JP2008003245A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain desired luminance distribution and to perform display having a high contrast ratio over a wide angle range in a liquid crystal display device provided with a light diffusion element. <P>SOLUTION: The liquid crystal display device is provided with a light source 1, a liquid crystal display panel 20 modulating light emitted from the light source 1 and the light diffusion element 30 disposed on a viewer side of the liquid crystal display panel 20 and diffusing light passed through the liquid crystal display panel 20. The light diffusion element 30 has a plurality of prism sets 32A, 32B and 32C each including a prism 31A having a first inclined surface 31s1 inclined at a certain angle α to the normal direction of a display surface and a prism 31B having a second inclined surface 31s2 inclined at an angle β different from the angle α to the normal direction of the display surface. The plurality of prism sets 32A, 32B and 32C are provided so that arrangement patterns and/or arrangement pitches of the prisms are different from each other between the adjacent prism sets. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device including a light diffusing element for diffusing light emitted from a liquid crystal display panel.

  In recent years, portable electronic devices represented by portable telephones and PDAs (Personal Digital Assistants) have been widely used. A liquid crystal display device having advantages such as thinness, light weight, and low power consumption is used for a display portion of a portable electronic device.

  Unlike a self-luminous display device such as a CRT or PDP (plasma display panel), a liquid crystal display device does not emit light. Therefore, in a transmissive liquid crystal display device, an illumination element called a backlight is provided on the back side of the liquid crystal display element, and the liquid crystal display element controls the amount of transmitted illumination light from the backlight for each pixel. The image is displayed by.

  Various types of liquid crystal display devices are known. However, some methods (for example, a method using a TN type or STN type liquid crystal display element) have a disadvantage that the viewing angle is narrow, and various technical developments have been made to solve the problem. Yes.

  As a typical technique for improving the viewing angle characteristics of a liquid crystal display device, there is a method of adding an optical compensator. Also known is a method in which light emitted from a backlight is made incident on a liquid crystal display element after increasing its directivity (parallelism), and light passing through the liquid crystal display element is diffused by a light diffusing element ( For example, Patent Document 1).

  An example of a liquid crystal display device provided with a light diffusing element is shown in FIG. 18 includes a liquid crystal display panel 520, a backlight 510 disposed on the back side of the liquid crystal display panel 520, and a light diffusing element 530 disposed on the viewer side of the liquid crystal display panel 520. I have.

  The liquid crystal display panel 520 includes a pair of substrates 521 and 522 and a liquid crystal layer 523 provided therebetween. Although not shown here, the electrodes for applying a voltage to the liquid crystal layer 523 and the alignment for defining the alignment direction of the liquid crystal molecules contained in the liquid crystal layer 523 are provided on the surfaces of the substrates 521 and 522 on the liquid crystal layer 523 side. A film is formed.

  The backlight 510 includes a light source 501 and a light guide plate 502 that guides light emitted from the light source 501 to the liquid crystal display panel 520. The light guide plate 502 has a front surface (light emitting surface) 502a that emits light toward the liquid crystal display panel 520, and a back surface 502b that faces the light emitting surface 502a. A plurality of prisms 503 are formed on the back surface 502 b of the light guide plate 502.

  The light emitted from the light source 501 is reflected on the liquid crystal display panel 520 side by the prism 503 formed on the back surface 502b while propagating through the light guide plate 502, and is emitted from the light emitting surface 502a. The prism 503 has two inclined surfaces inclined at predetermined angles different from each other with respect to the light emitting surface 502a, whereby light emitted from the backlight 510 is transmitted in the normal direction of the display surface (front direction). ) Is significantly stronger. That is, the light emitted from the backlight 510 is given high directivity.

  When the light emitted from the backlight 510 has high directivity, the light passing through the liquid crystal layer 523 can be modulated uniformly (that is, the light passing through the liquid crystal layer 523 is given uniform retardation). be able to). Therefore, the viewing angle dependence of display quality due to the refractive index anisotropy of liquid crystal molecules can be reduced. The light that has passed through the liquid crystal layer 523 has high directivity and has a large bias in luminance (that is, the luminance in the normal direction of the display surface is extremely high and the luminance in the oblique direction is low). By being diffused by 530, the luminance deviation is reduced and the viewing angle is widened. Therefore, the liquid crystal display device 500 can perform good display in a wide viewing angle range.

