CN115218160A

CN115218160A - Backlight module

Info

Publication number: CN115218160A
Application number: CN202210960552.1A
Authority: CN
Inventors: 傅嘉恩
Original assignee: AU Optronics Corp
Current assignee: AU Optronics Corp
Priority date: 2018-12-14
Filing date: 2019-06-25
Publication date: 2022-10-21
Also published as: TW202022455A; TWI688805B; CN110145723A

Abstract

The invention discloses a backlight module which comprises a light source, a multilayer film and a wavelength conversion layer. The multilayer film is arranged on the light source. The wavelength conversion layer is arranged on one surface of the multilayer film opposite to the light source. The wavelength conversion layer converts part of light from the light source into a plurality of color lights including a first color light and a second color light. The wavelength value corresponding to the intensity peak value of the first colored light is smaller than the wavelength value corresponding to the intensity peak value of the second colored light. The multilayer film has a reflection range with respect to the wavelength, the multilayer film reflects light having a wavelength falling within the reflection range, the reflection range of the multilayer film includes intensity peaks of the first color light and the second color light, and the transmittance of the multilayer film in the wavelength range of less than 500nm is greater than 50%. The invention can improve the light utilization rate.

Description

Backlight module

The application is a divisional application of patent application with the application number of 201910556922.3 and the application date of 2019, 06 and 25, and the invention name of the patent application is 'backlight module'.

Technical Field

The present invention relates to a backlight module; in particular, the present invention relates to a backlight module applied to a display device.

Background

The light emitting diode is combined with a light-excited material (such as phosphor) to provide backlight, which is a main backlight generation method adopted by the existing display device. Generally, the light-activated material is formed into an optical film and disposed over the light-emitting diode. When the light emitted from the led reaches the optical film, the particles (e.g., phosphor particles) in the optical film can be excited to generate light with different colors. However, some of the light generated by the excitation does not proceed toward the light emitting direction, which results in a decrease in light utilization efficiency. Therefore, the existing display device still needs to be improved.

Disclosure of Invention

An objective of the present invention is to provide a backlight module, which can improve the light utilization rate.

In order to achieve the above object, the present invention provides a backlight module, which includes a light source, a multilayer film, and a wavelength conversion layer. The multilayer film is arranged on the light source. The wavelength conversion layer is arranged on one surface of the multilayer film opposite to the light source. The wavelength conversion layer converts part of light from the light source into a plurality of color lights including a first color light and a second color light. The wavelength value corresponding to the intensity peak value of the first colored light is smaller than the wavelength value corresponding to the intensity peak value of the second colored light. The multilayer film has a reflection range with respect to the wavelength, reflects light rays having a wavelength within the reflection range, and a wavelength value of a lower limit of the reflection range is not greater than a wavelength value corresponding to the first color light intensity peak. The multilayer film reflects the light with specific wavelength range, so that the light which does not advance towards the light emergent direction is emitted along the light emergent direction instead, and the utilization rate of the light is improved.

The lower limit of the reflection range is located at one side of the first color light intensity decreasing with the decreasing wavelength value, and the wavelength value of the lower limit of the reflection range is not more than the wavelength value corresponding to 20% of the intensity peak value of the first color light.

The wavelength conversion layer is fluorescent glue and is directly coated on the multilayer film.

The wavelength conversion layer is a quantum dot membrane, the backlight module further comprises a base material, and the wavelength conversion layer and the multilayer membrane are arranged on two opposite surfaces of the base material.

Wherein, the reflectivity of the multilayer film in the reflection range is more than 80%.

Wherein the upper limit of the reflection range has a wavelength value of not more than 780nm.

The light source is a blue light emitting diode, the first color light is green light, and the multilayer film allows the blue light to penetrate through.

Wherein, the light transmittance of the light source in the wavelength range of 380nm to 500nm is more than 50%.

The light source is an ultraviolet light emitting diode, the first color light is blue light, and the multilayer film allows ultraviolet light to penetrate through.

The backlight module of the invention can improve the light utilization rate.

The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.

Drawings

FIG. 1 is a schematic view of a backlight module according to an embodiment of the present invention.

Fig. 2 is an enlarged schematic view of the backlight module.

FIG. 3 is a diagram of the reflection spectrum of a multilayer film and the luminous intensity of a wavelength conversion layer.

