Patent Application
20110084426
1. Field of the Invention
The present invention relates to a method of notching a brittle material, to a method of making a member having a notch, and a method of making a display device using the member having the notch.
2. Description of the Related Art
In a flat display device including a face plate and a rear plate that face each other, a spacer is disposed between the face plate and the rear plate. A brittle substance such as a glass or a ceramic is used as the spacer because of the mechanical strength (hardness) of glass and ceramic materials. Japanese Patent Laid-Open No. 6-342634 and Japanese Patent Laid-Open No. 2006-120534 disclose a spacer having a notch.
However, because a brittle substance is brittle, when a material (brittle material) made of a brittle substance is notched by performing contact machining such as cutting or grinding, the brittle material may break or chip, which may decrease the yield. Moreover, when notching is performed by grinding, dust is generated. If a spacer to which dust adheres is used for a display device that uses electron beams, such as a field emission display (FED), the dust may cause abnormal discharge.
Japanese Patent Laid-Open No. 2003-88989 describes a method of exfoliating a brittle material by forming a thermal distribution on a surface of the brittle material by irradiating the surface with a laser beam.
It is difficult to form a notch having a good desired shape in a brittle material by performing non-contact machining by irradiating the brittle material with a laser beam even if the beam diameter of the laser beam is sufficiently small. The present invention provides a method of notching that is suitable for a brittle material and by which a notch having a good desired shape can be formed in the brittle material.
According to an aspect of the present invention, a method of notching a brittle material includes heating the brittle material by forming a light beam spot on a predetermined face of the brittle material by irradiating an area of the predetermined face with a light beam; and forming a notch in the brittle material by exfoliating a fraction of the brittle material including the area from the brittle material by cooling a portion of the brittle material including the area after the heating the brittle material, wherein a length of the area in a longitudinal direction of the predetermined face is smaller than a total length of the predetermined face in the longitudinal direction, and a length of the light beam spot in a lateral direction of the predetermined face is equal to a total length of the predetermined face in the lateral direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Referring to
The brittle material 101 illustrated in
As illustrated in
The predetermined face 102 is irradiated with at least a part of the beam 201, which is one or more fluxes of light. The spot 202 is an irradiation portion of the beam 201 that is formed on the predetermined face 102 at the moment when the predetermined face 102, which is an image plane, is irradiated with the beam 201.
The spot 202 is not formed over the entire area of the predetermined face 102 in the X direction but in a partial area in the X direction. The irradiation area 222 is a part of the predetermined face 102 on which the spot 202 is formed, i.e., the area that is irradiated with the beam 201. Therefore, the irradiation area 222 has a length Ls in the X direction that is smaller than the length L of the predetermined face 102 of the brittle material 101. An unirradiated area 212 is an area of the predetermined face 102 excluding the irradiation area 222, i.e., an area that is not irradiated with the beam 201.
The spot 202 has a spot width Ws (length in the Y direction) that is equal to the width W of the predetermined face 102. Thus, the irradiation area 222 has a length in the Y direction that is equal to the width W of the predetermined face 102. This is achieved by making a beam width Wb, which is the length of the beam 201 that forms the spot 202 in the Y direction, be equal to or larger than the width W of the predetermined face 102.
By being irradiated with the beam 201, the temperature of the irradiation area 222 and the temperature of the vicinity of the irradiation area 222 are increased. Therefore, a high-temperature portion 108, which locally has a higher temperature than the surrounding area, is formed in the brittle material 101. The high-temperature portion 108 includes the irradiation area 222. The portion of the brittle material 101 excluding the high-temperature portion 108 will be referred to as a low-temperature portion. The low-temperature portion includes the unirradiated area 212 and has a lower temperature than the high-temperature portion 108. The increase in temperature is caused by absorption of the energy of the beam 201 by the brittle material 101. However, the high-temperature portion 108 is formed not only by the absorption of energy but also by heat conduction in the brittle material 101. Therefore, the range of the high-temperature portion 108 extends not only over the part of the brittle material 101 that is irradiated by the beam 201 but also to the surrounding area. In other words, the range of the high-temperature portion 108 can be controlled by appropriately setting the irradiation area 222 and the method of irradiation.
After irradiation with the beam 201 is finished, the part of the brittle material 101 including the irradiation area 222 is cooled. Alternatively, the entirety of the brittle material 101 may be cooled. As a result, as illustrated in
As heretofore described, notching is performed on the brittle material 101, which is a workpiece, through the heating step and the cooling step, whereby the brittle member 100 having the notch 109 is formed as a product. The exfoliated piece 110 may also be used as a product.
Hereinafter, an example of the present embodiment will be described in detail.
