KR102366365B1 - Reflective liquid crystal film and display device including the same - Google Patents

Abstract

The present embodiments disclose a reflective liquid crystal film and a display device including the same. The reflective liquid crystal film and the display device including the same according to the disclosed embodiments are disposed at a display panel and a rear surface of the display panel, and are positioned at a position where light emitted from the backlight unit and the light source assembly including the light source assembly is incident, and a plurality of At least one cholesteric liquid crystal layer containing liquid crystal molecules of Through this, the luminance of the display device and the color gamut of a color corresponding to a specific wavelength may be improved.

Description

Reflective liquid crystal film and display device including same

The present embodiments relate to a reflective liquid crystal film and a display device including the same.

A liquid crystal display (LCD) is a device that displays an image by injecting liquid crystal between two glass plates, applying power to the upper and lower glass plate electrodes, and changing the arrangement of liquid crystal molecules in each pixel. Unlike a cathode ray tube display (CRT), a plasma display panel (PDP), etc., the display by the liquid crystal display itself is non-luminescent, so it cannot be used in a place where there is no light. In order to compensate for this disadvantage and to enable use in a dark place, a lighting device irradiated uniformly on the information display surface, for example, a light source assembly is mounted.

A light source assembly used in a liquid crystal display is largely divided into two types. The first is an edge-type light source assembly that provides light from the side of the liquid crystal display, and the second is a direct-type light source assembly that provides light directly from the back of the liquid crystal display. In the case of the edge-type light source assembly, a light guide plate is provided so that light emitted from the light source is irradiated upward, and at least one optical channel is provided above the light guide plate to adjust optical characteristics of light passing through the light guide plate. In the case of the direct light source assembly, a diffusion plate may be provided to reduce a bright line of light emitted from the light source, and at least one optical sheet may be provided to control optical characteristics of light passing through the diffusion plate.

In addition, the liquid crystal display includes a polarizing plate disposed above and below the display panel. The upper polarizing plate positioned above the display panel includes a surface treatment layer to separate light incident from the display panel into a wavelength of red light and a wavelength of green light, or is used to attach the upper polarizer to the display panel A light-absorbing material is included in the pressure-sensitive adhesive (or adhesive) layer.

However, in this case, since the upper polarizing plate does not have a means for branching to the wavelength of blue light, the high color reproducibility of the light emitted from the display panel 100 to the outside is low. In addition, since a new material is required to separate the wavelength corresponding to blue light through the light absorbing material, there is a problem in that it is difficult to adjust the absorption band with the existing light absorbing material.

The present embodiments are intended to solve the above-described problems, and to provide a reflective liquid crystal film capable of improving color gamut and a display device including the same.

A reflective liquid crystal film and a display device including the same according to an embodiment include at least one cholesteric liquid crystal layer including a plurality of liquid crystal molecules, and a peak of a central wavelength of reflected light is 430 nm, and The full width at half maximum is 42 nm.

In addition, a reflective liquid crystal film and a display device including the same according to another embodiment are disposed at a display panel and a rear surface of the display panel, and are positioned at a position where light emitted from the backlight unit and the light source assembly including the light source assembly is incident, and a plurality of At least one cholesteric liquid crystal layer containing liquid crystal molecules of

Since the display device according to the present embodiments includes the reflective liquid crystal film, the luminance is improved through a recycling phenomenon that occurs due to continuous re-reflection of the light reflected by the reflective liquid crystal film, and It has the effect of increasing the color gamut of colors.

1 is a diagram illustrating a display device according to a first embodiment.
2 is a graph showing a central wavelength and a half maximum width of reflected light of the reflective liquid crystal film according to the first embodiment.
3 is a diagram illustrating a principle in which light having a specific wavelength is recycled by a reflective liquid crystal film in the display device according to the first embodiment.
4 is a graph comparing the wavelength of light re-incident to the display panel due to the reflective liquid crystal film according to the present embodiment and the wavelength of light incident to the display panel of the display device according to the comparative example.
5 is a graph showing the blue color coordinates of the display device according to the comparative example, the color coordinates of the DCI-P3 blue standard, and the blue color coordinates of the display device according to the present embodiment.
6 is a diagram illustrating a display device according to a second exemplary embodiment.
7 is a diagram illustrating a display device according to a third embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other shapes. And in the drawings, the size and thickness of the device may be exaggerated for convenience. Like reference numerals refer to like elements throughout.

