KR20050003645A - Shad0w mask for organic el - Google Patents

Abstract

PURPOSE: A shadow mask is provided to allow for uniform stretching all over the shadow mask by permitting cell regions and non-cell regions to have similar Young's moduli. CONSTITUTION: A shadow mask comprises a cell array constituted by a plurality of cells(160) and formed on an effective surface of a metal plate. A plurality of apertures which do not penetrate through the metal plate are formed in non-cell regions(130,140) between the cell arrays on the effective surface and certain parts(110,120) of a non-effective surface.

Description

Shadow mask for organic EL {SHAD0W MASK FOR ORGANIC EL}

The present invention relates to a shadow mask for organic electroluminescence (EL), and more particularly to a shadow mask for organic EL having a uniform stretching.

Organic EL is a flat panel display that uses electroluminescence of organic materials. Its response speed is CRT level faster than that of light receiving devices such as LCDs (1000 times faster than LCD). Wide viewing angle (more than 160 degrees), high brightness, high brightness, low DC voltage, ultra-thin (2mm or less), simpler manufacturing process than other displays, and stable operation at low temperature At present, research on organic EL is progressing at an alarming rate and is expected to have a great impact on the display industry.

In organic EL, the electrons and holes injected through the cathode and the anode recombine into the organic thin film of the low molecular weight or polymer to form an exciton, and when the formed exciton falls from the excited state to the ground state, the fluorescent molecules of the light emitting layer in the organic thin film emit light. This forms an image.

The basic layer structure of the organic EL is shown in FIG.

As shown in FIG. 1, the organic EL includes a substrate 1, a first electrode 2, a hole transport layer (HTL) 3, a light emitting layer (EML) 4, an electron transport layer (ETL) 5, and It is composed of two electrodes (6), and may include a hole injection layer (HIL) and an electron injection layer (EIL) separately.

The substrate 1 is mostly glass, and the first electrode 2 is made of a transparent metal oxide having a high work function and emitted light to the outside as an electrode for hole injection, which is most widely used as a metal oxide. The material to be used is indium tin oxide (ITO).

As the material of the light emitting layer 4, a low molecular organic EL material such as an aluminy chinolium complex (Alq ₃ ) and anthracene, as well as a polymer organic EL material such as PPV, PT, or derivatives thereof are used.

In the organic EL layer having a single layer structure, there is no hole transport layer 3 and an electron transport layer 5, but in the case of a multilayer structure, a hole transport layer 3 and an electron transport layer 5 are added. As the hole transport layer 3, TPD, which is a diamine derivative, and 9-vinylcarbazole, which is a photoconductive polymer, are used, and an oxadiazole derivative, etc., is used as the electron transport layer 5. Due to the addition of the transport layer, the driving voltage can be reduced by a two-step injection process through which the holes and electrons are not directly injected, and the holes and electrons injected into the light emitting layer 4 pass through the light emitting layer 4 to the opposite electrode. By moving to the blockage by the transport layer it is possible to control the recombination can increase the luminous efficiency.

The second electrode 6 is an electrode for electron injection, and a metal (Ca, Mg, Al, etc.) having a small work function is used.

Next, the light emitting mechanism of the organic EL will be described with reference to FIG.

When positive voltage (+) and negative voltage (-) are applied to the first electrode 2 and the second electrode 6, holes and electrons in the metal electrodes of the positive electrode 2 and the negative electrode 6 are tunneled ( is injected into the hole injection layer 7 and the electron injection layer 8 by tunneling or hot electron emission.

Holes and electrons injected into the hole injection layer 7 and the electron injection layer 8 pass through the hole transport layer 3 and the electron transport layer 5, respectively, into the light emitting layer 4, and are positive by interaction with the phonon. And negative polarons.

As the positive and negative polarons produced migrate to the opposite electrode, the positive and negative polarons recombine to produce the flaon-exiton 9. Then, the flaon-exciter 9 falls to the ground state to be stabilized, and at this time, energy is emitted and light is emitted by the fluorescent molecules of the light emitting layer 4.

As described above, the organic EL device has a structure in which a light emitting layer is formed between the positive electrode and the negative electrode, and the negative electrode and the light emitting layer are formed in a desired pattern by using a shadow mask.

Here, the shadow mask is manufactured by processing a metal plate made of nickel, AK, or INVAR by mechanical or chemical etching. An aperture is formed on the metal plate according to an organic pattern to manufacture a shadow mask.

In order to form an organic material pattern on the glass substrate, when the shadow mask is closely attached to the substrate and the organic material is evaporated, the organic material passing through the aperture of the mask adheres to the substrate to form an organic material pattern.

Fig. 3 shows a conventional shadow mask for organic EL, wherein the shadow mask is composed of an effective surface of the thick dotted line inner portion and an invalid surface of the other outer portion. On the effective surface of the shadow mask, a plurality of cells 20 form a cell array. In each cell 20, an aperture 21 is formed in a region related to a deposition pattern of an organic material. On the other hand, no aperture is formed between the cells of the invalid surface and the effective surface, that is, the portion 10. This pattern of mask is most commonly used as a shadow mask for organic EL.

