KR102269904B1 - Method for manufacturing open metal mask of large area for oled deposition - Google Patents

Abstract

A purpose of the present invention is to provide a method of manufacturing a large-area open metal mask for OLED deposition, capable of satisfying position precision, size precision and pattern precision as well as enabling manufacture with a mother glass substrate. To achieve the purpose, in the method of manufacturing a large-area open metal mask for OLED deposition, as to one of two invar thin plates, the major axis thereof is separated into a plurality of pieces at regular intervals, and then, a length variation (△L) and an elongation rate (△L/L × 100%) of each of the pieces are measured, and, as to the other one of the plates, the minor axis thereof is separated into a plurality of pieces at the same intervals as the regular intervals, and then, a length variation (△L) and an elongation rate (△L/L × 100%) of each of the pieces, and then, two sets of photomask films used in primary and secondary chemical etching processes are manufactured with a reduction by the measured elongation rates (△L/L × 100%), and then, a primary photochemical etching pre-process and a secondary photochemical etching pre-process are carried out, and then, tension is applied to make tension by the elongation rates, and then, the films are fixed to a mask frame through laser welding to manufacture a mask frame assembly.

Description

Manufacturing method of large-area open metal mask for OLED deposition {METHOD FOR MANUFACTURING OPEN METAL MASK OF LARGE AREA FOR OLED DEPOSITION}

The present invention relates to a method of manufacturing a large-area open metal mask for OLED deposition, and more particularly, manufacturing a large-area metal mask required for organic material deposition in a large-area glass substrate 6 Gh (925 mm × 1,500 mm) OLED process It relates to a method of manufacturing a large-area open metal mask for OLED deposition for

Flat panel displays are recently shifting from LCD (Liquid Crystal Display) to OLED (Organic Lighting Emitting Diodes).

OLED has very good performance such as self-luminescence, response speed, viewing angle, low voltage and low power consumption, contrast ratio, color reproducibility, and resolution.

This OLED is an organic thin film, and electrons and holes injected through the cathode and anode combine to form excitons, and the formed excitons are transferred from an excited state to a ground state and light of a specific wavelength is generated. .

The structure of OLED is a structure in which a transparent cathode and an anode through which light passes are formed on a glass substrate or transparent plastic, and a transport layer and conductive layer for electrons and holes and a light emitting layer are deposited in the middle between them.

1 is a diagram illustrating a basic structure and a light emitting principle of an OLED display.

The basic structure of an OLED display consists of an anode, a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), and a cathode (Cathode) from a transparent glass substrate. is made in the order of

OLED display module production is completed through the process of glass substrate (electrode process) → vacuum deposition → encapsulation → cell → module.

The electrode process of the glass substrate is a sputtering method to form an ITO thin film on the glass substrate.

Thereafter, multiple layers of organic thin films and metal thin films are continuously formed by deposition on a glass substrate under high vacuum.

The organic thin films are each deposited in a separate vacuum chamber.

This vacuum chamber includes a device for aligning the upper glass substrate and the lower metal mask frame, thin film deposition thickness monitor equipment, and an organic material evaporation source, and uses a vacuum pump to generate a 10 ^-7 Torr ultra-high vacuum in the chamber. and sublimate or evaporate the organic material in a thermal evaporation method within the range of 200 to 500 °C.

In order to perform precise deposition, a deposition mask must be accurately mounted on the bottom of the glass substrate.

The evaporated small organic material in molecular units is deposited with a predetermined size and thickness at a predetermined position on the glass substrate through a mask.

OLED organic deposition is carried out through different metal masks in different vacuum chambers in the order of an anode, a hole injection layer, a hole transport layer, a light emitting layer (RED), a light emitting layer (Green), a light emitting layer (Blue), an electron transport layer, an electron injection layer, and a cathode. is deposited

The total thickness of the deposited organic material is about 200 to 300 nm, and when a 0.7 mm glass substrate is used, the thickness of the organic material is a thin film of about 1/300 to 1/400 of the thickness of the glass.

As soon as the organic deposition process is completed, the encapsulation process is carried out. The encapsulation process is a process to block the light-emitting properties of organic materials and electrodes that emit light in OLEDs react very sensitively to oxygen and moisture and thus lose their light-emitting properties. is the process of preserving or enhancing

In the encapsulation process, a plurality of inorganic layers, an inorganic layer and an organic layer, or an inorganic layer and an organic layer are repeatedly formed.

A metal layer including LiF may be added between the first inorganic layers.

2 is a view showing an OLED organic deposition chamber and an OLED organic deposition and encapsulation process apparatus.

In the OLED organic deposition process and encapsulation process, FMM (Fine Metal Mask) and OMM (Open Metal Mask) are used.

For the realization of a full color display, basic pixels of the three primary colors of light, red, green, and blue, are required.

The FMM is a mask used for depositing the light emitting layer and RGB pixels, and the OMM is a mask used for the deposition process of the cavity layer of the cell.

For one model deposition process, FMM requires 3 masks, and OMM typically requires 6 to 8 masks.

