JP4695344B2 - Display device and electronic apparatus using the same - Google Patents

Description

  The present invention relates to a display device and an electronic apparatus using the display device, and more particularly to a reflective liquid crystal display device that reflects external light for display, a reflective type that reflects external light for display, and light source light. The present invention relates to a transflective display device that can be used in combination with a transmissive display device that transmits light and an electronic apparatus using the transflective display device.

  Conventional display devices using a liquid crystal panel include a reflective display device that performs display using external light and a transmissive display device that emits light from the back surface of the liquid crystal panel.

  Here, in the case of a reflective display device, the amount of external light decreases in a dark place, so that the display becomes difficult to see. On the other hand, in the case of a transmissive display device, the power consumption is increased by the amount of the light source regardless of the light place and the dark place, and is not particularly suitable for a portable display device operated by a battery.

  Thus, there is a transflective display device that can be used for both a reflective type and a transmissive type. In this display device, when used in a bright place, an optical element such as a liquid crystal or a polarizing plate arranged on the optical path is reflected while reflecting external light incident from the display screen by a light reflecting plate provided inside the device. The amount of light emitted from the display screen is controlled for each pixel to perform reflective display.

  On the other hand, when the display device is used in a dark place, the light source light is irradiated from the back side of the liquid crystal panel by a built-in light source such as a backlight, and the display is performed using the optical elements such as the liquid crystal and the polarizing plate. The transmissive display is performed by controlling the amount of light emitted from the screen for each pixel.

  In a display device that can be used in both a reflective type and a transmissive type, TN (Twisted Nematic) liquid crystal, STN (Super-Twisted Nematic) liquid crystal, or the like is used as the liquid crystal filled in the liquid crystal panel and applied to the pixels. Depending on the presence or absence of voltage, the polarization axis of the liquid crystal is rotated to make the transmission polarization axis variable.

  The polarizing plate transmits light having a linearly polarized light component in a predetermined direction.

  Here, a conventional transflective display device will be described with reference to FIG.

  In FIG. 10, reference numeral 5110 denotes a voltage application region of the TN liquid crystal panel, and 5120 denotes a voltage non-application region of the TN liquid crystal panel.

  Reference numeral 5130 denotes an upper polarizing plate, 5302 denotes an upper glass plate, 5304 denotes a lower glass plate, 5160 denotes a reflective polarizing plate, 5307 denotes a semi-transmissive light absorbing plate, and 5210 denotes a light source.

  First, a case where monochrome display is performed by reflective display will be described.

  Incident light 5601 incident from the outside of the display device becomes light having a linearly polarized component in a direction parallel to the paper surface by the upper polarizing plate 5130, and the polarization direction is twisted by approximately 90 ° in the voltage non-application region 5120 of the TN liquid crystal panel. Light having a linearly polarized component in the direction perpendicular to the paper surface is reflected by the reflective polarizing plate 5160 as light having a linearly polarized component in the direction perpendicular to the paper surface, and the polarization direction is again reflected in the voltage non-application region 5120 of the TN liquid crystal panel. The light having a linearly polarized light component that is twisted by approximately 90 ° and parallel to the paper surface is emitted from the upper polarizing plate 5130. Accordingly, when no voltage is applied to the TN liquid crystal panel, white display is performed.

  On the other hand, incident light 5603 incident from the outside of the display device becomes light having a linearly polarized light component in a direction parallel to the paper surface by the upper polarizing plate 5130, and enters the paper surface without changing the polarization direction in the voltage application region 5110 of the TN liquid crystal panel. Since the light having parallel linearly polarized light components is transmitted as it is and is absorbed by the latter half transmitted light absorbing plate 5307, black display is obtained.

  Next, a case where monochrome display is performed by transmissive display will be described.

  Light 5602 from the light source 5210 is transmitted through the opening formed in the semi-transmissive light absorbing plate 5307, becomes light having a linearly polarized component in a direction parallel to the paper surface by the reflective polarizing plate 5160, and is a voltage non-application region of the TN liquid crystal panel. In 5120, the polarization direction is twisted by approximately 90 ° to obtain light having a linearly polarized component perpendicular to the paper surface, and is absorbed by the upper polarizing plate 5130, resulting in black display.

  On the other hand, the light 5604 from the light source 5210 is transmitted through the opening formed in the semi-transmissive light absorbing plate 5307, becomes light having a linearly polarized light component in a direction parallel to the paper surface by the reflective polarizing plate 5160, and applies voltage to the TN liquid crystal panel. Even in the region 5110, the light having the linearly polarized light component in the direction parallel to the paper surface is transmitted without changing the polarization direction, and white display is performed.

  In general, in a display device using a liquid crystal panel, the thickness of the liquid crystal layer is as very small as about 5 μm to 10 μm. On the other hand, since the substrate thickness is 0.3 mm to 0.7 mm, it is much thicker than the liquid crystal layer.

