JP2014224006A - Member with sealing material layer, and method and apparatus for producing the member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a sealing material layer excellently and efficiently.SOLUTION: A method for producing a member with the sealing material layer comprises a substrate preparation step, an application step, and a firing step. At the substrate preparation step, a substrate having a sealing region is prepared. At the application step, the sealing material paste, which is prepared by mixing a sealing material containing sealing glass and a laser absorbing material with a vehicle containing an organic binder, is applied onto the sealing region of the substrate to form a coating layer. At the firing step, the whole of the coating layer is irradiated with a laser beam for firing and heated while scanning the laser beam along the coating layer so that the sealing material is fired to form the sealing material layer while removing the organic binder in the coating layer. At the firing step, the substrate is supported so that the coating layer is positioned on the downside of the substrate and a space is created around the coating layer and the coating layer is irradiated with the laser beam for firing through the substrate.

Description

  The present invention relates to a member with a sealing material layer, a manufacturing method thereof, and a manufacturing apparatus for a member with a sealing material layer.

  A flat panel display device (FPD) such as an organic electro-luminescence display (OELD) or a plasma display panel (PDP) has a light emitting element sealed by a glass package in which a pair of glass substrates are sealed. It has a structure. A liquid crystal display (LCD) also has a structure in which liquid crystal is sealed between a pair of glass substrates. Furthermore, solar cells such as organic thin film solar cells and dye-sensitized solar cells also have a structure in which a solar cell element (photoelectric conversion element) is sealed between a pair of glass substrates.

  Sealing glass is preferably used for sealing. Sealing with sealing glass is performed by, for example, arranging a sealing material layer containing sealing glass between a pair of glass substrates in a frame shape to form a glass assembly, and heating the sealing material layer to 400 to 600 ° C. Done. At this time, if the entire glass assembly is heated using a baking furnace, the electronic element portion such as the light emitting element is easily damaged by the heating. For this reason, the application of the laser sealing which heats only the sealing material layer using a laser beam (sealing laser beam) is examined.

  Specifically, laser sealing is performed as follows. First, a sealing material paste is prepared by mixing sealing glass with a vehicle. This sealing material paste is applied to a frame-shaped sealing region of one glass substrate on which the electronic element portion is not mounted to form a coating layer, and this coating layer is heated to the firing temperature of the sealing glass (above the softening temperature of the sealing glass). Temperature). As a result, the sealing glass is melted and baked on the glass substrate to form a sealing material layer. Next, after laminating the glass substrate having the sealing material layer and the other glass substrate on which the electronic element portion is mounted via the sealing material layer, the sealing material layer is irradiated with laser light for sealing through the glass substrate. Irradiation heats and melts the sealing material layer. Thereby, a pair of glass substrates are joined by the sealing layer which consists of sealing glass.

  Conventionally, the formation of the sealing material layer, that is, the firing of the coating layer, is performed by heating the entire glass substrate including the coating layer using a heating furnace. However, in the FPD package, an organic resin film such as a color filter is formed on a glass substrate on which a light emitting element or the like is not mounted. Therefore, when the entire glass substrate is heated, the organic resin film is damaged. Similarly, even in a dye-sensitized solar cell, an element film or the like is formed on a glass substrate on which a sealing material layer is formed. Therefore, when the entire glass substrate is heated, the element film or the like is damaged. In addition, when a heating furnace is used, it takes time to form the sealing material layer and the energy consumption increases.

  For these reasons, the use of laser light (firing laser light) for the formation of the sealing material layer has been studied. When the firing laser beam is used, only the coating layer is heated, so that damage to the organic resin film and the like is suppressed, and energy consumption is suppressed.

  However, when the laser beam for firing is directly irradiated onto the coating layer, only the surface portion is melted and vitrified before the entire coating layer is uniformly heated, so that the organic binder contained in the vehicle is thermally decomposed. Release of the generated gas to the outside is reduced. Thereby, bubbles are generated inside the sealing material layer, or deformation due to the bubbles is generated on the surface, and the airtightness, the bonding property and the like are lowered.

  For this reason, it is known that gas is released from the surface of the coating layer by irradiating through the glass substrate on the opposite side instead of directly irradiating the coating layer (see, for example, Patent Document 1). In addition, it is known to irradiate the second firing laser light after irradiating the first firing laser light to remove the organic binder (see, for example, Patent Document 2). Furthermore, the sealing material is formed by placing the glass substrate on which the coating layer is formed on a sample table whose surface is polished so that the coating layer is on the lower side, and irradiating the coating layer through the glass substrate. It is known to flatten the surface of a layer (see, for example, Patent Document 3). Further, it is known that a glass substrate on which a coating layer is formed is arranged on a sample stage so that the coating layer is on the upper side, and irradiation is performed from the lower side of the sample stage through the glass substrate (for example, (See Patent Document 4).

International Publication No. 2011/0104089 Pamphlet JP 2011-051811 A JP 2011-073956 A JP 2011-111343 A

  However, when the glass substrate on which the coating layer is formed is placed on the sample stage with the coating layer on the lower side and irradiated through the glass substrate, the coating layer is easily damaged by contact with the sample stage. In addition, the sealing material layer is easily damaged by adhesion to the sample stage.

  On the other hand, when a glass substrate on which a coating layer is formed is arranged on the sample stage so that the coating layer is on the upper side and irradiated through the glass substrate from the lower side of the sample stage, generally the lower side of the sample stage Since a support material and the like used for the support are disposed, if the laser irradiation head and its moving mechanism are further disposed, the manufacturing apparatus may be complicated. In addition, if the glass substrate is large, there is a risk that the in-plane irradiation status may not be constant due to deflection, and when a beam is provided to eliminate deflection, a part that cannot be irradiated as a shadow of the beam occurs, There is a possibility that the shape and arrangement of the coating layer may need to be changed. In addition, when the firing laser light is irradiated from the lower side to the upper side, the firing laser light is easily irradiated to the operator or the like, which is not preferable from the viewpoint of safety.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for forming a sealing material layer in a good and efficient manner. Moreover, this invention aims at provision of the manufacturing apparatus used for the member which has the sealing material layer formed by such a method, and such a method.

