WO2016010020A1 - ガラス基体の成形方法 - Google Patents
ガラス基体の成形方法 Download PDFInfo
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- WO2016010020A1 WO2016010020A1 PCT/JP2015/070107 JP2015070107W WO2016010020A1 WO 2016010020 A1 WO2016010020 A1 WO 2016010020A1 JP 2015070107 W JP2015070107 W JP 2015070107W WO 2016010020 A1 WO2016010020 A1 WO 2016010020A1
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- WIPO (PCT)
- Prior art keywords
- glass substrate
- mold
- glass
- molding
- contact surface
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B13/00—Rolling molten glass, i.e. where the molten glass is shaped by rolling
- C03B13/16—Construction of the glass rollers
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B13/00—Rolling molten glass, i.e. where the molten glass is shaped by rolling
- C03B13/08—Rolling patterned sheets, e.g. sheets having a surface pattern
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/03—Re-forming glass sheets by bending by press-bending between shaping moulds
- C03B23/033—Re-forming glass sheets by bending by press-bending between shaping moulds in a continuous way, e.g. roll forming, or press-roll bending
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
- C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
- C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Definitions
- the present invention relates to a method for forming a glass substrate.
- a display device such as a flat panel display or a projector has a lens function and a light scattering function with a fine concavo-convex structure before and after each pixel in order to realize a high brightness image by transmitting more light.
- An optical element is provided.
- MEMS Micro-Electro-Mechanical-System
- fluid control systems using MEMS a fine uneven structure is formed on the glass surface, and these are joined to form liquid flow paths and various types An analytical reaction mechanism is being created. Therefore, an efficient method for forming a fine concavo-convex structure on the glass surface is required in accordance with the purpose.
- This method is a method of transferring a fine pattern on a mold surface to glass by pressing a flat plate-shaped mold having a concave and convex shape formed on the mold surface against glass heated to a softening temperature (for example, , See Patent Document 1).
- Patent Document 2 proposes the following method. That is, the glass material and the flat plate-shaped mold are heated to a temperature T in the range of Tg ⁇ 150 ° C. ⁇ T ⁇ Tg + 100 ° C. with respect to the glass transition temperature Tg of the glass material, and the glass material is kept in contact with the glass material.
- a direct current voltage (preferably 100 V or more and 2000 V or less) is applied between the mold and the mold to generate an electrostatic attraction between the glass material and the surface of the mold, and pressurization is performed by this electrostatic attraction.
- a method of performing is proposed.
- a glass substrate for a cover such as a liquid crystal display
- a glass substrate that does not deteriorate the characteristics of various functional films is required. That is, conventionally, in a glass substrate for a cover of a display device such as a liquid crystal display, particularly a glass substrate in which a thin film of metal or oxide is formed on the surface, if the glass contains an alkali metal oxide, the glass surface Alkali metal ions eluted into the film diffuse into the thin film and deteriorate the film characteristics. Therefore, an alkali-free glass that does not substantially contain alkali metal ions is used.
- 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 large-area glass substrate at a low cost.
- the glass substrate molding method of the present invention comprises a pair of main surfaces, and at least one of the main surfaces of the glass substrate made of a glass material containing an alkali metal oxide has at least a mold surface having conductivity.
- the mold surface of the rotating mold is brought into contact, and the contact surface of the glass substrate with which the mold surface is brought into contact exceeds 100 ° C. (Tg + 50 ° C.) and below (where Tg is glass of the glass material)
- Tg is glass of the glass material
- the mold is rotated or rotated while a DC voltage is applied to the glass substrate with a higher voltage than the main surface side opposite to the main surface side while the glass substrate is maintained at the temperature of the transition temperature.
- the mold or the glass substrate is moved in a direction parallel to the contact surface of the glass substrate according to the rotation or rotation speed of the mold to form the contact surface of the glass substrate.
- the glass substrate molding method of the present invention has a pair of main surfaces, and at least one of the main surfaces of the glass substrate made of a glass material containing an alkali metal oxide has conductivity. The mold surface of the rotating or rotating mold is brought into contact, and the contact surface of the glass substrate with which the mold surface is contacted is over 100 ° C.
- the mold In the state where the glass transition temperature is maintained), the mold is applied to the glass substrate while applying a DC voltage with the contact surface side being positive and the opposite main surface side being ground or negative. At the same time, the mold or the glass substrate is moved in a direction parallel to the contact surface of the glass substrate in accordance with the rotation or rotation speed of the mold, and the contact surface of the glass substrate is rotated. Molding And wherein the Rukoto.
- the mold has a mold surface on which an uneven fine pattern is formed. Further, the application of the DC voltage may not generate corona discharge between the mold surface and one of the main surfaces. Further, it is preferable that the contact surface is further etched after the contact surface of the glass substrate is formed. And it is preferable that the said glass base
- the DC voltage is preferably in the range of 1 to 1000V.
- the molding is preferably performed in an atmosphere mainly composed of air or nitrogen.
- the glass substrate is disposed on a conductive substrate, and a DC voltage is applied with the mold surface of the mold as a positive electrode and the substrate as a ground or a negative electrode.
- a large-sized glass substrate can be molded without using a large-sized (large-area) mold, and low-cost molding is possible.
- a molding die in which a concave and convex fine pattern (hereinafter, simply referred to as a fine pattern or a concave and convex pattern) is formed on the mold surface, the concave and convex pattern on the mold surface is brought into contact with the glass substrate. It is possible to obtain a glass molded body that can be transferred with high accuracy and has a sufficiently high unevenness at low cost.
- molding method of this invention it is a figure explaining the relationship between the movement of the alkali metal ion by the voltage application to a glass base
- the mold surface 2a with respect to the glass substrate 1 made of a glass material containing an alkali metal oxide and having a pair of main surfaces. Is held so that the mold surface 2a is in contact with one of the main surfaces of the glass substrate 1. In this way, the contact surface 1a, which is the main surface of the glass substrate 1 with which the mold surface 2a of the rotary mold 2 is contacted, becomes the molding surface. It is preferable that an uneven pattern to be transferred to the glass substrate 1 is formed on the mold surface 2 a of the rotational mold 2. In FIG.
- reference numeral 3 denotes a base, which is a conductor serving as a ground or a negative electrode
- reference numeral 4 denotes a support for the rotational mold 2
- reference numeral 5 denotes an insulating portion.
- Reference numeral 1 b denotes an alkali low concentration region 1 b formed on the contact surface 1 a of the glass substrate 1. The alkali low concentration region 1b will be described in detail later.
- FIG. 1 describes an example in which the rotational mold 2 is a roll-shaped mold that rotates (rotates) around an axis
- the rotational mold is an endless belt that is spanned between a plurality of rotational rolls. It may be in a shape. Note that such an endless belt-shaped rotational mold will be further described in the section of a molding apparatus described later.
- the contact surface 1a of the glass substrate 1 exceeds 100 ° C. (Tg + 50 ° C.) or less (however, , Tg indicates the glass transition temperature of the glass material constituting the glass substrate 1).
- Tg indicates the glass transition temperature of the glass material constituting the glass substrate 1.
- the glass substrate 1 is rotated while a DC voltage is applied so that the contact surface 1a side has a positive potential and the opposite main surface (hereinafter referred to as a back surface) side has a ground or negative potential.
- the molding die 2 is rotated around the axis, and at the same time, the rotational molding die 2 or the glass substrate 1 is moved in a direction parallel to the contact surface 1a of the glass substrate 1 according to the rotation speed of the rotation molding die 2.
- the contact surface 1a of the glass substrate 1 is formed by the mold surface 2a of the rotary mold 2 while applying a DC voltage.
