JP2005157070A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display which can suppress reduction in brightness at reflection mode. <P>SOLUTION: The liquid crystal display is provided in a pixel region, with a reflection region 22 for reflecting external light and a transmission region 21 for transmitting the light of a backlight. A lower dielectric layer 26, consisting of any one among an oxide, a nitride, a sulfide and a carbide which contain at least one of Si and Ti is disposed commonly in the reflection region 22 and the transmission region 21 on a transparent substrate 11. A reflection film 25, comprising Al or Ag or the like, is disposed in the reflection region 22 on the lower dielectric layer 26. An upper dielectric layer 27 is disposed on the reflection film 25 of the reflection region 22 and on the lower dielectric layer 26 of the transmission region 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reflection mode for performing display by reflecting external light (external light) and a liquid crystal display device for performing display by transmitting light from a backlight.

  In recent years, liquid crystal display devices have been used in a wide range of applications, from large-sized devices used for televisions and personal computers to medium-sized devices used for portable information terminals. These liquid crystal display devices are selectively used according to their respective uses, and transmissive liquid crystal display devices are mainly used for televisions and the like used indoors. Reflection of external light is required for portable information terminals used outdoors. A reflection type liquid crystal surface device provided with means is used.

  In addition, a reflective transflective liquid crystal display device having both reflective and transmissive area functions is used as a reflective type that utilizes light from the outside (external environment) such as sunlight and fluorescent lamps, and is also used for liquid crystal display panels. A transmissive type using light from a backlight disposed on the opposite side of the display surface has been used in combination. In such a liquid crystal display device having both functions, a backlight is disposed on the back surface side (surface opposite to the display surface) of the liquid crystal display panel, and a translucent film is provided on the other transparent substrate on the back surface side. Was forming. (Patent Document 1: Japanese Patent Laid-Open No. 61-260202).

  FIG. 7 is a schematic cross-sectional view showing a general structure of a reflective transflective liquid crystal display device. Basically, it is composed of a liquid crystal display panel LP and a backlight BL. The liquid crystal display panel LP includes, for example, a glass substrate 3 that is one transparent substrate on the display surface side, for example, a glass substrate 11 that is the other transparent substrate on the back surface side, and a liquid crystal layer 8 disposed therebetween. Yes. A large number of transparent electrodes 4 are arranged in parallel on the inner surface sides of the glass substrate 3 and the glass substrate 11.

  The transparent electrode 4 of the glass substrate 3 is formed so as to extend in one direction, for example, in the left-right direction in FIG. 7, and the transparent electrode 4 of the glass substrate 11 extends in the other direction, for example, in the depth direction in FIG. It is formed as follows. That is, the glass substrate 3 and the glass substrate 11 are opposed to each other, the liquid crystal layer 8 is disposed therebetween, and the substrates 3 and 11 are bonded together by the sealing member 6. A region where the transparent electrodes 4 intersect is a pixel region. An alignment film 5 is formed on the transparent electrode 4.

A liquid crystal layer 8 having nematic liquid crystal molecules is disposed between the two members, and the liquid crystal molecules are twisted between 180 ° and 270 ° between the glass substrates 311 when no voltage is applied.

  A polarizing plate 1 and a retardation plate 2 are sequentially attached to the outer surface side of the glass substrate 3 of the liquid crystal display panel LP. A polarizing plate 13 and a retardation plate 12 are sequentially attached to the outer surface side of the glass substrate 11.

  The backlight BL includes a light guide plate 15 and a light source 14 and is disposed on the outer side of the other glass substrate 11. At this time, the light emitting surface of the light guide plate 14 is disposed so as to face a display region constituted by a plurality of pixel regions of the liquid crystal display panel LP.

  Here, between the glass substrate 11 and the transparent electrode 4, a reflective transflective layer 10 having a reflection and transmission function, and a color filter 9 and an overcoat 7 as necessary are interposed.

  The overcoat 7 prevents unevenness on the surface of the color filter 9, and the color filter 9 and the overcoat 7 are omitted in a liquid crystal display device in which the color filter 9 is not formed.

