JP2007224396A - Film-forming method, and mask used in forming film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a mask tightly contact with a substrate so as not to form a gap between them when forming a film. <P>SOLUTION: This film-forming method includes the steps of: making the mask 20 closely contact with the substrate 10 which has been arranged so as to direct the surface to be film-formed downward; and forming an organic electroluminescent layer of an organic electroluminescent element on the substrate 10. The film-forming method also includes; setting the substrate 10 and the mask 20 so that a deflection quantity of the substrate 10 is larger than that of the mask 20, before making them closely contact with each other pressing the mask 20 to the substrate 10 to make the mask 20 closely contact with the substrate 10 along the deflection shape of the substrate 10; and forming the film with a vapor deposition technique in the state. The film-forming method makes the mask 20 closely contact with the substrate 10 by using the deflection due to the tare mass of the substrate 10 without using a permanent magnet or a pressing device, and can form a highly precise pattern without causing the deviation of the pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film forming method and a film forming mask for manufacturing an organic EL (electroluminescence) element and the like.

  2. Description of the Related Art Conventionally, many organic EL element manufacturing methods employ a method in which a film formation mask (mask) is formed in close contact with a film formation substrate such as a glass substrate. Thus, the pattern of the organic EL layer can be formed with high accuracy by the mask film forming method in which the mask is closely attached. In recent years, patterning miniaturization has progressed with the increase in resolution of organic EL panels. For this reason, the quality deteriorates due to a slight geometric misalignment between the pixel pattern on the glass substrate and the mask pattern and poor adhesion between the glass substrate and the mask.

  In particular, it is known that poor adhesion between a glass substrate and a mask is caused by slight distortion of the mask or sagging of the mask itself due to its own weight. As an improvement measure, as disclosed in Patent Document 1, a deposition method is known in which a mask for attracting a mask is disposed on the back side of the substrate so that the mask and the substrate are in close contact with each other. The mask uses a magnetic material to be attracted to the magnet.

Furthermore, Patent Document 2 discloses a method of depositing the substrate and the mask in close contact by dynamically pressing the substrate against the mask.
JP 2001-3155 A JP 2005-281746 A

  However, since the vapor deposition method of patent document 1 is a method using a magnet, it is necessary to use a magnetic mask, and the mask material is limited. In addition, since the magnetic force is generated not only in the vertical direction but also in the horizontal direction with respect to the substrate or mask, positional displacement occurs when the magnet or mask is detached from the substrate, or the film deposited on the substrate is peeled off. There is a fear.

  The vapor deposition method of Patent Document 2 requires a device for pressing the substrate, which increases the cost, and it is necessary to control the pressing force constant for each mask in order to maintain the positional accuracy of the mask and the substrate. .

  In addition, regarding the problem of poor adhesion between the mask and the substrate, it is necessary to consider not only the deflection of the mask but also the deflection of the substrate itself. Since the amount of deflection differs depending on the thickness and rigidity of the mask and the substrate, the amount of deflection of the substrate 110 is the amount of deflection of the mask 120 when the substrate 110 and the deposition mask 120 are not in contact with each other, as shown in FIG. May be smaller. In such a situation, as shown in FIG. 5B, when the substrate and the mask are brought into close contact with each other, a gap is generated between the substrate 110 and the mask 120 by the difference in the amount of deflection between the two and the contact failure occurs. To do.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and provides a film forming method and a film forming mask capable of manufacturing a high-quality organic EL element and the like with high patterning accuracy. It is intended to provide.

  The film-forming method of the present invention is a film-forming method using a film-forming mask, and includes a step of supporting a film-forming substrate with a film-forming surface facing downward and a film-forming mask so as to face each other. The film-forming substrate and the film-forming mask are in close contact with each other, and the film-forming film is formed on the film-forming substrate through the closely-attached film-forming mask. The amount of deflection due to the weight of the film forming substrate before the deposition is greater than the amount of deflection due to the weight of the film forming mask.

