KR20170041325A - Liquid Crystal Display Device And Method Of Fabricating The Same - Google Patents

Abstract

The present invention provides a manufacturing method of a liquid crystal display device, comprising the following steps of: forming a first alignment film on an upper portion of a first substrate, and a second alignment film on an upper portion of a second substrate; aligning the first and the second alignment film; cleaning at least one of the first and the second substrate having the first and the second alignment film by using a cleaning solution mixed with a radical remover; forming a liquid crystal layer on at least one of the first and the second substrate; and bonding the first and the second substrate with the liquid crystal layer interposed therebetween. By cleaning a substrate after a step of forming alignment films and a step of aligning by using the cleaning solution mixed with the radical remover, free radicals generated in the alignment films and the liquid crystal layer are removed to prevent an afterimage, thereby improving reliability of the liquid crystal display device.

Description

[0001] The present invention relates to a liquid crystal display device, and more particularly,

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device with improved afterimage and reliability and a method of manufacturing the same.

[0002] As the society becomes a full-fledged information age, a display field for processing and displaying a large amount of information has been rapidly developed. In response to this, a liquid crystal display device (LCD), a plasma display various flat panel display devices such as a PDP, a field emission display (FED), and an organic light emitting diode (OLED) display device have been developed.

Among them, the liquid crystal display device is driven by using the optical anisotropy and the polarizing property of the liquid crystal layer. Since the liquid crystal molecules are thin and long in structure, the liquid crystal molecules have a directionality in arrangement, and an electric field is artificially applied to the liquid crystal layer, Can be controlled. Therefore, when an arbitrary electric field is applied to the liquid crystal layer, the arrangement direction of the liquid crystal molecules is changed, and light is refracted in the arrangement direction of the liquid crystal molecules due to optical anisotropy, so that image information can be displayed.

In general, a liquid crystal display device includes two substrates facing each other and a liquid crystal layer sandwiched between two substrates. Pixel electrodes and a common electrode are formed on inner surfaces of two substrates, respectively, for forming an electric field.

Such a liquid crystal display device is widely used as a so-called public display in which images of similar patterns are displayed in a public place. In the case of a public display, since a similar pattern image should be displayed for a long time, The reliability of the apparatus is deteriorated.

This decrease in reliability of the liquid crystal display device due to the afterimage occurs because the charges accumulated in the pixel electrode and the common electrode can not be escaped or neutralized by the long time operation.

In order to improve this, a method of changing the arrangement of the pixel electrodes and the common electrodes, a method of changing the polarity of the voltage applied to the pixel electrodes and the common electrode for each frame and / or for each pixel, the parasitic capacitance and the storage capacitance And a method of minimizing the pixel voltage fluctuation have been proposed.

However, this method solves only the DC after-image, which is not a fundamental solution, and there is a problem that the after-image due to the degradation of the restoring force of the liquid crystal molecules due to impurities and the deterioration of the function of the alignment film can not be solved.

Thus, although a method of mixing an additive into a liquid crystal layer or an orientation film has been proposed, it is possible to prevent the deterioration of the properties of the liquid crystal layer or the orientation film while preventing the function of the additive from deteriorating by directly mixing the additive into the material of the liquid crystal layer or the orientation film. There is a problem that it is required to secure

For example, the spreading property of the liquid crystal material dropped by the additive mixture is lowered to cause unevenness, or the additive in the small model reacts with the seal pattern to cause unevenness, or the photoinitiator of the seal pattern is eluted into the liquid crystal layer, Or a function may be deteriorated due to decomposition of the additive by a subsequent high temperature process.

Disclosure of the Invention The present invention has been proposed in order to solve such problems and provides a liquid crystal display device in which radicals generated in an alignment film and a liquid crystal layer are removed by mixing a radical scavenger in a cleaning solution after formation of an alignment film to clean the substrate, .

Another object of the present invention is to provide a liquid crystal display device and a manufacturing method thereof, in which after-image is prevented and reliability is improved by cleaning a substrate on which an alignment film is formed with a cleaning solution mixed with a radical scavenger.