As described above, the liquid crystal display device is designed to be used in a wide range of environments from a dark place to a bright place. That is, the reflective transflective film 10 formed to use both the reflective mode and the transmissive mode is configured by laminating transparent dielectric layers. Then, by controlling the refractive index and film thickness of each layer, external light is reflected at the surface of the reflective semi-transmissive film 10 or at the interface between the layers, and is allowed to pass through the reflective semi-transmissive film 10. The reflection efficiency and the transmission efficiency (100% in total) were controlled by the design of the reflective semi-transmissive film.
Japanese Patent Laid-Open No. 61-260202

  However, in the reflective transflective film 10 described above, an optical loss occurs in each of the reflective mode and the transmissive mode. For example, the reflective region and the transmissive region are completely divided into one pixel region. A reflective film made of a metal film was formed in the region. For example, Japanese Patent No. 2878231 proposes a configuration in which a part of a reflective film made of a metal film is formed by patterning an opening by a method such as an etching method.

  That is, in the reflection mode, the external light incident from the display surface side is reflected by the reflection region where the reflective film of the pixel region is formed and is emitted again from the display surface side. In the transmissive mode, the light of the backlight BL is emitted to the display surface side through the opening formed in the pixel region. Thus, a part of the pixel area is divided into a reflection area and the remaining part is divided into a transmission area, thereby increasing the light use efficiency during transmission.

  However, at present, high color reproducibility is demanded in liquid crystal display devices. For example, in a liquid crystal display device for color display, the transmittance decreases with the improvement of the color purity of the filter. The brightness in the mode, particularly the brightness in the reflection mode, has become insufficient. The brightness of display in the transmissive mode and the reflective mode is not limited to the color display liquid crystal display device, and generally has the same problem in the liquid crystal display device.

  The present invention has been devised in view of the above-described problems, and an object thereof is to provide a liquid crystal display device capable of suppressing a decrease in brightness in the reflection mode.

The liquid crystal display device of the present invention includes a transparent electrode extending in one direction and one transparent substrate formed by depositing an alignment film, and a transparent electrode extending in the other direction and the other transparent substrate formed by depositing an alignment film. A liquid crystal display panel in which the transparent electrode on the one transparent substrate and the transparent electrode on the other transparent substrate intersect with each other so as to form a pixel region and interpose liquid crystal, and
A backlight disposed outside the other member of the liquid crystal display panel, and
In the liquid crystal display device comprising a reflective region that reflects external light on the pixel region and a transmissive region that transmits the light of the backlight.
On the other transparent substrate, a lower dielectric layer made of any one of oxide, nitride, sulfide, and carbide containing at least one of Si or Ti in a reflective region and a transmissive region is disposed in common, A reflective film of a pure metal or an intermetallic compound containing at least one of Al and Ag, or an oxide, nitride, sulfide, and carbide is disposed in the reflective region on the lower dielectric layer. An upper dielectric layer made of oxide, nitride, sulfide or carbide containing at least one of Si and Ti is disposed on the reflective film and the lower dielectric layer in the transmissive region. To do.

  That is, in the reflective region, the lower dielectric layer, the reflective film, and the upper dielectric layer are laminated on the other transparent substrate, and in the transmissive region, the lower dielectric layer, An upper dielectric layer is laminated. The lower dielectric layer is a dielectric layer that is formed in common in the transmissive region and the reflective region, and serves as the base of the reflective film in the reflective region. The upper dielectric layer is a dielectric layer that is located above the dielectric layer of the laminated structure in the transmissive region and is formed on the reflective film in the reflective region, and is formed in the same process. Become. Each lower dielectric layer and upper dielectric layer may have a multilayer structure as necessary.

  In the liquid crystal display device of the present invention, a reflective region that reflects external light and a transmissive region that transmits light from a backlight are separately provided in a pixel region formed by intersecting two transparent electrodes. Yes. That is, in the reflective region, a reflective film made of pure metal or an intermetallic compound containing at least one of Al and Ag, or an oxide, nitride, sulfide, and carbide is formed from above and below Si or Ti. It is sandwiched between dielectric layers made of oxide, nitride, sulfide or carbide containing at least one kind. In the transmission region that transmits light from the backlight, a dielectric layer made of oxide, nitride, sulfide, or carbide containing at least one of Si or Ti is arranged in a laminated structure. As a result, the brightness in the reflection mode and the transmission mode can be improved.

