JP2002090732A - Method for manufacturing reflection plate for liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a reflection plate by etching a glass substrate with excellent controllability and reproducibility of projection and recession and at a low production cost. SOLUTION: The method for manufacturing the reflection plate for a liquid crystal display panel contains a first etching step to form a plurality of dotted recessing parts 2 with a first etching liquid containing hydrofluoric acid and an ammonium compound as main components and a second etching step to enlarge the diameter of the recessing parts 2 by etching using the recessing parts 2 as starting points for the etching with a second etching liquid containing hydrofluoric acid as a main component and containing no ammonium compound. Thereby the recessing parts 2 are formed with the excellent controllability. Also a photolithography step or a film forming step is not needed and a production cost is drastically reduced. Furthermore, because a resin layer is not used in the reflection plate, a heating process up to the softening temperature of the glass nearly 650 deg.C, is possible and restriction on heating for the succeeding processes is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a reflector for a reflection type liquid crystal display panel used as a flat display, and a structure of the reflector.

[0002]

2. Description of the Related Art With the advent of portable telephones, portable terminals and video cameras, there has been a demand for lighter and lower power consumption liquid crystal display panels. In order to respond to such needs, a liquid crystal display panel called a reflection type using external light without using a backlight, which accounts for most of power consumption, has been developed. Such a reflection type liquid crystal display panel is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-18874.
JP, JP-A-7-333602 or JP-A-9-333
-258219.

[0003] These reflection type liquid crystal display panels have a reflection plate. As a method of forming the reflection plate, a photosensitive resin is applied to a glass substrate, and then a photolithography process is used to form irregularities, on which a high reflection is formed. Forming a reflector by depositing a metal film having a high reflectivity, and forming a reflector by forming irregularities on a glass substrate itself by etching and depositing a metal film having a high reflectivity on the glass substrate itself There are two ways.

The former method is disclosed in JP-A-9-258219, JP-A-9-292504 or JP-A-11-292504.
-326615. In this method, since the uneven shape is formed in the resin by the photolithography process, the uneven shape can be manufactured with good controllability and reproducibility. Therefore, this method is now mainstream.

On the other hand, the latter method has a problem that when a flat glass substrate is etched, the etching proceeds while the surface is flat. As a method for solving this problem, Japanese Patent Publication No. 2610698 discloses a method of forming irregularities by etching a glass substrate roughened by an abrasive, or a method of forming a porous surface on a glass substrate. There is a method in which an oxide film is formed and then etched, and only the holes are selectively etched to form irregularities.

As a general method, there is a method of forming irregularities on a glass substrate by a photolithography step and an etching step, and this method is disclosed in Japanese Patent Application Laid-Open No. 8-313890.

[0007]

However, in the former method of forming irregularities on a resin on a glass substrate, other structures such as a reflective metal film, a color filter, and an ITO electrode are formed on the resin. The heat treatment sometimes causes dripping of the unevenness of the resin. Conversely, if this heat drooping is to be prevented, the temperature of the heating process will be limited in the subsequent steps.
There is a problem that a TO film cannot be formed. In addition, since this method generally requires a resin coating step and a photolithography step for forming a pattern, the steps are complicated, expensive production equipment is required, and it is difficult to reduce the production cost.

In the latter method of etching a glass substrate, a method of forming concavities and convexities by etching a glass substrate roughened by an abrasive or a method of forming a porous oxide film instead of a mask is used. However, there is a problem that the controllability and reproducibility of the unevenness are lacking. In addition, in the case of forming a mask pattern using a resist by a photolithography process, controllability is ensured in forming an uneven shape, but it also complicates the process, requires expensive production equipment, and leads to an increase in production cost. There's a problem.

Accordingly, an object of the present invention is to manufacture a reflection plate by etching a glass substrate with good controllability and reproducibility of unevenness and at a low production cost.

[0010] Still another object of the present invention is to provide a reflection plate having good reflection efficiency.

[0011]

SUMMARY OF THE INVENTION The present invention provides a glass substrate having a liquid crystal layer sandwiched between a pair of opposed substrates and provided on the back side of the liquid crystal display panel. A method for manufacturing a reflector for a liquid crystal display panel, comprising: a formed metal film having a high reflectivity, wherein the uneven shape of the glass substrate is formed only by an etching process. It is a manufacturing method of.

According to the present invention, a plurality of recesses are formed on the surface of a glass substrate only by an etching process, and a metal film having a high reflectance is formed on the surface of the glass substrate on which the plurality of recesses are formed. Thereby, a reflection plate is manufactured. Therefore, the reflector of the present invention does not require a resin layer as in the prior art, and can be heated to about 650 ° C., which is the softening point of glass.
That is, when a color filter, an ITO electrode, or the like is formed on the reflection plate, the heating treatment can be performed by raising the temperature to about the softening point of the glass without being restricted by heating.

[0013] In the present invention, the etching step may include a primary etching step of forming a plurality of recesses on the surface of the glass substrate by using an etching solution for partially generating an insoluble compound; A second etching step of enlarging the diameter of the concave portion by performing etching using the concave portion as an etching starting point and making each concave portion continuously adjacent to each other.

According to the present invention, in the first etching step, a plurality of recesses are formed on the surface of the glass substrate by using an etching solution for partially generating an insoluble compound. Thereafter, in the secondary etching process, the diameter of each concave portion is enlarged by performing etching using each concave portion formed in the primary etching process as an etching starting point. That is, a recess having a diameter required for the reflector can be formed on the entire surface of the glass substrate by two etching steps. Therefore, unlike the prior art, a photolithography process and a resin film forming process are not required, so that the manufacturing equipment of the reflector can be greatly simplified, and the manufacturing cost can be greatly reduced.

