JP2001033784A - Liquid crystal device and electronic appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device in which influences of a reflection plate having a rugged pattern on the electro-optic characteristics of a liquid crystal can be suppressed and defects in domains or the like are eliminated by forming an alignment layer having different film thickness for the projected part and for the recessed part of the reflection layer having a rugged pattern so that the film thickness of the alignment layer on the recessed part is larger than the film thickness of the alignment layer on the projecting part. SOLUTION: In this liquid crystal device, external light is transmitted through a polarizing plate, a phase difference plate, a color filter and a liquid crystal layer 202, then is reflected on a rugged reflection electrode 205, and then is exited again from the polarizing plate to the outside of the liquid crystal cell. The liquid crystal layer 202 is held between the alignment layer 201 on the upper substrate side and alignment layer 203 (204) on the lower substrate side (alignment layer 204 formed on the projecting part and alignment layer 203 formed on the recessed part). The rugged reflection electrode 205 is formed under the alignment layer 203 (204) on the lower substrate side. Thus, the alignment layer 204, 203 different in film thickness are formed on the projecting part and recessed part of the rugged reflection layer so that the film thickness of the alignment layer 203 on the recessed part is larger than that of the alignment layer 204 on the projecting part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device, and more particularly, to a structure of a liquid crystal device capable of performing reflective color display and an electronic apparatus using the liquid crystal device. Furthermore, the present invention relates to a transflective color liquid crystal device having an uneven reflection layer.

[0002]

2. Description of the Related Art Heretofore, as a reflection type liquid crystal device, a device in which a reflection plate is disposed on the back side of a liquid crystal cell in which a liquid crystal layer is sealed between two transparent substrates has been widely used. In such a reflective liquid crystal device, depending on the type of liquid crystal layer and the driving method, a polarizing plate is disposed before and after the liquid crystal cell, a polarizing plate is disposed only on the front side of the liquid crystal device, or a polarizing plate is disposed. In some cases, no board is required.

In such a reflective liquid crystal device, external light is incident on the liquid crystal layer through the transparent substrate on the front side,
After passing through the transparent substrate on the back side and being reflected by the reflector,
Again, it passes through the transparent substrate on the back side, the liquid crystal layer, and the transparent substrate on the front side and is visually recognized. In this case, there is a gap between the liquid crystal layer and the reflection surface of the reflection plate by the thickness of the transparent substrate on the rear surface side. Since the area is different from the pixel area or the dot area of the liquid crystal layer that passes after reflection, there is a problem that so-called display bleeding or double image due to so-called parallax occurs.

[0004] As a method of solving the above-mentioned problem, as described in Japanese Patent Application Laid-Open No. 9-113893, a reflector for reflecting external light is provided on the inner surface of a liquid crystal cell to eliminate parallax. There is something. However, in the reflection type liquid crystal device described in Japanese Patent Application Laid-Open No. 9-113893, a diffusion plate composed of two types of minute regions having different refractive indexes is arranged on the front surface of the liquid crystal cell. There is a problem that blurring (blurring) of display by the diffusion plate occurs. This diffuser is used to eliminate the specular or metallic appearance of the reflector and to obtain a bright display even if it is not in the direction of regular reflection of external light. Information will be mixed until it is recognized by the human eye. That is, if white display and black display are performed by adjacent pixels, the boundary between the white display and the black display is difficult to understand due to the diffusion plate, and the display is blurred.

To solve this problem, Japanese Patent Application Laid-Open No.
No. 258219, the reflection plate is made to have irregularities,
It has been proposed that a reflection plate be provided with a reflection function and a diffusion function at the same time. By forming a reflection plate having an uneven shape, it is possible to eliminate the distance between the diffusion plate and the specular reflection plate,
It is possible to suppress blurring of the display.

[0006]

However, when the reflection plate is provided with an uneven shape, the thickness of the liquid crystal layer is different between the convex portion and the concave portion, and the electro-optical characteristics are different between the convex portion and the concave portion.
This is because the retardation value R = Δnd (Δ
This is because (n: refractive index anisotropy of liquid crystal, d: thickness of liquid crystal layer) is different between the convex portion and the concave portion. In addition, alignment defects occur in the liquid crystal layer due to the unevenness.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a liquid crystal device in which unevenness of a reflection plate minimizes the influence on the electro-optical characteristics of liquid crystal and eliminates defects such as domains. . Another object is to provide an electronic device using the liquid crystal device.

