Display device

Abstract

To provide a display device capable of improving the display quality.SOLUTION: In an embodiment, a display device includes: a display panel comprising a polymer dispersed liquid crystal including polymer and a liquid crystal molecule in a display region to display images; a light source unit disposed along an edge part of the display panel; a glass member positioned on a side opposite to an observation position of the display panel; and a light control panel positioned between the display panel and the glass member and comprising a guest-host liquid crystal in a light control region overlapping with the display region. An initial orientation direction of the liquid crystal molecule in the display panel is parallel to an absorption axis of the light control panel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a display device. [Background technology]

[0002] Various display devices using polymer-dispersed liquid crystals have been proposed, which can switch between a scattering state that scatters incident light and a transparent state that transmits incident light. Display devices using polymer-dispersed liquid crystals sometimes use an edge-light system in which a light-emitting module is located at the edge of the display panel. Because of their high transmittance, such display devices are expected to be used in a variety of fields. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-16684 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiment is to provide a display device capable of improving display quality. [Means for solving the problem]

[0005] According to one embodiment, the display device comprises: The display device comprises a display panel having a polymer-dispersed liquid crystal containing a polymer and liquid crystal molecules in a display area that displays an image, a light source unit arranged along the edge of the display panel, a glass member located on the opposite side of the display panel from the viewing position, and a light control panel located between the display panel and the glass member and having a guest-host liquid crystal in a light control area that overlaps the display area, wherein the initial orientation direction of the liquid crystal molecules in the display panel is parallel to the absorption axis in the light control panel. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a display device 1. As shown in FIG. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the display panel 100 shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the display panel 100 shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of the configuration of the light control panel 300 shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view schematically showing an example of the configuration of the light control panel 300 shown in FIG. [Figure 6A] FIG. 6A is a diagram for explaining the operation of the light control panel 300 in the off state. [Figure 6B] FIG. 6B is a diagram for explaining the operation of the light control panel 300 in the on state. [Figure 7A] FIG. 7A is a diagram for explaining the operation of the light control panel 300 in the off state. [Figure 7B] FIG. 7B is a diagram for explaining the operation of the light control panel 300 in the on state. [Figure 8A] FIG. 8A shows the measurement results of Experiment 1. [Figure 8B] FIG. 8B shows the measurement results of Experiment 2. [Figure 9] FIG. 9 is a diagram for explaining matrix driving of the light control panel 300. In FIG. [Figure 10] FIG. 10 is a diagram for explaining the first application example. [Figure 11] FIG. 11 is a diagram for explaining the second application example. [Figure 12] FIG. 12 is a diagram for explaining the application example 3. In FIG. [Figure 13] FIG. 13 is a diagram for explaining the fourth application example. [Figure 14] FIG. 14 is a diagram illustrating an example of the configuration of a control system of the display device 1. As shown in FIG. [Figure 15] FIG. 15 is a diagram for explaining an example of control of the vertical alignment type light control panel 300. In FIG. [Figure 16] FIG. 16 is a diagram for explaining an example of control of the horizontally oriented light control panel 300. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment will be described with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily make while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment for the sake of clarity, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are designated by the same reference numerals, and redundant detailed descriptions may be omitted as appropriate.

[0008] In addition, to facilitate understanding, the drawings will depict mutually orthogonal X, Y, and Z axes as necessary. The direction along the X axis is referred to as the first direction X, the direction along the Y axis is referred to as the second direction Y, and the direction along the Z axis is referred to as the third direction Z. Viewing various elements parallel to the third direction Z is referred to as a planar view. Terms referring to the relative positions of two or more components, such as "on top," "above," "between," and "opposite," include not only cases where the two or more components are in direct contact with each other, but also cases where they are separated from each other by a gap or another component. The positive direction of the Z axis is referred to as "up" or "above."

[0009] FIG. 1 is a diagram showing an example of the configuration of a display device 1. As shown in FIG.

[0010] The display device 1 includes a display panel 100 configured to display an image, a light source unit 200 configured to illuminate the display panel 100, a dimming panel 300 configured to dim the display light emitted from the display panel 100, and a glass member (back panel) 400 located on the back side of the display panel 100.

[0011] The display panel 100 includes a polymer-dispersed liquid crystal in a display area 100A that displays an image. The polymer-dispersed liquid crystal includes a polymer and liquid crystal molecules, as will be described later. In the illustrated example, the initial alignment direction AD of the liquid crystal molecules is set to a first direction X. The initial alignment direction AD corresponds to the alignment direction of the liquid crystal molecules in an off-state where no voltage is applied to the liquid crystal molecules. That is, in the illustrated example, in the XY plane defined by the first direction X and the second direction Y, the liquid crystal molecules in the off-state are aligned with their major axes aligned along the first direction X. Furthermore, the polymer extends in the first direction X.

[0012] The light source unit 200 is disposed along an edge 100E of the display panel 100. In the illustrated example, the edge 100E extends in the first direction X. Illumination light emitted from the light source unit 200 enters through the edge 100E and illuminates the display area 100A.

[0013] The light control panel 300 includes a guest-host liquid crystal in a light control area 300A that overlaps with the display area 100A in the third direction Z. As will be described later, the guest-host liquid crystal has dichroic dye molecules as guest molecules and liquid crystal molecules as host molecules.

