JP2006251446A - Manufacturing method for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a liquid crystal display device in which display defects such as stains and unevenness are excellently prevented with relatively simple device constitution without using a cleaning agent such as a solvent and a surface active agent nor lowering production efficiency. <P>SOLUTION: Disclosed is the manufacturing method for the liquid crystal display device which includes a processing stage of filming a surface of a substrate W with pure water of ≤5 MΩm in specific resistance by making the pure water flow down in a curtain state at a nearly constant flow rate along the direction orthogonal to the conveying direction of the substrate while conveying the substrate W as a starting washing process in a washing stage carried out after an alignment film is formed on the substrate by coating and the rubbed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a liquid crystal display device, which prevents display defects such as spots and unevenness caused by foreign matters generated during rubbing.

  In general, a liquid crystal display device is configured by bonding a color filter substrate having RGB colors and a TFT substrate having transistors to form a cell, and injecting liquid crystal into the cell. . An alignment film is applied to the inner surface of the color filter substrate and the TFT substrate (hereinafter simply referred to as “substrate”).

  A general alignment film is a polyamic acid which is a polyimide and a precursor of polyimide, and a relief printing method or a spin coating method is usually employed as a method for applying the alignment film. The alignment film applied to the substrate is baked in an oven at 170 to 250 ° C. for about 10 minutes to 3 hours. The purpose of this firing is to make the film denser by using solvent when polyimide is used. When polyamic acid is used, the solvent is removed and the polyamic acid is hydrolyzed to form polyimide. Is to make it.

  Further, the position where the alignment film is formed on the substrate is limited only to the central portion of the substrate in terms of the manufacturing method of the liquid crystal display device. In addition, in the case of a large-sized substrate with multiple chamfers, that is, a substrate having a large number of single substrates separated by dicing (large substrate), each single substrate is oriented only at its central portion. A film is formed. Therefore, there is a portion where the substrate surface is exposed around the alignment film thus formed. The reason why the alignment film is formed only in the central part of the substrate is that the lead-out wiring connecting the TFT substrate and the module terminal is located around the alignment film, and a sealing material for bonding the two substrates is applied. This is because a part to be used is required. In addition, the material of the outermost surface of the substrate exposed portion is a wiring metal material such as a Cr / Al / Mo / ITO film, an insulating film material such as SiNx / SiOx or an organic insulating film, or glass.

  Next, the substrate with the alignment film is subjected to a rubbing process for aligning the alignment film molecules in one direction. The rubbing treatment is a step of rubbing the alignment film with a roll wound with a rubbing cloth. At this time, the exposed portion of the substrate located around the alignment film as well as the alignment film surface is rubbed at the same time. As the rubbing cloth material, cotton rayon or the like is generally used. In the rubbing process with this physical phenomenon, the shavings of the alignment film inevitably become a problem. The degree of scraping varies depending on the orientation film hardness, cloth hardness, and rubbing conditions (roll pressing amount, roll rotation speed, table or roll moving speed), but the shavings are still a problem.

  After the rubbing process, the substrate is cleaned. The purpose is to remove fibers (rubbing residue) and rubbing chips (polyimide residue) from the alignment film. Note that the shavings (polyimide residue) of the alignment film usually adheres to the rubbing cloth once treated with the alignment film, and then adheres again or is adsorbed onto the substrate surface on which the alignment film is not formed. At this time, fibers (rubbing residue) that have come off from the rubbing cloth are also attached or adsorbed together on the substrate surface on which the alignment film is not formed.

As a cleaning process after the rubbing process, for example, Patent Document 1 includes a process of first removing foreign matter with an air knife or the like, secondly covering the substrate surface with pure water, and thirdly cleaning with a cleaning agent. A method for cleaning a substrate is disclosed.
Patent Document 2 discloses a liquid crystal display having a step of flowing pure water on the surface from the central portion of the substrate toward the peripheral portion to reduce the adsorption activity of the alignment film surface, and a step of performing cleaning by pure water shower processing thereafter. An apparatus manufacturing method is disclosed.
JP-A-7-77777 Japanese Patent No. 3198504

  However, in the substrate cleaning method of Patent Document 1, since the cleaning process is performed using a cleaning agent in particular, there is a problem that the rinsing must be sufficiently performed, and thus the production efficiency is lowered. Further, there is a problem that the apparatus configuration becomes complicated in order to prevent elution of the silane coupling agent in the underlayer.

