JP5687180B2 - Display device and display method using display device - Google Patents

Description

  The present invention relates to a display element and a display device that perform display by switching the state of a light control layer between a scattering state in which incident light is scattered and a transparent state in which incident light is transmitted.

  A reflective display device has low power consumption and does not require a backlight, and thus is suitable for simple display. A transflective display device can display light with higher brightness than a reflective display device by using light incident from the back surface of the display device, such as light from a backlight, together with reflected light of external light. .

  FIG. 9 is a cross-sectional view of the liquid crystal display device of Patent Document 1. Patent Document 1 describes that an optical member 97 having a shape is used to obtain a bright display using light incident from the front side and light incident from the back side of the liquid crystal display device. ing.

  Specifically, the cross section of the optical member 97 has an uneven shape in which the front surface side in contact with the transparent substrate 92 is flat, and the back surface portion is continuously connected to the crest and trough portions.

  The optical member 97 reflects light incident from the front side of the liquid crystal display device with angle selectivity. The optical member 97 transmits light incident from the back side to the front side with angle selectivity. The liquid crystal display device of Patent Document 1 includes a dichroic dye in the liquid crystal layer 93, and performs bright and dark display by absorbing incident light of the dichroic dye.

  Patent Document 2 describes a retroreflector as a transflective reflector that is made of a prism sheet on which a metal vapor-deposited film is formed and can obtain a bright display in a wider range.

  Patent Document 3 describes a transmission / reflection plate that optimizes light transmission, reflection performance, and diffusion function in a well-balanced manner, and a transmission / reflection type liquid crystal display device using the same.

  Moreover, the following patent document 4 can be illustrated as a literature regarding a reflective transmission type liquid crystal display device.

Japanese Laid-Open Patent Publication No. 9-311332 (released on December 2, 1997) JP 2004-37831 A (published February 5, 2004) Japanese Patent Laying-Open No. 2001-350008 (released on December 21, 2001) JP 2002-107519 A (published April 10, 2002)

  However, the reflection / transmission (semi-transmission) display using the above-described conventional technique has the following problems.

  Specifically, the liquid crystal display device described in Patent Document 1 performs bright and dark display using the dichroic dye in the liquid crystal layer. Even when performing bright display, the incident light from the outside is displayed. Some do not contribute to the display and are lost. Moreover, although the incident light to the optical member is reflected or transmitted with angle selectivity, the incident direction of the light contributing to the brightness of the display is limited.

  Similarly, in Patent Documents 2 and 3, since the incident direction of light that contributes to the brightness of display is limited, the luminance is limited.

  In addition, when a liquid crystal that switches between a scattering state and a transmission state is used as a light control means in display, particularly when displaying a dark display in a scattering state, there is a problem that the luminance of the dark display is difficult to decrease. .

  And each said problem has caused the contrast fall of the display element.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to realize a display element having a high contrast.

  In particular, the present invention is to provide a reflection / transmission type display element having high luminance and suppressing negative / positive inversion.

  In order to solve the above problems, a display element of the present invention is a display element comprising opposing front and back substrates, and a light control layer sandwiched between the front and back substrates, and the light control layer Can be switched between a transparent state and a light scattering state, and a plurality of grooves are provided on the side of the back substrate that does not face the light control layer.

  With the above configuration, light incident from the back substrate side of the display element can be emitted at an angle corresponding to the shape of the groove. In addition, light incident from the front substrate side of the display element can be reflected at an angle corresponding to the shape of the groove.

  Thereby, the brightness | luminance of dark display can be reduced and the brightness | luminance in bright display can be improved. In particular, since it becomes easy to perform dark display using a light control layer in a transparent state, it becomes easier to lower the luminance than dark display using a light control layer in a conventional light scattering state. .

  As described above, a display element with high contrast can be realized.

  The groove has an inclined surface inclined with respect to the display surface of the front substrate.

  With the above configuration, by making the light control layer transparent, the reflected light of the light incident from the front substrate side is transmitted as it is, and the light incident from the rear substrate side is transmitted by changing the direction by the inclined surface. . Thereby, dark display can be performed.

  Further, by making the light control layer in the light scattering state, the reflected light of the light incident from the front substrate side is scattered, and the light incident from the rear substrate side is scattered by changing the direction by the inclined surface. Thereby, a bright display can be performed when scattered light enters an observer's eyes.

  As described above, the correspondence between the state of the light control layer and the brightness is the same in the display using the light incident from the front substrate side and the display using the light incident from the rear substrate side. Even when light is incident from both the substrate side and the light can be used as display light without canceling the light of both.

  Thereby, it is possible to display with high luminance.

  An angle formed between the normal line of the inclined surface and the normal line of the display surface is 36 degrees or more.

  With the above configuration, the reflection direction of light incident from the front substrate side and the emission direction of light incident from the rear substrate side can be set to appropriate directions.

  If the angle formed by the normal of the inclined surface and the normal of the display surface is smaller than 36 degrees, even if a material having a high refractive index (1.7) is used as a member for forming a groove, Since light also passes through the back surface, a high-luminance display cannot be obtained. By setting the angle to 36 degrees or more, when a groove is formed using a material having a refractive index of 1.7 or more, light incident from the front substrate side is reflected, and display luminance can be improved.

  When a material having a refractive index of 1.5 is used as the groove member, the angle needs to be 42 degrees or more.

  A cross-sectional shape of the groove in a plane perpendicular to the extending direction of the groove is a triangle.

