WO2007078090A1

WO2007078090A1 - Method and apparatus for encapsulating organic light emitting diodes

Info

Publication number: WO2007078090A1
Application number: PCT/KR2006/005782
Authority: WO
Inventors: Chang-Son Choi; Hyug-Dong Yoo; Taek-Sang Kang; Bon-Yee Ku
Original assignee: Doosan Mecatec Co., Ltd.
Priority date: 2005-12-30
Filing date: 2006-12-27
Publication date: 2007-07-12
Also published as: TW200725961A; CN101352100B; KR100689199B1; CN101352100A

Abstract

The present invention relates to a method and apparatus for encapsulating an organic light emitting diode. The encapsulating method for encapsulating a glass substrate with a cover according to the present invention comprises the steps of (a) carrying the glass substrate with an organic light emitting layer formed thereon and the cover with an adhesive made of an ultraviolet curable resin applied thereto and fixing the glass substrate and the cover to upper and lower stages, respectively; (b) causing the glass substrate and the cover to be brought into close contact with and primarily compressed toward each other by means of a relative movement between the upper and lower stages; and (c) secondarily compressing the glass substrate and the cover toward each other by means of a pressure difference produced by increasing pressure in the chamber in a state where the glass substrate and the cover are brought into close contact with each other. In particular, the step (b) is executed while the chamber is in a vacuum state, and the step (c) is executed by changing the chamber from the vacuum state to an atmospheric or positive pressure state.

Description

METHOD AND APPARATUS FOR ENCAPSULATING ORGANIC LIGHT EMITTING DIODES

Technical Field

[1] The present invention relates to a method and apparatus for encapsulating an organic light emitting diode, and more particularly, to a method and apparatus for encapsulating an organic light emitting diode wherein a pressure difference between an inner space, which is defined between a glass substrate and a cover, and the other space in a processing chamber excluding the inner space is induced in a state where the glass substrate and the cover are brought into primary contact with each other, so that the glass substrate and the cover can be compressed toward each other due to the pressure difference. Background Art

[2] Recently, with the rapid advancement of information communication technologies and the expansion of relevant markets, a flat panel display (FPD) has been widely used as a display device. Typically, a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED) and the like have been used as a flat panel display.

[3] Among them, the OLED has been widely used as a next generation display device, because there are very excellent advantages in that the OLED has a fast response time, high brightness, and lower power consumption than a conventional LCD, is lightweight, can be manufactured into an ultra-thin structure without need for an additional backlight, and the like.

[4] Such an OLED is obtained by sequentially forming an anode, an organic thin film and a cathode on a substrate. If a voltage is applied between the anode and the cathode layers, an adequate energy difference is created across the organic thin film such that light can be simultaneously emitted from the organic thin film. That is, the excitation energy remaining after injected electrons and holes are recombined with each other can be formed into light. At this time, since the wavelength of light can be adjusted in accordance with an amount of dopants in the organic material, full-color implementation can be made.

[5] Although the specific structure of the OLED has not been illustrated in the accompanying drawings, it is formed by sequentially laminating an anode, a hole injection layer, a hole transfer layer, a light emitting layer, an electron transfer layer, an electron injection layer and a cathode onto a substrate. In this case, the anode is primarily made of indium tin oxide (ITO) which has lower surface resistance and excellent transmissivity. The organic thin film is composed of a plurality of layers such as the hole injection layer, the hole transfer layer, the light emitting layer, the electron transfer layer and the electron injection layer in order to improve the light emitting efficiency of the OLED, wherein the light emitting layer is made of an organic material such as AIq₃, TPD, PBD, m-MTDATA, TCTA or the like. Further, the cathode is made of a LiF-Al metal film. Furthermore, since the organic thin film is very weak to moisture and oxygen in the air, a cover has been encapsulated to increase lifetime of the OLED.

[6] A structure of an OLED 100 encapsulated with a cover 120 made of a glass material will be described with reference to Fig. 1.

