CN112835234A

CN112835234A - Display device

Info

Publication number: CN112835234A
Application number: CN202010372420.8A
Authority: CN
Inventors: 尹晟在; 卢淳俊; 郑康燮; 金镇奭
Original assignee: Samsung Display Co Ltd
Current assignee: Samsung Display Co Ltd
Priority date: 2019-11-22
Filing date: 2020-05-06
Publication date: 2021-05-25
Also published as: KR20210063515A

Abstract

A display device is disclosed. A display device according to an embodiment may include: a first substrate including a pixel electrode; a second substrate including a common electrode; and the liquid crystal layer is clamped between the first substrate and the second substrate, wherein the liquid crystal layer respectively comprises the following components in parts by weight relative to 100 parts by weight of the whole liquid crystal composition: 19.5 to 24.5 parts by weight of a liquid crystal compound represented by chemical formula 1; 3.5 to 8.5 parts by weight of a liquid crystal compound represented by chemical formula 2; 3 to 8 parts by weight of a liquid crystal compound represented by chemical formula 3; 8.5 to 13.5 parts by weight of a liquid crystal compound represented by chemical formula 4; 18 to 23 parts by weight of a liquid crystal compound represented by chemical formula 5; 1 to 6 parts by weight of a liquid crystal compound represented by chemical formula 6; 11.5 to 16.5 parts by weight of a liquid crystal compound represented by chemical formula 7; and 15 to 20 parts by weight of a liquid crystal compound represented by chemical formula 8.

Description

Display device

Technical Field

The present invention relates to a display device.

Background

With the development of multimedia, the importance of display devices is increasing. In response to this, various Display devices such as a Liquid Crystal Display device (LCD), an Organic Light Emitting Display device (OLED), and the like are being used.

Among them, the liquid crystal display device, one of the most widely used flat panel display devices at present, includes two substrates on which field generating electrodes (field generating electrodes) such as pixel electrodes and common electrodes are formed, and a liquid crystal layer interposed therebetween. In the liquid crystal display device, an electric field is generated in the liquid crystal layer by applying a voltage to the electric field generating electrodes, and an image is displayed by determining the direction of liquid crystal molecules in the liquid crystal layer and controlling the polarization of incident light.

Disclosure of Invention

The present invention is intended to solve the problem of providing a display device capable of preventing electrostatic defects that may occur in a process.

The problem of the present invention is not limited to the above-mentioned problem, and other technical problems not mentioned can be clearly understood by those skilled in the art from the following description.

A display device according to an embodiment for solving the problem may include: a first substrate including a pixel electrode; a second substrate including a common electrode; and the liquid crystal layer is clamped between the first substrate and the second substrate, wherein the liquid crystal layer respectively comprises the following components in parts by weight relative to 100 parts by weight of the whole liquid crystal composition: 19.5 to 24.5 parts by weight of a liquid crystal compound represented by the following chemical formula 1; 3.5 to 8.5 parts by weight of a liquid crystal compound represented by the following chemical formula 2; 3 to 8 parts by weight of a liquid crystal compound represented by the following chemical formula 3; 8.5 to 13.5 parts by weight of a liquid crystal compound represented by the following chemical formula 4; 18 to 23 parts by weight of a liquid crystal compound represented by the following chemical formula 5; 1 to 6 parts by weight of a liquid crystal compound represented by the following chemical formula 6; 11.5 to 16.5 parts by weight of a liquid crystal compound represented by the following chemical formula 7; and 15 to 20 parts by weight of a liquid crystal compound represented by the following chemical formula 8.

[ chemical formula 1]

[ chemical formula 2]

[ chemical formula 3]

[ chemical formula 4]

[ chemical formula 5]

[ chemical formula 6]

[ chemical formula 7]

[ chemical formula 8]

In the chemical formulas 1 to 8, X and Y may each independently be an alkyl group or an alkenyl group having 1 to 7 carbon atoms.

The liquid crystal compound represented by the chemical formula 1 may include: a first liquid crystal compound, X and Y are alkyl groups; and the second liquid crystal compound, X is selected from alkyl or alkenyl, and Y is the other of the alkyl or alkenyl.