Fig. 4 is a schematic diagram of a multilayer film transmission spectrum.

Fig. 5 is an enlarged schematic view of another embodiment of the backlight module.

Fig. 6 is an enlarged schematic view of another embodiment of the backlight module.

FIG. 7 is a diagram illustrating the reflection spectrum of a multilayer film and the luminescence intensity of a wavelength conversion layer.

Fig. 8 is a diagram illustrating the light intensity of the backlight module.

Wherein, the reference numbers:

1 backlight module

10 light source

20 multilayer film

21 first side

22 second side

30 wavelength conversion layer

32,32B,32G,32R particles

34,34G,34R particles

40 base material

41 third surface

42 fourth face

C11, C12 color light

C21, C22, C23 color light

C3, C31, C32, C33 color light

C4 color light

Peak value of P1, P2, P3

R1, R2 reflection range

Detailed Description

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present.

It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a "first element," "component," "region," "layer," or "color light" discussed below could be termed a second element, component, region, layer, or color light without departing from the teachings herein.

As used herein, "about", "approximately", or "substantially" includes the stated value and the average value within an acceptable range of deviation of the specified value as determined by one of ordinary skill in the art, given the particular number of measurements and errors associated with the measurements in question (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations of the stated value, or within ± 30%, ± 20%, ± 10%, ± 5%. Further, as used herein, "about", "approximately" or "substantially" may be selected with respect to optical properties, etching properties, or other properties, with a more acceptable range of deviation or standard deviation, and not one standard deviation may apply to all properties.

Fig. 1 is a schematic view of a backlight module 1 according to an embodiment of the invention. As shown in fig. 1, the backlight module 1 includes a light source 10, a multilayer film 20, and a wavelength conversion layer 30. The multi-layer film 20 is disposed above the light source 10, and preferably has a distance with the light emitting surface of the light source 10, but not limited thereto. The multilayer film 20 has a first side 21 and a second side 22. The wavelength conversion layer 30 is disposed on a surface (as shown, the first surface 21) of the multilayer film 20 opposite to the light source 10, and converts a part of the light from the light source 10 into a plurality of color lights. The multilayer film 20 allows light from the light source 10 to penetrate through, and a part of the penetrated light is converted by the wavelength conversion layer 30, then returns to the multilayer film 20, and is emitted to the backlight module 1 after being at least partially reflected by the multilayer film 20. The multilayer film 20 is preferably an optical film composed of a plurality of media having different refractive indices, and reflects light in a specific wavelength range.

Specifically, please refer to the schematic diagram of fig. 2. As shown in fig. 2, light from the light source 10 passes through the multilayer film 20 to reach the wavelength conversion layer 30. The wavelength conversion layer 30 is filled with particles 32, and the particles 32 are excited by light from the light source 10 and can be converted into different color lights. In the example of fig. 2, a portion of the light from the light source 10 maintains the original color, and another portion turns to a different color through the particles 32. Specifically, a part of the light from the light source 10 is converted into color light (C11, C12) and color light (C21, C22, C23) by the particles 32G and the particles 32R, respectively. Another part of the light from the light source 10 is the color light C3 generated by the light source. As shown in fig. 2, the color light C3 directly exits after passing through the multilayer film 20 and the wavelength conversion layer 30, the color light C12 exits after being generated by the particles 32G, the color lights (C21, C22) exit after being generated by the particles 32R, and the color lights C11 and C23 exit after being reflected by the multilayer film 20.

The colored light (C11, C12) and the colored light (C21, C22, C23) are colored light of different wavelengths. The wavelength value corresponding to the intensity peak of the colored light (C11, C12) is smaller than the wavelength value corresponding to the intensity peak of the colored light (C21, C22, C23). For example, the light source 10 is a blue light emitting diode, and the multilayer film 20 allows blue light to pass through. The wavelength conversion layer 30 may be a fluorescent glue directly coated on the multilayer film 20, and the

particles

32G and 32R filled therein are green and red phosphors, respectively, to generate green light and red light, respectively. However, the invention is not limited thereto, and in other embodiments, the wavelength conversion layer 30 may also be a quantum dot film layer directly coated on the multilayer film 20, and the

