JP2005107140A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display device which has high display characteristics. <P>SOLUTION: The liquid crystal display device has a liquid crystal layer 4 between a front-side transparent substrate 3 and a back-side transparent substrate 8 which faces the front-side transparent substrate 3. A polarizing layer 1 is provided on an observer side of the front-side transparent substrate 3 and a polarizing layer 5 is provided between the liquid crystal layer 4 and back-side transparent substrate 8. Then a transflective layer 7 is provided between the polarizing layer 5 and back-side transparent substrate 8. In this constitution, linearly polarized light is incident on the liquid crystal layer 4 for both reflection type display and transmission type display. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transflective liquid crystal display device.

  Conventionally, as a liquid crystal display device, a transflective liquid crystal display that displays both a reflective display using outside light such as natural light and room light and a transmissive display using illumination light from a backlight. There is a display device (see, for example, Patent Document 1). This transflective liquid crystal display device performs reflective display using outside light in a bright environment where sufficient brightness of outside light can be obtained, and in a dark environment where sufficient brightness of outside light cannot be obtained. Then, transmissive display using illumination light from a backlight is performed. For this reason, the backlight is normally turned on when transmissive display is performed.

  Here, FIG. 6 shows a configuration example of a transflective liquid crystal display device. This example employs an STN (Super Twisted Nematic) system. In the figure, 1 is a polarizing layer, 2 is a retardation layer, 3 is a transparent substrate on the front side, 4 is a liquid crystal layer, 6 is a color filter (CF) layer, 7 is a semi-transmissive semi-reflective layer composed of a reflective layer 71 and a transmissive layer 72. Reference numeral 8 denotes a back side transparent substrate, 9 denotes a retardation layer, and 12 denotes a polarizing layer.

  In the case of a reflective display, the light A incident from the front is reflected by the reflective layer 71 via the polarizing layer 1, the retardation layer 2, the front transparent substrate 3, the liquid crystal layer 4, and the CF layer 6, and reverses the same path. Go ahead and emit from the front of the display. For this reason, the reflection characteristic is defined by the member configuration between the polarizing layer 1 and the reflective layer 71.

  More specifically, the transition of the light state will be described. When performing black display in the reflective display, the linearly polarized light emitted from the polarizing layer 1 is converted into elliptically polarized light by the retardation layer 2 and is incident on the liquid crystal layer 4. It is converted into circularly polarized light in the liquid crystal layer 4 and reflected by the reflective layer 71, and its phase is shifted by π. The circularly polarized light reflected by the reflective layer 71 becomes elliptically polarized light in the liquid crystal layer 4, and is converted from elliptically polarized light to linearly polarized light in the retardation layer 2. Although this linearly polarized light is incident on the polarizing layer 1, its vibration direction is not parallel to the transmission axis of the polarizing layer 1 and is absorbed by the polarizing layer 1.

  Next, when performing white display in the reflective display, the linearly polarized light emitted from the polarizing layer 1 is converted into elliptically polarized light by the retardation layer 2 and enters the liquid crystal layer 4. It is converted into linearly polarized light in the liquid crystal layer 4 and reflected by the reflective layer 71, and its phase is shifted by π. The linearly polarized light reflected by the reflective layer 71 becomes elliptically polarized light in the liquid crystal layer 4, and is converted from elliptically polarized light to linearly polarized light in the retardation layer 2. Since the vibration direction of the linearly polarized light is parallel to the transmission axis of the polarizing layer 1, it passes through the polarizing layer 1 and exits from the front surface.

  On the other hand, in the case of the transmissive display, the light B incident from a backlight (not shown) is the polarizing layer 12, the retardation layer 9, the back side transparent substrate 8, the transmissive layer 72, the CF layer 6, the liquid crystal layer 4, and the front side transparent substrate. 3. The light travels through the retardation layer 2 and the polarizing layer 1 and is emitted from the front surface of the display device. Therefore, the transmission characteristics are defined by the member configuration from the polarizing layer 12 on the most back side to the polarizing layer 1 on the most front side. Therefore, in the liquid crystal display device having such a configuration, two different optical configurations are mixed in one display.

