KR20080002242A - Liquid crystal display device - Google Patents

Abstract

An LCD(Liquid Crystal Display) is provided to refract light, passing through an LC panel, to a lower or upper field of view area of the LCD, thereby preventing gray-inversion or the like at the lower field of view area, and further preventing deterioration of image quality caused by the gray-inversion. An LCD(Liquid Crystal Display) comprises an LC panel, upper and lower polarizing plates(143) and a light path control film(170). The upper and lower polarizing plates are formed as having polarizer axes which are orthogonal to each other on upper and lower parts of the LC panel. The light path control film is disposed on the outer side of the upper polarizing plate and configured with a convex unit and material having an uneven surface. The light path control film refracts light, passing through the upper polarizing plate, to an upper or lower field of view area.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY DEVICE}

1 is an exploded perspective view schematically showing a general liquid crystal display device.

2A and 2B are cross-sectional views of a liquid crystal display device in twisted nematic mode, respectively, illustrating a liquid crystal movement according to voltage on / off.

FIG. 3 is a graph showing luminance characteristics according to vertical viewing angles of nine levels of gray levels from black to white of a conventional twisted nematic mode liquid crystal display.

4 is a schematic cross-sectional view of a twisted nematic liquid crystal display device having an optical path control film according to a first embodiment of the present invention.

5A and 5B are enlarged cross-sectional views of an optical path control film provided in the liquid crystal display according to the first embodiment of the present invention.

6A and 6B illustrate a path of light incident on the optical path control film according to the first embodiment having the form shown in FIGS. 5A and 5B, respectively.

FIG. 7 is a graph illustrating gradation change for each of the upper and lower viewing angles of gradation of nine levels from black to white of the twisted mode liquid crystal display equipped with the optical path control film according to the first embodiment of the present invention.

8 is a schematic cross-sectional view of a twisted nematic liquid crystal display device having an optical path control film according to a second embodiment of the present invention.

9A and 9B are enlarged cross-sectional views of the optical path control film provided in the liquid crystal display according to the second embodiment of the present invention, respectively.

10A and 10B show a path of light incident on the optical path control film according to the second embodiment having the form shown in FIGS. 9A and 9B, respectively.

FIG. 11 is a graph showing gradation change for each of the upper and lower viewing angles of the gradation of nine steps from black to white of the twisted nematic mode liquid crystal display having the optical path control film having the structure shown in FIG.

FIG. 12 is a view of a white gray level of a twisted nematic mode liquid crystal display device according to a second embodiment of the present invention having the light path control film shown in FIG. 9A and a general twisted nematic liquid crystal display device having no light path control film. Graph showing change with viewing angle.

FIG. 13 is a view of a white gray level of a twisted nematic mode liquid crystal display device according to a second embodiment of the present invention having the light path control film shown in FIG. 9A and a general twisted nematic liquid crystal display device having no light path control film. Graph showing the change in contrast.

FIG. 14 is a cross-sectional view of a unit unit of the upper polarizer and the optical path control film attached to the upper polarizer in the twisted nematic mode liquid crystal display device having the optical path control film according to the third embodiment of the present invention.

FIG. 15 is a graph illustrating gradation changes for up and down viewing angles of gradations of nine levels from black to white of a twisted mode liquid crystal display equipped with an optical path control film according to a third exemplary embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

143: upper polarizer

170: light path control film

170a: iron

170b: description

The present invention relates to a liquid crystal display device, and more particularly, to a twisted nematic liquid crystal display device capable of minimizing image quality deterioration due to gradation inversion.

Recently, with the rapid development of the information society, the necessity of flat panel displays having excellent characteristics such as thinning, light weight, and low power consumption has emerged. Among them, liquid crystal displays have a resolution, It is excellent in color display and image quality, and is actively applied to notebooks and desktop monitors.

In general, a liquid crystal display device arranges two substrates having electrodes formed on one surface thereof so that the surfaces on which the electrodes are formed face each other, interposes a liquid crystal material between the two substrates, and then applies a voltage to the electrodes formed on the substrates. The liquid crystal molecules are moved by an electric field generated by application, thereby representing an image by the transmittance of light that varies accordingly.

1 is an exploded perspective view schematically illustrating a general liquid crystal display device.

