JPH10197892A - Manufacture of reflection type display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form different kinds of medium layers to uniform thickness and to make cycles of variation in refractive index uniform as to the manufacture of the reflection type display element which reflects light with specific wavelength in visible light by periodic variation in internal refractive index. SOLUTION: On an electrode 12 formed on a substrate 11, high polymer layers 21a, 21b...21n and liquid crystal layers 22a, 22b...22m are formed alternately by printing such as screen printing or transfer to obtain a reflecting layer 20 which varies in refractive index periodically in the laminated multi-layered film. On the reflecting film 20, the side of the electrode 14 of a substrate 13 where an electrode 14 is formed is adhered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a reflective display device capable of displaying a color image.

[0002]

2. Description of the Related Art A reflective display device such as a reflective liquid crystal display device does not require a dedicated light source such as a backlight unlike a transmissive display device such as a transmissive liquid crystal display device, and consumes less power. Since it can be configured to be small and lightweight, it is suitable for display devices such as small information devices and portable information terminals.

Conventionally, as a reflection type display element capable of color display, an optical shutter is formed by arranging polarizing plates on both sides of a TN liquid crystal or STN liquid crystal cell, and incident light as external light is colored by a color filter. In addition, there is known a device that transmits light through an optical shutter and reflects the light on a reflecting plate. However,
Since the reflective display element uses a polarizing plate and a color filter, it has a disadvantage that light loss is large, reflected light of output is weak, and luminance is low.

Therefore, as a reflection type display element using no polarizing plate or color filter, at least one of the refractive indices changes between the electrodes of the two substrates on which the electrodes are formed due to an electric field, and the refractive indices mutually change. It is considered that two types of medium layers differing from each other are alternately formed in multiple layers to constitute a reflection layer that reflects light of a specific wavelength in visible light by periodic change in refractive index.

For example, Japanese Patent Application Laid-Open Nos. 4-355424 and 5-134266 disclose between electrodes 12, 14 of substrates 11, 13 on which electrodes 12, 14 are formed, as shown in FIG. In this figure, a reflective layer in which a polymer layer 21 and a liquid crystal layer 22 are alternately laminated is sandwiched.

In this display element, a liquid crystal layer 22 whose refractive index changes according to a voltage applied between the electrodes 12 and 14;
Due to the periodic difference in the refractive index from the polymer layer 21 that does not cause a change in the refractive index, light of a specific wavelength in the incident light is reflected and light in another wavelength region is transmitted by the principle of an interference filter.

For example, by making the refractive index of the liquid crystal for ordinary light equal to the refractive index of the polymer, when no voltage is applied between the electrodes 12, 14, the liquid crystal is oriented in a random direction. A difference in the refractive index occurs between the polymer layer 21 and the liquid crystal layer 22, causing a periodic change in the refractive index between the electrodes 12 and 14. As shown in FIG. Light 5 of specific wavelength in light 55
6 is reflected. The reflection wavelength is determined by the period of change in the refractive index, that is, by the thickness of the polymer layer 21 and the liquid crystal layer 22.

On the other hand, when a sufficient voltage is applied between the electrodes 12 and 14, the liquid crystal is arranged in a direction perpendicular to the substrates 11 and 13, and the polymer layer 21 and the liquid crystal layer 22 are refracted. When the indices become equal, the periodic change in the refractive index between the electrodes 12 and 14 disappears, and all the incident light 55 passes through the display element.

This reflective display element does not use a polarizing plate or a color filter, so that a light loss is small and a high reflectance is obtained, so that a high-luminance display is obtained.

As a method of manufacturing this reflection type display element, conventionally, a mixed liquid of a liquid crystal and a photopolymerizable monomer is injected between the electrodes 12 and 14, and the mixed liquid is irradiated with a laser beam having a predetermined wavelength and the same phase. Then, a method of forming a polymer layer 21 by polymerizing a photopolymerizable monomer by interference between the two and forming a liquid crystal layer 22 in a region other than the polymer layer 21 has been considered.

