JP2009008710A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device having a simple laminated structure even when stage effects like a shadowgraph is imparted to the display thereof. <P>SOLUTION: The liquid crystal display device has: a liquid crystal layer 11b which is held between two transparent substrates 11a, 11d and in which the state is switched between a transmissive state and a scattering state with a voltage applied by electrodes formed on the transparent substrates 11a, 11d; a transflective layer (a laminated body comprising transflective reflection plates 12, 13) which reflects a portion of incident light and transmits a portion thereof; a translucent layer 14 which has patterns, characters, marks etc. formed thereon; and a backlight device. The liquid crystal layer 11b, the transflective layer, the translucent layer 14 and light emitting face of the backlight device are laminated together sequentially from the viewer's side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device provided with a mode for displaying by reflecting external light and a mode for displaying by lighting a backlight.

  Conventionally, devices with a staging effect that a pattern such as a logo that cannot be seen in the reflective display mode appears as a background like a shadow picture when the backlighting device is turned on are widely known, and patents are examples of applications to watches There is one disclosed in Document 1. An example applied to a liquid crystal display device is disclosed in Patent Document 2.

  Patent Document 1 shows a laminated structure of an electroluminescent layer that is a light emitter, a printed layer on which a pattern is printed, a translucent layer made of a half mirror, and a white printed layer. In the reflection mode that uses external light, the amount of light that is transmitted through the half mirror and reflected by the electroluminescence layer after passing through the half mirror is remarkably smaller than the amount of light that is reflected by the half mirror. The pattern is not visible on the white print layer. On the other hand, in the transmission mode using the light emission of the electroluminescence layer, the pattern of the printing layer is projected onto the white printing layer so that it can be clearly seen.

  In the fifth embodiment of Patent Document 2, in a liquid crystal display device that displays a pattern or logo on the background when the backlighting device is turned on, the reflectance is adjusted so that it is difficult to see the pattern or logo in the reflective display mode. The one using a half mirror (semi-transmissive reflective layer) in which the axis of the reflective polarizing plate is shifted is disclosed.

  Embodiment 5 of Patent Document 2 will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the stacking situation of this prior art liquid crystal display device. The scale is changed as appropriate (the same applies hereinafter). The members of each layer are in close contact with each other, but are appropriately separated on the drawings for the sake of explanation (the same applies hereinafter).

  The laminated structure of this conventional member will be described with reference to FIG. Back illumination device 57, translucent film 56 on which a pattern is printed, scattering layer 55, second reflective polarizing plate 54, first reflective polarizing plate 53, two glass substrates 52a, 52d and seal 52c A liquid crystal cell 52 in which a liquid crystal 52b is sealed and an absorption type polarizing plate 51 are stacked in the formed space. The absorptive polarizing plate 51 transmits polarized light parallel to the transmission axis and absorbs polarized light perpendicular to the transmission axis. The reflective polarizing plates 53 and 54 transmit polarized light parallel to the transmission axis and reflect polarized light parallel to the reflection axis perpendicular to the transmission axis. The liquid crystal cell 52 is a twisted nematic liquid crystal cell in which liquid crystal molecules are twisted by 90 ° in the thickness direction. The reflection axis of the second reflective polarizing plate 54 is inclined by the angle θ from the reflective axis of the first reflective polarizing plate 53. The laminated body of the first and second reflective polarizing plates 53 and 54 is a half mirror whose reflectance (and transmittance) is determined by the angle θ. Further, it is assumed that the transmission axes of the absorption-type polarizing plate 51 and the first reflective-type polarizing plate 53 are vertical.

  First, the reflection mode will be described. The liquid crystal cell 52 has a sufficiently high voltage and a plane region (hereinafter referred to as an off region) in which a voltage higher than a threshold is not applied to the liquid crystal 52b by electrodes (not shown) formed on the inner surfaces of the transparent substrates 52a and 52d. Has a planar region (hereinafter referred to as an ON region).

In the off region, the polarized light passing through the absorption-type polarizing plate 51 is rotated by 90 ° in the liquid crystal layer and reaches the first absorption-type polarizing plate 53. At this time, since the absorption polarization direction and the transmission axis of the first absorption polarizing plate 53 are parallel, the polarized light passes through the first absorption polarizing plate 53 and reaches the second polarizing plate 54. Here, since the polarization direction and the transmission axis of the second absorptive polarizing plate 54 are in an angle θ (the reflection axis is 90 ° −θ), the reflection axis component SIN (θ) of the polarized light is reflected, and this is visually recognized. Come back to the side. Note that the light that passed through the second reflective polarizing plate 54 and reflected back from the backlight device 57 was ignored.