particles

32G and 32R filled therein are quantum dots capable of generating green light and red light, respectively. Taking fig. 2 as an example, the color lights (C11, C12) are green lights, and the color lights (C21, C22, C23) are red lights. The multilayer film 20 is, for example, a Dichroic filter (Dichroic filter) that reflects green and red light. In other words, the multilayer film 20 has a reflection range with respect to the wavelength, and the light having the wavelength within the reflection range is reflected by the multilayer film 20. In the foregoing example, the reflection range of the multilayer film 20 includes the wavelength bands of green light and red light. In one embodiment, the reflectivity of the multilayer film 20 in the reflection range is preferably greater than 80% to ensure the effect of improving the light utilization rate. As shown in fig. 2, for the converted color lights (C11, C12) and color lights (C21, C22, C23), wherein the color light C11 and the color light C23 originally go forward in the direction opposite to the light emitting direction, the multilayer film 20 reflects the color light C11 and the color light C23 and then emits the reflected color light along the light emitting direction, so that the light utilization rate is improved. The light-emitting direction preferably refers to a direction in which light can leave the wavelength conversion layer 30 from the light-emitting side of the wavelength conversion layer 30, and is not limited to a direction perpendicular to the surface of the wavelength conversion layer 30.

FIG. 3 is a diagram of the reflection spectrum of the multilayer film and the luminescence intensity of the wavelength conversion layer. In fig. 3, a curve L1 is a wavelength conversion layer emission spectrum, and a curve L2 is a multilayer film reflection spectrum. As shown by the curve L1, the color light converted by the wavelength conversion layer includes green light and red light. The intensity peak P1 of the green light corresponds to a wavelength value (about 530 nm) smaller than the intensity peak P2 of the red light (about 655 nm). In other words, the green light is the color light with the shortest wavelength corresponding to the color light peak value in the converted color light.

As shown by the curve L2, the multilayer film has different reflectivities for different wavelengths of light and has a reflection range R1 with respect to the wavelength. In the example of fig. 3, the reflectance corresponding to the reflection range R1 is approximately or close to 100%. Since the reflectance of each wavelength in the reflection range R1 may be slightly different, the foregoing reflectance value refers to the average reflectance in the reflection range R1. As shown in fig. 3, the green and red light bands fall within the reflection range R1 of the multilayer film, so the multilayer film reflects the green and red light.

Further, the reflection range R1 preferably has upper and lower limits of wavelength. In one embodiment, the upper limit of the reflection range R1 has a wavelength value of not more than 780nm. On the other hand, the wavelength value of the lower limit of the reflection range R1 is not greater than the wavelength value corresponding to the intensity peak of the color light of the shortest wavelength band after conversion. In other words, the lower limit of the reflection range R1 can be defined according to the wavelength value corresponding to the intensity peak (i.e. P1) of the colored light with the shortest wavelength. Taking fig. 3 as an example, the color light with the shortest wavelength is green light, and the wavelength value (about 510 nm) of the lower limit of the reflection range R1 is not greater than the wavelength value corresponding to the peak value P1 of the green light intensity. In other words, the multilayer film reflects the color light having a wavelength value greater than or equal to the wavelength value corresponding to the green light intensity peak P1 among the wavelength values of the converted color light.

The lower limit of the reflection range R1 is, for example, the lowest point of the rising edge of the multilayer reflectance curve. As shown in fig. 3, the curve L2 rises from an average low reflectance along the rising edge to an average high reflectance between the wavelengths 480nm and 530nm, and the reflection range R1 has the wavelength value corresponding to the lowest point of the rising edge as its lower limit.

In a preferred embodiment, the wavelength of the lower limit of the reflection range R1 is not greater than the wavelength corresponding to 20% of the peak intensity of the color light in the shortest wavelength band after conversion. Taking fig. 3 as an example, the color light with the shortest wavelength is green light, and the wavelength value of the lower limit of the reflection range R1 is not greater than the wavelength value corresponding to 20% of the peak value P1 of the intensity of green light. In other words, the multilayer film reflects the color light of which the wavelength value corresponds to 20% or more of the peak value P1 of the green light intensity among the wavelength values of the converted color light. It should be noted that the lower limit of the reflection range R1 corresponds to a side where the intensity of the color light in the shortest wavelength band decreases with decreasing wavelength value after conversion, that is, the wavelength value corresponding to 20% of the peak intensity value is located at the side of the short wavelength.