  Without using other external force such as a magnet, the adhesion between the film formation substrate and the film formation mask is improved, and there is little pattern deviation between the pixels etc. arranged on the film formation substrate, It becomes possible to manufacture an organic EL element or the like with good dimensional accuracy.

  By forming a thin-walled portion or an opening in the frame of the film-forming mask, the material used for the film-forming mask can be reduced, which can contribute to cost reduction and environmental burden reduction. In addition, by reducing the weight of the film formation mask, it is possible to reduce the burden of the film formation mask transfer device and handling.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 illustrates a process of forming an organic EL layer of an organic EL element by vapor deposition using a film forming method according to an embodiment. As shown in FIG. 1A, a mask (supported by a support unit 2) is supported on a lower side of a substrate (deposited substrate) 10 whose support surface 1 supports a deposition surface (film formation surface) downward. The film deposition mask) 20 is made to face and the mask deposition is performed while being in close contact with the substrate 10 as shown in FIG.

  Before the substrate 10 is brought into close contact with the mask 20, it is supported so that the amount of deflection of the mask 20 is smaller than the amount of deflection of the substrate 10 due to its own weight. It becomes possible to make it adhere closely.

  In order to calculate the deflection amount of the substrate 10 or the mask 20 due to its own weight, for example, the calculation may be performed using arithmetic processing by a finite element method. The calculation process by the finite element method and the analysis technique using the calculation process can be realized using a known technique.

  In this way, by controlling the amount of deflection between the substrate 10 and the mask 20 before being adhered, the substrate 10 and the mask 20 can be brought into close contact with each other without any external force such as a magnet or pressing. It becomes possible.

In order for the amount of deflection of the substrate supported opposite to the mask to be larger than the amount of deflection of the mask before adhesion under the same conditions as in vapor deposition, the following conditions may be satisfied. That is, the Young's modulus obtained by homogenizing the substrate and the mask is E _G , E _M , the specific gravity is ρ _G, ρ _M, and the cross-sectional second moment in the direction perpendicular to the substrate surface (deposition surface) and the mask surface is I _G , I _{When M} , the width of the substrate, and the mask are L _C and L _M , the following equation should be satisfied.
(ρ _G × L _G ³ ) / (E _G × I _G )> (ρ _M × L _M ³ ) / (E _M × I _M ) (1)

  Pixel portions and electrodes are formed on the surface of the substrate 10, and the mask 20 includes a plurality of mask portions 21 and a frame 22 that supports the mask portions 21 as shown in FIG. 2. The material properties such as Young's modulus and specific gravity of the substrate 10 and the mask 20 are anisotropic, and the material properties of the substrate 10 and the mask 20 as a whole can be applied with the homogenized material properties obtained by a known structural simulation. it can.

By the way, the deflection amount of a general flat plate is as follows: P is the gravity applied to the flat plate, L is the distance between the support points supporting the flat plate, E is the Young's modulus of the flat plate, and I is the moment of inertia of the cross section.
Deflection amount = (P × L ³ ) / (α × E × I) (2)
It can be expressed as Here, α is a constant that varies depending on the method of fixing and supporting the flat plate. In any object, gravity P that is equally loaded with respect to the mass of the object is proportional to the specific gravity of the object, so that gravity P can be replaced with specific gravity ρ when comparing the deflection amount of the substrate and the mask. When the substrate and the mask are brought into close contact with each other during vapor deposition and fixedly supported, α of the substrate and the mask can be set to the same value. Therefore, the conditional expression that causes the deflection amount of the substrate to be larger than the deflection amount of the mask is expressed by equation (1).

  When a substrate and a mask formed so as to satisfy the expression (1) are used, the amount of deflection of the substrate when opposed and supported under the same conditions becomes larger than the amount of deflection of the mask, and the substrate and the mask are brought into close contact during vapor deposition. It becomes possible.