There are several methods for the encapsulation process, and accordingly, the quantity of OMM may be changed.

3 shows an OLED deposition and encapsulation process and a metal mask required therefor.

Due to the recent technological development of OLED materials, processes, and equipment, and the explosive increase in demand, OLED display panel makers are converting their OLED mass production lines from the 4th and 5th generation (4G, 5G) levels to the 6th generation (6G) level.

As the glass substrate is changed to a large-area production method using a size of 6 Gh (925 mm × 1,500 mm), a mask frame assembly is required along with the appropriate FMM and OMM fabrication.

In the case of FMM, it is possible to manufacture a stick-shaped split mask and attach several to the mask frame.

However, in the case of OMM, since it is impossible to manufacture a split mask, it must be manufactured as a full size-one piece mask.

The OMM, which has the same size as the large-area 6 Gh (925 mm × 1,500 mm) glass substrate required by OLED display panel makers, requires more precise specifications than 4G and 5G in terms of positioning precision, dimensional precision, and pattern precision.

Since FMMs of 500 to 600 PPI are currently being produced at 200 to 300 PPI (Pixel Per Inch) pixel level, OMMs are also required to have a high level of precision in proportion to this.

However, in the case of manufacturing a large-area OMM, it is urgent to take measures against fundamental causes such as large-area Invar disk wave, etching deviation in large-area etching process, sagging of the mask due to its own weight, and problems with thermal deformation. the current situation.

In addition, as OLED panel manufacturers have recently switched to large-area OLED glass substrate 6 Gh (925 mm × 1,500 mm) production facilities, FMM and OMM, which are key elements required for OLED deposition, are being requested in large-area sizes, and in the case of FMM, Although a method of manufacturing a stick-type split mask and connecting it to a mask frame has been completed and applied, in the case of OMM, a stick-type split mask or a quarter split mask method is being studied, but it is not applied to actual mass production. .

That is, research on OMM of a large area for the deposition of a cavity layer in the organic deposition process is still insufficient.

In short, as OLED display panel makers switch to a production method that uses a large area of 6Gh (925mm X 1500mm) glass substrates to mass-produce more products with one deposition using a larger deposition mask, FMM corresponding to this Larger size of the mask frame assembly of (Fine Metal Mask) and OMM (Open Metal Mask) is requested together.

FMM, OMM, and mask frames all use Invar.

Invar is an alloy of iron and nickel (64% Fe, 36% Ni) and has a uniquely low coefficient of thermal expansion, so it is used for applications requiring dimensional stability and precision.

The thermal expansion coefficient of this Invar is 1.2 x 10 ^-6 K ^-1 (1.2ppm/°C).

FMM for light emitting layer deposition uses an ultra-thin plate with an invar thickness of 20 to 30 μm and can be manufactured as a stick-type split mask, so a number of split masks can be used while checking the positioning accuracy, dimensional accuracy, and pattern precision. A large-area FMM mask assembly can be completed by welding one by one to the mask frame.

However, the OMM is a large-area ledger-type mask, and it must be a complete mask with positional precision, dimensional precision, and pattern precision.

However, the quality level of the current large-area OMM is out of various precision tolerances, which affects the precision of the thin film deposited on the glass substrate, and thus the production yield is low.

The precision required for OMM for deposition of 6Gh (925 mm × 1,500 mm) glass substrates is shown in Table 1 below.

[Table 1]

Currently, OLED is at the level of QHD quality, 500~600 PPI (Pixel Per Inch), and the size of the pixel is about 30 ~ 40 ㎛, so the tolerance requested by OMM of a large area is ultra-precision level that is less than about one pixel. Therefore, it is difficult to manufacture a large-area OMM.

The reason why the current accuracy does not significantly reach the above precision is that, first, in order to produce an OMM for deposition of a 6Gh (925 mm × 1,500 mm) glass substrate, a 1,040 mm wide Invar thin plate must be used, and the 1,040 mm width is the maximum that can be produced by a material company.

Waves are generated in the rolling process of making thin plates in Invar thin plates with the maximum width.

The dimensional change due to the wave of the Invar thin plate greatly deviates from the tolerance range required for large-area OMMs such as positional precision, dimensional precision, and pattern precision required for an organic thin film deposition mask, providing a fatal cause of defects.

Second, the OMM must be processed into a mask that is precisely patterned where the organic material passes and where it is blocked by the photochemical etching method.

A photoresist (PR) is coated on the surface of Invar in the order of the photochemical etching process, which is a lithography method, and after exposure and development, the exposed surface of Invar is etched to form a cell, and then the PR is removed to form a desired pattern. Produces an open mask of

There are about 100 cells of the same size in OMM, and one cell corresponds to one display such as a smartphone.

In addition to the cell, the OMM consists of various patterns such as Align Key, Half Etching, Depth of Half Etching, Taper Angle of Etched Cross Section, and Step Height. .

