JP2009128403A - Display element and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel capable of suppressing reduction in luminance upon transmission display without requiring excessive alignment accuracy of a prism and a pixel. <P>SOLUTION: The pixel 23 including a transparent electrode 41 transmitting light and a reflection electrode 42 reflecting light and the prism 20 of a non-focal system guiding light made incident on a rear surface side of the reflection electrode 42 to the transparent electrode 41 side are formed and provided. Reduction in luminance upon transmission display can be suppressed by effectively utilizing light L made incident on the rear surface side of the reflection electrode 42 on the transparent electrode 41 side without requiring excessive alignment accuracy of the prism 20 and the pixel 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display element having a pixel including a transmissive electrode portion that transmits light and a non-transmissive electrode portion that reflects light incident on a display side, and a display device including the display element.

  A display device using a liquid crystal display element as a display element has features such as light weight, thinness, and low power consumption, and thus is applied to various fields such as OA equipment, information terminals, watches, and televisions.

  In particular, a liquid crystal display element using a thin film transistor (TFT) element, that is, a liquid crystal panel is used as many display devices such as a mobile phone, a television, and a computer because of its responsiveness.

  In recent years, with the reduction in size and weight of portable terminals, there has been a demand for display devices with high definition and wide viewing angles.

  High definition has been dealt with by miniaturization of the TFT array structure.

  On the other hand, for wide viewing angles, display devices using an OCB method, an MVA method, an IPS method, or the like using nematic liquid crystals have been studied.

  Further, in recent years, since the frequency of use outdoors has increased, a transflective liquid crystal system capable of partially reflecting display has been put into practical use in addition to the conventional transmissive display system.

  However, since the above-described transflective liquid crystal panel has a light-shielding reflective electrode and a translucent transparent electrode, it has excellent visibility both indoors and outdoors. Since the light is blocked, there is a problem that the luminance at the time of transmissive display is lowered.

Therefore, a configuration for improving transmittance and luminance is provided by providing a microlens array having individual microlenses in the vertical and horizontal directions and guiding the light irradiated from the backlight to the reflective electrode to the transparent electrode. Known (for example, see Patent Document 1).
JP 2006-126732 A

  However, the above-described display element has a problem that it is necessary to form a transparent electrode so as to be paired with each microlens, and alignment accuracy between the liquid crystal panel and the microlens is required. .

  The present invention has been made in view of these points, and provides a display element that can suppress a decrease in luminance during transmissive display without requiring alignment accuracy more than necessary between the optical path conversion element and the pixel. Objective.

  The present invention includes a pair of substrates disposed opposite to each other, a light modulation layer interposed between the substrates, a transmissive electrode portion that transmits light, and reflects light incident on the display side and on the back side. A pixel having a non-transmissive electrode portion that does not transmit incident light, and a non-focal optical path conversion element that guides light incident on the back side of the non-transmissive electrode portion to the transmissive electrode portion side It is.

  Then, a non-focal optical path conversion element is provided that guides light incident on the back side of the non-transmissive electrode part to the transmissive electrode part side.

  According to the present invention, light that is incident on the back surface side of the non-transmissive electrode portion is effectively used on the transmissive electrode portion side without requiring an alignment accuracy more than necessary between the optical path conversion element and the pixel. The decrease in luminance can be suppressed.

  Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to FIGS.

  In FIG. 4, reference numeral 11 denotes a liquid crystal display device as a display device. The liquid crystal display device 11 includes a liquid crystal panel 12 which is a liquid crystal display element as a display element, and a surface disposed on the back side of the liquid crystal panel 12. With a backlight 13 as a light source device, used by transmitting light from the backlight 13 in dark places such as indoors, and reflecting and using light from the observation surface side in bright places such as outdoors, It is a so-called transflective type.

  The liquid crystal panel 12 is a color type liquid crystal panel, in which an array substrate 15 which is a substrate and a counter substrate 16 which is a substrate are arranged to face each other, and a liquid crystal layer 17 as a light modulation layer and a gap between the substrates 15 and 16 are arranged. A liquid crystal panel main body 19 which is a liquid crystal display element main body as a display element main body constituted by adhering a peripheral portion thereof by an adhesive layer 18 with a spacer for holding the liquid crystal constant, and on the back side of the liquid crystal panel main body 19 A plurality of prisms 20 serving as optical path conversion elements arranged on the side facing a certain backlight 13 are provided, and a plurality of pixels 23 shown in FIGS. Arranged in a matrix.

