KR102162891B1 - Liquid crystal composition and liquid crystal display device having the same - Google Patents

Abstract

The present invention discloses a liquid crystal composition and a liquid crystal display device including the same. A liquid crystal display device of the present invention comprises: a first substrate on which a thin film transistor is formed; A second substrate formed to face the first substrate and formed with a color filter layer; A liquid crystal layer formed between the first substrate and the second substrate, wherein the liquid crystal layer includes a liquid crystal and a photoreactive compound, and the difference between the viscosity of the liquid crystal and the viscosity of the photoreactive compound is the viscosity of the liquid crystal It is characterized in that within 30% of.
Accordingly, the liquid crystal composition according to the present invention and a liquid crystal display device including the same may contain a liquid crystal and a photoreactive compound to maintain a cell gap and uniformly implement resistance to external impact. In addition, in the liquid crystal composition according to the present invention and a liquid crystal display including the same, as the viscosity deviation between the liquid crystal and the photoreactive compound is minimized, phase separation may be prevented and uniformity may be improved, thereby improving the quality of an electro-optical device.

Description

Liquid crystal composition and liquid crystal display device having the same

The present invention relates to a liquid crystal composition and a liquid crystal display device including the same, and more specifically, to maintain the cell gap of the liquid crystal, to uniformly implement resistance to external shock, to prevent the phase separation phenomenon of the liquid crystal composition, and to form uniformly. By doing so, it relates to a liquid crystal composition for securing uniformity of electro-optical properties, and a liquid crystal display device including the same.

In line with the recent information age, the display field has also developed rapidly, and in response to this, it is a flat panel display device (FPD) with advantages of thinner, lighter, and low power consumption. LCD), plasma display panel device (PDP), electroluminescence display device (ELD), field emission display device (FED), etc. have been introduced. ray tube: CRT) is rapidly replacing and attracting attention.

Among them, the liquid crystal display device is in the spotlight as a next-generation high-tech display device with low power consumption, good portability, and high added value. Among these liquid crystal displays, the active matrix liquid crystal display equipped with a thin film transistor, which is a switching element capable of adjusting the voltage on/off for each pixel, is the most It is attracting attention. The liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the two substrates, and the arrangement of the liquid crystal layers is adjusted according to the application of an electric field, and the transmittance of light is adjusted accordingly to display an image. to be.

Such liquid crystal display devices are most actively used in fields such as notebook computers, monitors, and TVs due to their excellent display of moving images and high contrast ratio. Liquid crystal displays applied to these various products need to maintain a cell gap and uniformly implement resistance to external impact.

An object of the present invention is to provide a liquid crystal composition including a liquid crystal and a photoreactive compound to maintain a cell gap and uniformly implement resistance to external impacts, and a liquid crystal display device including the same.

In addition, the present invention is to provide a liquid crystal composition capable of improving the quality of an electro-optical device by preventing phase separation and improving uniformity as the viscosity deviation between the liquid crystal and the photoreactive compound is minimized, and a liquid crystal display device including the same. There is this.

The liquid crystal composition of the present invention for solving the problems of the prior art as described above includes a liquid crystal and a photoreactive compound, and the difference between the viscosity of the liquid crystal and the viscosity of the photoreactive compound is within 30% of the viscosity of the liquid crystal. It is characterized.

In addition, a liquid crystal display device of the present invention comprises: a first substrate on which a thin film transistor is formed; A second substrate formed to face the first substrate and formed with a color filter layer; A liquid crystal layer formed between the first substrate and the second substrate, wherein the liquid crystal layer includes a liquid crystal and a photoreactive compound, and the difference between the viscosity of the liquid crystal and the viscosity of the photoreactive compound is the viscosity of the liquid crystal It is characterized in that within 30% of.

The liquid crystal composition and a liquid crystal display device including the same according to the present invention have a first effect of maintaining a cell gap including a liquid crystal and a photoreactive compound and uniformly implementing resistance to external impact.