The content of the second liquid crystal compound may be included in 18 to 36 parts by weight with respect to 100 parts by weight of the entire liquid crystal compound represented by the chemical formula 1.

The method can also comprise the following steps: a compound represented by the following chemical formula 9.

[ chemical formula 9]

The content of the compound represented by the chemical formula 9 may be 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition.

The liquid crystal panel of the liquid crystal composition has a phase difference (Δ nd) of 310nm to 350nm, the liquid crystal composition has an elastic modulus (K33) of 15pN to 18pN, and the following mathematical formula 1 can be satisfied.

[ mathematical formula 1]

Rotational viscosity (gamma 1)/elastic coefficient (K33) of not less than 6.95 but not more than 7.35

The liquid crystal composition may have a coefficient of elasticity (K11) of 13.5pN to 15.5 pN.

The liquid crystal composition may have a refractive index anisotropy (Δ n) of 0.1064 to 0.1068.

The liquid crystal composition may have a dielectric anisotropy (Δ ∈) of-3.1 to-3.5.

The liquid crystal composition may satisfy the following equation 2.

[ mathematical formula 2]

An elastic coefficient (K33)/| dielectric anisotropy (Delta epsilon) | ≦ 5.6

Additional embodiments are specifically included in the detailed description and the accompanying drawings.

According to the display device of an embodiment, the threshold voltage of the liquid crystal can be increased by increasing the elastic coefficient (K33) of the liquid crystal and decreasing the dielectric anisotropy (Δ ∈). Therefore, the display device according to an embodiment may reduce texture defects.

Effects according to the embodiments are not limited to those shown above, and more various effects are included in the present specification.

Drawings

Fig. 1 is an exploded perspective view illustrating a display device according to an embodiment.

Fig. 2 is a plan view showing a layout of the pixel of fig. 1.

Fig. 3 is a sectional view taken along the section line I-I' of fig. 2.

Fig. 4 is an enlarged view of the area a in fig. 3.

Fig. 5 is a picture of a display device with poor texture.

Fig. 6 and 7 are pictures of pixels according to dielectric anisotropy.

Fig. 8 and 9 are pictures of pixels according to an elastic coefficient.

Description of the symbols

150: pixel electrode 160: first alignment film

250: common electrode 260: second alignment film

LC: liquid crystal RM: reactive mesogen

Detailed Description

The advantages, features and methods of accomplishing the same of the present invention will become apparent by reference to the following detailed description of the embodiments taken in conjunction with the accompanying drawings. However, the present invention may take various forms different from each other, and is not limited to the embodiments disclosed below, which are provided only for completeness of disclosure of the present invention and for completeness of informing a person having ordinary knowledge in the art of the present invention of the scope of the present invention, which is defined only by the scope of the claims.

References to elements or layers being "on" other elements or layers include the case of immediately above the other elements or layers or the case of interposing the other layers or other elements therebetween. Like reference numerals refer to like elements throughout the specification. Since shapes, sizes, ratios, angles, numbers, and the like shown in the drawings for illustrating the embodiments are exemplary, the present invention is not limited to the illustrated contents.

Specific embodiments are described below with reference to the accompanying drawings.

Referring to fig. 1, the display device according to an embodiment may be applied to various home electric appliances or internet of things devices such as a smart phone, a Portable phone, a tablet computer, a Personal Digital Assistant (PDA), a Portable Multimedia Player (Portable Multimedia Player), a television, a game machine, a watch-type electronic device, a head-mounted display, a display of a Personal computer, a notebook computer, a car navigator, a car dashboard, a Digital camera, a Portable camera, an external advertisement board, an electro-optical board, a medical device, a detection device, a refrigerator, and a washing machine.

A display device according to an embodiment may include: a first substrate 100; a second substrate 200 facing the first substrate 100; and a liquid crystal layer 300 interposed between the first substrate 100 and the second substrate 200. The liquid crystal layer 300 includes a plurality of liquid crystals LC, and the liquid crystals LC may have negative dielectric anisotropy.

