CN103269988A

CN103269988A - Method for producing glass substrate for flat panel display

Info

Publication number: CN103269988A
Application number: CN2012800030805A
Authority: CN
Inventors: 小山昭浩; 苅谷浩幸
Original assignee: Avanstrate Inc
Current assignee: Avanstrate Inc
Priority date: 2011-09-30
Filing date: 2012-09-26
Publication date: 2013-08-28
Anticipated expiration: 2032-09-26
Also published as: JPWO2013047585A1; JP5555373B2; TW201323355A; KR101476520B1; TWI477459B; CN103269988B; KR20130073910A; WO2013047585A1

Abstract

The present invention provides a method with which a glass substrate ideal for LTPSTFT in that it has a thermal contraction rate that allows for control of pixel pitch shift can be produced without compromising productivity using glass having a composition that is ideal for obtaining a light weight. The disclosed invention is a method for producing a glass substrate for a flat panel display. The production method comprises (1) a melting step for preparing and melting the starting materials such that the resulting glass substrate will have a combined SrO and BaO content of less than 8 mass% and a strain point of 675 C or less, (2) a forming step for forming glass ribbon from the molten glass by the overflow downdraw method, and (3) a cooling step for cooling the formed glass ribbon under the following condition (A), where (A) is an average rate of cooling from the annealing point to a temperature of (the strain point - 50 C) = less than 0.5 to 5.5 C/second.

Description

The manufacture method of glass for flat panel display substrate

Technical field

The present invention relates to the glass for flat panel display substrate.In more detail, the present invention relates to the manufacture method of low-temperature polysilicon film transistor (below, be recited as LTPSTFT (Low-Temperature-Polycrystalline-Silicon Thin-Film-Transistor)) glass for flat panel display substrate.And, the present invention relates to the manufacture method of transparent oxide semiconductor thin film transistor (below, be recited as TOSTFT (Transparent Oxide-Semiconductor Thin-Film-Transistor)) glass for flat panel display substrate.Say in further detail, the present invention relates to form LTPS or TOS and the manufacture method of the employed glass substrate of flat-panel screens made at substrate surface.Say in further detail again, the present invention relates to above-mentioned flat-panel monitor and be the glass for flat panel display substrate of liquid-crystal display manufacture method, and above-mentioned flat-panel monitor be the manufacture method of the glass for flat panel display substrate of organic EL (Electroluminescence, electroluminescent) indicating meter.

Background technology

For reducing reason such as power consumption, LTPS is used in the indicating meter expectation that is equipped on small-sized machines such as portable unit in the manufacturing of thin film transistor (TFT), but need heat-treat with 400～600 ℃ relatively-high temperature in the manufacturing of LTPSTFT.On the other hand, more and more require height to become more meticulous to the indicating meter of small-sized machine in recent years.Therefore, expectation suppresses the spacing deviation (pitch shift) of pixel as far as possible, and the thermal contraction of the glass substrate during to the manufacturing indicating meter of the spacing deviation that causes pixel suppresses to become problem.And in the glass substrate that TOSTFT uses, suppressing thermal contraction becomes problem too.

Have report to point out, the percent thermal shrinkage of glass substrate can reduce (TOHKEMY 2009-196879 communique: patent documentation 1, it all is documented in this as open especially and quote) by reduce near the annealing point speed of cooling when making glass substrate.And, there is report to point out, the percent thermal shrinkage of glass substrate also can reduce (patent documentation 2: TOHKEMY 2011-20864 communique, it all is documented in this and quotes as disclosing especially) by when making glass substrate near the speed of cooling the annealing point being made as below the value that obtains with the form with the function of ANNEALING OF GLASS point.

Summary of the invention

The problem that invention will solve

Yet, as patent documentation 1 record, as if near the speed of cooling the excessive reduction annealing point in the manufacturing step of glass substrate, the producing apparatus gigantism, productivity is variation also.In the method for patent documentation 2 records, according to ANNEALING OF GLASS point control speed of cooling.Yet in this method, the productivity that fully reduces under the situation of percent thermal shrinkage is not high.And then the glass composition of use itself contains much more relatively SrO and BaO, and the glass substrate that obtains is that density is high and be unsuitable for the light-weighted glass of glass substrate.

Therefore, the object of the present invention is to provide a kind of manufacturing to be suitable for the method for the glass substrate that LTPSTFT uses, this method is used the glass that is suitable for light-weighted composition, can produce the glass substrate that degree De Hot Shrink with the spacing deviation that can suppress pixel leads under the situation of not damaging productivity.And then purpose of the present invention also is to provide a kind of manufacturing to have the method with the glass substrate of also suitable percent thermal shrinkage as TOSTFT, and this method is used the glass that is suitable for light-weighted composition, can make under the situation of not damaging productivity too.

The technique means of dealing with problems

The inventor discovers by glass is formed, and can produce the glass substrate that LTPSTFT with the percent thermal shrinkage below the regulation uses under the situation of not damaging productivity, thereby finish the present invention.And then find that also above-mentioned glass substrate has and also can be used as the following percent thermal shrinkage of regulation that TOSTFT uses, thereby has finished the present invention.

The present invention is as described below.

[1] (the 1st mode of the present invention)

A kind of manufacture method of glass for flat panel display substrate, this method comprises:

(1) fusion step, be in harmonious proportion raw material so that in the glass substrate of manufacturing the resultant of SrO and BaO have strain point more than 675 ℃ less than 8 quality % and this glass substrate, fuse;

(2) forming step goes out glass ribbon by overflow downdraw by the fusion glass ware forming that fuses; And

(3) cooling step, (A) cools off the glass ribbon that moulding obtains with following condition, (A) average cooling rate till the temperature from annealing point to (strain point-50 ℃): 0.5～less than 5.5 ℃/second.

[2] as the manufacture method of the glass for flat panel display substrate of [1], wherein, in fusion step (1), the blending raw material is so that (SiO in the glass substrate of manufacturing ₂+ 2 * Al ₂O ₃)/B ₂O ₃Show the mol ratio more than 9.5.

[3] as the manufacture method of [1] or [2], wherein, for the glass substrate that forms via cooling step (3) manufacturing, heat up with 10 ℃/min from normal temperature, kept 1 hour at 550 ℃, with 10 ℃/minute be cooled to normal temperature thereafter, again with 10 ℃ of/minute intensifications, kept 1 hour at 550 ℃, be cooled to normal temperature with 10 ℃/minute after, the percent thermal shrinkage of being represented by following formula is below the 75ppm

Percent thermal shrinkage (ppm)={ length of the glass before the shrinkage/thermal treatment of the glass before and after the thermal treatment } * 10 ⁶

[4] (the 2nd mode of the present invention)

(1) fusion step, the blending raw material is so that have (SiO in the glass substrate of manufacturing ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be that mol ratio, this glass substrate more than 9.5 do not contain BaO in fact and have strain point more than 680 ℃, fuse;

(3) cooling step, (A) cools off the glass ribbon that moulding obtains with following condition, (A) from light the average cooling rate till the temperature of (strain point-50 ℃) less than annealing: 0.5～less than 5.5 ℃/second.

The effect of invention

According to the present invention, can be provided at produce under the situation of not damaging productivity LTPSTFT flat-panel monitor with the following percent thermal shrinkage (for example less than 75ppm) of regulation with and the method for TOSTFT glass basal plates of flat panel display.

Description of drawings

Fig. 1 is the schematic synoptic diagram (sectional view) of overflow downdraw shaped device.

Fig. 2 is the schematic synoptic diagram (side-looking face) of overflow downdraw shaped device.

Fig. 3 is the figure of temperature distribution of the specified altitude position of expression glass ribbon.

Fig. 4 is the figure of example of speed of cooling of the glass ribbon of expression embodiment 1 (speed of cooling is 1 ℃/second example).