[0008]

Means taken by the present invention to solve the above problems are as follows.

The liquid crystal device according to claim 1, wherein a liquid crystal layer sandwiched between a first substrate and a second substrate, and a reflective layer having an uneven shape formed on a surface of the second substrate on the liquid crystal layer side. In the liquid crystal device, the alignment layer having different thicknesses is formed on the convex portion and the concave portion of the reflective layer having the uneven shape, and the thickness of the alignment film in the concave portion is larger than the thickness of the alignment film in the convex portion. It is characterized by the following.

According to this means, since a thin alignment film is formed in the convex portion and a thick alignment film is formed in the concave portion, the alignment regulating force applied to the liquid crystal by the alignment film differs. For example, JSR
When the soluble polyimide AL3000 series manufactured by Co., Ltd. is used, the pretilt angle increases as the film thickness increases. The pretilt angle is an angle formed by the major axis of the liquid crystal molecules with respect to the rubbed alignment-treated polyimide-coated surface. In other words, a low pretilt angle can be realized in the convex portion, and a high pretilt angle can be realized in the concave portion. If the pretilt angle is the same between the convex portion and the concave portion, the retardation value Δnd, which is the product of the birefringence (Δn) of the liquid crystal and the thickness (d) of the liquid crystal layer, is larger in the concave portion. In addition, different electro-optical characteristics are exhibited between the convex portion and the concave portion. However, by decreasing the pretilt angle of the convex portion and increasing the pretilt angle of the concave portion, the difference in retardation value when the liquid crystal cell is viewed from the front can be reduced. This is because if the pretilt angle is high, the birefringence (Δn) of the liquid crystal when the liquid crystal cell is viewed from the front becomes small.

Another advantage of the present invention is that it minimizes the effect of the uneven shape on the alignment of the liquid crystal. By increasing the thickness of the alignment film in the concave portions, the step between the concave and convex portions can be reduced.

In the liquid crystal device of the present invention, a polarizing plate is disposed on a side of the first substrate different from the liquid crystal layer, and at least one retardation plate is provided between the polarizing plate and the first substrate. By arranging, the contrast is high,
A display without unnecessary coloring can be realized.

Further, in the liquid crystal device according to the present invention, a reflective color display can be realized by providing a color filter layer on the liquid crystal layer side of the first substrate.

According to the present invention, there is provided an image forming apparatus comprising:
The invention can also be applied to a transflective color liquid crystal device as described in JP-A-109417.

According to a second aspect of the present invention, there is provided an electronic apparatus including the liquid crystal device according to the first aspect and a portable type mainly used for driving a battery.

According to this means, it is possible to realize a portable electronic device equipped with a reflective or transflective color liquid crystal device with low power consumption and no display defects. This electronic device can always perform high-quality display regardless of the use environment such as outdoors.

[0017]

Next, an embodiment according to the present invention will be described with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a schematic longitudinal sectional view showing the structure of a liquid crystal device according to a first embodiment of the present invention.
Although this embodiment is basically related to a simple matrix type liquid crystal display device, it can be applied to an active matrix type device, another segment type device, and other liquid crystal devices with the same configuration. .

In this embodiment, two substrates 104, 1
During the period 07, the liquid crystal layer 105 is sealed with a frame-shaped sealing material 106 to form a liquid crystal cell. Liquid crystal layer 10
Reference numeral 5 is composed of a nematic liquid crystal having a twist angle of 80 degrees. A color filter 108 is formed on the inner surface of the upper transparent substrate 104.
Three colored layers of R (red), G (green), and B (blue) are arranged in a predetermined pattern. A transparent protective film 109 is coated on the surface of the color filter.
9, a plurality of stripe-shaped transparent electrodes 110
It is formed by TO or the like. An alignment film is formed on the surface of the transparent electrode 110 and rubbed in a predetermined direction. A polarizing plate 101 and two retardation plates 102 and 103 are arranged on the outer surface of the upper transparent substrate 104.

