JP2000347179A - Color filter for transmissive liquid crystal display device and transmissive liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of reflected complementary color light due to external light in a color filter consisting of a selective transmissive and reflective liquid crystal layer. SOLUTION: This color filter 14 for a trasmissive liquid crystal display device 10 is composed of a selective transmissive and reflective liquid crystal layer 14A, for example, consisting of a cholesteric liquid crystal layer, and a colored layer 14B arranged on the external light incident side and colored with the same color as the light passing through the selective transmissive and reflective liquid crystal layer 14A. The light with a color other than the same color as the transmitted light is absorbed by the colored layer 14B before the external light is made incident on the selective transmissive and reflective liquid crystal layer 14A, thereby preventing the generation of reflected complementary color light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transmissive liquid crystal display device, and more particularly to a transmissive liquid crystal display device using a selective transmission / reflection type color filter.

[0002]

2. Description of the Related Art In a transmission type color liquid crystal display device, a backlight light is irradiated from behind a liquid crystal cell, and light transmitted through the liquid crystal cell or light before transmission is emitted from a liquid crystal panel surface through a color filter. , Color display.

[0003] As such a liquid crystal display device, there is a device in which a cholesteric film in which cholesteric liquid crystal is dispersed as a color filter is arranged on the light incident side of a liquid crystal cell, as disclosed in, for example, JP-A-9-318807. is there.

[0004] This color filter has excellent performance in luminance and color purity as compared with a color filter using a conventional pigment or dye. In particular, the use of an ultraviolet-curable cholesteric liquid crystal, which changes the wavelength of the selectively reflected light depending on the temperature and can maintain the liquid crystal state by irradiating ultraviolet rays, has an advantage that it can be easily manufactured as compared with the related art.

A cholesteric liquid crystal as described above, and
The chiral nematic liquid crystal has a property that the director spirally changes spatially in addition to the long-range alignment order of the liquid crystal molecular axis. That is, in a plane parallel to the liquid crystal molecular axis, the liquid crystal has the same alignment order as the nematic phase,
When moving to the adjacent plane, the local orientation direction is slightly rotated, so that the local orientation direction is successively formed into a spiral structure.

On the other hand, natural light can be divided into right-handed circularly polarized light and left-handed circularly polarized light. A cholesteric liquid crystal or a chiral nematic liquid crystal emits light of both the right-handed and left-handed components in parallel to the helical axis of the liquid crystal. When incident, reflects only the circularly polarized light component in the same rotation direction as the liquid crystal twist direction,
There is a characteristic that the other circularly polarized light component is transmitted.

At this time, since the phase of the reflected light does not change with respect to the incident light, the polarization direction before and after the incident of the reflected light is unchanged, and the wavelength of the reflected light is the twist of the cholesteric liquid crystal or the chiral nematic liquid crystal. It changes according to the pitch of. This pitch varies depending on the amount of a chiral agent that generates a twisting force in the liquid crystal and an appropriate external field (for example, temperature, electric field, magnetic field, etc.).

Accordingly, by controlling the above parameters in the visible range, it is possible to form transmitted light of red, green and blue, and to reflect light other than the transmitted light toward the light source. By reusing, the luminance can be set higher than that of the conventional color filter.

[0009]

However, when the above-mentioned color filter made of cholesteric liquid crystal or chiral nematic liquid crystal is used for a liquid crystal display, the backlight light from the back can be turned on / off with good contrast. Although it is possible, external light incident from the observation side is reflected by the color filter at wavelengths other than the wavelength at which the light is transmitted (complementary light). .

In this case, there is no problem when the use environment of the liquid crystal display is dark. However, in a bright environment, there is a problem that the color display on the display surface is disturbed by the color of the reflected light, thereby lowering the contrast. .

The present invention has been made in view of the above-mentioned conventional problems, and is a transmission type liquid crystal display device capable of obtaining accurate color display and high contrast on a display surface even in a bright place where there is a lot of external light. To provide a color filter and a transmission type liquid crystal display device.