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 a variety of different shapes, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. The sizes and relative sizes of layers and regions in the drawings may be exaggerated for clarity of description.

Reference to an element or layer to another element or “on” or “on” includes not only directly on the other element or layer, but also with other layers or other elements interposed therebetween. do. On the other hand, reference to an element "directly on" or "directly on" indicates that there are no intervening elements or layers.

Spatially relative terms "below, beneath", "lower", "above", "upper", etc. are one element or component as shown in the drawings. and can be used to easily describe the correlation with other devices or components. The spatially relative term should be understood as a term including different directions of the device during use or operation in addition to the directions shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above.

In addition, in describing the components of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, order, or number of the elements are not limited by the terms. When it is described that a component is “connected”, “coupled” or “connected” to another component, the component may be directly connected or connected to the other component, but other components may be interposed between each component. It should be understood that each component may be “interposed” or “connected”, “coupled” or “connected” through another component.

The terminology used herein is for the purpose of describing the embodiments, and thus is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprise” and/or “comprising” refers to the presence of one or more other components, steps, operations, and/or elements mentioned. or addition is not excluded.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a diagram illustrating a display device according to a first embodiment. Referring to FIG. 1 , the display device according to the first embodiment includes a display panel 100 and a backlight unit 200 . The display panel 100 includes a cell 110 including a lower substrate, an upper substrate, and a liquid crystal layer, polarizing plates 120 and 130 disposed below and above the cell, and a reflective liquid crystal attached to the lower polarizing plate 120 . a film 250 . Meanwhile, although not shown in the drawings, the display device according to the present embodiment may further include a driving unit for driving the display panel 100 , and in this case, at least one driving unit may be mounted in the display panel 100 . However, the present embodiment is not limited thereto.

Also, although not shown in FIG. 1 , the cell of the display panel 100 includes an upper substrate and a lower substrate, and includes a liquid crystal layer interposed between the upper substrate and the lower substrate. In this case, a plurality of thin film transistors may be disposed on the lower substrate, and a plurality of color filter layers may be disposed on one surface of the upper substrate. However, the display panel 100 according to the present embodiment is not limited thereto, and a plurality of color filter layers may be disposed on the lower substrate for each sub-pixel.

A common electrode and a pixel electrode are formed in the cell 110 of the display panel 100 to which the upper substrate and the lower substrate are bonded, and an electric field is applied to the liquid crystal layer. Data applied to the pixel electrode while a voltage is applied to the common electrode When the voltage of the signal is controlled, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode, thereby transmitting or blocking light for each pixel to display text or images. In addition, in order to control the voltage of the data signal applied to the pixel electrode for each pixel, a switching device such as a thin film transistor is individually provided in the pixels.

The upper polarizing plate 130 is disposed above the cell 110 configured as described above, and the lower polarizing plate 120 is disposed below the cell 110 . The lower polarizing plate 120 polarizes the light passing through the backlight unit 200 , and the upper polarizing plate 130 polarizes the light passing through the display panel.

The backlight unit 200 includes a plurality of optical sheets 230 , a light guide plate 220 , and a light source assembly 210 disposed under the display panel 100 .

When the backlight unit 200 is described in detail, the backlight unit 200 includes a plurality of optical sheets 230 disposed on the rear surface of the display panel 100 . In addition, the backlight unit 200 includes a light guide plate 220 disposed on the rear surface of the plurality of optical sheets 230 and a light source assembly 210 that generates light from at least one side of the light guide plate 220 .

The plurality of optical sheets 230 includes a diffusion sheet 231 , a lower prism sheet 232 , and an upper prism sheet 233 , and in some cases, a protective sheet may be further added. Specifically, the diffusion sheet 231 may be located on the light guide plate 220 , the lower prism sheet 232 may be located on the diffusion sheet 231 , and the upper prism sheet 233 may be located on the lower prism sheet It may be located on (232).

The diffusion sheet 231 disperses the light incident from the light guide plate 220 , thereby preventing the light from being partially concentrated and causing stains on the image displayed on the display panel 100 , and bend the angle vertically. The lower prism sheet 232 and the upper prism sheet 233 collect light incident from the diffusion sheet 231 and uniformly distribute it over the entire surface of the display panel 100 . In addition, the protective sheet may serve to protect the optical sheet 230 sensitive to dust or scratches, and to prevent the flow of the optical sheet 230 when the backlight unit is transported.