As the light diffusing element 530, for example, a prism array sheet 530 as shown in FIG. 19 can be suitably used. The prism array sheet 530 has a plurality of triangular prisms 531. Each prism 531 has an inclined surface 531s inclined with respect to the normal direction of the display surface, and light emitted from the liquid crystal display panel 520 is totally reflected (or refracted) by the inclined surface 531s of the prism 531. Diffused. A predetermined luminance distribution can be realized in the light emitted from the prism array 530 by appropriately setting the inclination angle of the inclined surface 531s according to the luminance distribution of the light emitted from the backlight 510.
JP-A-9-22011

  However, according to the study of the present inventor, even if the conventional prism array 530 is used, it is not always possible to realize a desired luminance distribution, and it is difficult to perform display with a high contrast ratio over a wide angle range. I understood it.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a desired luminance distribution and display with a high contrast ratio over a wide angle range in a liquid crystal display device including a light diffusing element. It is in.

  A liquid crystal display device according to the present invention includes a light source, a liquid crystal display panel that modulates light emitted from the light source, and a light diffusion that is disposed on an observer side of the liquid crystal display panel and diffuses light that has passed through the liquid crystal display panel. The light diffusing element includes a first prism having a first inclined surface inclined at a first angle with respect to the display surface normal direction, and a display surface normal direction. A plurality of prism sets each including a second prism having a second inclined surface inclined at a second angle different from the first angle, wherein the plurality of prism sets are adjacent prism sets. The prisms are arranged so that the arrangement pattern and / or the arrangement pitch of the prisms are different from each other, thereby achieving the above object.

  In a preferred embodiment, the plurality of prism sets are provided such that adjacent prism sets have different prism arrangement patterns and arrangement pitches.

  In a preferred embodiment, the azimuth angle in the normal direction of the first inclined surface is different from the azimuth angle in the normal direction of the second inclined surface.

  In a preferred embodiment, the first prism included in at least one prism set of the plurality of prism sets is different from the first angle and the second angle with respect to the normal direction of the display surface. It has a further inclined surface inclined at a different third angle.

  In a preferred embodiment, the liquid crystal display device according to the present invention includes a polarizing element disposed closer to the viewer than the light diffusing element.

  In a preferred embodiment, the liquid crystal display device according to the present invention includes an illumination element including the light source.

  In a preferred embodiment, the illumination element has a light distribution such that luminance in a direction forming an angle of 30 ° or more with respect to the normal direction of the display surface is 13% or less of luminance in the normal direction of the display surface. Have

  In a preferred embodiment, the illumination element has a light distribution such that luminance in a direction forming an angle of 30 ° or more with respect to the normal direction of the display surface is 3% or less of luminance in the normal direction of the display surface. Have

  In a preferred embodiment, the illumination element includes a directivity control element that controls the directivity of light emitted from the light source.

  The light diffusing element included in the liquid crystal display device according to the present invention has a plurality of prism sets each including a plurality of prisms. Each prism set includes a first prism having a first inclined surface inclined at a first angle with respect to the display surface normal direction, and a second angle different from the first angle with respect to the display surface normal direction. And the second prism having the second inclined surface inclined at (5), the light traveling direction can be converted into a plurality of directions. Therefore, in the liquid crystal display device according to the present invention, it is easier to realize a desired luminance distribution and the contrast ratio over a wide angle range than a liquid crystal display device having a conventional prism array sheet that can change the traveling direction of light in only one direction. High display can be performed. Further, since the plurality of prism sets are provided so that the prism arrangement patterns and / or arrangement pitches of adjacent prism sets are different from each other, moire due to the periodic arrangement of the plurality of prisms having different shapes is provided. Occurrence is prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

  FIG. 1 shows a liquid crystal display device 100 according to this embodiment. As shown in FIG. 1, the liquid crystal display device 100 is disposed on a liquid crystal display panel 20, an illumination element (backlight) 10 disposed on the back side of the liquid crystal display panel 20, and an observer side of the liquid crystal display panel 20. The light diffusing element 30 is provided.