  Therefore, when reflective display is performed using the above-described conventional display device, as shown in FIG. 11, the optical path in the liquid crystal layer of external light incident from the upper side of the liquid crystal panel may be significantly different between the forward path and the return path. is there. Therefore, depending on the incident angle of the external light incident on the liquid crystal panel, the pixels through which the external light passes in the forward path and the pixels through which the external light passes in the return path are different. When the observer sees the optical path difference from an oblique direction, a phenomenon in which the display is shaded in the case of monochrome display without using a color filter, a so-called parallax is caused. Further, in a display device using a color filter having a plurality of colors, the color passing through the light forward path and the return path is different, resulting in a problem of color mixing.

  In the above prior art, only the transflective display device is shown. However, these problems are the reflection of the structure in which the light transmitting plate 5307 is replaced with the light absorbing plate except for the light source 5210 from the display device of FIG. This also occurs in the type of display device.

  A first object of the present invention is to provide a reflective or transflective display device in which parallax generated in reflective display and color mixing are reduced.

  In the conventional transflective display device shown in FIG. 10, since the transflective light absorbing plate 5307 is employed, the light emitted from the light source 5210 is included in the transmissive display. Since a part or most of the light is absorbed by the semi-transmissive light absorbing plate 5307, there is a problem that the light emitted from the light source 5210 cannot be used effectively and the display becomes dark.

  A second object of the present invention is to realize a display device capable of bright transmission type display by effectively utilizing light emitted from a light source.

  Further, in the display device using the above-described reflective polarizer, based on the above display principle, positive display is performed during reflection type display and negative display is performed during transmission type display, and so-called positive / negative inversion occurs.

  A third object of the present invention is to prevent this positive / negative reversal in a transflective display device using a reflective polarizer.

In order to achieve the above object, a display device of the present invention includes a liquid crystal panel in which liquid crystal is sandwiched between substrates, a first polarizing plate provided on one side of the liquid crystal panel, and the other side of the liquid crystal panel. A light reflecting plate provided on the side, a light diffusing plate having a forward scattering characteristic disposed between the liquid crystal panel and the light reflecting plate, and provided between the liquid crystal panel and the light reflecting plate, In a display device having a second polarizing plate that separates incident light according to its polarization component, a red, green, and blue colored layer is provided between the first polarizing plate and the light diffusion plate. The external light incident from one side of the liquid crystal panel is colored red, green, and blue by the color filter in the voltage non-application region of the liquid crystal panel. Of the second polarizing plate After being emitted as light of a linearly polarized light component in the hyperaxial direction, it is emitted as light of the linearly polarized light component diffused from the light diffusing plate, is applied to the light reflecting plate and is reflected, and the liquid crystal panel In the voltage application region where black display is performed, a distance dimension between the light diffusing plate and the light reflecting plate is set to be d, which is absorbed by the second polarizing plate after passing through the color filter. (Mm) and the haze value of the light diffusing plate is H (%), d ≧ 0.3 and 5 ≦ H ≦ 95 , and the relationship of H ≧ −200d + 140 is satisfied.

  According to the display device of the present invention, the external light incident from the upper side of the liquid crystal panel is sufficiently diffused by the light diffusing means having the forward scattering characteristic, and then provided at a predetermined distance from the light diffusing means. The light is reflected by the light reflecting means and then sufficiently diffused by the light diffusing means, and the liquid crystal panel is irradiated from the back side. Therefore, no matter what incident angle the external light enters on the liquid crystal panel, the light reflected from the light reflecting means and irradiating the liquid crystal panel from the back side becomes sufficiently diffused light, so that no parallax occurs. .

  In one embodiment of the present invention, a color filter is provided between the first polarizing unit and the light diffusing unit, and the color filter includes a plurality of colored layers. To do.

  According to the display device of this aspect, the external light incident on the liquid crystal panel is once colored into a plurality of colors by the color filter, but is then sufficiently diffused by the light diffusing means having forward scattering characteristics and the plurality of colors are mixed. . Then, it is reflected by the light reflecting means and illuminates the liquid crystal panel from the back side. The light that irradiates the liquid crystal panel from the back side is light that is close to white in which a plurality of colors are mixed, so no color mixing occurs regardless of the incident angle of external light incident on the liquid crystal panel.

  In another aspect of the present invention, the color filter has red, green, and blue colored layers.

  According to the display device of this aspect, the external light incident on the liquid crystal panel is colored into a plurality of colors by the color filter having red, green, and blue colored layers, and then diffused by the light diffusing means. At that time, since red, blue and green are mixed, the diffused light becomes very white. Since the white light is irradiated from the back side of the liquid crystal panel, a display with excellent color balance can be obtained.

  In another aspect of the present invention, a second polarization unit that separates incident light according to a polarization component is provided between the liquid crystal panel and the light reflection unit. To do.

  According to the display device of this aspect, the bright and dark display is performed by polarization-separating the external light transmitted through the liquid crystal panel by the second polarizing means.

  As the second polarizing means, a polarizing means that substantially transmits the light of the first linearly polarized light component and substantially absorbs the light of the second linearly polarized light component that is substantially orthogonal to the first linearly polarized light component is adopted. Is preferred.