  The manufacturing method of the member with a sealing material layer of the present invention includes a substrate preparation step and a firing step. In the substrate preparation step, a substrate having a sealing region is prepared. The coating process forms a coating layer by applying a sealing material paste prepared by mixing a sealing material containing a sealing glass and a laser absorber and a vehicle containing an organic binder onto the sealing region of the substrate. To do. The firing process involves firing the sealing material by firing the laser beam for firing along the coating layer and heating the entire coating layer, thereby removing the organic binder in the coating layer and firing the sealing material. Form a layer. In the firing step, the substrate is supported so that the coating layer is vertically below the substrate and a space is provided around the coating layer, and the coating layer is irradiated with the laser beam for firing through the substrate. To do.

  The member with a sealing material layer of the present invention includes a substrate having a sealing region and a sealing material layer provided in the sealing region of the substrate, and the method for producing a member with a sealing material layer of the present invention Manufactured by.

  The electronic device manufacturing method of the present invention includes a substrate preparation step, a coating step, a firing step, a laminating step, and a sealing step. The substrate preparing step includes a first substrate having a first surface provided with a first sealing region, and a second surface provided with a second sealing region corresponding to the first sealing region. A second substrate having is prepared. In the coating step, a sealing material paste prepared by mixing a sealing material including a sealing glass and a laser absorbing material and a vehicle including an organic binder is applied onto the second sealing region of the second substrate. To form a coating layer. In the firing step, the sealing material is fired by firing the sealing material while removing the organic binder in the coating layer by irradiating a laser beam for firing while scanning the coating layer and heating the entire coating layer. Form a layer. In the stacking step, the first substrate and the second substrate are stacked via the sealing material layer while the first surface and the second surface are opposed to each other. In the sealing step, the sealing material layer is irradiated with a sealing laser beam through the first substrate or the second substrate, and the sealing material layer is melted to be interposed between the first substrate and the second substrate. A sealing layer for sealing the electronic element portion is formed. In the firing step, the second substrate is supported so that the coating layer is on the lower side in the vertical direction with respect to the second substrate, and a space is provided around the coating layer, and the second substrate is interposed through the second substrate. The coating layer is irradiated with a firing laser beam.

  The electronic device according to the present invention includes a first substrate having a first surface provided with a first sealing region, and a second substrate provided with a second sealing region corresponding to the first sealing region. And the electronic element portion is sealed between the first substrate and the second substrate. The second substrate is disposed so that the first surface and the second surface face each other. It has a sealing layer and is manufactured by the method for manufacturing an electronic device of the present invention.

  The manufacturing apparatus for a member with a sealing material layer according to the present invention includes a sample stage, a laser light source, a laser irradiation head, an output control unit, a moving mechanism, and a scanning control unit. The sample stage includes a substrate having a coating layer of a sealing material paste prepared by mixing a sealing material containing a sealing glass and a laser absorber and a vehicle containing an organic binder, and the coating layer is applied to the substrate. It supports so that it may become the lower side of a perpendicular direction, and a space may be provided around a coating layer. The laser light source emits firing laser light. The laser irradiation head has an optical system that irradiates a coating layer with laser light emitted from a laser light source via a substrate. The output control unit controls the output of the firing laser light irradiated on the coating layer from the laser irradiation head. The moving mechanism relatively moves the position of the sample stage and the laser irradiation head. The scanning control unit controls the moving mechanism so as to irradiate the firing laser light while scanning along the coating layer.

  The present invention supports the substrate so that the coating layer is vertically below the substrate and provides a space around the coating layer, and irradiates the laser beam for firing through the substrate. Thus, the sealing material layer can be formed satisfactorily and efficiently.

It is sectional drawing which shows the manufacturing process of an electronic device. It is a top view which shows the 1st board | substrate which has an electronic element part. It is the sectional view on the AA line of the 1st board | substrate shown in FIG. It is a top view which shows the 2nd board | substrate which has a sealing material layer. FIG. 5 is a cross-sectional view of the second substrate shown in FIG. 4 taken along line BB. It is sectional drawing which shows the formation process of a sealing material layer. It is a top view which shows the other support method of a 2nd board | substrate. It is CC sectional view taken on the line of the supporting method shown in FIG. It is a top view which shows one Embodiment of a manufacturing apparatus. It is a front view of the manufacturing apparatus shown in FIG. It is a figure which shows one Embodiment of a laser irradiation head. It is a figure explaining the open bubble of a sealing material layer.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
1-6 is a figure which shows one Embodiment of the manufacturing process of an electronic device.

  Electronic devices include, for example, lighting devices using light emitting elements such as FPDs such as OELD, FED, PDP and LCD, and OEL elements, dye-sensitized solar cells, thin film silicon solar cells, compound semiconductor solar cells, and the like. A stationary solar cell can be mentioned.

  First, as shown to Fig.1 (a), the 1st board | substrate 1 and the 2nd board | substrate 2 are prepared (board | substrate preparation process). For the first and second substrates 1 and 2, for example, glass substrates made of alkali-free glass or soda lime glass having a known composition are used. For the first and second substrates 1 and 2, glass ceramic substrates made of glass ceramics in which ceramic powder is dispersed in glass are used as necessary.

The alkali-free glass has a thermal expansion coefficient of about 30 to 50 × 10 ⁻⁷ / K. Soda lime glass has a thermal expansion coefficient of about 80 to 90 × 10 ⁻⁷ / K. As a typical glass composition of non-alkali glass, it is expressed by mass%, SiO ₂ 50-70%, Al ₂ O ₃ 1-20%, B ₂ O ₃ 0-15, MgO 0-30%, CaO 0 The thing containing 30%, SrO 0-30%, BaO 0-30% is mentioned. As a typical glass composition of soda lime glass, it is expressed by mass%, SiO ₂ 55 to 75%, Al ₂ O ₃ 0.5 to 10%, CaO 2 to 10%, SrO 0 to 10%, Na ₂ O. _1-10%, include those containing K 2 O 0~10%. The glass composition is not limited to these. Further, at least one of the first and second substrates 1 and 2 may be chemically strengthened glass or the like.

  As shown in FIGS. 2 and 3, the first substrate 1 has a surface 1 a provided with an element region 3. The element region 3 is provided with an electronic element unit 4 corresponding to the electronic device that is the object. The electronic element unit 4 is, for example, an OEL element for OELD or OEL illumination, an electron emitting element for FED, a plasma light emitting element for PDP, a liquid crystal display element for LCD, or a solar cell element for solar cell. Is provided. The element structure of the electronic element unit 4 is not particularly limited, and has various known structures. A frame-shaped first sealing region 5 is provided along the outer periphery of the element region 3 at the periphery of the surface 1 a of the first substrate 1.

