Large-size mask sheets and mask assemblies for OLED evaporation

Abstract

This invention relates to large-size mask sheets and assemblies for OLED evaporation. According to the invention, when manufacturing by welding multiple mask sheet substrates for application in large-size displays of the 5.5th generation (1300mm x 1500mm) and above, the stress-relieving patterns provided on the edges of the welded mask sheets or inside the sheet material at a predetermined distance from the edges can minimize wrinkles in the mask sheets that may occur due to welding and tension, thereby ensuring sufficient flatness expected when manufacturing large-size mask sheets.

Description

Technical Field

[0001] This invention relates to large-size mask sheets and mask assemblies for OLED evaporation. Background Technology

[0002] Well-known flat panel display devices include liquid crystal display devices (LCDs) and organic light-emitting display devices (OLEDs). OLEDs are thin-film light-emitting diodes whose light-emitting layer is made of organic compounds. In the common manufacturing process of OLEDs, the electrode layer, organic light-emitting layer, insulating film, and other thin-film layers are stacked and patterned using a vapor deposition process performed using mask assemblies with their respective corresponding patterns.

[0003] In the vapor deposition process, an open metal mask (OMM) is used to form the organic common layer that plays a functional role on the OLED substrate; while in the RGB vapor deposition process used to vapor deposit pixels that emit red (R), green (G) and blue (B) light respectively, a fine metal mask (FMM) is used.

[0004] The mask assembly used in the vapor deposition process has a structure in which a mask sheet or mask rod, which is a relatively thin metal film, is bonded to a mask frame with a relatively robust structure. The mask frame is a frame structure in the form of a window frame or door frame, with a thickness of about 5 mm to 80 mm, and its function is to stably maintain the shape of the mask assembly. In addition, the mask sheet or mask rod is formed by forming a predetermined pattern required for vapor deposition on a thin metal sheet or strip with a thickness of about 0.01 mm to 5.00 mm.

[0005] Common mask assemblies are manufactured using metals with a low coefficient of thermal expansion related to temperature changes, such as Invar-36 Alloy. Furthermore, when high pattern precision is not required, heat-resistant stainless steel such as SUS420 is used to manufacture the mask frame to reduce costs. As an example, the Open Metal Mask (OMM) assembly used in the organic common layer evaporation process of OLED displays can be manufactured by coating both surfaces of a photosensitive dry film (DFR) with UV exposure, followed by patterning on the mask through processes such as development and wet etching, and then bonding it to the mask frame under tension using laser welding.

[0006] Currently, the demand for large-size OLED panels from the 6th to the 8th generation is increasing significantly. However, the largest size of the Invar alloy mask sheet currently available is only about 1100mm wide, so it is impossible to use the mask sheet to manufacture mask assemblies for large-size OLEDs. In order to achieve large-size, a separate mask assembly form that stretches individual mask rods and joins them to the mask frame can be considered, or a method that welds multiple mask sheets to the mask frame can be considered.

[0007] On the other hand, in the aforementioned manufacturing method of large-size mask components for OLEDs, the latter method can be performed by using a laser welding method (butt welding) after multiple mask sheets are arranged in contact with each other. However, if wrinkles are generated on the flat mask sheet due to the welding, it is difficult to ensure that the large-size mask sheet has sufficient flatness. Therefore, when the large-size mask component comes into contact with the substrate, a bulge occurs because the large-size mask sheet portion is spaced apart from the substrate. As a result, the organic material flowing in to form the common layer may flow into unwanted areas, leading to product defects or a decrease in product precision. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The object of the present invention is to include one or more stress-relieving patterns for mitigating tension and stress within the mask sheet at or at a predetermined distance from the edge of the mask sheet to be welded, so as to minimize wrinkles in the mask sheet that may occur due to welding and tension when manufacturing a large mask sheet by welding multiple mask sheets, thereby ensuring the flatness expected when manufacturing a large mask sheet.

[0010] Furthermore, the individual mask sheets constituting the large-size mask sheet of the present invention include unit openings, such that protruding pieces with a predetermined width and thickness form the outer circumferential surface of the through hole. After the large-size mask sheet is stretched and joined to the mask frame, laser fine-tuning post-processing is performed on the ends of the protruding pieces. Since the thickness of the processed object portion after fine-tuning post-processing is significantly reduced compared to the prior art, the laser fine-tuning post-processing time can be shortened, achieving more accurate fine-tuning post-processing, thereby significantly improving the unit positioning accuracy (CPA).