  In the ON region, the polarized light that has passed through the absorption polarizing plate 51 is not rotated, so that it is reflected by the first reflective polarizing plate 53 and returns directly to the viewing side.

  As described above, this liquid crystal display device performs display in which the contrast ratio is 1 / SIN (θ) in the reflection mode. Since both the off region and the on region are specularly reflected, the display state is a metal tone.

  Next, the transmission mode when the backlight device 57 is turned on will be described. The pattern of the transmissive film 56 is projected onto the scattering layer 55 with the light emitted from the back lighting device 57. Of the light emitted from the scattering layer 55 to the viewing side, a component parallel to the transmission axis of the second reflective polarizing plate 54 is transmitted. Further, the transmission axis component COS (θ) of the first reflective polarizing plate 53 of this polarized light is transmitted.

  This polarized light is rotated by 90 ° in the liquid crystal in the off region and then transmitted through the absorptive polarizing plate 51, and is absorbed by the absorptive polarizing plate 51 because it is not rotated in the on region. The observer sees an image obtained by superimposing an image formed from the off region and the on region and a projection image formed on the scattering layer 55.

  The liquid crystal display device of Document 2 has a slightly complicated structure because it has a rendering effect of performing a mirror-like display in a reflection mode in addition to a shadowy rendering effect. If only the pattern is displayed when the back lighting device is turned on, it can be easily realized by the combination of Document 1 and Document 2. This sectional view is shown in FIG. The same members as those in the conventional example of FIG. 5 are denoted by the same reference numerals, and redundant description is omitted (the same applies hereinafter).

In FIG. 6, a back illumination device 57, a transmissive film 56, a half mirror 63, a scattering layer 62, a lower absorption polarizing plate 61, a liquid crystal cell 52, and an upper absorption polarizing plate 51 are laminated. This corresponds to a liquid crystal display device having a reflective display mode and a transmissive display mode in which a picture transmissive film 56 is inserted. Thus, the picture is projected onto the scattering layer 62 and can be visually recognized only in the transmissive display mode. When this function is added, the reflectance of the half mirror may be set high so that the picture cannot be seen in the reflection mode.
JP-A-8-305295 JP 2001-343634 A

  However, even a liquid crystal display device as shown in FIG. 6 has a complicated structure with many types and number of members to be laminated.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a liquid crystal display device capable of realizing a shadow effect with a simple laminated structure.

The present invention relates to a liquid crystal display device having a liquid crystal layer sandwiched between two substrates and an illumination device that illuminates the liquid crystal layer, wherein the liquid crystal layer can be switched between a transmission state and a scattering state. And a transflective layer that reflects part of incident light and transmits part of it, and is located between the transflective layer and the illumination device. A formed translucent layer;
It is characterized by providing.

  The transflective layer is preferably composed of a reflective polarizing plate that transmits polarized light in the transmission axis direction and reflects polarized light in the reflection axis direction.

  In this case, it is preferable that two reflective polarizing plates are laminated to form a semi-transmissive reflective layer, and the transmission axes of the respective reflective polarizing plates are directed in different directions.

  The transflective layer may be an intrinsic transflective layer formed between the liquid crystal layer and the substrate.

  The transflective layer may be made of metal.

  The transflective layer preferably has pores.

  The liquid crystal layer is preferably made of a polymer scattering type liquid crystal.

  The translucent layer may be a film on which a pattern, characters, marks, etc. are printed.

  The light transmissive layer may constitute a surface of the transflective layer on the lighting device side.

  The translucent layer may constitute the surface of the substrate.

    The light transmissive layer may constitute an emission surface of the lighting device.

  The scattering type liquid crystal is switched between a transmissive state and a non-transmissive state by a voltage applied to the liquid crystal layer by an electrode formed on the substrate.

  In the reflection mode, part of the external light incident on the plane area in the scattering state (hereinafter referred to as the scattering area) returns to the viewing side (hereinafter, the returned light is referred to as backscattered light), and part of the external light It is reflected by the semi-transmissive reflective layer and returns to the viewing side. The light transmitted through the transflective layer passes through the translucent layer and is reflected by the illuminating device, passes through the transmissive film and the transflective layer again, and returns to the scattering region. Compared to the amount of light reflected by the transflective layer and the backscattered light (light used in reflective display), the amount of light that passes through the transflective layer and returns to the scattering region (because the transflective layer was used) If the light (the generated noise component) is made small, the pattern on the translucent layer cannot be visually recognized.

