JP2006008486A - Setter for heat treatment, method of manufacturing the same and method of heat-treating glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a setter for heat treatment which has long term shape stability even when a local load is applied under a high temperature, is strong to thermal shock due to rapid heating and cooling in the inside and outside of a heat-treatment furnace and is easily large-sized. <P>SOLUTION: The setter for heat treatment is for placing a material to be heat-treated and comprises a Li<SB>2</SB>O-Al<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>based crystalline glass plate containing 81-95 mass% β-quartz solid solution as a crystal phase. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat treatment setter having a rectangular flat plate shape that is fed into a heating furnace in a state where a material (material to be heat treated) such as a glass substrate is placed.

  In recent years, with the diversification of display devices, a large-screen flat display attracts attention. A glass substrate used for manufacturing a typical plasma display panel (hereinafter referred to as PDP) is typically formed from a thin flat soda-lime glass plate having a thickness of about 2.8 mm. A paste is applied to the surface of the glass substrate in order to form a circuit pattern such as an electrode or an insulating layer, and the applied paste is fixed to the glass substrate at about 500 to 700 ° C. in a heating furnace. Heat treatment is performed in the temperature range.

  The above heat treatment is generally performed in a roller hearth kiln from the viewpoint of production efficiency and energy saving. The roller hearth kiln furnace includes transport means (roller conveyor) configured by arranging a plurality of rollers side by side in the transport direction of the glass substrate. At this time, if the glass substrate is conveyed on a roller conveyor, the glass substrate may be warped or distorted, or the surface may be damaged. Therefore, as shown in FIG. 1, the glass substrate 10 is placed on a rectangular flat plate-like setter 11, and the glass substrate 10 is moved so that the setter 11 moves on a large number of rollers 12 installed in the furnace. I am trying to carry it.

  The setter used for this heat treatment is used repeatedly many times, and since the thermal cycle of temperature raising, firing and cooling is repeated in a short time, it is required to have excellent thermal shock resistance.

  In particular, the glass substrate for PDP has a characteristic that it is relatively soft and easily deformed. Therefore, when the setter is deformed during the heat treatment, the glass substrate is also deformed along the deformation, and the flatness is lowered. When the flatness of the glass substrate is lowered, the arrangement of circuit patterns such as electrodes and insulating layers is shifted, and display performance is lowered. For this reason, the setter is required to have a flat and smooth mounting surface on which the glass substrate is placed, and to have as little dimensional change during firing as possible, that is, excellent shape stability. Furthermore, the PDP tends to increase in size, and the glass substrate used for the PDP is also increased in size, so that the setter must also be increased in size.

  Conventionally, as a setter for heat treatment, a setter made of SiC ceramic has been proposed. (For example, Patent Document 1) However, SiC ceramics have the disadvantages of high thermal expansion coefficient and low thermal shock resistance when used as a setter. Moreover, since the temperature range for sintering a ceramic is narrow at the time of manufacture, temperature control is very difficult. If the plate is further increased, cracks are likely to occur during drying and firing, which is not suitable for industrial production.

The sintered SiC ceramic has a relatively large arithmetic average roughness Ra on the surface. When such a material is used as a setter for heat treatment of a glass substrate such as a PDP, the glass substrate surface is likely to be scratched due to friction between the contact surfaces of the glass and ceramic due to the difference in hardness between glass and ceramic. The occurrence of this scratch becomes more prominent as the glass substrate becomes larger. Therefore, it has been conventionally proposed to polish and flatten the surface of the SiC ceramic. (For example, Patent Document 2)
However, SiC ceramics are high in hardness and inferior in workability, so that machining requires a long time. Furthermore, since the consumption of tools for processing SiC ceramics is severe, it is not preferable in terms of productivity and manufacturing cost.

Under such circumstances, it has been proposed to use a low-expansion crystallized glass as a setter for a large glass substrate. (For example, Patent Document 3)
JP 2002-137929 A JP 2002-274946 A JP 2002-160931 A

  Low-expansion crystallized glass has a thermal expansion coefficient close to zero, and therefore has excellent thermal shock resistance and is unlikely to undergo thermal deformation. In addition, it is easy to increase the size as compared with SiC ceramics. Furthermore, it is excellent in workability, and the surface can be made smooth relatively easily.