Embodiment

The present invention relates to the manufacture method of glass for flat panel display substrates such as LTPSTFT and TOSTFT.And, the glass substrate that is produced by manufacture method of the present invention can be used as the glass substrate of liquid-crystal display and OLED display, therefore, the present invention comprise liquid crystal display glass substrate manufacture method, and OLED display with the manufacture method of glass substrate.

The manufacture method of glass for flat panel display substrate of the present invention includes following fusion step (1), forming step (2) and cooling step (3).Below, be that example describes with the manufacture method of LTPSTFT glass for flat panel display substrate, but the manufacture method of TOSTFT glass for flat panel display substrate also can similarly be implemented.And liquid crystal display glass substrate and OLED display also can similarly be implemented with the manufacture method of glass substrate.

(1) fusion step

In fusion step (1), satisfy the mode of prescribed condition with the glass substrate of manufacturing raw material is concocted, also clarification of heating fusion, preparation can be in the fusion glass of moulding.The objective of the invention is to make the glass substrate with the following percent thermal shrinkage of regulation, and its purpose is, even if also can produce such glass substrate with condition (A) to the cooling that the glass ribbon through moulding carries out in the following cooling step (3).For this reason, the glass substrate with manufacturing satisfies the mode of prescribed condition with raw material blending, heating fusion.

In the 1st mode of the present invention, the blending raw material so that in the glass substrate of manufacturing the resultant of SrO and BaO have strain point more than 675 ℃ less than 8 quality % and this glass substrate.

SrO and BaO are the compositions that can reduce the devitrification temperature of glass.Be not to be essential composition in the glass substrate of the present invention, but then can improve devitrification resistance and fusion property if contain.Yet if content is too much, density and thermal expansivity rise.If thermal expansivity rises, then the LTPSTFT glass basal plates of flat panel display with the percent thermal shrinkage (for example less than 75ppm) below the regulation can't produced under the situation of not damaging productivity.And, if density rises, then also can't realize the lightweight of glass substrate, not good enough for the LTPSTFT purposes.Therefore, the resultant with SrO and BaO in the glass substrate of manufacturing is that SrO+BaO is made as less than 8 quality %.SrO+BaO is preferably 0～7 quality %, 0～5 quality % more preferably, and then be preferably the scope of 0～3 quality %, more preferably the scope of 0～1 quality % especially under the situation of the density that will reduce glass substrate, does not preferably contain SrO and BaO in fact.

The strain point of the glass substrate of manufacturing is more than 675 ℃.If the strain point of glass substrate is low, then thermal contraction becomes big in heat treatment step (when making indicating meter).The strain point of glass substrate of the present invention is preferably more than 680 ℃, more preferably more than 686 ℃, and then is preferably more than 690 ℃, more preferably more than 695 ℃, further is preferably more than 700 ℃.The strain point of glass substrate can suitably be selected according to the composition of glass substrate, forms and will narrate hereinafter about the glass that strain point can be made as more than 675 ℃.Among the present invention, be made as more than 675 ℃ by the strain point with the glass substrate of manufacturing, can obtain the little glass substrate of percent thermal shrinkage.Yet the percent thermal shrinkage of glass substrate is not only to depend on strain point, can change according to the cooling conditions in other characteristic or manufacturing step, the especially cooling step yet.

In the 2nd mode of the present invention, the blending raw material is so that have (SiO in the glass substrate of manufacturing ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be that mol ratio, this glass substrate more than 9.5 do not contain BaO in fact and have strain point more than 680 ℃.

In any one of the 1st mode of the present invention and the 2nd mode, the glass substrate of manufacturing is by containing SiO ₂, Al ₂O ₃, B ₂O ₃Glass constitute.In the 1st mode of the present invention, preferably with the mol ratio (SiO in the glass substrate ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be that mode more than 9.5 is concocted frit.And, in the 2nd mode of the present invention, with the mol ratio (SiO in the glass substrate ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be that mode more than 9.5 is concocted frit.Because part composition volatilization and/or disperse in the manufacturing processed, thereby the composition of the frit that forms of blending changes sometimes a little with the composition of making the glass substrate that forms.Among the present invention, blending is considered this volatile quantity during frit and is dispersed and the required composition of glass substrate.In addition, need only special instruction in this specification sheets, then the content of glass ingredient and mol ratio refer to the value in glass or glass substrate.

SiO ₂Al with 2 times ₂O ₃The i.e. (SiO of resultant ₂+ 2 * Al ₂O ₃) with respect to B ₂O ₃Mol ratio (SiO ₂+ 2 * Al ₂O ₃)/B ₂O ₃Become the index of high strain-point and devitrification resistance.If (SiO ₂+ 2 * Al ₂O ₃)/B ₂O ₃Less than 9.5, then can't fully improve strain point, be difficult to have the glass substrate that the LTPSTFT of percent thermal shrinkage (for example less than 75ppm) below the regulation uses producing under the situation of not damaging productivity.On the other hand, in order fully to reduce devitrification temperature to guarantee formability, (SiO ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be preferably below 25.0, more preferably below 19.0.According to above situation, (SiO ₂+ 2 * Al ₂O ₃)/B ₂O ₃Be preferably 9.5～25.0 scope, 9.5～19.0 scope more preferably, and then be preferably and surpass 9.5～17.0 scope, more preferably 10.0～15.5 scope further is preferably 11.0～15.0 scope.

For the glass substrate of manufacturing, in the 1st mode of the present invention, preferably do not contain BaO in fact.In the 2nd mode of the present invention, do not contain BaO in fact.Therefore, in this case, during the blending frit, do not use the compound that contains Ba as frit.Yet in this specification sheets, what is called does not contain BaO in fact and refers to BaO is contained in the glass substrate, is not precluded within the situation that BaO contains as sneaking into the impurity in the glass inevitably in frit or the manufacturing step.

As the composition of the glass substrate of manufacturing in manufacture method of the present invention, but illustration contains the SiO of 60～78mol% ₂, 3～20mol% Al ₂O ₃, 0.1～15mol% B ₂O ₃Glass form.Perhaps but illustration contains the SiO of 60～78mol% ₂, 3～20mol% Al ₂O ₃, 3～15mol% B ₂O ₃Glass form.This glass can further contain ZnO, the K of 0～0.8mol% of SrO, 0～5mol% of CaO, 0～10mol% of MgO, the 0～20mol% of 0～15mol% ₂The Fe of O, 0～0.1mol% ₂O ₃, other finings etc.And, preferably do not contain SB in fact ₂O ₃And do not contain As in fact ₂O ₃These aspects are general in above-mentioned the 1st mode and the 2nd mode.

SiO ₂Being the framework ingredient of glass, therefore is essential composition.If content tails off, then have to cause the tendency that strain point reduces, thermal expansivity increases.And, if SiO ₂Content is very few, then is difficult to make the glass substrate low densityization.On the other hand, if SiO ₂Content is too much, then has melt temperature obviously to uprise and the tendency that is difficult to fuse.If SiO ₂Content is too much, and the tendency that then also has devitrification resistance to reduce is so there is the tendency of formability variation.From this viewpoint, SiO ₂Content preferably be made as the scope of 60～78mol%.SiO ₂Content 62～75mol% more preferably, and then be preferably 63～72mol%, more preferably the scope of 65～71mol%.

Al ₂O ₃It is the essential composition that improves strain point.If content is very few, then strain point reduces.And then, the tendency that have Young's modulus also to reduce, etch-rate also reduces.If Al ₂O ₃Content is too much, then has the devitrification temperature of glass to rise and the tendency of formability variation.From this viewpoint, Al ₂O ₃Content be preferably the scope of 3～20mol%.Al ₂O ₃Content 5～18mol% more preferably, and then be preferably 5～15mol%, 7～14mol% more preferably, and then the scope of 10～14mol% more preferably.