In order to solve the above problems, the present invention provides a method of manufacturing a liquid crystal display device, comprising: forming a first alignment film on a first substrate and forming a second alignment film on a second substrate; aligning the first and second alignment films; Cleaning at least one of the first and second substrates having the first and second alignment layers using a cleaning solution mixed with a radical scavenger, and forming a liquid crystal layer on at least one of the first and second substrates And bonding the first and second substrates to each other with the liquid crystal layer interposed therebetween.

And, the radical scavenger may comprise an additive that reacts with at least one of positive and negative impurities and at least one of negative and negative radicals.

In addition, the radical scavenger may include a hindered amine light stabilizer (HALS).

The radical scavenger may be mixed with the cleaning solution at a ratio of not less than 0 parts by weight and not more than 50 parts by weight.

In addition, the cleaning solution may be prepared by dissolving or dispersing in a solvent selected from the group consisting of isopropyl alcohol (IPA), acetone, chloroform, ethanol, ethyl acetate, n-hexane, ), Methylene chloride, and toluene.

The manufacturing method of the liquid crystal display device may further include a step of aligning the first and second alignment films and a step of cleaning at least one of the first and second substrates, And then photo-aligning.

The manufacturing method of the liquid crystal display device may further include the steps of forming a thin film transistor and a pixel electrode on the first substrate, forming a black matrix, a color filter layer, and a common electrode on the second substrate, And forming a seal pattern on an edge of at least one of the first substrate and the second substrate.

According to another aspect of the present invention, there is provided a liquid crystal display device comprising first and second substrates facing each other, a first alignment film disposed on an inner surface of the first substrate, a second alignment film disposed on an inner surface of the second substrate, And a radical scavenger remaining in at least one of an interface between the first alignment film and the liquid crystal layer and an interface between the second alignment film and the liquid crystal layer, the liquid crystal display comprising: .

The radical scavenger may include a hindered amine light stabilizer (HALS).

The present invention has the effect of removing the radicals generated in the alignment film and the liquid crystal layer by cleaning the substrate by mixing the radical scavenger in the cleaning solution after formation of the alignment film.

Further, the present invention has an effect that the afterimage is prevented and the reliability is improved by cleaning the substrate on which the alignment film is formed with the cleaning solution mixed with the radical scavenger.

1 is a cross-sectional view illustrating a liquid crystal panel of a liquid crystal display device according to an embodiment of the present invention.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a liquid crystal display device.
3 is a process flow chart embodying the cell process of FIG.
Figure 4 is a process flow diagram embodying the orientation step of Figure 3;
5A is a graph showing a voltage holding ratio of a liquid crystal layer of a liquid crystal display device according to an embodiment of the present invention.
5B is a graph showing the ion density ratio of the liquid crystal layer of the liquid crystal display device according to the embodiment of the present invention.

A liquid crystal display device and a manufacturing method thereof according to the present invention will be described with reference to the accompanying drawings.

1 is a cross-sectional view illustrating a liquid crystal panel of a liquid crystal display device according to an embodiment of the present invention.

1, a liquid crystal panel 10 of a liquid crystal display device according to an embodiment of the present invention includes first and second substrates 20 and 50 which are spaced apart from each other and first and second substrates 20 and 50, And a liquid crystal layer (70) interposed between the first and second substrates (20, 50).

Specifically, a gate electrode 22 is formed in each pixel region P on the inner surface of the first substrate 20, and a gate insulating layer 24 is formed on the entire surface of the first substrate 20 above the gate electrode 22 .

A semiconductor layer 26 is formed on the gate insulating layer 24 corresponding to the gate electrode 22 and a source electrode 28 and a drain electrode 30 are formed on the semiconductor layer 26.

A protective layer 32 is formed on the entire surface of the first substrate 20 above the source electrode 28 and the drain electrode 30. The protective layer 32 has a contact hole exposing the drain electrode 30.

Here, the gate electrode 22, the semiconductor layer 26, the source electrode 28, and the drain electrode 30 constitute the thin film transistor T.

A pixel electrode 34 is formed in each pixel region P above the passivation layer 32. The pixel electrode 34 is connected to the drain electrode 30 through a contact hole.

A first alignment layer 36 is formed on the entire surface of the first substrate 20 above the pixel electrode 34.