  By adopting such a polarizing means, the dark light is displayed by absorbing the external light transmitted through the liquid crystal panel by the second polarizing means, and then brightly displayed by being transmitted through the second polarizing means and then reflected. Therefore, it is possible to realize a reflective display with extremely excellent contrast characteristics.

  According to another aspect of the present invention, the apparatus further includes an illumination device having a light-transmitting light guide and a light source capable of introducing light into the light guide, and the illumination device includes the light diffusing unit. And the light reflecting means.

  The display device according to this aspect relates to a so-called transflective display device that can perform transmissive display using light source light when dark and can perform reflective display using external light when bright. According to the display device of this aspect, a transflective display device capable of reflective display without parallax or color mixing is realized. Furthermore, since light emitted from the light source is sufficiently diffused by the light diffusing means having forward scattering characteristics even in the transmissive display, the liquid crystal panel can be irradiated with light uniformly. Further, since the light scattering means and the light reflecting means are separated from each other by the thickness of the light guide, the aforementioned separation dimension d is ensured.

  According to another aspect of the present invention, there is provided second polarizing means for separating incident light according to the polarization component between the liquid crystal panel and the illumination device, and the second Reflection that is provided between the polarizing means and the illumination device and substantially transmits the light of the first linearly polarized light component and reflects the light of the second linearly polarized light component substantially orthogonal to the one linearly polarized light component. It has a polarizer, and the transmission axis of the reflective polarizer and the transmission axis of the second polarizing means are substantially coincident.

  According to the display device according to this aspect, light having a polarization direction equal to the transmission axis direction of the reflective polarizer among the light emitted from the illumination device is transmitted through the reflective polarizer. On the other hand, light having a polarization direction equal to the reflection axis of the reflective polarizer is reflected by the reflective polarizer. Then, it is reflected by the light reflecting means and returns to the reflective polarizer again. And while repeating this reflection, any of them will pass through the reflective polarizer. That is, most of the light emitted from the illumination device is emitted toward the second polarizing means as light having a polarization direction equal to the transmission axis direction of the reflective polarizer. Then, this light is transmitted through the second polarizing means in which the transmission axis of the reflective polarizer and the transmission axis are set in parallel to be emitted toward the liquid crystal panel. For this reason, a bright transmissive display with extremely excellent utilization efficiency of light emitted from the illumination device is realized. Since the transmission axis of the reflective polarizer and the transmission axis of the second polarizing means are aligned, the external light incident from the upper side of the liquid crystal panel is not adversely affected by the reflective polarizer. Positive / negative reversal does not occur.

  The electronic apparatus of the present invention includes a liquid crystal panel having a liquid crystal sandwiched between substrates, and a first polarizing unit provided on one side of the liquid crystal panel and separating incident light according to its polarization component. In an electronic apparatus comprising a display device comprising: a light reflecting means provided on the other side of the liquid crystal panel; and a light diffusing means disposed between the liquid crystal panel and the light reflecting means. The means has a forward scattering characteristic, and when the distance between the light diffusing means and the light reflecting means is d (mm), the haze value H (%) of the light diffusing means is H ≧ −. 200d + 140 is satisfied.

  According to the electronic apparatus of the present invention, an electronic apparatus that does not cause parallax or color mixing is realized.

  Next, the display principle of the display device according to the present invention will be described in detail with reference to FIGS. In the following, a transflective display device is exemplified, but the reflective display principle does not change even in a reflective display device.

  In this liquid crystal display device, a TN liquid crystal panel 140 is used as a transmission polarization axis variable optical element. Further, an upper polarizing plate 130 is provided on the upper side of the TN liquid crystal panel 140, and a color filter 150 made of RGB (red, green, blue), a lower polarizing plate 160, and light are provided on the lower side of the TN liquid crystal panel 140. A diffusion plate 170 and a reflective polarizing plate 180 are sequentially provided. Further, a backlight 190 serving as a light source and a light reflecting plate 200 are sequentially provided below the reflective polarizing plate 180.

  The transmission axis of the upper polarizing plate 130 and the transmission axis of the lower polarizing plate 160 are substantially orthogonal to each other, and the transmission axis of the lower polarizing plate 160 and the transmission axis of the reflective polarizing plate 180 are parallel to each other. The light diffusing plate 170 performs forward scattering having a haze value H.

  Further, 141 on the left side indicates a voltage non-application area where no voltage is applied to the TN liquid crystal panel 140, and 142 on the right side indicates a voltage application area where a voltage is applied.

  With respect to the display device configured as described above, the operation of the reflective display will be described with reference to FIG.

  First, a case where light incident from the outside passes through the no-voltage application region 141 of the TN liquid crystal panel 140 will be described.