  By the way, in order to improve the heat treatment efficiency of the glass substrate, it is desirable to put as many glass substrates as possible into the heat treatment furnace at a time. Therefore, a method is known in which a plurality of setters are stacked in a shelf shape via spacers, a glass substrate is placed on each setter, and the state is put into a heat treatment furnace in this state. For example, as shown in FIG. 2, two setters 13 and 14 are prepared, rod-like (for example, columnar) spacers 15 are set up near the upper four corners of one setter 13, and the other setter 14 is placed on each spacer 15. A method is known in which two setters 13 and 14 are stacked and stacked, and then glass substrates 16 and 17 are placed on the center of the upper surface of each setter 13 and 14.

  According to this method, a fixed gap is formed between the upper and lower setters 13 and 14, and this gap allows free circulation of the atmosphere in the heat treatment furnace. As a result, the glass substrates 16 and 17 can be uniformly heat-treated.

  However, since the upper setter 14 is only point-supported at the four corners by the spacers 15, as shown in FIG. 3A, the weight of the upper setter 14 and the glass substrate placed thereon are provided. With the load of 17, it is easy to warp so that the center part of the upper setter 14 may hang down, and it is difficult to maintain flatness. Depending on the type of roller conveyor, the lower setter 13 may warp. That is, in the case of a heating furnace provided with a balled roller 18 as shown in FIG. 3B, the roller 18 and the lower setter 13 are in contact with each other slightly closer to the center, and both ends of the lower setter 13 Since the load of the upper setter 14 and the glass substrate 17 placed thereon is applied, the center portion of the lower setter 13 may warp so as to protrude upward.

  Thus, once the setter warps, it will never be restored to a flat shape. When a glass substrate such as that used for PDP is placed on the setter where the warpage has occurred and heat treatment is performed, the glass substrate softens and changes shape along the surface shape of the setter. Will occur. In particular, a setter used for heat-treating a large glass substrate is a large plate and has a large area, so that the warp of the central portion becomes large, and the warp of the glass substrate becomes more remarkable.

  The object of the present invention is that it has long-term shape stability even when a local load is applied at high temperatures, is resistant to thermal shock caused by rapid and rapid cooling inside and outside the heat treatment furnace, and can be easily made larger. Is to provide a setter for heat treatment.

The heat-treating setter of the present invention made to solve the above technical problem is a heat-treating setter for placing a material to be heat-treated, and contains 81 to 95% by mass of β-quartz solid solution as a crystal phase. characterized by comprising the _{li 2 O-Al 2 O 3} -SiO 2 based crystallized glass plate.

The manufacturing method of the heat treatment for the setter of the present invention, after preparing the _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass plate was subjected to heat treatment in a temperature range of 700 to 900 ° C., further 800 to 1100 ° C. By heat-treating in a temperature range, 81 to 95% by mass of β-quartz solid solution is precipitated inside.

The glass substrate heat treatment method of the present invention is a heat treatment method for a glass substrate in which a plurality of heat treatment setters are stacked in a shelf shape via a spacer, and the glass substrate is placed on each heat treatment setter. The setter for heat treatment is characterized by comprising a Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate containing 81 to 95% by mass of β-quartz solid solution as a crystal phase.

The setter for heat treatment of the present invention is a Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate (Li ₂ O, Al ₂ O ₃ and SiO ₂₎ containing 81 to 95% by mass of β-quartz solid solution as a crystal phase. Crystallized glass plate containing ₂ as an essential component), it has long-term shape stability even when a local load is applied at high temperatures, and rapid heating inside and outside the heat treatment furnace Resistant to thermal shock due to rapid cooling and easy to enlarge. Therefore, it is suitable as a setter for heat treatment of a large glass substrate for PDP.

The setter for heat treatment of the present invention is formed from a Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass plate. Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass is a material that exhibits the thermal expansion behavior of this crystal when β-quartz solid solution having a negative expansion coefficient is precipitated by heat treatment under predetermined conditions. It can be reflected in the whole. Therefore, the thermal expansion coefficient of crystallized glass can be brought close to substantially zero, and the material has excellent thermal shock resistance and shape stability.