On the other hand, on the inner surface of the lower substrate 107, a plurality of stripe-shaped reflective electrodes 112 formed for each colored layer of the color filter are arranged so as to intersect the transparent electrodes 110. In the case of an active matrix type device provided with an MIM element or a TFT element, each reflective electrode 112 is formed in a rectangular shape and connected to a wiring via the active element. This reflective electrode 112 is made of Cr or A
It is formed of a metal film mainly composed of l, Ag, or the like, and its surface is a reflection surface that reflects light incident from the transparent substrate 104 side. The base of the reflective electrode 112 is made of an acrylic photosensitive resin and has a random uneven shape with a step average of about 0.5 μm. Therefore, the reflection electrode 112 can reflect light at a wide angle, not in a mirror state. The method of forming the irregularities on the base of the reflective electrode 112 may be, for example, a method of directly applying irregularities to the lower glass substrate itself using a solution containing hydrofluoric acid in addition to using a photosensitive acrylic resin. There is.
An alignment film 113 is formed on the surface of the reflective electrode 112. As the alignment film 113, a soluble polyimide manufactured by JSR Corporation was used. The thickness of the alignment film 113 was about 10 nm at the convex portion of the reflective electrode 112 and about 100 nm at the concave portion.

The display method will be briefly described. The external light is a polarizing plate 101, two retardation plates 102, 1 in FIG.
03, the light passes through the color filter 109, passes through the liquid crystal layer 105, is reflected by the uneven reflection electrode 112, and is emitted again from the polarizing plate 101 to the outside of the liquid crystal cell.
At this time, the bright state, the dark state, and the intermediate brightness are controlled by the voltage applied to the liquid crystal layer 105. The uneven reflection electrode 112 has an effect of reflecting the reflected light at a wide angle so that a bright display can be recognized even in directions other than the specular reflection direction of the external light.

FIG. 2 shows the alignment films 111 and 11 in FIG.
3 is an enlarged view of a portion including a liquid crystal layer 105, and a reflective electrode 113 having an uneven shape. The liquid crystal layer 202 in FIG. 2 includes an alignment film 201 on the upper substrate side and an alignment film 203 on the lower substrate side.
04 (the alignment film 204 formed in the convex portion, the alignment film 203 formed in the concave portion), and the alignment film 20 of the lower substrate.
A reflective electrode 205 having a more uneven shape under the layers 3 and 204
Are formed. The average height of the uneven reflection electrode 205 is “H”, the thickness of the alignment film 204 formed in the projection is “A”, the thickness of the alignment film 203 formed in the recess is “B”, the thickness of the liquid crystal layer "d _a", "d _B" the thickness of the liquid crystal layer in the recesses, the pretilt angle of the liquid crystal molecules 206 of the alignment film 204 near formed on the protrusion "theta _a", formed in the recess The pretilt angle of the liquid crystal molecules 207 near the alignment film 203 is defined as “θ _B ”. The average of the convex liquid crystal layer, that is, the bulk pretilt angle is represented by “θ
_AM ”, the average of the concave portions of the liquid crystal layer, that is, the bulk pretilt angle, is defined as“ θ _BM ”. If the refractive index in the major axis direction of the liquid crystal molecule is defined as n‖ and the refractive index in the minor axis direction is defined as n⊥, the refractive index anisotropy Δn (θ) of the pretilt angle θ is

[0023]

(Equation 1)

It can be shown as follows. In the present embodiment, the average height H of the uneven reflection electrode 205 is 0.5 μm.
m, the film thickness A of the alignment film 204 formed on the projections A = 10 n
m, film thickness B of alignment film 203 formed in the concave portion = 100 n
and m, the thickness of the liquid crystal layer is _{d A = 3μm, d B =} 3.41
μm. The pretilt angle near the upper alignment film 201 is set to 5.1 degrees, and θ _A = 1.2 degrees and θ _B = 7.9.
Degrees, θ _AM = 3.0 degrees, and θ _BM = 7.0 degrees. The refractive index of the used nematic liquid crystal is n‖ = 1.60, n
⊥ = 1.53. The retardation value of the liquid crystal layer on the convex portion is R _A , and the retardation value of the liquid crystal layer on the concave portion is R
When _{B, R A = 0.209μm, R} B = 0.235
μm. The difference in retardation between the convex and concave portions is about 0.026 μm. If the alignment film of the convex portion and the concave portion has the same thickness (50 nm) and the pretilt angle near the convex / concave reflective electrode 205 is the same value (5.0 degrees) for both the convex portion and the concave portion, R _A = 0.212 μm, R _B = 0.240 μm, and the difference in retardation between the convex and concave portions is about 0.02
It becomes 8 μm.