The brittle material 101 will be described in detail. The brittle material 101 is not specifically limited, as long as the brittle material 101 can be broken and partially exfoliated by applying stress. For example, a glass; a crystal of quartz, sapphire, or silicon; a ceramics (sintered material), or a plastic can be used. In one embodiment, the heat conductivity of the brittle material 101 at 300 K be equal to or lower than 50 [W/(m·K)] and may be equal to or higher than 10 [W/(m·K)]. When using the brittle member 100 a spacer for a display device using electron beams as described below, the brittle material 101 can be an insulation material. However, when using a conductive material as the brittle material 101, the surface of the conductive material can be covered with an insulation film. As necessary, an electrically conductive film or a high-resistance film may be disposed on a surface of the brittle material 101. If the thickness of the film disposed on the surface is sufficiently smaller than the depth of the notch to be formed, the entire workpiece can be regarded as being brittle even if the film is not brittle. In one embodiment, the thickness of the film be equal to or smaller than 1/10 of the depth of the notch and may be equal to or smaller than 1/100 of the depth of the notch. If a film is formed on the predetermined face 102, the film is configured so as not to entirely reflect the beam 201. To be specific, the material and the thickness of the film are appropriately determined.
The predetermined face 102 on which the spot 202 is formed may be arbitrarily selected. When using the brittle member 100, which is a product, as a spacer described below, the length L of the predetermined face 102 can be larger than the width W. That is, the X direction can be the longitudinal direction and the Y direction can be the lateral direction.
As illustrated in
The first side face 1031 and the second side face 1032 will be collectively referred to as a side face 103. The distance between the first side edge 1041 and the second side edge 1042 in the Y direction corresponds to the width W. In some cases, the side edge 104, which is the boundary between the predetermined face 102 and the side face 103, is not clear. In such a case, the side edge 104 is determined as follows: in an arbitrary YZ cross section of the brittle material 101, a tangential line (a first line) is drawn at a vertex of the predetermined face 102 in the Z direction; a second line having an angle of 135° on the brittle material 101 side with respect to the tangent line is drawn such that the second line contacts to a surface of the brittle material 101; a tangent point of the second line and the surface of the brittle material 101 is obtained; and the tangent points for all YZ cross sections of the brittle material 101 are connected in the X direction to obtain the side edge 104. One of the two surfaces of the brittle material 101 that extend in the X direction and in the Y direction (parallel to the XY plane) and that is not the predetermined face 102 will be referred to as an opposite face.
In
If the predetermined face 102 is not rectangular, for example, a direction in which the first side edge 1041 extends is determined as the length direction, and a direction from an arbitrary point on the first side edge 1041 to an arbitrary point on the second side edge 1042 is determined as the width direction. The distance between an arbitrary point on the first side edge 1041 and an arbitrary point on the second side edge 1042 is determined as the width W. Even if the width W of the brittle material 101 is not uniform in the length direction, the distance between the arbitrary point on the first side edge 1041 and the arbitrary point on the second side edge 1042 corresponds to the width W. In practice, the width W is in the range from 50 μm to 5 mm. In one embodiment, the width W be equal to or smaller than 3 mm and may be equal to or smaller than 1 mm.
A light source that emits the beam 201 can have an output wavelength that is fit for the heat absorption spectrum of the brittle material 101.
As described above, the temperature of the brittle material 101 increases when the energy of the beam 201 is absorbed by the brittle material 101. The absorbed energy is converted to heat, which heats up the brittle material 101. Therefore, the wavelength of the light can be in the range in which the energy of the light is easily converted to heat. Infrared radiation (wavelength in the range from 0.7 μm to 1 mm) can be typically used.
The wavelength of the light can be in the range in which the light is easily absorbed by the brittle material 101. On the contrary, if the wavelength of the light is in the range in which the light is not absorbed by the brittle material 101 at all, the brittle material 101 is not heated. If the wavelength of the light is in the range in which the light is absorbed by the brittle material 101 only by a small amount, heat conduction occurs in the brittle material 101 before the brittle material 101 is sufficiently heated, so that it is difficult to generate a clear temperature difference between the high-temperature portion 108 and the low-temperature portion.
For example, a quartz glass having a thickness of 2 mm has a high light transmittance that is higher than 90% (a low light absorptance) with respect to light having a wavelength in the range from about 0.3 to 2 μm. In contrast, if the wavelength of light is equal to or larger than 3 μm, the light transmittance substantially decreases. The quartz glass has a low light transmittance lower than 20% (a high light absorptance) with respect to light having a wavelength equal to or larger than 4 μm. The light transmittance of the quartz glass with respect to light having a wavelength in the range from 2 to 3 μm considerably differs depending on whether or not a hydroxyl radical is present in the quartz glass. The absorption spectrum differs in accordance with the type of the brittle material 101 (for example, silicate glass includes types such as a quartz glass, a borosilicate, a soda lime glass, etc.). The absorption spectrum differs in accordance with the amount and the type of impurity contained in the substance.
The relationship between the brittle material 101 and the absorption of the beam 201 can be represented by the absorption constant with respect to the wavelength of the beam 201. In practice, the absorption constant of the brittle material 101 can be equal to or higher than 20. In one embodiment, the absorption constant of the brittle material 101 be equal to or higher than 150 and may be equal to or higher than 1000. In general, the longer the wavelength of infrared radiation, the higher the absorption constant. If the wavelength of light is equal to or larger than 4 μm, a general silicate glass described above has an absorption constant that is equal to or higher than 150. A quartz glass has an absorption constant of about 350 with respect to light having a wavelength of 4 μm. The wavelength of the light may be equal to or larger than 4.5 μm.
