JP2011221413A - Liquid crystal display device, production method of liquid crystal display device, and design method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device for performing reflection display of white while having favorable whiteness and securing brightness, and production method and design method thereof.SOLUTION: The retardation of a liquid crystal layer is 0.75 μm or more and 1.01 μm or less, the twist angle of a liquid crystal molecule of the liquid crystal layer is 70° or more and 100° or less, the angle obtained by subtracting the intersection angle between the optical absorption axis of a first polarizing filter and the optical absorption axis of a second polarizing filter from the twist angle is -16° or more and +16° or less, the bisector of the twist angle substantially matches the bisector of the intersection angle, and at least one of the first polarizing filter, the second polarizing filter, and a reflection layer or a semi-reflection layer is a white color system.

Description

  The present invention relates to a liquid crystal display device, a method for producing a liquid crystal display device, and a method for designing a liquid crystal display device.

  Patent Document 1 discloses a liquid crystal display device in which the whiteness of the display screen is improved as compared with the conventional art. In the liquid crystal display device described in Patent Document 1, a reflector having a peak reflectance within a wavelength band of 400 nm to 550 nm is used, and the whiteness of the display screen is improved in the reflective display.

JP 2000-275633 A

  However, in the liquid crystal display device described in Patent Document 1, visible light in a wavelength band other than 400 nm to other than 550 nm becomes dark, so that the reflective display is dark overall.

  The present invention has been made in view of the above problems, and includes a liquid crystal display device capable of performing white reflective display with good whiteness and sufficient brightness, a production method thereof, and a design method thereof. The purpose is to provide.

In order to solve the above problems, a liquid crystal display device according to the first aspect of the present invention provides:
A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A reflective or transflective liquid crystal display device comprising:
The retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less,
The twist angle of the liquid crystal molecules of the liquid crystal layer is 70 ° or more and 100 ° or less,
The angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is -16 ° or more and + 16 ° or less, And the angle bisector at the twist angle and the angle bisector at the intersection angle are substantially coincident,
At least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer is white.

In order to solve the above problems, a method for producing a liquid crystal display device according to the second aspect of the present invention provides:
A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A method for producing a reflective or transflective liquid crystal display device comprising:
A retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less, and a twist angle of liquid crystal molecules of the liquid crystal layer is 70 ° or more and 100 ° or less.
An angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is −16 ° to + 16 °. And the first polarizing filter and the second polarizing filter are arranged so that the angle bisector of the twist angle and the angle bisector of the intersection angle substantially coincide with each other,
At least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer is formed of a white system.

In order to solve the above problems, a method for designing a liquid crystal display device according to a third aspect of the present invention includes:
A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A method of designing a reflective or transflective liquid crystal display device comprising:
The retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less,
The twist angle of the liquid crystal molecules in the liquid crystal layer is set to 70 ° to 100 °,
An angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is set to −16 ° to + 16 °, and The angle bisector at the twist angle and the angle bisector at the intersection angle are substantially matched,
At least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer is white.

  According to the present invention, it is possible to provide a liquid crystal display device capable of performing white reflective display with good whiteness and sufficient brightness, and a production method and a design method thereof.

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention. It is a figure which shows the transmission spectrum of a normal polarizing filter and a white-type polarizing filter. It is a figure which shows the graph of the transmittance | permeability of a liquid-crystal layer. When the liquid crystal display device according to an embodiment of the present invention is viewed from above, the alignment direction of the first alignment film, the alignment direction of the second alignment film, the direction of the absorption axis of the first polarizing filter, and the second polarizing filter It is a figure which shows the relationship of the direction of an absorption axis. When the liquid crystal display device according to an embodiment of the present invention is viewed from above, the alignment direction of the first alignment film, the alignment direction of the second alignment film, the direction of the absorption axis of the first polarizing filter, and the second polarizing filter It is a figure which shows the relationship of the direction of an absorption axis. It is a figure which shows the table | surface of the relationship between the retardation in the liquid crystal display device which concerns on Embodiment 1 of this invention, a twist angle | corner, and a twist angle | corner angle. It is a figure which shows the table | surface of the relationship between the retardation in the liquid crystal display device which concerns on Embodiment 1 of this invention, a twist angle, and the chromaticity coordinate of a display color. It is a figure which shows the table | surface of the relationship between the retardation in the liquid crystal display device which concerns on Embodiment 1 of this invention, a twist angle, and a reflectance. It is a figure which shows the table | surface of the relationship between the retardation in the liquid crystal display device which concerns on Embodiment 1 of this invention, a twist angle, and contrast. It is a figure which shows an example of the performance of a polarizing filter. It is a figure which shows the various conditions of the liquid crystal display device based on each Example etc. which were actually produced. It is a figure which shows the reflection characteristic of the liquid crystal display device which actually produced and which concerns on each Example.