[0011] The technical problems to be solved by the present invention are not limited to those described above. Other technical problems not mentioned will be clearly understood by those skilled in the art through the following description.

[0012] means for solving problems

[0013] This specification provides a large-size mask sheet for OLED evaporation, which is a large-size mask sheet in which multiple mask sheets having one or more unit openings inside are joined together by welding at adjacent edge portions. It includes one or more stress-relieving patterns disposed at the edges of the welded mask sheets or inside the sheet spaced at a predetermined distance from the edges, in order to relieve tension and stress.

[0014] The stress relief pattern may be selected from at least one of through holes and semi-grooves.

[0015] The stress-relieving pattern can be circular, elliptical, or polygonal.

[0016] Multiple stress-relieving patterns are provided and can be configured in a straight line shape parallel to the edge of the mask sheet being welded.

[0017] The welding can be performed by one or more welding methods selected from butt welding, lap welding and pad welding.

[0018] The unit opening includes: a first recess having a first width and a first depth, formed by a first etching in a direction from the top surface to the bottom surface of the mask, the first recess being basin-shaped; a second recess having a second width and a second depth, formed by a second etching in a direction from the bottom surface to the top surface of the mask, the second recess being inverted basin-shaped; and a through hole such that the first recess and the second recess are connected and have a width less than the first width or the second width, wherein a protruding piece with a predetermined width and thickness due to the first etching and the second etching forms the outer circumferential surface of the through hole.

[0019] After the large-sized mask sheet is stretched and joined to the mask frame, the ends of the protruding pieces can be laser-trimmed and processed.

[0020] The cell positioning accuracy (CPA) of the large-size mask is within the range of ±20 μm (reference value).

[0021] The mask can be a mask used for large-size displays of 1300mm x 1500mm (5.5th generation) or larger.

[0022] As an example, the large-size mask can be formed by combining three rectangular mask sheets of 900mm x 2400mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long sides of each mask sheet together.

[0023] As an example, the large-size mask can be formed by combining three rectangular mask sheets of 800mm x 2700mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long sides of each mask sheet together.

[0024] As an example, the large-size mask can be formed by combining four rectangular mask sheets of 1200mm x 1350mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long and short sides of each mask sheet.

[0025] As an example, the large-size mask can be formed by combining two rectangular masks with a size of 300mm x 2700mm and two rectangular masks with a size of 900mm x 2700mm, and the long sides of each mask are welded together.

[0026] Furthermore, this specification provides a large-size mask assembly for OLED evaporation, comprising: the large-size mask sheet; and a mask frame to which the large-size mask sheet is stretched and attached.

[0027] The large mask sheet and mask frame can be made of Invar-36 Alloy or stainless steel (SUS420).

[0028] This specification provides a large-size mask sheet for OLED evaporation, wherein a large-size mask sheet, comprising multiple mask sheets having one or more unit openings internally, is joined together at adjacent edge portions by welding, includes: one or more stress-relieving patterns disposed at the edges of the welded mask sheets or within a sheet spaced at a predetermined distance from the edges to relieve tension and stress; the unit openings include: a first recess having a first width and a first depth, etched firstly in a direction from the top surface to the bottom surface of the mask sheet, the first recess being basin-shaped; a second recess having a second width and a second depth, etched secondly in a direction from the bottom surface to the top surface of the mask sheet, the second recess being inverted basin-shaped; and a through-hole such that the first recess communicates with the second recess and has a width less than the first width or the second width; a protruding piece with a width of less than 150 μm and a thickness of 15 μm to 35 μm, formed by the first and second etching, forms the outer circumferential surface of the through-hole.

[0029] Invention Effects

[0030] According to the present invention, when a large-size mask for OLED evaporation is manufactured by welding multiple mask sheets for application in large-size displays of the 5.5th generation (1300 mm x 1500 mm) and above, the stress-relieving pattern provided on the edge of the welded mask sheet or inside the sheet spaced at a predetermined distance from the edge can minimize wrinkles in the mask sheet that may occur due to welding and tension, thereby ensuring sufficient flatness expected when manufacturing large-size masks.

[0031] Furthermore, the large-size mask sheet for OLED evaporation according to the present invention includes a cell opening, such that a protruding piece with a predetermined width and thickness forms the outer circumferential surface of the through hole. After the large-size mask sheet is stretched and joined to the mask frame, a laser fine-tuning post-processing is performed. Since the thickness of the processed object portion after fine-tuning post-processing is significantly reduced compared with the prior art, the laser fine-tuning post-processing time can be shortened, and more accurate fine-tuning post-processing can be achieved, thereby significantly improving the cell positioning accuracy (CPA). Attached Figure Description

[0032] Figure 1 This is a front view showing a large-size mask sheet for OLED evaporation according to an embodiment of the present invention.