- it is sufficient that the contact surface 1a side of the glass substrate 1 is higher than the potential on the opposite main surface side.
- the rotary mold 2 is brought into contact with the glass substrate 1 to form a concavo-convex pattern, the glass substrate 1 is subjected to a pressure exceeding zero at least through the rotary mold 2.
- At least the contact surface 1a of the glass substrate 1, preferably the entire glass substrate 1 is heated and maintained at a temperature exceeding 100 ° C. and not higher than (Tg + 50 ° C.), for example, 100 V or less. Is applied to the abutment surface 1a of the glass substrate 1 so that the concavo-convex pattern of the mold surface 2a of the rotary mold 2 is accurately transferred. This is considered to be due to the following reasons.
- the “temperature of the glass substrate” means that at least the contact surface 1a of the glass substrate 1, preferably the entire glass substrate 1, is at the temperature.
- the temperature of the rotational mold 2 also means that at least the mold surface 2a, preferably the entire rotational mold 2 is at this temperature.
- the glass substrate 1 preferably the glass substrate 1 and the rotational mold 2
- Tg + 50 ° C. the glass substrate 1
- the alkali metal ions contained in the glass material constituting the glass substrate 1 are on the ground or negative electrode (hereinafter sometimes referred to as negative electrode) side. Move toward the back side.
- alkaline earth metal ions contained in the glass material try to move, but alkali metal ions having a monovalent cation and a smaller ion radius are closer to the back side, which is the negative electrode side. Easy to move toward.
- the degree of movement of alkali metal ions due to the difference in electric field strength between the concave portion and the convex portion of the mold surface 2a of the rotational mold 2 in contact with the surface layer portion ( Differences in travel distance) and travel direction. That is, as shown in FIG. 2A, in the surface layer portion on the abutting surface 1a side of the glass substrate 1, in a region in contact with the convex portion of the mold surface 2a of the rotational mold 2 (hereinafter referred to as a first region). As the alkali metal ions move toward the negative electrode side (back side), as shown in FIG.
- a glass base material means the glass material which comprises the glass base
- the region other than the low alkali concentration region 1b after being formed can be said to have a glass composition substantially similar to that of the glass base material.
- the molding of the glass substrate 1 is promoted, and as shown in FIG. 2C, the first region in contact with the convex portion of the mold surface 2a of the rotary mold 2 is formed on the molding surface which is the contact surface 1a of the glass substrate 1.
- a concavo-convex pattern is formed in which a concave portion is formed and the second region facing the concave portion of the mold surface 2a is a convex portion.
- pressurization may be performed in the state of voltage application, and voltage application may be performed while the pressurization state is continued.
- a low concentration region of alkali metal ions is formed in the vicinity of the concave portion of the molding surface.
- the vicinity of the surface means a portion from the surface to a depth of 0.1 to 10 ⁇ m.
- the alkali metal ion concentration in the vicinity of the convex portion of the molding surface is the same as that of the glass base material.
- the glass substrate contains a plurality of types of alkali metal oxides in its composition
- the plurality of types of alkali metal ions all move toward the ground electrode or the negative electrode side.As a result, in the low concentration region of the alkali metal ions, The content concentration of any alkali metal ion is lower than that of the glass base material.
- the main alkali metal ions that move when voltage is applied in the present invention are sodium ions, and a low concentration region of sodium ions is formed.
- the glass substrate used in the molding method of the embodiment of the present invention is composed of a glass material having an alkali metal oxide in composition, that is, a glass base material.
- the composition of the glass base material is not particularly limited as long as it has at least one alkali metal oxide. From the viewpoint of ease of molding, the total amount of alkali metal oxide and alkaline earth metal oxide is 15 mass. What contains it in the ratio exceeding% is preferable.
- SiO 2 is 50 to 80%
- Al 2 O 3 is 0.5 to 25%
- B 2 O 3 is 0 to 10%
- glass containing less than 10% in total, such as Fe 2 O 3 .
- SiO 2 is a component constituting the skeleton of glass.
- the content ratio of SiO 2 is preferably 60% or more. More preferably, it is 62% or more, and particularly preferably 63% or more.
- the content ratio of SiO 2 is more preferably 76% or less, and further preferably 74% or less.
- Al 2 O 3 is a component that improves the movement speed of ions.
- the content ratio of Al 2 O 3 is more preferably 1% or more, further preferably 2.5% or more, particularly preferably 4% or more, and most preferably 6% or more. If the content ratio of Al 2 O 3 exceeds 25%, the viscosity of the glass becomes high, and there is a possibility that homogeneous melting becomes difficult.
- the content ratio of Al 2 O 3 is preferably 20% or less. More preferably, it is 16% or less, and particularly preferably 14% or less.
- B 2 O 3 is not an essential component, but may be contained for improving meltability at high temperatures or glass strength.
- the content ratio is more preferably 0.5% or more, and further preferably 1% or more. Further, the content of B 2 O 3 is 10% or less. Since B 2 O 3 tends to evaporate due to coexistence with an alkali component, it may be difficult to obtain homogeneous glass.
- the content ratio of B 2 O 3 is more preferably 6% or less, and still more preferably 1.5% or less. In particular to improve the homogeneity of the glass, B 2 O 3 is preferably not contained.
- Na 2 O is a component that improves the meltability of the glass, and has main ions (sodium ions) that move when the DC voltage is applied.
- the content ratio of Na 2 O is more preferably 11% or more, and particularly preferably 12% or more.
- the content ratio of Na 2 O is 16% or less. If it exceeds 16%, the glass transition temperature Tg is lowered, the strain point is lowered accordingly, and the heat resistance may be inferior, or the weather resistance may be lowered.
- the content ratio of Na 2 O is more preferably 15% or less, further preferably 14% or less, and particularly preferably 13% or less.
- K 2 O is not an essential component, but may be contained because it is a component that improves the meltability of glass and is a component that easily moves when a DC voltage is applied.
- the content is preferably 1% or more, more preferably 3% or more. Further, the content of K 2 O is 8% or less. If the content ratio of K 2 O exceeds 8%, the weather resistance may be lowered. More preferably, it is 5% or less.
- Li 2 O is not an essential component like K 2 O, but may be contained because it is a component that improves the meltability of the glass and that is easily moved by application of a DC voltage.
- the content ratio is preferably 1% or more, and more preferably 3% or more. Further, the content of Li 2 O is 16% or less. If the content ratio of Li 2 O exceeds 16%, the strain point may be too low.
- the content ratio of Li 2 O is more preferably 14% or less, and particularly preferably 12% or less.
- the alkaline earth metal oxide is a component that improves the meltability of the glass and is an effective component for adjusting the glass transition temperature Tg.
- MgO is not an essential component, but is a component that increases the Young's modulus of the glass to improve the strength and improve the solubility. It is preferable to contain 1% or more of MgO.
- the content ratio of MgO is more preferably 3% or more, and particularly preferably 5% or more.
- the content ratio of MgO is 12% or less. If the MgO content exceeds 12%, the stability of the glass may be impaired.
- the content ratio of MgO is more preferably 10% or less, particularly preferably 8% or less.
- CaO is not an essential component, but when CaO is contained, its content is typically 0.05% or more. Moreover, the content rate of CaO is 10% or less. When the content ratio of CaO exceeds 10%, the amount of alkali metal ions transferred due to application of a DC voltage may decrease.
- the content ratio of CaO is more preferably 6% or less, further preferably 2% or less, and particularly preferably 0.5% or less.
- the total content (total amount) of the alkali metal oxide and alkaline earth metal oxide exceeds 15% in order to improve the meltability of the glass and to apply a stable voltage by adjusting the glass transition temperature Tg. Is preferred.
