JP3432125B2 - Reflective liquid crystal display device and method of manufacturing the same - Google Patents

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 device which does not require a backlight among liquid crystal display devices used in office automation equipment, personal computers, portable information terminals and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, application of liquid crystal display devices to personal computers, portable information terminals, televisions, etc. has been rapidly progressing. Especially in the field of notebook personal computers and portable information terminals as portable information tools with the progress of the multimedia society, power consumption has been reduced in order to make them thinner and lighter and to extend the usable time of the device. There is a demand for fewer liquid crystal display devices. Since the reflective liquid crystal display device does not use a backlight, it can reduce power consumption as compared with the conventional transmissive liquid crystal display device, and can be thin and lightweight.

In such a reflection type liquid crystal display device, a TN (twisted nematic) system, an STN has been conventionally used.
A (super twisted nematic) system and a phase transition type guest-host system as disclosed in JP-A-5-173158 are used.

In order to obtain a brighter display in these reflection type liquid crystal display devices, it is necessary to increase the intensity of light scattered in a direction perpendicular to the display screen with respect to incident light from all angles. . For this reason, JP-A-6-
In Japanese Patent No. 75237, it is described that the uneven shape is controlled and formed on an insulating glass substrate, and a reflecting plate having a metal film such as Al or Ag formed thereon is formed thereon. The reflective plate of the above proposal, by forming a columnar convex portion using a polymer material on the glass substrate surface by photolithography, by thermally deforming the corner of the upper edge portion of the columnar structure by heat treatment, Create a shape that makes the upper edge round,
Further, by stacking polymer resin films to fill the gaps in the columnar structure, a continuous wavy surface shape is formed. Further, a metal film of Al, Ag or the like is further formed on this to manufacture a reflection plate having a continuous wavy surface.

[0005]

However, in the production of the reflecting plate according to the above proposal, it is necessary to form a film structure of at least three layers, and three film forming steps and processing steps are required. There is a drawback that the number of steps increases. Furthermore, a heating step of at least 200 [° C.] or higher is required in order to make the upper edge of the columnar portion into a round shape with no corners. Therefore, the liquid crystal display device
When a polymer resin substrate is used as the substrate for the purpose of weight reduction, the substrate may be deformed or contracted during heating,
There is a problem that the process cannot be performed and the usable materials are limited to high heat resistant resins and the like. The present invention has been made to solve the above problems, and has a reflective electrode having a good reflective property in a simple process, and a reflective type resin substrate having low heat resistance can be used. An object of the present invention is to provide a liquid crystal display device and a manufacturing method thereof.

[0006]

A method of manufacturing a reflection type liquid crystal display device according to the present invention comprises a first substrate having a first electrode having a light reflecting function formed on a surface facing a second substrate. ,
A second substrate, which is disposed so as to face the first substrate and has a transparent second electrode formed on a surface facing the first substrate, and a liquid crystal layer enclosed between the first and second substrates. A method of manufacturing a reflective liquid crystal display device, characterized in that there is a portion provided with a photocurable resin between the first substrate and the first electrode in the reflective liquid crystal display device including A mask having a step of applying a photo-curable resin on a first substrate and a transparent portion provided so that a convex shape is formed in the first electrode, wherein the light transmittance of the transparent portion is controlled. Using a semitransparent mask that has been changed to a different shape, the step of deforming the photocurable resin by irradiating the photocurable resin with light,
A first light reflecting function on the deformed light curable resin;
Forming an electrode.

Further, it is preferable that the first and second electrodes are formed in a matrix and the deformed photocurable resin is formed in a continuous wavy shape over a wide area. It is preferable because the reflective property can be obtained. Further, it is preferable that both the first and second substrates are made of a polymer resin because they are thin and lightweight, and have strong resistance to impact and drop during movement. Furthermore, the fact that the first substrate and the photo-curable resin are formed as an integral unit makes it possible to make the device thinner and thinner.
It is preferable because it can be made lightweight. Further, it is preferable that all the manufacturing processes are carried out at a temperature of 150 ° C. or lower because the polymer resin used as the substrate is not limited to the one having high heat resistance.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments. (Embodiment 1) FIG. 1 shows a plan view and a sectional view of one pixel of a reflective liquid crystal display device according to Embodiment 1 of the present invention. In FIG. 1, T is placed on an insulating substrate 1 made of glass.
A plurality of electrode wirings 2 made of a are provided, and an insulating film 3 made of a Ta ₂ O ₅ thin film is formed on the surface of the electrode wirings 2 by the anodic oxidation method. An upper electrode 4 made of Ti, Cr, or the like is formed on a part of the electrode wiring 2 so as to overlap with the insulating film 3 interposed therebetween, thereby forming an MIM element 5. The MIM element 5 has a function as a switching element in the liquid crystal display device.