[0014] The guest molecules have different absorbances in the long axis direction and the short axis direction, and mainly absorb linearly polarized light components parallel to the long axis direction. Therefore, the dimming region 300A can be colored according to the color of the guest molecules. When the guest molecules are black dichroic dye molecules, the guest molecules absorb linearly polarized light components parallel to the long axis, and can form a light-shielding region in the dimming region 300A. The long axis direction of such guest molecules corresponds to the absorption axis AA in the dimming panel 300. The absorption axis AA is parallel to the initial alignment direction AD and is set to the first direction X in the illustrated example.

[0015] The glass member 400 is located on the opposite side of the display panel 100 from the viewing position O. The light control panel 300 is located between the display panel 100 and the glass member 400.

[0016] Here, a case will be described in which the letter "A" is displayed in the display area 100A as shown in the figure. The display light emitted from the display panel 100 is mainly linearly polarized light parallel to the first direction X. In other words, the display light traveling from the display panel 100 toward the glass member 400 is linearly polarized light parallel to the absorption axis AA of the light control panel 300, and is therefore absorbed by the light control panel 300. Therefore, very little of the display light reaches the glass member 400.

[0017] Therefore, when an image is displayed on display panel 100, it is possible to suppress undesired reflections on glass member 400. In other words, the generation of ghost images on the back side of display panel 100 is suppressed, and the display quality of the image observed at observation position O can be improved.

[0018] FIG. 2 is a diagram showing an example of the configuration of the display panel 100 shown in FIG.

[0019] The display panel 100 includes a transparent substrate 110, a transparent substrate 120, a liquid crystal layer LC1, and a seal SE1. Each of the transparent substrates 110 and 120 is formed in a flat plate shape parallel to the XY plane. The transparent substrates 110 and 120 overlap each other in a planar view. The transparent substrate 110 extends further in the second direction Y than the transparent substrate 120. In the illustrated example, the transparent substrates 110 and 120 are both formed in a quadrangle, but this is not limiting. For example, the transparent substrates 110 and 120 may have any shape other than a quadrangle, such as a polygon, a circle, an ellipse, or a semicircle.

[0020] The liquid crystal layer LC1 is located between the transparent substrate 110 and the transparent substrate 120 and sealed with a seal SE1. The alignment treatment direction D1 of the alignment film AL1 located between the transparent substrate 110 and the liquid crystal layer LC1 and the alignment treatment direction D2 of the alignment film AL2 located between the transparent substrate 120 and the liquid crystal layer LC1 are parallel to each other and directed in opposite directions. In the illustrated example, the alignment treatment direction D1 and the alignment treatment direction D2 are both parallel to the first direction X. The alignment treatments applied to the alignment films AL1 and AL2 may be rubbing treatments or photo-alignment treatments.

[0021] As shown enlarged and schematically in the figure, the liquid crystal layer LC1 comprises a polymer dispersed liquid crystal including a polymer PL and liquid crystal molecules LM. In one example, the polymer PL is a liquid crystal polymer. The polymer PL and the liquid crystal molecules LM each have optical anisotropy or refractive index anisotropy. The responsiveness of the polymer PL to an electric field is lower than that of the liquid crystal molecules LM to an electric field.

[0022] As described above, since the alignment treatment direction D1 and the alignment treatment direction D2 are parallel to the first direction X, the polymer PL is formed in stripes extending along the first direction X. The liquid crystal molecules LM are dispersed in the gaps between the polymer PL and are aligned with their major axes aligned along the first direction X. In other words, as shown in FIG. 1, the initial alignment direction AD of the liquid crystal molecules LM is set to the first direction X.

[0023] The alignment direction of the polymer PL hardly changes regardless of the presence or absence of an electric field. On the other hand, the alignment direction of the liquid crystal molecules LM changes in response to the electric field when a high voltage above the threshold is applied to the liquid crystal layer LC1. When no voltage is applied to the liquid crystal layer LC1, the optical axes of the polymer PL and the liquid crystal molecules LM are parallel to each other, and light incident on the liquid crystal layer LC1 is transmitted through the liquid crystal layer LC1 with almost no scattering within the liquid crystal layer LC1 (transparent state). When a voltage is applied to the liquid crystal layer LC1, the optical axes of the polymer PL and the liquid crystal molecules LM intersect with each other, and light incident on the liquid crystal layer LC1 is scattered within the liquid crystal layer LC1 (scattered state).

[0024] The configuration of the polymer dispersed liquid crystal including the polymer PL and the liquid crystal molecules LM is not limited to the above example.

[0025] The display area 100A includes a plurality of pixels PX arranged in a matrix in the first direction X and the second direction Y.

[0026] As shown enlarged in the figure, each pixel PX includes a switching element SW, a pixel electrode PE, a common electrode CE, a liquid crystal layer LC1, etc. The switching element SW is configured by, for example, a thin film transistor (TFT), and is electrically connected to a scanning line G and a signal line S.

[0027] The scanning lines G extend in the first direction X and are electrically connected to the switching elements SW in each of the pixels PX aligned in the first direction X. That is, the alignment treatment direction D1 and the alignment treatment direction D2 are parallel to the scanning lines G. The streaky polymer PL extends along the scanning lines G.