  Here, the action of the light incident from the display surface side, the reflection region for external light, and the transmission region will be described. In the reflection region of external light, the upper dielectric layer is disposed on the reflective film. Due to the increased reflection effect of the reflection region, the reflection efficiency is improved and the light is reflected. This is because when a reflection film is formed alone, for example, when external light is irradiated to the reflection film, a part of the reflection film is absorbed by the reflection film itself, but a dielectric layer is formed on the surface of the reflection film. The absorption generated in the reflective film itself can be kept small. As a result, by forming a dielectric film on the surface of the reflective film, the reflection efficiency of external light is improved as compared with the case where the reflective film is used alone.

  In the transmissive region, since the dielectric layer has a laminated structure, external light (light incident from the display surface side) is diverted depending on the material, refractive index, and film thickness of the dielectric layer. As a result, a part of the external light reaching the transmission region can be reflected and used. That is, since the reflected light that has been subjected to the enhanced reflection effect in the reflection region and the reflected light reflected in the transmission region can be used in the reflection mode, the brightness of the reflection mode can be improved.

  Next, the operation of the reflective region and the transmissive region with respect to the light incident from the backlight disposed on the back surface side opposite to the display surface will be described. In the transmissive region, the dielectric layer has a laminated structure. Therefore, depending on the material of the dielectric layer, the refractive index, and the film thickness, light incident from the backlight passes through the plurality of laminated dielectric layers to the liquid crystal display surface side. In addition, in the reflection region, an increasing reflection effect is generated by the reflection film and the lower dielectric disposed below the reflection film, and the light from the backlight is effectively reflected again to the backlight side. The light guide plate has reflecting means (such as a reflective layer inclined on the back surface or a groove for reflection) in order to guide light from the light source to the liquid crystal display panel side. Then, it is reflected again to the liquid crystal display panel side. That is, the light of the backlight that has not passed through the pixel region transmission region is confined between the other transparent substrate of the liquid crystal display panel and the backlight, and the light on the backlight side is substantially amplified. It will be. Thereby, the brightness of the transmission mode can be improved.

  That is, the brightness of display can be improved in both the reflection mode and the transmission mode in the liquid crystal display device.

  The liquid crystal display device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of a liquid crystal display device of the present invention, and FIG. 2 is a plan view showing the relationship between a reflective region and a transmissive region. In FIG. 1, the same parts as those in FIG.

  FIG. 1 is a schematic sectional view of a simple matrix type color liquid crystal display device. The liquid crystal display device includes a liquid crystal display panel LP and a backlight BL.

  The liquid crystal display panel LP is composed of, for example, a glass substrate 3 which is one transparent substrate, a glass substrate 11 which is the other transparent substrate, and a liquid crystal layer 8 disposed therebetween.

  A large number of transparent electrodes 4 are arranged in parallel on the inner surfaces of one glass substrate 3 and the other glass substrate 11. For example, the transparent electrode 4 of one glass substrate 3 is formed so as to extend in one direction, for example, the left-right direction in FIG. 1, and the transparent electrode 4 of the other glass substrate 11 is formed in the other direction, for example, the depth in FIG. Extending in the direction. That is, when one glass substrate 3 and the other glass substrate 11 are arranged to face each other, the transparent electrodes 4 of both the substrates 3 and 11 intersect each other. Thereby, a rectangular pixel region is formed as shown in FIG. This pixel area is shown in a rectangular shape when the transparent electrode 4 on the scanning side signal and the transparent electrode 4 on the data signal side intersect when viewed in plan. An alignment film 5 is formed on the transparent electrode 4 so as to be in contact with the liquid crystal layer 8.

  The liquid crystal layer 8 is composed of nematic liquid crystal molecules or the like and is omitted in FIG. 1, but spacers are dispersed so as to keep the thickness of the liquid crystal layer 8 constant. The liquid crystal molecules of the liquid crystal layer 8 are twisted and arranged by 180 ° to 270 ° in the non-application state of the drive voltage by controlling the alignment treatment direction of the alignment film 5 and the chiral substance contained in the liquid crystal layer 8. The substrates 3 and 11 are bonded around the display area by the seal member 6, and the liquid crystal layer 8 is filled in the area.