A laser beam can be used as the beam 201 because a high output power can be easily obtained and an optical system can be easily designed. The laser light source may be a pulse laser, which outputs laser light as a pulse wave, or a continuous wave (CW) laser, which outputs laser light a continuous wave. The laser light source may be a solid-state laser, a gas laser, or a semiconductor laser. Examples of the solid-state laser include a YAG laser, a ruby laser, etc. The YAG laser can be used because the use of infrared radiation is effective as described above. In particular, an Er:YAG laser (wavelength of about 3 μm), which has a larger wavelength than an Nd:YAG laser (wavelength of about 1 μm), can be used. Examples of the gas laser include a CO2 laser (wavelength in the range from 9 to 11 μm), a CO laser (wavelength from 5 to 7 μm), a He—Ne laser, an excimer laser, etc. A CO2 laser or a CO laser can be used, because the use of infrared radiation is effective as described above. In particular, a CO2 laser can be used.
However, the light may not be coherent in order to heat the brittle material 101, as long as the light has a certain degree of directivity so as to allow local irradiation. Instead of using laser light, for example, the beam 201 can be formed by using a lamp that emits light in random directions and a mask having an opening so that the light passes through the opening in a specific direction. As the lamp, an infrared radiation lamp, such as a halogen lamp, can be used.
The beam 201 is determined as a part of the flux of light having an energy intensity that is equal to or higher than 13.5% of the maximum value of the energy intensity distribution of the flux of light in the cross section of the flux of light on the predetermined face 102. Therefore, the range of the beam 201 for defining the width Wb of the beam 201 and the like is determined as the part having an energy intensity that is 13.5% of the maximum value of the energy intensity distribution. Thus, naturally, the energy intensity in the spot 202 is equal to or higher than 13.5% of the maximum value of the energy intensity distribution of the beam 201. This is because, even if the predetermined face 102 is irradiated with a part of the light beam having an energy intensity that is lower than 13.5% of the energy distribution of the flux of light in the cross section of the flux of light, such irradiation does not substantially contribute to heating of the brittle material 101. The maximum value may be determined in accordance with the wavelength of the light beam, the heat absorption spectrum and the heat conductivity of the brittle material 101, and the shape of the notch 109 to be formed. The maximum value of the intensity of the beam 201 may be determined so that an energy intensity that is 13.5% of the maximum value can heat the brittle material 101 to a degree that is sufficient for exfoliating a fraction of the brittle material 101.
The length Ls of the irradiation area 222 in the X direction may be the same as the length of the spot 202 in the X direction. However, the length Ls of the irradiation area 222 in the X direction can be controlled by scanning the control spot 202 in the X direction. When the spot 202 is not scanned, the area and the shape of the irradiation area 222 are the same as those of the spot 202. When the spot 202 is scanned, the area of the irradiation area 222 is larger than that of the spot 202. In other words, if the length of the spot 202 in the X direction is smaller than the length Ls of the irradiation area 222 in the X direction, the spot 202 is scanned in the X direction. By scanning the spot 202 in the X direction, even if the length Ls in the X direction is large, the spot 202 can be provided with a desired energy density without considerably increasing the output power of the laser. In one embodiment, t<Ls2/4α, where t [s] is the time interval between the time when the spot 202 that forms one of the edges of the irradiation area 222 that intersect the X direction is formed and the time when the spot 202 that forms the other of the edges is formed; α [m2/s]=λ/ρCp is the thermal diffusivity of the brittle material 101, where λ [W/(m·K)] is the heat conductivity of the brittle material 101, ρ [kg/m3] is the density of the brittle material 101, and Cp [J/(kg·K)] is the specific heat capacity of the brittle material 101; and Ls [m] is the length of the irradiation area 222 in the X direction. When the spot 202 is scanned in one of the X directions from one of the edges to the other of the edges, the scanning speed V [m/s] of the spot 202 satisfies V≦4α/Ls. The edges of the irradiation area 222 that intersect the X direction are the edges of the irradiation area 222 that are not the side edge 104 and generally correspond to a first end ridge 1061 and a second end ridge 1062 as described below. By scanning the spot 202 in this manner, the edge of the high-temperature portion 108 can be made clear, whereby a notch having a good shape can be formed. Regarding the shapes of the brittle material 101 and the irradiation area 222, if Ls>W and/or H>W is satisfied, the edge of the high-temperature portion 108 can be made clear, whereby a notch having a good shape can be formed.