[0011] For example, SPIE Vol.2152 / 303 ('94) "Develo
pment of photopolymer-liquid crystal composite mat
In the “erials for dynamic hologram applications”, the mixed solution 19 as described above is injected between the electrodes 12 and 14 as shown in FIGS. 10A and 10B, and the substrate 13 is formed as shown in FIG. , 11 or laser light 53, 54 from the substrate 13 side as shown in FIG. 4B, thereby increasing the height as shown in FIG. It is shown that a reflective layer in which a molecular layer 21 and a liquid crystal layer 22 are alternately laminated is obtained.

[0012]

In a reflection type display device as shown in FIG. 10C, a liquid crystal layer 22 and a polymer layer 21 are formed.
The more the periodic structure is uniform, and the more uniform the period of change in the refractive index, the more the intensity of the reflected light increases due to multiple reflection, and a display with high luminance can be obtained. On the contrary, if the periodic structure of the liquid crystal layer 22 and the polymer layer 21 is not uniform, incident light is irregularly reflected in the reflection layer, and the intensity of the reflected light is greatly reduced.

However, in the above-described conventional manufacturing method, the liquid crystal layer 22 and the polymer layer
1 are formed to have uniform thicknesses, and it is difficult to make the period of change in the refractive index uniform, and thus it is difficult to obtain reflected light of sufficient intensity.

Accordingly, the present invention provides a method of manufacturing a reflective display element for reflecting light of a specific wavelength in visible light by periodic changes in the internal refractive index. The thickness can be formed to be uniform, and the period of change in the refractive index can be made uniform.

[0015]

According to the first aspect of the present invention, a first medium layer whose refractive index is changed by an electric field is provided on an electrode side of a first substrate on which an electrode is formed, and the first medium layer has a refractive index. Second medium layers having different indices are alternately formed one by one by printing or transfer, respectively, to obtain a reflective layer in which the refractive index changes periodically in the laminated multilayer film, and an electrode is formed on the reflective layer. The electrode side of the second substrate on which is formed is adhered.

According to the second aspect of the present invention, the first substrate on which the electrode is formed has a refractive index changed by an electric field on the electrode side.
Medium layer, and a second medium layer having a different refractive index from the first medium layer.
The medium layers are alternately formed one by one by printing or transfer, respectively, and the first medium layer and the second medium layer are respectively printed or transferred one by one on the electrode side of the second substrate on which the electrodes are formed. The first substrate and the second substrate are bonded alternately, and a reflective layer having a periodically changing refractive index in the laminated multilayer film is obtained between the respective electrodes.

In this case, a liquid crystal or a ferroelectric can be used as the first medium layer whose refractive index changes according to the electric field.

[0018]

According to printing such as screen printing or transfer, an extremely thin layer or film can be reliably and easily formed with a predetermined thickness.

In the manufacturing method of the present invention, the first medium layer and the second medium layer are alternately formed one by one by printing or transfer, respectively. It can be formed with a uniform thickness, and the period of change in the refractive index can be made uniform. Therefore, it is possible to reliably and easily obtain a high-brightness reflective display element capable of obtaining reflected light of sufficient intensity.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1 as Manufacturing Method] FIGS. 1 and 2 show a series of steps of an example of the manufacturing method of the present invention.

In this example, first, as shown in FIG. 1A, the electrode 12 of the substrate 11 having the electrode 12 formed on one side is formed.
After printing and leveling a resin to be the polymer layer 21a, the polymer layer 21a is cured by heat or light according to the form of the resin to form the polymer layer 21a. Substrate 11 and electrode 1
2 is a light-transmitting material.