- the total content of alkali metal oxides and alkaline earth metal oxides is more preferably at least 17%, particularly preferably at least 20%, and the upper limit is preferably at most 35%.
- the glass constituting the glass substrate used in the molding method of the present invention may contain other components as long as the object of the present invention is not impaired.
- the total content of these components is preferably 10% or less, more preferably 5% or less. It is particularly preferable that the material substantially consists of the above components, that is, does not contain other components.
- the other components will be described as an example.
- SrO may be contained as necessary, but since the specific gravity of the glass is larger than that of MgO or CaO, the content is preferably less than 1% from the viewpoint of reducing the weight of the material.
- the content ratio of SrO is more preferably less than 0.5%, particularly preferably less than 0.2%.
- BaO has the largest effect of increasing the specific gravity of glass among the alkaline earth metal oxides. Therefore, from the viewpoint of reducing the weight of the material, BaO is not contained or even if contained, the content ratio is 1 % Is preferred.
- the content ratio of BaO is more preferably less than 0.5%, particularly preferably less than 0.2%.
- the total content thereof is preferably less than 1%.
- the total content of SrO and BaO is more preferably less than 0.5%, particularly preferably less than 0.2%.
- ZrO 2 is not an essential component, but may be contained for improving the chemical resistance of glass.
- the content ratio is more preferably 0.1% or more, further preferably 0.3% or more, and particularly preferably 1.5% or more.
- ZnO may be contained up to 2%, for example, in order to improve the melting property of the glass at a high temperature, but the content is preferably 1% or less.
- the content rate When manufacturing glass by the float process etc., it is preferable to make a content rate into 0.5% or less. If the content ratio of ZnO exceeds 0.5%, it may be reduced during float molding, resulting in a product defect. Typically no ZnO is contained.
- the glass containing each of these components may appropriately contain SO 3 , chloride, fluoride, and the like as a fining agent upon melting.
- the glass transition temperature Tg of such glass is preferably in the range of about 500 to 700 ° C.
- the glass transition temperature Tg of the glass material constituting the glass substrate used in the molding method of the present invention is not limited to the above range.
- the shape of the glass substrate composed of such glass is not particularly limited as long as it has a pair of main surfaces parallel to each other.
- the flat plate shape in which the pair of main surfaces are flat surfaces or the curved plate shape in which the pair of main surfaces are curved surfaces may be used.
- these flat or curved glass substrates are referred to as glass substrates, and in the following description, molding of glass substrates will be described.
- the thickness of the glass substrate is not particularly limited. Depending on the application of the glass molded body, for example, a glass substrate having a thickness of 1 ⁇ m to 5 mm can be used.
- FIG. 3 is a diagram schematically showing the configuration of the molding apparatus 10.
- the molding apparatus 10 includes a conductive substrate 11, a glass substrate 12 disposed on the substrate 11 so that one main surface (for example, a lower surface) is in contact with the substrate 11, and the other main surface of the glass substrate 12.
- the roll-shaped mold 13 held so that the outer peripheral surface that is the mold surface 13a abuts (for example, the upper surface, also referred to as the molding surface), and the glass substrate 12 and the roll-shaped mold 13 are heated and held at a predetermined temperature.
- an electric heater (not shown) arranged in contact with or in the vicinity thereof, the conductive substrate 11 as a ground electrode or a negative electrode, and the mold surface 13a of the roll-shaped mold 13 as a positive electrode And a DC power source 14 for applying a DC voltage to the glass substrate 12.
- the molding apparatus 10 includes a rotation mechanism (not shown) that rotates the roll-shaped mold 13 around its axis 13b, the roll-shaped mold 13, the mold surface 13a, and the molding surface of the glass substrate 12.
- a mold moving mechanism (not shown) for moving the glass substrate 12 in parallel with the molding surface of the glass substrate 12 is maintained.
- a pressurizing mechanism that presses the mold surface 13 a of the roll-shaped mold 13 against the molding surface of the glass substrate 12 may be provided.
- the rotation direction of the roll-shaped mold 13 and the moving direction of the roll-shaped mold 13 are indicated by arrows, respectively.
- the rotational speed of the roll-shaped mold 13 can be adjusted by the roll diameter, and the moving speed of the roll-shaped mold 13 is adjusted in synchronization with the rotational speed.
- Such a molding apparatus 10 is disposed in a chamber (not shown) held in a nitrogen atmosphere or the like. Note that when molding is performed in the atmosphere, the chamber is not included. Further, the mechanism for heating and holding the glass substrate 12 and the roll-shaped mold 13 at a predetermined temperature is not limited to the electric heater, and any mechanism that can heat and hold the glass substrate 12 or the like at a predetermined temperature. Good. Hereinafter, each member etc. which comprise such a shaping
- the substrate 11 on which the glass substrate 12 is placed serves as a ground or a negative electrode to which a DC voltage is applied during molding, and is made of a conductive material.
- the conductive material constituting the substrate 11 preferably has a mechanical strength that can withstand the pressurizing force described later.
- Examples of such conductive materials include metals and alloys such as silver, copper, aluminum, chromium, titanium, tungsten, palladium, and stainless steel, tungsten carbide (WC), silicon carbide (SiC), and carbon. From the viewpoint of mechanical strength, WC, SiC, stainless steel such as SUS304 and SUS318, and the like are preferable, and from the viewpoint of cost, carbon is preferable.
- the base 11 serving as the ground or the negative electrode has a shape and a structure in contact with the entire back surface (surface opposite to the molding surface) of the glass substrate 12.
- the base 11 can be formed by arranging a plurality of small rolls side by side so that each axis is parallel to the rotating shaft 13 b of the roll-shaped mold 13. That is, the glass substrate 12 can be arranged on the base 11 made of such a small roll, and the DC power supply 14 can be connected so that the entire small roll aggregate is grounded or negative.
- the glass substrate 12 can be conveyed using the base
- a DC power source 14 is connected to the rotating shaft 13b of the roll-shaped mold 13, and a mold surface 13a of the roll-shaped mold 13 serving as a positive electrode is electrically connected to the rotating shaft 13b.
- a positive voltage can be applied to the molding surface of the glass substrate 12 in contact with the mold surface 13a of the roll-shaped molding die 13 to apply a sufficiently strong electric field inside the glass substrate 12. .
- the roll-shaped mold 13 has a concavo-convex fine pattern on the mold surface 13 a in contact with the glass substrate 12.
- the roll-shaped mold 13 is also preferably made of a material having mechanical strength that can withstand the pressurizing force described later.
- at least the mold surface 13 a is made of a conductive material so that a predetermined positive voltage can be applied to the molding surface (contact surface) of the glass substrate 12.
- the roll-shaped mold 13 is preferably composed entirely of a material having mechanical strength and durability, including the mold surface 13a which is a roll surface.
- examples of the conductive material include metals and alloys such as nickel, chromium, molybdenum, stainless steel such as SUS304 and SUS318, noble metals such as platinum, iridium, and rhodium, carbon, SiC, and WC.
- a conductive organic material can be used as long as the material has heat resistance exceeding the heating temperature of the roll-shaped mold 13.
- the roll-shaped mold 13 may be entirely formed of the conductive material described above, or may be formed of the conductive material on at least the mold surface of a cylindrical mold body formed of an insulating material such as SiO 2.
- a thin film may be formed by coating, and the conductive thin film may be electrically connected to the positive electrode of the DC power supply 14 as described above.
- the glass substrate 12 is molded by applying a sufficiently low voltage (eg, 1000 V or less) at a sufficiently low temperature of (Tg + 50 ° C.) or less.
- a sufficiently low voltage eg, 1000 V or less
- Tg + 50 ° C. sufficiently low temperature
- the molding is performed by moving the roll-shaped mold 13 in a direction parallel to the contact surface of the glass substrate 12 according to the rotation speed.
