KR102426515B1 - Liquid crystal display device - Google Patents

Abstract

The present invention provides a transmissive liquid crystal display device, wherein the liquid crystal display device includes an upper substrate and a lower substrate each having a transmissive region and a reflective region, and a liquid crystal layer provided between the upper substrate and the lower substrate, Since the alignment direction of the liquid crystal oriented by the upper substrate in the reflective region and the alignment direction of the liquid crystal oriented by the lower substrate in the reflective region are different from each other, the reflectance of external light by the reflective part such as an electrode or wiring is reduced.

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display, and more particularly, to a transmissive liquid crystal display.

A liquid crystal display device includes an upper substrate, a lower substrate, and a liquid crystal layer formed between both substrates, and the arrangement of the liquid crystal layers is adjusted depending on whether or not an electric field is applied, and the transmittance of light is adjusted accordingly to display an image.

Such a liquid crystal display may be divided into a reflective type or a transmissive type.

The reflective liquid crystal display does not include a separate light source and displays by using the reflection of light incident from the outside. The downside is that it cannot be used.

The transmissive liquid crystal display includes an internal light source and displays by using the transmission of light emitted from the light source. It has the advantage that it can be used in an outdoor place where there is no external light, but it has a disadvantage in that it consumes more power than the reflective liquid crystal display. There is this.

In particular, when a transmissive liquid crystal display of a normally black mode that implements a black screen in a situation in which no voltage is applied is used in an outdoor place where external light is incident, external light may be There is a problem that the image quality is adversely affected when a black or low gray image is driven by reflection.

Also, recently, a liquid crystal display device having a color filter on TFT (COT) structure in which both an array unit and a color filter are formed on a lower substrate has been developed. Furthermore, conventionally, a liquid crystal display having a COT structure in which an aperture ratio and transmittance of a liquid crystal panel is improved by removing a black matrix included to distinguish a region of a color filter has been developed.

However, in the case of a transmissive liquid crystal display having a COT structure in which a black matrix is removed, external light is reflected through electrodes or wires disposed between the color filters, thereby degrading image quality.

1 is a cross-sectional view of a conventional transmissive liquid crystal display device.

As shown in FIG. 1 , a conventional transmissive liquid crystal display includes a lower polarizing plate 4 , a lower substrate 1 , a reflective unit 6 , a liquid crystal layer 3 , an upper substrate 2 and an upper polarizing plate 5 . to provide

The lower polarizing plate 4 polarizes the light incident from the backlight unit (not shown).

The lower substrate 1 and the upper substrate 2 are bonded with a liquid crystal layer 3 interposed therebetween for controlling the transmittance of light.

Further, on the lower substrate 1 , a reflective part 6 such as an electrode and a wiring for supplying power to the liquid crystal molecules of the liquid crystal layer 3 is provided. That is, since the electrode and the wiring are made of a metal material, light incident from the backlight unit or an external light source may be reflected.

The upper polarizing plate 5 is provided on the upper substrate 2 to polarize light irradiated through the upper substrate 2 or light incident from the outside. In particular, the absorption axes of the lower polarizing plate 4 and the upper polarizing plate 5 are perpendicular to each other so that the amount of transmitted light can be determined by adjusting the arrangement of liquid crystal molecules in the liquid crystal layer 3 .

Therefore, since the light incident to the transmission region of FIG. 1 is polarized by the upper polarizing plate 5 , it is absorbed without passing through the lower polarizing plate 5 having an absorption axis perpendicular to the upper polarizing plate 5 .

However, the light incident to the reflective region of FIG. 1 is polarized by the upper polarizing plate 5 and then reflected by the reflective unit 6 . Since the polarization of the light does not change during mirror reflection by the reflective unit 6 , the reflected light is transmitted to the upper There was a problem that the image quality was deteriorated by passing through the polarizing plate 5 as it is.

2 is a diagram illustrating a change in polarization state of external light incident on a reflective region of a conventional transmissive liquid crystal display device.

As shown in FIG. 2 , the external light incident on the upper polarizing plate 5 is linearly polarized by the absorption axis A of the upper polarizing plate 5, so that only the component L1 perpendicular to the absorption axis A is the liquid crystal layer 3 ) is investigated.

At this time, since the liquid crystal oriented perpendicular to the absorption axis A of the upper polarizing plate 5 cannot change the polarization state of the light, the linearly polarized light is incident (L2) into the reflection unit 6 as it is, and the same polarization state is reflected (L3) while maintaining .

And the reflected light passes through the liquid crystal layer 3 while maintaining the same polarization state (L4). At this time, the linearly polarized light is perpendicular to the absorption axis A of the upper polarizing plate 5, so the upper polarizing plate 5 It passes through (L5) as it is and is irradiated to the outside.

