JP2016118706A - Ffs mode liquid crystal display device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an FFS mode liquid crystal display device that can suppress display defects, such as afterimage, burn-in, and flicker in a wide temperature area (in particular, in high-temperature environment).SOLUTION: A manufacturing method of an FFS mode liquid crystal display device of the present invention includes: a first step of forming a polyimide alignment film having a volume resistivity of 10Ω cm or more on a surface of a pair of substrates; a second step of performing alignment treatment on the polyimide alignment film before cleaning the polyimide alignment film by using isopropyl alcohol; a third step of overlapping the pair of substrates obtained in the second step with a sealant therebetween before irradiating the sealant with a UV ray or heating the sealant while applying pressure to cure the sealant to form a liquid crystal cell; and a fourth step of injecting a liquid crystal material having a specific resistance of 10Ω cm or more into between the substrates of the liquid crystal cell obtained in the third step.SELECTED DRAWING: None

Description

  The present invention relates to an FFS mode liquid crystal display device and a manufacturing method thereof, and more particularly to an on-vehicle FFS mode liquid crystal display device and a manufacturing method thereof.

  An IPS (In-Plane Switching) mode liquid crystal display device is a liquid crystal display device of a type in which liquid crystal molecules aligned parallel to a substrate are switched by an electric field (transverse electric field) parallel to the substrate. Compared with other mode liquid crystal display devices such as the VA mode and the VA mode, the viewing angle is wide. On the other hand, in the IPS mode liquid crystal display device, two sets of comb-shaped electrodes (hereinafter referred to as “comb-shaped electrodes”) are formed only on one substrate (array substrate), and the upper portion of the comb-shaped electrodes is subjected to a horizontal electric field. That is, the liquid crystal molecules do not switch. Therefore, the IPS mode liquid crystal display device has the disadvantages that the area through which light is transmitted is narrow and the aperture ratio is low. Therefore, in order to improve the disadvantage of the low aperture ratio of the IPS mode liquid crystal display device, an FFS (Fringe Field Switching) mode liquid crystal display device has been proposed (for example, Patent Document 1).

  The FFS mode liquid crystal display device is a liquid crystal display device in which liquid crystal molecules aligned parallel to the substrate are switched by a fringe electric field, and the switching operation is the same as that of the IPS mode liquid crystal display device, so that the viewing angle is wide. And so on. In addition, since the FFS mode liquid crystal display device combines a surface electrode and a comb electrode and uses a transparent electrode for the electrode, a high aperture ratio can be realized. Further, the fringe electric field has a larger electric field strength than the electric field generated in the IPS mode, and the liquid crystal molecules on the surface electrode are switched, so that the liquid crystal molecules on the upper part of the electrode that are difficult to switch in the IPS mode can be switched. it can.

  In recent years, liquid crystal display devices have been used in various fields, but the operation (performance) guaranteed temperature differs depending on the field of use. For example, a general liquid crystal display device for home appliances has an operation guarantee temperature of 0 ° C. to 50 ° C., whereas an in-vehicle liquid crystal display device has an operation guarantee temperature of −30 ° C. to 85 ° C. Therefore, the in-vehicle liquid crystal display device requires operation guarantee in a wide temperature range (particularly in a high temperature environment) as compared with a general liquid crystal display device for home appliances.

  One of the performances required for a liquid crystal display device is to prevent display defects such as afterimage, image sticking, and flicker. Here, “burn-in” is a phenomenon in which, when the same image is displayed for a long time, the previous image remains lightly displayed even when the screen is switched to the next screen. Further, “afterimage” is the same phenomenon as burn-in and refers to a case where the phenomenon disappears in a relatively short time. Furthermore, “flicker” is a phenomenon in which the screen flickers. Display defects such as afterimage, image sticking, and flicker are caused by the fact that the charge accumulated in the alignment film is not immediately relaxed by the direct current (DC) voltage, and this is added to the liquid crystal layer between the electrodes as the residual DC voltage. It is believed that