[7] As shown in the figure, a desiccant 121 is attached to the inside of the cover 120 to reduce effects of external moisture/oxygen and gas generated from an organic light emitting layer 111 in the organic light emitting diode 100. The cover 120 has a planar rectangular shape, and each edge end of the cover 120 is formed with an extension protruding in one direction by a predetermined height. An adhesive 122 is applied to form a seal line with a predetermined width on an end surface of the extension, so that the cap cover 120 can be bonded to a glass substrate 110 with the organic light emitting layer 111 deposited thereon to prevent the moisture and oxygen from being permeated from the outside. At this time, a predetermined spaced gap 123 is defined between the cover 120 and the glass substrate 110.

[8] A conventional apparatus 200 for encapsulating an organic light emitting diode will be described with reference to Fig. 2. As shown in the figure, the conventional encapsulating apparatus 200 comprises a processing chamber 210 in which a bonding process is performed in a state where a vacuum atmosphere is maintained; an upper stage 220 formed with vacuum lines 221 for vacuum holding the glass substrate 110 in the processing chamber 210; an operating unit 223 and a ball screw 222 for moving the upper stage 220 up or down in a vertical direction; and a lower stage 240 which is positioned at a lower portion of the processing chamber 210 and on which an ultraviolet (UV) shielding mask 230 and the cover 120 with the adhesive 122 applied thereon are laminated. The ball screw 222 may be formed within the bellows in order to maintain the airtightness of the processing chamber 210. Although it has not been illustrated, an operating unit capable of moving the lower stage 240 up or down may be provided.

[9] Hereinafter, a conventional encapsulating method will be described with reference to Figs. 3 and 4. As shown in Fig. 3, the operating unit 223 is driven to move the upper stage 220 downward such that the glass substrate 110 can come into close contact with the cover 120. In such a state, if the upper stage 220 is further moved downward such that the glass substrate 110 can be further compressed, the glass substrate 110 and the cover 120 can be further brought into close contact with each other to form an adhesive layer 122a as shown in Fig. 4. Then, an UV lamp (not shown) is irradiated to cure the adhesive layer 122a such that the glass substrate 110 and the cover 120 can be bonded to each other.

[10] The aforementioned conventional process of bonding the glass substrate and the cover should have been performed in the processing chamber at a vacuum atmosphere in order to prevent bubble generation from the contact portion between the glass substrate and the cover.

[11] However, in a case where the bonding process is performed in a vacuum atmosphere of the processing chamber, the glass substrate and the cover should be compressed only by means of the upper stage, i.e. due to a mechanical compression means. Therefore, there is a problem in that it is impossible to perform uniform compression between the glass substrate and the cover throughout the entire surfaces. Disclosure of Invention Technical Problem

[12] The present invention is conceived to solve the aforementioned problem in the prior art. Accordingly, an object of the present invention is to provide a method and apparatus for encapsulating an organic light emitting diode wherein a pressure difference between an inner space, which is defined between a glass substrate and a cover, and the other space in a processing chamber excluding the inner space is induced in a state where the glass substrate and the cover are brought into primary contact with each other, so that the glass substrate and the cover can be compressed toward each other due to the pressure difference. Technical Solution

[13] According to an aspect of the present invention for achieving the object, there is provided a method for encapsulating a glass substrate with a cover, which comprises the steps of (a) carrying the glass substrate with an organic light emitting layer formed thereon and the cover with an adhesive made of an ultraviolet curable resin applied thereto and fixing the glass substrate and the cover to upper and lower stages, respectively; (b) causing the glass substrate and the cover to be brought into close contact with and primarily compressed toward each other by means of a relative movement between the upper and lower stages; and (c) secondarily compressing the glass substrate and the cover toward each other by means of a pressure difference produced by increasing pressure in the chamber in a state where the glass substrate and the cover are brought into close contact with each other. Preferably, the step (b) is executed while the chamber is in a vacuum state, and step (c) is executed by changing the chamber from the vacuum state to an atmospheric or positive pressure state. [14] According to another aspect of the present invention, there is provided an apparatus for encapsulating a glass substrate with a cover, which comprises a processing chamber in which the glass substrate with an organic light emitting layer formed thereon and the cover with an adhesive made of an ultraviolet curable resin applied thereto are bonded to each other; a substrate holding unit for fixing the glass substrate in the processing chamber; and a cover holding unit for fixing the cover in the processing chamber. More specifically, the substrate holding unit may include an upper stage placed in the processing chamber, an operating unit for moving the upper stage up or down, and a chuck formed with at least one vacuum line to vacuum hold the glass substrate and placed below the upper stage to be movable up or down together with the upper stage.