- the uneven step of the fine pattern formed on the mold surface 13a of the roll-shaped mold 13 (meaning the difference in height between the surface of the recess and the surface of the protrusion.
- mold step is preferably 100 nm or more. 200 nm or more is more preferable, 1 ⁇ m or more is more preferable, and 10 ⁇ m or more is particularly preferable.
- the mold step of the fine pattern is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and further preferably 20 ⁇ m or less.
- the height difference of the unevenness formed on the contact surface (molding surface) of the glass substrate 12 does not depend on the pitch of the fine pattern on the mold surface 13a, preferably 1 to 200 nm, more preferably 5 to 100 nm. 10 to 85 nm is more preferable, and 20 to 50 nm is particularly preferable.
- the mold level difference of the mold surface 13a of the roll-shaped mold 13 described above is not less than the height difference of the unevenness formed on the contact surface (molding surface) of the glass substrate 12. In this way, molding on the molding surface of the glass substrate 12 becomes possible by applying a sufficiently low voltage at a sufficiently low temperature of (Tg + 50 ° C.) or less.
- the pitch of the fine pattern formed on the mold surface 13a of the roll-shaped mold 13 is preferably 50 nm to 50 ⁇ m, more preferably 100 nm to 10 ⁇ m, and further preferably 300 nm to 900 nm.
- the same parts as those of the molding apparatus shown in FIG. 3 are denoted by the same reference numerals, and the same parts are denoted by the same reference numerals in the drawings.
- the rotation direction of the rotational mold and the moving direction of the substrate on which the glass substrate is mounted are indicated by arrows. Further, in FIG. 5 to FIG. 9, the DC power supply is omitted.
- the glass substrate conveyance mechanism (illustration omitted) is provided in the electroconductive base
- FIG. 1 shows with an arrow
- the glass substrate transport mechanism may be any mechanism that can move the conductive substrate 11 in the horizontal direction parallel to the mounting surface while the glass substrate 12 is mounted.
- the base 11 is configured by arranging a large number of conductive small rolls 11a side by side, and each small roll 11a is rotated to collect a large number of small rolls 11a. It is good also considering the base
- a plurality of (for example, two) roll-shaped molds 15 and 16 are arranged side by side at a predetermined interval.
- the molds 15 and 16 are rotationally driven around the rotation shafts 15b and 16b at the respective arrangement positions.
- substrate 11 which consists of an aggregate
- a belt-shaped mold 17 is used instead of the roll-shaped mold.
- the belt-shaped mold 17 is spanned between a plurality of (for example, two) rotating rolls 18 and rotates endlessly along the outer peripheral surface of the rotating rolls 18 according to the rotation of the rotating rolls 18. It is a belt-shaped mold constructed.
- the mold surface 17a which is the outer peripheral surface of the belt-shaped mold 17 has a concave and convex fine pattern, and the mold surface 17a is in contact with the molding surface of the glass substrate 12 as in the third example.
- the substrate 11 that functions as a glass substrate transport mechanism is configured to transport the glass substrate 12 in a horizontal direction parallel to the molding surface.
- the belt-shaped mold 17 is used as the rotational mold as in the fifth example.
- a glass substrate conveyance mechanism it is spanned between several (for example, two) base
- a conveyor belt 20 is provided.
- the glass substrate 12 is arrange
- the conveyance belt 20 is comprised with an electroconductive material, and is connected to DC power supply so that it may become earth
- the diameter of the rotating roll 18 that drives the belt-shaped mold 17 and the diameter of the base-side rotating roll 19 that drives the conveying belt 20 are not necessarily equal, but the mold surface 17a of the belt-shaped mold 17 is not necessarily the same.
- the moving speed of the conveyor belt 20, that is, the speed of conveying the glass substrate 12 in the horizontal direction is synchronized with the rotation speed of the belt-shaped mold 17 so that the sheet is brought into contact with the molding surface of the glass substrate 12 without slipping. Need to be adjusted.
- the length of the belt-shaped mold 17 that contacts the molding surface of the glass substrate 12 as the positive electrode and the length of the transport belt 20 that contacts the back surface of the glass substrate 12 as the ground or negative electrode are shown in FIG. Although it is preferable that they are equal as shown, as shown in FIG. 9, the length of the conveying belt 20 in contact with the back surface of the glass substrate 12 can be made longer.
- An eighth example of the forming apparatus is an apparatus for forming a main surface of a thin (for example, a thickness of 0.3 mm or less) sheet-like glass substrate (hereinafter referred to as a glass sheet).
- the molding apparatus continuously moves the glass sheet 12 a along the mold surface 13 a of the roll-shaped mold 13 disposed at a predetermined position, and the mold of the roll-shaped mold 13.
- the surface opposite to the contact surface of the glass sheet 12a is supported by the conductive substrate 11, and a DC voltage is applied with the roll-shaped mold 13 as the positive electrode and the substrate 11 as the ground or the negative electrode. It is comprised so that it may apply.
- reference numeral 21 denotes a feed roll
- 22 denotes a take-up roll (take-up roll)
- 23 denotes a guide roll.
- the traveling direction of the glass sheet 12a is indicated by an arrow.
- the molding conditions (the temperature of the glass substrate, the applied voltage, the molding atmosphere, etc.) in the embodiment of the present invention will be described.
- the molding apparatus of the first example it is preferable that the molding is performed under the following molding conditions not only in the embodiment using any of the molding apparatuses of the second to eighth examples.
- the temperature T of the glass substrate 12 is higher than 100 ° C., and the temperature is set to (Tg + 50 ° C.) or lower when the glass transition temperature of the glass material is Tg. That is, 100 ° C. ⁇ T ⁇ Tg + 50 ° C. Note that this temperature is the temperature of the molding surface of the glass substrate 12, and it is not always necessary to set the temperature of the portion other than the molding surface of the glass substrate 12, but in terms of heating efficiency and efficiency of the molding operation, the glass substrate The whole 12 is preferably heated to a temperature higher than 100 ° C. and lower than (Tg + 50 ° C.). From the viewpoint of ease of molding, it is preferable that the roll-shaped mold 13 or the belt-shaped mold 17 that is a rotational mold is also heated to the same temperature as the glass substrate 12.
- the temperature T of the glass substrate 12 By making the temperature T of the glass substrate 12 higher than 100 ° C., the movement of alkali metal ions in the glass material is facilitated, and a low alkali concentration region is formed on the surface layer portion of the molding surface of the glass substrate 12 to form the glass substrate 12. Can be easily performed.
- the temperature T of the glass substrate 12 by setting the temperature T of the glass substrate 12 to (Tg + 50 ° C.) or less, deformation of the glass material other than the molding surface can be minimized, and the roll-shaped mold 13 or the belt that is a rotational mold.
- the thermal damage to the shape molding die 17 hereinafter referred to as a rotational molding die
- the heating and heat shielding structure can be simplified.
- the temperature T of the glass substrate 12 is set to (Tg ⁇ 50 ° C.) or less, the viscous deformation of the glass can be suppressed, and the current flowing through the glass substrate 12 can be suppressed from increasing. Further, when the temperature T is set to (Tg ⁇ 150 ° C.) or lower, the mold surface 13a of the roll-shaped mold 13 or the mold surface 17a of the belt-shaped mold 17 does not become a high-temperature oxidizing atmosphere. Corrosion of the conductive material constituting the mold is hardly generated. Therefore, good releasability for glass and practical mold life can be obtained.