B ₂O ₃It is the essential composition that reduces glass melting temperature and improving fusion property.If B ₂O ₃Content is very few, then has to cause the reduction of fusion property, devitrification resistance to reduce, reach the tendency that thermal expansivity increases.And, if B ₂O ₃Content is very few, then is difficult to realize low densityization.If B ₂O ₃Content is too much, then causes the reduction of strain point and Young's modulus.From this viewpoint, B ₂O ₃Content is preferably the scope of 0.1～15mol%, the scope of 3～15mol% more preferably, and then be preferably 3～9.5mol%, more preferably 3～less than 8.9mol%, further be preferably 4～less than 8.9mol%, further be preferably 5～8.5mol%, again the scope of 6～8mol% more preferably.And, from fully preventing the viewpoint of devitrification, B ₂O ₃Content is preferably the scope of 0.1～15mol%, the scope of 3～15mol% more preferably, and then be preferably 5～13mol%, and 5～12mol% more preferably, further be preferably 6～less than the scope of 10mol%.

MgO is the composition that improves fusion property.And it is the composition that is difficult to increase density in the alkaline-earth metal, so if increase its content relatively, then realize low densityization easily.It is also nonessential, but can improve fusion by containing.Yet, if the content of MgO is too much, because the devitrification temperature of glass sharply rises so the formability variation.Especially under the situation that will reduce devitrification temperature, preferably do not contain MgO in fact.From this viewpoint, MgO content is preferably 0～15mol%, 0～10mol% more preferably, and then be preferably 0～5mol%, more preferably 0～less than 2mol%, further be preferably 0～1.5mol%, and then 0～1mol% more preferably, 0～0.5mol% more preferably again, and then more more preferably 0～less than 0.2mol%, most preferably be in fact and do not contain.

CaO is in the fusion that improves glass and to rapid effective composition aspect the devitrification temperature of lifting glass not.And it is the composition that is difficult to increase density in the alkaline-earth metal, so if increase its content relatively, then realize low densityization easily.If content is very few, then have because melt temperature rises to cause the reduction of fusion property and because the tendency that devitrification temperature rises and causes increased devitrification resistance to reduce.If CaO content is too much, then have to cause the tendency that thermal expansivity increases and density rises.CaO content is preferably 0～20mol%, 3.6～16mol% more preferably, and then be preferably 4～16mol%, 6～16mol% more preferably, further be preferably more than 7～16mol%, and then 8～15mol% more preferably, again the scope of 9～13mol% more preferably.

SrO is the composition that can reduce devitrification temperature.SrO is also nonessential, but devitrification resistance improves if contain then, and then fusion property also improves.If SrO content is too much, then density rises.SrO content is preferably 0～10mol%, 0～5mol% more preferably, and then be preferably 0～3mol%, 0～2mol% more preferably, further be preferably 0～1mol%, and then more preferably 0～less than 0.5mol%, more more preferably 0～less than the scope of 0.1mol%.Reduce under the situation of density of glass, preferably do not contain SrO in fact.

BaO is the composition that can reduce devitrification temperature.BaO is also nonessential, but devitrification resistance improves if contain then, and fusion property also improves.And, if BaO content is too much, then cause density to rise and the thermal expansivity increase.BaO content is preferably 0～10mol%, more preferably 0～less than 5mol%, and then is preferably 0～3mol%, and 0～2mol% more preferably further is preferably the scope of 0～1mol%.In addition, from the problem of environmental pressure, preferably do not contain BaO in fact.

Li ₂O and Na ₂O is the composition that improves the fusion property, but it might melt and the thermal expansivity that makes the TFT deterioration in characteristics or increase glass from glass substrate.Li ₂O and Na ₂The content of O is preferably 0～0.5mol%, 0～0.1mol% more preferably, and then be preferably 0～0.01mol%, further preferably in fact all do not contain Li ₂O and Na ₂O.

K ₂O is the composition that improves the basicity of glass and promote clarification property.And it is to reduce than resistance and reduce melting temperature (Tm) and improve the composition of fusion property.Though also nonessential, if contain the then property clarified raising, fusion property also improves.If K ₂O content is too much, then might melt from glass substrate and makes the TFT deterioration in characteristics.And thermal expansivity also has the tendency of increase.K ₂O content is preferably 0～0.8mol%, 0.01～0.5mol% more preferably, and then be preferably the scope of 0.1～0.3mol%.

The glass substrate that is obtained by manufacture method of the present invention can comprise finings.As finings, SnO ₂Suit.If SnO ₂Content very few, bubble quality variation then.If SnO ₂Content too much, then be easy to generate devitrification.SnO ₂Content preferably be made as the scope of 0.01～0.2mol%, 0.03～0.15mol% more preferably, and then be preferably the scope of 0.05～0.12mol%.

Fe ₂O ₃It is the composition that except the effect that has as finings, reduces the ratio resistance of glass.Viscosity in the high-temperature area is high and in the glass that is difficult to fuse, preferably contain Fe ₂O ₃To reduce the ratio resistance of glass.Yet, if Fe ₂O ₃Content is too much, glass coloring then, and transmitance reduces.Therefore, Fe ₂O ₃Content is the scope of 0～0.1mol%, is preferably 0～0.05mol%, 0.001～0.05mol% more preferably, and then be preferably 0.005～0.05mol%, the more preferably scope of 0.005～0.02mol%.

Consider the problem of environmental pressure, the glass substrate that is obtained by manufacture method of the present invention does not preferably contain As in fact ₂O ₃In the glass substrate of the present invention, consider the problem of environmental pressure, SB ₂O ₃Be preferably 0～0.5mol%, more preferably 0～0.1mol% does not most preferably contain SB in fact ₂O ₃

In addition, in this specification sheets, so-called " not containing in fact " refers to not use in the above-mentioned frit material of the raw material that becomes this composition, and is not precluded within the composition that contains with the impurity form in the frit of other composition, and melts sneaking into to the composition of glass by manufacturing installation.

If from SiO ₂Content in deduct Al ₂O ₃1/2 poor (SiO of content ₂-Al ₂O ₃/ 2) value is too small, though then can improve etch-rate, might reduce devitrification resistance.If this value is too high, then might reduce etch-rate.From this viewpoint, (SiO ₂-Al ₂O ₃/ 2) be preferably below the 66mol%, 50～66mol% more preferably, and then be preferably 56～64mol%, more preferably 57～63mol% further is preferably 58～62mol%.

If SiO ₂With Al ₂O ₃Resultant be SiO ₂+ Al ₂O ₃If very few, as then to have strain point to reduce tendency too much, then has the tendency of devitrification resistance variation.Therefore, SiO ₂+ Al ₂O ₃Be preferably more than the 75mol% 76～88mol% more preferably, and then be preferably 77～85mol%, more preferably 78～82mol%.

If B ₂O ₃With P ₂O ₅Resultant be B ₂O ₃+ P ₂O ₅Very few, the tendency of fusion property reduction is then arranged, if too much, then because B ₂O ₃+ P ₂O ₅Volatilization and cause the heterogeneity apparition of glass, be easy to generate striped.And then, the tendency that has strain point to reduce.Therefore, B ₂O ₃+ P ₂O ₅Be preferably 0.1～15mol%, 3～15mol% more preferably, and then be preferably 3～9.5mol%, more preferably 4～9mol% further is preferably 5～9mol%, and then 6～8mol% more preferably.And, from fully preventing the viewpoint of devitrification, B ₂O ₃+ P ₂O ₅Be preferably the scope of 0.1～15mol%, 3～15mol% more preferably, and then be preferably 5～13mol%, 5～12mol% more preferably, further be preferably 6～less than the scope of 10mol%.