[0033] Figure 2 This is a front view showing a large-size mask sheet for OLED evaporation according to yet another embodiment of the present invention.

[0034] Figure 3 This is a front view showing a large-size mask sheet for OLED evaporation according to yet another embodiment of the present invention.

[0035] Figure 4 This is a front view showing a large-size mask sheet for OLED evaporation according to yet another embodiment of the present invention.

[0036] Figure 5 This is a cross-sectional view showing the unit opening of an individual mask sheet constituting a large-size mask sheet for OLED evaporation according to an embodiment of the present invention.

[0037] Figure 6 This is an enlarged cross-sectional view showing a protruding piece disposed at the unit opening of an individual mask sheet constituting a large-size mask sheet for OLED evaporation according to an embodiment of the present invention.

[0038] Figure 7 This is a cross-sectional view showing the width and depth (thickness), etc., of each component of an individual mask sheet constituting a large-size mask sheet for OLED evaporation according to an embodiment of the present invention.

[0039] Figure 8 This is a cross-sectional view showing the evaporation process of a large-size mask for OLED evaporation using an embodiment of the present invention, and is along... Figure 1 The cross-sectional view taken by line a-a'.

[0040] Figure 9 This is a diagram showing the dimensional specifications of the glass substrate used to manufacture OLED displays. Detailed Implementation

[0041] In the following detailed description, embodiments of the invention will be provided with reference to the accompanying drawings to enable those skilled in the art to readily implement the invention. However, the invention can be implemented in various different forms and is not limited to the embodiments disclosed below.

[0042] In the following description, the large-size mask sheet 5 and mask assembly 10 for OLED evaporation according to the present invention will be described in more detail with reference to the accompanying drawings.

[0043] Large-size mask

[0044] According to an embodiment of the present invention, a large-size mask 5 for OLED evaporation is a large-size mask 5 in which a plurality of mask sheets 100 having one or more unit openings 101 inside are joined together by welding at adjacent edge portions. The large-size mask 5 may include one or more stress-relieving patterns P, which are disposed at the edge E of the welded mask sheet or inside the sheet spaced at a predetermined distance from the edge, in order to relieve tension and stress.

[0045] Specifically, the large-size mask sheet for OLED evaporation of the present invention can be used in the manufacture of OLED portable displays as an auxiliary metal mask for supporting fine metal masks (FMM), an open metal mask (OMM) for forming organic common layers, and a CVD mask for encapsulation processes. In particular, it can be used in the manufacture of OLED displays for large-size TVs as an open metal mask for forming organic common layers.

[0046] first, Figure 9 The dimensions of glass substrates currently manufactured / used in OLED displays are shown. Although the demand for large-size OLED panels from Gen 6 to Gen 8 and Gen 10 is increasing significantly, the maximum width of the Invar alloy mask sheets currently supplied by Hitachi Metals and others is only about 1100 mm. Therefore, it is difficult to manufacture mask components for OLEDs of Gen 5.5 (1300 mm x 1500 mm) and above using mask sheets.

[0047] Therefore, in order to manufacture the mask assembly to correspond to the large-size panel, a separate mask assembly form in which individual mask rods are stretched and combined to the mask frame can be considered, or a method of combining multiple mask sheets into the frame after welding multiple mask sheets can be considered. The large-size mask sheet according to the present invention adopts the latter method, in which multiple mask sheets are arranged adjacent to each other, and then the mask sheets are welded and combined at the edge portions, thereby achieving correspondence with the glass substrate of the 5.5th generation or higher.

[0048] See Figures 1 to 4 The invention discloses a large-size mask sheet. The large-size mask sheet can be used for applications to large-size displays of 1300mm x 1500mm (5.5th generation) and above. Specifically, the large-size mask sheet 5 can be a plurality of individual mask sheets 100 joined together by welding at adjacent edge portions.

[0049] As an example, welding according to one embodiment of the present invention can be performed by one or more welding methods selected from butt welding, lap welding, and pad welding. On the other hand, the welded portion W completed by the above method can be formed in the form of dots or lines.