  More specifically, the transition of the light state will be described. In the transmissive display, when black display is performed and when white display is performed, the transition is the same. In the polarizing layer 12, the incident light B is converted into linearly polarized light, and further converted into circularly polarized light by the retardation layer 9. This circularly polarized light enters the liquid crystal layer 4 and is converted into elliptically polarized light in the liquid crystal layer 4. This elliptically polarized light is converted into linearly polarized light in the retardation layer 2 and enters the polarizing layer 1. In the case of black display, the linearly polarized light is absorbed by the polarizing layer 1, and in the case of white display, the linearly polarized light is transmitted through the polarizing layer 1.

  In the case of the reflective display, the light A incident from the front is reflected by the reflective layer 71 via the polarizing layer 1 and passes through the liquid crystal layer 4 twice before reaching the polarizing layer 1 again. On the other hand, in the case of the transmissive display, the light B incident from the back passes through the liquid crystal layer 4 once from the polarizing layer 12 to the polarizing layer 1. Accordingly, the retardation effect received from the liquid crystal layer 4 differs between the reflective display and the transmissive display. For this reason, in a conventional transflective liquid crystal display device, a structure giving priority to either reflection characteristics or transmission characteristics has to be adopted. Further, the polarization state will be further described using the Poincare sphere in the black display of FIG. 6. Since the light A reflected by the reflective layer 71 is circularly polarized, it is represented in the pole portion on the Poincare sphere. Then, it must be converted into linearly polarized light located at a specific equator point on the Poincare sphere via the liquid crystal layer 4 or the like. This process of converting to linearly polarized light has no choice compared to the process of converting linearly polarized light to linearly polarized light (for example, the process of passing through the equator, the process of passing through the circularly polarized pole, and the elliptically polarized light that does not pass through the pole). Is. Furthermore, the short path of this conversion process means that the change in the state of light is small, in other words, the light utilization efficiency is low, and the contrast, which is the ratio between the white state and the black state, is poor. become. Therefore, if the starting point of light that has to be emitted with linearly polarized light to the observer (light before entering the liquid crystal layer 4) is circularly polarized, the appearance of low contrast is poor in display, and the optical characteristics of the liquid crystal In designing, the degree of freedom is low. Further, in the transmissive display portion, in order to match the reflective display portion, it is necessary to intentionally dispose a retardation layer that is not preferable for display.

  In general, when priority is given to the transmission characteristics, the reflection characteristics deteriorate, and therefore, a structure that sacrifices the transmission characteristics is often employed. In this case, the transmission characteristics reduce the utilization efficiency by about 50%. At this time, by changing the thickness of the liquid crystal layer 4 above the reflective layer 71 and the transmissive layer 72, the retardation values of the reflective region and the transmissive region can be set optimally. However, according to this method, since it is necessary to create a large step in the liquid crystal layer 4, there arises a problem that defects such as domains occur.

  FIG. 7 shows a configuration example of another transflective liquid crystal display device. In this configuration, the liquid crystal layer 4 and the partial reflection layer 71 are provided between the CF layer 6 and the back side transparent substrate 8.

  Usually, when a TN (twisted nematic) system is employed, the birefringence effect is not actively used in order to avoid coloring. However, when the partial reflection layer 71 is disposed between the back-side transparent substrate 8 and the liquid crystal layer 4, the reflected light before entering the liquid crystal layer 4 needs to be circularly polarized, and accordingly, a transmissive display In this case, it is necessary to use birefringence positively because it is necessary to use circularly polarized light. When birefringence is positively used, coloring becomes a problem when trying to obtain a high contrast ratio (CR), and low CR is caused when trying to avoid coloring.

In the configuration shown in FIG. 7, a step is provided in the liquid crystal layer 4 to optimally set the retardation values of the reflection region and the transmission region. Further, by adopting a horizontal alignment having a large margin with respect to the generation of domains due to the steps of the liquid crystal layer 4, that is, a 0 degree twist mode, high light utilization efficiency can be achieved. However, since it is necessary to create a large step in the liquid crystal layer 4, there arises a problem that an additional process is required.
JP 2000-187220 A

  As described above, in the conventional transflective liquid crystal display device, it is difficult to simultaneously improve display characteristics in both transmissive display and reflective display.

