 is a flowchart specifically illustrating a process of a heat treatment process and a cell gap process illustrated in FIG. 3.

As shown in the figure, in order to minimize the stress difference in the substrate according to the different processes in the step before proceeding the cell gap process (S150) is subjected to heat treatment of substantially the same temperature at the highest temperature of each process temperature ( S140).

The heat treatment condition is set to a high temperature condition of the process temperature of the array process and the color filter process to perform the heat treatment for about 1 ~ 180 minutes. For example, when the process temperature is 200 ° C. in the array process and the temperature is 150 ° C. in the color filter process, the heat treatment is performed by setting the optimum temperature time according to the high temperature of 200 ° C. in the array process.

Through such a heat treatment process, the stress difference between the array substrate and the color filter substrate can be minimized, and the substrate atmosphere can be formed in the same manner to proceed the bonding.

In order to proceed with the bonding, a silver paste is applied to the outer portion of the array substrate, the spacer is spread, and seal printing and firing are performed on the color filter substrate (S151 to S153). In this case, the spacer may be formed on the color filter substrate, and as the spacer, a column spacer (or a patterned spacer) having a shape fixed to the array substrate or the color filter substrate as the liquid crystal display panel is gradually enlarged. Can also be used.

Methods of forming the seal pattern include a method of printing with a screen mask and a method of forming a seal pattern having a desired shape by using a movable sealant dispenser.

The method of forming a seal pattern using the screen mask described above is currently the most common method because of the excellent convenience of the process. However, the screen mask method has a disadvantage in that the screen is in contact with the alignment film formed on the substrate, so that the alignment film is poor, and it is difficult to cope with the large area of the substrate. In addition, in order to form a seal pattern using the screen mask method, a sealant is applied to the entire surface of the screen on which the pattern is formed, and the seal is pushed with a rubber squeeze to print the sealant.

In the seal dispenser method, one or two syringe-type dispensers equipped with small circular or rectangular nozzles are moved to print the sealant on the seal area outside the substrate.

Thereafter, the array substrate and the color filter substrate are bonded to each other in a state where a constant cell gap is maintained by the seal pattern and the column spacer, and the sealant is cured by applying a pressure at a high temperature (S154 to S156).

The bonding process is a process of aligning and bonding the array substrate and the color filter substrate. The bonding process is performed by aligning the color filter substrate and the array substrate on the alignment marks of the array substrate on which the spacers are scattered, and then bonding them together. The adhesion margin is determined by the overlapping degree of the black matrix and the pixel electrode, and is generally about 5 μm, which is a cell gap level.

In addition, pressure curing is a process of curing a sealant while maintaining a constant cell gap by applying a uniform pressure and temperature to the entire substrate.

Thereafter, a cutting process of separating the cured substrate on which the cells are formed into individual cells is performed. The cutting process is a scribe (scribe) forming a cutting line on the surface of the substrate using a tungsten carbide cutting wheel on both sides of the cured substrate. ) And a break step of separating the cells into individual cells by applying a force to the cutting line.

Next, the liquid crystal is injected into the cell of the liquid crystal display panel divided into individual cells as described above to form a liquid crystal layer (S160).

Meanwhile, the method of forming the liquid crystal layer is largely divided into a vacuum injection method and a dropping method, which will be described in detail as follows.

First, in the vacuum injection method, the liquid crystal inlet of the unit liquid crystal display panel separated from the mother substrate of a large area is immersed in a container filled with liquid crystal in a chamber in which a constant vacuum is set, and then the degree of vacuum is changed. The liquid crystal is injected into the liquid crystal display panel by an external pressure difference. When the liquid crystal is filled in the liquid crystal display panel in this manner, the liquid crystal inlet is sealed to form the liquid crystal layer of the liquid crystal display panel. Therefore, when the liquid crystal layer is formed in the liquid crystal display panel through a vacuum injection method, a part of the seal pattern must be opened to have a function of the liquid crystal injection hole.

In the dropping method, a liquid crystal is dropped and dispensed into a pixel portion of a first mother substrate having a large area in which a plurality of array substrates are arranged or a second mother substrate in which a plurality of color filter substrates are disposed using a dispenser, The liquid crystal layer is formed by uniformly distributing the liquid crystal through the entire pixel portion by the pressure for bonding the first and second mother substrates together.

Therefore, when the liquid crystal layer is formed on the liquid crystal display panel by dropping, the seal pattern should be formed in a closed pattern surrounding the outer edge of the pixel portion so as to prevent the liquid crystal from leaking to the outside of the pixel portion.

The dropping method can drop the liquid crystal in a short time compared to the vacuum injection method, and even when the liquid crystal display panel is enlarged, the liquid crystal layer can be formed very quickly.

In addition, since only the required amount of liquid crystal is dropped on the substrate, the price competitiveness of the liquid crystal display panel due to the disposal of expensive liquid crystal, such as a vacuum injection method, is prevented, thereby enhancing the price competitiveness of the product.

Unlike the vacuum injection method, the liquid crystal display panel to which the drop method is applied is subjected to a cutting process of separating the unit liquid crystal panel from the large area mother substrate after the liquid crystal layer is formed.

Thereafter, the liquid crystal display panel is manufactured by performing an inspection process for covering the external appearance and electrical defect of each liquid crystal display panel (S170).

The final inspection is an automatic probe inspection for inspecting appearance and electrical defects, for example, a process of inspecting disconnection or short circuit of color filter protrusions, diagonal stains, rubbing stripes, pin holes, gate lines, and data lines.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

As described above, the method of manufacturing the flexible display according to the present invention can prevent substrate detachment and misalignment by minimizing the stress difference between upper and lower substrates according to different processes, and reduce related defects such as light leakage. .

Claims (6)

Performing a color filter process to form a color filter and a black matrix on the first substrate; Forming a gate line, a data line, and a switching device on the second substrate by performing an array process; Forming an alignment layer on surfaces of the first substrate subjected to the color filter process and the second substrate subjected to the array process; The first substrate and the second substrate on which the alignment layer is formed are simultaneously heat-treated at the same temperature to the first substrate and the second substrate in order to minimize the stress difference generated during the respective color filter process and the array process. step; And And bonding the first substrate and the second substrate subjected to the heat treatment, wherein the heat treatment is performed at the same temperature as the unit process proceeding at the highest temperature among the unit processes constituting the color filter process and the array process. Method of manufacturing a flexible display, characterized in that proceeding from. The method of claim 1, wherein the first substrate and the second substrate are formed of a flexible plastic substrate. The flexible substrate of claim 2, wherein the plastic substrate is formed of any one material selected from polyethylene terephthalate (PET), polyethylenapthanate (PEN), polycarbonate (PC), polyimide (PI), and polynorborneen (PNB). Method of manufacturing the display. delete delete The method of claim 1, wherein the heat treatment is performed for about 1 to 180 minutes under substantially the same temperature conditions.

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