Further, the present invention is characterized in that the etching solution in the first etching step contains hydrofluoric acid and an ammonium compound.

According to the present invention, insoluble ammonium silicofluoride ((NH ₄ ) ₂ SiF ₆ ) is partially deposited on the surface of the glass substrate by the hydrofluoric acid and the ammonium compound. Then, this ammonium fluorosilicate ((N
Since the progress of etching is stopped in the deposited portion of H ₄ ) ₂ SiF ₆ ) and the etching proceeds in the non-deposited portion, a plurality of concave portions are formed on the surface of the glass substrate. Therefore, a plurality of concave portions serving as etching starting points in the secondary etching step can be efficiently formed. Also,
By controlling the concentration of the etchant and the etching time, the number and depth of the concave portions can be accurately and easily controlled.

Further, the present invention is characterized in that the etching solution in the first etching step further contains sulfuric acid.

According to the present invention, since the etching solution in the first step further contains sulfuric acid in addition to hydrofluoric acid and ammonium fluoride, the number and depth of the concave portions can be controlled accurately and easily. it can.

Further, the present invention is characterized in that the ammonium compound is ammonium fluoride.

According to the present invention, an insoluble compound can be deposited on a glass substrate by using ammonium fluoride as a primary etching solution.

Further, the present invention is characterized in that the ammonium compound is ammonium sulfate.

According to the present invention, an insoluble compound can be deposited on a glass substrate by using ammonium sulfate as a primary etching solution.

Further, the invention is characterized in that the ammonium compound is ammonium hydrogen sulfate.

According to the present invention, an insoluble compound can be deposited on a glass substrate by using ammonium hydrogen sulfate as a primary etching solution.

Further, the present invention is characterized in that the ammonium compound is ammonium chloride.

According to the present invention, an insoluble compound can be deposited on a glass substrate by using ammonium chloride as a primary etching solution.

Further, the present invention is characterized in that the etching solution in the secondary etching step contains hydrofluoric acid as a main component and does not contain an ammonium compound.

According to the present invention, since a solution containing hydrofluoric acid as a main component and not containing an ammonium compound is used as an etching solution in the secondary etching step, no insoluble compound is generated during the secondary etching step. Therefore, 2
In the next etching step, the glass substrate is etched starting from the concave portion formed in the primary etching step, and the diameter of the concave portion increases. Therefore, the concave portions can be adjacent to each other over the entire surface of the glass substrate, and the concave curved surface of each concave portion is continuous.

Further, the present invention is characterized in that the etchant in the secondary etching step is an aqueous solution having a hydrofluoric acid dilution of 5 to 20 times.

According to the present invention, unevenness in the flow of the etchant due to the high viscosity of the etchant is prevented by making the degree of dilution of the hydrofluoric acid in the etchant in the secondary etching step five times or more. And a good etching finish can be obtained. Further, by setting the dilution of hydrofluoric acid in the etching solution to 20 times or less, an appropriate etching rate can be obtained.

Further, according to the present invention, a metal film having a high reflectivity is formed on the surface of a glass substrate having a plurality of concave portions formed continuously adjacent to each other. It is characterized in that a concave mirror is formed.

According to the present invention, a plurality of minute hemispherical concave mirrors are formed adjacent to each other on the surface of the reflector. Therefore, all surfaces except the central point of each concave mirror are continuous inclined surfaces having a predetermined angle with respect to the surface of the glass substrate. Therefore, the liquid crystal display device provided with this reflector can obtain a display with high scattering properties,
The reflection of a normal image like a mirror is prevented, and the appearance of paper can be obtained when viewed with the naked eye.

The present invention is also characterized in that the average value of the diameter of the concave mirror is 4 μm or more and 10 μm or less.

According to the present invention, since the average value of the diameters of the concave mirrors is formed in the range of 4 μm or more and 10 μm or less, the contrast of the liquid crystal display panel provided with this reflector takes a practical value of 10 or more.

Further, the present invention is characterized in that the average value of the diameter of the concave mirror is 5 μm or more and 7 μm or less.

According to the present invention, the average value of the diameter of each concave mirror is formed to be 5 μm or more and 7 μm or less,
The contrast of a liquid crystal display panel having this reflector is 2
0 or more, and a very clear display can be obtained.

In the present invention, the standard deviation of the diameter of the concave mirror is 2 μm or more and 4 μm or less.

According to the present invention, by setting the standard deviation of the diameter of the concave mirror to 2 μm or more and 4 μm or less, it is possible to obtain a reflection plate having a small wavelength dependency in reflectance. Therefore, it is reduced that the reflected light reflected by the reflector is colored and emitted with respect to the incident light that enters the liquid crystal display panel. That is, when white light is input from a white light source, reflected light as close as possible to incident light can be emitted, and a display close to white can be obtained.

Further, the present invention is characterized in that the step of unevenness of each concave mirror is 0.5 μm or more and 1.2 μm or less.

According to the present invention, the concave and convex steps of the concave mirror are
By making the thickness 0.5 μm or more and 1.2 μm or less, T
A sufficiently practical reflectance can be obtained in a range below the limit surface step reference value of 1.2 μm required for the FT type liquid crystal display panel.