Improve the viewpoint of fusion property when preventing that strain point from reducing, CaO is with respect to B ₂O ₃Mol ratio CaO/B ₂O ₃Be preferably more than 0.5, more preferably more than 0.9, and then be preferably and surpass 1.2, more preferably surpass 1.2～5 scope, more preferably surpass 1.2～3 scope again, further be preferably 1.3～2.5 scope, most preferably be 1.3～2 scope.And the viewpoint from abundant raising fusion property is preferably 0.5～5, more preferably 0.9～3, and then be preferably and surpass 1～2.5, more preferably surpass 1.2～2, and further be preferably and surpass 1.2～1.5 scope.

Mol ratio CaO/RO becomes the index of fusion property and devitrification resistance.CaO/RO is preferably 0.5～1, and more preferably 0.7～1, and then be preferably and surpass 0.85～1, more preferably 0.88～1, further be preferably 0.90～1 scope, and then more preferably 0.92～1, most preferably be 0.95～1.By being made as above-mentioned scope, can take into account devitrification resistance and fusion property.And then can realize low densityization.

If RO, ZnO and B ₂O ₃Resultant be RO+ZnO+B ₂O ₃Very few, the tendency of fusion property reduction is then arranged.On the other hand, if too much, the tendency that then has strain point to reduce.Therefore, RO+ZnO+B ₂O ₃Be preferably 7～30%, more preferably 7～less than 25mol%, 10～23mol% more preferably, and then be preferably 12～22mol%, 14～21mol% more preferably further is preferably the scope of 16～21mol%.And the viewpoint from abundant raising fusion property is preferably 7～30%, but more preferably 12～27%, 14～25mol% more preferably, and then be preferably the scope of 17～23mol%.

RO is with respect to SiO ₂With Al ₂O ₃Resultant (SiO ₂+ Al ₂O ₃) mol ratio RO/ (SiO ₂+ Al ₂O ₃) become the index of strain point and fusion property.From taking into account high strain-point that high strain-point with fusion property, also takes into account glass and viewpoint than the reduction of resistance, be preferably 0.07～0.2 scope, more preferably 0.08～0.18, and then be preferably 0.13～0.18,0.13～0.16 scope more preferably.

Li ₂O, Na ₂O and K ₂The resultant of O is R ₂Thereby being the oxidation that improves the basicity of glass, carry out finings easily, O given play to the composition of clarification property.And, thereby it is the composition that reduces than resistance and melting temperature (Tm) raising fusion property.R ₂O is also nonessential, but then improves bubble quality and fusion property if contain.Yet, if R ₂O content is too much, the tendency that then has thermal expansivity to increase.R ₂O is preferably 0～0.8mol%, 0.01～0.5mol% more preferably, and then be preferably 0.1～0.3mol%.

K ₂O and Li ₂O or Na ₂It is big that O compares molecular weight, so be difficult to melt from glass substrate.Therefore, contain R ₂Under the situation of O, preferably contain K ₂O.That is preferred K, ₂Mol% content＞Li of O ₂Mol% content and/or the K of O ₂Mol% content＞N of O ₂The mol% content of O.If Li ₂O and Na ₂The ratio of O is big, then melts and makes the possibility of TFT deterioration in characteristics become big from glass substrate.Mol ratio K ₂O/R ₂O is preferably 0.3～1, and more preferably 0.5～1, and then be preferably 0.8～1,0.9～1 scope more preferably.

The resultant of MgO, CaO, SrO and BaO is that RO is the composition that improves fusion property.If RO content is very few, then fusion property variation.If RO content is too much, then have to cause strain point reduction, density to rise, reach the tendency that Young's modulus reduces.And, if RO content is too much, the tendency that then also has thermal expansivity to increase.From this viewpoint, RO is preferably the scope of 3～25mol%, be preferably 4～16mol%, 4～15mol% more preferably, and then be preferably 5～less than the scope of 14mol%, the scope of 6～14mol% more preferably further is preferably the scope of 8～13mol%, and then the scope of 9～12mol% more preferably.

The devitrification temperature of glass substrate of the present invention is preferably below 1270 ℃, more preferably below 1260 ℃, and then is preferably below 1250 ℃, more preferably below 1200 ℃.If devitrification temperature is below 1270 ℃, then utilize glass tube down-drawing to carry out the moulding of sheet glass easily.If devitrification temperature is too high, then is easy to generate devitrification and can't be applicable to glass tube down-drawing.

The mean thermal expansion coefficients of glass substrate of the present invention (100～300 ℃) is preferably less than 55 * 10 ^-7℃ ^-1, more preferably 28 * 10 ^-7℃ ^-1～less than 40 * 10 ^-7℃ ^-1, and then be preferably 30 * 10 ^-7℃ ^-1～less than 39 * 10 ^-7℃ ^-1, more preferably 32 * 10 ^-7℃ ^-1～less than 38 * 10 ^-7℃ ^-1, further be preferably 34 * 10 ^-7℃ ^-1～less than 38 * 10 ^-7℃ ^-1Scope.And, from further dwindling the viewpoint of percent thermal shrinkage, be preferably less than 37 * 10 ^-7℃ ^-1, more preferably 28 * 10 ^-7℃ ^-1～less than 36 * 10 ^-7℃ ^-1, and then be preferably 30 * 10 ^-7℃ ^-1～less than 36 * 10 ^-7℃ ^-1, more preferably 31 * 10 ^-7℃ ^-1～35 * 10 ^-7℃ ^-1, further be preferably 32 * 10 ^-7℃ ^-1～less than 35 * 10 ^-7℃ ^-1Scope.If thermal expansivity is big, the tendency that then has percent thermal shrinkage to increase.On the other hand, if thermal expansivity is little, thus the situation that then exists the coupling that is difficult to obtain the metal, organic system binding agent isoperimetric sapwood material and the thermal expansivity that are formed on the glass substrate to cause circumferential component to be peeled off.By thermal expansivity being made as above-mentioned scope, can reduce the thermal stresses that is produced by thermal expansion difference.

The percent thermal shrinkage of glass substrate of the present invention is preferably below the 75ppm, more preferably below the 60ppm, and then is preferably below the 55ppm, more preferably below the 50ppm, further be preferably below the 48ppm, and then more preferably less than 45ppm, more more preferably below the 43ppm.If percent thermal shrinkage (amount) is excessive, then causes the spacing deviation that pixel is bigger and can't realize the indicating meter that height is meticulous.For percent thermal shrinkage (amount) is controlled in specialized range, preferably the strain point with glass substrate is made as more than 675 ℃.In addition, if desiring to make percent thermal shrinkage is 0ppm, then must do one's utmost to reduce the speed of cooling of cooling step (for example the 2nd cooling step), perhaps with cooling step described later thermal contraction is set differently and reduce treatment step.Particularly, reduce treatment step by thermal contraction is set after cut-out step described later, can reduce percent thermal shrinkage (off-line annealing).Yet, reduce treatment step if do one's utmost to reduce speed of cooling or with cooling step thermal contraction is set differently, cause productivity to reduce cost increase.If consider productivity and cost, then percent thermal shrinkage is preferably 5～75ppm, 5～60ppm more preferably, and then be preferably 8～55ppm, 8～50ppm more preferably, further be preferably 10～48ppm, and then more preferably 10～less than 45ppm, 15～43ppm more preferably again.

In addition, for percent thermal shrinkage, be 10 ℃/min and after 1 hour thermal treatment of 550 ℃ of maintenances, represent with following formula at twice warming and cooling rate of enforcement.More specifically, heat up with 10 ℃/min from normal temperature, kept 1 hour at 550 ℃, thereafter, be cooled to normal temperature with 10 ℃/minute, again with 10 ℃ of/minute intensification, 550 ℃ of maintenances 1 hour, be cooled to normal temperature with 10 ℃/minute.