Referring to fig. 4, a transmission spectrum of the multilayer film is shown, and a curve L3 is the transmission spectrum of the multilayer film. As previously described, the multilayer film is transparent to light from a light source. Taking a blue light source as an example, the transmittance of the multilayer film in a blue light range (450 nm to 495 nm) is preferably greater than 50%, and even can reach about 80%. In one embodiment, the multilayer film has a transmittance greater than 50% at a wavelength of light in the range from 380nm to 500 nm. Therefore, the light of the light source is ensured to be provided to the wavelength conversion layer, so that the light utilization rate is improved.

Fig. 5 is an enlarged schematic view of another embodiment of the backlight module 1. As shown in fig. 5, the backlight module 1 includes a light source 10, a multilayer film 20, a wavelength conversion layer 30, and a substrate 40. The multilayer film 20 is disposed on the light source 10. The wavelength conversion layer 30 is located on a side of the multilayer film 20 opposite the light source 10. The substrate 40 has a third face 41 and a fourth face 42 as opposed faces. The wavelength conversion layer 30 and the multilayer film 20 are provided on opposite surfaces of the base material 40. The wavelength conversion layer 30 converts a part of the light from the light source 10 into a plurality of color lights. The multilayer film 20 allows light of the light source 10 to pass therethrough and reflects the light converted by the wavelength conversion layer 30. The wavelength conversion layer 30 is filled with particles 34, and the particles 34 are excited by light from the light source 10 and converted into different color lights. For example, the light source 10 is a blue led, and the multilayer film 20 allows the blue light to pass through. The wavelength conversion layer 30 is a fluorescent glue or a quantum dot film or layer disposed on the multilayer film 20 via the substrate 40, and the

particles

34G and 34R filled therein can generate green light and red light, respectively. It should be added that, for the backlight module shown in fig. 5 using a substrate (i.e. the light is required to pass through the multilayer film 20, the substrate 40 and then reach the wavelength conversion layer 30), the refractive index of the substrate is preferably in the range of 1.35 to 1.65, so as to ensure that the light from the light source 10 is provided to the wavelength conversion layer.

Fig. 6 is an enlarged schematic view of another embodiment of the backlight module 1. As shown in fig. 6, light from the light source 10 passes through the multilayer film 20 to reach the wavelength conversion layer 30. The wavelength conversion layer 30 is filled with particles 32, and the particles 32 are excited by light from the light source 10 and converted into different color lights. In the example of fig. 6, a part of the light source 10 maintains the original color, and another part of the light is converted into a different color by the particles 32. Specifically, a part of the light from the light source 10 is converted into color light (C11, C12), color light (C21, C22) and color light (C31, C32, C33) by the

particles

32B,32G and 32R, respectively. Another portion of the light from the light source 10 is the colored light C4 generated by the light source 10. As shown in fig. 6, the color light C12 is emitted after being generated by the particles 32B, the color light C21 is emitted after being generated by the particles 32G, the color lights (C32, C33) are emitted after being generated by the particles 32R, and the color light C11, the color light C22, and the color light C31 are emitted after being reflected by the multilayer film 20.

The colored lights (C11, C12), colored lights (C21, C22) and colored lights (C31, C32, C33) are colored lights having different wavelengths. The wavelength value corresponding to the intensity peak of the colored light (C11, C12) is smaller than the wavelength value corresponding to the intensity peak of the colored light (C21, C22) and the wavelength value corresponding to the intensity peak of the colored light (C31, C32, C33). For example, the light source 10 is an ultraviolet light emitting diode, and the multilayer film 20 allows ultraviolet light to pass through. The wavelength conversion layer 30 may be a fluorescent glue directly coated on the multilayer film 20, and the

particles

32B,32G and 32R filled therein are blue, green and red phosphors, respectively, and can generate blue light, green light and red light, respectively. Taking fig. 6 as an example, the color lights (C11, C12) are blue lights, the color lights (C21, C22) are green lights, and the color lights (C31, C32, C33) are red lights. The multilayer film 20 can reflect blue, green, and red light. In other words, the multilayer film 20 has a reflection range with respect to the wavelength, and the light having the wavelength within the reflection range is reflected by the multilayer film 20. In the foregoing example, the reflection range of the multilayer film 20 includes the wavelength bands of blue, green, and red light. However, the present disclosure is not limited thereto, and in other embodiments, the wavelength conversion layer 30 may also be a quantum dot film layer directly coated on the multilayer film 20, and the

particles

32B,32G and 32R filled therein are quantum dots capable of generating blue light, green light and red light, respectively.

