Selecting method of light guide plate of backlight module

A selecting method of light guide plate of backlight module is described. The selecting method includes the steps of: calculating a plurality of mura indexes (MI) corresponding to a plurality of mura statuses of a plurality of first light guide plate (LGP) types, respectively; defining a plurality of film structures, wherein each of the film structures corresponds to each of mura indexes for mapping the mura indexes (MI) of the first LGP types with the film structures to construct a mapping database; and selecting one of the film structures and one of the mura indexes (MI) correspondingly from the mapping database for determining a critical dot dimension (CDD) of a second LGP type of the selected film structure. The selecting method avoids the mura, speed up the research and development procedure of the backlight module, labor cost and manufacturing cost when the LGP is assembled with the film structure.

FIELD OF THE INVENTION

The present invention relates to a selecting method, and more particularly to a selecting method of light guide plate of backlight module applicable to the manufacturing procedure of backlight module of a liquid crystal display (LCD).

BACKGROUND OF THE INVENTION

With the wide use of the LCD panel, LCD manufacturing is one of most popular industries. For an example of thin film transistor (TFT) LCD, i.e. a non-emission display, it is necessary to assemble the TFT LCD with a backlight module served as a light source besides an LCD panel for controlling the display screen. Conventionally, the backlight module includes a direct-type lighting module and an edge-type lighting module wherein the edge-type lighting module is widely utilized.

Based on the design requirement of the backlight module in the LCD, a variety of standards with different brightness and color chromaticity are adopted. However, the efficiency of LCD has to be considerably increased to meet tightly high requirement. Thus, the brightness, the amount or lighting power of LED, of the light source cannot be invariably enlarged to enhance the illumination of the backlight module. The film structures of the backlight module may be arranged to adjust the brightness of the backlight module.

After the film structures with different brightness gains are selected, the brightness and chromaticity of the backlight module may be adjusted though. However, the light convergence, the transmittance rate and the material of the film structures may be changed according to different film structures. Even if the film structures are different, however, their transmittance rates are the same so that the light guide plate under the film structure easily results in pattern mura effect. That is, after the brightness gain of the film structure is generated, the pattern mura effect occurs since the LGP assembled with the film structure is changed. The parameters of the film structure can be generated by try and error method to from the film structure for the identification of pattern mura. However, this manner will spend a lot of labor power and manufacturing cost, which results in the delay of the producing procedure.

Consequently, there is a need to develop a novel selecting method of LGP to solve the aforementioned problems of labor cost and manufacturing cost while producing the backlight module.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a selecting method of a light guide plate (LGP) used in a backlight module of a liquid crystal display (LCD) panel. The selecting method avoids the mura, speed up the research and development procedure of the backlight module, labor cost and manufacturing cost when the LGP is assembled with the film structure.

According to the above objective, the present invention sets forth a selecting method including the steps of:

calculating a plurality of mura indexes (MI) corresponding to a plurality of mura statuses of a plurality of first LGP types, respectively, wherein each of the first LGP types has a plurality of first dot patterns and each of the mura indexes is represented by an equation, MI=D1*T1/(P1*P1), and wherein MI represents each of the mura indexes, D1represents a dimension of each of the first dot patterns, P1represents a first interval distance between the first dot patterns and T1represents a first thickness of each of the first LGP types;

defining a plurality of film structures, wherein each of the film structures corresponds to each of mura indexes for mapping the mura indexes (MI) of the first LGP types with the film structures correspondingly to construct a mapping database; and

selecting one of the film structures and one of the mura indexes (MI) correspondingly from the mapping database for determining a critical dot dimension (CDD) of a second LGP type of the selected film structure, wherein the second LGP type comprises a plurality of second dot patterns, the critical dot dimension is positively related to the mura index of the selected film structure, the critical dot dimension is positively related to a second interval distance formed between the second dot patterns, and the critical dot dimension is inversely related to a second thickness of the second LGP type, for selecting the critical dot dimension based on the mura index of the selected film structure, the second interval distance and the second thickness of the selected film structure.

