JP3785303B2 - Touch panel - Google Patents

Description

【００２６】
【発明の効果】
以上の通り、本発明タッチパネルは、外光の反射がなく、明るくて視認性及び着色性に優れるので、入力操作者の目に優しく使いやすい。また、構成部材数も極めて少ないので薄型で安価に製造できる。
【図面の簡単な説明】
【図１】実施形態のタッチパネルを示す厚み方向断面図である。
る。
【図２】従来のタッチパネルを示す厚み方向断面図である。
【符号の説明】
１、３、１１、１３ 透明導電膜
６ 液晶セル
７ １／２波長板
８ １／４波長板
９ 偏光板
５、１５ スペーサ
１６ 液晶ディスプレイ[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a touch panel provided on the front surface of a liquid crystal cell and exhibiting a display function integrally with the liquid crystal cell, and particularly belongs to a resistive film type touch panel.
[0002]
[Prior art]
A touch panel that makes contact with a finger or an input pen, detects the contact position, and performs an input operation based on the signal is used in combination with a liquid crystal display. As a touch panel system, an optical system, an ultrasonic system, an electromagnetic induction system, a resistance film system, and a capacitance system are known. Among these, the combination with the liquid crystal display is often used in the resistive film type because the liquid crystal display is originally employed to achieve thinning and power saving.
[0003]
2. Description of the Related Art Conventionally, as shown in FIG. 2 as a sectional view in the thickness direction, a resistive film type touch panel includes a first transparent substrate 12 made of glass and having a transparent conductive film 11 formed on the main surface, a polyester resin (PET), and the like. The transparent conductive film 13 made of the same transparent resin and having the transparent conductive film 13 formed on the main surface is laminated so that the transparent conductive films 11 and 13 face each other with a spacer 15 interposed therebetween, and this is a liquid crystal display. 16 has a configuration in which the second transparent base material 14 is disposed on the front surface of the outermost layer. On the back surface of the liquid crystal display 16, a reflective plate is provided in the case of a reflective display, and a reflective plate is provided via a backlight light guide plate (not shown) in the case of a transmissive display. In the case of the reflective type, the power consumption is small as much as the backlight and the light guide plate are unnecessary, and the thickness and thickness are low.
[0004]
Although only a few spacers 15 are shown between the two transparent conductive films 11 and 13 for the sake of convenience, in reality, a large number of spacers are scattered in the surface direction, and an adhesive is present at the end. The transparent conductive films are bonded to each other by 18.
Then, by pressing the second transparent substrate 14 with a finger or a pen, the opposing transparent conductive films 11 and 13 come into contact with each other, and a command is issued to the control system based on the potential at the contact position. The transparent conductive films 11 and 13 used here are formed as thin films by vapor deposition or sputtering, and the materials thereof are metal oxides such as indium tin oxide (ITO) and tin antimonic acid, gold, palladium, and aluminum. Metals such as silver are common.
[0005]
By the way, these metal oxides and metal thin films have a very large reflectance compared to the glass substrate on the surface of the liquid crystal display in order to form a space and a boundary surface held by the spacer 15, and the touch panel The number of interfaces may increase by the number of layers, and the contrast of the liquid crystal display is remarkably lowered due to reflection of external light on the transparent conductive film, making it difficult to see the screen. This problem is remarkable in the case of a reflective display.
[0006]
Therefore, in order to eliminate this drawback, Japanese Patent No. 2509215 discloses a plurality of different refractive indexes including a transparent conductive film between the transparent conductive film 11 (or 13) and the transparent substrate 12 (or 14). It has been proposed to provide an antireflective film consisting of these layers. In JP-A-5-127822, a quarter-wave plate and a polarizing plate are sequentially laminated on the second transparent substrate 14, and the external light that has been linearly polarized through the polarizing plate is incident. By passing through a quarter-wave plate twice when reflected on the transparent conductive film, the phase is shifted by ½ wavelength and linearly polarized in the absorption axis direction of the polarizing plate so that it does not pass through the polarizing plate. A configuration is proposed. Furthermore, in JP-A-10-48625 and JP-A-11-134112, in addition to laminating a quarter-wave plate and a polarizing plate on the second transparent substrate 14, the first transparent substrate By interposing a quarter-wave plate between the liquid crystal display 16 and the liquid crystal display 16, the reflected light on the transparent conductive film is not transmitted and the reflected light on the reflective plate disposed on the back surface of the liquid crystal display 16. Has been proposed in which the phase is matched and transmitted.