  On the other hand, in the manufacturing method of the liquid crystal display device of Patent Document 2, since the cleaning water is spread from the central portion of the substrate toward the peripheral portion, a single-sided substrate or a unit substrate in which the substrate becomes a unit substrate as it is. Although effective for a substrate of about 2 to 3 substrates (a substrate having about 1 to 3 large unit substrates of relatively large size), a large number of medium and small unit substrates (for example, 5 It is difficult to apply this method to a substrate having more than one) because a large number of nozzles are required. That is, in order to spread the cleaning water on the substrate by setting the nozzle shower injection angle to 60 to 120 °, it is necessary to configure the nozzle shower so that the nozzle shower does not interfere with each other in a substrate having a large number of medium and small substrates. The structure of the apparatus becomes complicated and its control becomes very difficult, and as a result, the practicality is extremely low. In addition, this manufacturing method has a problem that the production efficiency is low because the processing is basically performed without carrying out the processing while the substrate is transported, but in a stopped state.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to use a relatively simple apparatus configuration without using a cleaning agent such as a solvent or a surfactant, and without reducing the production efficiency. Another object of the present invention is to provide a method of manufacturing a liquid crystal display device that can prevent display defects such as unevenness and unevenness.

As a result of intensive studies to achieve the above object, the present inventor obtained the following knowledge and completed the present invention based on this knowledge.
In general, the surface of the alignment film (polyimide film) immediately after rubbing is in a very active state as a result of rearrangement such as bond breaking and molecular chain extension when viewed at the molecular level. Then, the cut and rearranged portions of molecules in such an active state become adsorption sites such as rubbing residue and polyimide residue generated during rubbing, causing spots and unevenness by adsorbing these, resulting in This is thought to cause display defects.

  As a method for suppressing and avoiding such display defects, it is considered that when the alignment film surface is in an active state that functions as an adsorption site, foreign materials such as rubbing residue and polyimide residue are not brought into contact with the alignment film surface. One possible method is to inactivate the alignment film surface after rubbing. It should be noted that foreign matters such as rubbing residue and polyimide residue are attached or adsorbed on the substrate surface on which the alignment film is not mainly formed as described above.

As a method of inactivating the alignment film surface after rubbing, a method of leaving the surface in the atmosphere for a long time and hydrating the surface can be considered. However, in this method, in terms of panel manufacturing, throughput, siloxanes and phthalates derived from the clean room components contained in the clean room atmosphere, and other cleaning materials, sealing materials, and other organic substances caused by other process members are included. It is conceivable that the film adheres slightly to the alignment film surface from the atmosphere. Therefore, this method is not a good method for suppressing or avoiding the alignment unevenness.
Therefore, in the present invention, by forcibly reducing the adsorption activity of the alignment film, foreign matters such as rubbing residue and polyimide residue are promptly prevented from adsorbing on the alignment film surface, thereby preventing display defects such as spots and unevenness. did.

  That is, in the manufacturing method of the liquid crystal display device of the present invention, as the first cleaning process in the cleaning process after applying the alignment film on the substrate and rubbing it, the specific resistance is 5 MΩ · m or less pure water is flown down in a curtain shape at a substantially uniform flow rate in a direction orthogonal to the substrate transport direction, and the pure water is placed in a film form on the substrate surface. Yes.

  According to this method of manufacturing a liquid crystal display device, pure water is allowed to flow down in a curtain form and placed on the substrate surface in a film form, so that wetting unevenness is prevented. In addition, since pure water is placed on the surface of the substrate, the flow of pure water on the substrate surface is suppressed, so that the foreign water such as rubbing residue and polyimide residue moves to the alignment film surface due to the flow of pure water. Adhering to or adsorbing to the substrate is suppressed. Further, since pure water is deposited on the substrate surface in a film form without wetting unevenness, hydration occurs on the alignment film surface, and the function is deactivated from an active state that functions as an adsorption site. Therefore, even if the foreign matter on the substrate moves to the surface of the alignment film in the cleaning process after this processing step, it is prevented from being adsorbed here.

