JP3277132B2 - Manufacturing method of liquid crystal display element - Google Patents

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 a liquid crystal display device, and more particularly to a pressing method in a bonding step.

[0002]

2. Description of the Related Art In a manufacturing process of a liquid crystal display element, there is a bonding step of bonding a pair of substrates on which electrodes are formed via a sealing material and a spacer. In this bonding step, the gap between the pair of substrates (hereinafter referred to as a cell gap) is determined. If there is slight unevenness in the cell gap, display unevenness appears when the liquid crystal display element is turned on. Therefore, it is very important to make the cell gap uniform and to bond the cells.

Therefore, conventionally, in this laminating step,
After bonding a pair of electrode substrates via a sealing material provided around a display portion of the liquid crystal display element and a spacer uniformly dispersed in the display area, a plurality of pairs of the bonded electrode substrates are laminated. The cell gap is controlled by using a press machine or by evacuating the space between the substrates to perform the pressurization using the atmospheric pressure and heating at the same time. Typically,
A thermosetting resin containing glass beads or the like is used for the sealing material, and glass beads or plastic beads are used for the spacer.

In a method of pressing a substrate, when a press is used, the parallelism of the pressed surfaces may be deviated, or a foreign substance may be present between one pair of substrates and another pair of substrates. In some cases, a pressurizing method using atmospheric pressure is more preferable because a problem that the pressurizing is not performed may occur.

[0005] By the way, when bonding the electrode substrates, if the pressure and the heating are not balanced, the cell gap may become non-uniform. If the cell gap is non-uniform, a color shift occurs when a display is performed. For example, in Japanese Patent Application Laid-Open No. 7-64101, a predetermined temperature before the temperature reaches the curing temperature of the sealing material by heating is described. In Japanese Patent Application Laid-Open No. H11-157, a technique is disclosed in which the pressurizing pressure is continuously or stepwise changed from a predetermined high pressure to a predetermined low pressure to maintain a uniform cell gap.

[0006]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-64101, when the substrate is heated, the temperature is continuously changed from room temperature to the curing temperature of the sealing material. There is a problem that it is difficult to uniformly heat the entire surface. That is,
In the case of performing the bonding in which the substrate is pressurized by using the atmospheric pressure, the heating of the substrate is performed by blowing hot air from an outlet provided in the chamber and supplying heat to the substrate by circulating the hot air. However, the way in which heat is applied differs between the part near the hot air outlet and the part far from it. In general, the hot air outlet is provided on one side of the substrate housed in the chamber facing the short side direction, and the hot air blown out from the outlet is circulated along the longitudinal direction of the substrate. Has become.

FIG. 6 is a diagram showing how heat is applied to a portion near and far from the hot air outlet of the substrate put into the chamber. As can be seen from FIG. 6, the portion close to the hot air outlet is heated almost according to the set temperature in the chamber, but the portion far from the hot air outlet is heated out of the set temperature in the chamber. You can see that there is.

As described above, when unevenness occurs in the heating of the substrate, the following various problems occur.

First, in the process of curing the sealing material by heating, if impurities such as an organic solvent are present in the sealing material, these impurities are vaporized by heating, but after the sealing material starts to be cured, When the impurities are vaporized, the vaporized impurities are trapped in the sealing material,
So-called bubbles are generated. In addition, the vaporized impurities continue to expand thereafter, and when ruptured in the sealing material, the sealing edge is disturbed. Therefore, in the portion of the electrode substrate that is likely to be heated, the time to reach the curing start temperature of the sealing material is short, so that the above-described bubbles and the disorder of the sealing edge are likely to occur.

Second, in the process of heating the substrate,
Since gas is generated from the overcoat film formed on the substrate and air existing in the substrate expands, the pressure between the substrates is slightly higher than the set value. The pressure between the substrates can be brought close to the set value by continuously exhausting the space between the substrates. However, if there is unevenness in the heating of the substrates, the timing at which the sealing material hardens is partially different. The cell gap becomes larger only in the portion where the sealing material has hardened before the pressure reaches the set value as compared with the in-plane portion.

[0011] The above-mentioned problem becomes remarkable especially when the substrate size is increased.