Further, the present invention is characterized in that the step of the concave and convex of each concave mirror is 0.6 μm or more and 0.9 μm or less.

According to the present invention, the concave and convex steps of the concave mirror are
By making the thickness 0.6 μm or more and 0.9 μm or less, T
STN liquid crystal display panel which requires more flatness than FT type liquid crystal display panel.
Within this range, the optimum reflectance can be obtained.

Further, the present invention is characterized in that each of the concave mirrors has a radius of curvature of 5 μm or more and 20 μm or less.

According to the present invention, the radius of curvature of the concave mirror is 5
By setting the thickness to not less than 20 μm and not more than 20 μm, the reflectance is 2
A practical value of 0% or more can be obtained.

Further, the present invention is characterized in that each of the concave mirrors has a radius of curvature of 7 μm or more and 12 μm or less.

According to the present invention, the radius of curvature of the concave mirror is 5
By setting the thickness to not less than μm and not more than 20 μm, the reflectance is 2
A liquid crystal display panel having a reflection efficiency of 3.8% or more can be obtained.

[0047]

FIG. 1 is a view for explaining a method of manufacturing a reflector for a liquid crystal display panel according to an embodiment of the present invention. As shown in FIG. 1, the method for manufacturing a reflector for a liquid crystal display panel of the present invention includes a primary etching step and a secondary etching step.

In the first etching step, the insoluble compound 3 is partially generated on the surface of the glass substrate 1 by the first etching solution, and the surface of the glass substrate 1 is used as an etching mask by using the insoluble compound 3 as an etching mask. This is a step of selectively etching to form a plurality of minute concave portions 2 interspersed. The first etching solution is an aqueous solution containing hydrofluoric acid as a main component and containing ammonium fluoride. The first etching solution may contain sulfuric acid in addition to the above-mentioned hydrofluoric acid and ammonium fluoride.

When ammonium fluoride (NH ₄ F) is used as the ammonium compound, SiO ₂ , which is the main component of glass, and fluorine are reacted by the following chemical reaction formulas (1) and (2). Reacts with ammonium fluoride to form insoluble ammonium fluorosilicate ((NH ₄ ) ₂ Si)
The insoluble compound 3 composed of F ₆ ) partially deposits on the surface of the glass substrate 1. Then, the progress of the etching is stopped in the portion where the insoluble compound 3 is deposited, and the etching proceeds in the portion where the insoluble compound 3 is not deposited, so that a plurality of minute concave portions 2 are formed on the surface of the glass substrate 1. This minute recess 2
Is an etching starting point in the secondary etching step. _{SiO 2 + 4HF → SiF 4 +} 2H 2 O ... (1) 2NH 4 F + SiF 4 → (NH 4) 2 SiF 6) ... (2)

Here, by controlling the concentration of ammonium fluoride in the first etching solution, the formation density of the recess 2 can be improved.
In other words, the degree of scatter of the recess 2 can be controlled. Further, by controlling the etching time in the primary etching step, the groove depth of the concave portion 2 can be controlled.

As the ammonium compound, ammonium sulfate ((NH ₄ ) ₂
SO ₄ ), ammonium hydrogen sulfate ((NH ₄ ) HS
O ₄ ) and ammonium chloride (NH ₄ Cl) may be used. Also in this case, insoluble ammonium silicofluoride and the like are formed and deposited on the surface of the glass substrate 1 according to the chemical reaction formulas similar to the chemical reaction formulas (1) and (2) described above. However, in the case of these compounds, higher heat of reaction is generated than in the case of ammonium fluoride, so safety measures and liquid temperature control are important.

The formation of the insoluble compound 3 with other ammonium compounds, for example, ammonium sulfide ((NH ₄ ) ₂ S), ammonium bromide (NH ₄ Br), and ammonium iodide (NH ₄ I) is, in principle, essential. It is possible. However, in the case of these ammonium compounds, there is a problem of extremely high heat of reaction and generation of toxic gas, so that they are not practical.

In the secondary etching step, simple etching is performed with a second etching solution using each of the concave portions 2 formed in the primary etching step as an etching starting point.
This is a step of enlarging the diameter of each recess 2 and forming a hemispherical concave curved surface 4. The second etching solution is a solution containing hydrofluoric acid as a main component and not containing an ammonium compound.

As described above, in the secondary etching, since the etching simply proceeds, the etching progresses concentrically around the etching starting point. At this time, the reaction proceeds according to the following chemical reaction formulas (3) to (5),
The silicon fluoride (SiF ₄ ) reacts with water to become water-soluble hydrosilicofluoric acid (H ₂ SiF ₆ ), and no insoluble compound is deposited on the surface of the glass substrate 1. _{SiO 2 + 4HF → SiF 4 +} 2H 2 O ... (3) 3SiF 4 + 3H 2 O → H 2 SiO 3 + 2H 2 SiF 6 ... (4) SiF 4 + 2HF → H 2 SiF 6 ... (5)

If the etching time in the secondary etching step is lengthened, the concave portion 2 having a large diameter can be obtained. In other words, by controlling the etching time,
The diameter of each recess 2 can be controlled. In the secondary etching step, it is preferable to perform the etching until the concave curved surfaces of the concave portions 2 are continuously adjacent to each other.

