JP2002250940A - Reflection type liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display panel in which the driving voltage can be made uniform without depending on the pitch of a chiral nematic liquid crystal. SOLUTION: A pair of panel substrates 2 are disposed opposing to each other and the space between the opposing faces of the pair of panel substrates 2 is divided by a sealing material 3 to form a plurality of liquid crystal holding parts 4. The gap between the opposing faces in each liquid crystal holding part 4 is made different from others. Then chiral nematic liquid crystals 10 showing different selective reflection colors are sealed in the respective spaces between the opposing faces having different gaps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display panel suitable for performing color-coded display.

[0002]

2. Description of the Related Art As one type of display device for displaying information, a liquid crystal display device which is small and lightweight and requires a small installation space is known. A pair of panels is used as a display portion of such a liquid crystal display device. A liquid crystal display panel in which liquid crystal is sealed between substrates is used. In addition, as a type of liquid crystal display panel, a reflective liquid crystal display panel that performs display by reflecting light incident from the outside does not use a backlight, so that power consumption, thickness, weight, and cost are reduced. In recent years, it has been frequently used because it is possible to easily realize high density, high image quality, and the like. As one type of such a reflection type liquid crystal display panel, there is a type using a chiral nematic liquid crystal obtained by mixing a nematic liquid crystal and an optically active substance.

A reflection type liquid crystal display panel using a chiral nematic liquid crystal can exhibit selective reflection in a planar state and can exhibit a fine scattering state in a focal conic state. In order to make a transition to the planar state or the focal conic state, a predetermined voltage may be applied. Each state when no voltage is applied is maintained until a new voltage is applied. Therefore, this reflection type liquid crystal display panel is an element having a memory effect, can reduce power consumption, and can obtain a bright reflection display because there is no need to use a polarizing plate.

[0004] The principle of the selective reflection color will be described. The chiral nematic liquid crystal is sandwiched between a pair of parallel panel substrates, and the director, which is the arrangement direction of the chiral nematic liquid crystal, rotates at regular intervals. When the helical axis (helical axis) is arranged so as to be perpendicular to the panel substrate on average, circularly polarized light corresponding to the direction of the twist is reflected. The center wavelength of the reflected light is the distance (pitch) on the helical axis during one rotation of the director of the chiral nematic liquid crystal parallel to the panel substrate due to the twist.
It is the product of the nematic liquid crystal and the average refractive index in a two-dimensional plane parallel to the panel substrate surface. The phenomenon that such a chiral nematic liquid crystal reflects circularly polarized light of a specific wavelength by its pitch and the refractive index of the nematic liquid crystal is called selective reflection.

[0005] For these reasons, a reflective liquid crystal display panel using a chiral nematic liquid crystal can control the selective reflection color by using the same nematic liquid crystal and changing the pitch when the chiral nematic liquid crystal is used. .

[0006] From these facts, a reflection type liquid crystal display panel capable of displaying a plurality of colors by color separation is manufactured by dividing the opposing surfaces of a pair of panel substrates and sandwiching a chiral nematic liquid crystal exhibiting different selective reflection colors. Will be possible. A liquid crystal display device having a reflective liquid crystal display panel capable of performing color-coded display using a chiral nematic liquid crystal as a display portion can be used for applications such as price tags in supermarkets and convenience stores.

[0007]

In the above-mentioned conventional reflective liquid crystal display panel, the selective reflection color is controlled by changing the pitch of the chiral nematic liquid crystal. The drive voltage must be controlled for each chiral nematic liquid crystal exhibiting a different selective reflection color, and there is a problem that the types of drive drivers increase.

Therefore, there is a need for a reflective liquid crystal display panel capable of making the driving voltage the same regardless of the pitch of the chiral nematic liquid crystal.

The present invention has been made in view of such a point, and an object of the present invention is to provide a reflection type liquid crystal display panel which can make the driving voltage the same regardless of the pitch of the chiral nematic liquid crystal.

[0010]

In order to achieve the above-mentioned object, a reflective liquid crystal display panel according to the present invention according to claim 1 is characterized in that a pair of panel substrates are opposed to each other. A plurality of liquid crystal holding portions are formed by dividing the space between the opposing surfaces of the panel substrate with a sealing material, and the intervals between the respective opposing surfaces in these liquid crystal holding portions are formed to be different from each other, and the distances between these opposing surfaces are different. The point is that a chiral nematic liquid crystal exhibiting a different selective reflection color is sealed between the opposing surfaces. By adopting such a configuration, the distance between the liquid crystal holding portions can be controlled according to the pitch of the chiral nematic liquid crystal exhibiting different selective reflection colors, so that the driving voltage can be controlled regardless of the pitch of the chiral nematic liquid crystal. Can be identical.