A black matrix 52 corresponding to the boundary of the pixel region P and the thin film transistor T is formed on the inner surface of the second substrate 50 and a color filter layer 54 are formed.

A common electrode 56 is formed on the entire surface of the second substrate 50 under the color filter layer 54 and a second alignment layer 58 is formed on the entire surface of the second substrate 50 under the common electrode 56.

A liquid crystal layer 70 is formed between the first and second alignment films 36 and 58.

Although not shown, a backlight unit for supplying light to the liquid crystal panel 10 is disposed under the liquid crystal panel 10, and the liquid crystal panel 10 is connected to a driving circuit such as a timing controller, a data driver, and a gate driver, The panel 10, the backlight unit, and the drive circuit constitute a liquid crystal display device.

Here, a radical scavenger is present at the interface between the first and second alignment films 36 and 58 and the liquid crystal layer 70.

That is, first and second alignment layers 36 and 58 are formed on the first and second substrates 20 and 50, respectively, and then the first and second alignment layers 36 and 58 The first and second substrates 20 and 50 on which the first and second alignment films 36 and 58 are formed are then cleaned, A liquid crystal layer 70 is formed on the first and second substrates 20 and 50. The first and second substrates 20 and 50 are bonded together to complete the liquid crystal panel. The free radicals generated in the firing process or the alignment process free radical is removed and the radical scavenger remaining in at least one of the interface between the first alignment layer 36 and the liquid crystal layer 70 and the interface between the second alignment layer 58 and the liquid crystal layer 70 provides a continuous free radical Generation is prevented.

Thus, the deterioration of the characteristics of the liquid crystal layer 70 is prevented and the afterimage is prevented, thereby improving the reliability of the liquid crystal display device.

For example, the radical scavenger can be bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (bis (2,2,6,6, -tetramethyl-4- ) sebaceate, bis- (N-octyloxy-tetramethyl) piperidinyl sebacate, bis (1,2,2,6,6-pentamethyl- Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate), methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate (Methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate), tetrakis (2,2,6,6-tetramethyl-4-piperidyl) butane-1,2,3,4 Hindered amine light stabilizers such as tetrakis (2,2,6,6-tetramethyl-4-piperidyl) butane-1,2,3,4-tetracarboxylate, and HALS May also be referred to as radical scavengers.

The generation and removal of free radicals will be described in detail.

The first and second alignment layers 36 and 58 may be formed by coating and firing a precursor of polyamic acid (PAA).

That is, a polyamic acid polymer is formed from polyamic acid through a firing process at about 200 ° C. to about 250 ° C. according to the following chemical reaction formula 1, and a thermal imidization reaction The first and second alignment layers 36 and 58 are formed from the polyamic acid polymer.

[Chemical reaction formula 1]

[Chemical reaction formula 2]

At this time, since the polyamic acid does not react 100% during the firing process, there may be an un-cured monolayer between the polyamic acid polymer and the un-cured monolayer may cause the reliability to deteriorate.

When the carboxyl group (-COOH) remains in the polyamic acid polymer before the thermal imidization reaction, free radicals are generated from the carboxyl group (-COOH) by external stimuli such as impurities, water and ultraviolet rays, . ≪ / RTI >

That is, the free radical of the carboxyl group (-COOH) generated from the polyamic acid polymer is reacted with the alkenyl single of the liquid crystal molecule or the double bond or the triple bond of the liquid crystal molecule according to the following chemical reaction formula 3, And a large number of free radicals react with the polyamic acid polymer to generate a carboxyl group (-COOH). Such a process is continuously recycled, and the characteristics of the liquid crystal layer 70 may be deteriorated.

[Chemical reaction formula 3]

In the examples of the present invention, HALS represented by the following formula (1) is used as a radical scavenger to block the continuous generation of free radicals.

[Chemical Formula 1]

That is, free radicals such as R ^* or ROO ^* contained in the cleaning solution or remaining at the interface between the first and second alignment layers 36 and 58 and the liquid crystal layer 70 according to the following chemical reaction formula 4, ≪ / RTI >

[Chemical reaction formula 4]

In the chemical reaction equations 1 to 4, R, R ', and R "denote atomic groups composed of carbon and hydrogen.

