KR20090053000A - Backlight assembly for flexible lcd - Google Patents

Abstract

The present invention relates to a flexible liquid crystal display device, and more particularly, to a light source of a backlight assembly having flexible characteristics.

It is a feature of the present invention to use an optical fiber grating as a light source of a backlight assembly. As a result, a backlight assembly having a flexible characteristic can be provided, and high brightness can be realized with only low power consumption.

In addition, by using the optical fiber grating in the field sequential color driving method, it is possible to omit the color filter forming process of the color filter substrate during the liquid crystal panel manufacturing process, thereby reducing the process time and process cost.

Fiber Bragg Grating, Flexible Liquid Crystal Display

Description

Backlight assembly for flexible liquid crystal display {Backlight assembly for flexible LCD}

The present invention relates to a flexible liquid crystal display device, and more particularly, to a light source of a backlight assembly having flexible characteristics.

In recent years, as the society enters a full-scale information age, a display field for processing and displaying a large amount of information has been rapidly developed, and various various flat panel display devices have been developed and are in the spotlight.

Specific examples of such a flat panel display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescent display device. (Electroluminescence Display device: ELD), etc. These flat panel display devices are rapidly replacing the existing cathode ray tube (CRT) by showing excellent performance of thin, light weight, low power consumption.

Among them, liquid crystal display devices are used in various fields such as laptops, monitors, and TVs because of their high contrast ratio, suitable for moving picture display, and low power consumption. The principle of image realization is the optical anisotropy of liquid crystals. As is well known, the liquid crystal has a thin and long molecular structure, optical anisotropy having an orientation in an array, and polarization in which the direction of molecular arrangement changes depending on its size when placed in an electric field.

The liquid crystal display device is an essential component of a liquid crystal panel in which a pair of transparent insulating substrates on which a field generating electrode is formed to face each other with a liquid crystal layer interposed therebetween as an essential component. According to the electric field size therebetween artificially adjust the arrangement direction of the liquid crystal molecules interposed therebetween, and various images are displayed through the change of the transmittance of light.

A configuration of the liquid crystal display device will be described in more detail with reference to FIG. 1, which is an exploded perspective view of a general liquid crystal display device.

As shown in the figure, a liquid crystal panel 10 having an array substrate and a color filter substrate bonded to each other with a liquid crystal layer 50 interposed therebetween and a backlight assembly disposed thereunder In the structure of 60, a plurality of data lines 22 and gate lines 26 vertically and horizontally cross each other on one surface of the first substrate 21 called a dual array substrate to define the pixel P. As shown in FIG. Thin film transistors T are provided at the intersections of the two lines 22 and 26 so as to correspond one-to-one with the transparent pixel electrodes 28 provided in the pixel regions P. FIG.

In addition, the second substrate 31 facing the liquid crystal layer 50 between them is called an upper substrate or a color filter substrate, and one surface thereof has a data line 22 of the first substrate 21. A grid-like black matrix 32 is formed around the pixel region P so as to expose only the pixel electrode 28 while covering the non-display elements such as the gate line 26 and the thin film transistor T.

In addition, R (red), G (green), B (blue) color filters 34a, 34b, 34c, and all of them, which are sequentially and repeatedly arranged corresponding to each pixel region P in the lattice. A transparent common electrode 36 is included.

In addition, since the first substrate 21 has a larger size than the second substrate 31, one side edge of the first substrate 21 is exposed to the outside when the two substrates 31 are bonded to each other. A plurality of data pads 24 connected to the plurality of gate pads and a plurality of gate pads (not shown) connected to the plurality of gate lines 26 are positioned.

Accordingly, the on / off signal of the thin film transistor T is sequentially scanned and applied to the gate line 26 so that the image of the data line 22 is applied to the pixel electrode 28 of the selected pixel region P. FIG. When the signal is transmitted, the liquid crystal molecules are driven by the vertical electric field therebetween, and various images can be displayed by the change in the transmittance of light.

However, as described above, since the liquid crystal display device does not have a light emitting element, a separate light source is required. To this end, a backlight assembly 60 is provided on the back of the liquid crystal panel 10 to supply light.