Conventionally, it has been considered that charge accumulation is mainly caused by impurity ions contained in a liquid crystal layer of a liquid crystal display panel constituting a liquid crystal display device. Therefore, a method of reducing the residual DC voltage by forming a liquid crystal layer using a liquid crystal material having a high specific resistance with reduced impurity ions (specific resistance of 1.5 × 10 ¹⁴ Ω · cm or more) has been proposed. (For example, Patent Document 2).
However, in the FFS mode liquid crystal display device, since the electrode structure is asymmetrical, even if there are few impurity ions contained in the liquid crystal, the electrode has a charge compared to other systems such as the IPS mode in which the electrode structure is symmetric. It tends to remain. In particular, in the case of an in-vehicle FFS mode liquid crystal display device, the resistance between the electrodes becomes low under a high temperature environment (therefore, the time constant that is the product of the resistance between the electrodes and the volume becomes small). Will accumulate. For this reason, in the FFS mode liquid crystal display device, even if the liquid crystal layer is formed using a liquid crystal material having a high specific resistance, the residual DC voltage cannot be sufficiently reduced, and an afterimage, image sticking, flicker, etc. in a high temperature environment. There is a problem that display defects cannot be sufficiently suppressed.

On the other hand, as a method of suppressing display defects such as flicker and image sticking, a method of forming a liquid crystal layer using a liquid crystal material having a low specific resistance (specific resistance of 10 ⁹ Ω · cm to several 10 ¹² Ω · cm) is proposed. (For example, Patent Document 3).
However, in this method, a dopant must be added in order to reduce the specific resistance of the liquid crystal material, leading to an increase in cost and the reliability characteristics of the liquid crystal display device in some cases.

Japanese Patent No. 3742837 International Publication No. 2012/118006 Japanese Patent Laid-Open No. 11-302652

  The present invention has been made to solve the above-described problems, and an FFS mode liquid crystal capable of suppressing display defects such as afterimages, image sticking, and flicker in a wide temperature range (particularly in a high temperature environment). It is an object to provide a display device and a manufacturing method thereof.

  The present inventor has selected and used a specific material and process to suppress display defects such as afterimage, image sticking, and flicker in a wide temperature range (particularly in a high temperature environment). It was found that can be produced. In addition, as a result of intensive research on the FFS mode liquid crystal display device manufactured in this way, the time constant and the accumulated voltage of the liquid crystal display panel have afterimages, burn-in, flicker, etc. in a wide temperature range (particularly in a high temperature environment). It has been found that the above problem can be solved by controlling the time constant and the storage voltage of the liquid crystal display panel within a predetermined range based on the knowledge that they are closely related to the display defect.

That is, the present invention includes a first step of forming a polyimide alignment film having a volume resistivity of 10 ¹⁴ Ω · cm or more on the surface of a pair of substrates, and an alignment treatment of the polyimide alignment film, followed by isopropyl alcohol (hereinafter, The second step of cleaning using “IPA”) and the pair of substrates obtained in the second step are overlapped with the sealing material interposed therebetween, and then the sealing material is irradiated with UV or heated. A third step of forming a liquid crystal cell by pressurizing and curing, and a fourth step of injecting a liquid crystal material having a specific resistance of 10 ¹³ Ω · cm or more between the substrates of the liquid crystal cell obtained in the third step. A method for manufacturing an FFS mode liquid crystal display device.

  In addition, the present invention is an FFS mode liquid crystal display device including a liquid crystal display panel having a time constant of 300 seconds or more and an accumulated voltage of 1.0 V or less at 85 ° C.

  According to the present invention, it is possible to provide an FFS mode liquid crystal display device capable of suppressing display defects such as afterimage, burn-in, and flicker in a wide temperature range (particularly in a high temperature environment) and a method for manufacturing the same.

It is a cross-sectional schematic diagram of the liquid crystal display panel in a FFS mode liquid crystal display device.

Hereinafter, the FFS mode liquid crystal display device and the manufacturing method thereof according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a liquid crystal display panel in an FFS mode liquid crystal display device of the present invention. In FIG. 1, a liquid crystal display panel 1 includes a pair of substrates 2a and 2b facing each other, and a liquid crystal layer 3 sandwiched between the substrates 2a and 2b. Here, the substrate 2a is generally called an array substrate, and the substrate 2b is generally called a counter substrate. A surface electrode 4, an insulating layer 5 (also referred to as “barrier layer”), a comb electrode 6 and a polyimide alignment film 7 are sequentially formed on the surface of the substrate 2 a on the liquid crystal layer 3 side. A polyimide alignment film 7 is formed on the surface of the substrate 2b on the liquid crystal layer 3 side. The polyimide alignment film 7 is subjected to an alignment process, and the liquid crystal molecules 8 in the liquid crystal layer 3 are aligned in parallel to the substrates 2a and 2b.