  The reason why the crystallized glass is deformed when subjected to a local load at a high temperature is that the glass phase inside the crystallized glass is softened and deformed. Therefore, in order to suppress the deformation of the crystallized glass, it is necessary to increase the content ratio of the β-quartz solid solution, that is, the amount of crystals. That is, the β-quartz solid solution has a function of becoming a physical obstacle and suppressing the progress of deformation when the glass phase is softened and deformed by heat treatment, so that the larger the content thereof, the greater the effect of preventing deformation of the glass substrate.

According to the knowledge of the present inventors, the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate that has been conventionally used in heat setters has a crystal content of β-quartz solid solution of 50 to 75% by mass. If this is 81% or more, the proportion of the glass phase contributing to the deformation of the crystallized glass decreases, and the β-quartz solid solution becomes a physical obstacle to the deformation of the crystallized glass. The deformation of the vitrified glass can be suppressed. However, when the amount of crystal of the β-quartz solid solution exceeds 95% by mass, the thermal expansion coefficient of the crystallized glass becomes too large on the negative side, for example, as large as about 80 × 10 ⁻⁷ / ° C. like a glass substrate for PDP. When a glass substrate made of a material having a thermal expansion coefficient is heat-treated, friction occurs during the heat treatment due to the difference in thermal expansion between the setter and the glass substrate, and the glass substrate is likely to be deformed or scratched. A preferable range of the crystal amount of the β-quartz solid solution is 85 to 95% by mass, and a more preferable range is 85 to 90% by mass. In the present invention, crystals other than the β-quartz solid solution may be precipitated as long as the above effects are not impaired.

The Li ₂ O—Al ₂ O ₃ —SiO ₂ crystallized glass used in the present invention has an average linear thermal expansion coefficient at 30 to 750 ° C. in the range of −10 to + 10 × 10 ⁻⁷ / ° C. The thermal shock resistance of the crystallized glass is improved, and even if a temperature difference occurs inside the crystallized glass during heat treatment, it becomes difficult to break due to the difference in thermal expansion. In particular, if the average linear thermal expansion coefficient at 30 to 750 ° C. is in the range of −10 to + 5 × 10 ⁻⁷ / ° C., very excellent thermal shock resistance can be obtained.

The Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate preferably has an average transmittance of 30% or more at a wavelength of 400 to 800 nm at a thickness of 4 mm. If this average transmittance is 30% or more, the glass substrate can be confirmed through a setter. Therefore, when the setters are stacked in a shelf shape and heat-treated, the lower glass substrate can be visually recognized through the upper setter, thereby improving work safety. Further, when the glass substrate is placed on the setter, the upper glass substrate can be aligned while checking the position of the lower glass substrate, so that the work efficiency is also improved.

The Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate preferably has an average transmittance of 70% or more at a wavelength of 1 to 2 μm at a thickness of 4 mm. If this average transmittance is 70% or more (more preferably 75% or more), there are many heat rays that pass through the setter, and the glass substrate can be efficiently and uniformly heated.

  In the heat-treating setter of the present invention, the surface roughness (Ra) of the surface on which the heat-treated material is placed is preferably 1.0 μm or less. The reason is that when the surface roughness is larger than 1.0 μm, the surface of the heat-treated material is easily scratched by the friction generated between the setter and the heat-treated material. In particular, when the material to be heat-treated is a large plate such as a glass substrate for PDP, the contact area between the setter and the glass substrate is increased, and scratches are more likely to occur. A more preferable range of the surface roughness is 0.7 μm or less, and a more preferable range is 0.5 μm or less.

In addition, the setter for heat treatment of the present invention exhibits the effect of shape stability (warping prevention) remarkably when the surface area (one surface) on which the material to be heat treated is 14000 cm ² or more. Further, such a heat treatment setter having a large surface area is suitable for mounting a glass substrate for PDP. A preferable range of the surface area is 20000 cm ² or more, and a more preferable range is 22000 cm ² or more. In the heat treatment setter of the present invention, only one surface may be used as the mounting surface, or both surfaces (front surface and back surface) may be used as the mounting surface. The thickness of the setter for heat treatment is suitably about 2 to 10 mm. However, considering the strength, it is preferable to increase the thickness as the surface area increases. Specifically, when the surface area is 14000 cm ² or more, a thickness of 4 mm or more (preferably 5 mm or more) is suitable.