[15] The encapsulating apparatus of the present invention may further comprise a secondary operating unit for moving the chuck up or down separately from the upper stage.

Brief Description of the Drawings

[16] Fig. 1 is a sectional view showing a structure of a conventional organic light emitting diode.

[17] Fig. 2 is a sectional view showing a conventional apparatus for encapsulating the organic light emitting diode.

[18] Figs. 3 and 4 are views illustrating an operating state of the encapsulating apparatus shown in Fig. 2.

[19] Fig. 5 is a sectional view showing an encapsulating apparatus according to the present invention.

[20] Figs. 6 to 8 are views illustrating an operating state of the encapsulating apparatus shown in Fig. 4.

[21] Fig. 9 is a flowchart illustrating an encapsulating process according to the present invention. Best Mode for Carrying Out the Invention

[22] Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings.

[23] Referring to Fig. 5, an apparatus 10 for encapsulating an organic light emitting diode according to the present invention comprises a processing chamber 11 in which a pressure can be controlled to vacuum, atmospheric pressure or positive pressure; a substrate holding unit 20 for fixing a glass substrate 110 in the processing chamber 11 ; and a cover holding unit 40 on which a UV shielding mask 30 and a cover 120 are sequentially laminated at a lower portion of the processing chamber 11.

[24] The substrate holding unit 20 includes an upper stage 21 which moves up or down in the processing chamber 11 by an operating unit 21b and a ball screw 21a; and a chuck 22 which is formed with a plurality of vacuum lines 22a and formed below the upper stage 21 to be movable together with the upper stage 21. Specifically, the chuck 22 may be moved together with the upper stage 21, but it may be connected to retractable bellows 22b such that it can be moved up or down separately from the upper stage 21. In the latter case, a secondary operating unit (not shown) capable of retracting the bellows 22b may be provided.

[25] The cover holding unit 40 is formed with a plurality of vacuum lines 41 for vacuum holding the mask 30 and the cover 120. The UV shielding mask 30 is also formed with a plurality of vacuum holes corresponding to the vacuum lines 41. Accordingly, the cover holding unit 40 can vacuum hold the ultraviolet shielding mask 30 and the cover 120 at the same time.

[26] Meanwhile, in order to vacuum hold the glass substrate 110, the UV shielding mask

30 and the cover 120 as described above, it is apparent that the glass substrate 110, the UV shielding mask 30 and the cover 120 should be held at a degree of vacuum greater than the degree of vacuum within the processing chamber 11.

[27] Preferably, the ball screw 21a is formed within the bellows (not shown) to maintain the processing chamber 11 at an airtight state. Although it has not been illustrated, an additional operating unit capable of moving the cover holding unit 40 up or down may be provided.

[28] Hereinafter, an encapsulating method of the present invention will be described with reference to Figs. 6 to 8. As shown in Fig. 6, the operating unit 21b is operated to move the upper stage 21 downward (in an arrow direction shown in the figure) in a state where the processing chamber 11 is in a vacuum state. Then, the chuck 22 and the glass substrate 110 fixed thereto are also moved downward, and thus, the glass substrate 110 can be brought into close contact with the cover 120.

[29] At this time, as shown in Fig. 7, the secondary operating unit and the bellows 22b are used to further move the chuck 22 downward (in an arrow direction shown in this figure) separately from the upper stage 21 such that the glass substrate 110 can be further brought into contact with the cover 120. Then, an adhesive layer 122a is formed between the glass substrate 110 and the cover 120. At this time, it is apparent that the processing chamber 11 is still kept at the vacuum state.

