JP6890036B2 - Liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device.

Japanese Unexamined Patent Publication No. 2015-555805 (Patent Document 1) discloses a liquid crystal display device that switches between a reflection mode and a transmission mode using an electrodeposition element. This liquid crystal display device can be used as a reflective liquid crystal display device using external light by putting the electrodeposition element in a reflective state in an environment where external light is strong, such as directly under sunlight in the daytime. .. Further, this liquid crystal display device can be used as a transmissive liquid crystal display device using backlight light by putting the electrodeposition element in a transmissive state in an environment where external light is weak, such as at night.

By the way, in the above-mentioned conventional liquid crystal display device, it is possible to select two types of operation modes, a transmissive type and a reflective type. However, if a wider variety of operation modes can be realized, the commercial value of the liquid crystal display device will be further enhanced. It becomes possible to increase.

Japanese Unexamined Patent Publication No. 2015-555805

One of the specific aspects of the present invention is to provide a liquid crystal display device capable of realizing various operation modes.

[1] The liquid crystal display device of one aspect according to the present invention includes (a) a liquid crystal display panel, a pair of polarizing plates arranged to face each other with the liquid crystal display panel interposed therebetween, and a front side or a back side of the liquid crystal display panel. (B) The electro-optical element includes a pair of substrates and a light source which is arranged on the back side of the liquid crystal display panel and causes light to enter the liquid crystal display panel. It has a pair of electrodes provided on one side of each of the pair of substrates, and an electrolyte layer containing an electrodeposition material and arranged between the pair of electrodes, and (c) the pair. One of the electrodes has a concavo-convex shape on one side in contact with the electrolyte layer, and the value of Ra / RSm, which is the ratio of the surface roughness Ra of the concavo-convex shape to the average length RSm, is 0.0214. This is the liquid crystal display device.
[2] The liquid crystal display device of another aspect according to the present invention includes (a) a liquid crystal display panel, a polarizing plate arranged on at least one surface side of the liquid crystal display panel, and a front side or a back side of the liquid crystal display panel. (B) The electro-optical element includes a pair of substrates and a light source which is arranged on the front side of the liquid crystal display panel and causes light to enter the liquid crystal display panel. It has a pair of electrodes provided on one side of each of the pair of substrates, and an electrolyte layer containing an electrodeposition material and arranged between the pair of electrodes, and (c) the pair. One of the electrodes has a concavo-convex shape on one side in contact with the electrolyte layer, and the value of Ra / RSm, which is the ratio of the surface roughness Ra of the concavo-convex shape to the average length RSm, is 0.0214. This is the liquid crystal display device.

According to the above configuration, it is possible to provide a liquid crystal display device capable of realizing various operation modes.

FIG. 1 is a schematic side view showing the configuration of the liquid crystal display device of the first embodiment. FIG. 2 is a cross-sectional view showing a configuration example of a liquid crystal display panel. FIG. 3 is a schematic cross-sectional view showing a configuration example of the electro-optical element. FIG. 4 is a schematic cross-sectional view for explaining the configuration of the third electrode in detail. FIG. 5 is a schematic cross-sectional view for explaining the operating principle of the electro-optical element. FIG. 6 is a diagram showing an observation image of a surface-treated state in each sample of the electro-optical element of the example. FIG. 7 is a diagram showing screen characteristics of the electro-optical element of the embodiment. FIG. 8 is a diagram showing the relationship between the relative reflection brightness and the surface roughness of the electro-optical element of the embodiment. FIG. 9 is a diagram showing the relationship between the relative reflection brightness of the electro-optical element of the embodiment and Ra / RSm (ratio of Ra and RSm). FIG. 10 is a diagram showing the relationship between the size of surface irregularities and the scattering efficiency. FIG. 11 is a schematic cross-sectional view showing a configuration example of an electro-optical element of a modified example. FIG. 12 is a schematic plan view showing a configuration example of the electro-optical element of this modified example. FIG. 13 is a waveform diagram for explaining a driving method of the electro-optical device. FIG. 14 is a schematic side view showing the configuration of the liquid crystal display device of the second embodiment. FIG. 15 is a schematic side view showing the configuration of the liquid crystal display device of the third embodiment. FIG. 16 is a schematic side view showing the configuration of the liquid crystal display device of the fourth embodiment. FIG. 17 is a schematic side view showing the configuration of the liquid crystal display device of the fifth embodiment. FIG. 18 is a schematic side view showing the configuration of the liquid crystal display device of the sixth embodiment.

(First Embodiment)
FIG. 1 is a schematic side view showing the configuration of the liquid crystal display device of the first embodiment. The liquid crystal display device 100 shown in FIG. 1 includes a liquid crystal display panel 1, an electro-optical element (electro-deposition element) 2, a pair of polarizing plates 3, 4, and a backlight 5. In this liquid crystal display device 100, the liquid crystal display panel 1 is arranged between a pair of polarizing plates 3 and 4 arranged to face each other, and the electro-optical element 2 is on the back side of the liquid crystal display panel 1 and outside the polarizing plate 4. Is arranged, and a backlight 5 is arranged on the back side of the electro-optical element 2 so that the user can see it from the outside of the polarizing plate 3 (the side not close to the liquid crystal display panel 1).