Cell size, key size, key pitch, cell position accuracy (CPA: Cell Position Accuracy), key position accuracy (KPA: Key Position Accuracy), etc. are measured through the photochemical etching process. However, it is difficult to obtain etching uniformity of about 100 cells distributed throughout the entire area due to etching deviation occurring in the case of a large area.

Third, in the vacuum deposition equipment used by OLED display panel makers, the organic material evaporated by thermal evaporation from the organic material evaporation source at the bottom after fixing the glass substrate on the top by the upward deposition method and attaching the mask frame assembly under the glass substrate It is a structure in which deposition is performed at a desired position on a glass substrate through a mask.

In order to increase deposition precision and production yield, technology development that can improve OMM positional precision, dimensional precision, and pattern precision, as well as technology to reduce shadow effects as much as possible by improving the adhesion between the glass substrate and the mask Development is required, and there is an urgent need to improve deposition uniformity.

In the case of a large-area OMM welded to the mask frame assembly, the central part sags due to its own weight.

In addition, when the deposition process is repeated, thermal deformation occurs, resulting in mask distortion.

Due to this, the position and shape between each cell is distorted, leading to poor deposition, and thus yield is reduced.

Due to the above three problems, the overall precision required for a large-area OMM is not reached.

Republic of Korea Patent Publication No. 10-1173961 Republic of Korea Patent Publication No. 10-1322130 Republic of Korea Patent Publication No. 10-0708654 Republic of Korea Patent Publication No. 10-2017-0045427 Republic of Korea Patent Publication No. 10-1659960

An object of the present invention for solving the conventional problems as described above is to provide a method of manufacturing a large-area open metal mask for OLED deposition that can be manufactured with a ledger while satisfying positional precision, dimensional accuracy, and pattern precision will do

In order to achieve the above object, in the method of manufacturing a large-area open metal mask for OLED deposition according to the present invention, one of two Invar thin plates separates the long axis into a plurality at regular intervals and then changes each length (Δ L) and elongation (ΔL/L × 100%) are measured, and the other sheet is divided into a plurality of short axes at the same interval as the predetermined interval, and then each length change (ΔL) and elongation (ΔL/ a first step of measuring L x 100%); and a second step of reducing and manufacturing two sets of photomask films for the first and second photochemical etching by the measured elongation (ΔL/L×100%).

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, a third step of washing the surface after cutting the thin invar plate; and a fourth step of coating photoresist on both surfaces of the invar.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, the photoresist uses a liquid or dry film, is exposed using the first photomask film, and then developed using a developer. , a fifth step of performing an etching process after exposing only the area to be etched by removing the PR of the area where UV irradiation is blocked.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, the etching uses a ferric chloride solution or a ferric perchlorate solution, the specific gravity of the ferric chloride solution is 1.38 to 1.42, and the temperature is 50 to It is 55 ℃, the spray pressure of the etchant sprayed when the etchant is sprayed is characterized in that 2.5 ~ 3kg / ㎤.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, the region to be etched is a plurality of separated cells and an align key, and the positions of the cells and the key are etched by 30% to the thickness of the invar It is characterized in that it is maintained at 70%.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, a sixth step of coating a photoresist on both surfaces of the invar on which the primary etching is completed; characterized in that it further comprises.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, exposure, development, and etching processes are performed using the secondary photomask film, respectively, and then a peeling process is performed to perform a desired open metal (OMM) A seventh step of obtaining a Mask); characterized in that it further comprises.

In addition, in the method for manufacturing a large-area open metal mask for OLED deposition according to the present invention, the OMM formed by the first to seventh steps is mounted on the mask frame and then stretched by the elongation rate using a tensioner to achieve flatness characterized by maintaining

In addition, in the method of manufacturing a large-area open metal mask for OLED deposition according to the present invention, the key pitch, key position accuracy, and cell position accuracy of the OMM are measured, respectively, to be within the tolerance range, and then laser spot welding is performed, and the outer is removed to form a mask frame assembly.

In order to achieve the above object, the large-area open metal mask for OLED deposition according to the present invention is characterized in that it is manufactured by a method of manufacturing a large-area open metal mask for OLED deposition.

Specific details of other embodiments are included in "Details for carrying out the invention" and the accompanying "drawings".

Advantages and/or features of the present invention, and methods for achieving them, will become apparent with reference to the various embodiments described below in detail in conjunction with the accompanying drawings.

However, the present invention is not limited to the configuration of each embodiment disclosed below, but may also be implemented in a variety of different forms, and each embodiment disclosed herein only makes the disclosure of the present invention complete, and the present invention It is provided to fully inform those of ordinary skill in the art to which the scope of the present invention belongs, and it should be understood that the present invention is only defined by the scope of each of the claims.

According to the present invention, there is an effect of providing a method for manufacturing a large-area open metal mask for OLED deposition that can be manufactured as a ledger while satisfying positional precision, dimensional accuracy, and pattern precision.