- the conductive base 11 or the conveyor belt 20 described above is used as a ground or a negative electrode, and the mold surface 13a of the roll-shaped mold 13 or the mold surface 17a of the belt-shaped mold 17 (hereinafter, referred to as a mold surface of a rotational mold) is used. It is preferable to apply a DC voltage of 1 to 1000 V to the glass substrate 12 as the positive electrode. Even at a voltage of 1000 V or less, in the surface layer portion on the molding surface side close to the positive electrode of the glass substrate 12, the alkali metal ions contained in the composition of the glass constituting the glass substrate 12 are the ground 11 or the negative electrode 11 or the carrier It moves in the glass toward the surface (back surface) that contacts the belt 20.
- an alkali low concentration region is formed in the surface layer portion of a predetermined region of the molding surface of the glass substrate 12 (the first region in contact with the convex portion of the mold surface of the rotational mold), which is higher than 100 ° C. and (Tg + 50 Molding at the following temperature is possible.
- the insulation structure can be simplified. It is possible to mold with a small and simple device. Further, with an applied voltage of 1000 V or less, when a release film is formed on the mold surface of the rotational mold, there is an advantage that the release film is not consumed.
- the upper limit of the applied voltage is more preferably 800 V or less, more preferably 600 V or less, more preferably 500 V or less, and even more preferably 300 V or less.
- the applied voltage is more preferably 100 to 300V, and further preferably 200 to 300V.
- the DC voltage is applied for 10 to 900 seconds, preferably 10 to 300 seconds, although it depends on the applied voltage, the mold step of the mold surface of the rotational mold, the height difference of the irregularities formed on the contact surface of the glass substrate 12. Is more preferable, and 60 to 200 seconds is even more preferable.
- the applied voltage is preferably 100 to 300 V, and the application time is preferably 60 to 900 seconds.
- the application time is more preferably 300 to 900 seconds. This is presumably because a weak current flows even after polarization occurs in the glass substrate, so that the longer the time of application, the greater the amount of electricity supplied and the easier it is to etch.
- the state where corona discharge does not occur refers to a state where a sudden change due to the discharge of direct current is not detected.
- the atmosphere in which the glass substrate 12 is molded for example, the atmosphere in the chamber in which the molding apparatus 10 is disposed does not have to be a vacuum atmosphere or a rare gas atmosphere such as argon, but an atmosphere mainly composed of air or nitrogen. preferable. An atmosphere mainly composed of nitrogen is more preferable.
- the “atmosphere mainly composed of air or nitrogen” refers to a gas state in which the content ratio of air or nitrogen exceeds 50% by volume of the entire atmospheric gas.
- the pressurizing mechanism for the molding surface of the glass substrate 12 is not particularly limited as long as it is a mechanism capable of pressurizing the rotational mold with an external load or the like and pressing the mold surface of the rotational mold against the molding surface of the glass substrate 12. Moreover, you may pressurize with respect to the shaping
- the applied pressure is preferably in the range of 0.1 MPa to 10 MPa.
- the applied pressure is preferably 5 MPa or less, more preferably 4 MPa or less, and even more preferably 3 MPa or less.
- the pressurization may be performed before the DC voltage is applied, but it is preferable to continue the pressurization until the voltage is applied or to perform the pressurization while the voltage is applied. Further, in order to perform the molding efficiently, it is preferable to hold the rotary mold for a certain period of time in a pressurized state.
- the pressing time depends on the applied voltage in the above voltage application, the mold level difference of the mold surface of the rotational mold, the height difference of the irregularities formed on the contact surface of the glass substrate 12, and is preferably about 10 to 250 seconds, preferably 60 to 200 seconds is more preferable.
- the glass substrate 12 and the rotational mold are heated and held at a temperature exceeding 100 ° C. and not higher than (Tg + 50 ° C.), and a sufficiently low DC voltage is applied.
- Tg + 50 ° C. a temperature exceeding 100 ° C. and not higher than (Tg + 50 ° C.)
- a sufficiently low DC voltage is applied.
- the uneven fine pattern formed on the mold surface of the rotational mold can be accurately transferred to the molding surface which is the contact surface of the glass substrate 12.
- molding surface can be obtained, and low-cost shaping
- the glass substrate 12 and the rotational mold are heated to a temperature 150 ° C.
- the heat shielding structure and heat insulating structure of the apparatus can be simplified.
- the protective coating layer formed on the mold surface of the rotational mold can be made of a material that has lower heat resistance and corrosion resistance than conventional ones, enabling downsizing of the equipment and cost reduction of the constituent materials. It becomes. Further, the deterioration of the rotary mold due to heat is suppressed, and the lifetime of the rotary mold is increased, so that the cost can be reduced, and the time required for replacing the rotary mold can be saved, so that productivity is improved.
- the molding method of the present invention it is possible to obtain a glass molded body having a molding surface on which a concave and convex fine pattern is formed and having a low alkali concentration region formed on the surface layer portion of the concave portion of the molding surface.
- the level difference (hereinafter referred to as glass level difference) that is the level difference of the level difference can be in the range of 1 to 200 nm.
- the alkali low concentration region is usually a region where the concentration of sodium ions is lower than other regions, that is, a region lower than the glass base material.
- the concentration of sodium ions is on a molar basis.
- a region that is 1/10 or less of the initial value (glass base material) can be set as a low alkali concentration region.
- the concentration of sodium ions is a value measured by, for example, TOF-SIMS (time-of-flight secondary ion mass spectrometry).
- TOF-SIMS time-of-flight secondary ion mass spectrometry
- the glass molded body obtained by the molding method of the present invention has a larger glass step, which is the difference in level of irregularities, in the fine pattern of irregularities formed on the molding surface by etching using an etching solution. can do. This is thought to be because the etching rate of the surface layer portion of the concave portion is high because the surface layer portion of the concave portion of the molding surface of the glass molded body has a lower alkali concentration than the surface layer portion of the convex portion of the molding surface. .
- the main components of the etching solution include KOH, HF, BHF, HCl, a mixture of HF and KF, a mixture of HF and KCl, a mixture of HF and H 2 SO 4 , and HF, NH 4 F and an organic acid (for example, One or more selected from acetic acid) are preferred. More preferred is KOH, HF, or BHF, and most preferred is KOH.
- the time for immersing the glass substrate in the etching solution depends on the composition of the glass and the uneven shape to be formed, but is preferably within 48 hours, more preferably within 24 hours, even more preferably within 16 hours, and within 12 hours. Is more preferable, and within 5 hours is particularly preferable.
- the etching treatment method can be selected from methods such as immersion, stirring, and spraying. The spray method is preferable because the flow of the etchant on the glass surface is promoted and the unevenness of the unevenness can be further increased.
- the glass step which is the level difference of the concavo-convex is formed by the glass step formed on the molding surface of the glass molded body before the etching treatment. It can be 2 to 100 times. It is preferably 2 to 50 times, more preferably 2 to 10 times. Specifically, the glass step after the etching treatment can be in the range of 10 to 3000 nm. This glass step is preferably 20 to 1000 nm, more preferably 40 to 850 nm, and still more preferably 100 to 500 nm.
- the pitch of the fine pattern formed on the molding surface of the glass molded body obtained by the etching treatment is preferably 50 nm to 50 ⁇ m, more preferably 100 nm to 10 ⁇ m, and further preferably 300 nm to 900 nm.
- Example 3 As a glass substrate, in terms of mass% on an oxide basis, SiO 2 is 70%, Al 2 O 3 is 2%, Na 2 O is 13%, CaO is 10%, MgO is 4%, K 2 O, Fe 2.
- a soda-lime glass (glass transition temperature Tg 555 ° C.) substrate (made by Asahi Glass Co., Ltd., main surface is a rectangle of 30 mm ⁇ 80 mm and thickness is 1.0 mm) containing less than 1% in total of O 3 and SO 3 was used. .