  Embodiments according to the present invention will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment and drawing. It goes without saying that changes (including deletion of components) can be added to the following embodiments and drawings. Further, in the following description, in order to facilitate understanding of the present invention, description of known unimportant technical matters is appropriately omitted.

  In the following description, the front of the display surface of the liquid crystal display device (in the direction of the viewer of the liquid crystal display device) of the predetermined component is referred to as “up”, and the opposite side to the front of the display surface is referred to as “down”. In the drawings, components having similar functions will be described with the same reference numerals. Further, in the drawings, when there are a plurality of similar ones, only a part thereof will be described with reference numerals.

(Configuration of liquid crystal display device)
First, the configuration of the liquid crystal display device 100 according to the present embodiment will be described with reference to FIG.

  The liquid crystal display device 100 according to this embodiment includes a first polarizing filter 110, a liquid crystal element 120, a second polarizing filter 130, a semi-reflective layer 140, and a backlight 150. In FIG. 1, liquid crystal molecules to be described later are schematically drawn. The liquid crystal display device 100 according to the present embodiment is a normally white mode TN (Twisted Nematic) liquid crystal device.

  A liquid crystal element 120 is disposed under the first polarizing filter 110. A second polarizing filter 130 is disposed under the liquid crystal element 120. A semi-reflective layer 140 is disposed under the second polarizing filter 130. A backlight 150 is disposed under the semi-reflective layer 140. Each component is abutted or close to each other, or is fixed to each other.

  The first polarizing filter 110 emits light incident from the front surface side or the back surface side as linearly polarized light along a transmission axis perpendicular to the light absorption axis of the first polarizing filter 110. Hereinafter, the absorption axis of the first polarizing filter 110 is referred to as a first absorption axis. The second polarizing filter 130 emits light incident from the front surface side or the back surface side as linearly polarized light along the transmission axis perpendicular to the light absorption axis of the second polarizing filter 130. Hereinafter, the absorption axis of the second polarizing filter 130 is referred to as a second absorption axis. In the present embodiment, the first polarizing filter 110 and the second polarizing filter 130 are each configured by a polarizing plate.

  The liquid crystal element 120 includes a liquid crystal layer 121, a first substrate 122, and a second substrate 123.

  The liquid crystal layer 121 is sandwiched between the first substrate 122 and the second substrate 123. The liquid crystal layer 121 includes liquid crystal molecules 121a. The first substrate 122 and the second substrate 123 are overlapped and fixed so as to face each other with a predetermined distance between them with a seal member (not shown) interposed therebetween. Liquid crystal (here, nematic liquid crystal) is confined in a sealed space formed by the first substrate 122, the second substrate 123, and the sealing member, and the liquid crystal layer 121 is formed.

  The first substrate 122 includes a first base material 122a, a first electrode 122b, a first insulating film 122c, and a first alignment film 122d.

  The first base material 122a is a transparent substrate (for example, a transparent glass substrate) and transmits light.

  The first electrode 122b is a transparent electrode that transmits light (for example, formed of ITO (indium tin oxide)). The first electrode 122b is formed in a predetermined shape (for example, a shape capable of displaying a number or the like in a segment) on the main surface (the surface on the liquid crystal layer 121 side) of the first base material 122a. The first electrode 122b is formed by a known method (for example, sputtering, vapor deposition, or etching).

  The first insulating film 122c is a film (for example, formed of silicon dioxide) that insulates and protects the first electrode 122b, and is formed on the main surface of the first base material 122a so as to cover the first electrode 122b. Is done.