  The present invention has been made to solve such problems, and it is an object of the present invention to provide a liquid crystal display device capable of simultaneously improving display characteristics in both transmissive display and reflective display.

  The liquid crystal display device according to the present invention includes a first transparent substrate (for example, the front-side transparent substrate 3 according to the embodiment of the present invention) and a second transparent substrate (for example, a book) facing the first transparent substrate. A liquid crystal display device comprising a liquid crystal layer between a back side transparent substrate 8) according to an embodiment of the invention, the first polarizing layer (for example, provided on the viewer side of the first transparent substrate) A polarizing layer 1) according to an embodiment of the present invention, a second polarizing layer (for example, a polarizing layer 5 according to an embodiment of the present invention) provided between the liquid crystal layer and a second transparent substrate; And a transflective layer (for example, the transflective layer 7 according to an embodiment of the present invention) provided between the second polarizing layer and the second transparent substrate. . According to such a configuration, when the light reflected on the reflective layer is incident on the liquid crystal layer in the case of the reflective display, linearly polarized light is always incident regardless of black display / white display. In addition, since a configuration in which linearly polarized light is incident can be adopted in the case of transmissive display, high contrast can be realized without causing a coloring problem.

  It is preferable that a retardation layer for converting linearly polarized light emitted from the first polarizing layer into elliptically polarized light is provided between the first polarizing layer and the first transparent substrate.

  Furthermore, a color filter layer may be provided between the first transparent substrate and the second transparent substrate.

  In particular, the color filter layer is preferably provided between the second polarizing layer and the transflective layer. Thereby, generation | occurrence | production of the problem of color mixing can be suppressed.

  The second polarizing layer may be formed by a coating process. This is because when the polarizing film is formed, the polarizing film is deformed and deteriorates when high temperature treatment is performed in another process.

  A liquid crystal display device according to a preferred embodiment is a liquid crystal display device including a liquid crystal layer between a first transparent substrate and a second transparent substrate facing the first transparent substrate, wherein the first transparent substrate is the first liquid crystal display device. A first polarizing layer provided on an observer side of the transparent substrate; a retardation layer provided between the first polarizing layer and the first transparent substrate; the liquid crystal layer; and a second transparent substrate. A second polarizing layer provided between, a color filter layer provided between the second polarizing layer and the second transparent substrate, and between the color filter layer and the second transparent substrate. And a semi-transmissive / semi-reflective layer.

  Another liquid crystal display device according to a preferred embodiment is a liquid crystal display device including a liquid crystal layer between a first transparent substrate and a second transparent substrate facing the first transparent substrate, A first polarizing layer provided on an observer side of the first transparent substrate; a retardation layer provided between the first polarizing layer and the first transparent substrate; a liquid crystal layer; A color filter layer provided between two transparent substrates, a second polarizing layer provided between the color filter layer and the second transparent substrate, the second polarizing layer, and the second And a transflective layer provided between the transparent substrates.

  Furthermore, another liquid crystal display device according to a preferred embodiment is a liquid crystal display device including a liquid crystal layer between a first transparent substrate and a second transparent substrate facing the first transparent substrate, A first polarizing layer provided on an observer side of the first transparent substrate; a retardation layer provided between the first polarizing layer and the first transparent substrate; and the first transparent layer. A color filter layer provided between a substrate and the liquid crystal layer, a second polarizing layer provided between the liquid crystal layer and the second transparent substrate, the second polarizing layer, and the second And a transflective layer provided between the transparent substrates.

  According to the present invention, it is possible to provide a liquid crystal display device capable of simultaneously improving display characteristics in both transmissive display and reflective display.

Embodiment 1 of the Invention
FIG. 1 shows a configuration of a transflective liquid crystal display device according to Embodiment 1 of the present invention. This liquid crystal display device adopts the STN method or the TN method. As shown in the figure, in this liquid crystal display device, the polarizing layer 1, the retardation layer 2, the front-side transparent substrate 3, the liquid crystal layer 4, the polarizing layer 5, the CF layer 6, the reflective layer 71 and the transmissive layer 72 from the front side. A semi-transparent semi-reflective layer 7 and a back-side transparent substrate 8 made of

  The polarizing layer 1 is composed of, for example, a polarizing film, transmits a linearly polarized light whose transmission axis and absorption axis are orthogonal to each other, parallel to the transmission axis, and absorbs linearly polarized light parallel to the absorption axis. The retardation layer 2 is composed of a retardation plate, a retardation film, and a laminate thereof, and converts linearly polarized light into elliptically polarized light.