The _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass plate in the present invention, by mass _{percentage, SiO 2 55~70%, Al 2} O 3 15~30%, Li 2 O 2.5~6 %, 0~4% ZnO, BaO 0~5 %, TiO 2 1~6%, ZrO 2 0~4%, P 2 O 5 0~5%, 0~3% MgO, Na 2 O 0~4% It is preferable to contain a composition of 0 to 4% of K ₂ O.

The reason why the composition range of the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass plate is limited as described above is as follows.

SiO ₂ is a glass network former and a component constituting a β-quartz solid solution crystal. If its content is less than 55%, the glass tends to be devitrified, and the chemical durability is also improved. descend. On the other hand, when it exceeds 70%, the solubility of the glass is lowered. The preferable content of SiO ₂ is 60 to 70%.

Al ₂ O _{3 is} also a component constituting the crystal, but if it is less than 15%, the solubility of the glass is lowered. On the other hand, if it exceeds 30%, the glass tends to devitrify and the chemical durability is lowered. The preferable content of Al ₂ O ₃ is 15 to 25%.

Li ₂ O is also a component constituting the crystal, but if it is less than 2.5%, it becomes difficult to deposit a desired crystal. On the other hand, if it exceeds 6%, the chemical durability of the glass is lowered. The preferable content of Li ₂ O is 3 to 5%.

  ZnO is a component that facilitates the precipitation of crystals, but if it exceeds 4%, the glass tends to be devitrified, so that it becomes difficult to control the heat treatment during slow cooling or crystallization of the glass. The preferable content of ZnO is 0 to 3%.

  BaO is a component for improving the solubility of the glass and preventing the generation of devitrified substances. However, if it exceeds 5%, it is difficult to obtain the desired amount of crystals and the thermal expansion coefficient becomes high. , The thermal properties are reduced. The preferable content of BaO is 0 to 4%.

TiO ₂ is a component that acts as a nucleating agent. If the content is less than 1%, crystallization does not occur stably and the crystal becomes coarse, resulting in a decrease in chemical durability. On the other hand, if it exceeds 6%, the color tone becomes brown and the transparency is impaired. The preferable content of TiO ₂ is 1 to 5%.

ZrO _{2 is} also a component that acts as a nucleating agent, but it is difficult to dissolve it, so it is not preferable to contain a large amount. In particular, when it exceeds 4%, devitrified substances are likely to be generated in the glass. The preferable content of ZrO ₂ is 0 to 3%.

P ₂ O ₅ is a component that remarkably improves the poor solubility of ZrO ₂ , but if it exceeds 5%, the glass tends to phase-separate and it becomes difficult to obtain a uniform glass. The preferable content of P ₂ O ₅ is 0 to 3%.

  MgO is a component that facilitates precipitation of crystals, but if it exceeds 3%, the thermal expansion coefficient becomes too large. A preferable content of MgO is 0 to 2%.

Na ₂ O and K ₂ O are components that improve the meltability of the glass, but if they are more than 4% each, the chemical durability is remarkably lowered. Further, if the total amount of these components is more than 7%, the crystallinity is deteriorated and the thermal expansion coefficient becomes too high, which is not preferable.

In addition, in the present invention, in addition to the above components, components such as As ₂ O ₃ , Sb ₂ O ₃ , CaO, PbO and the like can be incorporated up to 2%, respectively, so that the solubility, workability, uniformity, etc. of the glass can be improved. Can be improved. However, As ₂ O ₃ is an environmentally hazardous substance and should be avoided as much as possible. Furthermore, in order to improve the stability of the glass, one or two or more selected from the group of F ₂ , Cl ₂ , SO ₃ and Fe ₂ O ₃ can be contained up to a total amount of 0.5%. .

The heat-treating setter of the present invention is prepared by preparing a Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass plate, then heat-treating (primary heat-treatment) in a temperature range of 700 to 900 ° C., and further 800 to 1100 ° C. It can be manufactured by heat treatment (secondary heat treatment) in a temperature range.

In order to produce a Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass plate, a glass raw material is prepared so as to be a glass having a desired composition, and then charged into a melting furnace at 1500 to 1650 ° C. , For 10 to 20 hours, and then formed into a sheet glass having a desired size by a roll-out method, a press method, or the like, and slowly cooled. Moreover, it is preferable to set the time for primary heat treatment to 30 to 180 minutes and the time for secondary heat treatment to 10 to 180 minutes. Further, if necessary, the surface (mounting surface) may be polished to make it smooth, or chamfering or chamfering may be performed to prevent end faces and corners from being chipped or cracked.