  With the above configuration, light incident from the back substrate side can be uniformly dispersed in the direction perpendicular to the extending direction of the groove and emitted.

  Thereby, it is possible to make the luminance uniform in the display surface.

  A plurality of the grooves are continuously provided in a direction perpendicular to the extending direction of the grooves, and the cross-sectional shape of the convex portion between adjacent grooves is perpendicular to the surface perpendicular to the extending direction of the grooves. It is a triangle.

  With the above-described configuration, it is possible to retroreflect light having a component in a direction perpendicular to the normal direction of the display surface and the extending direction of the groove out of light incident from the front substrate side. Since the retroreflected reflected light does not enter the eyes of the observer, dark display can be performed when the light control layer is in a transparent state.

  Thereby, the reversal of the brightness of a display can be suppressed.

  The said groove | channel is provided so that the space | interval of adjacent grooves may each differ.

  With the above configuration, the repetition period of the groove interval can be increased.

  Here, the interval between the grooves means the distance between the centers of two adjacent grooves.

  The center of the groove means the center position of the concave portion forming the groove in the direction perpendicular to the extending direction in the cross section of the groove in a plane perpendicular to the extending direction of the groove.

  As a result, generation of diffracted light (interference fringes) caused by diffracting light incident from the back substrate side of the display element or light incident from the front substrate side of the display element by the groove, and the diffracted light at a wide angle Can be prevented from spreading.

  Thereby, display quality can be improved.

  The said groove | channel is characterized by the space | interval of adjacent grooves being 6 micrometers or more.

  With the above configuration, the period of the groove interval can be increased.

  As a result, generation of diffracted light (interference fringes) caused by diffracting light incident from the back substrate side of the display element or light incident from the front substrate side of the display element by the groove, and the diffracted light at a wide angle Can be prevented from spreading.

  Thereby, display quality can be improved.

  A plurality of grooves are provided on a side of the back substrate that does not face the light control layer by laminating an optical member on which unevenness is formed on the back substrate.

  By forming irregularities on the surface of the back substrate, a plurality of grooves are provided on a side of the back substrate that does not face the light control layer.

  With the above structure, the structure of the display element can be simplified.

  Thereby, the productivity and weight reduction of the display element can be achieved.

  Further, since one air layer can be omitted, reflection at the interface between the back substrate and the air layer and the interface between the member provided with the groove and the air layer can be eliminated, so that a high contrast display can be achieved.

  A reflective film is provided on the side of the back substrate that does not face the light control layer.

  With the above configuration, it is possible to reflect all light incident from the front substrate side.

  Thereby, it is possible to display with high luminance.

  The plurality of grooves are provided so that their extending directions are in two orthogonal directions.

  With the above configuration, light incident from the back substrate side can be uniformly dispersed in the direction perpendicular to the extending direction of the groove and emitted. That is, light incident from the back substrate side can be dispersed in four directions.

  Thereby, it is possible to display with a wider viewing angle and higher contrast.

  A condensing film is provided on the back surface of the groove of the back substrate.

  With the above configuration, the directivity of light incident from the back substrate side can be enhanced.

  Thereby, the emission direction of light incident from the back substrate side can be narrowed down, and display with higher contrast can be performed.

  The groove is provided such that the extending direction of the groove is a direction corresponding to a display image displayed on the display surface.

  With the above configuration, it is possible to provide a display element in which a groove having a stretching direction corresponding to a display image on the display surface is formed. Here, the case where the extending direction of the groove is a direction corresponding to the display image displayed on the display surface means, for example, the case where the extending direction of the groove is a direction along the left-right direction of the display image.

  Of the light incident from the front substrate side, light having a component in a direction perpendicular to the normal direction of the display surface and the extending direction of the grooves is retroreflected. On the other hand, light having a component in a direction parallel to the extending direction of the groove out of light incident from the front substrate side is regularly reflected. Even if the observer observes the display surface tilted in a direction perpendicular to the extending direction of the groove, the change in the amount of the regular reflection light incident on the observer is small.

  Accordingly, even when the observer observes the display surface tilted in a direction perpendicular to the extending direction of the groove, it is possible to suppress the reversal of display brightness that occurs according to the angle between the observer and the display surface.

  The groove is provided such that the extending direction of the groove is parallel to the horizontal direction of the display image displayed on the display surface.

  With the above configuration, it is possible to provide a display element in which a groove having an extending direction parallel to the left-right direction of the display image on the display surface is formed. Of the light incident from the front substrate side, light having a component in a direction perpendicular to the normal direction of the display surface and the extending direction of the grooves is retroreflected. On the other hand, light having a component in a direction parallel to the extending direction of the groove out of light incident from the front substrate side is regularly reflected. Even if the observer observes the display surface tilted up and down, the change in the amount of the regular reflection light incident on the observer is small.

  Thereby, even if an observer observes the display surface tilted up and down, it is possible to suppress reversal of display brightness and darkness that occurs according to the angle between the observer and the display surface.

  In order to solve the above problems, a display method of the present invention is a display method using a display element including opposed front and back substrates and a light control layer sandwiched between the front and back substrates. The dimming layer can be switched between a transparent state and a light scattering state, and a plurality of grooves are provided on the side of the back substrate that does not face the dimming layer. In the transparent state, the reflection from the front substrate side is suppressed in the regular reflection direction, and the incident light from the back substrate side is suppressed from being emitted in the normal direction of the display surface of the front substrate. By performing dark display, on the other hand, with the light control layer in a light scattering state, incident light from the front substrate side and incident light from the rear substrate side are emitted in the normal direction, It is characterized by performing bright display.