As described above, since external light incident to the conventional transmissive liquid crystal display device is reflected by a configuration such as an electrode or wiring, there is a problem in that image quality is deteriorated when a black image is realized or a low gray image is implemented.

The present invention has been devised to solve the problems of the prior art, and an object of the present invention is to improve image quality by lowering the reflectance of external light by an electrode or wiring of a transmissive liquid crystal display device.

In addition, an object of the present invention is to allow the liquid crystal layer to serve as a black matrix in the region only by changing the optical properties of the liquid crystal layer in the region where the electrode or wiring is provided.

In order to achieve the above object, a liquid crystal display according to a first embodiment of the present invention includes an upper substrate and a lower substrate each having a transmissive region and a reflective region, and a liquid crystal layer provided between the upper substrate and the lower substrate, Since the alignment direction of the liquid crystal oriented by the upper substrate in the reflective region and the alignment direction of the liquid crystal oriented by the lower substrate in the reflective region are different from each other, the reflectance of external light by the reflective part such as an electrode or wiring is reduced.

A liquid crystal display according to a second embodiment of the present invention includes an upper substrate and a lower substrate each having a transmissive region and a reflective region, and a liquid crystal layer provided between the upper substrate and the lower substrate, wherein the upper substrate and the lower substrate are provided in the reflective region. The phase difference (dΔn) of the liquid crystal layer provided between the substrates is provided to satisfy dΔn = λ/4 + m*(λ/2) (m is an integer greater than or equal to 0). The reflectance of light is reduced.

According to the present invention as described above, there are the following effects.

According to the present invention, only by adjusting the alignment direction or phase difference of the liquid crystal layer between the upper substrate and the lower substrate in the reflective region, it is helpful to improve the image quality by lowering the reflectance of external light by the electrode or wiring.

In addition, according to the present invention, the black matrix can be removed from the liquid crystal display device having a COT structure because the liquid crystal layer in the corresponding region functions as a black matrix by lowering the reflectance of light irradiated between the upper and lower substrates in the reflective region. have.

1 is a cross-sectional view of a conventional transmissive liquid crystal display device.
2 is a diagram illustrating a change in polarization state of external light incident on a reflective region of a conventional transmissive liquid crystal display device.
3 is a view showing the alignment of liquid crystals in a transmissive region and a reflective region provided in the liquid crystal display according to the first embodiment of the present invention.
4 is a graph illustrating a change in reflectance according to an alignment direction of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region of the liquid crystal display according to the first exemplary embodiment of the present invention.
5A to 5C are views illustrating alignment directions of liquid crystals aligned by an upper substrate and a lower substrate in a transmissive region.
6 is a diagram illustrating alignment of liquid crystals in a transmissive region and a reflective region of the liquid crystal display according to the second exemplary embodiment of the present invention.
7 is a graph illustrating a change in reflectance according to an alignment direction of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region when the phase difference of the liquid crystal layer is constant.
8 is a graph illustrating a change in reflectance according to an alignment direction and a phase difference of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region of a liquid crystal display according to a second exemplary embodiment of the present invention.
9 is a view showing a liquid crystal display according to a second embodiment of the present invention including a buffer layer provided to adjust the thickness of the liquid crystal layer.
10 is a view illustrating a liquid crystal display device according to the present invention and a path of external light incident to the liquid crystal display device.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are illustrative and the present invention is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless specifically stated otherwise.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between two parts unless 'directly' is used.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described as 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless this is used.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

3 is a view showing the alignment of liquid crystals in a transmissive region and a reflective region provided in the liquid crystal display according to the first embodiment of the present invention.

As shown in FIG. 3 , the liquid crystal display according to the first embodiment of the present invention includes a lower substrate 10 , an upper substrate 20 , a liquid crystal layer 30 , a lower polarizing plate 40 , and an upper polarizing plate 50 . , and a reflective unit 60 .

The lower substrate 10, the upper substrate 20, and the liquid crystal layer 30 are provided in the liquid crystal panel and play a key role in image display. The lower substrate 10 and the upper substrate 20 are the liquid crystal panels. It is bonded face to face with the layer 30 interposed therebetween, and an image is displayed using light irradiated from a backlight unit (not shown).

At this time, although not shown in FIG. 3 , a plurality of gate lines and data lines intersect on the inner surface of the lower substrate 10 to define a pixel, and at each intersection of the gate line and the data line, a thin film transistor (Thin) Film Transistor, TFT) is provided and is connected one-to-one with the transparent pixel electrode formed in each pixel.

Accordingly, when the thin film transistor selected for each gate line is turned on by the on/off signal transmitted through the gate line, the signal voltage is transmitted to the corresponding pixel electrode through the data line, and the resulting electric field between the pixel electrode and the common electrode The liquid crystal arrangement of the liquid crystal layer 30 is changed to change the transmittance.