[0007]
[Problems to be solved by the invention]
However, in the configuration described in Japanese Patent No. 2509215, not only the refractive index but also the film thickness of each layer must be defined, so that the selection range of the transparent conductive film is limited. Further, in the configurations described in JP-A-5-127822 and JP-A-11-134112, reflection by the transparent conductive film is reduced, but the light from the reflector is not sufficiently transmitted, so the screen is dark and difficult to see. . The configuration described in Japanese Patent Laid-Open No. 10-48625 has been proposed in order to improve these. However, since a plurality of wavelength plates are used, there is a large number of inconsistencies in the phase difference due to the wavelength plates, causing discoloration. appear.
Therefore, an object of the present invention is to provide a touch panel that functions as a liquid crystal display, reduces reflection from a transparent conductive film, and has excellent visibility and colorability.
[0008]
[Means for Solving the Problems]
In order to solve the problem, the present invention
In the touch panel which is disposed on the front surface of the liquid crystal cell and has the first and second two layers of transparent conductive films facing each other with a spacer between the input operation surface and the liquid crystal cell,
The liquid crystal of the liquid crystal cell is a field effect type circularly polarizing element, and a reflection plate using external light as a light source is provided on the back surface of the liquid crystal cell. A four-wave plate, the first transparent conductive film, the second transparent conductive film, and a half-wave plate are arranged.
[0009]
According to this configuration, the light from the input operation surface side is linearly polarized by the polarizing plate and circularly polarized by the quarter wavelength plate. Here, when the light is reflected by the first or second transparent conductive film, it returns to linearly polarized light again by the quarter-wave plate, but the vibration direction is changed by 90 ° due to the reflection, so that it does not pass through the polarizing plate. Therefore, the reflected light by the transparent conductive film is substantially prevented.
[0010]
On the other hand, the circularly polarized light transmitted through the pair of transparent conductive films is compensated for the phase difference for each wavelength by the half-wave plate. Since the liquid crystal is a field effect type circularly polarizing element, when no voltage is applied, the circularly polarized light becomes linearly polarized light when passing through the liquid crystal, is reflected by the reflecting plate, passes through the liquid crystal again, and is circularly polarized, The light is returned to linearly polarized light by the quarter-wave plate to display white (normally white). Conversely, when voltage is applied, the circularly polarized light having the same phase is not affected by the liquid crystal, and after being reflected by the reflector, it passes through the half-wave plate and the quarter-wave plate again to be linearly polarized. Is done. However, the vibration direction is shifted by 90 ° when reflected by the reflector. Therefore, the black color is displayed through the polarizing plate. As a result, the touch panel of the present invention is integrated with the liquid crystal cell and also has a function as a liquid crystal display, and the screen is bright and has excellent contrast, visibility and colorability.
[0011]
The angle formed by the slow axis of the quarter-wave plate is 45 ± 5 degrees with respect to the absorption axis of the polarizing plate, and the angle formed by the slow axis of the half-wave plate is 135 ± 5 degrees. And preferred. This is because the phase difference of light of each wavelength from the liquid crystal cell toward the polarizing plate is almost the same, and the visibility and colorability are most excellent.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The touch panel of embodiment of this invention is shown as thickness direction sectional drawing in FIG. The touch panel 10 has a structure in which a half-wave plate 7, a quarter-wave plate 8, and a polarizing plate 9 are sequentially stacked on the liquid crystal cell 6. A reflective plate 4 is provided on the back surface of the liquid crystal cell 6. Transparent conductive films 1 and 3 are respectively formed on one main surface of the half-wave plate 7 and the quarter-wave plate 8. Then, the half-wave plate 7 and the quarter-wave plate 8 are aligned so that the transparent conductive films 1 and 3 face each other through the spacers 5 scattered in the plane direction, and are adhered at the ends. Bonded by the agent 20.
[0013]
The transparent conductive films 1 and 3 are formed as a thin film by a physical method such as vacuum vapor deposition, sputtering, ion plating, ion beam vapor deposition, or chemical vapor deposition, and the material thereof is indium tin oxide (ITO). ), Metal oxides such as tin antimonic acid, and metals such as gold, silver, copper, palladium, and aluminum. The transparent conductive films 1 and 3 may be formed on a film different from the wave plates 7 and 8 and bonded to the wave plates 7 and 8. However, in that case, in order not to affect the function of the wave plate, it is desirable that the retardation of another film at a wavelength of 550 nm is 30 nm or less.