A display device according to an embodiment may include a display area DA and a non-display area NA. The display area DA may be an area where an image is displayed, and the non-display area NA may be an area surrounding the display area DA and shielded from light. The display area DA includes a plurality of pixels PX. In order to realize color display, each of the pixels PX may display one of the primary colors. For example, the plurality of pixels PX may include a red pixel R displaying red, a green pixel G displaying green, and a blue pixel B displaying blue. The red, green and blue pixels R, G and B are repeatedly arranged along the first and second directions DR1 and DR2 and may be arranged in a matrix configuration. The gate lines GL are arranged to extend in the first direction DR1, and the data lines DL are arranged to extend in the second direction DR2, so that the gate driving signals and the data driving signals can be transferred to each of the plurality of pixels PX.

Fig. 2 is a plan view showing the layout of the pixel of fig. 1, fig. 3 is a cross-sectional view taken along a cut-off line I-I' of fig. 2, and fig. 4 is an enlarged view of a region a of fig. 3.

Referring to fig. 2 and 3, the first substrate 100 may be a substrate on which the switching element 120 for controlling the alignment direction of the liquid crystal LC within the liquid crystal layer 300 is disposed, and the second substrate 200 may be an opposite substrate for sealing the liquid crystal layer 300 together with the first substrate 100.

The first substrate 100 may include: a first insulating substrate 110; a conversion element 120 disposed on the first insulating substrate 110; and a pixel electrode 150 disposed on the conversion element 120.

The first insulating substrate 110 may be a transparent insulating substrate. For example, the first insulating substrate 110 may be a glass substrate or a plastic substrate. Also, the first insulating substrate 110 may have flexibility (flex).

A conversion element 120 may be disposed on the first insulating substrate 110. The conversion element 120 may be a thin film transistor including a gate electrode 121 disposed on the first insulating substrate 110, a semiconductor layer 122 disposed on the gate electrode 121, and a source electrode 123 and a drain electrode 124 disposed on the semiconductor layer 122 to be spaced apart from each other.

The gate electrode 121 is connected to the gate line GL and transmits a gate driving signal. The gate electrode 121 may be formed of any one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy thereof. The gate electrode 121 may be a multilayer made of any one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy thereof. For example, the gate electrode 121 may be a double layer of molybdenum/aluminum-neodymium or molybdenum/aluminum.

At the gate electrodeA gate insulating film 131 insulating the gate electrode 121 may be disposed on the gate electrode 121. The gate insulating film 131 may be made of silicon oxide (SiO)_x) Silicon nitride (SiN)_x) Or silicon oxynitride (SiO)_xN_y) And may be a single layer or a plurality of layers thereof.

A semiconductor layer 122 may be disposed on the gate insulating film 131. The semiconductor layer 122 may overlap with the gate electrode 121 on the gate insulating film 131. The semiconductor layer 122 may be formed of a silicon semiconductor or an oxide semiconductor. The silicon semiconductor may include amorphous silicon or crystallized polycrystalline silicon. Here, the polysilicon has a high mobility (100 cm)²Vs or more) can be used, and the oxide semiconductor can be selectively used as needed in the present embodiment because the Off-Current (Off-Current) is low.

A source electrode 123 and a drain electrode 124 spaced apart from each other may be disposed on the semiconductor layer 122. The source electrode 123 may be connected to the data line DL to transmit a data driving signal, and the drain electrode 124 may be electrically connected to the pixel electrode 150.

The source electrode 123 and the drain electrode 124 may be formed as a single layer or a multilayer. When the source electrode 123 and the drain electrode 124 are formed as a single layer, they may be formed of any one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy thereof. In the case where the source electrode 123 and the drain electrode 124 are formed in a multilayer, they may be formed of a double layer of copper/titanium or molybdenum/aluminum-neodymium, or a triple layer of titanium/aluminum/titanium, molybdenum/aluminum/molybdenum, or molybdenum/aluminum-neodymium/molybdenum.

A protective film 133 capable of protecting the conversion element 120 may be disposed on the aforementioned conversion element 120. The protective film 133 may be made of an inorganic substance, an organic substance, or a mixture thereof. In the case where the protective film 133 is an inorganic substance, it may be made of silicon oxide (SiO)_x) Silicon nitride (SiN)_x) Or silicon oxynitride (SiO)_xN_y) Or a plurality of layers thereof. In the case where the protective film 133 is an organic material, it may be made of, for example, polyimide (polyimide), benzocyclobutene series resin (benzocyclobutene series resin), acrylic acidEster resins (acrylate series resins) and the like. In the case where the protective film 133 is a mixture of inorganic and organic substances, the organic substances may be disposed on the inorganic substances to planarize the step of the lower portion.