  The first alignment film 122d is a film in contact with the liquid crystal layer 121 (eg, formed of polyimide). The first alignment film 122d is formed on the first insulating film 122c so as to cover the first insulating film 122c. The first alignment film 122d is rubbed in the direction of the arrow in FIGS. 4 and 5 to form fine grooves.

  The first insulating film 122c and the first alignment film 122d are each formed by a known method (for example, flexographic printing).

  Since the second substrate 123 has substantially the same configuration as the first substrate 122, detailed description thereof is omitted. Here, the first base material 122a corresponds to the second base material 123a. The first electrode 122b corresponds to the second electrode 123b. The first insulating film 122c corresponds to the second insulating film 123c. The first alignment film 122d corresponds to the second alignment film 123d.

  Note that the twist angle of the liquid crystal molecules 121a (the twist angle between the liquid crystal molecules 121a on the substrate 122 side and the liquid crystal molecules 121a on the substrate 123 side) is the alignment direction of the first alignment film 122d (hereinafter referred to as the first alignment direction). And the alignment direction of the second alignment film 123d (hereinafter referred to as the second alignment direction). Here, the alignment direction substantially coincides with the direction in which the groove formed in the alignment film extends. The liquid crystal molecules 121a in contact with the alignment film are aligned so that the longitudinal direction is along the alignment direction when no voltage is applied.

  The first electrode 122b and the second electrode 123b are a pair of electrodes facing each other with the liquid crystal layer 121 interposed therebetween. A voltage is applied to the pair of electrodes, and a voltage is applied to the liquid crystal layer 121. Thereby, the liquid crystal molecules 121a to which the voltage is applied in the liquid crystal layer 121 are arranged so that the longitudinal direction is along the thickness direction (vertical direction) of the liquid crystal layer 121. For this reason, the polarization direction of the light passing through the liquid crystal layer 121 is not changed, and black display is performed in the region where the voltage is applied.

  The semi-reflective layer 140 reflects light from above and transmits light from below, and is configured by, for example, a half mirror made of aluminum or the like. In the present embodiment, the semi-reflective layer 140 is directly formed on the lower surface of the polarizing plate constituting the second polarizing filter 130. The semi-reflective layer 140 may be formed of a semi-reflective plate that is separate from the second polarizing filter 130.

  The backlight 150 emits predetermined light in a planar shape to illuminate the liquid crystal element 120 and the like. The backlight 150 is configured by a combination of a light emitting diode and a light guide member, for example. The backlight 150 is used when the liquid crystal display device 100 performs transmissive display.

  In the liquid crystal display device 100, the twist angle is about 90 °. For this reason, when no voltage is applied, the polarization direction of the light passing through the liquid crystal layer 121 is inclined by about 90 °. The first orientation direction and the first absorption axis are substantially the same direction. Further, the second alignment direction and the second absorption axis are substantially the same direction. As described above, when external light is incident on the liquid crystal display device 100 in a region where no voltage is applied, the external light is polarized into linearly polarized light by the first polarizing filter 110 and then the polarization direction is changed by the liquid crystal element 120. Then, the light passes through the second polarizing filter 130 and is reflected by the semi-reflective layer 140. The linearly polarized light reflected by the semi-reflective layer 140 passes through the second polarizing filter 130 again, the polarization direction is changed by the liquid crystal element 120, passes through the first polarizing filter 110, and enters the human eye. As a result, white display is performed.

  The inventor of the present application, in the liquid crystal display device 100 configured as described above, the conditions of the liquid crystal (retardation of the liquid crystal layer 121, the twist angle of the liquid crystal molecules 121a), the polarization filter conditions (the first polarization filter 110 and the second polarization). It has been found that by setting the characteristics of the filter 130, the direction of the absorption axis, and the like to predetermined conditions, it is possible to configure the liquid crystal display device 100 that performs white reflective display with good whiteness and brightness. . Here, the retardation of the liquid crystal layer 121 is a product (Δn · d) of the thickness d of the liquid crystal layer and the refractive index anisotropy of the liquid crystal Δn.