This secondary etching step is a step having the meaning of expanding the diameter of the concave portion 2 centering on a minute etching starting point, and is a step in which etching unevenness is more conspicuous as compared with the primary etching step. Therefore, if the viscosity of the second etching solution is large, when the glass substrate 1 is immersed in the second etching solution, when the glass substrate 1 is pulled up from the second etching solution, or when the second etching solution is not sufficiently stirred during the secondary etching. For such reasons, flow unevenness is likely to occur in the glass substrate 1 after the etching process. Therefore, it is necessary to lower the viscosity of the second etchant in order to perform a favorable etching process.

That is, it is necessary to dilute the hydrofluoric acid of the second etching solution to at least about 5 times as a measure against the flow unevenness. Further, in order to obtain a practical etching rate, the diluting degree of hydrofluoric acid in the second etching solution needs to be 20 times or less. Therefore, in consideration of the balance between the two, the second etchant obtained by diluting hydrofluoric acid to about 10 times is optimal, and the dilution degree of hydrofluoric acid is preferably 5 times or more and 20 times or less.

As described above, the glass substrate 1 in which the concave curved surface 4 of each concave portion 2 is continuously adjacent is formed. On the surface of the glass substrate 1, a base film, a metal film with high reflectivity, and a protective film are formed by a film forming apparatus such as sputtering. This forms the reflector of the present invention in which concave mirrors adjacent to each other are formed.

FIG. 2 is an electron micrograph of the surface of the glass substrate 1 manufactured by the above-described method for manufacturing a reflector for a liquid crystal display panel. As shown in FIG. 2, in the reflector manufactured by the above-described manufacturing method, each concave mirror has a concave curved surface shape that is continuous with each other, and a plurality of minute concave mirrors have a shape adjacent to each other. Since the reflecting plate of the present invention is formed in the above shape, all surfaces except the central point of the concave mirror are continuous inclined surfaces having some angle with respect to the surface of the glass substrate 1. Therefore, the liquid crystal display panel provided with the reflection plate can obtain a display with high scattering properties and can obtain a paper-like appearance without reflecting a normal image like a mirror.

The inventor of the present invention has studied various characteristics of a liquid crystal display panel provided with a reflector manufactured by the above-described manufacturing method.
The results are shown in FIGS. Here, the reflectance and the reflection wavelength of the liquid crystal display panel are the reflectance for the diffused light source measured by a global diffused light reflectance meter, and are measured with the reflectance of the standard white plate BaSO ₄ being 100%.

FIG. 3 is a graph showing a change in contrast when the average value of the diameter of the concave mirror of the reflector is changed. The contrast is obtained by dividing the reflectance when the voltage is OFF (white display) by the reflectance when the voltage is ON (black display).

As shown in FIG. 3, when the concave-convex step of the concave mirror (in other words, the distance between the center of the concave portion and the vertex of the convex portion) is constant, if the average value of the diameter of the concave mirror becomes too small, The ratio of the surface having a large inclination angle increases, and the light scattering property increases. Therefore, when the voltage is ON (black display), the reflectance increases, and the contrast is reduced. Conversely, if the average value of the diameters of the concave mirrors is too large, the ratio of the surface having a small inclination angle increases, the light scattering property becomes too weak, and the reflectance when the voltage is OFF (white display) decreases. Therefore, the contrast is reduced.

Further, from FIG. 3, if the average value of the diameter of the concave mirror formed on the reflection plate is 4 μm or more and 10 μm or less, a practical value with a contrast of 10 or more can be obtained. If the average value of the diameter of the concave mirror is 5 μm or more and 7 μm or less, a very clear display having a contrast of 20 or more can be obtained. Therefore, in the reflector of the present embodiment, the average value of the diameter of the concave mirror is set to 4 μm to 10 μm.
m or less. More preferably, 5μ
m and 7 μm or less.

FIG. 4 is a graph showing the relationship between the standard deviation of the diameter and the reflection wavelength when the average value of the diameter of the concave mirror of the reflector is set to the optimum value of 6 μm. Each wavelength is 550nm
Are standardized assuming that the reflection wavelength intensity is 1. Here, the standard deviation of the diameter being 2 μm means that when the average diameter is 6 μm, the maximum value of the diameter is 8 μm and the minimum value is 4 μm. In FIG. 4, the standard deviation is 0.5 μm in the line L1, the standard deviation is 1 μm in the line L2, the standard deviation is 2 μm in the line L3, and the standard deviation is 4 μm in the line L4.

As shown in FIG. 4, the smaller the standard deviation of the diameter, the lower the reflectance with respect to the wavelength in the blue region. In other words, if the reflectance has wavelength dependence, the reflected light will be slightly reddish with respect to the incident light. In order to prevent this, the standard deviation of the diameter of the concave mirror needs to be 2 μm or more in order to keep the reflectance of each wavelength within the range of 90 to 110% with respect to the reflection wavelength of 550 nm. When the average diameter is 6 μm, it is technically difficult to control the standard deviation of the diameter to be 4 μm or more. Therefore, the standard deviation of the diameter is 2 μm or more and 4 μm
By forming the concave mirror as described below, it is possible to obtain a reflection plate having a small wavelength dependency in reflectance. That is, coloring of the reflected light with respect to the incident light can be suppressed, and a display closer to white than a white light source can be obtained.

FIG. 5 shows the voltage OF when the average value of the diameter of the concave mirror of the reflector is 6 μm, which is the optimum value, the standard deviation of the diameter is 3 μm, and the unevenness step is changed.
It is the graph which showed the reflectance at the time of F (white display).