The spot 202 can be scanned by moving the spot 202 relative to the predetermined face 102 of the brittle material 101. To be specific, the spot 202 is formed on the predetermined face 102 by irradiating a start point of the irradiation area 222 of the predetermined face 102 with the beam 201. Next, the spot 202 is scanned toward an end point of the irradiation area 222. The scanning may be performed by moving the light source, by scanning the beam 201 using an optical system, or by moving the brittle material 101. The beam 201 can be scanned, because, with this method, the precision of the spot width Ws, the uniformity of the incident angle of the beam 201, and the scanning speed can be achieved to a certain degree. To be specific, a light beam can be reflected by a galvano mirror or a polygon mirror, focused by a focusing lens, and the beam 201 can be scanned by driving the galvano mirror or the polygon mirror. By using a laser, which has a rapid ON/OFF response, as the light source of the beam 201, the irradiation area 222 can be clearly defined. In contrast, a general lamp has a slow ON/OFF response. Therefore, when a lamp is used as the light source, a shutter for switching between blocking and passing of the beam 201 can be disposed on the optical path. The beam 201 is a beam that determines the energy intensity and the energy distribution in the spot 202. If the beam passes through or is reflected by a plurality of optical elements, the beam 201 is the beam that has passed through one of the optical elements in the last stage. As necessary, the beam 201 may be scanned also in the Y direction. Even when the beam 201 is scanned in the Y direction, the beam width Wb is determined to be equal to or larger than the width W of the predetermined face 102, so that the spot width Ws becomes the same as the width W of the predetermined face 102 while the scanning in the Y direction is being performed.
The spot width Ws the spot 202, which is the length in the Y direction, is the same as the width W of the predetermined face 102. In other words, the spot 202 is formed so as to extend from the first side edge 1041 to the second side edge 1042 of the brittle material 101. That is, the spot 202 is formed also on the first side edge 1041 and on the second side edge 1042. The position of the spot 202 on the first side edge 1041 and the position of the spot 202 on the second side edge 1042 may not be on a straight line extending in the Y direction. The beam width Wb, which is the length of the beam 201 that forms the spot 202 in the Y direction, can be larger than the width W of the predetermined face 102, i.e., the spot width Ws of the spot 202. By making the width Wb of the beam 201 be larger than the width W of the predetermined face 102, the spot width Ws of the spot 202 can be made to be the same as the width W of the predetermined face 102. Therefore, the yield can be increased. This is effective when scanning the spot 202. In contrast, if the width Wb of the beam 201 is too large, the energy intensity per unit area (energy density) of the spot 202 decreases and thereby the efficiency decreases. Therefore, in practice, the beam width Wb of the beam 201 may be equal to or smaller than 120% of the width W of the predetermined face 102 and may be equal to or smaller than 110% of the width W. If the width W of the predetermined face 102 in the irradiation area 222 is not uniform in the X direction, the beam width Wb is determined so that the beam width Wb be equal to or larger than the maximum value of the width W or so that the spot width Ws of the spot 202 does not become smaller than the width W of the predetermined face 102 by dynamically changing the beam width Wb during scanning. The spot width Ws of the spot 202 can be measured by using a sensor (for example infrared radiation sensor) adapted to the wavelength of the beam 201.
The irradiation angle of the beam 201 may be arbitrarily determined. However, if the energy intensity distribution in the beam 201 when the laser is output and the energy intensity distribution in the spot 202 formed on the predetermined face 102 have a simple correspondence, the shape of the notch 109 can be easily controlled. In one embodiment, the irradiation angle of the beam 201 with respect to the predetermined face 102 be in the range from 75° to 105° and may be 90°.
The range of the high-temperature portion 108 is correlated with the shape of the notch 109. As described above, the increase in temperature is caused by the absorption of the beam 201 by the brittle material 101. However, the high-temperature portion 108 is formed not only by the absorption but also by the heat conduction in the brittle material 101. Therefore, the high-temperature portion 108 ranges not only over a region of the brittle material 101 through which the beam 201 passed but also to the vicinity of the region. Therefore, the range of the high-temperature portion 108 depends on the heat conductivity of the brittle material 101. The range of the high-temperature portion 108 in the X direction and the Y direction approximately corresponds to the irradiation area 222. However, the range in the Z direction is depends on the energy intensity of the beam 201. As will be described below in detail, the notch 109 having various shapes can be obtained by controlling the beam 201 in the method according to the present invention.
The temperature of the high-temperature portion 108 is higher than at least the temperature of the unirradiated area 212 of the brittle material 101. The temperature can be high so that the high-temperature portion 108 can be melted. That is, the temperature of the high-temperature portion 108 can be equal to or higher than the melting point of the brittle material 101. Although general brittle materials, such as glass, do not usually have a clear melting point, the temperature of the high-temperature portion 108 can be equal to or higher than the glass transition temperature.
The high-temperature portion 108, which has been irradiated with the beam 201, is cooled in the cooling step. As a result, the high-temperature portion 108 contracts and a residual stress is generated, whereby a crack is generated in the vicinity of the high-temperature portion 108. As the crack grows, a part of the brittle material 101 including the high-temperature portion 108 is exfoliated as the exfoliated piece 110. By making the width Ws of the spot be the same as the width W of the predetermined face 102 of the brittle material 101 in heating step, a boundary point is generated between the high-temperature portion 108 and the low-temperature portion on the side edge 104 of the brittle material 101. To be specific, four boundary points, including two boundary points that are in the vicinity of the boundaries between the irradiation area 222 and the unirradiated area 212 on the first side edge 1041 and two boundary points that are in the vicinity of the boundaries between the irradiation area 222 and the unirradiated area 212 on the second side edge 1042. Cracks originate at the boundary points, and the boundary points define the exfoliated surface 105. The origins of the cracks are usually located in the unirradiated area 212.