In addition, a desired image may be displayed while light irradiated from the backlight unit passes through the liquid crystal layer 30 of which transmittance is changed.

A lower polarizing plate 40 is provided under the lower substrate 10 to polarize light emitted from the backlight unit, and an upper polarizing plate 50 is provided on the upper substrate 20 to provide the liquid crystal layer 30 and The light passing through the upper substrate 20 is polarized.

In particular, the upper substrate 20 and the lower substrate 10 of the liquid crystal display according to the first embodiment of the present invention include a transmissive region and a reflective region. In the present invention, the transmissive region transmits light emitted from the backlight unit. The area where an image is displayed is an area where an image is displayed, and the reflective area is an area through which light irradiated from the backlight unit is not transmitted and refers to an area irrelevant to image display.

In particular, the reflective region is a region including a configuration capable of reflecting light incident from the outside, and means a region including the reflective unit 60 that reflects light, such as an electrode or wiring.

In addition, the liquid crystal display according to the present invention has, for example, red (R), green (G), and blue (B) color filters corresponding to each pixel on the thin film transistor provided on the lower substrate 10 . It may be a color filter on TFT (COT) type having a color filter.

In addition, the liquid crystal display according to the present invention does not include a black matrix that surrounds each of the color filters and covers non-display elements such as gate lines, data lines, and thin film transistors in the prior art. The liquid crystal layer 30 may function as a black matrix by adjusting the alignment of the liquid crystal.

In particular, according to the first embodiment of the present invention, the alignment direction of the liquid crystal 31a aligned by the upper substrate 20 in the reflection region and the alignment direction of the liquid crystal 31b aligned by the lower substrate 10 in the reflection region By providing different directions only, it is possible to lower the reflectance of incident external light.

In the first embodiment of the present invention, the liquid crystal oriented by the upper substrate means liquid crystal oriented in the alignment direction of the alignment layer (not shown) of the upper substrate in contact with the upper substrate, and the liquid crystal oriented by the lower substrate means the lower substrate It means a liquid crystal aligned in the alignment direction of the alignment layer (not shown) of the lower substrate in contact with. Accordingly, that the alignment direction of the liquid crystal oriented by the upper substrate and the alignment direction of the liquid crystal oriented by the lower substrate are the same means that the alignment direction of the alignment layer of the upper substrate and the alignment direction of the alignment layer of the lower substrate are the same.

In the liquid crystal display according to the first embodiment of the present invention, only the alignment of the liquid crystals 31a and 31b between the upper substrate 20 and the lower substrate 10 in the reflective region is different, as shown in FIG. The alignment of the liquid crystals 32a and 32b between the upper substrate 20 and the lower substrate 10 in the region is the same, thereby reducing the reflectance of external light incident on the entire region including the reflective region and the transmissive region.

Specifically, according to the first embodiment of the present invention, the alignment direction of the liquid crystal 32a aligned by the upper substrate 20 and the liquid crystal 32b aligned by the lower substrate 10 in the transmission region are mutually provided in the same way.

On the other hand, in the reflective region, the alignment direction of the liquid crystal 31a aligned by the upper substrate 20 and the alignment direction of the liquid crystal 31b aligned by the lower substrate 10 are different from each other.

That is, when external light is incident on the transmission region, the external light is polarized by the absorption axis A of the upper polarizing plate 50 , and only a component perpendicular to the absorption axis A is incident on the liquid crystal layer 30 . However, since the light incident on the liquid crystal layer 30 is parallel to the absorption axis B of the lower polarizing plate 40 , all of the light is absorbed by the lower polarizing plate 40 .

As described above, since external light incident to the transmission region may be absorbed through the polarization of the upper polarizing plate 50 and the lower polarizing plate 40 having absorption axes A and B perpendicular to each other, the first embodiment of the present invention In the embodiment, so as not to affect the polarization of the upper polarizing plate 50 and the lower polarizing plate 40, in the transmissive region, the alignment direction of the liquid crystal 32a oriented by the upper substrate 20 and the lower substrate 10 The alignment directions of the aligned liquid crystals 32b are identical to each other.

On the other hand, if there is no change in polarization through the liquid crystal layer 30 when external light is incident on the reflective region, the external light is polarized by the absorption axis A of the upper polarizing plate 50 and is Since only a component perpendicular to the liquid crystal layer 30 is incident, and the incident light is mirror-reflected by the reflection unit 60 , light having a component perpendicular to the absorption axis A is transmitted to the upper polarizing plate 50 . It passes through as it is and is irradiated to the outside.