The light guide plate 220 disposed on the rear surface of the plurality of optical sheets 230 converts the photometric light irradiated from the light source assembly 210 provided on at least one side of the light guide plate 220 into planar light to be irradiated onto the display panel 100 . there is. Meanwhile, the light guide plate 220 according to the present embodiment may be formed in an inclined shape.

For example, as shown in FIG. 1 , when the light source assembly 210 is provided on only one side of the light guide plate 220 , the area of the light guide plate 220 including the light incident surface through which light from the light source assembly 210 is incident is formed. The thickness of the light guide plate 220 may decrease as the distance from the light source assembly 210 increases. Through this, it is possible to prevent a phenomenon in which the light incident on the light guide plate 220 is not uniform and thus a bright spot is generated.

However, the present embodiment is not limited thereto, and the light source assembly 210 may be disposed on at least two side surfaces of the light guide plate 220 , and the light guide plate 220 may have a rectangular parallelepiped shape with a uniform thickness. In addition, in order to improve the uniformity of light incident on the light guide plate 220 , a plurality of protrusions may be further provided on the upper surface or the rear surface of the light guide plate 220 , or on both surfaces of the upper and rear surfaces.

In the following description, for convenience of explanation, the light source assembly 210 is provided on only one side of the light guide plate 220 , and the thickness of the region of the light guide plate 220 including the light incident surface through which light from the light source assembly 210 is incident is the greatest. A configuration in which the thickness of the light guide plate 220 becomes thinner as it is thick and farther away from the light source assembly 210 will be mainly described.

The light source assembly 210 provided on at least one side of the light guide plate 220 includes a light source array 201 and a light source printed circuit board (PCB) for driving the light source array 201 . Meanwhile, a plurality of light sources may be provided and may be arranged at equal intervals on the light source printed circuit board.

The light source assembly is mounted on the light source housing 202 , and the light source housing 202 can protect the light source assembly and prevent light loss by concentrating the light emitted from the plurality of light sources in the direction of the light guide plate 220 . In addition, the light source housing 202 may serve to improve the heat dissipation effect of the light source assembly.

Meanwhile, although not shown in the drawings, a reflective plate may be further disposed on the rear surface of the light guide plate 320 . Light emitted from the light source array 201 according to the present embodiment is incident on the side surface of the light guide plate 220 , and the reflective plate disposed on the rear surface of the light guide plate 220 transmits light transmitted through the rear surface of the light guide plate 220 to the light guide plate 220 . The light is reflected toward the plurality of optical sheets 230 on the upper surface to be emitted in the direction of the display panel 100 .

In addition, the backlight unit 200 according to the present embodiment may further include a cover bottom for accommodating the light guide plate 320 , and a guide panel for supporting the display panel 100 .

Meanwhile, the upper polarizing plate 130 includes a surface treatment layer or displays the upper polarizing plate 130 to separate the light incident from the display panel 100 into a wavelength of red light and a wavelength of green light. A light-absorbing material is included in the pressure-sensitive adhesive (or adhesive) layer used to attach to the panel 100 . Through this, interference between red light and green light is reduced to improve color purity.

However, in this case, since the upper polarizing plate 130 does not have a means for branching into the wavelength of blue light, the light emitted from the display panel 100 to the outside has an effect of expanding the color gamut to the blue wavelength region is insignificant. As a result, high color reproducibility is reduced. In addition, since the light absorption band of the light absorption material is an inherent property of the material, it is necessary to develop a new material in order to adjust the absorption band through the light absorption material. That is, since a new material is required to separate the wavelength corresponding to blue light through the light absorbing material, there is a problem in that it is difficult to adjust the absorption band with the existing light absorbing material.

The display device according to the first embodiment is to solve this problem, and includes a reflective liquid crystal film 250 disposed between the display panel 100 and the backlight unit 200 . Specifically, the reflective liquid crystal film 250 may be attached to the lower polarizing plate 120 of the display panel 100 . Since the reflective liquid crystal film 250 is attached to the lower polarizing plate 120 of the display panel 100 , the light generated from the light source assembly 210 may pass through the backlight unit 200 to be incident on the reflective liquid crystal film 250 . there is.