[0050] For example, butt welding can be performed by placing mask sheets adjacent to each other and then laser-welding the edge portions together along the interface, or by using brazing, i.e., injecting solid filler metal molten at a temperature lower than that of the mask sheet material along the interface for solidification. Compared to conventional welding, laser welding allows for very small weld widths and, due to minimized heat effects, easily prevents welding-induced deformation, making it potentially suitable for mask sheet welding. Additionally, lap welding is a method of welding where the edge portions of the mask sheets partially overlap. Similar to butt welding, pad welding involves joining two mask sheets together, then covering the boundary surface with a pad and welding. In this case, the surface opposite to where the pad is located is used as the substrate attachment surface.

[0051] As an example, the large-size mask can be formed by combining three rectangular mask sheets of 900mm x 2400mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long sides of each mask sheet together (see [link]). Figure 1 ).

[0052] As another example, the large-size mask can be formed by combining three rectangular masks with dimensions of 800mm x 2700mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long sides of each mask together (see [link]). Figure 2 ).

[0053] As another example, the large-size mask can be formed by combining four rectangular masks with dimensions of 1200mm x 1350mm to achieve a size of 2400mm x 2700mm, and by welding the edges of the long and short sides of each mask together (see [link]). Figure 3 ).

[0054] As another example, the large-size mask can be formed by combining two 300mm x 2700mm rectangular masks and two 900mm x 2700mm rectangular masks to achieve a size of 2400mm x 2700mm, and welding the long sides and edges of each mask together (see [link]). Figure 4 ).

[0055] On the other hand, Figures 1 to 4 In this context, the material placed on the large-sized mask can be a substrate.

[0056] When multiple individual mask sheets are welded according to the present invention to achieve large-scale production, or when the manufactured large-scale mask sheets are stretched and joined to the mask frame as described later, wrinkles may occur in the mask sheets due to the resulting tension and stress, making it difficult to ensure sufficient flatness of the large-scale mask sheets. Therefore, when the large-scale mask assembly comes into contact with the substrate, bulging may occur because the large-scale mask sheet portions are spaced apart from the substrate. Consequently, organic materials flowing in to form a common layer may flow into areas where they should not, causing product defects or potentially leading to a decrease in product precision.

[0057] To address this problem, the present invention may include one or more stress-relieving patterns P disposed at the edge E of the mask sheet being welded or within the sheet material spaced a predetermined distance from the edge, in order to alleviate tension and stress. Specifically, the stress-relieving pattern may be at least one selected from through-holes and semi-grooves, and may have a circular, elliptical, or polygonal shape. As an example, see [reference needed]. Figures 1 to 4 Multiple stress-relieving patterns can be provided, and they can be configured in a straight line shape parallel to the edge of the mask sheet being welded.

[0058] On the other hand, the stress-relieving pattern can be set not only at the edge, but also inside the sheet at a predetermined distance from the edge. For example, it can be set adjacent to the cell opening, which will be described later.

[0059] On the other hand, there are no particular limitations on the stress relief pattern. It can be pre-formed by a separate process such as etching or laser etching before welding, or it can be formed simultaneously with the etching or laser etching used to form the unit openings of individual mask sheets, which will be described later.

[0060] On the other hand, the individual mask sheets 100 that are joined by welding as described above to form the large-size mask sheet 5 may include one or more unit openings 101 inside them.

[0061] As an example, when the large-size mask for OLED evaporation of the present invention is an open metal mask for forming an organic common layer, organic material moves from the bottom surface to the top surface of the large-size mask through the unit openings 101 and is evaporated onto the substrate surface to form a thin film. The width of the thin film layer formed therefrom corresponds to the width of the final display product. On the other hand, the accompanying drawings of the present invention are schematically shown and do not consider the actual evaporation process, because it can be easily understood by those skilled in the art. The large-size mask 5 may include one or more unit openings 101, for example, corresponding to the number of desired display products. As an example, there may be several, dozens, or hundreds of unit openings.

[0062] On the other hand, the unit opening of the present invention can correspond to a pre-formed unit opening before the mask sheet is stretched, and considering the final desired size of the unit opening or through-hole of the large-size mask assembly 10, it can be determined empirically by specifically considering various factors such as the final unit opening / through-hole size, the mask sheet size, the final unit opening / through-hole shape, the applied tension, and the deformation state of the unit opening / through-hole. Furthermore, the shape of the unit opening 101 can be circular or polygonal, but there are no particular limitations.