Therefore, in the first embodiment of the present invention, by providing the orientation direction of the liquid crystal 31a aligned by the upper substrate 20 and the direction of the liquid crystal 31b aligned by the lower substrate 10 in the reflection region differently from each other, , lower the reflectance of external light.

Specifically, in the first embodiment of the present invention, the upper polarizing plate 50 so that the external light reflected by the reflecting unit 60 includes a component parallel to the absorption axis A of the upper polarizing plate 50 in part. ) by changing the polarization state of external light polarized through

In particular, in the first embodiment of the present invention, in the reflection region, at least one of the liquid crystal 31a oriented by the upper substrate 20 or the liquid crystal 31b oriented by the lower substrate 10 is the upper polarizing plate 50 . ) may be oriented to form a predetermined angle with the absorption axis (A).

At this time, the predetermined angle is set so that the external light polarized through the upper polarizing plate 50 is reflected from the reflection unit 60 and passes through the liquid crystal layer 30 as it is, so that the liquid crystals 31a and 31b can be suppressed. ) means an angle formed with the absorption axis A of the upper polarizing plate 50, and may preferably be 5° to 85°.

4 is a graph illustrating a change in reflectance according to an alignment direction of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region of the liquid crystal display according to the first exemplary embodiment of the present invention.

In particular, in FIG. 4, the phase difference (dΔn) of the liquid crystal layer 30 is set to 1/2λ, and external light is set to green (550 nm) that is most conspicuous to the human eye among visible light, and the upper part in the reflection region is It is a simulation result of changing the alignment direction of the liquid crystal oriented by the substrate and the lower substrate.

The alignment angle of the liquid crystal aligned by the lower substrate 10 and the alignment angle of the liquid crystal aligned by the upper substrate 20 described in FIG. 4 are the liquid crystal aligned with respect to the absorption axis A of the upper polarizing plate 50 . angles formed by each.

The X-axis of FIG. 4 means the alignment angle of the liquid crystal 31b oriented by the lower substrate 10 in the reflective region, and the Y-axis means the reflectance of external light. The reflectance is shown by changing the alignment angle of the liquid crystal 31b aligned by the lower substrate 10 to the angle of the X axis while changing the alignment angle of the liquid crystal 31a oriented by X1 to X10.

The results of FIG. 4 are briefly shown in Table 1 below.

Alignment angle [°] of liquid crystal oriented by the upper and lower substrates in the reflection area reflectivity[%] upper board lower substrate 0 0 31.3 90 90 31.3 90 0 15.5 0 90 15.5 90 30/150 4.6 0 60 4.6 80 145 0.2

As the reflectance is lower, it means that the external light reflected by the reflector 60 does not pass through the upper polarizing plate 50 as it is, so the liquid crystal 31a oriented by the upper substrate 20 at the lowest point of the graph. ) and the alignment angle of the liquid crystal 31b aligned by the lower substrate 10 are optimal conditions for lowering the reflectance of external light.

Therefore, referring to FIG. 4 and Table 1, the liquid crystal 31a oriented by the upper substrate 20 is oriented to form an angle of 80° with the absorption axis A of the upper polarizing plate 50, and the lower substrate When the liquid crystal 31b oriented by (10) is oriented to form an angle of 145° with the absorption axis A of the upper polarizing plate 50, it can be seen that the reflectance is close to zero.

That is, the alignment direction of the liquid crystal 31a oriented by the upper substrate 20 forms 80° with the absorption axis A of the upper polarizing plate 50, and the liquid crystal 31a oriented by the lower substrate 10 ( It can be seen that when the liquid crystals 31a and 31b are arranged differently so that the alignment direction of the liquid crystal 31b is 65° from the alignment direction of the liquid crystal 31a, there is almost no reflection of light incident from the outside.

As such, according to the first embodiment of the present invention, the alignment direction of the liquid crystals 32a and 32b of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the transmissive region, or the liquid crystal layer The reflectivity of external light can be lowered by providing different alignment directions of the liquid crystals 31a and 31b provided between the upper substrate 20 and the lower substrate 10 in the reflective region while maintaining the thickness of 30 as it is.

Meanwhile, in the first embodiment of the present invention, as described above, in the transmissive region, the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 is maintained as it is, while in the reflective region, the upper substrate 20 is ) and the lower substrate 10, since only the alignment directions of the liquid crystals 31a and 31b of the liquid crystal layer 30 provided are different, in the transmissive region and the reflective region in the upper substrate 20 or the lower substrate 10 The alignment directions of the liquid crystals are different from each other.

That is, at least one of the liquid crystal oriented by the upper substrate 20 or the liquid crystal oriented by the lower substrate 10 must have a different orientation direction for each specific domain, namely a transmissive region and a reflective region. In the embodiment, the liquid crystal is aligned on the upper substrate 20 or the lower substrate 10 in a non-contact alignment method such as photo alignment using ultraviolet rays.