  The liquid crystal display panel 20 includes a pair of substrates 21 and 22 and a liquid crystal layer 23 provided therebetween. On the surface of the substrate 21 and the substrate 22 on the liquid crystal layer 23 side, an electrode for applying a voltage to the liquid crystal layer 23 and an alignment film for defining the alignment direction of the liquid crystal molecules contained in the liquid crystal layer 23 (both are not suitable). (Shown) is formed. Hereinafter, of the pair of substrates 21 and 22, the substrate 21 disposed on the illumination element 10 side of the liquid crystal layer 23, that is, on the opposite side of the liquid crystal layer 23 from the observer is referred to as a “rear substrate”. The substrate 22 disposed on the viewer side with respect to the layer 23 is referred to as a “front substrate”. In the present embodiment, a color filter 24 is provided on the liquid crystal layer 23 side of the front substrate 22.

  The light diffusing element 30 is provided on the front substrate 22. On the light diffusing element 30, a phase difference compensating element 50a and a polarizing plate 40a are stacked. A retardation compensation element 50 b and a polarizing plate 40 b are also laminated on the back substrate 21. As the phase difference compensation elements 50a and 50b, various known phase difference plates are used. The number and arrangement of the phase difference compensation elements are not limited to those exemplified here.

  The lighting element 10 emits light with high directivity. A specific configuration of the illumination element 10 will be described later. If the light emitted from the illumination element 10 has high directivity, the light passing through the liquid crystal layer 23 can be uniformly modulated (that is, the light passing through the liquid crystal layer 23 is given uniform retardation). Therefore, the viewing angle dependency of the display quality due to the refractive index anisotropy of the liquid crystal molecules can be reduced. The light having passed through the liquid crystal layer 23 has high directivity as it is and has a large bias in luminance (that is, the luminance in the normal direction of the display surface is extremely high and the luminance in the oblique direction is low). By being diffused by 30, the unevenness of luminance is reduced, thereby widening the viewing angle.

  The light diffusing element 30 in the present embodiment is a prism array sheet having a plurality of prisms. FIG. 2 schematically shows a cross-sectional structure of the light diffusing element 30.

  As shown in FIG. 2, the light diffusing element 30 has a plurality of prism sets 32A, 32B, and 32C each including a plurality of prisms 31A and 31B. Here, the structure of the prisms 31A and 31B included in each prism set will be described with reference to FIG. FIG. 3 is an enlarged sectional view showing a prism set 32A.

  As shown in FIG. 3, the prisms 31A and 31B included in the prism set 32A have inclined surfaces 31s1 and 31s2 that are inclined with respect to the normal direction of the display surface. Hereinafter, the inclined surface 31s1 of one prism 31A is referred to as a “first inclined surface”, and the inclined surface 31s2 of the other prism 31B is referred to as a “second inclined surface”.

  The inclination angle α of the first inclined surface 31s1 with respect to the normal direction of the display surface is different from the inclination angle β of the second inclined surface 31s2 with respect to the normal direction of the display surface. That is, the prism set 32A includes a plurality of prisms 31A and 31B having different shapes. 3 shows only one prism set 32A, the other prism sets 32B and 32C similarly include a plurality of prisms 31A and 31B having different shapes (that is, different angles of inclined surfaces). It is out.

  When the inclination angle α of the first inclined surface 31s1 and the inclination angle β of the second inclined surface 31s2 are different from each other, the light totally reflected by the first inclined surface 31s1 and the light totally reflected by the second inclined surface 31s2 Are directed in different directions as shown schematically in FIG. Therefore, each prism set can convert the traveling direction of light into a plurality of directions. Therefore, the light diffusing element 30 is easier to realize a desired luminance distribution than the conventional prism array sheet 530 that can convert the traveling direction of light in only one direction. Therefore, the liquid crystal display device 100 according to the present embodiment can perform display with a high contrast ratio over a wide angle range.

  The effect of the light diffusing element 30 in this embodiment will be described more specifically. First, FIG. 4 shows an example of the luminance distribution of light emitted from the illumination element 10. As shown in FIG. 4, the light emitted from the illumination element 10 has a remarkably high brightness in the front direction and high directivity.