As described above, in the liquid crystal display device according to the embodiment of the present invention, the cleaning solution mixed with the radical scavenging agent after formation and orientation of the first and second alignment films 36 and 58 The free radicals generated in the firing step and the alignment step can be removed and the continuous generation of free radicals in the subsequent step can be prevented. As a result, deterioration of the properties of the liquid crystal layer 70 can be prevented, The afterimage is prevented and the reliability is improved.

Particularly, since the radical scavenger is used in the cleaning step between the formation of the first and second alignment films 36 and 58 including the predetermined process and the formation of the liquid crystal layer 70 including the dropping process, The decomposition of the radical scavenger is prevented, the deterioration of the spreading property of the liquid crystal material is prevented, the reaction of the radical scavenger and the seal pattern, and the elution of the sealant pattern of the seal pattern by the radical scavenger are prevented.

A manufacturing method of such a liquid crystal display device will be described with reference to the drawings.

FIG. 2 is a process flow chart for explaining a method of manufacturing a liquid crystal display device according to an embodiment of the present invention, FIG. 3 is a process flow chart embodying the cell process of FIG. 2, and FIG. As a process flow chart, Fig. 1 will be described together.

2, the liquid crystal display according to the embodiment of the present invention is manufactured through an array process (st100), a color filter process (st200), a cell process (st300), and a module process (st400).

In the array process (st100), a gate electrode 22, a gate insulating layer 24, a semiconductor layer 26, a source electrode 28, a drain (not shown) are formed on a first substrate 20 through a photolithographic process. The electrode 30, the protective layer 32, and the pixel electrode 34 are formed.

In the color filter process st200, a black matrix 52, a color filter layer 54, and a common electrode 58 are formed on the second substrate 50 through a photolithography process.

In the cell process (st300), first and second alignment layers 36 and 58 are formed on the first substrate 20 on which the array process st100 is completed and the second substrate 50 on which the color filter process st200 is completed A liquid crystal layer 70 is formed between the first and second alignment films 36 and 58 and the first and second substrates 50 are bonded together to complete the liquid crystal panel 10.

At least one of the first and second substrates 20 and 50 is cleaned with a cleaning solution containing a radical scavenger before forming the liquid crystal layer 70 after the first and second alignment films 36 and 58 are formed, Removes the free radicals produced in the process and orientation process and blocks the continuous production of free radicals.

In the module process (st400), a driving circuit is attached to the liquid crystal panel 10 in which the cell process (st300) is completed, and a backlight unit is disposed under the liquid crystal panel 10 to modularize the liquid crystal panel.

3, the cell process 300 includes an alignment film forming step (st310), an alignment step (st320), a seal pattern forming step (st330), a liquid crystal layer forming step (st340) st350), and a cutting step (st360).

In the alignment film formation step (st310), polyamic acid is coated on the first substrate 20 on which the array process (st100) is completed and on the second substrate 50 on which the color filter process (st200) is completed to form first and second orientations And a first and second alignment layers 36 and 58 are formed by performing a firing process of about 200 to about 250 degrees with respect to the first and second alignment material layers.

The polyamic acid of the first and second alignment material layers becomes the polyamic acid polymer by the firing process, and the first and second alignment films 36 and 58 are formed through the thermal imidization reaction.

In the alignment step st320, the first and second alignment films 36 and 58 are given a predetermined direction by optical alignment such as rubbing or ultraviolet (UV) irradiation.

At this time, after the orientation of the first and second alignment films 36 and 58 is completed, at least one of the first and second substrates 20 and 50 is cleaned with the cleaning solution mixed with the radical scavenger, Removes the free radicals produced in the process and blocks the continuous production of free radicals.

Since radical scavengers are used after formation of the first and second alignment films 36 and 58 through the firing process, decomposition of the radical scavenger is prevented.

In the seal pattern forming step (st330), a seal pattern is formed at the edge of one of the first and second substrates 20 and 50 in which the alignment step st320 is completed.

At this time, since the radical scavenger mixed and used in the cleaning solution partially remains on the first and second alignment films 36 and 58, the reaction of the radical scavenger and the seal pattern and the release of the photoinitiator of the seal pattern by the radical scavenger are minimized .