The reflective liquid crystal film 250 includes a cholesteric liquid crystal layer including a cholesteric liquid crystal (or chiral nematic liquid crystal). The cholesteric liquid crystal may include a nematic liquid crystal and a chiral dopant, but the present embodiment is not limited thereto. The cholesteric liquid crystal has a constant pitch and has a repeatedly twisted helical structure. The repeated twisted helical structure induces a Bragg reflection of light.

The reflective liquid crystal film 250 including the cholesteric liquid crystal layer may be formed of a single layer as shown in FIG. 1 , but the present embodiment is not limited thereto. In addition, all of the cholesteric liquid crystal molecules of the cholesteric liquid crystal layer included in the reflective liquid crystal film 250 may be made of the same material. Through this, the same optical characteristics can be induced in all regions of the cholesteric liquid crystal layer.

The cholesteric liquid crystal is classified into a right-handed cholesteric liquid crystal and a lefthanded cholesteric liquid crystal according to the twisted direction of the helical structure. Right-handed cholesteric liquid crystals reflect right-circularly polarized light but transmit left-circularly polarized light. The left-handed cholesteric liquid crystal transmits right-circularly polarized light but reflects left-circularly polarized light.

That is, when light including left-circularly polarized light and left-circularly polarized light is incident from the outside, the cholesteric liquid crystal layer reflects light having a wavelength corresponding to the liquid crystal pitch of each region among the left-circularly and right-circularly polarized light. For example, when the cholesteric liquid crystal layer includes a preferential cholesteric liquid crystal, when light including left-circular and right-circular polarization is incident from the outside, the cholesteric liquid crystal layer reflects the right-circularly polarized light, but Among the polarized light, light having a wavelength corresponding to the liquid crystal pitch of each region is reflected.

The pitch of the cholesteric liquid crystal is related to the wavelength of the reflected light. The central wavelength of the reflected light reflected by the cholesteric liquid crystal is generally proportional to the liquid crystal pitch. Here, the central wavelength of the reflected light may mean a wavelength maximum reflected within the bandwidth or an average wavelength of the bandwidth when the reflected light reflected by the cholesteric liquid crystal has a predetermined bandwidth.

That is, the central wavelength of the reflected light of the reflective liquid crystal film 250 including the cholesteric liquid crystal layer may be determined by the average refractive index of the cholesteric liquid crystal and the pitch of the cholesteric liquid crystal, and the spiral structure of the cholesteric liquid crystal The reflected circularly polarized light may be determined according to the twisted direction.

In the reflective liquid crystal film 250 including the cholesteric liquid crystal layer according to the present embodiment, the pitch of the cholesteric liquid crystal may be 275 nm to 280 nm, and the refractive index of the liquid crystal may be 1.53 to 1.56. Accordingly, the peak of the central wavelength of the reflected light of the reflective liquid crystal film 250 and the half width of the peak may be adjusted.

This will be reviewed in detail with reference to FIG. 2 as follows. 2 is a graph showing the central wavelength and full width at half maximum of the reflected light of the reflective liquid crystal film according to the first embodiment (transmittance and reflectance are measured three times each (transmittance 1 to 3, reflectance 1 to 3) for reliability of numerical values) did).

The wavelength range of the reflected light of the reflective liquid crystal film according to the present embodiment may be 370 nm to 500 nm. Specifically, the peak of the central wavelength of the reflected light may be 430 nm and the peak width at half maximum may be 42 nm. That is, the wavelength of the reflected light mainly reflected through the reflective liquid crystal film may be 388 nm to 472 nm. As described above, since the peak of the central wavelength of the reflected light of the reflective liquid crystal film is 430 nm and the peak width at half maximum is 42 nm, part of the light mainly having a wavelength of 388 nm to 472 nm among the light incident on the reflective liquid crystal film 250 is reflected and transmitted can do it

Specifically, the reflective liquid crystal film according to the present embodiment may reflect 12% to 50% of light having a central wavelength peak of 430 nm and a peak peak width of 42 nm, and the reflective liquid crystal film according to this embodiment has a central wavelength It is possible to transmit 50% to 88% of light having a peak wavelength of 430 nm and a peak width at half maximum of 42 nm. In addition, the reflective liquid crystal film according to the present embodiment may reflect 46% to 50% of light having a wavelength of 430 nm and transmit 50% to 54% of light having a wavelength of 430 nm.