The present invention has been made in view of the above-mentioned problems, and suppresses generation of bubbles in a seal material and disturbance of a seal edge, and has excellent cell gap uniformity between the vicinity of the seal material and an in-plane. It is intended to provide a method for manufacturing a liquid crystal display element.

[0013]

According to a first aspect of the present invention, there is provided a method of manufacturing a liquid crystal display element, comprising: bonding a pair of electrode substrates via a thermosetting sealing material and a spacer; By evacuation between the pair of electrode substrates while heating, a method of manufacturing a liquid crystal display element in which a cell gap is controlled by applying pressure by atmospheric pressure, wherein the heating is performed by:
The method is characterized in that the method includes a step of maintaining the sealing material at a first temperature, which is a curing start temperature , for a predetermined time, and thereafter, heating the sealing material to a second temperature, which is a curing end temperature.

According to a second aspect of the present invention, in the method for manufacturing a liquid crystal display element according to the first aspect , before the pair of electrode substrates reach the first temperature by the heating. In addition, the pressure between the pair of electrode substrates is
It is characterized by reaching 450 Torr .

According to a third aspect of the present invention, in the method for manufacturing a liquid crystal display element according to the second aspect, the pair of electrode substrates are heated to the second temperature by the heating. Before the pressure reaches the pressure between the pair of electrode substrates.
The pressure is higher than 450 Torr .

According to a fourth aspect of the present invention, in the method for manufacturing a liquid crystal display element according to the second or third aspect, the heating reaches the first temperature and the second temperature.
The pressure between the pair of electrode substrates is set within a range of 450 Torr or more and 600 Torr or less until the heating at a predetermined temperature is completed .

The operation of the above configuration will be described below.

According to the method of manufacturing a liquid crystal display device according to the first aspect of the present invention, when heating the pair of electrode substrates from room temperature to the temperature at which the sealing material has been cured, the predetermined temperature which is equal to or lower than the curing start temperature of the sealing material. By maintaining the temperature once, the temperature difference between the entire surfaces of the pair of electrode substrates can be reduced.

Further, according to the method of manufacturing a liquid crystal display element of the present invention, the gas generated from the overcoat film by heating the electrode substrate and the air expanding between the pair of electrode substrates are sealed. It can be sufficiently removed before the material hardens, and the difference in cell gap between the vicinity of the sealing material and the surface of the substrate can be reduced.

Further, according to the method of manufacturing a liquid crystal display device according to the third aspect of the present invention, by reducing the pressure applied to the substrate before the sealing material is cured, when the sealing material is actually cured, It is possible to prevent the spacer included in the sealing material from being sunk into the overcoat film.

Further, according to the method of manufacturing a liquid crystal display device of the present invention, the pressure between the substrates is set to 450
By setting it to rr or more, it is possible to prevent the spacer from being deformed, and by setting it to 600 Torr or less, it is possible to control the cell gap reliably.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a view showing a state of bonding substrates in a method of manufacturing a liquid crystal display element of the present invention.
2 is an electrode substrate, 3 is a sealing material, 4 is a spacer, 5 is a clamp jig, and 6 is an exhaust port. In FIG. 1, the air between the pair of electrode substrates 1 and 2 is exhausted from the exhaust port 6 while applying heat to the electrode substrates 1 and 2, and the pair of electrode substrates 1 and 2 are exhausted.
By lowering the pressure inside 2, the pair of electrode substrates 1 and 2 are uniformly pressed by the atmospheric pressure on the outer surface thereof, and the gap is controlled.

Hereinafter, a method of manufacturing the liquid crystal display device according to the present embodiment will be described.

First, a predetermined transparent electrode pattern is formed on a translucent substrate, an overcoat film and an alignment film are formed, and then an alignment process is performed to form electrode substrates 1 and 2.
The electrode substrates 1 and 2 are bonded via a thermosetting sealing material 3 and a spacer 4 as shown in FIG.

Next, the peripheral portions of the bonded pair of electrode substrates 1 and 2 are inserted into a chamber by sandwiching them with a clamp jig 5 and heated, and at the same time, the gap between the pair of electrode substrates 1 and 2 is removed. Is exhausted from the exhaust port 6, and the pair of electrode substrates 1,
2 is pressurized.

