KR20070051501A - Method of making display device - Google Patents

Abstract

The present invention relates to a method of manufacturing a display device, comprising: forming a thin film transistor on an insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Dropping ink in a rotating state on the electrode surrounded by the partition wall; And drying the ink to form an organic layer. As a result, a display device having a uniform quality of the organic layer is provided.

Description

Manufacturing method of display device {METHOD OF MAKING DISPLAY DEVICE}

1 is an equivalent circuit diagram of a pixel of a display device manufactured according to the present invention;

2 is a cross-sectional view of a display device manufactured according to the present invention;

3A to 3C are cross-sectional views sequentially illustrating a method of manufacturing a display device according to a first embodiment of the present invention.

4A and 4B illustrate a method of manufacturing a display device according to a second exemplary embodiment of the present invention.

Explanation of Signs of Major Parts of Drawings

10: insulated substrate 20: thin film transistor

31: protective film 32: pixel electrode

41: partition 51: hole injection layer

52 organic light emitting layer 61 common electrode

The present invention relates to a method for manufacturing a display device, and more particularly, to a method for manufacturing a display device for rotating an ink for forming an organic layer.

Among flat panel displays, organic light emitting diodes (OLEDs) have recently been in the spotlight due to advantages such as low voltage driving, light weight, wide viewing angle, and high speed response. OLEDs are classified into a passive matrix and an active matrix according to the driving method. The passive type has a simple manufacturing process, but the power consumption increases rapidly as the display area and resolution increase. Therefore, the passive type is mainly applied to small displays. Active type, on the other hand, has a complex manufacturing process but has the advantage of realizing a large screen and high resolution.

In the active OLED, a thin film transistor is connected to each pixel region to control light emission of the organic light emitting layer for each pixel region. Pixel electrodes are located in each pixel area, and each pixel electrode is electrically separated from adjacent pixel electrodes for independent driving. An organic layer such as a hole injection layer and an organic light emitting layer is present on the pixel electrode.

The organic layer is usually formed by an ink jet method. In the inkjet method, an ink in which an organic substance is dissolved is dropped between partition walls surrounding the pixel electrode, and then the ink is dried to form an organic layer. However, the ink dropped between the partition walls is not formed to have a uniform height, there is a problem that the quality of the organic layer is uneven depending on the location.

Accordingly, an object of the present invention is to provide a method of manufacturing a display device having a uniform quality of an organic layer.

An object of the present invention is to form a thin film transistor on an insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Dropping ink in a rotating state on the electrode surrounded by the partition wall; It is achieved by a method of manufacturing a display device comprising the step of drying the ink to form an organic layer.

It is preferable to apply an electromagnetic field to the ink when the ink is dripped.

It is preferable that the ink contains a polar solvent.

The polar solvent may be isopropyl alcohol (IPA), n-butanol, γ-butyl olactone, N-methylpyridone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) and derivatives thereof, It is preferable to contain at least any one selected from the group consisting of glycol ethers such as carbitol acetate and butyl carbitol acetate.

The organic layer preferably includes at least one of a hole injection layer and an organic light emitting layer.

An object of the present invention is to form a thin film transistor on an insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Dropping ink on the electrode surrounded by the partition wall; Rotating the insulating substrate while the ink is dripped; It is also achieved by a method of manufacturing a display device comprising the step of drying the ink to form an organic layer.

The insulating substrate is preferably rotated in a plane including the plate surface of the insulating substrate.

Preferably, the insulating substrate rotates about an axis passing through the insulating substrate.

Another object of the present invention is to form a thin film transistor on an insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Forming ink in a rotating state on the electrode surrounded by the partition wall; It is also achieved by a method of manufacturing a display device comprising the step of drying the ink to form an organic layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

In the description, 'on' or 'on' means that another layer (membrane) is interposed or not interposed between the two layers (membrane), and 'just on' indicates that the two layers (membrane) are in contact with each other.

1 is an equivalent circuit diagram of a pixel in a display device manufactured according to the present invention.

A plurality of signal lines are provided in one pixel. The signal line includes a gate line for transmitting a scan signal, a data line for transmitting a data signal, and a driving voltage line for transmitting a driving voltage. The data line and the driving voltage line are adjacent to each other and disposed side by side, and the gate line extends perpendicular to the data line and the driving voltage line.