  In the transmissive display using the backlight 150, the whiteness of the white display can be corrected by combining the backlight 150 or the like with a correction plate or the like for correcting the color of the emitted light. Will be described.

  Here, each condition will be described.

  In the conventional liquid crystal display device, the white displayed is greenish. This is because, like the transmission spectrum (dotted line) of the normal polarizing filter used in the conventional liquid crystal display device shown in FIG. 2, the normal polarizing filter has a low blue light transmittance. The reason is that the light of the blue component of the light (light entering the user's eyes) emitted in the reflective display becomes weak when the light passes through the polarizing filter four times in the reflective display.

  Conventionally, based on the Gooch-Tarry equation, the retardation value in the vicinity of the first peak of transmittance at a green wavelength (for example, 550 nm) that is highly visible to human eyes is used as the retardation value of the liquid crystal layer. This is also the reason why the white displayed is greenish.

  Here, FIG. 3 is a diagram showing the relationship between the transmittance of the liquid crystal layer (when no voltage is applied) and retardation (unit: μm) for each wavelength when the twist angle is 90 °. 3 is a relationship determined by Expression 1 in 3 (an expression determined by the Gooch-Tarry expression). For example, conventionally, in FIG. 3, the retardation value near the first peak of transmittance at 550 nm has been adopted (see double-headed arrow). In Expression 1, μ is μ = (2 × Δn · d / λ), λ is the wavelength of each light, and in FIG. 3, λ is 450 nm, 550 nm, or 650 nm. In Equation 1, θ is a twist angle, and is π / 2 in FIG. If the twist angle is different, the shape of the graph in FIG. 3 also changes.

  Here, when specifying each of the above conditions, considering the graph of FIG. 3 in which the angle of the twist angle is 90 °, the retardation of the liquid crystal layer 121 is the transmittance of light having a blue wavelength (450 nm). The retardation value (near 0.75 to 1.00 μm) corresponding to the vicinity of the second peak (for example, see the double-headed arrow in FIG. 3) is taken as the value. In addition, since the transmittance of the red wavelength (650 nm) is too bad at the first peak of the light having the blue wavelength, the retardation value corresponding to the first peak cannot be adopted. In addition, regarding the peak after the third peak of the transmittance of light having a blue wavelength, the retardation value is increased, and the thickness of the liquid crystal layer 121 is increased. In this case, since the response speed at the time of voltage application of the liquid crystal layer 121 is slow, the retardation value corresponding to the peak after the third peak cannot be adopted.

  In addition, if the twist angle is far from 90 °, the contrast between the black display and the white display may decrease, the reflective display may become dark, or the whiteness of the white display may deteriorate. Can be considered. Therefore, the twist angle is set to 60 ° to 110 °.

  Furthermore, in the following, in order to reduce the absorption of the blue component of light, the first polarizing filter 110 and the second polarizing filter 130 are made into a white polarizing filter. Details of the white polarizing filter will be described later.

  Based on the above, first, the retardation value is set to a predetermined value within 0.46 μm to 1.08 μm, and the twist angle is set to a predetermined value within 60 ° to 110 °. Then, for each predetermined value, the chromaticity coordinate (hue) of the display color in the reflective display is in a white range, and within x = 0.305 ± 0.13, y = 0.325 ± 0.05 (CIE table) The direction of the first absorption axis of the first polarizing filter 110 and the direction of the second absorption axis of the second polarizing filter 130 that enter the color system) are determined. As the chromaticity coordinates are closer to x = 0.305 and y = 0.325, the whiteness is better, that is, the white display is whiter.

  Here, the direction of the absorption axis will be described with reference to FIGS. 4 and 5 show the relationship between the first absorption axis, the second absorption axis, and the twist angle when the liquid crystal display device 100 is viewed from above. The direction of the first absorption axis (solid double-pointed arrow) and the direction of the second absorption axis (solid double-pointed arrow) are crossing angles that are angles at which the first absorption axis and the second absorption axis intersect from the twist angle θ1. Is defined by a value obtained by subtracting the angle θ2.