As illustrated, the liquid crystal display device 1 has a configuration in which the array substrate 10 and the color filter substrate 20 face each other with the liquid crystal layer 30 interposed therebetween. A plurality of gate wirings 14 and data wirings 16 are arranged on the top and bottom to define a plurality of pixel regions P, and the thin film transistor Tr is disposed at the intersections of the two wirings 14 and 16. Is provided and is connected one-to-one with the pixel electrode 18 provided in each pixel region P. As shown in FIG.

In addition, the color filter substrate 20 facing the array substrate 10 may cover the non-display area of the gate line 14, the data line 16, the thin film transistor Tr, and the like, with a rear surface thereof. A grid-like black matrix 25 is formed that borders the region P, and the red, green, and blue color filter patterns 26a and 26b are sequentially arranged to correspond to each pixel region P in the grid. And a color filter layer 26 including 26c, and a transparent common electrode 28 is provided over the entire surface of the black matrix 25 and the color filter layer 26.

In addition, the two substrates 10 and 20 may be separated from each substrate 10 and 20 in a state of being sealed with a sealant or the like along an edge to prevent leakage of the liquid crystal layer 30 interposed therebetween. The upper and lower alignment layers (not shown) which provide reliability in the molecular alignment direction of the liquid crystal are interposed at the boundary of the liquid crystal layer 30, and the polarizing plates are arranged such that polarization axes are perpendicular to each other on the outer surfaces of the substrates 10 and 20. (Not shown) are provided respectively.

In addition, a back-light (not shown) is provided on an outer surface of the array substrate 10 to supply light, so that the thin film transistor T is turned on / off through the gate line 14. When the off signals are sequentially scanned and applied, and the image signals of the data lines 16 are transferred to the pixel electrodes 18 of the selected pixel region P, the liquid crystal molecules are driven by the vertical electric fields therebetween. As a result, various images can be displayed by changing the transmittance of light.

The driving liquid crystal display device is called a vertical electric field type liquid crystal display device. A typical liquid crystal mode of the vertical electric field method is a twisted nematic mode used in most liquid crystal display devices today.

With reference to FIGS. 2A and 2B, which are cross-sectional views of the liquid crystal display of the twisted nematic mode showing the movement of the liquid crystal according to the voltage on / off, the voltage of the twisted nematic mode liquid crystal display according to the application of the voltage In operation, first, when the voltage is off, the optical axes (directors) of the liquid crystal molecules 57a and 57b are continuously disposed between the color filter substrate 51 and the array substrate 41 as shown in FIG. 2A. It can be seen that it is twisted 90 degrees.

Therefore, in the voltage off state, the polarization characteristic of the linearly polarized light that is emitted from the lower backlight (not shown) and passes through the lower polarizing plate 61 is changed while passing through the liquid crystal layer 55 (not shown), thereby changing the upper polarizing plate 63. Pass).

On the other hand, as shown in FIG. 2B in the voltage on state, when the voltage is turned on, that is, a voltage is applied to the upper common electrode 53 and the lower pixel electrode 43 and the liquid crystal is caused by the voltage difference. When an electric field is applied to each of (57a, 57b), the optical axis of the liquid crystal molecules (57a) located in the center portion of the liquid crystal layer 57 is parallel to the applied electric field to solve the 90 ° twisted structure.

Therefore, in the voltage on state, the linearly polarized light incident through the lower polarizer 61 passes through the liquid crystal layer 57, and its polarization characteristic is maintained as it is, and thus cannot pass through the upper polarizer 63.

Such a twisted nematic mode liquid crystal display has an advantage that the aperture ratio is relatively high and the brightness is excellent. However, when the LCD is viewed from the lower side of the viewing angle, that is, the lower side of the front side of the liquid crystal display, the gray scale is bright. The gray-inversion phenomenon that appears brighter than the gray scale appears.

FIG. 3 is a graph illustrating luminance characteristics according to up and down viewing angles of nine levels of gray levels from black to white of a conventional twisted nematic mode liquid crystal display. In this case, the x axis represents the viewing angle and the vertical axis represents the luminance. When the center of the LCD is viewed from the front, the angle viewed from the lower side with a viewing angle of 0 ° from the front is represented by '-' and the angle viewed from the upper side is represented by '+'. It was.

As shown, gray level inversion starts to occur at a lower viewing angle of about 15 °, and gray level inversion occurs for most of the gray levels in a region having a larger angle. It can be seen that the gray level inversion occurs in an area having an angle of about 20 ° and more for the bright white gray level. In this case, the grayscale inversion occurs only for white for the upper viewing angle, which is extremely fine. However, in the lower viewing angle, not only the white gray level but also various levels of grayscale show the gray level inversion so that the image quality deteriorates severely. It becomes a big problem.