Each pixel includes an organic light emitting element LD, a switching thin film transistor Tsw, a driving thin film transistor Tdr, and a capacitor C.

The driving thin film transistor Tdr has a control terminal, an input terminal, and an output terminal. The control terminal is connected to the switching thin film transistor Tsw, the input terminal is connected to a driving voltage line, and the output terminal is an organic light emitting diode ( LD).

The organic light emitting element LD has an anode connected to the output terminal of the driving thin film transistor Tdr and a cathode connected to the common voltage Vcom. The organic light emitting element LD displays an image by emitting light having a different intensity according to the output current of the driving thin film transistor Tdr. The current of the driving thin film transistor Tdr varies in magnitude depending on the voltage applied between the control terminal and the output terminal.

The switching thin film transistor Tsw also has a control terminal, an input terminal and an output terminal, the control terminal is connected to the gate line, the input terminal is connected to the data line, and the output terminal of the driving thin film transistor Tdr. It is connected to the control terminal. The switching thin film transistor Tsw transfers a data signal applied to the data line to the driving thin film transistor Tdr according to a scan signal applied to the gate line.

The capacitor C is connected between the control terminal and the input terminal of the driving thin film transistor Tdr. The capacitor C charges and maintains a data signal input to the control terminal of the driving thin film transistor Tdr.

A display device manufactured according to the present invention will be described with reference to FIG. 2.

The display device 1 manufactured according to the present invention includes a thin film transistor 20 formed on an insulating substrate 10, a pixel electrode 32 and a pixel electrode 32 electrically connected to the thin film transistor 20. It includes the organic layer 50 formed on the.

In the drawing, although the thin film transistor 20 using amorphous silicon is illustrated, a thin film transistor using polysilicon may be used.

Looking at the display device manufactured according to the present invention in detail as follows.

The gate electrode 21 is formed on an insulating substrate 10 made of an insulating material such as glass, quartz, ceramic, or plastic.

A gate insulating layer 22 made of silicon nitride (SiNx) or the like is formed on the insulating substrate 10 and the gate electrode 21. A semiconductor layer 23 made of amorphous silicon and an ohmic contact layer 24 made of n + hydrogenated amorphous silicon heavily doped with n-type impurities are sequentially formed on the gate insulating film 22 where the gate electrode 21 is located. Here, the ohmic contact layer 24 is separated on both sides with respect to the gate electrode 21.

The source electrode 25 and the drain electrode 26 are formed on the ohmic contact layer 24 and the gate insulating film 22. The source electrode 25 and the drain electrode 26 are separated around the gate electrode 21.

The passivation layer 31 is formed on the source electrode 25, the drain electrode 26, and the semiconductor layer 23 not covered by these. The passivation layer 31 may be formed of silicon nitride (SiNx) and / or an organic layer. The protective film 31 is provided with a contact hole 27 exposing the drain electrode 26.

The pixel electrode 32 is formed on the passivation layer 31. The pixel electrode 32 is also called an anode and supplies holes to the organic emission layer 52. The pixel electrode 32 is made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and is formed by a sputtering method. The pixel electrode 32 may be patterned in a substantially rectangular shape in plan view.

A partition wall 41 is formed between each pixel electrode 32. The partition wall 41 defines a pixel area by dividing the pixel electrodes 32 and is formed on the thin film transistor 20 and the contact hole 27. The partition wall 40 also serves to prevent the source electrode 25 and the drain electrode 26 of the thin film transistor 20 from being short-circuited with the common electrode 61. The partition wall 41 may be formed of a photoresist having heat resistance and solvent resistance, such as an acrylic resin and a polyimide resin, or an inorganic material such as SiO 2 or TiO 2, and may have a two-layer structure of an organic layer and an inorganic layer.

The hole injecting layer 51 and the organic emission layer 52 are positioned on the pixel electrode 32.

As the hole injection layer 51, a mixture of polythiophene derivatives such as poly (3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) can be used.

The organic light emitting layer 52 includes a red light emitting layer 52a for emitting red light, a green light emitting layer 52b for emitting green light, and a blue light emitting layer 52c for emitting blue light.