[0028] The signal lines S extend in the second direction Y, intersect with the scanning lines G, and are electrically connected to the switching elements SW in each of the pixels PX aligned in the second direction Y. In other words, the alignment treatment direction D1 and the alignment treatment direction D2 intersect or are perpendicular to the signal lines S. In addition, the stripe-shaped polymer PL extends so as to intersect with the signal lines S.

[0029] The pixel electrodes PE are electrically connected to the switching elements SW. Each pixel electrode PE faces a common electrode CE, and the liquid crystal layer LC1 (particularly, liquid crystal molecules LM) is driven by an electric field generated between the pixel electrodes PE and the common electrodes CE. The capacitance CS is formed, for example, between an electrode having the same potential as the common electrode CE and an electrode having the same potential as the pixel electrodes PE.

[0030] The scanning lines G, signal lines S, switching elements SW, and pixel electrodes PE are formed between the transparent substrate 110 and the liquid crystal layer LC1. The common electrode CE is formed between the transparent substrate 120 and the liquid crystal layer LC1.

[0031] The IC chip CP and a flexible printed circuit board (not shown) are mounted on the transparent substrate 110 .

[0032] The light source unit 200 is configured to emit illumination light for illuminating the liquid crystal layer LC1, and includes a plurality of light emitting elements LD arranged in the first direction X at intervals.

[0033] FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the display panel 100 shown in FIG.

[0034] In the display panel 100, the scanning lines, signal lines, switching elements, insulating films, etc. are not shown.

[0035] The transparent substrate 110 and the transparent substrate 120 face each other in the third direction Z. The liquid crystal layer LC1 is located between the transparent substrate 110 and the transparent substrate 120. The pixel electrode PE of each pixel PX is located between the transparent substrate 110 and the liquid crystal layer LC1 and is covered with an alignment film AL1. The common electrode CE facing the multiple pixel electrodes PE is located between the transparent substrate 120 and the liquid crystal layer LC1 and is covered with an alignment film AL2. The liquid crystal layer LC1 is in contact with the alignment films AL1 and AL2. The pixel electrode PE and the common electrode CE are transparent electrodes formed of a transparent conductive material such as indium tin oxide (ITO).

[0036] In the illustrated example, the display panel 100 further includes a transparent substrate 130 and a transparent substrate 140. The transparent substrate 130 is bonded to the transparent substrate 110 via a transparent adhesive layer AD1. The transparent substrate 140 is bonded to the transparent substrate 120 via a transparent adhesive layer AD2. A side surface 120E of the transparent substrate 120 and a side surface 140E of the transparent substrate 140 overlap in the third direction Z. For example, the side surface 140E corresponds to the edge portion 100E of the display panel 100 shown in FIG. 1. In the illustrated example, the main surface 130A of the transparent substrate 130 and the main surface 140A of the transparent substrate 140 are both parallel to the XY plane and are in contact with air.

[0037] The adhesive layer AD1 and the adhesive layer AD2 have the same refractive index as the transparent substrate 110, the transparent substrate 120, the transparent substrate 130, and the transparent substrate 140. Therefore, undesired interface reflection between the transparent substrate 110 and the transparent substrate 130 and between the transparent substrate 120 and the transparent substrate 140 is suppressed.

[0038] The light source unit 200 faces the side surface 140E of the transparent substrate 140 in the second direction Y. The light source unit 200 may face both the side surface 120E and the side surface 140E. The light source unit 200 includes a light-emitting element LD and a light guide LG. Although not described in detail, the light-emitting element LD includes a red light-emitting portion, a green light-emitting portion, and a blue light-emitting portion. These red light-emitting portion, green light-emitting portion, and blue light-emitting portion may be turned on sequentially or all at the same time. The light guide LG is located between the light-emitting element LD and the transparent substrate 140 in the second direction Y.

[0039] The transparent substrates 110, 120, 130, and 140 are, for example, glass substrates, but may also be resin substrates. The transparent substrates 130 and 140 function as cover members. The transparent substrate 140 also functions as a light guide plate that propagates the light emitted from the light source unit 200 along the second direction Y.

[0040] In one example, the transparent substrate 130 is thicker than the transparent substrate 110, and the transparent substrate 140 is thicker than the transparent substrate 120. The transparent substrates 130 and 140 may be omitted. When the transparent substrate 140 is omitted, the light source unit 200 is disposed so as to face the side surface 120E of the transparent substrate 120 in the second direction Y.

[0041] In such a display panel 100, when a voltage is applied to each pixel PX, light emitted from the light source unit 200 is scattered by the liquid crystal layer LC1 of each pixel PX to become display light, and an image is displayed in the display area 100 A. The display light emitted from the display panel 100 is linearly polarized light parallel to the first direction X. When the liquid crystal layer LC1 is in a transparent state, when the display panel 100 is observed from the side of the main surface 130A, the background can be observed through the display panel 100, and similarly, when the display panel 100 is observed from the side of the main surface 140A, the background can be observed through the display panel 100.

[0042] FIG. 4 is a diagram showing an example of the configuration of the light control panel 300 shown in FIG.