  With the above configuration, light incident from the front substrate side of the display element can be reflected at an angle corresponding to the shape of the groove and used as display light.

  Further, the light incident from the back substrate side is emitted at an angle corresponding to the shape of the groove, and can be used as display light.

  By making the light control layer transparent, the reflected light of the light incident from the front substrate side is transmitted in a regular reflection direction, and the direction of the light incident from the rear substrate side is changed by the inclined surface. Then, transmission in the normal direction of the display surface of the front substrate is suppressed. Thereby, dark display can be performed.

  Further, by making the light control layer in the light scattering state, the reflected light of the light incident from the front substrate side is scattered, and the light incident from the rear substrate side is scattered by changing the direction by the inclined surface. Thereby, a bright display can be performed when scattered light enters an observer's eyes.

  As described above, the correspondence between the state of the light control layer and the brightness is the same in the display using the light incident from the front substrate side and the display using the light incident from the rear substrate side. Even when light is incident from both the substrate side and the light can be used as display light without canceling the light of both.

  Furthermore, the incident direction of the light which contributes to the brightness of a display is not limited by performing the display according to transmission and scattering of light using the said light control layer which can be switched to a transparent state and a light-scattering state. Furthermore, it is not necessary to use a polarizing plate, and light loss can be suppressed.

  Thereby, it is possible to display with high luminance.

  A plurality of the grooves are continuously provided in a direction orthogonal to the extending direction of the grooves, and the cross-sectional shape of the groove in a plane perpendicular to the extending direction of the grooves is a triangle, and adjacent grooves The cross-sectional shape of the convex part between the two is a right-angled triangle in a plane perpendicular to the extending direction of the groove.

  With the above configuration, light incident from the back substrate side can be uniformly dispersed in the direction perpendicular to the extending direction of the groove and emitted.

  In addition, light incident from the front substrate side can be retroreflected. Since the retroreflected reflected light does not enter the eyes of the observer, dark display can be performed when the light control layer is in a transparent state.

  Thereby, the reversal of the brightness of a display can be suppressed.

  In the display element of the present invention, as described above, the light control layer can be switched between a transparent state and a light scattering state, and a plurality of grooves are formed on the side of the back substrate that does not face the light control layer. Is provided.

  Therefore, it is possible to realize a display element with high contrast, in particular, a high-brightness reflective / transmissive display element.

1 is a schematic cross-sectional view of a reflection-transmission type liquid crystal display device according to a first embodiment of the present invention. It is the schematic which shows the course of the light in case the reflective transmission type liquid crystal display device of 1st embodiment of this invention performs a reflective display, (a) represents the case where a liquid crystal layer is a transparent state, (b) is This represents a case where the liquid crystal layer is in a scattering state. It is the schematic which shows the course of the light in case the reflective transmission type liquid crystal display device of 1st embodiment of this invention performs a transmissive display, (a) represents the case where a liquid crystal layer is a transparent state, (b) is This represents a case where the liquid crystal layer is in a scattering state. It is the schematic which shows the course of the light in case the reflective transmissive liquid crystal display device of a comparative example performs reflective display, (a) represents the case where a liquid crystal layer is a transparent state, (b) is a liquid crystal layer being a scattering state. Represents the case. It is the schematic which shows the course of the light in case the reflective transmissive liquid crystal display device of a comparative example performs transmissive display, (a) represents the case where a liquid crystal layer is a transparent state, (b) is a liquid crystal layer being a scattering state. Represents the case. It is the perspective view and top view of a reflective transmission type liquid crystal display device of a second embodiment of the present invention. It is the cross-sectional schematic of the reflection type liquid crystal display device of 3rd embodiment of this invention. It is sectional drawing of the reflective transmissive liquid crystal display device of the modification of this invention. It is sectional drawing of the conventional liquid crystal display device.

  Hereinafter, embodiments of the present invention will be described in detail.

[Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS.

<Reflective transmission type liquid crystal display device 10>
FIG. 1 is a schematic cross-sectional view of a reflection-transmission type liquid crystal display device 10 of the present invention. As shown in FIG. 1, the reflection-transmission type liquid crystal display device 10 of the present invention includes a display element 5 and a backlight 6 (light source).

  The display element 5 includes a counter substrate 1 (front substrate), a liquid crystal layer 2 (light control layer), a TFT substrate 3 (back substrate), and an optical member 4, which are stacked in this order.

<Liquid crystal layer 2>
The liquid crystal layer 2 used in the reflective / transmissive liquid crystal display device 10 of the present invention is switched between a light scattering state and a transparent state by external control. The liquid crystal layer 2 scatters incident light when in a light scattering state, and transmits incident light when in a transparent state. For example, PNLC (Polymer network liquid crystal) or PDLC (Polymer disperse liquid crystal) can be used as the liquid crystal layer 2.

  By using these liquid crystals, it is not necessary to provide a polarizing plate in the display element 5, so that high luminance can be realized.

  The liquid crystal layer 2 is sandwiched between the counter substrate 1 and the TFT substrate 3. The TFT substrate 3 is provided with a TFT or the like (not shown). Under the control of the TFT, the liquid crystal layer 2 scatters incident light when in a scattering state, and transmits incident light when in a transparent state.