When the temperature slowly decreases, as in the case of natural cooling in room temperature atmosphere, the residual stress is relieved before the high-temperature portion 108 is cooled, so that generation of cracks may be impeded. Therefore, in the cooling step, the high-temperature portion 108 can be rapidly (forcedly) cooled so as to increase the probability of generation of cracks and increase the yield. Examples of the method of rapid cooling include air cooling in a low temperature atmosphere, wind cooling, water cooling, and liquid cooling. In particular, a coolant, such as dry ice or liquid nitrogen, can be used. In order to accelerate cooling, the entire brittle material 101 or the vicinity of the irradiation area 222 may be cooled before irradiating the brittle material 101 with the beam 201.
The brittle member 100, which is made by using the present embodiment, will be described. As illustrated in
The brittle member 100 includes a first unexfoliated side face 1131 and a second unexfoliated side face 1132. The first unexfoliated side face 1131 is one of the two surfaces (parallel to the XZ plane) of the brittle member 100 that extend in the X direction and in the Z direction. The second unexfoliated side face 1132 is the other of the two surfaces. The first unexfoliated side face 1131 and the second unexfoliated side face 1132 will be collectively referred to as an unexfoliated side face 113.
The unexfoliated side face 113 is a surface that is continuous with the exfoliated surface 105 through the side ridge 107 and corresponds to a part of the side face 103 of the brittle material 101. An unexfoliated predetermined face 112 is a surface that is continuous with the exfoliated surface 105 through the end ridge 106 and corresponds to a part of the predetermined face 102 of the brittle material 101. The unexfoliated predetermined face 112 includes at least the unirradiated area 212 in the heating step.
Thus, the notch 109 according to the present embodiment has a shape formed by removing a part of the side face 103 (a part of the first side face 1031 and a part of the second side face 1032) and a part of the predetermined face 102 from the brittle material 101. The unexfoliated side face 113 of the brittle member 100 has an opening. That is, the notch 109 in the present embodiment does not have a shape (so-called caved shape) that is formed by removing only a part of the predetermined face 102 of the brittle material 101 without removing the side face 103 of the brittle material 101. The notch 109 does not have a shape that is formed by removing only a part of the first side face 1031 of the brittle material 101 and a part of the predetermined face 102 without removing the second side face 1032 of the brittle material 101.
In the brittle member 100 made by using the present embodiment, the end ridge 106 and the side ridge 107 of the exfoliated surface 105 are clear. Moreover, the exfoliated surface 105, which defines the notch 109, is very smooth. Burrs and projections are not generated in a region surrounding the notch 109. With the exception of the exfoliated piece 110, dust or the like are not generated by a large amount. The internal stress of the brittle member 100 is not increased by forming the notch 109, so that the brittle member 100 is not easily broken by an external force. Therefore, as described below in detail, the brittle member 100 is suitable for use as a member (spacer) that is disposed between two members, such as the face plate and the rear plate of a flat panel display (FPD), in order to define the distance between the two members. The method of notching a brittle material according to the present invention can be used to make not only the spacer but also to process a substrate of the face plate and the rear plate, which is made of a glass or the like (for example, to process an end surface of such a member). Moreover, the method can be used to produce a member that is made of glass or ceramics and that is used for products other than a display device (for example, building materials and mechanical components).
Hereinafter, embodiments will be further described.
The brittle material 101 may be easily recurved during notching when, as illustrated in
Such recurving may cause defocus or displacement of the beam 201 and may considerably reduce the precision of the method. Moreover, the brittle member 100 may be recurved. Thus, the notching can be performed while suppressing the recurving of the brittle material 101 due to the expansion or the contraction of the brittle material 101.
To be specific, at least the heating step is performed while fixing at least two positions of the unirradiated area 212, the two positions being located on two sides of the irradiation area 222 of the predetermined face 102 of the brittle material 101 in the X direction. In other words, a portion of the predetermined face 102 of the brittle material 101 between the two fixed positions is irradiated with the beam 201. Devices that fix at least the two positions on the two sides of the irradiation area 222 of the brittle material 101 will be referred to as recurving limitation devices. The term “fix” means to immobilize, and it is not necessary that the two positions of the predetermined face 102 directly contact the recurving limitation devices.
The recurving limitation devices are not limited specific devices, as long as the recurving limitation devices can suppress the recurving of the brittle material 101. For example, a first fixing jig 301 fixes a position in the −X direction of the irradiation area 222, and a second fixing jig 302 fixes a position in the +X direction of the irradiation area 222.