  The twist angle is defined by the first alignment direction that is the alignment direction (dotted arrow) of the first alignment film 122d and the second alignment direction that is the alignment direction (dotted arrow) of the second alignment film 123d. The crossing angle is an angle that is open in the same direction as the twist angle among the four corners formed by the first absorption axis and the second absorption axis, and is a bisector (one-dot chain line) of the crossing angle. The twist angle bisector is substantially coincident (including a perfect coincidence and a substantially coincidence including an error).

  FIG. 4 shows a case where the twist angle θ1 is larger than the crossing angle θ2. In this case, a value obtained by subtracting the angle θ2 from the angle θ1 is a positive value. FIG. 5 shows a case where the twist angle θ1 is smaller than the crossing angle θ2. In this case, the value obtained by subtracting the angle θ2 from the angle θ1 is a negative value. The absolute value of the value obtained by subtracting the angle θ2 from the angle θ1 is the absolute value of the angle θ3 (the inclination angle of the second absorption axis with respect to the second alignment direction) and the angle θ4 (the inclination angle of the first absorption axis with respect to the first alignment direction). The sum of absolute values of The values of the angles θ3 and θ4 are positive values (θ4 in FIG. 4 and θ3 in FIG. 5) and are clockwise when the inclination is counterclockwise (counterclockwise) when viewed from above the liquid crystal display device 100. If it is (clockwise), a negative value (θ3 in FIG. 4 and θ4 in FIG. 5) is set.

  Thus, the direction of the first absorption axis and the direction of the second absorption axis are defined by the value obtained by subtracting the angle θ2 from the angle θ1. For this reason, if the value (difference value) which subtracted angle (theta) 2 from angle (theta) 1 is adjusted, the direction of a 1st absorption axis and the direction of a 2nd absorption axis can be prescribed | regulated. By changing the direction of the first absorption axis and the direction of the second absorption axis, the inclination between the direction of the first absorption axis and the first alignment direction is adjusted, and the direction of the second absorption axis and the second alignment direction are adjusted. Since the inclination is adjusted, the white color of the reflective display changes.

  In FIG. 6, the retardation value is one of 0.46, 0.59, 0.66, 0.75, 0.85, 0.94, 1.01, and 1.08 μm, and the twist angle is When the angle is any one of 60, 70, 80, 90, 100, and 110 °, the difference value adopted is shown. FIG. 7 shows the chromaticity coordinates of the display color of the white display in the reflective display at this time. Show.

  In FIG. 6, the difference value adopted when the retardation value is any one of the above values (vertical direction) and the twist angle is any one of the above values (horizontal direction) is shown in each column. It is shown. Referring to FIG. 6, for example, when the twist angle is 80 ° and the retardation is 0.75 μm, the difference value is 0 °. For example, when the twist angle is 90 ° and the retardation is 0.85 μm, the difference value is 10 °.

  In FIG. 7, the retardation value is set to one of the above values (vertical direction), the twist angle is set to any one of the above values (horizontal direction), and the difference value of FIG. 6 is adopted. The chromaticity coordinates (hereinafter simply referred to as chromaticity coordinates) of the display color of the white display in the reflective display at that time are shown in each column. Each column in FIG. 6 corresponds to each column in FIG. 7, and the chromaticity coordinates when the difference values in each column in FIG. 6 are adopted are described in each column in FIG. For example, if the twist angle is 80 °, the retardation is 0.75 μm, and the difference value is 0 °, the chromaticity coordinates at this time are x = 0.314 and y = 0.329. .

  Each such value can be derived by a predetermined simulation software (for example, Shintec Corporation, “LCD MASTER”). Here, first, the angle of the twist angle and the retardation value are determined, and the difference value is changed based on this value, and the chromaticity coordinates are x = 0.305 ± 0.13, y = 0.325 ± 0. By calculating the difference value and the chromaticity coordinates that fall within .05, the twist angle, the retardation value, the difference value, and the chromaticity coordinates are obtained. Note that the column “-” in FIG. 7 indicates the chromaticity falling within the above range regardless of the difference value when the retardation value and the twist angle value corresponding to this column are taken. Indicates that there are no conditions for obtaining coordinates. In addition, for the blank, the twist angle and the retardation value are not simulated.