According to a second aspect of the present invention, there is provided a reflective liquid crystal display panel according to the first aspect, wherein, as the center wavelength of the selectively reflected light of the chiral nematic liquid crystal becomes shorter, the opposing surface of the liquid crystal holding section becomes smaller. The point is that the space between them is formed narrow. By adopting such a configuration, it is possible to easily optimize the pitch of the chiral nematic liquid crystal exhibiting different selective reflection colors and the interval between the liquid crystal holding portions.

According to a third aspect of the present invention, there is provided a reflective liquid crystal display panel according to the first or second aspect, wherein the distance between the opposing surfaces of the liquid crystal holding portion is provided on at least one of the opposing surfaces. It is controlled by the presence or absence of a layer and its thickness. Then, by adopting such a configuration, the interval between the liquid crystal holding units can be easily controlled.

According to a fourth aspect of the present invention, there is provided a reflective liquid crystal display panel according to any one of the first to third aspects, wherein the substrate on the upstream side in the viewing direction among the pair of panel substrates. Is provided with a light-shielding layer in the non-lighting portion. And by adopting such a configuration,
The background can be dark and the display can be bright and excellent in visibility.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a plan view schematically showing an overall configuration of an embodiment of a reflection type liquid crystal display panel according to the present invention, and FIG.
3 is a schematic sectional view taken along line AA ′ of FIG.

The reflection type liquid crystal display panel of this embodiment is
The figure shows a display for displaying three colors of yellow, green and blue.

As shown in FIGS. 1 and 2, the reflection type liquid crystal display panel 1 of the present embodiment has a pair of panel substrates 2. One of the pair of panel substrates 2 shown on the lower side in FIG. 1 is a rear panel substrate 2R located on the downstream side in the viewing direction, and the other shown on the upper side in FIG. 1 is located on the upstream side in the viewing direction. The front panel substrate 2F is a counter substrate. The rear panel substrate 2R and the front panel substrate 2F are arranged substantially in parallel and are arranged so as to face each other. Further, a seal member 3 is disposed between the opposing surfaces of the pair of panel substrates 2 in a cross shape, and the opposing surfaces of the pair of panel substrates 2 are vertically divided into three. Each part surrounded by the sealing material 3 is a liquid crystal holding part 4. These liquid crystal holding units 4 each have a chiral nematic liquid crystal 10 exhibiting a different selective reflection color. For example, the liquid crystal holding unit 4a shown in the upper part of FIG. 1 has a chiral nematic liquid crystal 10a exhibiting a yellow selective reflection color, The liquid crystal holding part 4b shown in FIG. 1 has a chiral nematic liquid crystal 10b exhibiting a green selective reflection color, and the liquid crystal holding part 4c shown in the lower part of FIG. 1 has a chiral nematic liquid crystal 10c exhibiting a blue selective reflection color.
Are enclosed, thereby forming a three-color display of yellow, green and blue.

The number of divisions between the opposing surfaces of the pair of panel substrates 2 by the sealing material 3 can be selected from an arbitrary integer of 2 or more as needed for color-coded display according to the design concept or the like. . Further, each of the liquid crystal holding portions 4a, 4
The selective reflection color of the chiral nematic liquid crystal enclosed in b and 4c can be selected according to the design concept or the like.

The liquid crystal holding portions 4a, 4b, 4c are formed so that the distance between their opposing surfaces is different from each other, as described later. That is, the distance between the opposing surfaces of the liquid crystal holding unit 4 (reference numeral 4 generally refers to the three liquid crystal holding units 4a, 4b, and 4c) is determined by the chiral nematic liquid crystal 10 enclosed therein (reference numeral 10 denotes three liquid crystal holding units 4a, 4b, and 4c). Are set in accordance with the pitch of the chiral nematic liquid crystals 10a, 10b, and 10c). More specifically, the distance between the opposing surfaces of the liquid crystal holding unit 4 is controlled to be narrower as the center wavelength of the selectively reflected light of the chiral nematic liquid crystal becomes shorter. A method of controlling this interval will be described later.

Here, the reflection type liquid crystal display panel 1 of the present embodiment will be described in detail along with the manufacturing method.

FIG. 3 is an exaggerated plan view showing the liquid crystal holding portion forming region and the insulating layer of the rear panel substrate, and FIG. 4 is a left side view of FIG.

