JP2001154188A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antidazzle and low reflection treatment at a low cost without causing a blur or coloring to a reflection type liquid crystal display device. SOLUTION: Fine particles each in an approximately spherical form having <=780 nm particle size are dispersed on the display screen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a display device, and more particularly to a liquid crystal display device having a low reflection layer. Liquid crystal display devices are widely used today from video equipment to information processing equipment such as computers. Conventionally, low-reflection processing of a liquid crystal display device has been a major issue. Particularly, in a low-brightness liquid crystal display device used in a portable information processing device, which is likely to be used outdoors, the low-reflection processing is
This is particularly important for improving display quality.

[0002]

2. Description of the Related Art In a liquid crystal display device, anti-glare (AG) processing and anti-reflection (AR) processing are generally performed as low reflection processing. These low reflection processes are considered to be indispensable for high-quality large-screen display. In the AG treatment, generally, transparent beads having a particle size of about several μm are mixed in a binder, and the mixture is applied to a display surface, for example, the surface of a standard untreated surface polarizing plate. For example, see JP-A-7-181306. The transparent beads coated on the standard polarizing plate have a particle size larger than the wavelength of visible light used for display, and realize a desired anti-glare effect by scattering incident light. It has also been proposed to form unevenness having a size equal to or greater than the wavelength of visible light by sandblasting or embossing a reflective layer in a reflective liquid crystal display device.

[0003] However, such an AG treatment is an anti-glare treatment that is currently used in all liquid crystal display devices. However, the cost of a polarizing plate that has been subjected to such an anti-glare treatment is about as compared with the case where a standard polarizing plate is used. It will be doubled. Also, such AG
In the processing, the problem that the display image is blurred or the contrast is reduced due to scattering is inevitable. On the other hand, as the anti-reflection treatment, conventionally, a multilayer reflective film is known in which films having different refractive indexes are alternately laminated, and specularly reflected light from the ground surface is canceled out by internally reflected light having a phase shifted by half a wavelength. . That is, by optimizing the refractive index and the film thickness of the laminated refraction layer, it is possible to effectively reduce the reflected light. Also,
When such a multilayer reflective film is used, the blur of the display image and the decrease in contrast as in the AG processing described above do not occur.

[0004]

However, in the AR process using the multilayer reflective film, since each refraction layer needs to be formed by a process such as sputtering, the manufacturing cost of the liquid crystal display device becomes extremely high. I will. Further, it is considered that combining the AR processing with the AG processing enables more effective low-reflection processing. However, when these processings are combined, the manufacturing cost of the liquid crystal display device is further increased. Further, as described above, in the conventional AG processing, it is not possible to avoid that light is diffused when passing through the beads applied on the display surface and the display image is blurred.

Accordingly, the present invention has solved the above-mentioned problems.
It is a general object to provide a new and useful liquid crystal display device and a method for manufacturing the same. A more specific object of the present invention is to provide a liquid crystal display device having a low reflection layer which can be realized at low cost and which can achieve an effective anti-glare and reflection reduction effect, and a method for manufacturing the same.

[0006]

The present invention solves the above problems,
As described in claim 1, in a liquid crystal display device including a liquid crystal display panel and a low reflection layer provided in an optical path of light emitted from the liquid crystal display panel, the low reflection layer has a particle size. The problem is solved by a liquid crystal display device characterized by including substantially spherical fine particles of 780 nm or less.

According to a second aspect of the present invention, as described in the second aspect, the fine particles have a structure in which a plurality of layers having different refractive indexes are stacked. The problem is solved by the liquid crystal display device. According to the present invention, there is provided a liquid crystal display according to claim 1 or 2, wherein an air layer is interposed between the fine particles in the low reflection layer. Solve by device.

According to another aspect of the present invention, the liquid crystal display panel has an optically flat reflective surface, and the low reflective layer has a liquid crystal layer interposed therebetween. The liquid crystal display device according to any one of claims 1 to 3, wherein the liquid crystal display device is formed on an emission surface opposed to the reflection surface with a space therebetween.

According to the present invention, as described in claim 5, the low reflection layer is defined by a pair of optically flat main surfaces. ~
The problem is solved by the liquid crystal display device according to any one of the four aspects. FIG. 1 shows the principle of the present invention.