  The incident light 111 incident from the outside of the display device is transmitted only by the upper polarizing plate 130 with light having a linearly polarized component in the direction parallel to the paper surface, and then this light is applied by the voltage non-application region 141 of the TN liquid crystal panel 140. Light having a linearly polarized light component in a direction perpendicular to the plane of the paper whose polarization direction is twisted by approximately 90 °, and the color filter 150, the lower polarizing plate 160, the light diffusion plate 170, and the reflective polarizing plate 180 are straight in the direction perpendicular to the paper surface. The light is transmitted as a polarization component, passes through the transparent backlight 190, reaches the light reflection plate 200, and is reflected. Of the light reflected by the light reflecting plate 200, only the light 112 having the linearly polarized component in the direction perpendicular to the paper surface is again the backlight 190, the reflective polarizing plate 180, the light diffusing plate 170, the lower polarizing plate 160, the color. The light is transmitted through the filter 150 and twisted by about 90 ° by the no-voltage application region 141 to have light having a linearly polarized component in a direction parallel to the paper surface, and this light is emitted as emitted light 113.

The light reflected by the light reflecting plate 200 includes not only light 112 having a linearly polarized component in a direction perpendicular to the paper surface but also light 114 having a linearly polarized component in a direction parallel to the paper surface. For this reason, the light 114 is reflected by the reflective polarizing plate 180, is reflected again by the light reflecting plate 200, the polarization direction is changed, and the light 114 has a linearly polarized light component whose direction is perpendicular to the paper surface. Passes through the reflective polarizing plate 180.
By repeating this, light can be used effectively, and the outgoing light 113 emitted from the upper polarizing plate 130 can be brightened by about 1.6 times as compared with the case where the reflective polarizing plate 180 is not used. .

  Here, although the incident light 111 and the outgoing light 113 appear to pass through the color filters 150 having different colors, the light diffusion plate 170 is provided between the lower polarizing plate 160 and the reflective polarizing plate 180. When passing through the light diffusion plate 170, the light passing through the color filters 150 of each color is diffused. For this reason, the light reflected by the light reflecting plate 200 is not mixed with red, green, and blue, and a specific color is not strongly colored. As a result, the light 113 emitted from the upper polarizing plate 130 is colored in the color of the color filter 150 through which the light reflected by the light reflecting plate 200 passes.

  Next, a case where light incident from the outside passes through the voltage application region 142 of the TN liquid crystal panel 140 will be described.

  Of the incident light 116 incident from the outside of the display device, only light having a linearly polarized component in a direction parallel to the paper surface is transmitted by the upper polarizing plate 130, and then this light is polarized by the voltage application region 142 of the TN liquid crystal panel 140. It passes without changing its direction, passes through the color filter 150, is absorbed by the lower polarizing plate 160 and becomes dark.

  As described above, in the no-voltage application region 141, the light incident on the display device can be effectively used by the reflective polarizing plate 180, and the light reflected by the light reflecting plate 200 is colored by the color filter 150. 113 is emitted. On the other hand, in the voltage application region 142, light is absorbed by the lower polarizing plate 160 and becomes dark.

  Next, the operation of the transmissive display will be described with reference to FIG.

  First, the case where the light emitted from the backlight 190 passes through the no-voltage application region 141 of the TN liquid crystal panel 140 will be described.

  Of the light source light generated from the backlight 190, the light 121 having a linearly polarized component in the direction perpendicular to the paper surface passes through the reflective polarizing plate 180, the light diffusing plate 170, the lower polarizing plate 160, and the color filter 150, and TN. The voltage non-application region 141 of the liquid crystal panel 140 becomes light having a linearly polarized component in a direction parallel to the plane of the paper whose polarization direction is twisted by approximately 90 °, and this light is emitted from the upper polarizer 130 as emitted light 122.

  The light source light from the backlight 190 includes not only light 121 having a linearly polarized component in a direction perpendicular to the paper surface but also light 123 having a linearly polarized component in a direction parallel to the paper surface. Therefore, the light 123 is reflected by the reflective polarizing plate 180, reflected by the light reflecting plate 200, the polarization direction is changed, and part of the light 123 is reflected as light 124 having a linearly polarized component in a direction perpendicular to the paper surface. Passes through the polarizing plate 180. By repeating this, light can be used effectively and the emitted light 122 can be brightened.

  Next, the case where the light source light from the backlight 190 passes through the voltage application region 142 of the TN liquid crystal panel 140 will be described.

  Of the light source light of the backlight 190, the light 125 having a linearly polarized component in a direction perpendicular to the paper surface passes through the reflective polarizing plate 180, the light diffusing plate 170, the lower polarizing plate 160, and the color filter 150, and then this light. Passes through the voltage application region 142 of the TN liquid crystal panel 140 without changing the polarization direction, and is absorbed by the upper polarizing plate 130 and becomes dark.

  Of the light source light from the backlight 190, the light 126 having a linearly polarized component in a direction parallel to the paper surface is reflected by the reflective polarizing plate 180 and reflected by the light reflecting plate 200 to change the polarization direction. The light becomes a light 127 having a linearly polarized light component whose direction is perpendicular to the paper surface, and passes through the reflective polarizing plate 180. However, the light 127 also passes through the voltage application region 142 of the TN liquid crystal panel 140 without changing the polarization direction, and is absorbed by the upper polarizing plate 130 and becomes dark.

  Thus, the emitted light 113 and 122 colored by the color filter 150 is emitted by the combination of voltage application / non-application of the TN liquid crystal panel 140.