A pixel electrode 150 may be disposed on the protective film 133. The pixel electrode 150 may be connected to the drain electrode 124 through the contact hole 140 to be controlled by a data driving signal.

The pixel electrode 150 may include: a trunk portion 151, a plurality of branch portions 152 extending outward from the trunk portion 151 and spaced apart from each other with a slit 153 provided in the middle, and an extension portion 154 extending toward the conversion element 120.

The trunk 151 may include a transverse trunk extending along the first direction DR1 and a longitudinal trunk extending along the second direction DR 2. The trunk portion 151 may divide the pixel electrode 150 into sub regions, i.e., may be divided into domains. The trunk portion 151 may be formed in a cross shape, for example. In this case, the pixel electrode 150 may be divided into four sub-regions by the trunk portion 151. The directions in which the branch portions 152 located at the respective sub-regions extend from each other may be different. For example, as shown in fig. 2, the branch portion 152 of the sub region positioned in the upper right direction may extend obliquely in the upper right direction from the trunk portion 151, and the branch portion 152 of the sub region positioned in the lower right direction may extend obliquely in the lower right direction from the trunk portion 151. The branch portion 152 of the sub region located in the upper left direction may extend obliquely in the upper left direction from the trunk portion 151, and the branch portion 152 of the sub region located in the lower left direction may extend obliquely in the lower left direction from the trunk portion 151. The extension portion 154 may extend from the trunk portion 151 or the branch portion 152 to the conversion element 120 to be connected with the drain electrode 124 through the contact hole 140.

The pixel electrode 150 may include a transparent conductive substance through which light may be transmitted. The pixel electrode 150 may be made of Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), or Indium Tin Zinc Oxide (ITZO), but is not limited thereto, and any transparent and conductive material may be used.

A first alignment film 160 may be disposed on the pixel electrode 150. The first alignment film 160 may include a vertical aligner by which an initial vertical alignment of the liquid crystal LC in the liquid crystal layer 300 may be guided. The first alignment film 160 may include Polyamic acid (polyamide acid) or Polyimide (Polyimide).

In addition, the second substrate 200 may include: a second insulating substrate 210; a light shielding member 220 disposed on the second insulating substrate 210; a color filter 230; and a common electrode 250 disposed on the light shielding member 220 and the color filter 230.

The second insulating substrate 210 may be a transparent insulating substrate such as the first insulating substrate 110. The light blocking member 220 may be made of a substance that absorbs or reflects at least light of a specific wavelength band to block transmission of the light. For example, the light shielding member 220 may be a black matrix. The light shielding member 220 may be disposed at a boundary between adjacent pixels to prevent a color mixing failure.

The color filter 230 may be formed of a substance that absorbs a specific wavelength band of the transmitted light or shifts or converts the wavelength of the transmitted light into a specific wavelength. That is, the color filter 230 may selectively transmit only light of a specific wavelength band. Although fig. 3 illustrates a case where the light blocking member 220 and the color filters 230 are disposed on the second substrate 200, one or more of the light blocking member 220 and the color filters 230 may be disposed on the first substrate 100.

An overcoat layer 240 may be disposed on the light blocking member 220 and the color filter 230. The capping layer 240 may be formed including an organic substance. The cover layer 240 may planarize a step caused by the components stacked on the second substrate 210.

A common electrode 250 may be disposed on the capping layer 240. The common electrode 250 may be disposed on a plurality of pixels to apply a common voltage. The common electrode 250 may form a vertical electric field in the liquid crystal layer 300 together with the pixel electrode 150. The common electrode 250 may form an electric field in the liquid crystal layer 300 together with the pixel electrode 150 to control an alignment direction of the liquid crystal LC. Although fig. 3 illustrates a case where the pixel electrode 150 is disposed on the first substrate 100 and the common electrode 250 is disposed on the second substrate 200, the pixel electrode 150 and the common electrode 250 may be disposed on the same substrate.