Referring to FIG. 1, a scattering layer 2 composed of substantially spherical fine particles 2A having a particle size of about 780 nm or less is formed on the incident surface side of a transparent substrate 1 on which incident light is incident. The light reflected by the incident surface is scattered and absorbed. FIG. 2 shows the scattering angle characteristics of the single particle 2A in the medium when the diameter R of the particle 2A is variously changed. However, FIG.
The vertical axis represents the normalized scattering intensity, the horizontal axis represents the scattering angle, and the parameter α is defined as α = 2πR / λ, where λ is the wavelength of the incident light in the medium.

Referring to FIG. 2, the diameter R of the fine particles 2A is shown.
Is large, the scattering angle is almost zero, and the incident light incident on the fine particles 2A is almost as it is.
Pass through. On the other hand, when the diameter R decreases and the parameter α becomes 10 or less, for example, about 1, the scattering angle becomes ±
It can be seen that when the intensity of the 180 ° forward scattered light increases and the parameter α becomes about 0.1, the intensity of the forward scattered light and the backward scattered light having a scattering angle of 0 ° become almost the same. The light scattered in this manner is successively scattered and absorbed by the fine particles 2A. When the parameter α is set to 10 or less, the fine particle diameter R is given by R <5λ / π, and the fine particles 2A generally have a refractive index of about 1.
In the case of dispersing in a UV-curable or thermosetting resin of No. 6, the condition that the parameter α is 10 or less is realized by setting the particle diameter R to 780 nm or less, which is a visible light limit wavelength. It becomes possible to do.

FIG. 3A shows the result of determining the reflectance Y in the configuration of FIG. 1 for various light receiving angles θ _out .
However, the calculation in FIG. 3A shows that the incident angle θ _in of the incident light is 30.
° is set. In FIG. 3 (A), ● indicates a case where a polarizing plate is used as it is as the transparent substrate 1 of FIG. 1 (clear polarizing plate), ○ indicates a case where the clear polarizing plate is subjected to a normal AG treatment (AG), ◆ indicates the case where the clear polarizer is subjected to a normal AR process (HCAR); Δ indicates the case where the clear polarizer is subjected to a normal AG process and a normal AR process (AGAR); A case where a polarizing plate is used as a substrate 1 and a scattering layer 2 composed of fine particles 2A is formed on the clear polarizing plate as shown in FIG. However, in FIG.
In the configuration shown in FIG. 3, as shown in FIG. 3B, a two-layer structure in which the surface of an acrylic sphere having a refractive index of 1.52 is covered with a styrene layer having a refractive index of 1.4 has a diameter R of 380 nm on average. Was used as the fine particles 2A. The scattering layer 2,
The fine particles 2A can be formed by dispersing the fine particles 2A in isopropyl alcohol and applying the fine particles 2A to the transparent substrate 1 by spin coating. The relationship between the incident angle theta _in and acceptance angle theta _out is defined as shown in Figure 3 (C).
As is well known, in the case of total reflection, θ _in = θ _out holds.

Referring to FIG. 3A, when a clear polarizer is used, incident light is totally reflected, and the reflectance is 100 ° at a light receiving angle θ _out of 30 °, that is, a reflection angle corresponding to the incident angle. %. On the other hand, when the clear polarizing plate is subjected to the AG processing, the reflectance decreases to about 35% even at a reflection angle of 30 °, and when the AR processing is further performed, the reflectance becomes 25%. %. Also,
When the AG treatment and the AR treatment are performed on the clear polarizing plate, an intermediate reflectance is obtained. However,
As explained above, AR processing is very expensive.
Further, when the AG process is performed, as a result of light scattering, the reflectance increases even at a light receiving angle apart from the reflection angle of 30 °. For example, the reflectance increases at a light receiving angle of 26 ° or less or 34 ° or more. Is higher than that of the clear polarizing plate.

On the other hand, according to the configuration shown in FIG. 1, as shown by X in FIG.
When the light receiving angle deviates ± 4 ° from the reflection angle, the reflectance Y decreases to the same degree as in the AR processing. You can see it. That is, the configuration shown in FIG. 1 can realize the anti-glare processing and the low reflection processing of the liquid crystal display device.

FIG. 4 shows the relationship between the reflection intensity and the wavelength in the configuration of FIG. However, in FIG. 4, the light receiving angle θ _out
Is set to the same value as the incident angle θ _in . In the drawing, a thin solid line indicates the case where the clear polarizing plate is used, a thick solid line indicates the case where the present invention configuration of FIG. 1 is used (Example of the present invention), and ○ indicates that only the AG processing (AG) is performed. X indicates that only the AR processing was performed (HCAR), and □ indicates that the AG processing and the AR processing were performed (AGAR).