In shadow mask, it is important to stretch by stretching machine together with pattern precision. In general, the temperature rise by heat source is not so large in organic EL deposition process. In other words, the tension is not large. However, it is very important to design the mask to be advantageous for stretching and not to have a large reaction force, since the positional tolerance must be adjusted within several μm.

In the conventional mask structure, since the aperture is formed in the cell 20, and the aperture is not formed between the cells of the non-effective surface and the effective surface, that is, the portion 10 other than the cell, the portion other than the cell 10 ) And the Young's Modulus in the cell 20 is significantly different.

For example, when the material of the mask is AK (Aluminum Killed) steel and the aperture is formed in a slot shape, the Young's modulus in the X direction and the Y direction in the portion 10 and the cell 20 other than the cell is as follows. .

Part other than cell (10): E _X = E _Y = 210000 MPa

Cell 20: E _X = 40000 MPa, E _Y = 150000 MPa

As described above, when the Young's modulus is distributed in the X direction and the Y direction, the Young's modulus of the part 40 and the part 50 is about 1.4 times different in the Y direction, and the part 60 and the part 70 are in the X direction. Since the Young's modulus differs by about five times, it is not possible to expect uniform stretching in the portion 80. That is, since the Young's modulus is suddenly changed in the portion 80 and the displacement suddenly increases and decreases, as shown in FIG. 4, the mask is not uniformly stretched and deformed. Although this deformation range is only a few μm, this deformation amount is very large in the process tolerance of the display device.

In addition, when viewed in detail, as shown in FIG. 5, the upper portion of the cell 20 is easily stretched due to the difference in Young's modulus, and the upper portions between the cells are not relatively well stretched. When both the cell size a and the cell spacing b are small, there is no problem because the difference in displacement is not large. That is, it is not a problem if the desired positional tolerance is a few m and a and b are at or below mm. However, when a and b are greater than or equal to cm, deformations such as portion 80 may occur.

Such a deformation phenomenon causes a mismatching error between the pattern on the glass substrate and the organic material pattern, resulting in a problem of unevenness of luminance and deterioration of color purity.

The present invention was devised to solve the above-mentioned problems, and the organic modulus of uniform stretching can occur over the entire surface of the mask when a tensile force is applied so that the Young's modulus of the part where the cell is formed and the part where the cell is not formed is similar. It is an object to provide a shadow mask for EL.

To this end, the shadow mask for organic EL according to the present invention is a shadow mask for organic EL in which a cell array composed of a plurality of cells is formed on the effective surface of a metal plate, and between the cell array of the effective surface and other than the effective surface. A plurality of apertures, which do not penetrate the metal plate, are formed in a part of the portion (ineffective surface).

1 is a structural diagram showing a layer structure of an organic EL.

2 is an explanatory diagram for explaining a light emitting mechanism of an organic EL.

3 is a plan view of a shadow mask for a conventional organic EL.

4 is an exemplary view showing a deformation occurring in a conventional shadow mask for organic EL.

5 is an exemplary view showing non-uniform stretching occurring in an outer portion of a conventional shadow mask for organic EL.

Fig. 6 is a plan view of the shadow mask for organic EL according to the first embodiment of the present invention.

7 is a cross-sectional view of half etching.

8 is an enlarged view of one embodiment of an aperture formed by half etching.

9 is an enlarged view of an aperture of a cell portion.

10 is a plan view of a shadow mask for an organic EL according to a second embodiment of the present invention

11 is an enlarged view of another embodiment of an aperture formed by half etching.

** Explanation of Signs of Major Parts of Drawings **

1 substrate 2 first electrode (anode)

3: hole transport layer (HTL) 4: light emitting layer (EML)

5: electron transport layer (ETL) 6: second electrode (cathode)

7: hole injection layer (HIL) 8: electron injection layer (EIL)

9: exciton 20, 160: cell

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

In the present invention, in order to prevent deformation of the mask caused by the difference in Young's modulus of the part where the cell is formed and the part where the cell is not formed in the mask, certain physical processing is applied to the part where the cell is not formed. .

Fig. 6 shows a shadow mask for organic EL according to the first embodiment of the present invention.

The shadow mask for organic EL of this invention is comprised with the metal plate like the conventional shadow mask, the cell array is formed in the effective surface of the metal plate, and the aperture which penetrates a metal plate is formed in each cell 160. As shown in FIG.

The shadow mask for the organic EL of the present invention differs from the conventional mask as shown in Fig. 6, in which specific physical processing is performed on a portion where no cell is formed.

That is, as can be seen in Figure 6, the half etching (half etching) process according to the present invention is applied to the portion of the effective surface (130, 140) where the cell is not formed and the portion of the non-effective surface (110, 120) It is. Here, the half etching means etching to form an aperture thinner than the thickness of the metal plate without penetrating through the metal plate, not the aperture in the shape of a hole in the metal plate of the mask.

An aperture that does not penetrate the metal plate is represented by a vertical dotted line in FIG. 6, and an enlarged cross section of the half-etched portion when the metal plate is cut is shown in FIG. 7.