On the other hand, in the liquid crystal display device having such a configuration, glass substrates are generally used for the first and second substrates 21 and 31, which are the matrixes of the array substrate and the color filter substrate. Recently, laptops and personal digital assistants (PDAs) have been used. As small portable terminals, such as assistants, are widely used, liquid crystal panels using plastic substrates have been introduced, which are lighter, lighter, and more flexible than glass and have a low risk of damage.

However, although the liquid crystal panel 10 having such a flexible characteristic is commercialized and mass produced, the backlight assembly 60 still does not have a product having a flexible characteristic, and thus a liquid crystal display apparatus having a substantially flexible characteristic has not been commercialized.

The present invention has been made to solve the above problems, and an object thereof is to provide a backlight assembly having a flexible characteristic.

In order to achieve the object as described above, the present invention is a reflection sheet; An optical fiber mounted on the reflective sheet and having a grating formed therein to adjust a direction of light therein; And a plurality of optical sheets positioned above the optical fiber, wherein the optical fiber emits light toward the plurality of optical sheets in a direction perpendicular to the longitudinal direction. .

At this time, both ends of the optical fiber is characterized in that the light source for emitting light into the optical fiber, respectively.

In addition, the optical fiber is a double-cylindrical shape consisting of a core portion of the core (core) and the cladding (cladding) surrounding it, a plurality of gratings are provided in the core at minute intervals to form a grating portion, the grating The unit is characterized by being configured to be spaced apart at regular intervals along the longitudinal direction of the optical fiber.

(m = 정수, Λ = 격자 주기, λ₀ = 파장, n_eff = 유효굴절율)의 식을 통해 간격(Λ)이 조절되는 것을 특징으로 하며, 상기 m은 2인 것을 특징으로 한다. At this time, the plurality of gratings having a minute spacing

It is characterized in that the interval (Λ) is adjusted through the formula (m = integer, Λ = lattice period, λ ₀ = wavelength, n _eff = effective refractive index), wherein m is 2.

In addition, the optical fiber is characterized in that the bundle consisting of a close side by side on the reflection sheet, the reflection sheet is characterized in that formed of a polymer material selected from acrylic (acrylic), polycarbonate (polyester), polyester (polyester) It is done.

In this case, the plurality of optical sheets are characterized in that the diffusion sheet and the light collecting sheet formed of a material selected from each of acrylic (acrylic), polycarbonate (polyester), polyester (polyester).

In addition, the present invention provides a liquid crystal panel comprising a first and second substrates made of plastic; Located in the lower portion of the liquid crystal panel, and includes a backlight assembly using an optical fiber with a grating formed to adjust the direction of light therein as a light source, the optical fiber is characterized in that for emitting the light toward the liquid crystal panel Provided is a flexible liquid crystal display device.

In this case, the backlight assembly may include a reflective sheet positioned below the optical fiber and a plurality of optical sheets positioned above the optical fiber.

As described above, by using the optical fiber grating as a light source of the backlight assembly for a flexible liquid crystal display device according to the present invention, it is possible to provide a backlight assembly having a flexible characteristic, it is possible to implement a high brightness with low power consumption.

In addition, since the optical fiber grating can be used for the field sequential color driving method, the color filter forming process of the color filter substrate can be omitted during the liquid crystal panel manufacturing process, which can shorten the process time and reduce the process cost. It works.

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

2 is a cross-sectional view of a backlight assembly having a flexible characteristic and a liquid crystal panel disposed thereon according to an exemplary embodiment of the present invention.

As shown in the drawing, the backlight assembly 160 having the flexible characteristic and the liquid crystal panel 110 having the flexible characteristic are positioned thereon.

Here, we will look at each of these in more detail.

First, the liquid crystal panel 110 will be described in more detail with reference to FIG. 3, which is an exploded perspective view of the liquid crystal panel 110, wherein a plurality of data lines 122 are formed on one surface of the first substrate 121 called a lower substrate or an array substrate. ) And the gate line 126 cross vertically and horizontally to define the pixel area P. FIG. The thin film transistor T is provided at the intersection of these two lines, and is connected one-to-one with the transparent pixel electrode 128 provided in each pixel region P. FIG.