In particular, since pure water having a specific resistance of 5 MΩ · m or less is used, since this pure water has a certain degree of conductivity, static electricity is generated by molecular cutting or rearrangement on the alignment film surface immediately after rubbing. Even when a typical adsorption site is formed, the electrostatic activity can be deactivated by removing the charge from the adsorption site.
In addition, since pure water is used without using cleaning agents such as solvents and surfactants, it is not necessary to perform rinsing sufficiently, so production efficiency is high and production is also performed from the point of carrying out processing. Efficiency becomes good. Further, since the pure water is simply caused to flow down in the form of a curtain, the configuration of the apparatus is relatively simple.

Further, in the manufacturing method, it is preferable that the jumping direction when the pure water flows down is coincident with the transfer direction of the substrate, and in this case, the speed of the substrate transfer direction when the pure water flows is set to It is preferable to substantially match the transfer speed of the substrate.
Thus, if the flow direction of pure water is made coincident with the transfer direction of the substrate, when pure water is flowed down on the substrate surface, relative movement between the pure water and the substrate is reduced. It is possible to place pure water gently on the surface, so that the foreign matter is prevented from adhering to or adsorbing to the alignment film surface due to the flow of pure water, and further hydrated on the alignment film surface. Will happen more quickly.
Further, if the speed in the substrate transfer direction when the pure water flows is substantially equal to the substrate transfer speed, the relative movement between the pure water and the substrate is reduced.

In the manufacturing method, the substrate may be a multi-sided substrate.
Even if the substrate has a large number of medium and small unit substrates, for example, in the present invention, pure water is made into a curtain shape without using a nozzle that spreads cleaning water from the central portion of the substrate toward the peripheral portion. Since it is only necessary to have a device to flow down, the device configuration is simple and the control is very easy. Therefore, no matter how the unit substrates are arranged with respect to the substrate, it is possible and easy to cope with them.

Hereinafter, the manufacturing method of the liquid crystal display device of the present invention will be described in detail.
FIG. 1 is a diagram showing a schematic configuration of an example of an apparatus for carrying out a method for manufacturing a liquid crystal display device according to the present invention. Reference numeral 1 in FIG. 1 denotes a substrate cleaning apparatus. The substrate cleaning apparatus 1 is for performing cleaning after applying an alignment film on a substrate W and performing a rubbing process on the alignment film. The substrate cleaning apparatus 1 performs a first processing chamber 2 for performing a pre-cleaning process and a brushing process. A second processing chamber 3 for performing ultrasonic cleaning, a fourth processing chamber 5 for performing air knife cleaning and the like, and a fifth processing chamber 6 for performing a drying process. Are sequentially provided. The substrate cleaning apparatus 1 is provided with a transfer roller 7 for transferring the substrate W through the processing chambers 2 to 6 in a row, so that the substrate W can be transferred to the processing chambers 2 to 2. It is designed to pass through 6 spaces in this order.

  The first processing chamber 2 is a processing chamber for performing an initial cleaning process on the substrate W after the rubbing process, and is a processing chamber provided with a water supply device 8 for flowing pure water in a curtain shape. The water supply device 8 includes a rectangular parallelepiped box 9 and an overflow container 10 provided in the box 9, as shown in FIG. A slit 11 is formed in one long side on the bottom side of the box 9 along the long side direction, and this slit 11 serves as an outlet for allowing pure water to flow down.

  The overflow container 10 is formed with a first raised portion 12 a and a second raised portion 12 b along the long side direction of the box body 9. The overflow container 10 is formed between the first raised portion 12 a and the box body 9. One storage portion 13a is formed, and a second storage portion 13b is formed between the two raised portions 12a and 12b. The two raised portions 12a and 12b have a mountain shape in a side view, and the first raised portion 12a is formed higher than the second raised portion 12b. It is formed to have a uniform height. Based on such a configuration, the first storage portion 13 a and the second storage portion 13 b have a uniform depth shape in the length direction of the slit 11. The first and second reservoirs 13a and 13b are both stored in the reservoirs 13a and 13b because a side plate (not shown) of the box 9 is disposed on the side thereof. Pure water does not flow to the side.

