JPH0710569A - Float plate glass manufacturing method - Google Patents

Abstract

(57) [Summary] [Structure] A method for producing a float glass of 0.1 to 1.5 mm. Thickness of the central portion 81 of the glass ribbon 1 (unit:
mm) as D, the thickness of the ears 80 located outside the trace of the top roll 30 is D or more and 3 or less, and the percentage (unit:%) of the width of the ears to the total width of the glass ribbon is 1.0.
When ≦ D ≦ 1.5, it is set to 3 or more, and when 0.1 ≦ D <1.0, it is set to (5-2D) or more. [Effect] Glass with extremely little warpage and microcorrugation is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing float glass sheets.

[0002]

2. Description of the Related Art In order to produce a float sheet glass having a thickness less than the equilibrium thickness, for example, as disclosed in Japanese Patent Publication No. 44-23828, both ears of a glass ribbon are usually made of a heat-resistant alloy called a top roll. A method of pressing the rotating roll with grooves and teeth, applying tension to the glass ribbon in the direction orthogonal to the traveling direction, and stretching the glass ribbon in the traveling direction while suppressing contraction of the glass ribbon It is taken.

In "Encyclopedia of Glass" (Sakuo Sakuo, Asakura Shoten, p. 281), in the production of a thin plate having a thickness of 2 to 3 mm by the float method, when it is stretched as it is, the plate width and the plate width are significantly reduced. Therefore, once create a balanced plate thickness part, at a high temperature of about 850 to 950 ° C, press both ends of the plate from above with 1 to several top rolls and pull in the width direction to convey while preventing the plate width from shrinking. It is described that a roll is drawn horizontally to make a plate.

According to this method, if the plate thickness is in the range of 2 to 3 mm, it is possible to manufacture a plate glass without much technical restriction, or even if the glass is thinner than this, For example, in the case where the optical glass is not required to have a high degree of flatness, such as a windowpane for construction, the float method can be used for the production, although the difficulty is slightly increased. In the past, products with a partial plate thickness range of 0.55 mm or more have been supplied to the market.

By the way, if a method of stretching the glass ribbon floating on the tin surface in the widthwise direction with a top roll and stretching it also in the traveling direction is theoretically thinner than the equilibrium thickness, any desired It should be possible to obtain thick glass sheets.

However, as the ribbon becomes thinner, a strong warp occurs in the cooled ribbon after leaving the annealing furnace, and the surface of the product plate changes from a flat surface to a curved surface of various shapes, resulting in the required quality of the product. In addition, the ribbon is often broken near the exit of the molten metal bath, in the annealing furnace or in the process of cutting a product-sized plate from the ribbon. This tends to cause a temporary interruption of the process, but if the amount of drawing material suddenly changes unexpectedly in the glass manufacturing process, secondary melting defects in the melting process are more likely to occur, and after the ribbon drawing is resumed. Also, bubbles, gravel, striae, etc. are likely to appear in the plate, which may significantly reduce productivity. Further, in reality, as the thickness of the product plate becomes thinner, fine distortion becomes stronger.

The fine irregularities on the surface of the plate glass are fine in the width direction of the plate when the thickness of the plate is subtly different at the portion where the plate glass is present, even though the plate thickness is substantially constant. It is roughly divided into the case where it is wavy at a different pitch. In reality, a composite of the two is observed, but the results of studies conducted by the present inventors have revealed that the thinner the plate, the more predominant the fine streaks due to the latter mechanism.

The former is called "distortion" mainly due to local nonuniformity of the composition of the molten glass. It is easy to understand that the distortion is not so noticeable in a plate close to the equilibrium thickness, but the difference in the viscosity characteristics due to the heterogeneous composition of the molten glass becomes larger as the plate is thinly stretched from the equilibrium thickness. A basic measure against distortion is to improve the homogeneity of the molten glass, and various known measures such as mechanically stirring the molten glass in the melting process are taken for this. However, as the plate thickness becomes thinner, further homogenization measures are required.

It is considered that the latter is mainly generated in the process of thinly stretching the glass in a planar manner in the plate width direction and the traveling direction from the high temperature glass ribbon having the equilibrium thickness.

On a straight line pulled by a pair of top rolls facing each other in the width direction of the ribbon, an attempt is made by an external force to thin the line, and on a straight line connecting the intermediate portions of adjacent top rolls in the ribbon width direction, The force to return to the equilibrium thickness,
In order to compensate for the fact that both sides are pulled in the width direction and become thin, a force is supplied to the substrate to try to make it thin, and in the traveling direction, the transport roll of the annealing furnace pulls the ribbon. The force to stretch it acts. When these are combined, the viscous material floating on the molten tin is
At least planarly, complicated and uneven stresses are generated.