  As shown in FIGS. 4 and 5, the second substrate 2 has a surface 2 a that faces the surface 1 a of the first substrate 1. A frame-shaped second sealing region 6 corresponding to the first sealing region 5 is provided in the periphery of the surface 2a. The 1st and 2nd sealing area | regions 5 and 6 become a formation area of a sealing layer. The second sealing region 6 further becomes a region for forming a sealing material layer.

  The electronic element unit 4 is provided between the surface 1 a of the first substrate 1 and the surface 2 a of the second substrate 2. In the manufacturing process of the electronic device shown in FIG. 1, the first substrate 1 is an element substrate in which an element structure such as an OEL element or a PDP element is provided on the surface 1 a as the electronic element unit 4. The second substrate 2 serves as a sealing substrate for sealing the electronic element portion 4 formed on the surface 1 a of the first substrate 1. However, the configuration of the electronic element unit 4 is not limited to this.

  For example, when the electronic element unit 4 is a dye-sensitized solar cell element or the like, an element film such as a wiring film or an electrode film constituting an element structure on each of the surfaces 1a and 2a of the first and second substrates 1 and 2 Is formed. The element film constituting the electronic element unit 4 and the element structure based thereon are formed on at least one of the surfaces 1a and 2a of the first and second substrates 1 and 2. Furthermore, an organic resin film such as a color filter may be formed on the surface 2a of the second substrate 2 constituting the sealing glass substrate as described above.

  In the sealing region 6 of the second substrate 2, as shown in FIGS. 1A, 4, and 5, a sealing material layer 7 is formed on the entire periphery of the peripheral portion of the second substrate 2. The The sealing material layer 7 is a fired layer of a sealing material containing sealing glass and a laser absorber. The sealing material can contain inorganic fillers, such as a low expansion filler, as needed, and can also contain fillers and additives other than these.

  As the sealing glass, for example, low-melting glass such as tin-phosphate glass, bismuth glass, vanadium glass, and lead glass is used. Among these, in consideration of the sealing property (adhesiveness) to the first and second substrates 1 and 2, its reliability (adhesion reliability and sealing property), the influence on the environment and the human body, etc., tin -Low melting point sealing glass made of phosphate glass or bismuth glass is preferred.

Tin - phosphate glass is 55 to 68 mol% of SnO, and from 0.5 to 5 mol% of SnO _2, and 20 to 40 mol% of _P 2 _{O 5} (the total amount of essentially 100 mol% Are preferred.

The glass formed of the above three components has a low glass transition point and is suitable for a low-temperature sealing material, but a component that forms a glass skeleton such as SiO ₂ , ZnO, B ₂ O ₃ , Stable glass such as Al ₂ O ₃ , WO ₃ , MoO ₃ , Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO A component to be converted may be contained as an optional component. However, if the content of any component is too large, the glass becomes unstable and devitrification occurs, and the glass transition point and softening point may increase. Therefore, the total content of any component is 30 mol%. The following is preferred. The glass composition in this case is adjusted so that the total amount of the basic component and the optional component is basically 100 mol%.

Bismuth-based glass is composed of 70 to 90% by mass of Bi ₂ O ₃ , 1 to 20% by mass of ZnO, and 2 to 12% by mass of B ₂ O ₃ (the total amount is basically 100% by mass). It preferably has a composition.

The glass formed of the above three components has a low glass transition point and is suitable for a low-temperature sealing material, but Al ₂ O ₃ , CeO ₂ , SiO ₂ , Ag ₂ O, MoO ₃ , Nb ₂ O ₃ , Ta ₂ O ₅ , Ga ₂ O ₃ , Sb ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, CaO, SrO, BaO, WO ₃ , P ₂ O ₅ , SnOx ( and x may be any component such as 1 or 2. However, if the content of the optional component is too large, the glass becomes unstable and devitrification occurs, and the glass transition point and softening point may increase. Therefore, the total content of the optional component is 30% by mass or less. Is preferred. The glass composition in this case is adjusted so that the total amount of the basic component and the optional component is basically 100% by mass.

As the laser absorber, for example, at least one metal selected from Fe, Cr, Mn, Co, Ni, and Cu and / or at least one metal compound such as an oxide containing the metal is used. In addition, pigments other than these, for example, oxides of vanadium (specifically, VO, VO ₂ and V ₂ O ₅ ) may be used.

  The content of the laser absorber is preferably in the range of 0.1 to 40% by volume with respect to the sealing material. If the content of the laser absorber is less than 0.1% by volume, the sealing material layer 7 may not be sufficiently melted. If the content of the laser absorber exceeds 40% by volume, there is a risk of locally generating heat in the vicinity of the interface with the second substrate 2, and the fluidity at the time of melting of the sealing material deteriorates to cause the first substrate. Adhesiveness with 1 may be reduced. The content of the laser absorber is preferably 37% by volume or less.

  The sealing glass or glass frit, the laser absorbing material, and the low expansion filler are each in the form of powder or particles. Hereinafter, when the sealing glass powder is simply referred to as sealing glass, the laser absorber particles or laser absorber powder is simply referred to as laser absorber, and the low expansion filler particles or low expansion filler powder is simply referred to as low expansion filler. There is.

The sealing material contains a low expansion filler having a lower thermal expansion coefficient than that of the sealing glass, if necessary. Low expansion filler selected from silica, alumina, zirconia, zirconium silicate, aluminum titanate, mullite, cordierite, eucryptite, spodumene, zirconium phosphate compounds, quartz solid solution, soda lime glass, and borosilicate glass At least one selected from the above is preferred. Examples of the zirconium phosphate-based compound include (ZrO) ₂ P ₂ O ₇ , NaZr ₂ (PO ₄ ) ₃ , KZr ₂ (PO ₄ ) ₃ , Ca _0.5 Zr ₂ (PO ₄ ) ₃ , and NbZr (PO ₄ ). ₃ , Zr ₂ (WO ₃ ) (PO ₄ ) ₂ , or a composite compound thereof.