[0063] Reference Figures 5 to 7 The unit opening 101 inside the individual mask sheet 100 constituting the large-size mask sheet 5 of the present invention includes: a first recess 110, which is first etched in the direction from the top surface to the bottom surface of the mask sheet to have a first width D1 and a first depth T1, the first recess 110 being basin-shaped; a second recess 120, which is second etched in the direction from the bottom surface to the top surface of the mask sheet to have a second width D2 and a second depth T2, the second recess 120 being inverted basin-shaped; and a through hole 130, which connects the first recess and the second recess and has a width smaller than the first width D1 or the second width D2.

[0064] In this case, the unit opening 101 may be a component that causes the protruding piece 140 to form the outer circumferential surface of the through hole, the protruding piece 140 protruding with a predetermined width and thickness D0 due to the first and second etching. On the other hand, throughout the specification and claims of this invention, the term "top surface" refers to the surface of the mask 100 and the large-size mask 5 that contacts the substrate, and "bottom surface" refers to the surface on which the organic material for forming the organic common layer (thin film) and the RGB layer is incident.

[0065] The first recess 110 is formed in the direction from the top surface to the bottom surface of the individual mask 100, i.e., by a first etching into the interior of the mask 100. The first recess 110 can be formed as a basin shape, specifically having a first width D1 and a first depth T1, and can be a basin shape in which the first width D1 is larger than the first depth T1.

[0066] The two ends of the first width D1 of the first recess 110 can be determined to be sufficiently spaced in the horizontal direction to avoid interfering with the edge of the thin film layer. The first depth T1 of the first recess 110 can be formed as shallow as possible to minimize the size of the shadow area generated at the edge of the thin film layer. Specifically, the first depth T1 of the first recess 110 can be formed to be 10 μm to 25 μm, more specifically, it can be formed to be 10 μm to 20 μm. The first width D1 and the first depth T1 of the first recess 110 can be controlled by adjusting the concentration of the etchant or the etching time.

[0067] The second recess 120 is formed in the direction from the bottom surface to the top surface of the mask 100, i.e., by a second etching into the interior of the mask 100. Since the second recess 120 is formed on the opposite side to the first recess 110, i.e., on the bottom surface of the mask 100, it can be etched sequentially after the first recess 110 is formed, or simultaneously with the first recess 110. Furthermore, the second recess 120 has a second width D2 and a second depth T2, the second width D2 being longer than the second depth T2. When the second recess 120 is inverted, it can have the same basin shape (inverted basin shape) as the first recess 110.

[0068] The width range of the second width D2 of the second recess 120 can be determined such that the protrusion is formed to a size that allows for sufficient processing of the protrusion in the laser fine-tuning process described later. The second depth T2 of the second recess 120 can be determined by considering a predetermined thickness range for the protrusion, for example, 15 μm to 35 μm, specifically 20 μm to 30 μm, in order to significantly shorten the processing time in the laser fine-tuning process described later.

[0069] As an example, when the individual mask sheet 100 has a thickness of 50 μm to 200 μm, the second depth T2 of the second recess 120 can be formed to be 20 μm to 145 μm. Similar to the first recess 110, the second width D2 and the second depth T2 of the second recess 120 can be controlled by adjusting the concentration of the etchant or the etching time.

[0070] Reference Figures 5 to 7The through hole 130 is a hole for connecting the first recess 110 and the second recess 120, and it can be formed in the form of connecting the middle portion of the first recess 110 and the second recess 120.

[0071] On the other hand, the width of the through-hole 130 according to the present invention can be smaller than the first width D1 or the second width D2. As an example, the cross-section of the through-hole can have a bell shape, with the upper width narrower than the lower width. When the cross-section of the through-hole 130 is bell-shaped, the size of the thin film is determined by the sidewalls of the protruding tabs that form the outer circumferential surface of the through-hole 130 during the deposition of the organic material. Therefore, the shaded area formed at the edge of the thin film on the substrate should be minimized. Specifically, the lower sidewall of the through-hole has a taper angle of 40 to 45 degrees relative to the horizontal plane. In this case, the shaded area can be reduced to about 20 μm or less.

[0072] On the other hand, in one embodiment of the invention, the through-hole 130 is formed from the upper surface of the second recess 120 toward the interior of the sheet, and may include a through-hole bottom 131 having a third width D3 smaller than the second width D2. This can be formed by a third etching process, specifically, the through-hole 130 can be formed by forming an inverted basin-shaped second recess 120 having a second width D2 in the direction from the bottom surface to the top surface of the mask 100, and then performing a third etching from the upper surface of the second recess 120 toward the interior of the sheet to form a through-hole bottom 131 having a third width D3 smaller than the second width D2. In this case, the cross-section of the through-hole 130 may have a bell shape with a width at the top narrower than the width at the bottom.