Photo alignment is performed by irradiating polarized UV light to an organic alignment layer formed on a transparent substrate so that a chemical change occurs in molecules constituting the organic alignment layer according to the polarization direction of the UV light, and accordingly, the direction and initial gradient of liquid crystal alignment in the organic alignment layer ( Pretilt) is an orientation method to set the angle.

Using this photo-alignment method, a plurality of UV exposure lights irradiating UV rays at different angles with respect to the to-be-exposed surface of the upper substrate 20 are formed, and UV rays are irradiated in one direction to the transmission region through one opening of the mask. And, by irradiating ultraviolet rays to the reflective region through different openings of the mask, the liquid crystal may have different alignment directions with respect to the transmissive region and the reflective region of the upper substrate 20 .

However, since the first embodiment of the present invention is not limited thereto, various methods for aligning liquid crystals differently for multi-domains other than the above method may be used.

Meanwhile, as described above, in the first embodiment of the present invention, the polarization state of external light should not change while passing through the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the transmission region. do.

Specifically, the alignment direction of the liquid crystal oriented by the upper substrate 20 and the lower substrate 10 in the transmission region so as not to change the polarization state of external light is provided parallel or perpendicular to the absorption axis of the upper polarizing plate 50, or It is provided perpendicular to the upper polarizing plate 50 .

5A to 5C are views illustrating alignment directions of liquid crystals aligned by an upper substrate and a lower substrate in a transmissive region.

FIG. 5A is a case in which liquid crystals 32a and 32b aligned by the upper substrate 20 and the lower substrate 10 in the transmission region are oriented perpendicular to the absorption axis A of the upper polarizing plate 50, FIG. 5B is a case in which the liquid crystals 32a and 32b oriented by the upper substrate 20 and the lower substrate 10 in the transmission region are provided parallel to the absorption axis A of the upper polarizing plate 50, and FIG. 5c shows the transmission This is a case in which the liquid crystals 32c and 32d aligned by the upper substrate 20 and the lower substrate 10 in the region are provided perpendicular to the upper polarizing plate 50 itself.

As described above, in the present invention, in the transmission region, the liquid crystals 32a, 32b, 32c, and 32d aligned between the upper substrate 20 and the lower substrate 10 do not affect the polarization state of external light. By aligning them together, external light incident to the transmission region can be absorbed by the upper polarizing plate 50 and the lower polarizing plate 40 .

6 is a diagram illustrating alignment of liquid crystals in a transmissive region and a reflective region of the liquid crystal display according to the second exemplary embodiment of the present invention.

6 has the same configuration as the liquid crystal display device of FIG. 3 described above, except that the alignment directions of the liquid crystals 31a and 31b aligned by the upper substrate 20 and the lower substrate 10 in the reflective region are the same. . Accordingly, the same reference numerals are assigned to the same components.

As shown in FIG. 6 , the liquid crystal display according to the second embodiment of the present invention includes a lower substrate 10 , an upper substrate 20 , a liquid crystal layer 30 , a lower polarizing plate 40 , and an upper polarizing plate 50 . , and a reflective unit 60 .

The lower substrate 10, the upper substrate 20, and the liquid crystal layer 30 are provided in the liquid crystal panel and play a key role in image display. The lower substrate 10 and the upper substrate 20 are the liquid crystal panels. It is bonded face to face with the layer 30 interposed therebetween, and an image is displayed using light irradiated from a backlight unit (not shown).

At this time, although not shown in FIG. 6 , a plurality of gate lines and data lines intersect to define a pixel on the inner surface of the lower substrate 10 , and a thin film transistor (Thin) is formed at each intersection of the gate line and the data line. Film Transistor (TFT) is provided and is connected one-to-one with the transparent pixel electrode formed in each pixel.

Accordingly, when the thin film transistor selected for each gate line is turned on by the on/off signal transmitted through the gate line, the signal voltage is transmitted to the corresponding pixel electrode through the data line, and the resulting electric field between the pixel electrode and the common electrode The liquid crystal arrangement of the liquid crystal layer 30 is changed to change the transmittance.

In addition, a desired image may be displayed while light irradiated from the backlight unit passes through the liquid crystal layer 30 of which transmittance is changed.

The lower polarizing plate 40 is provided under the lower substrate 10 to polarize light emitted from the backlight unit, and the upper polarizing plate 50 is provided on the upper substrate 20 to provide the liquid crystal layer 30 and the upper portion. The light passing through the substrate 20 is polarized.

In particular, the upper substrate 20 and the lower substrate 10 of the liquid crystal display according to the second embodiment of the present invention include a transmissive region and a reflective region.