A second alignment film 260 may be disposed on the common electrode 250. Since the second alignment film 260 is configured similarly to the first alignment film 160, a repetitive description thereof will be omitted.

A liquid crystal layer 300 may be disposed between the first and

second substrates

100 and 200. The liquid crystal layer 300 may include a plurality of liquid crystals LC. The liquid crystal composition constituting the liquid crystal layer 300 may have negative dielectric anisotropy. The liquid crystal LC may be aligned with its long axis in a substantially perpendicular direction with respect to the alignment surface in an initial alignment state to maintain a stabilized state. Also, the liquid crystal LC may maintain a stabilized state with a predetermined pretilt angle.

The liquid crystal LC having negative dielectric anisotropy may have its long axis inclined at a predetermined angle with respect to the direction of the electric field due to the vertical electric field formed by the pixel electrode 150 and the common electrode 250. As the direction of the long axis of the liquid crystal LC changes, the phase difference retardation value is changed, and thereby, the amount of light transmitted through the liquid crystal layer 300 may be adjusted. In the embodiment, the initial alignment state refers to an alignment state of the liquid crystal LC in a state where the liquid crystal layer 300 does not form an electric field.

Referring to FIG. 4, a display device according to an embodiment may be a Polymer Stabilized-Vertical Alignment mode (PS-VA mode). The polymer stabilized vertical alignment mode can stabilize the pretilt alignment of the liquid crystal LC by a polymer network composed of a polymer of Reactive Mesogen (RM). The liquid crystal layer 300 may include liquid crystals LC and reactive mesogens RM. The reactive mesogen RM can form a polymer network composed of a polymer of the reactive mesogen RM through a UV exposure process.

If an electric field is formed in the liquid crystal layer 300, the liquid crystal LC may be inclined in a direction parallel to the length direction of the branch portion 152 of the pixel electrode 150 in response to the electric field, and the direction in which the liquid crystal LC is inclined in one pixel may be 4 directions in total. When UV is irradiated in a state where an electric field is applied to the liquid crystal layer 300, the reactive mesogens RM undergo a polymerization reaction to form a polymer network composed of the polymers in contact with the first alignment film 160 and the second alignment film 260. The liquid crystal LC may have an initial alignment direction determined to have a pretilt in the aforementioned direction by means of a polymer network.

The liquid crystal composition constituting the liquid crystal layer 300 according to an embodiment may include a neutral liquid crystal compound and a polar liquid crystal compound including at least one fluorine atom.

The neutral liquid crystal compound may include liquid crystal compounds represented by the following chemical formulas 1 to 4.

[ chemical formula 1]

[ chemical formula 2]

[ chemical formula 3]

[ chemical formula 4]

In the chemical formulas 1 to 4, X and Y may each independently be an alkyl group or an alkenyl group having 1 to 7 carbon atoms.

Specifically, each of chemical formulas 1 to 4 may include an alkyl group or an alkenyl group. In the case where X and Y are both alkyl groups or both alkenyl groups, the alkyl groups or alkenyl groups may be the same as or different from each other. The alkyl groups or alkenyl groups may have the same number of carbon atoms or different numbers of carbon atoms, respectively.

The liquid crystal compound represented by chemical formula 1 may be included by 19.5 to 24.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 1 is included by 19.5 to 24.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, the stability of the liquid crystal can be improved.

In particular, the liquid crystal compound represented by chemical formula 1 may include two compounds. For example, a first liquid crystal compound in which X and Y are alkyl groups and a second liquid crystal compound in which X (or Y) is an alkyl group and Y (or X) is an alkenyl group may be included. In this case, the second liquid crystal compound may be included by 18 to 36 parts by weight, and the remaining parts by weight may include the first liquid crystal compound, with respect to 100 parts by weight of the entire liquid crystal compound represented by chemical formula 1. If the second liquid crystal compound is included in an amount of 18 to 36 parts by weight with respect to the liquid crystal compound represented by chemical formula 1, the viscosity of the liquid crystal composition may be appropriately adjusted.

The liquid crystal compound represented by chemical formula 2 may be included by 3.5 to 8.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 2 is included by 3.5 to 8.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n), nematic phase-isotropic transition temperature (Tni), rotational viscosity (γ 1), and elastic modulus (K11, K33) can be improved.