[0073] On the other hand, in another embodiment of the invention, the through-hole 130 may include a through-hole bottom 131 and a through-hole top 132, the through-hole top 132 being formed from the lower surface of the first recess 110 toward the interior of the sheet and having a fourth width D4 smaller than the third width D3. This can be formed by a fourth etching process, specifically, the through-hole 130 can be formed by forming a basin-shaped first recess 110 having a first width D1 in the direction from the top surface to the bottom surface of the mask sheet 100, and then performing a fourth etching from the lower surface of the first recess 110 toward the interior of the sheet to form a through-hole top 132 having a fourth width D4 smaller than the third width D3. In this case, the cross-section of the through-hole 130 may have an hourglass shape.

[0074] On the other hand, the fourth and third etchings can be performed simultaneously or sequentially. On the other hand, when a bottom 131 and a top 132 of the through hole are formed on the through hole 130 as described above, the sidewall of the protruding piece forming the outer circumferential surface of the through hole 130 can have an edge shape that protrudes at the intersection of the bottom 131 and the top 132 of the through hole 130.

[0075] On the other hand, when a bottom 131 and a top 132 of the via are formed on the via 130 as described above, the bottom 131 can be formed to a third depth T3 and the top 132 can be formed to a fourth depth T4. In this case, the third depth T3 of the bottom 131 can be formed to be relatively deeper than the fourth depth T4 of the top 132. In the above case, the shadow area generated at the edge of the organic material thin film layer can be minimized.

[0076] Furthermore, when a bottom 131 and a top 132 of the through hole are formed on the through hole 130, the lower sidewall of the through hole may have a taper angle of 40 to 45 degrees relative to the horizontal plane, and the upper sidewall of the through hole may have a taper angle of 130 to 135 degrees relative to the horizontal plane.

[0077] On the other hand, according to an embodiment of the present invention, individual mask sheets 100 may have a thickness of 50 μm to 200 μm. In this case, the first depth of the first recess 110 may be 10 μm to 25 μm, and the depth of the second recess 120 may be 20 μm to 145 μm.

[0078] On the other hand, the protruding piece 140 according to the invention can have a predetermined width and thickness to shorten the process time required for laser fine-tuning post-processing and improve processing accuracy.

[0079] As an example, the thickness D0 of the protrusion corresponding to the depth of the through hole can be in the range of 15 μm to 35 μm, specifically, in the range of 20 μm to 30 μm. On the other hand, when the thickness of the protrusion is in the range of 20 μm to 30 μm, the process time required for the laser fine-tuning post-processing of each unit opening is about 3 to 5 minutes, which is significantly reduced compared to the case where the process time required for the laser fine-tuning post-processing of the opening end of the processing target component in the mask 100 according to the prior art is about 3 to 4 hours when the thickness is about 100 μm, the process time required is approximately 3 hours to 4 hours.

[0080] As another example, the width of the protrusion according to the invention can be 700 μm or less, specifically, it can be 150 μm or less. When the protrusion has the above-mentioned width range, the adjustable range can be widened, thereby improving cell positioning accuracy (CPA). On the other hand, when the protrusion exceeds the above-mentioned width and thickness range, there is a risk that the protrusion will be torn during the cleaning process of the mask and the assembly.

[0081] According to one embodiment of the present invention, when the protrusion is 20 μm thick and 150 μm wide, after laser fine-tuning post-processing, the cell positioning accuracy (CPA) value can be controlled within the range of ±20 μm of the reference value. Therefore, the error range is significantly reduced, and the accuracy and edge accuracy of the display product can be significantly improved.

[0082] Large-size mask assembly

[0083] On the other hand, according to an embodiment of the present invention, the large-size mask assembly 10 is manufactured by stretching the large-size mask sheet 5 for OLED evaporation to a predetermined size using the stretching process described above and by joining it to the mask frame 200.

[0084] The stretching process is performed using a stretcher after the edge (or support) portion of the large-size mask sheet 5 is fixed with a clamp. However, in the prior art, there is a problem that the positions of the unit opening 101 and the through hole 130 deviate from the predetermined positions during the stretching process. In order to solve the tension error, the unit opening 101 of the large-size mask sheet 5 that is engaged with the mask frame 200 is subjected to laser fine-tuning post-processing to complete the large-size mask assembly 10.