1 is a view showing the basic structure and light emission principle of an OLED display.
2 is a view showing an OLED vacuum deposition chamber and an apparatus for an OLED organic deposition and encapsulation process.
3 is a view showing a metal mask required for an OLED organic deposition and encapsulation process.
4 is a process diagram showing a photochemical etching process of a large-area OMM according to the present invention.
5 is a view showing various types of manufacturing patterns for minimizing sagging and thermal deformation of a large-area OMM.
6 is a view showing four types of manufacturing the same OMM.
7 is a manufacturing process diagram of a 6 Gh (925 mm × 1,500 mm) large-area OMM according to the present invention.
Figure 8 is a photograph of the original plate in a state of being stretched as much as ΔL with the original wave.
9 is a view showing ΔL and a reduction ratio for the long axis divided into 100 pieces at an interval of 10 mm.
10 is a view showing ΔL and a reduction ratio for a single axis divided into 150 pieces at an interval of 10 mm.
11 is a view showing the completed mask frame assembly after etching reduced by ΔL, stretching again by ΔL, welding, and removing the outline.
12 is a view showing the amount of deflection of the OMM mask frame assembly manufactured in four types.
13 is a view showing the shape of a mask frame assembly of a finished product manufactured by 4 types of etching OMM.

Before describing the present invention in detail, the terms or words used herein should not be construed as being unconditionally limited to their ordinary or dictionary meanings, and in order for the inventor of the present invention to describe his invention in the best way It should be understood that the concepts of various terms can be appropriately defined and used, and further, these terms or words should be interpreted as meanings and concepts consistent with the technical idea of the present invention.

That is, the terms used herein are only used to describe preferred embodiments of the present invention, and are not used for the purpose of specifically limiting the content of the present invention, and these terms represent various possibilities of the present invention. It should be noted that the term has been defined with consideration

Also, in the present specification, it should be understood that, unless the context clearly indicates otherwise, the expression in the singular may include a plurality of expressions, and even if it is similarly expressed in plural, it should be understood that the meaning of the singular may be included. .

In the case where it is stated throughout this specification that a component "includes" another component, it does not exclude any other component, but further includes any other component unless otherwise stated. It could mean that you can.

Furthermore, when it is described that a component is "exists in or is connected to" of another component, this component may be directly connected to or installed in contact with another component, and a certain It may be installed spaced apart by a distance, and in the case of being installed spaced apart by a certain distance, a third component or means for fixing or connecting the corresponding component to another component may exist, and now It should be noted that the description of the components or means of 3 may be omitted.

On the other hand, when it is described that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the third element or means does not exist.

Similarly, other expressions describing the relationship between components, such as "between" and "immediately between", or "neighboring to" and "directly adjacent to", have the same meaning. should be interpreted as

In addition, if terms such as "one side", "the other side", "one side", "other side", "first", "second" are used in this specification, with respect to one component, this one component is It is used to be clearly distinguished from other components, and it should be understood that the meaning of the component is not limitedly used by such terms.

In addition, in the present specification, terms related to positions such as "upper", "lower", "left", and "right", if used, should be understood as indicating a relative position in the drawing with respect to the corresponding component, Unless an absolute position is specified with respect to their position, these position-related terms should not be construed as referring to an absolute position.

In addition, in this specification, in specifying the reference numerals for each component of each drawing, the same component has the same reference number even if the component is shown in different drawings, that is, the same reference is made throughout the specification. Symbols indicate identical components.

In the drawings attached to this specification, the size, position, coupling relationship, etc. of each component constituting the present invention are partially exaggerated, reduced, or omitted for convenience of explanation or in order to sufficiently clearly convey the spirit of the present invention. may be described, and therefore the proportion or scale may not be exact.

In addition, in the following, in describing the present invention, a detailed description of a configuration determined that may unnecessarily obscure the subject matter of the present invention, for example, a detailed description of a known technology including the prior art may be omitted.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the related drawings.

Since large-area glass substrates are used in the OLED display production line in a size of 6Gh (925 mm × 1,500 mm), a large-area OMM suitable for this is required.

OMM is the most important element along with FMM in the deposition process, and it must satisfy positional precision, dimensional precision, and pattern precision, and must be manufactured as a full size-one piece mask.

In order to manufacture OMM for 6Gh (925mm × 1,500mm) glass substrate, a 1,040mm wide Invar plate must be used.

The 1,040mm width of thin sheet Invar is the largest size of sheet currently supplied by material companies. In order to produce thin sheet of Invar with a width of 1,040 mm, hot rolling → Cold Rolling → Annealing → Cold Rolling → Through several processes such as Annealing → Skin Pass → Annealing → TL (Tension Leveling) → SR (Stress Relieving), the physical properties such as crystal grain control, flatness improvement, and internal stress relief are adjusted and supplied as raw materials for OLED deposition masks.

Invar thin plate with a width of 1,040 mm is produced only by a specific material company, and it can be seen that there is a wave generated during the rolling process, and there is a large difference in the degree of wave for each production lot.