Next, a polymer film 6 made of a photocurable resin is formed so as to cover the entire surface of the substrate, and the pixel electrode portions 7 thereof are arranged irregularly by the photocurable resin.
A continuous wave-shaped portion 8 is formed by light irradiation. Further thereon, a reflective electrode 9 made of Al, Ag, etc.
Are formed and are connected to the upper electrode 4 of the MIM element 5 through the contact hole 10. Further, an alignment film (not shown) is formed on it.

On the other substrate 11, a color filter 12 and a black matrix 1 are provided in a portion facing the reflective electrode 9.
3 and a transparent electrode 14 made of striped ITO (Indium Tin Oxide). Both boards 1 and 12
Are bonded so that the reflective electrode 9, the color filter 12, and the transparent electrode 14 face each other so that they coincide with each other, and the liquid crystal 15 is injected therebetween. As described above, the active matrix reflective liquid crystal display device according to the first embodiment is completed. Hereinafter, a method for manufacturing the reflective liquid crystal display device according to the first embodiment will be described with reference to FIG.

First, T is placed on an insulating substrate 1 made of glass.
A metal film made of a is formed to a thickness of 100 [n by a sputtering method.
m] to form a film. The film forming conditions of this embodiment at this time are as follows: substrate temperature 150 [° C.], Ar pressure 0.5 [Pa],
The film was formed with an RF power of 3.4 [W / cm ² ]. Subsequently, the Ta film is patterned by photolithography and etching to form the electrode wiring 2 as shown in FIG.

Next, an anodic oxide film 3 made of Ta ₂ O ₅ is formed on the Ta electrode wiring 2 by an anodic oxidation process. As the anodizing conditions at this time, a 1% ammonium borate solution was used as the anodizing solution, the solution temperature was room temperature, the formation voltage was 31 [V], and the formation current was 200 [m.
A] is anodized for about 1 hour and the film thickness is 600 [Å]
To obtain an anodic oxide film 3.

Next, a Ti film is formed as an upper electrode by electron beam evaporation to a film thickness of 150 nm.
The film forming conditions at this time are: substrate temperature 100 [° C.],
Ultimate vacuum 5E-6 [Torr], acceleration voltage 4 [k]
V] and the film formation current was 120 [A]. Subsequently, the Ti film is patterned by photolithography and etching, and as shown in FIG.
To form. As described above, the MIM element 5 is formed on the glass substrate 1.
Is formed.

Next, a photocurable resin containing a photopolymerizable oligomer, a photopolymerizable monomer, and a photopolymerization initiator as main components is applied to the entire surface of the substrate. As the photopolymerizable oligomer, for example,
It is possible to use ester, ether acrylate, phenoxyethyl acrylate, dicyclopentenyl acrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, merimetylol propanate acrylate, dipentaerythritol acrylate, vinyl cyclohexene monooxide, cyclohexene diepoxide, etc. Is. In the first embodiment, pentaerythritol, which is an ester acrylate, is used as the photopolymerizable oligomer, and neopentyl glycol diacrylate is used as the photopolymerizable monomer.
To this, a photopolymerization initiator of about 2% was added and used.
This was applied to the entire surface of the substrate with a film thickness of 3 [μm].

Next, a method of forming a surface shape by light irradiation will be described with reference to FIG. First, as shown in FIG. 3A, the first light irradiation is performed using the mask 16 so that only a predetermined position of the pixel electrode portion is exposed. A mercury lamp was used as an exposure light source, and ultraviolet rays having a wavelength of 365 [nm] were irradiated. As the mask 16, a circular transparent portion having a diameter of about 3 to 40 [μm] is provided so that a convex shape randomly arranged in the pixel electrode is formed as shown in FIG. The light transmitted through the mask 16 is applied to the photocurable resin 17, and the photopolymerization reaction is promoted only in the transmissive portion. As a result, the photocurable resin 17 is consumed by the reaction in the irradiation area, and the unreacted components in the unexposed area diffuse into the reaction area. As a result, the curing reaction progresses in a shape (convex shape) that is higher in the irradiated portion than in the non-irradiated portion.

Subsequently, as shown in FIG. 3 (b), the mask 16 is removed, and the mask 18 as shown in FIG. 4 (b).
The portion other than the contact hole 10 is similarly exposed by using. As a result, the photopolymerization reaction is started on the entire surface except the contact hole portion, and the photocurable resin 17 is cured.
At this time, in the area previously exposed using the mask 16, the photopolymerization reaction is promoted as compared with other areas, so that a reaction speed difference occurs between the irradiated area and other areas. As a result, in the region irradiated with the convex shape, the convex shape rises in a shape that reflects the shape of the mask 16, and the convex shape is formed in a self-forming manner. Is formed into a flat surface. Such a method is, for example, C. Croutxe-Bar.
ghorn, et, al. (SPIE Proceedings '97, Vol.2998, pp222-2
As described in 31), research is being conducted to apply it to the production of microlens arrays and diffraction gratings. When used as an optical element such as a microlens array, the optical characteristics of the material are limited, but when only the surface shape is controlled as in the first embodiment, the limitation on the material is reduced. , A wider range of materials can be used.