[0014]
Wave plates 7 and 8 are obtained by stretching a polymer film by free-end uniaxial stretching, fixed-end uniaxial stretching, biaxial stretching, or thickness direction stretching, or by applying an alignment film made of a polymer liquid crystal or the like to a substrate. It is done. Although the film material is not particularly limited, the half-wave plate 7 is assumed to have low wavelength dispersion (the ratio of refractive index difference (Δn / Δn ₅₅₀ ) at each wavelength is small), and the quarter-wave plate. In No. 8, it is desirable that the wavelength dispersibility is high (the ratio of the refractive index difference (Δn / Δn ₅₅₀ ) at each wavelength is large).
[0015]
Specifically, when the thickness of the wave plate is d, the refractive index at λ = 550 nm is n ₅₅₀ , and the refractive index at λ = 400 nm is n ₄₀₀ , the retardation ratio Δn for a half-wave plate It is desirable that ₄₀₀ d / Δn ₅₅₀ d is smaller than 1.1. For example, in the case of a norbornene system, a product having a ratio of 1.03 is commercially available. Further, as the quarter wavelength plate, it is desirable that the ratio is larger than 1.1. For example, polycarbonate type 1.16 and polysulfone type 1.2 are commercially available. Thus, by laminating wave plates having different retardations with their slow axes crossing each other, the wavelength dispersion of the retardation in each wave plate can be superimposed or controlled, and a predetermined phase difference can be obtained over a wide wavelength region. And coloring can be suppressed.
[0016]
The polarizing plate 9 is obtained by mixing iodine with a transparent film and stretching. The surface of the polarizing plate may be subjected to various surface treatments such as curing treatment, antireflection treatment, antifouling treatment, and antiglare treatment in order to improve visibility and durability. Since the touch panel of the present invention has a polarizing plate and a quarter-wave plate in the touch panel, the polarizing plate and the quarter-wave plate generally used in a reflective display using a circularly polarized liquid crystal element can be omitted. .
[0017]
Compared with the structure of FIG. 2, in this embodiment, instead of the transparent base material 12 and the transparent base material 14, the half-wave plate 7 and the quarter-wave plate 8 are arranged, respectively. Since only the polarizing plate 9 is provided above, the number of layers is only increased by one.
[0018]
【Example】
Example 1
[Production of touch panel]
A polarizing film was obtained by uniaxially stretching a polyvinyl alcohol film by a conventional method, and a cellulosic film was laminated on both sides to obtain a polarizing plate. Separately, a polycarbonate film (Δn ₄₀₀ d / Δn ₅₅₀ d = 1.16) having a thickness of 50 μm was uniaxially stretched at 150 ° C. for 5%, and based on the birefringence generated thereby, the wavelength was reduced to ¼. A wave plate giving the phase difference of the wavelength was obtained. Also, a norbornene-based polymer film (Δn ₄₀₀ d / Δn ₅₅₀ d = 1.03) having a thickness of 100 μm was uniaxially stretched at 170 ° C. by 70%, and based on the birefringence generated thereby, with respect to light having a wavelength of 550 nm A wave plate giving a half-wave phase difference was obtained.
[0019]
Then, one surface of each wave plate was plasma-treated in an Ar atmosphere, a transparent conductive film made of ITO having a thickness of 0.03 μm was formed by sputtering, and a silver electrode was printed on the surface of the transparent conductive film. The obtained quarter-wave plate and half-wave plate are arranged so that the transparent conductive films face each other, and a spacer made of ultraviolet curable ink (manufactured by Seiko Advance) is interposed therebetween (usually, The edge part was adhere | attached with the epoxy-type adhesive agent. And the touch panel was produced by adhere | attaching a polarizing plate on the surface on the opposite side of a quarter wavelength plate.
[0020]
[Production of LCD cells]
After sputtering aluminum on a glass plate having a thickness of 1.1 mm, a polyimide alignment film was formed, and the alignment film was rubbed to produce a reflector. Separately, a transparent conductive film made of ITO was formed on an isomorphous and homogeneous glass plate by sputtering, a polyimide-based alignment film was formed, and the alignment film was rubbed to produce a transparent substrate. Then, a reflection type liquid crystal cell was produced by injecting field effect type (circular polarization) liquid crystal with the alignment films facing each other.