[0043] The light control panel 300 includes a transparent substrate 310, a transparent substrate 320, a liquid crystal layer LC2, and a seal SE2. The transparent substrates 310 and 320 are each formed in the shape of a flat plate parallel to the XY plane and overlap each other in a planar view. In the illustrated example, the transparent substrates 310 and 320 are both formed in a rectangular shape, but this is not limiting. For example, the transparent substrates 310 and 320 may have any shape other than a rectangular shape, such as a polygon, a circle, an ellipse, or a semicircle.

[0044] The liquid crystal layer LC2 is located between the transparent substrate 310 and the transparent substrate 320 and sealed with a seal SE2. The alignment treatment direction D3 of the alignment film AL3 located between the transparent substrate 310 and the liquid crystal layer LC2 and the alignment treatment direction D4 of the alignment film AL4 located between the transparent substrate 320 and the liquid crystal layer LC2 are parallel to each other and in opposite directions. The alignment treatment direction D3 and the alignment treatment direction D4 are also parallel to the alignment treatment direction D1 and the alignment treatment direction D2 described with reference to FIG. 2. In the illustrated example, the alignment treatment direction D3 and the alignment treatment direction D4 are both parallel to the first direction X. The alignment treatments applied to the alignment films AL3 and AL4 may be rubbing treatments or photo-alignment treatments.

[0045] FIG. 5 is a cross-sectional view schematically showing an example of the configuration of the light control panel 300 shown in FIG.

[0046] The transparent substrate 310 and the transparent substrate 320 face each other in the third direction Z. The liquid crystal layer LC2 is located between the transparent substrate 310 and the transparent substrate 320. In the dimming region 300A, the transparent electrode TEA is located between the transparent substrate 310 and the liquid crystal layer LC2 and is covered with an alignment film AL3. The transparent electrode TEB is located between the transparent substrate 320 and the liquid crystal layer LC2 and is covered with an alignment film AL4. The liquid crystal layer LC2 is in contact with the alignment films AL3 and AL4.

[0047] The transparent substrate 310 and the transparent substrate 320 are, for example, glass substrates, but may also be resin substrates.

[0048] The transparent electrodes TEA and TEB are formed of a transparent conductive material such as indium tin oxide (ITO), and are, for example, sheet electrodes disposed across the dimming region 300A.

[0049] Each of the transparent electrodes TEA and TEB may be a plurality of strip electrodes. In this case, a first strip electrode corresponding to the transparent electrode TEA and a second strip electrode corresponding to the transparent electrode TEB are arranged to intersect with each other in the dimming area 300A. The intersections of the first strip electrodes and the second strip electrodes form segments of the dimming area 300A. The liquid crystal layer LC2 of each segment is driven in response to the potential difference between the first strip electrodes and the second strip electrodes (simple matrix drive).

[0050] Alternatively, the transparent electrode TEA may be a plurality of segment electrodes arranged in a matrix, and the transparent electrode TEB may be a sheet electrode arranged across the dimming area 300A. In this case, each segment electrode is electrically connected to an active element. The area where one segment electrode faces the sheet electrode constitutes a segment of the dimming area 300A. The liquid crystal layer LC2 of the segment is driven in response to the potential difference between the segment electrode and the sheet electrode (active matrix drive).

[0051] The liquid crystal layer LC2 includes a guest-host liquid crystal containing dichroic dye molecules as guest molecules GM and liquid crystal molecules as host molecules HM. In one example, the guest molecules GM are black dichroic dye molecules. In the illustrated example, the guest molecules GM and the host molecules HM are each aligned in the first direction X. The thickness TLC of the liquid crystal layer LC2 between the alignment films AL3 and AL4 along the third direction Z is, for example, 5 μm or more and 20 μm or less, and preferably 10 μm±2 μm.

[0052] Next, the vertical alignment type light control panel 300 will be described.

[0053] 6A is a diagram for explaining the operation of the light control panel 300 in the off state. Note that only the configuration necessary for the explanation is shown here, and the illustration of the other configurations is simplified or omitted.

[0054] In the light control panel 300, the alignment film AL3 covering the transparent electrode TEA and the alignment film AL4 covering the transparent electrode TEB are both vertical alignment films, and have an alignment regulating force in their normal directions (i.e., the third direction Z). As described with reference to FIG. 4, the alignment films AL3 and AL4 have been subjected to an alignment treatment. The host molecules HM are liquid crystal molecules having negative dielectric anisotropy. The guest molecules GM are black dichroic dye molecules.

[0055] In the off state (OFF), no potential difference is formed between the transparent electrodes TEA and TEB. Therefore, no voltage is applied to the liquid crystal layer LC2. At this time, the host molecules HM are initially aligned so that their major axes are aligned along the third direction Z due to the alignment restraining forces of the alignment films AL3 and AL4. The guest molecules GM, like the host molecules HM, are aligned so that their major axes are aligned along the third direction Z. In other words, both the host molecules HM and the guest molecules GM are aligned vertically. Therefore, no absorption axis is formed in the light control panel 300.

[0056] When the display panel 100 is in the transparent state, at the observation position O, the glass member 400 can be observed through the display panel 100 and the light control panel 300, and furthermore, the background of the glass member 400 can be observed.