The liquid crystal compound represented by chemical formula 3 may be included by 3 to 8 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 3 is included by 3 to 8 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, the stability of the liquid crystal can be improved.

The liquid crystal compound represented by chemical formula 4 may be included by 8.5 to 13.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 4 is included by 8.5 to 13.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n), nematic phase-isotropic transition temperature (Tni), rotational viscosity (γ 1), and elastic modulus (K11, K33) can be improved.

The liquid crystal compounds represented by the foregoing chemical formulas 1 to 4 are neutral liquid crystal compounds, and can respectively improve the stability of liquid crystal.

In addition, the polar liquid crystal compound may include liquid crystal compounds represented by the following chemical formulas 5 to 8.

[ chemical formula 5]

[ chemical formula 6]

[ chemical formula 7]

[ chemical formula 8]

In the chemical formulas 5 to 8, X and Y may each independently be an alkyl group or an alkenyl group having 1 to 7 carbon atoms.

Specifically, each of chemical formulas 5 to 8 may include an alkyl group or an alkenyl group. In the case where X and Y are both alkyl groups or both alkenyl groups, the alkyl groups or alkenyl groups may be the same as or different from each other. The alkyl groups or alkenyl groups may have the same number of carbon atoms or different numbers of carbon atoms, respectively.

The liquid crystal compound represented by chemical formula 5 may be included by 18 to 23 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 5 is included by 18 to 23 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n) and elastic modulus (K11, K33) may be improved.

The liquid crystal compound represented by chemical formula 6 may be included by 1 to 6 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 6 is included by 1 to 6 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n), nematic phase-isotropic transition temperature (Tni), rotational viscosity (γ 1), and elastic modulus (K11, K33) can be improved.

The liquid crystal compound represented by chemical formula 7 may be included by 11.5 to 16.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 7 is included by 11.5 to 16.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n) and elastic modulus (K11, K33) may be improved.

The liquid crystal compound represented by chemical formula 8 may be included by 15 to 20 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. If the liquid crystal compound represented by chemical formula 8 is included by 15 to 20 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition, refractive index anisotropy (Δ n), nematic phase-isotropic transition temperature (Tni), rotational viscosity (γ 1), and elastic modulus (K11, K33) can be improved.

The liquid crystal compounds represented by the above chemical formulas 5 to 8 are polar liquid crystal compounds, and can respectively improve the refractive index anisotropy (Δ n) and the elastic modulus (K11, K33) of liquid crystal.

In addition, the liquid crystal composition according to an embodiment may further include a compound represented by the following chemical formula 9.

[ chemical formula 9]

The compound represented by chemical formula 9 is one of reactive mesogens (reactive mesogens) and may include a methacrylate ester having a large number of reactive bonds.

The compound represented by chemical formula 9 may be included by 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition. The compound represented by chemical formula 9 may form a polymer network composed of a polymer through a UV irradiation process. Here, the compound represented by chemical formula 9 may form a polymer network or remain in the liquid crystal layer 300 without forming a polymer network.

The liquid crystal composition according to an embodiment may include liquid crystal compounds respectively represented by the foregoing chemical formulas 1 to 8. In particular, 19.5 to 24.5 parts by weight of the liquid crystal compound represented by chemical formula 1, 3.5 to 8.5 parts by weight of the liquid crystal compound represented by chemical formula 2, 3 to 8 parts by weight of the liquid crystal compound represented by chemical formula 3, 8.5 to 13.5 parts by weight of the liquid crystal compound represented by chemical formula 4, 18 to 23 parts by weight of the liquid crystal compound represented by chemical formula 5, 1 to 6 parts by weight of the liquid crystal compound represented by chemical formula 6, 11.5 to 16.5 parts by weight of the liquid crystal compound represented by chemical formula 7, and 15 to 20 parts by weight of the liquid crystal compound represented by chemical formula 8 may be included.

The liquid crystal composition according to one embodiment described above may have the following physical properties.

In the liquid crystal composition, the phase difference (Δ nd) of the liquid crystal panel is 310nm to 350nm, the elastic modulus (K33) is 15pN to 18pN, and the following mathematical formula 1 can be satisfied.