In the liquid crystal layer forming step (st340), the liquid crystal layer 70 is formed by dropping and dotting a liquid crystal material on one of the first and second substrates 20 and 50 where the seal pattern is formed.

At this time, the radical scavenger is mixed with the cleaning solution prior to the formation of the liquid crystal layer 70. Since the radical scavenger is not mixed with the liquid crystal material, deterioration of the spreading property of the dropped liquid crystal material is prevented.

In the adhesion step (st 350), the first and second substrates 20 and 50 are bonded together using the seal pattern with the liquid crystal layer 70 interposed therebetween.

In the cutting step (st360), the bonded first and second substrates 20 and 50 are cut in cell units to complete the liquid crystal panel.

Specifically, the orientation step st320 includes, as shown in Fig. 4, a rubbing or photo alignment step st321, a solution cleaning step st322, a pure cleaning step st323, a brush cleaning step st324, A step (st325), and a drying step (st326).

In the rubbing or photo alignment step st321, rubbing or photo alignment is performed on the first and second alignment films 36 and 58 formed on the first and second substrates 20 and 50 through the alignment film formation step st310 To give a certain directionality.

In the solution cleaning step (st322), the cleaning solution mixed with the radical scavenger is used to form the first and second substrates 20, 20 having the first and second alignment films 36, 58 in which the rubbing or photo- 50) to remove free radicals generated in the firing and orientation processes and to prevent the continuous production of free radicals.

For example, the first substrate 20 may be cleaned using a cleaning solution mixed with a radical scavenger, the second substrate 50 may be cleaned using a cleaning solution not mixed with a radical scavenger, The second substrate 50 may be cleaned using a cleaning solution in which a radical scavenger is mixed or the radical scavengers may be mixed in the first and second substrates 20 and 50, The cleaning solution may be used.

At this time, the radical scavenger may comprise an additive that readily reacts with a positive and / or negative impurity or an amount and / or a negative radical, for example the radical scavenger may comprise HALS.

The cleaning solution may include a solvent capable of dissolving the radical scavenger. For example, the cleaning solution may include isopropyl alcohol (IPA), acetone, chloroform, ethanol, At least one of ethyl acetate, n-hexane, methanol, methylene chloride, and toluene.

And, the cleaning solution may be a solution diluted with deionized water (DI water), for example, the cleaning solution may be a solution diluted with pure water to about 30 parts by weight to about 50 parts by weight of isopropyl alcohol.

The radical additive may be mixed in an amount of more than 0 parts by weight and less than 50 parts by weight with respect to 100 parts by weight of the cleaning solution. Preferably, the proportion of the radical additives is more than 0.1 parts by weight to less than 50 parts by weight ≪ / RTI >

The solution cleaning step (st322) with the cleaning solution mixed with such radical scavenger may be repeated one or more times.

In the pure cleaning step st323, the first and second substrates 20 and 50, which have completed the solution cleaning step st322, are cleaned using deionized water (DI water).

In the brush cleaning step (st324), the first and second substrates 20 and 50, which have been subjected to the pure cleaning step st323, are cleaned using a brush.

In the ultrasonic cleaning step (st325), the first and second substrates 20 and 50, which have completed the brush cleaning step st324, are cleaned by ultrasonic waves using a cavitation jet or megasonic.

In the drying step st326, the orientation step st320 is completed by drying the first and second substrates 20 and 50, which have completed the ultrasonic cleaning step st325, by means such as an air knife .

The characteristics of the liquid crystal layer of the liquid crystal display device manufactured through such a manufacturing method will be described with reference to the drawings.

5A and 5B are graphs showing the voltage holding ratio and the ion density ratio of the liquid crystal layer of the liquid crystal display device according to the embodiment of the present invention, respectively, and will be described with reference to FIG.

5A and 5B, the reference example shows a liquid crystal layer of a liquid crystal display device manufactured without mixing radical scavenger, and the comparative example shows a liquid crystal layer of a liquid crystal display device manufactured by mixing a radical scavenger directly with a liquid crystal layer, 1 to 3 each represent a liquid crystal layer of a liquid crystal display manufactured by mixing a radical scavenger at a ratio of about 500 ppm, about 750 ppm, and about 1000 ppm to a cleaning solution of isopropyl.