As a method for printing the resin, for example, screen printing is used. In the screen printing, as shown in FIG. 4, the substrate 11 on which the electrodes 12 are formed is placed on a pedestal 31, and the screen 32 on which holes 32a are formed is mounted on the substrate 11.
And a resin paste 34 is applied on the screen 32 by the scraper 33, and the squeegee 3
5, the resin paste 34 is applied to the holes 32 of the screen 32.
and is printed on the substrate 11. However, if the resin paste 34 is placed in a direction in which the resin paste 34 is extruded by the squeegee 35, the scraper 33 may not be used.

Usually, the film thickness printed by one screen printing is 0.1 mm. It is several μm to several tens μm. However, when the screen 32 is a screen having a thin emulsion film or a plate-like screen (a thin film or fine line is obtained because wires are not woven), a print having a smaller film thickness can be obtained. The printed film thickness also changes depending on the form of the paste as a material. The film thickness of the material-soluble metallo organic paste containing no fine particles is 0.2 μm or less, and the resin paste can make the printed film thickness thinner than the metallo organic paste. Further, by diluting the resin component with a solvent or evaporating the solvent, an arbitrary film thickness can be obtained.

Here, the thickness of the resin paste 34 is set to 0.1.
The thickness is set to about 0.05 to 0.1 μm, and one layer of the polymer layer 21a is formed by one printing.

Next, a liquid crystal dispersed in a small amount of a thermosetting or photocurable resin is printed on the polymer layer 21a, leveled, and then cured by heat or light.
As shown in FIG. 1B, the liquid crystal layer 2 is formed on the polymer layer 21a.
2a is formed.

In this case, if the amount of the resin component is large, the liquid crystal is fixed by the resin, and the liquid crystal is not aligned even when a voltage is applied to the liquid crystal. Although it depends on the type of resin used, the resin component is preferably 10 parts or less, and more preferably 5 parts or less with respect to 100 parts of the liquid crystal. The liquid crystal layer 22a is also formed by one printing.

Next, as shown in FIG.
2a is printed with a resin to be a polymer layer 21b, leveled, and then cured by heat or light.
1b is formed. Next, a liquid crystal dispersed in a small amount of a thermosetting or photocurable resin is printed on the polymer layer 21b, leveled, and then cured by heat or light, as shown in FIG. As shown, a liquid crystal layer 22b is formed on the polymer layer 21b.

In this way, as shown in FIG. 2A, polymer layers 21a, 21b... 21n and liquid crystal layers 22a, 22b. And the reflection layer 20
Get.

In practice, the polymer layers 21a, 21b... 21n
The total number of the liquid crystal layers 22a, 22b... 22m is about 10 to 100 layers. As the number of layers increases, the intensity of reflected light from the obtained display element increases, but the number of steps also increases. Therefore, the number of stacked layers is determined in consideration of the intensity of reflected light necessary for the display element.

Next, as shown in FIG. 2 (B), the electrode 14 side of the substrate 13 having the electrode 14 formed on one surface is connected to the polymer layers 21a, 21b... 21n and the liquid crystal layers 22a, 22b.
.. Arranged on the reflection layer 20 of 22 m
Is sealed to obtain the display element 10. The substrate 13 and the electrode 14 are each light-transmitting.

In order to make the gap between the substrates 11 and 13 uniform, glass, resin fibers, beads or the like can be added to the sealing material and used as a spacer.
The polymer layers 21a, 21b... 21n and the liquid crystal layer 22a,
22m can be formed to a uniform thickness by screen printing, so that the substrate 11 on which the reflective layer 20 is formed on the electrode 12 and the substrate 13 on which the electrode 14 is formed are simply bonded together. A display element having a uniform gap between 11 and 13 can be obtained.

When the polymer layers 21a, 21b... 21n and the liquid crystal layers 22a, 22b... 22m are formed by screen printing, they are rubbed in the printing direction by the squeegee 35 shown in FIG. Can be made.

In the example shown in FIGS. 1 and 2, the polymer layers 21a and 21n are formed first and last. However, if the polymer layers and the liquid crystal layers are alternately formed one by one, either May be first or last.