The rear panel substrate 2R has a thickness of 0.2 to 1.1 made of transparent glass or resin.
It has a transparent substrate 5 of about mm. A black light-absorbing layer 11 having a light-absorbing function is provided on the lower surface in the figure, which is one main surface of the transparent substrate 5. The light absorbing layer 11 is formed by screen printing a black ink made of an alkyd resin or the like.

On the surface of the other main surface of the transparent substrate 5, three liquid crystal holding portion forming regions 6a, 6b and 6c for forming three liquid crystal holding portions 4 are provided. The liquid crystal holding section 6b shown in the center of FIG. 3 (center of FIG. 4) of the liquid crystal holding section 6a, 6b, 6c of FIG.
An insulating layer 7b having a thickness of about 0.7 μm is formed in order to make the interval between the opposing surfaces correspond to the pitch of the chiral nematic liquid crystal 10b exhibiting the green selective reflection color enclosed in b.

Further, in the liquid crystal holding portion forming region 6c shown in the lower portion of FIG. 3 (right in FIG. 4), a chiral nematic exhibiting a blue selective reflection color sealed in the liquid crystal holding portion 4c shown in the lower portion of FIG. 1 (right in FIG. 2). An insulating layer 7c having a thickness of about 1.2 μm is formed in order to make the interval between the opposing surfaces correspond to the pitch of the liquid crystal 10c.

The liquid crystal holding portion forming regions 6a, 6b, 6
The liquid crystal holding portion 4a shown in the upper part of FIG. 1 (the left of FIG. 2) is provided in the liquid crystal holding portion forming region 6a shown in the upper part of FIG.
In order to make the pitch between the opposing surfaces correspond to the pitch of the chiral nematic liquid crystal 10a exhibiting the yellow selective reflection color enclosed in the insulating layer 7, the insulating layer 7 (the symbol 7 collectively refers to the two insulating layers 7b and 7c) is formed. Absent.

That is, the optimum distance between the opposing surfaces according to the pitch of the chiral nematic liquid crystal 10 sealed in the liquid crystal holding portion 4 can be controlled by the presence or absence of the insulating layer 7 and the thickness thereof. .

The insulating layer 7 is formed on the surface of the transparent substrate 5 by using a spin coating method in this embodiment among spin coating, transfer, offset printing and the like.

For example, as shown in FIG. 5, the formation of the insulating layer 7 by the spin coating method includes two steps of coating the insulating film, and in the first step, the center of FIG. 3 corresponds to the liquid crystal holding portion 4b shown in FIG.
A mask MA for applying an insulating film, which is indicated by a hatched area in the upper left of FIG. 4, in which a portion corresponding to the liquid crystal holding portion forming area 6b shown in the center is an opening MAa, is disposed. After applying the insulating film forming coating agent to the liquid crystal holding portion forming region 6b, the mask is removed by temporarily drying at a temperature of about 80 ° C. × 10 minutes, and as shown in the upper right of FIG. An insulating film 7ba is formed at a portion corresponding to the liquid crystal holding portion forming region 6b.

Next, in the next step, the insulating film 7ba
On the surface of the transparent substrate 5 on which is formed, a portion corresponding to the liquid crystal holding portion forming region 6c is formed as an opening MBa so as to correspond to the liquid crystal holding portion 4c shown in the lower part of FIG. A mask MB for applying an insulating film is provided, and a coating material for forming an insulating film is applied to the liquid crystal holding portion forming region 6c by a spin coating method in the same manner as in the above step.
By removing the mask after the preliminary drying under the temperature condition of about one minute, the insulating film 7ca is formed on the surface of the liquid crystal holding part forming region 6c as shown in the lower right of FIG.

Thereafter, by performing the main drying, as shown in FIG. 3, there is no insulating layer 7 in the liquid crystal holding part forming area 6a shown in the upper part of FIG. An insulating layer 7b having a thickness of about 0.7 μm is formed on 6b.
A thickness of 1.2 μm is applied to the liquid crystal holding portion
About m of the insulating layer 7c is formed.

As the material of the insulating film, there are polyvinyl alcohol (Poval), polyimide, acrylic resin, epoxy acrylate resin, silicone resin and the like, but acrylic resin is preferable from the viewpoint of availability and workability. is there.

The thickness of the insulating layer 7 (the thickness of the insulating film) can be controlled by the solid concentration (viscosity) of the coating material for forming the insulating film.

Furthermore, the thickness of the insulating layer 7 is
And the pitch of the chiral nematic liquid crystal 10 enclosed therein. That is, the thickness of the insulating layer 7 may be increased so that the distance between the opposing surfaces of the liquid crystal holding unit 4 decreases as the center wavelength of the selectively reflected light of the chiral nematic liquid crystal 10 decreases.