As described above, the mask 20 includes the mask portion 21 and the frame 22 having a thickness H that supports the mask portion 21 by applying tension thereto. As shown in (b) of FIG. 2, when supporting the mask 20 by the support means 2 in the area on the two sides facing the frame 22, the width L _M of the mask 20 corresponds to the distance between the support and the two sides To do. The mask unit 21 has a plurality of vapor holes for mask vapor deposition. In FIG. 2, the plurality of mask portions 21 are provided. However, this is not limited as long as mask vapor deposition is possible. For example, a mask having only a single mask portion may be used. Further, the mask portion 21 is not limited to a rectangular shape, and may have any shape.

For the mask portion 21, a member such as copper, nickel, and stainless steel can be used. Alternatively, the mask portion 21 may be formed by electroforming using a nickel alloy such as nickel, a nickel-cobalt alloy, an invar material that is a nickel-iron alloy, or a super invar material that is a nickel-iron-cobalt alloy. In particular, since the thermal expansion coefficient of Invar material and Super Invar material is 1-2 × 10 ⁻⁶ / ° C., which is smaller than that of other metals, deformation of the mask 20 due to thermal expansion during vapor deposition can be suppressed.

  The frame 22 has a large rigidity for fixing and supporting the mask portion 21 in a state in which a tension is applied, and has a sufficient thickness and width to give the rigidity. In particular, it is preferable to increase the width of the outermost periphery of the frame 22, but this is not necessary as long as the accuracy of the mask portion 21 can be maintained. The frame 22 can be made of a material having a low thermal expansion coefficient such as an invar material that is a nickel-iron alloy or a super invar material that is a nickel-iron-cobalt alloy. By using a material having a low thermal expansion coefficient for the frame 22, the effect of suppressing deformation of the mask due to thermal expansion can be obtained as in the case of using the mask portion 21.

  As shown in FIG. 3, when performing vapor deposition while supporting two opposite sides of the mask 20, a thin portion in which the thickness of the frame portion parallel to the two opposite sides is smaller than the thickness of the remaining frame portion 22a may be provided.

Since the secondary moment of inertia I _M of the mask 20 is proportional to the cube of the thickness H of the mask 20, it is clear from the equation (2) that the amount of deflection increases as the thickness H is reduced. As shown in FIG. 3, when the mask 20 is supported by two opposing sides, the thickness of the frame portion in the direction perpendicular to the two sides greatly affects the cross-sectional second moment, that is, the deflection amount of the mask 20. On the other hand, the thickness of the frame portion parallel to the two sides to be supported is in a direction in which the influence on the deflection of the mask 20 is small, and therefore, the thickness of the frame portion in the vertical direction does not greatly affect the deflection amount. Therefore, even if the thin-walled portion 22a having a reduced thickness is provided, the influence on the cross-sectional secondary moment I _M is small, and the specific gravity ρ _{M of the} mask 20 is reduced by the reduction in the thickness of the frame. The amount can be made smaller. As a result, the right side of the equation (1) becomes small and works in a direction that satisfies the equation (1), so that the substrate 10 and the mask 20 can be brought into close contact with each other.

  The area in which the thickness of the frame 22 is reduced is not particularly limited, but the area close to the center of gravity of the mask 20 is preferable because it aims to reduce the amount of deflection of the mask 20.

Alternatively, as shown in FIG. 4, when vapor deposition is performed while supporting two sides of the frame 22, the opening 22 b may be formed in a frame portion parallel to the two supported sides. Even if the opening 22b is formed in a part of the frame 22, since the influence on the deflection of the mask 20 is small as described above, the deflection amount is not greatly affected unlike the frame portion in the vertical direction. That is, even if the opening 22b is formed in the frame 22, the influence on the cross-sectional secondary moment I _M is small, and the specific gravity ρ _{M of the} mask 20 is reduced by the amount of the opening 22b formed in the frame 22. The amount of deflection of 20 can be further reduced. As a result, the right side of the equation (1) becomes small and works in a direction that satisfies the equation (1), so that the substrate 10 and the mask 20 can be brought into close contact with each other.

  The region in which the opening 22b is formed is not particularly limited, but it is intended to reduce the amount of deflection of the mask 20, so that a region closer to the center of gravity of the mask 20 is preferable.