At this time, as shown in FIG. 2A, the heating is not changed continuously from the room temperature to the curing end temperature T2 of the sealing material 3, but is changed stepwise.
That is, the sealing material 3 is maintained at a predetermined temperature equal to or lower than the curing start temperature T1 for a certain time.

At this time, FIG. 2B shows a state where a portion near the hot-air outlet is heated, and FIG. 2C shows a state where a portion far from the hot-air outlet is heated. As described above, by performing the heating stepwise, (b) of FIG.
As shown in (c), the temperature difference between the entire surface of the electrode substrates 1 and 2 between the portion near the hot air outlet and the portion far from the hot air outlet can be suppressed.

In order to evaporate impurities such as an organic solvent contained in the sealing material 3 and remove the impurities from the sealing material 3 while maintaining the predetermined temperature for a certain time, the predetermined temperature is as high as possible. Is more desirable. In addition, the time maintained at this temperature needs to be a uniform temperature over the entire surface of the electrode substrates 1 and 2 and a time required to completely remove impurities contained in the sealing material 3.

As described above, the temperature difference between the entire surfaces of the electrode substrates 1 and 2 is kept small, and before the sealing material 3 starts to be cured, it is maintained at a predetermined temperature equal to or lower than the curing start temperature of the sealing material 3 for a certain period of time. Accordingly, the timing of curing of the sealing material 3 can be made substantially the same on the entire surface of the electrode substrates 1 and 2, and impurities vaporized in the sealing material 3 cause disturbance of the sealing edge from the sealing material 3 before curing. It can be removed without any problem. Further, an overcoat film (not shown) formed on the electrode substrates 1 and 2 by the heating.
Since the gas generated from the air and the air expanding between the electrode substrates 1 and 2 can be discharged before the sealing material 3 is cured, the gap between the pair of electrode substrates 1 and 2 is made uniform. Becomes possible.

In the pressurization, the gap can be controlled more uniformly as the pressure is increased.
If the pressure between the pair of electrode substrates 1 and 2 is excessively reduced in order to increase the pressure applied to the pair of electrode substrates 1 and 2, the spacer 4 provided between the pair of electrode substrates 1 and 2
Also, the electrode substrates 1 and 2 themselves are deformed. Therefore, the pressure between the pair of electrode substrates 1 and 2 is 450 Torr.
It is preferable to select from the range of r to 600 Torr.

When a liquid crystal material is injected between the pair of electrode substrates 1 and 2 bonded as described above, and a peripheral circuit, a backlight and the like are incorporated into the liquid crystal display element, generation of bubbles from the sealing material 3 In addition, since there is no problem and the seal edge is not disordered and the cell gap does not vary, a liquid crystal display device having excellent reliability and display quality can be obtained.

The heating / pressing profile in the present embodiment will be described in detail in the examples described later.

(Embodiment 2) The state of bonding substrates in the method of manufacturing a liquid crystal display element of the present embodiment is the same as that of Embodiment 1 shown in FIG.

Next, a method of manufacturing the liquid crystal display device according to the present embodiment will be described.

First, a predetermined transparent electrode pattern is formed on a translucent substrate, an overcoat film and an alignment film are formed, and then an alignment process is performed to form electrode substrates 1 and 2.
The electrode substrates 1 and 2 are bonded via a thermosetting sealing material 3 and a spacer 4 as shown in FIG.

Next, the peripheral portions of the bonded pair of electrode substrates 1 and 2 are inserted into a chamber by sandwiching them with a clamp jig 5 and heated, and at the same time, the gap between the pair of electrode substrates 1 and 2 is heated. Is exhausted from the exhaust port 6 to press the pair of electrode substrates 1 and 2.

At this time, the heating is changed stepwise as in the first embodiment. In addition, the pressurization of the electrode substrates 1 and 2 is performed by first increasing the pressure between the electrode substrates 1 and 2.
After the pressure is maintained at a second pressure higher than this, and before the heating reaches the curing end temperature of the sealing material, the pressure between the electrode substrates 1 and 2 is reduced to the second pressure. Try to reach pressure.

By doing so, the spacers 4 contained in the sealing material 3 do not sink into the overcoat film (not shown) provided on the electrode substrates 1 and 2, and a more uniform cell gap Can be obtained.