The liquid crystal display panel 1 receives a drive signal from the drive device and forms an arbitrary image. For example, the pair of polarizing plates 3 and 4 are arranged so that their absorption axes are substantially orthogonal to each other, and are arranged so as to face each other with the liquid crystal display panel 1 interposed therebetween. The electro-optical element 2 is an element that can selectively obtain any one of a specular reflection state, a transmission state, a scattering reflection state, and a scattering transmission state by receiving a driving signal from a driving device. The backlight 5 is a light source device that emits light necessary for forming an image of the liquid crystal display panel 1.

The liquid crystal display device 100 of the present embodiment can realize various operations as follows.
For example, when the surroundings are bright, the backlight 5 can be turned off and the electro-optical element 2 can be used as a reflective liquid crystal display device by putting it in a specular reflection state or a scattering reflection state. When the electro-optical element 2 is in a specular reflection state, a high-brightness image display can be obtained in a limited range (viewing angle range), which is suitable for personal use, for example. Further, when the electro-optical element 2 is put into a diffuse reflection state, an image display can be obtained in a wide range (viewing angle range), which is suitable for public use, for example.

Further, for example, when the surroundings are dark, the backlight 5 can be turned on and the electro-optical element 2 can be used as a transmissive liquid crystal display device by setting the electro-optical element 2 in a transmissive state or a scattered transmissive state. When the electro-optical element 2 is in a transmissive state, a high-brightness image display can be obtained in a relatively limited range (viewing angle range), which is suitable for personal use, for example. Further, when the electro-optical element 2 is put into a scattering transmission state, an image display can be obtained in a wide range (viewing angle range), which is suitable for public use, for example. In these cases, it is more preferable that the backlight 5 has high directivity.

Hereinafter, the liquid crystal display panel 1 and the electro-optical element 2, which are the main configurations of the liquid crystal display device 100, will be described in more detail.

FIG. 2 is a cross-sectional view showing a configuration example of a liquid crystal display panel. The liquid crystal display panel 1 shown in FIG. 2 has a first substrate 11 and a second substrate 12 arranged to face each other, a first electrode 13 provided on the first substrate 11, and a second electrode provided on the second substrate 12. It includes 14, a liquid crystal layer 17 arranged between the first substrate 11 and the second substrate 12, and a driving device 18. The liquid crystal display panel 1 of the present embodiment is configured so that the overlapping area of the electrodes forms a character or a design to be displayed, and basically can display only a predetermined character or the like, and is generally in the effective display area. It is a segment display type liquid crystal display panel in which an area of 70% or less, usually 50% or less in terms of area ratio contributes to the display of characters and the like. The liquid crystal display panel 1 may be a dot matrix display type in which a plurality of pixels are arranged in a matrix, or may be a mixture of a segment display type and a dot matrix type.

The first substrate 11 and the second substrate 12 are rectangular substrates in a plan view, and are arranged so as to face each other. As the first substrate 11 and the second substrate 12, for example, a transparent substrate such as a glass substrate or a plastic substrate can be used. As shown in the figure, for example, a large number of spacers are uniformly dispersed and arranged between the first substrate 11 and the second substrate 12, and the gap between the two substrates has a desired size (for example, about several μm) due to these spacers. It is kept in.

The first electrode 13 is provided on one surface side of the first substrate 11. Similarly, the second electrode 14 is provided on one surface side of the second substrate 12. The first electrode 13 and the second electrode 14 are each configured by appropriately patterning a transparent conductive film such as indium tin oxide (ITO). Although not shown, an insulating film may be further provided on the upper surface of each electrode. A drive voltage is appropriately supplied from the drive device 18 to the first electrode 13 and the second electrode 14.

The first alignment film 15 is provided on one surface side of the first substrate 11 so as to cover the first electrode 13. The second alignment film 16 is provided on one surface side of the second substrate 12 so as to cover the second electrode 14. As the first alignment film 15 and the second alignment film 16, a vertical alignment film that regulates the alignment state of the liquid crystal layer 17 to vertical alignment is used. Each of the alignment films 15 and 16 is subjected to a uniaxial alignment treatment such as a rubbing treatment, and has an orientation regulating force in one direction. The directions of the alignment treatments on the alignment films 15 and 16 are set to be staggered (antiparallel), for example.

The liquid crystal layer 17 is provided between the first substrate 11 and the second substrate 12. In the present embodiment, the liquid crystal layer 17 is formed by using a nematic liquid crystal material having a negative dielectric anisotropy Δε, no chiral material, and having fluidity. The liquid crystal layer 17 of the present embodiment is in a state where the orientation direction of the liquid crystal molecules is inclined in one direction when no voltage is applied, and is approximately 88 ° or more and 90 ° or more with respect to each substrate surface of the first substrate 11 and the second substrate 12. It is set to have a substantially vertical orientation with a pretilt angle within the range of less than °. Then, when a voltage is applied between the first electrode 13 and the second electrode 14, the liquid crystal molecules of the liquid crystal layer 17 are oriented in the direction regulated by the orientation treatment.

FIG. 3 is a schematic cross-sectional view showing a configuration example of the electro-optical element. The electro-optical element shown in FIG. 3 includes a third substrate 21, a fourth substrate 22, a third electrode 23, a fourth electrode 24, an electrolyte layer 25, and a driving device 28.