[ mathematical formula 1]

The liquid crystal composition may have a coefficient of elasticity (K11) of 13.5 to 15.5pN, a refractive index anisotropy (Δ n) of 0.1064 to 0.1068, and a dielectric anisotropy (Δ ∈) of-3.1 to-3.5.

The liquid crystal composition may satisfy the following formula 2.

[ mathematical formula 2]

An elastic coefficient (K33)/| dielectric anisotropy (Delta epsilon) | ≦ 5.6

The refractive index anisotropy of the liquid crystal composition may be adjusted to have a certain value matching the cell gap within the phase difference range of the liquid crystal panel, and the phase difference of the liquid crystal panel may be adjusted to have a range of 310nm to 350 nm.

The liquid crystal composition having the above composition ratio and physical properties can increase the elastic modulus (K33) of the liquid crystal and reduce the dielectric anisotropy (Δ ∈) to prevent texture defects.

Fig. 5 is a picture of a display device with poor texture.

Referring to fig. 5, texture (texture) defects may be generated in corner regions of the pixel electrode due to static electricity generated in the manufacturing process of the display device. The texture defect is a phenomenon in which liquid crystal is partially accumulated by static electricity, and the liquid crystal is not restored to lower the luminance, thereby causing horizontal lines or vertical lines.

The texture defects may be weakened when the threshold voltage of the liquid crystal is increased. For this reason, referring to the following equation 3, if the dielectric anisotropy is decreased or the elastic coefficient (K33) is increased, the threshold voltage may be increased. (here, Vth is a threshold voltage, K is an elastic coefficient, ε is a vacuum dielectric constant, and Δ ε is dielectric anisotropy.)

[ mathematical formula 3]

Therefore, the liquid crystal composition according to an embodiment can increase the threshold voltage by increasing the elastic coefficient (K33) of the liquid crystal and decreasing the dielectric anisotropy (Δ ∈), thereby reducing texture defects.

Fig. 6 and 7 are pictures of pixels according to dielectric anisotropy, and fig. 8 and 9 are pictures of pixels according to elastic coefficients.

Referring to fig. 6, a pixel of a display device including a liquid crystal composition having a dielectric anisotropy (Δ ∈) of-3.7 had poor texture at the corner of a pixel electrode. In contrast, referring to fig. 7, the pixel of the display device including the liquid crystal composition having the dielectric anisotropy (Δ ∈) of-3.1 exhibited a reduction in texture defects as compared to fig. 6.

Further, referring to fig. 8, a pixel of the display device including the liquid crystal composition having the elastic modulus (K33) of 10 has a defective texture at a corner of the pixel electrode. In contrast, referring to fig. 9, the pixel of the display device including the liquid crystal composition having the elastic modulus (K33) of 17 has less texture defects than that of fig. 8.

Accordingly, it is known that the liquid crystal composition according to an embodiment can increase the dielectric anisotropy (Δ ∈) by increasing the elastic coefficient (K33) of the liquid crystal, thereby increasing the threshold voltage and reducing the texture defect.

Hereinafter, examples and comparative examples for the liquid crystal composition according to the foregoing one example are disclosed.

< example >

The display device shown in fig. 3 was manufactured using the liquid crystal composition shown in table 1 below.

[ Table 1]

< comparative example >

Display devices were manufactured in the same manner as in the examples, except that the liquid crystal compositions of table 2 below were used.

[ Table 2]

Table 3 below shows the measurement of refractive index anisotropy, dielectric anisotropy, rotational viscosity, elastic modulus (K11, K33), and elastic coefficient (K33)/| dielectric anisotropy | of the liquid crystal compositions manufactured according to the comparative examples and examples described above. The cell gap and the phase difference of the liquid crystal panel are also shown.

[ Table 3]

Referring to the table 3, in the liquid crystal composition according to the example, the elastic coefficient (K33) is increased by about 4.2, and the value of the elastic coefficient/| dielectric anisotropy (K33/Δ ∈) is increased by about 1.16, as compared to the comparative example.

The display devices manufactured according to the foregoing comparative examples and examples were respectively subjected to a test using an electrostatic induction pad to show texture defect rates in the following table 4. At this time, the test was performed by using an Oven robot (Oven robot arm) of an odf (Oven Drop filling) device having a polyimide-attached electrostatic induction pad for the display device manufactured as described above.