  The planar area in the transmissive state is different from the scattering area in that there is no backscattered light and the reflected light from the semi-transmissive reflective layer is not scattered, so that it appears as a mirror surface (metal tone). The noise component is small as in the scattering region.

  In the transmission mode in which the lighting device is turned on, the intensity of the light emitted from the lighting device is modulated by a light-transmitting layer on which a pattern, characters, marks, and the like are formed. Of these, the component that has been transmitted through the semi-transmissive reflective layer projects a pattern or the like onto the scattering region.

  As is apparent from the above description, according to the present invention, since the pattern is projected onto the scattering portion of the liquid crystal layer, the layered structure of the liquid crystal display device can be simplified as much as the scattering layer is unnecessary. This is a result of the combined use of the liquid crystal layer for information display applications and projection screen applications. In addition, the preferred characteristics of the scattering-type liquid crystal can be utilized, such as the fact that polarized light is not used, and thus the absorption-type polarizing plate on the viewing side is not necessary, and since there is no polarizing plate, the display is bright and white is clear.

  When a polymer scattering type liquid crystal is used as the liquid crystal layer, it is not necessary to pass a current other than charging / discharging between the electrodes when a voltage is applied. Therefore, a secondary effect that low power consumption can be achieved is obtained.

  In general, a half mirror has a sum of reflectance and transmittance of 1 if there is no loss. In this case, if the reflectance is increased, the transmittance is lowered, so that the display becomes dark in the transmissive mode using the backlight. On the other hand, when a reflective polarizing plate having a reflectance of ½ is used as the semi-transmissive reflective layer, the ratio of the outgoing light transmitted from the illumination device through the reflective polarizing plate in the transmissive mode is greater than ½. For this reason, a secondary effect that bright display is possible when using illumination is obtained. Note that multiple reflections between the reflective polarizing plate and the illumination device are used to enhance the transmittance. Further, it is assumed that the absorption of the light transmitting layer is small.

  The transflective layer is made of a laminate of two reflective polarizing plates, and the reflectance of the transflective layer is reduced to 1 / by directing the transmission axes of the respective reflective polarizing plates in different planes. Can be set between 2 and 1. If the transflective layer of another configuration has a low reflectivity and the picture can be seen in the reflection mode, the use of this transflective layer can increase the reflectivity and make it difficult to see the picture. .

  In the transflective layer formed between the liquid crystal layer and the transparent substrate (hereinafter referred to as an internal transflective layer), there is no secondary parallax (also referred to as parallax) caused by the distance between the liquid crystal layer and the reflective layer. An effect is obtained.

  By using an intrinsic semi-transmissive reflective layer as a metal, a secondary effect that a manufacturing method that can easily control the film thickness (transmittance) such as a sputtering method can be used can be obtained.

  The metal thin film is colored by transmitted light. If the metal film used for the internal transflective layer is made thick and pores are provided, the reflectance and transmittance can be determined only by the aperture ratio of the pores, so that it is possible to avoid coloring the transmitted light. Effects can be obtained.

  If the light-transmitting layer is a film on which a pattern, characters, marks, etc. are printed, a secondary effect that the pattern can be easily changed by simply replacing the film is obtained.

  If the translucent layer is a surface on the back illumination side of a reflective polarizing plate on which a pattern, characters, marks, etc. are formed, the laminated structure is simplified and the need to mechanically fix the translucent layer is eliminated. The following effects can be obtained.

  When the internal transflective layer is provided, the laminated structure is simplified if the transparent layer is the surface on the liquid crystal layer side of the transparent substrate on which the pattern, characters, marks, etc. are formed, or the surface on the lighting device side. In addition, there is a secondary effect that it is not necessary to mechanically fix the light transmitting layer.

  If the light-transmitting layer is the exit surface of the lighting device on which a pattern, characters, marks, etc. are formed, the laminated structure is simplified and there is a secondary effect that it is not necessary to mechanically fix the light-transmitting layer. can get.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.
(First embodiment)

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a liquid crystal display device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the liquid crystal display device according to the first embodiment of the present invention.

  The laminated structure will be described with reference to FIG. From the viewing side, a polymer dispersed liquid crystal cell 11, a first reflective polarizing plate 12, a second reflective polarizing plate 13, a picture film 14, and a light guide plate 15 are laminated. An arrow T1 on the first reflective polarizing plate 12 indicates the direction of the transmission axis. Similarly, an arrow T2 on the second reflective polarizing plate 13 indicates the direction of the transmission axis. On the left side of the light guide plate 15 is an LED element 16. An arrow from the LED element 16 toward the light guide plate 15 indicates the traveling direction of light. The traveling direction of the light is changed by the light guide plate 15, and the light is emitted toward the pattern film 14.