[30] Next, if an atmospheric or positive pressure state is built in the processing chamber

11, a pressure difference between an inner space defined by the glass substrate 110 and the cover 120 and the other space in the processing chamber excluding the inner space is created as shown in Fig. 8. Such a pressure difference causes the glass substrate 110 and the cover 120 to be further compressed toward each other (in an arrow direction as shown in Fig. 8). Specifically, since not a mechanical compression but a compression due to the pressure difference is applied, the glass substrate 110 and the cover 120 can be further compressed toward and brought into close contact with each other throughout the entire surfaces.

[31] Hereinafter, the encapsulating method of the present invention will be described with reference to. Fig. 9.

[32] First, the glass substrate is carried into the processing chamber and then vacuum held by the chuck provided below the upper stage (step SIl). Next, the cover is also carried into the processing chamber (step S 12). Then, the UV shielding mask is brought into close contact with an upper surface of the cover and vacuum held together with the cover by means of the cover holding unit (step S 13).

[33] Next, the upper stage is moved downward and the chuck is further moved downward such that the glass substrate can be brought into close contact with the cover (step S 14). Of course, this step is executed in a state where the processing chamber is in a vacuum state.

[34] At this state, the processing chamber is returned to the atmospheric or positive pressure state such that the pressure difference between the inner space defined by the glass substrate and the cover and the other space in the processing chamber excluding the inner space can be created (step S 15). Such a pressure difference can cause the glass substrate and the cover to be uniformly compressed toward and brought into close contact with each other throughout the entire surfaces.

[35] Next, after the glass substrate and the cover have been uniformly compressed toward each other due to the pressure difference, UV light is irradiated to cure the adhesive (step S 16).

[36] The glass substrate and cover bonded together according to the aforementioned method of the present invention is carried out of the processing chamber (step S 17). Industrial Applicability

[37] According to the present invention, there is an advantage in that if a pressure difference between an inner space, which is defined by a glass substrate and a cover, and the other space in the processing chamber excluding the inner space can be created in a state where the glass substrate and the cover are brought into primary contact with each other, the glass substrate and the cover can be compressed toward each other due to the pressure difference.

[38] Accordingly, the glass substrate and the cover can be uniformly compressed toward each other throughout the entire surfaces by means of a compression due to the pressure difference as well as a mechanical compression. Therefore, the glass substrate and the cover can be further brought into close contact with each other.

Claims

[1] An organic light emitting diode encapsulation method for encapsulating a glass substrate with a cover, the method comprising the steps of:

(a) carrying the glass substrate with an organic light emitting layer formed thereon and the cover with an adhesive made of an ultraviolet curable resin applied thereto, and fixing the glass substrate and the cover to upper and lower stages, respectively;

(b) causing the glass substrate and the cover to be brought into close contact with and primarily compressed toward each other by means of a relative movement between the upper and lower stages; and

(c) secondarily compressing the glass substrate and the cover toward each other by means of a pressure difference produced by increasing pressure in the chamber in a state where the glass substrate and the cover are brought into close contact with each other.

[2] The method as claimed in claim 1, wherein step (b) is executed while the chamber is in a vacuum state, and step (c) is executed by changing the chamber from the vacuum state to an atmospheric or positive pressure state. [3] The method as claimed in claim 1, wherein in step (a), the glass substrate and the cover are vacuum held onto the upper and lower stages, respectively. [4] The method as claimed in claim 1, further comprising the step of, after step (a), bringing an ultraviolet shielding mask into close contact with the cover. [5] An organic light emitting diode encapsulation apparatus for encapsulating a glass substrate with a cover, the apparatus comprising: a processing chamber in which the glass substrate with an organic light emitting layer formed thereon and the cover with an adhesive made of an ultraviolet curable resin applied thereto are bonded to each other; a substrate holding unit for fixing the glass substrate in the processing chamber; and a cover holding unit for fixing the cover in the processing chamber. [6] The apparatus as claimed in claim 5, wherein the substrate holding unit includes: an upper stage placed in the processing chamber; an operating unit for moving the upper stage up or down; and a chuck formed with at least one vacuum line to vacuum hold the glass substrate and placed below the upper stage to be movable up or down together with the upper stage. [7] The apparatus as claimed in claim 6, further comprising a secondary operating unit for moving the chuck up or down separately from the upper stage. [8] The apparatus as claimed in claim 5, wherein the cover is vacuum held by the cover holding unit.