  The front-side transparent substrate 3 is a transparent substrate disposed on the viewer side, and is made of, for example, glass or transparent resin, and is formed with a transparent electrode such as ITO. The liquid crystal layer 4 is a layer made of, for example, nematic liquid crystal provided between the front side transparent substrate 3 and the back side transparent substrate 8.

  The polarizing layer 5 is formed on the CF layer 6 by a coating process, and allows only linearly polarized light having a vibration direction parallel to a specific transmission axis to pass therethrough. The polarizing layer 5 has a thickness of, for example, 500 nm. The embodiment of the present invention is characterized in that the polarizing layer 5 is provided between the front side transparent substrate 3 and the back side transparent substrate 8 as described above.

  The polarizing layer 5 is arranged on the back side transparent substrate 8 subjected to orientation treatment, or oriented by irradiating light after applying the dye, and further along the coating direction at the time of dye coating. The absorption axis is defined by orienting the dye. For example, a method disclosed in US Pat. No. 6,174,394 can be used as a method for applying the polarizing layer 5. A transparent electrode such as ITO is formed on the upper surface of the polarizing layer 5.

  The CF layer 6 has R (red), G (green), and B (blue) regions, and realizes color display by controlling the amount of light that passes through these regions. The CF layer 6 has a thickness of 2 μm, for example.

  The reflective layer 71 is provided in the same layer as the transmissive layer 72 and reflects light incident from the front side to the front side. The transmissive layer 72 transmits light incident from the front side and emits it to the back side, and also transmits light incident from the back side and emits it to the front side. The reflective layer 71 and the transmissive layer 72 are formed by metal sputtering or the like. At this time, the reflectance and the transmittance can be controlled by controlling the film thickness. Alternatively, the transparent portion can be intermittently formed by patterning the complete reflection layer, and the reflectance and transmittance can be controlled.

  The back side transparent substrate 8 is, for example, a glass substrate or a transparent resin substrate. No retardation layer is provided on the back side of the back side transparent substrate 8.

  The liquid crystal display device can be constituted by various members such as a drive circuit, a backlight, a frame, an antireflection film, and a light guide plate, but is not illustrated.

  In the liquid crystal display device having the configuration shown in FIG. 1, a case of a reflective display and a case of a transmissive display will be described.

  In the case of the reflective display, the light A incident from the front surface is first transmitted through the polarizing layer 1 as linearly polarized light having a vibration direction parallel to the transmission axis of the polarizing layer 1 and enters the retardation layer 2. In the retardation layer 2, the linearly polarized light is converted into elliptically polarized light and is incident on the front transparent substrate 3.

  The elliptically polarized light incident on the front transparent substrate 3 passes through as it is and enters the liquid crystal layer 4. In both the state where the voltage is applied to the liquid crystal layer 4 and the state where no voltage is applied, the elliptically polarized light incident on the liquid crystal layer 4 is converted into linearly polarized light and emitted.

  The linearly polarized light emitted from the liquid crystal layer 4 is transmitted by the polarizing layer 5 only to the linearly polarized light having a vibration direction parallel to the transmission axis of the polarizing layer 5 and enters the CF layer 6. The linearly polarized light that has entered the CF layer 6 is reflected by the reflective layer 71, passes through the CF layer 6 again, and enters the polarizing layer 5. When the light is reflected by the reflective layer 71, the phase of the linearly polarized light is shifted by π. The linearly polarized light incident on the polarizing layer 5 passes through the polarizing layer 5 and enters the liquid crystal layer 4. The linearly polarized light incident on the liquid crystal layer 4 is converted into elliptically polarized light and is incident on the front-side transparent substrate 3.