  The array substrate 15 includes, for example, a glass substrate 25 having translucency. On the main surface of the glass substrate 25 on the liquid crystal layer 17 side (upper side in FIG. 4), as shown in FIG. The scanning lines (gate wirings) 31 and the plurality of signal lines (source wirings) 32 are arranged in a lattice pattern so as to be substantially orthogonal to each other, and the scanning lines 31 and the signal lines 32 intersect each other. A thin film transistor (TFT) 33 as a switching element is provided at a position, and an alignment film such as a vertical alignment film (not shown) for aligning liquid crystal molecules of the liquid crystal layer 17 is formed so as to cover them.

  The thin film transistor 33 is a scanning line driving circuit in which a gate electrode is connected to the scanning line 31, a source electrode is connected to the signal line 32, and a pixel electrode 35 (FIG. 1 or the like) is connected to the drain electrode. Switching is controlled by applying a signal from the gate driver 36 to the gate electrode via the scanning line 31, and the pixel corresponding to the signal inputted via the signal line 32 from the source driver 37 which is a signal line driving circuit. By applying a voltage to the electrode 35 (FIG. 1), each of the pixels 23 is turned on / off independently.

  Each pixel electrode 35 includes a transparent electrode 41 that is a transmissive display portion as a transmissive electrode portion, and a reflective electrode 42 that is a reflective display portion as a non-transmissive electrode portion. The transparent electrode 41 and the reflective electrode 42 are configured to be electrically connected to each other and to be applied with the same voltage in each pixel 23.

  The transparent electrode 41 is formed in a substantially square shape by a sputtering method or the like with a transparent conductive material such as ITO (Indium Tin Oxide).

  The reflective electrode 42 is formed in a substantially square shape by a sputtering method or the like with a reflective conductive material such as aluminum, and has an area substantially equal to that of the transparent electrode 41, for example.

  Further, in the present embodiment, the transparent electrode 41 and the reflective electrode 42 are adjacent to each other in the direction intersecting (orthogonal) with respect to the scanning line 31 as shown in FIGS. For this reason, each pixel electrode 35 has a longitudinal direction in a direction intersecting (orthogonal) with respect to the scanning line 31.

  On the other hand, the counter substrate 16 includes a light-transmitting glass substrate 45, and a color filter layer (not shown), a counter electrode, an alignment film (not shown), and the like are sequentially stacked on the glass substrate 45.

  The counter electrode is formed by a sputtering method or the like at a position corresponding to the pixel electrode 35 in the display region 22 by using a transparent conductive material such as ITO.

  The liquid crystal layer 17 is a light modulation layer formed of a predetermined liquid crystal material, and can use almost all modes such as a TN mode, an IPS mode, an MVA mode, and a homogeneous mode.

  On the other hand, each prism 20 is a non-focal element formed of, for example, a photosensitive acrylic resin, and at least a portion corresponding to the display region 22 on the back side of the liquid crystal panel main body 19, each reflective electrode in the present embodiment. The liquid crystal panel main body 19 (glass substrate 25) is attached at a position corresponding to the back side of 42 respectively. Each prism 20 is formed as a continuous band that is continuous in a strip shape parallel to the scanning line 31, and a vertical surface 20a formed substantially perpendicular to the liquid crystal panel body 19, and the vertical surface 20a. In FIG. 1, the cross section has a substantially right-angled triangular shape having an inclined surface 20b inclined obliquely to the upper left.

  Further, in the present embodiment, each vertical surface 20a is at a position corresponding to the upper end portion of the reflective electrode 42 in the drawing, and each inclined surface 20b extends from the vertical surface 20a to the lower end portion of the reflective electrode 42 in the drawing. Is extended substantially linearly to a position corresponding to.

  Each prism 20 acts so that the interface with the air, that is, the inclined surface 20b bends the light according to the refractive index ratio n between the air and the material constituting the prism 20. In the present embodiment, the refractive index of the substance constituting each prism 20 is set larger than the refractive index of air.

  Therefore, each prism 20 corresponds to the refractive index ratio n with respect to the direction perpendicular to the inclined surface 20b, and the light that goes straight from the backlight 13 (FIG. 4) to the back side of each reflective electrode 42. The light is refracted downward in FIG. 1 in a direction inclined by an angle and guided to the transparent electrode 41 of the same pixel 23 or the transparent electrode 41 of the adjacent pixel 23.