[0012]

According to the present invention, a light-transmitting substrate is disposed on a light-transmitting substrate by patterning at least corresponding to each of red, green, and blue, and a wavelength of the corresponding color is provided. Of the light, selectively transmissive reflection liquid crystal layer composed of one of cholesteric liquid crystal or chiral nematic liquid crystal that transmits only one circularly polarized light of right-handed circularly polarized light or left-handed circularly polarized light, and reflects the other circularly polarized light and light of a wavelength not corresponding thereto. The above object is attained by a color filter for a transmission type liquid crystal display device having a colored layer of the same color as transmitted light formed on the outside light incident side of the selective transmission / reflection liquid crystal layer.

In the color filter for a liquid crystal display, the coloring layer may be made of a light transmitting resin colored by dispersing a pigment or a dye.

Further, the invention of a transmission type liquid crystal display device comprises a backlight device for emitting backlight from a light emitting surface, a color filter arranged on the light emitting surface side of the backlight device, and a light emitting device of the color filter. Placed on the side,
A liquid crystal cell that shifts or does not shift the phase of polarized light transmitted by ON / OFF of an applied voltage and controls the amount of transmitted light by a voltage; and one of the liquid crystal cell on the light emitting surface side or between the color filter and the liquid crystal cell. A 波長 wavelength plate that shifts the phase of transmitted light by ４ wavelength; and a 位置 wavelength plate disposed on the light output surface side of the liquid crystal cell and on the light output surface side of the ４ wavelength plate. A linearly polarizing plate that transmits linearly polarized light emitted from the one at the time of ON, and blocks linearly polarized light when no voltage is applied, wherein the color filter has at least red light on the light transmitting substrate. , Green, and blue are arranged in a pattern corresponding to each color, among the wavelength light of the corresponding color, transmit only one circularly polarized light of right-handed circularly polarized light or left-handed circularly polarized light, and the other circularly polarized light and not correspondingly Cholester reflecting wavelength light Characterized by having a selective transmission / reflection liquid crystal layer composed of one of a transparent liquid crystal and a chiral nematic liquid crystal, and a colored layer of the same color as the transmitted light formed on the external light incident side of the selective transmission / reflection liquid crystal layer. The above object is achieved by a transmissive liquid crystal display device described above.

According to the present invention, the color filter for the transmission type liquid crystal display device comprises: a selective transmission / reflection liquid crystal layer comprising one of cholesteric liquid crystal and chiral nematic liquid crystal;
Since it is composed of the transmitted light formed on the external light incident side of the selective transmission and reflection liquid crystal layer and the colored layer of the same color, even when used in a bright environment with a lot of external light, the incident external light is selectively transmitted. The backlight light that is absorbed by the coloring layer before reaching the reflective liquid crystal layer and that has passed through the color filter is rarely absorbed by the coloring layer. The adverse effects of the above can be reduced.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a transmissive liquid crystal display device 10 according to an embodiment of the present invention is a backlight device that emits backlight light including wavelength lights of red, green, and blue colors. 12 and patterned for each pixel, the red,
A selective transmission / reflection type color filter 14 that transmits only light of the corresponding wavelengths of green and blue and reflects the other light, and further includes a circularly polarized light separator disposed facing the light exit surface of the backlight device 12. A film 16, the color filter 14, the liquid crystal cell 20, a quarter-wave plate 22, and a linear polarizer 24 are laminated in this order.

The color filter 14 and the liquid crystal cell 20
Is disposed between the pair of glass substrates 18A and 18B.

The backlight device 12 is composed of, for example, a thin-film-shaped electroluminescence cell sandwiched between transparent resin sheets having transparent electrodes, and has, on its back side (the lower side in FIG. 1), a metal thin film, for example. The reflection layer 12 </ b> A is disposed.

The reflection layer 12A reflects, for example, a right-handed circularly polarized light component emitted from the electroluminescence cell and reflected by the circularly polarized light separating film 16 (described later) in the direction of the circularly polarized light separating film 16 again. The light utilization factor is improved by inverting the phase of the component or making the component non-polarized, and all or part of the component is a left-handed circularly polarized component that can pass through the circularly polarized light separating film 16.

Here, in FIG. 1, symbols R and L indicate right-handed circularly polarized light and left-handed circularly polarized light, respectively. Also, "← →",
“·” (See FIG. 3) indicates an electric field vibration vector of linearly polarized light, “← →” indicates an in-plane direction of the paper, and “•” indicates a direction perpendicular to the paper surface.