As shown in FIG. 5A, the voltage holding ratio (VHR) increases in the comparative example and the first to third embodiments as compared with the reference example. In particular, as compared with the reference example, the voltage holding ratio Retention characteristics. From this, it can be seen that the voltage holding characteristics of the liquid crystal layer of the liquid crystal display device are improved and the reliability of the liquid crystal display device is improved.

As shown in FIG. 5B, the ion density of the reference example and the ion density ratio of the ion density ratios of the first to third embodiments are all 1 or more. In particular, It is understood that they have better ion density characteristics than those of Examples 1 and 2 and that the charge accumulation characteristics of the liquid crystal layer of the liquid crystal display device are improved to prevent the afterimage of the liquid crystal display device and improve the reliability.

That is, since the resistance of the liquid crystal layer is inversely proportional to the ion density of the liquid crystal layer, the charge accumulated in the liquid crystal layer adjacent to the pixel electrode and the common electrode can be easily removed as the ion density of the liquid crystal layer is higher, do.

As described above, in the liquid crystal display device according to the embodiment of the present invention, the first and second substrates 20 and 50 are formed of the cleaning solution mixed with the radical scavenging agent after the formation of the first and second alignment films 36 and 58, The free radicals generated in the firing step and the alignment step can be removed and the continuous generation of the free radicals in the subsequent step can be prevented. As a result, deterioration of the properties of the liquid crystal layer 70 can be prevented, And the reliability is improved.

Particularly, since the radical scavenger is used in the cleaning step between the formation of the first and second alignment films 36 and 58 including the predetermined process and the formation of the liquid crystal layer 70 including the dropping process, The decomposition of the radical scavenger is prevented, the deterioration of the spreading property of the liquid crystal material is prevented, the reaction of the radical scavenger and the seal pattern, and the elution of the sealant pattern of the seal pattern by the radical scavenger are prevented.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

10: liquid crystal panel 20: first substrate
36: first alignment layer 50: second substrate
58: second orientation film 70: liquid crystal layer

Claims (9)

Forming a first alignment layer on the first substrate and a second alignment layer on the second substrate;
Orienting the first and second alignment layers;
Cleaning at least one of the first and second substrates having the first and second alignment films using a cleaning solution mixed with a radical scavenger;
Forming a liquid crystal layer on at least one of the first and second substrates;
Attaching the first and second substrates together with the liquid crystal layer interposed therebetween
And the second electrode is electrically connected to the second electrode.
The method according to claim 1,
Wherein the radical scavenger comprises an additive that reacts with at least one of positive and negative impurities and at least one of negative and negative radicals.
The method according to claim 1,
Wherein the radical scavenger comprises a hindered amine light stabilizer (HALS).
The method according to claim 1,
Wherein the radical scavenger is mixed in an amount of 0 to 50 parts by weight based on 100 parts by weight of the cleaning solution.
The method according to claim 1,
The cleaning solution may be a solvent such as isopropyl alcohol (IPA), acetone, chloroform, ethanol, ethyl acetate, n-hexane, methanol, And at least one of methylene chloride, toluene, and the like.
The method according to claim 1,
Further comprising a step of rubbing or photo-aligning the first and second alignment films between the step of orienting the first and second alignment films and the step of cleaning at least one of the first and second substrates, ≪ / RTI >
The method according to claim 1,
Forming a thin film transistor and a pixel electrode on the first substrate;
Forming a black matrix, a color filter layer, and a common electrode on the second substrate;
Forming a seal pattern on an edge of at least one of the first and second substrates
The method comprising the steps of:
First and second substrates spaced apart from each other;
A first alignment layer disposed on the inner surface of the first substrate;
A second alignment layer disposed on the inner surface of the second substrate;
A liquid crystal layer disposed between the first and second substrates;
A radical remover remaining on at least one of an interface between the first alignment layer and the liquid crystal layer and an interface between the second alignment layer and the liquid crystal layer,
And the liquid crystal display device.
9. The method of claim 8,
Wherein the radical scavenger comprises a hindered amine light stabilizer (HALS).

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