In Figure 7, it can be seen that the aperture by the half etching is formed thinner than the thickness of the metal plate without penetrating the metal plate.

The regions 110-140 formed by the half etching process are similar to the Young's modulus of the region of the cell 160 because the Young's modulus becomes smaller than the metal plate due to the presence of the aperture. As such, the Young's modulus of the portion in which the cell is formed and the Young's modulus of the portion in which the cell is not formed are similar to ensure uniform displacement characteristics during stretching.

Of course, if the apertures between the cell arrays 130 and 140 and the non-effective surfaces 110 and 120 of the effective surface are formed in the same shape as the cell 160 instead of the half etching, the same Young's modulus can be obtained to achieve almost uniform stretching. However, if the hole is formed, the deposition material passes through the undesired portion, thereby losing its function as a mask. Therefore, half etching is performed so that the Young's modulus can be as close as possible to the area of the cell 160 while maintaining the function as a mask.

In addition, if the half-etching range is extended to the portion 150 beyond the portions 110 and 120 from the ineffective surface, a more uniform stretching may be achieved, but if the stretching machine is half-etched to the portion of the clapping mask, Stress is concentrated in the clapping area, which may cause deformation of the mask. Therefore, the half-etching treatment is not performed on the outer portion 150 of the metal plate on which the mask is clad.

8 is an enlarged view of an embodiment of a shape of an aperture formed in a portion where half etching is performed.

As described above, in order to make the Young's modulus of the region of the cell 160 and the Young's modulus of the parts 110-140 similar, half etching is performed on the parts 110-140, where the half etching is performed. Young's modulus depends on the size of the aperture formed.

In a situation where half etching of the entire invalid surface is not possible, in order to maximize the Young's modulus between the area of the cell 160 and the portions 110-140 as close as possible, the width A of the aperture by half etching is at least a cell ( It should be larger than the width B of the aperture formed in 160 (see FIG. 9). In other words, A? B relationship must be established to have a similar Young's modulus. Of course, even if the relationship of A <B, it is possible to obtain better stretching characteristics than the mask without half etching, but for more uniform stretching, the width of the aperture by half etching is the width of the aperture of the cell. It is preferable to be larger.

The shape of the apertures shown in FIGS. 8 and 9 may be in the form of slots or in the form of dots or grilles.

Fig. 10 shows a shadow mask for organic EL according to the second embodiment of the present invention.

In the shadow mask for organic EL according to the second embodiment, a plurality of apertures (i.e., half-etched regions) in a part of the ineffective surface are formed differently from the first embodiment. That is, the half-etching region 170 is formed by being separated from the effective surface 180 by a predetermined interval with the portion 190 having no aperture formed therebetween.

By forming the half etching region in this way, the weldability can be improved when the mask is welded to the frame.

11 is an enlarged view of another embodiment of the shape of an aperture formed in a portion where half etching is performed.

The shape of the aperture shown in FIG. 11 can be applied in common to the masks of the first and second embodiments of the present invention.

As shown in FIG. 11, the length of the aperture of the portion where the half etching is performed is getting smaller as the outer portion of the metal plate is approached. That is, it can be seen that the length C of the aperture in the inner side of the metal plate is larger than the length D of the aperture in the outer side.

Since half-etching is performed only on the part of the invalid surface to secure the clamp area of the mask, the part with the half-etching and the non-effective surface suddenly forms a boundary, which is undesirable in order to secure a more uniform stretch. not.

Therefore, by performing a grading process that gradually reduces the length of the aperture toward the outside of the metal plate, the Young's modulus can be smoothly changed at the boundary between the half-etched portion and the half-etched portion. In this manner, the more uniform stretching can be ensured by the grading treatment.

As described above, the present invention forms an aperture that does not penetrate the metal plate through half etching on the portion where the cell is not formed in the shadow mask, thereby making the Young's modulus of the portion where the cell is formed and the portion where the cell is not formed similar. By removing the sharply changing portion of the mask, a uniform displacement of tension can be applied across the mask. As a result, an error can be suppressed in the assembly process of the mask and the frame, thereby improving brightness and color purity.

Claims (5)

In a shadow mask for an organic EL, in which a cell array composed of a plurality of cells is formed on an effective surface of a metal plate, A shadow mask for organic EL, wherein a plurality of apertures which do not penetrate the metal plate are formed between the cell array of the effective surface and a part of a portion (ineffective surface) other than the effective surface. The method of claim 1, A plurality of apertures in a portion of the non-effective surface are formed by a predetermined distance apart from the effective surface with a portion where the aperture is not formed therebetween, the shadow mask for organic EL. The method of claim 1, A shadow mask for organic EL, characterized in that the width of the aperture not penetrating the metal plate is equal to or larger than the width of the aperture penetrating the metal plate formed in the cell. The method of claim 1, The length of the aperture that does not penetrate the metal plate becomes smaller toward the outer side of the metal plate, the shadow mask for organic EL. The method of claim 1, The shadow mask for organic EL, wherein the aperture penetrating the metal plate formed in the cell and the aperture not penetrating the metal plate are slots, dots, or grilles.