  The laminated members will be described with reference to FIG.

  The polymer-dispersed liquid crystal cell 11 has transparent substrates 11a and 11d facing each other at an interval of about 10 μm, and a polymer-dispersed liquid crystal material before curing in a space formed by the seal 11c and the two transparent substrates 11a and 11d. And then cured to form the liquid crystal layer 11b. As the transparent substrate, polycarbonate having a thickness of 100 μm was used. This substrate has flexibility, and driving electrodes (not shown) are formed on the liquid crystal surface. A polymer network liquid crystal manufactured by Dainippon Ink Co., Ltd. was used as the polymer dispersed liquid crystal. When cured with ultraviolet light, the polymer material becomes a porous structure like a sponge, and the liquid crystal remains in the pores. The liquid crystal layer 11b when no voltage is applied scatters incident light (scattering state) because the refractive index of the liquid crystal and that of the polymer region are different. On the other hand, when the voltage is applied, the refractive index of the liquid crystal and that of the polymer region are equal, so that the incident light travels straight (transmission state). The polymer-dispersed liquid crystal cell 11 has a threshold value but lacks steepness (relationship between transmittance and applied voltage; TV curve), and therefore static driving is employed.

  The first and second reflective polarizing plates 12 and 13 employed as the semi-transmissive reflective layer (half mirror) were DBEF films manufactured by Sumitomo 3M. The crossing angle between the respective transmission axis directions (arrows T1, T2) is 80 °.

  The pattern film 14 is a transparent polystyrene sheet having a thickness of 100 μm, and a pattern 17 is printed on the surface thereof.

  The lighting device includes a light guide plate 15, a reflecting plate 15 a, and an LED element 16, and shows a back (type) lighting device. A fine prism (not shown) is formed on the upper surface of the light guide plate 15. Light emitted from the LED element 16 and incident from the side surface of the light guide plate 15 is reflected several times between the fine prism and the reflection plate formed on the back surface of the light guide plate 15 and then emitted toward the pattern film 14. In addition, the surface of the light guide plate 15 facing the pattern film 14 becomes the exit surface of the lighting device.

  The light emitted from the light guide plate 15 in parallel is incident on the pattern film 14 and is subjected to intensity modulation such that the pattern 17 is weakened. Part of this light passes through the reflective polarizing plates 13 and 12 which are semi-transmissive reflective layers, and reaches the liquid crystal layer 11b. In this way, the pattern 17 is projected onto the liquid crystal layer 11b. The shape of the pattern 17 and the transmission region of the liquid crystal layer 11b are configured to match.

As described above, the liquid crystal display element according to the embodiment of the present invention is characterized by using a polymer dispersed liquid crystal cell. In the case of a TN liquid crystal provided with an absorptive polarizing plate, light that does not pass through the pattern is absorbed by the absorptive polarizing plate, and the amount of light decreases. However, according to the liquid crystal display element according to the embodiment of the present invention, light that does not pass through the pattern is not absorbed by repeatedly scattering (reflecting) in the scattering region, so that the light use efficiency is higher than that of TN liquid crystal or the like. The effect is obtained.
(Second Embodiment)

  A second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a sectional view showing a liquid crystal display device according to the second embodiment of the present invention. FIG. 4 is an enlarged plan view of the transflective layer 33 according to the second embodiment of the present invention.

  The laminated structure and members will be described with reference to FIG. From the viewing side, the polymer dispersed liquid crystal cell 31 and the light guide plate 15 are laminated. (Back) The same lighting device as that of the first embodiment is used.

  In the polymer-dispersed liquid crystal cell 31, a liquid crystal layer 31b exists in a space formed by the transparent substrates 31a and 31d and the seal 31c. The same materials as those in the first embodiment were used. A transparent electrode 32 is formed on the surface of the upper transparent substrate 31a on the liquid crystal layer 31b side. A transflective layer 33 is laminated on the lower transparent substrate 31d. A pattern 34 is printed on the lower surface of the lower transparent substrate 31d.

  The transparent electrode 32 has a thickness of 0.03 μm and is made of ITO. Since the static drive with less influence of the wiring resistance is adopted, the transparent electrode layer 32 can be made thin. Moreover, flexibility was also ensured by setting it as this thickness. The transflective layer 33 is made of aluminum having a thickness of 0.1 μm, and has transparency by having pores.