The density of glass substrate of the present invention is preferably 2.6g/cm ³Below, 2.5g/cm more preferably ³Below, and then be preferably 2.45g/cm ³Below, 2.42g/cm more preferably ³Below.If density is too high, then the lightweight of glass substrate becomes difficult, also can not realize the lightweight of indicating meter.

If the Tg step-down of glass then has the tendency of the thermal contraction of being easy to generate in the heat treatment step when making indicating meter.The Tg of glass substrate of the present invention is preferably more than 720 ℃, more preferably more than 730 ℃, and then is preferably more than 740 ℃, more preferably more than 750 ℃.For the Tg with glass substrate is made as above-mentioned scope, in the compositing range of glass substrate of the present invention, increase for example SiO that improves Tg ₂And Al ₂O ₃Suit Deng composition.

The temperature (melt temperature) of the demonstration viscosity (100dPas) of glass melting liquid of the present invention is preferably below 1750 ℃, 1600～1750 ℃ scope more preferably, and then be preferably 1620～1730 ℃, more preferably 1650～1720 ℃ scope.The easy step-down of the strain point of the glass that melt temperature is low.In order to improve strain point, also must improve melt temperature to a certain extent.Yet, if melting temperature (Tm) uprises, big to the burden change of fusion groove.And, because a large amount of energy that uses, so cost also uprises.For glass melting being made as above-mentioned scope, in the compositing range of glass substrate of the present invention, contain for example B that reduces viscosity ₂O ₃, composition such as RO suits.

The ratio resistance of melten glass of the present invention (1550 ℃ time) is preferably 50～300 Ω cm, 50～250 Ω cm more preferably, and then be preferably 50～200 Ω cm, the more preferably scope of 100～200 Ω cm.If more too small than resistance, it is excessive and restriction on the equipment might occur then to fuse required current value.If the ratio resistance of melten glass is excessive, be not in glass, to flow but the possibility that in the heat resisting brick that forms the fusion groove, flows and cause fusing the groove melting loss thereby then there is electric current.The ratio resistance of melten glass mainly can be by control RO, K ₂O, and Fe ₂O ₃Content and be adjusted into above-mentioned scope.

The liquid phase viscosity of glass of the present invention is preferably more than 30, the 000dPas, and more preferably 40, more than the 000dPas, and then be preferably the above scope of 50,000dPas.By being in the above-mentioned scope and when moulding, be difficult to produce the devitrification crystal, so utilize overflow downdraw formed glass substrate easily.

The Young's modulus of glass substrate of the present invention is preferably more than the 70GPa, more preferably more than the 73GPa, and then is preferably more than the 74GPa, more preferably more than the 75GPa.If Young's modulus (GPa) is little, then the deflection owing to the caused glass of conducting oneself with dignity because of glass makes glass breakage easily.For the Young's modulus (GPa) of glass substrate, can be by in the compositing range of glass substrate of the present invention, increasing the stronger for example Al of tendency that makes Young's modulus (GPa) change ₂O ₃Deng content increase the Young's modulus (GPa) of glass substrate.

The ratio Young's modulus (Young's modulus/density) of glass substrate of the present invention is preferably more than 28, more preferably more than 29, and then is preferably more than 30, more preferably more than 31.If littler than Young's modulus, then the deflection owing to the caused glass of conducting oneself with dignity because of glass makes glass breakage easily.

(2) forming step

In the forming step (2), go out glass ribbon by overflow downdraw by fusing through heating and clarifying the fusion glass ware forming that forms.The method of overflow downdraw itself is known method.Overflow downdraw for example can be with reference to communiques such as TOHKEMY 2009-298665 communique, TOHKEMY 2010-215428 communique, TOHKEMY 2011-168494 communiques, and it all is documented in this as especially openly quoting.The explanatory view of the device that uses in the overflow downdraw is shown in Fig. 1 and Fig. 2.

Fig. 1 and Fig. 2 represent the schematic formation of the shaped device 40 that uses in the overflow downdraw.Fig. 1 is the sectional view of shaped device 40.Fig. 2 is the side-looking face of shaped device 40.

Shaped device 40 comprises the passage that glass ribbon GR passes through and surrounds the space of passage.The space that surrounds passage by overflow chamber 20, moulding chamber 30, and cooling chamber 80 constitute.

Shaped device 40 mainly by formed body 41, distance member 50, cooling roller 51, temperature adjustment unit 60, down withdrawing roll 81a～81d, well heater 82a～82h, and shut-off device 90 constitute.And then shaped device 40 possesses control device 91 (not shown).Overflow chamber 20 is to make the melten glass that transports from clarifying plant (not shown) be shaped to the space of glass ribbon GR.By adopting overflow downdraw to need not the grinding steps of the glass baseplate surface after the moulding.

(3) cooling step

In the cooling step (3), cool off with the glass ribbon of following condition (A) to moulding in the forming step.

(A) annealing point is to the average cooling rate of the temperature of (strain point-50 ℃): 0.5～less than 5.5 ℃/second

Formed glass ribbon one side is extended the one side cooling downwards.Be known about the extension of glass ribbon and usual method and the condition of cooling.In the method for the present invention, use the online annealing that formed glass ribbon in the overflow shaped device is directly cooled off, and then cut off, make sheet glass.

Moulding chamber 30 is to be disposed at the below of overflow chamber 20 and to be used for adjusting the thickness of glass ribbon GR and the space of amount of warpage.In the moulding chamber 30, implement the part of the 1st cooling step S41 described later.Particularly, in moulding chamber 30, the upstream region of glass ribbon GR is cooled off.The upstream region of so-called glass ribbon GR is the zone that the temperature of the central part C of glass ribbon GR is higher than the glass ribbon GR of annealing point.The central part C of glass ribbon GR is the width center of glass ribbon GR.Near till the temperature that comprises the central part C of glass ribbon GR in the upstream region reaches the annealing point temperature province.Glass ribbon GR is by after in the moulding chamber 30, in cooling chamber 80 described later.

Cooling chamber 80 shown in Fig. 1 and 2 is the spaces that are disposed at the below of overflow chamber 20 and moulding chamber 30 and are used for adjusting the dependent variable of glass ribbon GR.In the overflow chamber 20, implement a part, the 2nd cooling step S42, and the 3rd cooling step S43 of following the 1st cooling step S41.Particularly, in cooling chamber 80, pass through the annealed point of glass ribbon GR, strain point in the moulding chamber 30, be cooled near the temperature of room temperature.In addition, the inside of cooling chamber 80 is divided into a plurality of spaces by heat insulating member 80b.

The cooling step of glass ribbon comprises: the 1st cooling step, about 1,100 ℃～1,250 ℃ glass ribbon cools that will form in the overflow shaped device extremely surpass till the annealing point; The 2nd cooling step, self-annealing are lighted and are cooled to till the temperature of (strain point-50 ℃); And the 3rd cooling step, till the temperature less than (strain point-50 ℃) is cooled near (strain point-200 ℃) temperature.And then in the present invention, the average cooling rate of glass ribbon central part in the 2nd cooling step is made as 0.5～less than 5.5 ℃/second (condition A).Be made as above-mentioned scope by the average cooling rate with glass ribbon central part in the 2nd cooling step, can under the situation of not damaging productivity, obtain the glass substrate that percent thermal shrinkage has reduced.In addition, in this specification sheets, the speed of cooling of glass ribbon then refers to the average cooling rate of the central part of glass ribbon as long as do not put down in writing especially.More specifically, can be with reference to Japanese Patent Application 2012-525566 number etc., wherein whole are documented in this as open especially and quote.In addition, in this specification sheets, (strain point-50 ℃) refers to the temperature than low 50 ℃ of strain point, and (strain point-200 ℃) refers to the temperature than low 200 ℃ of strain point.