  The content of the low expansion filler is preferably set so that the thermal expansion coefficient of the sealing glass approaches the thermal expansion coefficient of the first and second substrates 1 and 2. Specifically, although it depends on the thermal expansion coefficient of the sealing glass and the first and second substrates 1 and 2, the range of 0.1 to 50% by volume with respect to the sealing material is preferable. The content can be appropriately changed depending on the thickness of the sealing material layer 7 and the like. However, if the content exceeds 50% by volume, the fluidity at the time of melting of the sealing material may be deteriorated, and the adhesiveness to the first substrate 1 may be lowered. Preferably it is 45 volume% or less. Since the total content with the laser absorber affects the properties of the sealing material, the total content is preferably in the range of 0.1 to 50% by volume.

  A sealing material is prepared by blending the sealing glass with a laser absorbing material, a low expansion filler and the like. Further, a sealing material paste is prepared by mixing the sealing material with a vehicle.

  The vehicle is prepared by dissolving an organic binder in a solvent. Examples of the organic binder include cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, oxyethyl cellulose, benzyl cellulose, propyl cellulose, and nitrocellulose; methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, 2 An organic resin such as an acrylic resin obtained by polymerizing at least one acrylic monomer such as hydroxyethyl acrylate is used. Solvents such as terpineol, butyl carbitol acetate, and ethyl carbitol acetate are used in the case of cellulose resins, and solvents such as methyl ethyl ketone, terpineol, butyl carbitol acetate, and ethyl carbitol acetate are used in the case of acrylic resins. Is used.

  The viscosity of the sealing material paste may be adjusted to the viscosity corresponding to the apparatus applied to the second substrate 2 and can be adjusted by the ratio of the organic binder and the solvent and the ratio of the sealing material and the vehicle. You may add the additive in a well-known glass paste like an antifoamer and a dispersing agent to sealing material paste. For preparing the sealing material paste, a known method using a rotary mixer equipped with a stirring blade, a roll mill, a ball mill, or the like can be applied.

  Thereafter, a sealing material paste is applied over the entire periphery of the frame-shaped sealing region 6 provided in the peripheral portion of the second substrate 2 and dried to form an application layer (application process). The sealing material paste is applied by applying a printing method such as screen printing or gravure printing, or is applied using a dispenser or the like. For example, the coating layer is preferably dried at a temperature of 120 ° C. or higher for 10 minutes or longer. Drying is performed to remove the solvent in the coating layer. If the solvent remains in the coating layer, the organic binder may not be sufficiently removed in the subsequent firing step.

  The thickness of the coating layer is preferably such that the thickness after firing is 1 μm or more, that is, the thickness of the sealing material layer 7 is 1 μm or more. In such a case, the coating layer can be baked satisfactorily by adjusting the formation conditions of the coating layer, the irradiation conditions of the firing laser light 9, and the like. The thickness of the coating layer is more preferably such that the thickness after firing is 150 μm or less. From the viewpoint of uniform firing, it is more preferable that the thickness of the coating layer is 20 μm or less after firing. The width of the coating layer is preferably 0.1 to 5.0 mm after baking, more preferably 0.2 to 3.0 mm, and further 0.5 to 2.0 mm. preferable.

  Next, irradiation is performed while scanning the laser beam 9 for baking along the coating layer 8 (baking step). In the firing step, first, as shown in FIG. 6A, first, the coating layer 8 is positioned on the lower side in the vertical direction with respect to the second substrate 2 and a space is provided around the coating layer 8. 2 substrates 2 are supported. The support of the second substrate 2 is performed, for example, by attaching an edge support portion 12 having a frame shape that supports the edge of the second substrate 2 to the sample stage 22. After that, as shown in FIG. 6B, the coating layer 8 is irradiated with the firing laser light 9 through the second substrate 2. Thus, the sealing material is baked while removing the organic binder in the coating layer 8 to form the sealing material layer 7 as shown in FIG.

  Application is performed via the second substrate 2, supporting the second substrate 2 so that the application layer 8 is on the lower side of the second substrate 2 and providing a space around the application layer 8. By irradiating the layer 8 with the laser beam 9 for firing, the gas generated by the thermal decomposition of the organic binder can be effectively discharged from the surface of the coating layer 8, and even when the heating rate of the coating layer 8 is high, the gas can be discharged. It can be effectively discharged. Thereby, generation | occurrence | production of the bubble in the sealing material layer 7 can be suppressed, and airtightness, bondability, etc. can be made favorable.

  Further, by providing a space around the coating layer 8, damage to the coating layer 8 due to contact with the sample table 22, damage to the sealing material layer 7 due to adhesion with the sample table 22, and the like can be suppressed. Further, by providing a space around the coating layer 8, heat transfer from the coating layer 8 to the sample stage 22 is suppressed, and the cooling time of the coating layer 8 becomes longer, so that a reduction in residual stress can be expected.

  Further, by irradiating the firing laser light 9 from the upper side to the lower side, a laser irradiation head for irradiating the firing laser light 9 and a moving mechanism for moving the same are arranged on the upper side of the sample stage 22. Thus, the complexity of the manufacturing apparatus can be suppressed, and the safety can be improved by suppressing the irradiation of the firing laser light 9 to the worker or the like. Further, even when the second substrate 2 is large and easily bent, it can be appropriately supported from the lower side and the in-plane irradiation state can be made constant.

  The shape of the edge part support part 12 will not be restrict | limited especially if the 2nd board | substrate 2 can be supported effectively, It does not necessarily restrict to the frame shape continuous to the whole circumferential direction. As long as the second substrate 2 can be effectively supported, it may have a discontinuous part. The edge support portion 12 may be a plurality of columnar bodies. In this case, the arrangement of the plurality of columnar bodies is not particularly limited as long as the second substrate 2 can be effectively supported. In some cases, a color filter or the like may be formed inside the coating layer 8. If such a portion is used for support, the color filter or the like is damaged. Therefore, the inside of the coating layer 8 may not be used for support. preferable.

  FIG. 7 is a plan view showing another method for supporting the second substrate 2. 8 is a cross-sectional view taken along the line CC of the method for supporting the second substrate 2 shown in FIG.