  The front transparent substrate 3 emits the incident elliptically polarized light as it is to the retardation layer 2. In the phase difference layer 2, the incident elliptically polarized light is converted into linearly polarized light and emitted. The linearly polarized light emitted from the retardation layer 2 transmits only the linearly polarized light having a vibration direction parallel to the transmission axis of the polarizing layer 1 and is output from the front side of the display device. At this time, the relative angle between the vibration direction of the linearly polarized light emitted from the phase difference layer 2 and the direction of the transmission axis of the polarizing layer 1 is different according to the application of the voltage to the liquid crystal layer 4. For example, in the normally white mode, the vibration direction of the linearly polarized light emitted from the retardation layer 2 in a state where no voltage is applied to the liquid crystal layer 4 and the direction of the transmission axis of the polarizing layer 1 are parallel.

  On the other hand, in the case of the transmissive display, light B incident from a backlight (not shown) passes through the back side transparent substrate 8, the transmissive layer 72, and the CF layer 6 and enters the polarizing layer 5. The light incident on the polarizing layer 5 transmits linearly polarized light having a vibration direction parallel to the transmission axis of the polarizing layer 5 and enters the liquid crystal layer 4.

  When the voltage is applied to the liquid crystal layer 4 and when no voltage is applied, the elliptically polarized light incident on the liquid crystal layer 4 is emitted in the state of elliptically polarized light.

  The front transparent substrate 3 emits the incident elliptically polarized light to the retardation layer 2 as it is. In the phase difference layer 2, the incident elliptically polarized light is converted into linearly polarized light and emitted. The linearly polarized light emitted from the retardation layer 2 transmits only the linearly polarized light having a vibration direction parallel to the transmission axis of the polarizing layer 1 and is output from the front side of the display device. At this time, the relative angle between the vibration direction of the linearly polarized light emitted from the phase difference layer 2 and the direction of the transmission axis of the polarizing layer 1 is different according to the application of the voltage to the liquid crystal layer 4.

  In the liquid crystal display device having the structure shown in FIG. 1, the light A incident from the front surface in the case of a reflective display passes through the liquid crystal layer 4, is converted into linearly polarized light by the polarizing layer 5, and then is reflected by the reflective layer 71. Then, it enters the liquid crystal layer 4 in the state of linearly polarized light. Accordingly, even in the case of transmissive display, it is only necessary to enter the liquid crystal layer 4 in the state of linearly polarized light, and therefore it is not necessary to positively use birefringence. Therefore, it is possible to avoid the coloring problem that tends to occur when trying to obtain a high contrast ratio (CR) when birefringence is used.

  Here, in the liquid crystal display device according to the embodiment of the present invention, since the polarizing layer 5 is newly provided on the back side of the liquid crystal layer 4, it is inevitable that light loss occurs in the polarizing layer 5. However, since the polarized light in the state of being emitted from the polarizing layer 5 and the polarized light in the state of being incident on the polarizing layer 5 after being reflected by the reflective layer 71 are shifted by π, the polarization state is equal, and the loss of such light is 5 % And so on.

  If the CF layer 6 and the reflective layer 71 are located at a distance, for example, light that has passed through the R region of the CF layer 6 is reflected by the reflective layer 71 and easily causes a color mixing problem that passes through the G region. However, since the CF layer 6 and the reflective layer 71 are in contact with each other in the liquid crystal display device having the structure shown in FIG. 1, such a problem does not occur.

  Further, in the liquid crystal display device having the structure shown in FIG. 1, the reflective layer 71, the transmissive layer 72, and the CF layer 6 having similar manufacturing processes can be continuously manufactured on the back side transparent substrate 8, so that the manufacturing is easy. There is an effect that.

Embodiment 2 of the Invention
FIG. 2 shows a configuration of a transflective liquid crystal display device according to the second exemplary embodiment of the present invention. This liquid crystal display device employs the STN method. As shown in the figure, in this liquid crystal display device, the polarizing layer 1, the retardation layer 2, the front transparent substrate 3, the liquid crystal layer 4, the CF layer 6, the polarizing layer 5, and the semi-transmissive semi-transparent from the front (display surface) side. A reflective layer 7 and a back side transparent substrate 8 are disposed. That is, this embodiment differs from the first embodiment shown in FIG. 1 only in that the positions of the CF layer 6 and the polarizing layer 5 are interchanged.