In the FFS mode liquid crystal display device including the liquid crystal display panel 1 having the above structure, a liquid crystal molecule 8 is formed on the substrate by generating a fringe electric field (lateral electric field) between the surface electrode 4 and the comb electrode 6. It can be rotated in a plane parallel to 2a and 2b.
Note that the liquid crystal display panel 1 of FIG. 1 shows only a basic configuration, and can have other members (for example, a polarizing plate) known in the technical field.

The manufacturing method of the FFS mode liquid crystal display device of the present invention includes four steps (first step to fourth step) as essential steps.
In the first step, a polyimide alignment film 7 having a volume resistivity of 10 ¹⁴ Ω · cm or more is formed on the surfaces of the pair of substrates 2a and 2b. Here, in this specification, the volume resistivity of the polyimide alignment film 7 is a value measured in a room temperature environment. If the volume resistivity of the polyimide alignment film 7 is less than 10 ¹⁴ Ω · cm, display defects such as afterimage, image sticking, and flicker may occur in a high temperature environment. The volume resistivity of the polyimide alignment film 7 is preferably 2 × 10 ¹⁴ Ω · cm or more, more preferably 5 × 10 ¹⁴ Ω · cm or more, and further preferably 8 × 10 ¹⁴ Ω · cm or more. The upper limit of the volume resistivity of the polyimide alignment film 7 is not particularly limited, but is preferably 10 ²⁰ Ω · cm, more preferably 10 ¹⁸ Ω · cm, and still more preferably 10 ¹⁶ Ω · cm. Here, “room temperature environment” in this specification means 25 ° C.
In addition, since the surface electrode 4, the insulating layer 5, and the comb electrode 6 are formed in advance on the surface of the substrate 2a, the polyimide alignment film 7 is formed on the surfaces of these members.

A method for forming the polyimide alignment film 7 is not particularly limited, and can be performed according to a method known in the technical field. Specifically, the polyimide alignment film 7 can be formed by applying a polyimide solution to the surfaces of the substrates 2a and 2b and then baking.
The thickness of the polyimide alignment film 7 formed on the surfaces of the substrates 2a and 2b is not particularly limited, and may be appropriately adjusted according to the size of the FFS mode liquid crystal display device to be manufactured.

  The pair of substrates 2a and 2b, the surface electrode 4, the insulating layer 5 and the comb electrode 6 are not particularly limited, and materials known in the technical field can be used. For example, the substrate 2a is preferably an active matrix substrate in which active elements such as TFTs and electrodes to be subpixels are provided in a matrix on the liquid crystal layer side. The substrate 2b is preferably a glass substrate. The surface electrode 4 and the comb electrode 6 are preferably formed from a transparent conductive material such as ITO or IZO. The insulating layer 5 is preferably formed from a transparent insulating material such as silicon nitride or silicon oxide.

  In addition, although not an essential step, a pretreatment such as cleaning may be performed on the pair of substrates 2a and 2b from the viewpoint of removing dirt attached to the pair of substrates 2a and 2b before the first step. . Although it does not specifically limit as a pre-processing, The process by cleaning process using a cleaning agent, UV, ozone, etc. is mentioned.

In the second step, the polyimide alignment film 7 is subjected to an alignment treatment and then cleaned using IPA. If cleaning after the alignment treatment is performed with another solvent, display defects such as afterimages, image sticking, and flickering may occur in a high temperature environment.
The washing method using IPA is not particularly limited, and can be performed according to a method known in the art. Examples of the cleaning method include spray cleaning and immersion cleaning.
The method for the alignment treatment is not particularly limited and can be performed according to a method known in the technical field. Examples of the alignment treatment include a rubbing treatment in which a roller around which a cloth such as nylon or polyester is wound is rotated to rub the polyimide alignment film 7 in a certain direction. An alignment process etc. are mentioned.