There has been a proposal to apply a pulling force in a continuous line along the end of the ribbon instead of the top roll, which makes contact only at discrete points near the end of the ribbon. Kosho 49-5206) did not reach final success. As a result, wrinkles can be generated even if the substrate has good homogeneity.

The wrinkles of glass generated by this mechanism are referred to as corrugation in this specification. When the thickness of the plate is 1.5 mm or less, the corrugation pitch is about 25 mm, and the ridges and valleys are as fine as about 0.1 to 0.3 μm. Therefore, in the present specification, this is referred to as microcorrugation. I will call it.

The plate thickness is 1.5 to 3.0 m by the float method.
A technique for reducing the distortion in the range of m can be found in Japanese Patent Publication No. 58-37257. Microcorrugation is hardly a problem in this thickness region, so there is no description corresponding to the publication cited herein, but a molten metal bath used for thinning the ribbon by using 6 pairs (examples) of top rolls. A technique for obtaining a glass sheet by preventing the turbulent flow of the tin flow in the molten metal bath by keeping the tin depth near the outlet of the molten iron larger than the tin depth upstream thereof is disclosed.

Especially, the thickness of the plate of the product is 1.5 m
If thinner than m, producing optically flat plates becomes significantly more difficult, especially due to the formation of microcorrugations. Even if the desired thickness of the plate is obtained, the ones that pass the quality requirements for electronic applications such as liquid crystal substrates, solar cell substrates, and photomask blanks have not been conventionally obtained as long as known techniques are used. It was

[0015]

DISCLOSURE OF THE INVENTION The present invention has a thickness of 0.1 to 1.
It is intended to provide a method for manufacturing a 5 mm float plate glass.

[0016]

According to the present invention, a plurality of pairs of top rolls are pressed against both ears of a glass ribbon floating on a molten metal bath, and tension is applied in the width direction of the glass ribbon to form a glass ribbon. In a method for producing a float sheet glass for producing a thin sheet glass while suppressing the contraction, when the minimum thickness (unit: mm) of the central portion of the glass ribbon after cooling is D, traces of the top roll of the glass ribbon after cooling The maximum thickness (unit: mm) of the ears located on the outer side of the glass ribbon is D or more and 3 or less, and the percentage (unit:%) of the width (one side) of the ears of the glass ribbon to the entire width of the glass ribbon is 1.0 ≦ D. ≤1.
3 or more when 5 and 0.1 ≦ D <1.0 (5-2
It is a method for producing a float glass sheet in which D) is kept above D) and D is 0.1 or more and 1.5 or less.

A description will be given below with reference to the drawings. FIG. 1 is a horizontal sectional view of an apparatus for carrying out the present invention, and FIG. 2 is K of FIG.
An enlarged view of the K cross section, and FIG. 3 is a cross section of the glass ribbon.

As shown in FIG. 1, the molten glass supplied onto the molten metal bath 5 forms a glass pool near the equilibrium thickness in the high temperature region 42, and is formed on the glass ribbon 1. This glass ribbon 1 has lift-out rolls 60, 61, 6
2. By the slow cooling furnace roll 71, it advances to the right and reaches the region 43 where the temperature is near 900 ° C. In this area 43, 10 pairs of top rolls (a part of the top rolls is omitted in the drawing) 30 are provided, and the rotation axes of the top rolls forming the pair are expanded to the left. It is arranged to do.

As shown in FIG. 2, the teeth of each top roll press the ears of the glass ribbon, and the tension in the width direction is applied to the glass ribbon to prevent the glass ribbon from contracting. While passing through this region, the glass ribbon is stretched to a substantially final shape as shown in FIG. 3 having a desired thickness at the center thereof. It is important to make the shape of this glass ribbon into the following specific shape.

That is, the shape of this glass ribbon is composed of an ear portion 80 and a center portion 81 to be a product.
Is composed of a portion 82 having a trace of the top roll and a portion 83 outside thereof having no trace of the top roll.

The total width (unit: mm) of the glass ribbon is W, the width of the central portion 81 is A, and the width (unit: mm) of the portion 82 having the trace of the top roll is B, and there is no trace of the top roll. The width (unit: mm) of the portion 83 is C.
Further, the minimum thickness (unit: mm) in the central portion 81 of the glass ribbon is D, and the portion 8 where there is no trace of the top roll
The maximum thickness (unit: mm) of 3 is E.