The third substrate 21 is, for example, a rigid substrate having translucency (for example, a glass substrate). On one surface side of the third substrate 21, a third electrode 23 having a fine uneven shape is provided over almost the entire surface thereof. Similarly, the fourth substrate 22 is, for example, a light-transmitting hard substrate (for example, a glass substrate). On one surface side of the fourth substrate 22, a fourth electrode 24 that is flat over almost the entire surface is provided.

The third substrate 21 and the fourth substrate 22 are arranged so that one side of each other faces each other. In the present embodiment, a gap material (for example, a diameter of 50 μm) is added to a sealing material (not shown) that seals the electrolyte layer 25, and the distance between the third substrate 21 and the fourth substrate 22 is increased by the gap material. Secure (cell thickness). When the third substrate 21 and the fourth substrate 22 have a large area, it is preferable to disperse the gap materials in the substrate surface in order to reduce the unevenness of the cell thickness.

The electrolyte layer 25 is configured by using an electrolytic solution containing an electrodeposition material, and is arranged between each one surface side of the third substrate 21 and the fourth substrate 22. Specifically, the electrolytic solution constituting the electrolyte layer 25 is composed of an electrochromic material, a mediator, a supporting electrolyte, a solvent, a gelling polymer, and the like.

As an example of the material constituting the electrolyte layer 25, AgBr of 350 mM can be used as the electrochromic material, CuCl ₂ of 30 mM can be used as the mediator, LiBr of 700 mM can be used as the supporting electrolyte, and triglime can be used as the solvent.

The silver compound is not limited to the above, and silver chloride, silver oxide, silver bromide, silver iodide, silver nitrate and the like can be used. The concentration of the silver compound is preferably, but is not limited to, 5 mM or more and 500 mM or less, for example.

The supporting electrolyte is not particularly limited as long as it promotes the oxidation-reduction reaction of the coloring material, for example, lithium salts (LiCl, LiBr, LiI, LiBF ₄ , LiClO _4, etc.), potassium salts (KCl, KBr, KI, etc.). ), Sodium salts (NaCl, NaCl, NaI, etc.) can be preferably used. The concentration of the supporting electrolyte is preferably, but is not limited to, 10 mM or more and 1 M or less, for example.

The solvent is one that can stably hold the color-developing material and the like, and is not particularly limited as long as the refractive index n is close to or similar to that of the constituent materials of the third substrate 21 and the fourth substrate 22. It is desirable that the refractive indexes are about the same in order to improve the transparency by preventing reflection at the interface as much as possible when the electro-optical element is in a transparent state. For example, assuming that the refractive index of each substrate is 1.52 non-alkali glass, if the refractive index difference between the solvent and the glass is ± 0.15, the interfacial reflection can be reduced to 1% or less, and the refractive index difference is ±. If it is 0.10, the interfacial reflection can be reduced to 0.5% or less. As such a solvent, a polar solvent such as propylene carbonate, a non-polar organic solvent, an ionic liquid, an ionic conductive polymer, a polymer electrolyte, or the like can be used. Specifically, triglime (n = 1.432), propylene carbonate (n = 1.419), dimethyl sulfoxide (n = 1.479), N, N-dimethylformamide (n = 1.431), tetrahydrofuran ( n = 1.409), γ-butyrolactone (n = 1.436) and the like can be used.

The drive device 28 is connected to the third electrode 23 and the fourth electrode 24, and supplies a drive voltage to the electrolyte layer 25 via these.

FIG. 4 is a schematic cross-sectional view for explaining the configuration of the third electrode in detail. Several modes can be considered as the configuration of the third electrode 23. The third electrode 23 of the embodiment shown in FIG. 4A is configured to include a conductive film 32 provided along the surface shape of a large number of fine recesses 31 formed on one surface side of the third substrate 21. There is. As shown in the drawing, the conductive film 32 is provided along the surface shape of the recess 31, and has a concave-convex shape composed of a large number of recesses 34 on one surface side of the third substrate 21. The third electrode 23 of the embodiment shown in FIG. 4B has a conductive film 33 provided on one surface side of the third substrate 21, and the conductive film 33 is formed from a large number of fine recesses 34 on the one surface side thereof. It has an uneven shape. A third electrode 23 having a fine uneven shape can be obtained by any of these aspects.

FIG. 4C is a schematic cross-sectional view for explaining in detail the uneven shape of the third electrode. The unevenness on the surface of the conductive film 32 (or 33) of the third electrode 23 can be defined by, for example, the depth L and the width W of the recess 34 as shown in the figure. The depth L of the recess 34 is, for example, about 400 nm, and the width W of the recess 34 is, for example, several μm. Although a hemispherical shape as shown in the figure is considered as a shape model of the concave portion 34, it is considered that the concave shape 34 actually has a random shape close to a hemispherical shape, and the depth and width thereof are not constant and may have variations in a certain range. ..