  The third step and the fourth step correspond to a liquid crystal injection method generally called a vacuum dip injection method. Other methods such as the ODF method exist as the liquid crystal injection method, but when other methods are used, display defects such as afterimages, image sticking, and flickering occur in a high temperature environment.

In the third step, a pair of substrates 2a and 2b obtained in the second step are overlapped with a sealing material interposed therebetween, and then the sealing material is UV-irradiated or heated and pressurized and cured to form a liquid crystal cell. To do.
Specifically, first, a sealing material is applied to the peripheral portion of the surface of either one of the pair of substrates 2a and 2b. Next, the pair of substrates 2a and 2b are opposed to each other with a predetermined interval, and after the sealing material is sandwiched therebetween, the sealing material is cured by UV irradiation or heating in a state where the sealing material is mechanically pressurized with a metal jig. To form a seal portion. In the seal portion, an injection port is provided in advance for injecting the liquid crystal material in the fourth step.

  It does not specifically limit as a sealing material used at this process, A well-known thing can be used in the said technical field. Examples of the sealing material include a heat curable sealing material or a UV curable sealing material. Similarly, the conditions for curing the sealing material are not particularly limited, and may be set as appropriate according to the sealing material to be used.

In the fourth step, a liquid crystal material having a specific resistance of 10 ¹³ Ω · cm or more is injected between the substrates 2a and 2b of the liquid crystal cell obtained in the third step.
Specifically, first, the liquid crystal cell and the liquid crystal material are separated from each other in the liquid crystal injection tank and evacuated to a vacuum state. Next, the exhaust is stopped, the injection port of the liquid crystal cell is immersed in the liquid crystal material, and the liquid crystal injection tank is returned to atmospheric pressure or pressurized to inject the liquid crystal material into the liquid crystal cell. Next, when the injection of the liquid crystal material is completed, the liquid crystal cell is separated from the liquid crystal material. Finally, the inlet is sealed using a UV curable sealant.

The liquid crystal material used in this step is 10 ¹³ Ω · cm or more, preferably 2 × 10 ¹³ Ω · cm or more, more preferably 5 × 10 ¹³ Ω · cm or more, and most preferably 8 × 10 ¹³ Ω · cm. It has the above specific resistance. Here, in this specification, the specific resistance of the liquid crystal material means a value measured in a room temperature environment using a commercially available device such as a liquid crystal specific resistance measurement system SR-6517 manufactured by Toyo Technica Co., Ltd. To do. If the specific resistance of the liquid crystal material is less than 10 ¹³ Ω · cm, display defects such as afterimage, image sticking, and flicker may occur in a high temperature environment. The upper limit of the specific resistance of the liquid crystal material is not particularly limited, but is preferably 10 ¹⁹ Ω · cm, more preferably 10 ¹⁷ Ω · cm, and still more preferably 10 ¹⁵ Ω · cm.

  The liquid crystal material may be a single liquid crystal component or a mixed liquid crystal containing two or more liquid crystal components. Among these, a fluorine-based mixed nematic liquid crystal is preferable. Here, in the present specification, the “fluorine-based mixed nematic liquid crystal” means a mixed liquid crystal employed in a liquid crystal display device including one or more types of fluorine-based nematic liquid crystal. Since such a mixed liquid crystal is commercially available, the commercially available product can be used.

  Further, although not an essential step, after the fourth step, the liquid crystal cell into which the liquid crystal material has been injected is heated to a temperature above the NI point of the liquid crystal material (depending on the type of the liquid crystal material, but generally 100 ° C. or higher, preferably May further include a fifth step of heating to 105 ° C. or higher, more preferably 110 ° C. or higher. The liquid crystal molecules can be realigned by heating to a temperature above the NI point of the liquid crystal material. Although the upper limit of heating temperature is not specifically limited, Preferably it is 120 degreeC, More preferably, it is 115 degreeC. Moreover, although heating time is not specifically limited, Preferably it is 5 minutes-60 minutes, More preferably, they are 6 minutes-30 minutes, More preferably, they are 8 minutes-20 minutes.