Manufacture method of the present invention in the cooling step of the glass ribbon of moulding, except satisfying above-mentioned condition (A) also preferably with following condition (B) and (C) cooled glass band.

(B) temperature of the glass ribbon of moulding reaches average cooling rate till the annealing point in the forming step (2): more than 5.5 ℃/second;

(C) in above-mentioned (B) temperature of glass ribbon reach average cooling rate till the annealing point than the temperature of above-mentioned glass ribbon from fast less than the average cooling rate till above-mentioned (strain point-50 ℃) to (strain point-200 ℃).

Manufacture method of the present invention in the cooling step of the glass ribbon of moulding, except satisfy above-mentioned condition (A) or (A)～(C), also can satisfy condition (D).(D) temperature of above-mentioned glass ribbon is fast from the average cooling rate of lighting than the temperature self-annealing of above-mentioned glass ribbon less than the average cooling rate till above-mentioned (strain point-50 ℃) to above-mentioned (strain point-200 ℃) till (strain point-50 ℃).

Condition (B) is the cooling conditions in the 1st cooling step till the temperature of glass ribbon reaches annealing point, and the average cooling rate of the glass ribbon central part of moulding in the forming step is made as more than 5.5 ℃/second.The average cooling rate of glass ribbon central part is preferably 5.5 ℃/second～50.0 ℃/second in the 1st cooling step, more preferably 8.0 ℃/second～16.5 ℃/second.If the average cooling rate of glass ribbon central part is less than 5.5 ℃/second in the 1st cooling step, then productivity reduces.On the other hand, if the average cooling rate of glass ribbon central part surpasses 50.0 ℃/second in the 1st cooling step, then be difficult to carry out the temperature control of the width of the glass ribbon that carries out in order to suppress plane strain or warpage.And the 1st edge part speed of cooling among the 1st cooling step S41 is preferably 5.5 ℃/second～52.0 ℃/second, more preferably 8.3 ℃/second～17.5 ℃/second.And the average cooling rate of glass ribbon central part is preferably faster than the average cooling rate of glass ribbon central part in the 2nd cooling step and the 3rd cooling step in the 1st cooling step.Condition (C) be average cooling rate in the 1st cooling step till the temperature of glass ribbon reaches annealing point faster than the temperature of glass ribbon from less than the average cooling rate in the 3rd cooling step till above-mentioned (strain point-50 ℃) to (strain point-200 ℃).By setting like this, can improve the temperature controlled precision of the width of glass ribbon.

Condition (A) is the cooling conditions of the glass ribbon in the 2nd cooling step, annealing point to the average cooling rate of the glass ribbon central part of the temperature of (strain point-50 ℃) is 0.5～less than 5.5 ℃/second, be preferably 1.0 ℃/second～5.5 ℃/second, more preferably 1.5 ℃/second～5.0 ℃/second.If the average cooling rate of glass ribbon central part is less than 0.5 ℃/second in the 2nd cooling step, producing apparatus gigantism and cause productivity to reduce then.On the other hand, if more than 5.5 ℃/second, then can't fully reduce percent thermal shrinkage.And the edge part speed of cooling in the 2nd cooling step is preferably 0.3 ℃/second～5.3 ℃/second, more preferably 0.8 ℃/second～2.8 ℃/second.And the average cooling rate of glass ribbon central part preferably is slower than the average cooling rate of glass ribbon central part in the 1st cooling step in the 2nd cooling step.

Among the present invention, there is no particular restriction to the speed of cooling of glass ribbon central part in the 3rd cooling step, is preferably 1.5 ℃/second～7.0 ℃/second, more preferably 2.0 ℃/second～5.5 ℃/second.If the speed of cooling of glass ribbon central part is less than 1.5 ℃ of/second then productivity reductions in the 3rd cooling step.On the other hand, if more than 7.0 ℃/second, the possibility that exists glass ribbon to break because of the glass quenching then.And the edge part speed of cooling is preferably 1.3 ℃/second～6.8 ℃/second among the 3rd cooling step S43, more preferably 1.5 ℃/second～5.0 ℃/second.

And the average cooling rate of glass ribbon central part can be faster than the average cooling rate of glass ribbon central part in the 2nd cooling step in the 3rd cooling step.Condition (D) is the average cooling rate of temperature in the 2nd cooling step of lighting faster than the temperature self-annealing of above-mentioned glass ribbon less than the average cooling rate in the 3rd cooling step till above-mentioned (strain point-50 ℃) to above-mentioned (strain point-200 ℃) till (strain point-50 ℃) of glass ribbon.By setting like this, can further improve the temperature controlled precision of the width of glass ribbon sometimes.Yet, even if the temperature of glass ribbon is lighted average cooling rate in the 2nd cooling step till (strain point-50 ℃) from the temperature self-annealing that is slower than above-mentioned glass ribbon less than the average cooling rate in the 3rd cooling step till above-mentioned (strain point-50 ℃) to above-mentioned (strain point-200 ℃), as long as satisfy above-mentioned condition (A) to (C), then also can carry out the temperature control of the width of glass ribbon with required precision.(D) can further improve its precision by satisfying condition.

That is, in the aforesaid way, preferably in contained three the cooling step S41～S43 of the cooling step S4 of glass ribbon GR at least among cooling step S41 and the S42 with different speed of cooling cooling plate-like glass SG.The speed of cooling of cooling step S42 and S43 no matter comparatively fast all can by which person.Particularly, the speed of cooling of the 1st cooling step S41 among three cooling step S41～S43 is the fastest, the speed of cooling of the speed of cooling of the 2nd cooling step S42 and the 3rd cooling step S43 no matter which person is very fast or be identical speed, and the temperature that all can improve glass ribbon when keeping higher productivity controls, the temperature controlled precision of width especially.

Below, with reference to Fig. 3 and Fig. 4, the temperature treatment of the glass ribbon GR among each cooling step S41～S43 is elaborated.Fig. 3 represents the temperature distribution of the specified altitude position of glass ribbon GR.Fig. 4 represent to satisfy condition speed of cooling of the glass ribbon GR (0.7mm) that makes among the embodiment 1 of (D).

(3-1) the 1st cooling step

The 1st cooling step S41 is with near the step of the temperature being cooled to annealing point at the melten glass that collaborates under the formed body 41.Particularly, in the 1st cooling step, about 1,100 ℃～1,250 ℃ glass ribbon GR is cooled near the temperature (with reference to Fig. 4) of annealing point.Herein, annealing point is that viscosity is 10 ¹³Temperature during dPas.

Among the 1st cooling step S41, carry out the temperature treatment of glass ribbon GR based on the 1st temperature distribution TP1～the 4th temperature distribution TP4.The 1st cooling step comprises: the 1st temperature controlling step is lower than temperature by the temperature of the middle section CA of end clamping and the middle section CA uniform mode that becomes with the temperature of the end of the width of glass ribbon GR and carries out; And the 2nd temperature controlling step, after carrying out the 1st temperature controlling step, carry out towards the mode of end step-down from central part with the temperature of the width of glass ribbon GR.Herein, the become temperature that evenly refers to middle section CA of the temperature of so-called middle section CA is contained in the temperature province of regulation.The temperature province of so-called regulation is the scope of reference temperature ± 20 ℃.Reference temperature is the medial temperature of the width of middle section CA.The temperature of the width of so-called glass ribbon GR refers to form gradient (thermograde) in the temperature of the temperature of central part C and edge part R, L towards the end step-down from central part.In addition, herein, so-called thermograde is the value of the temperature gained that deducts edge part R, L of the temperature from central part C divided by the width W of glass ribbon GR (for example 1650mm, with reference to Fig. 3) divided by the value after the value of 2 gained ((temperature of the temperature of central part C-edge part R, L)/(width W of plate glass/2)).