[0085] On the other hand, after performing the above-mentioned stretching process and the joining process of the mask frame 200, in order to further improve the unit positioning accuracy, the large-size mask sheet 5 is subjected to laser fine-tuning post-processing so that the through hole 130 can be positioned in the predetermined position.

[0086] The laser fine-tuning post-processing can be a process of removing a portion of the protrusion by irradiating it with an ultra-short wavelength laser so that the through hole 130 is positioned at a predetermined cell location. As an example, the laser fine-tuning post-processing can be performed using processing equipment such as a pico-second laser or a femto-second laser, and can be performed by removing the end of the protrusion of one or more of the multiple cell openings 101.

[0087] On the other hand, when a femtosecond laser is used in the fine-tuning process of the large-size mask 5, the workpiece surface immediately evaporates into granular form without melting. Since the processing is completed before heat is transferred to the surrounding area, processing can be performed in a way that generates almost no heat to the workpiece. Therefore, when using a femtosecond laser, fine and precise fine-tuning processing can be performed on the large-size mask 5 or the unit opening 101 in the fine-tuning step without causing other damage.

[0088] On the other hand, when using picosecond or femtosecond lasers for trimming post-processing, the process time required for each unit opening with a standard thickness of 100μm at the opening end of the mask 100 is about 3 to 4 hours. The thicker the large-size mask 5 part for fine-tuning, the longer the process time will be, and the economic efficiency of the process may be reduced. Moreover, due to the thickness, it is difficult to perform precision machining, so it may not be possible to fully improve the unit positioning accuracy.

[0089] In contrast, the thickness D0 of the protrusion to be fine-tuned in the large-size mask 5 and mask assembly 10 with the structure according to the invention is 15 μm to 35 μm, specifically, in the range of 20 μm to 30 μm. Therefore, compared with the prior art, the time required for laser fine-tuning is significantly reduced due to the reduced thickness of the workpiece, thus enabling more precise fine-tuning.

[0090] As a result, due to the significant improvement in unit positioning accuracy, the final precision of the manufactured display product and the edge precision of the product are improved, thus enabling the production and design of more diverse precision displays.

[0091] On the other hand, a large-size mask assembly 10 for OLED evaporation according to an embodiment of the present invention may include: the large-size mask sheet 5 for OLED evaporation; and a mask frame 200, wherein the large-size mask sheet 5 is stretched and joined to the mask frame 200. The large-size mask sheet 5 of the present invention may be made of metal, specifically, it may be made of Invar-36 Alloy or stainless steel (SUS420). Furthermore, the mask frame 200 may also be made of Invar-36 Alloy or stainless steel (SUS420).

[0092] In addition, the large-size mask assembly 10 for OLED evaporation according to an embodiment of the present invention, as described above, can be manufactured by a predetermined process sequence.

[0093] First, the individual mask sheet 100 can be manufactured through the following steps: a first etching step, preparing a mask sheet made of metal such as Invar alloy, and forming a first recess 110 on the mask sheet; a second etching step, forming a second recess 120 on the mask sheet; and forming a protrusion 140 by forming a through hole 130 for connecting the first recess and the second recess. Alternatively, the through hole 130 can be formed by a third etching step or a combination of the third and fourth etching steps as described above. Furthermore, the etching can be performed using conventional methods known in the art, such as wet etching, dry etching, or laser etching.

[0094] Multiple mask sheets 100 manufactured as described above are prepared, arranged adjacent to each other, then their edges are joined together, and the aforementioned welding is performed at the interface using a laser or similar method to manufacture a large-size mask sheet 5. Stresses generated during this process are absorbed by a pre-formed stress-relieving pattern P, thereby minimizing deformation or flatness variations in the large-size mask sheet.

[0095] Next, in order to attach the prepared large-size mask sheet 5 to the prepared mask frame 200, the large-size mask assembly 10 is manufactured by stretching it to a predetermined size and attaching it to the mask frame. After attachment, a portion of the protrusion 140 formed on the unit opening 101 of the large-size mask sheet 5 is removed, and a laser fine-tuning post-processing is performed to position the through hole 130 in a predetermined position. This is the same as described above.

[0096] On the other hand, the tension generated during the stretching process is absorbed by the pre-formed stress-relieving pattern P, thereby minimizing the deformation or flatness change of the mask sheet.