  Next, the FFS mode liquid crystal display device of the present invention manufactured through the steps as described above includes a liquid crystal display panel 1 having a time constant of 300 seconds or more and an accumulated voltage of 1.0 V or less at 85 ° C. By controlling the time constant and the accumulated voltage of the liquid crystal display panel 1 within the above ranges, display defects such as afterimages, image sticking, and flicker can be suppressed in a wide temperature range (particularly in a high temperature environment).

Here, in this specification, the time constant and the accumulated voltage of the liquid crystal display panel 1 can be measured or calculated using a commercially available apparatus such as a 6254 type liquid crystal property evaluation apparatus manufactured by Toyo Technica Co., Ltd.
The time constant is the product of resistance and capacitance between the electrodes. For example, when a 6254 type liquid crystal physical property evaluation apparatus manufactured by Toyo Technica Co., Ltd. is used, the resistance and capacitance between the electrodes can be calculated from a waveform obtained by applying a triangular wave of ± 10 V and 0.01 Hz.
The accumulated voltage is the maximum value of the potential difference generated between the electrodes after voltage application. That is, the accumulated voltage is the maximum value of the residual DC voltage observed after the DC voltage is applied for a certain period of time and then the application of the DC voltage is stopped. For example, when using a 6254 type liquid crystal physical property evaluation apparatus manufactured by Toyo Technica Co., Ltd., a DC voltage of 5.5 V is applied, and after 10 minutes, the application of the DC voltage is stopped, and then the residual DC voltage is measured. The smaller the value of the accumulated voltage, the less display defects such as afterimage, image sticking, and flicker.

The time constant at 85 ° C. of the liquid crystal display panel 1 is preferably 320 seconds or more, more preferably 350 seconds or more, still more preferably 360 seconds or more, and most preferably 380 seconds or more. The upper limit of the time constant of the liquid crystal display panel 1 is not particularly limited, but is preferably 1000 seconds, more preferably 900 seconds, still more preferably 800 seconds, and most preferably 700 seconds.
The accumulated voltage at 85 ° C. of the liquid crystal display panel 1 is preferably 0.9 V or less, more preferably 0.8 V or less, still more preferably 0.7 V or less, and most preferably 0.6 V or less. The upper limit of the storage voltage of the liquid crystal display panel 1 is not particularly limited, but is preferably 0.1 V, more preferably 0.2 V, and still more preferably 0.3 V.

  Since the FFS mode liquid crystal display device of the present invention can suppress display defects such as afterimage, image sticking, and flicker in a wide temperature range (particularly in a high temperature environment), it can be used as an in-vehicle FFS mode liquid crystal display device. Is suitable.

Hereinafter, although an Example and a comparative example demonstrate the detail of this invention, this invention is not limited by these.
Example 1
First, an array substrate was produced as follows. An insulating film (thickness 300 nm) made of SiN was formed on the ITO film by a sputtering apparatus using a 10 cm × 10 cm glass substrate (manufactured by EHC Sea) on which an ITO film (thickness 50 nm) was formed. Here, in order to form the lead-out wiring region, an insulating film was not formed on a part of the ITO film. Next, an ITO film was formed on the insulating film with a sputtering device, and then an etching process was performed to form a comb electrode. The electrode width and electrode interval of the comb-teeth electrodes were both 10 μm.
Next, a 9.5 cm × 9 cm glass substrate (manufactured by Eetch Sea) was used as the counter substrate, and 3 μm × 20 μm × 20 μm column spacers were arranged on the glass substrate at predetermined intervals. In addition, the column spacer was arrange | positioned using the method common in the said technical field.

Next, a polyimide solution is applied to each of the surface of the array substrate on the comb-teeth electrode side and the surface of the counter substrate on the column spacer side by spin coating, and then temporarily baked on a 65 ° C. hot plate for several minutes. The solution coating was dried. Next, a polyimide alignment film (AL-16470 manufactured by JSR Corporation) having a thickness of 1000 ± 100 mm is obtained by performing main firing in a heating chamber (CL0-9CH manufactured by Joyo Engineering Co., Ltd.) at 233 ° C. for 1100 seconds. A volume resistivity of 10 ¹⁵ Ω · cm) was formed.
Next, the polyimide alignment film was rubbed using a rubbing apparatus having a roll wound with a cotton cloth under the conditions of a roll rotation speed of 1000 rpm, a stage moving speed of 25 mm / second, and an indentation length of 0.4 mm.