The 1st temperature distribution TP1 shown in Figure 3 realizes by the cooling roller 51 and the temperature adjustment unit 60 that are controlled in the die cavity chamber 30.Particularly, edge part R, the L by cooling roller 51 cooled glass band GR.For the edge part R of glass ribbon GR, the temperature of L, be cooled to the temperature than the low specified temperature (for example 200 ℃～250 ℃) of temperature of middle section CA.For the 1st temperature distribution TP1, suppress glass ribbon GR and on width, shrink by edge part being carried out quenching, thereby make the thickness of slab of glass ribbon GR even.

The 2nd temperature distribution TP2 and the 3rd temperature distribution TP3 realize by the temperature adjustment unit 60 that is controlled in the die cavity chamber 30.Particularly, by edge part R, the L of cooling

unit

64,65 cooled glass band GR, by the middle section CA of cooling

unit

62,63 cooling plate-like glass.By carrying out this cooling, can constantly apply tension force at the central part of glass ribbon GR, can suppress the warpage of glass ribbon GR.

In addition, the 4th temperature distribution TP4 realizes by the well heater 82a in the control cooling chamber 80.By making thermograde TG4 among the 4th temperature distribution TP4 less than the thermograde TG3 among the 3rd temperature distribution TP3 of upstream, can constantly apply tension force at the central part of glass ribbon GR, can suppress the warpage of glass ribbon GR.

(3-2) the 2nd cooling step

The 2nd cooling step S42 is near the step (with reference to Fig. 4) that the glass ribbon GR that will reach near the temperature the annealing point is cooled to strain point-50 ℃.Herein, strain point is that the viscosity of glass is 10 ^14.5The temperature of dPas.

Among the 2nd cooling step S42, carry out the temperature treatment of glass ribbon GR based on the 5th temperature distribution TP5 and the 6th temperature distribution TP6.The 2nd cooling step comprises the 3rd temperature controlling step, and the 3rd temperature controlling step is with along with near near the strain point of glass, and carry out with the mode of the thermograde of central part reduction the end of the width of above-mentioned plate glass.

The 5th temperature distribution TP5 realizes by the well heater 82b in the control cooling chamber 80.By making thermograde TG5 among the 5th temperature distribution TP5 less than the thermograde TG4 among the 4th temperature distribution TP4 of upstream, can constantly apply tension force at the central part of glass ribbon GR, can suppress the warpage of glass ribbon GR.

Among the 6th temperature distribution TP6, the temperature of the width of glass ribbon GR (edge part R, the L of width is to the temperature of central part C) is even.In other words, the 6th temperature distribution TP6 is following temperature distribution: on the width of glass ribbon GR, the thermograde minimum of the temperature of the temperature of edge part R, L periphery and central part C periphery, the temperature of the temperature of edge part R, L periphery and central part C periphery is same degree.

Herein, the temperature of the so-called temperature that evenly refers to edge part R, L periphery and central part C periphery is contained in the temperature province of regulation.The temperature province of so-called regulation is the scope of reference temperature ± 5 ℃.Reference temperature is the medial temperature of the width of glass ribbon GR.

In addition, the 6th temperature distribution TP6 realizes by the well heater 82c in the control cooling chamber 80.And the 6th temperature distribution TP6 realizes near strain point.Refer to comprise the temperature province of the regulation of strain point herein, near the so-called strain point.The temperature province of so-called regulation is the zone of from " (annealing point+strain point)/2 " to " strain point-50 ℃ ".The 6th temperature distribution TP6 is that near (place of flow direction) more at least strain point realizes.

(3-3) the 3rd cooling step

The 3rd cooling step S43 is the step (with reference to Fig. 4) that the glass ribbon GR that will reach near the temperature the strain point-50 ℃ is cooled near the temperature the strain point-200 ℃.

Among the 3rd cooling step S43, carry out the temperature treatment of glass ribbon GR based on the 7th temperature distribution TP7～the 10th temperature distribution TP10.The 3rd cooling step comprises the 4th temperature controlling step, and the 4th temperature controlling step is to carry out towards the mode of central part step-down from the end of the width of above-mentioned plate glass with the temperature of the width of above-mentioned plate glass.In other words, among the 3rd cooling step S43, preferably the temperature of above-mentioned central part less than near the zone the strain point of glass in, to control the temperature of above-mentioned glass ribbon towards the mode of above-mentioned central part step-down from the above-mentioned both ends of above-mentioned glass ribbon (edge part).

In addition, the 7th temperature distribution TP7～the 10th temperature distribution TP10 realizes by the well heater 82d～82g in the control cooling chamber 80.Particularly, realize the 7th temperature distribution TP7 by well heater 82d, realize the 8th temperature distribution TP8 by well heater 82e, realize the 9th temperature distribution TP9 by well heater 82f, realize the 10th temperature distribution TP10 by well heater 82g.The temperature of the central part C of middle section CA is minimum, the temperature of edge part R, L is the highest, and increase thermograde TG7～10 among the 7th temperature distribution TP7～the 10th temperature distribution TP10 gradually along the flow direction of glass ribbon GR, can constantly apply tension force at the central part of glass ribbon GR thus, can suppress the warpage of glass ribbon GR.

And, in above-mentioned the 1st～the 3rd cooling step, for the central part at the width of above-mentioned glass ribbon makes tension force work in the conveyance direction of glass ribbon, can carry out temperature control as follows: add that from the glass annealing point 150 ℃ temperature (annealing point+150 ℃) deducts to strain point of glass in the temperature province of 200 ℃ temperature (strain point-200 ℃) in the temperature of the central part of the width of above-mentioned glass ribbon at least, the speed of cooling of the central part of the width of above-mentioned glass ribbon is faster than the speed of cooling at the both ends of above-mentioned width.

As mentioned above, preferred in above-mentioned the 1st～the 3rd cooling step: (1) is that the both ends of the width of above-mentioned glass ribbon in the zone more than the glass softening point are lower than temperature by the temperature of the central part of above-mentioned both ends clamping and the above-mentioned central part uniform mode that becomes and control the temperature of above-mentioned glass ribbon with the temperature at the central part of the width of above-mentioned glass ribbon; (2) at the central part of the width of above-mentioned glass ribbon, for the tension force that makes glass ribbon conveyance direction plays a role in the temperature of the above-mentioned central part of above-mentioned glass ribbon in less than glass softening point and the zone more than or equal to strain point of glass, control the temperature of above-mentioned glass ribbon towards the mode of above-mentioned both ends step-down from above-mentioned central part with the temperature distribution of the width of above-mentioned glass ribbon; And (3) above-mentioned both ends of becoming the width of above-mentioned glass ribbon in the temperature province of strain point of glass with the temperature at the above-mentioned central part of above-mentioned glass ribbon and the mode of the thermograde disappearance of above-mentioned central part are controlled the temperature of above-mentioned glass ribbon.

Embodiment

Below, further describe the present invention by embodiment.Yet the present invention is not defined as the intention of embodiment.

Embodiment 1

(making of sample glass)

To become the mode that the glass shown in the table 1 is formed, using common frit is silicon-dioxide, aluminum oxide, boron oxide, salt of wormwood, alkaline magnesium carbonate, calcium carbonate, Strontium carbonate powder, tindioxide and ferric oxide, blending frit batch of material (hereinafter referred to as batch of material).

Use possesses batch of material that the continuous fusing device of the adjustment groove of the fusion groove of refractory brick system and platinum alloy system forms above-mentioned blending with 1560～1640 ℃ of fusions, with 1620～1670 ℃ of clarifications and with after 1440～1530 ℃ of stirrings, use the manufacturing installation of the glass substrate shown in Fig. 1 and 2, the width that is shaped to glass ribbon GR by overflow downdraw is that 1600mm, thickness are the lamellar of 0.7mm, under prescribed condition, anneal, obtain liquid-crystal display (OLED display is used) glass substrate.The annealing conditions of regulation is shown in table 2～6.In addition, about following each characteristic, by the test glass substrate of making 30mm * 40mm * 0.7mm with the glass substrate that annealing conditions was obtained of table 3.