When a liquid crystal material is injected between the pair of electrode substrates 1 and 2 bonded as described above, and a peripheral circuit, a backlight and the like are incorporated into the liquid crystal display element, generation of bubbles from the sealing material 3 In addition, since the liquid crystal display element has no defects, the seal edge is not disordered, and the cell gap does not vary, a liquid crystal display device having more excellent reliability and display quality can be obtained.

The heating / pressing profile in the present embodiment will be described in detail in the examples described later.

[0041]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, the heating / pressing profile described in the first embodiment will be described. In addition,
In the present embodiment, the sealing material 3 used in the first embodiment is a material whose viscosity starts to increase after 100 ° C. and starts to harden, and is completely hardened at 150 ° C.

FIG. 3 shows a heating / pressing profile in the bonding step of the electrode substrate in this embodiment. In addition,
In the figure, the solid line indicates the pressure profile, and the dashed line indicates the heating profile.

The heating profile in FIG.
Starting from room temperature, the curing start temperature of the sealing material is 100
C. (hereinafter referred to as a predetermined temperature T1). In this embodiment, the temperature is set so as to reach the predetermined temperature T1 in 20 minutes from the normal temperature.

Next, the predetermined temperature T1 is maintained for a predetermined time. In this embodiment, the temperature is set to be maintained at the predetermined temperature T1 for 10 minutes. This time is based on the electrode substrates 1, 2
It is selected so that the entire surface reaches the predetermined temperature T1 and impurities in the sealing material 3 are completely removed.

Further, from the predetermined temperature T1, the sealing material 3
Is continuously heated to 150 ° C. (hereinafter referred to as thermosetting temperature T2) which is the temperature at the end of curing. In this embodiment, the temperature is set so as to reach the thermosetting temperature T2 in 30 minutes from the predetermined temperature T1.

Further, the heating profile is maintained at the thermosetting temperature T2 for a certain period of time, and the heating profile is completed. In this embodiment, the heat curing temperature T2 is maintained for 60 minutes.

The pressing profile in FIG.
It starts in synchronization with the heating profile. First, the pressure between the electrode substrates 1 and 2 is increased from atmospheric pressure to 4
The electrode substrates 1 and 2 are pressurized by continuously evacuating until the pressure reaches 50 Torr (hereinafter referred to as a first pressure P1). In this embodiment, the pressure is set to 450 Torr in 10 minutes from the atmospheric pressure. In addition,
The unit of pressurization in FIG. 3 indicates the pressure between the electrode substrates 1 and 2 in an atmospheric pressure atmosphere. Therefore,
The smaller the value, the greater the pressure.

Then, the pressure between the electrode substrates 1 and 2 is increased to 4
The pressure is maintained for a certain period of time while maintaining the pressure at 50 Torr, and the pressurization profile ends. In this embodiment, in order to synchronize with the heating profile, the pressure is maintained at 450 Torr for 110 minutes.

Further, an after-baking process is performed on the bonded electrode substrates 1 and 2, a liquid crystal material is injected between the pair of electrode substrates 1 and 2, and a peripheral circuit, a backlight, and the like are incorporated into the liquid crystal display element. Was completed.

The liquid crystal display device thus manufactured is heated stepwise in the step of bonding the electrode substrates 1 and 2, and before the heating reaches a predetermined temperature T1, the pressure is reduced. By reaching the desired pressure, the entire surface of the electrode substrates 1 and 2 is uniformly heated,
Gas generated from the overcoat film by heating and air expanding between the substrates could be efficiently discharged, so that no bubbles were generated from the sealing material 3 and the seal edge was not disturbed. There was no gap unevenness between them, and it was excellent in reliability and display quality.

Embodiment 2 Another embodiment of the present invention will be described below with reference to FIG.

In this embodiment, the heating / pressing profile described in the second embodiment will be described. In addition,
In this example, the same material as in Example 1 was used as the sealing material 3 in Embodiment 2 described above.

FIG. 4 shows a heating / pressing profile in the electrode substrate bonding step in this embodiment. In addition,
In the figure, the solid line indicates the pressure profile, and the dashed line indicates the heating profile.

The heating profile in FIG. 4 is the same as that described in the first embodiment, and the description is omitted.