Referring to FIG. 4, a large reflection intensity is observed at any wavelength in the clear polarizing plate.
When the G processing is performed, the reflection intensity is reduced regardless of the wavelength. On the other hand, when only the AR processing is performed, or when the AR processing is performed in addition to the AG processing, 430
The reflectivity increases at wavelengths below nm and above 680 nm, indicating that the resulting display is colored magenta.

On the other hand, in the present invention shown by the bold solid line in FIG. 4, the wavelength dependence of the reflection intensity is slightly larger than the case of only the AG processing, but the AR processing or the AG processing.
It can be seen that it is substantially reduced compared to the case of + AR processing. As a result, when the present invention is applied to a liquid crystal display device,
The problem of display coloring that has occurred in the conventional AR processing or AG + AR processing is substantially eliminated.

[0018]

FIG. 5 shows the structure of a liquid crystal display device 10 according to a first embodiment of the present invention. FIG.
Referring to FIG. 1, a liquid crystal display device 10 is a reflection type liquid crystal display device, and a lower glass substrate 11 carrying a mirror reflection electrode 11A such as Al, a transparent ITO electrode 12A, and the transparent ITO electrode 12A An upper glass substrate 12 is provided so as to face the mirror reflection electrode 11A on the lower glass substrate 11, and a twisted nematic (TN) mode liquid crystal layer 13 is provided between the substrates 11 and 12.
Is enclosed.

Further, in the reflection type liquid crystal display device 10, the scattering layer in which substantially spherical fine particles 2A having a particle diameter of 780 nm or less and having a configuration described above with reference to FIG. 2 are formed. More specifically, the surface of an acrylic sphere having a refractive index of 1.52, which is available as Nippon Paint Co., Ltd. as a microgel as the fine particles 2A, is covered with a styrene film having a refractive index of 1.43. Is about 380 nm
Using composite resin fine particles (with a minimum particle size of 60 nm), the fine particles are dispersed in a solvent such as isopropyl alcohol and applied to the glass substrate 12 by spin coating. Conventionally, such composite resin fine particles have been added in the field of paints for the purpose of improving the mechanical durability of the resin film. However, as described with reference to FIG. It was found that fine particles having a parameter α of 10 or less could obtain a wide scattering property, and it was found that the composite resin fine particles used for improving the durability of the coating film could provide such optical scattering properties. .

In the liquid crystal display device 10 of FIG. 5, a １ ／ λ retardation film 15 is further formed on the forward scattering layer 14,
Further, a polarizing plate 16 is formed on the １ ／ λ retardation film 15. In the reflection type liquid crystal display device 10 of FIG. 5, the incident light is first polarized to a predetermined polarization plane when passing through the polarizing plate 16, and is further polarized when passing through the １ ／ λ retardation film 15 thereunder. Is rotated 45 °. The incident light is further transmitted to the forward scattering layer 14, the glass substrate 12, and the transparent electrode 12A.
Pass through the liquid crystal layer 13 and enter the mirror reflection electrode 11A.
And the reflected light formed as a result of the reflection passes through the liquid crystal layer 13, the transparent electrode 12A, the glass substrate 12, and the forward scattering layer 14, and enters the １ ／ λ phase difference film 15. At this time, when the liquid crystal display device 10 is in an inactive state and no driving voltage is applied between the transparent electrode 12A and the specular reflection electrode 11A, the polarization plane of the incident light rotates in the liquid crystal layer 13. Instead, the reflected light is blocked by the polarizing plate 16 after the polarization plane is further rotated by 45 ° in the １ ／ λ retardation film 15. On the other hand, when the liquid crystal display device 10 is activated and a driving voltage is applied between the electrodes 11A and 12A, the reflected light is not blocked by the polarizing plate 16 and the polarized light is not blocked. The emitted light exits through the plate 16.

In the reflection type liquid crystal display device 10,
By forming the forward scattering layer 14 in which fine particles having a diameter equal to or smaller than the visible light limit are dispersed on the glass substrate 12, effective scattering is induced in the forward scattering layer 14, and as a result, antiglare and low reflection Processing can be achieved at low cost and without undesirable coloration of the displayed image. In addition,
The forward scattering layer 14 is formed by dispersing the fine particles 2A in isopropyl alcohol and forming an adhesive layer on the surface of the fine particles in the same manner as a commercially available adhesive spacer. After that, the adhesive layer can be formed by curing the adhesive layer. In this case, a gap filled with air is formed between the fine particles 2A in the forward scattering layer 14.