[0057] When the display panel 100 is in a scattering state and an image is displayed, the display light DL is emitted toward the observation position O and also toward the light control panel 300. As described above, the display light DL is linearly polarized light parallel to the first direction X. At the observation position O, the image on the display panel 100 is observed. The display light DL heading toward the light control panel 300 is hardly absorbed by the light control panel 300, passes through the light control panel 300, and reaches the glass member 400.

[0058] In a relatively dark place around the display device, the display light DL reflected by the glass member 400 is easily visible, which can result in a ghost image. On the other hand, in a relatively bright place around the display device, the display light DL reflected by the glass member 400 is difficult to see. Therefore, at the observation position O, the image on the display panel 100 can be observed, and the glass member 400 can also be observed through the display panel 100 and the light control panel 300, and further, the background of the glass member 400 can also be observed.

[0059] FIG. 6B is a diagram for explaining the operation of the light control panel 300 in the on state.

[0060] In the on state (ON), a potential difference is formed between the transparent electrodes TEA and TEB. Therefore, a voltage is applied to the liquid crystal layer LC2. At this time, the host molecules HM are aligned so as to intersect with the electric field formed in the liquid crystal layer LC2. As described above, since the alignment films AL3 and AL4 are aligned in the first direction X, the host molecules HM are aligned so that their major axes are aligned along the first direction X. The guest molecules GM follow the host molecules HM and are aligned so that their major axes are aligned along the first direction X. In other words, both the host molecules HM and the guest molecules GM are aligned horizontally. As a result, an absorption axis AA parallel to the first direction X is formed in the light control panel 300.

[0061] When the display panel 100 is in the transparent state, at the observation position O, the glass member 400 can be observed through the display panel 100 and the light control panel 300, and further, the background of the glass member 400 can be observed. However, in the light control panel 300, the polarized light component along the first direction X is absorbed, and therefore the transmittance is reduced compared to the light control panel 300 in the off state.

[0062] When the display panel 100 is in a scattering state and an image is displayed, the image on the display panel 100 is observed at the observation position O. Most of the display light DL directed toward the light control panel 300 is absorbed by the light control panel 300. This reduces reflection of the display light DL on the glass member 400. This reduces the generation of ghost images regardless of whether the display panel 100 is in a dark or bright place, thereby improving the visibility of the image on the display panel 100.

[0063] Next, the horizontally aligned light control panel 300 will be described.

[0064] 7A is a diagram for explaining the operation of the light control panel 300 in the off state. Note that only the configuration necessary for the explanation is shown here, and the illustration of the other configurations is simplified or omitted.

[0065] In the light control panel 300, the alignment film AL3 covering the transparent electrode TEA and the alignment film AL4 covering the transparent electrode TEB are both horizontal alignment films that have an alignment restriction force in the first direction X. The host molecules HM are liquid crystal molecules with positive dielectric anisotropy. The guest molecules GM are black dichroic dye molecules.

[0066] In the off state (OFF), no potential difference is formed between the transparent electrodes TEA and TEB. Therefore, no voltage is applied to the liquid crystal layer LC2. At this time, the host molecules HM are initially aligned such that their major axes are aligned along the first direction X due to the alignment restraining forces of the alignment films AL3 and AL4. The guest molecules GM, like the host molecules HM, are aligned such that their major axes are aligned along the first direction X. In other words, both the host molecules HM and the guest molecules GM are aligned horizontally. As a result, an absorption axis AA parallel to the first direction X is formed in the light control panel 300.

[0067] In the OFF state of such a horizontally aligned light control panel 300, the same effect as in the ON state of the vertically aligned light control panel 300 described with reference to FIG. 6B can be obtained.

[0068] FIG. 7B is a diagram for explaining the operation of the light control panel 300 in the on state.

[0069] In the on state (ON), a potential difference is formed between the transparent electrodes TEA and TEB. Therefore, a voltage is applied to the liquid crystal layer LC2. At this time, the host molecules HM are aligned along the electric field formed in the liquid crystal layer LC2. That is, the host molecules HM are aligned with their major axes aligned along the third direction Z. The guest molecules GM follow the host molecules HM and are aligned with their major axes aligned along the third direction Z. That is, both the host molecules HM and the guest molecules GM are aligned vertically. Therefore, no absorption axis is formed in the light control panel 300.

[0070] In the on state of such a horizontally aligned light control panel 300, the same effect as in the off state of the vertically aligned light control panel 300 described with reference to FIG. 6A can be obtained.

[0071] Next, a description will be given of the optical characteristics of the light control panel 300. Here, an experiment was carried out to measure the transmittance of the vertical alignment type light control panel 300.

[0072] The experimental conditions were as follows: a light source, a polarizer, a light control panel, and a detector were arranged in this order in an environment of 25°C. The light source was configured to emit unpolarized illumination light. With the light source turned on, the voltage applied to the liquid crystal layer of the light control panel was changed, and the detector detected the light transmitted through the light control panel to measure the transmittance.

[0073] In Experiment 1, the transmittance was measured under the condition that the alignment treatment direction D3 and the alignment treatment direction D4 were parallel to the absorption axis of the polarizer. In Experiment 2, the transmittance was measured under the condition that the alignment treatment direction D3 and the alignment treatment direction D4 were perpendicular to the absorption axis of the polarizer. In Experiments 1 and 2, the transmittance was measured when the thickness TLC of the liquid crystal layer LC2 was 5 μm, 10 μm, and 20 μm, respectively.