It should be noted that forming the polymer layers 21a, 21b... 21n and the liquid crystal layers 22a, 22b.
21n to a uniform thickness and a liquid crystal layer 22
a, 22b... 22m are formed to have a uniform thickness, but not to equalize the thickness of the polymer layer and the liquid crystal layer.

[Second Embodiment as Manufacturing Method] FIG. 3 shows a series of steps in another example of the manufacturing method of the present invention.

In this example, as shown in FIG. 3A, polymer layers 21 and liquid crystal layers 22 are alternately formed one by one by screen printing on the electrodes 12 of the substrate 11 on which the electrodes 12 are formed. I do.

At the same time or before or after this,
As shown in FIG. 1B, the substrate 1 on which the electrodes 14 are formed
A polymer layer 21 and a liquid crystal layer 22 on the third electrode 14;
Each layer is formed alternately by screen printing.

However, the uppermost layer on the substrate 11 is the polymer layer 2
When it is set to 1, the uppermost layer on the substrate 13 is the liquid crystal layer 22.

Next, as shown in FIG.
The side on which the polymer layer 21 and the liquid crystal layer 22 are formed is disposed on the side of the substrate 11 on which the polymer layer 21 and the liquid crystal layer 22 are formed.
Is sealed to obtain the display element 10 in which the reflection layer 20 is formed between the electrodes 12 and 14.

Also in this case, the polymer layer 21 and the liquid crystal layer 2
2 can be formed to a uniform thickness by screen printing, so that the substrate 11 on which the polymer layer 21 and the liquid crystal layer 22 are formed and the substrate 13 on which the polymer layer 21 and the liquid crystal layer 22 are formed are simply attached. Just put together, and board 1
A display element having a uniform gap between 1 and 13 can be obtained.

[Another Example of Manufacturing Method]
Although the polymer layer and the liquid crystal layer are formed by screen printing, they can be formed by other printing methods.

Further, the polymer layer and the liquid crystal layer can be formed by transfer. In the case of transfer, a print is temporarily applied to a transfer body and then transferred to a print. For example, as shown in FIG. 5, the substrate 1 on which the electrode 12 is formed
The transfer material 39 is supplied to the transfer body 38 from the transfer material supply roller 37, and the transfer material 39 is transferred onto the substrate 11 while rotating the transfer body 38. When the transfer member 38 makes one rotation and the transfer material 39 runs out, the transfer material 39 is supplied from the transfer material supply roller 37. However, it is desirable that the transfer to the substrate 11 be completed by one rotation of the transfer body 38. In the case where the diameter of the transfer body 38 is small and the transfer is performed by rotating the transfer body 38 several times, the rotation cuts may overlap,
Adjust so that there are no gaps between cuts.

Also in the case of such transfer, the polymer layer 21 and the liquid crystal layer 22 can be formed to have uniform thicknesses.

In the above example, the liquid crystal layer is used as the medium layer whose refractive index changes according to the electric field. However, the medium layer whose refractive index changes according to the electric field may be used as the ferroelectric layer. When the ferroelectric layer is used, the ferroelectric layer paste is printed or transferred, and after leveling, the solvent component is dried and baked at a predetermined temperature.
Obtain a ferroelectric layer.

[Operation as Display Element] FIG. 6 (A)
(B) shows a display element obtained by the above-described manufacturing method, in which the medium layer whose refractive index changes by an electric field is a liquid crystal layer, that is, the substrate 1 on which the electrodes 12 and 14 are formed.
This is a case where a reflective layer 20 in which a polymer layer 21 and a liquid crystal layer 22 are alternately formed is sandwiched between the electrodes 12 and 14 of the first and the thirteenth electrodes.

In this case, as shown in FIG.
The refractive index of the liquid crystal layer 22 when no voltage is applied between the electrodes 2 and 14 is n1, and the refractive index of the liquid crystal layer 22 when a sufficient voltage is applied between the electrodes 12 and 14 as shown in FIG. Is set to n2. However, n1 <n2. Polymer layer 21
The refractive index n3 is, for example, n1 <n2 ≦ n3 in relation to the refractive indexes n1 and n2 of the liquid crystal layer 22.