  In addition, when heat-treating a glass substrate using the heat-treating setter of the present invention, stacking in a shelf shape via a spacer and heat-treating the glass substrate placed on each heat-treating setter improves production efficiency. preferable.

  In this case, it is preferable to form a recess at a predetermined position of the heat treatment setter and fit a spacer into the recess or to fix the spacer to the predetermined position of the heat treatment setter because the setter is prevented from collapsing or being displaced. Any spacer can be used as long as it can hold the setter for heat treatment at regular intervals. The shape is suitable to be cylindrical, prismatic, plate, spherical, etc., and the material is ceramic. Crystallized glass, metal, nitride and the like are suitable.

  Hereinafter, the present invention will be described based on examples.

First, by mass percentage, SiO ₂ 65.9%, Al ₂ O ₃ 22.0%, MgO 0.1%, Li ₂ O 4.0%, Na ₂ O 0.5%, K ₂ O 0.5% , P ₂ O ₅ 1.5%, ZrO ₂ 2.5%, BaO 0.5%, TiO ₂ 2.0%, As ₂ O ₃ 0.5% After melting at 1580 ° C. for 16 hours using a platinum crucible, the glass plate was cast on a carbon table and formed into a 4 mm thick plate glass by roller molding.

  Next, the plate-like glass was heated to 780 ° C. (primary heat treatment temperature) at a rate of 300 ° C./hour, held at that temperature for 120 minutes to perform nucleation, and further at a rate of 80 ° C./hour, The temperature was raised to the temperatures shown in the following Table 1 (secondary heat treatment temperature), and crystals were precipitated by holding at each temperature for 60 minutes.

  The crystallized glass thus obtained was examined for crystal phase and crystal amount, average transmittance at wavelengths of 400 to 800 nm and wavelengths of 1 to 2 μm, thermal expansion coefficient, surface roughness (Ra), and deformation amount, and the results are also shown. It was shown in 1. In the table, β-Q means β-quartz solid solution.

As is clear from Table 1, in Examples 1 to 3, a β-quartz solid solution was precipitated as a crystal phase, and the amount of crystals was 83% by mass or more. The average transmittance at 400 to 800 nm is 40 to 70%, the average transmittance at 1 to 2 μm is 85%, the thermal expansion coefficient is −4 to −5 × 10 ⁻⁷ / ° C., and the surface roughness (Ra) is 0. 2. Furthermore, the amount of deformation was 20 × 10 ⁻⁴ % or less.

On the other hand, in Comparative Example 1, although β-quartz solid solution was precipitated, the deformation amount was 45 × 10 ⁻⁴ %, which was significantly deformed as compared with the Example.

  The crystal phase in the table was confirmed by a powder X-ray diffraction method (RINT2100 manufactured by Rigaku Corporation), and the amount of crystals was calculated from the diffraction pattern obtained by the powder X-ray diffraction method using the peak area method. did.

  The average transmittance was measured using a spectrophotometer (Shimadzu UV 2500PC) after processing the sample glass into a predetermined dimension and polishing both surfaces so that the thickness was 4 mm.

  The coefficient of thermal expansion measured the average linear thermal expansion coefficient in the temperature of 30-750 degreeC using the differential detection type relative dilatometer.

  The surface roughness (Ra) was measured using a stylus type surface roughness meter (JP7200F manufactured by JUKI Corporation).

  The amount of deformation was determined by the following method. First, a specimen having a width of 5 mm, a length of 75 mm, and a thickness of 2.5 mm was cut out from each sample glass. Next, as shown in FIG. 4, the test body 22 was placed on the two support bars 20, 21 arranged in parallel on the surface plate 19 with a spacing of 60 mm. Next, a 500 g weight 23 was suspended at the center of the test body 22 and heated at 750 ° C. for 24 hours with a vertical load applied. The amount of deformation was calculated by measuring the amount of central deformation of the specimen 22 after heating and substituting that value into the following equation.