First, regarding the thickness of the ear portion, E
D ≦ E ≦ 3. When E is less than D, cracks are generated in the unrolled portion 83 of the top roll in the annealing furnace, and the entire ribbon is easily damaged from here, and stable production cannot be performed. When E exceeds 3, warpage and micro corrugation increase. Particularly preferably, D + 1.4 ≦ E ≦ D +
Forming the ears to be 1.8.

Next, regarding the width of the ear portion, (B + C) / W
The percentage (unit:%) of 3 when 1.0 ≦ D ≦ 1.5
As described above, when 0.1 ≦ D <1.0, (5-2D) or more. If the percentage is smaller than the above range, the glass ribbon moves in the width direction to deteriorate the quality, and the top roll is easily separated from the glass ribbon, which makes stable production impossible. On the other hand, if this percentage becomes too large, the good parts that can be sampled will be too small.
It is preferable that this percentage is 15 or less.

Further, the width B (unit: mm) of the traced portion 82 of the top roll formed on both ears of the plate after cooling
Regarding, the B / W percentage (unit:%) is, for example, 1.5 or less, and particularly in the case of a thin ribbon having a thickness of 1.5 mm or less, the teeth of the cold top roll fall within the narrow width of the ribbon ear. As a result of intensive cooling and cutting into the surface of the ribbon,
The top roll in the vicinity of the most downstream part breaks through the glass ribbon to make stable production impossible, or unfavorable residual strain is generated in the ribbon surface, and warping is apt to increase, which is likely to damage the ribbon, which is not preferable. The preferable B / W percentage (unit:%) is in the range of 3 to 15.

There are the following methods for forming the glass ribbon into such a shape. As a method of increasing the thickness of the traceless portion 83 of the top roll, there are weakening the pressing of the top roll, slowing down the traveling speed of the glass ribbon, and increasing the temperature in the vicinity of the region 43.

As a method of widening the width of the ear portion of the glass ribbon, there are methods such as slowing down the traveling speed of the glass ribbon and moving the downstream top roll to the center side.

The number of top rolls is 10 pairs or more and 3
The number of pairs is preferably 0 or less, and particularly preferably 15 or more and 30 or less. The reason is as follows.

When the number of top rolls is 9 pairs or less, the glass ribbon contracts between adjacent top rolls, and the glass ribbon expands in the next top roll. The ribbon expands in accordance with the pitch of the top roll. And repeat the width reduction. As a result, microcorrugation is likely to occur. Further, the tension in the width direction required for each pair of top rolls becomes excessive, and the glass ribbon is strongly pushed below the bath surface. As a result, the unevenness of the traces of the top roll formed on the glass ribbon becomes large, the flatness of the central portion is impaired, and waviness of several cm pitch, which is larger than that of microcorrugation, is likely to occur.

On the other hand, when the number of top rolls exceeds 30 pairs, the window for monitoring the floating state of the glass ribbon is blocked by the top rolls, which makes monitoring and workability difficult.
Further, the temperature near the ears of the glass ribbon is lowered, and the glass ribbon is easily damaged near the outlet of the molten metal bath and inside the annealing furnace.

Next, the glass ribbon is cooled by the coolers 53, 5.
4 is cooled to about 600 ° C., taken out from the bath surface of the molten metal bath, passed through the lift-out rolls 60, 61 and 62 and introduced into the annealing furnace 70.

The slow-cooling furnace is a tunnel type furnace in which a ribbon transfer mechanism, for example, a large number of metal rolls 71 are built in. Usually, a combustion gas or an electric heater is used to supply a controlled amount of heat to a required position in the furnace. However, it has a function of slowly cooling the glass ribbon to a temperature range close to room temperature.

In the case of soda lime glass, when D (unit: mm) is 1.5, E (unit: mm) is 2.9 to.
About 3.0, D is 1.0, E is 2.4 to 2.8, D is 0.55, E is 1.9 to 2.4, and D is 0.3, E is 1.7 to 2. 1 and D is 0.2, E is 1.6 to 2.0
But each has good results. Also, regarding the borosilicate composition, exactly the same results were obtained with the corresponding plate thickness.