FIG. 5 is a schematic cross-sectional view for explaining the operating principle of the electro-optical element.
FIG. 5A shows an operating principle when the scattering reflection state (white state) is realized. By applying a DC voltage between the third electrode 23 and the fourth electrode 24 so that the third electrode 23 side has a relatively low potential, metal nuclei are generated and grown, and as shown in the figure, the third electrode 23 A metal film 40 is deposited on the recess 34 of the three electrodes 23. As shown in the drawing, the metal film 40 deposited here is a dense film formed so as to follow a minute uneven shape including each recess 34. If the uneven shape at this time is equal to or larger than the wavelength size of visible light, the incident light is scattered and reflected, so that the appearance is white.

FIG. 5B shows the operating principle when realizing the mirror surface state. By applying a DC voltage between the third electrode 23 and the fourth electrode 24 so that the fourth electrode 24 side has a relatively low potential, a metal nucleus is generated and grows, and as shown in the figure, a third electrode is formed. A flat metal film 40 is deposited on the surface of the four electrodes 24. Since the incident light on the flat metal film 40 at this time is specularly reflected, it looks like a mirror surface.

Although not shown, in a state where no voltage is applied between the third electrode 23 and the fourth electrode 24 (state in which no voltage is applied), the metal film does not precipitate, so that the appearance is transparent. Further, when a DC voltage is applied between the third electrode 23 and the fourth electrode 24 so that the third electrode 23 side has a relatively low potential, the potential difference is made relatively small, so that the third electrode has a relatively low potential. The amount of the metal film 40 deposited on the recess 34 of the electrode 23 is relatively small, and as shown in FIG. 5C, the metal film 40 is partially interrupted, so that the incident light is scattered and transmitted. ..

As described above, the electro-optical element 2 of the present embodiment has a diffuse reflection state, a mirror surface state, a transparent state, and a scattering transmission state in appearance, depending on the state of voltage application between the third electrode 23 and the fourth electrode 24. Each state of can be selectively obtained.

Next, a method of manufacturing the electro-optical element of the present embodiment will be described. Here, the case where the third electrode 23 is configured to include the conductive film 32 provided in a large number of fine recesses 31 on one surface side of the third substrate 21 (see FIG. 4A) is suitable. An example of the manufacturing method will be described.

By subjecting one surface of a transparent substrate such as a non-alkali glass substrate to a blast treatment, for example, a fine uneven shape is formed on one surface side of the transparent substrate. As a result, the third substrate 21 having a fine uneven shape on one surface side can be obtained. At this time, by appropriately setting various conditions for the blasting process, it is possible to control the roughness of the uneven shape of the third substrate 21. When the blast treatment is used, the conditions include the particle size of the projection material (abrasive grains), the material of the projection material, the projection pressure, the projection angle, the substrate distance during the treatment, the treatment time, and the like. A wet etching process or the like may be used instead of the blast process. Conditions for the wet etching treatment include chemical composition, concentration, treatment time, and the like.

Next, a conductive film is formed on the surface of the third substrate 21 having an uneven shape. For example, a transparent conductive film (ITO film) made of ITO (indium tin oxide) is formed by a sputtering method. As a result, the third electrode 23 composed of the conductive film 32 provided in a large number of fine recesses 31 provided on one surface side of the third substrate 21 can be obtained. The sheet resistance of the ITO film as the conductive film 32 is, for example, about 5 Ω / sq., And the film thickness is several hundred nm.

Further, another transparent substrate such as a non-alkali glass substrate is prepared, and a conductive film is formed on one surface thereof. For example, an ITO film is formed by a sputtering method. As a result, the fourth substrate 22 having the fourth electrode 24 on one surface side is obtained. The sheet resistance of the ITO film as a conductive film is, for example, about 5 Ω / sq., And the film thickness is several hundred nm.

The transparent conductive film is not particularly limited as long as it has high light transmittance in the visible light region, and for example, a ZnO film, a Ga ₂ O ₅ film, a graphene film, or the like can be used. Further, the method for forming the transparent conductive film is not particularly limited, and various methods such as a vacuum deposition method, an ion plating method, and a spin coating method can be considered.

Next, a sealing material to which a gap material is added is applied to one of the substrates, for example, one surface side of the third substrate 21. As the sealing material, various materials such as an ultraviolet curable type, a thermosetting type, and a mixed type of ultraviolet curing and thermosetting can be used.

Further, the gap material is sprayed on one surface side of the other fourth substrate 22. At this time, the spraying amount is preferably 1 to 3 / mm ² from experience, but is not limited to this. Instead of the gap material, the gap may be controlled by forming protrusions such as ribs on the substrate. In this case, it is preferable that the aspect ratio of the protrusion is as high as possible.

Next, an electrolytic solution containing an electrodeposition material is sealed between the third substrate 21 and the fourth substrate 22. This step can be performed, for example, by the one-drop filling method (ODF method). Specifically, after dropping the electrolytic solution into the region surrounded by the sealing material on the one side of the third substrate 21, one surface of the third substrate 21 and one surface of the fourth substrate 22 face each other and both are attached. match. Then, the sealing material is cured by applying ultraviolet rays and / or heat. As a result, a sealing material and an electrolyte layer 25 whose periphery is sealed by the sealing material are obtained. The third substrate 21 and the fourth substrate 22 may be bonded first, and then the electrolytic solution may be injected between them by a vacuum injection method, or another method may be used.