  Next, FIG. 5 shows an example of the luminance distribution of the light diffused by the light diffusing element 30. First, it can be seen that the luminance deviation is reduced compared to the luminance distribution shown in FIG. In addition to the peak near 0 °, a shoulder is present near ± 30 °, and a peak is also present near ± 60 °. The shoulder near ± 30 ° is caused by total reflection on the first inclined surface 31s1, and the peak near ± 60 ° is caused by total reflection on the second inclined surface 31s2.

  Next, FIG. 6 shows the luminance distribution of the light diffused by the conventional prism array sheet 530. As shown in FIG. 6, although the luminance deviation itself is reduced, there is no clear shoulder or peak except near 0 °. This is because the prism array sheet 530 can change the traveling direction of light in only one direction.

  As can be seen by comparing FIG. 5 and FIG. 6, according to the light diffusing element 30 in the present embodiment, the luminance can be increased over a wide angle range, and the contrast ratio can be increased over a wide angle range. .

  The inclination angle α of the first inclined surface 31s1 and the inclination angle β of the second inclined surface 31s2 are appropriately set according to the desired luminance distribution. The light traveling in the normal direction of the display surface is reflected by the first inclined surface 31s1 in a direction that forms an angle 2α with respect to the normal direction of the display surface, and the second inclined surface 31s2 has an angle 2β with respect to the normal direction of the display surface. It is reflected in the direction that makes. Therefore, the inclination angles α and β may be set according to the angle at which the peak or shoulder is desired to be generated. In addition, since the width of the peak or shoulder generated in the luminance distribution of the diffused light depends on the high directivity of light from the illumination element 10 (for example, expressed by a half-value angle), the inclination angles α and β are set. In doing so, it is preferable to take this into consideration. From the viewpoint of increasing the contrast ratio in a sufficiently wide angle range, the difference between the inclination angle α of the first inclined surface 31s1 and the inclination angle β of the second inclined surface 31s2 is preferably 15 ° or more.

  Each prism included in the prism set may have two or more types of inclined surfaces having different inclination angles. For example, in the prism set 32D shown in FIG. 7, the prism 31A has a further inclined surface 31s3 inclined at an angle γ different from the inclination angle α of the first inclined surface s1 and the inclination angle β of the second inclined surface s2. . Therefore, the prism set 32D can convert the traveling direction of light into three directions. As described above, by increasing the types of inclined surfaces included in the prism set, it is possible to further change the traveling direction of the light into multiple directions, and to realize more various luminance distributions.

  Further, each prism included in the prism set is not limited to a total reflection type prism. As the prism, a refraction type prism that diffuses light using refraction at an inclined surface may be used.

  Up to this point, it has been explained that a desired luminance distribution can be realized in a plane parallel to the normal direction of the display surface, that is, in the polar angle direction. However, by providing a plurality of prisms having different shapes, A desired luminance distribution can be realized in a plane parallel to the plane, that is, also in the azimuth direction. The reason will be described with reference to FIG. FIG. 3 shows a cross section of the prism set 32A along a direction perpendicular to the display surface, while FIG. 8 shows a cross section of the prism set 32A along a direction parallel to the display surface.

  As shown in FIG. 8, the first inclined surface 31s1 and the second inclined surface 31s2 face different directions. In other words, the azimuth angle in the normal direction of the first inclined surface 31s1 and the azimuth angle in the normal direction of the second inclined surface 31s2 are different from each other. Therefore, the light totally reflected by the first inclined surface 31s1 and the light totally reflected by the second inclined surface 31s2 are not only directed to mutually different polar angles as schematically shown in FIG. As shown schematically in FIG. 8, they are directed in different azimuth directions. Therefore, the light diffusing element 30 can easily achieve a desired luminance distribution in the azimuth angle direction.

  As described above, by providing a plurality of prisms having different shapes, a desired luminance distribution can be realized. However, depending on the arrangement of the prisms, moire caused by a plurality of periodic structures existing in the prism array sheet may occur, and the display quality may deteriorate. For example, when two types of prisms are simply arranged alternately, moire tends to occur.

  If a plurality of prism sets are provided so that the prism arrangement pattern and / or pitch is different between adjacent prism sets, the moire caused by the periodic structure as described above is unlikely to occur, and the display quality deteriorates. Hateful.