 This grayscale inversion occurs because the refractive index changes depending on the viewing angle. That is, in the twisted nematic mode liquid crystal display device, when the voltage is off, the liquid crystal is twisted by 90 °, so that the birefringence change hardly occurs at any viewing angle.

However, when the voltage is on, the average director of the liquid crystal molecules is slightly inclined about the up / down direction so that the actual birefringence of light passing through the liquid crystal varies depending on the viewing angle. Therefore, gradation inversion occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a twisted nematic liquid crystal display device capable of minimizing image degradation caused by gray level inversion.

The twisted nematic liquid crystal display device according to the present invention comprises: a liquid crystal panel; Upper and lower polarizing plates each having upper and lower polarization axes perpendicular to each other and formed on the upper and lower portions of the liquid crystal panel; Located on the outer surface of the upper polarizing plate, consisting of a substrate having a convex portion and a flat surface, and comprises a light path control film, characterized in that for refracting the light passing through the upper polarizing plate to the upper or lower viewing angle region It is done.

At this time, the convex portion, characterized in that the cross-sectional shape of the basis of the surface of the substrate is a right triangle or isosceles triangle shape, the isosceles triangle is a form that the base side is in contact with the substrate surface, the right triangle is other than the hypotenuse It is characterized in that the side is in contact with the substrate surface and the hypotenuse is inclined with respect to the substrate surface.

In addition, the convex portion is characterized in that the first unit and the second pattern having different cross-sectional shapes of the protruding portion relative to the base surface and the third pattern of the rectangular form having a parallel surface with the base surface as one unit unit. In this case, the first pattern is a right triangle of the form where one base is in contact with the base surface, and the second pattern is an isosceles triangle where the base is in contact with the base surface. In this case, the unit unit has a structure arranged in the order of the third pattern, the first pattern, the third pattern, the second pattern, the third pattern, the unit unit is the size of one pixel in the liquid crystal panel When the size of the unit unit is 10, the area occupancy of the third pattern, the first pattern, the third pattern, the second pattern, and the third pattern in one pixel area is respectively Characterized in that formed to be 1.5, 3, 2, 2, 1.5.

In addition, in the optical path control film, the angle of refraction of the light passing through the convex portion is controlled by adjusting an angle at which the upper surface or the side edge of the convex portion forms with the substrate surface.

In addition, the optical path control film is characterized in that the convex portion is configured in contact with the upper polarizing plate or the substrate is provided so as to contact the upper polarizing plate.

In addition, the substrate and the iron portion is PMMA (polymethylmethacrylate), vinyl chloride, acrylic resin, PC (polycarbonate), PET (polyethylene therephtalate), PE (polyethylene), PS (polystryrene), PP (polypropylene), PI It is preferable that it consists of (polyimide) resin.

The liquid crystal panel may further include a first substrate on which a common electrode is formed; A second substrate facing the first substrate and having a pixel electrode formed thereon; And a liquid crystal layer interposed between the first and second substrates, wherein the liquid crystal molecules in the liquid crystal layer are controlled by a vertical electric field generated by the common electrode and the pixel electrode.

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

In the present invention, in order to minimize the gray scale inversion, the light transmitted through the liquid crystal panel is refracted in the direction in which the gray scale inversion occurs, thereby minimizing the area of the gray scale inversion.

That is, since a large amount of gray scale inversion is generated at a viewing angle lower than the average director of liquid crystal molecules, in order to minimize the generation region of gray scale inversion, the light path control film having a specific pattern of light passing through the liquid crystal panel is minimized. By refracting in the lower direction of the liquid crystal panel through the user's eyes to feel the light transmitted in the short direction of the average director even at a lower viewing angle.

Therefore, the area of gray level inversion that the user actually feels becomes much smaller. Accordingly, display quality can be improved by minimizing grayscale inversion.

<First Embodiment>

4 is a schematic cross-sectional view of a twisted nematic liquid crystal display device having an optical path control film according to a first embodiment of the present invention.