  Moreover, in the display device according to the present invention, the light diffusing plate 170 and the light reflecting plate 200 are provided, so that the light having the linearly polarized component in the direction parallel to the paper surface, like the incident light 111 shown in FIG. By passing, for example, red of the color filter 150, the light is colored red and passes through the lower polarizing plate 160, the light diffusing plate 170, the reflective polarizing plate 180, and the backlight 190, and reaches the light reflecting plate 200. Since the red light is scattered forward when passing through the light diffusion plate 170, the light reaching the light reflection plate 200 passes not only the light passing through the red color filter 150 but also green and blue. The light that has undergone green and blue coloring will be mixed and approach white light. For this reason, the light 112 reflected by the light reflecting plate 200 seems to be red in FIG. 2, but substantially receives the coloring of other colors (green, blue) diffused by the light diffusing plate 160. Since the reflected light is reflected in the same manner, the reflected light is white. Then, the white light passes through the backlight 190, the reflective polarizing plate 180, the light diffusing plate 170, and the lower polarizing plate 160 again and passes through a specific color (for example, green) among the color filters 150, and the liquid crystal panel 140. The light emitted through the upper polarizing plate 130 is colored green.

  Furthermore, the present inventor conducted a sharp experiment in order to reduce parallax (parallax) or the like that occurs when monochrome display is performed by reflective display in the display device having the above-described configuration. In this experimental method, as shown in FIG. 4, after tilting the display device by 30 degrees, incident light is incident from a direction tilted by 45 degrees with respect to the display device. The experimental results shown in Table 1 were obtained. In Table 1, the haze value H indicates the diffusivity (5 to 95%) of the light diffusion plate 170, and the separation dimension d indicates the separation dimension (mm) between the light diffusion plate 170 and the light reflection plate 200.

However, in Table 1, ◎: The shadow is blurred and the display is easy to understand. ○: The shadow is blurred. Thus, when the relationship between the haze value H and the separation dimension d is expressed as an equation, the following equation (1) is obtained.

H ≧ −200d + 140 (1)
Therefore, the display device is configured to satisfy the formula (1).

  Thereby, the light diffusing plate 170 can be applied to the light reflecting plate 200 in a state where the light emitted from the light diffusing plate 170 is sufficiently diffused, and the occurrence of parallax can be reduced.

  On the other hand, when color display is performed by reflection type display, when incident light is colored when passing through the color filter 150 and reflected by the light reflection plate 200 in an insufficient diffusion state by the light diffusion plate 170. In this case, light incident on the TN liquid crystal panel 140 again is mixed as a base color with a previously colored color, resulting in uneven display.

  Therefore, by setting the display device so as to satisfy the formula (1), it is possible to make the light colored in red, green, and blue reaching the light reflecting plate 200 sufficiently diffused. . Thereby, the light reflected by the light reflecting plate 200 can be white light in which red, green, and blue are uniformly mixed. As a result, the light emitted from the back side of the liquid crystal panel 140 at the time of reflective display is white, so that a clear color display without color unevenness can be realized.

  Further, if the color filter 150 is a dot matrix display composed of red, green, and blue, multicolor display and further full color display are possible.

  In the above description, the normally white mode has been described, but a normally black mode may be used. In addition, in the normally white mode, there is an effect that the display is brightened by the reflective polarizing plate 180 and the light reflecting plate 200 in both cases of the reflective display and the transmissive display.

  In the above configuration, the TN liquid crystal panel 140 has been described as an example. However, instead of the TN liquid crystal panel 140, other transmission polarization axes such as an STN liquid crystal panel and an ECB (Electrically Controlled Birefringence) liquid crystal panel can be changed by a voltage or the like. Even if one is used, the basic operation principle is the same.

  In the display device, the reflective polarizing plate 180 is provided between the light diffusing plate 170 and the backlight 190 in order to brighten the emitted light 113 and 122, but the reflective polarizing plate 180 is omitted. Also good.

  Further, it can be configured as a reflective display device in which the backlight 190 is omitted.

  Next, the principle of the reflective polarizing plate will be described with reference to FIGS. FIG. 1 is a schematic perspective view of a reflective polarizing plate serving as a reflective polarizing means, and FIGS. 2 and 3 are schematic views of a display device using the reflective polarizing plate.

  First, the structure of the reflective polarizing plate 180 will be described with reference to FIG. The reflective polarizing plate 180 has a laminated structure in which two different layers 1 (A layer) and 2 (B layer) are alternately laminated. Here, in the layers 1 and 2, the refractive index (nAY) in the Y direction of the A layer 1 and the B layer 2 are different from the refractive index (nAX) in the X direction and the refractive index (nAY) in the Y direction of the A layer 1. Is formed so as to be substantially equal to the refractive index (nBY) in the Y direction.

  Accordingly, light having a linearly polarized light component in the Y direction out of light incident on the reflective polarizer 180 from a direction perpendicular to the upper surface 5 of the reflective polarizer 180 is transmitted through the reflective polarizer 180 and transmitted in the Y direction from the lower surface 6. It is emitted as light having a linearly polarized light component. Conversely, light having a linearly polarized light component in the Y direction out of light incident on the reflective polarizer 180 from a direction perpendicular to the lower surface 6 of the reflective polarizer 180 is transmitted through the reflective polarizer 180 and transmitted from the upper surface 5 to the Y direction. Is emitted as light having a linearly polarized light component. Here, the direction in which light is transmitted (Y direction) is referred to as a transmission axis.