  The opening may be provided after the thickness of the frame part parallel to the two sides to be supported is made smaller than the thickness of the frame part in the vertical direction.

  There may be a single opening or a plurality of openings. For the purpose of reducing the volume of the frame, the opening may have a recessed shape that is not open, or both the opening and the recessed shape may be formed.

  Although the vapor deposition mask for depositing the organic EL layer has been described here, the same applies to the mask for depositing the protective film of the organic EL element by CVD.

An anhydrous alkali glass substrate (Young's modulus 7 × 10 ¹⁰ Pa, specific gravity 2.5) having a size of 400 mm × 500 mm and a thickness of 0.7 mm was used as the substrate. Thin film transistors, electrode wirings, and pixel electrodes are formed in a matrix on this substrate by a conventional method. The mask for vapor deposition of the organic EL layer is a size of 400 mm × 500 mm made of Invar material (Young's modulus 14.4 × 10 ¹⁰ Pa, specific gravity 8.85), and is 1 mm thick on the substrate side surface. The mask portion was formed by electroforming while adjusting the pattern accuracy. The mask portion was 40 mm × 60 mm in size and 20 μm thick, and was arranged in a total of 42 matrices of 6 × 7 for one mask.

  When the amount of deflection of the substrate was measured while supporting the opposing long sides of the substrate, the amount of deflection from the supported side to the region of the substrate that bent most downward was 4.2 mm. Similarly, when the amount of deflection of the mask is measured while supporting the opposite long sides of the mask, the amount of deflection from the supported side to the area of the mask that is most bent downward is 1.6 mm, which is the amount of deflection of the substrate. The value was larger than the amount of deflection of the mask.

The known Young's modulus and specific gravity of the mask were found to be 14.0 × 10 ¹⁰ Pa and 4.4, respectively, by a known structural calculation using the finite element method. Based on these material characteristic values, the ratio of the left side and the right side of Equation (1) is found to be about 3: 1, which is a measured value of the deflection amount of each of the substrate and the mask, 4.2 mm and 1. It became almost the same as the ratio of 6 mm.

  Position alignment was performed so that the vapor passage hole portion of the pattern portion of the mask and the pixel pattern on the substrate coincided, and the long sides facing the substrate and the mask were supported and adhered.

  Thus, the organic EL element in which the pattern of the organic EL layer with good dimensional accuracy is formed on the substrate is manufactured by improving the adhesion between the mask and the substrate and performing vacuum deposition using a known light emitting material. Thus, an organic EL display device free from display unevenness could be realized.

  The organic EL layer was formed under the same conditions as in Example 1 except that the thickness of the frame portion parallel to the opposing long sides of the mask was 0.5 mm and the thickness of the frame portion in other regions was 0.7 mm. Vapor deposited.

  When the amount of deflection of the substrate was measured while supporting the opposing long sides of the substrate, the amount of deflection from the supported side to the most downwardly bent region was 4.2 mm. Similarly, when the amount of deflection of the mask is measured while supporting the opposing long sides of the mask, the amount of deflection from the supported side to the most downwardly deflected region is 4.1 mm, and the amount of deflection of the substrate is greater than that of the mask. The value was larger than the amount of deflection.

  Position alignment was performed so that the vapor passage hole portion of the pattern portion of the mask and the pixel pattern on the substrate coincided, and the long sides facing the substrate and the mask were supported and adhered.

  Thus, the organic EL element in which the pattern of the organic EL layer with good dimensional accuracy is formed on the substrate is manufactured by improving the adhesion between the mask and the substrate and performing vacuum deposition using a known light emitting material. Thus, an organic EL display device free from display unevenness could be realized.

  The thickness of the frame part parallel to the opposing long sides of the mask is 0.5 mm, and a total of 12 openings of 1 mm × 30 mm are provided in the frame near the center of gravity of the mask. An organic EL layer was deposited under the same conditions as in Example 1 except that the thickness was 0.7 mm.