[0021]
[assembly]
The touch panel was superimposed on the opposite surface of the glass plate on which the transparent conductive film of the liquid crystal cell was formed, thereby completing a touch panel (hereinafter referred to as an LCD touch panel) that also functions as a liquid crystal display having a layer structure shown in FIG. The direction of each plate is set so that the slow axis of the quarter-wave plate is 45 ° and the slow axis of the half-wave plate is 135 ° when the absorption axis of the polarizing plate is 0 °. did.
[0022]
[Evaluation]
The LCD touch panel was placed 2 m below the 60 W fluorescent lamp indoors, and the display screen contrast, brightness, degree of external light reflection, visibility, and colorability were evaluated. An evaluation result is shown in Table 1 with the following Examples 2-5 and a comparative example. In the table, ◯ indicates good, Δ indicates normal, and X indicates poor.
[0023]
-Example 2-
The polycarbonate film used as the material of the quarter-wave plate in Example 1 is used as the material of the half-wave plate, and the norbornene-based polymer film used as the material of the half-wave plate in Example 1 is 1 / An LCD touch panel was produced and evaluated under the same conditions as in Example 1 except that it was used as the material of the four-wave plate. As a result, the reflection of external light was eliminated and the display was bright, but the coloration was strong and the visibility was lowered due to the influence.
-Example 3-
An LCD touch panel was produced and evaluated under the same conditions as in Example 1 except that both the half-wave plate and the quarter-wave plate were made of the norbornene polymer film. As a result, the reflection of external light was eliminated and the display was bright, but the coloration was strong and the visibility was lowered due to the influence.
Example 4
An LCD touch panel was manufactured and evaluated under the same conditions as in Example 1 except that both the half-wave plate and the quarter-wave plate were made of the polycarbonate film. As a result, the reflection of external light was eliminated and the display was bright, but the coloration was strong and the visibility was lowered due to the influence.
[0024]
-Example 5
Other than setting the direction of each plate so that the slow axis of the quarter wave plate is 60 ° and the slow axis of the half wave plate is 165 ° when the absorption axis of the polarizing plate is 0 ° The LCD touch panel was manufactured and evaluated under the same conditions as in Example 1. As a result, external light reflection was eliminated and the display was bright, but there was a slight coloration, and the visibility was also lowered due to the influence.
[0025]
[Table 1]

[0026]
【The invention's effect】
As described above, the touch panel of the present invention has no reflection of external light, is bright and has excellent visibility and colorability, and is therefore easy to use for the input operator. Further, since the number of constituent members is extremely small, it can be manufactured thinly and inexpensively.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view in a thickness direction showing a touch panel of an embodiment.
The
FIG. 2 is a cross-sectional view in the thickness direction showing a conventional touch panel.
[Explanation of symbols]
1, 3, 11, 13 Transparent conductive film 6 Liquid crystal cell 7 1/2 wavelength plate 8 1/4 wavelength plate 9 Polarizing plate 5, 15 Spacer 16 Liquid crystal display

Claims (4)

In the touch panel which is disposed on the front surface of the liquid crystal cell and has the first and second two layers of transparent conductive films facing each other with a spacer between the input operation surface and the liquid crystal cell,
The liquid crystal of the liquid crystal cell is a field effect type circularly polarizing element, and a reflection plate using external light as a light source is provided on the back surface of the liquid crystal cell. A touch panel comprising a four-wavelength plate, the first transparent conductive film, the second transparent conductive film, and a half-wave plate. The angle formed by the slow axis of the quarter-wave plate with respect to the absorption axis of the polarizing plate is 45 ± 5 degrees, and the angle formed by the slow axis of the half-wave plate is 135 ± 5 degrees. The touch panel according to claim 1. 3. The touch panel according to claim 1, wherein the first transparent conductive film and the second transparent conductive film are directly formed as thin films on the quarter-wave plate and the half-wave plate, respectively. When the thickness of the wave plate is d, the refractive index at λ = 550 nm is n ₅₅₀ , and the refractive index at λ = 400 nm is n ₄₀₀ , the half-wave plate has a retardation ratio Δn ₄₀₀ d / Δn. ₅₅₀ d is smaller than 1.1, the touch panel according to any one of the quarter-wave plate is the ratio of greater than 1.1 according to claim 1 to 3.

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