For example, the brittle material 101 may be clamped from the side face 103 by pressing the brittle material 101 from the first side face 1031 and from the second side face 1032 of the brittle material 101 using the first fixing jig 301. Alternatively, the brittle material 101 may be clamped from the predetermined face 102 by pressing the brittle material 101 from the predetermined face 102 of the brittle material and from the opposite face of the brittle material 101 using the first fixing jig 301. The same method can be used for the second fixing jig 302. The first fixing jig 301 and the second fixing jig 302 are fixed to a rigid body. A tension may be applied in the X direction between the first fixing jig 301 and the second fixing jig 302.
The method of clamping the brittle material 101 from the side face 103 suppresses recurving by using friction between the first fixing jig 301 and the side face 103 and friction between the second fixing jig 302 and the side face 103. Therefore, if a fixing jig slips over the brittle material 101, the side face 103 of the brittle material 101 may be scratched. With consideration of the combination with a counter-warping mechanism described below, the method of clamping the predetermined face 102 can be used. In order to prevent the brittle material 101 from being scratched, a soft member can be disposed at contact portions 311 between the first fixing jig 301 and the brittle material 101 and between the second fixing jig 302 and the brittle material 101.
In order to reduce the pressure applied to the predetermined face of the brittle material 101, the lengths (in the X direction) of the contact portions 311 between the brittle material 101 and the first fixing jig 301 and between the brittle material 101 and the second fixing jig 302 can be as long as possible.
In order to suppress warping as much as possible, the distance between the jigs can be as small as possible provided that the beam 201 is not blocked. However, if the distance between the first fixing jig 301 and the second fixing jig 302 is small, when the brittle material 101 is irradiated with the beam 201 and heated, the temperatures of the first fixing jig 301 and the second fixing jig 302 may be increased. Therefore, the contact portions 311, which are disposed between the brittle material 101 and the first fixing jig 301 and between the brittle material 101 and the second fixing jig 302, can be heat resistant. For the reasons described above, the contact portions 311, which are between the brittle material 101 and the fixing jigs, can be heat resistant and soft. Examples of such materials include heat resistant plastics such as PPS resin and PEEK resin.
In order to increase probability of exfoliation and increase the yield during cooling or after cooling, another step of for increasing a residual stress can be performed in addition to the cooling step. To be specific, a bending stress is applied to the brittle material 101 so that the predetermined face 102 of the brittle material 101 is warped to have a convex shape in a counter-warping direction that is counter to the direction in which the brittle material 101 is warped due to contraction of the high-temperature portion 108 as illustrated in
Moreover, as illustrated in
In order to apply a bending stress by as small a force as possible, the bending stress can be applied after irradiating the brittle material 101 with the beam 201 and increasing the distance between the first fixing jig 301 and the second fixing jig 302. For example, as illustrated in
Referring to
Thus, by changing the energy intensity distribution in the spot 202, the shape of the notch 109 in the YZ direction can be controlled.
As illustrated in
Thus, by changing the shape of the spot 202, the shape of the notch 109 in the XY direction can be controlled.
As described above, the brittle member 100 having the notch 109 is suitable for use as a spacer of a flat panel display (FPD). In particular, the brittle member 100 is suitable for use as a spacer of a field emission display (FED) including electron-emitting devices and a fluorescent film and using electron beams.
Referring to
The face plate 1 includes a first insulating substrate 6 that is transparent, a fluorescent film 7 that is disposed on the first insulating substrate 6, and an anode electrode 8 that is disposed so as to cover the fluorescent film 7. The fluorescent film 7 is a light-emitting member that functions as a display material. An anode potential Va is supplied to the anode electrode 8 from a high-voltage terminal Hv.
The rear plate 2 includes a second insulating substrate 5, wiring 4 that is disposed on the second insulating substrate 5, and electron-emitting devices 9 connected to the wiring 4. The electron-emitting devices 9 are connected to the wiring 4, which is single-matrix wiring including X-direction wiring Dx1 to Dxm and Y-direction wiring Dy1 to Dyn. As the electron-emitting devices 9, various types of cold cathode devices including a surface conduction type, a Spindt-type, a CNT-type, and an MIM-type are used.
Electron beams emitted by the electron-emitting devices 9 are accelerated by the anode potential Va supplied to the anode electrode 8, and phosphors of the fluorescent film 7 emit light by being irradiated with the electron beams. The anode potential Va is in the range from +1 kV to +50 kV, and typically is +10 kV. The anode electrode 8 also functions as a metal back that increases the light utilization ratio by reflecting a part of light that is reflected from the fluorescent film 7.