  The backlight 13 converts light from a light source such as a lamp into planar light by a light guide plate that is a light guide, and irradiates the entire back side of the liquid crystal panel 12 with the planar light. .

  Next, the operation of the first embodiment will be described.

  When the liquid crystal display device 11 is used in a bright place such as outdoors (during reflective display), the thin film transistor 33 is sequentially driven by a signal from the gate driver 36 with the backlight 13 turned off, and the thin film transistor 33 turned on. A voltage corresponding to the signal from the source driver 37 generated corresponding to the image signal is applied to the pixel electrode 35 (the transparent electrode 41 and the reflective electrode 42), and the liquid crystal of the liquid crystal layer 17 corresponding to the applied voltage An image is displayed by changing the tilt angle of the molecule and reflecting the light incident from the outside on the display side by the reflective electrode 42 of each pixel 23.

  On the other hand, when the liquid crystal display device 11 is used in a dark place such as indoors (during transmissive display), the backlight 13 is turned on and the pixel electrode 35 (the transparent electrode 41 and the reflective electrode 42) is applied in the same manner as described above. The image is displayed by changing the tilt angle of the liquid crystal molecules of the liquid crystal layer 37 according to the applied voltage and transmitting the light incident from the backlight 13 through the transparent electrode 41 of each pixel 23. The

  At this time, the light from the backlight 13 irradiates the entire back surface of the liquid crystal panel 12 in a planar shape, but the light L incident on the reflecting electrode 42 when passing through the inclined surface 20b of each prism 20 is: The reflective electrode 42 is guided to the transparent electrode 41 located on the lower side in FIG. 1, and is transmitted through the transparent electrode 41 and emitted to the display side.

  As described above, in the first embodiment, the non-focal prism 20 that guides the light incident on the back side of each reflective electrode 42 toward the transparent electrode 41 is provided.

  For example, in the conventional case of using an optical path conversion element provided with a microlens array of a focal system that refracts light incident on the back side of the reflective electrode 42 and guides it to the transparent electrode side, the focal position of each microlens is While it is necessary to match the position of the pixel 23 and high alignment accuracy is required, in this embodiment, the alignment accuracy of each prism 20 and the pixel 23 is required more than necessary. The light L incident on the back side of each reflective electrode 42 can be easily and reliably guided to the transparent electrode 41 side, and the light L that is reflected by the reflective electrode 42 and is not used in a normal case is transmitted to the transparent electrode 41. It can be used effectively on the side to improve the apparent transmittance and suppress a decrease in luminance during transmissive display.

  Further, since the apparent transmittance is improved and the decrease in luminance at the time of transmissive display can be suppressed, the luminance of the backlight 13 does not need to be increased more than necessary even during transmissive display, and energy saving can be achieved.

  Moreover, in the conventional case using a microlens array, the light from the backlight 13 must also be ideal parallel light (collimated light), and obtaining such parallel light is incident from the backlight 13. However, the light L can be guided to the transparent electrode 41 while maintaining the alignment characteristics of the backlight 13 by using the non-focal prism 20 as in the present embodiment. A sufficient increase in transmittance can also be expected with the backlight 13 having a luminance peak in the front direction, that is, a Gaussian orientation characteristic, used in a typical product.

  In particular, when the liquid crystal layer 17 is in the MVA mode or the homogeneous mode using a circularly polarizing plate for the liquid crystal panel 12, the transmittance increasing effect is further increased.

  Furthermore, by forming the prism 20 as a continuous body that is continuous in parallel with the scanning line 31, it is possible to design the positioning accuracy in the direction parallel to the scanning line 31 with almost no requirement, thereby improving the productivity. To do.

  Next, a second embodiment will be described with reference to FIG. In addition, about the structure and effect | action similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, a prism sheet 53 as an optical path conversion element is bonded to the liquid crystal panel 12 (glass substrate 25) instead of the prism 20 of the first embodiment.

  The prism sheet 53 includes a sheet main body 54 that is a transmission portion as an optical path conversion element main body formed into a sheet shape by a member having translucency, and a plurality of optical path conversion portions that are integrally formed with the sheet main body 54. And a prism portion 55. The prism sheet 53 is formed by, for example, melt extrusion molding or an imprint technique using a photosensitive resin material.