On the other hand, when the thickness of the A layer 1 in the Z direction is tA, the thickness of the B layer 2 in the Z direction is tB, and the wavelength of the incident light is λ,
tA · nAX + tB · nBX = λ / 2 (2)
The reflective polarizing plate 180 is formed so as to satisfy the above.

  As a result, light having a linearly polarized component in the X direction out of light having a wavelength λ incident on the reflective polarizer 180 from a direction perpendicular to the upper surface 5 of the reflective polarizer 180 is reflected by the reflective polarizer 180. . In addition, light having a linearly polarized light component in the X direction out of light incident on the reflective polarizing plate 180 from a direction perpendicular to the lower surface 6 of the reflective polarizing plate 180 is reflected by the reflective polarizing plate 180. Here, the direction in which light is reflected (X direction) is referred to as a reflection axis.

  Then, the reflective polarizing plate 180 varies the thickness tA in the Z direction of the A layer 1 and the thickness tB in the Z direction of the B layer 2 to satisfy the above formula (2) over the entire wavelength range of visible light. Thus, not only a single color but also the light having the X direction linearly polarized light is reflected as the light having the X direction linearly polarized light over the entire white light, and the light having the Y direction linearly polarized light is reflected by the Y direction linearly polarized light. It will be transmitted as light having.

  For example, a layer obtained by stretching polyethylene naphthalate (PEN) is used for the A layer of the reflective polarizing plate 180, and a copolyester (coPEN; copolyester) of naphthalene dicarboxylic acid and terephthalic acid is used for the B layer. of naphthalene dicarboxylic acid and terephthalic or isothalic acid). In addition, the material of the reflective polarizing plate 180 used for this invention is not limited to this, The material can be selected suitably. The details of such a reflective polarizing plate are disclosed as a reflective polarizer in, for example, JP-T-9-506985.

  As described above, in the display device according to the present invention, the relationship between the haze value H of the light diffusing unit and the separation dimension d between the light diffusing unit and the light reflecting unit is set to H ≧ −200d + 140. When performing black and white display, the light emitted from the light diffusing means toward the light reflecting means can reach the light reflecting means in a sufficiently diffused state. Can be reduced.

  In addition, when performing color display, incident light colored red, green, and blue can reach the light reflecting means in a sufficiently diffused state, and the light reflecting means uniformly mixes these lights. The white light is reflected as a white light, and a clear color display can be realized.

  Next, an embodiment of the present invention will be described with reference to the drawings.

1. Embodiment <First Embodiment>
FIG. 5 is a schematic configuration diagram of the color display device 10 according to the first embodiment. The display device 10 uses the STN cell 20 as a transmission polarization axis varying unit. In addition, the retardation film 14 and the upper polarizing plate 12 are sequentially provided on the upper side of the STN cell 20, and the light diffusion plate 30 and the lower polarizing plate 15 are sequentially provided on the lower side of the STN cell 20. A reflective polarizing plate 40, a light source 70, and a light reflecting plate 80 are sequentially provided below the lower polarizing plate 15.

  Here, the light source 70 uses an LED (Light Emitting Diode) 71, and the light guide 72 emits light upward. The light guide 72 is formed to a thickness of about 0.3 mm to 2 mm by a transparent resin such as acrylic resin, polycarbonate resin, and amorphous polyolefin resin, an inorganic transparent material such as glass, or a composite thereof. In addition, a plurality of small protrusions are formed on the surface of the light guide 72, and the size of each protrusion is such that the wavelength of visible light is about 380 nm to 700 nm. About 5 μm or more is necessary, and 300 μm or more is desirable for the size of the projections to be invisible to the naked eye.

  Further, the light reflecting plate 80 is made of aluminum film or silver film on a PET film, aluminum foil or the like.

  Further, the STN cell 20 constitutes a liquid crystal panel by sealing the STN liquid crystal 26 in a cell composed of two glass substrates 21 and 22 and a seal member 23. A transparent electrode 24 is formed on the lower surface of the glass substrate 21 and a transparent electrode 25 is provided on the upper surface of the glass substrate 22 to constitute a dot matrix. The transparent electrodes 24 and 25 are made of ITO (Indium Tin Oxide), tin oxide, or the like. Further, a color filter 27 made of red 27R, green 27G, and blue 27B is formed on the lower surface of the transparent electrode 24, and matches the electrode pattern of the transparent electrode 25. The color filter 27 may be formed between the glass substrate 21 and the transparent electrode 24 instead of the lower surface of the transparent electrode 24.

  The phase difference film 14 is used as an optical anisotropic body for color compensation, and corrects the coloring generated in the STN cell 20 to enable black and white display.

  The reflective polarizing plate 40 in the present embodiment uses the reflective polarizing plate 180 described with reference to FIG. 1, and the direction of the transmission axis of the reflective polarizing plate 40 and the direction of the transmission axis of the lower polarizing plate 15 are It almost matches.