[0074] FIG. 8A shows the measurement results of Experiment 1. FIG. 8B shows the measurement results of Experiment 2. 8A and 8B, the horizontal axis represents the voltage E (V) applied to the liquid crystal layer, and the vertical axis represents the transmittance T (%).

[0075] As shown in Figure 8A, according to Experiment 1, the transmittance T is almost constant regardless of the magnitude of the applied voltage E. In other words, it was confirmed that the absorption axis of the light control panel formed when a voltage is applied to the liquid crystal layer LC2 is parallel to the absorption axis of the polarizer.

[0076] As shown in Figure 8B, Experiment 2 showed that the transmittance T decreased as the applied voltage E increased. When the thickness TLC was 5 µm, the transmittance T became 10% or less when a voltage of 5 V or more was applied. When the thickness TLC was 10 µm, the transmittance T became 1% or less when a voltage of 5 V or more was applied. When the thickness TLC was 20 µm, the transmittance T became 1% or less when a voltage of 4 V or more was applied.

[0077] Thus, the light control panel 300 having a thickness TLC of 5 μm or more and 20 μm or less can sufficiently absorb linearly polarized illumination light transmitted through the polarizer. However, when the thickness TLC is 20 μm, the transmittance in the off state (applied voltage E is 0 V) ​​is 30% or less. Therefore, to achieve a transmittance T of 1% or less in the on state while ensuring transparency in the off state, it is desirable that the thickness TLC be 10 μm ± 2 μm.

[0078] FIG. 9 is a diagram for explaining matrix driving of the light control panel 300. In FIG.

[0079] The dimming area 300A has a plurality of segments SG arranged in a matrix in the first direction X and the second direction Y. As described above, each segment SG may be configured as an intersection between a first strip electrode and a second strip electrode, or as an area where a segment electrode electrically connected to an active element faces a sheet electrode. This allows each segment SG to individually drive the guest-host liquid crystal in the liquid crystal layer LC2.

[0080] The light control panel 300 is driven so that an absorption axis AA is formed when an image is displayed on the display panel 100, and no absorption axis is formed and the light control panel 300 has high transparency when no image is displayed on the display panel 100. Furthermore, by applying matrix driving to the light control panel 300, the absorption axis AA can be formed only in the segments SG that overlap with the image displayed on the display panel 100.

[0081] In the illustrated example, in the dimming area 300A, four segments SG are lined up in the first direction X, and five segments are lined up in the second direction Y (five rows and four columns). Of the multiple segments SG, an absorption axis AA is formed in the upper two-row and four-column segment SG, and no absorption axis is formed in the lower three-row and four-column segment SG.

[0082] By forming the absorption axis AA only in the segment SG that overlaps with the image, the visibility of the image can be improved, and in other areas, the background can be more easily observed.

[0083] An application example of the display device 1 of this embodiment will be described below.

[0084] FIG. 10 is a diagram for explaining the first application example.

[0085] A user U is a driver or a passenger of a vehicle. The display panel 100 faces the user U and is installed, for example, on the dashboard of the vehicle. The glass member 400 is the windshield of the vehicle. The light control panel 300 is located between the display panel 100 and the glass member 400, and is adhered to the display panel 100 in the illustrated example.

[0086] In Application Example 1, when an image is displayed on the display panel 100, an absorption axis AA is formed in the light control panel 300. This suppresses reflection of the image on the glass member 400. The user U can observe the image on the display panel 100 without viewing a ghost image.

[0087] Furthermore, when no image is displayed on the display panel 100, no absorption axis AA is formed in the light control panel 300. Therefore, the user U can observe the area ahead of the vehicle through the display panel 100, the light control panel 300, and the glass member 400.

[0088] FIG. 11 is a diagram for explaining the second application example.

[0089] Application example 2 differs from application example 1 in that the light control panel 300 is spaced apart from the display panel 100 and is bonded to the glass member 400. In this application example 2, the same effects as in application example 1 can be obtained.

[0090] FIG. 12 is a diagram for explaining the application example 3. In FIG.

[0091] The glass member 400 is a window glass. The glass member 400 and another window glass GL are fixed to a frame FL in a state where they face each other with an air layer AR interposed therebetween, thereby constituting a double glazing. The display panel 100 is bonded to the window glass GL. The light control panel 300 is bonded to the glass member 400. An air layer AR is interposed between the display panel 100 and the light control panel 300.

[0092] The display panel 100 may be bonded to the window glass GL with the display panel 100 and the light control panel 300 bonded to each other. In this case, an air layer AR is interposed between the light control panel 300 and the glass member 400. Furthermore, in a state where the display panel 100 and the light control panel 300 are bonded to each other, the light control panel 300 may be bonded to the glass member 400. In this case, an air layer AR is interposed between the display panel 100 and the window glass GL.

[0093] In such a display device 1, the observation position O is set on the side facing the window glass GL.

[0094] FIG. 13 is a diagram for explaining the fourth application example.