The organic light emitting layer 52 may be formed of a polyfluorene derivative, a (poly) paraphenylene vinylene derivative, a polyphenylene derivative, a polyvinylcarbazole, a polythiophene derivative, or a perylene-based pigment, a laumine-based pigment, Rubene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, nile red, coumarin 6, quinacridone and the like can be used by doping.

Holes transferred from the pixel electrode 32 and electrons transferred from the common electrode 61 are combined in the organic emission layer 52 to form excitons, and then generate light in the process of deactivating excitons.

The hole injection layer 51 and the organic light emitting layer 52 are formed to have a uniform thickness irrespective of the distance from the partition wall 41. As a result, the shorting of the pixel electrode 32 and the common electrode 61 through the portion where the organic layer 50 is not formed is reduced.

The common electrode 61 is positioned on the partition 41 and the organic emission layer 52. The common electrode 61 is also called a cathode and supplies electrons to the organic emission layer 52. The common electrode 61 may be formed by stacking a calcium layer and an aluminum layer. At this time, it is preferable that a calcium layer having a low work function is disposed on the side close to the organic light emitting layer 52.

Since lithium fluoride increases the luminous efficiency depending on the material of the organic light emitting layer 52, a lithium fluoride layer may be formed between the organic light emitting layer 52 and the common electrode 61. When the common electrode 61 is made of an opaque material such as aluminum or silver, the light emitted from the organic emission layer 52 is emitted toward the insulating substrate 10, which is referred to as a bottom emission method.

Although not shown, the display device 1 may further include an electron transfer layer and an electron injection layer between the organic emission layer 52 and the common electrode 61. In addition, a protective film for protecting the common electrode 61, a sealing member for preventing the penetration of moisture and air into the organic layer 50 may be further included. The sealing member may be formed of a sealing resin and a sealing can.

Hereinafter, a method of manufacturing a display device according to a first embodiment of the present invention will be described with reference to FIGS. 3A to 3C.

First, as shown in FIG. 3A, the thin film transistor 20, the pixel electrode 32, and the partition wall 41 are formed on the insulating substrate 10.

The thin film transistor 20 has a channel portion made of amorphous silicon and may be manufactured by a known method.

After the thin film transistor 20 is formed, the passivation layer 31 is formed on the thin film transistor 20. When the protective layer 31 is silicon nitride, chemical vapor deposition may be used. Thereafter, the protective layer 31 is photographed to form a contact hole 27 exposing the drain electrode 26. After forming the contact hole 27, the pixel electrode 32 connected to the drain electrode 26 is formed through the contact hole 27. The pixel electrode 32 may be formed by depositing and patterning ITO by sputtering.

The partition wall 41 may be formed by coating a photosensitive material on the pixel electrode 32, followed by exposure and development.

Thereafter, as shown in FIG. 3B, the hole injection ink 55, which is a polymer solution containing a hole injection material, is dropped onto the pixel electrode 32 using an inkjet method to form the hole injection layer 51. The hole injection ink 55 may include a mixture of polythiophene derivatives such as poly (3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS), and a polar solvent in which these mixtures are dissolved. . As a polar solvent, for example, isopropyl alcohol (IPA), n-butanol, γ-butylolactone, N-methylpyridone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) And glycol ethers such as derivatives thereof, carbitol acetate and butyl carbitol acetate, and the like.

During dropping, an electromagnetic field is applied to the hole injection ink 55. The electromagnetic field is not limited thereto, but may be applied by the electromagnetic field generating device 100 positioned below the insulating substrate 10. The electromagnetic field generating device 100 may be formed of a rod-shaped iron core 110 and a coil 120 surrounding the iron core 110. Although not shown, the coil 120 is connected to a power supply.

The hole injection ink 55 includes a polar solvent, which is rotated by an electromagnetic field. As a result, the hole injection ink 55 is dripped onto the pixel electrode 32 in the rotating state, and is formed to have a uniform height on the pixel electrode 32 by the rotational force. When the hole injection ink 55 is dried, a hole injection layer 51 having a uniform thickness can be formed.

Drying the hole injection ink 55 can be performed by lowering the pressure to about 1 Torr at room temperature under a nitrogen atmosphere. If the pressure is too low, there is a risk that the hole injection ink 55 breaks rapidly. On the other hand, when the temperature is higher than or equal to room temperature, the solvent evaporation rate increases, which makes it difficult to form a film of uniform thickness, which is not preferable.