Next, the polyimide alignment film subjected to the rubbing treatment was washed using IPA (manufactured by Kanto Chemical Co., Inc.).
Next, a thermosetting sealing material (XN-741TR manufactured by Mitsui Chemicals, Inc.) was applied to the peripheral edge of the counter substrate on the polyimide alignment film side and dried at 90 ° C. for 10 minutes. Thereafter, the array substrate and the counter substrate were overlaid, and the thermosetting sealing material was cured by heating and pressing to form a liquid crystal cell. At this time, in the heating chamber, the heating was performed at 150 ° C. for 3 hours, and the mechanical pressure was 0.3 kgf / cm ² .
Next, as a vacuum dip injection method, a metal boat in which about 1 cc of a liquid crystal material (fluorine-based mixed nematic liquid crystal; specific resistance 10 ¹⁴ Ω · cm; NI point 108.5 ° C.) is placed in a vacuum chamber (manufactured by Joyo Engineering Co., Ltd.) (VF-555AT), and the inlet of the liquid crystal cell was immersed in the liquid crystal material in a vacuum state (0.1 Mpa or less). Thereafter, the inside of the vacuum chamber is returned to atmospheric pressure, and a liquid crystal material is injected between the substrates of the cell, and the injection port is sealed using a UV curable sealing material (Photorec A-704 manufactured by Sekisui Chemical Co., Ltd.). .
Finally, in order to reorient the liquid crystal material injected into the liquid crystal cell, it was heated in a heating chamber at 110 ° C. for 10 minutes, and then a polarizing plate was attached to the surface of the liquid crystal cell to obtain a liquid crystal display panel.

(Comparative Example 1)
A liquid crystal display panel was produced in the same manner as in Example 1 except that water was used instead of IPA during the cleaning after the rubbing treatment.
(Comparative Example 2)
A liquid crystal display panel was manufactured in the same manner as in Example 1 except that the liquid crystal display panel was manufactured using an ODF (One Drop Fill) method as a liquid crystal injection method. The ODF method was performed as follows.
First, after cleaning the polyimide alignment film subjected to the rubbing treatment, a UV / heat combination curable sealing material (SWB-21 manufactured by Sekisui Chemical Co., Ltd.) is applied to the peripheral portion of the surface on the polyimide alignment film side of one substrate. The seal part was formed. Next, a liquid crystal material is dropped on the substrate surrounded by the seal portion, put in a vacuum chamber and superposed on the other substrate in a vacuum state (0.1 MPa or less), and the inside of the vacuum chamber is returned to atmospheric pressure. Then, 150 mW / cm ² of UV was irradiated for 40 seconds to cure the seal portion. Finally, the liquid crystal cell into which the liquid crystal material was injected was further heated in a heating chamber at 130 ° C. for 40 minutes to obtain a liquid crystal display panel in which the seal portion was completely cured.

(Comparative Example 3)
Other than using polyimide alignment film (AL-16301 manufactured by JSR Corporation; volume resistivity 10 ¹² Ω · cm) instead of polyimide alignment film (AL-16470 manufactured by JSR Corporation; volume resistivity 10 ¹⁵ Ω · cm) Produced a liquid crystal display panel in the same manner as in Example 1.
(Comparative Example 4)
Instead of the liquid crystal material (fluorine mixed nematic liquid crystal; specific resistance 10 ¹⁴ Ω · cm; NI point 108.5 ° C.), the liquid crystal material (fluorine mixed nematic liquid crystal; specific resistance 10 ¹² Ω · cm; NI point 108.5). A liquid crystal display panel was produced in the same manner as in Example 1 except that the temperature was used. Here, a liquid crystal material having a specific resistance of 10 ¹² Ω · cm was prepared by storing a liquid crystal material having a specific resistance of 10 ¹⁴ Ω · cm in a heating chamber at 150 ° C. for 5 days.