  The second raised portion 12b is formed on the slit 11 side, and on the lower end edge of the inclined surface 14 on the opposite side of the second reservoir portion 13b of the second raised portion 12b, A slit 11 is formed. A pipe 15 is connected to a side plate of the box 9 that forms the first storage portion 13a, and a pure water storage tank 16 is connected to the pipe 15 via a pump (not shown). ing. The pure water storage tank 16 stores pure water having a specific resistance adjusted to 5 MΩ · m or less.

With this configuration, in the water supply device 8, when pure water is supplied from the pure water storage tank 16 through the pipe 15, the pure water is temporarily stored in the first storage unit 13 a. When pure water continues to be supplied, the pure water overflowing from the first reservoir 13a overflows over the first raised portion 12a and is stored in the second reservoir 13b. If pure water continues to be supplied, pure water also overflows in the second reservoir 13b, overflows over the first raised portion 12a, flows down the inclined surface 14, and flows down (outflows) from the slit 11. .
At this time, as described above, since the two storage portions 13a and 13b have a uniform depth shape in the length direction of the slit 11, the flow rate of pure water flowing down from the slit 11 is 11 is almost uniform in the length direction.

In addition, since the inclination angle of the inclined surface 14 in the 2nd protruding part 12b becomes a factor which determines the relative speed between the pure water and the board | substrate W which are supplied so that it may mention later, It is set to be.
Further, the water supply device 8 having such a configuration is arranged so that the length direction of the slit 11 coincides with the direction orthogonal to the transport direction of the substrate W indicated by an arrow in FIG. The first storage part 13a is on the rear side in the transport direction of the substrate W and the second storage part 13b is on the front side in the transport direction of the substrate W so as to be positioned on the transport direction side of the substrate W. Be placed. With such an arrangement, the flow direction (flow direction) of pure water supplied from the water supply device 8 in the horizontal direction, that is, the jumping direction at the time of flow, coincides with the transport direction of the substrate W.

  Of course, the water supply device 8 is disposed at a height at which the water supply device 8 does not interfere with the substrate W transported on the transport roller 7. At this time, the height position of the slit 11 is on the surface of the substrate W. On the other hand, it arrange | positions so that it may become the height which opened about 5-20 mm, for example, Preferably about 10 mm. Thus, by setting the height position of the slit 11 with a relatively small gap from the surface of the substrate W, the pure water flowing down from the slit 11 does not fall on the surface of the substrate W with a strong impact, It falls gently, and as a result, it comes to rest on the surface of the substrate W gently.

  In order to perform the first cleaning process on the substrate W after the rubbing process using the water supply apparatus 8 having such a configuration, the substrate W is transported in the arrow direction by the transport roller 7 as shown in FIG. . Further, in the pure water storage tank 16, as described above, the pure water adjusted to a specific resistance of 5 MΩ · m or less, in this embodiment 1 MΩ · m or less, preferably about 0.2 to 0.5 MΩ · m, Store it. By adjusting the specific resistance to 1 MΩ · m or less in this way, the electrostatic activity on the alignment film surface can be reliably deactivated as will be described later.

Here, as such pure water, the specific resistance is adjusted to the above value by a CO ₂ bubbler or the like with respect to ultrapure water having a specific resistance of about 18 MΩ · m used in a semiconductor manufacturing factory or the like. Preferably used. By using pure water whose specific resistance is adjusted in this way, the concentration of microparticles, microorganisms, and organic matter in the pure water are maintained at the same level as that of ultrapure water. This is preferable because unevenness and further stains and unevenness due to this are reliably prevented.

  Then, as described above, pure water is allowed to flow from the slit 11 by continuing to supply pure water from the pure water storage tank 16 to the water supply device 8. Then, since this pure water has a substantially uniform flow rate in the length direction of the slit 11, the pure water flows down in a curtain shape at a substantially uniform flow rate in a direction orthogonal to the transport direction of the substrate W. It will be a thing. In this way, the substrate W is transported under the state where pure water is allowed to flow, and passes under the slit 11. Then, the pure water flowing down from the slit 11 gently falls on the surface of the substrate W and is placed on the surface in a film form.