After the drying is completed, heat treatment may be performed for about 10 minutes at about 200 ° C. in nitrogen, preferably in vacuum, and the solvent or water remaining in the hole injection layer 51 is removed through this process.

3C shows that the light emitting ink 56, which is a polymer solution containing a light emitting material, is dropped onto the pixel electrode 32 on which the hole injection layer 51 is formed.

The light emitting ink 56 also contains a polar solvent and is dropped while being rotated by an electromagnetic field. Thereby, the organic light emitting layer 52 of uniform quality can be obtained.

The ink rotation by the electromagnetic field in the process of forming the organic layer 50 may be applied to only one of the hole injection layer 51 and the organic light emitting layer 52.

Nonpolar solvents insoluble to the hole injection layer 51, for example cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, tetra, to prevent re-dissolution of the hole injection layer 51 as a solvent of the luminescent ink 56 Methylbenzene and the like can be used, in which case no ink rotation is caused by the electromagnetic field. In this case, the light emitting ink 56 may be formed to have a uniform quality by using the method according to the second embodiment to be described later.

When the light emitting ink 56 is dried to form the organic light emitting layer 52 and the common electrode 61 is formed, the display device as shown in FIG. 2 is completed.

Hereinafter, a method of manufacturing a display device according to a second exemplary embodiment of the present invention will be described with reference to FIGS. 4A and 4B.

4A shows a state in which the hole injection ink 55 is dripped onto the pixel electrode 32 between the partition walls 41. The hole injection ink 55 has a high central portion on the pixel electrode 32 and a low portion near the partition 41. When dried in this state, the quality of the hole injection layer 51 becomes uneven due to the height difference.

4B shows that the insulating substrate 10 is rotated in the state where the dropping of the hole injection ink 55 is completed. The insulator substrate 10 is rotated by the spin apparatus 200, which is connected to the seating table 210 and the seating table 210 on which the insulator substrate 10 is seated to connect the seating table 210. Rotating member 220 to rotate. Although not shown, the rotating member 220 is connected to a rotating device such as a motor. As the spin device 200, a device used for spin coating an organic layer may be used.

Rotation of the insulating substrate 10 is performed in a state in which the level of the insulating substrate 10 is maintained horizontally. Due to the rotation of the insulating substrate 10, the hole injection ink 55 is formed at a uniform height. When the hole injection ink 55 is dried in this state, the hole injection layer 51 of uniform quality can be obtained. The organic light emitting layer 52 can also be formed in a similar manner.

Unlike the first embodiment, the method of rotating the insulating substrate 10 has an advantage of not being affected by the polarity of the ink solvent.

Although some embodiments of the invention have been shown and described, those skilled in the art will recognize that modifications can be made to the embodiments without departing from the spirit or principles of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, a method of manufacturing a display device having a uniform quality of an organic layer is provided.

Claims (9)

Forming a thin film transistor on the insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Dropping ink in a rotating state on the electrode surrounded by the partition wall; Drying the ink to form an organic layer. The method of claim 1, And applying an electromagnetic field to the ink during the dropping of the ink. The method of claim 2, The ink is a manufacturing method of a display device, characterized in that it comprises a polar solvent. The method of claim 3, The polar solvent may be isopropyl alcohol (IPA), n-butanol, γ-butyl olactone, N-methylpyridone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) and derivatives thereof, And at least one selected from the group consisting of glycol ethers such as carbitol acetate and butyl carbitol acetate. The method of claim 1, The organic layer may include at least one of a hole injection layer and an organic light emitting layer. Forming a thin film transistor on the insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Dropping ink on the electrode surrounded by the partition wall; Rotating the insulating substrate while the ink is dripped; Drying the ink to form an organic layer. The method of claim 6, And the insulating substrate rotates in a plane including the plate surface of the insulating substrate. The method of claim 7, wherein And the insulating substrate is rotated about an axis passing through the insulating substrate. Forming a thin film transistor on the insulating substrate; Forming an electrode electrically connected to the thin film transistor; Forming a partition wall surrounding the electrode; Forming ink in a rotating state on the electrode surrounded by the partition wall; Drying the ink to form an organic layer.

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