  For example, when PNLC is used as the liquid crystal layer 2, when no voltage is applied to the liquid crystal layer 2, the liquid crystal molecules are irregularly arranged along the network polymer fibers inside the liquid crystal layer 2 and incident. The light is scattered and the display becomes opaque. In a state where a voltage is applied to the liquid crystal layer 2, the liquid crystal molecules are aligned perpendicular to the display surface, so that incident light is transmitted and the display becomes transparent.

<Optical member 4>
The optical member 4 is a plate-like member and has a plurality of line-shaped groove shapes on one surface. The groove shape has an inclined surface, and is preferably composed of peak portions (convex portions) and valley portions (recess portions), and the peak portions and the valley portions are provided alternately and continuously. That is, it is preferable that a plurality of irregularities are provided continuously.

  As shown in FIG. 1, the optical member 4 preferably has a triangular cross-sectional shape on a plane perpendicular to the extending direction of the groove shape. Thereby, the light incident from the TFT substrate 3 side can be uniformly dispersed in the direction perpendicular to the extending direction of the groove shape and emitted.

  Moreover, as shown in FIG. 1, it is preferable that the apex angle of the peak part and trough part of an optical member is 90 degrees. That is, the cross-sectional shape of the convex part between adjacent grooves on a plane perpendicular to the extending direction of the groove shape is a right triangle. Thereby, the light incident from the counter substrate 1 side can be retroreflected.

  The optical member 4 is provided such that the surface not provided with the groove shape faces the TFT substrate and the surface provided with the groove shape faces the backlight 6.

  The optical member 4 is a transparent member in the visible light region. As the optical member 4, a BEF film manufactured by Sumitomo 3M Co., Ltd. can be suitably used.

  When observed in an environment where a particularly strong point light source exists due to diffraction caused by continuously provided grooves, the light is dispersed and a rainbow is generated. This diffracted light has a characteristic that it spreads over a wide angle especially when the interval between successive grooves (the period of the groove interval) is small, leading to a reduction in display quality.

  In order to increase the interval between successive grooves (period of groove interval), the grooves are preferably provided such that the intervals between adjacent grooves are different from each other.

  Further, in order to increase the interval between successive grooves (period of groove interval), for example, the interval between adjacent grooves is preferably 6 μm or more.

  As a preferable specific example, for example, a groove having a repetition period of 96 μm is formed so that the interval between adjacent grooves repeats in the order of 12 μm, 9 μm, 7 μm, 9 μm, 12 μm, 6 μm, 11 μm, 8 μm, 12 μm, and 10 μm. To do. Thereby, the problem of visibility that a rainbow is generated is improved.

  Here, the interval between the grooves means the distance between the centers of two adjacent grooves. The center of the groove means the center position of the concave portion forming the groove in the direction perpendicular to the extending direction in the cross section of the groove in a plane perpendicular to the extending direction of the groove.

<Backlight 6>
The backlight 6 is provided so as to face the surface of the optical member 4 where the groove shape is provided. The backlight 6 preferably emits light having strong directivity in the normal direction of the display surface of the reflective / transmissive liquid crystal display device 10.

  Further, in the reflective / transmissive liquid crystal display device 10 of the present invention, the backlight 6 is not an essential component. Even when the backlight 6 is not used, external light such as sunlight can be used as a light source.

<Reflection display>
A reflective display using the reflective transmission type liquid crystal display device 10 of the present invention will be described with reference to FIG.

  FIG. 2 is a schematic diagram showing the path of light when the reflective / transmissive liquid crystal display device 10 performs reflective display, and the arrow indicates the path of light. FIG. 2A shows a state where the liquid crystal layer 2 is in a transparent state and the reflection / transmission type liquid crystal display device 10 performs dark display. FIG. 2B shows a state where the liquid crystal layer 2 is in a light scattering state and the reflection / transmission type liquid crystal display device 10 performs a bright display.

  As shown in FIG. 2A, when the liquid crystal layer 2 is in a transparent state, the incident light 11 enters the reflection / transmission type liquid crystal display device 10 and is emitted to the outside as emitted light 12.

  Specifically, for example, when the refractive index of the optical member 4 is 1.59, the direction perpendicular to the extending direction of the groove shape from the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10 ( Incident light 11 incident on the optical member 4 with an incident angle within about 9.6 degrees in the X direction) is totally reflected by the groove-shaped surface of the optical member 4.

  That is, among the components of the incident light 11, the component in the direction perpendicular to the groove extending direction (X direction) is retroreflected or specularly reflected. In addition, among the components of the incident light 11, the component in the direction parallel to the groove-shaped extending direction (Y direction) is regularly reflected.

  As shown in FIG. 2A, when the liquid crystal layer 2 is in a transparent state, when the retroreflected or specularly reflected light from a relatively strong light source does not directly enter the observer, the display is dark for the observer. Display. Here, since it is difficult for the observer to be a light source, retroreflected light does not enter the observer. Therefore, when the liquid crystal layer 2 is in a transparent state, the display is a dark display.

  As shown in FIG. 2B, when the liquid crystal layer 2 is in the light scattering state, the incident light 13 enters the reflection / transmission type liquid crystal display device 10 and finally becomes scattered light 16 and is emitted to the outside.

  Specifically, first, the incident light 13 is scattered by the liquid crystal layer 2 in a light scattering state, and a part thereof becomes the scattered light 14.