That is, referring to FIGS. 1 and 2 , in the reflective liquid crystal film 250 according to the present embodiment, a peak of a central wavelength of light provided from the backlight unit 200 is 430 nm and a portion of the light having a peak width at half maximum of 42 nm is displayed. The remaining portion of light transmitted in the direction of the panel 100 and having a peak of a central wavelength of 430 nm and a peak width of 42 nm at half maximum may be reflected in the direction of the backlight unit 200 . In addition, the reflective liquid crystal film 250 transmits most of the light in the remaining wavelength bands in the direction of the display panel 100 except for light having a peak center wavelength of 430 nm and a peak width of 42 nm. This is because the light of the wavelength band other than the 42 nm light is not included in the bandwidth of the reflected light of the reflective liquid crystal film 250 .

Meanwhile, some of the light reflected by the reflective liquid crystal film 250 among the light having a central wavelength peak of 430 nm and a peak width of 42 nm may be recycled and incident on the display panel 100 . This configuration is reviewed with reference to FIG. 3 as follows.

3 is a diagram illustrating a principle in which light having a specific wavelength is recycled by a reflective liquid crystal film in the display device according to the first embodiment. The display device according to FIG. 3 may include the same components as those of FIG. 1 described above. A description overlapping with FIG. 1 described above may be omitted. Also, the same components have the same reference numerals.

Referring to FIG. 3 , the display device according to the first embodiment includes a display panel 100 , a display panel 100 , a backlight unit 200 disposed on a rear surface of the display panel 100 , and a lower polarizing plate of the display panel 100 . (120) and a reflective liquid crystal film 250 attached to the rear surface. Here, the reflective liquid crystal film 250 may be provided between the display panel 100 and the backlight unit 200 .

In the display device according to the first embodiment, light generated from the light source assembly 210 passes through the light guide plate 220 and the plurality of optical sheets 230 to reach the reflective liquid crystal film 250 attached to the rear surface of the lower polarizing plate 120 . do. Since the reflective liquid crystal film 250 includes a cholesteric liquid crystal layer, a portion of light in a specific wavelength range may be reflected and the remaining portion may be transmitted.

Specifically, in the reflective liquid crystal film 250 , a portion (a) of light provided from the backlight unit 200 with a central wavelength peak of 430 nm and a peak full width of 42 nm can be transmitted in the direction of the display panel 100 . In addition, the remaining part (b) of the light having a central wavelength peak of 430 nm and a peak width at half maximum of 42 nm is reflected toward the backlight unit 200 .

The light reflected in the direction of the backlight unit 200 is reflected by a reflective plate disposed on the rear surface of the light guide plate 220 to reach the reflective liquid crystal film 250 again, and a portion of the light reaching the reflective liquid crystal film 250 is It is transmitted in the direction of the display panel 100 , and the remaining part may be reflected in the direction of the backlight unit 200 . That is, the light reflected in the direction of the backlight unit 200 by the reflective liquid crystal film 250 film is continuously re-reflected between the reflective plate of the backlight unit 200 and the reflective liquid crystal film 250, thereby recycling the light A (recycling) effect may appear to improve the luminance of the display panel 100 .

As described above, by using the reflective liquid crystal film 250 according to the present embodiment, the light generated from the light source assembly 210 is not incident toward the display panel 100 , but the reflected light is recycled to the display panel 100 . can be re-enrolled. Meanwhile, the re-incident light may be incident on the display panel 100 with its wavelength converted. A review of this configuration with reference to FIG. 4 is as follows.

4 is a graph comparing the wavelength of light re-incident to the display panel due to the reflective liquid crystal film according to the present embodiment and the wavelength of light incident to the display panel of the display device according to the comparative example. Here, the display device according to the comparative example means a display device that does not include the reflective liquid crystal film according to the present embodiment. That is, the display device according to the comparative example includes only the display panel and the backlight unit disposed on the rear surface of the display panel.

Referring to FIG. 4 , a peak corresponding to blue light among the lights incident on the display panel of the display device according to the present embodiment is blue light among the lights incident on the display panel of the display device according to the comparative example. It can be seen that the peak corresponding to is moved in the long wavelength direction.