  In the light diffusing element 30 illustrated in FIG. 2, the shapes of the prisms 31 </ b> A and 31 </ b> B included in the prism sets 32 </ b> A, 32 </ b> B, and 32 </ b> C are different between adjacent prism sets, thereby changing the arrangement pattern of the prisms. . In the structure illustrated in FIG. 2, the prism arrangement pitch P is also different between adjacent prism sets.

  As described above, in the prism array 30 according to the present embodiment, the prism sets 32A, 32B, and 32C are provided such that the prism arrangement patterns and the arrangement pitches are different between adjacent prism sets. Despite the provision of prisms, moire is unlikely to occur.

  FIG. 2 shows a structure in which each prism set includes two prisms, but each prism set may include three or more prisms. Further, the number of prisms included in each prism set need not be the same.

  In order to suppress the occurrence of moiré, at least one of the prism arrangement pattern and the arrangement pitch may be different between adjacent prism sets, and it is not always necessary to make both different. Hereinafter, this point will be described using the prism set 32 shown in FIG. 9 as an example.

  The prism set 32 shown in FIG. 9 includes four prisms 31A, 31B, 31C and 31D having different shapes. Examples of arrangement of such a prism set 32 are shown in FIG. 10, FIG. 11 and FIG. 10, FIG. 11 and FIG. 12 are diagrams schematically showing the arrangement of the prisms as viewed from the normal direction of the display surface, and are denoted by reference numerals “A”, “B”, “C” and “D”. The rectangles indicate the prisms 31A, 31B, 31C, and 31D shown in FIG.

  As shown in FIG. 10, when the prism arrangement pattern and the arrangement pitch are the same between adjacent prism sets 32, moire due to the periodic structure is likely to occur, and the display quality is liable to deteriorate.

  On the other hand, as shown in FIG. 11, when the prism arrangement patterns are made different between adjacent prism sets 32, the occurrence of moire is suppressed. As shown in FIG. 12, the occurrence of moire can also be suppressed by making the prism arrangement pitches different between adjacent prism sets 32.

  The arrangement pitch P of the prisms and the width W and height H (see FIG. 2) of each prism are appropriately set according to the pixel pitch of the liquid crystal display panel 20 and the like. The arrangement pitch P of the prisms is, for example, about several tens of μm (10 μm to 80 μm). The width W of each prism is, for example, about several tens of μm (10 μm to 50 μm), and the height H of each prism is, for example, about several μm (1 μm to 10 μm).

  When the prism arrangement pattern is different between adjacent prism sets, the prism arrangement pitch P can be determined independently of the pixel pitch of the liquid crystal display panel 20.

On the other hand, when the prism arrangement pattern is the same between adjacent prism sets, the prism arrangement pitch P is preferably determined in consideration of the pixel pitch of the liquid crystal display panel 20. In order to more reliably suppress the occurrence of moiré, for example, as disclosed in Japanese Patent Laid-Open No. 6-273653, the prism arrangement pitch P is X, the pixel pitch is X, the pixel arrangement direction, and the prism ridgeline It is preferable that the relationship of the following formula is satisfied, where θ is the angle formed by: In the following formula, n is a natural number, k is a number in the range of 0.4 to 0.6, and θ is 0 ° to 45 °.
X / (P · cos θ) = n + k

  FIG. 13 shows an example of the arrangement pitch P of the prisms. In this example, the width along the row direction of each pixel is 60 μm, the width along the column direction is 200 μm, and the pixel interval is 15 μm in both the row direction and the column direction. That is, the pixel pitch X is 75 μm in the row direction and 215 μm in the column direction. The prism arrangement pitch P is 47 μm with respect to the pixel pitch X described above. Of course, the arrangement pitch P of the prisms and the pixel pitch X are not limited to the numerical values exemplified here.

  FIG. 11 shows a configuration in which only the prism arrangement pattern differs between adjacent prism sets, and FIG. 12 shows a configuration in which only the prism arrangement pitch differs between adjacent prism sets. In order to suppress the occurrence of this, it is preferable to vary both the arrangement pattern and the arrangement pitch of the prisms.

  The light diffusing element 30 in the present embodiment can be formed by a known method using various materials (for example, a resin such as a thermosetting resin or an ultraviolet curable resin). For example, a mold corresponding to the shape of the prism may be prepared in advance, and a dry film formed from an ultraviolet curable resin may be press-molded using the mold and then cured with ultraviolet rays. Alternatively, after molding an ultraviolet curable resin or a thermosetting resin into the mold using a spin coating method, these molded resins may be cured.