In addition, the liquid crystal display according to the present invention has, for example, red (R), green (G), and blue (B) color filters corresponding to each pixel on the thin film transistor provided on the lower substrate 10 . It may be a color filter on TFT (COT) type having a color filter.

In addition, the liquid crystal display according to the present invention does not include a black matrix covering non-display elements such as a gate line, a data line, and a thin film transistor by covering each of the color filters in the prior art. It can perform the role of a black matrix through phase difference and alignment control on the liquid crystal layer.

In particular, in the liquid crystal display according to the second embodiment of the present invention, the alignment direction of the liquid crystal 31a aligned by the upper substrate 20 and the alignment direction of the liquid crystal 31b aligned by the lower substrate 10 in the reflection region Provided in the same direction, but by adjusting the angle formed by the liquid crystals 31a and 31b aligned on the upper substrate 20 and the lower substrate 10 with the absorption axis A of the upper polarizing plate 50, respectively, It is characterized in that it lowers the reflectance of external light.

In the second embodiment of the present invention, the liquid crystal oriented by the upper substrate means liquid crystal oriented in the alignment direction of the alignment layer (not shown) of the upper substrate in contact with the upper substrate, and the liquid crystal oriented by the lower substrate means the lower substrate It means a liquid crystal aligned in the alignment direction of the alignment layer (not shown) of the lower substrate in contact with. Accordingly, that the alignment direction of the liquid crystal oriented by the upper substrate and the alignment direction of the liquid crystal oriented by the lower substrate are the same means that the alignment direction of the alignment film of the upper substrate and the alignment direction of the alignment film of the lower substrate are the same.

However, the phase difference dΔn of the liquid crystal layer 30 is generally provided with a predetermined value {λ*(1/2)}, and the phase difference of the liquid crystal layer 30 is constant, and the upper substrate ( When the alignment direction of the liquid crystal 31a aligned by 20) and the alignment direction of the liquid crystal 31b aligned by the lower substrate 10 are the same, compared to the absorption axis A of the upper polarizing plate 50 Even if the alignment angle of the liquid crystals 31a and 31b is changed, the reflectance does not change significantly.

7 is a graph illustrating a change in reflectance according to an alignment direction of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region when the phase difference of the liquid crystal layer is constant.

The X-axis of FIG. 7 means the alignment angle of the liquid crystals 31a and 31b aligned by the upper substrate 20 and the lower substrate 10 in the reflection region, and the Y-axis means the reflectance of external light. The reflectance is shown by changing the alignment angle of the liquid crystals 31a and 31b while changing the phase difference of the liquid crystal layer 30 between the upper substrate 20 and the lower substrate 10 as in Y1 to Y3 in the region.

As shown in FIG. 7 , it can be seen that even if the alignment angle of the liquid crystals 31a and 31b is changed, the reflectivity is not affected in a state where the phase difference of the liquid crystal layer 30 is maintained at λ*(1/2). In the state where the phase difference of the liquid crystal layer 30 is changed to ±10% compared to λ*(1/2), the reflectance is slightly lowered when the alignment angle of the liquid crystals 31a and 31b is 45° or 135° can confirm.

However, in the state where there is no change in the phase difference of the liquid crystal layer 30, even if the alignment angle of the liquid crystals 31a and 31b is optimally adjusted, the reflectance is only improved by about 10%, so in the second embodiment of the present invention, Optimum that can lower reflectance by further changing the phase difference of the liquid crystal layer 30 as well as the alignment angle of the liquid crystals 31a and 31b aligned by the upper substrate 20 and the lower substrate 10 in the transmission region conditions were derived.

8 is a graph illustrating a change in reflectance according to an alignment direction and a phase difference of a liquid crystal layer between an upper substrate and a lower substrate in a reflective region of a liquid crystal display according to a second exemplary embodiment of the present invention.

The X-axis of FIG. 8 means the phase difference (unit λ) of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the reflective region, and the Y-axis means the reflectance of external light, FIG. 8 In the reflection region, the reflectance caused by changing the phase difference of the liquid crystal layer 30 while changing the alignment angle of the liquid crystals 31a and 31b aligned by the upper substrate 20 and the lower substrate 10 as Z1 to Z10 indicates.

Referring to FIG. 8 , the reflective region is provided in a state where the phase difference of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the reflective region is λ/4 or 3*(λ/4). When the alignment angle of the liquid crystals 31a and 31b aligned by the upper substrate 20 and the lower substrate 10 is 45° or 135°, it can be seen that the reflectance is close to zero.

The optimum retardation dΔn of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the reflective region according to the second embodiment of the present invention derived through FIG. 8 is obtained by the following equation equal to 1.

That is, in the reflective region, the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 is expressed in Equation 1 such as λ/4, 3*(λ/4), 5*(λ/4), etc. When the phase difference of , the reflectance of external light can be lowered.