  FIG. 8 shows the reflectance in white display when the twist angle, retardation value, and difference value shown in FIG. 6 are taken (this can also be calculated by the simulation software). In FIG. 8, the retardation value is set to one of the above values (vertical direction), the twist angle is set to any one of the above values (horizontal direction), and the difference value shown in FIG. 6 is adopted. In each column, the reflectance of external light in the reflective display of the liquid crystal display device 100 is shown. The reflectance is the ratio of the light emitted from the liquid crystal display device 100 to the light incident on the liquid crystal display device 100 in the reflective display, and is the ratio when the reflection in the air is 100%. If the reflectance is high, the white display becomes brighter. Therefore, a larger reflectance is better.

  Each column in FIG. 6 corresponds to each column in FIG. 8, and the chromaticity coordinates when the difference values in each column in FIG. 6 are adopted are described in each column in FIG. For example, if the twist angle is 80 °, the retardation is 0.75 μm, and the difference value is 0 °, the reflectance at this time is 24.2%.

  FIG. 9 shows the contrast when the twist angle, retardation value, and difference value shown in FIG. 6 are taken (this can also be calculated by the simulation software). In FIG. 9, the retardation value is one of the above values (vertical direction), the angle of the twist angle is one of the above values (horizontal direction), and the difference value of FIG. 6 is adopted. Each column shows the contrast in the reflective display of the liquid crystal display device 100 when it is done. The contrast is a value of the ratio of the reflectance in the black-displayed area and the white-displayed area (for example, the background) in the liquid crystal display device 100, and the luminance of the black-displayed reflectance is 1. If the contrast is large, the display by the liquid crystal display device 100 is easy to see. Therefore, the higher the contrast, the better.

  Each column in FIG. 6 corresponds to each column in FIG. 9, and the chromaticity coordinates when the difference values in each column in FIG. 6 are adopted are described in each column in FIG. For example, if the twist angle is 80 °, the retardation is 0.75 μm, and the difference value is 0 °, the contrast at this time is 90.

  With reference to the tables of FIGS. 6 to 9, the angle of the twist angle, the retardation value, and the difference value when the reflectance, contrast, and chromaticity coordinates take good values are known. Thereby, the manufacturing conditions of the liquid crystal display device 100 in which a good white display is performed can be understood.

  6 to 9, for example, the retardation value is set to any value between 0.75 μm and 1.01 μm, the twist angle is set to a value between 70 ° and 100 °, and the difference value is set. Is set to −16 ° or more and + 16 ° or less, the liquid crystal has good white display whiteness (see the chromaticity coordinates) in the reflective display, and the brightness of the white display is ensured without low reflectivity. A display device 100 is obtained. Further, the liquid crystal display device 100 in which the contrast in the reflective display is not low can be obtained. In the above range, there is a condition that at least one of reflective display and contrast is particularly excellent. The above range was set such that, at a minimum, whiteness x = 0.305 ± 0.13, y = 0.325 + 0.05, contrast ≧ 20, and reflectance ≧ 20.0%. In such a range, the whiteness is good, the brightness is secured, and the minimum contrast is secured. In particular, the retardation value is preferably 0.85 μm or more and 1.01 μm or less. The twist angle is desirably 80 ° or more and 90 ° or less. When the difference value exceeds the above range, the inclination of the first alignment direction with respect to the light transmission axis, orthogonal to the first absorption axis, and the second alignment direction with respect to the light transmission axis, orthogonal to the second absorption axis. Since the inclination of is increased, it is considered undesirable.

  In the above description, the first polarizing filter 110 and the second polarizing filter 130 are white polarizing filters. This is because the first polarizing filter 110 and the second polarizing filter 130 also reduce the absorption of the blue component of light. The light transmission characteristics of the white polarizing filter are shown in the solid line graph of FIG. As shown by the solid line graph in FIG. 2, the white polarizing filter has better transmittance of blue component light than the normal polarizing filter. There are known white polarizing filters. Here, for example, the white polarizing filter has a hue of external light (L * a * b * color system) transmitted through a single white polarizing filter or two parallel absorption axes as a *, b *. It is assumed that each value is −2.0 or more and +2.0 or less. In the above simulation, the first polarizing filter 110 and the second polarizing filter 130 are polarizing filters having hues of a * = − 0.9 and b * = 1.2, respectively.