  In addition, a polarizing plate 1 and a retardation plate 2 are attached to the outer surface side of one glass substrate 3 of the liquid crystal display panel LP, and a light scattering layer 17 is disposed as necessary. A polarizing plate 13 and a retardation plate 12 are attached to the outer surface side of the other glass substrate 11.

  The backlight BL includes a light guide plate 15 and a light source 14 and is disposed outside the other glass substrate 11. Specifically, the liquid crystal display panel LP and the backlight BL are fixed in a predetermined positional relationship by a frame member that supports and fixes them. In other words, the display area composed of a plurality of pixel areas of the liquid crystal display panel LP and the light emission surface of the light guide plate 14 are arranged to face each other.

  Here, between the inner surface of the other glass substrate 11 and the transparent electrode 4, a reflective transflective layer 16 having a multilayered dielectric layer, a color filter 9 and an overcoat 7 are interposed.

  Here, the reflective transflective layer 16 includes a reflective film 25, a lower dielectric layer 26, and an upper dielectric layer 27, and includes a reflective region 21 partitioned into one pixel region. The layer structure of the transmission region 22 is different.

  For example, a part of one pixel region in plan view of the pixel region of the liquid crystal display panel LP is a reflective region 22, and the reflective region 22 includes a reflective film 25. Specifically, the layer structure of the reflective region 22 is such that a lower dielectric layer 26, a reflective film 25, and an upper dielectric layer 27 are sequentially laminated from the glass substrate 11 side.

  In addition, a region where the reflective film 25 is not formed in one pixel region is a transmissive region 21 and is a region that transmits light of the backlight BL from the back surface side of the liquid crystal display panel LP to the display surface side. Specifically, in the layer configuration of the transmissive region 21, a lower dielectric layer 26 and an upper dielectric layer 27 are formed in this order from the glass substrate 11 side. The space between the pixel regions is indicated by reference numeral 23 in FIG. 2 and has the same configuration as the reflective region 21, for example. Note that a black matrix, which is a kind of the color filter 9, may be formed on the pixel region to form a black matrix.

  A color filter 9 corresponding to one pixel per pixel is formed on the upper dielectric layer 27 of the reflective region 22 and the transmissive region 21. Further, on the color filter 9, the thickness of the reflective film 25 and the color filter are formed. In order to absorb surface irregularities caused by the thickness of 9, an overcoat 7 is deposited. Note that an overcoat 7 is also formed in a liquid crystal display device that does not include the color filter 9. The surface of the overcoat 7 is excellent in smoothness, and the transparent electrode 4 and the alignment film 5 are laminated in this order on the surface.

  The transmissive region 21 for transmitting light from the backlight BL used in this transmissive mode is obtained by etching a part of the reflective film 25 formed in the reflective region 22 to form the reflective film 25 on the pixel region. An opening pattern is formed, and this opening region becomes the transmission region 21.

  In addition, although it is the same layer structure as the reflective area | region 22 between pixel areas, as the color filter 9, R (blue), G (green) B (blue) (C (cyan) M (Manzeda) Y (yellow) A blocking film made of a black resin may be formed.

  The liquid crystal display device as described above is designed to be used in a wide range of environments from dark places to bright places. In other words, liquid crystal display is mainly performed using reflection of external light in the reflection mode when using in a bright place, and liquid crystal display using light from the backlight BL mainly using in a transmission mode. Done.

  Here, the lower dielectric layer 26 is formed in common between the reflective region 22, the transmissive region 21, and the pixel region, and is an oxide, nitride, or sulfide containing at least one of Si or Ti. Or any one of carbides.

Since the lower dielectric layer 26 is a film formed below the reflective film 25, it is referred to as the lower dielectric layer 26, and the lower dielectric layer 26 itself may have a multilayer structure. Therefore, for example, SiO ₂ , Si ₃ N ₄ , SiC, TiO ₂ , Ti ₃ N ₄ , and TiC can be used as this material, but the lower dielectric layer 26 itself may have a multilayer structure of different materials. .