That is, in the display device according to the present embodiment, a light recycling phenomenon occurs due to the reflective liquid crystal film attached to the rear surface of the lower polarizing plate of the display panel, and a peak corresponding to blue light due to the light re-incident to the display panel can be moved in the long-wavelength direction. As such, by shifting the wavelength of the peak corresponding to the blue light, the blue color coordinates may also be changed.

In addition, since the peak of the central wavelength of the reflected light of the reflective liquid crystal film according to the present embodiment is 430 nm and the half width of the peak is 42 nm, the wavelength of the reflected light is narrowed, so that the recycled reflected light is clear blue light may be moved in the direction of the peak corresponding to .

Specifically, when the peak width of the wavelength of the reflected light is wide, the width of the reflected light whose wavelength is shifted in the long wavelength direction after being recycled will also be wide. Instead, it may include wavelengths corresponding to wavelengths of other colors. In this case, since a wavelength corresponding to a color other than blue light is incident on the display panel, color gamut may decrease. That is, since the wavelength width of the reflected light of the reflective liquid crystal film according to the present exemplary embodiment is narrowed, the color reproducibility of the display panel can be improved.

This configuration is reviewed with reference to FIG. 5 as follows. 5 is a graph showing the blue color coordinates of the display device according to the comparative example, the color coordinates of the DCI-P3 blue standard, and the blue color coordinates of the display device according to the present embodiment. Here, the display device according to the comparative example has the same configuration as the display device according to the comparative example described above with reference to FIG. 4 .

Referring to FIG. 5 , since the display device according to the present embodiment includes the reflective liquid crystal film, it can be moved by (-0.01, 0.03) in the blue color coordinate system in the CIE 1976 color coordinate system according to the comparative example. As such, by moving the blue color coordinates of the display device according to the present embodiment by (-0.01, 0.03) from the blue color coordinates of the display device according to the comparative example, the color coordinates of the DCI-P3 Blue standard (0.175, Blue color coordinates close to 0.158) can be made.

In this case, the blue color coordinates of the display device according to the present embodiment have an effect that the overlapping area with the DCI-P3 blue standard is improved by 3% compared to the blue color coordinates of the display device according to the comparative example. In other words, the blue color coordinates of the display device according to the present embodiment increase the overlapping area with the DCI-P3 blue standard compared to the blue color coordinates of the display device according to the comparative example, so that the It is possible to increase the color gamut of the display device.

Next, the display device according to the second embodiment will be reviewed with reference to FIG. 6 . 6 is a diagram illustrating a display device according to a second exemplary embodiment. The display device according to the second embodiment may include the same components as the display device according to the first embodiment described above. A description that overlaps with the display device according to the first exemplary embodiment described above may be omitted. Also, the same components have the same reference numerals.

Referring to FIG. 6 , the display device according to the second embodiment includes a display panel 500 and a backlight unit 300 disposed on the rear surface of the display panel 100 . In addition, the backlight unit 300 may include a reflective liquid crystal film 350 . The reflective liquid crystal film 350 may be attached on the plurality of optical sheets 230 . In this case, the light generated from the light source assembly 210 may be incident on the reflective liquid crystal film 350 through the light guide plate 220 and the plurality of optical sheets 230 .

Specifically, the liquid crystal film 350 for reflection may be attached on the upper prism sheet 233 . However, this embodiment is not limited thereto, and when the plurality of optical sheets 230 includes a protective sheet disposed on the upper prism sheet 233 , the liquid crystal film 350 for reflection may be attached on the protective sheet. can That is, it is sufficient if the liquid crystal film 350 for reflection according to the present embodiment is attached to the optical sheet located closest to the display panel 100 among the plurality of optical sheets 230 .

In this way, the light transmitted or recycled through the reflective liquid crystal film 350 through the light guide plate 220 and the plurality of optical sheets 230 may be incident on the display panel 100 . The light incident on the display panel 500 passing through the reflective liquid crystal film 350 according to the second exemplary embodiment may be converted into light including a clear blue wavelength, and accordingly, the display panel 500 ), light including a clear blue wavelength may be incident.

In addition, the position of the liquid crystal film 350 for reflection is not limited thereto, and may be located as shown in FIG. 7 . 7 is a diagram illustrating a display device according to a third embodiment. The display device according to the third exemplary embodiment may include the same components as the display device according to the above-described exemplary embodiments. A description overlapping with the display device according to the above-described embodiments may be omitted. Also, the same components have the same reference numerals.