  For example, when the refractive index of the optical member 4 is 1.59, the normal direction (Z direction) of the display surface of the reflective transmission type liquid crystal display device 10 is perpendicular to the extending direction of the groove shape (X direction). Of the components of the incident light 13 incident on the optical member 4 with an incident angle of about 9.6 degrees or less in polar angle, the component that has not been scattered becomes the emitted light 15 as described above. The outgoing light 15 and the scattered light 14 are scattered by the liquid crystal layer 2 in the light scattering state to become the scattered light 16.

  As shown in FIG. 2B, when the liquid crystal layer 2 is in the light scattering state, the scattered light 16 is incident on the observer, so that the display is bright for the observer.

  As described above, when the liquid crystal layer 2 is in the transparent state, the reflection / transmission type liquid crystal display device 10 can perform dark display, and when the liquid crystal layer 2 is in the light scattering state, the reflection / transmission type liquid crystal display device. 10 can be brightly displayed.

  The incident light incident on the optical member 4 with an incident angle larger than the polar angle of about 9.6 degrees of the reflection / transmission type liquid crystal display device 10 is partly removed from the back surface of the optical member 4, so that the display is possible. Does not contribute.

  Further, when the optical member 4 is formed of a material having a refractive index of 1.7, the direction perpendicular to the extending direction of the groove shape (from the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10) ( Incident light incident on the optical member 4 with an incident angle of about 15.3 degrees or less in the polar angle in the X direction) can be used for display without leaving the back surface of the optical member 4.

  Thus, by forming the optical member 4 with a high refractive index material, it is possible to widen the incident angle of the incident light contributing to the display without a part of the incident light being lost from the back surface of the optical member 4.

  The optical member 4 made of such a high refractive index material can be formed, for example, by dispersing titanium oxide in a resin such as PMMA (Poly methyl methacrylate).

  When the angle formed by the inclined surface of the groove of the optical member 4 and the normal line of the display surface is smaller than 36 degrees, a material having a refractive index of 1.7 as the material of the optical member 4 can be used. Since light from the counter substrate 1 side passes through the back surface, a high-luminance display cannot be obtained. Further, when a material having a refractive index of 1.5 is used as the material of the optical member 1, the angle formed above needs to be 42 degrees or more.

  As described above, the angle formed by the inclined surface of the groove of the optical member 4 and the normal line of the display surface is preferably 36 degrees or more, and more preferably 42 degrees or more.

<Transparent display>
A transmissive display using the reflective transmissive liquid crystal display device 10 of the present invention will be described with reference to FIG.

  FIG. 3 is a schematic view showing the path of light when the reflective / transmissive liquid crystal display device 10 performs transmissive display, and the arrow indicates the path of light. FIG. 3A shows a state where the liquid crystal layer 2 is in a transparent state and the reflection / transmission type liquid crystal display device 10 performs dark display. FIG. 3B shows a state in which the liquid crystal layer 2 is in a light scattering state and the reflection / transmission type liquid crystal display device 10 performs bright display.

  As shown in FIG. 3A, when the liquid crystal layer 2 is in a transparent state, incident light 17 having a strong directivity that is emitted from the backlight 6 and incident on the groove-shaped surface of the optical member 4 is Then, the light is emitted to the outside of the reflective / transmissive liquid crystal display device 10.

  Specifically, the light incident on the optical member 4 from the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10 is the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10. ) In a direction perpendicular to the extending direction of the groove shape (X direction) at a polar angle of about 30 degrees. That is, the incident light from the TFT substrate 3 side is suppressed from being emitted in the normal direction of the display surface.

  At this time, if the display surface of the reflective transmission type liquid crystal display device 10 is not observed from the emission direction of the outgoing light 18, the display is dark.

  As shown in FIG. 3B, when the liquid crystal layer 2 is in a light scattering state, incident light 19 emitted from the backlight 6 and incident on the groove-shaped surface of the optical member 4 is reflected as scattered light 21. The light is emitted outside the transmissive liquid crystal display device 10.

  Specifically, the light incident on the optical member 4 from the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10 is the normal direction (Z direction) of the display surface of the reflective / transmissive liquid crystal display device 10. ) From the extending direction of the groove shape in the direction perpendicular to the groove (X direction) at a polar angle of about 30 degrees, and becomes the emitted light 20. The emitted light 20 is scattered by the liquid crystal layer 2 in a light scattering state to become scattered light 21.

  As shown in FIG. 3B, when the liquid crystal layer 2 is in the light scattering state, the scattered light 21 is incident on the observer, so the display is bright for the observer.

  As described above, when the liquid crystal layer 2 is in the transparent state, the reflection / transmission type liquid crystal display device 10 can perform dark display, and when the liquid crystal layer 2 is in the light scattering state, the reflection / transmission type liquid crystal display device. 10 can be brightly displayed.

  As described above, according to the display method of the reflective / transmissive liquid crystal display device 10 of the present invention, it is possible to obtain a very bright display without light loss in the bright display.

  In addition, light with strong directivity is obtained by, for example, superimposing one or more BEF films manufactured by Sumitomo 3M on the backlight 6 as a condensing film.

  As described above, the optical member 4 of the present invention has a groove shape on one surface. Since the groove shape is a simple structure, the optical member 4 is easy to create. In addition, when light enters from the groove shape forming surface of the optical member 4, the direction of the light directly coming out to the surface of the optical member 4 where the groove shape is not formed is simple. The effect that it is easy to decide can be acquired.