(strain point, annealing point)

Use camber beam determinator (manufacturing of Tokyo Industries, Inc) to measure, (ASTMC-598) obtains strain point and annealing point by calculating according to the camber beam method.

(percent thermal shrinkage)

Glass substrate is heated up with 10 ℃/min from normal temperature, kept 1 hour at 550 ℃, thereafter, be cooled to normal temperature with 10 ℃/minute, with 10 ℃ of/minute intensifications, kept 1 hour at 550 ℃ again, be cooled to normal temperature with 10 ℃/minute, the shrinkage of the glass substrate of use behind aforesaid operations is obtained percent thermal shrinkage by following formula.

Percent thermal shrinkage (ppm)

={ length of the glass before the shrinkage/thermal treatment of the glass before and after the thermal treatment } * 106

In the present embodiment, particularly, carry out the mensuration of shrinkage by the following method.

(measuring method of devitrification temperature)

Above-mentioned glass substrate is pulverized, by the sieve of 2380 μ m, obtained to residue in the glass grain on the sieve of 1000 μ m.Impregnated in this glass grain in the ethanol and after carrying out ultrasonic cleaning, in thermostatic bath, carry out drying.On the platinum boat of width 12mm, length 200mm, degree of depth 10mm, so that the mode that above-mentioned glass grain 25g becomes constant thickness drops into the glass grain of drying.In having 1080～1320 ℃ the electric furnace of thermograde, keep this platinum boat 5 hours, thereafter, in stove, take out, result from the devitrification of glass inside with 50 times observation by light microscope.The top temperature of observing devitrification is made as devitrification temperature.

(the mean thermal expansion coefficients α in 100～300 ℃ the scope and the measuring method of Tg)

Use differential dilatometer (Thermo Plus2TMA8310), the temperature in the mensuration temperature-rise period and the stroke of glass.The heat-up rate of this moment is 5 ℃/min.Based on the measurement result of the stroke of said temperature and glass, measure mean thermal expansion coefficients and Tg in 100～300 ℃ the temperature range.

(density)

For the density of glass, by the Archimedian method above-mentioned Young's modulus working sample is measured.

(Young's modulus, than Young's modulus)

For Young's modulus, make the glass of thickness 5mm, measure by the ultrasonic pulse method.Calculated by Young's modulus and density than Young's modulus.

(melt temperature, liquid phase viscosity)

Melt temperature is that the temperature when calculating viscosity as 102.5dPas according to the measurement result of using the automatic viscosimeter of platinum ball pull-type obtains.Liquid phase viscosity is to obtain according to the viscosity that the said determination result calculates under the devitrification temperature.

(than resistance)

Use the 4192A LF impedance analysis device of Hewlett-Packard Corporation's manufacturing and utilize four-terminal method to measure, calculate 1550 ℃ ratio resistance value according to the said determination result.

The composition of glass (mol%), devitrification temperature (℃), annealing point (℃), strain point (℃), mean thermal expansion coefficients (* 10 ^-7℃ ^-1), density (g/cm ³), Young's modulus (GPa), than Young's modulus, melt temperature (℃), liquid phase viscosity (dPas), Tg (℃) and more as shown in table 1 than resistance (Ω cm).

[table 1]

The temperature variation of glass ribbon GR among the expression cooling step S4 in table 2～5 (℃) and the average cooling rate (℃/second) of the central part C of the measured value of required time (second) of temperature variation and glass ribbon GR.Average cooling rate (℃/second) among the table 2～table 5 expression S42 (annealing point is to the scope of the temperature of strain point-50 ℃) is respectively 0.9,1.1,2.9, and 5.1 o'clock value.And then the average cooling rate (℃/second) among the table 8 expression S42 is respectively 0.9,1.1,2.9, and 5.1 situation under the percent thermal shrinkage of the glass substrate that manufactures.

[table 2]

[table 3]

[table 4]

[table 5]

Embodiment 2

The composition of glass (mol%), devitrification temperature (℃), annealing point (℃), strain point (℃), mean thermal expansion coefficients (* 10 ^-7℃ ^-1), density (g/cm ³), Young's modulus (GPa), than Young's modulus, melt temperature (℃), liquid phase viscosity (dPas), Tg (℃) and more as shown in table 1 than resistance (Ω cm).And the width of glass ribbon GR is 1600mm, and thickness is 0.7mm.

The temperature variation of glass ribbon GR among the table 6～7 expression cooling step S4 (℃) and the average cooling rate (℃/second) of the central part C of the measured value of required time (second) of temperature variation and glass ribbon GR.Table 6～7th, the average cooling rate (℃/second) among the expression S42 are respectively 2.1, reach 3.0 o'clock value.And then, in the table 8 average cooling rate (℃/second) of expression among the S42 be respectively 2.1, and 3.0 situation under the percent thermal shrinkage of the glass substrate that manufactures.

[table 6]

[table 7]

[table 8]

According to the result shown in the table 8 as can be known, the average cooling rate in the 2nd cooling step is 0.5～less than between 5.5 ℃/second the time, can obtain percent thermal shrinkage is the following glass substrate of 60ppm.

Comparative example

The temperature variation of glass ribbon GR among the table 9 expression cooling step S4 (℃) and the measured value of required time (second) of temperature variation, based on the measured value interpolation about the value (interpolate value) of the time till arriving annealing point (715 ℃), strain point-50 ℃ (610 ℃), reaching strain point-200 ℃ (460 ℃) and the speed of cooling (℃/second) of central part C.

Among the cooling step S4, be that speed of cooling among maximum value, the 3rd cooling step S43 is that speed of cooling among second largest value, the 2nd cooling step S42 is that the mode of minimum value is implemented cooling step with the speed of cooling among the 1st cooling step S41.The percent thermal shrinkage of the glass substrate that obtains is as shown in table 8 to be 86ppm.

[table 9]

Claims

1. the manufacture method of a glass for flat panel display substrate, this method comprises:

(1) fusion step, the blending raw material so that in the glass substrate of manufacturing the resultant of SrO and BaO have strain point more than 675 ℃ less than 8 quality % and this glass substrate, fuse;

(3) cooling step, (A) cools off the glass ribbon that moulding obtains with following condition, (A) average cooling rate till the temperature from annealing point to (strain point-50 ℃): 0.5 ℃/second～less than 5.5 ℃/second.

2. the manufacture method of glass for flat panel display substrate as claimed in claim 1, wherein, in fusion step (1), the blending raw material is so that (SiO in the glass substrate of manufacturing ₂+ 2 * Al ₂O ₃)/B ₂O ₃Show the mol ratio more than 9.5.

3. the manufacture method of glass for flat panel display substrate as claimed in claim 1 or 2, wherein, for the glass substrate that forms via cooling step (3) manufacturing,, kept 1 hour at 550 ℃ with 10 ℃ of/minute intensifications from normal temperature, with 10 ℃/minute be cooled to normal temperature thereafter, again with 10 ℃ of/minute intensifications, kept 1 hour at 550 ℃, be cooled to normal temperature with 10 ℃/minute after, the percent thermal shrinkage of being represented by following formula is below the 75ppm

4. the manufacture method of a glass for flat panel display substrate, this method comprises:

(3) cooling step, (A) cools off the glass ribbon that moulding obtains with following condition, (A) from light the average cooling rate till the temperature of (strain point-50 ℃) less than annealing: 0.5 ℃/second～less than 5.5 ℃/second.