  Also in the liquid crystal display device having such a configuration, as in the first embodiment of the invention, the light A incident from the front surface in the case of the reflective display passes through the liquid crystal layer 4 and is then linearly polarized by the polarizing layer 5. After the conversion, the light is reflected by the reflective layer 71 and enters the liquid crystal layer 4 in a linearly polarized state. Therefore, even in the case of transmissive display, it is only necessary to enter the liquid crystal layer 4 in the state of linearly polarized light, so there is no need to use extra birefringence. Therefore, when using a large polarization state change, it is possible to avoid coloring problems that occur particularly when trying to obtain a high contrast ratio (CR).

Embodiment 3 of the Invention
FIG. 3 shows the configuration of a transflective liquid crystal display device according to Embodiment 3 of the present invention. This liquid crystal display device employs a TN system. As shown in the figure, in this liquid crystal display device, the polarizing layer 1, the retardation layer 2, the front transparent substrate 3, the CF layer 6, the liquid crystal layer 4, the polarizing layer 5, and the reflecting layer 71 from the front (display surface) side. The transparent layer 72 and the rear transparent substrate 8 are disposed. That is, the second embodiment of the invention shown in FIG. 2 is different only in that the positions of the CF layer 6 and the liquid crystal layer 4 are interchanged.

  Also in the liquid crystal display device having such a configuration, as in the first embodiment of the invention, the light A incident from the front surface in the case of the reflective display passes through the liquid crystal layer 4 and is then linearly polarized by the polarizing layer 5. After the conversion, the light is reflected by the reflective layer 71 and enters the liquid crystal layer 4 in a linearly polarized state. Therefore, even in the case of transmissive display, since it is sufficient to enter the liquid crystal layer 4 in a state of linearly polarized light, one retardation layer necessary for obtaining circularly polarized light is omitted and birefringence is achieved. There is no need to use. Therefore, when using a large polarization state change, it is possible to avoid coloring problems that occur particularly when trying to obtain a high contrast ratio (CR).

Example 1.
The transflective liquid crystal display device having the structure shown in FIG. 4 was evaluated.

  First, the structure of the liquid crystal display device will be described with reference to FIG. As shown in the figure, in this liquid crystal display device, the polarizing layer 1, the retardation layer 2, the diffusion layer 10, the front transparent substrate 3, the liquid crystal layer 4, the polarizing layer 5, the CF layer 6, and the reflecting layer 71 from the front side. In addition, a transmissive layer 72 (semi-transmissive / semi-reflective layer 7) and a back-side transparent substrate 8 are disposed. In FIG. 4, 101 is the angle θpp11 of the absorption axis of the polarizing layer 1, 102 is the angle θfp1 of the alignment axis of the phase difference layer 2, and the twist angle θftw1 of the phase difference layer 2, and 104 is the orientation on the front side of the liquid crystal layer 4. The axis angle θlcp1 and the twist angle θlctw1 in the alignment direction, and 105 the angle θpp21 of the absorption axis of the polarizing layer 5, respectively. In the following description, the clockwise direction is “+”, the counterclockwise direction is “−”, and the 12 o'clock direction is 0 °.

  In Example 1, first, a transflective layer 7 made of APC (AgPdCu alloy material) was formed on a back transparent substrate 8 made of a glass substrate. The area ratio between the reflective region and the transmissive region of the semi-transmissive / semi-reflective layer 7 was 8 to 2. A CF layer 6 was formed above the transflective layer 7. Further, the polarizing layer 5 was formed by applying a dye on the CF layer 6 using a slit coater. Further, a transparent conductive film or alignment film made of ITO was formed on the polarizing layer 5.

  On the front-side transparent substrate 3, a transparent conductive film made of ITO, an alignment film, and the like were formed. Thereafter, a liquid crystal cell was formed by sandwiching liquid crystal between the front side transparent substrate 3 and the back side transparent substrate 8.

  Δn · d, which is the product of the distance d between both substrates and the liquid crystal birefringence Δn, was set to 0.84 (μm), and the alignment direction of the liquid crystal was adjusted to twist θlctw1 = −240 ° through the two substrates. Thereafter, the diffusion layer 10 was provided above the liquid crystal cell. Furthermore, a twisted phase difference plate having θftw1 = 240 ° twisted and Δn · d of 0.80 (μm) was disposed on the diffusion layer 10 as the phase difference layer 2. The polarizing layer 1 is disposed above the diffusion layer 10.