The surface of each of the liquid crystal holding portion forming regions 6a where the insulating layer 7 is not formed and the surface of the liquid crystal holding portion forming regions 6b and 6c where the insulating layer 7 is formed, as is conventionally known, is formed of indium tin oxide. After forming a transparent conductive film such as (ITO) by a thin film forming method, the transparent electrode 12R having a predetermined shape is formed by patterning by a photolithographic method or the like.
Are formed.

As a method of forming a thin film, there are vapor deposition, sputtering, CVD and the like, but sputtering is preferred. Further, as the arrangement pattern of the transparent electrodes, various types such as a stripe type for displaying dots, a segment type, and the like are selected and used as required according to a design concept or the like. In the present embodiment, it is of a stripe type.

On the surface of the transparent electrode 12R, a resin film 13 made of a polymer such as polyimide is coated by a transfer method or the like in order to keep the interface with the liquid crystal layer uniform. . On the surface of the transparent substrate 5 on which the resin film 13 is formed, spacers (not shown) formed in a spherical shape for controlling the distance between the opposing surfaces are scattered.

When the spacers are scattered, it is not necessary to change the size of the spacer for each of the liquid crystal holding portion forming regions 6 (symbol 6 denotes three liquid crystal holding portion forming regions 6a, 6b, 6c). . This is because the spacer is buried to some extent in the insulating layer 7 by performing a normal thermocompression bonding process for bonding the rear panel substrate 2R and the front panel substrate 2F. Due to this phenomenon, many portions are buried in the thick portion of the insulating layer 7, and no portion is buried in the portion where the insulating layer 7 is not provided, so that a uniform interval is formed in the plane. However, considering the embedding of the spacer in the insulating layer 7, the hardness of the spacer is preferably hard, and a hard resin or glass beads is preferable.

The front panel substrate 2F is made of the same transparent glass or resin as the rear panel substrate 2R and has a thickness of about 0.2 to 1.1 mm.
have. Like the rear panel substrate 2R, a transparent conductive film such as indium tin oxide (ITO) is formed on the surface of the transparent substrate 5 by a thin film forming method, and then patterned by a photolithographic method or the like to form a transparent electrode 12F having a predetermined shape. (A counter electrode) is formed. And
A light-shielding layer 14 is formed on one surface of the transparent substrate 5. The light-shielding layer 14 is coated with a photosensitive resin such as black, dark blue, or dark purple by a method having excellent film thickness uniformity such as a spin coating method, and is not turned on except for a lighted portion serving as a pixel at the time of display. Exposure is performed using a photomask whose portions are shielded from light, followed by development, drying, and baking. On the surface of this transparent electrode 12F,
A resin film 13 made of polyimide is formed. Then, in order to form each liquid crystal holding part 4, the seal material 3 is applied so as to surround the periphery of each liquid crystal holding part forming area 6 by a screen printing method or the like.

The front panel substrate 2F is superimposed on the rear panel substrate 2R, and at a temperature of about 120 to 200 ° C., preferably about 180 ° C., and a pressure of about 0.01 to 0.1 MPa, preferably about 0.06 MPa. By thermocompression bonding, three liquid crystal holding portions 4a, 4 having different distances between the opposing surfaces are provided.
Thus, an empty reflective liquid crystal display panel 1 having b and 4c is formed. Then, the empty reflective liquid crystal display panel 1
A predetermined chiral nematic liquid crystal 1
0 is filled through an injection port (not shown) provided in each of the liquid crystal holding sections 4, and then the injection port is sealed with an ultraviolet curable adhesive or the like, whereby the reflective liquid crystal display panel 1 is filled. Can be obtained.

In general, the rear panel substrate 2R and the front panel substrate 2F have transparent electrodes 12 (the reference numeral 12 is a generic name for the transparent electrodes 12F and 12R) in order to simultaneously form a plurality of liquid crystal display panels. A mother substrate provided with a plurality of liquid crystal display panel formation regions is used. Then, a pair of mother substrates are overlapped, cut so as to expose the injection port, the liquid crystal is sealed from the injection port, and then a portion located in the liquid crystal display panel forming region is divided to thereby provide individual reflection type liquid crystal display. Panel 1 is provided.

Next, the operation of the present embodiment having the above-described configuration will be described.