  As a support method, in addition to the method of supporting the edge of the second substrate 2 by the edge support 12 as shown in FIG. 6, when a plurality of coating layers 8 are arranged as shown in FIGS. May support the edge portion of the second substrate 2 by the edge portion support portion 12 and support portions other than the edge portion by the columnar internal support portion 13. Examples of the portion used for such support include a straight portion in a lattice-like non-formed portion where the coating layer 8 is not formed, and a crossing portion where these straight portions intersect, and are necessary from these. It can be appropriately selected depending on the situation.

Although not shown, when a plurality of the coating layers 8 are arranged, a portion other than the edge portion of the second substrate 2 may be supported only by the internal support portion 13 and the edge portion may not be supported. Also,
The shape of the internal support portion 13 is not particularly limited as long as the second substrate 2 can be effectively supported, and can be a cylindrical shape, a quadrangular prism shape, or other shapes.

  The firing laser light 9 is not particularly limited, but a desired laser light from a semiconductor laser, a carbon dioxide gas laser, an excimer laser, a YAG laser, a HeNe laser, or the like is used. The same applies to sealing laser light described later.

The firing temperature T ₁ of the coating layer 8 is preferably within the range of (T ₀ +80) to (T ₀ +550) [° C.] when the softening temperature of the sealing glass is T ₀ [° C.]. Here, the softening temperature T ₀ of the sealing glass indicates a temperature at which it softens and flows but does not crystallize. The firing temperature T ₁ of the coating layer 8 when irradiated with the firing laser light 9 is a value measured with a radiation thermometer.

By irradiating the firing laser beam 9 so that the firing temperature T ₁ of the coating layer 8 is in the range of (T ₀ +80) to (T ₀ +550) [° C.], the sealing glass in the sealing material is By melting well, the sealing material is baked onto the second substrate 2 to form the sealing material layer 7. When the firing temperature T ₁ of the coating layer 8 does not reach (T ₀ +80) [° C.], the entire coating layer 8 may not be melted uniformly. When the firing temperature T ₁ of the coating layer 8 exceeds (T ₀ +550) [° C.], the second substrate 2 and the sealing material layer 7 are likely to be cracked or broken. Further, by setting the temperature within the above temperature range, the organic binder is effectively thermally decomposed and removed from the sealing material layer 7.

  The scanning speed of the firing laser light 9 is preferably in the range of 3 to 30 mm / s. When the scanning speed is less than 3 mm / s, the firing speed is lowered, and thus the sealing material layer 7 cannot be efficiently formed. On the other hand, when the scanning speed exceeds 30 mm / s, the ability to release the gas generated by the thermal decomposition of the organic binder decreases. As a result, bubbles may be generated inside the sealing material layer 7 or the surface may be deformed by bubbles, and the amount of residual carbon tends to increase. When the sealing material layer 7 having a poor organic binder removal state is used to seal between the first and second substrates 1 and 2, the bonding strength between the first and second substrates 1 and 2 and the sealing layer is increased. The airtightness may be reduced. The scanning speed of the firing laser light 9 is more preferably in the range of 5 to 25 mm / s, and more preferably in the range of 7 to 23 mm / s.

  In the scanning of the firing laser light 9, the position of the second substrate 2 may be fixed and the firing laser light 9 may be moved, or the position of the firing laser light 9 may be fixed and the second substrate 2 moved. 2 may be moved, or both may be moved with respect to each other.

The output density of the laser beam 9 for firing is preferably in the range of 100 to 1100 W / cm ² . If the output density is less than 100 W / cm ² , the entire coating layer 8 may not be heated uniformly. If the output density exceeds 1100 W / cm ² , the second substrate 2 is excessively heated, and cracks, cracks, and the like are likely to occur.

  The beam shape (that is, the shape of the irradiation spot) of the firing laser light 9 is not particularly limited. The beam shape of the firing laser beam 9 is generally circular, but is not limited to a circle. The beam shape of the firing laser light 9 may be an ellipse having a minor axis in the width direction of the coating layer 8. According to the firing laser light 9 whose beam shape is shaped into an ellipse, the irradiation area of the firing laser light 9 on the coating layer 8 can be increased, and the scanning speed of the firing laser light 9 can be increased. By these, the baking time of the application layer 8 can be shortened.

  The beam diameter of the laser beam 9 for firing is preferably 0.5 to 3 mm. The beam diameter of the firing laser light 9 is defined in a region where the beam intensity is 13.5% of the maximum beam intensity. When the beam shape is other than a circular shape, the beam diameter is set such that the beam intensity is 13.5% of the maximum beam intensity in the scanning direction.

  Baking with the laser beam 9 for baking selectively heats the coating layer 8, so that even when the surface 2 a of the second substrate 2 has an organic resin film such as a color filter or an element film, the organic resin The sealing material layer 7 can be satisfactorily formed without causing thermal damage to the film or the element film. Furthermore, since it is excellent also in the removal property of an organic binder, the sealing material layer 7 excellent in sealing property, reliability, etc. can be obtained.

  Of course, the firing by the firing laser beam 9 can be applied even when an organic resin film, an element film, or the like is not formed on the surface 2a of the second substrate 2. The sealing material layer 7 having excellent properties and the like can be obtained. Furthermore, the firing with the firing laser light 9 consumes less energy than the firing process by the conventional heating furnace, and contributes to the reduction of manufacturing man-hours and manufacturing costs. Therefore, firing from the firing laser beam 9 is also effective from the viewpoint of energy saving and cost reduction.

Here, a laser baking apparatus as a manufacturing apparatus for a member with a sealing material layer will be described.
9 and 10 show an embodiment of a laser baking apparatus.

  The laser baking apparatus 21 includes, for example, a sample stage 22 on which the second substrate 2 having the coating layer 8 is placed, a laser light source 23, and a laser that irradiates the coating layer 8 with laser light emitted from the laser light source 23. And an irradiation head 24.

  The sample stage 22 only needs to support the second substrate 2 so that the coating layer 8 is on the lower side of the second substrate 2 and a space is provided around the coating layer 8. Examples of the sample stage 22 include those having an edge support portion 12 having a frame shape or the like that supports the edge of the second substrate 2 as shown in FIG. Moreover, as the sample stand 22, for example, as shown in FIGS. 7 and 8, the sample base 22 has a frame-like portion 221 that supports the edge of the second substrate 2, and a columnar shape that supports a portion other than the edge. You may have the internal support part 13 which has.