  10 has a normal polarizing filter (hue a * = − 1.4, b * = 4.0) having the transmission spectrum (dotted line graph line) of FIG. 2 and the transmission spectrum (solid line graph) of FIG. The performance of a white polarizing filter (hue a * = − 0.9, b * = 1.2) is shown. In FIG. 10, when a normal polarizing filter or a white polarizing filter is used as the first polarizing filter 110 and the second polarizing filter 130, various conditions (retardation, twist angle, crossing angle ( The details show the optical characteristics (reflectance, chromaticity coordinates, contrast (see above for details)) in the reflective display of the liquid crystal display device 100 when a predetermined value is adopted as above))). The relationship between the values is calculated by the simulation software. In FIG. 10, “> 500” indicates that the value exceeds 500.

  According to FIG. 10, when the white polarizing filter is used for the first polarizing filter 110 and the second polarizing filter 130 (see the lower stage), the retardation, twist angle, and crossing angle are any cases. Even in such a case, the contrast is inferior, but the reflectance and chromaticity coordinates in white display are excellent. Therefore, in this embodiment, in order to improve the whiteness and brightness of white display, the first polarizing filter 110 and the second polarizing filter 130 are white polarizing filters.

  Next, a conventional liquid crystal display device, the liquid crystal display device 100 according to the present embodiment, and a liquid crystal display device in which the first polarizing filter 110 and the second polarizing filter 130 are normal polarizing filters are actually created. The performance of each liquid crystal display device is compared.

  FIG. 11 shows various conditions (retardation, etc.) of a conventional liquid crystal display device (having the same structure as the liquid crystal display device 100) actually produced, and four liquid crystal display devices 100 in which various conditions are changed (Examples 1 to 4). The various conditions in 4) and various conditions (comparative examples) of the liquid crystal display device in which the first polarizing filter 110 and the second polarizing filter 130 are normal polarizing filters are shown. The unit of the thickness d and retardation of the liquid crystal layer is μm. The unit of the angle of the twist angle, the angle of the crossing angle, and the angle of the twisting angle−the angle of the crossing angle is °. Moreover, the polarizing plate was employ | adopted about the 1st polarizing filter and the 2nd polarizing filter. As a 1st polarizing filter, in the past and the comparative example, the polarizing plate of SKN-18243T made from Polatechno Co., Ltd. was used. Moreover, as a 2nd polarizing filter, the polarizing plate (with a semi-reflective layer) of SKN-18243HN-31 made from Polatechno Co., Ltd. was used in the conventional and comparative examples. In Examples 1 to 4, a SKW-18245T white polarizing plate (white polarizing plate) manufactured by Polatechno Co., Ltd. was used as the first polarizing filter. In Examples 1 to 4, a white polarizing plate (with a semi-reflective layer) of SKW-18245N-31 manufactured by Polatechno Co., Ltd. was used as the second polarizing filter.

  FIG. 12 shows the reflection characteristics (consisting of the above-described reflectance, chromaticity coordinates, and contrast, see above for each item) of each liquid crystal display device of FIG. In any of the liquid crystal display devices 100 according to the first to fourth embodiments, the whiteness of white display is good as can be seen from the chromaticity coordinates as compared with the conventional and comparative examples. In addition, the liquid crystal display devices 100 according to Examples 1 to 4 are inferior in contrast to the conventional and comparative examples, but the reflectance is better than that of the comparative example and is not too low. However, since Example 1 has a relatively low contrast, Examples 2 to 4 have better reflection characteristics. Furthermore, when the chromaticity coordinates and contrast are taken into consideration, the reflection characteristics of Example 3 are preferable. The reflectance, hue (chromaticity coordinates) and contrast were measured by a method using a ring light source and a reflection colorimeter (Yokogawa Meter & Instruments Co., Ltd.) (20 ° incidence / 0 ° measurement).