As described above, the spacer 100 is made by exfoliating a fraction of the brittle material 101, and the spacer 100 has the notch 109. Japanese Patent Laid-Open No. 2000-311608 discloses a method that can be used to make the brittle material 101 for use as a spacer. That is, the brittle material 101 can be made by heating and drawing a base material to form the shape of the brittle material 101. When “a heating and drawing method” is used, a tensile stress generated in the brittle material 101 is lower than the tensile stress that is generated when a sheet material is cut, so that generation of unwanted cracks is suppressed and notching can be appropriately performed. The notch 109 can be formed at an appropriate position of the spacer 100 in accordance with the shapes of the face plate 1 and the rear plate 2. For example, the notch 109 can be formed at a position at which the spacer 100 straddles members of the display device, such as the electron-emitting devices 9 and the wiring 4. Alternatively, the members of the display device may contact the exfoliated surface 105 of the notch 109. There is almost no projections and burrs around the notch 109 of the spacer 100 made by using the method described above. Dust is not generated by a large amount during notching, with the exception of the exfoliated piece 110. Therefore, it is unlikely that foreign substances (so-called particles) are generated from chips, which are broken off the projections and burrs, and dust, which adheres to the spacer during notching. Therefore, the probability of abnormal discharge or shortage due to the foreign substances can be decreased.
Next, an example of application of the spacer 100 to the display device 10 will be described.
Thus, by disposing the spacer 100 so that the notch 109 faces the gap g, the space surrounding the gap g can be increased. By increasing the space, the magnitude of an electric field formed among the anode electrode 8, the low potential electrode 11, and the spacer 100 by the anode potential Va and the lower potential Vr can be decreased. Moreover, the creepage distance in the vicinity of the gap g can be increased. Therefore, discharge in the vicinity of the gap g can be suppressed.
If there is a portion having an angle smaller than 75° in the vicinity of the notch 109 of the spacer 100, the electric field may concentrate on the portion and may cause a discharge. Therefore, the angle θ between the exfoliated surface 105 and the unexfoliated predetermined face 112 and the angle φ between the exfoliated surface 105 and the unexfoliated side face 113 can be equal to or larger than 75°. That is, the notch 109 can be formed by using a method of irradiation with the beam 201 as described using the
The face plate 1 is in contact with the spacer 100. However, small gaps may be generated between the face plate 1 and the spacer 100. To be specific, small gaps between the face plate 1 and the spacer 100 may be generated between the anode electrode 8 and the unexfoliated predetermined face 112 of the spacer 100 and between the low potential electrode 11 and the unexfoliated predetermined face 112 of the spacer 100. An intense electric field may be generated in such small gaps and may cause a discharge. There are almost no projection on the unexfoliated predetermined face 112 in the vicinity of the notch 109 of the spacer 100 made by using the method according to the present invention. Moreover, there are almost no round portions in the unexfoliated predetermined face 112 in the vicinity of the notch 109. Therefore, the number of small gaps that may be generated between the face plate 1 and the spacer 100 can be reduced as far as possible, whereby discharge between the face plate 1 and the spacer 100 can be suppressed.
As illustrated in
Referring to
Referring to
A high-resistance film, which is well-known, may be disposed on the unexfoliated side face 113 of the spacer 100. The high-resistance film may be formed on the brittle material 101 before the notch 109 is formed, or may be formed on the brittle member 100 after the notch 109 has been formed.
A glass plate having a length L of 1000 mm, a width W of 0.2 mm, and a height H of 1.5 mm was prepared as the brittle material 101 illustrated in
As illustrated in
In order to prevent the brittle material 101 from being scratched at the contact portions 311 between the jig and the brittle material 101, a material made of PPS resin was used for the contact portions 311 of the first fixing jig 301 and the second fixing jig 302.
Next, the heating step was performed by irradiating the predetermined face 102 of the brittle material 101 with a laser beam. The length Ls of the irradiation area 222 was 4.0 mm, which was the distance between a position on the brittle material 101 that was distanced from an end in the longitudinal direction by 3.4 mm and a position on the brittle material 101 that was distanced from an end in the longitudinal direction by 7.4 mm. A CO2 laser was used as the light source. The light source emitted a laser beam having a wavelength λ of 10.6 μm, a diameter of 2.0 mm, an output power of 20 W, and a pulse duty of 80%. The beam diameter of the emitted laser beam was expanded to about 8 mm by using a beam expander having a magnification of 4 times, and the laser beam was guided through a galvano mirror and a focusing lens so that the beam diameter was decreased to 220 μm. At this time, the beam width Wb of the beam 201 was about 10% larger than the width (0.2 mm) of the predetermined face 102. The beam 201 had a circular shape as illustrated in
Next, the cooling step was performed to cool the brittle material 101. Natural cooling at room temperature was used. The high-temperature portion 108 contracted due to cooling, and a stress was generated at the boundary between the high-temperature portion 108 and the low-temperature portion. As a result, a crack was generated due to delayed fracture. The crack was generated at the boundary between the high-temperature portion 108 and the low-temperature portion on the side edge 104 of the brittle material 101. The crack grew along the boundary between the high-temperature portion 108 and the low-temperature portion. In the periphery of the irradiation area 222 scanned by the spot 202, the exfoliated piece 110 having a length (in the X direction) of about 4 mm, a width (in the Y direction) of 200 μm, and the maximum depth (the Z direction) of about 100 μm was generated. Accordingly, the notch 109 having the same shape as the exfoliated piece 110 was formed.