[0033]

【Example】

[Example 1] Molten glass was introduced into a molten metal bath having a length of about 50 m, which was constructed so that the total width of the ribbon after cooling was about 4 m, as in the apparatus shown in Fig. 1. A glass ribbon was formed on. The designed draw-out amount is about 400 tons / day, but in order to avoid fluctuations in the temperature of the kiln temperature while changing the ribbon speed of the lift-out roll and the annealing furnace roll to set the conditions, part of the molten glass is melted. I drained out from the upstream of the bath. The top roll has a known shape having rotating teeth made of a heat-resistant and corrosion-resistant alloy, and the inside of the support of the rotating shaft is water-cooled.

In forming the glass ribbon, the advancing speed, the pressing force of the top roll 30, the position of the top roll in the width direction, and the temperature of the glass ribbon near the region 43 are adjusted.
The cross-sectional shape of the glass ribbon was adjusted.

The glass composition is a general-purpose soda-lime composition used for architectural windows and some liquid crystal substrates.
O ₂ 72%, Al ₂ O ₃ 2%, CaO 8%, MgO
4%, Na ₂ O 13%, K ₂ O 1%.

With respect to the glass ribbon after cooling, the minimum thickness D of the central portion, the width W of the glass ribbon, the maximum thickness E of the unmarked portion of the ears, the width C of the unmarked portion of the ears, and the trace of the ears Measure the width B of the part with (B + C), (B +
The values of C) / W and (5-2D) were determined. Furthermore, the degree of microcorrugation (MC) was evaluated for samples cut from the glass ribbon after cooling, and warpage and cracking were also evaluated. The results are shown in Table 1 together with the number of top rolls.

The warpage was measured by placing a rectangular sample plate cut into a 300 mm square on a surface plate, and inserting a clearance gauge between the surface plate and the lower surface of the sample. The measurement is performed on the four sides of the sample plate, and then
The sample plate was inverted and the same measurement was performed, and the maximum value was taken as the warp of the sample plate. This warp was evaluated by ranking it as follows.

When the plate thickness is 1.5 to 0.55 mm, ∘: warp is 0.1 mm or less Δ: Warp is more than 0.1 mm and 0.2 mm or less x: Warp is 0.2 mm or more Plate thickness 0.55 to 0. At 2 mm, ◯: Warp is 0.2 mm or less Δ: Warp is more than 0.2 mm and 0.4 mm or less ×: Warp is 0.4 mm or more

With regard to microcorrugation, since extremely fine unevenness on the sample surface is measured as compared with warpage, the stylus-type surface is measured by the method specified in JIS B0601-1982 (Definition and display of surface roughness). Roughness meter surfcom, measuring length 200 mm 0.8
The maximum roughness R _max (μm) when a bandpass filter having a size of 25 mm or more and 25 mm or less was used was measured. This R _max
Was ranked and evaluated as follows.

When the plate thickness is 1.5 to 0.55 mm, ◯: R _max is 0.3 μm or less Δ: R _max is more than 0.3 μm and 0.65 μm or less ×: R _max is 0.65 μm or more Plate thickness 0.55 At 0.2 mm, ◯: R _max is 0.4 μm or less Δ: R _max is more than 0.4 μm and 0.65 μm or less ×: R _max is 0.65 μm or more

As for cracks, if gravel and devitrification flow out from the fusion zone or the spout periphery to the ribbon, they tend to occur from the starting point, but in comparison with these external influences, It was ranked and evaluated as follows. In addition,
The glass ribbon, which has a strong warp, is likely to break before reaching the cutting site after molding, so the ranking was limited to qualitative evaluation. ○ No crack occurred △ Cracked after the slow cooling furnace × Cracked near the molten metal bath outlet

Comparative Example 1 The cross-sectional shape of the glass ribbon is
A float plate glass was manufactured in the same manner as in Example 1 except that the difference from Example 1 was used, and the same measurements as in Example 1 were performed. The results are shown in Table 2.

[Embodiment 2] The total width of the ribbon after cooling is about 3
Example 1 of about 20 m in length, constructed to be m.
Molten glass was introduced from a spout into a smaller metal molten metal bath to form a glass ribbon on tin. The design draw-out amount is about 30 tons / day for the melting and molding equipment, but in order to avoid fluctuations in the temperature conditions of the kiln, a part of the amount of molten material was drained out from the kiln before the molten metal bath inlet. In forming the glass ribbon, the cross-sectional shape of the glass ribbon was adjusted in the same manner as in Example 1.