The controllability of the convex shape formed in a self-forming manner depends on the irradiated light energy. That is, the shape of the convex portion can be controlled by controlling the light irradiation time or the light irradiation energy. FIG. 5 shows the relationship between the irradiation energy density and the height of the convex portion. From this, by controlling the irradiation energy density, 2
It is possible to control the height of the convex portion within a range of about [μm].

Subsequently, the substrate is washed with an organic solvent to wash away the unreacted photo-curable resin in the contact hole which is the unexposed portion, so that the upper electrode as shown in FIG. The contact hole 10 connected to 4 is simultaneously formed. Through the above steps, a predetermined continuous wavy surface shape is formed only on the reflective electrode portion by light irradiation.

Using the above method, in the first embodiment, a semi-transmissive mask in which the light transmittance of the transparent portion of the mask 16 in FIG. 3A is partially changed (hatched portion in FIG. 4) is used. The height of the convex portion used is 1.0 [μm] and 1.5 [μm]
An irregularly arranged continuous wavy polymer film 6 having two heights was prepared. The irradiation energy at this time is 1.2 [J / cm ² ] and 1.5 [J / cm ² ] respectively.
cm ² ].

Next, as shown in FIG. 2 (d), Al is used as a reflective electrode film by a sputtering method for 0.1 to 1 [μ].
The film thickness is about m]. In the first embodiment, film formation was performed with a film thickness of 0.5 [μm], a substrate temperature of 100 [° C.], an Ar pressure of 0.5 [Pa], and an RF power of 3.4 [W / cm ² ]. Subsequently, the Al film is patterned into a predetermined shape by photolithography and etching to form the reflective electrode 9. By reflecting the surface shape of the polymer film 6, the reflective electrode 9 becomes a reflective electrode having an irregularly arranged continuous wavy surface shape.

Next, an alignment film (not shown) made of polyimide is applied on the entire surface of the substrate, baked at 150 [° C.] for 2 hours, and then rubbed. Next, as a counter substrate, a transparent electrode 1 made of ITO and a color filter 12 is provided on a glass substrate 11 at a position facing the reflective electrode 9.
After preparing the counter side substrate 11 on which No. 4 is formed and applying the alignment film, firing and rubbing, a spacer (not shown) is provided so as to face the other substrate 1 and form a predetermined cell film. It sticks by a seal (not shown).

Subsequently, the liquid crystal display device according to the first embodiment is manufactured by injecting and sealing liquid crystal between the substrates. Although the MIM (Metal-Insulator-Metal) element is used as the switching element in the first embodiment, the present invention is not limited to this, and the TFT (Thin Film Transi
The present invention can be applied to an active matrix reflection type liquid crystal display device using other switching elements such as a storage device, a diode and a varistor, or a simple matrix reflection type liquid crystal display device not using a switching element.

(Embodiment 2) In Embodiment 2 of the present invention, a resin substrate made of a polymer material is used as the substrates 1 and 11 constituting the reflection type liquid crystal display device in FIG. As shown in the first embodiment, since the process temperature including the MIM element fabrication is 150 [° C.] or lower, if the polymer material has a heat resistant temperature of 150 [° C.] or higher,
It can be used as a substrate of the reflective liquid crystal display device of the second embodiment. As a usable substrate material, materials such as polycarbonate (PC), polyarylate, polyether sulfone (PES), and polyether ether ketone (PEEK) can be used.

In the second embodiment, 0.4 [mm] thick polyether sulfone (PE) is used as the substrate material.
Using the S) substrate, the reflective liquid crystal display device shown in FIG. 1 was manufactured. Since the MIM element and the reflective electrode are all manufactured in the same manner as in Embodiment 1 and all process temperatures are 150 [° C.] or less, problems such as deformation and shrinkage of the resin substrate occur. There wasn't.

(Third Embodiment) FIG. 6 shows a reflective liquid crystal display device according to a third embodiment of the present invention. In the third embodiment, the photo-curable resin that constitutes the concave and convex portion below the reflective electrode is used as it is as the substrate that constitutes the reflective liquid crystal display device. The method of manufacturing the reflective liquid crystal display device according to the third embodiment will be described below. FIG. 7 shows the third embodiment.
A simple manufacturing process of the resin substrate with unevenness is shown. First, as shown in FIG. 7A, the photocurable resin 21 used in the first embodiment is formed on the glass substrate 20 in a film thickness of 0.3 to 1 [mm].
Apply by degree. At this time, the final film thickness of the substrate is determined by the film thickness. In the third embodiment, the photocurable resin is applied with a film thickness of 0.45 [mm]. Subsequently, the first exposure is performed only on the reflective electrode region on the substrate from the photocurable resin surface side through the mask 22.