  Although not shown, the laser irradiation head 24 has an optical system that condenses the laser light emitted from the laser light source 23, shapes the laser light into a predetermined beam shape, and irradiates the coating layer 8. In particular, the laser irradiation head 24 is disposed on the upper side of the sample stage 22 and irradiates the coating layer 8 via the second substrate 2. The optical system will be described later. The laser light emitted from the laser light source 23 is sent to the laser irradiation head 24. The output of the laser beam is controlled by the output control unit 25. The output control unit 25 controls the output of the laser beam by controlling the current input to the laser light source 23, for example. The output control unit 25 may include an output modulator that controls the output of the laser light emitted from the laser light source 23.

  The firing laser light 9 irradiated from the laser irradiation head 24 is irradiated while scanning along the coating layer 8. That is, the laser irradiation head 24 moves in the X direction (that is, in the horizontal direction on the paper surface of FIG. 10) by the X stage 26. The X stage 26 is moved in the Y direction by two Y stages 27A and 27B. The X stage 26 moves above the fixed sample stage 22 in the Y direction (that is, in the direction perpendicular to the paper surface of FIG. 10). The positional relationship between the laser irradiation head 24 and the sample stage 22 is adjusted by the X stage 26 and the Y stages 27A and 27B. The X stage 26 and the Y stages 27A and 27B constitute a moving mechanism. The moving mechanism may be constituted by, for example, an X stage 26 that moves the laser irradiation head 24 in the X direction and a Y stage that moves the sample stage 22 in the Y direction.

  The X stage 26 and the Y stages 27A and 27B are controlled by the scanning control unit 28. The laser baking apparatus 21 includes a main control system 29 that comprehensively controls the output control unit 25 and the scanning control unit 28. Furthermore, the laser baking apparatus 21 includes a radiation thermometer (not shown) that measures the baking temperature (heating temperature) of the coating layer 8. The laser firing device 21 preferably includes a suction nozzle, a blower nozzle, and the like that prevent the organic binder removed from the coating layer 8 from adhering to the optical system and the second substrate 2.

  For example, as shown in FIG. 11, the laser irradiation head 24 includes an optical fiber 31 that transmits the laser light emitted from the laser light source 23, and a condensing lens 32 that condenses the laser light and shapes it into a desired beam shape. The imaging lens 33 and the CCD imaging device 34 for observing the irradiated portion of the firing laser light 9 and the light other than the laser light from the irradiated portion of the firing laser light 9 are reflected (the laser light is transmitted) and the CCD A dichroic mirror 35 and a reflection mirror 36 are guided to the image sensor 34. Further, a radiation thermometer 37 for measuring the temperature of the irradiated portion of the firing laser light 9 is installed.

  Next, as shown in FIG. 1 (b), the first substrate 1 and the second substrate 2 on which the sealing material layer 7 is formed in the periphery thereof are opposed so that the surfaces 1a and 2a face each other. Are laminated via the sealing material layer 7 (lamination step). Thereafter, as shown in FIG. 1 (c), the sealing material layer 7 is irradiated with the sealing laser beam 10 through the second substrate 2 from above the second substrate 2 to seal the electronic element portion 4. The sealing layer 11 to be formed is formed (sealing step).

  The sealing laser beam 10 may be applied to the sealing material layer 7 through the first substrate 1 from below the first substrate 1 on the side opposite to the second substrate 2. Further, even if the sealing laser beam 10 is irradiated from above both from above the second substrate 2 and from below the first substrate 1 opposite to the second substrate 2 of the laminated glass assembly, Good.

  The sealing laser beam 10 is irradiated while scanning along the sealing material layer 7. The sealing material layer 7 is melted in order from the portion irradiated with the laser beam 10, and is rapidly cooled and solidified and fixed to the first substrate 1 when the sealing laser beam 10 is irradiated. Then, the sealing laser beam 10 is irradiated over the entire circumference of the sealing material layer 7 to seal between the first substrate 1 and the second substrate 2 as shown in FIG. A deposition layer 11 is formed. In this way, an electronic device 12 in which the electronic element portion 4 is hermetically sealed between the first substrate 1 and the second substrate 2 is manufactured.

  According to the manufacturing process of the electronic device 12 of the embodiment, even when an organic resin film, an element film, or the like is formed on the surface 2a of the second substrate 2, the sealing material does not cause thermal damage to these. The layer 7 and the sealing layer 11 can be formed satisfactorily. Therefore, the electronic device 12 having excellent hermetic sealing properties and reliability can be manufactured with good reproducibility without deteriorating the function of the electronic device 12 and its reliability.

  Next, specific examples of the present invention and evaluation results thereof will be described. In addition, the following description does not limit this invention, The modification | change in the form along the meaning of this invention is possible.

Example 1
Bismuth glass frit having a composition of 83% by weight of Bi ₂ O _3, 5% by weight of B ₂ O ₃ , 11% by weight of ZnO and 1% by weight of Al ₂ O ₃ and having an average particle diameter of 1 μm (softening temperature: 410 ° C. ), Cordierite powder having an average particle size of 0.9 μm and a specific surface area of 12.4 m ² / g as a low expansion filler, Fe ₂ O ₃ —Al ₂ O ₃ —MnO—CuO composition, A laser absorber having a particle size of 0.6 μm and a specific surface area of 8.3 m ² / g was prepared.

The specific surface areas of the cordierite powder and the laser absorbing material were measured using a BET specific surface area measuring device (manufactured by Mountec, device name: Macsorb HM model-1201). Measurement conditions are adsorbate: nitrogen, carrier gas: helium, measurement method: flow method (BET one-point method), degassing temperature: 200 ° C., degassing time: 20 minutes, degassing pressure: N ₂ gas flow / atmospheric pressure The sample mass was 1 g. The same applies to the following examples.