As described above, the electro-optical element of the present embodiment can be manufactured. In addition, also in the case where the third electrode 23 is configured by providing a large number of fine recesses 34 on one surface of the conductive film 33 provided on the one surface side of the third substrate 21 (see FIG. 4B), the third electrode 23 is also the first. A manufacturing method similar to the above can be used except for the step of obtaining the three electrodes 23. Regarding the step of obtaining the third electrode 23, for example, the conductive film 33 is formed on one surface of the third substrate 21 by an appropriate film forming method such as a sputtering method, and one surface of the conductive film 33 is blasted or etched. A large number of recesses 34 may be formed by processing with. In addition, it is also possible to form a recess by forming a conductive film 33 containing fine particles made of a conductive material such as ITO.

Next, an example of the electro-optical element will be described. Here, as an example, a production example of some samples will be described. The layer thickness of the electrolyte layer 25 of each sample was 50 μm. As the electrolyte, the solvent was triglime, 350 mM of AgBr was added as an electrochromic material, 700 mM of LiBr was added as a supporting electrolyte, and 30 mM _{of CuCl 2 was added as a mediator.} Further, as the third electrode 23 and the fourth electrode 24, an ITO film having a sheet resistance of 5 Ω / sq. Was used, respectively.

Regarding the uneven shape of the surface of the third electrode 23, by changing the blast condition, the surface condition, specifically, the average roughness (arithmetic mean roughness) Ra, the average length RSm, and the average depth Rc can be obtained. Different samples were prepared. The average roughness (arithmetic mean roughness) Ra, the average length RSm, and the average depth Rc referred to here correspond to those defined by the JIS standard (JIS B 0601: 2001).

Sample 1: Ra = 0.12 μm, RSm = 20.0 μm, Rc = 0.43 μm
Sample 2: Ra = 0.49 μm, RSm = 18.5 μm, Rc = 1.77 μm
Sample 3: Ra = 0.54 μm, RSm = 25.2 μm, Rc = 1.93 μm

FIG. 6 is a diagram showing an observation image of a surface-treated state in each sample of the electro-optical element of the example. Specifically, FIG. 6 (A) is an observation image of the sample 1, and FIG. 6 (B) is an observation image of the sample 2. The observation image of sample 3 is omitted. As shown in the figure, the sample 1 has a surface roughness Ra of 0.12 μm and a diameter of each recess 34 formed on the surface of approximately 2 to 5 μm. In sample 2, the surface roughness Ra is 0.49 μm, and the diameter of each recess 34 formed on the surface is approximately 3 to 7 μm.

Next, the viewing angle characteristics of each sample will be described. Generally, the characteristic of the viewing angle is evaluated by the angle dependence of the reflected brightness at each angle with respect to the reflected brightness at an angle inclined by 5 ° with respect to the normal direction of the substrate surface of the object to be measured. The range in which the image can be visually recognized is called the viewing range angle, and is the angle at which the relative reflection brightness is halved. In order to obtain an image display with a wide viewing angle, it is preferable that the viewing range angle is 60 ° or more. For each sample, the reflection brightness at each angle was measured every 5 ° in the range of 5 ° to 60 °.

FIG. 7 is a diagram showing screen characteristics of the electro-optical element of the embodiment. The measurement was performed with LCD5200. This is the result of dividing the reflection brightness at each angle by the reflection brightness of the standard diffuser plate (magnesium oxide) at the same angle, and further standardizing the value at 5 °. In sample 1, the viewing range angle is about 10 °, but in samples 2 and 3, the viewing range angle is at least 60 ° or more, and it can be seen that the sample 1 has sufficient reflection characteristics. The surface roughness Ra of each of Samples 2 and 3 is 0.25 μm or more. Generally, it is said that scattering is strengthened when Ra is ½ or more of the wavelength, and it is considered that the scattering of visible light is 550 nm, and it can be seen that a result consistent with this is obtained.

FIG. 8 is a diagram showing the relationship between the relative reflection brightness and the surface roughness of the electro-optical element of the embodiment. When the surface roughness Ra becomes larger than 0.15 μm, the viewing range angle tends to increase, but the relative reflection brightness at 60 ° with respect to the surface roughness Ra does not necessarily increase monotonically. This is considered to be related to the density of the surface unevenness of the third electrode 23. Surface irregularities exist at intervals of an average length of RSm, but as RSm increases with respect to Ra, the density of surface irregularities decreases and scattering decreases.

FIG. 9 is a diagram showing the relationship between the relative reflection brightness of the electro-optical element of the embodiment and Ra / RSm (ratio of Ra and RSm). As shown in the figure, it can be seen that the larger the Ra / RSm, the larger the relative reflection brightness at 60 °. According to the approximate curve obtained based on each plot, it can be seen that the value of Ra / RSm should be at least 0.018 or more in order to make the relative reflection brightness at 60 ° 0.5 or more.