In addition, the liquid crystal composition according to the present invention and the liquid crystal display device including the same, as the viscosity deviation between the liquid crystal and the photoreactive compound is minimized, the second phase separation is prevented and uniformity is improved, thereby improving the quality of the electro-optical device. It works.

1 is a diagram showing a cross-sectional view of a liquid crystal display device according to the present invention.
2 is a diagram illustrating an exposure process of a liquid crystal display device according to the present invention.
3 is a diagram showing an experiment result according to a difference in viscosity.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the size and thickness of the device may be exaggerated for convenience. The same reference numbers throughout the specification denote the same elements.

1 is a diagram showing a cross-sectional view of a liquid crystal display device according to the present invention.

Referring to FIG. 1, a liquid crystal display device includes a liquid crystal panel in which a first substrate 110 and a second substrate 124 are bonded to each other with a liquid crystal layer 150 therebetween. Further, although not shown in the drawings, a backlight may be disposed under the liquid crystal panel. A seal pattern 170 is formed along an edge between the first substrate 110 and the second substrate 124 to prevent leakage of the liquid crystal layer 150. Further, although not shown in the drawings, a column spacer for maintaining a cell gap between the first substrate 110 and the second substrate 124 may be additionally formed.

The first substrate 110 is a lower substrate or an array substrate, and on one surface of the first substrate 110, a gate wiring and a data wiring cross each other vertically with a gate insulating layer 113 interposed therebetween. Define area (P). A thin film transistor Tr is provided in the pixel region P and is connected to each other in a one-to-one correspondence between the transparent pixel electrode 119 provided in each pixel region P and a contact hole formed in the interlayer insulating layer 118.

The thin film transistor Tr includes a gate electrode 112, a gate insulating layer 113, an active layer 114, ohmic contact layers 115a and 115b, a source electrode 116, and a drain electrode 117. In addition, although not shown in the drawings, the thin film transistor may be formed in a top gate structure in which a gate electrode is disposed on the semiconductor layer in addition to a bottom gate structure in which a gate electrode is disposed under the semiconductor layer. .

In addition, the second substrate 124 facing the liquid crystal layer 150 interposed therebetween is called an upper substrate or a color filter substrate, and one surface thereof is a thin film transistor Tr of the first substrate 124 A grid-shaped black matrix 122 surrounding the pixel area P is configured to expose only the pixel electrode 119 while covering non-display elements such as the back.

In addition, as an example in which the R(red), G(green), and B(blue) color filters 123 are sequentially and repeatedly arranged to correspond to each pixel area P within these grids, and a transparent common electrode covering all of them ( 121).

A liquid crystal molecule is interposed between the liquid crystal layer 150 and the pixel electrode 119 and the common electrode 121 with first and second alignment layers 120a and 120b each rubbing a surface facing the liquid crystal in a predetermined direction. Evenly align the initial arrangement state and orientation direction.

However, the drawing is a simplified illustration of the device substrate including the thin film transistor according to the present invention, but is not limited thereto. That is, although it is expressed as one thin film transistor in the drawing, the thin film transistor may be composed of a combination of one or more thin film transistors, depending on the characteristics of operation, and is not limited to the representation of the drawing. In addition, various changes and modifications may be made to the configuration of the thin film transistor within a range not departing from the technical idea of the present invention.

In addition, the method of adjusting the arrangement of liquid crystal molecules can be variously applied to IPS (In Plane Switching) mode or FFS (Fringe Field Switching) mode in addition to TN (Twisted Nematic) mode and VA (Vertical Alignment) mode. . Accordingly, the configuration of the pixel electrode and the common electrode may be changed and modified.

In addition, since such a liquid crystal display device does not have a self-luminous element, a separate light source is required. To this end, a backlight is provided on the back of the liquid crystal panel to supply light. In this case, a polarizing plate that selectively transmits only specific polarized light may be further attached to the outer surfaces of the first and second substrates 110 and 124.