  Also, the angle θpp11 of the absorption axis of the polarizing layer 1 is 15 °, the angle θfp1 of the alignment axis of the retardation layer 2 is 15 °, the angle θlcp1 of the alignment axis on the front side of the liquid crystal layer 4 is 120 °, and the absorption of the polarizing layer 5 The shaft angle θpp21 was set to 105 °. Further, a backlight comprising a light source and a light guide plate (not shown) is disposed below the liquid crystal cell.

  In the liquid crystal display device having such a structure, when the backlight is turned on in a dark room, the transmittance is 0.002% and the CIE (x, y) is (0) when no voltage is applied to the liquid crystal layer 4. .230, 0.150). Further, in a state where a predetermined voltage was applied to the liquid crystal layer 4, a bright state with a transmittance of 2.1% and CIE (x, y) of (0.339, 0.404) was displayed.

  Further, when the liquid crystal display device was irradiated with light and measured in a reflection state, the reflectance was 0.002% and the CIE (x, y) was (0.230, when no voltage was applied to the liquid crystal layer 4. 0.150) was displayed. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a bright state was displayed in which the reflectance was 27.5% and CIE (x, y) was (0.339, 0.404). In addition to the configuration shown in FIG. 4, the same characteristics can be obtained if the CF layer 6 is between the reflective layer 71 and the front transparent substrate 3.

  Further, in order to compare with the conventional example, the same experiment was performed by removing the CF layer 6 and the reflective layer 71. Then, when the backlight was turned on in a dark room, a dark state with a transmittance of 0.04% was displayed when no voltage was applied to the liquid crystal layer 4. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a bright state with a transmittance of 34.4% was displayed. FIG. 8 shows the voltage-transmittance characteristics at that time. As shown in the figure, the transmittance was significantly improved while the comparative example had a transmittance of around 25.7%.

  Further, when the CF layer 6 is removed and the liquid crystal display device provided with the reflective layer 71 is irradiated with light and measured in a reflective state, the reflectance is 0.036 in a state where no voltage is applied to the liquid crystal layer 4. % Dark state was displayed. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a bright state with a reflectance of 31.0% was displayed.

Example 2
The transflective liquid crystal display device having the structure shown in FIG. 5 was evaluated.

  First, the structure of the liquid crystal display device will be described with reference to FIG. As shown in the figure, in this liquid crystal display device, the polarizing layer 1, viewing angle compensation layer 11, diffusion layer 10, front side transparent substrate 3, CF layer 6, liquid crystal layer 4, polarizing layer 5 from the front (display surface) side. A reflective layer 71, a transmissive layer 72 (semi-transmissive / semi-reflective layer 7), and a back side transparent substrate 8 are disposed. In FIG. 5, 101 is the angle θpp12 of the absorption axis of the polarizing layer 1, 104 is the angle θlcp2 of the alignment axis on the front side of the liquid crystal layer 4 and the twist angle θlctw2 of the alignment direction, and 105 is the angle of the absorption axis of the polarizing layer 5. θpp22 is shown respectively. In the following description, the clockwise direction is “+”, the counterclockwise direction is “−”, and the 12 o'clock direction is 0 °.

  In Example 2, first, the transflective layer 7 made of APC (AgPdCu alloy material) was formed on the back side transparent substrate 8 made of a glass substrate. The area ratio between the reflective region and the transmissive region of the semi-transmissive / semi-reflective layer 7 was 8 to 2. A polarizing layer 5 was formed by applying a dye above the transflective layer 7 using a slit coater. Further, a transparent conductive film or alignment film made of ITO was formed on the polarizing layer 5.

  On the front transparent substrate 3, a CF layer 6, a transparent conductive film made of ITO, an alignment film, and the like were formed. Thereafter, a liquid crystal cell was formed by sandwiching liquid crystal between the front side transparent substrate 3 and the back side transparent substrate 8.

  Δn · d, which is the product of the distance d between the two substrates and the liquid crystal birefringence Δn, was set to 0.490 (μm), and the alignment direction of the liquid crystal was adjusted to twist θlctw2 = −90 ° between the two substrates. Thereafter, the diffusion layer 10 was provided above the liquid crystal cell.