  The above-mentioned bismuth-based glass frit 85.0% by mass, cordierite powder 6.6% by mass, and laser absorber 8.4% by mass were mixed to prepare a sealing material. 90% by mass of this sealing material was mixed with 10% by mass of a vehicle to prepare a sealing material paste. The vehicle is obtained by dissolving ethyl cellulose (5% by mass) as an organic binder in a solvent (95% by mass) composed of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

Next, a second glass substrate (dimensions: 90 mm × 90 mm × 0.7 mmt) made of alkali-free glass (thermal expansion coefficient: 38 × 10 ⁻⁷ / K) was prepared and applied by a dispense printing method. The print pattern was a frame-like pattern with a line width of 0.5 mm, 80 mm × 56 mm, and a corner radius of curvature of 0.7 mm. After drying this frame-like pattern under the conditions of 120 ° C. × 10 minutes to form a coating layer (coating step), irradiation is performed while scanning the firing laser light along the coating layer, and the film thickness is reduced. A sealing material layer having a thickness of 8 μm and a line width of 0.5 mm was formed (firing step).

Hereinafter, the firing process will be specifically described.
First, as shown in FIG. 6 (a), the edge of the second glass substrate so that the coating layer is on the lower side and a 3 mm air layer is interposed between the coating layer and the sample stage. The second glass substrate on which the coating layer was formed was fixed on the sample stage of the laser baking apparatus with the part supported by the edge support part. Note that the irradiation surface of the firing laser light was the substrate surface of the second glass substrate on which the coating layer was formed. That is, a laser beam for baking is irradiated from the upper side to the second glass substrate fixed so that the coating layer is on the lower side on the sample stage, and the coating layer is applied to the coating layer through the second glass substrate. The laser beam for firing was irradiated.

In this way, a circular firing laser beam having a wavelength of 808 nm, an output density of 589 W / cm ² , and a beam shape of 1.5 mm in diameter is passed through the second glass substrate along the coating layer at a speed of 10 mm / s. Irradiated while scanning. The shape of the beam was measured using a laser beam profiler (manufactured by OFIR, device name: BS-USB-SP620), and the diameter at which the beam intensity was 13.5% of the peak value was defined as the beam diameter. The laser output was measured using a power meter (manufactured by Coherent, device name: FieldMaxll-TO) and a head (manufactured by Coherent, device name: PM100-19C). Sintering temperature T ₁ of the coating layer at this time was 800 ° C.. A two-color radiation thermometer (manufactured by Chino, device name: IR-FAQI) is used for temperature measurement, and the sealing material layer is heated with a hot plate, and the two-color radiation temperature is confirmed at 450 ° C. with a K thermocouple. Calibration of the meter (determining the emissivity ratio) was performed. Thus, the whole coating layer was baked with the laser beam for baking, and the sealing material layer was formed.

  When the cross-sectional state of the sealing material layer was observed with an SEM, it was confirmed that the entire sealing material layer was vitrified well, and no bubbles due to the organic binder were observed. Moreover, when the surface state of the sealing material layer was confirmed with an optical microscope, no generation of open bubbles was observed, and it was confirmed that a uniform sealing material layer was obtained. In addition, an open bubble is what exposes a 2nd glass substrate, Comprising: It does not contact the side surface of a sealing material layer. Furthermore, when the amount of residual carbon in the sealing material layer was measured, it was confirmed that it was the same as the amount of residual carbon when the coating layer of the same sealing material paste was baked in an electric furnace (480 ° C. × 10 minutes). It was.

  Next, the second glass substrate having the sealing material layer described above and a first glass substrate (an alkali-free glass substrate having the same composition and shape as the second glass substrate) were stacked. Thereafter, irradiation is performed while scanning the sealing material layer along the sealing material layer through the second glass substrate to melt and rapidly solidify the sealing material layer, and the first glass substrate and the second glass An airtight container was produced by sealing the substrate. It was confirmed that the obtained airtight container was excellent in appearance, bonding strength and the like, and excellent in airtightness.

(Examples 2 to 5)
The coating layer was fired with the firing laser light in the same manner as in Example 1 except that the scanning speed, beam diameter, output density, coating layer thickness, and firing temperature of the firing laser light were changed to the conditions shown in Table 1. After forming the sealing material layer, it was sealed with the first glass substrate to produce an airtight container. When the same evaluation as in Example 1 was performed, the evaluation result was good as shown in Table 1.

(Comparative Example 1)
The 2nd glass substrate in which the coating layer was formed was fixed on the sample stand of a laser baking apparatus so that a coating layer might become an upper side. Note that the irradiation surface of the firing laser beam was the coating layer surface of the second glass substrate on which the coating layer was formed. That is, the second glass substrate fixed on the sample stage so that the coating layer is on the upper side is irradiated with the firing laser light from the upper side, and the coating layer is directly irradiated with the firing laser light It was. Thereafter, as shown in Table 1, except that the irradiation intensity of the laser beam for firing was changed, a sealing material layer was formed in the same manner as in Example 1, and then sealed with the first glass substrate to produce an airtight container. did. When the same evaluation as in Example 1 was performed, the evaluation result was good as shown in the table.

(Comparative Examples 2-6)
After forming the sealing material layer in the same manner as in Comparative Example 1 except that the scanning speed, beam diameter, power density, coating layer thickness, and firing temperature of the firing laser light were changed to the conditions shown in Table 1, 1 was sealed with a glass substrate to prepare an airtight container. When the same evaluation as in Example 1 was performed, bubbles and open bubbles were observed in any sealing material layer, and it was recognized that the bonding strength of the airtight container became weak and the airtightness deteriorated. .

  For Comparative Examples 2 to 6, for example, as shown in FIG. 12, the second glass substrate 2 is exposed to the sealing material layer 7 formed on the second glass substrate 2 and the side surface 71 is not contacted. A contact opening bubble 41 is generated, which becomes a starting point of cracking or cracking at the time of sealing with the first glass substrate, and the adhesive strength of the airtight container becomes weak and airtightness deteriorates. In the case of the contact-opening foam 42 in contact with the side surface 71 of the sealing material layer 7, since the sealing material flows in at the time of sealing, the adhesive strength and the airtightness are good. On the other hand, in the case of the non-contact open foam 41, not only air stays during lamination with the first glass substrate, but also the residual stress increases because the surrounding temperature locally rises due to the heat insulation effect of the air. Cause cracks and cracks.

  The generation mechanism of the open bubbles 41 and 42 is considered as follows. That is, when the coating layer is on the upper side with respect to the substrate and this coating layer is irradiated while scanning with a firing laser beam (when the irradiation surface is the coating layer surface), the irradiation on the tip side in the scanning direction In the initial stage, the glass powder grain boundaries disappear due to softening flow near the surface of the sealing material layer, but the glass powder grains do not sufficiently soften and flow near the interface between the substrate and the sealing material layer. The boundary remains, and in such a state, the gas generated by the thermal decomposition of the organic binder rises and moves toward the surface of the sealing material layer, so that the glass powder is blown away and the surface of the substrate is exposed. Open bubbles 41 and 42 are generated.