The glass composition is borosilicate glass having excellent water resistance used for liquid crystal substrates, and the composition is SiO ₂ 72
%, B ₂ O ₃ 9.5%, BaO 4%, Al ₂ O ₃ 5
%, CaO 0.4%, ZnO 3%, Na ₂ O 6
%, K ₂ O 0.5%. Table 3 shows the results of evaluation performed by the same method as in Example 1 on the plate glass sample cut out from the ribbon after cooling.

[Comparative Example 2] The cross-sectional shape of the glass ribbon was
A float plate glass was produced in the same manner as in Example 2 except that the difference was different from that in Example 2, and the same measurements as in Example 2 were performed. The results are shown in Table 4.

Example 3 The same molten metal bath as used in Example 2 was tested using a borosilicate composition for liquid crystal substrates with a further reduced alkaline component. The composition used is SiO ₂
62%, B ₂ O ₃ 4.5%, ZnO 6%, Al ₂ O ₃
15%, CaO 4%, MgO 7%, Na ₂ O 1.
Shown at 5%. In forming the glass ribbon, the cross-sectional shape of the glass ribbon was adjusted in the same manner as in Example 1. Table 5 shows the results of evaluation of the plate glass samples cut out from the ribbon after cooling in the same manner as in Example 1.

[Comparative Example 3] The cross-sectional shape of the glass ribbon was
A float plate glass was manufactured in the same manner as in Example 3 except that the difference was different from that in Example 3, and the same measurements as in Example 3 were performed. The results are shown in Table 6.

Example 4 The same molten metal bath used in Example 2 was tested using a borosilicate composition for liquid crystal substrates and thin film transistors that was substantially free of alkali components. The composition used is SiO ₂ 53%, B ₂ O ₃ 11
%, BaO 14%, Al ₂ O ₃ 11%, CaO 3
%, MgO 2%, SrO 6%, Na ₂ O <0.1%
Indicated by. In forming the glass ribbon, the cross-sectional shape of the glass ribbon was adjusted in the same manner as in Example 1. Table 7 shows the results of evaluation of the plate glass sample cut out from the ribbon after cooling, performed in the same manner as in Example 1.

[Comparative Example 4] The cross-sectional shape of the glass ribbon was
A float plate glass was produced in the same manner as in Example 4 except that it was different from that in Example 4, and the same measurements as in Example 4 were performed. The results are shown in Table 8.

As is clear from any of the examples, the float plate glass with extremely small warpage and microcorrugation is manufactured.

[0051]

[Table 1]

[Table 2]

[0052]

[Table 3]

[Table 4]

[0053]

[Table 5]

[Table 6]

[0054]

[Table 7]

[Table 8]

[0055]

According to the present invention, a float glass sheet having extremely little warpage and microcorrugation can be manufactured.

[Brief description of drawings]

FIG. 1 is a horizontal cross-sectional view of an apparatus for carrying out the present invention.

FIG. 2 is a sectional view taken along the line KK of FIG.

FIG. 3 is a sectional view of a glass ribbon.

[Explanation of symbols]

 1: Glass ribbon 5: Molten metal bath 30: Top roll 81: Central part of glass ribbon 80: Ear part of glass ribbon

Claims (4)

[Claims] 1. A thin sheet glass that suppresses the contraction of the glass ribbon by pressing a plurality of pairs of top rolls against both ears of the glass ribbon floating on the molten metal bath to apply tension in the width direction of the glass ribbon. In the method for producing a float sheet glass for producing, when the minimum thickness (unit: mm) of the central portion of the glass ribbon after cooling is D, after cooling, of the ears located outside the trace of the top roll of the glass ribbon. The maximum thickness (unit: mm) is D or more and 3 or less, and the percentage (unit:%) of the width (one side) of the edge portion of the glass ribbon to the entire width of the glass ribbon is 3 or more when 1.0 ≦ D ≦ 1.5 , 0.1
When ≦ D <1.0, it is maintained at (5-2D) or more, and D is 0.
The manufacturing method of the float plate glass which is 1 or more and 1.5 or less. 2. The method for producing a float sheet glass according to claim 1, wherein tension is applied to the glass ribbon by 10 pairs or more and 30 pairs or less of top rolls. 3. The method for producing a float glass sheet according to claim 2, wherein tension is applied to the glass ribbon by 15 pairs or more and 30 pairs or less of top rolls. 4. When the maximum thickness (unit: mm) of the ears without traces of the top roll is E, D + 1.4 ≦ E ≦ D +
The method for producing a float plate glass according to claim 1, wherein the float plate glass has a thickness of 1.8.