  The reflective film 25 formed in the reflective region 22 is composed of a pure metal material containing at least one of Al or Ag or an alloy material thereof, an oxide, a nitride, a sulfide, or a carbide thereof, The film thickness is 800 to 30000 mm.

Further, the upper dielectric layer 27 is formed across the transmissive region 21 and the reflective film 25. Although the upper dielectric layer 27 is formed regardless of the presence or absence of the reflective film 25, the upper dielectric layer 27 is formed in a step shape because of the thickness of the reflective film 25. The upper dielectric layer 27 may have either a single layer structure or a multilayer structure, and the material per layer is composed of, for example, SiO ₂ , Si ₃ N ₄ , SiC, TiO ₂ , Ti ₃ N ₄ , or TiC. ing.

  As described above, in the reflection region 22, the upper dielectric layer 27 is deposited on at least the reflection film 25, and external light incident from the display surface side of the liquid crystal display panel LP in the reflection mode is applied to the liquid crystal layer 8. When the light passes through and reaches the reflection region 22, the upper dielectric layer 27 and the reflection film 25 act to reflect again to the liquid crystal layer 8 side and exit from the display screen side.

  At this time, since the upper dielectric layer 27 is formed on the reflective film 25 mainly composed of metal, the light absorbed by the reflective film 25 can be effectively suppressed by the dielectric layer 27. As a result, an increased reflection effect is generated, so that a very bright reflected light can be obtained as compared with the case of using only a reflective film.

  At the same time, when the outside light reaches the transmission region 21, the layer structure of the transmission region 21 has a multilayer structure of dielectric layers. Therefore, the surface of the upper dielectric layer 27, the upper dielectric layer 27, an interface between each single layer constituting the upper dielectric layer 27, an interface between the upper dielectric layer 27 and the lower dielectric layer 26, an interface between each single layer constituting the lower dielectric layer 26, and the lower dielectric layer 26 and the glass substrate 11. Reflection occurs at the interface or the like and reflects outside light although not as much as the reflection region 22. The reflected light is combined with the light reflected by the reflection region 22 to enable bright display in a reflection mode using external light.

  Further, the light of the backlight BL incident from the back side of the liquid crystal display panel LP in the transmissive mode passes through the liquid crystal layer 8 via the transmissive region 21 and displays display information on the display surface side. At the same time, the light incident on the reflection region 22 by the light of the backlight BL is the interface between the glass substrate 11 and the lower dielectric layer 26, the interface between each single layer constituting the lower dielectric layer 26, and the lower surface of the reflection film 25. And reflected on the backlight BL side. The reflected light is a reflecting means (reflecting means for reflecting the light from the light source 14 to the liquid crystal display panel LP, which is formed on the back side of the light guide plate 15 constituting the backlight BL, and an inclined reflecting layer. And reflected again). That is, the light incident on the reflection region 22 by the light of the backlight BL is confined between the reflection film 25 of the glass substrate 11 of the liquid crystal display panel LP and the reflection means of the backlight BL, and as a result, a plurality of times. In the process of being reflected, the light passes through the transmissive region 21 and exits from the display surface via the liquid crystal layer 8.

  That is, the light irradiated on the reflection region 21 by the light of the backlight BL is also reflected on the backlight BL side by improving the reflection efficiency by the increased reflection action of the lower dielectric layer 26 and the reflection film 25. Furthermore, the reflected light can be confined between the liquid crystal display panel LP and the backlight BL, and the confined light can be transmitted through the transmission region 21. That is, the light applied to the reflection region 21 can also be finally used as light that contributes to display, and bright display in the transmission mode is possible.

  As described above, the back surface of the light guide plate 15 on which the reflecting means is formed is inclined so as to irradiate the liquid crystal display panel LP from the light source 14 as shown in FIG. However, the reflection does not repeat between the reflection film 25 and the reflection means permanently, and as a result, the reflected light is emitted to the liquid crystal display panel LP side through the transmission region 21.