  On the other hand, when the coating layer is irradiated to the coating layer while scanning the laser beam for firing through the substrate with the coating layer on the lower side (when the irradiated surface is the substrate surface), the sealing material layer Although the glass powder grain boundaries remain near the surface of the glass, the vicinity of the interface between the substrate and the sealing material layer sufficiently softens and flows, and the glass powder grain boundaries disappear. The glass powder is not blown away because it enters the softened and fluidized portion near the interface with the adhesive material layer. The gas that has entered the softened and fluidized portion is released from the surface of the sealing material layer when irradiation of the laser beam for firing proceeds and the entire sealing material layer softens and flows. Thereby, generation | occurrence | production of the open bubbles 41 and 42 is suppressed.

As in Comparative Example 1, even when the coating layer is on the upper side of the substrate and this coating layer is irradiated with scanning laser light while scanning, the thickness of the coating layer is H [mm]. When the scanning speed of the laser beam for firing is V [mm / s], the beam diameter is D [mm], and the firing temperature is T ₁ [° C.], the heating rate (H · V · T ₁ / D) is When it is less than 41 ° C./s·mm, the state of the sealing material layer, the adhesive strength, and the airtightness are good. Therefore, from the viewpoint of obtaining a remarkable effect, when the rate of temperature increase (H · V · T ₁ / D) is 41 ° C./s·mm or more, the coating layer should be on the lower side with respect to the substrate. Thus, it is preferable to irradiate the coating layer while scanning the laser beam for firing through the substrate.

  DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate, 1a ... surface, 2 ... 2nd board | substrate, 2a ... surface, 3 ... element area | region, 4 ... electronic element part, 5 ... 1st sealing area | region, 6 ... 2nd sealing area | region 7 ... sealing material layer, 8 ... coating layer, 9 ... laser light for firing, 10 ... laser light for sealing, 11 ... sealing layer, 12 ... edge support, 13 ... internal support, 21 ... laser firing Apparatus, 22 ... Sample stage, 23 ... Laser light source, 24 ... Laser irradiation head, 25 ... Output control unit, 26 ... X stage, 27A, 27B ... Y stage, 31 ... Optical fiber, 32 ... Condensing lens, 33 ... Imaging Lens: 34 ... CCD image sensor, 35 ... Dichroic mirror, 36 ... Reflection mirror, 37 ... Radiation thermometer, 41 ... Non-contact open bubble, 42 ... Contact open bubble

Claims (8)

A substrate preparation step of preparing a substrate having a sealing region;
Application that forms a coating layer by applying a sealing material paste prepared by mixing a sealing material containing a sealing glass and a laser absorber and a vehicle containing an organic binder onto the sealing region of the substrate. Process,
The sealing material is baked and sealed while removing the organic binder in the coating layer by irradiating while scanning the laser beam for firing along the coating layer and heating the entire coating layer. A firing step of forming a material layer,
In the firing step, the substrate is supported so that the coating layer is vertically below the substrate and a space is provided around the coating layer, and the coating layer is interposed through the substrate. The manufacturing method of the member with the sealing material layer which irradiates to the said laser beam for baking.   The method for manufacturing a member with a sealing material layer according to claim 1, wherein an edge portion of the substrate is supported in the firing step.   The method for producing a member with a sealing material layer according to claim 1 or 2, wherein a plurality of the coating layers are formed in the coating step, and a portion other than the edge of the substrate is supported in the baking step.   The method for producing a member with a sealing material layer according to any one of claims 1 to 3, wherein the substrate is a glass substrate. A member with a sealing material layer having a substrate having a sealing region and a sealing material layer provided in the sealing region of the substrate,
The member with the sealing material layer manufactured by the manufacturing method of the member with the sealing material layer of any one of Claims 1 thru | or 4. A first substrate having a first surface provided with a first sealing region, and a second substrate having a second surface provided with a second sealing region corresponding to the first sealing region A substrate preparation step of preparing a substrate of
A sealing material paste prepared by mixing a sealing material containing a sealing glass and a laser absorber and a vehicle containing an organic binder is applied onto the second sealing region of the second substrate and applied. A coating process for forming a layer;
The sealing material is baked and sealed while removing the organic binder in the coating layer by irradiating a laser beam for firing while scanning the coating layer to heat the entire coating layer. A firing step for forming a material layer;
A laminating step of laminating the first substrate and the second substrate through the sealing material layer while facing the first surface and the second surface;
The sealing material layer is irradiated with sealing laser light through the first substrate or the second substrate, and the sealing material layer is melted to be between the first substrate and the second substrate. And a sealing step of forming a sealing layer for sealing the electronic element part,
In the firing step, the second substrate is supported so that the coating layer is on the lower side in the vertical direction with respect to the second substrate, and a space is provided around the coating layer, A method for manufacturing an electronic device, comprising: irradiating the coating layer with the laser beam for firing through a substrate of 2; A first substrate having a first surface provided with a first sealing region, and a second surface provided with a second sealing region corresponding to the first sealing region; A second substrate disposed so that the first surface and the second surface face each other; and sealing for sealing an electronic element portion between the first substrate and the second substrate An electronic device having a layer,
An electronic device manufactured by the method for manufacturing an electronic device according to claim 6. A substrate having a coating layer of a sealing material paste prepared by mixing a sealing material containing a sealing glass and a laser absorber and a vehicle containing an organic binder, the coating layer being perpendicular to the substrate. A sample stage for supporting the lower side and providing a space around the coating layer;
A laser light source that emits a laser beam for firing;
A laser irradiation head having an optical system for irradiating the coating layer with the laser light emitted from the laser light source through the substrate;
An output controller for controlling the output of the laser beam for firing irradiated from the laser irradiation head to the coating layer;
A moving mechanism for relatively moving the position of the sample stage and the laser irradiation head;
An apparatus for manufacturing a member with a sealing material layer, comprising: a scanning control unit that controls the moving mechanism so as to irradiate the firing laser light while scanning along the coating layer.

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