FIG. 10 is a diagram showing the relationship between the size of surface irregularities and the scattering efficiency. Scattering due to surface irregularities has different scattering efficiencies depending on the height of the irregularities. When the surface unevenness of the third electrode 23 made of a silver film is approximated by a sphere, the scattering efficiency for one uneven portion of each size is as shown in the figure. The scattering cross section was determined by the Mie scattering theory, and the scattering efficiency was determined by the ratio of the scattering cross section to the projected cross section of one uneven portion. The scattering efficiency was set to 1 when the scattering cross section was larger than the projected cross section. From FIG. 10, the scattering efficiency is about 0.5 in the visible light region when the size of the surface unevenness is 10 μm. That is, 50% is a normal reflection component, which has a reflection characteristic close to specular reflection. Therefore, it can be seen that the average depth Rc of the surface unevenness needs to be smaller than this, and should be 10 μm or less. Further, in general, when the size of the surface unevenness is 1/10 or less of the wavelength of the incident light, scattering does not occur, so it can be seen that the size should be larger than this. The average depth Rc of the samples 2 and 3 having the viewing range angle of 60 ° or more is 1.77 μm and 1.93 μm, respectively, which are in good agreement with the size of the surface unevenness having high scattering efficiency obtained by calculation.

FIG. 11 is a schematic cross-sectional view showing a configuration example of an electro-optical element of a modified example. Further, FIG. 12 is a schematic plan view showing a configuration example of the electro-optical element of this modified example. The electro-optical element 2a shown in each figure is different from the electro-optical element 2 described above in that the third electrode 23 has a plurality of segment electrodes 23a, 23b, 23c, 23d, 23e, 23f. Other than that, it has the same configuration. A detailed description of the configuration common to both will be omitted.

The segment electrodes 23a to 23f as the third electrode 23 are arranged separately from each other with a gap (for example, about 100 μm) between them, and a voltage is individually applied by the driving device 28. In the illustrated example, each of the segment electrodes 23a and the like is formed in a rectangular shape, and is arranged in two rows of three along the left-right direction in FIG. Further, the fourth electrode 24 is arranged so as to face each of the segment electrodes 23a and the like, and functions as a common electrode.

In the electro-optical element 2a of this modified example, when the electrodeposition material is deposited on the fourth electrode 24 by applying a voltage, the region becomes a mirror surface state, and the electrodeposition material is placed on any of the segment electrodes 23a or the like by applying a voltage. When precipitated, the region where the electrodeposition material is deposited becomes a diffuse reflection state or a diffuse transmission state. Further, when no voltage is applied, it becomes a transmission state. By controlling the voltage application to each of the segment electrodes 23a and the like individually, different optical states (mirror surface, diffuse reflection, diffuse transmission, transmission) can be obtained for each region corresponding to each segment electrode 23a and the like. Obtainable. In order to operate the segment electrodes 23a to 23f in a mirrored state and a light-shielded state at the same time, for example, the driving method described below can be used.

FIG. 13 is a waveform diagram for explaining a driving method of the electro-optical device. In this embodiment, the driving device 28 drives the adjacent segment electrodes with a time-division polarity inversion signal (DC) so that a high voltage is not applied between the adjacent segment electrodes.

For example, a reference potential (0V in this case) is applied to the fourth electrode 24 as a common electrode and the segment electrodes 23a and 23c, respectively, and the reference potential and + V1 (+ 2.8V as an example) are given to the segment electrodes 23e and 23f at regular intervals. Is applied to a rectangular wave (see FIG. 13 (A)) that repeats the above at a frequency of 50 Hz or higher, and the segment electrodes 23b and 23d are periodically subjected to a reference potential and −V1 (2.8 V as an example) at 50 Hz. Is given a repeating rectangular wave (see FIG. 13B).

As shown in the figure, the rectangular wave of FIG. 13 (A) and the rectangular wave of FIG. 13 (B) are shifted by 1/2 cycle from each other at the timing when the absolute value becomes higher than the reference potential, so that they do not overlap each other. It has become. That is, during the period when the potential of the square wave of FIG. 13 (A) is + V1, the square wave of FIG. 13 (B) becomes the reference potential, and the potential of the square wave of FIG. 13 (A) becomes the reference potential. During the period, the square wave of FIG. 13B is −V1, and the period of + V1 and the period of −V1 do not overlap. As a result, the lateral voltage generated between the segment electrodes 23b and 23d and the segment electrodes 23e and 23f becomes V1 in absolute value at the maximum. That is, it is possible to prevent a high voltage from being applied between adjacent segment electrodes.

When the electro-optical element is driven by such a drive waveform, the region corresponding to the segment electrodes 23b and 23d is in a diffuse reflection state or a diffusion transmission state, and faces the segment electrodes 23e and 23f of the fourth electrode 24 as a common electrode. The region corresponding to the segment electrodes 23a and 23c is in a transparent state. Note that this is an example, and by controlling the voltage application to each segment electrode, different optical states (mirror surface, diffuse reflection, diffuse transmission, transmission) can be obtained for each region corresponding to each segment electrode. Can be done.

According to the first embodiment as described above, a liquid crystal display device capable of selectively using various display states according to the usage situation can be obtained. Further, when the electro-optical element of the modified example is used, it is possible to individually control and use various display states for each fixed region.