  The ratio of the reflectance and transmittance of the liquid crystal display panel LP can be arbitrarily adjusted by adjusting the area ratio between the transmissive region 21 and the reflective region 22 in one pixel region. 3A to 3D are plan views of a part of one pixel region, and show patterns with a transmissive region 21 and a reflective region 22. Reference numeral 23 denotes an interval portion of the pixel region, for example, a black matrix portion.

Next, a method for forming the reflective transflective layer 16 will be described with reference to FIG.

Method for Forming Reflective Transflective Layer 16 As shown in FIG. 4A, a lower dielectric layer 26 constituting a part of the reflective transflective film 16 is formed on a glass substrate 11 which is the other transparent substrate. For example, the lower dielectric layer 26 is formed using an oxide, nitride, sulfide, or carbide containing at least one of Si or Ti by sputtering or vapor deposition. The lower dielectric layer 26 may be a single layer film, a multilayer film of the same material, or a multilayer film of different materials.

  Subsequently, a reflective thin film 25 a to be the reflective film 25 is formed on the lower dielectric layer 26. This reflective thin film is a pure metal containing at least one of Al or Ag or an alloy thereof, an oxide, a nitride, a sulfide, or a carbide thereof, and is formed by sputtering, vapor deposition, or plating. Yes, its thickness is 800?

  Further, an acrylic photosensitive resin 19 is applied to the entire surface of the reflective thin film 25a.

  Next, as shown in FIG. 4B, the glass substrate 11 described above is pre-baked by a hot plate 28 at 90 ° C. for 2 minutes, for example.

  Next, as shown in FIG. 4C, an exposure process is performed on the upper side of the acrylic photosensitive resin 19 through a photolithographic mask 20. For this exposure, ultraviolet light (UV) is used in the normal direction of the glass substrate 11, for example, the acrylic photosensitive resin 19 exposed from the mask is exposed.

  Next, as shown in FIG. 4D, the acrylic photosensitive resin 19 is developed.

  Next, as shown in FIG. 4E, the developed glass substrate 11 is post-baked using a hot plate 28 at 200 ° C. for 2 minutes to cure the acrylic photosensitive resin 19.

Next, as shown in FIG. 4 (f), the reflective thin film 25 a is etched using the acrylic photosensitive resin 19 as a mask, and a part of the reflective thin film 25 a is removed to form an opening in a region that becomes the transmissive region 21. Form. As this etchant, for example, a mixture of H ₃ PO ₄ , HN ₃ and CH ₃ COOH is used. As a result, the reflective thin film 25 a becomes a reflective film 25 having a predetermined shape, and a part of the lower dielectric layer 26 is exposed at a part of the reflective film 25.

  Next, as shown in FIG. 4G, the acrylic photosensitive resin 19 remaining on the reflective film 25 that has been subjected to the etching treatment is stripped with a resist stripping solution.

  Next, as shown in FIG. 4H, the upper dielectric layer 27 is formed. The upper dielectric layer 27 is formed by using a sputtering method or a vapor deposition method with an oxide, nitride, sulfide, or carbide containing at least one of Si and Ti. However, when the dielectric layers 26 and 27 have a multilayer structure through the upper dielectric layer 27 and the lower dielectric layer 26, Si oxide, nitride, sulfide, carbide and Ti oxide Nitride, sulfide and carbide must be formed alternately. This is a multilayer structure composed of a lower dielectric layer 26 and an upper dielectric layer 27 in the transmissive region 21, and minimizes absorption of light when the reflective transflective layer reflects or transmits external light. It is to do.

  In the above-described manufacturing method, as the reflective transflective film 16, the transmission region 21 and the reflection region 22 have a common lower dielectric layer 26 (single layer), the reflection region 22 on the reflection film 25, and the transmission region. This is an example in which an upper dielectric layer 27 is formed as a single layer (single layer) on the lower dielectric layer 26 of FIG.

  Instead of this, as shown in FIG. 5, the upper dielectric layer 27 may have a multilayer structure as the reflective transflective film 16. In the example of FIG. 5, the upper dielectric layer 27 has a multilayer structure of three dielectric layers 27 a to 27 c. In this case, the material of each layer (whether it is formed of the above-mentioned Si compound system or Ti compound) takes into consideration the thickness of the film, the frequency (wavelength) of light to be transmitted and reflected, and the refractive index of the film. To be formed.