As illustrated in
In the cooling step of EXAMPLE 1, forced cooling was performed using liquid nitrogen. A nozzle of a liquid nitrogen supplying apparatus was directed to the predetermined face 102 and liquid nitrogen was dropped. The dropped amount was about 1 cc so that the liquid nitrogen did not flow down along the side face 103 of the brittle material 101. Because liquid nitrogen evaporated in a short time, irradiation with the beam 201 and scanning of the beam 201 were performed before the liquid nitrogen evaporated. The heating step was performed in the room temperature atmosphere, and scanning was started 0.1 to 0.2 seconds after the liquid nitrogen had been dropped and the scanning was finished in 0.1 seconds. In EXAMPLE 2, the probability of exfoliation was higher than that of EXAMPLE 1, and the yield improved.
After the laser irradiation in EXAMPLE 1, as illustrated in
In the cooling step of EXAMPLE 3, forced cooling was performed as in EXAMPLE 2. As a result, the probability of exfoliation was higher than that of EXAMPLE 3, and the yield improved.
In EXAMPLE 1, the brittle material 101 was fixed by using only the second fixing jig 302 and without using the first fixing jig 301, and the same process as that of EXAMPLE 1 was performed. As a result, the precision was lower than that of EXAMPLE 1.
Instead of the brittle material 101 used in EXAMPLE 5, the brittle material 101 having a height H of 10 mm was prepared and the same process was performed. As a result, the probability of exfoliation and the precision ware higher than those of EXAMPLE 5. This was presumably because the degree of warping decreased due to the increase in the height H of the brittle material 101.
In EXAMPLE 1, the width of the beam 201 was decreased to 120 μm so as to form a spot having a width of 120 μm in the Y direction at the center of the predetermined face 102, and the spot was scanned in the X direction. At this time, a spot was not formed on the side edges 104 of the predetermined face 102. In other respects, COMPARATIVE EXAMPLE 1 was the same as EXAMPLE 1.
Notching was performed on ten brittle materials 101, and only one of them was exfoliated. Moreover, the shape of the exfoliated surface 105 was considerably different from the shape of the irradiation area 222, which was unsymmetrical with respect to the Y direction.
In EXAMPLE 1, the width of the beam 201 was decreased to 120 μm so as to form a spot having a width of 110 μm on the predetermined face 102 in the Y direction from one of the side edges 104, and the spot was scanned in the X direction. Next, the brittle material 101 was moved in the Y direction by 110 μm, a spot was formed on the predetermined face 102 so as to have a width from the other of the side edges 104 in the Y direction by a width of 110 μm, and the spot was scanned in the same X direction. In other respects, COMPARATIVE EXAMPLE 2 was the same as EXAMPLE 1.
Notching was performed on ten brittle materials 101, and only two of them were exfoliated. Moreover, the shapes of the exfoliated surfaces 105 of the two brittle materials 101 were different from each other.
In the heating step of EXAMPLE 4, a mask having a rectangular opening was disposed between the beam expander and the galvano mirror so as to make the shape of the spot 202 formed on the predetermined face 102 is substantially rectangular as illustrated in
In the heating step of EXAMPLE 4, a mask having an hourglass-shaped opening was disposed between the beam expander and the galvano mirror so as to form the spot 202 having an hourglass shape as illustrated
In the heating step of EXAMPLE 7, the energy intensity distribution of the spot 202 on the predetermined face 102 was made to be flat as illustrated in
In the heating step of EXAMPLE 7, as illustrated in
The brittle member made in one of EXAMPLES 4 and 7 to 10 was used as a spacer, and the display device 10 illustrated in
First, the face plate 1 illustrated in
A power supply capable of applying a voltage of 5 kV or higher was connected to the high-voltage terminal Hv of the display device 10. The low potential electrode 11, the X-direction wiring, and the Y-direction wiring were grounded. The power supply was switched ON so that 10 kV was applied to the high-voltage terminal Hv, and the display device 10 was observed for twelve hours. In any of the display devices in which the brittle members made in EXAMPLES 4 and 8 to 11 were used as the spacers 100, discharge was not observed.
The applied voltage was increased from 15 kV by 1 kV per hour. In the display device using the spacer 100 made in EXAMPLE 4, discharge did not occur below 17 kV. In the display device using the spacer 100 made in EXAMPLES 7 and 9, discharge did not occur below 19 kV. In the display device using the spacer 100 made in EXAMPLES 8 and 9, discharge did not occur below 20 kV.
Spacers were made by grinding the brittle material 101 prepared in EXAMPLE 1 using a diamond grindstone so as to form a notch having a length (in the X direction) of about 4 mm, a width (in the Y direction) of about 200 μm, and the maximum depth (in the Z direction) of about 100 μm. By using the spacers, the display device 10 was made in the same manner as in EXAMPLE 11. The display device 10 was less resistant to discharge than the display device using the spacers 100 made in EXAMPLE 4.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Applications No. 2009-236433, filed Oct. 13, 2009 and No. 2010-206729 filed Sep. 15, 2010, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-236433 | Oct 2009 | JP | national |
| 2010-206729 | Sep 2010 | JP | national |