  In the configuration shown in FIG. 1, a polarizing plate (polarizing element) 40a is arranged on the viewer side with respect to the light diffusing element 30, but as shown in FIG. 14, the polarizing plate 40a is on the viewer side. A light diffusing element 30 may be disposed. As shown in FIG. 1, when the polarizing plate 40a is disposed on the viewer side with respect to the light diffusing element 30, external light incident on the light diffusing element 30 from the viewer side is absorbed by the polarizing plate 40a, and the amount thereof is reduced. Is done. Therefore, reflection of external light on the surface of the light diffusing element 30 is suppressed, and glare on the display surface is prevented.

  Next, a specific configuration of the illumination element (backlight) 10 will be described. FIG. 15 shows an example of a specific configuration of the lighting element 10.

  The illumination element 10 shown in FIG. 15 includes a light source 1 and a light guide plate 2 that guides light emitted from the light source 1 to the liquid crystal display panel 20. The light source 1 is, for example, a light emitting diode (LED) or a cold cathode tube. The light guide plate 2 has a structure for emitting light emitted from the light source 1 and entering the light guide plate 2 to the liquid crystal display panel 20 side. For example, a prism or a texture is formed on at least one of the two main surfaces of the light guide plate 2.

  The illumination element 10 further includes a prism array sheet 3 that controls the directivity of light emitted from the light guide plate 2. The prism array sheet 3 functioning as a directivity control element is provided between the light guide plate 2 and the liquid crystal display panel 20.

  The prism array sheet 3 has a plurality of prisms 4 formed on the main surface on the light guide plate 2 side. As shown in FIG. 16, the light emitted from the light guide plate 2 is utilized by using the total reflection phenomenon. Oriented in the normal direction of the display surface. Thus, the light emitted from the light guide plate 2 is given high directivity by the prism array sheet 3.

  Of course, the illumination element 10 is not limited to that illustrated in FIG. 15, and various backlights can be used. However, in order to obtain a higher contrast ratio, light with higher directivity can be emitted. It is preferable to use one. Specifically, the illumination element 10 has a light distribution such that the luminance in a direction that forms an angle of 30 ° or more with respect to the display surface normal direction is 13% or less of the luminance in the display surface normal direction. The light distribution is more preferably 3% or less. FIGS. 17A, 17B, and 17C show examples of preferable light distribution of the illumination element 10. FIG.

  In the light distribution shown in FIG. 17A, the luminance in a direction that forms an angle of 30 ° or more with respect to the display surface normal direction is 8% to 13% or less of the luminance in the display surface normal direction (0 °). It is. By using the lighting element 10 having such a light distribution, an excellent display quality can be obtained.

  In the light distribution shown in FIGS. 17B and 17C, the luminance in the direction forming an angle of 30 ° or more with respect to the display surface normal direction is the luminance in the display surface normal direction (0 °). 3% or less. By using the illumination element 10 having such a light distribution, even better display quality can be obtained.

  The directivity to the extent shown in FIG. 17A can be easily realized by using, for example, the illumination element 10 provided with the total reflection prism sheet 3 shown in FIG. Further, the directivity of the degree shown in FIGS. 17B and 17C can be realized by using the backlight disclosed in US Pat. No. 5,499,933 and US Pat. No. 5,598,281. The above-mentioned US Pat. No. 5,499,933 discloses an edge light type backlight in which a lenticular microprism is provided on the main surface of a light guide plate. In addition, the above-mentioned US Pat. No. 5,598,281 discloses a direct type backlight that allows light emitted from a light source to enter a microcollimator and a microlens through an opening.

  According to the present invention, in a liquid crystal display device provided with a light diffusing element, a desired luminance distribution can be realized and display with a high contrast ratio can be performed over a wide angle range. The present invention is suitably used for transmissive liquid crystal display devices in general, and in particular, it is suitably used for liquid crystal display devices in display modes (for example, STN mode, TN mode, and ECB mode) with low viewing angle characteristics.