[ Table 4]

Referring to the above table 4, the value of the elastic coefficient/| dielectric anisotropy agent (K33/Δ ∈) of the display device of the example was increased by 1.146 and the texture defect rate was reduced by 32.2%, as compared to the comparative example. Wherein an increase in the value of the elastic coefficient/| dielectric anisotropy agent (K33/Δ ∈) indicates a decrease in the dielectric anisotropy (Δ ∈) or an increase in the elastic coefficient (K33). The liquid crystal composition according to an embodiment may significantly reduce texture defects by increasing the elastic coefficient (K33) compared to the comparative example.

As described above, the liquid crystal composition according to an embodiment can increase the threshold voltage of the liquid crystal by increasing the elastic coefficient (K33) and decreasing the dielectric anisotropy (Δ ∈), thereby reducing texture defects.

While the embodiments of the present invention have been described with reference to the drawings, it will be understood by those having ordinary skill in the art to which the present invention pertains that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. The embodiments described above are therefore to be considered in all respects as illustrative and not restrictive.

Claims

1. A display device, comprising:

a first substrate including a pixel electrode;

a second substrate including a common electrode; and

a liquid crystal layer interposed between the first substrate and the second substrate,

wherein, the liquid crystal layer respectively comprises the following components in parts by weight relative to 100 parts by weight of the whole liquid crystal composition:

19.5 to 24.5 parts by weight of a liquid crystal compound represented by the following chemical formula 1;

3.5 to 8.5 parts by weight of a liquid crystal compound represented by the following chemical formula 2;

3 to 8 parts by weight of a liquid crystal compound represented by the following chemical formula 3;

8.5 to 13.5 parts by weight of a liquid crystal compound represented by the following chemical formula 4;

18 to 23 parts by weight of a liquid crystal compound represented by the following chemical formula 5;

1 to 6 parts by weight of a liquid crystal compound represented by the following chemical formula 6;

11.5 to 16.5 parts by weight of a liquid crystal compound represented by the following chemical formula 7; and

15 to 20 parts by weight of a liquid crystal compound represented by the following chemical formula 8,

[ chemical formula 1]

[ chemical formula 2]

[ chemical formula 3]

[ chemical formula 4]

[ chemical formula 5]

[ chemical formula 6]

[ chemical formula 7]

[ chemical formula 8]

In the chemical formulas 1 to 8,

x and Y are each independently an alkyl group or an alkenyl group having 1 to 7 carbon atoms.

2. The display device according to claim 1,

the liquid crystal compound represented by the chemical formula 1 includes:

a first liquid crystal compound, X and Y are alkyl groups;

and the second liquid crystal compound, X is selected from alkyl or alkenyl, and Y is the other of the alkyl or alkenyl.

3. The display device according to claim 2,

the content of the second liquid crystal compound is included in an amount of 18 to 36 parts by weight with respect to 100 parts by weight of the entire liquid crystal compound represented by the chemical formula 1.

4. The display device according to claim 1, further comprising:

a compound represented by the following chemical formula 9,

[ chemical formula 9]

5. The display device according to claim 4,

the content of the compound represented by the chemical formula 9 is 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the entire liquid crystal composition.

6. The display device according to claim 1,

the liquid crystal panel of the liquid crystal composition has a phase difference of 310nm to 350nm, the liquid crystal composition has a modulus of elasticity K33 of 15pN to 18pN, and satisfies the following equation 1,

[ mathematical formula 1]

The rotational viscosity/elastic coefficient K33 is more than or equal to 6.95 and less than or equal to 7.35.

7. The display device according to claim 6,

the liquid crystal composition has a coefficient of elasticity K11 of 13.5pN to 15.5 pN.

8. The display device according to claim 7,

the liquid crystal composition has a refractive index anisotropy of 0.1064 to 0.1068.

9. The display device according to claim 8,

the liquid crystal composition has a dielectric anisotropy of-3.1 to-3.5.

10. The display device according to claim 9,

the liquid crystal composition satisfies the following formula 2,

[ mathematical formula 2]

The elastic coefficient K33/| dielectric anisotropy | is more than or equal to 4.3 and less than or equal to 5.6.