In one embodiment, the reflectivity of the multilayer film 20 in the reflection range is preferably greater than 80% to ensure the effect of improving the light utilization rate. As shown in fig. 6, for the converted color lights (C11, C12), color lights (C21, C22) and color lights (C31, C32, C33), wherein the color lights C11, C22 and C31 originally go forward in the direction opposite to the light emitting direction, the multilayer film 20 reflects the color lights C11, C22 and C31 and then emits the light in the light emitting direction, so as to improve the light utilization rate. The light-emitting direction preferably refers to a direction in which light can leave the wavelength conversion layer 30 from the light-emitting side of the wavelength conversion layer 30, and is not limited to a direction perpendicular to the surface of the wavelength conversion layer 30.

FIG. 7 is a diagram illustrating the reflection spectrum of a multilayer film and the luminescence intensity of a wavelength conversion layer. In fig. 7, a curve L4 is a wavelength conversion layer emission spectrum, and a curve L5 is a multilayer film reflection spectrum. As shown by the curve L4, the color light converted by the wavelength conversion layer includes blue light, green light, and red light, and has intensity peaks P1, P2, and P3, respectively. The intensity peak P1 of the blue light corresponds to a wavelength value (about 445 nm) smaller than the intensity peak P2 of the green light (about 530 nm), and also smaller than the intensity peak P3 of the red light (about 655 nm). In other words, the blue light is the color light with the color light peak value corresponding to the shortest wavelength in the converted color light.

As shown by the curve L5, the multilayer film has different reflectances for different wavelengths of light and has a reflection range R2 with respect to the wavelength. In the example of fig. 7, the reflectance corresponding to the reflection range R2 is approximately or close to 100%. Since the reflectance of each wavelength in the reflection range R2 may be slightly different, the foregoing reflectance value refers to the average reflectance in the reflection range R2. As shown in fig. 7, the blue, green and red light bands fall within the reflection range R2 of the multilayer film, so the multilayer film reflects the blue, green and red light.

Further, the reflection range R2 preferably has upper and lower limits of wavelength. In one embodiment, the upper limit of the reflection range R2 has a wavelength value of no more than 780nm. On the other hand, the lower limit of the reflection range R2 has a wavelength value not greater than the wavelength value corresponding to the peak intensity value (i.e., P1) of the color light in the shortest wavelength band after conversion. In other words, the lower limit of the reflection range R2 can be defined according to the wavelength value corresponding to the intensity peak of the color light with the shortest wavelength. Taking fig. 7 as an example, the colored light with the shortest wavelength is blue light, and the wavelength value (about 405 nm) at the lower limit of the reflection range R2 is not greater than the wavelength value corresponding to the peak value P1 of the intensity of blue light. In other words, the multilayer film reflects the color light with a wavelength value greater than or equal to that corresponding to the blue light intensity peak P1 among the wavelength values of the converted color light. The lower limit of the reflection range R2 is, for example, the lowest point of the rising edge of the multilayer reflectance curve. As shown in fig. 7, the curve L5 rises from the average low reflectance to the average high reflectance along the rising edge between the wavelengths 380nm and 430nm, and the reflection range R2 has the wavelength corresponding to the lowest point of the rising edge as its lower limit.

In a preferred embodiment, the wavelength of the lower limit of the reflection range R2 is not greater than the wavelength corresponding to 20% of the peak intensity of the color light in the shortest wavelength band after conversion. Taking fig. 7 as an example, the color light with the shortest wavelength is blue light, and the wavelength value of the lower limit of the reflection range R2 is not greater than the wavelength value corresponding to 20% of the peak value P1 of the intensity of blue light. In other words, the multilayer film reflects the color light having a wavelength value corresponding to 20% or more of the peak value P1 of the blue light intensity among the wavelength values of the converted color light. It should be noted that the lower limit of the reflection range R2 corresponds to a side where the intensity of the color light in the shortest wavelength band decreases with decreasing wavelength value after conversion, that is, the wavelength value corresponding to 20% of the peak intensity value is located at the side of the short wavelength.