In one embodiment of the selecting method, the critical dot dimension (CDD) is represented by an equation, CDD=MI*(P2*P2)/T2, and wherein MI represents the selected mura index, P2represents the second interval distance between the second dot patterns and T2represents the second thickness of the second LGP type.

In one embodiment of the selecting method, when the selected film structure is composed of two overlapped diffusion plates, the mura index of the selected film structure is determined by a range from 0.44 to 0.66 and the CCD of the second LGP type is determined by a range from 0.44*(P2*P2)/T2to 0.66*(P2*P2)/T2.

In one embodiment of the selecting method, when the selected film structure is composed of a diffusion plate, a brightness enhancement film (BEF) and a micro-lens which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.57 to 0.85 and the CCD of the second LGP type is determined by a range from 0.57*(P2*P2)/T2to 0.85*(P2*P2)/T2, and wherein the diffusion plate is adjacent to the first LGP type and the second LGP type.

In one embodiment of the selecting method, when the selected film structure is composed of a first diffusion plate, a brightness enhancement film (BEF) and a second diffusion plate which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.71 to 1.07 and the CCD of the second LGP type is determined by a range from 0.71*(P2*P2)/T2to 1.07*(P2*P2)/T2, and wherein the first diffusion plate is adjacent to the first LGP type and the second LGP type.

In one embodiment of the selecting method, when the selected film structure is composed of a diffusion plate, a brightness enhancement film (BEF) and a reflective brightness enhancement film which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.68 to 1.02 and the CCD of the second LGP type is determined by a range from 0.68*(P2*P2)/T2to 1.02*(P2*P2)/T2, and wherein the diffusion plate is adjacent to the first LGP type and the second LGP type.

In one embodiment of the selecting method, when the selected film structure is composed of a first brightness enhancement film, a second brightness enhancement film and a diffusion plate which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.66 to 0.99 and the CCD of the second LGP type is determined by a range from 0.66*(P2*P2)/T2to 0.99*(P2*P2)/T2, and wherein the first brightness enhancement film is adjacent to the first LGP type and the second LGP type.

The selecting method of a light guide plate (LGP) used in a backlight module of a liquid crystal display (LCD) panel avoids the mura, speed up the research and development procedure of the backlight module, labor cost and manufacturing cost when the LGP is assembled with the film structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and 1Bare schematic relationship views of dot pattern102a,102bdimension and mura index (MI) therebetween on the light guide plates (LGPS)100a,100baccording to embodiments of the present invention. InFIG. 1A, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the first dot pattern102adisposed under the first LGP100a. The light beam106is reflected by the first dot pattern102aand emits through the upper surface of the first LGP100a. Since the geometric shapes and distribution statuses of first dot pattern102aare differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the first LGP100a. InFIG. 1B, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the second dot pattern102bdisposed under the first LGP100a. The light beam106is reflected by the second dot pattern102band emits through the upper surface of the second LGP100b. Since the geometric shapes and distribution statuses of second dot pattern102bare differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the second LGP100b. The dimension, e.g. diameter, of each second dot pattern102bis greater than the dimension, e.g. diameter, of each first dot pattern102a. The brightness intensity variation on the region distribution108in the above-mentioned descriptions is termed as pattern mura. When the total area of the first dot patterns102ais equal to the total area of the second dot patterns102b, the second LGP100bcomposed of second dot patterns102bwith greater size easily results in pattern mura in comparison with the first LGP100bcomposed of first dot patterns102awith smaller size.