As shown, the liquid crystal display device 100 according to the first exemplary embodiment of the present invention has a twisted nematic mode including a lower substrate 101 and an upper substrate 121 bonded together with the liquid crystal layer 160 interposed therebetween. The liquid crystal panel 130 and an outer side surface of the upper substrate 121 are provided with an upper polarizing plate 143 serving as an analyzer having a light transmission axis in a specific direction, and an outer side surface of the lower substrate 103. A lower polarizer 141 having a light transmission axis orthogonal to the light transmission axis of the upper polarizer 143 is provided.

In this case, a liquid crystal layer 160 is filled in the liquid crystal panel 130, and a color filter layer having red, green, and blue color filter patterns including a common electrode 123 on an inner surface of the upper substrate 121. (Not shown) and the thin film serving as a switching element for controlling the pixel electrode 103 and the pixel electrode 103 corresponding to the common electrode 123 to form a vertical electric field on the lower substrate 101. Gates and data lines (not shown) are formed including transistors (not shown).

In addition, an optical path control film 150 for controlling light transmitted through the liquid crystal panel 130 is formed on an outer surface of the upper polarizing plate 143 as the most characteristic part of the present invention. In this case, the optical path control film 150 serves to refract the light passing through the upper polarizer 143 in a specific direction.

In the liquid crystal display device 100 having the above-described structure, a voltage is applied to the common electrode 123 and the pixel electrode 103 of the liquid crystal panel 130, whereby the liquid crystal is in an on state in which a vertical electric field is generated. The optical axis of the liquid crystal molecules 161 positioned in the middle of the layer 160 is parallel to the vertical electric field to solve the twisted structure. In this case, the average director of the liquid crystal molecules 161 in the liquid crystal layer 160 is It will be slightly inclined around the up / down direction.

Therefore, the polarized light passing through the lower polarizer 141 and incident on the liquid crystal panel 130 passes through the liquid crystal layer 160, and thus its polarization characteristic is maintained as it is, thereby preventing the upper polarizer 143 from passing through. Black is implemented.

Here, the light transmitted through the upper polarizer 143 is refracted by the light path control film 150 toward the lower side of the liquid crystal panel 110. Accordingly, the light transmitted in the uniaxial direction of the average director of the liquid crystal molecules 161 is refracted toward the lower direction of the liquid crystal panel 130 at the exit surface of the liquid crystal panel 130, so that even at a lower viewing angle to the eyes of the user The light transmitted in the short axis direction of the average director is felt.

Therefore, the gray level inversion area that the user actually feels becomes much smaller.

5A and 5B are enlarged cross-sectional views of optical path control films provided in the liquid crystal display according to the first embodiment of the present invention, respectively.

Referring to these drawings, the optical path control films 170 and 180 are largely composed of two parts. That is, triangular convex portions 170b having a smooth surface on both sides of the substrate 170a and 180b, and an inclined surface in the direction of refraction with respect to each of the surfaces of the flat substrate on the upper or lower surface of the substrates 170a and 180a. , 180b).

Specifically, the materials forming the substrates 170a and 180a and the convex portions 170a and 180b include PMMA (polymethylmethacrylate), vinyl chloride, acrylic resin, PC (polycarbonate), PET (polyethylene therephtalate), and PE (polyethylene). , PS (polystryrene), PP (polypropylene), PI (polyimide) resin, glass, silica and the like can be used.

At this time, looking at the refractive index of the material forming the substrate (170a, 180a) and the convex portion (170b, 180b), generally PMMA 1.49, PC 1.53, PS 1.58, PP 1.49, PET 1.57, PS about 1.59 Becomes

On the other hand, when the structure of the optical path control film 170 according to Figure 5a in more detail, the portion attached to the upper polarizing plate 143 is formed with a concave-convex shape, the convex portion 170b of the concave-convex shape The cross section is formed in a right triangle shape, characterized in that the length of one side is longer than the length of the other side. At this time, the upper polarizing plate 143 is characterized in that it is provided so that the vertices where the hypotenuse and the bottom side (shortest surface) meet.

At this time, the path to the progress of light passing through the optical path control film 170 having the structure as described above will be described.

Referring to FIG. 6A, which illustrates the path of light incident on the optical path control film 170 having the shape illustrated in FIG. 5A, the optical path control film 170 passes through the upper polarizer 143 and is perpendicular to the optical path control film 170. It can be seen that the light incident in one direction is incident at an angle of θa with respect to the convex portion 170b having a right triangle structure.

In addition, the incident light has an angle of θa with respect to the optical path control film 170, and the incident light has an angle of θ based on Snell's law as it moves from the optical path control film 170 to the air layer. By being refracted in the direction, the angle at which gray level inversion of the lower viewing angle is reduced or is formed so as not to occur.