[0097] Although specific embodiments of the present invention have been described and illustrated above, the present invention is not limited to the embodiments described above. It will be apparent to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the present invention. Therefore, these modifications or changes should not be understood solely from the technical spirit or viewpoint of the present invention, and the modified embodiments should be understood to fall within the scope of the claims of the present invention.

[0098] Explanation of reference numerals in the attached figures

[0099] E: The edge of the mask being welded

[0100] P: Stress relief pattern W: Welded section

[0101] 5: Large-size mask sheet; 10: Large-size mask assembly

[0102] 100: Mask sheet; 101: Unit opening.

[0103] 110: First concave portion 120: Second concave portion

[0104] 130: Through hole; 131: Bottom of through hole

[0105] 132: Top of through hole; 140: Protruding piece

[0106] 200: Mask frame

[0107] D0: Protrusion thickness (through-hole depth) D1: First width

[0108] D2: Second width; D3: Third width

[0109] D4: Fourth width; T1: First depth

[0110] T2: Second Depth T3: Third Depth

[0111] T4: Fourth Depth; OM: Organic Material

Claims

1. A large-size mask for OLED evaporation deposition, wherein, As a large-sized mask sheet comprising multiple mask sheets having one or more unit openings internally joined together by welding at adjacent edge portions, including: One or more stress-relieving patterns are disposed at the edge of the mask sheet being welded or within the sheet at a predetermined distance from the edge, in order to alleviate tension and stress. The unit opening includes: A first recess, having a first width and a first depth, is first etched in a direction from the top surface to the bottom surface of the mask, and the first recess is basin-shaped; a second recess, having a second width and a second depth, is second etched in a direction from the bottom surface to the top surface of the mask, and the second recess is inverted basin-shaped; and a through hole, such that the first recess and the second recess communicate and have a width less than the first width or the second width. The protruding tabs, with a width of less than 150 μm and a thickness of 15 μm to 35 μm, formed by the first and second etching, form the outer circumferential surface of the through hole.

2. The large-size mask for OLED evaporation according to claim 1, wherein, The stress relief pattern is selected from at least one of through holes and semi-grooves.

3. The large-size mask for OLED evaporation according to claim 1, wherein, The stress-relieving pattern is circular, elliptical, or polygonal.

4. The large-size mask for OLED evaporation according to claim 1, wherein, Multiple stress-relieving patterns are provided and arranged in a straight line shape parallel to the edge of the mask sheet being welded.

5. The large-size mask for OLED evaporation according to claim 1, wherein, The welding is performed by one or more welding methods selected from butt welding, lap welding and pad welding.

6. The large-size mask for OLED evaporation according to claim 1, wherein, After the large-sized mask sheet is stretched and joined to the mask frame, the ends of the protruding pieces are laser-trimmed and processed.

7. The large-size mask for OLED evaporation according to claim 1, wherein, The unit positioning accuracy of the large-size mask is within the range of ±20μm (reference value).

8. The large-size mask for OLED evaporation according to claim 1, wherein, The large-size mask is used in 5.5th generation large-size displays with dimensions of 1300mm x 1500mm or larger.

9. The large-size mask for OLED evaporation according to claim 1, wherein, The large-size mask sheet is formed by combining three rectangular mask sheets with a size of 900mm x 2400mm to achieve a size of 2400mm x 2700mm, and the edges of the long sides of each mask sheet are welded together.

10. The large-size mask for OLED evaporation according to claim 1, wherein, The large-size mask sheet is formed by combining three rectangular mask sheets with a size of 2400mm x 2700mm, and welding them together at the edges of the long sides of each mask sheet.

11. The large-size mask for OLED evaporation according to claim 1, wherein, The large-size mask sheet is formed by combining four rectangular mask sheets with a size of 1200mm x 1350mm to achieve a size of 2400mm x 2700mm, and the edges of the long and short sides of each mask sheet are welded together.

12. The large-size mask for OLED evaporation according to claim 1, wherein, The large-size mask sheet is formed by combining two 300mm x 2700mm rectangular mask sheets and two 900mm x 2700mm rectangular mask sheets to form a size of 2400mm x 2700mm, and the edges of the long sides of each mask sheet are welded together.

13. A large-size mask assembly for OLED evaporation, comprising: The large-size mask sheet as described in claim 1; as well as A mask frame to which the large mask sheet is stretched and attached.

14. The large-size mask assembly for OLED evaporation according to claim 13, wherein, The large-sized mask sheet and mask frame are made of Invar alloy or stainless steel.

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