As described above, the lower dielectric layer 26 may have a multilayer structure as well as a single layer structure.

About pattern of transmission region As shown in Fig. 4 (f), the transmission region 21 includes a pure metal or a metal alloy containing at least one of Al and Ag, or an oxide, nitride, sulfide. Then, a part of the reflective thin film 25a formed of carbide is patterned by a photolithography method, thereby forming a transmission region portion 21 that transmits light from the backlight BL. For this reason, in the transmissive region 21, since the dielectric layers 26 and 27 have a multilayer structure through the upper dielectric layer 27 and the lower dielectric layer 26, both the light reflective property and the light transmissive property are provided. Moreover, it is preferable that no phase difference occurs when sandwiched between two polarizing plates.

Regarding the pattern of the reflective region , the reflective region 22 corresponds to a region where the reflective film 25 is formed. A lower dielectric layer 26 is disposed on the lower side of the reflective film 25, and an upper dielectric layer 27 is disposed on the upper side. Thereby, when the external light incident from the display surface side of the liquid crystal display panel LP is reflected, the reflection efficiency film is improved by the increased reflection effect. Further, the reflection efficiency when the light of the backlight BL is irradiated from the lower surface side of the reflective film 25 is improved, and thus the backlight light can be effectively used.

Regarding the area ratio of the transmissive region portion 21 and the reflective region 22 In one pixel region, the reflectance and the transmittance of the liquid crystal display panel LP are arbitrarily changed by appropriately changing the ratio of the area of the transmissive region 21 and the reflective region 22. Is possible. For example, when the area ratio between the reflective region and the transmissive region is 80:20, the reflectance (%) of the entire reflective semi-transmissive film 16 including the reflective film 25 = the reflectance (%) of the reflective region 22 × 0.8 (reflective) Area ratio of region 22) + reflectance of transmission region 21 × 0.2 (area ratio of reflection semi-transmission region 21). This ratio can be obtained by designing a mask used in the photolithography method after forming the reflective thin film 25a.

  The lower dielectric layer 26 and the upper dielectric layer 27 are used for such a reflective transflective layer 16, and the film thickness should be 800 mm or more, thereby providing both the light shielding and light reflecting functions. Can do.

  If the area of the transmissive region 21 is increased, the configuration is suitable for the transmissive display mode, and if the area is reduced, the configuration is suitable for the reflective display mode.

In order to confirm the effect of the present invention, the optical characteristics of the liquid crystal display device according to the present invention were evaluated. The structure of the reflective transflective liquid crystal display device to be measured is as shown in FIG. The structure of the lower dielectric layer 26 and the upper dielectric layer 27 of the reflective transflective layer 16 is shown in FIG. That, SiO ₂ the product of the respective refractive index and thickness of the SiO ₂ and TiO _2, it is important to 1/4 of the wavelength of light λ desired to be transmitted. Thus, λ / 4 and TiO ₂ are preferably λ / 2, and absorption when light passes through each layer can be minimized. At this time, the reflectance of the reflection region 22 was 95%, the reflectance of the transmission region portion 21 was 30%, and the transmittance was 70%. Moreover, the area ratio of the reflective region 22 and the transmissive region 21 was set to 60:40. In this configuration, the ratio between the reflectance and the transmittance of the reflective semi-transmissive layer 16 is 69%, and the transmittance of the reflective semi-transmissive layer 16 is 28%.

  On the other hand, in a conventional reflective transflective liquid crystal display device, Al is used for the reflective transflective layer, and the Al film thickness is adjusted so that the ratio of reflectance to transmittance is 60:20. Further, in order to make the scattering characteristics in the reflection mode and the transmission mode equal, a forward scattering plate is provided between the phase difference plate 2 and the glass substrate in both the example and the comparative example. The haze value of the front scattering plate is 80% in both the example and the comparative example.

Table 1 and FIG. 6 show the results of measuring the reflectance and transmittance of the liquid crystal display devices of the example and the comparative example.

The reflectance was measured by changing the incident angle from the light source from 10 ° to 45 ° with the light receiving angle constant in the normal direction to the display surface of the liquid crystal display panel LP. The transmittance was calculated by dividing the surface luminance of the liquid crystal display panel LP by the luminance of the light source.