- a stainless steel (SUS304) As the roll-shaped mold, a stainless steel (SUS304) having a diameter of 30 mm and an effective width in the axial direction of 30 mm was used.
- the roll surface of the roll-shaped mold is provided with a mold surface having a concavo-convex pattern having a convex part width of 100 ⁇ m, a concave part width of 330 ⁇ m, a convex part pitch of 430 ⁇ m, and a convex part height (mold step) of 100 ⁇ m. It was. And such a roll-shaped shaping
- the glass substrate and the roll mold are heated to 500 ° C. ( ⁇ Tg + 50 ° C.) with the mold surface of the roll mold placed in contact with the upper surface (mold surface) of the glass substrate,
- a DC voltage of 400 V was applied, 450 V in Example 2, and 500 V in Example 3.
- the roll-shaped mold was moved at a speed of 0.02 mm / second in a direction parallel to the molding surface of the glass substrate and along the long side of the glass substrate.
- the roll-shaped mold thus rotated was moved along the long side of the glass substrate for 50 minutes to form the entire main surface of the glass substrate.
- the glass level difference which is the height difference of the unevenness transferred and formed on the molding surface.
- the measurement results are shown in Table 1.
- the obtained glass molded body was immersed in a 55% by weight KOH aqueous solution maintained at 70 ° C. for a predetermined time (10 hours and 20 hours) to etch the molded surface, and the glass step on the molded surface after etching was etched. Was measured.
- the measurement results are shown in Table 1. Note that the glass step was measured using an atomic force microscope before and after etching.
- the measurement result of the glass step is shown in the graph of FIG. 11 with the etching time as the horizontal axis.
- Table 1 and the graph of FIG. That is, by using a roll-shaped mold having a concavo-convex pattern on the mold surface and applying a DC voltage of 400 to 500 V while being heated at a predetermined heating temperature, the concavo-convex shape of the glass substrate is formed.
- a glass molded product having a sufficiently high glass level difference can be obtained.
- step difference in a molded object becomes large by an etching. In particular, when the applied voltage is 450 V and 500 V, it can be seen that the glass level difference greatly increases linearly as the etching time increases.
- Examples 4 to 8 As a glass substrate, a soda lime glass (glass transition temperature Tg 555 ° C.) substrate (made by Asahi Glass Co., Ltd., main surface is 10 mm ⁇ 10 mm rectangle and thickness is 1.0 mm) having the same composition as in Examples 1 to 3 is used. did. On the roll surface of the molding die, a mold surface having a concavo-convex pattern having a convex portion width of 60 ⁇ m, a concave portion width of 360 ⁇ m, a convex portion pitch of 420 ⁇ m, and a convex portion height (mold step) of 40 ⁇ m was formed. And this shaping
- Example 7 in a state where the mold surface of the roll-shaped mold is in contact with the upper surface (molding surface) of the glass substrate, the glass substrate and the mold are 350 in Example 4, 400 in Example 5, and 450 in Example 6.
- Example 7 while heating to 550 ° C. in Example 8, using the substrate under the glass substrate as the negative electrode and the mold as the positive electrode, a 200 V DC voltage was applied for 840 seconds, and the boosting time was 30 seconds. The pressure was increased to 3 MPa. Thus, unevenness was formed on the glass substrate. At this time, a sudden change due to the discharge of the direct current was not detected, and no corona discharge occurred.
- the obtained glass molded body was immersed in an aqueous KOH solution having a concentration of 55% by mass held at 70 ° C. for 10 hours to etch the molded surface, and the glass level difference on the molded surface after etching was measured with a surface roughness meter. .
- a groove having a glass step of about 1 ⁇ m and relatively faithful to the shape of the mold could be formed.
- the amount of electricity was 12, 27, 24, 22, and 21 millicoulombs (mC) in this order. These electric quantities are larger than those at 16 to 17 millicoulombs when the voltage is 400 V for generating corona discharge, the application time is 90 seconds, and the heating temperature is 350 to 500 ° C., except when the heating temperature is 350 ° C. Met.