As described above, the alignment films having different thicknesses are formed on the convex portions and the concave portions of the reflective electrode having the uneven shape, and the thickness of the alignment film in the concave portions is larger than the thickness of the alignment film in the convex portions. As a result, the difference in retardation value affecting the electro-optical characteristics of the liquid crystal could be reduced.
In addition, since the difference between the thickness of the liquid crystal layer at the convex portion and the thickness of the liquid crystal layer at the concave portion could be reduced, defects such as domains could be eliminated.

In the present embodiment, the protective film 109 is used for the purpose of protecting the color filter 108. However, in a TFT active matrix liquid crystal device, patterning of the transparent electrode on the color filter is unnecessary, so that it can be omitted.

The coloring layer of the color filter used in this embodiment will be described. In each embodiment, when performing a reflective display, the incident light once passes through one of the color layers of the color filter, passes through the liquid crystal layer, is reflected by the reflective electrode, and passes through the same color layer again. Released from Therefore, unlike a normal transmissive liquid crystal device, light passes through the color filter twice, and the display becomes dark with a normal transmissive color filter.
Therefore, in the present embodiment, R, G, B
Has a minimum transmittance of 30 to 50 in the visible region of each colored layer.
%. Lightening of the colored layer is achieved by reducing the thickness of the colored layer or reducing the concentration of the pigment or dye mixed in the colored layer.

In this embodiment, the uneven reflection layer itself is used as the reflection electrode. However, a transparent electrode such as ITO may be formed on the uneven reflection layer to separate the electrode function from the reflection function. Even in this case, the present invention can be applied as long as there are convex portions and concave portions.

(Second Embodiment) Three examples of the electronic device according to the second aspect of the present invention will be described. Since the liquid crystal device of the present invention is a reflection type or a transflective type, it is used in various environments,
In addition, it is suitable for portable devices that require low power consumption. For example, FIG. 3A shows a mobile phone, FIG. 3B shows a watch, and FIG. 3C shows a portable information device. Since the liquid crystal device of the present invention has high display quality without display irregularities or defects due to the reflective electrode having the uneven shape, it is optimal when high-definition display is required. 2. Description of the Related Art In recent years, with the increase in the amount of information and the improvement of information infrastructure, many electronic devices that are frequently carried have been manufactured and sold. The liquid crystal device of the present invention is most suitable for the display section of such an electronic device, and particularly when color display is required, it can display a very good color.

[0030]

As described above, according to the present invention, defects (brightness unevenness, contrast unevenness, unnecessary coloring) that the reflection layer having the uneven shape exerts on the electro-optical characteristics of the liquid crystal,
Further, defects (discretion generation, domain unevenness) on the liquid crystal alignment can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a schematic structure of a first embodiment of a liquid crystal device according to the present invention.

FIG. 2 is a detailed diagram for explaining the first embodiment.

FIG. 3 is a diagram illustrating an example of an electronic apparatus equipped with the liquid crystal device according to the present invention.

[Explanation of symbols]

Reference Signs List 101 polarizing plate 102, 103 retardation plate 104 upper substrate 105, 202 liquid crystal layer 106 sealant 107 lower substrate 108 color filter 109 protective film 110 transparent electrode 111, 113, 201 alignment film 112, 205 uneven reflection electrode 203 on concave portion Alignment film 204 Alignment film on convex portion 206 Liquid crystal molecule near convex portion 207 Liquid crystal molecule near concave portion A Thickness of alignment film on convex portion B Thickness of alignment film on concave portion H Step of uneven reflection electrode d _A convex the pretilt angle of the liquid crystal molecules pretilt angle theta _B recess near the thick theta _a protrusion liquid crystal molecules in the vicinity of the liquid crystal layer in the thickness d _B recess of the liquid crystal layer in the section

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Osamu Okumura 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 2H090 HA15 HD14 JA03 JB13 JC03 LA01 LA15 LA20 MA10

Claims (2)

[Claims] 1. A liquid crystal device comprising: a liquid crystal layer sandwiched between a first substrate and a second substrate; and a reflective layer having an uneven shape formed on a surface of the second substrate on the liquid crystal layer side. ,
A liquid crystal device, wherein an alignment film having a different thickness is formed on a convex portion and a concave portion of the reflection layer having the uneven shape, and the thickness of the alignment film in the concave portion is larger than the thickness of the alignment film in the convex portion. 2. A portable electronic device comprising the liquid crystal device according to claim 1 and mainly used for battery driving.