Next, as shown in FIG. 7B, the entire substrate 20 is exposed from the back surface (glass surface) side of the substrate to cure the photocurable resin 21 and the substrate of the third embodiment. 23 is produced. As a result, in the previously exposed reflective electrode region, a continuous wavy surface shape is formed on the surface of the resin substrate as in the first embodiment, and the other portions are smoothed on the surface of the lower glass substrate 20. The liquid crystal display device substrate 23 having a smooth substrate surface reflecting the properties is produced. In the third embodiment, the substrate film thickness is 0.
4 mm and selectively 1.0 to only in the reflective electrode region
A substrate 23 having a surface uneven shape of 1.2 μm was produced.

The glass substrate 20 may be removed after the substrate 23 is manufactured, or if necessary, it may be removed after all the processes on the substrate 21 are completed. Hereinafter, similarly to the first embodiment, the MIM element 24 and the reflective electrode film 25 shown in FIG. 6 are manufactured, and the counter substrate 26 having the color filter 27, the black matrix 28, and the transparent electrode 29.
The reflective liquid crystal display device according to the third embodiment is manufactured by bonding the substrate with the liquid crystal 30 and enclosing the liquid crystal 30 between the substrates.

[0028]

Therefore, according to the present invention, good reflection characteristics can be obtained by the simple structure of two layers of the photocurable resin and the electrode having the light reflection function. Further, by utilizing the photo-curing property of the photo-curing resin, it is possible to manufacture a reflection type liquid crystal display device having a good reflecting property in a small number of steps.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of one pixel of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of manufacturing the reflective liquid crystal display device of FIG.

FIG. 3 is a diagram illustrating a method for forming a surface shape by light irradiation according to the present invention.

FIG. 4 is a plan view of an example of a mask used for forming the surface shape of FIG.

FIG. 5 is a graph showing a relationship between a light irradiation energy density and a height of a convex portion with respect to a photocurable resin.

FIG. 6 is a sectional view of a reflective liquid crystal display device according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a method of manufacturing the reflective liquid crystal display device of FIG.

[Explanation of symbols]

1, 11 Insulating substrate 2 electrode wiring 3 insulating film 4 Upper electrode 5, 24 MIM element 6 Photocurable resin film 7 Reflective electrode area 8 Wavy shape part 9,25 reflective electrode 10 contact holes 12, 27 color filter 13, 28 Black matrix 14, 29 Transparent electrodes 15, 30 Liquid crystal layer 16,18,22 mask 17,21 Photocurable resin 20 glass substrates 23 board

Continuation of the front page (56) Reference JP-A-9-90426 (JP, A) JP-A-6-18908 (JP, A) JP-A-5-232454 (JP, A) JP-A-7-191297 (JP , A) JP-A-7-295520 (JP, A) JP-A-8-87248 (JP, A) Actually developed 63-162328 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G02F 1/13-1/141

Claims (5)

(57) [Claims] 1. A first substrate having a first electrode having a light reflecting function formed on a surface facing the second substrate;
And a liquid crystal layer enclosed between the first and second substrates and a transparent second electrode formed on the surface of the substrate facing the first substrate. A reflective liquid crystal display device comprising: a method of manufacturing a reflective liquid crystal display device, characterized in that there is a portion provided with a photo-curable resin between the first substrate and the first electrode. A step of applying a photo-curable resin on the substrate, and a mask having a transmissive portion so that a convex shape is formed in the first electrode, wherein the light transmittance of the transmissive portion is partially reduced. A step of deforming the photocurable resin by irradiating the photocurable resin with light using a changed translucent mask; and a first step having a light reflecting function on the deformed photocurable resin.
And a step of forming the electrode, and a method for manufacturing a reflective liquid crystal display device. 2. The first and second electrodes are each formed in a matrix, and the deformed photo-curable resin is formed in a continuous wavy shape. A method for manufacturing the reflective liquid crystal display device described. 3. The method of manufacturing a reflection type liquid crystal display device according to claim 1, wherein both the first and second substrates are made of polymer resin. 4. The first substrate and the photocurable resin are integrally formed.
A method for manufacturing the reflective liquid crystal display device described. 5. The manufacturing process is 150 ° C.
The method for manufacturing a reflective liquid crystal display device according to claim 1, wherein the method is performed at the following temperature.