At this time, with respect to the amount of pure water supplied from the pure water storage tank 16 to the water supply device 8, the supply of pure water from the water supply device 8 to the substrate W determined by this supply amount is the slit 11 as described above. In the longitudinal direction, the flow rate is uniform and is made into a curtain shape, whereby the flow rate is such that pure water is gently placed on the surface of the substrate W in the form of a film.
For example, when the length of the slit 11 is 450 mm, the supply amount to the water supply device 8 (that is, the supply amount from the water supply device 8) is set to about 10 to 20 liters / minute. Further, the transport speed of the substrate W at this time is set to 1800 mm / min, for example. Note that the width of the substrate W is naturally equal to or less than the length of the slit 11, and when the length of the slit 11 is 450 mm as described above, the width of the substrate W is, for example, about 400 mm.

  Further, the flow rate in the horizontal direction of pure water supplied (flowed down) from the water supply device 8 is adjusted so as to substantially coincide with the transport speed of the substrate W. In other words, the flow rate of pure water supplied from the pure water storage tank 16 to the water supply device 8 and the inclination angle of the inclined surface 14 in the second raised portion 12b are appropriately set so as to be supplied to the substrate W. The flow rate of the pure water in the horizontal direction is substantially equal to the transport speed of the substrate W, thereby making the relative speed of both substantially zero. Accordingly, it is possible to realize a state in which the pure water supplied onto the substrate W is quietly placed on the surface of the substrate W and hardly flows on the surface of the substrate W.

In this way, when pure water flows down (drops) from the slit 11 of the water supply device 8 onto the surface of the substrate W in the form of a curtain and is placed on the surface in the form of a film, the pure water flows in the width direction of the substrate W (slit 11), the surface of the substrate W can be uniformly wetted with pure water without causing wetting unevenness.
Further, by placing pure water on the surface of the substrate W, it is possible to suppress the flow of the pure water on the surface of the substrate W. Therefore, foreign matter such as rubbing residue and polyimide residue is caused on the alignment film surface by the flow of the pure water. It can suppress moving and adhering or adsorbing here.

  In addition, since pure water is placed in a film form on the surface of the substrate W without wetting unevenness, hydration is caused on the surface of the alignment film, and the function is deactivated from an active state that functions as an adsorption site. it can. Therefore, in the processing (cleaning processing) after the second processing chamber 3 following the processing step in the first processing chamber 2, even if the foreign matter on the substrate W moves to the alignment film surface, it is adsorbed here. Can be prevented. Therefore, it is possible to prevent display defects such as spots and unevenness due to uneven alignment due to foreign matter adsorption.

In particular, since pure water having a specific resistance of 5 MΩ · m or less is used, this pure water has a certain degree of conductivity, so that molecules are cut or rearranged on the alignment film surface immediately after rubbing. Even when an electrostatic adsorption site is formed by this, electrostatic activity can also be deactivated by removing charges from this adsorption site.
In addition, even if the foreign matter moves to the alignment film surface and adheres thereto, the foreign matter is merely physically placed without being electrically or chemically adsorbed as described above, This can be easily removed by the cleaning process after the second processing chamber 3.
Moreover, according to such a cleaning process, since pure water is used without using a cleaning agent such as a solvent or a surfactant, it is not necessary to perform rinsing sufficiently. The production efficiency is also good from the point of carrying out the transfer. Further, since the pure water is simply caused to flow down in the form of a curtain, the configuration of the apparatus is relatively simple.