- a concave / convex fine pattern formed on a mold surface of a rotary mold such as a roll-shaped mold can be accurately transferred to the molding surface of a glass substrate, and the concave / convex pattern with high shape accuracy. It is possible to obtain a glass molded body having a lower cost than conventional ones. Therefore, it can be applied to various fields such as various optical components such as optical elements used in display devices, light control devices using MEMS, and microchemical analysis devices.
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Abstract
Description
本発明においては、こうして得られたガラス成形体の成形面をエッチング処理することが好ましい。エッチング処理を行うことにより、ガラス成形体の成形面に形成された凹凸パターンにおける、凹凸の高低差をより大きくすることができる。
本発明の実施形態の成形方法で用いられるガラス基体は、組成においてアルカリ金属酸化物を有するガラス材料、すなわちガラス母材から構成される。ガラス母材の組成は、少なくとも1種のアルカリ金属酸化物を有するものであれば特に限定されないが、成形の容易性の観点から、アルカリ金属酸化物およびアルカリ土類金属酸化物を合計で15質量%を超える割合で含有するものが好ましい。
SiO2の含有割合が80%超では、ガラスの粘性が増大し、溶融性が著しく低下するおそれがある。SiO2の含有割合は、より好ましくは76%以下、さらに好ましくは74%以下である。
Al2O3の含有割合が25%超では、ガラスの粘性が高くなり、均質な溶融が困難になるおそれがある。Al2O3の含有割合は20%以下が好ましい。より好ましくは16%以下、特に好ましくは14%以下である。
また、B2O3の含有割合は10%以下である。B2O3は、アルカリ成分との共存により蒸発しやすくなるため、均質なガラスを得にくくなるおそれがある。B2O3の含有割合は、より好ましくは6%以下、さらに好ましくは1.5%以下である。ガラスの均質性を特に改善するためには、B2O3は含有しないことが好ましい。
Na2Oの含有割合は16%以下である。16%超では、ガラス転移温度Tgが低下し、それにしたがって歪点が低くなり、耐熱性が劣る、または耐候性が低下するおそれがある。Na2Oの含有割合は、より好ましくは15%以下、さらに好ましくは14%以下、特に好ましくは13%以下である。
また、K2Oの含有割合は8%以下である。K2Oの含有割合が8%超では、耐候性が低下するおそれがある。より好ましくは5%以下である。
また、Li2Oの含有量は16%以下である。Li2Oの含有割合が16%超では、歪点が低くなりすぎるおそれがある。Li2Oの含有割合は、より好ましくは14%以下、特に好ましくは12%以下である。
アルカリ土類金属酸化物のうちで、MgOは必須成分ではないが、ガラスのヤング率を上げて強度を向上させ、溶解性を向上させる成分である。MgOを1%以上含有することが好ましい。MgOの含有割合は、より好ましくは3%以上、特に好ましくは5%以上である。また、MgOの含有割合は12%以下である。MgOの含有割合が12%超では、ガラスの安定性が損なわれるおそれがある。MgOの含有割合は、より好ましくは10%以下、特に好ましくは8%以下である。
SrOとBaOを含有する場合、それらの含有割合の合計は1%未満が好ましい。SrOとBaOの含有割合の合計は、より好ましくは0.5%未満、特に好ましくは0.2%未満である。
さらに、これらの各成分を含有するガラスは、溶融の際の清澄剤として、SO3、塩化物、フッ化物などを適宜含有してもよい。
ガラス基板の厚さは特に限定されない。ガラス成形体の用途に応じて、例えば、1μm~5mmの厚さのガラス基板を使用することができる。
本発明の成形方法に用いられる成形装置の第1の例を、図3に示す。図3は、成形装置10の構成を概略的に示す図である。
この成形装置10は、導電性を有する基盤11と、この基盤11の上に、一方の主面(例えば下面)が接触するように配置されたガラス基板12と、ガラス基板12の他方の主面(例えば上面。成形面ともいう。)に型面13aである外周面が当接するように保持されたロール状成形型13と、ガラス基板12とロール状成形型13を加熱し所定の温度に保持するために、これらに接してまたはこれらの近傍に配置された電熱ヒータ(図示を省略。)と、導電性の基盤11をアース極または負極とし、ロール状成形型13の型面13aを正極として、ガラス基板12に対して直流電圧を印加するための直流電源14とを備えている。
以下、このような成形装置10を構成する各部材などについて、さらに説明する。
ガラス基板12が載せられる基盤11は、成形の際に直流電圧が印加されるアースまたは負極となるものであり、導電性の材料から構成される。基盤11を構成する導電性の材料は、後述する加圧力に耐える機械的強度を有するものが好ましい。
ロール状成形型13の回転軸13bには直流電源14が接続され、正極となるロール状成形型13の型面13aは、この回転軸13bと電気的に接続されている。このような構造にすることで、ロール状成形型13の型面13aと接するガラス基板12の成形面に、正電圧を負荷して、ガラス基板12内部に十分な強度の電界をかけることができる。
なお、ロール状成形型13の型面13aにおいては、ガラス基板12の主面に当接される領域の両側に、ロール支持部分の熱変形を防ぐために、セラミックからなる断熱層を設けることが好ましい。
なお、図4~図9において、図3に示す成形装置と同じ部分には同じ符号を付し、各図面においても同じ部分には同じ符号を付している。また、回転成形型の回転方向およびガラス基板を搭載した基盤等の移動方向を、矢印で示す。さらに、図5~図9において、直流電源は省略している。
成形装置10の第2の例では、図4に示すように、ガラス基板12を搭載した導電性の基盤11に、ガラス基板搬送機構(図示を省略。)が設けられている。そして、ガラス基板12を、ロール状成形型13の型面13aと当接した状態を保ったままで、成形面に平行な水平方向(矢印で示す。)に搬送するように構成されている。
成形装置の第4の例では、図6に示すように、複数個(例えば2個)のロール状成形型15,16が、所定の間隔をおいて並べて配置されており、これらのロール状成形型15,16は、それぞれの配置位置で回転軸15b,16bの周りに回転駆動されている。そして、小ロール11aの集合体からなる基盤11がガラス基板搬送機構として機能し、ガラス基板12をその成形面に平行な水平方向に搬送するように構成されている。
成形装置10の第5の例では、図7に示すように、ロール状成形型に代わって、ベルト状成形型17が用いられている。ベルト状成形型17は、複数個(例えば2個)の回転ロール18の間に架け渡され、回転ロール18の回転に応じてこれらの回転ロール18の外周面に沿ってエンドレスに輪転するように構成されたベルト状の型である。そして、ベルト状成形型17の外周面である型面17aに凹凸形状の微細パターンを有し、この型面17aをガラス基板12の成形面に当接した状態で、前記第3の例と同様にガラス基板搬送機構として機能する基盤11により、ガラス基板12をその成形面に平行な水平方向に搬送するように構成されている。
図8に示す成形装置10の第6の例、および図9に示す第7の例では、回転成形型として、第5の例と同様にベルト状成形型17が用いられている。また、ガラス基板搬送機構としては、複数個(例えば2個)の基盤側回転ロール19の間に架け渡され、これら基盤側回転ロール19の回転に応じて外周面に沿ってエンドレスに輪転し移動する搬送ベルト20が設けられている。そして、この搬送ベルト20の上にガラス基板12が配置され、ガラス基板12をその成形面に平行な水平方向に搬送するように構成されている。また、搬送ベルト20は、導電性材料で構成され、アースまたは負極となるように直流電源に接続されている。
成形装置の第8の例は、薄い(例えば厚さが0.3mm以下)シート状のガラス基板(以下、ガラスシートという。)の主面を成形する装置である。この成形装置は、図10に示すように、所定の位置に配置されたロール状成形型13の型面13aに沿わせて、ガラスシート12aを連続的に走行させ、ロール状成形型13の型面13aとの当接部で、ガラスシート12aの当接面と反対側の面を導電性の基盤11により支持し、ロール状成形型13を正極とし基盤11をアースまたは負極とする直流電圧を印加するように構成されている。
なお、図10において、符号21は送り出しロール、22は巻き取りロール(引き取りロール)、23はガイドロールを示す。また、ガラスシート12aの走行方向を矢印で示す。
ガラス基板12の温度Tは、100℃より高く、かつガラス材料のガラス転移温度をTgとしたとき、(Tg+50℃)以下の温度とする。すなわち、100℃<T≦Tg+50℃とする。なお、この温度は、ガラス基板12の成形面の温度であり、ガラス基板12の成形面以外の部位は必ずしもこの温度にする必要はないが、加熱効率および成形作業の効率の点で、ガラス基板12全体が100℃より高くかつ(Tg+50℃)以下の温度に加熱されることが好ましい。また、成形の容易性の点から、回転成形型であるロール状成形型13またはベルト状成形型17も、ガラス基板12と同じ温度に加熱することが好ましい。