(Second Embodiment)
FIG. 14 is a schematic side view showing the configuration of the liquid crystal display device of the second embodiment. The liquid crystal display device 100a shown in FIG. 14 includes a liquid crystal display panel 1, an electro-optical element 2, a pair of polarizing plates 3, 4 and a backlight 5. In this liquid crystal display device 100a, the liquid crystal display panel 1 is arranged between a pair of polarizing plates 3 and 4 arranged opposite to each other and close to the polarizing plate 3, and the polarizing plate is on the back side of the liquid crystal display panel 1. It differs from the liquid crystal display device 100 of the first embodiment in that the electro-optical element 2 is arranged inside the fourth embodiment, and has the same configuration except for the above. In addition, instead of the electro-optical element 2, the electro-optical element 2a of the above-mentioned modified example may be used (the same applies hereinafter).

The liquid crystal display device 100a of the second embodiment also has the same effect as the liquid crystal display device 100 of the first embodiment. Further, since the polarizing plate 4 is arranged outside the electro-optical element 2, when the electro-optical element 2 is controlled to a mirror surface state or a diffuse reflection state and used as a reflection type liquid crystal display device, incident light and Since the reflected light is transmitted only through the polarizing plate 3, the transmittance can be improved and the amount of emitted light can be increased.

(Third Embodiment)
FIG. 15 is a schematic side view showing the configuration of the liquid crystal display device of the third embodiment. The liquid crystal display device 100b shown in FIG. 15 includes a liquid crystal display panel 1, an electro-optical element 2, a pair of polarizing plates 3, 4 and a backlight 5. In the liquid crystal display device 100b, the liquid crystal display panel 1 is arranged between a pair of polarizing plates 3 and 4 arranged to face each other, and the front side (visual side) of the polarizing plate 3 is not close to the liquid crystal display panel 1. The point that the electro-optical element 2 is arranged and the backlight 5 is arranged on the back side, which is not close to the liquid crystal display panel 1 of the polarizing plate 4, is the same as the liquid crystal display device 100 of the first embodiment described above. They are different and otherwise have similar configurations.

Various operation modes can also be realized by such a third embodiment 100b. Further, the light after passing through the liquid crystal display panel 1 can be diffused and transmitted by the electro-optical element 2 to improve the viewing angle characteristics of the liquid crystal display panel 1. Further, since the electro-optical element 2 can be brought into a normal transmission state, a liquid crystal display device capable of switching the viewing angle characteristics can be obtained. Further, when the electro-optical element 2 is in the diffuse reflection state, the appearance of the liquid crystal display device 100b can be made to look like a white sheet, and when the electro-optical element 2 is in the mirror surface reflection state, the appearance of the liquid crystal display device 100b can be seen. Can be made to look like a mirror, so that the appearance of the liquid crystal display device when the image is not displayed can be selected in various ways.

(Fourth Embodiment)
FIG. 16 is a schematic side view showing the configuration of the liquid crystal display device of the fourth embodiment. The liquid crystal display device 100c shown in FIG. 16 includes a liquid crystal display panel 1, an electro-optical element 2, a pair of polarizing plates 3, 4 and a backlight 5. In the liquid crystal display device 100c, the point that the polarizing plate 3 is arranged on the front side (visual side) and the electro-optical element 2 is arranged on the back side of the polarizing plate 3 is the liquid crystal display device of the third embodiment described above. It is different from 100b and has the same configuration other than that.

Even with such a fourth embodiment 100c, the same effect as that of the liquid crystal display device 100b of the third embodiment can be obtained. Further, by arranging the polarizing plate 3 on the front surface side, there is an advantage that the reflection of external light can be suppressed and the appearance can be improved.

(Fifth Embodiment)
FIG. 17 is a schematic side view showing the configuration of the liquid crystal display device of the fifth embodiment. The liquid crystal display device 100d shown in FIG. 17 includes a liquid crystal display panel 1, an electro-optical element 2, a pair of polarizing plates 3, 4, and a front light 6. The front light 6 includes, for example, a flat light guide plate and a light emitting element (LED or the like) that causes light to enter the end of the light guide plate, and receives light from the front side of the liquid crystal display panel 1. It is used to make it. The liquid crystal display device 100d of the fifth embodiment uses the front light 6 instead of the backlight 5, and the point that the front light 6 is arranged on the front side, which is the outside of the polarizing plate 3, is described above. It is different from the liquid crystal display device 100 of the embodiment, and has the same configuration other than that.

According to the liquid crystal display device 100d of the fifth embodiment, for example, it is possible to display images having different appearances when the electro-optical element 2 is in a specular reflection state and when it is in a diffuse reflection state. Further, it is possible to realize an image display that is easy to see in both the case where the front light 6 is turned on and the case where the front light 6 is turned off and external light is used. Further, when the electro-optical element 2 is in the diffusion transmission state or the transmission state, the back side of the electro-optical element 2 is seen to be transmitted, so that, for example, a pattern or a character is placed on the back side of the electro-optic element 2. By arranging the attached medium, those patterns and the like can be visually recognized by the user together with the display image of the liquid crystal display panel 1.

In the liquid crystal display device 100d of the fifth embodiment, the polarizing plate 4 may be omitted (not shown). In this case, the transmittance can be improved and the amount of emitted light can be increased.