  Further, the angle θpp12 of the absorption axis of the polarizing layer 1 was set to 45 °, the angle θlcp2 of the alignment axis on the front side of the liquid crystal layer 4 was set to 45 °, and the angle θpp22 of the absorption axis of the polarizing layer 5 was set to 135 °. Further, a backlight comprising a light source and a light guide plate (not shown) is disposed below the liquid crystal cell.

  In the liquid crystal display device having such a structure, when the backlight is turned on in a dark room, the transmittance is 3.6% and the CIE (x, y) is (0) when no voltage is applied to the liquid crystal layer 4. .323, 0.342). Further, when a predetermined voltage was applied to the liquid crystal layer 4, a dark state in which the transmittance was 0.024% and the CIE (x, y) was (0.303, 0.315) was displayed.

  Further, when the liquid crystal display device was irradiated with light and measured in a reflection state, the reflectance was 29.1% and the CIE (x, y) was (0.323, when no voltage was applied to the liquid crystal layer 4. A bright state of 0.342) was displayed. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a dark state in which the reflectance was 24.6% and CIE (x, y) was (0.303, 0.342) was displayed. In addition to the configuration shown in FIG. 5, the same characteristics can be obtained if the CF layer 6 is between the reflective layer 71 and the front transparent substrate 3.

  Further, in order to compare with the conventional example, the same experiment was performed by removing the CF layer 6 and the reflective layer 71. Then, when the backlight was turned on in a dark room, a light state with a transmittance of 36.4% was displayed when no voltage was applied to the liquid crystal layer 4. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a dark state with a transmittance of 0.04% was displayed.

  Further, when the CF layer 6 is removed and the liquid crystal display device provided with the reflection layer 71 is irradiated with light and measured in the reflection state, the reflectance is 32.8 in the state where no voltage is applied to the liquid crystal layer 4. % Light state was displayed. Further, when a predetermined voltage was applied to the liquid crystal layer 4, a dark state with a reflectance of 0.036% was displayed.

Example 3
The backlight is removed from the liquid crystal display devices of Example 1 and Example 2, the light source is disposed on the side surface of the back side transparent substrate 8, and the back side transparent substrate 8 is subjected to a printing process to perform the back side transparent. The substrate 8 was used as a light guide plate. In this case, the light from the light source incident from the side surface of the back side transparent substrate 8 travels inside the transparent substrate while being totally reflected at the interface between air and the transparent substrate (here, glass), and is scattered by the printing unit. . The light scattered by the printing unit is emitted to the front (observer) side. Even in the liquid crystal display device having such a configuration, the same results as those in the first and second embodiments could be obtained.

  Further, in the third embodiment, since it is not necessary to provide a light guide plate, there is an advantage that the number of parts of the liquid crystal display device can be reduced and the size can be reduced.

It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the conventional liquid crystal display device. It is a fragmentary sectional view of the conventional liquid crystal display device. FIG. 3 is a diagram showing voltage-transmittance characteristics of the liquid crystal display device in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing layer 2 Retardation layer 3 Front side transparent substrate 4 Liquid crystal layer 5 Polarizing layer 6 CF layer 7 Transflective layer 8 Back side transparent substrate 10 Diffusion layer 11 Viewing angle compensation layer 12 Polarizing layer

Claims (5)

A liquid crystal display device comprising a liquid crystal layer between a first transparent substrate and a second transparent substrate facing the first transparent substrate,
A first polarizing layer provided on the viewer side of the first transparent substrate;
A second polarizing layer provided between the liquid crystal layer and a second transparent substrate;
A liquid crystal display device comprising: the second polarizing layer; and a transflective layer provided between the second transparent substrate.   2. The liquid crystal according to claim 1, further comprising a retardation layer for converting linearly polarized light emitted from the first polarizing layer into elliptically polarized light between the first polarizing layer and the first transparent substrate. Display device.   The liquid crystal display device according to claim 1, wherein a color filter layer is provided between the first transparent substrate and the second transparent substrate.   4. The liquid crystal display device according to claim 3, wherein the color filter layer is provided between the second polarizing layer and the transflective layer. The liquid crystal display device according to claim 1, wherein the second polarizing layer is formed by a coating process.

Images