The present invention has a fundamental problem that the wave shape of Invar is not constant for each supplied lot, and cannot satisfy the positional precision, dimensional precision, and pattern precision of OMM due to dimensional change due to wave, and fundamentally solves this problem. In order to do this, the dimensional change (ΔL) and elongation (ΔL/L × 100%) of the 1,040 mm wide Invar plate must be identified in advance and measures should be taken.

As a result of research on a method to measure the dimensional change (ΔL) and elongation (ΔL/L × 100%) caused by waves existing in a 1,040 mm wide Invar plate, the present invention has After separation, measure the length of each to calculate the elongation.

Separate the thin Invar plate (1,000 mm × 1,500 mm) in the form of 100 sticks at intervals of 10 mm in the long side direction, measure the length of each, and then separate 150 sticks at intervals of 10 mm in the short axis direction, and then separate the lengths of each is measured to calculate the increased dimension (ΔL) and elongation (ΔL/L × 100%).

The stick type separation method uses PR as a lithographic method, and after exposure with a photomask film, development and etching are performed.

After determining the dimensional change (ΔL) and elongation (ΔL/L × 100%) of the 1,040 mm wide Invar wave supplied from a material company, the mask pattern data is plotted to produce the photo required for OMM production. When manufacturing the mask film, a photomask film with the elongation reduced in advance is manufactured and used, and by applying tension in the OMM tensioning process to stretch by the elongation, the dimensional change due to the wave is offset and welded.

Dimensional change (ΔL) and elongation (ΔL/L × 100%) should be measured for each lot and applied when manufacturing a photomask film.

The OMM is manufactured by a photochemical etching process using a lithography method.

There are about 100 cells in the large-area OMM, and the cell size (corresponding to one display) of all cells opened by photochemical etching is within ±40㎛, and the cell positioning accuracy of all 100 cells ( Cell Position accuracy), it is impossible to control the etching deviation to maintain the precision within ±40㎛.

Currently, OMMs are manufactured using thin Invar plates with a thickness of 200 μm, a width of 1,040 mm, and a length of 1,800 mm.

In addition to about 100 cells in a large-area OMM, various components such as alignment key, half-etching, taper angle of the etching cross-section, and step height are all patterned on one OMM.

In the case of manufacturing an OMM by one etching using the existing 200㎛ thick Invar plate, the cell size, cell positioning accuracy, key pitch, and key positioning accuracy, etc., are within the tolerance range due to etching deviation occurring in about 100 cells. Precise machining is impossible.

In the present invention, a method of using an Invar having a thickness of 100 μm, which cannot be used in a large-area OMM manufacturing process, was studied.

In the case of a thin 100㎛ Invar plate, due to its too thin thickness, it cannot be applied to mass production due to excessive generation of defects when used in the photochemical etching process of a large-area OMM.

In the present invention, a 100 μm thick thin plate is used for a large-area OMM through process improvement, equipment development, process automation, etc. to enable normal production.

The present invention provides an etching method capable of securing precision of cells and keys by first performing single-sided etching and then penetrating through double-sided etching secondarily to minimize etching deviation.

In the present invention, the cell and key are etched by double-sided etching only with the remaining thickness of 70 μm again through the second pre-photochemical etching process after first etching the cross section of about 30 μm through the pre-photochemical etching process with a 100 μm-thick Invar thin plate. By forming it, it is possible to manufacture an OMM that minimizes etching deviation and processes positional accuracy, dimensional accuracy, and pattern accuracy within tolerances.

When using 200㎛, the etching deviation occurs more than 20㎛, but when etching a thin 70㎛ as in the present invention, the etching deviation is only about 5 ~ 6㎛.

4 shows a photochemical etching method of the present invention.

In the case of large-area OMM, even if it is accurately tensioned and welded to the mask frame, deflection occurs in the middle part due to the OMM's own weight.

In addition, repeated use in the deposition process causes thermal deformation, causing pattern errors during the deposition process, resulting in quality problems due to shadow effects.

Therefore, in the case of a large-area OMM, a method for reducing its own weight is required.

In the present invention, 100 μm inbar is used instead of 200 μm thick, and the final mask weight is greatly reduced by partially half-etching the ribs, outer edges, or cells of the pattern, thereby minimizing sagging and thermal deformation.

5 is a method for minimizing sagging and thermal deformation by reducing the weight of the mask, ① in FIG. 5 shows half etching of the cell and rib, and ② and ③ in FIG. 5 are outer parts It shows that it penetrates in various shapes, and ④, ⑤, ⑥, ⑦ of FIG. 5 shows half-etching of one side or both sides.

Although configured as described above for ease of description, the present invention is not limited to such a configuration, and may be implemented in various forms.

The present invention manufactures a photomask film that is reduced by the elongation by grasping the elongation of the invar wave, and in the photochemical etching process, it is divided into a first pre-process and a second pre-process, and is 1/3 thick through the second pre-process. By double-sided etching the reduced 70㎛ to form cells and keys, the etching deviation is minimized. Also, by devising 4 manufacturing types for manufacturing OMM, tension and welding are easy, and sagging and thermal deformation are minimized to minimize the mask frame. It is possible to increase the efficiency of assembly production.