<Comparative example>
As a comparative example, a reflection-transmission type liquid crystal display device 100 that does not include the optical member 4 of the present invention will be described with reference to FIGS.

  FIG. 4 is a schematic view showing the path of light when the reflective / transmissive liquid crystal display device 100 performs reflection display, and the arrow indicates the path of light. FIG. 4A shows the path of light when the liquid crystal layer is in a transparent state. FIG. 4B shows a light path when the liquid crystal layer is in a light scattering state.

  As shown in FIG. 4, the reflective / transmissive liquid crystal display device 100 includes a display element 105 and a backlight 106. The configuration of the display element 105 includes a counter substrate, a liquid crystal layer, and a TFT substrate (not shown), similarly to the display element 5 of the reflective transmission liquid crystal display device 10 of the present invention. However, unlike the display element 5 of the reflective / transmissive liquid crystal display device 10, the optical member 4 is not provided, but a mirror (not shown) is provided instead. That is, the reflection / transmission type liquid crystal display device 100 is intended to realize high-luminance display by reflecting incident light with a mirror.

  The backlight 106 of the reflective / transmissive liquid crystal display device 100 emits light with low directivity.

  The reflection / transmission type liquid crystal display device 100 that does not use the optical member 4 has a problem that negative / positive reversal of display, that is, reversal of brightness and darkness, and a decrease in contrast occur. This will be specifically described below.

  As shown in FIG. 4A, when the liquid crystal layer is in a transparent state, the incident light 111 is incident on the reflection / transmission type liquid crystal display device 100 and is specularly reflected by a mirror to become specularly reflected outgoing light 112 to the outside. Eject.

  When the liquid crystal layer of the reflective / transmissive liquid crystal display device 100 is in a transparent state, the specularly reflected outgoing light 112 does not enter the observer at the position A, so that the display is dark for the observer at the position A. On the other hand, even if the liquid crystal layer is in a transparent state, the observer at position B observes the specularly reflected outgoing light 112, and the display is bright for the observer at position B.

  Further, as shown in FIG. 4B, when the liquid crystal layer is in a light scattering state, the incident light 113 enters the reflection / transmission type liquid crystal display device 100 and is specularly reflected by a mirror to become specularly reflected outgoing light 114. The specularly reflected outgoing light 114 is scattered by the liquid crystal layer and becomes scattered light 115.

  When the liquid crystal layer of the reflective / transmissive liquid crystal display device 100 is in the light scattering state, the scattered light 115 is incident on the observer at the position A, so that the display is bright for the observer at the position A. On the other hand, when the liquid crystal layer is in the light scattering state, the scattered light 115 enters the observer at position B, and the display is bright for the observer at position B. At this time, the observer at position B feels that the scattered light 115, which is indirect light, has a lower luminance than the regular reflected outgoing light 112, which is direct light.

  As described above, in the reflection-transmission type liquid crystal display device 100 that does not include the optical member 4, the brightness is reversed between the position A and the position B when the liquid crystal layer is in a transparent state.

  Further, in the reflection / transmission type liquid crystal display device 100 that does not include the optical member 4, the observer at the position A performs dark display when the liquid crystal layer is in a transparent state and bright display when the liquid crystal layer is in a light scattering state. On the other hand, for the observer at position B, a bright display is obtained when the liquid crystal layer is in a transparent state, and a dark display is obtained when the liquid crystal layer is in a light scattering state. That is, the display is negative / positive inverted.

  FIG. 5 is a schematic view showing the path of light when the reflective / transmissive liquid crystal display device 100 performs transmissive display, and the arrow indicates the path of light. FIG. 5A shows the path of light when the liquid crystal layer is in a transparent state. FIG. 5B shows a light path when the liquid crystal layer is in a light scattering state.

  As shown in FIG. 5A, when the liquid crystal layer is in a transparent state, incident light 116 having low directivity is emitted as it is to the outside of the reflection / transmission type liquid crystal display device 100 and enters the observer.

  Further, as shown in FIG. 5B, when the liquid crystal layer is in the light scattering state, the incident light 118 having low directivity is scattered by the liquid crystal layer, so that the scattered light 119 is reflected and transmitted by the liquid crystal display device 100. Is emitted outside and enters the observer.

  As described above, when transmissive display is performed by the reflective / transmissive liquid crystal display device 100, even if the light scattering state and the transparent state of the liquid crystal layer are switched, the light is incident on the observer in any case, so the contrast of light and dark High display cannot be obtained.

(Summary of Embodiment 1)
Compared to a conventional transflective display device in which a reflective portion and a transmissive portion are provided in a pixel, the reflective / transmissive liquid crystal display device 10 of the present invention can simultaneously use the entire opening for reflective display and transmissive display, Since a polarizing plate is not used, a display with high light utilization efficiency can be obtained.

  In addition, since the state of the liquid crystal layer corresponding to light and dark is the same when using reflected light and when using transmitted light, light is incident from both the display surface and the back surface of the reflective / transmissive liquid crystal display device 10. Even in the state of being, it is possible to use each light without canceling.

  Furthermore, by installing in an environment in which highly directional sunlight or the like is irradiated from the back surface of the reflective transmission type liquid crystal display device 10, for example, an environment such as a window, display using sunlight in the daytime and room light in the nighttime is possible. The liquid crystal layer 2 is dark when the liquid crystal layer 2 is in a transparent state, and a very bright display is obtained in a light scattering state.