前記した導電性の基盤11または搬送ベルト20をアースまたは負極とし、ロール状成形型13の型面13aまたはベルト状成形型17の型面17a(以下、回転成形型の型面と示す。)を正極として、ガラス基板12に対して1~1000Vの直流電圧を印加することが好ましい。1000V以下の電圧であっても、ガラス基板12の正極に近い成形面側の表層部において、ガラス基板12を構成するガラスの組成に含まれるアルカリ金属イオンが、アースまたは負極である基盤11または搬送ベルト20に接する面(裏面)側に向って、ガラス中を移動する。その結果、ガラス基板12の成形面の所定の領域(回転成形型の型面の凸部に接する第1の領域)の表層部に、アルカリ低濃度領域が形成され、100℃より高くかつ(Tg+50℃)以下の温度での成形が可能となる。
成形型の型面の凹凸パターンをガラス基板の当接面に対して、いっそう精度よく転写する一つの方法として、成形型の型面とガラス基板との間でコロナ放電を発生させない方が好ましい。この場合の印加電圧は100~300Vが好ましく、印加する時間は60~900秒間が好ましい。また、この場合において、成形型の凹凸の高低差が十分でないときには、ガラス基板の移動速度、成形型の回転または輪転する速度を減少し、印加する時間は長い方がよい。この場合の印加する時間は、300~900秒間がより好ましい。これは、ガラス基板に分極が生じた後も微弱な電流は流れるため、印加する時間が長い程、供給した電気量が大きくなり、エッチングしやすくなるためと考えられる。ここで、コロナ放電が発生しない状態とは、直流電流の放電による急激な変化が検知されない状態をいう。
ガラス基板12の成形が行われる雰囲気、例えば、前記成形装置10が配置されるチャンバ内の雰囲気は、真空雰囲気またはアルゴン等の希ガス雰囲気とする必要はなく、空気または窒素を主体とする雰囲気が好ましい。窒素を主体とする雰囲気がより好ましい。ここで、「空気または窒素を主体とする雰囲気」とは、空気または窒素の含有割合が雰囲気ガス全体の50体積%を超える気体状態をいう。成形を空気または窒素を主体とする雰囲気で行うことにより、真空中または希ガス中で行う場合に比べて、装置を小型簡易化できるとともに、装置構成の自由度が向上する。
ガラス基板12の成形面に対する加圧機構は、回転成形型を外部からの荷重等により加圧し、回転成形型の型面をガラス基板12の成形面に押圧できる機構であれば、特に限定されない。また、特に加圧機構を用いず、回転成形型の自重により、ガラス基板12の成形面に対する加圧を施してもよい。加圧により、より短時間で安定して成形を行うことが可能となる。加圧力は0.1MPa~10MPaの範囲が好ましい。加圧力をこの範囲とすることで、ガラス基板12および回転成形型に損傷を与えることなく、ガラス基板12の成形面と回転成形型の型面とを確実に当接させ、型面の微細パターンをガラス基板12の成形面に精度良く転写できる。加圧力は5MPa以下が好ましく、4MPa以下がより好ましく、3MPa以下がさらに好ましい。
こうして本発明の成形方法で得られるガラス成形体は、エッチング液を用いてエッチング処理を行うことにより、成形面に形成された凹凸形状の微細パターンにおいて、凹凸の高低差であるガラス段差をより大きくすることができる。これは、ガラス成形体の成形面の凹部の表層部が、成形面の凸部の表層部に比べてアルカリ濃度が低くなっているために、凹部の表層部のエッチングレートが大きいためと考えられる。
エッチング液における固形分濃度は、高濃度であるほど生産性(エッチング効率)が高く、1質量%~65質量%が好ましい。より好ましくは、10質量%~60質量%である。
エッチング液にガラス基板を浸漬する時間は、ガラスの組成と形成される凹凸形状にも依存するが、48時間以内が好ましく、24時間以内がより好ましく、16時間以内がよりいっそう好ましく、12時間以内がさらに好ましく、5時間以内が特に好ましい。
エッチング処理方法としては、浸漬、撹拌、スプレー等の方法から選択できる。ガラス表面のエッチャントの流れを促進し、凹凸の高低差をより大きくできることから、スプレー法が好ましい。
ガラス基板として、酸化物基準の質量%表示で、SiO2を70%、Al2O3を2%、Na2Oを13%、CaOを10%、MgOを4%、K2O、Fe2O3、SO3を合計で1%未満含有するソーダライムガラス(ガラス転移温度Tg555℃)の基板(旭硝子株式会社製、主面は30mm×80mmの矩形で厚さは1.0mm)を使用した。また、ロール状成形型として、直径30mmで軸方向の有効幅が30mmのステンレス(SUS304)製のものを使用した。なお、ロール状成形型のロール面には、凸部の幅100μm、凹部の幅330μm、凸部のピッチ430μm、凸部の高さ(型段差)100μmの凹凸パターンを有する型面が形成されていた。そして、このようなロール状成形型と前記ガラス基板とを、図3に示す成形装置10にセットし、大気雰囲気とした。
さらに、得られたガラス成形体を、70℃に保持した濃度55質量%のKOH水溶液に所定の時間(10時間および20時間)浸漬して成形面をエッチングし、エッチング後の成形面のガラス段差を測定した。測定結果を表1に示す。なお、ガラス段差の測定は、エッチング前およびエッチング後のいずれにおいても、原子間力顕微鏡を用いて行った。
表1の測定結果および図11のグラフから、以下のことがわかる。すなわち、型面に凹凸パターンを有するロール状成形型を使用し、所定の加熱温度で加熱しながら400~500Vの直流電圧を印加してガラス基板の凹凸を成形することで、凹凸の高低差であるガラス段差が十分に高いガラス成形体を得ることができる。また、成形体におけるガラス段差は、エッチングにより大きくなる。特に、印加電圧が450Vおよび500Vの場合は、エッチング時間の増大とともに、ガラス段差が直線的に大きく増大していることがわかる。
ガラス基板として、実施例1~3と同じ組成を有するソーダライムガラス(ガラス転移温度Tg555℃)の基板(旭硝子株式会社製、主面は10mm×10mmの矩形で厚さは1.0mm)を使用した。成形型のロール面には、凸部の幅60μm、凹部の幅360μm、凸部のピッチ420μm、凸部の高さ(型段差)40μmの凹凸パターンを有する型面が形成されていた。そして、この成形型と前記ガラス基板とを、図3に示す成形装置10にセットし、窒素雰囲気とした。
この結果、全ての加熱条件(実施例4~8)で、1μm程度のガラス段差を有し、成形型の形状に比較的忠実な溝を形成できた。350、400、450、500、550℃の加熱温度に対して、電気量は、順に、12、27、24、22、21ミリクーロン(mC)となった。なお、これらの電気量は、加熱温度350℃の場合を除いて、コロナ放電が発生する電圧400V、印加時間90秒、加熱温度350~500℃の場合の16~17ミリクーロンに比べて大きな量であった。
Claims (11)
- 一対の主面を有し、アルカリ金属酸化物を含有するガラス材料からなるガラス基体の前記主面の一方に、少なくとも型面が導電性を有する、回転または輪転する成形型の前記型面を当接させるとともに、
前記型面が当接された前記ガラス基体の当接面を、100℃を超え(Tg+50℃)以下(ただし、Tgは前記ガラス材料のガラス転移温度を示す。)の温度に保持した状態で、前記ガラス基体に、前記当接面側が反対の主面側に対して高い電圧とする直流電圧を印加しながら、
前記成形型を回転または輪転させ、同時に前記成形型または前記ガラス基体を、前記ガラス基体の当接面に平行な方向に前記成形型の回転または輪転速度に合わせて移動させ、
前記ガラス基体の前記当接面を成形することを特徴とするガラス基体の成形方法。 - 一対の主面を有し、アルカリ金属酸化物を含有するガラス材料からなるガラス基体の前記主面の一方に、少なくとも型面が導電性を有する、回転または輪転する成形型の前記型面を当接させるとともに、
前記型面が当接された前記ガラス基体の当接面を、100℃を超え(Tg+50℃)以下(ただし、Tgは前記ガラス材料のガラス転移温度を示す。)の温度に保持した状態で、前記ガラス基体に、前記当接面側を正とし反対の主面側をアースまたは負とする直流電圧を印加しながら、
前記成形型を回転または輪転させ、同時に前記成形型または前記ガラス基体を、前記ガラス基体の当接面に平行な方向に前記成形型の回転または輪転速度に合わせて移動させ、
前記ガラス基体の前記当接面を成形することを特徴とするガラス基体の成形方法。 - 前記成形型は、凹凸形状の微細パターンが形成された型面を有する、請求項1または2に記載のガラス基体の成形方法。
- 前記直流電圧の印加は、前記型面と前記主面の一方との間でコロナ放電を発生させない、請求項1~3のいずれか1項に記載のガラス基体の成形方法。
- 前記ガラス基体の前記当接面を成形した後、更に、該当接面をエッチングする、請求項1~4のいずれか1項に記載のガラス基体の成形方法。
- 前記ガラス基体は、アルカリ金属酸化物とアルカリ土類金属酸化物を合計で15質量%を超える割合で含有するガラス材料からなる、請求項1~5のいずれか1項に記載のガラス基体の成形方法。
- 前記成形において、前記ガラス基体の当接面とともに前記成形型の型面を、100℃を超え(Tg+50℃)以下の温度に保持する、請求項1~6のいずれか1項に記載のガラス基体の成形方法。
- 前記直流電圧は1~1000Vの範囲である、請求項1~7のいずれか1項に記載のガラス基体の成形方法。
- 前記成形において、0.1MPa~10MPaの圧力を前記ガラス基体の当接面に加える、請求項1~8のいずれか1項に記載のガラス基体の成形方法。
- 前記成形は空気または窒素を主体とする雰囲気で行う、請求項1~9のいずれか1項に記載のガラス基体の成形方法。
- 前記ガラス基体を導電性の基盤上に配置し、前記成形型の型面を正極とし前記基盤をアースまたは負極とする直流電圧を印加する、請求項1~10のいずれか1項に記載のガラス基体の成形方法。
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