Snell's law

n ₁ sin θ ₁ = n ₂ sin θ ₂ , where n ₁ and n ₂ represent refractive indices, θ ₁ represents an angle of incidence, and θ ₂ represents a refractive angle.

Using this, the refractive angle θ after passing through the optical path control film 170 of the incident light with an angle of θa with respect to the convex portion 170b of the optical path control film 170 is obtained. The sine value for

---①

--- ①

It may be represented as. In this case, n is the refractive index of the optical path control film 170, and light passing through the optical path control film 170 is emitted to the air layer, so n 'is the refractive index of the air layer.

FIG. 7 is a graph illustrating gradation changes for up to down viewing angles of nine levels of gradation from black to white of the twisted mode liquid crystal display equipped with the optical path control film according to the first embodiment of the present invention. In this case, the graph uses the optical path control film 170 shown in FIG. 5A, and the oblique angle of inclination θa of the convex portion has 44 ° with respect to the substrate, such that light incident vertically with respect to the substrate has the convex portion. The gradation change for the incidence angle of 44 ° with respect to the normal to the oblique plane of is shown.

In the case of a liquid crystal display device without a conventional optical path control film, referring to FIG. 3, a gray level inversion phenomenon occurs from a lower viewing angle region of about -15 °, but the optical path control film according to the first embodiment of the present invention In the case of the liquid crystal display device having the present invention, it can be seen that there is no part showing gray level inversion in the lower viewing angle region of -15 ° or less, and that no gray level inversion portion occurs in the upper viewing angle region. Able to know.

Meanwhile, referring to FIG. 5B, the structure of another optical path control film 180 according to the first exemplary embodiment of the present invention is a surface attached to the upper polarizer 143 to be a portion of the substrate 180a having a flat structure. Instead, the convex portion 180b having the concave-convex structure is formed on the opposite side of the surface attached to the upper polarizing plate 143. In this case, the convex portion 180b forms a right triangle shape, and the convex portion 180b of the triangle is formed. ) Is characterized in that the hypotenuse is arranged so that the upper side and the lower side (shortest side) are located on the side.

At this time, the path to the progress of light passing through the optical path control film 180 having the structure as described above will be described.

Referring to FIG. 6B, which illustrates a path of light incident on the optical path control film 180 having the shape illustrated in FIG. 5B, the optical path control film 180 passes through the upper polarizer 143 and is perpendicular to the optical path control film 180. The light incident in one direction maintains a perpendicular state with respect to the substrate 180a of the optical path control film 180, has an inclined surface of θa with respect to the substrate 180a surface, and has a right triangle shape in cross section thereof. It can be seen that it is incident with θa with respect to the hypotenuse of the convex portion 180b having a, and has an inflection angle of θ with respect to the hypotenuse.

In this case as well, the light incident perpendicularly to the substrate 180b of the optical path control film 180 has an angle of θ based on Snell's law as it moves from the optical path control film 180 to the air layer. By refracting toward the lower viewing angle of the panel (not shown), the angle of gray level inversion in the lower viewing angle region is formed to be small.

In this case, the refractive angle θ is expressed by the following equation.

---②

--- ②

In this case, n is the refractive index of the light path control film 180, n 'is the refractive index of the emission layer, that is, the air layer.

In this case as well, although the graph according to the gradation change in the upper and lower viewing angle regions is not presented, the same result as the optical path control film shown in FIG. 5A can be obtained.

Second Embodiment

8 is a schematic cross-sectional structure of a twisted nematic liquid crystal display device having an optical path control film according to a second embodiment of the present invention.

As shown, the liquid crystal display according to the second exemplary embodiment of the present invention is a liquid crystal panel of a twisted nematic mode including a lower substrate 201 and an upper substrate 221 bonded together with a liquid crystal layer 260 interposed therebetween. 230 and an upper polarizing plate 243 serving as an analyzer having a light transmission axis in a specific direction on an outer surface of the upper substrate 221, and an upper polarizing plate on an outer surface of the lower substrate 203. A lower polarizing plate 241 having a light transmission axis perpendicular to the light transmission axis of 243 is provided.