In addition, the second substrate 131 facing the liquid crystal layer 150 therebetween is called an upper substrate or a color filter substrate, and one surface thereof has a data line 122 of the first substrate 121. A grid-like black matrix 132 is formed around the pixel region P so as to expose only the pixel electrode 128 while covering the non-display elements such as the gate line 126 and the thin film transistor T.

In addition, the lattice covering the R (rea), G (green), and B (blue) color filters 134a, 134b, and 134c, and all of them, are sequentially arranged to correspond to each pixel area P in the lattice. The transparent common electrode 136 is included.

In this case, the first and second substrates 121 and 131 may be made of a plastic material having flexible characteristics.

Although not clearly shown in the drawings, upper and lower alignment layers for determining the initial molecular alignment direction of the liquid crystal are interposed between the two substrates 121 and 131 and the liquid crystal layer 150, and filled therebetween. In order to prevent leakage of the liquid crystal layer 150, a seal pattern is formed along edges of both substrates 121 and 131, and only specific light is formed on the outer surfaces of the first and second substrates 121 and 131. A polarizing plate that selectively transmits can be attached.

In addition, since the first substrate 121 has a larger size than the second substrate 131, one side edge of the first substrate 121 is exposed to the outside when they are bonded to each other, and each of the plurality of data lines 122 is included therein. And a plurality of data pads 124 connected to each other and a plurality of gate pads (not shown) connected to the plurality of gate lines 126.

Therefore, when the thin film transistor T selected for each gate line 126 is turned on by the on / off signal of the thin film transistor T scanned and transferred to the gate line 126, the corresponding pixel is turned on. The image signal of the data line 122 is transmitted to the electrode 128, and the arrangement direction of the liquid crystal molecules is changed by the electric field between the pixel electrode 128 and the common electrode 136 generated thereby, indicating a difference in transmittance. .

In addition, the flexible liquid crystal display according to the present invention is provided with a backlight assembly 160 for supplying light from the rear surface thereof so that the difference in transmittance of the liquid crystal panel 110 is expressed to the outside.

The flexible backlight assembly 160 is composed of a reflective sheet 122, a plurality of fiber bragg grating unit (200) and a plurality of optical sheet 126, a plurality of on the reflective sheet 122 The optical fiber grid unit 200 is arranged, a plurality of optical sheets 126 are positioned above the optical fiber grid 200.

First, the reflective sheet 122 is provided to improve the brightness of the light by reflecting the light emitted to the rear surface of the optical fiber grid unit 200 toward the liquid crystal panel 110.

The reflective sheet 122 is made of a polymer material such as acrylic, polycarbonate, polyester, or the like, or a copolymer of the above material, which has excellent flexibility, and thus has a very high surface reflectivity. It is formed by depositing a metallic material such as or coating a white insulating material with excellent reflectance.

The plurality of optical fiber grid units 200 arranged on the reflective sheet 122 are devices in which a lattice for periodically changing the refractive index is permanently engraved in the core of the optical fiber and irradiates light into the core of the optical fiber grid 212. While the light is traveling along the longitudinal direction of the optical fiber lattice 212, the light of some wavelengths is emitted by the lattice to the side of the optical fiber lattice 212, that is, the direction perpendicular to the longitudinal direction of the optical fiber lattice 212. Done.

This, the optical fiber grid 212 is configured to a thickness thinner than the hair, very flexible.

In addition, the plurality of optical sheets 126 positioned on the optical fiber grid unit 200 includes a diffusion sheet 126a, at least one light collecting sheet 126b, and a protective sheet 126c.

Here, the plurality of optical sheets 126 also have the same material forming the above-described reflective sheet 122, that is, acrylic, polycarbonate, polyester or one of these materials in order to have a flexible characteristic of the most important in the present invention It is preferable that it consists of a copolymer of.

Looking at this in more detail, the diffusion sheet 126a is a base film made of a material selected from acrylic, polycarbonate, polyester, and an acrylic resin layer containing light diffusing agents such as beads on both sides of the base film. Configure.

The diffusion sheet 126a prevents spots due to partial concentration of light by dispersing the incident light, and adjusts the direction of the light to propagate toward the light collecting sheet 126b.

In addition, the light collecting sheet 126b is also formed of a base film made of a material selected from acryl, polycarbonate, and polyester, and the prism acid is arranged on the upper surface of the base film so that the light collecting sheet 126b is largely formed by the prism acid. It has two optical characteristics, reflection and focusing.