According to this, as shown in FIG.
In the state where no voltage is applied between the polymer layers 21 and 14, the polymer layer 21
The difference in the refractive index between the liquid crystal layer 22 and the liquid crystal layer 22 increases, and the display element 10 reflects light 56 of a specific wavelength in the incident light (external light) 55 and transmits other light. The reflection wavelength is determined by the period of change in the refractive index, that is, by the thickness of the polymer layer 21 and the liquid crystal layer 22.

On the other hand, as shown in FIG.
When a sufficient voltage is applied between the polymer layers 2 and 14, the difference in the refractive index between the polymer layer 21 and the liquid crystal layer 22 becomes small,
Most of the incident light 55 passes through the display element 10.

Not n1 <n2 ≦ n3, but n3 ≦ n1 <
On the other hand, when n2 is applied, when no voltage is applied between the electrodes 12 and 14, the difference in refractive index between the polymer layer 21 and the liquid crystal layer 22 becomes small, and the incident light 55 Is transmitted through the display element 10, and when a sufficient voltage is applied between the electrodes 12 and 14, the difference in the refractive index between the polymer layer 21 and the liquid crystal layer 22 increases, and the display element 10 55
The light 56 of the specific wavelength inside is reflected.

Even if n1 <n3 <n2, n3 is equal to n1.
Or, if it is close to n2, the state changes similarly depending on whether a sufficient voltage is applied between the electrodes 12 and 14.

[Example of Full-Color Display Device] As described above, the display element obtained by the manufacturing method of the present invention can be used when no voltage is applied between the electrodes 12 and 14 or when a sufficient voltage is applied. And reflects light having a wavelength determined by the period of change in the refractive index.

Therefore, the wavelengths of the three types of display elements, which are determined by the periods of the changes in the refractive index, are red, green, and red, respectively.
By using the blue wavelength region, it is possible to obtain three types of display elements that selectively reflect red, green, and blue light, respectively. Further, in each display element, the refractive index of the liquid crystal layer 22 or the ferroelectric layer changes according to the voltage applied between the electrodes 12 and 14, and by changing the voltage, the reflectance becomes 0%. The reflectance can be controlled from a transmission state to a constant reflectance state. Therefore, a high-luminance reflective full-color display device can be realized.

FIG. 7 shows an example of the reflection type full-color display device, and the display element 10 manufactured by the method of the present invention and selectively reflecting red, green and blue light, respectively.
R, 10G, and 10B are arranged in one direction in the same plane to form one pixel 1.

However, the above-mentioned substrates 11 and 13 are common to each of the display elements 10R, 10G and 10B and each of the pixels 1, and the reflection layers 20 in which the polymer layers 21 and the liquid crystal layers 22 are alternately formed one by one. Is separately formed for each of the display elements 10R, 10G, and 10B. In addition, a black or gray layer 15 is formed on the back surface of the substrate opposite to the outside light incident side.

In the full-color display device of this example,
When any one of the display elements 10R, 10G, and 10B of a certain pixel is in a reflective state, the pixel displays red, green, or blue, and when any two are in a reflective state, cyan, magenta, or yellow. Is displayed, and when everything is in the reflection state, white is displayed.

When all of the display elements 10R, 10G, and 10B are in the transmissive state, black is displayed. Even when all of the display elements 10R, 10G, and 10B are in the transmission state, the substrates 11, 13 and the electrodes 12, 14,
Part of the incident light is birefringent by the polymer layer 21 and the liquid crystal layer 22, and the intensity of the transmitted light with respect to the incident light is significantly reduced. Therefore, even if the layer 15 is gray, black is displayed.