  As described above, the retardation value is set to one of 0.75 μm to 1.01 μm, the twist angle is set to 70 ° to 100 °, and the difference value is −16 ° to +16. The liquid crystal display device 100 in which the first polarizing filter 110 and the second polarizing filter 130 are white polarizing filters has a good white display whiteness (see the chromaticity coordinates) in the reflective display. The reflectance is not low and the brightness of white display is ensured. Further, the liquid crystal display device 100 in which the contrast in the reflective display is not low can be obtained. In addition, good contrast may be obtained as appropriate within the above range. In particular, when the retardation value is 0.85 μm or more and 1.01 μm or less, whiteness, reflectance, and contrast are improved. Further, when the twist angle is not less than 80 ° and not more than 90 °, whiteness, reflectance, and contrast are improved.

  In the above description, the white polarizing filter is adopted for both the first polarizing filter 110 and the second polarizing filter 130. However, the above effect can be obtained to some extent even if only one of them is white. The semi-reflective layer 140 may be a reflective layer. In this case, the backlight 150 is only unnecessary, and the basic configuration is not changed. Such a liquid crystal display device is of a reflective type. The semi-reflective layer 140 or the reflective layer may be white. In this case, for the reflected light, the absorption of the blue component of the light is suppressed. However, in this way, the semi-reflective layer 140 and the reflective layer that color the reflected light may be difficult to form, and it is better to make the polarizing filter white. Moreover, since the absorption of the blue component of the light in a polarizing filter is reduced by making a polarizing filter into a white system, it is better for a polarizing filter to be a white system. Thereby, the whiteness in the reflective display of the white display is improved.

100 liquid crystal display device 110 first polarizing filter 120 liquid crystal element 121 liquid crystal layer 121a liquid crystal molecule 122 first substrate 122a first base material 122b first electrode 122c first insulating film 122d first alignment film 123 second substrate 123a second base material 123b Second electrode 123c Second insulating film 123d Second alignment film 130 Second polarizing filter 140 Semi-reflective layer

Claims (5)

A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A reflective or transflective liquid crystal display device comprising:
The retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less,
The twist angle of the liquid crystal molecules of the liquid crystal layer is 70 ° or more and 100 ° or less,
The angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is -16 ° or more and + 16 ° or less, And the angle bisector at the twist angle and the angle bisector at the intersection angle are substantially coincident,
At least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer is white.
A liquid crystal display device characterized by the above. The retardation of the liquid crystal layer is 0.85 μm or more and 1.01 μm or less.
The liquid crystal display device according to claim 1. The twist angle of the liquid crystal layer is not less than 80 ° and not more than 90 °.
The liquid crystal display device according to claim 1 or 2. A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A method for producing a reflective or transflective liquid crystal display device comprising:
A retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less, and a twist angle of liquid crystal molecules of the liquid crystal layer is 70 ° or more and 100 ° or less.
An angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is −16 ° to + 16 °. And the first polarizing filter and the second polarizing filter are arranged so that the angle bisector of the twist angle and the angle bisector of the intersection angle substantially coincide with each other,
Configuring at least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer in a white system;
A method for producing a liquid crystal display device. A first polarizing filter; a liquid crystal element positioned below the first polarizing filter; a second polarizing filter positioned below the liquid crystal element; and a reflective layer or semi-reflective layer positioned below the second polarizing filter The liquid crystal element includes a first alignment film positioned on the upper side, a second alignment film positioned on the lower side, and a liquid crystal layer positioned between the first alignment film and the second alignment film. A method of designing a reflective or transflective liquid crystal display device comprising:
The retardation of the liquid crystal layer is 0.75 μm or more and 1.01 μm or less,
The twist angle of the liquid crystal molecules in the liquid crystal layer is set to 70 ° to 100 °,
An angle obtained by subtracting the angle of the intersection angle between the light absorption axis of the first polarizing filter and the light absorption axis of the second polarizing filter from the twist angle is set to −16 ° to + 16 °, and The angle bisector at the twist angle and the angle bisector at the intersection angle are substantially matched,
At least one of the first polarizing filter, the second polarizing filter, and the reflective layer or the semi-reflective layer is a white system,
A method for designing a liquid crystal display device.

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