In this case, a liquid crystal layer 260 is filled in the liquid crystal panel 230, and a color filter layer having a red, green, and blue color filter pattern including a common electrode 223 on an inner surface of the upper substrate 221. (Not shown), and the thin film serving as a switching element for controlling the pixel electrode 203 and the pixel electrode 203 corresponding to the common electrode 223 to form a vertical electric field on the lower substrate 201. Gates and data lines (not shown) are formed including transistors (not shown).

On the other hand, as the most characteristic part of the present invention, the optical path control film 250 for controlling the light transmitted through the liquid crystal panel 230 is formed on the outer surface of the upper polarizing plate 243. In this case, the light path control film 250 serves to refract the light passing through the upper polarizer 243 in a specific direction.

Here, the light transmitted through the upper polarizer 243 is refracted by the optical path control film 250 toward the upper and lower viewing angle directions of the liquid crystal panel 230. Accordingly, the light transmitted in the uniaxial direction of the average director of the liquid crystal molecules 261 is refracted in the lower or upper viewing angle direction of the liquid crystal panel 230 at the exit surface of the liquid crystal panel 230, thereby further causing the user's eyes. Even at a low viewing angle and a higher viewing angle, light transmitted in the short axis direction of the average director is felt.

Therefore, when the user views the liquid crystal display 200 in the viewing angle area or the viewing angle area, the gradation inversion area that is actually felt becomes much smaller.

The liquid crystal display device having such a characteristic has a lower luminance at the center of the liquid crystal display device, but when used as a wall-mounted TV attached to a higher eye level, the liquid crystal display device is viewed from the bottom to the top. In this case, viewing of excellent display quality without gray scale inversion becomes possible.

9A and 9B show enlarged cross-sectional views of the optical path control film provided in the liquid crystal display according to the second embodiment of the present invention, respectively. At this time, the material of the optical path control film according to the second embodiment is made of the same material mentioned in the first embodiment described above, the description thereof will be omitted. 9A and 9B, the optical path control films 270 and 280 according to the second exemplary embodiment shown in FIGS. 9A and 9B are formed with respect to the lower surface or the upper surface of the substrate 270a and 280a and the substrate 270a and 280a respectively having flat surfaces. It is a feature that the convex portions 270b and 280b having an isosceles triangular cross section are formed. At this time, the convex portions 270b and 280b have a structure where the bottom sides are attached to the lower and upper surfaces of the substrates 270a and 280b, respectively, so that the convex portions 270b and 280b pass through the liquid crystal panel (not shown). Fold and mix in the up and down directions.

At this time, by adjusting the angle of the vertex formed by the hypotenuse of the convex portion (270b, 280b) to adjust the angle of the light exiting the optical path control film (270, 280) bent in the upper and lower viewing angle direction of the liquid crystal display device Done.

9A shows that the convex portion 270b is formed in contact with the surface of the upper polarizing plate 243. FIG. 9B shows that the substrate 280a is in contact with the upper polarizing plate 243 and the convex portion 280b is formed on the outer surface. It is showing.

Meanwhile, referring to FIG. 10A, which illustrates the path of light incident on the optical path control film 270 having the shape illustrated in FIG. 9A, the optical path control film 270 passes through the upper polarizer 243. Light incident in a direction perpendicular to the light is incident at an angle of θa with respect to the convex portion 270b having an isosceles triangular structure, and assumes that an angle of a vertex of the convex portion 270b is θb. When the angle with respect to the surface of the substrate 270a of the light emitted outside the optical path control film 270 is θ, the light passing through the substrate 270a is finally passed by the optical path control film 270. The angle θ refracted with respect to the surface of the base material 270a in the same manner as in the first equation mentioned in the first embodiment

Expressed as

In this case, the incident angle θa to the convex portion 270b may be expressed by the following equation.

Therefore, the incident angle of light incident on the optical path control film 270 may be changed by changing the angle θ b of the vertex of the convex part 270 b, whereby the light exiting the optical path control film 270 may be changed. The angle of refraction can be adjusted.

FIG. 11 is a graph illustrating gradation change for each of the upper and lower viewing angles of the gradation of nine levels from black to white of the twisted nematic mode liquid crystal display having the optical path control film 270 having the structure shown in FIG. 9A. In this case, the gradation of the angle between the hypotenuse of the convex portion and the surface of the substrate, that is, the angle at which light is incident on the convex portion is 70 ° and the angle of the vertex is 40 ° is illustrated.

As shown in the figure, there is no place where the gray level inversion occurs because there is no intersection with each other for the white and black gray levels of the nine steps.