About the 2nd processing chamber 3-the 5th processing chamber 6 following this 1st processing chamber 2, the process similar to the past is performed fundamentally.
That is, as shown in FIG. 1, the second processing chamber 3 for performing the brushing process has the substrate W transported by the transport roller 7 after the surface of the alignment film is deactivated in the first processing chamber 2. The back surface is brushed by the rotating brush 17. During the brushing process, ultrapure water having a specific resistance of about 18 MΩ · m is supplied from the water supply pipe 18 to the surface of the substrate W. By supplying the ultrapure water in this manner, it is possible to remove mainly large foreign matters attached to the surface of the substrate W. Here, when removing the foreign matter by supplying the ultrapure water, the surface of the alignment film is deactivated in the first processing chamber 2 as described above. Therefore, even if the foreign matter passes over the surface of the alignment film. Then, it is washed out of the substrate W by ultra pure water without being adsorbed here. A pipe 19 is connected to the water supply pipe 18, and an ultrapure water storage tank 20 for storing ultrapure water is connected to the pipe 19 via a pump (not shown).

  In the third processing chamber 4 for performing the ultrasonic cleaning, the surface of the substrate W after the brushing process is processed by the cavitation jet 21, and subsequently, a high-frequency (megahertz) ultrasonic wave is applied. Processing with the sound wave 22 is performed. These ultrasonic treatments are also performed while supplying ultrapure water from the ultrapure water storage tank 20 to the surface of the substrate W through the pipe 19. The cavitation jet 21 mainly removes medium foreign matter, and the megasonic ultrasonic wave 22 mainly removes small foreign matter.

In the fourth processing chamber 5 for performing the air knife cleaning or the like, the surface of the substrate W after the ultrasonic treatment is ejected from the spray tube 23 to finally clean the surface of the substrate W. Subsequently, the air knife 24 connected to a pressurized air source (not shown) blows pressurized air toward the surface of the cleaned substrate W to drain the surface of the substrate W.
In the fifth processing chamber 6 for performing the drying process, the substrate W is dried by heating in a drying furnace or a hot plate after draining, thereby sufficiently removing the slight moisture remaining on the surface of the substrate W.

  According to the substrate cleaning method in the liquid crystal display device using such a substrate cleaning apparatus 1, the alignment film surface is changed from an active state immediately after rubbing to an inactivated state, particularly in the first processing chamber 2 as described above. Therefore, it is possible to prevent foreign matter from adsorbing on the alignment film surface not only in the processing in the first processing chamber 2 but also in the subsequent cleaning processing. Therefore, according to the manufacturing method of the present invention, it is possible to prevent display defects such as spots and unevenness due to alignment unevenness due to foreign matter adsorption.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the configuration of the water supply device 8 is not limited to the configuration shown in FIG. 2, and pure water is allowed to flow down in a curtain shape at a substantially uniform flow rate in a direction orthogonal to the transport direction of the substrate W. Any device can be used as long as the device can place the pure water on the surface of the substrate W in a film shape.
In addition, the flow rate when pure water flows may have a certain relative speed with the substrate as long as it can be placed on the surface of the substrate W in the form of a film.
Furthermore, the specific content of the cleaning process after the second processing chamber 3 is not limited to the above embodiment, and any conventionally known cleaning process can be arbitrarily combined.

It is a schematic block diagram of an example of the board | substrate cleaning apparatus which concerns on the manufacturing method of this invention. It is a perspective view which shows schematic structure of the water supply apparatus which looked at one part by the side cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate cleaning apparatus, 2 ... 1st process chamber, 8 ... Water supply apparatus, 9 ... Box
DESCRIPTION OF SYMBOLS 10 ... Overflow container, 11 ... Slit, 14 ... Inclined surface, 16 ... Pure water storage tank

Claims (4)

As an initial cleaning process in the cleaning process after applying an alignment film on the substrate and rubbing it,
While transporting the substrate, pure water having a specific resistance of 5 MΩ · m or less is allowed to flow down in a curtain shape at a substantially uniform flow rate along a direction orthogonal to the substrate transport direction, and the pure water is deposited on the substrate surface. A method for manufacturing a liquid crystal display device, comprising a processing step of placing the substrate on a surface.   The method for manufacturing a liquid crystal display device according to claim 1, wherein a protruding direction when the pure water flows is made to coincide with a transfer direction of the substrate.   3. The method of manufacturing a liquid crystal display device according to claim 2, wherein a flow velocity in the direction of transport of the substrate when the pure water flows is substantially matched with a transport speed of the substrate. The method for manufacturing a liquid crystal display device according to claim 1, wherein the substrate is a multi-sided substrate.

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