As shown in FIG. 5, the uneven step is 0.5 μm.
When the value is more than the above, a practical reflectance of 20% or more can be obtained. When the unevenness is 0.6 μm or more and 1.3 μm or less, a reflectance of 95% or more with respect to the optimum reflectance of 25%, that is, a reflectance of 23.8% or more can be obtained.

However, if the unevenness is too large, the shape of the unevenness can be reduced even if an attempt is made to eliminate the unevenness by applying a color filter or an overcoat material on the reflector. Works up to. This causes a problem in the alignment of the liquid crystal.

In an active drive liquid crystal display panel such as a TFT liquid crystal display panel or an MIM liquid crystal display panel, it is required that the limit value of the step is relatively loose and the step of the unevenness is 1.2 μm or less. However, in the STN liquid crystal panel, the limit value of the step is more severe than that of the active drive liquid crystal display panel, and the uneven step is required to be 0.9 μm or less.

Therefore, the unevenness of the concave mirror is set to 0.5 μm.
It is preferable to control the thickness to not less than m and not more than 1.2 μm. As a result, a sufficiently practical reflectance can be obtained in a range below the limit surface step reference value of 1.2 μm required for a TFT liquid crystal display device or the like. In addition, controlling the concave-convex step of the concave mirror to be 0.6 μm or more and 0.9 μm or less,
More preferred. Thereby, the flatness is required for S
An optimum reflectance can be obtained in a range below the critical surface step reference value 0.9 μm required for a TN liquid crystal display device or the like.

FIG. 6 shows that when the average value of the diameter of the concave mirror of the reflecting plate is 6 μm which is the optimum value, the standard deviation of the diameter is 3 μm, and the unevenness step is 0.8 μm, the radius of curvature of the concave mirror is changed. When the voltage is OFF (displayed in white)
FIG.

As shown in FIG. 6, when the radius of curvature is too large, the inclination angle of the end of the concave mirror becomes too large. If the angle of inclination exceeds 21 °, the light is confined inside the glass substrate 1 even if it is vertically incident light, and is not emitted outside the liquid crystal display panel. Conversely, if the inclination angle is too small, it will be close to specular reflection and will not reflect anything other than specularly reflected light, and the reflectance for the diffuse light source will be reduced.

Therefore, from the experimental results shown in FIG. 6, by controlling the radius of curvature of the concave mirror to be 5 μm or more and 20 μm or less, the liquid crystal display panel obtains a practical value with a reflectance of 20% or more. More preferably, the radius of curvature is 7μ.
By controlling it to m or more and 12 μm or less, it is possible to obtain a liquid crystal panel having a reflection efficiency of 95% or more, that is, 23.8% or more with respect to the optimum maximum reflectance of 25% and having a high reflection efficiency.

Example 1 FIG. 7 shows a reflector 130 manufactured by the method of manufacturing a reflector for a liquid crystal display panel according to the present invention.
1 is a cross-sectional view of an STN (Super Twisted Nematic) liquid crystal display panel 100 provided with: STN liquid crystal display panel 10
0 denotes a first substrate 101 having a stripe-shaped ITO scanning electrode 109 and a reflector 130 and a stripe-shaped IT
In this configuration, a second substrate 111 having an O signal electrode 114 is attached, and a gap is filled with a liquid crystal 121. Further, the ITO signal electrode 114 and the ITO scanning electrode 109 are orthogonal to each other, and their intersections form one pixel.

First, a method for forming the first substrate 101 will be described. First, the glass substrate 1 is subjected to a primary etching step in which a large number of minute concave portions 2 serving as an etching starting point are formed. In this first etching step, the weight ratio of hydrofluoric acid: ammonium fluoride: water = 5: 1: 10 or hydrofluoric acid: sulfuric acid: ammonium fluoride: water = 5: 1:
Etching is performed for about 100 seconds with a first etching solution having a liquid temperature of 40 ° C. mixed at 1:10. Then, a large number of concave portions 2 are formed on the surface of the glass substrate 1 in a dotted manner.

Thereafter, cleaning with pure water and brush cleaning using a cleaning brush are performed to remove insoluble ammonium fluorosilicate on the surface of the glass substrate 1. At this point, if it is desired to increase the number of the concave portions 2 which are the starting points of the etching, the concentration of ammonium fluoride in the first etching solution may be reduced. Further, in order to increase the unevenness of the concave mirror, it is preferable to increase the etching time and increase the depth of the etching starting point.

By performing this primary etching step a plurality of times with a first etching solution having a different ammonium fluoride concentration, etching starting points having various sizes, densities and depths can be formed. Thus, the standard deviation of the diameter of the concave mirror can be increased.

The glass substrate 1 thus obtained is subjected to a secondary etching step for enlarging the diameter of the recess 2. In this secondary etching step, for example, the weight ratio of hydrofluoric acid: water = 1: 1
Etching is performed for about 15 minutes using the second etching solution 10 which is diluted hydrofluoric acid at a solution temperature of 30 ° C. which does not contain ammonium fluoride. Then, a hemispherical concave curved surface 4 is formed in the concave portion 2 around the etching starting point formed in the primary etching step.
Is formed. At this time, the longer the etching time, the larger the diameter of the concave portion 2. Since this step is simple etching, the etching is characterized by the fact that the etching progresses concentrically around the etching starting point, and a smooth continuous inclined surface is obtained. Thereafter, cleaning with pure water and cleaning with a brush are performed to obtain a glass substrate 1 having a continuous concave curved surface in which the concave portions 2 are adjacent to each other. If only one side processing is desired, it can be realized by attaching an acid-resistant adhesive film to one side before the etching treatment.