In Example 1, four samples were produced, and in Comparative Examples 1 to 4, two samples were produced.
About the liquid crystal display panel obtained by said Example and comparative example, the time constant in 85 degreeC, the storage voltage, and the display defect (especially afterimage) were evaluated.
The capacitance and resistance between electrodes necessary for calculation of the time constant, and the accumulated voltage were measured or calculated at 85 ° C. using a 6254 type liquid crystal property evaluation apparatus manufactured by Toyo Technica Co., Ltd.
In addition, the display defect was applied at 85 ° C. using a function generator (Model AFG3022 manufactured by Tektronix), wiring with the electrode part of the sample, applying a DC voltage of 5 V between the electrodes for 1 minute, and then switching to 0 V and applying The brightness difference between the electrode part and the non-electrode part was immediately evaluated visually. In this evaluation, a case where a luminance difference was not confirmed is indicated by ◯, a case where a slight luminance difference is confirmed is indicated by Δ, and a case where a large luminance difference is confirmed is indicated by ×.
Each evaluation result is shown in Table 1.

As shown in the results of Table 1, in the liquid crystal display panel of Example 1 manufactured using specific materials and processes, display defects could be suppressed at 85 ° C. On the other hand, in the liquid crystal display panels of Comparative Examples 1 to 4 that did not use specific materials and processes, display defects could not be suppressed at 85 ° C.
When Example 1 and Comparative Examples 1 to 4 are compared, there is a large difference in the time constant and the storage voltage of the liquid crystal display panel. By controlling the time constant and the storage voltage of the liquid crystal display panel to a specific range, 85 ° C. It was found that display defects can be suppressed.

  As can be seen from the above results, according to the present invention, an FFS mode liquid crystal display device capable of suppressing display defects such as afterimage, burn-in, and flicker in a wide temperature range (particularly in a high temperature environment) and a method for manufacturing the same. Can be provided.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel, 2a, 2b board | substrate, 3 liquid crystal layer, 4 surface electrode, 5 insulating layer, 6 comb-tooth electrode, 7 polyimide alignment film, 8 liquid crystal molecule.

Claims (10)

A first step of forming a polyimide alignment film having a volume resistivity of 10 ¹⁴ Ω · cm or more on the surface of a pair of substrates;
A second step of cleaning the alignment layer with isopropyl alcohol after the alignment treatment;
A third step of forming a liquid crystal cell by superposing the pair of substrates obtained in the second step with a sealing material sandwiched between them, and then applying UV irradiation or heating and pressurizing and curing the sealing material;
And a fourth step of injecting a liquid crystal material having a specific resistance of 10 ¹³ Ω · cm or more between the substrates of the liquid crystal cell obtained in the third step.   2. The FFS mode liquid crystal according to claim 1, further comprising, after the fourth step, a fifth step of heating the liquid crystal cell into which the liquid crystal material is injected to a temperature equal to or higher than the NI point of the liquid crystal material. Manufacturing method of display device.   The method for manufacturing an FFS mode liquid crystal display device according to claim 2, wherein the heating temperature in the fifth step is 120 ° C. or less.   The method for manufacturing an FFS mode liquid crystal display device according to claim 1, wherein the liquid crystal material is a fluorine-based mixed nematic liquid crystal.   The method for manufacturing an FFS mode liquid crystal display device according to any one of claims 1 to 4, wherein the FFS mode liquid crystal display device is for vehicle use.   An FFS mode liquid crystal display device comprising a liquid crystal display panel having a time constant of 300 seconds or more and an accumulated voltage of 1.0 V or less at 85 ° C.   7. The FFS mode liquid crystal display device according to claim 6, wherein the time constant is 350 seconds or more and the accumulated voltage is 0.8 V or less. 8. The FFS mode liquid crystal display device according to claim 6, wherein the liquid crystal layer of the liquid crystal display panel has a specific resistance of 10 ¹³ Ω · cm or more.   9. The FFS mode liquid crystal display device according to claim 6, wherein the liquid crystal layer of the liquid crystal display panel is formed of a fluorine-based mixed nematic liquid crystal. 10.   The FFS mode liquid crystal display device according to any one of claims 6 to 9, wherein the FFS mode liquid crystal display device is for vehicle use.

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