  Each prism portion 55 is a non-focal optical element portion, similarly to the prism 20 of the second embodiment, is formed at a position corresponding to the back side of each reflective electrode 42, and the scanning line 31. A vertical surface 55a formed continuously in a strip shape parallel to the sheet body 54 and formed substantially perpendicular to the sheet body 54, and an inclined surface 55b inclined obliquely upward to the left in FIG. 5 with respect to the vertical surface 55a. The cross section has a substantially right triangle shape.

  When the liquid crystal display device 11 is used in a bright place such as outdoors (during reflective display), the liquid crystal panel 12 operates in the same manner as in the first embodiment, and the liquid crystal display device 11 is used indoors. When used in a dark place (when transmissive display), the liquid crystal panel body 19 operates in the same manner as in each of the above embodiments, and the light from the backlight 13 is irradiated onto the entire back surface of the liquid crystal panel 12 in a planar shape. However, when passing through the inclined surface 55b of each prism portion 55 of the prism sheet 53, the light L incident on the reflective electrode 42 is guided to the transparent electrode 41, so that the transparent electrode 41 is transmitted and displayed. Emitted to the side.

  As described above, the light beam L is guided to the transparent electrode 41 by each prism portion 55 of the prism sheet 53 which is a non-focal optical element. The same effects as those of the first embodiment can be achieved.

  Further, the optical path conversion element is constituted by the prism sheet 53 in which the sheet main body 54 and the prism portion 55 are integrally formed in advance, so that the prism sheet 53 is simply attached to the liquid crystal panel main body 19 (glass substrate 25). Since each prism portion 55 is arranged at a position corresponding to each reflective electrode 42, each prism portion 55 and each pixel 23 (reflective electrode 42) are compared with the case where the individual prism portions 55 are independently aligned. ) Can be easily aligned.

  In each of the above embodiments, the non-transmissive electrode portion is not limited to the reflective electrode 42 that can reflect light incident from the backlight 13 side, but includes a light absorbing portion that absorbs light from the backlight 13 side. Any light reflecting electrode that does not transmit light incident from the back side and reflects light incident from the display side can be selected arbitrarily.

  Further, the light modulation layer is not limited to the liquid crystal layer 17.

  Further, each prism 20 and each prism portion 55 of the prism sheet 53 can achieve the same effect even if they are arranged in parallel to any other wiring such as the signal line 32 or the auxiliary capacitance line. Can do.

  Each prism 20 and each prism portion 55 of the prism sheet 53 are formed upside down in FIG. 1 or FIG. 5, and the light L is transmitted to the transparent electrode 41 located above the reflective electrode 42. Even if it is configured to guide, the same effects can be obtained.

  As the optical path conversion element, it is possible to use not only a prism but also any non-focal optical element such as a diffraction grating or a reflection plate.

It is explanatory sectional drawing which shows the principal part of the display element of the 1st Embodiment of this invention. It is a front view which shows the principal part of a display element same as the above. It is a circuit diagram which shows a display element same as the above. It is explanatory sectional drawing which shows the display apparatus provided with the display element same as the above. It is explanatory sectional drawing which shows the principal part of the display element of the 2nd Embodiment of this invention.

Explanation of symbols

11 Liquid crystal display device as a display device
12 Liquid crystal panels as display elements
13 Backlight
Array substrate which is 15 substrate
16 counter substrate
17 Liquid crystal layer as light modulation layer
20 Prism as optical path conversion element
23 pixels
31 Scanning lines that are wiring
41 Transparent electrode as transparent electrode
42 Reflective electrode as non-transmissive electrode
53 Prism sheet as an optical path conversion element

Claims (3)

A pair of substrates disposed opposite each other;
A light modulation layer interposed between these substrates,
A pixel having a transmissive electrode portion that transmits light, and a non-transmissive electrode portion that reflects light incident on the display side and does not transmit light incident on the back side;
A non-focal optical path conversion element for guiding light incident on the back side of the non-transmissive electrode part to the transmissive electrode part side. A wiring connected to the pixel;
The display element according to claim 1, wherein the optical path conversion element is a continuous body formed continuously in parallel with a part of the wiring. A display element according to claim 1 or 2,
A display device comprising: a backlight for irradiating light from the back side to the display element.

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