In addition, due to the characteristics of the optical path control film shown in the second embodiment, the light incident to the inside of the optical path control film is refracted to the upper and lower parts of the liquid crystal display to emit light. It can be seen that the overall fall.

12 and 13 illustrate a twisted nematic mode liquid crystal display device according to a second embodiment of the present invention having the light path control film shown in FIG. 9A and a general twisted nematic liquid crystal display device having no light path control film. It is a graph which shows the change according to the viewing angle of white grayscale, and the change of contrast ratio, respectively. In this case, the white point is a general liquid crystal display device, and the black point is a liquid crystal display device according to the present invention.

As shown, in the case of the twisted nematic mode liquid crystal display device having the optical path control film according to the present invention, the luminance at the front surface of the twisted nematic mode liquid crystal display device is reduced due to the inherent optical properties in the central viewing angle region. In the case of the white gradation, the luminance is maintained at 100 or more in the upper and lower viewing angle regions instead of the center portion, and thus the luminance is improved at the high viewing angle.

   The liquid crystal display according to the second exemplary embodiment of the present invention having the above characteristics has low luminance at the front viewing angle and excellent luminance characteristics at the upper viewing angle and the lower viewing angle, so that the monitor or the wall is used below the eye level of the user. When used as a TV to be attached to the ceiling and positioned above the eye level of the user, the display quality is superior to that of a general LCD.

On the other hand, also in another optical path control film 280 according to the second embodiment of the present invention shown in Figure 9b, referring to Figure 10b showing the path of the light incident on the optical path control film 280, The light incident through the upper polarizer 243 and perpendicular to the surface of the substrate 280a of the optical path control film 280 has both end angles of θa with respect to the surface of the substrate 280a and the size of the vertex angle is The angle of refraction θ of the light emitted through the isosceles triangular convex portion 280b having θ b is expressed by the equation (2) of the first embodiment described above.

In this case, θa which is both end angles of the convex portion 280b and the incident angle to the convex portion 280b is

It can be represented as In this case, n is the refractive index of the optical path control film 280, n 'is the refractive index of the emission layer, in this case, the air layer has a value of about 1 bar.

The twisted nematic liquid crystal display device having the optical path control film of the second embodiment shown in FIG. 9B may also have the same result as the liquid crystal display device having the optical path control film shown in FIG. 9A described above.

Third Embodiment

The liquid crystal display device having the optical path control films shown in the first and second embodiments described above has no gray level inversion in the upper or lower viewing angle region and improves the contrast ratio, while in the case of the liquid crystal display front surface, especially in the case of the second embodiment. It was found that the luminance decreased.

Therefore, in the third embodiment, the shape of the optical path control film and the liquid crystal having the same to prevent the gray level inversion in the mode viewing angle region and the luminance decrease by optimizing the shape of the optical path control film presented through the first and second embodiments Provide a display device.

That is, by combining the shapes of the convex portions of the optical path control films presented through the first and second embodiments, there is provided a light path control film which does not have a sudden decrease in luminance even in the front viewing angle region and does not cause grayscale inversion in the upper and lower viewing angles. do.

FIG. 14 is a cross-sectional view of an upper polarizer and a unit of the optical path control film attached to the upper polarizer in the twisted nematic mode liquid crystal display device having the optical path control film according to the third embodiment of the present invention. One drawing.

As shown, the optical path control film composed of the base and the iron portion is characterized in that the iron portion having a plurality of different forms formed in one unit unit.

In this case, the convex portions formed in the unit unit have a cross-sectional shape of the right triangular shape (called the first convex part) shown in the first embodiment and the isosceles triangular shape (called the second convex part) shown in the second embodiment, and these convex parts. It is characterized by consisting of a combination of three types of substrate portions exposed in between (this portion is substantially a substrate, but is referred to as a third convex portion for convenience of explanation).

The shape of the unit unit of the optical path control film 370 according to FIG. 14, which is shown as an example of a cross-sectional shape of the optical path control film 370 according to the third embodiment, may include a first convex portion between the third convex portions 370a, respectively. 370b and the second convex portion 370c have an alternate form. That is, the third convex part 1.5, 370a, the first convex part 3, 370b, the third convex part 2, 370a, the second convex part 2, 370c, and the third convex part 1.5, 370c. It is characterized by having).