In this embodiment, the circularly polarized light separating film 16 transmits the left-handed circularly polarized light L and reflects the right-handed circularly polarized light R, and comprises three or more birefringent films. And a 更 に wavelength layer is further laminated thereon. The film having birefringence as described above can be obtained by stretching a material having in-plane birefringence such as a polycarbonate-based resin, a polyester-based resin, and a polyvinyl alcohol-based resin.

Further, the circularly polarized light separating film includes:
By using cholesteric liquid crystal and giving this cholesteric liquid crystal a spectrum, in all visible light regions,
The right-handed circularly polarized light R can be reflected.

As shown in FIG. 2, the color filter 14 comprises a selective transmission / reflection liquid crystal layer 14A and a colored layer 14B formed on the light exit surface side. Reference numeral 14C in FIG. 2 indicates a black matrix.

The selective transmission / reflection liquid crystal layer 14A is composed of a cholesteric liquid crystal layer or a chiral nematic liquid crystal layer laminated on the glass substrate 18A. The transmitted left-handed (or right-handed) circularly polarized light is adapted to reflect the corresponding wavelength light other than red, green, and blue.

The coloring layer 14B is patterned for each pixel similarly to the selective transmission / reflection liquid crystal layer 14A, and is colored with a pigment or dye of the same color as the light transmitted through the corresponding selective transmission / reflection liquid crystal layer 14A. It is formed by being dispersed in a curable transparent resin.

The selective transmission / reflection layer 14A of the color filter 14 may be made of, for example, a cholesteric film or a chiral nematic film as disclosed in JP-A-9-318807.

FIG. 1 shows four pixels in the liquid crystal cell 20 and respective parts corresponding thereto. Further, as shown in FIG.
Each pixel has R, G, and B regions, and each region is light in a respective wavelength region, transmitting only left-handed circularly polarized light L,
It reflects left-handed circularly polarized light L in another wavelength region.

The liquid crystal cell 20 has a birefringence control (EC
B), which controls the birefringence of the liquid crystal layer in the liquid crystal cell 20 by applying an electric field,
There are N type, PAN type, HAN type, etc., and the phase shift amount of transmitted light is 0 or π by ON / OFF of applied voltage.
It is to be.

Accordingly, when the applied voltage is ON, the incident left-handed circularly polarized light L has a phase shift of 0, and thus is transmitted as it is, and when OFF, the phase shift is π as shown in FIG. Therefore, the light is converted into right-handed circularly polarized light R and emitted.

The quarter-wave plate 22 is a phase plate made of a polymer material such as polyimide, and has a function of converting incident circularly polarized light into linearly polarized light or vice versa. Therefore, the quarter-wave plate 22 converts the left-handed circularly polarized light L and the right-handed circularly polarized light R incident from the liquid crystal cell 20 into two types of linearly polarized light whose polarization planes are orthogonal to each other.

The linear polarizing plate 24 is arranged so that the polarization direction of the transmitted light coincides with the direction of the electric field vibration vector of the linearly polarized light “← →” obtained by converting the left-handed circularly polarized light L.

In the transmission type liquid crystal display device 10, as for the unpolarized light emitted from the backlight device 12, only the left-handed circularly polarized light L passes through the circularly polarized light separating film 16 and enters the color filter 14. .

In the color filter 14, in the R, G, and B regions of each pixel of the selective transmission / reflection liquid crystal layer 14A, only light in the corresponding wavelength region is transmitted, and light in other wavelength regions is reflected. You.

The coloring layer 14B is patterned into R, G, and B in the same manner as the selective transmission / reflection liquid crystal layer 14A, and is colored in the same color as the selective transmission / reflection liquid crystal layer 14A. The light of each color transmitted through
This is transmitted without being absorbed, and enters the liquid crystal cell 20.

In the liquid crystal cell 20, an applied voltage O
In the state of N, the incident left-handed circularly polarized light L is transmitted as it is and enters the quarter-wave plate 22, where the phase of the light is 1 /
The light is converted into linearly polarized light “← →” by being shifted by four wavelengths, and emitted from the linearly polarizing plate 24 as display light. At this time, the transmitted light intensity and the display light intensity of the liquid crystal cell 20 increase with the applied voltage.