  Further, the display device 10 according to the present embodiment is set so as to satisfy the above-mentioned formula 2. In the display device 10, the haze value H of the light diffusing plate 30 is set to 82%, for example, and the separation dimension d between the light diffusing plate 30 and the light reflecting plate 80 is set to 0.7 mm, for example, so as to satisfy the formula (1). It is what.

  Next, the operation of the display device 10 according to the present embodiment will be described.

  First, in the voltage non-application region of the STN cell 20 in the reflective display, light incident from the outside becomes light having a linearly polarized component in a predetermined direction by the upper polarizing plate 12, and then the polarization direction is changed by a predetermined angle screw by the STN cell 20. The light having the linearly polarized light component is transmitted through the light diffusing plate 30, the lower polarizing plate 15, and the reflective polarizing plate 40, passes through the light guide 72, and is reflected by the light reflecting plate 80. The reflected light again passes through the light guide 72, the reflective polarizing plate 40, the lower polarizing plate 15, and the light diffusing plate 30, and light having a linearly polarized light component whose polarization direction is twisted by a predetermined angle by the STN cell 20. The light is emitted from the upper polarizing plate 12.

  Moreover, even in the light reflected by the light reflection plate 80, the light whose polarization direction is changed is repeatedly reflected between the reflection polarizing plate 40 and the light reflection plate 80, and eventually from the reflection polarizing plate 40 to the STN cell 20. Since the light is emitted toward, bright display can be obtained. At this time, if the reflected light passes through the color filter 27, the light can be colored in any of red, green, and blue.

  In the voltage application region of the STN cell 20, light incident from the outside becomes light having a linearly polarized component in a predetermined direction by the upper polarizing plate 12, and then passes through the STN cell 20 as light having this linearly polarized component. It is absorbed by the lower polarizing plate 15 and darkens.

  Next, in the non-voltage application region of the STN cell 20 in the transmissive display, the light emitted from the light source 70 is transmitted as light having a linearly polarized component in a predetermined direction by the reflective polarizing plate 40 and is polarized by the STN cell 20. Light having a linearly polarized light component whose direction is twisted by a predetermined angle is emitted through the upper polarizing plate 12. At this time, the emitted light is colored in the color of the color filter 27 that passes therethrough.

  On the other hand, in the voltage application region of the STN cell 20, light emitted from the light source 70 is transmitted as light having a linearly polarized component in a predetermined direction by the reflective polarizing plate 40, and light having this linearly polarized component is transmitted through the STN cell 20. And passes through the upper polarizing plate 12 and becomes dark.

  As described above, in the display device 10 according to the present embodiment, bright color display can be realized by the color filter 27 composed of three colors of red, green, and blue in both the reflective display and the transmissive display.

  Furthermore, in the display device 10 according to the present embodiment, the relationship between the diffusivity (haze value H) of the light diffusing plate 30 and the separation dimension d between the light diffusing plate 30 and the light reflecting plate 80 is expressed by the equation (1). It is formed to satisfy. As a result, the light diffusing plate 30 can be uniformly applied to the light reflecting plate 80 in a state where the light colored by the color filter 27 has been sufficiently diffused from the light diffusing plate 30 to each of red, green and blue. In addition, the light reflected by the light reflecting plate 80 can be white light in which red, green, and blue are mixed.

  For example, of the incident light, the light colored red when passing through the red 27 </ b> R of the color filter 27 reaches the light reflecting plate 80 while being sufficiently diffused by the light diffusing plate 30. Further, the light colored green when passing through the green 27G of the color filter 27 reaches the light reflecting plate 80 in a state where it is sufficiently diffused by the light diffusing plate 30. Further, the light colored blue when passing through the blue 27 </ b> B of the color filter 27 reaches the light reflecting plate 80 in a state where it is sufficiently diffused by the light diffusing plate 30. Here, the light reflection plate 80 reflects these three colors of light as uniformly mixed white light and reflects it again to the STN cell 20 through the reflection polarizing plate 40, the light polarizing plate 30 and the lower polarizing plate 15. Incident. At this time, since the light incident on the STN cell 20 is white when reflected by the light reflector 80, the light emitted from the display device 10 is colored only by the color of the color filter 27 that passes therethrough. Is done.

  As a result, white light is emitted from the back side of the liquid crystal panel 140 during the reflective display, thereby preventing color unevenness and color display and realizing a clear color display. .

<Reference example>
FIG. 6 is a schematic diagram of a display device that performs monochrome display according to a reference example. That is, in the display device 10, an STN cell 20 ′ that does not include the color filter 27 is used instead of the STN cell 20 that includes the color filter 27. A lower polarizing plate 15, a light diffusing plate 30, a reflective polarizing plate 40, a light source 70, and a light reflecting plate 80 are sequentially provided below the STN cell 20 ′.

  Also in the display device 10 according to the reference example configured as described above, similarly to the display device 10 according to the first embodiment described above, light is sequentially reflected between the reflective polarizing plate 40 and the light reflecting plate 80 to obtain a predetermined value. Only light having a linearly polarized component in the direction is irradiated from the reflective polarizing plate 40 toward the STN cell 20 '. Thereby, the screen can be brightened in the reflective display.