According to the reflection type liquid crystal display panel 1 of this embodiment, the interval between the opposing surfaces of the liquid crystal holding section 4 can be controlled according to the pitch of the chiral nematic liquid crystal 10 exhibiting different selective reflection colors. A plurality of color-coded displays can be clearly displayed regardless of the pitch of the chiral nematic liquid crystal 10, and the driving voltage of the chiral nematic liquid crystal 10 exhibiting different selective reflection colors can be the same. As a result, the type of the driver is one, and the chiral nematic liquid crystal 10 having different selective reflection colors enclosed in the three liquid crystal holders 4 is provided.
Can be shared by driving drivers for driving the driving.

Further, according to the reflection type liquid crystal display panel 1 of the present embodiment, as the center wavelength of the selective reflection light of the chiral nematic liquid crystal 10 becomes shorter, the interval between the opposing surfaces of the liquid crystal holding section 4 becomes narrower. Therefore, the pitch of the chiral nematic liquid crystal 10 exhibiting different selective reflection colors and the interval between the liquid crystal holding portions 4 can be easily optimized.

Further, according to the reflective liquid crystal display panel 1 of the present embodiment, the distance between the opposing surfaces of the liquid crystal holding unit 4 is controlled by the presence or absence of the insulating layer 7 provided on at least one of the opposing surfaces and its thickness. Therefore, the distance between the opposing surfaces of the liquid crystal holding unit 4 can be easily controlled.

Further, according to the reflection type liquid crystal display panel 1 of the present embodiment, the light-shielding layer 14 is provided on the non-lighted portion of the pair of panel substrates except for the lighted portion serving as a pixel when displaying the front panel substrate 2F. Is provided, the background can be dark, and the display can be bright and excellent in visibility.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified as needed.

[0047]

As described above, according to the reflection type liquid crystal display panel of the present invention, the distance between the liquid crystal holding portions is controlled according to the pitch of the chiral nematic liquid crystal exhibiting different selective reflection colors. Therefore, an extremely excellent effect such as the same drive voltage can be obtained regardless of the pitch of the chiral nematic liquid crystal.

According to the reflection type liquid crystal display panel of the present invention, the pitch of the chiral nematic liquid crystal exhibiting different selective reflection colors and the distance between the liquid crystal holding portions can be easily optimized. Has an extremely excellent effect.

Further, according to the reflection type liquid crystal display panel of the present invention according to the third aspect, there is an extremely excellent effect that the interval between the liquid crystal holding portions can be easily controlled.

Further, according to the reflection type liquid crystal display panel of the present invention according to the fourth aspect, an extremely excellent effect such as a dark background and a bright display with excellent visibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing an overall configuration of a reflective liquid crystal display panel according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view taken along line A-A 'of FIG.

FIG. 3 is an exaggerated plan view showing a liquid crystal holding portion forming region and an insulating layer of the rear panel substrate of FIG. 1;

FIG. 4 is a left side view of FIG. 3;

FIG. 5 is a schematic plan view illustrating a configuration for forming an insulating layer on the rear panel substrate of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reflective liquid crystal display panel 2 Panel substrate 2R Rear panel substrate 2F Front panel substrate 3 Sealing material 4, 4a, 4b, 4c Liquid crystal holding part 5 Transparent substrate 6, 6a, 6b, 6c Liquid crystal holding part formation area 7, 7b, 7c Insulation Layer 10, 10a, 10b, 10c Chiral nematic liquid crystal 11 Light absorbing layer 12, 12F, 12R Transparent electrode 13 Resin film 14 Light shielding layer MA, MB Mask (for coating insulating film) MAa, MBa Opening

Claims (4)

[Claims] In a reflection type liquid crystal display panel using a chiral nematic liquid crystal, a pair of panel substrates are opposed to each other, and a plurality of liquid crystal holding portions are divided by dividing a facing surface of the pair of panel substrates with a sealing material. And that the gaps between the opposing surfaces of these liquid crystal holding portions are formed so as to be different from each other, and that chiral nematic liquid crystals exhibiting different selective reflection colors are enclosed between the opposing surfaces having the different gaps. Characteristic reflective liquid crystal display panel. 2. The liquid crystal display according to claim 1, wherein the distance between the opposing surfaces of the liquid crystal holding portion is reduced as the center wavelength of the selectively reflected light of the chiral nematic liquid crystal becomes shorter. Reflective liquid crystal display panel. 3. The method according to claim 1, wherein the distance between the opposing surfaces of the liquid crystal holding unit is controlled by the presence or absence of an insulating layer provided on at least one of the opposing surfaces and the thickness thereof. The reflective liquid crystal display panel as described in the above. 4. The light-emitting device according to claim 1, wherein a light-shielding layer is provided on a non-lighting portion of the substrate on the upstream side in the viewing direction of the pair of panel substrates. The reflective liquid crystal display panel as described in the above.