In this case, λ means the wavelength of external light, which may reflect the wavelength of external light incident in a space where the liquid crystal display according to the present invention is mainly used, and preferably green (550 nm) that is easily visible to humans. The phase difference of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the reflection region may be set by reflecting the wavelength.

In addition, the optimum of the liquid crystals 31a and 31b oriented by the upper substrate 20 and the lower substrate 10 in the reflection region with respect to the absorption axis A of the upper polarizing plate 50 according to the second embodiment of the present invention The orientation angle (deg) of is expressed in Equation 2 below.

Hereinafter, when the liquid crystal layer 30 between the upper substrate 20 and the lower substrate 10 in the reflective region is provided to satisfy Equations 1 and 2, the path of external light incident to the reflective region will be examined. let's see

As shown in FIG. 6 , the external light incident to the reflection region is linearly polarized by the absorption axis A of the upper polarizing plate 50 , so that only the component L1 perpendicular to the absorption axis A is the liquid crystal layer 30 . is investigated with

And, as the phase difference of the liquid crystal layer 30 between the upper substrate 20 and the lower substrate 10 in the reflection region satisfies the λ/4 condition, the linearly polarized external light passes through the liquid crystal layer 30 and is As the polarized (L2) and circularly polarized external light is reflected by the reflection unit 60, the direction of the circularly polarized light is reversed (L3).

Then, the circularly polarized external light L3 is linearly polarized while passing through the liquid crystal layer 30 again (L4). Since the linearly polarized external light has a component parallel to the absorption axis A of the upper polarizing plate 50, the Most of it is absorbed by the upper polarizing plate 50 .

As described above, in the second embodiment of the present invention, the polarization state of external light is changed by adjusting the phase difference dΔn and the orientation angle of the liquid crystal layer 30 between the upper substrate 20 and the lower substrate 10 in the reflection region. By doing so, the reflectance can be lowered.

Meanwhile, in the second embodiment of the present invention, the polarization state of external light should not be changed while passing through the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the transmissive region.

Specifically, the alignment direction of the liquid crystal oriented by the upper substrate 20 and the lower substrate 10 in the transmission region so as not to change the polarization state of external light is provided parallel or perpendicular to the absorption axis of the upper polarizing plate 50, It is provided perpendicular to the upper polarizing plate 50 .

That is, the alignment direction of the liquid crystal aligned by the upper substrate 20 and the lower substrate 10 in the transmission region may be provided as shown in FIGS. 5A to 5C described above.

9 is a view showing a liquid crystal display according to a second embodiment of the present invention including a buffer layer provided to adjust the thickness of the liquid crystal layer.

As described above, in the second embodiment of the present invention, it is necessary to change the polarization state of external light by adjusting the phase difference of the liquid crystal layer 30 between the upper substrate 20 and the lower substrate 10 in the reflective region, FIG. The phase difference of the liquid crystal layer 30 may be adjusted by variously adjusting the thickness of the liquid crystal layer 30 as shown in FIGS. 9A to 9F .

9A is a view in which the thickness of the liquid crystal layer 30 is adjusted through the buffer layer 70 convexly provided on the lower substrate 10 and the reflective layer 60, and FIG. 9B is the upper substrate 20. It is a view in which the thickness of the liquid crystal layer 30 is adjusted through the buffer layer 70 provided to be convex, and FIG. 9C is convex on the lower substrate 10 , the reflective layer 60 , and the lower portion of the upper substrate 20 . It is a view in which the thickness of the liquid crystal layer 30 is adjusted through a buffer layer 70 provided in the upper part of the liquid crystal layer, and FIG. The thickness of the layer 30 is adjusted, and FIG. 9E is a view in which the thickness of the liquid crystal layer 30 is adjusted through the buffer layer 70 concavely provided under the upper substrate 20, and FIG. 9F is The thickness of the liquid crystal layer 30 is adjusted through the buffer layer 70 concavely provided on the lower substrate 10 , the reflective layer 60 , and on the lower portion of the upper substrate 20 .

The buffer layer 70 may be formed of an inorganic insulating material, for example, a silicon oxide layer (SiOX) or a silicon nitride layer (SiNX), but is not limited thereto.

As shown in FIGS. 9A to 9C , the thickness dR of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the reflective region is the same as the upper substrate 20 and the upper substrate 20 in the transmissive region. It may be formed thinner than the thickness dT of the liquid crystal layer 30 provided between the lower substrate 10, and as shown in FIGS. 9D to 9F, the upper substrate 20 and the lower substrate ( 10) The thickness dR of the liquid crystal layer 30 provided between them is thicker than the thickness dT of the liquid crystal layer 30 provided between the upper substrate 20 and the lower substrate 10 in the transmissive region. it might be

That is, the liquid crystal display device according to the second embodiment of the present invention includes the buffer layer 70 in various forms, so that the liquid crystal layer 30 is provided between the upper substrate 20 and the lower substrate 10 in the reflective region. The thickness of the liquid crystal layer 30 may be adjusted so that the phase difference of the liquid crystal layer 30 satisfies Equation 1, and the thickness of the liquid crystal layer 30 may be adjusted through various methods not described.