[0095] In Application Example 4, the display panel 100, the dimming panel 300, and the glass member 400 are bonded to one another. That is, the glass member 400 faces the dimming panel 300 in the third direction Z and is bonded to the transparent substrate 310 of the dimming panel 300 by a transparent adhesive layer AD1. The dimming panel 300 faces the display panel 100 in the third direction Z. The transparent substrate 320 of the dimming panel 300 is bonded to the transparent substrate 110 of the display panel 100 by a transparent adhesive layer AD3. Furthermore, the transparent substrate 140 is bonded to the transparent substrate 120 of the display panel 100 by a transparent adhesive layer AD2.

[0096] The light source unit 200 faces the side surface 140E of the transparent substrate 140 in the second direction Y.

[0097] The glass member 400 and the transparent substrate 140 function as a cover member. The transparent substrate 140 also functions as a light guide plate that propagates the light emitted from the light source unit 200 along the second direction Y.

[0098] The display region 100A overlaps the dimming region 300A in the third direction Z. Furthermore, the plurality of pixel electrodes PE and the common electrode CE overlap the transparent electrodes TEA and TEB in the third direction Z.

[0099] In such a display device 1, the observation position O is set on the side opposite to the transparent substrate 140.

[0100] FIG. 14 is a diagram illustrating an example of the configuration of a control system of the display device 1. As shown in FIG.

[0101] The display device 1 includes a display panel 100, a light source unit 200, a light control panel 300, an illuminance sensor 500, and a control unit 600. The illuminance sensor 500 is configured to measure the illuminance around the display device 1.

[0102] The control unit 600 is configured to control the display panel 100, the light source unit 200, the light control panel 300, and the illuminance sensor 500, respectively.

[0103] For example, the control unit 600 drives each pixel of the display panel 100 and drives the light source unit 200 in synchronization with the timing of driving the display panel 100. The control unit 600 also drives the light control panel 300 in accordance with the illuminance measured by the illuminance sensor 500. As described with reference to FIG. 9 , the control unit 600 can drive the light control panel 300 so that an absorption axis AA is formed in a segment SG that overlaps with an image displayed on the display panel 100, among the multiple segments SG of the light control panel 300.

[0104] FIG. 15 is a diagram for explaining an example of control of the vertical alignment type light control panel 300. In FIG.

[0105] First, the control unit 600 controls the illuminance sensor 500 to measure the illuminance (step ST1). Then, the control unit 600 determines whether the measured illuminance LX is equal to or less than a predetermined threshold value LX_th (step ST2).

[0106] Based on the determination that the illuminance LX is equal to or less than the predetermined threshold value LX_th (step ST2, YES), the control unit 600 sets the light control panel 300 to the ON state (step ST3). That is, the control unit 600 applies a voltage to each of the transparent electrodes TEA and TEB. This applies a voltage to the liquid crystal layer LC2, driving the guest-host liquid crystal. In the liquid crystal layer LC2, the host molecules HM and the guest molecules GM are horizontally aligned, and an absorption axis AA is formed in the light control panel 300. This reduces reflection of the image displayed on the display panel 100 on the glass member 400 in a dark place.

[0107] On the other hand, the control unit 600 determines that the illuminance LX is higher than the predetermined threshold LX_th (step ST2, NO), and sets the light control panel 300 to the off state (step ST4). That is, the control unit 600 does not apply a voltage to each of the transparent electrodes TEA and TEB. In the liquid crystal layer LC2, the host molecules HM and the guest molecules GM are vertically aligned, and no absorption axis AA is formed. Therefore, in bright places, the background can be observed through the light control panel 300 and the glass member 400.

[0108] FIG. 16 is a diagram for explaining an example of control of the horizontally oriented light control panel 300. In FIG.

[0109] First, the control unit 600 controls the illuminance sensor 500 to measure the illuminance (step ST11). Then, the control unit 600 determines whether the measured illuminance LX is equal to or greater than a predetermined threshold value LX_th (step ST12).

[0110] Based on the determination that the illuminance LX is equal to or greater than the predetermined threshold value LX_th (step ST12, YES), the control unit 600 sets the light control panel 300 to the ON state (step ST13). That is, the control unit 600 applies a voltage to each of the transparent electrodes TEA and TEB. This applies a voltage to the liquid crystal layer LC2, driving the guest-host liquid crystal. In the liquid crystal layer LC2, the host molecules HM and guest molecules GM are vertically aligned, and no absorption axis AA is formed. Therefore, in bright places, the background can be observed through the light control panel 300 and the glass member 400.

[0111] On the other hand, the control unit 600 determines that the illuminance LX is lower than the predetermined threshold value LX_th (step ST12, NO), and sets the light control panel 300 to the off state (step ST14). That is, the control unit 600 does not apply a voltage to each of the transparent electrodes TEA and TEB. In the liquid crystal layer LC2, the host molecules HM and the guest molecules GM are horizontally aligned, forming an absorption axis AA. Therefore, in a dark place, reflection of an image displayed on the display panel 100 onto the glass member 400 is suppressed.