  In a display mode using birefringence such as the STN mode, the display is adversely affected by light obliquely incident on the liquid crystal layer. Therefore, highly directional light is incident on the liquid crystal layer and modulated by the liquid crystal layer. It is preferable to use a viewing angle expansion technique for diffusing light with a light diffusing element, and the significance of using the present invention is great.

It is sectional drawing which shows typically the liquid crystal display device 100 in suitable embodiment of this invention. 3 is a cross-sectional view showing a light diffusing element (prism array sheet) included in the liquid crystal display device 100. FIG. It is sectional drawing which shows the prism set which a light-diffusion element has. 6 is a graph showing an example of a luminance distribution of light emitted from an illumination element included in the liquid crystal display device 100. 4 is a graph showing an example of a luminance distribution of light diffused by a light diffusing element included in the liquid crystal display device 100. It is a graph which shows an example of the luminance distribution of the light diffused by the conventional prism array sheet. It is sectional drawing which shows the other example of a prism set. It is a figure which shows the cross section of the prism set along the direction parallel to a display surface. It is sectional drawing which shows the other example of a prism set. It is a figure which shows typically arrangement | positioning of the prism seen from the display surface normal line direction. It is a figure which shows typically arrangement | positioning of the prism seen from the display surface normal line direction. It is a figure which shows typically arrangement | positioning of the prism seen from the display surface normal line direction. It is a figure which shows an example of the arrangement pitch of a prism, and a pixel pitch. It is sectional drawing which shows typically the other structure of the liquid crystal display device 100 in suitable embodiment of this invention. 3 is a side view showing an example of an illumination element (backlight) included in the liquid crystal display device 100. FIG. It is a figure for demonstrating the function of the prism array sheet | seat with which the illumination element shown in FIG. 15 is provided. (A), (b) and (c) is a graph which shows the example of the light distribution of the light radiate | emitted from an illumination element. It is sectional drawing which shows the conventional liquid crystal display device 500 typically. It is sectional drawing which shows the conventional prism array sheet typically.

Explanation of symbols

10 Lighting element (backlight)
20 Liquid crystal display panel 21 Rear substrate 22 Front substrate 23 Liquid crystal layer 24 Color filter 30 Light diffusing element 31A, 31B, 31C, 31D Prism 31s1 First inclined surface 31s2 Second inclined surface 32, 32A, 32B, 32C, 32D Prism set 40a , 40b Polarizing plate 50a, 50b Phase difference compensation element 100 Liquid crystal display device

Claims (9)

A light source;
A liquid crystal display panel that modulates light emitted from the light source;
A light diffusing element that is disposed on the viewer side of the liquid crystal display panel and diffuses light that has passed through the liquid crystal display panel, and a liquid crystal display device comprising:
The light diffusing element includes a first prism having a first inclined surface inclined at a first angle with respect to a display surface normal direction, and a second prism different from the first angle with respect to the display surface normal direction. A plurality of prism sets each including a second prism having a second inclined surface inclined at an angle of
The plurality of prism sets are provided such that adjacent prism sets have different prism arrangement patterns and / or arrangement pitches.   2. The liquid crystal display device according to claim 1, wherein the plurality of prism sets are provided such that both the prism arrangement pattern and the arrangement pitch are different between adjacent prism sets.   The liquid crystal display device according to claim 1, wherein an azimuth angle in a normal direction of the first inclined surface and an azimuth angle in a normal direction of the second inclined surface are different from each other.   The first prism included in at least one of the plurality of prism sets is inclined at a third angle different from the first angle and the second angle with respect to the normal direction of the display surface. The liquid crystal display device according to claim 1, further comprising a further inclined surface.   The liquid crystal display device according to claim 1, further comprising a polarizing element disposed closer to an observer than the light diffusing element.   The liquid crystal display device according to claim 1, further comprising an illumination element including the light source.   The illumination device has a light distribution such that luminance in a direction forming an angle of 30 ° or more with respect to a normal direction of the display surface is 13% or less of luminance in the normal direction of the display surface. Liquid crystal display device.   The lighting device has a light distribution such that luminance in a direction forming an angle of 30 ° or more with respect to a normal direction of the display surface is 3% or less of luminance in the normal direction of the display surface. Liquid crystal display device.   The liquid crystal display device according to claim 6, wherein the illumination element includes a directivity control element that controls directivity of light emitted from the light source.

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