Table 1 shows that the first etching solution consisting of hydrofluoric acid: ammonium fluoride: water = 5: 1: 10 was used for the primary etching, and the hydrofluoric acid: water = 1: 10 was used for the secondary etching.
An example of the shape of the concave curved surface 4 obtained when the etching conditions were changed using a secondary etching solution consisting of As shown in Table 1, when the etching time in the primary etching step is increased, the unevenness level increases, and when the etching time in the secondary etching step is increased, the average value of the diameter increases.

[0080]

[Table 1]

As described above, a plurality of continuous recesses 2
A base film 103 made of SiO ₂ , a metal film 104 having a high reflectivity such as Al or Ag, and a protective film 105 made of SiO ₂ are formed on the glass substrate 1 on which is formed by a film forming apparatus such as sputtering. 30 nm thick, 200
The reflector 130 of the present invention is formed by forming a film with a thickness of 100 nm and a thickness of 100 nm. Thereafter, a color filter 106 having a thickness of 1 to 1.5 μm is formed on the reflection plate 130 in accordance with each pixel.

Further, the overcoat layer 107 was formed to a thickness of 2 μm.
After the unevenness of the surface of the reflection plate 130 is eliminated as much as possible, a base film 108 made of SiO ₂ and a transparent electrode 109 made of ITO are further formed to a film thickness of 30 n.
The first substrate 101 is obtained by forming a film with a thickness of m and 150 nm and patterning the transparent electrode 109. In the present invention, the reflector 1
Since no resin is used for forming the irregularities of the 30, the process of forming the color filter 106 and the overcoat 107 and the process of forming the transparent electrode 109 are not limited to the heat-resistant temperature of the resin as in the prior art. Therefore, sintering of these materials at the limit temperature and high-temperature film formation are possible.

On the opposing second substrate 111, a base film 113 made of SiO ₂ and a transparent electrode 114 made of ITO are formed on a glass substrate 112 to a thickness of 30 nm and 150 nm by a film forming apparatus such as sputtering. It is obtained by patterning the transparent electrode 114. The thus obtained first substrate 101 and second substrate 111 are coated with polyimide films 110 and 115, rubbed, bonded together, and injected with a liquid crystal 121 into the gap to obtain an STN liquid crystal display panel. This reflective STN
The liquid crystal display panel is of a so-called normally white display type. According to this method of manufacturing a reflector for a liquid crystal display panel, a reflector having a high reflectance and a high scattering property can be formed, and a reflective liquid crystal display panel giving a paper-like appearance can be obtained.

(Embodiment 2) FIG. 8 shows an active drive liquid crystal display panel 20 in which an active element 216 composed of a thin film transistor or a thin film diode is incorporated in each pixel.
0 is a cross-sectional view when a so-called TFT (Thin Film Transistor) liquid crystal panel or MIM (Metal Insulator Metal) liquid crystal panel is provided with a reflector 230 manufactured by the manufacturing method of the present invention.

The liquid crystal display panel 200 has an active matrix substrate 211 having pixel electrodes 214 and active elements 216 arranged in a matrix, and a counter substrate 201 having stripe-shaped ITO electrodes 209 and a reflector 230. In addition, the gap is filled with the liquid crystal 221.

First, a method for forming the reflection plate 230 will be described. First, the glass substrate 1 is subjected to a primary etching step of forming a large number of recesses 2 serving as etching starting points.
The glass substrate 1 whose surface has been cleanly cleaned is left as it is, and the weight ratio is hydrofluoric acid: sulfuric acid: ammonium sulfate: water = 5: 1:
Etching is performed for about 140 seconds using a primary etching solution having a liquid temperature of 40 ° C. mixed at 1:10. Thereafter, cleaning with pure water and brush cleaning with a cleaning brush are performed to remove insoluble ammonium silicofluoride on the surface.

At this point, in order to increase the number of etching starting points, the concentration of ammonium sulfate may be lowered.
Further, in order to increase the unevenness of the concave mirror, it is preferable to lengthen the etching time and increase the depth of the etching starting point. Also, by repeating this primary etching step a plurality of times with a first etching solution having a different ammonium sulfate concentration, various sizes, densities,
An etching starting point having a depth can be formed on the glass substrate 1, and as a result, the standard deviation of the diameter of the concave mirror can be increased.

A secondary etching step for determining the diameter of the concave mirror is performed on the glass substrate 1 on which the plurality of minute concave portions 2 which are scattered as described above are formed. For example, etching is performed for about 15 minutes using a second etching solution composed of diluted hydrofluoric acid having a weight ratio of hydrofluoric acid: water = 1: 10 and not containing ammonium sulfate and having a liquid temperature of 30 ° C. Then, the etching proceeds around the etching starting point created in the primary etching step, and the concave portion 2 is formed in a hemispherical concave curved surface shape. The longer the etching time, the larger the diameter of the recess 2. This process is characterized in that the etching proceeds concentrically around the starting point of etching for simple etching, and a smooth continuous inclined surface is obtained in the concave portion 2. Thereafter, pure glass cleaning and brush cleaning are performed to obtain the glass substrate 1 in which the concave curved surfaces of the concave portions 2 are continuously adjacent. If only one side processing is desired, it can be realized by attaching an acid-resistant adhesive film to one side before the etching treatment.