At this time, the liquid crystal layer 150 is formed of a photoreactive liquid crystal composition including a liquid crystal 130 and a photoreactive compound 200 between the first substrate 110 and the second substrate 124.

The arrangement of the liquid crystal 130 is adjusted by an electric field formed by the pixel electrode 119 and the common electrode 121. The liquid crystal 130 may be formed of a positive liquid crystal or a negative liquid crystal.

The positive liquid crystal is a liquid crystal having a dielectric anisotropy (Δε=ε∥-ε⊥) having a positive (+) value, that is, a horizontal dielectric constant (ε∥) greater than a vertical dielectric constant (ε⊥), and The same positive liquid crystal has a characteristic that the directors of the liquid crystal are arranged in a direction parallel to the electric field direction.

In addition, the negative liquid crystal is a liquid crystal having a dielectric anisotropy (Δε=ε∥-ε⊥) having a negative (-) value, that is, a horizontal dielectric constant (ε∥) less than a vertical permittivity (ε⊥). , Such a negative liquid crystal has a characteristic that a director of the liquid crystal is arranged in a direction perpendicular to the electric field direction.

At this time, the photoreactive compound 200 is formed in an amount of 10 wt% to 30 wt% with respect to the total liquid crystal composition. The photoreactive compound 200 is a compound that solidifies when light (UV) is irradiated. For example, the photoreactive compound 200 may be a monomer compound including a carbon double bond. In addition, the photoreactive compound 200 may be formed including a photoinitiator. When light is irradiated to the photoreactive compound 200, a partition wall may be formed in the liquid crystal layer 150. When described together with the drawings as follows.

2 is a diagram illustrating an exposure process of a liquid crystal display device according to the present invention.

Referring to FIG. 2, a mask 250 including a blocking portion A and a transmitting portion B is disposed on the second substrate 124 and irradiated with light. The light may be UV. A partition wall 210 is formed in the liquid crystal layer 150 in the area irradiated with the light. The partition wall 210 is formed by solidifying the photoreactive compound 200 of the liquid crystal layer 150 as light is irradiated.

For this reason, in the present invention, even after the first substrate and the second substrate are bonded to each other and a liquid crystal layer is formed therebetween, a partition wall for maintaining the cell gap of the liquid crystal can be formed as needed. In addition, due to this, resistance to external impact can be uniformly implemented.

However, in the photoreactive liquid crystal composition, phase separation may occur in the bonding process due to a difference in viscosity between the liquid crystal 130 and the photoreactive compound 200. That is, there is a problem in that the liquid crystal 130 and the photoreactive compound 200 cannot be uniformly mixed due to a difference in moving speed in the bonding process. In addition, when the photoreactive liquid crystal composition is not uniformly formed due to the phase separation phenomenon, even if the exposure process is performed, the uniformity may be reduced.

Accordingly, it is necessary to minimize the difference in viscosity between the liquid crystal 130 and the photoreactive compound 200 in order to prevent the phase separation phenomenon and to form the liquid crystal composition uniformly. The liquid crystal 130 is formed to have a viscosity of about 5 cps to 50 cps. At this time, the viscosity of the photoreactive compound 200 is formed so that the difference between the viscosity of the photoreactive compound 200 and the viscosity of the liquid crystal is 30% or less of the viscosity of the liquid crystal.

For example, when the viscosity of the liquid crystal is 20 cps, the difference between the viscosity of the photoreactive compound and the viscosity of the liquid crystal should be formed to be less than 30% of the viscosity of the liquid crystal 20 cps. That is, the difference between the viscosity of the photoreactive compound and the viscosity of the liquid crystal should be formed to be 6 cps or less. For this reason, the viscosity of the photoreactive compound is formed to have a viscosity of 14 cps to 26 cps. The experimental results according to the difference in viscosity are as follows.