Fig. 8 is a diagram illustrating the light intensity of the backlight module. In fig. 8, a curve L6 (solid line) is a light emitting spectrum of the backlight module according to the embodiment of the invention, the backlight module has the aforementioned multilayer film and uses the fluorescent layer as the wavelength conversion layer and the blue light emitting diode as the light source. Curve L7 (dashed line) is the light emission spectrum of the backlight module as a control experimental group, the control backlight module having only a fluorescent layer without the arrangement of the multilayer films. As shown in fig. 8, the intensity of the curve L6 at a wavelength of 500nm or more is significantly improved compared to the curve L7 by the arrangement of the multilayer film.

Further, as shown in table one, the relationship between the backlight module of the embodiment of the present invention and the backlight module of the control experimental group in terms of structure, brightness and brightness percentage is listed. The luminance is an integrated value of the area under the curve L6 (or L7). The brightness percentage is based on the brightness of the backlight module of the control experiment group, and therefore the brightness percentage of the backlight module of the control experiment group is defined as 100%. As shown in table one, the brightness of the backlight module according to the embodiment of the present invention is increased by more than 80%, so that the backlight module according to the embodiment of the present invention can effectively improve the light utilization rate.

Watch 1

	L6	L7 (control)
			Superstructure	Fluorescent layer	Fluorescent layer
Understructure	Multilayer film	Is free of
			Luminance (nits)	504	275
％	183％	100％

In addition, different setting modes are selected to observe brightness change. In table two, sample a is the backlight module of the embodiment of the invention, the backlight module has multiple layers and uses the fluorescent layer as the wavelength conversion layer and the blue light emitting diode as the light source. Sample B is a comparative backlight module, which has the same composition as sample a but a different arrangement. In sample B, the multilayer film was instead disposed on the side of the phosphor layer opposite the light source. As shown in Table two, the luminance of sample B is only 13% based on the backlight luminance of sample A (100%). Therefore, the light converted by the fluorescent layer can be reflected by the multilayer film, when more layers of films of the fluorescent layer are arranged to be closer to the light source, the fluorescent layer can firstly convert part of the light source into different color light, and then the light converted by the fluorescent layer is almost reflected by the multilayer film, so that the light utilization rate can be obviously improved by adopting the sample A.

Watch 2

	Sample A	Sample B (control)
			Upper layer structure	Fluorescent layer	Multilayer film
Understructure	Multilayer film	Fluorescent layer
			Luminance (nits)	504	65
％	100％	13％

The present invention has been described in relation to the above embodiments, which are only exemplary of the implementation of the present invention. It should be noted that the disclosed embodiments do not limit the scope of the invention.

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A backlight module, comprising:

a light source;

a multilayer film disposed on the light source;

the wavelength conversion layer is arranged on one surface of the multilayer film opposite to the light source, converts part of light from the light source into a plurality of colored lights, and comprises a first colored light and a second colored light, wherein the wavelength value corresponding to the intensity peak value of the first colored light is smaller than the wavelength value corresponding to the intensity peak value of the second colored light;

the multilayer film reflects light with wavelength falling within the reflection range, the reflection range comprises the intensity peak values of the first colored light and the second colored light, and the transmittance of the multilayer film in the wavelength range of less than 500nm is more than 50%.

2. The backlight module of claim 1, wherein the wavelength conversion layer is a fluorescent glue and is directly coated on the multilayer film.

3. The backlight module of claim 1, wherein the wavelength conversion layer is a quantum dot film, the backlight module further comprises a substrate, and the wavelength conversion layer and the multilayer film are disposed on two opposite sides of the substrate.

4. The backlight module of claim 1, wherein the lower limit of the reflection range is located at a side where the first color light intensity decreases with decreasing wavelength value, and the wavelength value of the lower limit of the reflection range is not greater than the wavelength value corresponding to 20% of the peak value of the first color light intensity.

5. The backlight module of claim 1, wherein the upper limit of the reflection range has a wavelength not greater than 780nm.

6. The backlight module of claim 1, wherein the light source is a blue light emitting diode, the first color light is green light, and the multilayer film allows the blue light to pass through.

7. The backlight module of claim 1, wherein the light source is an ultraviolet light emitting diode, the first color light is blue light, and the multilayer film allows ultraviolet light to pass through.

8. The backlight module of claim 1, wherein the reflectivity of the multilayer film in the reflective range is greater than 80%.