Alternatively, the forward scattering layer 14 can be formed by dispersing the fine particles 2A in an ultraviolet curable resin or a thermosetting resin. In this case, the resin layer in which the fine particles 2A are dispersed is applied to the glass substrate 1
After application on the substrate 2, it is cured by ultraviolet light or heat. Further, in the forward scattering layer 14, the fine particles 2A do not need to have the same particle diameter, and fine particles having different particle diameters or belonging to a plurality of populations can be mixed and used. [Second Embodiment] FIG. 6 shows the configuration of a reflection type color liquid crystal display device 20 according to a second embodiment of the present invention. However, in FIG. 6, the same reference numerals are given to the parts described above, and the description will be omitted.

Referring to FIG. 6, the reflection type liquid crystal display device 20 is a modified example of the reflection type liquid crystal display device 10 of FIG. 5, and in one pixel region, the mirror surface Al reflection electrode 11A is a red pixel. An electrode (11A) corresponding to _R ;
An electrode (11A) _G corresponding to the green pixel G and a blue pixel B
Filter with being divided into the electrode (11A) and _B correspond, also on the upper substrate 12, between the transparent ITO electrode 12A and the substrate 12, R, G, three colors filter patterns B to The layer 12B is provided on each of the electrodes (11
A) It is formed so as to correspond to _R , (11A) _G and (11A) _B.

In this embodiment, similarly to the embodiment of FIG. 5, the forward scattering layer 14 is formed continuously on the upper glass substrate 12, but as described above with reference to FIG. In addition, the spread of the scattered light is smaller in the forward scattering layer 14 of the present invention than in the case where the normal AG processing is performed, and the deterioration of the color display quality due to the color bleeding is suppressed. Also, expensive AR
The problem of coloring that occurs when the treatment is performed can also be effectively avoided. [Third Embodiment] FIG. 7 shows a configuration of a reflection type liquid crystal display device 30 according to a third embodiment of the present invention. However, in FIG. 7, the parts described above are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIG. 7, in the present embodiment, the filter layer 12B is formed of the mirror surface Al reflective electrode (11).
A) It is formed directly on _R , (11A) _G and (11A) _B. That is, the R, G, and B filter patterns constituting the filter layer 12 are directly applied to the electrodes (11).
A) Forming on _R , (11A) _G and (11A) _B can further reduce color bleeding.

In each of the above embodiments, although not shown, the low reflection layer 14 may be formed on the outer surface of the polarizing plate 16. The fine particles contained in the low reflection layer 14 are also used for improving the durability of the paint, and improve the mechanical durability of the polarizing plate 16. Further, the low reflection layer 14 of the present invention can be used for a transmission type liquid crystal display device.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the appended claims. is there.

[0028]

According to the first to fifth aspects of the present invention, the anti-glare and low-reflection treatment can be performed by forming the low reflection layer of the liquid crystal display device with fine particles having a particle size of 780 nm or less. It can be performed at low cost without blurring or coloring of the image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is another diagram illustrating the principle of the present invention.

FIGS. 3A to 3C are still other views illustrating the principle of the present invention.

FIG. 4 is yet another diagram illustrating the principle of the present invention.

FIG. 5 is a diagram illustrating a configuration of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of a reflective liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a reflective liquid crystal display device according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 11,12 Substrate 2 Low reflection layer 2A Fine particle 2a Acrylic sphere 2b Styrene layer 10,20,30 Reflection type liquid crystal display device 11A, (11A) _R , (11A) _G , (11A) _B
Mirror electrode 12A transparent electrode 13 liquid crystal layer 14 low reflection layer 15 λ / 4 retardation plate 16 polarizing plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 BA02 BA20 2H091 FA08X FA11X FA14Y FA31X FA37X FB02 FB12 FD06 GA16 LA03 LA12

Claims (5)

[Claims] 1. A liquid crystal display device comprising: a liquid crystal display panel; and a low reflection layer provided in an optical path of light emitted from the liquid crystal display panel, wherein the low reflection layer has a particle size of approximately 780 nm or less. A liquid crystal display device comprising spherical fine particles. 2. The liquid crystal display device according to claim 1, wherein the fine particles have a structure in which a plurality of layers having different refractive indexes are stacked. 3. The liquid crystal display device according to claim 1, wherein an air layer is interposed between the fine particles in the low reflection layer. 4. The liquid crystal display panel has an optically flat reflective surface, and the low reflective layer is formed on an output surface facing the reflective surface with a liquid crystal layer interposed therebetween. The liquid crystal display device according to claim 1, wherein: 5. The low reflection layer is defined by a pair of optically flat main surfaces.
5. The liquid crystal display device according to any one of 4.