  In addition, by designing the relationship between the haze value H of the light diffusing plate 30 and the distance d between the light diffusing plate 30 and the light reflecting plate 80 so as to satisfy the formula (1), the light diffusing plate 30 When the light radiated toward the light reflecting plate 80 reaches the light reflecting plate 80, the light can be sufficiently diffused, and the parallax generated during monochrome display can be reduced and the screen display can be made clear.

<Second Embodiment>
FIG. 7 is a schematic view of a display device according to the second embodiment. In this embodiment, in the display device 10 according to the first embodiment, the positions of the lower polarizing plate 15 and the light diffusing plate 30 are changed, and the lower polarizing plate 15 and the light diffusing plate 30 are placed below the STN cell 20. They are arranged in order.

<Third Embodiment>
FIG. 8 is a schematic view of a display device according to the third embodiment. In this embodiment, in the display device 10 according to the second embodiment, the reflective polarizing plate 40 is disposed between the lower polarizing plate 15 and the light diffusing plate 30, and the lower polarizing plate 15 is disposed below the STN cell 20. The reflective polarizing plate 40 and the light diffusing plate 30 are sequentially arranged.

<Fourth Embodiment>
FIG. 9 is a schematic view of a display device according to the fourth embodiment. In this embodiment, the lower polarizing plate 15 is omitted from the display device according to the third embodiment. Thus, in the display device according to the present embodiment, the display can be brightened by reducing the number of members through which light passes.

2. Modifications In each of the above-described embodiments, the STN cell 20 is described as an example of the liquid crystal panel. However, the present invention is not limited to this, and the transmission polarization axis is set to the voltage in addition to the TN liquid crystal panel and the ECB liquid crystal panel. Any change may be made.

  Further, the display device 10 described above includes personal computers, pagers, liquid crystal televisions, viewfinder type, monitor direct view type video tape recorders, car navigation devices, electronic notebooks, calculators, word processors, workstations, mobile phones, videophones, The present invention can be applied to an electronic device having a POS terminal and a touch panel.

It is a perspective view which shows the reflective polarizing plate used for the display apparatus by this invention. It is explanatory drawing which shows the principle of the reflection type display by this invention. It is explanatory drawing which shows the principle of the transmissive display by this invention. It is explanatory drawing which shows the parallax measurement experiment. 1 is a schematic configuration diagram illustrating a display device according to a first embodiment. It is a schematic block diagram which shows the display apparatus by a reference example. It is a schematic block diagram which shows the display apparatus by 2nd Embodiment. It is a schematic block diagram which shows the display apparatus by 3rd Embodiment. It is a schematic block diagram which shows the display apparatus by 4th Embodiment. It is a schematic block diagram which shows the display apparatus by a prior art. Explanatory drawing which shows the state in which the parallax has generate | occur | produced in the display apparatus by a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Display apparatus 12, 130 ... Upper polarizing plate 15, 160 ... Lower polarizing plate 20 ... STN cell (liquid crystal panel)
26 ... Liquid crystal 27, 150 ... Color filters 30, 170 ... Light diffuser plate 40, 180 ... Reflective polarizing plate 70 ... Light source 80, 200 ... Light reflector plate 140 ... TN LCD panel 190 ... Backlight

Claims (2)

A liquid crystal panel having a liquid crystal sandwiched between substrates, a first polarizing plate provided on one side of the liquid crystal panel, a light reflecting plate provided on the other side of the liquid crystal panel, and the liquid crystal panel; A light diffusing plate having a forward scattering characteristic disposed between the light reflecting plate, a second light diffusing plate provided between the liquid crystal panel and the light reflecting plate, and separating incident light according to its polarization component; In a display device having a polarizing plate,
A color filter having red, green and blue colored layers is provided between the first polarizing plate and the light diffusion plate,
The external light incident from one side of the liquid crystal panel is colored in red, green and blue colors by the color filter in the voltage non-application region of the liquid crystal panel, and is emitted from the second polarizing plate. After being emitted as light of a linearly polarized light component in the direction of the transmission axis, it is emitted as light of the linearly polarized light component diffused from the light diffusing plate, is applied to the light reflecting plate and is reflected, and the liquid crystal panel In the voltage application region for performing black display, the light is absorbed by the second polarizing plate after passing through the color filter,
When the distance dimension between the light diffusion plate and the light reflection plate is d (mm) and the haze value of the light diffusion plate is H (%), d ≧ 0.3 and 5 ≦ H a ≦ 95, display device characterized by satisfying the relationship of H ≧ -200d + 140. 2. The display device according to claim 1, wherein the light of the first linearly polarized light component is substantially transmitted between the second polarizing plate and the light reflecting plate and substantially orthogonal to the first linearly polarized light component. A reflective polarizer that substantially reflects light of the second linearly polarized light component is provided, and the transmission axis of the reflective polarizer and the transmission axis of the second polarizing plate are substantially aligned with each other. Display device.

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