On the other hand, as shown in FIG.
When the applied voltage of 0 is OFF, the phase of the transmitted light is π
Since the light is shifted, the incident left-handed circularly polarized light L is converted to right-handed circularly polarized light R, and is further converted into “•” linearly polarized light by the quarter-wave plate 22, which passes through the linearly polarizing plate 24. Cannot be performed, so that the display becomes dark.

When the use environment of the transmission type liquid crystal display device 10 is bright and external light is large, external light enters through the linear polarizer 24, the 波長 wavelength plate 22 and the liquid crystal cell 20, and the external light enters the color filter 14. To reach.

In the color filter 14, there is a colored layer 14B on the external light incident side, and the colored layer 14B has the same color as that of the light transmitted through the selective transmission / reflection liquid crystal layer 14A. Only light of the same wavelength is transmitted, and the others are absorbed.

The light transmitted through the colored layer 14B is also transmitted through the selective transmission / reflection liquid crystal layer 14A of the same color.

Therefore, the external light is selectively transmitted and reflected by the liquid crystal layer 14A.
In this case, reflected light of complementary colors does not occur, and a display with higher contrast can be obtained even in a bright place.

The coloring layer 14B is formed by dispersing a pigment in a light-transmitting resin and coloring it. However, the present invention is not limited to this.
Any material may be used as long as it is colored in the same color as the light transmitted through A.

The quarter-wave plate 22 is used for the liquid crystal cell 20.
And the linear polarizing plate 24, but may be disposed between the color filter 14 and the liquid crystal cell 20. In this case, the liquid crystal cell 20 is of a type that controls the direction of the plane of polarization of linearly polarized light.

[0044]

EXAMPLE An example of the above color filter will be described in detail.

First, in order to form a cholesteric liquid crystal layer as a selective transmission / reflection liquid crystal layer, a black pigment-dispersed photocurable resin is applied in a thickness of 1.5 μm on an alkali-free glass, and a black mask is applied using a photomask. Exposure was performed in a matrix.

Thereafter, a black matrix pattern is formed by performing alkali development, and then a photocurable cholesteric liquid crystal is applied thereon to a thickness of 5 μm, and the temperature is adjusted so that the center wavelength of the cholesteric liquid crystal becomes 450 nm. To the RGB (red, green,
One of the three pixel patterns (blue) was exposed.

Thereafter, the temperature was changed so that the central wavelength of reflection by the cholesteric liquid crystal layer was adjusted to 550 nm, and the remaining portion was entirely exposed.

Further, a photocurable resin is applied thereon with a thickness of 5 μm, and the same mask exposure is performed to obtain a reflection center wavelength of 45 μm.
Adjustment was made so as to be a portion at 0 nm and a portion at a reflection center wavelength of 650 nm.

At this time, by forming the cholesteric liquid crystal layer having a reflection center wavelength different from that of the previously formed cholesteric liquid crystal layer, a certain pixel reflects RG light, transmits only B light, and a certain pixel reflects RB light. To transmit only G light,
Further, in a certain pixel, it is possible to reflect only the RGB light and transmit only the R light, thereby forming a selective transmission / reflection liquid crystal layer patterned into three colors of RGB.

Next, a red pigment-dispersed photocurable resin (manufactured by Fuji Film Ohlin) is applied to a thickness of 1 μm on the formed selective transmission / reflection liquid crystal layer, and the selective transmission / reflection is performed using a photomask. A red filter was formed only on the red transmitting portion of the liquid crystal layer.

In the same procedure, each color of green and blue was repeated to finally form a patterned colored layer, thereby forming a color filter as shown in FIG.

Next, a liquid crystal cell group was formed using the color filters. Sekisui Fine Chemical SP-203 (3 μm) was sprayed as a spacer, and a liquid crystal of Merck ZLI-4792 was injected into the cell. This allows
Birefringence occurs due to the retardation and thickness of the liquid crystal, and a liquid crystal cell whose phase changes by π depending on whether or not a voltage is applied is constructed.

Further, on the liquid crystal cell, a commercially available ４
A wave plate was attached, and a linear polarizing plate was attached at an angle of 45 ° with respect to the fast axis.