The pressure profile in FIG. 4 starts in synchronization with the heating profile. First, the pressure between the electrode substrates 1 and 2 is changed from atmospheric pressure to 4 pressure.
The electrode substrates 1 and 2 are pressurized by continuously evacuating until the pressure reaches 50 Torr (hereinafter referred to as a first pressure P1). In the present embodiment, the first pressure P1 is set in 10 minutes from the atmospheric pressure.

Next, the first pressure P1 is maintained for a certain time. In the present embodiment, it was set to be maintained for 10 minutes.

Further, the pressure between the pair of electrode substrates 1 and 2 is changed from the first pressure P1 to 600 Torr (hereinafter referred to as a second pressure P2). In the present embodiment, the second pressure is applied for 10 minutes from the first pressure P1.
The pressure was set to be P2.

Then, the pressure is maintained at the second pressure P2 for a certain period of time, and the pressurization profile ends. In this embodiment, the second pressure P2 is maintained for 90 minutes in order to synchronize with the heating profile.

Further, an after-baking process is performed on the bonded electrode substrates 1 and 2, a liquid crystal material is injected between the pair of electrode substrates 1 and 2, and a peripheral circuit, a backlight, and the like are incorporated. Was completed.

The liquid crystal display device thus manufactured is heated stepwise in the step of bonding the electrode substrates 1 and 2, and before the heating reaches a predetermined temperature T1, the pressure is reduced. Desired pressure (ie, first pressure P1)
And before the heating reaches the curing end temperature of the sealing material, the pressure is increased to the first pressure P1.
By making the second pressure P2 slightly higher than the above, the entire surface of the substrate is uniformly heated as in the liquid crystal display element shown in Embodiment 1, and the gas or substrate generated from the overcoat film by the heating is heated. The air that expands between the air was efficiently discharged, and the pressure was slightly reduced when the sealing material hardened, so no bubbles were generated from the sealing material or the seal edge was disturbed. There was no gap unevenness between the substrate and the surface, and the spacer did not sink into the overcoat film, and was excellent in reliability and display quality.

Next, as a comparative example of the present invention, a case where the heating profile is continuously performed from the normal temperature to the temperature at which the curing of the sealing material is completed will be described with reference to FIG.

(Comparative Example 1) FIG. 5 shows a heating / pressing profile showing a comparative example with respect to Examples 1 and 2. In the figure, the solid line indicates the pressure profile, and the dashed line indicates the heating profile.

The pressure profile in this comparative example is the same as the pressure profile in Example 2 described above. Further, the heating profile is one that is continuously changed from the normal temperature to the curing end temperature of the sealing material in 60 minutes.

An electrode substrate is bonded in accordance with the heating / pressing profile shown in FIG. 5, an after-baking process is performed on the pair of bonded electrode substrates 1 and 2, and a liquid crystal material is interposed between the pair of electrode substrates 1 and 2. And a liquid crystal display element was completed by incorporating a peripheral circuit, a backlight, and the like.

In the liquid crystal display device manufactured in this manner, since the entire surface of the substrate could not be uniformly heated, air bubbles were generated in the sealing material 3 or the seal edge was disturbed in the rapidly heated portion. There has occurred. Also,
Since the timing at which the sealing material 3 cures differs over the entire surface of the substrate, the cell gap in the portion where the sealing material 3 is cured before the gas generated from the overcoat film or the air expanded by heating is sufficiently exhausted is larger than the in-plane. It has grown.

Table 1 shows the evaluations of the liquid crystal display elements which were subjected to the laminating process according to the heating and pressing profiles in Examples 1 and 2 and Comparative Example 1.

[0068]

[Table 1]

As can be seen from Table 1, in the bonding step of the electrode substrate in the manufacturing process of the liquid crystal display element, the heating profile is not stepwise but stepwise.
The entire surface of the substrate can be heated almost uniformly. Therefore, it is possible to suppress the generation of air bubbles in the sealing material and the disturbance of the sealing edge, and to make the cell gap uniform in the plane with the sealing portion.

In the above-described first and second embodiments, numerical values such as setting the predetermined temperature T1 to 100 ° C. and setting the time from normal temperature to the predetermined temperature T1 to 10 minutes are given. The numerical value may be selected so as to be optimal according to the material of the resin included in the sealing material and the size of the substrate.