FIGS. 1C and 1Dare schematic relationship views of dot pattern102c,102darea and mura index (MI) on the LGPS100c,100daccording to embodiments of the present invention. InFIG. 1C, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the third dot pattern102cdisposed under the third LGP100c. The light beam106is reflected by the third dot pattern102cand emits through the upper surface of the third LGP100c. Since the geometric shapes and distribution statuses of third dot pattern102care differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the third LGP100c. InFIG. 1D, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the fourth dot pattern102ddisposed under the fourth LGP100d. The light beam106is reflected by the fourth dot pattern102dand emits through the upper surface of the fourth LGP100d. Since the geometric shapes and distribution statuses of fourth dot pattern102dare differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the fourth LGP100d. When the total area of the third dot patterns102cis less than to the total area of the fourth dot patterns102d, the third LGP100ccomposed of third dot patterns102cwith smaller total area easily results in pattern mura in comparison with the fourth LGP100dcomposed of fourth dot patterns102dwith greater total area.

FIGS. 1E and 1Fare schematic relationship views of the LGP thickness and mura index (MI) on the light guide plates (LGP)100e,100faccording to embodiments of the present invention. InFIG. 1E, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the fifth dot pattern102edisposed under the fifth LGP100e. The light beam106is reflected by the fifth dot pattern102eand emits through the upper surface of the fifth LGP100e. Since the geometric shapes and distribution statuses of fifth dot pattern102eare differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the fifth LGP100e. InFIG. 1F, the light source104, e.g. light-emitted diode (LED), emits the light beam106to the sixth dot pattern102fdisposed under the sixth LGP100f. The light beam106is reflected by the sixth dot pattern102fand emits through the upper surface of the sixth LGP100f. Since the geometric shapes and distribution statuses of sixth dot pattern102fare differently arranged, a region distribution108with brightness intensity variation is formed on the upper surface of the sixth LGP100f. When the thickness of the sixth LGP100fis less than the thickness of the fifth LGP100e, the sixth LGP100fwith smaller thickness easily results in pattern mura in comparison with the fifth LGP100ewith greater thickness.

Please refer toFIG. 2AandFIG. 2B.FIG. 2Ais a flow chart of selecting method for choosing the second LGP type207according to one embodiment of the present invention.FIG. 2Bis a schematic structural view of a backlight module200according to one embodiment of the present invention. The selecting method for choosing the second LGP type207is applicable to the backlight module200of LCD. The backlight module200includes a light source204, the second LGP type207, a reflector209and a second film structure210. The light beam206is reflected by the critical dot patterns212and emits through the upper surface of the second LGP type207to form a region distribution208with brightness intensity variation. As shown inFIG. 2A, the selecting method for choosing the second LGP type207includes the following steps.

In step S201, a plurality of mura indexes (MI) corresponding to a plurality of mura statuses of a plurality of first LGP types respectively are calculated. As shown inFIGS. 1A-1F, each of the first LGP type has a plurality of first dot pattern types and each of the mura indexes is represented by an equation, MI=D1*T1/(P1*P2), and wherein MI represents each of the mura indexes, D1represents a dimension of each first dot pattern, P1represents a first interval distance between the first dot patterns and T1represents a first thickness of the first LGP type. The first LGP includes a first LGP100athrough sixth LGP100fshown inFIGS. 1A-1F. The first dot pattern types include the first dot pattern102athrough sixth dot pattern102f. The mura index represents the shielding ability of the film structure to the mura effect and relates to the types or/and models of the material layers forming the film structure. The first dot pattern dimension D1, the first interval distance P1between the first dot patterns and the first thickness T1of the first LGP type are related to the first LGP type. On one hand, if the mura index is decreased, the shielding ability of the film structure to the mura effect of the first LGP type is increased. On the other hand, if the mura index is increased, the shielding ability of the film structure to the mura effect of the first LGP type is decreased.

For example, if the thickness is 3 mm, the dot pattern dimension, e.g. diameter, is 0.43 mm and the interval distance between the dot patterns is 1.17 mm, the mura index, 0.94 (calculated by 0.43*3/(1.17*1.17) or less than 0.94, has a shielding ability of the film structure to mura effect to improve the backlight module.