The liquid crystal cell including the color filter completed as described above was placed on a backlight device on which a circularly polarized light separating film was placed. When no voltage was applied to the liquid crystal cell, the liquid crystal cell passed through a linear polarizing plate. Almost no light leakage was observed, and in the state where a voltage was applied to the liquid crystal cell, colored light was seen to pass through the applied pixel portion, and the liquid crystal cell could be used as a liquid crystal display panel.

On the other hand, when external light was made to enter from the front by brightening the use environment, the reflection of the complementary color light in the selective transmission / reflection liquid crystal layer (cholesteric liquid crystal layer) was hardly observed. In contrast, the contrast of the liquid crystal display was improved about three times as compared with the case of a color filter having only a cholesteric liquid crystal layer without using a coloring layer.

[0056]

Since the present invention is constructed as described above, almost no complementary-color reflected light of external light incident on the liquid crystal display device is generated, thereby greatly improving the contrast of an image on the display surface. It has an excellent effect that it can be produced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a transmission type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a color filter in the transmission type liquid crystal display device.

FIG. 3 is a schematic sectional view showing a dark state of the transmission type liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Transmissive liquid crystal display device 12 ... Backlight device 14 ... Color filter 14A ... Selective transmission reflection liquid crystal layer 14B ... Coloring layer 16 ... Circularly polarized light separation film 20 ... Liquid crystal cell 22 ... 1/4 wavelength plate 24 ... Linear polarizing plate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/00 322 G09F 9/00 322E 5G435 322A 9/30 349 9/30 349B 349D 349E F term (reference) 2H048 BA45 BA47 BB02 BB08 BB42 2H049 BA02 BA05 BA07 BA16 BA43 BB03 BB66 BC22 2H088 EA49 GA02 GA03 GA12 HA12 HA14 HA17 HA18 HA28 JA09 MA02 MA06 2H091 FA02Y FA08X FA08Z FA11X FA35Y FA41Z FB02 AFC13A10 FC10 ED11 ED14 ED20 FA01 FA02 FB01 5G435 AA02 AA04 BB12 BB15 CC09 CC12 DD12 EE25 FF03 FF05 FF12 FF14 GG12

Claims (3)

[Claims] 1. A light-transmitting substrate, which is arranged in a pattern corresponding to at least each of red, green, and blue colors, and one of right-handed circularly polarized light and left-handed circularly polarized light of wavelength light of the corresponding color. A selective transmission / reflection liquid crystal layer made of one of cholesteric liquid crystal and chiral nematic liquid crystal that transmits only circularly polarized light and reflects the other circularly polarized light and light having no corresponding wavelength, and is formed on an external light incident side of the selective transmission / reflection liquid crystal layer. And a colored layer of the same color as the transmitted light. 2. A color filter for a transmission type liquid crystal display device according to claim 1, wherein said coloring layer is made of a light transmitting resin colored by dispersing a pigment or a dye. 3. A backlight device for emitting backlight light from a light output surface, a color filter disposed on the light output surface side of the backlight device, and a color filter disposed on the light output side of the color filter for turning on an applied voltage. A liquid crystal cell that shifts or does not shift the phase of polarized light transmitted by / OFF, and controls the amount of transmitted light by voltage, and is disposed on the light emitting surface side of the liquid crystal cell or between the color filter and the liquid crystal cell; 1/4 shifts the phase of transmitted light by 1/4 wavelength
A wavelength plate and a light-emitting surface side of the liquid crystal cell and a position on the light-emitting surface side of the quarter-wave plate. And a linear polarizing plate that blocks linearly polarized light at the time, and the color filter is disposed on the light-transmitting substrate at least in a pattern corresponding to each color of red, green, and blue. Selective transmission reflection consisting of one of cholesteric liquid crystal and chiral nematic liquid crystal that transmits only one of right-handed circularly polarized light and left-handed circularly polarized light, and reflects the other circularly polarized light and uncorresponding wavelength light. A transmission type liquid crystal display device comprising: a liquid crystal layer; and a colored layer formed on the side of the selective transmission / reflection liquid crystal layer on the outside light incident side and having the same color as transmitted light.