Deformation amount = (center deformation amount / (length of specimen) ² × 100)
Further, two crystallized glass plates (setters for heat treatment) having a length of 1700 mm, a width of 1300 mm, and a thickness of 5 mm were produced under the same conditions as in Example 3. As shown in FIG. 2, spacers were formed near the upper four corners of one setter. The other setter was stacked in a shelf shape, and a 42-inch PDP glass substrate (PP-8 manufactured by Nippon Electric Glass Co., Ltd.) was placed on each setter and heat-treated at 600 ° C. for 1000 hours. However, no change in shape was observed in the setter or the glass substrate.

  The setter for heat treatment of the present invention is suitable as a setter for heat-treating a glass substrate used in various flat displays, and is particularly suitable as a setter for a glass substrate for a large area PDP.

It is a perspective view which shows the use condition of the setter for heat processing. It is a perspective view which shows the state which mounted the glass substrate on the setter for two heat processing. It is explanatory drawing which shows the state which the curvature produced in the setter for heat processing. It is explanatory drawing which shows the measuring method of the deformation amount of a test body (crystallized glass plate).

Explanation of symbols

10, 16, 17 Glass substrate 11, 13, 14 Heat treatment setter 12 Roller 15 Spacer 18 Ball roller 19 Surface plate 20, 21 Support rod 22 Specimen 23 Weight

Claims (16)

A heat-treating setter for placing a material to be heat-treated, comprising a Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass plate containing 81 to 95% by mass of β-quartz solid solution as a crystal phase. A setter for heat treatment characterized by The Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass plate is characterized in that an average linear thermal expansion coefficient in a temperature range of 30 to 750 ° C. is −10 to + 10 × 10 ⁻⁷ / ° C. The setter for heat treatment according to claim 1. The Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate has an average transmittance of 4% in thickness of 30% or more at a wavelength of 400 to 800 nm. Setter for heat treatment. The Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass plate has an average transmittance at a thickness of 4 mm of 70% or more at a wavelength of 1 to 2 μm. A setter for heat treatment according to claim 1. _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass plate, in _{mass%, Li 2 O 2.5~6%,} Al 2 O 3 15~30%, SiO 2 55~70%, ZnO 0 ~4%, BaO 0~5%, TiO 2 1~6%, ZrO 2 0~4%, P 2 O 5 0~5%, 0~3% MgO, Na 2 O 0~4%, K 2 O The setter for heat treatment according to any one of claims 1 to 4, comprising a composition of 0 to 4.   The setter for heat treatment according to claim 1, wherein the material to be heat treated is a glass substrate for flat display.   The setter for heat treatment according to claim 6, wherein the glass substrate for flat display is a glass substrate for PDP. The setter for heat treatment according to claim 1, wherein the surface area of the surface on which the heat-treated material is placed is 14000 cm ² or more.   The setter for heat treatment according to claim 1, wherein the surface roughness Ra of the surface on which the material to be heat treated is placed is 1.0 μm or less. After preparing a Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass plate, heat treatment is performed in a temperature range of 700 to 900 ° C., and further heat treatment is performed in a temperature range of 800 to 1100 ° C. A method for producing a setter for heat treatment, wherein 81 to 95% by mass or more of quartz solid solution is precipitated. The Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass plate is, by mass, Li ₂ O 2.5-6%, Al ₂ O ₃ 15-30%, SiO ₂ 55-70%, ZnO 0. ~4%, BaO 0~5%, TiO 2 1~6%, ZrO 2 0~4%, P 2 O 5 0~5%, 0~3% MgO, Na 2 O 0~4%, K 2 O The manufacturing method of the setter for heat processing of Claim 10 containing the composition of 0-4. A heat treatment method for a glass substrate in which a plurality of heat treatment setters are stacked in a shelf shape via a spacer, and the glass substrate is placed on each heat treatment setter, wherein the heat treatment setter is a crystal A glass substrate heat treatment method comprising a Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass plate containing 81 to 95% by mass of β-quartz solid solution as a phase.   The method for heat-treating a glass substrate according to claim 12, wherein the glass substrate is a glass substrate for flat display.   14. The glass substrate heat treatment method according to claim 13, wherein the glass substrate for flat display is a glass substrate for PDP. The glass substrate heat treatment method according to any one of claims 12 to 14, wherein the setter for heat treatment has a surface area of a surface on which the glass substrate is placed of 14000 cm ² or more.   16. The heat treatment method for a glass substrate according to claim 12, wherein the setter for heat treatment has a surface roughness (Ra) of a surface on which the glass substrate is placed, of 1.0 [mu] m or less.