In step S203, a plurality of film structures are defined, wherein each of the film structures corresponds to each of mura indexes for mapping the mura indexes (MI) of the first LGP types with the film structures to construct a mapping database.

In one embodiment of the selecting method, when the selected film structure is composed of two overlapped diffusion plates, the mura index of the selected film structure is determined by a range from 0.44 to 0.66.

In one embodiment of the selecting method, when the selected film structure is composed of a diffusion plate, a brightness enhancement film (BEF) and a micro-lens which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.57 to 0.85. The diffusion plate is adjacent to the first LGP and the second LGP type207.

In one embodiment of the selecting method, when the selected film structure is composed of a first diffusion plate, a brightness enhancement film (BEF) and a second diffusion plate which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.71 to 1.07. The first diffusion plate is adjacent to the first LGP and the second LGP type207.

In one embodiment of the selecting method, when the selected film structure is composed of a diffusion plate, a brightness enhancement film (BEF) and a reflective brightness enhancement film which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.68 to 1.02. The diffusion plate is adjacent to the first LGP and the second LGP type207.

In one embodiment of the selecting method, when the selected film structure is composed of a first brightness enhancement film, a second brightness enhancement film and a diffusion plate which are sequentially overlapped, the mura index of the selected film structure is determined by a range from 0.66 to 0.99. The first brightness enhancement film is adjacent to the first LGP and the second LGP type207.

In step S205, one of the film structures210and one of the mura indexes (MI) correspondingly from the mapping database are selected for determining a critical dot dimension (CDD)212of a second LGP type207of the selected film structure210. The second LGP type207comprises a plurality of second dot patterns, the critical dot dimension212is positively related to the mura index of the selected film structure210, the critical dot dimension212is positively related to a second interval distance P2formed between the second dot patterns, and the critical dot dimension212is inversely related to a second thickness T2of the second LGP type207, for selecting the critical dot dimension T2based on the mura index, the second interval distance P2and the second thickness T2of the selected film structure210. The critical dot dimension (CDD)212is represented by an equation, CDD=MI*(P2*P2)/T2wherein MI represents the selected mura index, P2represents the second interval distance between the second dot patterns and T2represents the second thickness of the second LGP type207. In other words, after the film structure210, the thickness of the second LGP type207and the interval distances between the dot patterns are selected, the mura index of the film structure210can be inquired for calculating the critical dot dimension (CDD) of the second LGP type207so that the mura effect is improved after the second LGP type207is assembled with the film structure210.

In one embodiment of the selecting method, when the mura index of the selected film structure is determined by a range from 0.44 to 0.66 and the CCD of the second LGP type207is determined by a range from 0.44*(P2*P2)/T2to 0.66*(P2*P2)/T2.

In one embodiment of the selecting method, when the mura index of the selected film structure is determined by a range from 0.57 to 0.85 and the CCD of the second LGP type207is determined by a range from 0.57*(P2*P2)/T2to 0.85*(P2*P2)/T2.

In one embodiment of the selecting method, when the mura index of the selected film structure is determined by a range from 0.71 to 1.07 and the CCD of the second LGP type207is determined by a range from 0.71*(P2*P2)/T2to 1.07*(P2*P2)/T2.

In one embodiment of the selecting method, when the mura index of the selected film structure is determined by a range from 0.68 to 1.02 and the CCD of the second LGP type207is determined by a range from 0.68*(P2*P2)/T2to 1.02*(P2*P2)/T2.

In one embodiment of the selecting method, when the mura index of the selected film structure is determined by a range from 0.66 to 0.99 and the CCD of the second LGP type207is determined by a range from 0.66*(P2*P2)/T2to 0.99*(P2*P2)/T2.

According to the above-mentioned descriptions, the selecting method avoids the mura, speed up the research and development procedure of the backlight module, labor cost and manufacturing cost when the LGP is assembled with the film structure.