6 shows four types of OMMs of the same model, but is not limited thereto, and may be implemented in various forms.

As OLED display panel makers switch from 4th, 5th, and 6th generation large-area glass substrates to a production method using 6Gh (925mm × 1,500mm) in order to mass-produce large quantities with one deposition, an essential increase There has been a request for enlargement of the wearable metal masks FMM and OMM.

FMM for light emitting layer deposition is required for red, green, and blue deposition for pixel formation, and can deposit sub-pixels with a size of 10 to 20 μm using an ultra-thin plate with a thickness of 20 to 30 μm in Invar. It can be manufactured as a split mask with multiple through-holes, and a large number of split masks are welded one by one to a large mask frame while checking the positional precision, dimensional accuracy, and pattern precision, then the mask frame assembly of a large FMM used in the deposition process is manufactured. can be completed

However, since OMM for co-layer deposition is impossible to manufacture a split mask like FMM, it is a single completed mask with positional precision, dimensional precision, and pattern precision. It is manufactured as a large-area ledger-type mask and used in the deposition process. A large OMM (Open Metal Mask) mask frame assembly is required.

While various methods for manufacturing and using a stick-type segmentation mask have been studied for manufacturing the mask frame assembly of a large FMM, the method of manufacturing a mask frame assembly of a large OMM is not practically applied.

The present invention established a ledger-type mask and mask assembly manufacturing method with positional precision, dimensional precision, pattern precision, etc. using a large-area OMM using one thin sheet of Invar, thereby greatly improving the deposition uniformity and yield. have.

Analyze the dimensional change (ΔL) and elongation (ΔL/L × 100%) due to waves existing in a large-area thin plate of Invar, and reduce the photomask film used in the lithographic photochemical etching process by the elongation. The etched OMM is stretched again as much as the elongation rate to achieve accurate precision.

In addition, in the method of using 200㎛ thickness of Invar thin plate used for large-area OMM production, 100㎛ thickness is used, and the lithographic photochemical etching process is performed through the first and second pre-processes to precisely align keyholes with cells. By processing (Align Key Hole), etc., the etching deviation problem can be solved.

In addition, it is possible to reduce the weight by half-etching around the cells and ribs of the thin Invar plate used for manufacturing large-area OMMs, and to minimize sagging and thermal deformation of the mask by processing various shapes of the outer part.

The present invention solves all these various problems in a holistic way to manufacture a complete OMM with positioning precision, dimensional precision, pattern precision, etc. for a large-area OMM required for organic material deposition on a large-area 6Gh (925 mm × 1,500 mm) glass substrate. can do.

In a specific embodiment of the present invention, OMM for deposition of 90 cells of smartphone standard (73 mm × 157 mm) is manufactured, but in addition to smartphones, foldable phones with high-resolution pixels of 600 ppi, smart watches, PCs, notebooks, and automobile displays It is possible to manufacture large-area OMMs for , monitors, etc., so it can be applied to mass production of various products.

In addition, the present invention is a technology capable of making a large-area OMM can be applied in various ways.

When the cell size is very large and the quantity is small, if the gap between the ribs is wide or the width of the ribs is narrow, so that sagging or deformation of the mask is concerned, it is possible to manufacture a photomask film by applying a reduction ratio larger than the elongation of the original plate. It is possible to manufacture an OMM of a large area with precision by applying tension to it.

In addition, when it is necessary to further increase the current cell position accuracy, cell size, etc., it is also possible to finely trim the cross section of the OMM completed by the manufacturing method of the present invention using a laser.

In addition, in order to increase the organic deposition efficiency, it is possible to adjust the cell cross section of the OMM to various patterns.

Since the Half Depth can be adjusted from 5 to 70㎛, the taper angle from 30 to 80 ^ㅇ , and the step height to about 5 to 40㎛, it is possible for OLED display panel makers to design more diverse patterns of FMM or OMM. It is possible.

In addition, according to the present invention, even when changing from the maximum glass substrate 6Gh (925mm × 1,500mm) applied to mass production by OLED display panel makers to a larger size, OMM corresponding to this can be manufactured.

The OMM required for the deposition of a large-area 6Gh (925 mm × 1,500 mm) glass substrate must be manufactured in the form of a full size - One Piece Mask, and the cell position accuracy ( Cell Position Accuracy), Key Position Accuracy, dimensional accuracy, and accuracy of key pitch, cell size, and key size indicating pattern precision must be secured.

A fundamental solution to the numerical change (ΔL) and elongation (ΔL/L × 100%) caused by waves in a large-area, 1,040 mm thin Invar plate, and the A large-area OMM that satisfies precision through a solution that can overcome the etching deviation and a method that can minimize the occurrence of deposition defects due to the occurrence of sagging due to the weight of the completed OMM and the distortion of the cell due to thermal deformation can be manufactured, thereby maximizing the precision of the deposition pattern overall.

The large-area OMM manufacturing process established in the present invention is shown in FIG. 7 .