  When the amount of deflection of the substrate was measured while supporting the opposing long sides of the substrate, the amount of deflection from the supported side to the most downwardly bent region was 4.2 mm. Similarly, when the amount of deflection of the mask is measured while supporting the opposing long sides of the mask, the amount of deflection from the supported side to the most downwardly deflected region is 4.0 mm, and the amount of substrate deflection is greater. The value was larger than the deflection amount of the mask.

  Position alignment was performed so that the vapor passage hole portion of the pattern portion of the mask and the pixel pattern on the substrate coincided, and the long sides facing the substrate and the mask were supported and adhered.

  Thus, the organic EL element in which the pattern of the organic EL layer with good dimensional accuracy is formed on the substrate is manufactured by improving the adhesion between the mask and the substrate and performing vacuum deposition using a known light emitting material. Thus, an organic EL display device free from display unevenness could be realized.

(Comparative example)
The organic EL layer was deposited under the same conditions as in Example 1 except that the thickness of the entire frame of the deposition mask was 0.5 mm.

  When the amount of deflection of the substrate was measured while supporting the opposing long sides of the substrate, the amount of deflection from the supported side to the most downwardly bent region was 4.2 mm. Similarly, when the amount of deflection of the mask is measured while supporting the opposite long sides of the mask, the amount of deflection from the supported side to the most downwardly deflected region is 11.5 mm, and the amount of deflection of the substrate is larger than that of the mask. The value was smaller than the amount of deflection.

  Position alignment was performed so that the vapor passage hole portion of the pattern portion of the mask and the pixel pattern on the substrate coincided, and the long sides facing the substrate and the mask were supported and adhered.

  In this vapor deposition method, the deflection amount of the mask is larger than the deflection amount of the substrate, and it is difficult to closely adhere the mask and the substrate without a gap. When vacuum deposition was performed using a known light emitting material, the pattern of the organic EL layer formed on the substrate was shifted, and display unevenness occurred in the obtained organic EL element.

  The film formation method and the film formation mask of the present invention can be widely applied in a film formation process using a mask in a vapor deposition process, a CVD process, or the like in which the deflection of the substrate or the mask is a problem.

It is process drawing explaining the film-forming method by one Embodiment. The structure of a mask is shown, (a) is the perspective view, (b) is a top view. It is a top view which shows the mask by Example 1 and Example 2. FIG. 10 is a plan view showing a mask according to Example 3. FIG. It is process drawing explaining a prior art example.

Explanation of symbols

1, 2 Support means 10 Substrate 20 Mask 21 Mask part 22 Frame 22a Thin part 22b Opening part

Claims (4)

A film forming method using a film forming mask,
A process of supporting the deposition target substrate with the deposition surface facing downward and the deposition mask facing each other;
A step of closely attaching the deposition target substrate and the deposition mask facing each other;
Forming a film on the substrate to be deposited through a film-forming mask adhered thereto, and
A film forming method characterized in that the amount of deflection due to the weight of the film forming substrates before being adhered to each other is larger than the amount of deflection due to the weight of the film forming mask. A film formation mask used in a film formation method for forming a film on a film formation substrate with a film formation surface facing downward,
The Young's modulus obtained by homogenizing the film-forming substrate is E _G , the specific gravity is ρ _G, the cross-sectional second moment in the direction perpendicular to the film-forming surface of the film-forming substrate is I _G , and the film-forming substrate the width of the wood and L _G, said the film formation mask homogenized Young's modulus E _M, specific gravity [rho _M, the perpendicular direction of the second moment to the mask surface of the film formation mask I _M, the when the width of the film formation mask was L _M,
(ρ _G × L _G ³ ) / (E _G × I _G )> (ρ _M × L _M ³ ) / (E _M × I _M )
A film forming mask characterized by satisfying the above.   The film-forming mask is configured to support regions on two opposite sides of the frame, and the frame includes a thin portion or an opening that extends in parallel to the two sides. The film-forming mask according to claim 2.   An organic EL device is produced using the film forming method according to claim 1, wherein the organic EL device is produced.

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