[Embodiment 2]
The second embodiment of the present invention will be described with reference to FIG.

  For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

<Reflective transmission type liquid crystal display device 30>
FIG. 6 is a perspective view and a plan view of the reflection-transmission type liquid crystal display device 30 according to the second embodiment of the present invention. Arrows indicate the path of light. In FIG. 6, for the sake of explanation, intervals are provided between the respective members, but the present invention is not limited to this.

  Unlike the reflection / transmission type liquid crystal display device 10 of the first embodiment, the reflection / transmission type liquid crystal display device 30 includes two optical members, an optical member 31 and an optical member 32.

  The optical member 31 and the optical member 32 are provided such that the groove-shaped extending direction of the optical member 31 and the groove-shaped extending direction of the optical member 32 are two directions orthogonal to each other in plan view.

  The backlight 6 preferably emits light having strong directivity in the normal direction of the display surface of the reflective / transmissive liquid crystal display device 30.

  Incident light 33 emitted from the backlight 6 enters an optical member 31 provided immediately above the backlight 6, is dispersed in the left-right direction (X direction), and is emitted as incident light 34. The incident light 34 enters an optical member 32 provided immediately above the optical member 31, and is dispersed in the vertical direction (Y direction) and emitted as incident light 35.

  The light emitted from the backlight 6 is dispersed in the directions from the center of the reflective / transmissive liquid crystal display device 30 toward the four corners in plan view. In other words, the light emitted from the backlight 6 is 4 degrees of 45 degrees, 135 degrees, 225 degrees, and 315 degrees when the + Y direction from the center of the reflective transmission type liquid crystal display device 30 is 0 degrees in plan view. Separate into two azimuth directions.

  At this time, when a resin having a refractive index of 1.59 is used as the optical members 31 and 32, the polar angle direction of each incident light 35 is about 30 degrees.

  When the incident light 35 enters the liquid crystal layer 2, when the liquid crystal layer 2 is in a transparent state, it exits as the emitted light 36 in the above four azimuth directions, and is a dark display for an observer who observes at least from the normal direction of the panel. It becomes.

  In addition, when the liquid crystal layer 2 is in the light scattering state, the emitted light 36 is scattered, thereby providing a bright display for the observer.

  In the reflection / transmission type liquid crystal display device 30 of the present embodiment, the light incident from the display surface side is reflected by the optical member 32 in the same manner as described in the first embodiment, and a reflective display can be performed.

  Further, when light is incident from the back surface of the reflective transmission type liquid crystal display device 30 by a highly directional backlight or the like, the light is inverted in the vicinity of the front surface, the direction inclined in the vertical direction, and the direction inclined in the horizontal direction. Therefore, a transmissive display with high contrast can be achieved. In other words, even when observing from a direction having a certain polar angle with respect to the display surface of the reflective / transmissive liquid crystal display device 30, a transmissive display with high contrast that prevents negative / positive inversion can be achieved. That is, high-contrast transmissive display can be performed while preventing negative / positive reversal at a wide viewing angle.

  In addition, since the state of the liquid crystal layer corresponding to light and dark is the same when using reflected light and when using transmitted light, light is incident from both the display surface and the back surface of the reflective / transmissive liquid crystal display device 30. Even in the state of being, it is possible to use each light without canceling.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG.

  For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

<Reflective liquid crystal display device 50>
FIG. 7 is a schematic cross-sectional view of the reflective liquid crystal display device 50 of the present invention.

  The reflective liquid crystal display device 50 does not include the backlight 6. In addition, a reflective film 51 is provided on the groove shape forming surface of the optical member 4. The reflective liquid crystal display device 50 is mainly specialized in reflective display.

  The reflective film 51 is formed of, for example, a metal film or a dielectric multilayer film.

  Since the reflective / transmissive liquid crystal display device 10 does not include the reflective film 51, for example, when the refractive index of the optical member 4 is 1.59, from the normal direction (Z direction) of the display surface to the extending direction of the groove shape. The incident light incident on the optical member 4 with an incident angle larger than the polar angle of about 9.6 degrees in the vertical direction (X direction) does not contribute to display because a part of the incident light passes through the back surface of the optical member 4. .

  However, since the reflective liquid crystal display device 50 of the present embodiment includes the reflective film 51, it can reflect all light incident from the display surface. Thereby, a brighter reflection type display can be performed.

  For incident light inclined from the normal direction (Z direction) of the display surface to a direction perpendicular to the extending direction of the groove shape (X direction), a certain ratio depending on the angle is retroreflected. For this reason, it is possible to perform display with less regular reflection and less negative / positive reversal than when a reflection plate that performs flat mirror reflection is used.

<Modification>
A modification of the present invention will be described with reference to FIG.

  For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 8 is a cross-sectional view of a reflective / transmissive liquid crystal display device 60 according to a modification of the present invention. In the reflection / transmission type liquid crystal display device 60, the counter substrate 1, the liquid crystal layer 2, and the TFT optical substrate 61 are laminated in this order. The TFT optical substrate 61 has a groove shape on the surface opposite to the surface facing the liquid crystal layer 2. The TFT optical substrate 61 has the functions of both the TFT substrate 3 and the optical member 4 described above.

  As a result, the configuration of the reflection / transmission type liquid crystal display device 60 can be simplified, so that productivity and weight reduction can be achieved.