Referring to FIG. 7 , the display device according to the third embodiment includes a display panel 500 and a backlight unit 400 disposed on the rear surface of the display panel 100 . In addition, the backlight unit 400 may include a reflective liquid crystal film 450 . The reflective liquid crystal film 450 may be positioned between the light source assembly 211 and the light guide plate 220 . In this case, the light generated from the light source assembly 211 may be incident on the reflective liquid crystal film 450 .

Here, the reflective liquid crystal film 450 may reflect and transmit a portion of the light having a central wavelength peak of 430 nm and a peak width at half maximum of 42 nm among the light generated from the light source assembly 211 . In this case, the light reflected by the reflective liquid crystal film 450 may be re-reflected by the reflective plate 203 provided inside the light source housing 202 to pass through the reflective liquid crystal film 450 . The reflection plate 203 provided inside the light source housing 202 may be provided in the entire area or a partial area of the light source housing 202 in which the light source assembly 201 is not disposed.

As described above, the light passing through the reflective liquid crystal film 450 may be incident on the display panel 100 through the light guide plate 220 and the plurality of optical sheets 230 . That is, light before being incident on the light guide plate 220 through the reflective liquid crystal film 450 according to the third embodiment may be converted into light including a clear blue wavelength, and accordingly, the display panel 500 . Light having a clear blue wavelength may be incident there.

As described above, the liquid crystal film for reflection according to the present embodiments may be positioned at various positions in the display device, and may reflect and transmit light of a specific wavelength. Here, the light reflected by the reflective liquid crystal film may bring about a luminance improvement effect of a display device through a recycling phenomenon in which re-reflection occurs continuously, and color gamut of a color corresponding to a specific wavelength may be increased.

In addition, when the liquid crystal film for reflection according to the present embodiments is used, there is an effect that the absorption band can be adjusted without additionally developing a light absorption material.

Features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications that have not been made are possible. For example, each component specifically shown in the embodiments may be implemented by modification. And the differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

100: display panel
110: cell
120: lower polarizing plate
130: upper polarizing plate
200: backlight unit
210: light source assembly
220: light guide plate
230: a plurality of optical sheets
250: liquid crystal film for reflection

Claims (12)

At least one cholesteric liquid crystal layer comprising a plurality of liquid crystal molecules,
The peak of the central wavelength of the reflected light is 430 nm and the peak width at half maximum is 42 nm,
A pitch of the liquid crystal molecules is 275 nm to 280 nm, and a refractive index of the liquid crystal molecules is 1.53 to 1.56.
delete delete The method of claim 1,
The cholesteric liquid crystal layer is a reflective liquid crystal film comprising the same type of cholesteric liquid crystal molecules.
display panel;
a backlight unit disposed on a rear surface of the display panel and including a light source assembly; and
It is positioned at a position where the light emitted from the light source assembly is incident, and includes at least one cholesteric liquid crystal layer including a plurality of liquid crystal molecules, and has a central wavelength peak of 430 nm and a peak half width of 42 nm. and a reflective liquid crystal film having a pitch of the liquid crystal molecules of 275 nm to 280 nm, and a refractive index of the liquid crystal molecules of 1.53 to 1.56.
delete delete 6. The method of claim 5,
The cholesteric liquid crystal layer includes the same type of cholesteric liquid crystal molecules.
6. The method of claim 5,
The display panel includes a cell including a lower substrate, an upper substrate, and a liquid crystal layer, an upper polarizing plate disposed above the cell, and a lower polarizing plate disposed below the cell,
The reflective liquid crystal film is adhered to a rear surface of the lower polarizing plate.
6. The method of claim 5,
The backlight unit includes a light guide plate and a plurality of optical sheets disposed on the light guide plate,
The reflective liquid crystal film is disposed on the plurality of optical sheets.
6. The method of claim 5,
The backlight unit includes a light guide plate and a light source assembly disposed on at least one side of the light guide plate,
The reflective liquid crystal film is disposed between the light guide plate and the light source assembly.
12. The method of claim 11,
The light source assembly includes a light source assembly and a light source housing on which the light source assembly is mounted,
A display device in which a reflector is provided in a portion or an entire area inside the light source housing in which the light source assembly is not disposed.

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