From the results shown in Table 1 and FIG. 6, it can be seen that both the reflectance and transmittance of the liquid crystal display device of the present invention are improved compared to the comparative example. This is caused by the difference in light utilization efficiency of the reflective transflective layer 16. Since the reflective semi-transmissive layer used in the comparative example uses a semi-transmissive film, light is absorbed when reflecting and transmitting external light, resulting in low light utilization efficiency. In the reflective transflective layer 16 used in the embodiment, a reflection region 22 that completely reflects light from outside light in one pixel region, and transmission that reflects outside light and transmits light from a backlight. Although the region 22 is divided, the reflection region 22 is designed so that the absorption of external light in the reflection mode is minimized by forming the upper dielectric layer 27 made of SiO ₂ and TiO ₂ on Ag. It is because it has been. On the other hand, in the transmissive region 21, the reflective semi-transmissive film 16 made of at least the lower dielectric layer 26 and the upper dielectric layer 27 made of SiO ₂ or TiO ₂ is used. Absorption of external light is minimized.

  From the above, the light use efficiency in the reflection mode and the transmission mode of the reflective transflective layer is improved by the effect of the present invention.

  In the above-described embodiment, the reflective semi-transmissive film 16 is directly deposited on the glass substrate 11 which is the other transparent substrate. However, between the glass substrate 11 and the reflective semi-transmissive film 16, A light scattering plate may be formed to make the luminance uniform in the display area.

It is sectional drawing of the liquid crystal display device of this invention. It is a top view which shows the arrangement | positioning relationship between the reflective area | region and transmissive area | region used for the liquid crystal display device of this invention. (A)-(d) is a top view which shows the relationship between a reflective area | region and a permeation | transmission area | region in this invention. (A)-(h) shows the manufacturing process of the reflective semi-transmissive film | membrane which is the main processes of the manufacturing method of the liquid crystal display device of this invention. It is sectional drawing which shows an example of the structure of the reflective semi-transmissive film | membrane of the liquid crystal display device of this invention. It is a characteristic view which shows the comparison of the reflectance of the liquid crystal display device (Example) of this invention, and the conventional liquid crystal display device (comparative example). It is sectional drawing of the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Polarizing plate 2 ... Phase difference plate 3 ... One transparent substrate (glass substrate)
4 ... Transparent electrode 5 ... Alignment film 7 ... Overcoat layer 8 ... Liquid crystal layer 9 ... Color filter 10 ... Reflective transflective layer 11 ... The other transparent substrate (glass substrate) )
DESCRIPTION OF SYMBOLS 12 ... Phase difference plate 13 ... Polarizing plate 14 ... Light source part 15 ... Light guide plate 16 ... Reflective transflective layer 25 Reflective film 26 Lower dielectric layer 27 Upper dielectric layer LP ...・ Liquid crystal display panel BL ・ ・ ・ Backlight

Claims (1)

A transparent electrode extending in one direction, one transparent substrate formed by depositing an alignment film, and
A transparent electrode extending in the other direction, the other transparent substrate formed by depositing an alignment film,
A liquid crystal display panel in which the transparent electrode on the one transparent substrate and the transparent electrode on the other transparent substrate cross each other to form a pixel region and are bonded with liquid crystal interposed therebetween;
A backlight disposed outside the other transparent substrate of the liquid crystal display panel, and
In the liquid crystal display device comprising a reflective region that reflects external light on the pixel region and a transmissive region that transmits the light of the backlight.
In the other transparent substrate, a lower dielectric layer made of any of oxide, nitride, sulfide, and carbide containing at least one of Si or Ti in a reflective region and a transmissive region is commonly disposed, A reflective film of a pure metal or an intermetallic compound containing at least one of Al and Ag, or an oxide, nitride, sulfide, and carbide is disposed on the lower dielectric layer on the lower dielectric layer, and the reflective area An upper dielectric layer made of oxide, nitride, sulfide or carbide containing at least one of Si and Ti is disposed on the reflective film and the lower dielectric layer in the transmissive region. A liquid crystal display device.

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