  Further, since one air layer can be omitted, reflection at the interface between the back substrate and the air layer and the interface between the member provided with the groove and the air layer can be eliminated, so that a high contrast display can be achieved.

  When observing the display image, it is observed from the normal direction of the display surface of the reflective / transmissive liquid crystal display device 10, 30, 60 or the reflective liquid crystal display device 50, or the display surface is tilted up and down with respect to the viewer. It is thought that it is rare to incline from side to side.

  Therefore, for incident light inclined in the direction perpendicular to the groove extending direction (X direction) from the normal direction (Z direction) of the display surface, the characteristic that a certain ratio depending on the angle is retroreflected is utilized. The optical member 4 (or the TFT optical substrate 61) is preferably arranged so that the extending direction of the groove shape corresponds to the display image.

  Here, the case where the extending direction of the groove shape is a direction corresponding to the display image means, for example, the case where the extending direction of the groove shape is a direction along the left-right direction of the display image, and the like. More preferably, the horizontal direction is parallel.

  Thereby, even if an observer observes the display surface tilted up and down, it is possible to suppress reversal of display brightness and darkness that occurs according to the angle between the observer and the display surface.

  Thereby, a display with little negative / positive reversal can be obtained.

  Note that the display element of the present invention can be appropriately applied not only to a reflective / transmissive (semi-transmissive) liquid crystal display device but also to a reflective or transmissive liquid crystal display device.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the present invention can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The present invention can be used for a reflective display device or a reflective transmission display device with high luminance.

DESCRIPTION OF SYMBOLS 1 Opposite substrate 2 Liquid crystal layer 3 TFT substrate 4 Optical member 5 Display element 6 Backlight 10 Reflective transmission type liquid crystal display device 11 Incident light 12 Emission light 13 Incident light 14 Scattered light 15 Emission light 16 Scattered light 17 Incident light 18 Emission light 19 Incident light 20 Emission light 21 Scattered light 30 Reflective transmission type liquid crystal display device 31 Optical member 32 Optical member 33 Incident light 34 Incident light 35 Incident light 36 Emission light 50 Reflective liquid crystal display device 60 Reflective transmission type liquid crystal display device 61 TFT optical substrate DESCRIPTION OF SYMBOLS 100 Reflective transmission type liquid crystal display device 105 Display element 106 Backlight 111 Incident light 112 Regular reflection outgoing light 114 Regular reflection outgoing light 113 Incident light 115 Scattered light 119 Scattered light 116 Incident light 118 Incident light

Claims (11)

A display device including a front substrate and a rear substrate facing each other, a display element including a light control layer sandwiched between the front substrate and the rear substrate, and a backlight.
The light control layer can be switched between a transparent state and a light scattering state,
A plurality of grooves are provided on the side of the back substrate that does not face the light control layer,
The groove is formed between a plurality of convex portions having an apex angle of 90 °,
At least a part of the light incident on the groove from the front substrate side is retroreflected by reflecting on two surfaces constituting the groove,
The display device according to claim 1, wherein the light emitted from the backlight is incident on the light control layer from any surface constituting the groove.   The display device according to claim 1, wherein the groove has an inclined surface inclined with respect to the display surface of the front substrate.   The display device according to claim 2, wherein an angle formed by a normal line of the inclined surface and a normal line of the display surface is 36 degrees or more.   The display device according to claim 1, wherein a cross-sectional shape of the groove in a plane perpendicular to the extending direction of the groove is a triangle. A plurality of the grooves are continuously provided in a direction orthogonal to the extending direction of the grooves,
The display device according to claim 4, wherein a cross-sectional shape of a convex portion between adjacent grooves in a plane perpendicular to the extending direction of the grooves is a right triangle.   The display device according to claim 1, wherein the grooves are provided such that intervals between adjacent grooves are different from each other.   The display device according to claim 1, wherein the groove has an interval between adjacent grooves of 6 μm or more.   A plurality of grooves are provided on a side of the back substrate that does not face the light control layer by laminating an optical member having irregularities formed on the back substrate. Item 8. The display device according to any one of Items 1 to 7.   The unevenness is formed on the surface of the back substrate, so that a plurality of grooves are provided on the side of the back substrate that does not face the light control layer. The display device according to claim 1. A display device comprising a front substrate and a rear substrate facing each other, and a light control layer sandwiched between the front substrate and the rear substrate, and a display method using a backlight,
The light control layer can be switched between a transparent state and a light scattering state,
A plurality of grooves are provided on the side of the back substrate that does not face the light control layer,
The groove is formed between a plurality of convex portions having an apex angle of 90 °,
The light emitted from the backlight is incident on the light control layer from any surface constituting the groove,
The light control layer is in a transparent state, and at least a part of the light incident on the groove from the front substrate side is reflected by two surfaces constituting the groove so as to be retroreflected in the regular reflection direction. In addition to suppressing reflection, the incident light from the back substrate side performs dark display by suppressing emission in the normal direction of the display surface of the front substrate,
On the other hand, a bright display is performed by setting the light control layer in a light scattering state and emitting the incident light from the front substrate side and the emitted light of the backlight in the normal direction. . A plurality of the grooves are continuously provided in a direction orthogonal to the extending direction of the grooves,
The cross-sectional shape of the groove in a plane perpendicular to the extending direction of the groove is a triangle,
The display method according to claim 10 , wherein a cross-sectional shape of a convex portion between adjacent grooves in a plane perpendicular to the extending direction of the grooves is a right triangle.

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