The area of the display element of each display color may not be uniform. FIG. 8 shows an example of this case, in which one pixel 1
Is divided into four parts, a display element 10R that reflects red color light in one area thereof, a display element 10G that reflects green color light in one area diagonally located with respect to the display element 10R, and the remaining two elements. The display element 10B that reflects blue light is formed in each of the two regions. In this example, two display elements 10B that reflect blue light are arranged in one pixel 1. However, it is preferable to arrange two display elements having a display color with low reflected light intensity.

FIG. 9 shows still another example of the reflection type full-color display device, in which display elements 10B, 10R, and 10G that respectively reflect blue, red, and green color lights are arranged from the side opposite to the outside light incident side. The layers are stacked in this order. A black or gray layer 15 is formed on the back surface of the display element 10B. By laminating the respective display elements in the above order, a clear full-color display can be obtained, but it is not always necessary to laminate in this order.

In the examples of FIGS. 7, 8 and 9, the contrast can be increased by forming the black or gray layer 15, but it is not always necessary to form the layer 15.

[0060]

As described above, according to the present invention, a plurality of types of medium layers each having a plurality of layers can be formed with a uniform thickness, and the period of change in the refractive index can be made uniform. . Therefore, it is possible to reliably and easily obtain a high-brightness reflective display element capable of obtaining reflected light of sufficient intensity. Also, since high brightness can be obtained,
Although the luminance is slightly reduced, the viewing angle can be widened by disposing a scattering plate.

[Brief description of the drawings]

FIG. 1 is a view showing some steps of a first example of a manufacturing method of the present invention.

FIG. 2 is a diagram showing the remaining steps of the first example of the manufacturing method of the present invention.

FIG. 3 is a view showing a second example of the manufacturing method of the present invention.

FIG. 4 is a view schematically showing a method of forming a medium layer by screen printing.

FIG. 5 is a view schematically showing a method of forming a medium layer by transfer.

FIG. 6 is a diagram for explaining the operation of the display element obtained by the manufacturing method of the present invention.

FIG. 7 is a diagram showing an example of a reflective full-color display device obtained by the manufacturing method of the present invention.

FIG. 8 is a diagram showing another example of a reflective full-color display device obtained by the manufacturing method of the present invention.

FIG. 9 is a view showing still another example of the reflection type full-color display device obtained by the manufacturing method of the present invention.

FIG. 10 is a diagram showing a conventional manufacturing method and an example of a display element obtained by the method.

[Explanation of symbols]

10, 10R, 10G, 10B Display element 11, 13 Substrate 12, 14 Electrode 20 Reflective layer 21, 21a, 21b ... 21n Polymer layer (second medium layer) 22, 22a, 22b ... 22m Liquid crystal layer (first medium layer) )

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taketo Hikiji 430 Sakai, Nakai-machi, Ashigarashimo-gun, Kanagawa Green Tech Nakai Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A first medium layer whose refractive index is changed by an electric field and a second medium layer having a different refractive index from the first medium layer are printed on the electrode side of the first substrate on which the electrodes are formed. Alternatively, a reflection layer in which the refractive index changes periodically in the laminated multilayer film is formed alternately one by one by transfer, and the electrode side of the second substrate on which the electrode is formed is formed on the reflection layer. A method of manufacturing a reflective display element, comprising bonding. 2. A first medium layer whose refractive index is changed by an electric field and a second medium layer having a different refractive index from the first medium layer are printed on the electrode side of the first substrate on which the electrodes are formed. Alternatively, the first medium layer and the second medium layer are alternately formed one by one by printing or transfer, respectively, on the electrode side of the second substrate on which the electrodes are formed, while being alternately formed one by one by transfer. A reflective display element, wherein the first substrate and the second substrate are adhered to each other to obtain a reflective layer having a periodically changing refractive index in a laminated multilayer film between the respective electrodes. Manufacturing method. 3. The method according to claim 1, wherein a liquid crystal is used as the first medium layer. 4. A method according to claim 1, wherein a ferroelectric material is used as said first medium layer.