[0071]

As described above, according to the method of manufacturing a liquid crystal display element of the present invention, a pair of electrode substrates is bonded via a thermosetting sealing material and a spacer. In the method for manufacturing a liquid crystal display element in which a cell gap is controlled by evacuating the pair of electrode substrates while heating to thereby control the cell gap by applying pressure by the atmospheric pressure, the first heating is a first temperature at which the sealing material starts to cure. By maintaining the temperature at the temperature for a certain period of time, and then heating the sealing material to the second temperature, which is the temperature at which curing of the sealing material ends, the temperature difference over the entire surface of the substrate can be suppressed to a small value.

Therefore, there is no portion where the sealing material provided on the substrate is rapidly heated, so that there is no effect that air bubbles are generated and the sealing edge is not disturbed in this portion. Further, since the sealing material provided on the substrate is cured almost at the same time, there is an effect that gap unevenness due to partially different curing timings can be eliminated.

Further, since the pressure between the pair of electrode substrates reaches 450 Torr before the pair of electrode substrates reaches the first temperature by the heating, heat is generated from the overcoat film by the heating. Gas and air expanded between the electrode substrates can be efficiently exhausted before the sealing material is cured.

Therefore, when the sealing material is cured, no residual gas remains between the electrode substrates, and the pressure between the electrode substrates can be set to a desired pressure. To prevent the occurrence of
There is an effect that the cell gap can be made uniform.

Further, by the heating, the pressure between the pair of electrode substrates reaches a pressure higher than 450 Torr before the pair of electrode substrates reaches the second temperature, whereby the sealing material is hardened. Sometimes, the spacer can be prevented from sinking into the overcoat film, so that the cell gap can be made more uniform.

Further, when the heating reaches the first temperature and the second
The pressure between the pair of electrode substrates is set within the range of 450 Torr or more and 600 Torr or less until the heating at the temperature of the above is completed, so that deformation of the spacer due to excessive pressurization can be prevented. In addition, there is an effect that the cell gap can be reliably controlled.

[Brief description of the drawings]

FIG. 1 is a view showing a state of bonding substrates in a method of manufacturing a liquid crystal display element.

FIG. 2 is a diagram showing a state of heating a substrate in a portion near a hot-air outlet and a portion far from the hot-air outlet in the present invention.

FIG. 3 is a diagram showing a heating / pressing profile in a method for manufacturing a liquid crystal display element according to one embodiment of the present invention.

FIG. 4 is a view showing a heating / pressing profile in a method of manufacturing a liquid crystal display element according to another embodiment of the present invention.

FIG. 5 is a diagram showing a heating / pressing profile in a comparative example of the present invention.

FIG. 6 is a diagram illustrating a state of heating the substrate in a portion near the hot air outlet and a portion far from the hot air outlet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode board 2 Electrode board 3 Seal material 4 Spacer 5 Clamp jig 6 Exhaust port

Claims (4)

(57) [Claims] 1. A pair of electrode substrates are bonded together via a thermosetting sealing material and a spacer, and the pair of electrode substrates is evacuated while heating the pair of electrode substrates.
In a method for manufacturing a liquid crystal display element in which a cell gap is controlled by applying pressure by atmospheric pressure, the heating is maintained at a first temperature, which is a curing start temperature of a sealing material, for a certain period of time, and thereafter, at a curing end temperature of the sealing material. A method for manufacturing a liquid crystal display element, comprising a step of heating to a certain second temperature. 2. The liquid crystal according to claim 1, wherein the pressure between the pair of electrode substrates reaches 450 Torr by the heating before the pair of electrode substrates reaches the first temperature. A method for manufacturing a display element. 3. The pressure between the pair of electrode substrates reaches a pressure higher than 450 Torr by the heating before the pair of electrode substrates reaches a second temperature. The liquid crystal display device according to the above. 4. The method according to claim 1, wherein said heating reaches a first temperature and a second temperature.
Until the end the heating in degrees, pressure between the pair of electrode substrates, the production of liquid crystal display device according to claim 2 or 3, wherein it is set in the 600Torr following range of 450Torr Method.