[0112] In the above embodiments, for example, transparent substrate 110 corresponds to the first transparent substrate, transparent substrate 120 corresponds to the second transparent substrate, transparent substrate 310 corresponds to the third transparent substrate, and transparent substrate 320 corresponds to the fourth transparent substrate. Alignment film AL1 corresponds to the first alignment film, alignment film AL2 corresponds to the second alignment film, alignment film AL3 corresponds to the third alignment film, and alignment film AL4 corresponds to the fourth alignment film. Liquid crystal layer LC1 corresponds to the first liquid crystal layer, and liquid crystal layer LC2 corresponds to the second liquid crystal layer.

[0113] In the above embodiment, the case where the rear plate of the display device 1 is the glass member 400 has been described, but this is not limiting. For example, the rear plate may be a transparent member different from the glass member, or an opaque member such as a screen or a whiteboard. Furthermore, an object may be placed in place of the rear plate.

[0114] As described above, according to this embodiment, it is possible to provide a display device capable of improving display quality.

[0115] All display devices that can be implemented by a person skilled in the art by appropriately modifying the design based on the display devices described above as embodiments of the present invention also fall within the scope of the present invention as long as they include the gist of the present invention.

[0116] Within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications, and these modifications are also understood to fall within the scope of the present invention. For example, even if a person skilled in the art appropriately adds or deletes components or modifies the design of the above-described embodiment, or adds or omits steps or modifies conditions, these modifications are also included within the scope of the present invention as long as they maintain the gist of the present invention.

[0117] Furthermore, with regard to other effects brought about by the aspects described in the above embodiments, those that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0118] 1...Display device 100...Display panel 100A...Display area PX...Pixel 110...Transparent substrate 120...Transparent substrate LC1...Liquid crystal layer AL1...Alignment film AL2...Alignment film G...Scanning line S...Signal line SW...Switching element PE...Pixel electrode 200...Light source unit 300...Dimming panel 300A...Dimming area SG...Segment 310...Transparent substrate 320...Transparent substrate LC2...Liquid crystal layer GM...guest molecule HM...host molecule AL3...Alignment film AL4...Alignment film 400...Glass member 500...Illuminance sensor 600...Control unit

Claims

1. a display panel including a polymer dispersed liquid crystal containing a polymer and liquid crystal molecules in a display area for displaying an image; a light source unit disposed along an edge of the display panel; a glass member located on the opposite side of the display panel from the viewing position; a light control panel located between the display panel and the glass member, the light control panel including a guest-host liquid crystal in a light control area overlapping the display area; the initial alignment direction of the liquid crystal molecules in the display panel is parallel to the absorption axis of the light control panel; Display device.

2. The display panel includes: a first transparent substrate; a second transparent substrate; a first liquid crystal layer located between the first transparent substrate and the second transparent substrate and including the polymer dispersed liquid crystal; a first alignment film located between the first transparent substrate and the first liquid crystal layer; a second alignment film located between the second transparent substrate and the first liquid crystal layer; The dimming panel is a third transparent substrate; a fourth transparent substrate; and a second liquid crystal layer located between the third transparent substrate and the fourth transparent substrate and including the guest-host liquid crystal; a third alignment film located between the third transparent substrate and the second liquid crystal layer; a fourth alignment film located between the fourth transparent substrate and the second liquid crystal layer, the alignment treatment directions of the first alignment film, the second alignment film, the third alignment film, and the fourth alignment film are parallel to each other; The display device according to claim 1 .

3. The display panel further comprises: The scan line and signal lines intersecting the scanning lines; a switching element electrically connected to the scanning line and the signal line; a pixel electrode electrically connected to the switching element, the alignment treatment direction of the first alignment film is parallel to the scanning lines; The display device according to claim 2 .

4. the polymer is formed in stripes extending along the scanning lines; The display device according to claim 3 .

5. the guest-host liquid crystal has dichroic dye molecules as guest molecules and liquid crystal molecules having negative dielectric anisotropy as host molecules, each of the third alignment film and the fourth alignment film is a vertical alignment film; The display device according to claim 2 .

6. In addition, an illuminance sensor, a control unit that controls the second liquid crystal layer to apply a voltage when the illuminance measured by the illuminance sensor is equal to or lower than a predetermined threshold value, The display device according to claim 5 .

7. the guest-host liquid crystal has dichroic dye molecules as guest molecules and liquid crystal molecules having positive dielectric anisotropy as host molecules, each of the third alignment film and the fourth alignment film is a horizontal alignment film; The display device according to claim 2 .

8. In addition, an illuminance sensor, a control unit that controls the second liquid crystal layer to apply a voltage when the illuminance measured by the illuminance sensor is equal to or greater than a predetermined threshold value, The display device according to claim 7 .

9. The thickness of the second liquid crystal layer is 5 μm or more and 20 μm or less. The display device according to claim 2 .

10. The thickness of the second liquid crystal layer is 10 μm±2 μm. The display device according to claim 2 .

11. The dimming region has a plurality of segments arranged in a matrix, Each of the plurality of segments is configured to be able to individually drive the guest-host liquid crystal. The display device according to claim 1 .

12. The display panel and the light control panel are bonded to each other. The display device according to claim 1 .

13. the display panel and the light control panel face each other via an air layer; The display device according to claim 1 .

14. The glass member is a vehicle windshield. The display device according to claim 1 .

15. The glass member is a window glass. The display device according to claim 1 .

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