Table 2 shows that an etching solution composed of hydrofluoric acid: sulfuric acid: ammonium sulfate: water = 5: 1: 1: 10 was used as the first etching solution, and a hydrofluoric acid:
An example of the shape of the concave curved surface obtained when the etching conditions were respectively changed using an etching solution consisting of water = 1: 10 will be described. As shown in Table 2, when the etching time in the primary etching step is increased, the unevenness level increases,
As the etching time in the secondary etching step is increased, the average diameter increases. Further, as other ammonium compounds, ammonium sulfate, ammonium hydrogen sulfate, and ammonium chloride may be used as in the case of ammonium sulfate.

[0090]

[Table 2]

An under film 203 made of SiO ₂ , Al or Ag is formed on the glass substrate 1 by a film forming apparatus such as sputtering.
The reflective plate 2 of the present invention is formed by forming a high-reflectance metal film 204 and a protective film 205 made of SiO ₂ to a thickness of 30 nm, 200 nm and 100 nm, respectively.
Obtain 30. After that, a color filter 206 having a thickness of 1 to 1.5 μm is formed in accordance with each pixel electrode 214. Further, an overcoat 207 is applied to a film thickness of 2 μm to eliminate as much as possible unevenness on the surface, and then a base film 208 made of SiO ₂ and a transparent electrode 20 made of ITO are formed.
9 is formed to a thickness of 30 nm and 150 nm, respectively, and the transparent electrode 209 is patterned to form a substrate facing substrate 2.
Get 01.

In the present invention, since no resin is used for forming the unevenness of the reflection plate 230, the process of forming the color filter 106 and the overcoat 107 and the process of forming the transparent electrode 109 are limited to the heat resistant temperature of the resin. In addition, it is possible to perform sintering at a limit temperature and high-temperature film formation of those materials.

Also, the opposing active matrix substrate 2
11 is a method of forming SiO 2 on the glass substrate 212. _TwoBase film 2 made of
13 and the ITO pixel electrode 214
Film thickness of 30 nm and 15 nm, respectively.
An active element 216 is formed by forming a film with a thickness of 0 nm. This
The counter substrate 201 thus obtained and the active matrix
Polyimide films 210 and 215 between
After applying and rubbing, they are stuck together.
The liquid crystal 221 is injected into the gap, and the active driving liquid crystal table shown in FIG.
The display panel 200 is obtained. This reflective active drive liquid crystal
The display panel 200 is a so-called normally white display.
You. According to the method of manufacturing the reflection plate 230, the reflectance and
A highly scattering reflector can be formed, giving a paper-like appearance
Reflective active liquid crystal display panel 200
Can be

[0094]

According to the present invention, since no resin layer is required unlike the prior art, this reflector can be heated to about 650 ° C., which is the softening point of glass. That is, when a color filter, an ITO electrode, or the like is formed on the reflection plate, the heating treatment can be performed by raising the temperature to about the softening point of the glass without being restricted by heating.

According to the present invention, as in the prior art,
Since a photolithography step and a resin film formation step are not required, the manufacturing equipment for the reflector can be greatly simplified, and the manufacturing cost can be greatly reduced.

Further, according to the present invention, it is possible to efficiently form a plurality of concave portions serving as starting points of etching in the secondary etching step. Further, by controlling the concentration of the etching solution and the etching time, the number and depth of the concave portions can be accurately and easily controlled.

Further, according to the present invention, the number and depth of the concave portions can be controlled accurately and easily.

Further, according to the present invention, an insoluble compound can be deposited on a glass substrate.

Further, according to the present invention, an insoluble compound can be deposited on a glass substrate.

Further, according to the present invention, an insoluble compound can be deposited on a glass substrate.

According to the present invention, an insoluble compound can be deposited on a glass substrate.

According to the present invention, the concave portions can be adjacent to each other over the entire surface of the glass substrate, and the concave curved surface of each concave portion is continuous.

Further, according to the present invention, it is possible to prevent uneven flow of the etchant, obtain a good etching finish, and obtain an appropriate etching rate.

Further, according to the present invention, the liquid crystal display panel comprises:
It is possible to obtain a display having high scattering properties, prevent a normal image from being reflected like a mirror, and obtain a paper-like appearance when viewed with the naked eye.

According to the present invention, the contrast of the liquid crystal display panel takes a practical value of 10 or more.

Further, according to the present invention, the contrast of the liquid crystal display panel becomes 20 or more, and a very clear display can be obtained.

Further, according to the present invention, it is possible to obtain a reflection plate having a reflectance with a small wavelength dependency. Therefore, it is reduced that the reflected light reflected by the reflector is colored and emitted with respect to the incident light that enters the liquid crystal display panel.

Further, according to the present invention, a sufficiently practical reflectance can be obtained in a range below the limit surface step reference value of 1.2 μm required for the TFT type liquid crystal display panel.

Further, according to the present invention, it is possible to obtain an optimum reflectance in a range below the reference value of the critical surface step difference of 0.9 μm of the STN liquid crystal display panel.

According to the present invention, a practical value having a reflectance of 20% or more can be obtained. Further, according to the present invention, it is possible to obtain a liquid crystal display panel having a high reflection efficiency of 23.8% or more.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method for manufacturing a reflector for a liquid crystal display panel according to one embodiment of the present invention.

FIG. 2 is an electron micrograph of a surface of a glass substrate 1 manufactured by the above-described method for manufacturing a reflector for a liquid crystal display panel.

FIG. 3 is a diagram showing the relationship between the average value of the diameter of the concave mirror of the reflector of the present invention and the contrast.