3 is a diagram showing an experiment result according to a difference in viscosity.

Referring to FIG. 3, an experiment result of comparing Comparative Example (A) in which the viscosity deviation between the liquid crystal and the photoreactive compound is not minimized and Example (B) in which the viscosity deviation between the liquid crystal and the photoreactive compound is minimized. The comparative example (A) includes a photoreactive compound formed with a viscosity in which the difference between the viscosity of the photoreactive compound and the viscosity of the liquid crystal is 30% or more of the viscosity of the liquid crystal. Example (B) includes a photoreactive compound formed with a viscosity in which the difference between the viscosity of the photoreactive compound and the viscosity of the liquid crystal is 30% or less of the viscosity of the liquid crystal.

In Comparative Example (A) in which the viscosity deviation was not minimized, it can be seen that there is a problem in that white and black are not implemented in the panel and the pixel before UV irradiation. In particular, looking at the white of the panel, it can be seen that due to the difference in viscosity, the liquid crystal composition is not uniformly mixed, and the liquid crystal and the photoreactive compound are phase separated. In addition, even if UV irradiation may be improved than before UV irradiation, white and black are still not uniformly implemented in panels and pixels.

On the other hand, it can be seen that Example (B) in which the viscosity deviation is minimized can implement good black and white compared to Comparative Example (A). In particular, it can be seen that the liquid crystal composition is uniformly formed even before UV irradiation.

Accordingly, the liquid crystal composition according to the present invention and a liquid crystal display device including the same may contain a liquid crystal and a photoreactive compound to maintain a cell gap and uniformly implement resistance to external impact. In addition, in the liquid crystal composition according to the present invention and a liquid crystal display including the same, as the viscosity deviation between the liquid crystal and the photoreactive compound is minimized, phase separation may be prevented and uniformity may be improved, thereby improving the quality of an electro-optical device.

It will be appreciated by those skilled in the art through the above description that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

110: first substrate
123: color filter
124: second substrate
130: liquid crystal
150: liquid crystal layer
200: photoreactive compound
P: pixel area
Tr: thin film transistor

Claims (11)

Including liquid crystals and photoreactive compounds,
The viscosity of the photoreactive compound is less than the viscosity of the liquid crystal, and the difference between the viscosity of the liquid crystal and the viscosity of the photoreactive compound is within 30% of the viscosity of the liquid crystal.
The method of claim 1,
The photoreactive compound is a liquid crystal composition, characterized in that formed in an amount of 10 wt% to 30 wt% based on the total liquid crystal composition.
The method of claim 1,
The photoreactive compound is a liquid crystal composition comprising a photoinitiator.
The method of claim 1,
The photoreactive compound is a liquid crystal composition, characterized in that solidified when irradiated with light.
The method of claim 1,
The liquid crystal composition, characterized in that the viscosity of the liquid crystal is 5 cps to 50 cps.
A first substrate on which a thin film transistor is formed;
A second substrate formed to face the first substrate and formed with a color filter layer;
Including; a liquid crystal layer formed between the first substrate and the second substrate,
The liquid crystal layer includes a liquid crystal and a photoreactive compound,
The viscosity of the photoreactive compound is less than that of the liquid crystal, and the difference between the viscosity of the liquid crystal and the viscosity of the photoreactive compound is within 30% of the viscosity of the liquid crystal.
The method of claim 6,
The liquid crystal display device, wherein the photoreactive compound is solidified when light is irradiated.
The method of claim 7,
The liquid crystal layer further comprises a partition wall formed of a photoreactive compound solidified by irradiation with light.
The method of claim 6,
The photoreactive compound is formed in an amount of 10 wt% to 30 wt% with respect to the entire liquid crystal layer.
The method of claim 6,
The liquid crystal display device, wherein the photoreactive compound includes a photoinitiator.
The method of claim 6,
The liquid crystal display device, characterized in that the viscosity of the liquid crystal is 5 cps to 50 cps.

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