That is, the light incident on the light collecting sheet 126b collects some light in the upward direction through refraction by the prism acid, but some light is reflected in the downward direction of the light collecting sheet 126b.

At this time, the light reflected in the downward direction is reflected by the reflective sheet 122 and supplied back to the diffusion sheet 126a, and the light loss is minimized through the circulation of the light.

At this time, the prism acid of the light collecting sheet 126b is protected through the protective sheet 126c.

When light is emitted from the plurality of optical fiber grids 212 in the above-described configuration, the light is processed into a more uniform surface light source through the plurality of optical sheets 126, and is incident on the liquid crystal panel 110.

The backlight assembly 160 is very flexible and can be used as a backlight of the liquid crystal panel 110 having flexible characteristics.

4A to 4B, the side light emission principle of the optical fiber grating will be described in more detail.

In general, an optical fiber is a medium that can transmit voice and video signals as a light signal, and the optical fiber that is thinner than the hair after modulating light from a laser or a light emitting diode through a semiconductor device that is converted into electromagnetic waves. Tens of thousands of pieces of information can be delivered simultaneously.

As such, the principle of light passing through the fiber strands without loss is simple. This is to use the phenomenon that complete reflection of light occurs when the angle of incidence of light at the interface between two transparent materials having different refractive indices is met.

Among these optical fibers, especially single mode optical fiber has low dispersion and low loss and is widely used for long distance transmission and large capacity communication. Such single fiber optical fiber is also very flexible, and only the portion required by localization and division is required. It can illuminate, and it can bend freely and send it to the desired place.

Accordingly, as shown in FIG. 4A, the optical fiber grating 212 used as the light source of the backlight assembly 160 of the present invention is also thinner than the hair, and the optical fiber grating 212 has a central core portion 216. And a cladding (218) surrounding the shape of a double cylinder.

Although not shown in the drawing, the exterior of the cladding 218 is wrapped with a synthetic resin coating layer to protect it from impact.

At both ends of the optical fiber grid 212, light sources 214 capable of emitting light to the optical fiber grid 212, such as a laser diode (LD), are positioned close to each other.

At this time, the refractive index of the core 216 of the optical fiber grid 212 is higher than the refractive index of the cladding 218. When light such as a laser shines thereon, the core 216 and the cladding 218 of the optical fiber grid 212 are irradiated. Only reflection occurs at the interface and no refraction occurs so that no light is emitted and reaches the end of the optical fiber grid 212.

Meanwhile, as shown in FIG. 4B, a grating part 220 including a plurality of gratings having minute spacings is formed inside the core 216 of the optical fiber grating 212, and the grating part 220 is an optical fiber grating 212. Of the light (T1) incident along the () is a filter (filter) that reflects the light (T4) of a specific wavelength and transmits the remaining light (T3).

That is, the light (T1, T2, T3, T4) traveling along the inside of the optical fiber grid 212 repeats the complex reflection and transmission process at the interface of the refractive index change. Accordingly, light T4 having a constant wavelength is reflected by the grating part 220, and light T3 having another wavelength not satisfying the condition is transmitted without being affected by the grating part 220.

Therefore, the emission direction of the light T1, T2, T3, T4 can be adjusted by using the characteristics of the optical fiber grid 212, the optical fiber grid 212 is a light of a predetermined wavelength in accordance with the period and the effective refractive index of the grating Only T3 and T4 reflect and transmit or emit light T2 in a specific direction.

The correlation between the period and the effective refractive index of the grating and the light (T1, T2, T3, T4) emitted and emitted can be expressed by Equation (1) below.

...............식(1)

............... Equation (1)

(m = integer, Λ = lattice period, λ ₀ = wavelength, n _eff = effective refractive index)

Here, referring to Equation (1) and FIG. 5, the light (T1, T2, T3, T4) reflected and transmitted from the optical fiber grating 212 and emitted perpendicularly to the longitudinal direction of the optical fiber grating 212 may be described above. It can be seen that it may vary depending on the effective refractive index and the spacing of the grating 220a (hereinafter referred to as a grating period).