10 is a view illustrating a liquid crystal display device according to the present invention and a path of external light incident to the liquid crystal display device.

Referring to FIG. 10 , the liquid crystal display according to the present invention includes a transmissive region and a reflective region, and external light incident between the upper substrate 20 and the lower substrate 10 in the transmissive region is transmitted by the upper polarizing plate 50 . The polarized, polarized external light is absorbed by the lower polarizer 40 .

In addition, external light incident between the upper substrate 20 and the lower substrate 10 in the reflective region is polarized by the upper polarizing plate 50 , and the polarization state is changed as the polarized external light passes through the liquid crystal layer 30 . Therefore, after being reflected by the reflector 60 , it is absorbed by the upper polarizing plate 50 .

That is, the liquid crystal display device according to the present invention has a different alignment direction of the liquid crystal oriented by the upper substrate 20 and the liquid crystal oriented by the lower substrate 10 in the reflective region, or the upper substrate in the reflective region. By providing such that the phase difference and alignment angle of the liquid crystal layer 30 provided between the 20 and the lower substrate 10 satisfy predetermined conditions, the reflectance of external light by the reflector 60 can be reduced.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

10: lower substrate 20: upper substrate
30: liquid crystal layer 40: lower polarizing plate
50: upper polarizer 60: reflector
70: buffer layer

Claims (11)

an upper substrate and a lower substrate each having a transmissive region and a reflective region;
a liquid crystal layer provided between the upper substrate and the lower substrate; and
and an upper polarizing plate provided on an upper portion of the upper substrate,
The alignment direction of the liquid crystal oriented by the upper substrate in the reflective region and the alignment direction of the liquid crystal oriented by the lower substrate in the reflective region are different from each other,
At least one of the liquid crystal oriented by the upper substrate in the reflective region or the liquid crystal oriented by the lower substrate in the reflective region is provided to form a predetermined angle with the absorption axis of the upper polarizing plate,
The liquid crystal oriented by the upper substrate in the reflective region is oriented to form an angle of 80° with the absorption axis of the upper polarizing plate, and the liquid crystal oriented by the lower substrate in the reflective region is aligned with the absorption axis of the upper polarizing plate 145 in the reflective region. A liquid crystal display oriented to form an angle of °. According to claim 1,
At least one of the liquid crystal oriented by the upper substrate and the liquid crystal oriented by the lower substrate is oriented differently in the transmissive region and the reflective region. 3. The method of claim 2,
The alignment direction of the liquid crystal aligned by the upper substrate in the transmissive region and the alignment direction of the liquid crystal aligned by the lower substrate in the transmissive region are the same as each other. According to claim 1,
The liquid crystal display device further comprising a lower polarizing plate provided under the lower substrate. delete 5. The method of claim 4,
An alignment direction of the liquid crystal aligned by the upper and lower substrates in the transmission region is parallel or perpendicular to an absorption axis of the upper polarizing plate, or perpendicular to the upper polarizing plate. delete delete delete an upper substrate and a lower substrate having a transmissive region and a reflective region;
a liquid crystal layer provided between the upper substrate and the lower substrate;
an upper polarizing plate provided on the upper substrate; and
a buffer layer provided on a lower portion of the upper substrate or an upper portion of the lower substrate;
The phase difference (dΔn) of the liquid crystal layer provided between the upper substrate and the lower substrate in the reflective region is,

is satisfied with
d is the thickness of the liquid crystal layer provided between the upper substrate and the lower substrate in the reflection region, Δn is the refractive index of the liquid crystal layer provided between the upper substrate and the lower substrate, and λ is the wavelength of incident light,
The liquid crystal oriented by the upper substrate in the reflective region is oriented to form an angle of 80° with the absorption axis of the upper polarizing plate, and the liquid crystal oriented by the lower substrate in the reflective region is aligned with the absorption axis of the upper polarizing plate 145 in the reflective region. A liquid crystal display oriented to form an angle of °. 11. The method of claim 10,
The alignment direction of the liquid crystal oriented by the upper substrate in the transmissive region and the alignment direction of the liquid crystal oriented by the lower substrate in the transmissive region are the same as each other,
An alignment direction of the liquid crystal aligned by the upper and lower substrates in the transmission region is parallel or perpendicular to an absorption axis of the upper polarizing plate, or perpendicular to the upper polarizing plate.

Images