In this case, the unit unit is preferably formed to have a size enough to correspond to one pixel area defined by the gate and the data line to cross each other of the liquid crystal panel. In this case, each of the convex portions 370a, 370b, and 370c in each unit unit may be formed in a stripe type. If the stripe is viewed from the front, each pixel area in the vertical direction may be formed. It is preferable to configure so that all the convex portions 370a, 370b, and 370c constituting the one unit unit are formed therein.

In this case, the numerical values shown in the drawing show an example of the area ratio occupied by the convex portions 370a, 370b, and 370c in the pixel area in one pixel area whose size is 10. FIG.

Thus, the third convex portion (1.5) (370a) / the first convex portion (3) (370b) / the third convex portion (2) (370a) / the second convex portion (2) (370c) / third convex portion (1.5) (370c) FIG. 15 is a graph showing gradation change for each of the upper and lower viewing angles of the nine levels of gradation from black to white of the twisted nematic mode liquid crystal display having the optical path control film 370 having a unit unit formed to have an area ratio composed of FIG. It can be seen that the luminance does not decrease even in the central viewing angle region, and that grayscale inversion does not occur in the entire viewing angle region.

The above embodiments are merely examples of the present invention, and various changes and modifications can be made without departing from the technical spirit of the present invention through the described contents.

The liquid crystal display device having the optical path control film according to the present invention refracts the light transmitted through the liquid crystal panel in the direction of the lower viewing angle or the upper viewing angle of the liquid crystal display device, thereby preventing the grayscale inversion in the field of the field of view, and further, the grayscale inversion. There is an effect of preventing the deterioration of the image quality.

In addition, by providing the optical path control film composed of the convex portion having a specific cross-sectional form as one unit unit, it is possible to prevent the grayscale inversion in the entire viewing angle range, and further to prevent the luminance decrease in the central portion.

Claims (13)

A liquid crystal panel; Upper and lower polarizing plates each having upper and lower polarization axes perpendicular to each other and formed on the upper and lower portions of the liquid crystal panel; Located on the outer surface of the upper polarizing plate, consisting of a substrate having a convex portion and a flat surface, the optical path control film, characterized in that for refracting the light passing through the upper polarizing plate to the upper or lower viewing angle region Liquid crystal display device comprising the. The method of claim 1, The convex portion has a cross-sectional shape with respect to the surface of the substrate, characterized in that the right triangle or isosceles triangle shape. The method of claim 2, The isosceles triangle has a bottom side in contact with the substrate surface. The method of claim 2, The right triangle has a shape in which a side other than the hypotenuse is in contact with the substrate surface, and the hypotenuse is inclined with respect to the substrate surface. The method of claim 1, The convex portion includes a first unit and a second pattern having different cross-sectional shapes of portions protruding from the base surface and a third pattern having a rectangular shape having a surface parallel to the base surface as one unit unit. The method of claim 5,      The first pattern is a right triangle of which one bottom side is in contact with the substrate surface, and the second pattern is an isosceles triangle whose bottom side is in contact with the substrate surface. The method of claim 5,      Wherein the unit unit has a structure arranged in the order of the third pattern, the first pattern, the third pattern, the second pattern, and the third pattern. The method of claim 5, And the unit unit has a size corresponding to one pixel area in the liquid crystal panel. The method of claim 8, When the size of the unit unit is 10, an area occupancy rate of the third pattern, the first pattern, the third pattern, the second pattern, and the third pattern in one pixel area is 1.5, 3, 2, 2, Liquid crystal display device characterized in that formed to be 1.5. The method of claim 1, In the light path control film, the angle of refraction of light passing through the convex portion is And a top surface or side edge of the convex portion is controlled by adjusting an angle formed with the base surface. The method of claim 1, The optical path control film may be configured such that the convex portion is in contact with the upper polarizing plate or the substrate is in contact with the upper polarizing plate. The method of claim 1, The substrate and the iron portion are PMMA (polymethylmethacrylate), vinyl chloride, acrylic resin, PC (polycarbonate), PET (polyethylene therephtalate), PE (polyethylene), PS (polystryrene), PP (polypropylene), PI (polyimide) Liquid crystal display device made of a) resin. The method of claim 1, The liquid crystal panel, A first substrate having a common electrode formed thereon; A second substrate facing the first substrate and having a pixel electrode formed thereon; Liquid crystal layer interposed between the first and second substrates And liquid crystal molecules in the liquid crystal layer by a vertical electric field generated by the common electrode and the pixel electrode.

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