FIG. 4 is a diagram showing the relationship between the standard deviation of the diameter of the concave mirror of the reflector of the present invention and the reflection wavelength.

FIG. 5 is a diagram showing the relationship between the unevenness of the concave mirror of the reflector of the present invention and the reflectance.

FIG. 6 is a diagram showing the relationship between the radius of curvature of the concave mirror of the reflector of the present invention and the reflectance.

FIG. 7 is a cross-sectional view of an STN liquid crystal display panel 100 provided with a reflector 130 manufactured by the method of manufacturing a reflector for a liquid crystal display panel of the present invention.

FIG. 8 is a cross-sectional view of an active matrix drive liquid crystal display panel 200 provided with a reflector 230 manufactured by the method of manufacturing a reflector for a liquid crystal display panel of the present invention.

[Explanation of symbols]

Reference Signs List 1 glass substrate 2 concave portion 3 insoluble compound 4 concave curved surface 101, 201 first substrate 103, 203 SiO ₂ base film 104, 204 Al reflective film 105, 205 SiO ₂ protective film 106, 206 color filter 107, 207 overcoat 108, 208 SiO ₂ base film 109, 209 ITO scan electrode 110, 210 Polyimide film 111, 211 Second substrate 112, 212 Glass substrate 113, 213 SiO ₂ base film 114, 214 ITO signal electrode 115, 215 Polyimide film 116, 216 Active element 121 liquid crystal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/30 349 G09F 9/30 349D F term (Reference) 2H042 BA04 BA15 BA16 DA02 DA04 DA12 DA15 DA18 DC02 DC08 DD01 DE00 2H090 JA02 JB02 JC03 JD01 KA05 KA08 LA15 LA20 2H091 FA03Y FA17Y GA01 GA03 GA06 GA07 HA07 HA10 LA12 LA17 LA18 5C094 AA43 AA44 BA43 EA04 EA05 EA07 EB02 EB04 GB10

Claims (18)

[Claims] 1. A glass substrate provided on the back side of a liquid crystal display panel having a liquid crystal layer sandwiched between a pair of opposed substrates, and a glass substrate having a concave portion formed on the surface and a high reflectance formed on the surface of the glass substrate. A method of manufacturing a reflector for a liquid crystal display panel, comprising: forming a concave and convex shape of the glass substrate by only an etching process. 2. The etching step includes: a primary etching step of forming a plurality of recesses on the surface of the glass substrate by using an etchant that partially generates an insoluble compound; and etching each of the recesses. 2. A method of manufacturing a reflector for a liquid crystal display panel according to claim 1, further comprising a secondary etching step of enlarging the diameter of the concave portion by performing etching as a starting point and making each concave portion continuously adjacent to each other. . 3. The method according to claim 2, wherein the etchant in the first etching step contains hydrofluoric acid and an ammonium compound. 4. The method according to claim 3, wherein the etchant in the first etching step further includes sulfuric acid. 5. The method for manufacturing a reflector for a liquid crystal display panel according to claim 3, wherein the ammonium compound is ammonium fluoride. 6. The method according to claim 3, wherein the ammonium compound is ammonium sulfate. 7. The method for manufacturing a reflector for a liquid crystal display panel according to claim 3, wherein the ammonium compound is ammonium hydrogen sulfate. 8. The method according to claim 3, wherein the ammonium compound is ammonium chloride. 9. The reflection liquid crystal display panel according to claim 2, wherein the etchant in the second etching step contains hydrofluoric acid as a main component and does not contain an ammonium compound. Plate manufacturing method. 10. The liquid crystal according to claim 2, wherein the etchant in the second etching step is an aqueous solution having a hydrofluoric acid dilution of 5 to 20 times. A method for manufacturing a reflector for a display panel. 11. A plurality of concave mirrors continuously adjacent to each other are formed by forming a metal film having a high reflectance on a surface of a glass substrate on which a plurality of concave portions are successively formed. The method for manufacturing a reflector for a liquid crystal display panel according to any one of claims 1 to 10, wherein: 12. The average value of the diameter of the concave mirror is 4 μm.
The method for manufacturing a reflector for a liquid crystal display panel according to claim 11, wherein the thickness is not less than 10 µm. 13. The average value of the diameter of the concave mirror is 5 μm.
The method for manufacturing a reflector for a liquid crystal display panel according to claim 11, wherein the thickness is not less than 7 μm. 14. The standard deviation of the diameter of the concave mirror is 2 μm.
11. The structure according to claim 11, wherein the length is not less than m and not more than 4 μm.
13. The method for manufacturing a reflector for a liquid crystal display panel according to any one of items 13. 15. The step of unevenness of each concave mirror is 0.5.
The method for manufacturing a reflector for a liquid crystal display panel according to any one of claims 11 to 14, wherein the thickness is not less than μm and not more than 1.2 μm. 16. The step of unevenness of each concave mirror is 0.6.
The method for manufacturing a reflector for a liquid crystal display panel according to any one of claims 11 to 15, wherein the thickness is not less than μm and not more than 0.9 μm. 17. The method according to claim 11, wherein the radius of curvature of each concave mirror is not less than 5 μm and not more than 20 μm.
7. The method for manufacturing a reflector for a liquid crystal display panel according to any one of 6. 18. The method according to claim 11, wherein a radius of curvature of each of the concave mirrors is not less than 7 μm and not more than 12 μm.
8. The method for manufacturing a reflector for a liquid crystal display panel according to any one of the above items 7.