That is, the optical fiber grating 212 divides the multi-wavelength light T1, T2, T3, and T4 into light T1, T2, T3, and T4 having different center wavelengths through the internal grating portion 220. .

At this time, the present invention is characterized in that the value of m is fixed to 2, wherein the value of m indicates the direction in which the light (T1, T2, T3, T4) proceeds, along the longitudinal direction of the optical fiber grid 212 It means the first direction (T1, T3) and the second direction (T2) which is a direction perpendicular to the longitudinal direction of the optical fiber grid (212).

Accordingly, light T4 having a plurality of wavelengths divided among the light T1, T2, T3, and T4 incident into the core 216 of the optical fiber grating 212 is returned to the direction in which it was reflected by the grating 220a. Some of the light T2 is emitted or diffused by the grating part 220 to leak out in a direction perpendicular to the longitudinal direction of the optical fiber grid 212, and the remaining light T3 penetrates the grating part 220. Will continue.

In the present invention, the light is supplied to the liquid crystal panel 110 (see FIG. 2) having flexible characteristics through the light T2 emitted in a direction perpendicular to the longitudinal direction of the optical fiber grid 212.

That is, the light T2 emitted in the direction perpendicular to the longitudinal direction of the optical fiber grid 212 is incident on the plurality of optical sheets 126 of FIG. While passing through (126 in FIG. 2), it is processed into a uniform surface light source and supplied to the liquid crystal panel (110 in FIG. 2).

At this time, some of the light (T2) emitted in a direction perpendicular to the longitudinal direction of the optical fiber grid 212 may leak toward the reflective sheet (122 of FIG. 2), such light is reflected sheet (122 of FIG. 2) is reflected back to the plurality of optical sheets (126 in FIG. 2), and its light is also processed into a uniform surface light source and supplied to the liquid crystal panel (110 in FIG. 2).

On the other hand, the grating portion 220 in the optical fiber grating 212 is formed periodically at a predetermined interval along the longitudinal direction of the optical fiber grating 212, the light T3 that continues to pass through the first grating portion is the second The light is reflected back by the grating part or exits in a direction perpendicular to the longitudinal direction of the optical fiber grid 212, or continues through the second grating part.

This process is repeatedly generated until the end of the optical fiber grid 212.

At this time, the amount of light between the adjacent grating portion 220 is increased. That is, for example, the light T4 reflected by the second grating portion is added to the light T3 transmitted through the first grating portion, so that the amount of light T3 and T4 between the first grating portion and the second grating portion is large. It will have an amplifying effect of light.

Therefore, high brightness can be realized with only low power consumption.

In addition, by using the characteristics that can split the light (T1, T2, T3, T4) according to the wavelength of the optical fiber grid 212, the three primary colors of red, green, blue colors are emitted through the optical fiber grid 212 It can be seen that.

That is, referring to Equation (1) above, the color of the red, green, and blue colors is changed to the optical fiber grid 212 by adjusting the spacing of the lattice 220a according to the wavelengths of red, green, and blue, respectively. Will be emitted from).

Therefore, the optical fiber grating 212 can be applied to a field sequential color driving method.

That is, without using the red, green, and blue color filters (134a, 134b, and 134c of FIG. 3), the light source of the three primary colors of red, green, and blue are sequentially emitted from the optical fiber grid 212, which is caused by the human eye. The afterimage effect can be used to display color.

As a result, the process of forming the color filters (134a, 134b, and 134c of FIG. 3) of the color filter substrate (131 of FIG. 3) can be omitted in the manufacturing process of the liquid crystal panel (110 of FIG. 2). Can reduce the cost.

The optical fiber grid 212 is made up of bundles and arranged side by side on the reflective sheet 122 at a predetermined interval.

6 is a view schematically showing the appearance of an optical fiber grating arranged on a reflective sheet.

As shown, the optical fiber grating 212 having the grating portion 220 of FIG. 4 formed at a predetermined cycle is closely arranged side by side at a predetermined interval on the reflective sheet 122 having a flexible characteristic. Light is emitted to the upper surface opposite to the reflective sheet 122.

Opposite ends of the optical fiber grid 212 are LDs 214 for injecting light into the optical fiber grid 212.