In addition, FIG. 8 is a photograph showing the original plate changed to a flat state while the wave is finely stretched by ΔL when it is separated by 10 mm from the Invar plate having waves.

- OMM manufacturing method for large area deposition -

1. Elongation (ΔL/L × 100%) calculation and photomask film production

First, prepare two thin 100㎛ Invar plates with a size of 1,000 mm × 1,500 mm, and one sheet separates the long axis (1,500 mm) into 100 pieces at an interval of 10 mm, and then measures the change in length of 100 pieces to determine ΔL and Calculate the elongation.

The calculated result is shown in FIG. 9 .

The other sheet divides the short axis (1,000mm) into 150 pieces at 10mm intervals, then measures the change in length of 150 pieces and calculates ΔL and elongation.

The result calculated in this way is shown in FIG. 10 .

It can be seen that ΔL of the major axis is 500 μm and the elongation (ΔL/L × 100%) is 0.033% as 500 μm/1,500 mm × 100%.

It can be seen that ΔL of the short axis is 300 μm and the elongation (ΔL/L × 100%) is 0.03% as 300 μm/1,000 mm × 100%.

While the dimensional accuracy required for the key pitch of the major axis is ±40㎛, the dimensional change (ΔL) by invar wave used for OMM production reaches 500㎛, which is more than 10 times the dimensional accuracy required for OMM. It can be seen that it is out of

The data on the drawing of the OMM to be made in the embodiment of the present invention is the key pitch (1,485 mm long axis, 950 mm short axis), the cell size (73 mm × 157 mm), and the number of cells is 90.

Therefore, in the present invention, the photomask film is manufactured by reducing the data on the original drawing of the pattern by an elongation of 0.033%.

Photochemical etching The primary photomask film and the secondary photomask film are produced with data reduced by the elongation rate.

2. Photochemical etching/tensile, welding

After cutting the thin Invar plate with a thickness of 100㎛ and a width of 1,040㎜ to 1,800㎜ in length, the surface is washed.

PR is coated on both sides of Invar.

In this case, a liquid or dry film may be used for PR, and both positive and negative types may be used.

After UV exposure using a photomask film reduced by elongation (ΔL/L × 100%) for primary photochemical etching and developing using a developer, the PR in the area blocked from UV irradiation is removed and etched Only the part to be made is exposed.

For etching, a ferric chloride solution or a ferric perchlorate solution is used, and a ferric chloride solution is mainly used.

The specific gravity of the ferric chloride solution is 1.38 ~ 1.42, the temperature is 50 ~ 55℃, and the spray pressure is 2.5 ~ 3kg / ㎤ is suitable.

Specific gravity, temperature, pressure, etc. can be changed to different conditions depending on the equipment used (steps 1 to 7 of FIG. 4 ).

The most important factor in the etching process is to ensure the etching uniformity by always maintaining the etching rate constant.

In the first photochemical etching process, the thickness is reduced to about 70 μm by etching about 30 μm at the cell and key positions.

When the first pre-process is completed, the PR is coated on both sides again.

After performing exposure, development, and etching processes using a photomask film prepared for secondary photochemical etching, the desired OMM can be obtained by peeling the PR using a stripper (Steps 8 to 13 in FIG. 4 ) ).

In the secondary process, the PR coating must be perfect, and it is important to match the photomask film for the secondary process in the correct position with the primary etched product.

In the mask on which the secondary photochemical etching process has been completed, 90 cells are etched and open, and it can be seen that the etching deviation of 90 cells is within ±5 μm.

After the OMM manufactured by repeating the photochemical etching process twice is mounted on the mask frame, the OMM is stretched as much as the elongation using a tensioner to maintain flatness, and the key pitch, key positioning accuracy, cell positioning accuracy, etc. are measured to tolerance After confirming that it is within the range, laser spot welding is performed and the outline is removed to complete the mask frame assembly.

11 shows the final mask frame assembly completed by manufacturing an etching mask reduced by the elongation, then stretching and welding the etching mask by the elongation, and then removing the outer portion.

- Examples 1 to 4 -

To fabricate a large-area OMM of 90 cells with a key pitch (major axis: 1,485 mm, short axis 953 mm) and cell size (73 mm × 157 mm), 100 μm thick and size (,1040 mm × 1,800 mm) Prepare the Invar sheet.

In order to measure ΔL and elongation (ΔL/L × 100%) due to the wave of the same lot invar, the long axis is divided into 100 equal parts and the short axis is divided into 150 equal parts, and the change in length is measured, and the elongation rate is 0.033% It can be confirmed that

A photomask film for primary photochemical etching and secondary photochemical etching processes is manufactured by reducing the pattern based on the original drawing data by the elongation (0.033%).

Four types of photomask films of different types that can produce the same OMM are also manufactured in the same way.

According to the manufacturing process of the present invention, the pre-primary photochemical etching process can obtain a mask having a cross section of 30 μm etched through the PR coating, exposure, development, etching, and peeling processes.