(Sixth Embodiment)
FIG. 18 is a schematic side view showing the configuration of the liquid crystal display device of the sixth embodiment. The liquid crystal display device 100e shown in FIG. 18 includes a liquid crystal display panel 1, an electro-optical element 2, a pair of polarizing plates 3, 4, and a front light 6. In the liquid crystal display device 100e of the sixth embodiment, the electro-optical element 2 is arranged on the back side of the front light 6 and closer to the front light 6 than the liquid crystal display panel 1, according to the fifth embodiment described above. It is different from the liquid crystal display device 100d of the above, and has the same configuration other than that.

Various operation modes can be realized by such a sixth embodiment 100e. Further, since the electro-optical element 2 is arranged on the front side of the liquid crystal display panel 1, the pixel pattern (segment pattern) of the liquid crystal display panel 1 becomes more conspicuous when the electro-optical element 2 is used in the diffusion transmission state. It can be made difficult. Further, when the electro-optical element 2 is in the diffuse reflection state, the appearance of the liquid crystal display device 100e can be made to look like a white sheet, and when the electro-optical element 2 is in the mirror surface reflection state, the appearance of the liquid crystal display device 100e. Can be made to look like a mirror, so that the appearance of the liquid crystal display device when the image is not displayed can be selected in various ways.

In the liquid crystal display device 100e of the sixth embodiment, the polarizing plate 4 can be omitted and replaced with a reflector (not shown). In this case, the transmittance can be improved and the amount of emitted light can be increased.

(Modified Embodiment)
The present invention is not limited to the contents of the above-described embodiment, and can be variously modified and implemented within the scope of the gist of the present invention. For example, in the liquid crystal display device of each of the above-described embodiments, a viewing angle compensation plate such as a C plate may be further arranged between each polarizing plate and the liquid crystal display panel. Further, the configuration of the liquid crystal display panel described above is an example, and the present invention is not limited to this, and a liquid crystal display panel having various known operation modes can be used.

Further, when a low-duty character display type is used as the liquid crystal display panel, it is also preferable to pattern the electrode shape of the electro-optical element corresponding to one of several character display units that is particularly desired to be emphasized. .. Alternatively, it is also preferable to pattern the electrode shape of the electro-optical element corresponding to a portion other than the character display portion to be particularly emphasized. In this case, when the operation mode of the liquid crystal display panel and the pair of polarizing plates is the negative display mode, it is preferable that the electrode pattern of the electro-optical element is one size larger than the electrode size of the character display unit to be emphasized. How large the size is depends on the distance between the liquid crystal layer of the liquid crystal display panel and the electrolyte layer of the electro-optical element (corresponding to the thickness of the substrate in contact with each other). For example, when this distance is 1.4 mm, Assuming that a viewing angle range of 30 ° is secured, the electrode size of the electro-optical element may be made wider by about 1 mm than the electrode size of the liquid crystal display panel. In this case, the entire electrode is 2 mm larger. On the other hand, when the operation mode is the positive display mode, the electrode size of the character display unit to be emphasized and the electrode size of the electro-optical element may be the same or slightly narrower. In this case, if it is made too narrow, the image itself becomes dark, so it is preferable to keep it at a maximum of about 100 μm.

1: Liquid crystal display panel 2: Electro-optical element 3, 4: Plate plate 5: Backlight 6: Front light 11: First substrate 12: Second substrate 13: First electrode 14: Second electrode 15: First alignment film 16: Second alignment film 17: Liquid crystal layer 18: Drive device 21: Third substrate 22: Fourth substrate 23: Third electrode 24: Fourth electrode 25: Electrode layer 28: Drive device 31, 34: Recesses 32, 33 : Conductive 100: Liquid crystal display device

Claims (4)

Liquid crystal display panel and
A pair of polarizing plates arranged opposite to each other across the liquid crystal display panel,
Electro-optic elements arranged on the front side or the back side of the liquid crystal display panel,
A light source arranged on the back side of the liquid crystal display panel to inject light into the liquid crystal display panel,
Including
The electro-optical element is
A pair of boards and
A pair of electrodes provided on one side of each of the pair of substrates,
An electrolyte layer containing an electrodeposition material and arranged between the pair of electrodes,
One of the pair of electrodes has a concavo-convex shape on one side in contact with the electrolyte layer, and is the ratio of the surface roughness Ra of the concavo-convex shape to the average length RSm Ra /. The value of RSm is 0.0214 or more,
Liquid crystal display device. Liquid crystal display panel and
A polarizing plate arranged on at least one surface side of the liquid crystal display panel,
Electro-optic elements arranged on the front side or the back side of the liquid crystal display panel,
A light source arranged on the front side of the liquid crystal display panel to inject light into the liquid crystal display panel,
Including
The electro-optical element is
A pair of boards and
A pair of electrodes provided on one side of each of the pair of substrates,
An electrolyte layer containing an electrodeposition material and arranged between the pair of electrodes,
One of the pair of electrodes has a concavo-convex shape on one side in contact with the electrolyte layer, and is the ratio of the surface roughness Ra of the concavo-convex shape to the average length RSm Ra /. The value of RSm is 0.0214 or more,
Liquid crystal display device. The surface roughness Ra of the uneven shape is 0.49 μm or more .
The liquid crystal display device according to claim 1 or 2. The average depth Rc of the uneven shape is 10 μm or less .
The liquid crystal display device according to any one of claims 1 to 3 .

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