  The transparent electrode 32 is a segment electrode, and the transflective layer 33 also serves as a common electrode. A region where the transparent electrode 32 and the transflective layer 33 overlap in a plane is a pixel. The picture 34 is printed in an area that does not overlap the pixel in FIG. For this reason, when the area | region of the pattern 34 is seen from the visual recognition side, it is always cloudy, and when the LED element 16 is turned on, the shadow of the pattern 34 is projected on the liquid crystal layer 31b.

  The pores will be described with reference to FIG. The transflective layer 33 has 4 μm square pores 41 open. If the pore 41 is made small, the liquid crystal in the pore 41 part is switched together with the surrounding liquid crystal by the electric field received from the surroundings during driving to switch between the scattering state and the transmission state. That is, the pore 41 is not visually recognized. The transmittance is approximately 10%, equal to the aperture ratio. The reflectance is about 80% with loss. The transflective layer 33 is formed by forming an outer peripheral portion and pores 41 by etching after forming an aluminum film on the transparent substrate 31d by a sputtering method.

  In order to make the pores 41 a little larger, the semi-transmissive reflective layer and the common electrode may be formed separately. At this time, an insulating layer is provided between the transflective layer and the common electrode.

  The transflective layer may be formed only by forming an aluminum film of about 0.05 μm on the transparent substrate. At this time, the reflectance is about 80%. A metal film having a small pore or a thin metal film can be formed not only on the internal transflective layer but also on the illumination side of the transparent substrate, or used as an independent half mirror. Since the illumination device only needs to have a flat light emission surface, it may be a sheet using electroluminescence or a combination of a fluorescent tube and a diffusion plate. Since the light-transmitting layer having a pattern may be provided between the transflective layer and the lighting device, the surface of the reflective polarizing plate on the lighting device side or the light emitting surface of the lighting device can also be used.

  Embodiments 1 and 2 are intended to utilize properties unique to resin materials such as being light, unbreakable, thin, and easy to form. An inorganic material such as glass may be used instead of the resin material.

1 is a perspective view showing a liquid crystal display device according to a first embodiment of the present invention. 1 is a cross-sectional view showing a liquid crystal display device according to a first embodiment of the present invention. It is sectional drawing which shows the liquid crystal display device which concerns on the 2nd Embodiment of this invention. It is an enlarged plan view which shows the liquid crystal display device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the conventional liquid crystal display device. It is sectional drawing which shows the liquid crystal display device of the other conventional form.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 31 ... Polymer dispersion type liquid crystal cell, 11a, 11d, 31a, 31d, 52a, 52d ... Transparent substrate, 11b, 31b, 52b ... Liquid crystal layer, 11c, 31c, 52c ...... Seal, 12, 13, 53, 54 ... reflective polarizing plate (semi-transmissive reflective layer), 14, 56 ... picture film (translucent layer), 15 ... light guide plate (illuminating device), 15a ... reflective layer (illuminating device), 16 ... LED element (illuminating device) , 17, 34 ... pattern, 32 ... transparent electrode, 33 ... intrinsic transflective layer, 41 ... pore, 51, 61 ... absorption polarizing plate, 57 ... back illumination device, 55, 62 ... diffusion layer, T1 , T2 ... Arrow indicating transmission axis

Claims (11)

In a liquid crystal display device having a liquid crystal layer sandwiched between two substrates and an illumination device for illuminating the liquid crystal layer,
The liquid crystal layer can be switched between a transmission state and a scattering state,
A transflective layer that is disposed between the liquid crystal layer and the illumination device and reflects a part of incident light and transmits a part thereof;
A translucent layer located between the transflective layer and the lighting device, on which a pattern, characters, marks, etc. are formed;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, wherein the transflective layer is formed of a reflective polarizing plate that transmits polarized light in the transmission axis direction and reflects polarized light in the reflection axis direction.   3. The reflection type polarizing plate is laminated to form the semi-transmissive reflection layer, and the transmission axes of the reflection type polarizing plates are directed in different directions. Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the transflective layer is an internal transflective layer formed between the liquid crystal layer and the substrate.   The liquid crystal display device according to claim 4, wherein the transflective layer is made of metal.   6. The liquid crystal display device according to claim 4, wherein the transflective layer has pores.   The liquid crystal display device according to claim 1, wherein the liquid crystal layer is made of a polymer scattering type liquid crystal.   The liquid crystal display device according to claim 1, wherein the translucent layer is a film on which a pattern, characters, marks, and the like are printed.   The liquid crystal display device according to claim 1, wherein the translucent layer constitutes a surface of the transflective layer on the illumination device side.   The liquid crystal display device according to claim 1, wherein the light transmitting layer constitutes a surface of the substrate. The liquid crystal display device according to claim 1, wherein the light transmissive layer constitutes an emission surface of the illumination device.

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