In the pre-process of the secondary photochemical etching, after PR coating, exposure, and development, double-sided etching of 70 μm thick Invar, and peeling, minimize the etching deviation of 90 cells to obtain etching uniformity.

In the present invention, the etching deviation can be minimized because the cell and the key are formed by double-sided etching after processing to a thickness of 70 μm, which is about 1/3 compared to the conventional 200 μm thick invar.

After mounting the OMM manufactured by performing the photochemical etching process twice on the mask frame, it uses a tensioner to maintain flatness and, at the same time, stretch the long axis and the short axis by the elongation rate. Key positioning accuracy, cell positioning accuracy, key pitch, Measure cell size, key size, etc.

After confirming the precision within the tolerance, laser spot welding is performed on the mask frame to complete the mask frame assembly.

After completing the mask frame assembly by tensioning and welding the OMMs manufactured in the four types (A, B, C, and D types) proposed in the present invention, the results of measuring each precision are shown in Table 2 below.

The precision measurement is measured with a US Visiontec model MVP 1552 measuring machine.

[Table 2]

It can be seen that Example 2 (Type B) is the best in all precision.

In the case of Example 1 (Type A), the cell position accuracy is slightly lower than that of Type B, but it is within the precision tolerance, and in the case of Examples 3 (C type) and 4 (D type), mask frame assembly such as tensioning and welding is manufactured However, it can be seen that the precision of OMM is somewhat inferior.

It can be seen that the amount of deflection is large for C and D types as shown in FIG. 12 .

13 shows an OMM (Open Metal Mask) manufactured in four different shapes and a final completed mask frame assembly that is tensile-welded to a mask frame.

In the above, although several preferred embodiments of the present invention have been described with some examples, the descriptions of various various embodiments described in the "Specific Contents for Carrying Out the Invention" item are merely exemplary, and the present invention Those of ordinary skill in the art will understand well that the present invention can be practiced with various modifications or equivalents to the present invention from the above description.

In addition, since the present invention can be implemented in various other forms, the present invention is not limited by the above description, and the above description is for the purpose of completing the disclosure of the present invention, and it is common in the technical field to which the present invention pertains. It is to be understood that this is only provided to fully inform those with knowledge of the scope of the present invention, and that the present invention is only defined by each of the claims.

Claims (10)

One of the two thin sheets of Invar separates the long axis into a plurality of sheets at regular intervals and measures the change in length (ΔL) and elongation (ΔL/L × 100%) of each, and the other sheet refers to the short axis. a first step of measuring a change in length (ΔL) and an elongation (ΔL/L × 100%) of each after separating a plurality of pieces at the same interval as a predetermined interval; and
a second step of reducing and producing two sets of photomask films for primary and secondary use for primary and secondary photochemical etching by the measured elongation (ΔL/L × 100%); doing,
A method for manufacturing a large-area open metal mask for OLED deposition.
The method of claim 1,
a third step of washing the surface after cutting the thin Invar plate; and
A fourth step of coating photo resist (Photo Resist) on both sides of the invar; characterized in that it comprises,
A method for manufacturing a large-area open metal mask for OLED deposition.
3. The method of claim 2,
The photoresist uses a liquid or dry film,
A fifth step of performing an etching process after UV exposure using the primary photomask film and developing using a developer to remove the photoresist in the area to be etched by removing the photoresist in the area to be etched; characterized in that
A method for manufacturing a large-area open metal mask for OLED deposition.
4. The method of claim 3,
The etching uses a ferric chloride solution or a ferric perchlorate solution,
The specific gravity of the ferric chloride solution is 1.38 ~ 1.42, the temperature is 50 ~ 55 ℃, characterized in that the spray pressure of the etchant sprayed when the etchant is sprayed is 2.5 ~ 3kg / ㎤,
A method for manufacturing a large-area open metal mask for OLED deposition.
4. The method of claim 3,
The area to be etched is an align key with a plurality of separated cells,
characterized in that the thickness of the invar is maintained at 70% by etching the position of the cell and the key by 30%,
A method for manufacturing a large-area open metal mask for OLED deposition.
6. The method of claim 5,
A sixth step of coating a photoresist on both sides of the invar after the etching has been completed; characterized in that it further comprises,
A method for manufacturing a large-area open metal mask for OLED deposition.
7. The method of claim 6,
A seventh step of obtaining a desired Open Metal Mask (OMM) by performing exposure, development, and etching processes using the secondary photomask film, respectively, and then performing a peeling process; characterized in that it further comprises,
A method for manufacturing a large-area open metal mask for OLED deposition.
8. The method of claim 7,
After mounting the OMM formed by the first to seventh steps on the mask frame, it is characterized in that the flatness is maintained while stretching by the elongation rate using a tensioner,
A method for manufacturing a large-area open metal mask for OLED deposition.
9. The method of claim 8,
A mask frame assembly is formed by measuring the key pitch, key position accuracy, and cell position accuracy of the OMM, confirming that they are within a tolerance range, performing laser spot welding, and removing the outer periphery,
A method for manufacturing a large-area open metal mask for OLED deposition.
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