Although not shown in the drawing, a plurality of optical sheets (126 of FIG. 2) having flexible characteristics are positioned on the optical fiber grid 212, thereby completing a backlight assembly (160 of FIG. 2) having flexible characteristics. That is, the backlight assembly (160 of FIG. 2) according to the present invention is free to warp in any of the X and Y directions shown in the drawings.

By providing a liquid crystal panel (110 of FIG. 2) having flexible characteristics on the backlight assembly (160 of FIG. 2), a liquid crystal display having flexible characteristics may be completed.

At this time, the plurality of optical fiber grating 212 is uniformly incident light to a plurality of optical sheets (126 of FIG. 2) and processed into a uniform surface light source in the process of passing through a plurality of optical sheets (126 of FIG. 2) liquid crystal panel It is incident on (110 of FIG. 2), and the liquid crystal panel (110 of FIG. 2) is finally used to display an image of high brightness.

Meanwhile, in addition to the flexible liquid crystal display device, the backlight assembly (160 of FIG. 2) having the flexible characteristics of the present invention has various flat panel display devices (FPD) having excellent characteristics such as thinning, light weight, and low power consumption. In particular, it can be used for a recently introduced so-called digital paper display (DPD).

Digital paper displays are much cheaper to produce than traditional flat panel displays, and require no additional backlighting, so they can be driven with very little energy. They are clear, have a wide viewing angle and, most importantly, resolution and contrast Contrast is a paper that can bend repeatedly without change. It is currently applied to portable computers, electronic newspapers, and smart cards, and will be widely replaced in the near future by replacing traditional print media such as books, newspapers, and magazines. It is a display device.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is an exploded perspective view of a typical liquid crystal panel.

2 is a cross-sectional view of a backlight assembly having a flexible characteristic and a liquid crystal panel disposed thereon according to an embodiment of the present invention.

3 is an exploded perspective view of a part of a liquid crystal panel according to an exemplary embodiment of the present invention.

4a to 4b schematically illustrate the side light emission principle of the optical fiber grating.

5 schematically shows the spacing of the grids;

6 is a schematic view showing the appearance of an optical fiber grating arranged on a reflective sheet;

Claims (11)

A reflective sheet; An optical fiber mounted on the reflective sheet and having a grating formed therein to adjust a direction of light therein; A plurality of optical sheets positioned on the optical fiber And the optical fiber emits light toward the plurality of optical sheets in a direction perpendicular to the length direction. The method of claim 1, And a light source disposed at both ends of the optical fiber to emit light into the optical fiber, respectively. The method of claim 1, The optical fiber is a backlight assembly for a flexible liquid crystal display, characterized in that the center of the core (core) and the cladding (cladding) surrounding it. The method of claim 3, wherein The plurality of gratings are provided inside the core at minute intervals to form a grating portion, wherein the grating portion is configured to be spaced apart at regular intervals along the longitudinal direction of the optical fiber. The method of claim 1, The plurality of gratings having a minute spacing

A backlight assembly for a flexible liquid crystal display according to claim 1, wherein the distance Λ is adjusted through the formula (m = integer, Λ = lattice period, λ ₀ = wavelength, n _eff = effective refractive index). The method of claim 5, wherein M is 2, the backlight assembly for a flexible liquid crystal display device. The method of claim 1, The optical fiber is a backlight assembly for a flexible liquid crystal display, characterized in that consisting of a bundle arranged in close contact on the reflection sheet. The method of claim 1, The reflective sheet is a backlight assembly for a flexible liquid crystal display device, characterized in that formed of a polymer material selected from acrylic (acrylic), polycarbonate, polyester (polyester). The method of claim 1, The plurality of optical sheets are a diffuser sheet and a light collecting sheet formed of a material selected from acrylic, polycarbonate, and polyester, respectively. A liquid crystal panel composed of plastic first and second substrates; Located in the lower portion of the liquid crystal panel, the backlight assembly using an optical fiber formed with a grating to adjust the direction of light therein as a light source The optical fiber is a flexible liquid crystal display, characterized in that for emitting the light toward the liquid crystal panel. The method of claim 10, The backlight assembly may include a reflective sheet positioned below the optical fiber, and a plurality of optical sheets positioned above the optical fiber.

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